CN103957642B - A kind of LED power drive circuit - Google Patents

Abstract

The present invention proposes an LED power drive circuit, which includes a rectifier circuit and a switch control circuit. The switch control circuit includes a comparison circuit, a trigger circuit, and a switch tube. The comparison circuit includes a first comparison circuit, a second comparison circuit, and a first comparison circuit. The positive pole of the rectifier circuit is connected to the positive pole output terminal of the rectifier circuit, the negative pole is connected to the first reference voltage, and the first comparison circuit outputs the first comparison voltage which changes periodically; the positive pole of the second comparison circuit is connected to the positive pole output terminal of the rectification circuit, and the negative pole is connected to the first reference voltage Two reference voltages, the second comparison circuit outputs a periodically changing second comparison voltage; the first comparison voltage and the second comparison voltage are connected to the input end of the trigger circuit, and the trigger circuit outputs a periodically changing third voltage to control the conduction of the switch tube And cut-off, to realize the charge and discharge of the capacitor, the positive pole of the capacitor is connected to the positive pole of the load, and the negative pole is connected to the negative pole of the load. The invention simplifies the circuit structure, reduces the cost and improves the power factor.

Description

A LED power drive circuit

technical field

The invention relates to a power drive circuit, in particular to a low-cost, energy-saving and environment-friendly LED power drive circuit.

Background technique

In order to keep the voltage at both ends of the LED load (lamp bead) basically constant and realize voltage regulation, the conventional LED power supply drive circuit generally adopts two structures, one is a drive circuit controlled by PWM as shown in Figure 1, and the other is a drive circuit as shown in Figure 2. A power drive circuit using a transformer is shown.

It can be seen from Figure 1 and Figure 2 that this conventional LED circuit usually has components such as transformers and inductors, which will inevitably result in a large circuit size. Since the transformer and inductor have a coil structure in practice, they play the role of electromagnetic conversion in the circuit, which will cause Generate reactive power, resulting in low power factor and low circuit efficiency. In addition, as shown in Figure 1, the driving circuit of the switching tube that generates PWM in the conventional LED circuit generally uses a dedicated chip, which is expensive.

Contents of the invention

In order to overcome the above defects in the prior art, the purpose of the present invention is to provide a LED power drive circuit, which simplifies the circuit structure, reduces the cost and improves the power factor.

In order to achieve the above object of the present invention, the present invention provides a LED power drive circuit, which includes a rectifier circuit and a switch control circuit, the input end of the rectifier circuit is connected to the power supply, and the output end of the rectifier circuit is connected to the switch control circuit The input terminal is connected; the switch control circuit includes a comparison circuit, a trigger circuit and a switch tube, and the output terminal of the switch tube is connected to a capacitor; the comparison circuit includes a first comparison circuit, a second comparison circuit, and the first The positive input terminal of the comparison circuit is connected to the positive output terminal of the rectification circuit, the negative input terminal of the first comparison circuit is connected to the first reference voltage, and the first comparison circuit outputs a periodically changing first comparison voltage; the first comparison circuit The positive input terminal of the second comparison circuit is connected to the positive output terminal of the rectification circuit, the negative input terminal of the second comparison circuit is connected to the second reference voltage, and the second comparison circuit outputs a periodically changing second comparison voltage; The first comparison voltage is connected to one input terminal of the trigger circuit, the second comparison voltage is connected to the other input terminal of the trigger circuit, the output terminal of the trigger circuit outputs a periodically changing third voltage, and the output terminal of the trigger circuit is connected to the control terminal of the switch tube , control the on and off of the switch tube to realize the charging and discharging of the capacitor, the positive pole of the capacitor is connected to the positive pole of the load, and the negative pole of the capacitor is connected to the negative pole of the load.

The LED power supply drive circuit of the present invention does not need to use electromagnetic components such as transformers and inductors and high-priced drive chips, and realizes constant voltage output by using a cheap trigger, which simplifies the circuit structure and reduces costs. No components such as transformers and inductors are used, which can reduce the volume of the circuit. At the same time, there is no electromagnetic transformation in the circuit, and no reactive power will be generated, which improves the power factor and circuit efficiency.

