LED driving circuit and LED driving system

Abstract

The application belongs to the technical field of electronic circuits, and provides an LED driving circuit and an LED driving system. The output resistance module in the driving circuit comprises n switch units and n resistance units, the second input end of the error amplifier module is connected with the first end of the switch module and the n resistance units respectively, the output end of the error amplifier module is connected with the control end of the switch module, the second end of the switch module is connected with the negative electrode of the LED lamp, the n resistance units are connected with the n switch units one by one, and the n switch units are all grounded. The total output impedance of the output resistance module remains constant, the output resistance module determines the number of switch units to be turned on according to the output current of the LED lamp, and then connects the corresponding number of resistance units with the ground. Through the design, the output impedance of the output resistance module is greater than the total output impedance, the current error caused by the mismatch voltage is effectively reduced, and the current control precision and working stability of the display product are significantly improved.

Description

Technical Field

[0001] This application belongs to the field of electronic circuit technology, and in particular relates to an LED driver circuit and an LED driver system. Background Technology

[0002] LEDs (Light Emitting Diodes) are widely used in backlight displays of electronic products such as mobile phones and laptops due to their advantages of being environmentally friendly, energy-saving, highly efficient, and long-lasting. To ensure the normal illumination and basic functions of the backlight display, an LED driver circuit that provides stable current is an essential core component. The LED driver circuit provides stable and compatible current and voltage to the LED, and is a dedicated circuit that ensures constant brightness and long lifespan for the LED. Its core function is to suppress large current fluctuations caused by minute voltage waveforms, while also enabling additional functions such as dimming.

[0003] Current accuracy is a core performance indicator of LED driver circuits, directly determining the consistency and stability of LED brightness. However, current LED driver circuits suffer from excessive current error, which leads to poor brightness consistency in display products, degraded visual effects, and shortened LED lifespan. Summary of the Invention

[0004] This application provides an LED driving circuit and an LED driving system, which can solve the problem of large current error in current LED driving circuits.

[0005] In a first aspect, embodiments of this application provide an LED driving circuit, including an error amplification module, a switching module, and an output resistor module. The output resistor module includes n switching units and n resistor units. The first input terminal of the error amplification module is used to receive a first voltage. The second input terminal of the error amplification module is connected to the first terminal of the switching module and the first terminals of the n resistor units respectively. The voltage on the second input terminal of the error amplification module is a second voltage. The output terminal of the error amplification module is connected to the control terminal of the switching module. The second terminal of the switching module is used to connect to the negative terminal of the LED. The second terminals of the n resistor units are connected one-to-one with the first terminals of the n switching units. The second terminals of the n switching units are all grounded. The total output impedance of the output resistor module remains constant, and n is a natural number greater than 0. The error amplification module is used to output a control signal based on the first voltage and the second voltage; the switching module is used to turn on according to the control signal, so that the output resistor module is connected to the negative terminal of the LED; the output resistor module is used to determine the number of switching units to be turned on according to the output current of the LED, so that the corresponding number of resistor units are connected to ground.

[0006] In one possible implementation of the first aspect, the resistor unit includes a first resistor, a first end of which is connected to a second input terminal of the error amplification module and a first terminal of the switching module, and a second end of the first resistor is connected to a first terminal of the switching unit.

[0007] In one possible implementation of the first aspect, the switching unit includes a first switch, a first terminal of which is connected to a second terminal of the resistor unit, and the second terminal of the first switch is grounded.

[0008] In one possible implementation of the first aspect, the error amplification module includes a first error amplifier, the switching module includes a first switching transistor, a first input terminal of the first error amplifier is used to receive a first voltage, a second input terminal of the first error amplifier is connected to the source of the first switching transistor and the first terminals of n resistor units respectively, the voltage on the second input terminal of the first error amplifier is a second voltage, the output terminal of the first error amplifier is connected to the gate of the first switching transistor, and the drain of the first switching transistor is used to connect to the negative terminal of the LED lamp.

