KR101597461B1 - LED Current Estimation Circuit Using the Time Information for LED Driver - Google Patents

Abstract

Disclosed are a method for estimating a light-emitting diode (LED) current using time information and a system thereof. According to the present invention, the LED current estimation method using the time information can comprise: a step of acquiring turn-on time information of first side and second side circuits not using current information of the first side and second side circuits; a step of counting a clock value by using the turn-on time information of the first side and second side circuits, and converting the clock value into a digital value; and a step of estimating an LED current by applying the digital value to a current-mirror structure switch.

Description

[0001] The present invention relates to an LED current estimation circuit using time information,

The present invention relates to an AC-DC converter based on a single-stage fly-back converter, in which information of an LED current connected to a secondary circuit is inferred using time information of a primary circuit And a system.

In an AC-DC converter based on a single-stage fly-back converter, when LEDs are used in the secondary circuit, the amount of LED current must be fed back to control the LED current to be used as a control signal. The basic structure is shown in Fig.

1 is a diagram showing the configuration of a conventional single stage fly-back converter. The conventional single stage fly-back converter includes a primary side 110, a secondary side 120, and a feedback circuit 130 as shown in FIG. 1 And may include a pulse width modulator (PWM) and a load.

The reason for using a fly-back converter in the power stage is due to the safety that can be achieved with isolation. However, additional devices and circuits such as an opto-coupler are required for safety in order to feedback the amount of LED current to the control stage. Therefore, it is possible to infer and control the amount of LED current on the secondary side from the amount of primary side current by using the fact that the values of the primary side current and the secondary side current have turns ratios.

2 is a diagram showing a configuration of a fly-back converter using a primary side control circuit according to the prior art. 2 is a basic structure using a primary side control scheme. In the conventional method, the average value of the primary current is calculated by using a low pass filter (LPF) or the peak value of the primary current is sampled and held. However, when a low pass filter (LPF) is used, a lot of additional area is generated due to a low pass filter (LPF). When a peak value is used, a precise sample & If the circuit is not designed, the speculative value and the actual value may be different.

SUMMARY OF THE INVENTION The present invention is directed to an AC-DC converter based on a single-stage fly-back converter, in which the information of the LED current connected to the secondary circuit is stored in a time- And to provide a method and system for designing a small area by reducing the number of external elements used by using a method of guessing by using the method. In addition, by increasing the clock frequency by using the counter, the precision can be increased and the design can be made easily.

In one aspect of the present invention, there is provided a method of estimating an LED current using time information proposed in the present invention, which uses the current information of a primary circuit and a secondary circuit without using the current information of the primary circuit and the secondary circuit, Counting a clock value using the turn-on time information of the primary circuit and the secondary circuit, converting the digital value into a digital value, applying the digital value to a switch of a current mirror structure And estimating the LED current.

The step of obtaining the turn-on time information of the primary circuit and the secondary circuit obtains the turn-on time information of the primary circuit and the secondary circuit from the signal of the power switch gate signal and the auxiliary winding .

When the power switch gate signal is turned on and a current flows through the primary side circuit, the signal of the auxiliary winding is a negative value, and the power switch gate signal is turned off so that current flows to the secondary side The signal of the auxiliary winding is a positive value, and parasitic ringing may occur when the value of the secondary side current becomes '0'.

On time information of the secondary side circuit can be obtained by fixing when the power switch gate signal falls to a low level and resetting the signal when the signal of the auxiliary winding becomes lower than a specific voltage.

Wherein when the turn-on time information of the primary circuit and the secondary circuit is used, the AC input voltage scaled down to infer the LED current and the turn-on time of the primary circuit and the secondary circuit The product of the time information can be used.

The method for estimating the LED current is calculated using the following equation,

Herein, N is the winding ratio, V _in is the AC input voltage, T _on-p is the turn-on time information of the primary circuit, T _on-s is the turn-on time information of the secondary circuit, And T represents a switching period. The LED current estimation method using time information.

In another aspect, an LED current estimation system using time information proposed in the present invention includes a primary circuit including the LED current estimation circuit, a secondary circuit including an LED driving circuit, The LED current can be estimated using the turn-on time information of the primary circuit and the secondary circuit without using the current information of the secondary circuit and the secondary circuit.

