Power-off protection device of motor and clothes processing equipment

Abstract

The utility model relates to a power-off protection device of a motor and clothes processing equipment. The power-off protection device of the motor comprises a voltage division circuit, a comparison circuit, a driving circuit and a switching circuit. The voltage division circuit is connected with an input power rectification circuit of the motor; the voltage division circuit is connected with the comparison circuit; the comparison circuit is connected with the driving circuit; the driving circuit is connected with the switching circuit; the switching circuit is connected between the voltage end of the microcontroller of the motor and the first voltage source. In the actual use process, the power-off protection device monitors the output voltage of the input power supply rectifying circuit of the motor, and when it is monitored that the output voltage of the input power supply rectifying circuit of the motor is lower than a set threshold value, the power supply of the first voltage source to the microcontroller is cut off. Therefore, when the motor is powered off, the power supply of the microcontroller is cut off at the first time, the problem that the microcontroller continues to send control signals to the motor driving board is avoided, the bus voltage of the motor and the strong oscillation of the phase line current of the motor can be effectively eliminated, and a power device is prevented from being damaged.

Description

Technical Field

[0001] The utility model relates to the technical field of motors, in particular to a power-off protection device for a motor and clothing processing equipment. Background Art

[0002] When the BLDC (Brushless Direct Current Motor) motor is running stably, the three-phase current inside it is stable. Existing motor protection measures usually detect the power-off state of the input power supply. When the input power supply is off, the driving voltage of the motor drive board is cut off to solve the problem of excessive current in the motor phase line at the moment of power off.

[0003] However, when the driving voltage of the motor driver board is cut off, it takes a certain amount of time for the driving voltage on the driver board to drop to zero due to the presence of capacitance in the circuit, and the driving voltage often lags behind the drop in the bus voltage. When the bus voltage drops to a certain lower level, if the driving voltage does not drop below the turn-on threshold of the power device, and the control signal of the microcontroller of the driver board is still output, it may cause the bus voltage and the motor phase line current to oscillate violently, damaging the power device. Summary of the invention

[0004] Based on this, it is necessary to provide a motor power-off protection device and a clothing processing device to address the problem that when the driving voltage of the motor drive board is traditionally cut off, the bus voltage and the motor phase current are prone to strong oscillations, which may damage the power devices.

[0005] A power-off protection device for a motor, comprising a voltage dividing circuit, a comparison circuit, a driving circuit and a switch circuit;

[0006] The voltage divider circuit is connected to the input power rectifier circuit of the motor; the voltage divider circuit is connected to the comparison circuit; the comparison circuit is connected to the drive circuit; the drive circuit is connected to the switch circuit; the switch circuit is connected between the voltage end of the motor's microcontroller and the first voltage source.

[0007] In one embodiment, the voltage divider circuit includes a first resistor and a second resistor;

[0008] The first end of the first resistor is connected to the input power rectification circuit of the motor, and the second end is respectively connected to the first end of the second resistor and the comparison circuit; the second end of the second resistor is grounded.

[0009] In one embodiment, the comparison circuit includes a comparator and a third resistor;

[0010] The positive input terminal of the comparator is respectively connected to the second end of the first resistor and the first end of the second resistor, the negative input terminal is connected to the second voltage source, the positive power supply terminal is connected to the third voltage source, the negative power supply terminal is grounded, and the output terminal is connected to the first end of the third resistor; the second end of the third resistor is connected to the driving circuit.

[0011] In one embodiment, the driving circuit includes an optically coupled isolator;

[0012] The first input terminal of the optical coupling isolator is connected to the second end of the third resistor, the second input terminal is grounded, the first output terminal is connected to the switch circuit, and the second output terminal is grounded.

[0013] In one embodiment, the switch circuit includes a fourth resistor, a fifth resistor and a field effect transistor;

[0014] The first end of the fourth resistor is respectively connected to the first output end of the optical coupling isolator and the first end of the fifth resistor, and the second end is respectively connected to the source of the field effect transistor and the first voltage source; the second end of the fifth resistor is connected to the gate of the field effect transistor; the drain of the field effect transistor is connected to the voltage end of the microcontroller.

