An isolated power supply circuit for intelligent circuit breakers

Abstract

This utility model relates to an isolated power supply circuit for intelligent circuit breakers, which includes an isolated power supply unit, a current sampling unit, a voltage sampling unit, a signal detection unit, a liquid crystal display unit, an execution control unit, a storage circuit, a key circuit, a clock circuit, a 485 circuit, and a 32-bit MCU. Compared with traditional circuit breaker power supply circuits, this utility model adopts the above-mentioned structure, which has a more reasonable structural design, improves the reliability and stability of the power supply, improves the accuracy of current and voltage sampling, and makes human-machine interaction more convenient.

Description

Technical Field

[0001] This utility model relates to a power supply circuit, and more particularly to an isolated power supply circuit for intelligent circuit breakers. Background Technology

[0002] The power supply circuit of the existing intelligent circuit breaker controller is relatively simple. The system power supply circuit has not been divided into detailed circuits, and the anti-interference ability between the circuits is poor, which leads to the instability of the whole system. In addition, the processor uses a 16-bit microcontroller, which has limited data processing speed, resulting in large measurement accuracy errors and a high possibility of false tripping. The human-machine interaction is also relatively simple, and there is no intuitive human-machine interaction display operation platform. Utility Model Content

[0003] The technical problem to be solved by this utility model is to provide an isolated power supply circuit for intelligent circuit breakers, which has strong anti-interference ability, fast data processing speed, and intuitive and convenient human-computer interaction.

[0004] To address the aforementioned technical problems, this utility model provides an isolated power supply circuit for intelligent circuit breakers, comprising an isolated power supply unit, a current sampling unit, a voltage sampling unit, a signal detection unit, a liquid crystal display unit, an execution control unit, a storage circuit, a key circuit, a clock circuit, a 485 circuit, and a 32-bit MCU. The outputs of the current sampling unit, voltage sampling unit, and signal detection unit are respectively connected to the inputs of the 32-bit MCU, responsible for processing the power grid signal sampling and handing over the pre-processed signal to the MCU. The output of the 32-bit MCU is connected to the inputs of the LCD display unit and the execution control unit, responsible for real-time feedback and display of the processed information, and outputting action signals through the execution control unit. The storage circuit, button circuit, clock circuit, and 485 circuit are bidirectional connections between the MCU peripheral circuit and the 32-bit MCU. The peripheral circuit assists the MCU in performing related data storage and time uploading functions. The output of the isolated power supply unit provides operating voltage to the 32-bit MCU, current sampling unit, voltage sampling unit, signal detection unit, and execution control unit respectively.

[0005] This utility model's power supply circuit employs three different grounding methods, dividing the entire circuit system into three zones: a high-voltage grid processing module with SGND, a low-voltage system operating module with GND, and a communication transmission module with G485. Each zone operates relatively independently, exhibiting strong anti-interference capabilities and resulting in a more stable and reliable system.

[0006] The isolated power supply unit includes a current transformer, a voltage sampling line, an isolated power supply circuit, and a chopper protection power supply circuit. The isolated power supply unit adopts two power supply methods: direct sampling of grid voltage and induction power supply by current transformer. It also isolates the circuit, providing a stable and reliable power supply and ensuring the operational stability of the entire system.

[0007] The current sampling signal unit includes a current transformer input and an analog input signal from an ABC three-phase current amplifier circuit, wherein the ABC phases of the signal amplifier circuit adopt a consistent multi-stage amplification form.

[0008] The voltage sampling signal unit includes a voltage sampling line and an ABC phase voltage clamping sampling circuit. The voltage clamping sampling circuit adopts a consistent step-down form, and the step-down circuit achieves isolation between the high and low voltage circuits by adopting a non-common ground form.

[0009] The 485 circuit is grounded and isolated from other circuits by a digital isolator.

[0010] The peripheral circuits also include storage circuits, clock circuits, key circuits, liquid crystal display circuits, and external signal detection circuits.

[0011] The beneficial effects of this utility model are as follows: the isolated power supply circuit design of the intelligent circuit breaker is more reasonable, its circuit anti-interference capability is strong, its data processing speed is fast, its human-computer interaction is intuitive and convenient, and the stability of the power application system is improved. Attached Figure Description

[0012] Figure 1 This is a block diagram illustrating the circuit principle of an embodiment of this utility model.

