JP6530468B2 - Electronic lighting system and method - Google Patents

Description

  The invention relates to the field of electronic systems arranged in series. In particular, the present invention discloses, but is not limited to, techniques for providing power and control signals to drive electronic components such as light emitting diodes in series wiring.

  Light emitting diodes (LEDs) are very efficient electronic light sources. Early LEDs emitted red light with low power. However, modern LEDs can emit light over visible, ultraviolet and infrared wavelengths. Moreover, modern LEDs can be supplied with a significant amount of current to produce sufficient light for the LED to be used as a light source.

  LEDs have many advantages over conventional light sources, such as energy efficiency, long life, high durability, small form factor, and fast switching. These many advantages have facilitated the use of LEDs in a wide variety of applications. However, LEDs still have a relatively high initial cost as compared to conventional incandescent and fluorescent light sources. Moreover, LEDs generally require more accurate current management and thermal management than conventional light sources. The first generation LEDs were mainly used as indicator lights of electronic devices. LEDs have been ideal for portable electronic devices because of their low energy consumption and small form factor. However, in recent years, new LED color and brightness improvements have made it possible to use LEDs in many new applications.

  The small size of the LEDs and the ability to control switching using digital control systems has enabled the development of LEDs based on display systems. In particular, words and images can be displayed using a two-dimensional array of individually controlled LEDs. Thus, LEDs are light sources for very large video display systems such as the many electronic billboards and sports arenas used today and the large video display systems found in Times Square in New York City.

  Although LED-based display systems have proven to be highly functional, the difficulties and costs inherent in the manufacture of such LED-based video display systems and the like make LED-based video display systems popular. Has been suppressed. The carefully measured and individually controlled power must be supplied to each LED in the two dimensional array of LEDs forming the LED based video display system. To build a monochrome high definition display system with a resolution of 1920 × 1080 image elements (pixels), the system needs to supply carefully controlled power to the 2,073,600 LEDs. To produce a multi-color high definition display system, each pixel requires three different colors (red, green, blue), so 6,220,800 LEDs need to receive carefully controlled power. is there. As such, such large video display systems are both complex and expensive to design and manufacture.

  The task of controlling many LEDs separately results in the cost of millions of dollars for large LED-based video display systems, resulting in large LED-based video displays only for very high end applications such as large sports arenas You can not buy the system. Public video display systems in other situations generally use a smaller display technology than the conventional display associated with a television display or use a pre-defined array of LED patterns for large electronic billboards with team scores or match times Use a display system much simpler than this, such as that used to display Therefore, it is desirable to simplify the task of designing and constructing LED-based displays and lighting systems.

  The figures are not necessarily to scale and like numerals refer to substantially similar elements throughout the several views. The same reference numerals but different subscripts indicate different cases of substantially equivalent elements. The drawings generally describe the various embodiments addressed herein by way of example but not by way of limitation.

FIG. 16 is a block diagram of an example computer system form of example machine capable of executing a set of instructions to cause the machine to perform one or more of the methods described herein. FIG. 1 is a block diagram illustrating the overall architecture of a single wired multiple LED unit control system according to the present disclosure. It is a figure which shows an example of the data packet which can be transmitted to a LED unit. FIG. 5 is a timing diagram of digital information modulated as a deviation of the current ramp from a rated current value. FIG. 5 is a timing diagram of digital information modulated as a deviation of a sinusoidal curve around a rated current value. FIG. 5 is a timing diagram of digital information modulated as a current dip deviation from a rated current value. It is a figure which shows the LED line driver circuit of 1st Embodiment. It is a figure which shows the LED line driver circuit of 2nd Embodiment. FIG. 7 is a diagram showing how the LED line driver circuit turns on the external field effect transistor to raise the lamp of the line current. FIG. 7 illustrates the LED line driver circuit turning off the external field effect transistor to lower the ramp of the line current. FIG. 5B shows the current modulated by the circuit of FIGS. 5A and 5B. FIG. 2 shows an ideal symmetrical current pulse and a non-ideal current pulse. It is a graph which shows a mode that a computer performs the timing which switches FET. FIG. 7 illustrates a timeline of stages in a single data bit cycle. FIG. 7 shows a lamp mode modulated current signal when reducing the rated current level to conserve energy. FIG. 7 illustrates one embodiment of individually controlled LED units. It is a flowchart which shows a mode that the power supply system of the LED unit controlled individually operate | moves. FIG. 7 illustrates data cycles resulting in an incorrect alignment in ramp mode modulation. FIG. 5 is a diagram showing data cycles resulting in an incorrect alignment in dip mode modulation. FIG. 2 illustrates a pulse generated by conventional pulse width modulation, and a pulse generated by a flicker reduction modulation system. A diagram showing the generation of the output pattern of flicker mitigation modulation, a diagram showing imperfect current pulses and an ideal square pulse, and after various randomizations to rearrange the pulses, the flicker mitigation modulation of FIG. 10C is performed It is a figure showing a data pattern which was FIG. 1 is a block diagram illustrating a first LED lighting system that may be made in accordance with the teachings of the present disclosure. FIG. 11B shows the LED lighting system of FIG. 11A controlling multiple LED lighting fixtures with a single controller. FIG. 7 is a block diagram illustrating a second LED lighting system that may be made in accordance with the teachings of the present disclosure. FIG. 5 illustrates the LED drive system of the present disclosure implemented as a DMX 512-A protocol based stage lighting system. FIG. 7 illustrates an application where a single LED line driver circuit is driving 64 individually controlled LED units arranged in an 8 × 8 array. FIG. 15 illustrates the concept of combining small modular two-dimensional arrays (shown in FIG. 14) to produce a large two-dimensional display system. FIG. 5 illustrates hanging several strings of individually controlled LED units in parallel with one another to create a two-dimensional display system. Fig. 6 is a flow chart showing a method of arranging, calibrating and operating a display system made from multiple strings of LED units. FIG. 6 is a data flow chart that illustrates decoding an incoming video signal, processing it with a model of the LED display system, and generating LED control commands to drive a display system made by arranging a set of LED strings.

  The following detailed description includes references to the accompanying drawings, which form a part of the specification. The drawings are in accordance with the illustrative embodiments. These embodiments are also referred to herein as "examples" and are described in sufficient detail to enable those skilled in the art to practice the invention. It will be apparent to those skilled in the art that the specific details in the exemplary embodiments are not necessary to practice the present invention. For example, while the exemplary embodiments are primarily disclosed with respect to a system that effectively transmits power and data to control light emitting diodes (LEDs), the teachings of the present disclosure transmit power and data otherwise. Can be used to control any type of electronic device. The exemplary embodiments may be combined, other embodiments may be used, and structural, logical and electrical changes may be made without departing from the scope of the claims. Therefore, the following detailed description should not be taken in a limiting sense, the scope of which is defined by the appended claims and their equivalents.

  As used herein, the term "a" or "an" is used to include one or more than one as is often used in patent documents. As used herein, the term "or" is used to denote a non-exclusive meaning, ie, "A or not B," unless otherwise specified as "A or B." Includes the meaning of B "and" A and B "rather than A. Additionally, all publications, patents and patent documents cited herein are hereby incorporated by reference in their entirety as if individually incorporated by reference. Where the use herein and the use in these documents thus incorporated by reference are inconsistent, the use in the incorporated reference should be considered as a supplement to the use herein. That is, contradictory inconsistencies are restricted for use herein.

Computer System The present disclosure relates to computer systems, as computer systems are generally used to control LED lighting and display systems. FIG. 1 is a block diagram illustrating a machine in an example form of computer system 100, which may partially implement the present disclosure. Within computer system 100 is an instruction set 124, which when executed may cause a machine to perform one or more of the methods described herein. In a networked deployment, this machine can operate within the capacity of a server machine or client machine in a client-server network environment, or as a peer machine in a peer-to-peer (or delivery) network environment. The machine may be a personal computer (PC), a tablet computer, a set top box (STB), a personal digital assistant (PDA), a mobile phone, a web appliance, a network appliance, a network router, a switch or bridge, or a computer that specifies the action that the machine takes. Any machine that can execute an instruction set (continuous or not). Furthermore, although only a single machine is illustrated, the term "machine" may refer to one or more of the one or more instruction sets (or sets of instruction sets) executed separately or jointly. Consider a collection of any number of machines that perform the method.

  An example computer system 100 includes a processor 102 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), or both), a main memory 104 and a static memory 106, which communicate with one another via a bus 108. . Computer system 100 may also include a video display adapter 110 that drives a video display system 115, such as a liquid crystal display (LCD) or a cathode ray tube (CRT). Computer system 100 also includes an alphanumeric input device 112 (eg, a keyboard), a cursor control device 114 (eg, a mouse or trackball), a disk drive unit 116, an output signal generator 118, and a network interface device 120.

  The disk drive unit 116 comprises a machine-readable medium 122 on which one or more computer instructions to implement or be used by one or more of the methods or functions described herein. Stores sets and data structures (eg, instructions 124 known as "software"). The instructions 124 may also be completely or at least partially in the main memory 104 and / or in the processor 102 being executed by the computer system 100, the main memory 104 and the processor 102 also constituting a machine readable medium is there. It should be noted that the illustrated computer system 100 is only one possible example and that the other computers do not have all the components shown in FIG.

  The instructions 124 may further be sent and received on computer network 126 via network interface device 120. Such transmission may be performed using any one of a number of known transfer protocols, such as File Transfer Protocol (FTP).

  Although machine-readable medium 122 is illustrated in the exemplary embodiment as a single medium, the term “machine-readable medium” may refer to a single medium or multiple mediums storing one or more instruction sets (eg, central) It should be considered to include databases that have been aggregated or distributed, and / or their associated caches and servers. The term "machine-readable medium" may also store, encode or transmit an instruction set to be executed by a machine, cause the machine to perform one or more methods described herein, or the like It should also be considered to include any medium that can be used by, or capable of storing, encoding or transmitting, data structures associated with the instruction set. Thus, the term "machine-readable medium" should be considered to include, but is not limited to, solid state storage, optical media and magnetic media.

  For the purpose of this specification, the term "module" may be a code, a calculation or an executable instruction, data, or an identifiable part of a calculation object to achieve a particular function, operation, process, procedure. Including. There is no need to implement modules in software. That is, the modules may be implemented in software, hardware / circuitry, or a combination of software and hardware.

  In the present disclosure, a computer system may be provided with a microminiature microcontroller system. The microcontroller is a single integrated that incorporates the four major components that make up the computer system: an arithmetic logic unit (ALU), a control unit, a memory system, and an input / output system (collectively referred to as I / O). A circuit can be provided. Microcontrollers are very small, low cost integrated circuits and are very often used in digital electronics.

Overview of Control System Controlling Multiple LEDs In order to control multiple light emitting diodes (LEDs) or any other controllable electronic devices (such as other types of electronic light sources), herein connected in series configuration Discloses a single-wire series configuration of power and control systems for multiple units. In particular, in one embodiment, the individually controlled electronic units controlling the LEDs are arranged in a series configuration and driven by a control unit located in the series configuration. The separate series of individually controlled electronic units may be referred to as "lines" or "strings" of lighting devices. The control unit used to provide power and data to the series of electronic units may be referred to as a "line driver", "string driver", or "head end controller". The control unit supplies power and control signals to drive all the individually controlled electronic units on the line or string. Although the present disclosure focuses on controlling LEDs or other light sources, the teachings of the present disclosure are directed to the control of acoustic systems, motors, sensors, cameras, liquid crystal displays (LCDs), and any other electronic devices. You may use it.

  FIG. 2A is a block diagram illustrating the overall architecture of a single wire multiple LED unit control system built using the teachings of the present disclosure. The LED line driver circuit 220 is installed in a series of individually controlled LED units (250-1 to 250-N). In the exemplary embodiment of FIG. 2A, the LED line driver circuit 220 receives power from the external power supply circuit 210, which will be described in more detail later herein. The LED line driver circuit 220 also receives LED control data from the master LED controller system 230. (Although this specification also describes “LED line driver circuit,” the line driver circuit sends power and data to other types of circuits connected to the driver line that perform operations other than control of the LED. Note that it can be used for

  The master LED controller system 230 can be used to turn on / off the various LEDs in the individually controlled LED units (250-1 to 250-N) on the string and the brightness of each of the LEDs that are on. Provide detailed control data describing the In one embodiment, the master LED controller system 230 provides color values and brightness since each individually controlled LED unit 250 has multiple LEDs of different colors.

  Master LED controller system 230 may be any type of digital electronic system that provides LED control data to LED line driver circuit 220 in a suitable format. The master LED controller system 230 can range from a simple single chip microcontroller to advanced computer systems that coordinate and drive multiple LED strings. For example, in a relatively simple embodiment, the master LED controller system 230 with microcontroller components, the power supply 210 and the LED line driver circuit 220 can be a single LED driver circuit system 239 that controls a string of LED units 250 Can be incorporated into the In a further advanced embodiment, an external computer system such as computer system 100 as shown in FIG. 1 is used as an LED suitable for LED line driver circuit 220 using signal generator 118 or any other suitable data output system. It can be programmed to output control data signals.

  In one particular embodiment, LED control data 231 is provided from master LED controller system 230 to LED line driver circuit 220 using a known serial peripheral interface (SPI). In this manner, many LED strings can be connected to a single master LED controller system 230, such as computer system 100, to control these LED strings. However, in alternative embodiments, other suitable digital communication systems such as Universal Serial Bus (USB), Ethernet, or IEEE 1394 interface (Fire Wire) may be used to control the LED control data to LED line driver circuit 220. It can be used to provide. In embodiments intended for use for stage lighting, the data interface can be programmed to correspond to the known DMX 512-A protocol used to control stage lighting. In such embodiments, multiple LED line drivers can be connected in a daisy chain configuration to control multiple strings of individually controlled LED units.

  Using the power 211 received from the power supply 210 and the LED control data 231 received from the master LED controller system 230, the LED line driver circuit 220 controls the individually controlled LED units (250-1 to 250-N). The electronic signal is driven by a current loop (consisting of lines starting at 221 and returning to 229) supplying both power and control data to the entire string. This system, which provides both power and control data on a single line, greatly simplifies the design and construction of LED lighting and display systems. Moreover, by using a single wire to transmit both power and control data, the construction costs of multiple LED displays or lighting systems etc. are significantly reduced. In accordance with the disclosed system, a single current loop (also referred to as a driver line) may provide seven or more different functions for individually controlled LED units on the string, eg, (1) to LED unit 250. Power, (2) Control and configuration commands to LED unit, (3) LED output data, (4) Clock reference value used to generate local clock signal, (5) Calibrate current output to LED Functions such as (6) heat dissipation, and (7) physical structure to support the individually controlled LED units (250-1 to 250-N). The details of each function will be described in a later section of this specification.

  FIG. 2B shows an embodiment of a data frame that can be modulated on driver lines linked with individually controlled LED units (250-1 to 250-N). The beginning of the data frame is a synchronization byte 291. Because there are no separate clock signals sent to the LED unit 250, the LED unit 250 uses the sync byte to assist in tracking the digital data signal and to determine the start of each new data frame. The command field 292 then specifies the particular command that the receiving LED unit 250 is to execute. The address field 293 designates a specific address (or address group) to select an LED unit (250-1 to 250-N) responding to this command. Following the address field 293 is a data field 294 containing the payload of data. Finally, an optional cyclic redundancy check (CRC) code 295 may be used to perform data integrity.

