TWI807724B - Trimming circuit, LED display driver chip, and LED display device - Google Patents

Abstract

The invention mainly discloses a trimming circuit, which is applied in an LED display driving chip, and includes: a logic gate, an external terminal, a trimming unit coupled to the external terminal, and a switch element. When an LED display driver chip undergoes a final test before leaving the factory, if it is necessary to perform trimming processing on the LED display driver chip, a control signal is sent to the switch element, the logic gate and the trimming unit, so that the switch element disconnects the path between the trimming unit and the reference current generating circuit of the LED display driver chip; at this time, a fuse signal is input to the trimming unit through the peripheral terminal, and at the same time, the logic gate transmits an input trimming code to the trimming unit according to the control of the control signal to complete the trimming process.

Description

Trimming circuit, LED display driver chip, and LED display device

The invention relates to the field of LED display technology, especially a trimming circuit applied to LED display driving chips.

Light-emitting diodes (Light-emitting diodes, LEDs) have many advantages such as small size, light weight, long service life, and high luminous efficiency, and have been widely used in lighting devices and display devices. The LED display device is a self-illuminating flat display device, which has the advantages of bright colors, wide dynamic range, high brightness, long life, and high reliability. The LED display device with a large screen has been widely used in large squares, commercial advertisements, stadiums, information dissemination, news releases, and stock trading places as a public display medium.

FIG. 1 shows a structure diagram of a conventional LED display device. As shown in FIG. 1 , a conventional LED display device 1a includes: an LED display panel 11a, a display control unit 14a and a plurality of LED display driver chips 13a. Electronic engineers who are familiar with the design and manufacture of LED displays must know that the display control unit 14a controls each of the LED display driver chips 13a to simultaneously light up the entire display area of the LED display panel 11a or only light up at least one display area of the LED display panel 11 according to different image display requirements.

To explain in more detail, the LED display driver chip 13a is usually a constant current driver chip, and thus includes a constant current generating circuit. FIG. 2 shows a block diagram of a constant current generating circuit 131 a included in the LED display driver chip 13 a shown in FIG. 1 . As shown in FIG. 2 , the conventional constant current generating circuit 131a includes a reference current generating unit 1311a, a current mirroring unit 1312a and a current output unit 1313a. As shown in FIG. 2, the reference current generating unit 1311a is coupled to an external resistor R1a, and is used to generate a reference current I0. On the other hand, the current mirroring unit 1312a is used for performing a current mirroring process on the reference current I0 to generate a first current I1. Finally, the current output unit 1313a generates an output current IOUT according to the first current I1 and transmits it to an output channel (or called a driving channel), so as to drive a designated LED sub-pixel to emit light.

It is worth noting that, with the improvement of display effect requirements, the size of the LED sub-pixels of the LED display panel 11a is continuously reduced, so that the accuracy requirements of the output current IOUT are also continuously improved. However, the process deviation of the semiconductor chip manufacturing and packaging of the LED display driver chip 13a will cause the parameter deviation of the semiconductor elements constituting the LED display driver chip 13a, resulting in that adjacent LED display driver chips 13a may have different output currents. Therefore, engineers usually add a trimming circuit inside the LED display driver chip 13a to improve the output current accuracy.

FIG. 3 is an exemplary topology diagram of the reference current generating unit 1311a shown in FIG. 2 . As shown in FIG. 3 and FIG. 2 , the conventional reference current generation unit 1311a included in the LED display driver chip 13a includes: an operational amplifier 1314a, a first MOSFET element 1315a, an external resistor R1a, a digital-to-analog converter 1316a, and a trimming circuit 1317a. Further, FIG. 4 is an exemplary topological diagram of the trimming circuit 1317a shown in FIG. 3 . As shown in FIG. 4 and FIG. 3 , the conventional trimming circuit 1317a included in the reference current generating unit 1311a includes: a second MOSFET element 1318a, a fuse resistor R2a, and a readout unit 1319a.