[0013] Figure 2 This is an isolated power supply unit according to an embodiment of the present invention.

[0014] Figure 3 This is a current sampling unit according to an embodiment of the present invention.

[0015] Figure 4 This is a voltage sampling unit according to an embodiment of the present invention.

[0016] Figure 5 This is the execution control unit of this utility model embodiment.

[0017] Figure 6 This is the circuit of embodiment 485 of this utility model.

[0018] Figure 7 This is a 32-bit MCU according to an embodiment of the present invention.

[0019] Figure 8 This is a clock circuit according to an embodiment of the present invention.

[0020] Figure 9 This is a storage circuit according to an embodiment of the present invention.

[0021] Figure 10 This is a key circuit according to an embodiment of the present invention.

[0022] Figure 11 This is a signal detection unit according to an embodiment of the present invention.

[0023] Figure 12 This is a liquid crystal display unit according to an embodiment of the present utility model. Detailed Implementation

[0024] like Figure 1 As shown, this utility model is an isolated power supply circuit for an intelligent circuit breaker. The system includes an isolated power supply unit, a current sampling unit, a voltage sampling unit, a signal detection unit, an LCD display unit, an execution control unit, a storage circuit, a button circuit, a clock circuit, a 485 circuit, and a 32-bit MCU. The outputs of the current sampling unit, voltage sampling unit, and signal detection unit are respectively connected to the inputs of the 32-bit MCU, responsible for processing the power grid signal sampling and handing over the pre-processed signal to the MCU for use. The output of the 32-bit MCU is connected to the inputs of the LCD display unit and the execution control unit, responsible for real-time feedback and display of the processed information, and outputting action signals through the execution control unit. The storage circuit, button circuit, clock circuit, and 485 circuit are bidirectional connections between the MCU peripheral circuit and the 32-bit MCU, assisting the MCU in performing related data storage and time uploading functions. The output of the isolated power supply unit provides suitable operating voltages to the 32-bit MCU, current sampling unit, voltage sampling unit, signal detection unit, and execution control unit.

[0025] This utility model's power supply circuit employs three different grounding methods, dividing the entire circuit system into three zones: a high-voltage grid processing module with SGND, a low-voltage system operating module with GND, and a communication transmission module with G485. Each zone operates relatively independently, exhibiting strong anti-interference capabilities and resulting in a more stable and reliable system.

[0026] like Figure 2As shown, one method involves the power grid inputting into an isolated power supply circuit via terminals UA, UB, UC, and UN. Rectification, filtering, and voltage regulation circuits then provide two stable low-voltage power supplies for use by other circuit modules in the system. Another method involves connecting external current transformers (A, B, C) to rectifier bridges U4, U5, and U7 respectively to obtain the transformer's induced current. Rectification, filtering, and voltage regulation circuits then provide a stable low-voltage power supply. These two different power supply modes solve the problem of low conversion efficiency of current transformers leading to power instability when the current is small, and also improve the accuracy of current and voltage sampling. The isolated power supply circuit includes inductors L1-L3, a mode filter L4, thermistors RTV1-RTV3, diodes D1-D12, varistors RV1, resistors R1-R12, capacitors C1-C19, a transformer U1, a power chip U2, and a transistor U3. One end of the inductor L1 is connected to the A-phase voltage sampling line, and the other end is connected in series with the thermistor RTV1, rectifier diodes D1 and D2 for half-wave rectification. The cathode of diode D2 is connected to one end of varistor RV1, varistor RV1, capacitor C8, and the input terminal of common-mode filter L4 in parallel, and the other end is grounded (SGND). The output terminal of common-mode filter is connected to pin 1 of transformer U1 and connected in parallel with capacitor C9 to ground (GND). The ground is segmented by common-mode filter. One end of resistor R4 and capacitor C7 in parallel is connected to capacitor C9. Resistor R11 and capacitor C15 in parallel are connected in series with capacitor C9. The other end of resistor R11 is grounded (SGND). Resistor R2 and capacitor C6 are connected in parallel, one end of which is connected to transformer pin 1, and the other end is connected in series with resistor R5 and diode D4. The other end of diode D4 is connected to transformer pin 3 and pins 5, 6, and 7 of chip U2. Resistor R6 and ground R7 are connected in parallel, one end of which is connected to pin 4 of chip U2, and the other end is grounded (SGND). Pin 2 of chip U2 is grounded (SGND). Pin 1 is connected to capacitors C18 and C19 and one end of the negative terminal of diode D8. Capacitors C18 and C19 are connected in parallel, and the other end is grounded (SGND). The positive terminal of diode D8 is connected in series with resistor R8 and then to transformer pin 5 and one end of resistor R9. The other end of resistor R9 is connected to chip U2 pin 3, capacitor C16, and one end of resistor R12. Capacitor C16 and resistor R12 are connected in parallel and then grounded (SGND). Transformer U1 pin 9 is grounded (GND). Transformer U1 pin 10 is connected to resistor R1 and one end of the positive terminal of diode D3. Resistor R1 and capacitor C5 are connected in series and then in parallel with diode D3 for half-wave rectification. Resistor R3 and capacitors C1, C2, C3, and C4 are connected in parallel, with one end connected to the cathode of diode D3. The other end of resistor R3 is grounded (GND) for filtering, outputting a 12V voltage. Pin 6 of transformer U1 is grounded (GND), and pin 7 of transformer U1 is connected in series with the anode of diode D7 for half-wave rectification. Resistor R10 and capacitors C13 and C14 are connected in parallel, with one end connected to the cathode of diode D7.The other end of resistor R10 is grounded (GND) for filtering. Zener transistor pin 3 is connected to diode D7, pin 1 is grounded (G485), and pin 2 is connected to one end of capacitor C10. Capacitors C10, C11, and C12 are connected in parallel, with one end connected to transistor pin 2 and the other end grounded (G485), outputting a 5V power supply for 485 communication. Transformer U1 outputs two power supplies with isolation: one generates 12V, and the other generates 5V, reducing harmonic interference and ensuring communication stability.