[0015] A clothes processing device, comprising a power failure protection device, an input power rectification circuit, a voltage transformation device, a microcontroller, a driving chip, an on-off circuit and a motor;

[0016] The input power rectification circuit is respectively connected to the input power supply of the voltage divider circuit, the power-off protection device and the voltage transformation device; the voltage transformation device is respectively connected to the microcontroller, the drive chip and the on-off circuit; the power-off protection device is connected between the voltage end of the microcontroller and the first voltage source; the microcontroller is connected to the drive chip; the drive chip is connected to the on-off circuit; the on-off circuit is connected to the motor;

[0017] When the power-off protection device detects that the output voltage of the input power rectifier circuit is lower than a set threshold, the power-off protection device cuts off the first voltage source from supplying power to the microcontroller.

[0018] In one embodiment, the power-off protection device includes a voltage divider circuit, a comparison circuit, a drive circuit, and a switch circuit;

[0019] The voltage divider circuit is connected to the input power rectifier circuit; the voltage divider circuit is connected to the comparison circuit; the comparison circuit is connected to the drive circuit; the drive circuit is connected to the switch circuit; the switch circuit is connected between the voltage end of the microcontroller and the first voltage source.

[0020] In one embodiment, the voltage divider circuit includes a first resistor and a second resistor;

[0021] The first end of the first resistor is connected to the input power rectification circuit, and the second end is respectively connected to the first end of the second resistor and the comparison circuit; the second end of the second resistor is grounded.

[0022] In one embodiment, the comparison circuit includes a comparator and a third resistor;

[0023] The positive input terminal of the comparator is respectively connected to the second end of the first resistor and the first end of the second resistor, the negative input terminal is connected to the second voltage source, the positive power supply terminal is connected to the third voltage source, the negative power supply terminal is grounded, and the output terminal is connected to the first end of the third resistor; the second end of the third resistor is connected to the driving circuit.

[0024] In one embodiment, the driving circuit includes an optical coupling isolator; the switch circuit includes a fourth resistor, a fifth resistor and a field effect transistor;

[0025] The first input terminal of the optical coupling isolator is connected to the second terminal of the third resistor, the second input terminal is grounded, the first output terminal is respectively connected to the first terminal of the fourth resistor and the first terminal of the fifth resistor, and the second output terminal is grounded;

[0026] The second end of the fourth resistor is connected to the source of the field effect transistor and the first voltage source respectively; the second end of the fifth resistor is connected to the gate of the field effect transistor; and the drain of the field effect transistor is connected to the voltage end of the microcontroller.

[0027] One of the above technical solutions has the following advantages and beneficial effects:

[0028] The power-off protection device of the motor provided in each embodiment of the present application includes a voltage divider circuit, a comparison circuit, a drive circuit and a switch circuit. Among them, the voltage divider circuit is connected to the input power rectifier circuit of the motor. The voltage divider circuit is connected to the comparison circuit. The comparison circuit is connected to the drive circuit. The drive circuit is connected to the switch circuit. The switch circuit is connected between the voltage terminal of the microcontroller of the motor and the first voltage source. In actual use, the power-off protection device monitors the output voltage of the input power rectifier circuit of the motor, and when it is detected that the output voltage of the input power rectifier circuit of the motor is lower than the set threshold, the power supply of the first voltage source to the microcontroller is cut off. Thereby, when the motor is powered off, the power supply of the microcontroller is cut off at the first time, avoiding the problem that the microcontroller continues to send control signals to the motor drive board during the period when the drive voltage of the motor drive board lags down due to the presence of the capacitor, thereby effectively eliminating the strong oscillation of the bus voltage of the motor and the phase current of the motor, and avoiding damage to the power device. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and other purposes, features and advantages of the present application will become clearer through a more specific description of the preferred embodiments of the present application shown in the accompanying drawings. The same reference numerals indicate the same parts in all the accompanying drawings, and the drawings are not deliberately scaled to the actual size, and the focus is on illustrating the subject matter of the present application.

[0030] Figure 1This is a schematic diagram of the structure of the power-off protection device according to an embodiment of the present application.

[0031] Figure 2 Schematic diagram of the structure of the power-off protection device in the embodiment of the present application.