In a preferred embodiment of the present invention, the first comparison circuit includes a first comparator, the positive input terminal of the first comparator is connected to the positive output terminal of the rectification circuit, and the negative terminal of the first comparison circuit The input end is connected to the first reference voltage. When the voltage Ui output by the positive output end of the rectification circuit is greater than the first reference voltage V1, the first comparator outputs a high level. When the voltage Ui output by the positive output end of the rectification circuit When Ui is smaller than the first reference voltage V1, the first comparator outputs a low level. Thus, a periodically changing first comparison voltage is formed.

In a preferred embodiment of the present invention, the second comparison circuit includes a second comparator, the positive input terminal of the second comparator is connected with the positive output terminal of the rectification circuit, and the negative terminal of the second comparison circuit The input end is connected to the second reference voltage. When the voltage Ui output by the positive output end of the rectification circuit is less than the second reference voltage V2, the second comparator outputs a low level. When the voltage Ui output by the positive output end of the rectification circuit When Ui is greater than the second reference voltage V2, the second comparator outputs a high level. Thus, a periodically changing second comparison voltage is formed.

In a preferred embodiment of the present invention, the first reference voltage V1 is smaller than the second reference voltage V2. Therefore, the duty cycles of the first comparison voltage and the second comparison voltage are different.

In a preferred embodiment of the present invention, the trigger circuit is an RS flip-flop, the first comparison voltage is connected to the S input terminal of the RS flip-flop, and the second comparison voltage is connected to the R input terminal of the RS flip-flop. The constant voltage output is realized by adopting the cheap flip-flop, which simplifies the circuit structure and reduces the cost.

In a preferred embodiment of the present invention, the first comparison circuit includes a first resistor, a second resistor and a first optocoupler, and the first resistor and the second resistor are connected in series at the two output terminals of the rectification circuit Between, the anode of the input loop of the first optocoupler is connected to the series line between the first resistor and the second resistor, and the cathode of the input loop of the first optocoupler is connected to the second rectifier circuit Output terminal, the anode of the output circuit of the first optocoupler is connected to the first output terminal of the rectifier circuit, and the negative pole of the output circuit of the first optocoupler is connected to the second output terminal of the rectifier circuit through the fourth resistor .

The first reference voltage V1 is realized by dividing the voltage between the first resistor and the second resistor, and the structure is simple. The photoelectric isolation of the input end and the output end is realized through the first optocoupler, which improves safety and reliability.

In a preferred embodiment of the present invention, the second comparison circuit includes a fifth resistor, a sixth resistor and a second optocoupler, and the fifth resistor and the sixth resistor are connected in series at the two output terminals of the rectification circuit Between, the anode of the input loop of the second optocoupler is connected to the series line between the fifth resistor and the sixth resistor, and the cathode of the input loop of the second optocoupler is connected to the second rectifier circuit Output terminal, the positive pole of the output circuit of the second optocoupler is connected to the first output terminal of the rectifier circuit through the eighth resistor, and the negative pole of the output circuit of the second optocoupler is connected to the second output terminal of the rectifier circuit .

The second reference voltage V2 is realized through voltage division by the sixth resistor and the fifth resistor, and the structure is simple. The photoelectric isolation of the input end and the output end is realized through the second optocoupler, which improves safety and reliability.

In the present invention, the first reference voltage is realized by voltage dividing by the first resistor and the second resistor, and the second reference voltage is realized by voltage dividing by the sixth resistor and the fifth resistor. By adopting closed-loop feedback, not only wide-range voltage input can be realized, but also the output voltage can be adjusted simultaneously. The accuracy can be well controlled, which ensures that the brightness of the LED is still stable when the power supply voltage fluctuates greatly.

In a preferred embodiment of the present invention, the switch tube is a field effect transistor, the cathode of the first optocoupler is connected to the R terminal of the RS flip-flop, and the anode of the second optocoupler is connected to the RS flip-flop The S terminal of the RS trigger, the Q output terminal of the RS flip-flop is connected to the gate of the field effect transistor, the drain of the field effect transistor is connected to the second output terminal of the rectification circuit, and the source of the field effect transistor is connected to the rectifier through a capacitor. the first output of the circuit.