[0009] In one possible implementation of the first aspect, the n switching units are encoded with an n-bit thermometer, and the resistance values ​​of the n resistor units are all the same.

[0010] Secondly, embodiments of this application provide an LED driving system, including a plurality of LEDs and an LED driving circuit as described in any of the first aspects. In the plurality of LED driving circuits, the second terminal of the switching module is connected to the negative terminal of the plurality of LEDs in a one-to-one correspondence, and the positive terminal of the plurality of LEDs receives a first power supply voltage.

[0011] In one possible implementation of the second aspect, the LED driving system further includes multiple digital-to-analog conversion circuits, which are connected one-to-one with the first input terminals of the error amplification modules in the multiple LED driving circuits. The digital-to-analog converter circuit is used to output an analog voltage based on a reference voltage and an m-bit input range, and to filter the analog voltage to obtain a first voltage; where m is a natural number greater than 0.

[0012] In one possible implementation of the second aspect, the digital-to-analog conversion circuit includes a digital-to-analog conversion unit and a filtering unit, wherein the filtering unit is connected to the digital-to-analog conversion unit and the first input terminal of the error amplification module, respectively. The digital-to-analog converter unit is used to output an analog voltage based on the reference voltage and the m-bit input range; the filtering unit is used to filter the analog voltage to obtain a first voltage.

[0013] In one possible implementation of the second aspect, the LED driving system further includes a voltage generation circuit, which is connected to the first input terminal of the error amplification module in each of the plurality of LED driving circuits. The voltage generation circuit is used to output an analog voltage based on a reference voltage and an m-position input level, filter the analog voltage to obtain a filtered analog voltage, and output multiple first voltages based on the filtered analog voltage; where m is a natural number greater than 0.

[0014] In one possible implementation of the second aspect, the voltage generation circuit includes a digital-to-analog converter, a second resistor, a first capacitor, a second error amplifier, a second switch, a third switch, a third resistor, and multiple current mirror branches. Each current mirror branch includes a fourth switch and a fourth resistor. The first terminal of the second resistor is connected to the digital-to-analog converter. The second terminal of the second resistor is connected to the first terminal of the first capacitor and the first input terminal of the second error amplifier. The second input terminal of the second error amplifier is connected to the source of the second switch and the first terminal of the third resistor. The output terminal of the second error amplifier is connected to the gate of the second switch. The drain of the second switch is connected to the drain of the third switch, the gate of the third switch, and the gates of the multiple fourth switches. The source of the third switch and the sources of the multiple fourth switches all receive a second power supply voltage. The drain of the fourth switch is connected to the first terminal of the fourth resistor and the first input terminal of the error amplifier module. The second terminal of the third resistor, the second terminal of the first capacitor, and the second terminal of the multiple fourth resistors are all grounded.

[0015] Thirdly, embodiments of this application provide a display device including the LED driving system described in any one of the second aspects.

[0016] The beneficial effects of the embodiments of this application compared with the prior art are: This application provides an LED driving circuit, including an error amplification module, a switching module, and an output resistor module. The output resistor module includes n switching units and n resistor units. The first input terminal of the error amplification module receives a first voltage. The second input terminal of the error amplification module is connected to the first terminal of the switching module and the first terminals of the n resistor units, respectively. The voltage at the second input terminal of the error amplification module is a second voltage. The output terminal of the error amplification module is connected to the control terminal of the switching module. The second terminal of the switching module is connected to the negative terminal of the LED. The second terminals of the n resistor units are connected one-to-one with the first terminals of the n switching units. The second terminals of the n switching units are all grounded. The total output impedance of the output resistor module remains constant, and n is a natural number greater than 0.

[0017] The error amplification module outputs a control signal based on the first and second voltages. The switching module is used to turn on the LED based on the control signal, connecting the output resistor module to the negative terminal of the LED. The output resistor module determines the number of switching units to be turned on based on the output current of the LED, thereby connecting the corresponding number of resistor units to ground.