[0027] The chopper protection power supply circuit includes rectifier bridges U4-U6, diodes D13-D14, MOSFET V1, amplifier U7, resistors R13-R19, and capacitors C20-C22. The rectifier circuit connects the input terminal of rectifier bridge U4 to the A-phase output signal of the current transformer, and its output terminal is connected in series with diode D13 to output a 12V power supply. The B and C phase circuits are identical. One end of the bidirectional TVS diode D14 is connected to the output terminal of rectifier bridge U4, and the other end is grounded (GND). The drain of MOSFET V1 is connected to the output terminal of rectifier bridge U4, and its source is grounded (GND). The gate of MOSFET V1 is connected to one end of resistors R18 and R16. The other end of resistor R18 is grounded (GND), and the other end of resistor R16 is connected to the output of amplifier U7. One end of resistor R13 and one end of resistor R17 are connected. The other end of resistor R13 is connected to the cathode of diode D13. The other end of resistor R17 is connected to one end of resistor R19, one end of resistor R15, and the positive input terminal of amplifier U7. The other end of resistor R15 is connected to the cathode of diode D13. The other end of resistor R19 is grounded (GND). One end of resistor R14 is connected to the cathode of diode D13, and the other end is connected sequentially to the cathode of Zener diode D15, one end of capacitor C22, and the inverting input terminal of amplifier U7. The anode of diode D15 is connected in parallel with capacitor C22 and grounded (GND). One end of capacitors C20 and C21 is connected in parallel to the cathode of diode D13, and the other end is grounded (GND). This circuit constitutes a negative feedback amplifier circuit. When the detected voltage is too high, the signal feedback MOSFET V1 is chopped to release the voltage.