In the present invention, the periodically changing third voltage is output by the RS flip-flop, and the charging and discharging of the capacitor is realized by controlling the on-off of the switch tube, so as to realize voltage stabilization.

In a preferred embodiment of the present invention, a first diode is further included, and the first diode is connected between the capacitor and the first output terminal of the rectification circuit. Prevent current backflow and ensure the normal operation of LED lamp beads.

In a preferred embodiment of the present invention, a third resistor and a seventh resistor are also included, one end of the third resistor is connected to the positive pole of the input circuit of the first optocoupler, and the other end of the third resistor is connected to On the series line between the first resistor and the second resistor; one end of the seventh resistor is connected to the positive pole of the input loop of the second optocoupler, and the other end of the seventh resistor is connected to the sixth resistor and the fifth resistor on the series line between them.

The third resistor and the seventh resistor limit the current to ensure normal operation of the circuit.

Additional aspects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and comprehensible from the description of the embodiments in conjunction with the following drawings, wherein:

Fig. 1 is the circuit diagram of the drive circuit that adopts PWM control in the prior art;

Fig. 2 is a circuit diagram of a drive circuit controlled by a transformer in the prior art;

Fig. 3 is a block diagram of the LED power drive circuit in a preferred embodiment of the present invention;

Fig. 4 is a waveform diagram of each node shown in Fig. 3;

Fig. 5 is a circuit diagram of an LED power drive circuit in a preferred embodiment of the present invention.

detailed description

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be mechanical connection or electrical connection, or two The internal communication of each element may be directly connected or indirectly connected through an intermediary. Those skilled in the art can understand the specific meanings of the above terms according to specific situations.

The invention provides an LED power drive circuit, which includes a rectification circuit and a switch control circuit, wherein the input end of the rectification circuit is connected to the power supply, and the output end of the rectification circuit is connected to the input end of the switch control circuit. In this embodiment, the power supply is a commercial power supply or other AC power supply, and the rectification circuit is a rectification bridge circuit.

The switch control circuit includes a comparison circuit, a trigger circuit and a switch tube, and the output terminal of the switch tube is connected with a capacitor. Wherein, the comparison circuit includes a first comparison circuit and a second comparison circuit, the positive input terminal of the first comparison circuit is connected with the positive output terminal of the rectification circuit, the negative input terminal of the first comparison circuit is connected with the first reference voltage, and the first comparison circuit A first comparison voltage that changes periodically is output. The positive input terminal of the second comparison circuit is connected with the positive output terminal of the rectification circuit, the negative input terminal of the second comparison circuit is connected with the second reference voltage, and the second comparison circuit outputs the second comparison voltage which changes periodically; the first comparison voltage is connected One input terminal of the trigger circuit and the second comparison voltage are connected to the other input terminal of the trigger circuit, the output terminal of the trigger circuit outputs a periodically changing third voltage, the output terminal of the trigger circuit is connected to the control terminal of the switch tube, and the control terminal of the switch tube is controlled. On and off to realize the charging and discharging of the capacitor, the positive pole of the capacitor is connected to the positive pole of the load, and the negative pole of the capacitor is connected to the negative pole of the load.

The invention keeps the voltage at both ends of the load basically constant, and the LED power drive circuit does not need to use electromagnetic components such as transformers and inductors and high-priced drive chips, and the constant voltage output is realized by using a cheap trigger, which simplifies the circuit structure , reducing costs. No components such as transformers and inductors are used, which can reduce the volume of the circuit. At the same time, there is no electromagnetic transformation in the circuit, and no reactive power will be generated, which improves the power factor and circuit efficiency.

As shown in Figure 3, in a preferred embodiment of the present invention, the first comparison circuit includes a first comparator, the positive input terminal of the first comparator is connected with the positive output terminal of the rectification circuit, and the negative pole of the first comparison circuit The input end is connected to the first reference voltage, when the voltage Ui output by the positive output end of the rectification circuit is greater than the first reference voltage V1, the first comparator outputs a high level, and when the voltage Ui output by the positive output end of the rectification circuit is smaller than the first reference voltage V1 When the reference voltage V1 is used, the first comparator outputs a low level. Thus, a periodically changing first comparison voltage is formed.

