Power grid voltage detection circuit, PCB and controller

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By using a filter unit, a switching power supply unit, a control unit, a voltage detection unit, and a current detection unit to form a power grid voltage detection circuit, the safety hazards and insufficient detection accuracy of the voltage divider method without isolation resistors are solved, thus achieving high-precision power grid voltage measurement and stable system operation.

CN223784380UActive Publication Date: 2026-01-09GUANGDONG SHENLING ENVIRONMENT SYST CO LTD

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Patent Information

Application Number: CN202423076513.9
Authority / Receiving Office: CN · China
Patent Type: Utility models(China)
Current Assignee / Owner
Filing Date: 2024-12-12
Publication Date: 2026-01-09
Estimated Expiration: 2034-12-12

AI Technical Summary

Technical Problem

In the existing technology, the resistor voltage divider method without isolation poses safety hazards in the field of power grid voltage detection where safety isolation is required, and the detection accuracy is insufficient.

Method used

A power grid voltage detection circuit consisting of a filtering unit, a switching power supply unit, a control unit, a voltage detection unit, and a current detection unit is used. The current detection unit monitors the current in real time to obtain the voltage correction compensation value, and the voltage detection unit monitors the voltage in real time to improve the accuracy of power grid voltage measurement.

Benefits of technology

It achieves high-precision grid voltage measurement, ensuring stable system operation, and eliminates the need for additional isolation power supplies or complex isolation operational amplifier circuits. It is low-cost, has a simple circuit structure, strong applicability and compatibility, and a small controller size.

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Abstract

The utility model discloses a power grid voltage detection circuit, a PCB and a controller. The power grid voltage detection circuit comprises a filtering unit, a switching power supply unit, a control unit, a voltage detection unit, a current detection unit and a voltage stabilization unit. The input end of the filtering unit is used for obtaining power grid voltage, the output end of the filtering unit is connected with the input end of the switching power supply unit, and the output end of the switching power supply unit is connected with the input end of the voltage stabilizing unit; the input end of the voltage detection unit and the input end of the current detection unit are respectively connected with the sampling end of the voltage stabilization unit, and the output end of the voltage detection unit and the output end of the current detection unit are respectively connected with the input end of the control unit; according to the power grid voltage detection circuit, the current detection unit is introduced to monitor the current in real time so as to obtain the voltage correction compensation value, the voltage detection unit is introduced to monitor the voltage in real time so as to calculate and correct the power grid voltage in real time, and the power grid voltage measurement precision can be effectively improved.

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Description

Technical Field

[0001] This utility model relates to the field of voltage detection technology, and in particular to a power grid voltage detection circuit, PCB board and controller. Background Technology

[0002] Power electronic systems and industrial air conditioning systems must accurately detect the mains voltage. For example, in thyristor systems, triggering operations require setting the trigger delay time based on the mains voltage. When two or more mains grids are connected in parallel, their phase synchronization must be ensured to guarantee stable system operation. In addition, air conditioning systems, variable frequency DC motors, AC motors, and other drive equipment rely on the detection of mains voltage to achieve overvoltage and undervoltage protection functions. In fields such as industrial air conditioning systems and heat pump air conditioning systems, whether it is a split-type or integrated controller, it is necessary to detect the mains voltage and execute corresponding control or processing measures based on the detection results.

[0003] Traditional grid voltage detection methods typically employ non-isolated resistor voltage dividers. This method is relatively simple to design and inexpensive, and therefore widely used in many situations. However, this technique is not suitable for controller detection applications with strict safety isolation requirements. In environments requiring isolation protection, the lack of necessary isolation measures may lead to safety hazards when using non-isolated resistor voltage dividers.