  Referring again to FIG. 2A, a number of individually controlled LED units (250-1 to 250-N) are connected in series configuration (starting from 221 and back to 229) to the driver lines. Each individually controlled LED unit 250 includes one or more LEDs, an LED control circuit, and other additional components necessary to complete the individually controlled LED unit 250. In one embodiment, the only additional electronic components required for each LED unit 250 are the LED control circuit and a capacitor that stores an electrical energy storage for driving the LEDs of the individually controlled LED unit 250. In addition to capacitors used to store electrical energy, external diodes and small heat sinks may be used in other embodiments that handle higher currents. When there are two or more LEDs connected to the individually controlled LED units 250, the different LEDs of the LED units 250 will be referred to as the LED "channels" of the LED units 250 respectively.

  In some embodiments, two or more capacitors can be used to store power for operating the individually controlled LED units 250. For example, in one embodiment, different capacitors are used to store power for different LEDs. In this way, the different color LEDs operate at different voltage levels, and by combining capacitors with each of the different color LEDs, it is necessary to use the capacitors to drive the specific color LEDs It is possible to store only the voltage amount of. In this way, LEDs that require a high voltage content can be provided with a high voltage content, but LEDs that require a low voltage content can be provided with a low voltage content. This prevents the voltage drop circuit from being used inefficiently and simply consuming excess voltage as waste heat.

  An important component in each of the individually controlled LED units (250-1 to 250-N) is the LED controller circuit. The LED controller circuit performs most of the tasks necessary to reasonably control the various LEDs of the individually controlled LED units 250. These tasks include obtaining the electrical energy from the driver line, storing this electrical energy in the power capacitors used to power the LED units, and adjusting the voltages required to power the LED controller circuitry. Producing, demodulating the data signal modulated by the driver line, decoding the demodulated data signal to obtain a data frame, executing the command received in the data frame, and various LEDs specific brightness Driving at the level etc. is included. The details of each of these functions are described in the section on individually controlled LED units.

LED Line Driver As described in the section above, the LED line driver circuit 220 of FIG. 2A is a driver line starting from 221 and returning to 229, individually controlled LED units (directly connected to the LED line driver circuit 220 250-1 to 250-N) play a role in supplying both power and LED control data. To make the construction of the LED lighting and display system simple and inexpensive, the LED line driver circuit 220 supplies both power and control data to all of the LED units 250 with a single driver line. Although this single-line driver line greatly simplifies the construction of a lighting and display system that uses a large number of individually controllable lighting elements, this means that such individually controllable lighting elements can be used for each lighting element. This is because it can be configured in a simple daisy chain configuration connected by a single wire.

  In order to power the individually controlled LED units 250, the LED line driver circuit 220 functions as a current source to drive a direct current (DC) signal with a single driver line. In some embodiments, the DC signal is driven at a nominally constant level. However, the main purpose is to provide a data signal that each LED unit 250 can track and a current sufficient to supply the LED unit 250 with energy. The individually controlled LED units (250-1 to 250-N) connected to the driver line in the series configuration respectively demodulate data from the DC current signal and perform necessary operations from the DC current signal driven by the driver line Draw power.

  In order to provide LED control data to all of the individually controlled LED units 250 on the string, the LED line driver circuit 220 modulates the data with the current driven by the driver line. Various different methods may be used to modulate data. Although the two different methods used are described herein, other data modulation systems may be implemented as would be understood by one skilled in the art.

  In one embodiment, the line driver circuit modulates data on the driver line by using a current ramp slightly above and below the rated current level. In such an embodiment, each data bit period is divided into two cycles including either a positive current ramp followed by a negative current ramp or a negative current ramp followed by a positive current ramp. be able to. The two different data patterns can be used to represent a "1" or "0" for a digital communication system. FIG. 3A is a graph showing the current of the driver line controlled by the LED line driver circuit 220 when modulating data with current. In the example of FIG. 3A, a logical "0" represents a positive current ramp followed by a negative current ramp, and a "1" represents a negative current ramp followed by a positive current ramp. It should be noted that the average current value on the line is the rated current level 310, since the content of each data phase includes both positive and negative current ramps. FIG. 3B shows a similar embodiment using sinusoidal current changes around the rated current level 310.

  Other data coding means include those using Manchester coding and Non-Return-To-Zero with Manchester. Other means of modulating data with current may be used. For example, in one alternative embodiment, a first current level may be used to specify a logical "0" and a second current level may be used to specify a logical "1". . In this way, the stream of data bits can be encoded by switching between two current levels.

  FIG. 3C shows another data modulation system, "dip mode" modulation. In the dip mode modulation system shown in FIG. 3C, each data bit cycle is divided into the first half and the second half. Next, the modulation system modulates data by generating a dip in current either in the first half or the second half of the data bit period. In the particular embodiment of FIG. 3C, data bits of “0” represent that a current dip occurred in the first half, and data bits of “1” represent that a current dip occurred in the second half. An example of a modulation circuit for the ramp mode and dip mode data modulation systems shown in FIGS. 3A and 3C, respectively, will be described.

Embodiment of First LED Line Driver Circuit Using Lamp Mode FIG. 4A is a block diagram showing the nature of the LED line driver circuit 425 for an embodiment of modulating data using the system shown in FIG. 3A. The LED line driver circuit 425 of FIG. 4A implements a current modulation system called "lamp mode" modulation. The lamp mode modulation system is designed for low cost implementations where data can be modulated using one LED line driver IC 420, one field effect transistor (FET), one inductor, and several resistors. It is done.

  The main component of the LED line driver circuit 425 is an advanced LED line driver IC (integrated circuit) 420 that controls the overall operation of the LED line driver circuit 425. The LED line driver IC 420 includes a clock circuit block 485 for generating a clock signal necessary to drive a digital circuit. Clock circuit block 485 receives an input from external clock 486 (or a resonator) to generate the various internal clock signals needed. The clock circuit block 485 is a prescaler to reduce the speed of the clock signal sent from the external clock 486 for internal core clock generation, several synchronous logic circuits to ensure that the chip clock is properly started after power reset, A timing generator can be provided to transmit the data modulated at the driver line at the correct data rate.

  Looking to the lower left of the LED line driver IC 420 of FIG. 4A, the data interface 430 is receiving control data from an external controller, such as the master LED controller system 230 shown in FIG. 2A. Data interface 430 extracts input control data and transfers this control data to command parser and handler circuit 440. In a simple embodiment, the LED line driver IC 420 itself may include circuitry that generates a pattern of LED control data and may not require an external LED controller.

  In one particular embodiment, data interface 430 implements a known serial peripheral interface (SPI) protocol. The SPI implementation includes the standard data in 432, data out 431, data clock (not shown) and chip select (not shown) pins typically used by the Serial Peripheral Interface (SPI) protocol. It is also good. The operation of the SPI system varies depending on the particular implementation. In a conventional SPI implementation, an external SPI master (such as master LED controller system 230 in FIG. 2A) sends data to the data in pins 432 of each of the LED line driver ICs 420, and which LED line driver circuits are the respective LED line driver ICs. Specifies whether data should be acted upon by activating the chip select pin of. Because the SPI protocol is a bi-directional protocol, individual LED line driver circuits can send status information back to the external SPI master system. One embodiment of the LED line driver circuit uses a return data path to respond to status queries such as calibration information and requests for buffer status. In an alternative implementation of the SPI protocol, the data out 431 line can be connected to the data in interface of another LED line driver circuit in a daisy chain configuration, thus a series of LED line driver circuits in a single master LED controller system Can be controlled by

  The command parser and handler circuit 440 validates incoming control data and responds appropriately to incoming control data. In one embodiment, the LED line driver IC 420 sends the driver line to three main types of commands (configuration request, status request, and individually controlled LED units connected to this driver line). Process a request to transfer data down). The configuration request can instruct the LED line driver IC 420 to set the designated control register in the control and status register block 441. The configuration request can also instruct the LED line driver IC 420 to blow the fuse of the non-volatile configuration of the LED line driver IC 420 and program the LED line driver IC 420 for permanent configuration information. The input status request can request status information such as buffer status, operation status, and current configuration from the LED line driver IC 420. Such status requests sent to the LED line driver IC 420 may be processed by fetching the information from the control and status register 441 and sending a response to the master controller located on the data outline 431.

  The requests sent from the master LED controller to the LED line driver IC 420 to transfer LED control data from the driver line to the individually controlled LED units generally account for the majority of communication with the LED line driver IC. The command parser and handler circuit 440 processes these LED control data, transferring requests by transferring the LED control data to the line data transmission block 450. Line data transmission block 450 stores control data in a frame buffer. In the embodiment of FIG. 4A, since the LED line driver IC 420 comprises two frame buffers (451 and 452), the LED line driver IC 420 can control the LED control data input from the master LED controller to the first frame buffer. While being able to receive, the LED control data sent from the second frame buffer are simultaneously modulated with the driver line. The frame buffer (451 and 452) temporarily stores LED control data for one or more individually controlled LED units (470-1 to 470-N) connected to the driver line.

  In some embodiments, LED unit 470 can communicate back to LED line driver IC 420. For example, by turning on / off the shunt transistor in a designated time zone, the LED unit 470 can send a signal back to the LED line driver IC 420 so that the LED line driver IC 420 can detect the effect. . In such an embodiment, the status request message input to data in 432 can request status from the individually controlled LED unit 470 connected to the driver line. The command parser and handler circuit 440 then translates this LED unit status request into a second status request message, which is then sent to the line data transmission block 450 and modulated with the driver line. Upon receiving a response from the LED unit 470, the LED line driver IC 420 sends a corresponding response message to the data outline 431.

  The line data transmission block 450 is responsible for transmitting LED control data (also status request in some embodiments) to the LED unit 470 on the driver line. The line data transmission block 450 fetches the control data (or status request) transferred to this block from the command parser and handler circuit 440 and fills the next available frame buffer. In one embodiment, line data transmission block 450 may calculate (if control register 441 specifies to do so) bytes of the cyclic redundancy check (CRC) that are optional frames. In one embodiment, if there is no pending LED control data (or status) in the line data transmission block 450 to modulate on the driver line, the line data transmission block 450 modulates an idle data frame on the driver line. While idle data frames are not the subject of any of the individually controlled LED units 470, these individually controlled LED units 470 maintain synchronization with the driver line modulated data stream. Assist with

  Line data transmission block 450 transfers the formatted data frame from the frame buffer (451 and 452) to current modulation block 490. The current modulation block 490 serves to modulate a (nominally) constant DC current signal at the driver line to provide a data stream to the LED unit 470 on the driver line. In particular, the current modulation block 490 modulates the current by rapidly increasing or decreasing the current and transmits the LED control data downstream of the driver line to control the LED unit 470. In one embodiment, current modulation block 490 achieves this goal by controlling an external transistor that biases the inductor at the driver line.

  Before describing the current modulation block 490 in further detail, it may be helpful to outline the power source. Most electronic circuits are configured to power electronic circuits using voltage power as a power source. An ideal voltage source is a conceptual mathematical model that can generate an infinite current at a specifically set voltage level to drive a load circuit and has zero internal resistance. Of course, real-world voltage sources, such as batteries and DC power supplies, can not produce infinite current and do not have zero internal resistance. However, as long as the load circuit powered by the real world voltage source does not exceed the current capacity of the real world voltage source and adds a non-zero internal resistance in series with the load circuit, the ideal voltage for the circuit modeling the voltage source You can use the source.

  When designing an electronic circuit, there are far fewer ways to use a current source to model the power source. An ideal voltage source is a mathematical model of a power source that has infinite internal resistance and can generate infinite voltage at specific current levels to drive a load circuit. Again, none of the real-world current sources can supply infinite voltage, and none of the real-world current sources have infinite resistance. However, unless the total resistance of the load circuit driven by a real-world current source is too high and you do not need very high voltage values, the ideal with non-infinite internal resistance in parallel with the ideal current source It can model real-world current sources as current sources (circuits known as Norton equivalent circuits). In the present disclosure, a current source is used as a power source model. In particular, the LED line driver IC 420 and the current modulation block 490 of the supporting external circuitry may also be used to drive the current on the driver line specifying an adjustable rating level during operation. In addition, the current modulation block 490 varies the current level around a specific rated current value by slightly increasing or decreasing the current, and the rating used to modulate data with the current as described in FIGS. 3A-3C. It can be varied away from the current value.

  Referring again to FIG. 4A, the external power supply 410 produces a current that is transmitted downstream of the driver line through the LED unit 470. The output voltage (denoted Vsupply 411) of the external power supply 410 at the top of the driver line is a potential that exceeds the amount required by the total of all the LED units 470 on the driver line. After all the current has passed through the LED units 470 on the string, it flows through the inductor 462 and the field effect transistor (FET) 461 to ground. Current modulation block 490 carefully modulates the current level on the driver line by controlling inductor 462 with FET 461 to produce the modulated current pattern shown in FIG. 3A. It should be noted that the FET 461 is generally implemented external to the LED line driver IC 420, since the FET 461 can handle relatively high potentials that can not be handled in conventional CMOS semiconductors.

  Referring again to the current graph shown in FIG. 3A, the current of the driver line fluctuates slightly above and below the constant rated current value 310 used to modulate data in the driver line, and the constant rated current value It is modulated before and after 310. 5A, 5B, and 5C illustrate how the LED line driver circuit uses FET 561 to modulate the current around the specified rated current value 310 to control the inductor 562. FIG. Note that current control circuits other than FETs may be used instead.

  In steady state direct current (DC) circuits, the inductor acts as a short without affecting the circuit. However, when the state changes, the inductor will counter the change in current level. Thus, as the current through the inductor increases, the inductor delays the increase in current by storing energy in the magnetic field. Likewise, when the current passing through the inductor decreases, the inductor counteracts the current decrease by using the energy stored in the magnetic field and supplements the decelerating current.

  Referring to FIG. 5A, when the LED line driver circuit 425 is turned on first, the LED line driver circuit turns on the FET 561 so that current flows from Vsupply 511 downward to all the LED units 570 on the string, and the inductor 562 is turned on. (To control the current) and finally flow through resistor 564 to ground 565 of the power supply. This electrical path from the external power supply Vsupply 511 to the external power supply ground 565 is called a current loop. Note that current flows from the external power supply through the second voltage source Vclamp 512 to the diode 563 as there is a branch circuit after the inductor 562. However, since Vclamp 512 is at a higher potential than ground 565, no current flows to Vclamp 512 even if FET 561 is turned on.

  When the FET 561 is first turned on, the current increases on the driver circuit as shown in FIG. 5C. However, the current increase is slowed by the inductor 562 corresponding to the rapid current increase by storing energy in the magnetic field. Thus, the current of the driver line slopes upward at the start step 521 as shown in FIG. 5C. Note that there is a voltage drop across inductor 562 as indicated by the “+” and “−” signs in FIG. 5A. The LED line driver IC 420 keeps the FET 561 on during this initiation phase 521 to allow the driver line current level to increase until it exceeds the desired rated current level 510 by a specified amount.

  When the current through the driver line exceeds the desired rated current level 510 by a specified amount, the LED line driver IC 420 turns off the FET 561 so that current does not flow through the FET 561 to the power supply ground 565 as shown in FIG. 5B. Do. However, the inductor 562 resists abrupt changes in current flow, and instead causes the current to begin to ramp downward as shown by the current drop 531 in FIG. 5C. Since current no longer flows through FET 561 to ground 565, instead a slowed current flows through the branch circuit, as shown in FIG. 5B, which shows the current flow when FET 561 is turned off. Flow towards Vclamp 512 through 563. This occurs even if the voltage at Vclamp 512 is higher than Vsupply 511. Because the inductor 562 continues to drive the current using the energy that is in the magnetic field.

  The current starts falling only by turning off the FET 561, but the falling ramp which occurs only by turning off the FET 561 is relatively slow. (The rise and fall of the current ramp is asymmetric as it is slow compared to the ramp where the current rises when the FET 561 is on.) The current ramping ramp is accelerated, thereby causing upward and downward currents In order to approximately match the lamp, Vclamp 512 is set to a higher potential than Vsupply 511, and inductor 562 is reverse biased (as indicated by the "+" and "-" signs in FIG. 5B) to Try to accelerate the ramp downwards.