The second comparison circuit includes a second comparator, the positive input terminal of the second comparator is connected to the positive output terminal of the rectification circuit, the negative input terminal of the second comparison circuit is connected to the second reference voltage, when the positive output terminal of the rectification circuit outputs When the voltage Ui is less than the second reference voltage V2, the second comparator outputs a low level, and when the voltage Ui output by the positive output terminal of the rectifier circuit is greater than the second reference voltage V2, the second comparator outputs a high level . Thus, a periodically changing second comparison voltage is formed.

In this embodiment, the first reference voltage V1 is smaller than the second reference voltage V2. Therefore, the duty cycles of the first comparison voltage and the second comparison voltage are different.

In this embodiment, the trigger circuit is an RS flip-flop, the first comparison voltage is connected to the S input terminal of the RS flip-flop, and the second comparison voltage is connected to the R input terminal of the RS flip-flop. The constant voltage output is realized by adopting the cheap flip-flop, which simplifies the circuit structure and reduces the cost.

In this embodiment, the switch transistor is a field effect transistor.

As shown in Figure 3, the working process of this circuit is that the rectifier circuit rectifies the 50Hz alternating current into direct current Ui, as shown in Figure 4(a). After the DC current Ui passes through the switch control circuit, a sawtooth DC voltage with small deviation is generated at both ends of the capacitor C, as shown in Figure 4(e). The working state of the field effect transistor (MOSFET) and the generation process of the sawtooth wave at both ends of the capacitor C will be described below.

According to the load condition, set the value of V1, V2. V1 and V2 affect the charging time of capacitor C, the larger V1 and V2 are, the longer the charging time is. In this embodiment, V1 is compared with Ui. If Ui is greater than V1, the comparator outputs a high level, otherwise it outputs a low level. The waveform of the output signal A1 is shown in FIG. 4(b). Compare V2 with Ui, if Ui is greater than V2, the comparator outputs low level, otherwise it outputs high level, and the output signal waveform A2 is shown in Figure 4(c). Connect the A1 signal to the S terminal of the RS flip-flop, connect the A2 signal to the R terminal of the RS flip-flop, and output the signal A3 at the output terminal Q, and the waveform is shown in Figure 4(d). The MOSFET transistor is used as a switch. When the A3 signal is at a high level, the switch tube S is turned on, and the capacitor C is charged; when the A3 signal is at a low level, S is turned off, and the capacitor C is discharged, so that the alternating on and off makes Uc a sawtooth wave Stable near Ud, as shown in Figure 4(e), where Ud is the rated voltage of the load.

In another preferred embodiment of the present invention, as shown in FIG. 5, the first comparison circuit includes a first resistor R1, a second resistor R2 and a first optocoupler U1, wherein the first resistor R1 and the second resistor R2 is connected in series between the two output terminals of the rectifier circuit, the anode of the input loop of the first optocoupler U1 is connected to the series line between the first resistor R1 and the second resistor R2, the input of the first optocoupler U1 The negative pole of the loop is connected to the second output terminal of the rectifier circuit, the positive pole of the output loop of the first optocoupler U1 is connected to the first output terminal of the rectifier circuit, and the negative pole of the output loop of the first optocoupler is connected through the fourth resistor R4 at the second output terminal of the rectifier circuit. In this embodiment, the first reference voltage V1 is realized through voltage division by the first resistor R1 and the second resistor R2, and the structure is simple. The photoelectric isolation of the input end and the output end is realized through the first optocoupler U1, which improves safety and reliability.

In this embodiment, a third resistor R3 is also provided in the circuit, one end of the third resistor R3 is connected to the positive pole of the input circuit of the first optocoupler U1, and the other end of the third resistor R3 is connected to the first resistor R1 On the series line between the second resistor R2 and the second resistor R2, the current is limited to ensure the normal operation of the circuit.

