A voltage monitoring circuit

Abstract

The utility model provides a kind of voltage monitoring circuit, belong to power supply circuit field.The utility model voltage monitoring circuit includes power input and processing module, main control module, respectively with the indication module and / or isolated communication module of main control module connection, still include isolated power module and sampling module respectively with power input and processing module connection, the isolated power module is used to provide power supply for voltage detection circuit, the output end of the sampling module is connected with the input end of main control module, the indication module is used to indicate the working state of power detection circuit, the isolated communication module is used to report voltage monitoring data to external device.The utility model has the beneficial effect that: different voltage input equipment operating voltage under working state can be monitored and recorded in real time, so that equipment runs in reasonable voltage range, improves equipment operation safety.

Description

Technical Field

[0001] This utility model relates to the field of power supply circuits, specifically to a voltage monitoring circuit. Background Technology

[0002] In oil depots, oil dispensing requires stringent safety measures to ensure safety, as any abnormalities could lead to accidents. Abnormal voltage conditions can occur at oil depots, potentially causing problems with various equipment. For example, ghosting on color screens, erratic screen activity due to power supply quality issues, or frequent start-stop cycles during dispensing due to unstable voltage, can all lead to malfunctions. To overcome these potential problems, it is necessary to implement a voltage monitoring circuit for real-time input voltage monitoring, thereby enhancing the safety of oil depot operations. Utility Model Content

[0003] To address the problems in the prior art, this utility model provides a voltage monitoring circuit.

[0004] This utility model discloses a voltage monitoring circuit, including a power input and processing module, a main control module, an indicator module and / or an isolated communication module connected to the main control module, and an isolated power supply module and a sampling module connected to the power input and processing module. The isolated power supply module provides power to the voltage detection circuit, the output terminal of the sampling module is connected to the input terminal of the main control module, the indicator module indicates the operating status of the power detection circuit, and the isolated communication module reports voltage monitoring data to external devices. The power input and processing module receives a 0-24V DC voltage at its input terminal and outputs it to the sampling module through a sampling interface. The sampling module includes a first sampling unit and a second sampling unit. The first sampling unit is used to sample the 24V / 5V working voltage, and the second sampling unit is used to sample the 12V working voltage, thereby realizing real-time monitoring of multi-range power supplies.

[0005] Furthermore, the power input and processing module includes a first power branch, a second power branch, and a voltage conversion unit. The first power branch provides 24V power, and the second power branch provides 12V power. The input terminal of the voltage conversion unit is connected to the first power branch. The input terminal of the isolation power module is connected to the voltage conversion unit and the second power branch, respectively. The voltage detection circuit also includes a power failure detection module. The input terminal of the power failure detection module is connected to the output terminal of the isolation power module, and the output terminal is connected to the power failure detection port of the main control module.

[0006] Furthermore, the power failure detection module includes a reference voltage unit and a voltage detection unit. The voltage detection unit includes resistors R12, R19, and R14 connected in series. One end of the three resistors is connected to a 3.3V power supply, and the other end is connected to the analog power supply ground. It also includes a capacitor C13 connected in parallel with resistor R14. One end of capacitor C13 is grounded, and the power failure detection port is connected to the other end of capacitor C13. The reference voltage unit uses a reference voltage chip. Its input terminal is connected to the output terminal of the isolated power supply module, and its output terminal outputs a reference voltage VREF.

[0007] Furthermore, the voltage monitoring circuit also includes a clock module connected to the input terminal of the main control module.

[0008] Furthermore, the voltage monitoring circuit also includes a temperature detection module connected to the input terminal of the main control module, and the temperature detection module is located at the power supply terminal of the isolation power supply module to the main control module.

[0009] Furthermore, the main control module includes a main control MCU chip U1, a power processing unit, a crystal oscillator unit, and a ground isolation unit, all connected to the main control MCU chip U1. The power processing unit is used to supply a stable 3.3V operating power supply to the main control MCU chip U1. The power processing unit is provided with a digital ground terminal GND2, which is connected to the power ground AGND through a resistor R3.