  Referring to FIG. 5C, when the current 531 drops below a specified amount and falls below the desired rated current value 510, the LED line driver turns on the FET 561 (returning to the state of FIG. 5A), illustrated by the current rise 532. To become a ramp to rise again. The LED line driver IC 420 prevents the driver line current from becoming the final steady state of DC current. Conversely, the driver circuit repeats FET 561 on and off to maintain the driver line current around the desired rated current level 510.

  By turning the FET 561 on / off, the LED line driver IC 420 can modulate the amount of current flowing through the driver line with the rising and falling ramps relatively stable. By turning the FET 561 on / off in a manner that correlates control data, the LED line driver IC 420 can modulate the control data on the driver line in the same manner as the current pattern shown in data step 522 of FIG. 5C. It should be noted that if there is not enough data to be sent to the LED line driver IC 420, the LED line driver IC 420 will modulate an empty packet on the driver line. In this way, the various LED units on the driver line can maintain synchronization with the data stream modulated by the LED line driver IC 420.

  Referring again to FIG. 4A, current modulation block 490 receives a data frame from line data transmission block 450 and modulates with the driver line as a pattern of current ramps. As described above, the current modulation block 490 turns on the external FET 461 (raising the current by passing the current to the ground 465 of the power supply 410) or drops the current by applying a reverse bias to the inductor 462 ) This task can be accomplished by turning off the external FET 461.

  In certain embodiments that use the driver line current as a reference current value, the current modulation block 490 ensures that the average of the current is desired, even though the data is modulated on the driver line by changes in current. It plays the role of ensuring the proper rated direct current (DC) level. Thus, the LED unit connected to the driver line can detect the average current level of the driver line and use this current level as a reference current value. In particular, the LED unit connected to the driver line can use the average current level on the driver line as a reference current in generating the current used to drive the LED connected to the LED unit.

  The current modulation block 490 can control the external FET 461 by controlling its own internal FET 493. In one embodiment, the internal FET 493 is designed to handle 10 volt variations so that it can control the larger external FET 461, which directly plays a role in controlling the current in the driver line.

  Modulating data with driver line current is not an easy process. Operating the various LED units 470 on the driver line makes it difficult for the LED line driver circuit 425 to stably control current on the driver line. In particular, as in FIG. 5A, the various LED units 570 either conduct current to charge the local capacitor (which causes a larger voltage drop across the LED units) or shunt the line current (which causes the LED units to Only a small voltage drop) causes the voltage drop between Vsupply 511 and Vline 514 to fluctuate depending on the presence or absence of LED unit shunting. As a result, the voltage across inductor 562 will vary as well, so the rising current ramp (when FET 561 is on) will not always have exactly the same slope. The same phenomenon occurs with falling current ramps. In particular, as shown in FIG. 5B, when the voltage applied to the LED unit 570 fluctuates, the reverse voltage bias applied from Vclamp 512 to Vline 514 via the inductor is not always the same, so the slope of the falling current lamp fluctuates. To mitigate this phenomenon, it is necessary to limit the various LED units 570 from stopping on time in the vicinity of the data bit edge. Nevertheless, the fact that the LED unit 570 shunts or shuts off near the edge of the data bit still affects the data modulation and demodulation task.

  Ideally, the current ramps generated by the LED line driver circuit 425 always start / end at the rated current value 610, as shown by the ideal current ramps in dashed lines in FIG. It is to be symmetrical. However, as the conditions on the driver line change, such an ideal current ramp may not always be achieved. For example, if a relatively small voltage drop occurs in the LED unit 570 accumulating on the driver line, then a higher voltage is applied to the inductor 562 and the current increases faster than the ideal current ramp (shown in dashed lines) of FIG. 6A. It should be noted that the exact height of the peak of the current ramp is less important if it is larger than the amount of threshold required for detection.

  To compensate for this, the falling current ramp must start at an appropriate time (determined by taking into account the predicted falling slope) and the current level must cross the rated current level 610 at the middle of the data period. In the example of FIG. 6A, since the falling current slope is less than the ideal slope, the falling phase starts earlier than normal, and the peak of the current ramp is shifted slightly to the left. In general, if the absolute value of the slope in the first half of the lamp is greater than the absolute value of the slope in the second half of the lamp, the peak shifts earlier (the time axis in the figure to the left) and in the first half of the lamp If the absolute value of the slope of is smaller than the absolute value of the slope in the second half of the ramp, the peak shifts later (the time axis of the figure to the right).

  To generate the current ramp carefully, the current modulation block 490 of the LED line driver circuit 425 can create a current behavior model to estimate the exact time to change the external FET 461. Various different methods can be used to model the current ramp. In one particular implementation, current modulation block 490 uses an analog computer to model the current ramp to determine when to turn the FET on / off.

  Referring to FIG. 4A, current modulation block 490 comprises two substantially identical analog computer circuits labeled lamp A 491 and lamp B 492. The current modulation block 490 alternates between the two analog computer circuits, using one analog computer in the first half of the data cycle and another analog computer in the second half of the data cycle. Two analog computer circuits each estimate the time to turn on / off the gate signal of field effect transistor (FET) 493 using an analog ramp circuit (thus actually turning on / off the larger external transistor 461) 2.), return the end of the current ramp to the rated line current value again at the end of the half bit period. In one embodiment, these analog ramp circuits create a model of how much current changes in the other half of the bit period when switching FET 493 instantaneously. In the case of a rising slope, this model clarifies how much current drops from the current amount when switching FET 493 instantaneously. This is because a large amount of current may drop when the FET 493 is switched at the start of a half bit period, or the current may not change at all even if the FET 493 is switched at the end of the half bit period. is there.

  As mentioned above, the rate at which the current changes depends on the voltage across the inductor 462. In order to calculate the voltage applied to the inductor 463, three different voltage values of Vline 414, Vclamp 412 and Vfetsrc 417 are prepared for the current modulation circuit 490. When the FET 461 is turned on, the voltage across the inductor 462 is calculated as the voltage difference from Vline 414 to Vfetsrc 417 (minus the slight drop across FET 461). When FET 461 is turned off, the voltage across inductor 462 can be calculated as the voltage difference from Vline 414 to Vclamp 412 (minus the slight drop across diode 463). These voltage values can be used to estimate the rate of current change (indicated by the slope) and use this rate to determine the exact time to switch FET 461. It should be noted that although these voltage values can actually be read as currents flowing through the resistor, this current is proportional to the voltage according to Ohm's law.

  The analog computer circuit (lamp A 491 and lamp B 492) can be implemented using a ramp circuit and a multiplication circuit. The ramp circuit is used to generate a ramp signal that starts at a fixed full scale value and falls to zero at the end of a half bit period. The ramp signal is then multiplied by the analog multiplier circuit with the value of the voltage difference which determines the rate of current change (shown as a slope in the graph). At that time, when the FET 493 is turned on, the ramp signal is multiplied by an amount correlated with Vclamp 412-Vline 414. This amount is a voltage applied to the inductor 462 when the FET 493 is turned off. At that time, when the FET 493 is turned off, the ramp signal is multiplied by an amount correlated with Vfetsrc 417-Vline 414. This amount is the voltage applied to the inductor 462 when the FET 493 is turned on again.

  The output of the analog ramp circuit is combined with the value of the current time (or the estimated time this current flows) when the current flows through the driver line. The state of the FET 461 changes when the absolute value, which is the difference between the current and rated current levels, equals the amount of current change that will occur as expected in the lamp circuit. The current of the driver line when the FET 461 is turned on can be calculated from the voltage value of Vfetsrc 417. This is because the current of the driver line is equal to the voltage of Vfetsrc 417 divided by the resistance value of the resistor 464 according to Ohm's law. However, when the FET 461 is turned off, the driver current when the FET 461 is turned off using the line current estimation circuit 495 using the last measured current value and the voltage value applied to the inductor 462 determined by Vline 414 and Vclamp 412. Current can be estimated.

  To best describe the operation of the lamp circuit, several examples are provided with reference to FIG. 6B. At the beginning of the data cycle, one of the ramp circuits is charged and multiplied by the voltage difference across the inductor to produce a value corresponding to the amount of current change that occurs when the FET 493 is switched instantaneously. The amount of this current change drops to zero at the end of the half bit period (assuming proper charging). This concept is illustrated in FIG. 6B as lines 651, 652, and 653 depicting various different voltage values across the inductor. Each line starts from the point where the current drop with respect to the rated current level 610 is maximum when switching the FET instantaneously, and drops to current zero at point 691 at the end of the half bit period. The slopes of the different lines 651, 652, and 653 indicate how fast the current changes based on the voltage across the inductor.

  In order to use the output of the analog computer, the current value (relative to the rated current level 610) is compared to the current drop expected by the ramp circuit to occur in the other half of the bit period. When the current value crosses the predicted amount of current drop, the FET 493 is switched. Three different examples are shown in the graph of FIG. 6B. In the first example, since the current increase 661 is faster than the predicted current drop rate 651, the system needs to switch FET 493 before midpoint 631 to slightly shift the peak of the current ramp to the left . It should be noted that since the current rise rate and the current drop rate are both affected by the voltage applied to the inductor, the current drop rates to be predicted are different for each of the current rise rates in the different examples. In another example, the current increase 663 is slower than the predicted current drop rate 653 so the system needs to switch FET 493 after midpoint 631 to slightly shift the peak of the current ramp to the right. If the current ramp rate 662 is substantially equal to the predicted current ramp rate 652, an ideal lamp centered at the midpoint 631 is formed. However, as long as the peak of the current ramp is within a reasonable distance from the midpoint 631, there is no problem with the demodulation logic in correctly identifying the current ramp.

  As described above, when the FET 493 is turned off, it is difficult to calculate the current flowing through the driver line because the current temporarily flows toward Vclamp 512 as shown in FIG. Therefore, the technique of calculating the current by measuring the voltage at Vfetsrc 417 in FIG. 4 can not be used because the current for generating the voltage does not flow in the resistor 464. Alternatively, another ramp circuit, line current estimation circuit 495, can be used to estimate the current in the falling ramp. Thus, referring again to FIG. 6B, the line current estimation circuit 495 can be used to predict the current of the driver line as indicated by the prediction line 680. It should also be noted that the rate of change of current is correlated with the voltage drop across the inductor. Similarly, either of the ramp circuits (491 or 492) is used to predict the amount by which the current will increase in the other half of the bit period if the FET 493 is switched instantaneously. When the two prediction circuits output the same absolute value (with respect to the rated line current), the FET 493 is switched.

  The internal logic of current modulation block 490 may be implemented in a variety of different ways. In one embodiment, the system digitally calculates the current in the line while FET 493 is measuring the voltage on Vfetsrc 417. Then, a digital-to-analog converter (DAC) converts this digital current value to an analog current value, and compares it with the analog current drop predicted value output from the analog ramp generator (491 or 492). If the two values are the same, the system switches FET 493 (which actually turns on / off the larger external transistor 461).

  Referring to FIG. 6C, the entire data cycle is shown, followed by a rising current ramp followed by a falling current ramp. In time interval 620, one of the analog lamp circuits (such as lamp A 491) is charged to assist in the calculation of the transition time. At time 621, the FET 461 is turned on (if not already turned on) to start the current increase and activate the circuit 491 of the charged analog lamp A (how much the current drops when the FET is switched off) To display the At time interval 622, the driver line current (calculated from the Vfetsrc 417 voltage value) is compared with the output of the analog lamp A circuit 491 and how much the current drops in the other half of the bit period when the FET 493 is turned off Predict. If the two values are substantially equal (within each other's threshold), current modulation block 490 switches FET 461 so that the current level can drop back to rated current value 610 at time interval 624.

  The time to determine that the system should change the state of FET 461, and the time that the effect of this change is detectable by FET 461, will not be equal due to the propagation delay. In particular, there is a delay in the comparison circuit, a delay when the internal driver circuit FET 493 is activated, and a delay when the external FET 461 is activated. In order to compensate for these propagation delays, the ramp circuit (491 or 492) may be required to use a tuning factor to change the state of the FET shortly before the two values become equal. This can be implemented in one embodiment by setting a constant offset at the input of the comparator circuit so that the comparator can be triggered early. Thus, the system changes the state of the FET when the two values (current value and predicted current drop value) fall within each other's predetermined threshold. In this way, the FET switches a little earlier than the exact time when the two values (line current and expected current drop) actually cross. A closed loop system may be used to calculate an accurate value to adjust for a constant offset to the comparator.

  At time interval 624, the driver line current drops again towards the rated current value 610. If the system accurately predicts the behavior of the current, the current level passes through the rated current value 610 at the midpoint 625 of the data bit period. During the falling time interval 624, the current modulation block 490 charges the other analog ramp circuit (ramp A 491 used in the first half of the data cycle, eg lamp B 492), and the amount of current rise when FET 493 is turned on again Predict. In embodiments that predict driver line current instead of measuring with a falling current ramp, the system also charges a line current estimation circuit 495 that predicts the current level when falling.

  At the midpoint of the data cycle 625, the charged analog lamp B circuit 492 and the charged line current estimation circuit 495 are activated. Furthermore, did the system accurately calculate the transition time (in the first half of the bit period) needed to return the current level to the rated current level 610 by sampling the current level at the midpoint 625 of the data period? You can see If there is no current sample available, then the final output of the ramp circuit at the midpoint 625 of the data bit period may be examined. If the current level (real or expected) at waypoint 625 is lower than rated current level 610, adjust the parameters using the analog lamp A circuit to soften the drop (reduce the rate of prediction of current drop) Can. Conversely, if the (real or predicted) current level at waypoint 625 is higher than the rated current level 610, adjust the parameters using the analog lamp A circuit to accelerate the drop (the rate of prediction of the current drop) Raise).

  In the second half of the data period, when the current level of the driver line estimated (as estimated using the line current estimation circuit 495) is compared with the output of the analog lamp B circuit 492 and the FET 493 is turned on instantaneously. Predict how much the current will rise in the other half of the bit period. If this comparison is within a certain threshold at point 627, FET 493 is turned off and the current level begins to rise. Again, a factor that adjusts the propagation delay (such as a threshold) can be used to request that FET 493 be turned on shortly before the two values become equal. After turning FET 493 back on, the current level rises during time interval 628 until the end of the data period reaches point 629. In time interval 628, current modulation circuit 490 charges another analog ramp circuit (lamp A 491 in this example) to be used in the next data cycle.

  At the end of the data cycle 629, the current modulation circuit 490 samples the current level to determine if the system has accurately estimated the transition time for the current level to return to the rated current level 610. If the current level at the final point 629 is lower than the rated current level 610, adjust the parameters using the analog lamp B circuit to accelerate the drop. Conversely, if the current level at the final point 629 is higher than the rated current level 610, adjust the parameters using the analog lamp B circuit to soften the drop.

  In the particular embodiment shown in FIG. 4A, current modulation circuit 490 uses analog ramp circuits (491 and 492) as analog computers and line current when FET 461 switches to estimate when to switch FET 461. We made a model that predicted the behavior of Analog lamp circuits (491 and 492) are calibrated by a digital system that checks the results after use each time to determine if the parameters for the analog lamp circuit need to be adjusted, thereby forming a closed loop system Be done.

  However, in various other alternative embodiments, a digital system can be used to predict when to switch FET 461 back to the rated current level at the end of a half bit period. In such systems, an analog to digital converter is used to sample various relevant values, and then a digital computer system such as a digital signal processor (DSP) is used to determine when to switch FETs. In such an embodiment, a digital computer system may be used to model the future behavior of the driver line current when the FET 461 is switched. Similarly, digital computer systems can also estimate line current when the current can not be easily sampled. However, the implementation of such digital systems requires high-speed analog-to-digital converters, more die area to implement digital processes, and consumes more power than analog systems as previously disclosed .