In more detail, the trimming is to use the trimming code and the fuse voltage VFUSE to cause a large current to flow through the second MOSFET element 1318a and enter the fuse resistor R2a, and the fuse resistor R2a will heat up and be blown. Before the fuse resistor R2a is blown, the readout unit 1319a outputs a logic 0; on the contrary, after the fuse resistor R2a is blown, the readout unit 1319a outputs a logic 1. After trimming, the resistance state of the fuse resistor R2a will not change again, so as to ensure that the trimming code will not change due to power failure, which is a non-volatile memory element (Non-Volatile Memory, NVM).

Practical experience shows that the conventional trimming circuit 1317a included in the reference current generating unit 1311a has the following main application defects: (1) When the LED display driver chip 13a is in the working state or in other non-adjusting time, if the input trimming code is sent to the trimming circuit 1317a by mistake, it may cause the output current IOUT to change and affect the luminous brightness of the LED sub-pixel; and (2) In addition, the trimming circuit 1317a needs to provide a large current outside the chip to blow the fuse resistor R2a, but there is no single pin coupled with an external circuit in the general-purpose LED display driver chip 13a to provide a large current to the trimming circuit 1317a.

From the above description, it can be known that a novel trimming circuit is urgently needed in the field.

The main purpose of the present invention is to provide a trimming circuit, which is used in an LED display driver chip, and includes: a logic gate, a peripheral terminal, a trimming unit coupled to the peripheral terminal, and a switch element. If it is necessary to perform trimming processing on the LED display driver chip, a control signal is sent to the switch element, the logic gate and the trimming unit, so that the switch element disconnects the path between the trimming unit and the reference current generating circuit of the LED display driver chip; at this time, a fuse signal is input to the trimming unit through the peripheral terminal, and at the same time, the logic gate transmits an input trimming code to the trimming unit according to the control of the control signal, and the trimming process is completed.

In order to achieve the above object, the present invention proposes an embodiment of the trimming circuit, which is applied to an LED display driver chip, and includes: A logic gate has two input terminals respectively coupled to a control signal and an input trimming code; a peripheral terminal; A trimming unit has a first input terminal, a second input terminal, and an output terminal, wherein the peripheral terminal is coupled to the first input terminal and a reference current generating unit contained in the LED display driver chip, the second input terminal is coupled to the output terminal of the logic gate, and the output terminal is coupled to the reference current generating unit; and A switch element, having a first terminal coupled to an operating voltage, a second terminal coupled to the reference current generating unit, and a control terminal coupled to the control signal; Wherein, during trimming, the switch element is turned off according to the control of the control signal, so that a fuse signal is input to the trimming unit through the peripheral terminal, and at the same time, the logic gate transmits the input trimming code to the trimming unit according to the control of the control signal.

In one embodiment, a peripheral resistor is coupled to the peripheral terminal.

In one embodiment, the logic gate is an OR gate or an AND gate.

In one embodiment, the switching element is any one selected from the group consisting of a P-type MOSFET switch, an N-type MOSFET switch and a CMOS switch.

In one embodiment, the trimming unit includes: An operational amplifier having a positive input terminal, a negative input terminal and an output terminal; a first MOSFET element having a source terminal coupled to the reference current generating unit, a drain terminal and a gate terminal coupled to the output terminal of the operational amplifier; and A second MOSFET element has a source terminal coupled to the drain terminal of the first MOSFET element, a gate terminal coupled to the control signal, and a drain terminal coupled to a common terminal between the peripheral terminal and the peripheral resistor, and the drain terminal is also coupled to the positive input terminal of the operational amplifier.

In one embodiment, the negative input terminal of the operational amplifier is coupled to a digital-to-analog converter, and the digital-to-analog converter generates a second reference voltage according to the input trimming code and a first reference voltage and sends it to the negative input terminal of the operational amplifier.

