LED drive circuit

Abstract

The invention relates to an LED drive circuit, which comprises a current well, a comparator, a control module, a power supply module and a sampling circuit, and is characterized in that the current well comprises a first resistor, an error amplifier, a switch module, a fourth transistor, a sixth transistor and a second resistor; the sampling circuit comprises a first current source, a first transistor, a second transistor, a third transistor, a fifth transistor and a third resistor; the switch module is used for realizing periodic on and off through a pulse width modulation signal, so that the grid electrode of the fourth transistor and the output end of the error amplifier are periodically connected and disconnected; the control module is used for outputting 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. According to the LED driving circuit provided by the invention, the well voltage of the current well can change along with the minimum well voltage of the current well, and a small difference is always kept between the well voltage and the minimum well voltage, so that the power consumption is reduced, and the driving efficiency is improved.

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, LED lamps are widely used in various industries due to their ability to directly convert electrical energy into light, such as automotive electronics, home appliances, and consumer electronics. Since LED lamps have a fast light response, specific drive circuits are required to control their current and thus their light brightness.

[0003] like Figure 1 As shown, the existing LED driving circuit includes a current sink 10, a voltage providing 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 light string 60, that is, 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 providing 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. The resistance value of the variable resistor R30 can be changed as needed, thereby making the voltage V output by the voltage providing circuit 20 HEADROOM =I2×R30 can also be changed. The LED light string 60 is formed by a plurality of LED lights 61 connected in series in sequence. The positive electrode of the LED light string 60 is connected to the power supply module 50. The negative electrode of the LED light 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 is the well voltage. In order for the LED light string 60 to work properly, VOUT needs to be greater than the minimum well voltage, that is, V OUT >Isink×(REP M10 +REP M20 +R20), where REP M10 and REP M20 are the on-resistances of transistors M10 and M20 respectively; the comparator 30 is used to HEADROOM With V OUT The control module 40 is used to control the voltage V output by the power supply module 50 according to the high and low level signals output by the comparator 30. LED The size of V OUT The size of V OUT Greater than the preset V HEADROOM , so that the LED light string 60 can light up.

[0004] In actual use, there are multiple LED light strings 60, each LED light string 60 is equipped with a driving circuit, and the driving circuit drives the corresponding LED light string 60 to light up, and each driving circuit shares a voltage supply circuit 20, that is, a shared V HEADROOM However, even if the current sink 10 provides the same Isink current to each LED string 60, due to the influence of various factors such as process, temperature, voltage, etc., the minimum sink voltage of each current sink 10 is also different. In order to light up all LED strings 60, it is necessary to make V HEADROOM large enough so that the well voltage V OUT are all greater than the maximum value of the minimum well voltage of each current well 10, and the minimum well voltages corresponding to each LED light string 60 are quite different, so the V of the circuit with the lowest minimum well voltage is OUT The large difference from the minimum well voltage results 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, wherein the well voltage of the current well can follow the change of its minimum well voltage, so that the well voltage and the minimum well voltage always maintain a small gap, thereby reducing power consumption and improving driving efficiency.

[0006] Based on the above purpose, the present invention provides an LED driving circuit, including a current sink, a comparator, a control module, a power supply module and a sampling circuit, wherein the current sink includes a first resistor, an error amplifier, a switch module, a fourth transistor, a sixth transistor and a second resistor, and 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, 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 The first end of the switch module is connected to the gate of the fourth transistor, the source of the fourth transistor, one end of the second resistor and the in-phase 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 in-phase 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 achieve 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.

[0007] Furthermore, 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.

[0008] Furthermore, a proportionality coefficient of a current mirror formed by the first transistor and the second transistor is 1.

[0009] Further, 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.

[0010] Furthermore, the switch module is a transistor, the source of the switch module is connected to the output end of the error amplifier, the drain of the switch module is connected to the gate of the fourth transistor, and the gate of the switch module is connected to the pulse width modulation signal.

[0011] Furthermore, the LED light string includes a plurality of LED lights, which are connected in series in sequence, 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.

[0012] Further, 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, 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 interconnected, 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.

[0013] Furthermore, 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.

[0014] Furthermore, when the output signal of the comparator is at a high level, the control signal increases the number of switches turned on in each branch to increase 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 switches turned on in each branch unchanged to keep the output voltage of the power supply module stable.

