LED driving circuit

Abstract

The present invention relates to an LED driving circuit, which includes a current trap, a comparator, a control module, a power supply module and a sampling circuit. The current trap includes a first resistor, an error amplifier, a switching module, a fourth transistor, a sixth transistor and a second resistor. The sampling circuit includes a first current source, a first transistor, a second transistor, a third transistor, a fifth transistor and a third resistor. The switching module is used to periodically turn on and off through a pulse width modulation signal, so that the gate of the fourth transistor is periodically connected to and disconnected from the output terminal of the error amplifier. The control module is used to output a control signal to the power supply module according to the output signal of the comparator, so as to adjust the output voltage of the power supply module through the control signal. In the LED driving circuit of the present invention, the trap voltage of the current trap can follow the change of its minimum trap voltage and always maintain a small gap with the minimum trap voltage, thereby reducing power consumption and improving driving efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of LED driving, and more particularly to an LED driving circuit. Background Art

[0002] As a new type of light source, the LED light source is widely used in various industries due to its characteristic of directly converting electrical energy into light, such as automotive electronics, household appliances, and consumer electronic products. Since the LED light emits light with a relatively fast response, a specific driving circuit is required to control its current and thus control its light emission brightness.

[0003] As Figure 1 shown, the existing LED driving circuit includes a current sink 10, a voltage supply circuit 20, a comparator 30, a control module 40, and a power supply module 50. The current sink 10 is used to configure the current of the LED lamp string 60, i.e., the sink current I sink. The current sink 10 includes a first current source 11, a resistor R10, an error amplifier EA, a switch module 12, a transistor M10, a transistor M20, and a resistor R20. The voltage supply circuit 20 includes a second current source 21 and a variable resistor R30. The second current source 21 is used to provide a current I2, and the resistance value of the variable resistor R30 can be changed as needed. Thus, the voltage V HEADROOM output by the voltage supply circuit 20 = I2 × R30 can also be variable. The LED lamp string 60 is formed by a plurality of LED lamps 61 connected in series in sequence. The positive pole of the LED lamp string 60 is connected to the power supply module 50, and the negative pole of the LED lamp string 60 is connected to the drain of the transistor M2 and forms an OUT terminal. The OUT terminal is connected to the inverting input terminal of the comparator 30. The voltage V OUT at the OUT terminal is the sink voltage. In order to enable the LED lamp string 60 to operate normally, it is necessary to make VOUT greater than the minimum sink voltage, i.e., V OUT >Isink × (REP M10 +REP M20 +R20), where REP M10 and REP M20 are the on-resistances of the transistor M10 and the transistor M20 respectively; the comparator 30 is used to output a high or low level signal according to the comparison result of V HEADROOM and V OUT . The control module 40 is used to control the magnitude of the voltage V LED output by the power supply module 50 according to the high or low level signal output by the comparator 30, thereby changing the magnitude of V OUT , until V OUT is greater than a preset V HEADROOM , so that the LED lamp string 60 can be lit.

[0004] In actual use, there are multiple strings of LED lamp strings 60, and each LED lamp string 60 is equipped with a driving circuit. The corresponding LED lamp string 60 is driven to light up by this driving circuit, and all the driving circuits share a voltage supply circuit 20, that is, they share a V HEADROOM , but even if the current sink 10 supplies the same Isink current to each string of LED lamp strings 60, due to the influence of various factors such as process, temperature, and voltage, the minimum well voltage of each current sink 10 is not the same. To light up each LED lamp string 60, it is necessary to make V HEADROOM large enough so that the well voltage V OUT of each current sink is greater than the maximum value of the minimum well voltages of all current sinks 10. However, the minimum well voltages corresponding to each LED lamp string 60 vary greatly. Therefore, the difference between V OUT of the circuit with the lowest minimum well voltage and the minimum well voltage is large, resulting in increased power consumption and lower driving efficiency. Summary of the Invention

[0005] The object of the present invention is to provide an LED driving circuit, in which the well voltage of the current sink can follow the change of its minimum well voltage, so that the difference between the well voltage and the minimum well voltage is always small, thereby reducing power consumption and improving driving efficiency.