In this embodiment, the second comparison circuit includes a fifth resistor R5, a sixth resistor R6, and a second optocoupler U2, and the fifth resistor R5 and the sixth resistor R6 are connected in series between the two output terminals of the rectifier circuit. The anode of the input loop of the second optocoupler U2 is connected to the series line between the fifth resistor R5 and the sixth resistor R6, the cathode of the input loop of the second optocoupler U2 is connected to the second output terminal of the rectifier circuit, and The anode of the output loop of the second optocoupler U2 is connected to the first output end of the rectification circuit through the eighth resistor R8, and the cathode of the output loop of the second optocoupler U2 is connected to the second output end of the rectification circuit. In this embodiment, the second reference voltage V2 is realized through voltage division by the sixth resistor R6 and the fifth resistor R5, and the structure is simple. The photoelectric isolation of the input end and the output end is realized by the second optocoupler U2, which improves safety and reliability.

In this embodiment, a seventh resistor R7 is also provided in the circuit, one end of the seventh resistor R7 is connected to the positive pole of the input circuit of the second optocoupler U2, and the other end of the seventh resistor R7 is connected between the sixth resistor R6 and the second optocoupler U2. on the series line between five resistors R5. The seventh resistor R7 limits the current to ensure the normal operation of the circuit.

In the present invention, the first reference voltage is realized by dividing the voltage of the first resistor R1 and the second resistor R2, and the second reference voltage is realized by dividing the voltage of the sixth resistor R6 and the fifth resistor R5, and the closed-loop feedback can not only realize wide voltage input, At the same time, the accuracy of the output voltage can be well controlled, ensuring that the brightness of the LED is still stable when the power supply voltage fluctuates greatly.

In this embodiment, the cathode of the first optocoupler U1 is connected to the R terminal of the RS flip-flop, the anode of the second optocoupler U2 is connected to the S terminal of the RS flip-flop, and the Q output terminal of the RS flip-flop is connected to the field effect transistor. The gate and the drain of the field effect transistor are connected to the second output terminal of the rectification circuit, and the source of the field effect transistor is connected to the first output terminal of the rectification circuit through a capacitor. In the present invention, the periodically changing third voltage is output by the RS flip-flop, and the charging and discharging of the capacitor is realized by controlling the on-off of the switch tube, so as to realize voltage stabilization.

In another preferred embodiment of the present invention, a first diode D1 is also provided in the circuit, and the first diode is connected between the capacitor and the first output terminal of the rectifier circuit to prevent the current from flowing back and ensure that the LED The lamp beads work normally.

In this embodiment, the load circuit includes an array of LED lamp beads, which can be combined in series or in series and parallel. The positive end of the capacitor is connected to one end of the ninth resistor R9, and the other end of the ninth resistor R9 is connected to the voltage regulator tube VD. The positive pole, the negative pole of the regulator tube VD is connected to the negative pole of the capacitor C, one end of the tenth resistor R10 is connected to the negative pole of the capacitor C, and the other end is connected to the drain of the voltage regulator transistor Q2, and the gate of the voltage regulator transistor Q2 is connected to the stabilizer The positive pole of the voltage tube VD, the source of the voltage regulator transistor Q2 are connected to the negative pole of the LED bead array, and the positive pole of the capacitor C is connected to the positive pole of the LED bead array.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structure, material or characteristic is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the invention is defined by the claims and their equivalents.

Claims (11)

