Microcomputer power supply protection circuit

Abstract

The utility model discloses a microcomputer power supply protection circuit, which relates to the technical field of microcomputer power supply and comprises a power supply module used for accessing alternating current electric energy, transforming voltage and rectifying and filtering; the alternating current detection module is used for voltage division sampling, signal phase shift and signal superposition processing; the electric energy change judgment module is used for detecting whether the voltage output by the alternating current detection module is zero potential; the timing control module is used for controlling the power supply protection module to cut off power when the duration of the received signal output by the electric energy change judgment module exceeds the timing time; the power supply protection module is used for controlling electric energy transmission and supplying power to a microcomputer connected with the microcomputer module; and the overvoltage detection module is used for detecting overvoltage and controlling the power supply protection module to be powered off when overvoltage occurs. The microcomputer power supply protection circuit can carry out power-off protection in advance when the fluctuation duration of alternating current electric energy exceeds the timing time, and also can carry out power-off protection when overvoltage occurs, thereby improving the power supply safety of a microcomputer.

Description

Technical Field

[0001] The utility model relates to the technical field of microcomputer power supply, in particular to a microcomputer power supply protection circuit. Background Art

[0002] A microcomputer is a small electronic computer composed of large-scale integrated circuits. It is a bare machine based on a microprocessor, equipped with internal memory, input and output interface circuits and corresponding auxiliary circuits. In order to avoid overvoltage and other situations in the power supply of the microcomputer and improve the safety of the microcomputer power supply, microcomputers in the existing technology generally use components such as comparators to detect overvoltage of the input electrical energy and perform power-off protection when overvoltage occurs. However, it is impossible to protect the microcomputer's electrical energy in advance, resulting in certain safety hazards in the microcomputer power supply, and therefore needs to be improved. Utility Model Content

[0003] The embodiment of the present utility model provides a microcomputer power supply protection circuit to solve the problems raised in the above background technology.

[0004] To achieve the above objectives, the present invention provides the following technical solutions:

[0005] A microcomputer power supply protection circuit includes: a power supply module, an AC detection module, an electric energy change judgment module, a timing control module, a power supply protection module, a microcomputer module and an overvoltage detection module;

[0006] A power module, configured to receive AC power, transform the AC power and output a first electric energy, and rectify and filter the first electric energy and output a second electric energy;

[0007] an AC detection module connected to the power module, configured to perform voltage division sampling processing on the first electric energy and phase shift processing on the sampled signal, superimpose the sampled signal and the phase-shifted signal and output a first detection signal;

[0008] an electric energy change judgment module, connected to the AC detection module, configured to detect the voltage of the first detection signal and output a first control signal when the first detection signal is not at zero potential;

[0009] a timing control module connected to the electric energy change judgment module, configured to set a timing time and output a first protection signal when the duration of the received first control signal exceeds the timing time;

[0010] a power supply protection module connected to the power supply module, the timing control module, the overvoltage detection module and the microcomputer module, configured to transmit the second electrical energy to the microcomputer module and stop transmitting the second electrical energy upon receiving the first protection signal or the second protection signal output by the overvoltage detection module;

[0011] a microcomputer module, configured to transmit the second electric energy transmitted by the power supply protection module to a connected microcomputer;

[0012] The overvoltage detection module is connected to the microcomputer module and is used to sample the voltage of the second electric energy input to the microcomputer module and output a second protection signal when the sampled signal is greater than a set overvoltage threshold.

[0013] As a further solution of the present invention: the power supply module includes a power supply interface, a first transformer, a first rectifier and a third capacitor; the power supply protection module includes an eleventh resistor, a first power tube and a first switch tube; the microcomputer module includes a microcomputer power supply interface;

[0014] Preferably, the first end and the second end of the power interface are respectively connected to the first end and the second end of the primary side of the first transformer, the first end and the second end of the secondary side of the first transformer are respectively connected to the first end and the second end of the first rectifier, the third end of the first rectifier is connected to one end of the third capacitor and the drain of the first power tube and is connected to the gate of the first power tube and the collector of the first switching tube through the eleventh resistor, the source of the first power tube is connected to the first end of the microcomputer power interface, the fourth end of the first rectifier is connected to the other end of the third capacitor, the emitter of the first switching tube, the second end of the microcomputer power interface and the ground, and the base of the first switching tube is connected to the overvoltage detection module and the timing control module.