[0006] For the above purposes, the present invention provides an LED driving circuit, including a current trap, a comparator, a control module, a power supply module, and a sampling circuit. The current trap includes a first resistor, an error amplifier, a switching module, a fourth transistor, a sixth transistor, and a second resistor. The sampling circuit includes a first current source, a first transistor, a second transistor, a third transistor, a fifth transistor, and a third resistor. One end of the first current source is grounded, and the other end of the first current source is connected to the drain, gate of the first transistor, the gate of the second transistor, and the gate of the third transistor respectively. The source of the first transistor, the source of the second transistor, and the source of the third transistor are connected to the power supply voltage respectively. The drain of the second transistor, one end of the first resistor, and the inverting input terminal of the error amplifier are connected to each other, and the other end of the first resistor is grounded; the output terminal of the error amplifier is connected to one end of the switching module, the other end of the switching module is connected to the gate of the fourth transistor, the source of the fourth transistor, one end of the second resistor, and the non-inverting input terminal of the error amplifier are connected to each other, and the other end of the second resistor is grounded; the drain of the fourth transistor, the source of the sixth transistor, and the inverting input terminal of the comparator are connected to each other, the gate of the sixth transistor is connected to the power supply voltage, the drain of the sixth transistor is connected to the negative electrode of the LED string, the drain of the third transistor, the drain of the fifth transistor, and the non-inverting input terminal of the comparator are connected to each other, the gate of the fifth transistor is connected to the power supply voltage, the source of the fifth transistor is connected to one end of the third resistor, and the other end of the third resistor is grounded; the output terminal of the comparator is connected to one end of the control module, the other end of the control module is connected to the power supply module, and the other end of the power supply module is connected to the positive electrode of the LED string;

[0007] The switching module is used to achieve periodic on and off through a pulse width modulation signal, so that the gate of the fourth transistor is periodically connected and disconnected from the output terminal of the error amplifier; the control module is used to output a control signal to the power supply module according to the output signal of the comparator, so as to adjust the output voltage of the power supply module through the control signal.

[0008] Further, when the output signal of the comparator is at a high level, the control signal raises the output voltage of the power supply module; when the output signal of the comparator is at a low level, the control signal keeps the output voltage of the power supply module stable.

[0009] Further, the proportional coefficient of the current mirror formed by the first transistor and the second transistor is 1.

[0010] Further, the fourth transistor and the fifth transistor satisfy the following relational expression:

[0011] (K2 / K1)× (REP M5 +R3)=(R1 / R2)×(REP M4 +R2),

[0012] wherein, K1 is the proportionality coefficient of the current mirror formed by the first transistor and the second transistor, K2 is the proportionality coefficient of the current mirror formed by the first transistor and the third transistor, REP M5 is the on-resistance of the fifth transistor, REP M4 is the on-resistance of the fourth transistor, R3 is the resistance value of the third resistor, and R2 is the resistance value of the second resistor.

[0013] Further, the switching module is a transistor. The source of the switching module is connected to the output terminal of the error amplifier. The drain of the switching module is connected to the gate of the fourth transistor. The gate of the switching module is connected to the pulse width modulation signal.

[0014] Further, the LED string includes a plurality of LED lamps which are connected in series in sequence. The positive electrode of the first LED lamp forms the positive electrode of the LED string, and the negative electrode of the last LED lamp forms the negative electrode of the LED string.