[0018] The error amplification module has a mismatch voltage, which causes an error in the output current of the LED. The current error is calculated by dividing the mismatch voltage by the output impedance of the output resistor module. When the total output impedance of the output resistor module remains constant, the output resistor module determines the number of switching units to be turned on based on the output current of the LED, and then connects the corresponding number of resistor units to the output current branch of the LED. Through this design, the output impedance of the output resistor module is made greater than its total output impedance, effectively reducing the current error caused by the mismatch voltage and significantly improving the current control accuracy and operational stability of the display product.

[0019] It is understood that the beneficial effects of the second and third aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a traditional LED driver circuit. Figure 2 This is a schematic diagram of an LED driving circuit provided in one embodiment of this application; Figure 3 This is a circuit connection diagram of an LED driving circuit provided in an embodiment of this application; Figure 4 This is a schematic diagram of the LED lamp output current using binary encoding in this application; Figure 5 This is a schematic diagram of the output current of the LED lamp using the thermometer encoding method in this application; Figure 6 This is a schematic diagram of an LED driving system provided in an embodiment of this application; Figure 7 This is a circuit connection diagram of an LED driving system provided in an embodiment of this application; Figure 8 This is a schematic diagram of an LED driving system provided in another embodiment of this application; Figure 9 This is a schematic diagram of an LED driving system provided in another embodiment of this application; Figure 10 This is a circuit connection diagram of an LED driving system provided in another embodiment of this application; Figure 11 This is a schematic diagram of an LED driving system provided in another embodiment of this application; Figure 12 This is a circuit connection diagram of an LED driving system provided in another embodiment of this application; Figure 13 This is a typical application diagram of this application.

[0022] In the diagram: 1. LED driving system; 10. LED driving circuit; 11. Error amplification module; 12. Switching module; 13. Output resistor module; 131. Switching unit; 132. Resistor unit; 20. Digital-to-analog conversion circuit; 21. Digital-to-analog conversion unit; 22. Filtering unit; 30. Voltage generation circuit. Detailed Implementation

[0023] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0024] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0025] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0026] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if [the described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [the described condition or event] is detected," or "in response to detection of [the described condition or event]."

[0027] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0028] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0029] The structure of a traditional LED driver circuit is as follows: Figure 1 As shown, it mainly consists of a DAC (Digital-to-Analog Converter), an error amplifier EA, resistors, capacitors, and NMOS transistors. In the DAC, VREF is the reference voltage, and rSET... <m:1>The input range is m-bit, and the input range is selected digitally. The reference voltage VREF is divided by resistors to output the analog voltage VDC, where VDC = VREF * (rSET) / (2^(m)), and rSET is the selected range. After the analog voltage VDC is filtered by RC, the first voltage Vp is obtained. The first voltage Vp is used as the positive input voltage of the error amplifier EA. The gate of the NMOS transistor is connected to the output of the error amplifier EA, and the source is connected to the negative input of the error amplifier EA. The voltage at the negative input is the second voltage Vn, where Vn = Vp. Rled is the total output impedance. The output current iLED of the LED is VDC / Rled. To change the output current iLED of the LED, the selected range rSET can be adjusted to change the analog voltage VDC.

[0030] Since the error amplifier EA has a mismatch voltage Voff, Voff=Vp-Vn, then iLED is: (VDC-Voff) / Rled, and the current error is Voff / Rled. No matter how the analog voltage VDC changes, the error will not change significantly.

[0031] To address the aforementioned issues, this application provides an LED driver circuit. In this circuit, when the total output impedance of the output resistor module remains constant, the output resistor module determines the number of switching units to be turned on based on the output current of the LED, and then connects the corresponding number of resistor units to the output current branch of the LED. This design ensures that the output impedance of the output resistor module is greater than its total output impedance, effectively reducing current errors caused by mismatch voltage and significantly improving the current control accuracy and operational stability of the display product.

[0032] To illustrate the technical solution described in this application, specific embodiments are provided below.