[0015] As a further solution of the utility model: the AC detection module includes a first resistor, a second resistor, a third resistor, a first capacitor, a fifth resistor, a second capacitor, a fourth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor and a first operational amplifier;

[0016] Preferably, one end of the first resistor is connected to the first end of the secondary side of the first transformer, the other end of the first resistor is connected to one end of the ninth resistor and one end of the third resistor and is connected to the second end of the secondary side of the first transformer through the second resistor, the other end of the third resistor is connected to one end of the fifth resistor and the inverting end of the first operational amplifier through the first capacitor, the non-inverting end of the first operational amplifier is connected to one end of the seventh resistor and one end of the fourth resistor and the ground through the sixth resistor, the other end of the fourth resistor is connected to the other end of the fifth resistor through the second capacitor, the output end of the first operational amplifier is connected to the other end of the seventh resistor and the first end of the eighth resistor, and the second end of the eighth resistor is connected to the other end of the ninth resistor and the electric energy change judgment module.

[0017] As a further solution of the present utility model: the electric energy change judgment module includes a first comparator, a second comparator, a tenth resistor, a first diode and a second diode;

[0018] Preferably, the non-inverting end of the first comparator is connected to the inverting end of the second comparator and the second end of the eighth resistor, the inverting end of the first comparator is connected to the non-inverting end of the second comparator and is grounded through the tenth resistor, the output end of the first comparator is connected to the anode of the first diode, the output end of the second comparator is connected to the anode of the second diode, and the cathode of the first diode is connected to the cathode of the second diode and the timing control module.

[0019] As a further solution of the present invention: the timing control module includes a first power supply, a second switch tube, a twelfth resistor, a fourth capacitor, a thirteenth resistor, a third switch tube, a fourteenth resistor and a third diode;

[0020] Preferably, the first power supply is connected to the collector of the second switching tube and the collector of the third switching tube, the base of the second switching tube is connected to the cathode of the first diode, the emitter of the second switching tube is connected to one end of the twelfth resistor and one end of the fourth capacitor and is connected to the base of the third switching tube through the thirteenth resistor, the emitter of the third switching tube is connected to the anode of the third diode and is connected to the other end of the fourth capacitor, the other end of the twelfth resistor and the ground through the fourteenth resistor, and the cathode of the third diode is connected to the base of the first switching tube.

[0021] As a further solution of the present utility model: the overvoltage detection module includes a fifteenth resistor, a sixteenth resistor, a first potentiometer, a fourth diode and a fifth diode;

[0022] Preferably, one end of the fifteenth resistor is connected to the first end of the microcomputer power interface, the other end of the fifteenth resistor is connected to one end of the first potentiometer and is connected to the second end of the microcomputer power interface through the sixteenth resistor, the other end of the first potentiometer and the slider end are both connected to the cathode of the fourth diode, the anode of the fourth diode is connected to the anode of the fifth diode, and the cathode of the fifth diode is connected to the base of the first switching tube.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: the microcomputer power supply protection circuit of the present invention can transmit the electric energy output by the power supply module to the microcomputer module through the power supply protection module, and detect whether the AC power connected to the power module fluctuates through the AC detection module in conjunction with the electric energy change judgment module, and when the electric energy fluctuation time exceeds the timing time set by the timing control module, the timing control module will control the power supply protection module to perform power-off protection in advance, and at the same time, the overvoltage detection module will perform overvoltage detection on the DC power provided by the power module. When overvoltage occurs, the power supply protection module is controlled to perform power-off protection, thereby improving the power supply safety of the microcomputer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 The present invention provides a schematic block diagram of a microcomputer power supply protection circuit.

[0026] Figure 2 The present invention provides a circuit diagram of a microcomputer power supply protection circuit.