  In a very different embodiment of current modulation circuit 490, a current mirror can be used to drive the correct current in the driver line. However, such implementations have been found to combine transistors 461 as disclosed and to be less efficient than controlling the inductor 462, which controls the current in the driver line.

  Referring again to FIG. 4A, the LED line driver IC 420 comprises a power system circuit block 480. The power supply system circuit block 480 receives a power supply from the external power supply 410, uses this power to generate a necessary power signal, and operates the LED line driver IC 420. In one embodiment, power supply system circuit block 480 receives power from a relatively high voltage source of approximately 10 volts, which is used to drive FET 493 in current modulation block 490. The other required voltage levels are generated from the input voltage source and form a voltage source for the other circuits in the LED line driver IC 420. A bandgap reference voltage circuit is used by the power supply system circuit block 480 to create various voltage levels. In one embodiment, a high voltage input is used to produce a 5 volt power supply adjusted to drive analog circuitry and a 3 volt power supply to power digital circuitry within the LED line driver IC 420.

  In one embodiment, the 3-volt power supply and / or 5-volt power supply derived from the power supply system circuit block 480 is capable of producing extra current so that this 3-volt power supply and / or 5-volt power supply is , Can be used to power small external devices. For example, a 3 volt power supply and / or a 5 volt power supply derived from power supply system circuit block 480 can be used to power a small master LED controller system such as a microcontroller device connected to LED line driver circuit 425 .

  The LED line driver IC 420 can implement a Ground Fault Interrupter (GFCI) system for safety and regulatory compliance. In particular, the power supply system 480 of the LED line driver IC 420 can receive information from the external power supply 410 as to how much current is sent downstream of the driver line starting from the point of the VS upply 411. Alternatively, the LED line driver IC 420 can detect this current in several known ways according to the prior art, such as using a current sensor. The amount of source current can then be compared to the amount of current at the end of the driver line (output current). For example, the amount of current reaching the end of the driver line can be detected by measuring the voltage at the point Vfetsrc 417. (Note that the current flowing through this location also needs to be considered since some currents also flow towards the location of VClamp 412.) If the source current is significantly different from the output current, some current will be the driver There may be a leak to ground at a position other than the ground 465 of the power supply 410 which is the end of the line. If there is a leaking current at locations other than the points Vfetsrc 417 and V Clamp 412, several potentially dangerous failures may occur. As a response to this, the LED line driver IC 420 can turn off the system and stop the current drive downstream of the driver line. In some embodiments, the LED line driver IC 420 can stop operation for a while and then resume operation to determine if it is misdiagnosing a problem or just a transient problem. When a transient or critical problem is detected, the LED line driver IC 420 sends error and diagnostic information to the controller system using data output 431.

Second Embodiment of LED Line Driver Circuit Using Dip Mode As mentioned earlier, there are various different methods that can be used to modulate data on the driver line. FIG. 4B shows a second embodiment for the LED line driver circuit 425, which uses different types of current modulation block 490 along with various external circuits for modulating data with current. In particular, current modulation block 490 and its external circuitry implement a "dip mode" modulation system in which data dips are used to modulate data at rated current as shown in the timing diagram of FIG. 3C. Do.

  Referring to FIG. 4B, the LED line driver circuit 425 uses two external field effect transistors (FETs) (481 and 482) and a double winding inductor 483. The current modulation block 490 uses the first FET 481 to maintain the rated current of the driver line loop configured with a standard forward converter using the primary winding of the inductor 483. The current modulation block 490 uses a second FET 482 to drive the secondary winding of the inductor 483 to allow the second FET 482 to quickly drop the current in the loop to zero. This current drop is referred to as a "current dip" and the current modulation block 490 modulates data on the line using such current dips. The current modulation block 490 includes a loop current sensing circuit 496 that monitors the current in the driver line by measuring the voltage just before the resistor 464 going to ground 465.

  In one embodiment, current modulation block 490 modulates data on the driver line by modulating the timing of the current drop. In this way, the LED unit connected to the driver line detects the current drop and demodulates the data by calculating the relative timing of the various current drops. For example, in the timing diagram of FIG. 3C, the line driver circuit generates a current dip at 1⁄4 of the data bit time interval to modulate a “0” data bit and 3⁄4 of the data bit time interval. At the instant, a current dip is generated to modulate the "1" data bit.

  Rather than using a single double-winding inductor, it is better to implement two different inductors in the system. The first inductor can be used to maintain the driver line current. A second inductor can be used to generate a current drop using the second current drop driver circuit FET 482. In such an embodiment, a resistor in the source terminal of the FET towards ground is used to turn off FET 481, which acts as a sustaining current when the loop current reaches an appropriate value, and the second FET 482 makes a bit The loop current can be sensed by modulating and turning on the FET 481 again when the current falls below an appropriate value.

Adjustable Current Based on Energy Requirements In the system of the present disclosure, the current used to drive the circuit on the unit connected to the driver line is decoupled from the current driven by the driver line. In particular, each unit connected to the driver line generates its own local energy storage in the capacitor and operates using this local energy storage. Therefore, it is possible to generate in each unit a local current (such as a current used to drive an LED) much larger than the current of the driver line. However, the sum of the power averages used by all individual nodes on the driver line does not exceed the sum of the averages supplied by the line driver circuit to the driver line. As such, the peak power used by the individual units may temporarily exceed the power available on the driver line due to the use of local capacitors acting as energy storage.

If the accumulated power used by all the individual units connected to the driver line is significantly lower than the amount of power available at the driver line current, some of the power obtained from the driver line current will be wasted. In particular, the various resistive elements on the driver line, such as shunts to individual units and the driver line wiring itself, waste power proportional to I ² R. Here, I is the current of the driver line, and R is the cumulative resistance value of the resistive element on the driver line.

  To prevent this unnecessary energy loss, when it is known that the individual nodes on the driver line need less power, the line driver can instead reduce the amount of current on the driver line. For example, if the individual units on the driver line are LED units used to make digital LED signs in the field, the power required by these individual LED units at night is significantly less. At night, the human pupil spreads more light into the eye, so less energy is needed to make the sign visible. Thus, when operating the digital LED sign at night, much less power is required to activate the sign. This improves the visibility of the sign and saves energy.

The advantage of this fact is that the LED line driver can supply enough power to operate all the individual LED units even if the amount of rated current is reduced to a low level. With moderate current, individual LED units on the line still drive their local LEDs, but use shorter duty cycles to reduce the brightness of the LEDs. The reduced duty cycle requires less power, so less power is drawn from the individual LED units from the driver line. Therefore, the line driver can lower the rated current level on the driver line. Since the loss of power caused by the accompanying resistance is proportional to the square of the current (power loss of I ² R), reducing the rated current can significantly reduce the amount of energy.

  It should be noted that since the master control system supplies data to control the brightness of the LEDs, the master control system recognizes when it is appropriate to reduce the current level output by the line driver . As such, the master control system determines when the various line drivers should lower (and raise) the rated current level.

  FIG. 6D shows a timing diagram of the current signal produced by the line driver, showing the transition from the daytime operating mode to the nighttime operating mode to reduce the required energy. The line driver is slowly reducing the rated current level 610. This data is continuously modulated around the rated current level. Each LED unit can adjust itself to a gradually changing rated current level 610, as long as each individual LED unit on the line can track where the rated current level is.

AC Current Line Driver Although the main embodiments disclosed herein mainly describe embodiments powered by direct current (DC), it is also possible to create embodiments of alternating current (AC) is there. The direct current embodiment has the advantage that the integrated circuit is inherently operated using direct current. However, the unit connected to the AC line may be equipped with additional circuitry to create a local DC current feeding the integrated circuit on the unit.

  There are several different ways to create a system that operates with alternating current. The first way is to power the AC line driver unit to two different strings. Using a diode in the line driver, one string is operated with positive pulses and the other string is operated with negative pulses.

  In another embodiment, diodes are used in individual line units so that each line unit operates with a half wave rectifier. Using local diodes, the chips of the individual line units can be configured to target current in one direction only. Half of the individual units can be configured to target positive pulse currents, and the other half of the individual units can be configured to target negative pulse currents. In a further costly embodiment, a full wave rectification system may be provided on each line unit connected to the driver line to maximize current utilization.

  A variety of different systems can be used to modulate the data on the driver line with an AC current. The modulation system can use phase, frequency, duty cycle, or run length coding. By driving the current loop with alternating current AC several advantages are achieved. For example, since alternating current enables transformer coupling, a loop voltage higher than that produced by readily available semiconductors is obtained at each unit on the driver line.

Individually Controlled LED Units As described in the previous section and shown in FIG. 2A, the LED line driver circuit 220 connects to one or more individually controllable LED units (250-1 to 250-N) The current source modulated on the driver line 221 is driven. The only means of electrical contact to the LED unit 250 is through a single driver line 221. Therefore, the LED unit 250 must receive from this single driver line 221 all the resources that the LED unit 250 needs for operation. In order to realize this, the driver line 221 performs a plurality of functions for the LED unit 250. Each LED unit (250-1 to 250-N) draws necessary operating power from the current on the driver line 221. Each LED unit also demodulates the LED control data that the LED line driver circuit 220 has modulated with this current. In one embodiment, each LED unit 250 also uses the level of rated current driven by a single driver line 221 as a reference current value. In this section, the inside of the LED unit 250 will be described in more detail.

  FIG. 7 is a block diagram illustrating one embodiment of an individually controllable LED unit 750. In the particular embodiment shown in FIG. 7, the LED unit 750 is comprised of an LED controller 760, four light emitting diodes (LEDs) 781 and a power supply capacitor 729. The power supply capacitor 729 acquires, stores and supplies operating power to the LED unit 750. LED controller 760 may be an integrated circuit that provides most of the functionality of LED unit 750.

  The LED unit 750 is connected to the string driven by the upstream LED line driver circuit (such as the LED line driver circuit 425 shown in FIG. 4A) via the input 721 to the driver line. In particular, input 721 to the driver line provides a modulated current source to power supply system 720 on LED controller 760. The operation of the power supply system 720 will be described with reference to FIG.

  When a line of LED units is operating in a normal operating mode, there is very little LED unit trying to draw charge power from the driver line at the same time, so the accumulated drop for all LED units connected to this line Will not be so big. For example, if there are 48 LED units in a driver line, and each LED unit takes 4 volts while charging, but it is going to charge only 1⁄4 of the LED units at a specific time, the total power is 48 units It is only necessary to supply 4 volts / unit × 1/4 or 48 volts. However, when the line driver first starts operation, the line driver needs to operate all the LED units on the driver line. Initially, all LED units in the same driver line attempt to charge simultaneously to begin operation. If there is only 48 volts available from the power supply at start up, each LED unit will be charging up to about 1 volt (48 volts / 48 LED units) and will be inoperable. Therefore, once the entire system has been initialized, a certain amount of power supply voltage may be sufficient to operate the line of the LED unit, but this same power supply voltage activates all of the LED units connected to the driver line. Can cause problems.

  To solve this potential problem, each power supply system mounted on the chip of the LED controller is equipped with an analog bootstrap power supply circuit, which allows the LED controller to reach its specified extreme low voltage limit. The chip is powered and the power supply system at start up switches off when the voltage increases. As such, when the LED controller 760 is powered down, the analog bootstrap power system initially operates as described in step 805. The analog bootstrap power supply system checks at step 807 whether the current has flowed incrementally while passing the specified low voltage threshold (about 1.3 volts in one embodiment). When the analog bootstrap power system reaches a specified voltage threshold, the analog bootstrap power system is turned off and the main power system 720 is activated. The main power system 720 begins to charge the driver line to charge the local power capacitor 729 in step 810.

  Charging the local power supply capacitor 729 in this manner increases the voltage drop across the LED controller 760 from the driver line input 721 to the driver line output 722. As the voltage drop across this LED controller 760 increases, the voltage to the other LED controllers on the same line will decrease, so the other LED controllers will not reach the threshold to start charging. When the LED controller completes charging, the LED controller's power system 720 shunts current directly from the driver line input 721 to the driver line output 722 and operates with local power from the local power capacitor 729 so that the LED controller 760 Voltage drop is significantly reduced. This allows other LED controllers in the same line to receive an increased voltage so that any of the other LED controllers will exceed the threshold voltage and start charging.

  In order for the start up system to function properly, the average voltage of the LED controller chip needs to be lowered once the LED controller chip has been charged. Therefore, the operating current of the LED controller chip is divided by the threshold to switch off and multiplied by the current, which must be smaller than the current that triggers the loop. In order to meet this requirement, the line driver on the string determines that all the LED units on the loop are fully activated, and sends a small amount of current until it can send a command to allow normal operation. Design the LED controller chip. In one embodiment, the LED controller chip has an activation threshold voltage of 1.3 volts for 15 milliamperes and an initial operating current of 2.4 milliamperes for 3.5 volts. Since 2.4 × (3.5 / 1.3) is less than 15 milliamperes, the conditions at startup are satisfied. Therefore, to ensure that all the LED units connected to the line start up properly, the line driver should only be able to generate a voltage of a number that is 1.3 volts multiplied by the number of LED controller chips on the line. Good.

  Referring again to FIG. 8, after the LED controller exceeds the threshold voltage, the power supply system 720 charges the external power supply capacitor 729 in step 810, and the power supply system 720 converts the external power supply capacitor 729 into the LED controller 760 in step 815 (power system Continue to charge until it is determined that there is sufficient power to operate the logic circuits in (including 720). The external power supply capacitor 729 acts as a substantially small battery to power the LED controller 760 in the LED unit 750. Power supply system 720 periodically shuts off shunting, draws current from driver line 721, and recharges power supply capacitor 729 according to the power requirements.

  Once enough power is stored in the external capacitor 729 to start up, the circuitry within the LED controller 760 enters start-up mode at step 820 and only a subset of the circuitry is active. For example, the LED driver circuit 780 is not yet active. During start-up mode, the control circuit in the LED controller 760 performs a series of start-up actions in which the LED controller 760 configures itself based on the state of the non-volatile fuse in the fuse block 741. Then, in step 825, the LED controller 760 waits for a command to start normal operation. In this step 825, the LED controller wakes up every LED, takes in a small amount of power to charge the other LED units in the same driver line, and enters the wake-up mode without producing a high accumulated voltage on the driver line. Basically, during this wait state 825, the LED controller only tracks the driver line data stream and follows the commands, and may occasionally capture power for continued operation.

  After the line driver determines that the entire loop has been activated, the line driver sends various commands to configure the LED unit to the LED unit so that the LED unit can start normal operation. The commands sent to configure the LED unit include current fine-tuning, calibration, brightness scaling, addressing, and commands for driver circuit routing as described in later sections. Once the appropriate command is received, the LED controller 760 enters a normal operating mode at step 840.

  During normal operation 840, the power supply system 720 monitors the charge state of the power supply capacitor and switches from line shunting to capacitor charging as needed, with sufficient charge on the external capacitor 729 to operate the LED controller 760. Make sure you can use it. In particular, when power is required, the shunt is turned off and charge is stored on the external capacitor 729. When the capacitor seems full, the power supply system 720 stops charging and shunts the current in the line, causing only a small voltage drop, and the current flowing in the driver line input 721 causes the power supply system 720 to It flows through to the output 722 of the driver line. The current coming out of the driver line output 722 then drives the granular LED unit and finally rounds around the LED line driver circuit and terminates this circuit.