[0015] Further, the power supply module includes a Boost boost circuit and a voltage regulating circuit. The voltage regulating circuit includes a main path, a plurality of branch paths, a fourth resistor, and a fifth resistor. The main path includes a second current source and a seventh transistor. Each branch path includes an eighth transistor and a switch. One end of the second current source is connected to the power supply voltage. The other end of the second current source is respectively connected to the drain of the seventh transistor, the gate of the seventh transistor, and the gates of the eighth transistors of each branch path. The source of the seventh transistor is grounded. The sources of the eighth transistors of each branch path are all grounded. The drain of the eighth transistor of each branch path is connected to one end of the switch of that branch path. The other ends of the switches of each branch path, one end of the fourth resistor, one end of the fifth resistor, and the feedback voltage point of the Boost boost circuit are connected to each other. The other end of the fourth resistor is grounded. The other end of the fifth resistor is connected to the output terminal of the Boost boost circuit and then forms the output terminal of the power supply module. The control module is respectively connected to the switches of each branch path and is used to control the conduction and cutoff of the switches of each branch path through the control signal.

[0016] Further, the eighth transistor of each branch path and the seventh transistor form a current mirror to copy the current on the main path to that branch path; the current of each branch path is the same as the current of the main path.

[0017] Further, when the output signal of the comparator is at a high level, the control signal increases the number of turned-on switches in each branch to raise the output voltage of the power supply module; when the output signal of the comparator is at a low level, the control signal keeps the number of turned-on switches in each branch unchanged to keep the output voltage of the power supply module stable.

[0018] Further, the comparator is set to be turned on and output a signal only when the error amplifier is connected to the gate of the fourth transistor. Description of the Drawings

[0019] Figure 1 is a schematic structural diagram of an existing LED driving circuit;

[0020] Figure 2 is a schematic structural diagram of an LED driving circuit according to an embodiment of the present invention;

[0021] Figure 3 is a schematic structural diagram of a power supply module of an LED driving circuit according to an embodiment of the present invention. Detailed Embodiment

[0022] The following will give and describe in detail the preferred embodiments of the present invention in conjunction with the accompanying drawings.