Wherein the LED current estimation circuit includes switches of a plurality of current mirror structures and counts a clock value using the turn-on time information of the primary circuit and the secondary circuit, converts the clock value into a digital value, A digital value can be applied to the switches of the plurality of current mirror structures to infer the LED current.

According to embodiments of the present invention, the use amount of an additional circuit such as an opto-coupler and a low pass filter (LPF) can be greatly reduced, thereby reducing the size and cost of the entire system. In addition, the use of the counter is expected to contribute to lowering the price because it is easy to design. If you want to increase the precision, you can easily design the counter by increasing the clock frequency.

1 is a diagram showing the configuration of a conventional single stage fly-back converter.
2 is a diagram showing a configuration of a fly-back converter using a primary side control circuit according to the prior art.
3 is a flowchart illustrating an LED current estimation method using time information according to an embodiment of the present invention.
4 is a diagram illustrating a configuration of a LED current estimation system using time information according to an embodiment of the present invention.
5 is a diagram illustrating a proposed LED current estimation circuit according to an embodiment of the present invention.
6 is a diagram showing an operation waveform in an AC cycle according to an embodiment of the present invention.
7 is a diagram illustrating a change in reference voltage according to an LED current according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a flowchart illustrating an LED current estimation method using time information according to an embodiment of the present invention.

The method of estimating LED current using time information includes the steps of obtaining (310) the turn-on time information of the primary circuit and the secondary circuit without using the current information of the primary circuit and the secondary circuit, Counting a clock value using the turn-on time information of the primary circuit and the secondary circuit, and converting the counted value to a digital value (320), applying the digital value to the switch of the current mirror structure, And guessing (step 330).

First, in step 310, the turn-on time information of the primary circuit and the secondary circuit can be obtained without using the current information of the primary circuit and the secondary circuit. At this time, the turn-on time information of the primary circuit and the secondary circuit can be obtained from the signal of the power switch gate signal and the auxiliary winding. For example, when the power switch gate signal is turned on and a current flows through the primary side circuit, the signal of the auxiliary winding is a negative value, and when the power switch gate signal is turned off and current flows to the secondary side, The signal is a positive value. When the value of the secondary side current becomes '0', parasitic ringing may occur. Then, when the power switch gate signal falls to a low level, the secondary side circuit is turned on and reset when the signal of the auxiliary winding becomes lower than a specific voltage, thereby obtaining the turn-on time information of the secondary side circuit.

 Then, in step 320, the clock value may be counted using the turn-on time information of the primary circuit and the secondary circuit, and converted into a digital value.

Then, in step 330, a digital value can be applied to the switch of the current mirror structure to infer the LED current. The LED current estimation circuit using the proposed time information can be applied to the switch of the current mirror structure to estimate the LED current. When the turn-on time information of the primary circuit and the secondary circuit is used, a product of the scaled down AC input voltage and the turn-on time information of the primary circuit and the secondary circuit is used to estimate the LED current .

의 적분 값으로 계산할 수 있다.The equation for estimating the LED current is given by the following equation (1): < EMI ID = 1.0 >

As shown in FIG.

수학식1

Equation 1

Here, T represents a switching period.

In the case of using the S / H circuit, the equation for estimating the LED current can be calculated using the peak value of the primary side current as shown in Equation (2).

수학식2

Equation 2

Here, N is the AC input voltage winding ratio, V _in, I _pk-p is the primary side peak value of the current, T _on-p is the first turn at the side of the circuit-on time information, T _on-s On time information of the secondary side circuit, and T denotes a switching period.

In the case of using the LPF, the formula for estimating the LED current can be calculated by using the average value Isw, avg of the primary side current passed through the LPF as shown in Equation (3).

수학식3

Equation 3

Herein, N is the winding ratio, V _in is the AC input voltage, T _on-s is the turn-on time information of the secondary circuit, and T is the switching period.

In the case of using the time information, the equation for estimating the LED current is obtained by multiplying the AC input voltage Vin scaled down as shown in Equation (4) by the turn-on time of the primary circuit and the turn-on time of the secondary circuit .