  In addition to holding the charge required for operation in the capacitor, the power supply system 720 can also be used to carefully monitor the power required by the LED controller 760 in step 845, so the amount of charge stored in the capacitor can be Can be adjusted. For example, if the LED controller 760 initially turns on the blue LED, then the system will proceed to step 850 to indicate the additional power needed to drive the blue LED, as the power needed for the LED controller 760 will increase. Thereafter, when the LED controller 760 turns off the blue LED and turns on red which consumes less power, the LED controller 760 proceeds to step 860 and indicates that less power is required to drive the LED. can do. In this manner, the LED controller 760 uses power in a very efficient manner to maintain only the minimum voltage necessary for the operation of the LED unit 750 in the external capacitor 729.

  If there are multiple LED units 750 in a single driver line, the accumulated voltage of the plurality of LED units 750 connected in series may be high as each LED unit 750 tries to charge the local capacitor. In the worst case, the accumulated voltage drop on the line causes the voltage drop across each LED unit when charging to the LED units on the line, as each LED unit 750 of the driver line tries to simultaneously charge. It will be multiplied by the number. In driver lines with a large number of LED units, this cumulative voltage drop can be a problem due to regulatory and power supply limitations.

  To prevent the worst case, the driver line current can be increased and multiple LED units 750 on the same driver line can be commanded to flow charge in a coordinated manner. For example, only a limited number of LED units 750 may be able to shut off the shunt to simultaneously charge the local power supply capacitor. Increasing the amount of current on the line allows each LED unit 750 on the line to charge the power supply capacitor at a faster rate. By increasing the current in the line and simultaneously limiting the number of units that can carry the current, the overall voltage of the line can be maintained within a defined range.

  One way to adjust the shunts of the various LED units 750 is on a bit-by-bit basis. Each data bit in a data frame can be assigned a number from zero to N-1 where N is the number of bits in the data frame. Thereafter, each LED unit 750 can only be instructed to stop the shunt for every X bit, where X is the number selected by the LED line driver circuit. For example, if a number of 4 is selected for X, the first group of LED units 750 will only stop shunting if the number of bits modulo 4 becomes 0 (bits 0, 4, 8 etc). The second group of LED units 750 only stops shunting if the number of bits is 1 modulo 4 (bits 1, 5, 9 etc). The third group of LED units 750 only stops shunting if the number of bits is 2 modulo 4 (bits 2, 6, 10, etc.). The fourth group of LED units 750 only stops shunting if the number of bits is 3 modulo 4 (bits 3, 7, 11 etc). By adjusting the shunt stop bit by bit (as opposed to the long interval), each LED unit 750 has to wait for a long time until the LED unit has time to get more charge from the driver line There is no

  The power supply system 720 may include an analog circuit section capable of generating a bandgap reference voltage and setting the adjusted voltage to the proper amount to turn on all the local LEDs as described above. The power supply system 720 monitors for false LED outputs (short or open circuit) and attempts to regulate the voltage to the lowest voltage level required to operate with the powered-on LEDs. All changes involved in shunting the current in the line and in the act of stopping the shunt are performed in coordination with the data on the line, so all LED chips transition simultaneously. This adjustment is done to minimize potential data errors.

  The analog section of the power supply system 720 includes a band gap reference that is used as a reference voltage for three of the four main power related functions of the power supply system. First, a band gap reference is used to generate a voltage source (about 2.8 to 3.2 volts) for core digital circuits. Second, the bandgap reference is the reference for the digitally controlled voltage divider circuit, which samples the power supply of the LED driver circuit and compares it to the bandgap reference. Finally, the bandgap reference voltage can be used in an over voltage / over current detector. The over voltage detector uses a carefully matched poly resistor to detect excess voltage at the LED driver circuit power source and to measure line current. The over voltage detector is activated whenever the capacitor 729 is charging. The chip transitions immediately to protect the chip if there is a capacitor such that an over voltage condition is detected due to insufficient dimensions.

  The fourth function of the power supply system 720 is the line shunting operation performed by the line shunt and line current rectifier sections, thereby shunting the line current to the output 722 of the driver line, or the power supply capacitor 729. Digitally set to charge. In normal operation, the power supply system 720 periodically shuts off the line current shunting, causing the current to tend to recharge the power supply capacitor 729. The stopping of this shunt may be performed in a coordinated manner with other LED units connected to the same driver line so that multiple LED units do not try to simultaneously draw current from the driver line.

  It is a very important function for the LED controller 760 that the power supply system 720 shuts down the driver line 721 to charge the power supply capacitor 729. This is because charging of the power supply capacitor is necessary to obtain the power necessary for the operation of the LED controller 760. Similarly, stopping the shunting of the driver line 721 after charging the power supply capacitor is also very important. Because, if the power supply system 720 can not quickly shunt current to the output driver line 722 when the power supply capacitor 729 is fully charged, then the LED controller 760 will be correctly by the over voltage that destroys the integrated circuit of the LED controller 760 It may not work. Therefore, shunting and shunting of the input driver line 721 is a task that requires careful control by the power supply system 720.

  Fortunately, this situation, which requires careful balancing, is very common, as a malfunction of an LED controller on a driver line connected in series with another LED controller does not significantly affect other LED controllers on the same driver line. Provides a convenient way. In particular, the circuit in the malfunctioning LED controller 760 becomes inoperable and the power supply system 720 stops charging the external power supply capacitor 729, but instead becomes permanently shunted. 720 acts as a short circuit through which the line current flows (generally a slight voltage drop with respect to the shunt). As such, the other individual LED controllers in the same driver line continue to receive current from the line driver circuit.

  On the other hand, the circuit in the malfunctioning LED controller 760 has a different form from the above, that is, the power supply system 720 stagnates in the state of shunt stop and continues to charge the external power supply capacitor continuously. In the event of a shunt condition towards the capacitor), the power supply system 720 acts as an open circuit and affects all LED controllers in the same driver line. However, the total current flowing through the LED controller 760 causes the voltage across the power supply system 720 of the LED controller 760 to run until the voltage across the power supply system 720 eventually causes the integrated circuit (a circuit similar to a zener diode or perhaps just a short circuit) to break. To increase. Once such a failure occurs, the driver line current flows again from the driver line input 721 through the malfunctioning LED controller 760 and out to the driver line output 722. The current passing through the malfunctioning LED controller 760 allows other LED controllers in the same driver line (721 and 722) to continue operating normally. To further add protection, a breakdown voltage device (such as a Zener diode or equivalent) that requires a higher voltage than the LED controller 760 normally can be placed in parallel with the LED controller 760. In this manner, even if the LED controller 760 becomes open circuit malfunctioning, the voltage increases until it reaches the higher voltage required to operate the breakdown device, thereby causing an electrical path around the malfunctioning LED controller 760 Can.

  To prevent damage to the LED controller 760, the temperature system may monitor the temperature of the integrated circuit of the LED controller 760. If the temperature exceeds the danger threshold, power system 720 enters a shutdown state to prevent damage to LED controller 760. In one embodiment, the power supply system 720 may be in a state where the power supply system 720 permanently enters a shunt state and the current flowing to the driver line input 721 flows directly to the driver line output 722. In this way, other LED units in the same driver line can continue to operate normally. If a particular LED controller 760 is repeatedly in such a shutdown state, this LED controller 760 may need to be replaced. In other embodiments, the LED controller 760 is in a degraded state in which only some electrons continue to operate, and in this state it is rare to stop the shunt to reserve extra power. . In this manner, the LED controller 760 periodically performs a temperature check and reactivates itself if the temperature drops.

  Two functions independent of the power that the power supply system 720 can provide are generation of a reference current value and generation of a current copy for data acquisition. In order to drive the LED with the most stable light output characteristics, a certain amount of current must flow through the LED. When controlling the brightness of the LED by changing the amount of current flowing through the LED, the spectrum of the color emitted by the LED changes depending on the amount of current flowing through the LED. Because it is an ideal goal that the color spectrum be constant, the technique of modulating the amount of current does not provide the desired performance. Moreover, it is difficult to accurately control the LED brightness using current variations, as the LED brightness is not linearly related to the current intensity.

  Instead of using current intensity to control the brightness of the individual LEDs, the brightness of the LEDs is controlled by controlling the duty cycle of the constant current quantity in a typical manner to regularly turn on / off. Known systems implementing this technique of controlling power are commonly known as "pulse width modulation". This is because the luminance of the LED is proportional to the pulse width of the constant current intensity in a predetermined time interval. In one embodiment, the system of the present disclosure uses different techniques to modulate both the number of constant current pulses in a predetermined time interval and the width of these constant current pulses to obtain the desired brightness. This alternative system is termed "Reduced Flicker Modulation" (RFM) and will be described in detail in a later section, including the LED driver circuit 780.

  In order to optimize the output performance of the LED, the amount of current used to drive the LED 781 with each constant current pulse needs to be as stable as possible. Therefore, a stable reference current value is required. Various different methods can be used to generate the reference current value. Herein, two different systems are provided that cause power supply system 720 to generate a reference current value.

  The first method of generating a stable reference current value in the power supply system 720 uses a reference voltage value. In particular, after a stable reference voltage value is generated using a band gap circuit, a stable reference current value can be generated by supplying the stable reference voltage to the resistor. Next, when the reference current value is supplied to the LED driver circuit 780, the driver circuit uses the reference current to generate a constant current, which is used to drive the LED 781 in a stable manner.

  In an alternative embodiment, power supply system 720 may generate the reference current by sampling the current of the driver line. In particular, the power supply system 720 samples the driver line current to calculate an average current value (rated line current as shown in FIG. 3A) of the driver line flowing from the driver line 721. Next, the average value of the line current is used as a reference current value for the LED driver circuit 780. The average driver line current is updated / calculated only while the power supply system 720 shunts the driver line.

  Another power independent function performed by the power supply system 720 is the generation of line current copies for data acquisition. In order to be able to recover the data modulated by the line current of the driver line 721, the power supply system 720 data extracts a reduced copy of either the sensing result of the current shunt or the sensing result (or diode) of the current shunt stop. Supply to block 730. The sense result of the current shunt is supplied when the power supply system 720 is in shunt mode, and the sense result (or the diode) of the current shunt stop is that the power supply system 720 charges the external power supply capacitor 729. When supplied.

  The clocking / data extraction block 730 receives a copy of the driver line current from the power supply system 720, and the data modulated by the LED line driver circuit 425 of FIG. 4A with the driver line current (LED controller configuration command and current LED control data Etc.) plays a role. In order to demodulate the data coming from the driver line current, the data extraction block 730 must first generate its own internal clock signal and then use its digital phase lock loop circuit (DPLL) to generate its own internal clock signal. And the data rate of the data modulated by the driver line current, and finally, the internal clock signal of its own and the current ramp modulated by the driver line current are appropriately aligned to obtain data.

  To generate the internal clock signal, the digital subsection of the clocking / data extraction block 730 implements a high speed ring oscillator and includes its associated digital logic operating at a high speed ring oscillator rate. This high speed oscillator rate digital logic sub-section provides several functions that can only be provided with a higher clock rate. The first function is that the high speed clock section provides digital support to ensure that the centering logic located in the middle of the current ramp is exactly in the middle of the line current data stream. The second function is to divide the high speed free running ring oscillator clock by the counter count N. When divided by the counter count N, only the core clock boundary is updated to help prevent glitches. The value divided by the counter N from the high speed clock section helps to implement a DPLL circuit that tracks the data modulated by the driver line 721. The data rate of the data stream on the driver line obtained using the digital phase lock loop circuit is used to generate the core clock signal used to drive most LED controllers 760. In one embodiment, the core clock rate operates at eight times (8 ×) the data rate of the driver line.

  In one embodiment, the clock logic circuit initially sets a fixed value to divide by the counter count N and counts the shunt by the level crossing method with the A / D converter to obtain an initial estimate of the data clock frequency value. Generate The clock logic circuit then loads this initially estimated frequency value into the digital phase lock loop circuit which attempts to track the driver line data rate. If the clock logic circuit can not obtain tracking confirmation from the digital phase lock loop circuit within a specific time, the clock logic circuit enters a resynchronization mode which restarts the clock frequency measurement process.

  The main part of the clocking / data extraction block 730 operates at the core clock rate generated using digital phase lock loop circuitry. Most of the main part of the clocking / data extraction block 730 comprises the circuitry used to implement this digital phase lock loop circuit (with assistance from the high speed clock section).

  In addition to the digital phase lock loop circuit, the main part of the clocking / data extraction block 730 comprises data extraction logic which extracts the actual data from the driver line signal. Data extraction logic serves to distinguish transitions between data centers and data edges. The reason is that digital phase lock loop circuits may track transitions of data bit edges rather than the centers of data bits. In particular, referring to FIG. 9A, the ramp mode signal of the appropriate data bit time 921 is almost identical to the signal of the wrong data bit time 922 where the DPLL tracks transitions of the data bit edge instead of the center of the data bit. appear. To avoid this problem, the data extraction logic looks for signals before the center of the data bit that differ from signals after the center. This is because the correct data bits always appear this way. In particular, the wrong data bit time 925 indicates how the forward 931 and backward 932 signals of the wrong data center (the actual data bit edge) look the same. This informs the data extraction logic that the digital phase lock loop has tracked the transitions of the data bit edges instead of the centers of the data bits. If the forward and backward values become too often the same, the data extraction logic moves the array of half bit periods to exactly align with the data bit centers.

  FIG. 9B illustrates the same problem found in dip mode modulation signals. Referring to FIG. 9B, the dip mode signal at the appropriate data bit time 971 looks almost identical to the dip mode signal at the wrong data bit time 972. The centering circuit ensures that the first half and the second half of the data bit period are different to prevent improper tracking of the wrong data bit period. Thus, if the bit time interval does not include a dip as shown in time interval 975, or if the bit time interval includes two dips as shown in time interval 976, then the centering logic is incorrect. It is determined that the time interval has been tracked.

  Referring again to FIG. 7, after correctly tracking the data rate and correctly aligning with the centers of the data bits, the clocking / data extraction block 730 transfers the demodulated data stream to the data processing core 740. Data processing core 740 is a block of digital logic that processes received LED control data. In one embodiment, data processing core 740 identifies individual data frames, parses data frames to obtain LED controller configuration commands, LED control commands and LED parameter data, and then retrieves them from LED control data. It plays the role of executing the command.

  In one embodiment, the first action performed by data processing core 740 on received LED control data is descrambling of the data stream. The data stream decoded at driver line 721 may be scrambled for a variety of different reasons.

  One reason for scrambling is to prevent the LED unit 750 from tracking the wrong data framing signal. If the value of LED control data redundantly transmitted to a specific LED unit 750 happens to be the same as the value of the sync header to be framed, then the LED controller will track the wrong location of the data stream and validate the data There is a possibility that I do not pay attention to the frame. Scrambling the data prevents this situation. Even if the payload of the data is a fixed value, the scramble of the data causes the respective data frames to be different on the driver line. As such, scrambling the data greatly reduces the possibility of generating an erroneous framing pattern in the data stream. Another reason to scramble the data is to reduce the problem of electromagnetic interference by scrambling the data and dissipating the energy. To process the scrambled data stream, a descrambling unit 742 in the data processing core 740 processes the received data first by looking for a frame synchronization marker and then descrambles the data frame into the data frame. Get the actual data command of.

  In one particular embodiment, the LED control data frame consists of 40 bytes as shown in FIG. 2B. The following table shows the structure of the data frame shown by way of example in FIG. 2B.

  In the above table, the first byte is the frame header used to indicate the beginning of the data frame. The bytes of the frame header are not scrambled and the remaining 39 bytes are v. It can be scrambled using a 34 self-synchronous scrambler. The data frame detection logic of descrambling unit 742 retrieves input data for repeating frame headers within the data stream. The descrambling unit 742 tries to track such patterns. If a data frame is found after some time, descrambling unit 742 informs clocking / data extraction block 730 of the problem. The clocking / data extraction block 730 switches to the new frequency and again exercises the synchronization signal. This action resets the frame lock that could have been initiated and activates the claim detection logic of the descrambling unit 742 to retrieve the data frame again.