[0023] Such as Figure 2As shown in the figure, an embodiment of the present invention provides an LED driving circuit, which includes a current trap 100, a comparator 200, a control module 300, a power supply module 400, and a sampling circuit. The current trap 100 includes a first resistor R1, an error amplifier EA, a switching module 110, a fourth transistor M4, a sixth transistor M6, and a second resistor R2. The sampling circuit includes a first current source 500, a first transistor M1, a second transistor M2, a third transistor M3, a fifth transistor M5, and a third resistor R3. One end of the first current source 500 is grounded, and the other end of the first current source 500 is connected to the drain, gate of the first transistor M1, the gate of the second transistor M2, and the gate of the third transistor M3 respectively. The source of the first transistor M1, the source of the second transistor M2, and the source of the third transistor M3 are connected to the power supply voltage VDD respectively. The drain of the second transistor M2, one end of the first resistor R1, and the inverting input terminal of the error amplifier EA are connected to each other. The other end of the first resistor R1 is grounded. The output terminal of the error amplifier EA is connected to one end of the switching module 110. The other end of the switching module 110 is connected to the gate of the fourth transistor M4. The source of the fourth transistor M4, one end of the second resistor R2, and the non-inverting input terminal of the error amplifier EA are connected to each other. The other end of the second resistor R2 is grounded. The drain of the fourth transistor M4, the source of the sixth transistor M6, and the inverting input terminal of the comparator 200 are connected to each other. The gate of the sixth transistor M6 is connected to the power supply voltage VDD. The drain of the sixth transistor M6 is connected to the negative electrode of the LED string 600, and forms the OUT point of the current trap 100. The voltage of the OUT point is V OUT , the drain of the third transistor M3, the drain of the fifth transistor M5, and the non-inverting input terminal of the comparator 200 are connected to each other. The voltage input to the non-inverting input terminal of the comparator 200 is V HEADROOM , the gate of the fifth transistor M5 is connected to the power supply voltage VDD. The source of the fifth transistor M5 is connected to one end of the third resistor R3. The other end of the third resistor R3 is grounded; the output terminal of the comparator 200 is connected to one end of the control module 300. The other end of the control module 300 is connected to one end of the power supply module 400. The other end of the power supply module 400 is connected to the positive electrode of the LED string 600, and is used to provide the power supply voltage V LED to the LED string 600. The first current source 500 is used to provide a current I REF . By forming a current mirror with the first transistor M1 and the second transistor M2, the current I REF can be copied to generate a current I REF1 . By forming a current mirror with the first transistor M1 and the third transistor M3, the current I REF can be copied to generate a current I REF2 . I REF1 flows into the first resistor R1 to generate V REF , that is, VREF = I REF1 × R1, V REF is the voltage input to the inverting input terminal of the error amplifier EA. The voltage input to the non-inverting input terminal of the error amplifier EA is V FB1 , the current provided by the current sink 100 is Isink, so the current flowing through R2 is also Isink, then V FB1 = Isink × R2. The error amplifier EA is used to make V FB1 equal to V REF , then there is V REF == I REF1 × R1 = V FB1 = Isink × R2, so Isink = (R1 / R2) × I REF1 , I REF1 is determined by the current mirror ratio of the current mirror composed of IREF, the first transistor M1 and the second transistor M2. When the two are determined, the value of I REF1 is also determined. At this time, by adjusting the value of R1 / R2, the value of Isink can be changed, so as to freely configure the current of the LED string 600; the switch module 110 is used to realize periodic on and off through a pulse width modulation signal, so that the gate of the fourth transistor M4 is periodically connected and disconnected from the output terminal of the error amplifier EA. When the gate of the fourth transistor M4 is connected to the output terminal of the error amplifier EA, the fourth transistor M4 will conduct. When the gate of the fourth transistor M4 is disconnected from the output terminal of the error amplifier EA, the fourth transistor M4 will turn off. Thus, the on and off of the fourth transistor M4 can be controlled by the duty cycle of the pulse width modulation signal, so as to realize the dimming of the LED string 600; the control module 300 is used to output a control signal to the power supply module 400 according to the output signal of the comparator 200. The control signal is used to control the power supply module 400 to adjust its output voltage V LED , when the voltage V DSAT at the inverting input terminal of the comparator 200 is less than V HEADROOM , the comparator 200 will output a high level. The control signal generated by the control module 300 according to the high level signal will make the power supply module 400 raise V LED , that is, output a higher V LED . When V LED increases, V OUT and V DSAT will also increase. As V DSAT increases to be greater than V HEADROOM , the comparator 200 will output a low level. The control signal generated by the control module 300 according to the low level signal will make the power supply module 400 no longer raise V LED , but keep it stable. Thus, V OUT and V DSATwill also remain stable, i.e., the control module 300 can make V DSAT gradually increase and remain at a stable value higher than V HEADROOM . Since V OUT ≥V DAST , when V DSAT is higher than V HEADROOM , V OUT will be higher than the minimum well voltage of the current well 100, and the LED string 600 can be lit. By inputting VDSAT instead of VOUT into the comparator 200, the process variation of the on-resistance of the transistor M6 can be avoided from affecting the lighting of the LED string 600.

[0024] According to Figure 2 , it can be known that: V HEADROOM =I REF2 ×(REP M5 +R3), where REP M5 is the on-resistance of the transistor M5.

[0025] The minimum value of VDSAT required to enable the LED string 600 to be lit is:

[0026] (V DSAT ) min =Isink×(REP M4 +R2)=(R1 / R2)×I REF1 ×(REP M4 +R2), where REP M4 is the on-resistance of the transistor M4.

[0027] To enable the LED string 600 to be lit, it is necessary to make V HEADROOM =(V DSAT ) min , that is, it is necessary to make:

[0028] I REF2 ×(REP M5 +R3)=(R1 / R2)×I REF1 ×(REP M4 +R2), that is, (I REF2 / I REF1 )× (REP M5 +R3)=(R1 / R2)×(REP M4 +R2).