[0015] Further, the comparator is configured to be turned on and output a signal only when the error amplifier is connected to the gate of the fourth transistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of an existing LED driving circuit; Figure 2 is a schematic structural diagram of an LED driving circuit according to an embodiment of the present invention; Figure 3 FIG. 4 is a schematic diagram of the structure of a power supply module of an LED driving circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0018] like Figure 2As shown, an embodiment of the present invention provides an LED driving circuit, including a current sink 100, a comparator 200, a control module 300, a power supply module 400 and a sampling circuit, the current sink 100 includes a first resistor R1, an error amplifier EA, a switch 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, the other end of the first current source 500 is respectively connected to the drain of the first transistor M1, the gate of the first transistor M1, the gate of the second transistor M2 and the gate of the third transistor M3, the source of the first transistor M1, the source of the second transistor M2 and the source of the third transistor M3 are respectively connected to the drain of the first transistor M1, the gate of the first transistor M1, the gate of the second transistor M2 and the gate of the third transistor M3. The output terminal of the error amplifier EA is connected to the power supply voltage VDD, 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 switch module 110, the other end of the switch 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 light string 600, and forms the OUT point of the current sink 100, and 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, and 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, and the other end of the third resistor R3 is grounded; the output end 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, and the other end of the power supply module 400 is connected to the positive electrode of the LED light string 600, for providing the power supply voltage V LED The first current source 500 is used to provide a current I REF The first transistor M1 and the second transistor M2 form a current mirror to control the current I REF Replication generates current I REF1 The first transistor M1 and the third transistor M3 form a current mirror to control the current I REF Replication generates current I REF2 , I REF1 flows into the first resistor R1 to generate V REF , that is, VREF =I REF1 ×R1,V REF That is, the voltage input to the 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 With V REF If they are equal, then V REF ==I REF1 ×R1=V FB1 =Isink×R2, so Isink=(R1 / R2)×I REF1 , I REF1 The current mirror ratio of IREF and the current mirror composed of the first transistor M1 and the second transistor M2 is determined. When the two are determined, I REF1 The value of is determined. At this time, the value of Isink can be changed by adjusting the value of R1 / R2, so as to freely configure the current of the LED light string 600; the switch module 110 is used to realize periodic opening and closing through the pulse width modulation signal, so that the gate of the fourth transistor M4 and the output end of the error amplifier EA are periodically connected and disconnected. When the gate of the fourth transistor M4 is connected to the output end of the error amplifier EA, the fourth transistor M4 will be turned on, and when the gate of the fourth transistor M4 is disconnected from the output end of the error amplifier EA, the fourth transistor M4 will be turned off. Therefore, 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 light 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, and the control signal is used to control the power supply module 400 to adjust its output voltage V LED , when the voltage V at the inverting input terminal of the comparator 200 DSAT Less than V HEADROOM When the comparator 200 outputs a high level, the control module 300 generates a control signal according to the high level signal to make the power supply module 400 raise V LED , that is, output a higher V LED , when V LED After increasing, V OUT and V DSAT will also increase as V DSAT Increases to greater than V HEADROOM , the comparator 200 will output a low level, and the control module 300 will generate a control signal according to the low level signal to make the power supply module 400 no longer raise V LED , but to keep it stable, so V OUT and V DSATwill also remain stable, that is, the control module 300 can make V DSAT Gradually increase and remain above V HEADROOM The stable value of V OUT ≥V DAST , so when V DSAT Higher than V HEADROOM When V OUT 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 light string 600 .

[0019] according to Figure 2 It can be seen that: V HEADROOM =I REF2 ×(REP M5 +R3), where REP M5 is the on-resistance of transistor M5.

[0020] The minimum VDSAT required to light up the LED string 600 is: (V DSAT ) min =Isink×(REP M4 +R2)=(R1 / R2)×I REF1 ×(REP M4 +R2), where REP M4 is the on-resistance of transistor M4.

[0021] In order to light up the LED light string 600, V HEADROOM =(V DSAT ) min , that is, we need to make: 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).

[0022] In some embodiments, transistors M4, M5 and resistors R2 and R3 may be pre-set to satisfy: REP M4 ×R3 / R2=REP M5 Thus, the equation that satisfies the LED light string 600 to light up can be simplified to: REF2 / I REF1)×(R3 / R2)=R1 / R2.