  When the frame detection logic of descrambling unit 742 detects a data frame pattern, descrambling unit 742 returns a valid frame signal to clocking / data extraction block 730 to indicate valid data. In one embodiment, descrambling unit 742 wakes up at least one frame before data parser block 743 gets valid data and descrambling unit 742 tracks the data stream being input, and the correct output. Make sure you have the data. This ensures that the descrambling unit 742 has synchronized with the incoming data stream. When the descrambling unit 742 correctly performs tracking of the input data and completes the descrambling process, the descrambling unit 742 sends the descrambled data frame to the data parser 743 to process the contents of the data frame. Forward.

  Data parser 743 parses the data frame. The data parser 743 identifies the command in the data frame (LED controller configuration command or LED control command) and decodes the payload of the data frame (LED controller configuration parameter or LED control data parameter). In one embodiment, data parser 743 optionally performs a cyclic redundancy code (CRC) check, and if the data is correct, data parser 743 transfers the decoded command and parameter data to execution logic in data processing core 740. Do.

  In one embodiment, data parser 743 has a plurality of different pixel addressing modes and uses this mode to determine whether a particular data frame received should be applied to this particular LED controller 760. In the address field of the data frame, a standard addressing mode sets the address of a particular LED unit. In one embodiment, this address specifies the starting address for the LED control data in the data field. The particular LED unit identified in the address field uses the first item of LED control data in the payload field until the width of the LED control data is reached. The next LED unit addressed subsequently uses the next item of LED control data in the payload field until the width of the LED control data is reached, and so on. In other embodiments, the address can specify a single LED unit or a specified number of consecutive LED units. It should be noted that in the present system, since the size of the data payload is 288 bits, multiple 2, 4, 6, 8 or 12 bit wide data values may be stored.

  In the group address mode, LED control data in the data payload is applied only to the LED units assigned to a particular group. Control data can simply be applied to all the LED units in the group. In one embodiment, the system uses a bitmap processing engine that examines the bitmaps in the payload to change which portion of the group's LED unit members changes, and these LED unit members It can be determined how it changes. As such, each LED can be individually addressed in a standard linear addressing system, and each LED can be individually addressed as part of an assigned group.

  Data errors detected by cyclic redundancy code (CRC) checking may be addressed in a variety of different ways. In one embodiment, if optional CRC protection is enabled, data processing core 740 will begin to ignore data if two errors are detected by the CRC while processing approximately 25 data frames. Furthermore, during this time, the output of the LED can be turned off, and the data processing core 740 does not respond to new commands. In one embodiment, data processing core 740 continues examining the received LED control data frames until it receives four data frames with the correct CRC value. At this point, data processing core 740 begins processing the new command.

  The LED controller 760 can implement a wide variety of commands. In one particular embodiment, three main types of commands are implemented. It is a command to update pixel data without global update, a command to update pixel data by global update, and a command to write to a control register in the LED controller 760. In the update of pixels not to be updated globally, a series of parameters for driving one or more LEDs are stored in a shadow register. However, these LED parameters are not used immediately. Thus, upon receiving a global update command (for this LED controller 760 or any other LED controller), the stored pixel data parameters are used to change the output of the LED driver circuit 780. In this way, changes in multiple pixels can be synchronized as required by video displays and other display systems in which different display frames operate sequentially.

  When data processing core 740 receives a command to write to a control register, data processing core 740 identifies the appropriate control register in control register / fuse block 741 and writes the associated data value to this control register. The contents of the control register are volatile control bits that control the operation of the circuitry within the LED controller 760. Several patterns can be used to write to the control register to activate various functions instead of just setting the specified control register value.

  In addition to volatile control registers, control register / fuse block 741 also includes a series of non-volatile fuses. The fuses can be blown to specify a set of permanent configuration information in the LED controller 760. For example, in one embodiment of the LED unit 750, eight fuses are used to implement an 8-bit address value. In this way, a string of uniquely addressable 256 LED units can be connected to a single LED line driver circuit. In order to program the fuse in the control register / fuse block 741, a specific write pattern is transmitted to the address of the designated control register. (Note that the address of such a specific control register may or may not be the actual control register.) If the correct write pattern is sent to the specified control register address Data processing core 740 blows the particular fuse identified in control register / fuse block 741.

  The fuses in control register / fuse block 741 can be used by both the manufacturer of LED controller 760 and the user of LED controller 760. Manufacturers can use the fuses in the control register / fuse block 741 to create a wide variety of different LED controllers with different performance characteristics and features from the same integrated circuit design. For example, the fuses in control register / fuse block 741 may include the number of LEDs controlled by LED controller 760, the accuracy of the LED control (in one embodiment, 4 bits, 6 bits, 8 bits or 12 bits), and various others. Can be used to specify possible or impossible features of the LED controller. In this manner, manufacturers of LED controllers 760 can segment the market for LED controllers 760 according to how many features are needed for a particular application.

  The fuses in the control register / fuse block 741 can also be used to store calibration information in the LED controller 760. Because of the imperfection and instability of semiconductor processing techniques, the behavior of the two integrated circuits will not be completely the same. In purely digital integrated circuits, minor differences do not affect operation, as digital circuits use discrete data values that are quantized. (If the manufacturing of a digital integrated circuit device is significantly incomplete, an inoperable device is created and discarded.) For the LED controller 760, if there are a large number of analog circuits, LED controllers with various manufacturing differences Significantly affect the behavior of the

  To address this difference in behavior, each individual LED controller 760 is examined and various calibration differences between different LED controllers are stored to calibrate the slight differences between the different LED controllers. It can be compensated by using a fuse. For example, the brightness of the LED is controlled by the amount of current flowing through the LED. However, since the manufacture of the integrated circuit is not perfect, the amount of current supplied by the LED driver circuits 780 of different LED controllers when instructed to supply the completely same luminance level is not the same. Therefore, the fuse in the control register / fuse block 741 can be used to store the current fine adjustment value designed to calibrate the current flowing to the LED by the LED driver circuit 780. Different LED channels in the LED controller 760 can individually receive unique current fine tuning values.

  It should be noted that the LEDs themselves are also adversely affected by imperfect manufacturing technology. Even though different LEDs receive exactly the same amount of current, they do not output completely the same brightness. As such, by connecting the LED 781 to the LED controller 760 prior to testing, slight manufacturing differences in both the LED controller 760 and the LED 781 can be used to program the LED controller 760 with calibration data that fine-tunes the current. It can be compensated. This ability to calibrate the current output supplied by the LED driver circuit 780 allows the LED controller 760 to use less expensive LEDs that have not passed the strict brightness calibration test. This is because the current calibration value compensates for the fluctuating LED in addition to the fluctuating LED driver circuit 780.

  The user of LED controller 760 can program a series of accessible fuses for the user for a variety of different applications of the particular features available to the user. For example, the LED controller 760 can be designed to operate either a common anode LED or a common cathode LED. The use of a CRC value to test a data frame due to an error can be specified by the fuse. Also, as previously described, the address fuses of a series of devices can also be programmed by the user.

  In very rare cases, if various elements in the integrated circuit are moved due to heat or other factors, the blown fuse may appear to be unblown. When this occurs, the programming of the fuses performed for the LED controller 760 may be disabled and the device may not operate properly. To avoid this phenomenon, in one embodiment, an extra fuse may be blown to perform an error correction coding (ECC) scheme. Thus, if the fuses are not blown, the ECC can be used to determine which fuses have not changed, and the operation of the LED controller 760 can be adjusted accordingly.

  As previously described, in some embodiments of the disclosed system, the LED unit responds to the status request, including the requested information, to allow the LED line driver to request status from the LED unit. Similarly, in some embodiments, the LED unit acknowledges after receiving a command. To respond (or acknowledge) the status request, data processing core 740 can request power supply system 720 to operate the shunt circuit in a manner that is detectable by the LED line driver circuit in a specified time frame. . To determine which LED units 750 are responding, the LED line driver circuit can only request one at a time, or provide each of the LED units 750 with a different time frame to respond within that time. Another signal transmission method using the shunt circuit is a method of causing the power supply system to transmit high frequency burst signals of the operation of stopping the shunt and the operation of shunting so that the LED line driver circuit can detect the frequency. .

  Referring back to FIG. 7, the final circuit block of the LED controller 760 is a circuit block including the LED driver circuit 780 that drives the LED 781. The LED controller 760 has an independent LED driver circuit for the output of each LED. In the embodiment of FIG. 7, there are four different LED driver circuits driving four different LEDs 781. However, other embodiments include LED driver circuits that handle a different number of LEDs 781. In the particular embodiment shown in FIG. 7, the LEDs 781 are wired in a cathode common configuration. In the common anode configuration, the LED symbol points in another direction.

  Independent LED driver circuits each include both digital and analog circuit portions. The digital circuitry portion is coupled to data processing core 740 and control register / fuse 741. The digital circuitry portion receives digital information specifying an intensity value indicating how much power the LED should receive. This intensity value is then adjusted according to various factors and used to drive a constant power output. The analog LED driver circuit receives a reference current from the power supply system 729 to generate a constant current, which is used to actually drive the associated device.

  The digital portion of the LED driver circuit precisely controls when to turn on / off the associated LED. The digital portion queries the control register / fuse 741 for configuration information to determine how to drive the LED correctly. The control resistor / fuse 741 may operate the LED or is it providing current (using the anode common mode or cathode common mode shown in FIG. 7), the LED Some of the current fine tuning values for can be specified, as well as several different parameters such as LED lighting delay factors. This LED configuration information is combined with the LED control information received in the LED control data frame that specifies the LED intensity value (zero if the LED is turned off) to determine how to drive the LED. A variety of different output modulation systems can be used to drive the LEDs.

  In addition to the current fine adjustment values fixed as specified by the fuses, the LED driver circuit 780 can also significantly adjust the current through the LEDs. For example, the output of the temperature detection circuit may be supplied to the LED driver circuit 780. Then, the LED driver circuit 780 can adjust the current supplied to the LED in response to room temperature. In this manner, the LED driver circuit 780 can adjust for temperature differences that may affect the performance of the LED and the LED driver circuit itself. It should be noted that the provision of the internal temperature sensors in the individual LED units allows the disclosed system to provide accurate pixel-by-pixel correction. Therefore, if some of the LED units are bright and the remaining LED units are not bright (such as by yellow), then each LED unit will make an appropriate correction based on its own local situation.

  In conventional pulse width modulation (PWM) embodiments, the output power is determined by the pulse width output during a predetermined time interval. For example, in FIG. 10A, the time of 16 time units is defined, and it is defined how the pulse width modulated power represents the 4-bit intensity value in this time interval. If the intensity is zero ("0000"), there is no pulse. If the intensity value is 1 ("0001"), a pulse having a width of one time slot is output. If the intensity value is 2 ("0010"), a pulse having a width of two time slots is output. Thus, it continues until it becomes intensity 15 ("1111") which the pulse of a time slot | zone for 15 times is output. The conventional pulse width modulation described with reference to FIG. 10A can be used with the LED driver circuit 780 in the LED controller of the present disclosure. However, a novel output method may be used, called "reduced flicker modulation" (RFM), which has several advantages.

  The flicker mitigation modulation system has at least three advantages over conventional pulse width modulation systems. In particular, the flicker mitigation modulation system (1) increases the frequency of switching (switch on and off) to a higher frequency range, thereby reducing perceived flicker and (2) using current over time intervals Because of the spreading, peak power requirements are reduced and (3) randomization is introduced to reduce the impact of different patterns depending on the data on the output in a significant manner. Spreading the use of current is important in systems with limited available power. For example, if the average available current (buffered with capacitors) is only 140 mA and there are two LEDs operating at 100 mA constant current, and each set operates at 60% duty cycle, then average There is enough current. However, when using a PWM system to drive LEDs, in PWM both LEDs operate for at least 10% of the time, and during this time a total of 200 milliamps flow through the two LEDs, so they can be used on average More current flows than current. In RFM systems, the utilization of current spreads evenly over the time interval so that on average there is no more current flowing through the two LEDs, thus avoiding overloading of the current supply from the line Be done.

  In order to increase the frequency of switching and spread the utilization of current more evenly, the flicker reduction modulation system provides constant current output for substantially the same number of time units for a predetermined time as a PWM system, but constant current The time units when turning on are equally distributed over the time interval. FIG. 10B shows how the flicker mitigation modulation outputs a constant current pulse for the same energy output as the PWM example shown in FIG. 10A.

  To generate the output pattern of FIG. 10B, the four patterns of FIG. 10C associated with each bit position can be OR'd if each bit position of the intensity value is on. For example, specifying intensity level 9 ("1001"), the pattern associated with the most significant bit position ("1000") and the pattern associated with the least significant bit position ("0001") are shown in FIG. 10C. You can take a logical OR together.

  Comparing the output of the pulse width modulation system of FIG. 10A with the output of the flicker reduction modulation system of FIG. 10B, there are more individual pulses generated per time interval when outputting power in the flicker reduction modulation system. In particular, while the pulse width modulation system of FIG. 10A only has one constant current pulse per time interval, the flicker reduction modulation system which spreads energy more equally to the time interval has a plurality of constant current pulses. There is. Each constant current pulse generated by either system does not completely form an ideal square pulse. FIG. 10D is an enlarged view of an ideal current pulse drawn with a broken line and a more realistic current pulse drawn with a thick solid line. As shown in FIG. 10D, the rise time and fall time of the constant current pulse are not zero as shown by the ideal square pulse. For an actual constant current pulse, the rise time is generally longer than the fall time. (This rise in rise time is referred to herein as "turn on delay.") Therefore, the amount of energy output during an actual constant current pulse is the ideal square constant current. Less than the amount of energy output during the pulse. Thus, this reduced energy output causes the output of the LED to be less than the desired output. Without compensating for this effect, the magnitude of the output of the intensity is not linear.

  In order to compensate for this effect, the digital circuit of the LED driver circuit 780 counts the number of generated constant current pulses, and after specifying a plurality of constant current pulses, adds an extra constant current pulse time unit. For example, if the actual constant current pulse of a single time unit outputs 5% less energy than the ideal square constant current of a single time unit, add an extra constant current time unit for every 20 pulses generated . 20 × 5% = 100%, that is, the pulse of the whole time unit is lost. In one embodiment, the adjustable LED lighting delay value stores a value representing the amount of energy lost in each pulse. The value of the LED lighting delay is added to the accumulator of the associated LED after each constant current pulse. When the accumulator becomes over capacity, extra time units are added at the time the LED is "on" to compensate for this lost energy.

  As described in the description of clocking / data extraction block 730, LED controller 760 uses a free running internal ring oscillator to generate a core clock signal that is used to drive the circuit. The high speed free running ring oscillator clock can have some clock jitter. To generate the core clock, the high speed free running ring oscillator clock is reduced by division by a counter count N controlled by a digital phase lock loop circuit. Using a digital phase lock loop circuit to generate the core data clock causes some quantization error in the core clock. As a result, the internal core clock has a slightly different length of time for each core clock period. Since the core clock is used to drive the output of the LED, the time units when the LED is on are thus slightly different in length of time.