Moreover, the present invention also proposes an LED display driver chip, which has at least one constant current generating circuit, and the constant current generating circuit includes a reference current generating unit, a current mirroring unit, and a current output unit; it is characterized in that the reference current generating circuit has at least one trimming circuit, and the trimming circuit includes: A logic gate has two input terminals respectively coupled to a control signal and an input trimming code; a peripheral terminal; A trimming unit has a first input terminal, a second input terminal, and an output terminal, wherein the peripheral terminal is coupled to the first input terminal and a reference current generating unit contained in the LED display driver chip, the second input terminal is coupled to the output terminal of the logic gate, and the output terminal is coupled to the reference current generating unit; and A switch element, having a first terminal coupled to an operating voltage, a second terminal coupled to the reference current generating unit, and a control terminal coupled to the control signal; Wherein, during trimming, the switch element is turned off according to the control of the control signal, so that a fuse signal is input to the trimming unit through the peripheral terminal, and at the same time, the logic gate transmits the input trimming code to the trimming unit according to the control of the control signal.

In one embodiment, a peripheral resistor is coupled to the peripheral terminal.

In one embodiment, the logic gate is an OR gate or an AND gate.

In one embodiment, the trimming unit includes: An operational amplifier having a positive input terminal, a negative input terminal and an output terminal; a first MOSFET element having a source terminal coupled to the reference current generating unit, a drain terminal and a gate terminal coupled to the output terminal of the operational amplifier; and A second MOSFET element has a source terminal coupled to the drain terminal of the first MOSFET element, a gate terminal coupled to the control signal, and a drain terminal coupled to a common terminal between the peripheral terminal and the peripheral resistor, and the drain terminal is also coupled to the positive input terminal of the operational amplifier.

In one embodiment, the negative input terminal of the operational amplifier is coupled to a digital-to-analog converter, and the digital-to-analog converter generates a second reference voltage according to the input trimming code and a first reference voltage and sends it to the negative input terminal of the operational amplifier.

Furthermore, the present invention also proposes an LED display device, which includes: an LED display panel, a display control unit, and at least one LED display driver chip of the present invention as described above.

In a feasible embodiment, the LED display panel includes X×Y LED elements, where X and Y are both positive integers, and the LED elements are any one selected from the group consisting of conventional LED elements, quantum dot LED elements, perovskite LED elements, Mirco-LED elements and Mini-LED elements.

In order to enable your examiners to further understand the structure, features, purpose, and advantages of the present invention, drawings and detailed descriptions of preferred specific embodiments are hereby attached.

FIG. 5 shows a structure diagram of an LED display device of the present invention. As shown in FIG. 5 , the LED display device 1 of the present invention includes: an LED display panel 11 , a display control unit 14 and a plurality of LED display driver chips 13 . In particular, the present invention adds at least one trimming circuit to the display driver chip 13, and the trimming circuit is used to trim the reference current I0 generated by the reference current generating unit included in the LED display driver chip 13 according to a trimming code, so as to realize the trimming of the output current of a driving channel of the LED display driver chip 13. In more detail, the LED display driver chip 13 is usually a constant current driver chip, and thus includes at least one constant current generating circuit. FIG. 6 is a block diagram of a constant current generating circuit 131 included in the LED display driver chip 13 shown in FIG. 5 . As shown in FIG. 6 , the constant current generating circuit 131 includes a reference current generating unit 1311 , a current mirroring unit 1312 , a current output unit 1313 and a trimming circuit of the present invention.