[0010] Furthermore, the sampling interface includes a 12V sampling pin, a 5V / 24V sampling pin, and a power ground pin. The first sampling unit includes a first voltage follower and a range switching unit. The first voltage follower includes an operational amplifier U8A, whose inverting input terminal is connected to its output terminal, its non-inverting input terminal is connected to a range switching unit, and its output terminal is connected to the first sampling terminal of the main control module through a resistor R20. The range switching unit includes resistors R27, R21, R25, R23, and capacitor C19. One end of resistor R27 is connected to a 3.3V power supply, and the other end is connected to the 5V / 24V sampling pin of the sampling interface and grounded through jumper J5. One end of resistor R21 is connected to the 5V / 24V sampling pin, and the other end is connected to one end of resistor R25 and one end of jumper J4. The other end of resistor R25 and the other end of jumper J4 are connected to one end of resistor R23 and one end of capacitor C19, respectively, and connected to the non-inverting input of operational amplifier U8A through resistor R2. The other end of resistor R23 and the other end of capacitor C19 are connected to power ground.

[0011] Furthermore, the second sampling unit includes an operational amplifier U8B, resistors R4 and R22, capacitor C21, resistor R26, and resistor R13. The inverting input terminal of the operational amplifier U8B is connected to its output terminal, and the non-inverting input terminal is connected to one end of resistors R4, R22, and capacitor C21 through resistor R13. The other ends of resistors R22 and capacitor C21 are connected to the power supply ground, and the other end of resistor R4 is connected to the 12V sampling pin. The output terminal of the operational amplifier U8B is connected to the second sampling terminal of the main control module through resistor R26.

[0012] Furthermore, the isolated communication module adopts an isolated 485 chip U7 and is also provided with a communication interface J1. The isolated 485 chip U7 is provided with an isolated first digital power ground pin and a second digital power ground pin, as well as a first power pin and a second power pin. The first digital power ground pin is connected to digital power ground GND2, and the second digital power ground pin is connected to digital power ground GND3. The first power pin is connected to power supply 5V_1, and the second power pin is connected to power supply 5V_2. It also includes an overcurrent protection unit and a filtering unit disposed at both ends of the isolated 485 chip U7, and a transient suppression unit disposed at the communication interface end.

[0013] Furthermore, the overcurrent protection unit includes resettable fuses F1 and F2, and overcurrent protection resistors R5, R6, R7, R8, R9, and R10. The first communication pin A of the communication interface J1 is connected in series with resettable fuse F1, and the first communication pin B of the communication interface J1 is connected in series with resettable fuse F2. The two ends of the overcurrent protection resistor R7 are respectively connected to the ends of resettable fuses F1 and F2 furthest from the communication interface J1. One end of resistor R5 is connected to digital power ground GND3, and the other end is connected to one end of resistor R7 and the B communication pin of the isolation 485 chip U7. One end of resistor R10 is connected to a 5V power supply, and the other end is connected to the other end of resistor R7 and the A communication pin of the isolation 485 chip U7. Resistors R6, R8, and R9 are respectively connected in series with the three communication pins of the isolation 485 chip U7 and the main control module. The filtering unit includes polarized capacitors C17 and C6 respectively disposed between the first power supply pin and the first digital power ground pin, and polarized capacitors C18 and C3 disposed between the second power supply pin and the second digital power ground pin. Capacitors C3 and C6 are used to filter out high-frequency noise, and polarized capacitors C17 and C18 are used to filter out low-frequency disturbances.

[0014] Compared with the prior art, the beneficial effects of this utility model are: it can monitor and record the operating voltage of the device under different voltage inputs (24V, 12V, 5V) in real time, so that the device operates within a reasonable voltage range. When the deviation value is exceeded, it is an abnormality, and the status is indicated in time or an alarm is sent to the host computer through the isolation communication module, so that the operation and maintenance personnel can deal with it in time, avoid safety hazards caused by abnormal voltage, and improve the safety and stability of the device. Attached Figure Description

[0015] To more clearly illustrate the solutions in this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a structural block diagram of the present utility model; Figure 2 This is a structural block diagram of an embodiment of the present utility model; Figure 3 This is the circuit schematic diagram of the main control module of this utility model; Figure 4 This is the circuit schematic for the power failure detection module; Figure 5 Schematic diagrams of the circuits for each interface and indicator module; Figure 6 A circuit schematic diagram of an embodiment of an isolated power supply module; Figure 7 This is the schematic diagram of the first sampling unit circuit; Figure 8 This is the schematic diagram of the second unit circuit. Figure 9 This is the circuit schematic for the isolation communication module. Detailed Implementation

[0017] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, and accompanying drawings are used to distinguish different objects, not to describe a particular order.