[0033] Figure 2 A schematic block diagram of an LED driving circuit 10 according to an embodiment of this application is shown. Figure 2 As shown, the LED driver circuit 10 includes an error amplification module 11, a switching module 12, and an output resistor module 13. The output resistor module 13 includes n switching units 131 and n resistor units 132. The first input terminal of the error amplification module 11 is used to receive a first voltage Vp. The second input terminal of the error amplification module 11 is connected to the first terminal of the switching module 12 and the first terminals of the n resistor units 132, respectively. The voltage on the second input terminal of the error amplification module 11 is a second voltage Vn. The output terminal of the error amplification module 11 is connected to the control terminal of the switching module 12. The second terminal of the switching module 12 is used to connect to the negative terminal of the LED. The second terminals of the n resistor units 132 are connected to the first terminals of the n switching units 131, and the second terminals of the n switching units 131 are all grounded. The total output impedance Rled of the output resistor module 13 remains constant, and n is a natural number greater than 0.

[0034] Specifically, the error amplification module 11 outputs a control signal based on the first voltage Vp and the second voltage Vn. The switching module 12 is turned on according to the control signal, connecting the output resistor module 13 to the negative terminal of the LED. The output resistor module 13 determines the number of switching units 131 to be turned on based on the output current iLED of the LED, thereby connecting the corresponding number of resistor units 132 to ground.

[0035] Because the error amplification module 11 has a mismatch voltage Voff, this mismatch voltage Voff will cause an error in the output current iLED of the LED. The current error is calculated by dividing the mismatch voltage Voff by the output impedance of the output resistor module 13. When the total output impedance Rled of the output resistor module 13 remains constant, the output resistor module 13 determines the number of switching units 131 to be turned on based on the output current iLED of the LED, and then connects the corresponding number of resistor units 132 to the output current branch of the LED. Through this design, the output impedance of the output resistor module 13 is greater than its total output impedance Rled, effectively reducing the current error caused by the mismatch voltage Voff, and significantly improving the current control accuracy and working stability of the display product.

[0036] In one embodiment of this application, such as Figure 3 As shown, the error amplification module 11 includes a first error amplifier EA1, and the switching module 12 includes a first switching transistor M1. The first input terminal of the first error amplifier EA1 is used to receive a first voltage Vp. The second input terminal of the first error amplifier EA1 is connected to the source of the first switching transistor M1 and the first terminals of n resistor units 132, respectively. The voltage at the second input terminal of the first error amplifier EA1 is a second voltage Vn. The output terminal of the first error amplifier EA1 is connected to the gate of the first switching transistor M1, and the drain of the first switching transistor M1 is used to connect to the negative terminal of the LED. In this embodiment, the first input terminal of the first error amplifier EA1 is a positive input terminal, serving as the first input terminal of the error amplification module 11, and the second input terminal of the first error amplifier EA1 is a negative input terminal, serving as the second input terminal of the error amplification module 11. The gate of the first switching transistor M1 serves as the control terminal of the switching module 12, the source of the first switching transistor M1 serves as the first terminal of the switching module 12, and the drain of the first switching transistor M1 serves as the second terminal of the switching module 12. The first switching transistor M1 is an NMOS transistor.

[0037] The switching unit 131 includes a first switch S1, the first end of which is connected to the second end of the resistor unit 132, and the second end of the first switch S1 is grounded. In this embodiment, the first switch S1 is an NMOS transistor with low drain-source on-resistance.

[0038] The resistor unit 132 includes a first resistor R1. The first end of the first resistor R1 is connected to the second input terminal of the error amplifier module 11 and the first end of the switch module 12, respectively. The second end of the first resistor R1 is connected to the first end of the switch unit 131.

[0039] Specifically, the output current iLED of the LED can be changed by adjusting the magnitude of the first voltage Vp; without adjusting the first voltage Vp, the output current iLED of the LED can also be changed by selecting the number of conducting switches S1.