[0032] Figure 3 It is a schematic diagram of the structure of the clothing processing device in the embodiment of the present application. DETAILED DESCRIPTION

[0033] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0034] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to the other element and combined with it as a whole, or there may be an intermediate element at the same time. The terms "disposed", "one end", "the other end" and similar expressions used herein are for illustrative purposes only.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0036] When the motor encounters a sudden power outage, due to the presence of capacitors in the motor circuit, it takes a certain amount of time for the power supply voltage of each module in the circuit to drop to zero. If the circuit is improperly controlled or the power device is not properly selected, the bus voltage and phase current fluctuations of the motor may increase during the power outage, causing the stress on the power device to increase and cause damage. In order to solve the above problems, Figure 1 As shown, a power-off protection device 11 for a motor is provided, comprising a voltage divider circuit 111, a comparison circuit 113, a drive circuit 115 and a switch circuit 117. The specific connection relationship is as follows: the voltage divider circuit 111 is connected to the input power rectifier circuit 13 of the motor; the voltage divider circuit 111 is connected to the comparison circuit 113; the comparison circuit 113 is connected to the drive circuit 115; the drive circuit 115 is connected to the switch circuit 117; the switch circuit 117 is connected between the voltage end of the microcontroller 15 of the motor and the first voltage source 17.

[0037] The voltage divider circuit 111 receives the output voltage of the input power rectifier circuit 13, divides the output voltage of the input power rectifier circuit 13, and transmits it to the comparison circuit 113. It should be noted that the input power rectifier circuit 13 is used to rectify the AC power into DC power. Specifically, the input power rectifier circuit 13 is connected to the neutral line and the live line of the three-phase power to convert the three-phase AC power into DC power. There are many ways to implement the voltage divider circuit 111. In one example, Figure 2 As shown, a feasible implementation is provided, the voltage divider circuit 111 includes a first resistor R1 and a second resistor R2. The first end of the first resistor R1 is connected to the input power rectifier circuit 13 of the motor, and the second end is respectively connected to the first end of the second resistor R2 and the comparison circuit 113; the second end of the second resistor R2 is grounded.

[0038] The comparison circuit 113 is used to compare the voltage transmitted by the voltage divider circuit 111 with the reference voltage. When the voltage transmitted by the voltage divider circuit 111 is greater than the reference voltage, the comparison circuit 113 transmits a first control signal to the drive circuit 115 to control the drive circuit 115 to turn on the switch circuit 117 and maintain the first voltage source 17 to supply power to the microcontroller 15. When the voltage transmitted by the voltage divider circuit 111 is less than the reference voltage, the comparison circuit 113 transmits a second control signal to the drive circuit 115 to control the drive circuit 115 to turn off the switch circuit 117 and cut off the first voltage source 17 from supplying power to the microcontroller 15. The comparison circuit 113 can be implemented in various ways. In one example, Figure 2 As shown, a feasible implementation is provided, where the comparison circuit 113 includes a comparator A1 and a third resistor. The positive input terminal of the comparator A1 is respectively connected to the second end of the first resistor R1 and the first end of the second resistor R2, the negative input terminal is connected to the second voltage source, the positive power supply terminal is connected to the third voltage source, the negative power supply terminal is connected to the third voltage source, and the output terminal is connected to the first end of the third resistor; the second end of the third resistor is connected to the driving circuit 115.

[0039] The driving circuit 115 is used to control the driving switch circuit 117 to be turned on or off when receiving the signal from the comparison circuit 113. There are many ways to implement the driving circuit 115. In one example, Figure 2 As shown, a feasible implementation is provided, the driving circuit 115 includes an optical coupling isolator OC. The first input terminal of the optical coupling isolator OC is connected to the second end of the third resistor, the second input terminal is grounded, the first output terminal is connected to the switch circuit 117, and the second output terminal is grounded.