As shown in FIG. 6, the trimming circuit of the present invention includes: a logic gate 1318, a peripheral terminal REXT, a trimming unit 1317, and a switch element 1319, wherein the logic gate 1318 is an OR gate or an AND gate, has two input terminals and an output terminal, and the two input terminals are respectively coupled to a control signal and an input trimming code. On the other hand, the trimming unit 1317 has a first input terminal (fuse terminal), a second input terminal (trimming code input terminal), and an output terminal, wherein the peripheral terminal REXT is coupled to the first input terminal of the trimming unit 1317 and the reference current generating unit 1311 of the LED display driver chip 13, the second input terminal is coupled to the output terminal of the logic gate 1318, and the output terminal is coupled to the reference current generating unit 1311. On the other hand, the switching element 1319 has a first terminal coupled to a working voltage VDD, a second terminal coupled to the reference current generating unit 1311 , and a control terminal coupled to the control signal. In a feasible embodiment, the switching element 1319 may be a P-type MOSFET switch, an N-type MOSFET switch or a CMOS switch.

FIG. 7 is a circuit topology diagram of the trimming unit 1317 shown in FIG. 6 . According to FIG. 6 and FIG. 7 , the trimming circuit of the present invention shares the peripheral terminal REXT with the reference current generating unit 1311 , and an external resistor R1 is coupled to the peripheral terminal REXT. In more detail, the trimming unit 1317 includes: an operational amplifier 1314 having a positive input terminal, a negative input terminal and an output terminal, a first MOSFET element 1315 , and a second MOSFET element 1310 . Wherein, the first MOSFET element 1315 has a source terminal coupled to the reference current generating unit 1311 , a drain terminal coupled to the output terminal of the operational amplifier 1314 , and a gate terminal coupled to the output terminal of the operational amplifier 1314 . On the other hand, the second MOSFET element 1310 has a source terminal coupled to the drain terminal of the first MOSFET element 1315 , a gate terminal coupled to a gate control signal, and a drain terminal coupled to a common terminal between the peripheral terminal REXT and the external resistor R1 , and the drain terminal is also coupled to the positive input terminal of the operational amplifier 1314 . Moreover, as shown in FIG. 7 , the DAC 1316 has a first input terminal coupled to a first reference voltage, a second input terminal and an output terminal coupled to the negative input terminal of the operational amplifier 1314 .

According to this design, when the LED display driver chip 13 undergoes the final test (Final test, FT) before leaving the factory, if it is necessary to perform trimming processing on the LED display driver chip 13, a control signal is sent to the switch element 1319 to make the switch element 1319 closed (open), thereby disconnecting the current path from the operating voltage VDD to the first input terminal (Fuse terminal) of the trimming unit 1317 through the reference current generating unit 1311. At the same time, the logic gate 1318 transmits the input trimming code to the trimming unit 1317 according to the control of the control signal, and a fuse signal is input into the trimming unit 1317 through the peripheral terminal REXT to form a drain current in the drain of the second MOSFET element 1310 to flow into the peripheral resistor R1, thereby completing the trimming process and realizing the adjustment of the reference current I0 generated by the reference current generating unit 1311.

During the non-trimming period (or the normal working period of the chip), the control signal controls the switching element 1319 to be turned on (close), so that the working voltage is transmitted to the reference current generating unit 1311 through the switching element 1319, so that the reference current generating unit 1311 works normally. At the same time, the logic gate 1318 stops transmitting the input trimming code to the trimming unit 1317 according to the control of the control signal, so that no trimming action can occur.

In more detail, as shown in FIG. 7 , the negative input terminal and the positive input terminal of the operational amplifier 1314 are respectively coupled to a common node between a digital-to-analog converter 1316 and a drain terminal of the second MOSFET element 1310 and the external resistor R1. In other words, after transmitting a fuse signal (for example: fuse current) to the peripheral terminal REXT, the second MOSFET element 1310 generates a drain current, thereby forming a peripheral reference voltage VEXT between the peripheral resistor R1 and the ground terminal, and the peripheral reference voltage VEXT is transmitted to the positive input terminal of the operational amplifier 1314 . On the other hand, the DAC 1316 has a first input terminal, a second input terminal and an output terminal coupled to the positive input terminal of the operational amplifier 1314, wherein the first input terminal is coupled to a first reference voltage, and the second input terminal is coupled to the input trimming code. During trimming, the digital-to-analog converter 1316 generates a second reference voltage VREF2 according to the input trimming code and the first reference voltage VREF1 and sends it to the negative input terminal of the operational amplifier 1314 .