[0040] Currently, the encoding method for the n first switches S1 is binary encoding, such as... Figure 4 As shown, assuming a 3-bit binary encoding is used, this corresponds to three first switches S1. The lowest bit of the first switch S1 outputs 1uA, the next higher bit outputs 2uA, and the highest bit outputs 4uA, achieving current outputs from 1uA to 7uA. However, in practical applications, the higher the bit's current output (e.g., 4uA), the worse the matching becomes, leading to a larger deviation between the higher bit's current output and the ideal current. To solve this problem, the encoding method for the n first switches S1 in this application uses an n-bit thermometer encoding, and the resistance values ​​of the n first resistors R1 are all the same. Compared to binary encoding, thermometer encoding requires 2... a -1 switches, where 'a' corresponds to the number of bits in the binary code. From the least significant bit to the most significant bit, (2... a -1) Each first switch S1 is turned on sequentially, and the output current of each first switch S1 is the same. Furthermore, a subsequent first switch S1 will only turn on after all the preceding first switches S1 have been turned on. Figure 5 As shown, compared to Figure 4 The binary encoding of the thermometer requires the use of 7 first switches S1, each of which outputs 1uA, thus achieving a current output from 1uA to 7uA. At the same time, the maximum current output of each first switch S1 is controlled at 1uA, which improves the matching of the high-order current output, making it deviate less from the ideal current and improving the accuracy of the current output.

[0041] Figure 3 The LED driver circuit 10 shown uses thermometer encoding. The resistance value of each of the n first resistors R1 is Ro, and the total output impedance of the output resistor module 13 is Rled. When the first first switch S1 is turned on, the output impedance of the output resistor module 13 is Ro, and the output current iLED of the LED is Vp / Ro. When all n first switches S1 are turned on, the output impedance of the output resistor module 13 is Ro / n, that is, the total output impedance Rled = Ro / n, and the output current iLED of the LED is Vp*n / Ro = Vp / Rled. Because the first error amplifier EA1 has a mismatch voltage Voff, resulting in Vp-Vn=Voff, when the first first switch S1 is turned on, the output current iLED of the LED is (Vp-Voff) / Ro, and the current error is Voff / Ro=Voff / Rled*n; when the first first switch S1 and the second first switch S1 are turned on, the output current iLED of the LED is 2*(Vp-Voff) / Ro, and the current error is 2Voff / Ro=2Voff / Rled*n; from the formula, it can be seen that when all n first switches S1 are turned on, the output current iLED of the LED is n*(Vp-Voff) / Ro, and the current error is nVoff / Ro=nVoff / Rled*n=Voff / Rled. When the output current iLED of the LED is b / n times the maximum output current (b represents the number of times the first switch S1 is turned on), the current error will be reduced to b / n times the original compared to the traditional structure. Compared to the traditional structure, where the current error will not change no matter how large the output current iLED is, this application can achieve the effect of smaller current error as the output current iLED is smaller.

[0042] This application also provides an LED driving system 1, such as Figure 6 As shown, the LED driving system 1 includes multiple LED lights and multiple LED driving circuits 10. The second terminal of the switching module 12 in the multiple LED driving circuits 10 is connected to the negative terminal of the multiple LED lights one by one, and the positive terminal of the multiple LED lights receives the first power supply voltage.

[0043] Specifically, the LED driving system 1 includes multiple LED driving circuits 10. The first input terminal of the error amplification module 11 in each LED driving circuit 10 is used to receive the first voltage Vp. Currently, the following is adopted: Figure 7 The structure shown generates the first voltage Vp, which is the reference voltage in the DAC, where VREF is the reference voltage and rSET is the reference voltage. <m:1>The input range is m-bit, and the input range is selected digitally. The reference voltage VREF is divided by resistors to output the analog voltage VDC, where VDC = VREF * (rSET) / (2^(m)), and rSET is the selected range. After the analog voltage VDC is filtered by RC, the first voltage Vp required by all error amplifier modules 11 is obtained. Although this saves circuit area, in the layout design, when the same voltage (i.e., the first voltage Vp) is output to multiple error amplifier modules 11, the trace lengths vary greatly, which will introduce different parasitic resistances and capacitances to each error amplifier module 11. This will cause a large difference in the mismatch voltage of multiple error amplifier modules 11, which in turn will cause the current values ​​of multiple LEDs to be inconsistent, ultimately resulting in uneven brightness on the screen. To solve this problem, this application proposes... Figure 8 The structure shown is as follows: Figure 8 As shown, the LED driving system 1 also includes multiple digital-to-analog conversion circuits 20, which are connected one-to-one with the first input terminals of the error amplification modules 11 in the multiple LED driving circuits 10.