[0040] The switch circuit 117 is used to receive the drive of the drive circuit 115, and cut off or turn on the first voltage source 17 to supply power to the microcontroller 15. There are many ways to implement the switch circuit 117. In one example, Figure 2As shown, a feasible implementation is provided, the switch circuit 117 includes a fourth resistor R4, a fifth resistor R5 and a field effect transistor Q1. The first end of the fourth resistor R4 is respectively connected to the first output end of the optical coupling isolator OC and the first end of the fifth resistor R5, and the second end is respectively connected to the source of the field effect transistor Q1 and the first voltage source 17; the second end of the fifth resistor R5 is connected to the gate of the field effect transistor Q1; the drain of the field effect transistor Q1 is connected to the voltage end of the microcontroller 15.

[0041] The power-off protection device 11 of the motor provided in each embodiment of the present application includes a voltage divider circuit 111, a comparison circuit 113, a drive circuit 115 and a switch circuit 117. The voltage divider circuit 111 is connected to the input power rectifier circuit 13 of the motor. The voltage divider circuit 111 is connected to the comparison circuit 113. The comparison circuit 113 is connected to the drive circuit 115. The drive circuit 115 is connected to the switch circuit 117. The switch circuit 117 is connected between the voltage terminal of the microcontroller 15 of the motor and the first voltage source 17. In actual use, the power-off protection device 11 monitors the output voltage of the input power rectifier circuit 13 of the motor, and when it is detected that the output voltage of the input power rectifier circuit 13 of the motor is lower than the set threshold, the first voltage source 17 is cut off from supplying power to the microcontroller 15. Therefore, when the motor is powered off, the power supply of the microcontroller 15 is cut off immediately to avoid the problem that the microcontroller 15 continues to send control signals to the motor drive board during the period when the driving voltage of the motor drive board lags and decreases due to the presence of the capacitor. This can effectively eliminate the strong oscillations of the motor's bus voltage and the motor's phase line current, avoiding damage to power devices.

[0042] In addition, since the power-off protection device 11 of the present application can timely cut off the power supply of the microcontroller 15, avoiding strong oscillations of the motor bus voltage and the motor phase line current, the power devices in the motor circuit no longer need to bear large current stress, which is conducive to reducing the requirements for power devices and reducing production costs. Moreover, the power-off protection device 11 of the present application can be applied to both non-isolated voltage power supply and isolated voltage power supply, while traditional technology can only be applied to non-isolated voltage power supply.

[0043] like Figure 3 As shown, a clothing processing device is also provided, including a power-off protection device 11, an input power rectification circuit 13, a transformer, a microcontroller 15, a driver chip, an on-off circuit, and a motor. The specific connection relationship is: the input power rectification circuit 13 is respectively connected to the input power of the voltage divider circuit, the power-off protection device 11, and the transformer; the transformer is respectively connected to the microcontroller 15, the driver chip, and the on-off circuit; the power-off protection device 11 is connected between the voltage end of the microcontroller 15 and the first voltage source 17; the microcontroller 15 is connected to the driver chip; the driver chip is connected to the on-off circuit; and the on-off circuit is connected to the motor.

[0044] It should be noted that the input power rectifier circuit 13 is used to rectify AC power into DC power. Specifically, the input power rectifier circuit 13 is connected to the neutral line and the live line of the three-phase power to convert the three-phase AC power into DC power. The transformer is used to transform the output voltage of the input power rectifier circuit 13 to power the microcontroller 15, the driver chip and the motor. The microcontroller 15 is used to send a control signal to the driver chip to instruct the driver chip to drive the on-off circuit to turn on and off. The on-off circuit is used to receive the drive of the driver chip and turn on or off the power supply of the transformer to the motor.

[0045] When the power-off protection device 11 detects that the output voltage of the input power rectifier circuit 13 is lower than a set threshold, the first voltage source 17 is cut off from supplying power to the microcontroller 15. Figure 1 In one example, the power-off protection device 11 includes a voltage divider circuit 111, a comparison circuit 113, a drive circuit 115, and a switch circuit 117. The voltage divider circuit 111 is connected to the input power rectifier circuit 13; the voltage divider circuit 111 is connected to the comparison circuit 113; the comparison circuit 113 is connected to the drive circuit 115; the drive circuit 115 is connected to the switch circuit 117; and the switch circuit 117 is connected between the voltage terminal of the microcontroller 15 and the first voltage source 17.