[0018] In this invention, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment to other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0020] like Figure 1 and Figure 2 As shown, the voltage monitoring circuit of this utility model is installed at the power input terminal of the device for real-time detection of the device's operating voltage. The voltage detection circuit in this example includes a power input and processing module, a main control module, an indicator module and / or an isolation communication module connected to the main control module, and an isolation power supply module and a sampling module connected to the power input and processing module. The isolation power supply module is used to provide power to the voltage detection circuit. The output terminal of the sampling module is connected to the input terminal of the main control module. The indicator module is used to indicate the operating status of the power detection circuit. The isolation communication module is used to report voltage monitoring data to external devices.

[0021] The power input and processing module receives a 0-24V DC voltage at its input terminal and outputs it to the sampling module through a sampling interface. The sampling module includes a first sampling unit and a second sampling unit. The first sampling unit is used to sample the 24V / 5V working voltage, and the second sampling unit is used to sample the 12V working voltage, thereby realizing real-time monitoring of multi-range power supplies.

[0022] The power input and processing module in this example includes a first power branch, a second power branch, and a voltage conversion unit. The first power branch provides 24V power, and the second power branch provides 12V power. The input terminal of the voltage conversion unit is connected to the first power branch. The input terminal of the isolated power module is connected to both the voltage conversion unit and the second power branch. The voltage detection circuit also includes a power failure detection module. The input terminal of the power failure detection module is connected to the output terminal of the isolated power module, and the output terminal is connected to the power failure detection port of the main control module. This module is used for power failure detection. When a power failure occurs, the main control module can detect the power failure signal, promptly save the voltage monitoring data, and also send alarm information to the host computer through the isolated communication module.

[0023] In this example, the isolated power supply module is simultaneously connected to the output terminals of the first power supply branch (powered via a voltage conversion unit) and the second power supply branch. Even if one of these branches malfunctions, the voltage monitoring circuit of this invention can still operate normally, thus collecting voltage anomaly information and reporting it to the host computer. For example, if the 24V power supply branch malfunctions, the entire circuit is powered by the 12V power supply branch. The first sampling unit detects the 24V power supply anomaly, triggers an alarm, and reports it. Conversely, if the 12V power supply branch malfunctions, the 24V power supply branch provides power. This invention achieves power supply and sampling through different power sources. This cross-power supply handling method prevents inaccurate measurements caused by power failure at the monitoring end, effectively ensuring the accuracy and precision of voltage monitoring.

[0024] To improve time accuracy, this example also includes a clock module connected to the input of the main control module. The clock module in this example can use an 8-bit clock chip, such as the DS1302 clock chip. This example also includes a reset module, which can be a CAT809S reset chip, etc.

[0025] Preferably, this example also includes a temperature detection module connected to the input terminal of the main control module. The temperature detection module is located at the power supply terminal of the isolated power supply module to the main control module, enhancing the safety of the equipment operation. When the temperature exceeds a threshold, the main control module issues an alarm message. This alarm message can be indicated by an indicator module, which can be an audio-visual component; in this example, an LED light is used. Figure 5 As shown, this example has two LEDs. One is green, representing normal operation, and the other is red, used for alarms.

[0026] like Figure 3 As shown, the active module in this example includes a main control MCU chip U1, a power processing unit and a ground isolation unit connected to the main control MCU chip U1 respectively. The power processing unit is used to provide the main control MCU chip U1 with a stable 3.3V operating power supply. The power processing unit has a digital ground terminal GND2, which is connected to the power ground AGND through a resistor R3. It also includes a crystal oscillator X1 connected to pins 14 and 15 of the main control MCU chip U1.

[0027] In this invention, the peripheral circuitry of the main control MCU chip is responsible for processing the operating voltage data and transmitting it to the lower-level machine. The lower-level machine then transmits this information to the upper-level machine and a color screen for display.

[0028] like Figure 4As shown, the power-down detection module in this example includes a reference voltage unit and a voltage detection unit. The voltage detection unit includes resistors R12, R19, and R14 connected in series. One end of the three resistors is connected to a 3.3V power supply, and the other end is connected to the analog power supply ground. It also includes a capacitor C13 connected in parallel with resistor R14. One end of capacitor C13 is grounded, and the power-down detection port is connected to the other end of capacitor C13. The reference voltage unit uses a reference voltage chip. Its input terminal is connected to the output terminal of the isolated power supply module, and its output terminal outputs a reference voltage VREF.