[0028] like Figure 3As shown, the current sampling unit includes a current transformer input and an ABC three-phase current amplification circuit to simulate the input signal. The ABC phase signal amplification circuits employ a consistent multi-stage amplification method, using different amplification factors for different signal inputs to improve the accuracy of current sampling. The A-phase sampling multi-stage amplification circuit includes resistors R20~R27, capacitors C23~C27, and a quad operational amplifier U2. Resistor R24 ​​is the power resistor of the A-phase current sampling unit, with one end grounded and the other end connected to the current transformer and resistor R21. The other end of resistor R21 is connected to capacitor C9, and the other end of capacitor C9 is grounded (GND). Resistor R2 and capacitor C9 form an RC filter circuit to filter harmonic signals. Resistor R22 is connected in series with resistor R21, and the other end of resistor R22 is connected to the first inverting input terminal of the quad operational amplifier U2. The first non-inverting input terminal of the operational amplifier is grounded (GND). One end of resistor R20 is connected to the first inverting input terminal of amplifier U2, and the other end is connected to the first output terminal of amplifier U2. Capacitor C22 and resistor 20 are connected in parallel to filter out high-frequency noise. Resistor R23 is connected in series with resistor R20. The other end of resistor R23 is connected to the ADC input terminal of the MCU chip and capacitor C23. The other end of capacitor C23 is grounded. Resistor R23 and capacitor C23 form an RC filter circuit, serving as the primary processing circuit for the sampled current signal. It has a relatively large amplification factor and is used to process small current sampling input signals. Resistor R26 is connected in series with resistor R21. The other end of resistor R25 is connected to the second inverting input terminal of the quad operational amplifier U2. The non-inverting input terminal of the operational amplifier is grounded. One end of resistor R25 is connected to the second inverting input terminal of amplifier U2, and the other end is connected to the second output terminal of amplifier U2. Capacitor C25 and resistor R25 are connected in parallel to filter out high-frequency noise. Resistor R27 is connected in series with resistor R25. The other end of resistor R27 is connected to the ADC input terminal of the MCU chip and capacitor C26. The other end of capacitor C26 is grounded. Resistor R27 and capacitor C26 form an RC filter circuit, which serves as a secondary processing circuit for the sampled current signal. It has a small amplification factor and is used to process large current sampling signal inputs.

[0029] like Figure 4As shown, the voltage sampling unit includes a voltage sampling line and ABC phase voltage clamping sampling circuits. The voltage clamping sampling circuits employ a consistent step-down method, using a non-common ground configuration to isolate the high and low voltage circuits, enhancing system safety. The A-phase voltage clamping step-down circuit includes resistors R28-R34, capacitors C27 and C28, and a Zener diode D16. One end of resistor R28 is connected to the A-phase sampling line, and the other end is connected in series with resistors R32, R29, and R30 to achieve rapid voltage reduction. The other end of resistor R30 is connected to one end of resistors R31 and R33, and capacitor C28. Resistor R33 and capacitor C28 are connected in parallel to ground (GND1). The other end of resistor R28 is connected to resistor R70, capacitor C65, and the negative terminal of Zener diode D16. Zener diode D16, resistor R34, and capacitor C27 are connected in parallel to ground (GND) to form a voltage regulation and filtering circuit. The output signal is connected to the ADC input terminal of the MCU chip.

[0030] Figure 6 As shown, the 485 circuit is grounded (G485) and isolated from other circuits by a digital isolator, ensuring the stability and anti-interference of the 485 circuit.

[0031] According to the above embodiments, the isolated power supply circuit of this utility model improves the system stability, current and voltage sampling accuracy and data processing speed, and enhances the convenience of human-computer interaction and the intelligence of remote power grid information detection.

[0032] The execution control unit circuit, clock circuit, storage circuit, key circuit, signal detection unit, and liquid crystal display unit circuit used in this embodiment are all conventional existing technologies and will not be described in detail.

[0033] The above-described specific embodiments should not be construed as limiting the scope of protection of this utility model. Any alternative improvements or modifications made to the embodiments of this utility model by those skilled in the art will fall within the scope of protection of this utility model. Any aspects not described in detail in this utility model are well-known technologies to those skilled in the art.

Claims

1. An isolated power supply circuit for a smart circuit breaker, characterized in that: It includes an isolated power supply unit, a current sampling unit, a voltage sampling unit, a signal detection unit, an LCD display unit, an execution control unit, a storage circuit, a key circuit, a clock circuit, a 485 circuit, and a 32-bit MCU. The outputs of the current sampling unit, voltage sampling unit, and signal detection unit are respectively connected to the inputs of the 32-bit MCU, responsible for processing the power grid signal sampling and handing over the pre-processed signal to the MCU. The output of the 32-bit MCU is connected to the inputs of the LCD display unit and the execution control unit, responsible for real-time feedback and display of the processed information, and outputting action signals through the execution control unit. The storage circuit, button circuit, clock circuit, and 485 circuit are bidirectional connections between the MCU peripheral circuit and the 32-bit MCU. The peripheral circuit assists the MCU in performing related data storage and time uploading functions. The output of the isolated power supply unit provides operating voltage to the 32-bit MCU, current sampling unit, voltage sampling unit, signal detection unit, and execution control unit respectively.