[0046] The voltage divider circuit 111 receives the output voltage of the input power rectifier circuit 13, divides the output voltage of the input power rectifier circuit 13 and transmits it to the comparison circuit 113. There are many ways to implement the voltage divider circuit 111. In one example, Figure 2 As shown, a feasible implementation is provided, the voltage divider circuit 111 includes a first resistor R1 and a second resistor R2. The first end of the first resistor R1 is connected to the input power rectifier circuit 13, and the second end is respectively connected to the first end of the second resistor R2 and the comparison circuit 113; the second end of the second resistor R2 is grounded.

[0047] The comparison circuit 113 is used to compare the voltage transmitted by the voltage divider circuit 111 with the reference voltage. When the voltage transmitted by the voltage divider circuit 111 is greater than the reference voltage, the comparison circuit 113 transmits a first control signal to the drive circuit 115 to control the drive circuit 115 to turn on the switch circuit 117 and maintain the first voltage source 17 to supply power to the microcontroller 15. When the voltage transmitted by the voltage divider circuit 111 is less than the reference voltage, the comparison circuit 113 transmits a second control signal to the drive circuit 115 to control the drive circuit 115 to turn off the switch circuit 117 and cut off the first voltage source 17 from supplying power to the microcontroller 15. The comparison circuit 113 can be implemented in various ways. In one example, Figure 2As shown, a feasible implementation is provided, where the comparison circuit 113 includes a comparator A1 and a third resistor. The positive input terminal of the comparator A1 is respectively connected to the second end of the first resistor R1 and the first end of the second resistor R2, the negative input terminal is connected to the second voltage source, the positive power supply terminal is connected to the third voltage source, the negative power supply terminal is grounded, and the output terminal is connected to the first end of the third resistor; the second end of the third resistor is connected to the driving circuit 115.

[0048] The driving circuit 115 is used to control the driving switch circuit 117 to be turned on or off when receiving the signal from the comparison circuit 113. There are many ways to implement the driving circuit 115. In one example, Figure 2 As shown in FIG. 1 , a feasible implementation is provided, wherein the driving circuit 115 includes an optical coupling isolator OC. The switch circuit 117 is used to receive the drive of the driving circuit 115, and cut off or turn on the first voltage source 17 to supply power to the microcontroller 15. There are various implementations of the switch circuit 117. In one example, Figure 2 As shown, a feasible implementation is provided, the switch circuit 117 includes a fourth resistor R4, a fifth resistor R5 and a field effect transistor Q1. The first input end of the optical coupling isolator OC is connected to the second end of the third resistor, the second input end is grounded, the first output end is respectively connected to the first end of the fourth resistor R4 and the first end of the fifth resistor R5, and the second output end is grounded; the second end of the fourth resistor R4 is respectively connected to the source of the field effect transistor Q1 and the first voltage source 17; the second end of the fifth resistor R5 is connected to the gate of the field effect transistor Q1; the drain of the field effect transistor Q1 is connected to the voltage end of the microcontroller 15.

[0049] The clothing processing device provided in each embodiment of the present application includes a power-off protection device 11. In actual use, the power-off protection device 11 monitors the output voltage of the input power rectifier circuit 13 of the motor, and cuts off the power supply from the first voltage source 17 to the microcontroller 15 when the output voltage of the input power rectifier circuit 13 of the motor is detected to be lower than the set threshold value. Therefore, when the motor is powered off, the power supply of the microcontroller 15 is cut off immediately, avoiding the problem that the microcontroller 15 continues to send control signals to the motor drive board during the period when the drive voltage of the motor drive board lags down due to the presence of the capacitor, thereby effectively eliminating the strong oscillation of the bus voltage of the motor and the phase current of the motor, and avoiding damage to the power device.

[0050] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0051] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as constraints on the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A power-off protection device for a motor, characterized in that: It includes a voltage divider circuit, a comparison circuit, a drive circuit and a switch circuit; the voltage divider circuit is connected to the input power rectifier circuit of the motor; the voltage divider circuit is connected to the comparison circuit; The comparison circuit is connected to the driving circuit; The driving circuit is connected to the switching circuit; The switch circuit is connected between a voltage terminal of a microcontroller of the motor and a first voltage source.