  This slight inaccuracies that occur in clocking when the LED is on, when clocking overlaps with the pattern of the LED control data that is in the incorrect phase, the effect of the LED's output is significantly affected due to its synergy There is a risk of receiving. This slight imperfection of clocking in combination with the LED on / off data pattern does not have a negative effect on the LED output performance, so the LED on / off data pattern is LED Introduce output on / off randomization. In particular, the time for which the LEDs are lit can be moved randomly within the time interval. However, because the LEDs remain on for the same amount of time during the time interval, the net LED power output does not change. For example, FIG. 10E shows three possible different examples of the output pattern randomization of FIG. 10C. In one embodiment, this randomization is added to the LED on / off control pattern using a linear feedback shift register (LFSR) that generates a pseudorandom bit string. This randomization introduced in the LED on / off output pattern effectively eliminates the possibility of data dependency on the imperfect clocking and interacting patterns, and negatively affects the LED strength. Do.

  In addition to the two constant current methods of controlling LED intensity described above (pulse width modulation and flicker reduction modulation), other means may be used to drive the LED 781. For example, the brightness 781 of the LED can be controlled using a method of changing the current intensity supplied to the LED. However, this method should be avoided as it does not provide good and stable color output.

  The digital circuit portion uses the analog portion of the LED driver circuit 780 to drive the associated LED. The analog LED driver circuit uses the reference current received from the power supply system 720 to drive the LED with a constant current pulse. The analog LED driver circuit signals the power system 720 when the analog LED driver circuit does not have enough voltage from the power system 720 to operate properly. The analog LED driver circuit also signals the power supply system 720 when the LED appears to be malfunctioning. In particular, if the current through the LED is too high or zero, the LED driver circuit can determine that the LED looks like a short circuit or an open circuit respectively. When an LED malfunctions, the system stops activating that LED. The system periodically rechecks the LEDs to determine if a malfunction is incorrectly detected or the problem is transient. When the system determines that one LED has become inoperable, the LED controller deactivates many other LEDs associated with this malfunctioning LED. For example, if one LED with a set of red, green and blue LEDs used to generate a color pixel fails, then all three LEDs associated with that pixel may be turned off.

  In one embodiment, the LED driver circuit monitors the current supplied to the LED and makes calibration adjustments based on the current flowing through the LED. For example, if there are multiple LEDs of the same type, but some LEDs draw more current than other LEDs, then the LED driver circuitry may adjust the rate of the constant current pulses supplied to the LEDs accordingly it can. For example, the LED that receives less current may be set to a higher current pulse rate to equalize the power output of different LEDs.

  Techniques for adjusting the rate of the current pulse to the detected current difference can be used regardless of whether the current difference is intentional or intentional. The current difference can be intentionally generated to improve energy efficiency. In particular, by consuming the excess voltage as heat, the system supplies the same voltage to different LEDs instead of carefully adjusting the voltage supplied to each different LED to run the same amount of current in each LED be able to. However, due to manufacturing errors between different LEDs, different amounts of current may flow in each LED. To equalize the current difference, different rates of current pulses corresponding to this difference can be supplied to each LED. Low current LEDs receive high rate current pulses. Thus, by adjusting the rate of the current pulses supplied to each LED instead of equalizing the current in a manner that consumes excess energy inefficiently, the different LEDs are equalized.

  The LED line driver circuit 425 of FIG. 4A connected to the set of LED units 750 of FIG. 7 forms a very efficient LED lighting system that minimizes the amount of power wasted. In the LED line driver circuit 425, since the main line driver FET 461 is always completely on or completely off, it dissipates very little power as heat. In the individual LED units 750, all the current flows to the next LED unit on the line, as the local power system 720 shunts the line current when charging the local power capacitors of the LED units. Inside the individual LED units 750, the control circuit uses minimal power, so the LED driver circuit 780 distributes most of the power to the turned on LEDs 781. Therefore, the overall controlled LED lighting system is very efficient. The system draws only a limited amount of power when the LED is off. Also, when the LED is on, the system wastes little power.

  As shown in the embodiment of FIG. 7, each LED unit controls four different LEDs, but other embodiments may have a different number of LEDs. To further optimize power usage (and reduce costs), each uses a group of three LED units controlling N LEDs, each of the three LED units supporting one color (each red, N pixels can be implemented by having green and blue LEDs). For example, in the embodiment of FIG. 7, four independent pixels can be generated by having each LED unit control four LEDs of the same color. This deployment of the LED unit further optimizes the use of power. This is because different colored LEDs require different amounts of power, and each LED unit only draws the power needed to support a particular colored LED (red, green or blue).

Advanced Color System In an alternative embodiment, the individual LED units can be implemented as pixel circuits in which the LED units comprise color data for driving color pixels consisting of red, green and blue LEDs. Each LED unit can control one or more pixels. The pixel circuit receives color / brightness information for each pixel controlled by the pixel circuit. The pixel circuit can operate using the following scheme to encode a number of different colors.
Color Space of YUV or YCrCb or YPbPr Color Space of RGB (Red, Green, and Blue) HSV (Hue, Saturation, and Value) Colors Space CMYK (Cyan, Magenta, Yellow, and Black) color space

  The pixel circuit converts the received color information into values needed to drive the red, green and blue sets of pixels to produce the desired color. The individual pixel circuits can factor in the current supplied to the LED and the current temperature to produce a very sharp color. The pixel circuit adjusts the output intensity values for the different color LEDs according to the current temperature and the current supplied to the LEDs.

  Display systems that perform color space conversion at the pixel level offer several advantages. The system for providing display information can be simplified as the system for providing image data does not need to perform color space conversion. Instead, this color space conversion is performed where pixel light is generated.

  Furthermore, a system that supplies all color information to the pixel light source can use the original color space directly, and can provide higher quality output. For example, the color space of YCbCr is more efficient than the color space of RGB because the RGB color space has a lot of mutual overlap. Furthermore, there is no quantization error that occurs during the color conversion process. Therefore, a system (pixel circuit) that renders pixel light by providing YCbCr-encoded color information to the system that renders pixel light, uses all of the color information to produce the clearest color. Reproduction can be generated.

  The system is energy efficient by efficiently supplying a voltage source that is not carefully calibrated to obtain the exact desired voltage, but instead approximately supplies the desired current, as previously described. Can be improved. In such systems, the emission spectrum of the LED may be affected. As described above, in the pixel circuit that performs color control, the color circuit can adjust the color output to the current supplied to the LED. So, when the current supplied to the LED changes the color output of the LED, the color control circuit can take this change in color output into account and adjust the output of all the LEDs for this pixel, so that Finally, accurate color output can be generated. In this way, the current actually supplied to the various different color LEDs used to generate color pixels is an input to the color circuitry which determines the correct output intensity for each color LED.

Automatic Addressing System As mentioned above, if all of the individual LED controller units in a single driver line can be individually controlled, each individual LED controller unit (760 in FIG. 7) has its own unique address. There is a need to. It connects the LED line driver circuit to a single discrete LED controller unit located on the driver line, sends commands from the LED line driver circuit to this single LED controller unit, and addresses its address fuse at a specific address It can be achieved by fusing to the value. After that, a series of LED controller units, each having a unique address, are connected together in series on a single driver line in a specific pattern, and a driver line in which the individually controllable LED controller units are arranged in a known manner It can be made.

  In order to facilitate the fabrication of such a string of LED controller units, the address programming logic can be improved by the addition of a "Hall Effect" sensor. Hall effect sensors are electrical sensors that can detect local magnetic fields. To improve the address programming logic, Hall effect sensors may be added in such a way that the address programming logic can be activated only when the Hall effect sensor detects a particular magnetic field. Thus, the address programming logic does not operate if the LED controller unit is not at a predetermined magnetic field. In this way, several LED controller units that have not yet been addressed by fuse blowing can be connected to the same driver line. Next, in order to assign unique addresses to the LED controller units on the driver line, the individual LED controller units are sequentially arranged in an appropriate magnetic field (one at a time), and the driver line is commanded to program the unique addresses. Send downstream of Since there is only one LED controller unit in the proper magnetic field, only this one LED controller unit responds to the command of addressing by fuse blow. Other LED controllers in the same driver line ignore the command for address assignment due to fuse blowout. Therefore, by placing each LED controller unit sequentially in the appropriate magnetic field and sending a command to program with a unique address, each LED controller unit already connected together in a single driver line has its own address It can be programmed.

Application Overview The single-wire multiple LED power and control system described in the previous section and shown in FIG. 2A can be used in a wide variety of applications. In the most basic application, a string of individually controlled lighting units 250 can be placed in a simple control decorative lighting system, such as a series of lights for a Christmas tree. In such an embodiment, the driver line 221 may be an insulated wire, in addition to transmitting power, providing encoded control data, providing a reference current value, and serving as a heat sink for the individual LED units 250. It is possible to give the string a physical structure. In such an arrangement, the master LED controller system 230 may be a small microcontroller with a set of different lighting patterns. These lighting patterns have no limiting factor other than the imagination of the person programming the master LED microcontroller system 230. For example: fixed lighting with a spectrum of colors, lighting patterns that flash differently in different colors, progressively activating the LED unit to make the light source appear to move the string, and so on.

  The number of possible applications for the single-wired multiple LED power and control systems described in the above section is nearly limitless, so the number is beyond the scope of this specification. However, the following sections will highlight some of the many possible applications for the disclosed system.

Controlled Lighting Applications As described in the background of this specification, LEDs are currently used in many traditional lighting systems. The two main reasons for this are the energy efficiency of the LEDs and the fact that the LEDs are robust and require little maintenance of the LED lighting system. (LEDs do not have to be replaced as often as filament-based incandescent bulbs or small fluorescent lights.) However, LED-based lighting systems are limited in their placement due to their high price. The single wired multiple LED power and control system according to the present disclosure reduces the cost of the LED based lighting system while improving the series of features of the LED based lighting system. As such, the single wire multiple LED power and control system according to the present disclosure can expand the market for LED based lighting systems.

  The single-wire, multiple-LED power and control system of the present disclosure reduces the complexity of the line involved in the design, manufacture and installation of LED-based lighting systems, resulting in the cost of LED-based lighting systems Will be reduced. In particular, the single driver line (and the feedback supply line to complete the circuit) greatly simplifies the lines needed to build an LED based lighting system. As shown in FIG. 2A, in one possible embodiment, the functionality of the master LED controller system 230, the power supply 210, and the LED line driver circuit 220 is incorporated into a single LED driver circuit system 239, a single The driver line 221 (and its feedback line 229) only drives a large number of individually controlled LED units (250-1 to 250-N). In this way, the manufacture of the lighting system is greatly simplified. However, with the LED lighting system of FIG. 2A, the LED units 250 (with a plurality of LEDs of different colors) will all be individually controlled, so that a highly polychromatic pattern can be generated.

  11A-12 are block diagrams of possible LED lighting systems that may be constructed using the teachings of the present disclosure. It should be noted that these are only two of the myriad possible lighting fixtures that can be generated using the teachings of the present disclosure.

  In the embodiment of FIG. 11A, the LED lighting system was divided into two units. LED lighting fixtures 1125 and master LED controller and power line data encoder system 1130. The embodiment of FIG. 11A can be used in a conventional alternating current (AC) lighting environment. A portion of the LED lighting fixture 1125 is typically installed like a conventional lighting fixture that switches to and controls AC current. However, rather than a conventional light switch, a master LED controller and power line data encoder system 1130 is installed where the on / off switch is typically installed.

  The master LED controller and power line data encoder system 1130 comprises a power supply, a microcontroller, a user interface, and a power line data encoder. A user interacts with a user interface on the master LED controller / power line data encoder system 1130 to provide control commands (eg, turn on, turn off, set light to blue, display rainbow pattern, etc.). The microcontroller power line data encoder then modulates control commands on the power lines connecting the master LED controller power line data encoder system 1130 to the LED lighting fixture 1125. Various different known power line data modulation systems can be used.

  In the possible embodiment shown in FIG. 11A, the user interface at the master LED controller and power line data encoder system 1130 can comprise a pair of dials. The first brightness indicator panel 1135 can be used to control whether the LED lighting installation is turned on and how bright the LED should be lit. The second hue indicator panel 1136 allows the user to select a particular hue for the LED unit. When white is set on the hue pointer board 1136, the LED lighting equipment 1125 can operate as a normal white light source.

  The master LED controller and power line data encoder system 1130 drives an LED light fixture 1125 that can be installed like a conventional light fixture. A power and data extractor 1110 within the LED lighting fixture 1125 receives, modulates and extracts control commands from the control and power line 1131. The power supply and data extractor 1110 then transfers the extracted control data and the required power to the LED line driver circuit 1110 to drive the series of LED units 1150 as described in the previous section of this specification.

  A single master LED controller and power line data encoder system 1130 is capable of driving multiple LED lighting fixtures. For example, in the embodiment shown in FIG. 11B, a single master LED controller and power line data encoder system 1130 is used to control three LED lighting fixtures (just like conventional lighting switches control multiple overhead lighting fixtures) Control 1125, 1126, and 1127).

  FIG. 12 shows an alternative embodiment of a lighting system controlled by a wireless control system. In particular, FIG. 12 shows an alternative embodiment of a lighting system comprising LED lighting fixtures 1229 and a wireless LED control transmitter 1238. The LED lighting fixture 1229 may be co-located with a conventional AC current lighting fixture. The AC power 1211 sent to the power supply 1210 in the LED lighting fixture 1229 generates the necessary DC power for the LED line driver circuit 1220 and the master LED controller system 1230. (Note that in one embodiment, the master LED controller system 1230 can receive operating power from the LED line driver circuit 1220.)

  The master LED controller system 1230 includes sensor circuitry 1232 that receives wireless commands from the LED control transmitter 1238. The master LED controller system 1230 decodes the command received from the LED control transmitter 1238 and transfers this command to the LED line driver circuit 1220. The wireless system can use Bluetooth®, infrared light, or any other suitable wireless data transfer system. When using an infrared transfer system, the functions of the LED control transmitter 1238 are operated by a programmable infrared remote control system. As such, the LED lighting fixture 1229 of FIG. 12 is ideal for use in a room equipped with a home theater system. AC power 1211 to power the LED lighting fixture 1229 is obtained from a conventional wall mounted lighting switch. In keeping with general expectations, the master LED controller system 1230 always powers on the LED lighting fixture with white light in default mode. In this manner, the LED lighting fixture 1229 operates like a normal lighting fixture when the LED control transmitter 1238 is not in use.

Use of LED String Technology for Stage Lighting Systems Music concerts and stage performances use special lighting systems to enhance live performance rendering. There is a specialized industry dedicated to developing and selling lighting hardware and control systems for stage lighting. To enable the exchange of information between various devices, the American Theater Technology Association (USITT) has developed a standard communication protocol known as DMX 512-A, used to control stage lighting and effects. The DMX 512-A communication protocol is an EIA-485 based serial protocol for sending commands to stage lighting and effects units.

  For beneficial use in the stage lighting market, the teachings of the present invention can be implemented in conjunction with the generic DMX 512-A communication protocol. In the first embodiment, the conversion unit can be used to convert the DMX 512-A communication protocol for the LED line driver unit into a native protocol. For example, referring to FIG. 2A, the master LED controller system 230 can be a microcontroller unit (MCU), which receives commands at the DMX 512-A communication protocol or input 232 and converts these commands. Thereafter, these commands are output to the control data 231, and this control data is transmitted to the LED line driver unit 220 by the native protocol. The LED line driver unit 220 then drives the individually controlled LED units 250 as described in the previous section of this specification. The master LED controller system 230 relays DMX 512-A communication protocol information to the next DMX 512-A based device in a daisy chain configuration.

  Also, the teachings of the present disclosure may be used with a dedicated DMX 512-A based system. FIG. 13 shows a system implementation of line driver circuitry 1320 dedicated to a DMX 512-A based stage lighting system 1339. Using the conventional DMX 512-A based controller system 1330, the DMX 512-A formatted data 1331 is sent to the DMX 512-A based line driver circuit 1320. The current sent to the power supply 1310 can also be transmitted on the same line. The DMX 512-A data interface 1325 in the line driver circuit 1320 receives and decodes a DMX 512-A protocol type command.