수학식4

Equation 4

Herein, N is the winding ratio, V _in is the AC input voltage, T _on-p is the turn-on time information of the primary circuit, T _on-s is the turn-on time information of the secondary circuit, And T represent switching cycles.

4 is a diagram illustrating a configuration of a LED current estimation system using time information according to an embodiment of the present invention.

The LED current estimation system using time information may include a primary side circuit 410 including an LED current estimation circuit, and a secondary side circuit 420 including an LED driving circuit 450. The LED current estimation system using the proposed time information has devised a LED current estimation circuit 470 using time information so that it is easy to design even with a small area. The turn-on time information 431 of the primary side circuit and the turn-on time information 432 of the secondary side circuit are set to be the same, without using the current information of the primary side circuit 410 and the secondary side circuit 420 The winding ratio 440 of the primary side circuit 410 and the secondary side circuit 420 can be obtained. Therefore, after counting the clocks based on the time information 431 and 432 and converting them into digital values, the overall structure of the proposed system is as shown in FIG. 4, and is applied to a switch of a mirror structure in the LED current estimation circuit 470 The LED current 451 can be inferred. Ton_p 431 and Ton_s 432, which are the turn-on time information of the primary circuit and the secondary circuit, from the power switch gate signal (Qsw) 460 and the auxiliary winding signal (Vaux) Can be obtained.

Referring to FIG. 4, it can be confirmed that the two signals obtained by the calculation are the ILed_est 471 and the target reference value Io_ref 472, which are passed through the error amplifier 480. The magnitude of the Vcs_REF 492 amplitude is determined by the value of Vctrl (491) obtained by the difference between the two signals. If the ILed_est 471 is larger than the reference value Io_ref 472, the value of Vctrl 491 gradually decreases and the amplitude of Vcs_REF 492 decreases.

5 is a diagram illustrating a proposed LED current estimation circuit according to an embodiment of the present invention.

The proposed LED current estimation circuit can be applied to the switch 510 of the current mirror structure to estimate the LED current. By using the method of estimating the information of the LED current connected to the secondary circuit using the time information of the primary circuit, the number of external devices used can be reduced to design a low area. From the power switch gate signal (Qsw) and the signal of the auxiliary winding, Ton_p (521), which is the turn-on time information of the primary circuit, and Ton_s (522), which is the turn- Can be obtained. By increasing the clock frequency using the counter 530, the precision can be increased and the design can be made easily. Thereafter, the product Ton_p * Ton_s 550 of Ton_p 521 and Ton_s 522 can be obtained by using a multiplier 540.

6 is a diagram showing an operation waveform in an AC cycle according to an embodiment of the present invention.

Assuming to operate in discontinuous conduction mode (DCM), when the power switch gate signal 611 is turned on and the current 612 flows into the primary side circuit, the signal Vaux 620 of the secondary winding, When the power switch gate signal 611 is off (630) and the current 622 flows into the secondary circuit, the signal of the secondary winding is positive and the value of the secondary current is negative 0 < / RTI > (640) a parasitic ringing 650 occurs. At this time, when the power switch gate signal 611 falls to a low level, it is set, and when the auxiliary winding signal Vaux 620 is lower than a predetermined voltage Vaux_th 660, So that the waveform of Ton_s, which is the turn-on time information of the secondary circuit, can be obtained. On the basis of the turn-on time information 613 of the primary circuit converted into the digital signal, the turn-on time information 633 of the secondary circuit converted into the digital signal, On time information 613 of the secondary circuit and the turn-on time information 633 of the secondary circuit converted into the digital signal.

7 is a diagram illustrating a change in reference voltage according to an LED current according to an embodiment of the present invention.

The ILed_est (710) obtained by the calculation as described in FIG. 5 and the target reference value Io_ref can be passed through an error amplifier (Error Amplifier). Then, the magnitude of Vcs_REF (720) amplitude can be determined by the Vctrl value obtained by the difference between the two signals. If the IL_est (710) is larger than the reference value, the value of Vctrl gradually decreases and the amplitude of Vcs_REF (720) becomes smaller as shown in FIG.