[0029] like Figure 5 and Figure 6 As shown, to enhance the safety of the voltage monitoring circuit, the isolated power supply module, after receiving DC power through the power input interface J2, is equipped with two isolated power supplies and a 5V to 3.3V step-down circuit. Both isolated power supplies are isolated by an isolated power supply chip. The 3.3V power supply is used for the operation of various chips in the power monitoring circuit. In this example, the first isolated power supply serves as the main power supply, using a 12V to 5V conversion to generate another 12V to 5V isolated power supply for communication isolation power supply.

[0030] like Figure 5 and Figure 7 As shown, sampling interface J3 includes a 12V sampling pin, a 5V / 24V sampling pin, and a power ground pin. The first sampling unit includes a first voltage follower and a range switching unit. The first voltage follower includes an operational amplifier U8A, whose inverting input terminal is connected to its output terminal, its non-inverting input terminal is connected to a range switching unit, and its output terminal is connected to the first sampling terminal of the main control module through a resistor R20. The range switching unit includes resistors R27, R21, R25, R23, and capacitor C19. One end of resistor R27 is connected to a 3.3V power supply, and the other end is connected to the 5V / 24V sampling pin of the sampling interface and grounded through jumper J5. One end of resistor R21 is connected to the 5V / 24V sampling pin, and the other end is connected to one end of resistor R25 and one end of jumper J4. The other end of resistor R25 and the other end of jumper J4 are connected to one end of resistor R23 and one end of capacitor C19, respectively, and connected to the non-inverting input of operational amplifier U8A through resistor R2. The other end of resistor R23 and the other end of capacitor C19 are connected to power ground.

[0031] Furthermore, the second sampling unit includes an operational amplifier U8B, resistors R4 and R22, capacitor C21, resistor R26, and resistor R13. The inverting input terminal of the operational amplifier U8B is connected to its output terminal, and the non-inverting input terminal is connected to one end of resistors R4, R22, and capacitor C21 through resistor R13. The other ends of resistors R22 and capacitor C21 are connected to the power supply ground, and the other end of resistor R4 is connected to the 12V sampling pin. The output terminal of the operational amplifier U8B is connected to the second sampling terminal of the main control module through resistor R26.

[0032] The sampling module of this invention uses a resistor voltage divider to input voltage to the microcontroller. The microcontroller's reference power supply is 2.5V. When detecting 24V, the maximum voltage is 30V, which is the full-scale range (reference voltage) for AD sampling. When detecting 12V, the maximum voltage is 15V, which is the full-scale range (reference voltage) for AD sampling. When detecting 5V, the maximum voltage is 7.5V, which is the full-scale range (reference voltage) for AD sampling. Furthermore, different detection ranges are set through two jumpers. The circuit is simple, reliable, and highly compatible.

[0033] like Figure 9 As shown, the isolated communication module uses an isolated 485 chip U7 and also has a communication interface J1. The isolated 485 chip U7 has an isolated first digital power ground pin and a second digital power ground pin, as well as a first power pin and a second power pin. The first digital power ground pin is connected to digital power ground GND2, and the second digital power ground pin is connected to digital power ground GND3. The first power pin is connected to power supply 5V_1, and the second power pin is connected to power supply 5V_2. It also includes an overcurrent protection unit and a filtering unit set at both ends of the isolated 485 chip U7, and a transient suppression unit set at the communication interface end.

[0034] Furthermore, the overcurrent protection unit includes resettable fuses F1 and F2, and overcurrent protection resistors R5, R6, R7, R8, R9, and R10. The first communication pin A of the communication interface J1 is connected in series with resettable fuse F1, and the first communication pin B of the communication interface J1 is connected in series with resettable fuse F2. The two ends of the overcurrent protection resistor R7 are respectively connected to the ends of resettable fuses F1 and F2 furthest from the communication interface J1. One end of resistor R5 is connected to digital power ground GND3, and the other end is connected to one end of resistor R7 and the B communication pin of the isolation 485 chip U7. One end of resistor R10 is connected to a 5V power supply, and the other end is connected to the other end of resistor R7 and the A communication pin of the isolation 485 chip U7. Resistors R6, R8, and R9 are respectively connected in series with the three communication pins of the isolation 485 chip U7 and the main control module. The filtering unit includes polarized capacitors C17 and C6 respectively disposed between the first power supply pin and the first digital power ground pin, and polarized capacitors C18 and C3 disposed between the second power supply pin and the second digital power ground pin. Capacitors C3 and C6 are used to filter out high-frequency noise, and polarized capacitors C17 and C18 are used to filter out low-frequency disturbances.