[0044] Specifically, the digital-to-analog converter circuit 20 is used to determine the reference voltage VREF and the m-bit input level rSET. <m:1>The analog voltage VDC is output, and the first voltage Vp is obtained by filtering the analog voltage VDC. Here, m is a natural number greater than 0.

[0045] As can be seen from the above, this application sets up multiple digital-to-analog conversion circuits 20, each of which outputs a first voltage Vp to its corresponding error amplification module 11. In the layout design, arranging each error amplification module 11 and its corresponding digital-to-analog conversion circuit 20 close together can shorten the trace length from the digital-to-analog conversion circuit 20 to the error amplification module 11, thereby improving the matching between different LED driving circuits 10 and achieving uniform screen brightness.

[0046] like Figure 9 As shown, the digital-to-analog converter circuit 20 includes a digital-to-analog converter unit 21 and a filter unit 22. The filter unit 22 is connected to the first input terminal of the digital-to-analog converter unit 21 and the error amplifier module 11, respectively.

[0047] Specifically, the digital-to-analog converter 21 is used to determine the reference voltage VREF and the m-bit input range rSET. <m:1>The output is an analog voltage VDC. The filter unit 22 is used to filter the analog voltage VDC to obtain the first voltage Vp.

[0048] like Figure 10 As shown, the digital-to-analog converter unit 21 includes a DAC, in which VREF is the reference voltage and rSET is the input voltage. <m:1>For m-bit input ranges, the input range is selected digitally. The reference voltage VREF is divided by resistors to output an analog voltage VDC, where VDC = VREF * (rSET) / (2^(m)), and rSET is the selected range.

[0049] like Figure 10 As shown, the filter unit 22 includes resistors and capacitors. After the analog voltage VDC is filtered by RC, the first voltage Vp is obtained.

[0050] It should be noted that in practical applications, the first voltage Vp required by multiple error amplification modules 11 is usually the same value; in special application scenarios, the first voltage Vp required by multiple error amplification modules 11 can be set to different values.

[0051] Figure 8 The structure shown results in a large layout area. To address this issue, this application proposes... Figure 11 The structure shown is as follows: Figure 11 As shown, the LED driving system 1 also includes a voltage generation circuit 30, which is connected to the first input terminal of the error amplification module 11 in the plurality of LED driving circuits 10.

[0052] Specifically, the voltage generation circuit 30 is used to generate voltages based on the reference voltage VREF and the m-bit input level rSET. <m:1>The system outputs an analog voltage VDC, filters it to obtain a filtered analog voltage, and then outputs multiple first voltages Vp based on the filtered analog voltage. Here, m is a natural number greater than 0.