[0027] Figure 3 This is a connection circuit diagram of the overvoltage detection module provided by an example of the present utility model. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] In one embodiment, see Figure 1 , a microcomputer power supply protection circuit, comprising: a power supply module 1, an AC detection module 2, an electric energy change judgment module 3, a timing control module 4, a power supply protection module 5, a microcomputer module 6 and an overvoltage detection module 7;

[0030] Specifically, the power module 1 is used to receive AC power, transform the AC power and output a first electric energy, rectify and filter the first electric energy and output a second electric energy;

[0031] an AC detection module 2 connected to the power module 1, configured to perform voltage division sampling processing on the first electric energy and perform phase shift processing on the sampled signal, superimpose the sampled signal and the phase-shifted signal and output a first detection signal;

[0032] The electric energy change judgment module 3 is connected to the AC detection module 2 and is used to detect the voltage of the first detection signal and output a first control signal when the first detection signal is not at zero potential;

[0033] The timing control module 4 is connected to the electric energy change judgment module 3 and is used to set a timing time and output a first protection signal when the duration of the received first control signal exceeds the timing time;

[0034] a power supply protection module 5 connected to the power supply module 1, the timing control module 4, the overvoltage detection module 7, and the microcomputer module 6, configured to transmit the second electrical energy to the microcomputer module 6, and stop transmitting the second electrical energy upon receiving the first protection signal or the second protection signal output by the overvoltage detection module 7;

[0035] The microcomputer module 6 is used to transmit the second electric energy transmitted by the power supply protection module 5 to the connected microcomputer;

[0036] The overvoltage detection module 7 is connected to the microcomputer module 6 and is used to sample the voltage of the second electric energy input to the microcomputer module 6 and output a second protection signal when the sampled signal is greater than a set overvoltage threshold.

[0037] In a specific embodiment, the power supply module 1 may adopt a power supply circuit composed of a power interface, a transformer, a rectifier, etc., which may be connected to AC power and perform voltage transformation, rectification and filtering on the AC power; the AC detection module 2 may adopt an AC detection circuit composed of resistors, capacitors and operational amplifiers, which may divide the transformed electric energy, and perform 180-degree phase shift processing on the divided signal, superimpose the phase-shifted signal and the voltage-divided signal and output a first detection signal. When no voltage mutation occurs, the potential of the superimposed first detection signal is zero; the electric energy change judgment module 3 may adopt an electric energy change judgment circuit composed of a comparator, a resistor and a diode, detect whether the first detection signal is zero potential, and when the first detection signal is not zero When the first control signal is output, the first control signal is output; the timing control module 4 can adopt a timing control circuit composed of a transistor, a resistor, a capacitor, etc., can set the timing time, and output the first protection signal when the duration of receiving the first control signal exceeds the timing time; the power supply protection module 5 can adopt a power supply protection circuit composed of a field effect tube, a resistor and a transistor, can control the power transmission and perform power-off protection when receiving the signal output by the timing control module 4 or the overvoltage detection module 7; the microcomputer module 6 can adopt a microcomputer power supply interface to be connected to the power supply end of the microcomputer; the overvoltage detection module 7 can adopt an overvoltage detection circuit composed of a resistor, a potentiometer and a diode to perform voltage division sampling on the input power, and compare the sampled signal with the voltage of the set overvoltage threshold.

[0038] In another embodiment, see Figure 1 、 Figure 2 and Figure 3 The power supply module 1 includes a power supply interface, a first transformer B1, a first rectifier T1 and a third capacitor C3; the power supply protection module 5 includes an eleventh resistor R11, a first power tube Q1 and a first switch tube V1; the microcomputer module 6 includes a microcomputer power supply interface;

[0039] Specifically, the first end and the second end of the power interface are respectively connected to the first end and the second end of the primary side of the first transformer B1, the first end and the second end of the secondary side of the first transformer B1 are respectively connected to the first end and the second end of the first rectifier T1, the third end of the first rectifier T1 is connected to one end of the third capacitor C3 and the drain of the first power tube Q1 and is connected to the gate of the first power tube Q1 and the collector of the first switching tube V1 through the eleventh resistor R11, the source of the first power tube Q1 is connected to the first end of the microcomputer power interface, the fourth end of the first rectifier T1 is connected to the other end of the third capacitor C3, the emitter of the first switching tube V1, the second end of the microcomputer power interface and the ground, and the base of the first switching tube V1 is connected to the overvoltage detection module 7 and the timing control module 4.