[0035] The working principle of this example is as follows: The voltage is directly input from the 12V terminal of the non-test power supply to the microcontroller input. The analog signal of the voltage from the test power supply is converted into a digital signal by the ADC port inside the main control MCU chip. Then, the microcontroller performs voltage judgment and converts it into a RS-485 communication signal, which is then used to communicate with other devices through an isolation communication module.

[0036] In actual oil depot operations, the detection port measures the voltage of the AI / DI port, which consists of two voltages: 12V and 24V, requiring separate detection. Therefore, two detection circuits are used for cross-detection, with a measurement range of 0-24V. This circuit can accept DC external input voltages from 0 to 24V and performs analog-to-digital conversion via the internal AD converter of the main control MCU chip. To ensure circuit safety and stability, an isolated power supply circuit is used to isolate the circuit from other components. The circuit also includes a 485 interface and a connected isolated communication module for data transmission and exchange. Furthermore, this example divides the grounding power supply into analog power ground, power ground, and analog ground, fully meeting the isolation requirements of each module and making the circuit safer and more reliable.

[0037] Compared with the prior art, the beneficial effects of this utility model are: This invention can monitor and record the operating voltage of the device under different voltage inputs (24V, 12V, 5V) in real time, so that the device operates within a reasonable voltage range. When the voltage exceeds the deviation value, it is considered abnormal, and the device will promptly indicate the status or send an alarm to the host computer through the isolation communication module. This allows maintenance personnel to handle the situation in a timely manner, avoid safety hazards caused by abnormal voltage, and improve the safety and stability of the device.

[0038] The specific embodiments described above are preferred embodiments of this utility model, and are not intended to limit the specific scope of this utility model. The scope of this utility model includes but is not limited to the specific embodiments described above. All equivalent changes made in accordance with this utility model are within the protection scope of this utility model.

Claims

1. A voltage monitoring circuit, characterized in that: The system includes a power input and processing module, a main control module, an indicator module and / or an isolated communication module connected to the main control module, and an isolated power supply module and a sampling module connected to the power input and processing module. The isolated power supply module provides power to the voltage detection circuit, the output of the sampling module is connected to the input of the main control module, the indicator module indicates the operating status of the power detection circuit, and the isolated communication module reports voltage monitoring data to external devices. The power input and processing module receives a 0-24V DC voltage at its input terminal and outputs it to the sampling module through a sampling interface. The sampling module includes a first sampling unit and a second sampling unit. The first sampling unit is used to sample the 24V / 5V working voltage, and the second sampling unit is used to sample the 12V working voltage, thereby realizing real-time monitoring of multi-range power supplies.

2. The voltage monitoring circuit according to claim 1, characterized in that: The power input and processing module includes a first power branch, a second power branch, and a voltage conversion unit. The first power branch provides 24V power, and the second power branch provides 12V power. The input terminal of the voltage conversion unit is connected to the first power branch. The input terminal of the isolation power module is connected to the voltage conversion unit and the second power branch, respectively. The voltage detection circuit also includes a power failure detection module. The input terminal of the power failure detection module is connected to the output terminal of the isolation power module, and the output terminal is connected to the power failure detection port of the main control module.

3. The voltage monitoring circuit according to claim 2, characterized in that: The power failure detection module includes a reference voltage unit and a voltage detection unit. The voltage detection unit includes resistors R12, R19, and R14 connected in series. One end of the three resistors is connected to a 3.3V power supply, and the other end is connected to the analog power supply ground. It also includes a capacitor C13 connected in parallel with resistor R14. One end of capacitor C13 is grounded, and the power failure detection port is connected to the other end of capacitor C13. The reference voltage unit uses a reference voltage chip. Its input terminal is connected to the output terminal of the isolated power supply module, and its output terminal outputs a reference voltage VREF.

4. The voltage monitoring circuit according to claim 1, characterized in that: The voltage monitoring circuit also includes a clock module connected to the input terminal of the main control module.