It is supplemented that, in the case that the LED display driver chip 13 includes K constant current generating circuits, it correspondingly includes K trimming units 1317 . As shown in FIG. 7 , K trimming units 1317 are coupled to the digital-to-analog converter 1316 at the same time. At this time, the input trimming code also includes K bits, and the digital-to-analog converter 1316 generates K second reference voltages VREF2 according to the input trimming code including K bits and the first reference voltage VREF1, and sends them to the negative input terminals of the operational amplifiers 1314 respectively.

In this way, the above has completely and clearly described a trimming circuit of the present invention; and, through the above, it can be known that the present invention has the following advantages:

(1) The present invention discloses a trimming circuit, which is used in an LED display driver chip, and includes: a logic gate, a peripheral terminal, a trimming unit, and a switch element. If it is necessary to perform trimming processing on the LED display driver chip, a control signal is sent to the switch element, the logic gate and the trimming unit, so that the switch element disconnects the path between the trimming unit and the reference current generating circuit of the LED display driver chip; at this time, a fuse signal is input to the trimming unit through the peripheral terminal, and at the same time, the logic gate transmits an input trimming code to the trimming unit according to the control of the control signal, and the trimming process is completed.

(2) The present invention also discloses an LED display device, which includes: an LED display panel, a display control unit, and at least one LED display driver chip of the present invention as described above. In a feasible embodiment, the LED display panel includes X×Y LED elements, where X and Y are both positive integers, and the LED elements are any one selected from the group consisting of conventional LED elements, quantum dot LED elements, perovskite LED elements, Mirco-LED elements and Mini-LED elements.

It must be emphasized that the above-mentioned disclosure in this case is a preferred embodiment. For example, any partial changes or modifications derived from the technical ideas of this case and easily deduced by those who are familiar with the technology are within the scope of the patent right of this case.

To sum up, regardless of the purpose, means and efficacy of this case, it shows that it is very different from the conventional technology, and its first invention is practical, and indeed meets the patent requirements of the invention. I sincerely hope that your review committee will be aware of it, and grant a patent as soon as possible to benefit the society. This is my best prayer.

1a: LED display device 11a: LED display panel 13a: LED display driver chip 14a: Display control unit 131a: Constant current generating circuit 1311a: reference current generating unit 1312a: current mirror unit 1313a: current output unit 1314a: Operational amplifier 1315a: first MOSFET element 1316a: Digital to Analog Converter 1317a: trimming circuit 1318a: Second MOSFET element 1319a: readout unit R1a: Peripheral resistor R2a: Fuse resistor 1: LED display device 11: LED display panel 13: LED display driver chip 14: Display control unit 131: Constant current generating circuit 1311: Reference current generating unit 1312: current mirror unit 1313: Current output unit 1314: Operational Amplifier 1315: The first MOSFET component 1310: second MOSFET element 1316: Digital to Analog Converter 1317: Trimming unit 1318: logic gate 1319: switch element R1: Peripheral resistor REXT: peripheral terminal

FIG. 1 is a structural diagram of a conventional LED display device; FIG. 2 is a block diagram of a constant current generating circuit included in the display driver chip shown in FIG. 1; FIG. 3 is an exemplary topological diagram of the reference current generating unit shown in FIG. 2; FIG. 4 is an exemplary topological diagram of the trimming circuit shown in FIG. 3; 5 is a structural diagram of an LED display device of the present invention; FIG. 6 is a block diagram of a constant current generating circuit included in the LED display driver chip shown in FIG. 5; and FIG. 7 is a circuit topology diagram of the trimming unit shown in FIG. 6 .