1. A kind of LED power supply drive circuit, it is characterized in that, comprise rectification circuit, switch control circuit, the input end of described rectification circuit is connected with power supply, the output end of described rectification circuit is connected with the input end of switch control circuit; The switch control circuit includes a comparison circuit, a trigger circuit and a switch tube, and the output end of the switch tube is connected to a capacitor; The comparison circuit includes a first comparison circuit and a second comparison circuit, the positive input terminal of the first comparison circuit is connected to the positive output terminal of the rectification circuit, the negative input terminal of the first comparison circuit is connected to the first reference voltage, The first comparison circuit outputs a first comparison voltage that changes periodically; The positive input terminal of the second comparison circuit is connected to the positive output terminal of the rectification circuit, the negative input terminal of the second comparison circuit is connected to the second reference voltage, and the second comparison circuit outputs a periodically changing second comparison voltage ; The first comparison voltage is connected to one input terminal of the trigger circuit, the second comparison voltage is connected to the other input terminal of the trigger circuit, the output terminal of the trigger circuit outputs a periodically changing third voltage, and the output terminal of the trigger circuit is connected to the switch tube. The control terminal controls the on and off of the switch tube to realize the charging and discharging of the capacitor, the positive pole of the capacitor is connected to the positive pole of the load, and the negative pole of the capacitor is connected to the negative pole of the load. 2. The LED power drive circuit according to claim 1, wherein the first comparison circuit comprises a first comparator, the positive input terminal of the first comparator is connected to the positive output terminal of the rectifier circuit, and the The negative input terminal of the first comparison circuit is connected to the first reference voltage. When the voltage Ui output by the positive output terminal of the rectification circuit is greater than the first reference voltage V1, the first comparator outputs a high level. When the rectification circuit When the voltage Ui output by the positive output terminal of the first comparator is lower than the first reference voltage V1, the first comparator outputs a low level. 3. The LED power drive circuit according to claim 1, wherein the second comparison circuit comprises a second comparator, the positive input terminal of the second comparator is connected to the positive output terminal of the rectifier circuit, and the The negative input terminal of the second comparison circuit is connected to the second reference voltage, and when the voltage Ui output by the positive output terminal of the rectification circuit is less than the second reference voltage V2, the second comparator outputs a low level, and when the rectification circuit When the voltage Ui output by the positive output terminal of the second comparator is greater than the second reference voltage V2, the second comparator outputs a high level. 4. The LED power drive circuit according to any one of claims 1, 2, and 3, wherein the first reference voltage V1 is smaller than the second reference voltage V2. 5. The LED power drive circuit according to claim 1, wherein the trigger circuit is an RS flip-flop, the first comparison voltage is connected to the S input terminal of the RS flip-flop, and the second comparison voltage is connected to the RS flip-flop the R input. 6. The LED power drive circuit according to claim 1, wherein the first comparison circuit comprises a first resistor, a second resistor and a first optocoupler, and the first resistor and the second resistor are connected in series Between the two output terminals of the rectifier circuit, the anode of the input loop of the first optocoupler is connected to the series line between the first resistor and the second resistor, and the cathode of the input loop of the first optocoupler connected to the second output end of the rectifier circuit, the positive pole of the output loop of the first optocoupler is connected to the first output end of the rectifier circuit, and the negative pole of the output loop of the first optocoupler is connected to the The second output terminal of the rectifier circuit. 7. The LED power drive circuit according to claim 1, wherein the second comparison circuit comprises a fifth resistor, a sixth resistor and a second optocoupler, and the fifth resistor and the sixth resistor are connected in series Between the two output terminals of the rectifier circuit, the anode of the input loop of the second optocoupler is connected to the series line between the fifth resistor and the sixth resistor, and the cathode of the input loop of the second optocoupler Connected to the second output terminal of the rectifier circuit, the positive pole of the output loop of the second optocoupler is connected to the first output terminal of the rectifier circuit through the eighth resistor, and the negative pole of the output loop of the second optocoupler is connected to The second output terminal of the rectifier circuit. 8. The LED power drive circuit according to any one of claims 5, 6, and 7, wherein the switch tube is a field effect transistor, the cathode of the first optocoupler is connected to the R terminal of the RS flip-flop, and the second optocoupler The anode of the device is connected to the S terminal of the RS flip-flop, the Q output terminal of the RS flip-flop is connected to the gate of the field effect transistor, the drain of the field effect transistor is connected to the second output terminal of the rectifier circuit, and the source of the field effect transistor The pole is connected to the first output terminal of the rectifier circuit through a capacitor. 9. The LED power drive circuit according to claim 8, further comprising a first diode connected between the capacitor and the first output terminal of the rectifier circuit. 10. The LED power drive circuit according to claim 6, further comprising a third resistor, one end of the third resistor is connected to the positive pole of the input circuit of the first optocoupler, and the other end of the third resistor is One end is connected to the series line between the first resistor and the second resistor. 11. The LED power drive circuit according to claim 7, further comprising a seventh resistor, one end of the seventh resistor is connected to the positive pole of the input circuit of the second optocoupler, and the other end of the seventh resistor is One end is connected to the series line between the sixth resistor and the fifth resistor.