The prior art requires a precise design in order to obtain an accurate peak value by occupying a large area by using a low pass filter (LPF) or by using a sample & hold method. However, the method and system for estimating the LED current using the proposed time information greatly reduces the use of additional circuits such as an opto-coupler and a low pass filter (LPF) by using the above-described method, It is expected to reduce the size and cost of the system. In addition, the use of a counter is expected to contribute to lowering the price because it is easy to design. If you want to increase the precision, you can easily design the counter by increasing the clock frequency.

The apparatus described above may be implemented as a hardware component, a software component, and / or a combination of hardware components and software components. For example, the apparatus and components described in the embodiments may be implemented within a computer system, such as, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable array (FPA) A programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to execution of the software. For ease of understanding, the processing apparatus may be described as being used singly, but those skilled in the art will recognize that the processing apparatus may have a plurality of processing elements and / As shown in FIG. For example, the processing unit may comprise a plurality of processors or one processor and one controller. Other processing configurations are also possible, such as a parallel processor.

The software may include a computer program, code, instructions, or a combination of one or more of the foregoing, and may be configured to configure the processing device to operate as desired or to process it collectively or collectively Device can be commanded. The software and / or data may be in the form of any type of machine, component, physical device, virtual equipment, computer storage media, or device , Or may be permanently or temporarily embodied in a transmitted signal wave. The software may be distributed over a networked computer system and stored or executed in a distributed manner. The software and data may be stored on one or more computer readable recording media.

The method according to an embodiment may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions to be recorded on the medium may be those specially designed and configured for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. For example, it is to be understood that the techniques described may be performed in a different order than the described methods, and / or that components of the described systems, structures, devices, circuits, Lt; / RTI > or equivalents, even if it is replaced or replaced.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

Claims (8)

In the LED current estimation method using time information,
Obtaining the turn-on time information of the primary circuit and the secondary circuit without using the current information of the primary circuit and the secondary circuit;
Counting a clock value using the turn-on time information of the primary circuit and the secondary circuit, and converting the clock value into a digital value; And
Applying the digital value to the switch of the current mirror structure to infer the LED current
The method comprising the steps of: The method according to claim 1,
The step of obtaining the turn-on time information of the primary circuit and the secondary circuit includes:
And the turn-on time information of the primary circuit and the secondary circuit is obtained from the signal of the power switch gate signal and the auxiliary winding. 3. The method of claim 2,
When the power switch gate signal is turned on and a current flows through the primary side circuit, the signal of the auxiliary winding is a negative value. When the power switch gate signal is turned off and a current flows to the secondary side, And the parasitic ringing occurs when the value of the secondary side current becomes '0'. 3. The method of claim 2,
On time information of the secondary side circuit is obtained by fixing the power switch gate signal when the power switch gate signal falls to a low level and resetting the signal when the signal of the auxiliary winding becomes lower than a specific voltage. Guessing method. The method according to claim 1,
Wherein when the turn-on time information of the primary circuit and the secondary circuit is used, the AC input voltage scaled down to infer the LED current and the turn-on time of the primary circuit and the secondary circuit Wherein the time information is a product of time information. 6. The method of claim 5,
The method for estimating the LED current is calculated using the following equation,

Herein, N is the winding ratio, V _in is the AC input voltage, T _on-p is the turn-on time information of the primary circuit, T _on-s is the turn-on time information of the secondary circuit, And T represents a switching period. An LED current estimation system using time information,
A primary side circuit including the LED current estimation circuit; And
A secondary-side circuit including an LED driving circuit
Lt; / RTI >
And estimates the LED current using the turn-on time information of the primary circuit and the secondary circuit without using the current information of the primary circuit and the secondary circuit. LED current estimation system using. 8. The method of claim 7,
Wherein the LED current estimation circuit includes switches of a plurality of current mirror structures,
Counting a clock value using the turn-on time information of the primary circuit and the secondary circuit, converting the clock value into a digital value, applying the digital value to the switches of the plurality of current mirror structures, And estimating the LED current based on the time information.

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