131: Constant current generating circuit

1311: Reference current generating unit

1312: current mirror unit

1313: Current output unit

1317: Trimming unit

1318: logic gate

1319: switch element

R1: Peripheral resistor

REXT: peripheral terminal

Claims (11)

A trimming circuit is applied to an LED display driver chip, and includes: a logic gate with two input terminals respectively coupled to a control signal and an input trimming code; a peripheral terminal; a trimming unit with a first input terminal, a second input terminal, and an output terminal, wherein the peripheral terminal is coupled to the first input terminal and a reference current generation unit contained in the LED display driver chip, the second input terminal is coupled to the output terminal of the logic gate, and the output terminal is coupled to the reference current generation unit; A first end connected to a working voltage, a second end coupled to the reference current generating unit, and a control end coupled to the control signal; wherein, during trimming, the switch element is disconnected according to the control of the control signal, so that a fuse signal is input to the trimming unit through the peripheral end, and at the same time, the logic gate transmits the input trimming code to the trimming unit according to the control of the control signal. The trimming circuit according to claim 1, wherein an external resistor is coupled to the external terminal. The trimming circuit according to claim 1, wherein the logic gate is an OR gate or an AND gate. The trimming circuit according to claim 2, wherein the trimming unit includes: an operational amplifier having a positive input terminal, a negative input terminal and an output terminal; A first MOSFET element has a source terminal coupled to the reference current generating unit, a drain terminal and a gate terminal coupled to the output terminal of the operational amplifier; and a second MOSFET element has a source terminal coupled to the drain terminal of the first MOSFET element, a gate terminal coupled to a gate control signal, and a drain terminal coupled to a common terminal between the peripheral terminal and the peripheral resistor, and the drain terminal is also coupled to the positive input terminal of the operational amplifier. The trimming circuit as described in claim 4, wherein the negative input terminal of the operational amplifier is coupled to a digital-to-analog converter, and the digital-analog converter generates a second reference voltage according to the input trimming code and a first reference voltage and sends it to the negative input terminal of the operational amplifier. An LED display driver chip has at least one constant current generation circuit, and the constant current generation circuit includes a reference current generation unit, a current mirror unit, and a current output unit; it is characterized in that the reference current generation unit has at least one trimming circuit, and the trimming circuit includes: a logic gate, with two input terminals respectively coupled to a control signal and an input trimming code; A reference current generating unit contained in the drive chip, the second input terminal is coupled to the output terminal of the logic gate, and the output terminal is coupled to the reference current generating unit; and a switch element has a first terminal coupled to an operating voltage, a second terminal coupled to the reference current generating unit, and a control terminal coupled to the control signal; Wherein, during trimming, the switch element is turned off according to the control of the control signal, so that a fuse signal is input to the trimming unit through the peripheral terminal, and at the same time, the logic gate transmits the input trimming code to the trimming unit according to the control of the control signal. In the LED display driver chip as claimed in claim 6, an external resistor is coupled to the external terminal. The LED display driver chip according to claim 6, wherein the logic gate is an OR gate or an AND gate. The LED display driver chip as described in claim 7, wherein the trimming unit includes: an operational amplifier having a positive input terminal, a negative input terminal and an output terminal; a first MOSFET element having a source terminal coupled to the reference current generating unit, a drain terminal and a gate terminal coupled to the output terminal of the operational amplifier; and a second MOSFET element having a source terminal coupled to the drain terminal of the first MOSFET element, a gate terminal coupled to a gate control signal, and a gate terminal coupled to the output terminal of the operational amplifier. A drain terminal of a common terminal between the peripheral terminal and the peripheral resistor, and the drain terminal is also coupled to the positive input terminal of the operational amplifier. The LED display driver chip as described in Claim 9, wherein the negative input terminal of the operational amplifier is coupled to a digital-to-analog converter, and the digital-analog converter generates a second reference voltage according to the input trimming code and a first reference voltage and sends it to the negative input terminal of the operational amplifier. An LED display device, comprising: an LED display panel, a display control unit and at least one LED display driver chip according to any one of claims 6-10.

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