[0029] In some embodiments, the transistors M4, M5 and the resistors R2 and R3 can be preset to satisfy: REP M4 ×R3 / R2=REP M5 , in this way, the equation satisfied for enabling the LED string 600 to be lit can be simplified to: (IREF2 / I REF1 )×(R3 / R2)=R1 / R2。

[0030] Among them, I REF2 / I REF1 is determined by the current mirror ratio of M1 and M2 (i.e., the proportionality coefficient of the current mirror) and the current mirror ratio of M1 and M3. Assuming that K1 is the current mirror ratio of M1 and M2, and K2 is the current mirror ratio of M1 and M3, then I REF2 / I REF1 =K2 / K1; R EPM5 and R EPM4 are the inherent parameters of transistors M5 and M4 respectively. Therefore, by presetting the parameters of M1, M2, M3, M4 and M5 and the values of R1, R2 and R3, V HEADROOM =(V DSAT ) min , and no matter how (V DSAT ) min changes, V HEADROOM can be equal to it, that is, V HEADROOM can also change with (V DSAT ) min , so that V DSAT is always greater than (V DSAT ) min and the gap between the two is small. In this way, all the LED strings 600 can be fully lit, and V DSAT will not be too large, thereby reducing power consumption and improving efficiency. When there are multiple LED strings 600, V DSAT of the driving circuit of each LED string 600 will change with (V DSAT ) min and the two maintain a small gap.

[0031] In some embodiments, the current mirror ratio of the current mirror formed by the first transistor M1 and the second transistor M2 can be set to 1 by setting the parameters of the first transistor M1 and the second transistor M2, that is, making I REF1 =I REF .

[0032] In some embodiments, the switch module 110 can be a transistor, the source and drain of which are respectively connected to the output terminal of the error amplifier EA and the gate of the fourth transistor M4, and its gate is connected to the pulse width modulation signal, and the conduction or cutoff of the switch module 110 is controlled by the pulse width modulation signal.

[0033] In some embodiments, the LED string 600 is formed by sequentially connecting a plurality of LED lights 610 in series end to end. The positive electrode of the first LED light 610 is formed as the positive electrode of the LED string 600, and the negative electrode of the last LED light 610 is formed as the negative electrode of the LED string.

[0034] As Figure 3 shown, the power supply module 400 includes a Boost boost circuit 410 and a voltage regulating circuit. The voltage regulating circuit includes a main path, a plurality of branches, a fourth resistor R4, and a fifth resistor R5. The main path includes a second current source 420 and a seventh transistor M7. Each branch includes an eighth transistor M8 and a switch S. One end of the second current source 420 is connected to the power supply voltage VDD, and the other end of the second current source 420 is respectively connected to the drain of the seventh transistor M7, the gate of the seventh transistor M7, and the gates of the eighth transistors M8 of each branch. The source of the seventh transistor M7 is grounded. The source of each eighth transistor M8 of each branch is grounded. The drain of each eighth transistor M8 of each branch is connected to one end of the switch S of the corresponding branch. The other end of the switch S of each branch, one end of the fourth resistor R4, one end of the fifth resistor R5, and the feedback voltage point FB2 of the Boos boost circuit 410 are interconnected. The other end of the fourth resistor R4 is grounded. The other end of the fifth resistor R5 is connected to the output end of the Boost boost circuit 410 and then forms the output end of the power supply module 400 for outputting V LED , the control module 300 is respectively connected to the switches S of each branch and is used to control the conduction and cut-off of each switch S according to the high and low level signals output by the comparator 200; the second current source 420 is used to provide a reference current I1, that is, to make the current on the main path be I1. Each eighth transistor M8 of each branch and the seventh transistor M7 form a current mirror to copy the current I1 on the main path to the branch. For example, the current mirror ratio can be set to 1 so that the current on each branch is also I1. The current flowing through the fifth resistor R5 is I2, I2 = n × I1, where n is the number of conducting branches (that is, the number of branches where the switch S is in the conducting state), V LED =V FB2 ×(1 + R5 / R4)+I2×R5, where V FB2 is the voltage at FB2. Therefore, by changing the conduction and cut-off of the switch S on the control branch, the number of conducting branches can be changed, thereby changing the value of I2, and further changing V LED , the more the number of conducting branches, the larger I2, and the larger V LED will be. When the control module 300 receives the high level signal output by the comparator 200, the number of conducting switches S can be increased, thereby raising V LED ; the control module 300 can be set to make a preset number (for example, 1) of additional switches S conduct each time a high level signal is received, thereby gradually raising VLED ; When the control module 300 receives the low-level signal output by the comparator 200, the control module 300 no longer turns the switch S on and off, so that I2 is maintained at the current value, and V LED also remains at the current value.