2. The power-off protection device for a motor according to claim 1, characterized in that: The voltage divider circuit includes a first resistor and a second resistor; the first end of the first resistor is connected to the input power rectifier circuit of the motor, and the second end is respectively connected to the first end of the second resistor and the comparison circuit; the second end of the second resistor is grounded.

3. The power-off protection device for a motor according to claim 2, characterized in that: The comparison circuit includes a comparator and a third resistor; the positive input terminal of the comparator is respectively connected to the second end of the first resistor and the first end of the second resistor, the negative input terminal is connected to the second voltage source, the positive power supply terminal is connected to the third voltage source, the negative power supply terminal is grounded, and the output terminal is connected to the first end of the third resistor; the second end of the third resistor is connected to the driving circuit.

4. The power-off protection device for a motor according to claim 3, characterized in that: The driving circuit comprises an optical coupling isolator; a first input terminal of the optical coupling isolator is connected to the second end of the third resistor, a second input terminal is grounded, a first output terminal is connected to the switch circuit, and a second output terminal is grounded.

5. The power-off protection device for a motor according to claim 4, characterized in that: The switching circuit includes a fourth resistor, a fifth resistor and a field effect transistor; the first end of the fourth resistor is respectively connected to the first output end of the optical coupling isolator and the first end of the fifth resistor, and the second end is respectively connected to the source of the field effect transistor and the first voltage source; the second end of the fifth resistor is connected to the gate of the field effect transistor; the drain of the field effect transistor is connected to the voltage end of the microcontroller.

6. A clothes processing device, characterized in that: A power-off protection device for a motor according to any one of claims 1 to 5, further comprising an input power rectifier circuit, a transformer, a microcontroller, a driver chip, a switch circuit and a motor; the input power rectifier circuit is respectively connected to the input power of the voltage divider circuit of the power-off protection device, the power-off protection device and the transformer; The voltage transformation device is respectively connected to the microcontroller, the driving chip and the on-off circuit; The power-off protection device is connected between the voltage terminal of the microcontroller and the first voltage source; the microcontroller is connected to the driver chip; the driver chip is connected to the on-off circuit; The on-off circuit is connected to the motor; wherein, when the power-off protection device detects that the output voltage of the input power rectifier circuit is lower than a set threshold, it cuts off the first voltage source from supplying power to the microcontroller.

7. The clothes processing device according to claim 6, characterized in that: The power-off protection device comprises a voltage divider circuit, a comparison circuit, a drive circuit and a switch circuit; the voltage divider circuit is connected to the input power rectifier circuit; the voltage divider circuit is connected to the comparison circuit; The comparison circuit is connected to the driving circuit; The driving circuit is connected to the switching circuit; The switch circuit is connected between the voltage terminal of the microcontroller and the first voltage source.

8. The clothes processing device according to claim 7, characterized in that: The voltage divider circuit includes a first resistor and a second resistor; the first end of the first resistor is connected to the input power rectifier circuit, and the second end is respectively connected to the first end of the second resistor and the comparison circuit; the second end of the second resistor is grounded.

9. The clothes processing device according to claim 8, characterized in that: The comparison circuit includes a comparator and a third resistor; the positive input terminal of the comparator is respectively connected to the second end of the first resistor and the first end of the second resistor, the negative input terminal is connected to the second voltage source, the positive power supply terminal is connected to the third voltage source, the negative power supply terminal is grounded, and the output terminal is connected to the first end of the third resistor; the second end of the third resistor is connected to the driving circuit.

10. The clothes processing device according to claim 9, characterized in that: The driving circuit includes an optical coupling isolator; the switching circuit includes a fourth resistor, a fifth resistor and a field effect transistor; the first input end of the optical coupling isolator is connected to the second end of the third resistor, the second input end is grounded, the first output end is respectively connected to the first end of the fourth resistor and the first end of the fifth resistor, and the second output end is grounded; the second end of the fourth resistor is respectively connected to the source of the field effect transistor and the first voltage source; the second end of the fifth resistor is connected to the gate of the field effect transistor; and the drain of the field effect transistor is connected to the voltage end of the microcontroller.

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