[0040] In a specific embodiment, the first power tube Q1 can be an N-channel field effect tube; and the first switch tube V1 can be an NPN transistor.

[0041] Furthermore, the AC detection module 2 includes a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C1, a fifth resistor R5, a second capacitor C2, a fourth resistor R4, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9 and a first operational amplifier OP1;

[0042] Specifically, one end of the first resistor R1 is connected to the first end of the secondary side of the first transformer B1, the other end of the first resistor R1 is connected to one end of the ninth resistor R9 and one end of the third resistor R3 and is connected to the second end of the secondary side of the first transformer B1 through the second resistor R2, the other end of the third resistor R3 is connected to one end of the fifth resistor R5 and the inverting end of the first operational amplifier OP1 through the first capacitor C1, the non-inverting end of the first operational amplifier OP1 is connected to one end of the seventh resistor R7 and is connected to one end of the fourth resistor R4 and the ground through the sixth resistor R6, the other end of the fourth resistor R4 is connected to the other end of the fifth resistor R5 through the second capacitor C2, the output end of the first operational amplifier OP1 is connected to the other end of the seventh resistor R7 and the first end of the eighth resistor R8, and the second end of the eighth resistor R8 is connected to the other end of the ninth resistor R9 and the electric energy change judgment module 3.

[0043] In a specific embodiment, the first resistor R1 and the second resistor R2 perform voltage sampling; the first operational amplifier OP1 can optionally use an OP07 operational amplifier, and cooperate with the third resistor R3, the first capacitor C1, the fifth resistor R5, the second capacitor C2, the fourth resistor R4, the sixth resistor R6, the seventh resistor R7 and the eighth resistor R8 to perform phase shifting processing, and the phase-shifted signal is superimposed with the signal transmitted by the ninth resistor R9.

[0044] Furthermore, the electric energy change judgment module 3 includes a first comparator A1, a second comparator A2, a tenth resistor R10, a first diode D1 and a second diode D2;

[0045] Specifically, the non-inverting end of the first comparator A1 is connected to the inverting end of the second comparator A2 and the second end of the eighth resistor R8, the inverting end of the first comparator A1 is connected to the non-inverting end of the second comparator A2 and grounded through the tenth resistor R10, the output end of the first comparator A1 is connected to the anode of the first diode D1, the output end of the second comparator A2 is connected to the anode of the second diode D2, and the cathode of the first diode D1 is connected to the cathode of the second diode D2 and the timing control module 4.

[0046] In a specific embodiment, both the first comparator A1 and the second comparator A2 can be LM358 comparators.

[0047] Furthermore, the timing control module 4 includes a first power supply VCC1, a second switch tube V2, a twelfth resistor R12, a fourth capacitor C4, a thirteenth resistor R13, a third switch tube V3, a fourteenth resistor R14 and a third diode V3;

[0048] Specifically, the first power supply VCC1 is connected to the collector of the second switching tube V2 and the collector of the third switching tube V3, the base of the second switching tube V2 is connected to the cathode of the first diode D1, the emitter of the second switching tube V2 is connected to one end of the twelfth resistor R12 and one end of the fourth capacitor C4, and is connected to the base of the third switching tube V3 through the thirteenth resistor R13, the emitter of the third switching tube V3 is connected to the anode of the third diode V3, and is connected to the other end of the fourth capacitor C4, the other end of the twelfth resistor R12, and the ground through the fourteenth resistor R14, and the cathode of the third diode V3 is connected to the base of the first switching tube V1.