[0035] In some embodiments, the control module 300 can be a digital-to-analog converter, which can convert the high and low level signals output by the comparator 200 into a DAC (digital-to-analog conversion) code to adjust V LED , for example, when the comparator 200 outputs a high level, the control module 300 will increase I2 by increasing the DAC code within a fixed period, thereby raising V LED , if the increased current I2 is not sufficient to make the output of the comparator 200 become low level, continue to increase the DAC code to continue raising V LED , until the output of the comparator 200 becomes low level.

[0036] The Boost boost circuit 410 can adopt any existing boost circuit, and its specific structure and working principle are well known in the art and will not be elaborated here.

[0037] In some embodiments, the comparator 200 is set to be turned on and output a signal only when the pulse width modulation signal is high (that is, when the error amplifier EA is connected to the gate of the fourth transistor M4), so as to save circuit power consumption.

[0038] In the LED driving circuit according to the embodiment of the present invention, by setting the parameters of M1, M2, M3, M4 and M5 and the values of R1, R2 and R3, V HEADROOM can follow (V DSAT ) min and change together, and always remain equal, so that V DSAT is always greater than (V DSAT ) min and the gap between the two is small, so that all the LED strings 600 can be lit, and V DSAT will not be too large, thereby reducing power consumption and improving efficiency.

[0039] The above are only the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. The above embodiments of the present invention can also make various changes. That is, all simple, equivalent changes and modifications made according to the claims and the content of the specification of the present invention application fall within the scope of the claims of the present invention patent. What is not described in detail in the present invention is all conventional technical content.

Claims

1. An LED driving circuit, characterized in that: The invention comprises a current sink, a comparator, a control module, a power supply module and a sampling circuit, wherein the current sink comprises a first resistor, an error amplifier, a switch module, a fourth transistor, a sixth transistor and a second resistor, and the sampling circuit comprises a first current source, a first transistor, a second transistor, a third transistor, a fifth transistor and a third resistor, wherein one end of the first current source is grounded, and the other end of the first current source is respectively connected to the drain of the first transistor, the gate of the first transistor, the gate of the second transistor and the gate of the third transistor, the source of the first transistor, the source of the second transistor and the source of the third transistor are respectively connected to a power supply voltage, the drain of the second transistor, one end of the first resistor and the inverting input end of the error amplifier are connected to each other, and the other end of the first resistor is grounded; the output end of the error amplifier is connected to one end of the switch module, and the output end of the switch module is connected to the output end of the first resistor. The other end is connected to the gate of the fourth transistor, the source of the fourth transistor, one end of the second resistor and the non-inverting input end of the error amplifier are connected to each other, and the other end of the second resistor is grounded; the drain of the fourth transistor, the source of the sixth transistor and the inverting input end of the comparator are connected to each other, the gate of the sixth transistor is connected to the power supply voltage, the drain of the sixth transistor is connected to the negative electrode of the LED light string, the drain of the third transistor, the drain of the fifth transistor and the non-inverting input end of the comparator are connected to each other, the gate of the fifth transistor is connected to the power supply voltage, the source of the fifth transistor is connected to one end of the third resistor, and the other end of the third resistor is grounded; the output end of the comparator is connected to one end of the control module, the other end of the control module is connected to the power supply module, and the other end of the power supply module is connected to the positive electrode of the LED light string; The switch module is used to realize periodic opening and closing through a pulse width modulation signal, so that the gate of the fourth transistor and the output end of the error amplifier are periodically connected and disconnected; the control module is used to output a control signal to the power supply module according to the output signal of the comparator, so as to adjust the output voltage of the power supply module through the control signal; The fourth transistor and the fifth transistor satisfy the following relationship: (K2 / K1)× (REP M5 +R3)=(R1 / R2)×(REP M4 +R2) Wherein, K1 is the proportional coefficient of the current mirror composed of the first transistor and the second transistor, K2 is the proportional coefficient of the current mirror composed of the first transistor and the third transistor, REP M5 is the on-resistance of the fifth transistor, REP M4 is the on-resistance of the fourth transistor, R3 is the resistance value of the third resistor, and R2 is the resistance value of the second resistor.