5. The voltage monitoring circuit according to claim 1, characterized in that: The voltage monitoring circuit also includes a temperature detection module connected to the input terminal of the main control module. The temperature detection module is located at the power supply terminal of the isolation power supply module to the main control module.

6. The voltage monitoring circuit according to any one of claims 1-5, characterized in that: The main control module includes a main control MCU chip U1, a power processing unit, a crystal oscillator unit, and a ground isolation unit, all connected to the main control MCU chip U1. The power processing unit is used to provide a stable 3.3V operating power supply to the main control MCU chip U1. The power processing unit is provided with a digital ground terminal GND2, which is connected to the power ground AGND through a resistor R3.

7. The voltage monitoring circuit according to any one of claims 1-5, characterized in that: The sampling interface includes a 12V sampling pin, a 5V / 24V sampling pin, and a power ground pin. The first sampling unit includes a first voltage follower and a range switching unit. The first voltage follower includes an operational amplifier U8A, whose inverting input terminal is connected to its output terminal, its non-inverting input terminal is connected to a range switching unit, and its output terminal is connected to the first sampling terminal of the main control module through a resistor R20. The range switching unit includes resistors R27, R21, R25, R23, and capacitor C19. One end of resistor R27 is connected to a 3.3V power supply, and the other end is connected to the 5V / 24V sampling pin of the sampling interface and grounded through jumper J5. One end of resistor R21 is connected to the 5V / 24V sampling pin, and the other end is connected to one end of resistor R25 and one end of jumper J4. The other end of resistor R25 and the other end of jumper J4 are connected to one end of resistor R23 and one end of capacitor C19, respectively, and connected to the non-inverting input of operational amplifier U8A through resistor R2. The other end of resistor R23 and the other end of capacitor C19 are connected to power ground.

8. The voltage monitoring circuit according to claim 7, characterized in that: The second sampling unit includes an operational amplifier U8B, resistors R4 and R22, capacitor C21, resistor R26, and resistor R13. The inverting input terminal of the operational amplifier U8B is connected to its output terminal. The non-inverting input terminal is connected to one end of resistors R4, R22, and capacitor C21 through resistor R13. The other ends of resistors R22 and capacitor C21 are connected to the power supply ground. The other end of resistor R4 is connected to the 12V sampling pin. The output terminal of the operational amplifier U8B is connected to the second sampling terminal of the main control module through resistor R26.

9. The voltage monitoring circuit according to any one of claims 1-5, characterized in that: The isolated communication module uses an isolated 485 chip U7 and also has a communication interface J1. The isolated 485 chip U7 has an isolated first digital power ground pin and a second digital power ground pin, as well as a first power pin and a second power pin. The first digital power ground pin is connected to digital power ground GND2, and the second digital power ground pin is connected to digital power ground GND3. The first power pin is connected to power supply 5V_1, and the second power pin is connected to power supply 5V_2. It also includes an overcurrent protection unit and a filtering unit set at both ends of the isolated 485 chip U7, and a transient suppression unit set at the communication interface end.

10. The voltage monitoring circuit according to claim 9, characterized in that: The overcurrent protection unit includes resettable fuses F1 and F2, and overcurrent protection resistors R5, R6, R7, R8, R9, and R10. The first communication pin A of the communication interface J1 is connected in series with resettable fuse F1, and the first communication pin B of the communication interface J1 is connected in series with resettable fuse F2. The two ends of the overcurrent protection resistor R7 are respectively connected to the ends of resettable fuses F1 and F2 furthest from the communication interface J1. One end of resistor R5 is connected to digital power ground GND3, and the other end is connected to one end of resistor R7 and the B communication pin of the isolation 485 chip U7. One end of resistor R10 is connected to a 5V power supply, and the other end is connected to the other end of resistor R7 and the A communication pin of the isolation 485 chip U7. Resistors R6, R8, and R9 are respectively connected in series with the three communication pins of the isolation 485 chip U7 and the main control module. The filtering unit includes polarized capacitors C17 and C6 respectively disposed between the first power supply pin and the first digital power ground pin, and polarized capacitors C18 and C3 disposed between the second power supply pin and the second digital power ground pin. Capacitors C3 and C6 are used to filter out high-frequency noise, and polarized capacitors C17 and C18 are used to filter out low-frequency disturbances.

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