  The line driver circuit 1320 then converts these commands and sends the converted commands downstream of the driver line 1321 along the current feeding the individually controlled LED units 1350. The individually controlled LED units 1350 receive this command and execute appropriately. It should be noted that the individually controlled LED units 1350 can not only illuminate the LEDs at different intensity levels, but also perform other additional functions. For example, individually controlled LED units 1350 can additionally incorporate features such as LED pans and tilts and the use of gobos. (Gobos are filters or patterns used on the front of the light source to affect the light output.)

  The DMX 512-A data interface 1325 can output the DMX 512-A protocol so that the next DMX 512-A based unit 1327 in a daisy chained string also receives control data. Similarly, the next DMX 512-A based unit 1327 can send power signals from the power supply 1310.

Use of LED Strings in Automotive Applications A large number of different light sources are used in vehicles. For example, in a typical automobile, at least four turn indicator lamps, two brake lamps, an inside light, a license plate lamp, a centrally mounted brake lamp, a trunk light, a bonnet light, a reverse indicator lamp, and the like. There is a lamp other than. For each such different lamp, different types of light bulbs can be used depending on the specific brightness and color needs. In order to drive such different lamps, harnesses of various different sizes are installed around the vehicle. Because there are various types and configurations of cars, a wide variety of line harnesses are required. This prior art system presents a difficult inventory control problem, as a large number of different line harnesses and light bulbs must be stocked.

  To simplify automotive wiring, strings of multiple single-wired LED units described in the previous section can be used in the automotive environment. A single wire can be run around the car, and all the outputs of the different lamps installed in the car can be connected (with the extra power at each lamp's output). For example, starting with a single wiring from the control position, then front left indicator lamp, front right indicator lamp, inside light, rear right indicator lamp, rear right brake lamp, rear left indicator lamp, rear left The position of the brake lights, reverse indicator lights, license plate lights, trunk / hatch lights, and any other required lights, and finally the central control position can be wired back. Next, this wiring is cut at each location where a light source is required, and the LED lamp unit to be controlled 250) is connected to the wiring continuously.

  Control of all lamp units of the string is handled by a central control unit (such as LED drive system 239). The central control unit can use the same lamp output unit at all different places in order to control exactly how light is output from each lamp unit (color, brightness, and changes in these). For example, the central control unit reliably blinks the turn signal indicator lamp in yellow, outputs the brake lamp in red, and outputs the reverse indicator lamp in white. To improve security, two independent strings are run in parallel, and if one string fails, the other strings continue to operate. Even two systems operating in parallel, such as a two-wire system, are far simpler than the countless wires used in conventional automotive electrical harnesses.

  Because the lighting system of the present disclosure is fully controllable, a central control unit mounted on a motor vehicle can be used in a manner different from that normally used for lighting a motor vehicle. For example, if the car is stolen, a wireless communication system (such as a cellular network or General Motors provided OnStar network) instructs the lighting system to start lighting all the lamps of the vehicle in a noticeable pattern. Stolen cars can be made eye-catching. It can also use the same technology to make it easier for people to find a car if it can not find a car in a large parking lot. The lamps mounted on the car can also be used to output information in various ways. For example, the external lamp train of a car can be used to output the battery charge (or other data) in the form of a bar graph. The controlled lamp output can also be used to output the encoded information to various sensors located along the road. For example, sensors that detect various identification patterns can be installed at parking lots and toll stations to recognize a particular car for use of the service and to charge that car.

  In addition to simplifying automotive design and inventory management of automotive parts, the LED string system of the present disclosure is very energy efficient. The efficiency of any electrical system in a car becomes crucial as the car eventually transitions from gasoline to electricity. As such, the LED-based lighting system of the present disclosure may be ideal for use inside an electric vehicle. The system not only uses energy efficient LEDs as a light source, but also can carefully control the amount of light as needed. For example, the brake lights need to output a large amount of light during the day to be visible, but can be adjusted to reduce the output at night (thus saving energy).

  In addition to automotive applications, LED string systems are also ideal for use inside aircraft. While weight considerations are key in aircraft, lightweight LED string systems can provide the lowest weight lighting. Furthermore, the lighting is controlled so that the same lighting can be used for multiple purposes such as regular white light, mood light and emergency exit light.

Use of LED Strings in a Modular Display System The single wired multiple LED power and control system described in the previous section can be used to create a display system. In particular, referring to FIG. 2A, the individually controlled LED units 250 can be arranged in a two-dimensional pattern so that the individually controlled LED units 250 can be controlled as individual pixels in the display system.

  FIG. 14 shows a system using a single LED line driver circuit 1420 to drive 64 individually controlled LED units (1450-1 to 1450-64) arranged in an 8.times.8 two-dimensional array. An example is shown. An array of 16 × 16 can be made with 256 individually controlled LED units on a single driver line. (This is merely an example, and it should be noted that modules of different sizes and shapes may be made, and such modules may be combined with any desired pattern.) A single power supply 1410 is an LED Power is provided to the entire array of line driver circuits 1420 and individually controlled LED units (1450-1 to 1450-64). The most important aspect of the two-dimensional array system shown in FIG. 14 is that all of the individually controlled LED units (1450-1 to 1450-64) are connected to the driver line 1421 using only a single wire. It is. This makes the array system of FIG. 14 very easy to build.

  The LED line driver 1420 controls the master LED controller system 1430 that transmits the pixel control data 1432 to the LED line driver 1420. In addition to controlling the LED line driver 1420, the master LED controller system 1430 controls many other LED line drivers, each also driving its own 8x8 array. By combining multiple arrays modularly, larger display systems can be combined. For example, FIG. 15 shows the concept of a 10 × 8 array of even smaller two-dimensional module arrays. Using the 8.times.8 array of FIG. 14 in the configuration of FIG. 15, the overall display is 80.times.64 pixels. More individually controlled LED units can be used in each modular unit and / or more units to create high resolution displays.

  In addition to two-dimensional display systems, the disclosed LED strings can be configured in a three-dimensional pattern. A three dimensional LED string can generate a three dimensional image.

Use of LED Strings in String Display Systems The single wired multiple LED power and control system described in the previous section can be used to create a variety of different display systems that are not conventional. For example, several long strings of individually controlled LED units can be attached in parallel to one another to create a two-dimensional display system as shown in FIG. At the beginning of each string, a line driver unit drives a single line to control all of the individually controlled LED units on the string. All line driver circuits can be controlled by a single master controller system that delivers the appropriate data to render the image on the array. The display system of FIG. 16 can be easily rolled, carried and installed anywhere that a large display system is required. In another embodiment, the individually controlled LED units can be attached to a flexible sheet, such as a conventional roll-up reflective projection screen. Flat and flexible wiring can be used to connect the individually controlled LED units. Such display systems can be rolled, carried, and installed like carpets anywhere that a large display system is required.

  By arranging a plurality of strings of individually controlled LED units, virtually any surface can be created in the display system (a surface is not necessary when hanging strings). There is no need to do so in a prudent manner to arrange multiple strings of individually controlled LED units. Once several types of two-dimensional patterns are made, a calibration system can be used to identify two-dimensional patterns and calibrate the patterns. An example is given with reference to FIGS. 17 and 18.

  Referring to FIG. 17, fabrication of the freeform display system begins with placing several strings of individually controlled LED units in step 1710. The strings are arranged in any way that produces at least some two-dimensional patterns when viewed from other advantages than LED strings. For example, if it is a building, several different LED strings can be attached to one side of the building. Multiple two-dimensional arrays may be generated and controlled. For example, a track can be covered with a plurality of LED strings so that the major two sides of the track can function as a two dimensional array.

  Next, at step 1720, all LED strings are connected to a single master LED control system, such as a computer system. The master LED control system obtains information on the number of attached LED strings and the number of LED strings provided with addressing information, and this information enables the master LED control system to individually address each LED unit. At this point, it should be noted that the master LED control system does not have any information on the positional relationship of the arranged LED strings.

  Next, at step 1730, the calibration camera system is positioned at the display system at an advantageous point of view. In the example of an LED string attached to the side of a building, a suitable and advantageous point would be a sidewalk from the building. In the example of a truck, a suitable and advantageous point would not be 6 meters (20 feet) from the side of the truck. (Note that two different calibrations should be performed for both sides of the track.) After installing the calibration camera system, the master LED control system displays a series of calibration patterns at step 1740. The calibration pattern is used to identify the position and relative brightness of each LED unit of the various LED strings. This calibration makes it possible to identify a two-dimensional pattern of the arranged LED units. LED units that are not visible from the calibration camera (because the example of the LED units on the other side of the track is obstructed) are ignored.

  This calibration system appears to require a connection between the master controller system and the calibration system to facilitate the correlation between the calibration pattern of the displayed current and the image captured by the calibration system. . However, the calibration screen can also be matched with the captured calibration image using a coding system that transmits the address of each LED unit by color output, flicker pattern, or a combination of the two.

  After capturing the calibration patterns and identifying the relative position and brightness of each LED unit using these patterns, the calibration information is stored in the master LED control system at step 1750. At this point, the master LED control system has information about the positional relationship of all visible LED units used to create a two dimensional array model. After converting the image using this model, the master LED control system can render the image by sending the appropriate message to the LED unit. The master LED control system can distribute portions of the calibration operation to the individual LED units by sending portions of the calibration information to the individual LED units, as described in optional step 1760. For example, a particular LED unit can not be directed to an advantageous point of the calibration camera system with the appearance of lower brightness than the other LED units. To compensate for this, calibration data in this particular LED unit can be specified to increase the brightness of this LED unit.

  Having placed the LED strings, captured calibration information, and created a model of the two-dimensional array, the freeform display system is ready to operate at step 1770. However, if more than one two-dimensional array is to be manufactured using LED strings, more than one display system may be defined. For example, in a track covered with LED strings, a second display system can be created by selecting a second advantageous point on the opposite side of the track. So, at step 1765, the user has the option to repeat steps 1730 to 1760 for another two-dimensional surface (ie the other side of the track) to model another display system from the same series of LED strings. Do.

  FIG. 18 illustrates how a series of LED strings arranged with the display model created using the method of FIG. 17 can be used to display video information. The display system uses this model to convert video information into LED control commands sent to the individual LED units.

  As viewed from the left of FIG. 18, any type of suitable video source, such as computer system 1810, DVD 1811, HDMI 1812, Blu-ray 1813 or other video source, is provided to frame decoder 1820. Frame decoder 1820 decodes the original video source into a series of digital frame representations. Below the frame decoder 1820 is an illustration of the concept of video frames.

  Next, a frame counter 1830 adjusts the scale of the original source frame to a size compatible with the display. For example, the resolution of the original video frame may need to be reduced or increased using interpolation. The frame counter 1830 can reduce the amount of video information that needs to be accessed and processed only a portion of the original video frame. Below the frame counter 1830 is an illustration of the concept of a video frame that has been scaled down from the original video frame below the frame decoder 1820.

  Next, at step 1840, remapping of the source video position relationship is performed. Free-form display systems do not appear to be a suitable two-dimensional array that exactly corresponds to a conventional rectangular video frame. Therefore, image clipping, frame distortion, and pixel interpolation can be performed to make the video source frame compatible with the freeform display system. Below the positional remapping step 1840 is an image concept that distorts the frame to compensate that the freeform display is not rectangular.

  Finally, the data delivery system 1850 scans the modified source frame, generates a series of LED unit commands, and sends them to the appropriately addressed LED units according to the display model. Beneath the data delivery system 1850 are model concepts of the various display strings that make up the free form display system. The data distribution system 1850 sends LED update commands to the various LED string controllers (1880-1-1880-N). A series of LED strings (with individually controlled LED units) and models of LED strings arranged as produced by the method of FIG. 17 by repeating steps 1820 to 1850 for the original source video frame The video information can be displayed on a free form display system made using it.

  The above technical disclosure is intended to be illustrative and not restrictive. For example, the embodiments described above (or one or more aspects of these embodiments) can be used in combination with one another. Other embodiments will be apparent to those skilled in the art upon reviewing the above description. Accordingly, the claims should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms "including" and "in which" refer to plain English equivalent to the terms "comprising" and "where in" respectively It is used as. Also, in the following claims, the terms "including" and "comprising" are unlimited, ie, elements other than those listed after such terms in the claims Systems, devices, objects or processes that include are considered to be within the scope of this claim. Furthermore, in the following claims, terms such as "first", "second" and "third" are used as mere labels, and the subject matter thereof It is not intended to give numerical requirements to things.

Claims (16)

A light emitting diode (LED) based electronic lighting system,
A power supply that generates a rated constant current,
A lighting control system that receives input data that determines how light is to be output and that processes the input data into control data for driving the LEDs;
A modulator circuit that modulates control data for driving the LED onto the rated constant current;
A plurality of LED driver nodes having a single port and a single output port and connected in series with the modulator circuit to receive the rated constant current;
Each of the plurality of LED driver nodes is
With a local capacitor,
If by the rated constant current received at the input port periodically directing to said local capacitor to generate a local power supply, also not towards the rated constant current to the local capacitor, said output port of said rated constant current Power subcircuits that shunt to
A data extraction subcircuit that demodulates the control data from the rated constant current;
An electronic lighting system comprising: at least one LED driver circuit controlled using said control data demodulated from said rated constant current. The electronic lighting system according to claim 1, wherein the modulator circuit modulates the control data on the rated constant current by generating a detectable current deviation from a rated constant current level. The electronic lighting system according to claim 1, wherein the input data received by the lighting control system is received on a wireless data system. The electronic lighting system according to claim 1, wherein the input data includes color and intensity. Each of the plurality of LED driver nodes comprises at least three LED driver circuits such that each of the plurality of LED driver nodes can independently generate three colors by driving three colored LEDs. An electronic lighting system according to Item 1. The electronic lighting system according to claim 1, wherein each of the plurality of LED driver nodes is assigned an address such that the lighting control system can independently control each of the plurality of LED driver nodes. The electronic lighting system according to claim 1, wherein the LED driver circuit operates using the local power supply in the local capacitor. The electronic lighting system according to claim 1, wherein the plurality of LED driver nodes are all synchronized with a periodic signal modulated on the rated constant current by the modulator circuit. A method of driving a light emitting diode (LED) in a lighting system, comprising:
Receiving input data to a lighting control system, said input data specifying how said lighting system should output light;
Processing the input data into control data for driving a plurality of LEDs;
Generating a rated constant current by the power supply circuit;
Modulating the control data on the rated constant current by a modulator circuit;
Performing a sub-process at a plurality of LED driver nodes connected in series with the modulator circuit to receive the rated constant current, the sub-process including the rated constant current from an input port Periodically to the local capacitor to generate a local power supply,
Shunting the rated constant current to an output port if the rated constant current is not directed to the local capacitor;
Demodulating control data from the rated constant current ;
Driving at least one LED driver circuit using the control data demodulated from the rated constant current. 10. The method of claim 9 , wherein modulating the control data on top of the rated constant current comprises generating a detectable current deviation from a rated constant current level. The method of claim 9 , wherein the input data received by the lighting control system is received on a wireless data system. The method according to claim 9 , wherein the input data includes color and intensity information. Each of the plurality of LED driver nodes comprises at least three LED driver circuits such that each of the plurality of LED driver nodes can independently generate three colors by driving three colored LEDs. 10. A method according to item 9 . 10. The method of claim 9 , wherein each of the plurality of LED driver nodes is assigned an address such that the lighting control system can independently control each of the plurality of LED driver nodes. 10. The method of claim 9 , wherein the LED driver circuit operates using the local power supply in the local capacitor. 10. The method of claim 9 , wherein the plurality of LED driver nodes are all synchronized with the periodic signal modulated onto the rated constant current by the modulator circuit.

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