2. The LED driving circuit according to claim 1, characterized in that: When the output signal of the comparator is at a high level, the control signal increases the output voltage of the power supply module; when the output signal of the comparator is at a low level, the control signal keeps the output voltage of the power supply module stable.

3. The LED driving circuit according to claim 1, characterized in that: The proportionality coefficient of the current mirror formed by the first transistor and the second transistor is 1.

4. The LED driving circuit according to claim 1, characterized in that: The switch module is a transistor, a source of the switch module is connected to the output end of the error amplifier, a drain of the switch module is connected to the gate of the fourth transistor, and a gate of the switch module is connected to the pulse width modulation signal.

5. The LED driving circuit according to claim 1, characterized in that: The LED light string comprises a plurality of LED lights, which are sequentially connected in series, wherein the positive pole of the first LED light forms the positive pole of the LED light string, and the negative pole of the last LED light forms the negative pole of the LED light string.

6. The LED driving circuit according to claim 2, characterized in that: The power supply module includes a Boost circuit and a voltage regulating circuit. The voltage regulating circuit includes a main circuit, multiple branches, a fourth resistor and a fifth resistor. The main circuit includes a second current source and a seventh transistor. Each branch includes an eighth transistor and a switch. One end of the second current source is connected to the power supply voltage. The other end of the second current source is respectively connected to the drain of the seventh transistor, the gate of the seventh transistor, and the gate of the eighth transistor of each branch. The source of the seventh transistor is grounded, the source of the eighth transistor of each branch is grounded, and the drain of the eighth transistor of each branch is connected to one end of the switch of the branch. The other end of the switch of each branch, one end of the fourth resistor, one end of the fifth resistor, and the feedback voltage point of the Boost circuit are connected to each other. The other end of the fourth resistor is grounded, and the other end of the fifth resistor is connected to the output end of the Boost circuit to form the output end of the power supply module. The control module is respectively connected to the switch of each branch, and is used to control the conduction and shutdown of the switch of each branch through the control signal.

7. The LED driving circuit according to claim 6, characterized in that: The eighth transistor of each branch forms a current mirror with the seventh transistor to copy the current on the main path to the branch; the current of each branch is the same as the current of the main path.

8. The LED driving circuit according to claim 6, characterized in that: When the output signal of the comparator is at a high level, the control signal increases the number of switches in each branch that are turned on, so that the output voltage of the power supply module is raised; when the output signal of the comparator is at a low level, the control signal keeps the number of switches in each branch unchanged, so that the output voltage of the power supply module remains stable.

9. The LED driving circuit according to claim 1, characterized in that: The comparator is configured to be turned on and output a signal only when the error amplifier and the gate of the fourth transistor are connected.

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