[0053] like Figure 12 As shown, the voltage generation circuit 30 includes a digital-to-analog converter (DAC), a second resistor R2, a first capacitor C1, a second error amplifier EA2, a second switch M2, a third switch M3, a third resistor R3, and multiple current mirror branches. Each current mirror branch includes a fourth switch M4 and a fourth resistor R4. The first terminal of the second resistor R2 is connected to the DAC, and the second terminal of the second resistor R2 is connected to the first terminal of the first capacitor C1 and the first input terminal of the second error amplifier EA2. The second input terminal of the second error amplifier EA2 is connected to the source of the second switch M2 and the third resistor R4. The first terminal of R3 is connected, the output terminal of the second error amplifier EA2 is connected to the gate of the second switch M2, the drain of the second switch M2 is connected to the drain of the third switch M3, the gate of the third switch M3, and the gates of the plurality of fourth switches M4, respectively. The source of the third switch M3 and the sources of the plurality of fourth switches M4 all receive the second power supply voltage VDD. The drain of the fourth switch M4 is connected to the first terminal of the fourth resistor R4 and the first input terminal of the error amplifier module 11, respectively. The second terminal of the third resistor R3, the second terminal of the first capacitor C1, and the second terminal of the plurality of fourth resistors R4 are all grounded. In this embodiment, the first input terminal of the second error amplifier EA is the positive input terminal, and the second input terminal of the second error amplifier EA is the negative input terminal.

[0054] Specifically, the analog voltage VDC is first output through the DAC, then filtered by resistors and capacitors to output a filtered analog voltage. According to the circuit connection structure of the second error amplifier EA2, this filtered analog voltage will generate a current in the third resistor R3. This current is replicated by multiple current mirrors and outputs multiple first voltages Vp across multiple fourth resistors R4. Figure 8 Compared to the structure shown, this structure significantly saves circuit area.

[0055] Figure 13 A typical application example of LED driver system 1 is shown. For example... Figure 13 As shown, there are two LEDs, and the first voltage Vp is generated using... Figure 10 The structure shown includes two digital-to-analog converter circuits 20. The first inductor L1, input capacitor CIN, output capacitor COUT, equivalent series resistance RESR, fifth switch M5, and first diode D1 form a BOOST boost circuit, converting the input voltage VIN into an output voltage VOUT to power two LEDs. The first feedback voltage VFB1 is the feedback voltage of the output voltage VOUT after passing through the first LED, and the second feedback voltage VFB2 is the feedback voltage of the output voltage VOUT after passing through the second LED. The first and second feedback voltages VFB1 and VFB2 are filtered by a voltage filtering circuit to select the lower voltage as the target feedback voltage VFB. The target feedback voltage VFB contains information about the change in the output voltage VOUT. This, along with the set voltage VSAT, is output via a bootstrap error amplifier BST_EA, which outputs a voltage signal indicating the deviation of the output voltage VOUT from the target value. Calibration is performed through BOOST loop feedback adjustment. The BOOST boost circuit, combined with the LED driver system 1, outputs a high-precision LED current by adjusting the conduction of rSET and n first switches S1.

[0056] This application also provides a display device, including the LED driving system described above. Since the display device provided in this application adopts all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be elaborated upon here.