2. The isolated power supply circuit for intelligent circuit breakers according to claim 1, characterized in that: The isolated power supply unit includes a current transformer, a voltage sampling line, an isolated power supply circuit, and a chopper protection power supply circuit. The isolated power supply unit adopts two power supply methods: direct sampling of grid voltage and induction power supply by current transformer.

3. The isolated power supply circuit for intelligent circuit breakers according to claim 1, characterized in that: The current sampling signal unit includes a current transformer input and an analog input signal from an ABC three-phase current amplifier circuit, wherein the ABC three-phase current amplifier circuit adopts a consistent multi-stage amplification form.

4. The isolated power supply circuit for intelligent circuit breakers according to claim 1, characterized in that: The voltage sampling signal unit includes a voltage sampling line and an ABC phase voltage clamping sampling circuit. The voltage clamping sampling circuit adopts a consistent step-down form and uses a non-common ground form to achieve isolation between high and low voltage circuits.

5. The isolated power supply circuit for an intelligent circuit breaker according to claim 1, characterized in that: The 485 circuit is grounded and isolated from other circuits by a digital isolator.

6. The isolated power supply circuit for a smart circuit breaker according to claim 2, characterized in that: The isolated power supply circuit includes inductors L1-L3, a common-mode filter L4, thermistors RTV1-RTV3, diodes D1-D12, varistor RV1, resistors R1-R12, capacitors C1-C19, transformer U1, power chip U2, and transistor U3. One end of inductor L1 is connected to the A-phase voltage sampling line, and the other end is connected in series with thermistor RTV1 and rectifier diodes D1 and D2 for half-wave rectification. The cathode of diode D2 is connected to one end of varistor RV1, and varistor RV1, capacitor C8, and the input terminal of common-mode filter L4 are connected in parallel, with the other end grounded. The output terminal of common-mode filter is connected to pin 1 of transformer U1. A common-mode filter is used to segment the ground connection between capacitor C9 and capacitor C7. Resistor R4 is connected in parallel with capacitor C7, one end of which is connected to capacitor C9. Resistor R11 is connected in parallel with capacitor C15 and then in series with capacitor C9. The other end of resistor R11 is grounded. Resistor R2 is connected in parallel with capacitor C6, one end of which is connected to transformer pin 1, and the other end is connected in series with resistor R5 and diode D4. The other end of diode D4 is connected to transformer pin 3 and pins 5, 6, and 7 of chip U2. Resistor R6 is connected in parallel with ground resistor R7, one end of which is connected to pin 4 of chip U2, and the other end is grounded. Pin 2 of chip U2 is grounded. Pin 1 is connected to capacitors C18 and C19, and one end of the negative terminal of diode D8. Capacitor C1... 8 is connected in parallel with capacitor C19, with the other end grounded. The positive terminal of diode D8 is connected in series with resistor R8 and then connected to transformer pin 5 and one end of resistor R9. The other end of resistor R9 is connected to pin 3 of chip U2, one end of capacitor C16 and resistor R12. Capacitor C16 and resistor R12 are connected in parallel and then grounded. Pin 9 of transformer U1 is grounded. Pin 10 of transformer U1 is connected to resistor R1 and one end of the positive terminal of diode D3. Resistor R1 and capacitor C5 are connected in series and then in parallel with diode D3 for half-wave rectification. Resistor R3 and capacitors C1, C2, C3, and C4 are connected in parallel, with one end connected to the negative terminal of diode D3. The other end of resistor R3 is grounded for filtering. The output terminal... The transformer U1 outputs a 12V voltage. Pin 6 of the transformer U1 is grounded, and pin 7 of the transformer U1 is connected in series with the positive terminal of diode D7 for half-wave rectification. One end of the parallel connection of resistor R10 and capacitors C13 and C14 is connected to the negative terminal of diode D7, and the other end of resistor R10 is grounded for filtering. Pin 3 of the Zener transistor is connected to diode D7, pin 1 is grounded, and pin 2 is connected to one end of capacitor C10. One end of the parallel connection of capacitors C10, C11, and C12 is connected to pin 2 of the Zener transistor, and the other end is grounded. The transformer U1 outputs two power supplies with isolation: one generates a 12V power supply, and the other generates a 5V power supply.