[0049] In a specific embodiment, the second switch tube V2 and the third switch tube V3 can both be NPN transistors; the twelfth resistor R12, the fourth capacitor C4 and the thirteenth resistor R13 set the timing time. When the electric energy stored in the fourth capacitor C4 triggers the third switch tube V3 to turn on, it means that the timing time has exceeded.

[0050] Furthermore, the overvoltage detection module 7 includes a fifteenth resistor R15, a sixteenth resistor R16, a first potentiometer RP1, a fourth diode D4 and a fifth diode D5;

[0051] Specifically, one end of the fifteenth resistor R15 is connected to the first end of the microcomputer power interface, the other end of the fifteenth resistor R15 is connected to one end of the first potentiometer RP1 and is connected to the second end of the microcomputer power interface through the sixteenth resistor R16, the other end of the first potentiometer RP1 and the slider end are both connected to the cathode of the fourth diode D4, the anode of the fourth diode D4 is connected to the anode of the fifth diode D5, and the cathode of the fifth diode D5 is connected to the base of the first switching tube V1.

[0052] In a specific embodiment, the fifteenth resistor R15 and the sixteenth resistor R16 perform voltage division sampling; the first potentiometer RP1 and the fourth diode D4 set the overvoltage threshold.

[0053] In a microcomputer power supply protection circuit of the present embodiment, AC power is connected to the power interface, the first transformer B1 performs voltage transformation and outputs the first power, the first rectifier T1 and the third capacitor C3 perform rectification and filtering and output the second power, the first resistor R1 and the second resistor R2 perform voltage sampling processing on the first power, the first operational amplifier OP1 cooperates with the third resistor R3, the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, the eighth resistor R8, the first capacitor C1 and the second capacitor C2 to perform 180-degree phase shift processing, and the phase-shifted power is superimposed on the signal transmitted by the ninth resistor R9. When the potential of the superimposed signal is greater than zero, the first comparator A1 outputs a high level or the superimposed signal When the potential of is less than zero, the second comparator A2 outputs a high level. The high level output, i.e., the first control signal, controls the second switch tube V2 to turn on, and the fourth capacitor C4 to store electrical energy. When the stored electrical energy can trigger the third switch tube V3 to turn on, the third switch tube V3 turns on, and then triggers the first switch tube V1 to turn on, controlling the first power tube Q1 to turn off for power-off protection. The fifteenth resistor R15 and the sixteenth resistor R16 can sample the voltage of the electrical energy transmitted by the first power tube Q1. If the sampled signal is greater than the overvoltage threshold set by the first potentiometer RP1 and the fourth diode D4, the fourth diode D4 is broken down, and then triggers the first switch tube V1 to turn on, controlling the first power tube Q1 to turn off for power-off protection.

[0054] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be encompassed within the present invention. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0055] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A microcomputer power supply protection circuit, characterized in that: The microcomputer power supply protection circuit includes: a power supply module, an AC detection module, an electric energy change judgment module, a timing control module, a power supply protection module, a microcomputer module and an overvoltage detection module; The power supply module is used to receive AC power, transform the AC power and output a first electric energy, and rectify and filter the first electric energy and output a second electric energy; The AC detection module is connected to the power supply module, and is used to perform voltage division sampling processing on the first electric energy and phase shift processing on the sampled signal, superimpose the sampled signal and the phase-shifted signal and output a first detection signal; The electric energy change judgment module is connected to the AC detection module and is used to detect the voltage of the first detection signal and output a first control signal when the first detection signal is not at zero potential; The timing control module is connected to the power change judgment module and is used to set a timing time and output a first protection signal when the duration of the received first control signal exceeds the timing time; The power supply protection module is connected to the power supply module, the timing control module, the overvoltage detection module and the microcomputer module, and is used to transmit the second electric energy to the microcomputer module, and stop transmitting the second electric energy when receiving the first protection signal or the second protection signal output by the overvoltage detection module; The microcomputer module is used to transmit the second electric energy transmitted by the power supply protection module to the connected microcomputer; The overvoltage detection module is connected to the microcomputer module and is used to sample the voltage of the second electric energy input to the microcomputer module, and output a second protection signal when the sampled signal is greater than a set overvoltage threshold.