[0057] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0058] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. An LED driving circuit, characterized in that, The system includes an error amplification module, a switching module, and an output resistor module. The output resistor module comprises n switching units and n resistor units. The first input terminal of the error amplification module is used to receive a first voltage. The second input terminal of the error amplification module is connected to the first terminal of the switching module and the first terminals of the n resistor units, respectively. The voltage on the second input terminal of the error amplification module is a second voltage. The output terminal of the error amplification module is connected to the control terminal of the switching module. The second terminal of the switching module is used to connect to the negative terminal of the LED. The second terminals of the n resistor units are connected one-to-one with the first terminals of the n switching units. The second terminals of the n switching units are all grounded. The total output impedance of the output resistor module remains constant, and n is a natural number greater than 0. The error amplification module is used to output a control signal based on the first voltage and the second voltage; the switching module is used to turn on according to the control signal, so that the output resistor module is connected to the negative terminal of the LED; the output resistor module is used to determine the number of switching units to be turned on according to the output current of the LED, and then connect the corresponding number of resistor units to ground, so that the output impedance of the output resistor module is greater than its total output impedance, effectively reducing the current error caused by the mismatch voltage; The resistor unit includes a first resistor, the first end of which is connected to the second input terminal of the error amplification module and the first terminal of the switching module, and the second end of the first resistor is connected to the first terminal of the switching unit. The switching unit includes a first switch, a first end of the first switch is connected to a second end of the resistor unit, and the second end of the first switch is grounded. The n switching units are coded with an n-bit thermometer, and the resistance values ​​of the n resistor units are all the same. The resistance of each of the n first resistors is Ro, and the total output impedance of the output resistor module is Rled. When the first switch is turned on, the output impedance of the output resistor module is Ro, and the output current iLED of the LED is Vp / Ro. When all n first switches are turned on, the output impedance of the output resistor module is Ro / n, that is, the total output impedance Rled = Ro / n, and the output current iLED of the LED is Vp. n / Ro=Vp / Rled. Due to the mismatch voltage Voff in the error amplifier module, Vp-Vn=Voff. When the first switch is turned on, the output current iLED of the LED is (Vp-Voff) / Ro, and the current error is Voff / Ro=Voff / (Rled). When the first and second switches are turned on, the output current iLED of the LED is 2. (Vp-Voff) / Ro, current error is (2Voff) / Ro=(2Voff) / (Rled) As shown in the formula, when all n first switches are turned on, the output current iLED of the LED is n. (Vp-Voff) / Ro, current error is (nVoff) / Ro=(nVoff) / (Rled) n) = Voff / Rled. When the output current iLED of the LED lamp is b / n times the maximum output current, the current error will be reduced to b / n times the original compared with the traditional structure. Where b represents the number of the first switch on; Vp represents the first voltage; and Vn represents the second voltage.

2. The LED driving circuit according to claim 1, characterized in that, The error amplification module includes a first error amplifier, and the switching module includes a first switching transistor. The first input terminal of the first error amplifier is used to receive a first voltage. The second input terminal of the first error amplifier is connected to the source of the first switching transistor and the first terminals of n resistor units, respectively. The voltage on the second input terminal of the first error amplifier is a second voltage. The output terminal of the first error amplifier is connected to the gate of the first switching transistor, and the drain of the first switching transistor is used to connect to the negative terminal of the LED.

3. An LED driving system, characterized in that, It includes multiple LED lights and multiple LED driving circuits as described in any one of claims 1-2, wherein the second terminal of the switching module in the multiple LED driving circuits is connected to the negative terminal of the multiple LED lights one by one, and the positive terminal of the multiple LED lights receives the first power supply voltage. The LED driving system also includes a voltage generation circuit, which is connected to the first input terminal of the error amplification module in each of the multiple LED driving circuits. The voltage generation circuit is used to output an analog voltage based on a reference voltage and an m-position input level, filter the analog voltage to obtain a filtered analog voltage, and output multiple first voltages based on the filtered analog voltage; where m is a natural number greater than 0. The voltage generation circuit includes a digital-to-analog converter, a second resistor, a first capacitor, a second error amplifier, a second switch, a third switch, a third resistor, and multiple current mirror branches. Each current mirror branch includes a fourth switch and a fourth resistor. The first terminal of the second resistor is connected to the digital-to-analog converter. The second terminal of the second resistor is connected to the first terminal of the first capacitor and the first input terminal of the second error amplifier. The second input terminal of the second error amplifier is connected to the source of the second switch and the first terminal of the third resistor. The output terminal of the second error amplifier is connected to the gate of the second switch. The drain of the second switch is connected to the drain of the third switch, the gate of the third switch, and the gates of the multiple fourth switches. The source of the third switch and the sources of the multiple fourth switches all receive a second power supply voltage. The drain of the fourth switch is connected to the first terminal of the fourth resistor and the first input terminal of the error amplifier module. The second terminal of the third resistor, the second terminal of the first capacitor, and the second terminal of the multiple fourth resistors are all grounded. The analog voltage is output through a digital-to-analog converter, and after being filtered by resistors and capacitors, the filtered analog voltage is output. According to the circuit connection structure of the second error amplifier, the filtered analog voltage will generate a current in the third resistor. After being replicated by multiple current mirrors, the current will output multiple first voltages in multiple fourth resistors.

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