7. The isolated power supply circuit for intelligent circuit breakers according to claim 2, characterized in that: The chopper protection power supply circuit includes rectifier bridges U4-U6, diodes D13-D14, MOSFET V1, amplifier U7, resistors R13-R19, and capacitors C20-C22. The rectifier circuit connects the input terminal of rectifier bridge U4 to the A-phase output signal of the current transformer, and its output terminal is connected in series with diode D13 to output a 12V power supply. The B and C phase circuits are identical. One end of the bidirectional TVS diode D14 is connected to the output terminal of rectifier bridge U4, and the other end is grounded. The drain of MOSFET V1 is connected to the output terminal of rectifier bridge U4, and its source is grounded. The gate is connected to one end of resistors R18 and R16. The other end of resistor R18 is grounded, and the other end of resistor R16 is connected to the output terminal of amplifier U7, one end of resistor R13, and one end of resistor R17. The circuit consists of two terminals: one end of resistor R13 is connected to the negative terminal of diode D13; the other end of resistor R17 is connected to one end of resistor R19, one end of resistor R15, and the positive input terminal of amplifier U7; the other end of resistor R15 is connected to the negative terminal of diode D13; the other end of resistor R19 is grounded; one end of resistor R14 is connected to the negative terminal of diode D13, and the other end is connected sequentially to the negative terminal of Zener diode D15, one end of capacitor C22, and the inverting input terminal of amplifier U7; the positive terminal of diode D15 is connected to ground in parallel with capacitor C22; and one end of capacitors C20 and C21 is connected to the negative terminal of diode D13 in parallel, with the other end grounded. This circuit forms a negative feedback amplifier circuit. When the detected voltage is too high, the signal feedback MOSFET V1 performs chopping to release the voltage.

8. The isolated power supply circuit for a smart circuit breaker according to claim 3, characterized in that: The ABC three-phase current amplification circuit includes resistors R20~R27, capacitors C23~C27, and a quad operational amplifier U2. Resistor R24 ​​is the power resistor for the A-phase current sampling unit; one end is grounded, and the other end is connected to the current transformer and resistor R21. The other end of resistor R21 is connected to capacitor C9, and the other end of capacitor C9 is grounded. Resistor R2 and capacitor C9 form an RC filter circuit to filter harmonic signals. Resistor R22 is connected in series with resistor R21, and the other end of resistor R22 is connected to the first inverting input of the quad operational amplifier U2. The first non-inverting input of the operational amplifier is grounded. One end of resistor R20 is connected to the first inverting input of amplifier U2, and the other end is connected to the first output of amplifier U2. Capacitor C22 is connected in parallel with resistor R20 to filter high-frequency noise. Resistor R2...

3. Resistor R23 is connected in series with resistor R20. The other end of resistor R23 is connected to the ADC input terminal of the MCU chip and capacitor C23. The other end of capacitor C23 is grounded. Resistor R23 and capacitor C23 form an RC filter circuit. Resistor R26 is connected in series with resistor R21. The other end of resistor R25 is connected to the second inverting input terminal of the quad operational amplifier U2. The non-inverting input terminal of the operational amplifier is grounded. One end of resistor R25 is connected to the second inverting input terminal of amplifier U2, and the other end is connected to the second output terminal of amplifier U2. Capacitor C25 is connected in parallel with resistor R25 to filter out high-frequency noise. Resistor R27 is connected in series with resistor R25. The other end of resistor R27 is connected to the ADC input terminal of the MCU chip and capacitor C26. The other end of capacitor C26 is grounded. Resistor R27 and capacitor C26 form an RC filter circuit.

9. The isolated power supply circuit for a smart circuit breaker according to claim 4, characterized in that: The ABC phase voltage clamping sampling circuit includes resistors R28~R34, capacitors C27 and C28, and a Zener diode D16. One end of resistor R28 is connected to the A phase sampling line, and the other end is connected in series with resistors R32, R29, and R30 to achieve rapid voltage reduction. The other end of resistor R30 is connected to one end of resistors R31 and R33 and capacitor C28. Resistor R33 and capacitor C28 are connected in parallel to ground. The other end of resistor R28 is connected to resistor R70, capacitor C65, and the negative terminal of Zener diode D16. Zener diode D16, resistor R34, and capacitor C27 are connected in parallel to ground to form a voltage stabilizing filter circuit. The output signal is connected to the ADC input terminal of the MCU chip.

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