2. A microcomputer power supply protection circuit according to claim 1, characterized in that: The power supply module includes a power supply interface, a first transformer, a first rectifier and a third capacitor; the power supply protection module includes an eleventh resistor, a first power tube and a first switch tube; the microcomputer module includes a microcomputer power supply interface; The first end and the second end of the power interface are respectively connected to the first end and the second end of the primary side of the first transformer, the first end and the second end of the secondary side of the first transformer are respectively connected to the first end and the second end of the first rectifier, the third end of the first rectifier is connected to one end of the third capacitor and the drain of the first power tube and is connected to the gate of the first power tube and the collector of the first switching tube through an eleventh resistor, the source of the first power tube is connected to the first end of the microcomputer power interface, the fourth end of the first rectifier is connected to the other end of the third capacitor, the emitter of the first switching tube, the second end of the microcomputer power interface and the ground, and the base of the first switching tube is connected to the overvoltage detection module and the timing control module.

3. A microcomputer power supply protection circuit according to claim 2, characterized in that: The AC detection module includes a first resistor, a second resistor, a third resistor, a first capacitor, a fifth resistor, a second capacitor, a fourth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor and a first operational amplifier; One end of the first resistor is connected to the first end of the secondary side of the first transformer, the other end of the first resistor is connected to one end of the ninth resistor and one end of the third resistor and is connected to the second end of the secondary side of the first transformer through the second resistor, the other end of the third resistor is connected to one end of the fifth resistor and the inverting end of the first operational amplifier through the first capacitor, the non-inverting end of the first operational amplifier is connected to one end of the seventh resistor and one end of the fourth resistor and the ground through the sixth resistor, the other end of the fourth resistor is connected to the other end of the fifth resistor through the second capacitor, the output end of the first operational amplifier is connected to the other end of the seventh resistor and the first end of the eighth resistor, and the second end of the eighth resistor is connected to the other end of the ninth resistor and the electric energy change judgment module.

4. A microcomputer power supply protection circuit according to claim 3, characterized in that: The electric energy change judgment module includes a first comparator, a second comparator, a tenth resistor, a first diode and a second diode; The non-inverting end of the first comparator is connected to the inverting end of the second comparator and the second end of the eighth resistor, the inverting end of the first comparator is connected to the non-inverting end of the second comparator and is grounded through the tenth resistor, the output end of the first comparator is connected to the anode of the first diode, the output end of the second comparator is connected to the anode of the second diode, and the cathode of the first diode is connected to the cathode of the second diode and the timing control module.

5. A microcomputer power supply protection circuit according to claim 4, characterized in that: The timing control module includes a first power supply, a second switch tube, a twelfth resistor, a fourth capacitor, a thirteenth resistor, a third switch tube, a fourteenth resistor and a third diode; The first power supply is connected to the collector of the second switching tube and the collector of the third switching tube, the base of the second switching tube is connected to the cathode of the first diode, the emitter of the second switching tube is connected to one end of the twelfth resistor and one end of the fourth capacitor and is connected to the base of the third switching tube through the thirteenth resistor, the emitter of the third switching tube is connected to the anode of the third diode and is connected to the other end of the fourth capacitor, the other end of the twelfth resistor and the ground through the fourteenth resistor, and the cathode of the third diode is connected to the base of the first switching tube.

6. A microcomputer power supply protection circuit according to claim 2, characterized in that: The overvoltage detection module includes a fifteenth resistor, a sixteenth resistor, a first potentiometer, a fourth diode and a fifth diode; One end of the fifteenth resistor is connected to the first end of the microcomputer power interface, the other end of the fifteenth resistor is connected to one end of the first potentiometer and is connected to the second end of the microcomputer power interface through the sixteenth resistor, the other end of the first potentiometer and the slider end are both connected to the cathode of the fourth diode, the anode of the fourth diode is connected to the anode of the fifth diode, and the cathode of the fifth diode is connected to the base of the first switching tube.

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