[0023] Among them, I REF2 / I REF1 It is determined by the current mirror ratio of M1 and M2 (i.e., the proportional 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 intrinsic 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 regardless of (V DSAT ) min How to change V HEADROOM can be equal to it, that is, V HEADROOM You can also follow (V DSAT ) min change together, making V DSAT Always greater than (V DSAT ) min And the difference between the two is small, so that all 600 LED light strings can be lit without causing V DSAT When there are multiple LED light strings 600, the V of the driving circuit of each LED light string 600 is DSAT Will follow (V DSAT ) min changes and the gap between them remains small.

[0024] In some embodiments, the parameters of the first transistor M1 and the second transistor M2 can be set so that the current mirror ratio of the current mirror formed by the first transistor M1 and the second transistor M2 is 1, that is, REF1 =I REF .

[0025] In some embodiments, the switch module 110 can be a transistor, whose source and drain are respectively connected to the output end of the error amplifier EA and the gate of the fourth transistor M4, and whose gate is connected to the pulse width modulation signal, and the pulse width modulation signal is used to control the conduction or shutdown of the pulse width adjustment module 110.

[0026] In some embodiments, the LED light string 600 is formed by connecting a plurality of LED lights 610 in series end to end, wherein the positive pole of the first LED light 610 forms the positive pole of the LED light string 600 , and the negative pole of the last LED light 610 forms the negative pole of the LED light string.

[0027] like Figure 3 As shown, the power supply module 400 includes a Boost circuit 410 and a voltage regulating circuit, the voltage regulating circuit includes a main circuit, multiple branches, a fourth resistor R4 and a fifth resistor R5, the main circuit 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 gate of the eighth transistor M8 of each branch, and the seventh transistor M The source of the eighth transistor M7 is grounded, the source of the eighth transistor M8 of each branch is grounded, the drain of the eighth transistor M8 of each branch is connected to one end of the switch S of the 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 connected to each other, the other end of the fourth resistor R4 is grounded, and the other end of the fifth resistor R5 is connected to the output end of the Boost boost circuit 410 to form an output end of the power supply module 400 for outputting V LED , the control module 300 is respectively connected to the switch S of each branch, and is used to control the on and off of each switch S according to the high and low level signals output by the comparator 300; the second current source 420 is used to provide a reference current I1, that is, the current on the main road is I1, and the eighth transistor M8 of each branch forms a current mirror with the seventh transistor M7 to copy the current I1 on the main road to the branch. For example, the current mirror ratio can be set to 1, so that the current on each branch is also I1, and the current flowing through the fifth resistor R5 is I2, I2=n×I1, where n is the number of branches that are turned on (that is, the number of branches where the switch S is in the on state), V LED =V FB2 ×(1+R5 / R4)+I2×R5, where V FB2 is the voltage at FB2, so by changing the on and off of the switch S on the control branch, the number of branches that are turned on can be changed, thereby changing the value of I2 and thus changing V LED The more branches that are turned on, the larger I2 is, and V LED When the control module 300 receives the high level signal output by the comparator 200, the number of switches S that are turned on can be increased, thereby raising V LED The control module 300 may be configured to turn on a preset number (eg, 1) of switches S each time a high level signal is received, thereby gradually raising V LED 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 remains at the current value, V LED Also remains at the current value.

[0028] In some embodiments, the control module 300 may be a digital-to-analog converter, which may 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 increases I2 by increasing the DAC code within a fixed period, thereby raising V LED If the increased current I2 is not enough to make the output of the comparator 200 low, the DAC code is increased to continue to raise V LED , until the output of comparator 200 becomes a low level.

[0029] The Boost circuit 410 may adopt any existing boost circuit, and its specific structure and working principle are well known in the art and will not be described in detail here.

[0030] In some embodiments, the comparator 200 is configured to be turned on and output a signal only when the pulse width modulation signal is high (ie, when the error amplifier EA and the gate of the fourth transistor M4 are connected) to save circuit power consumption.

[0031] The LED driving circuit of the embodiment of the present invention can make V HEADROOM Follow(V DSAT ) min change together and always remain equal, so that V DSAT Always greater than (V DSAT ) min And the difference between the two is small, so that all 600 LED light strings can be lit without causing V DSAT Too large, thereby reducing power consumption and improving efficiency.

[0032] The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The above embodiment of the present invention can also be modified in various ways. That is, all simple, equivalent changes and modifications made according to the claims and the description of the present invention fall within the scope of protection of the claims of the present invention. The contents not described in detail in the present invention are all conventional technical contents.

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 achieve 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.

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 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.

5. 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.

6. 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.

7. 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.

8. The LED driving circuit according to claim 7, 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.

9. The LED driving circuit according to claim 7, 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.

10. 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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