[0004] It is evident that existing technologies still need improvement and enhancement. Utility Model Content

[0005] In view of the shortcomings of the prior art, the purpose of this utility model is to provide a power grid voltage detection circuit that can effectively improve the accuracy of power grid voltage measurement and has the advantages of low cost, simple circuit structure and high detection accuracy.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A power grid voltage detection circuit includes a filtering unit, a switching power supply unit, a control unit, a voltage detection unit, a current detection unit, and a voltage regulator unit. The input terminal of the filtering unit is used to acquire the power grid voltage. The output terminal of the filtering unit is connected to the input terminal of the switching power supply unit, and the output terminal of the switching power supply unit is connected to the input terminal of the voltage regulator unit. The input terminals of the voltage detection unit and the current detection unit are respectively connected to the sampling terminal of the voltage regulator unit. The output terminals of the voltage detection unit and the current detection unit are respectively connected to the input terminal of the control unit, which is used to generate protection commands.

[0008] In the aforementioned mains voltage detection circuit, the filtering unit includes a connector CN1, a fuse FUSE1, a varistor ZNR1, and a common-mode inductor L1. The connector CN1 is used to acquire the mains voltage. Pin 1 of the connector CN1 is connected to one end of the fuse FUSE1, and the other end of the fuse FUSE1 is connected to one end of the varistor ZNR1. The varistor ZNR1 is also connected to one end of the common-mode inductor L1, and the other end of the common-mode inductor L1 is connected to the input terminal of the switching power supply unit.

[0009] In the aforementioned power grid voltage detection circuit, the control unit includes a third control chip U3, pin 42 of which is connected to the output terminal of the current detection unit, and pin 41 of which is connected to the output terminal of the voltage detection unit.

[0010] In the aforementioned power grid voltage detection circuit, the switching power supply unit includes a rectifier bridge QD1, a primary coil of transformer T1, an auxiliary coil of transformer T1, a second control chip U2, and an optocoupler OP1. The input terminal of the rectifier bridge QD1 is connected to the output terminal of the filter unit, and the output terminal of the rectifier bridge QD1 is connected to the primary coil of transformer T1. The primary coil of transformer T1 is induced to the input terminal of the voltage regulator unit and the auxiliary coil of transformer T1. Pin 5 of the auxiliary coil of transformer T1 is connected to pin VCC of the second control chip U2. The input terminal of the optocoupler OP1 is used to connect to a DC power supply device, and the output terminal of the optocoupler OP1 is connected to pin FB of the second control chip U2.

[0011] In the aforementioned power grid voltage detection circuit, the voltage regulation unit includes the secondary coil of transformer T1 and a first control chip U1. The primary coil of transformer T1 is induced to be connected to its secondary coil. Pin 10 of the secondary coil of transformer T1 is connected to pin IN of the first control chip U1, and pin OUT of the first control chip U1 is used to output a 3.3V DC voltage.

[0012] In the aforementioned power grid voltage detection circuit, the voltage detection unit includes a fifteenth resistor R15, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twelfth capacitor C12, and a fourth diode D4. One end of the seventeenth resistor R17 and the negative terminal of the fourth diode D4 are connected to pin 6 of the secondary coil of the transformer T1. One end of the fifteenth resistor R15 is used to connect to a 3.3V DC voltage. The other ends of the fifteenth resistor R15 and the seventeenth resistor R17 are respectively connected to one end of the nineteenth resistor R19 and one end of the eighteenth resistor R18. The positive terminal of the fourth diode D4 is connected to the other end of the nineteenth resistor R19 and one end of the twelfth capacitor C12 through the twentieth resistor R20. The other end of the twelfth capacitor C12 is grounded. The other end of the eighteenth resistor R18 is connected to pin 41 of the third control chip U3.

[0013] In the aforementioned power grid voltage detection circuit, the current detection unit includes a sampling resistor RS1, a seventh resistor R7, a tenth resistor R10, an eighth capacitor C8, a ninth resistor R9, a ninth capacitor C9, and an operational amplifier U4. One end of the sampling resistor RS1 and one end of the tenth resistor R10 are respectively connected to pin 6 of the secondary coil of the transformer T1. One end of the seventh resistor R7 is connected to the other end of the sampling resistor RS1. The other end of the seventh resistor R7 and one end of the eighth capacitor C8 are respectively connected to pin 1 of the operational amplifier U4. The other end of the tenth resistor R10 and the other end of the eighth capacitor C8 are respectively connected to pins 3 and 4 of the operational amplifier U4 and one end of the ninth resistor R9. Pin 4 of the operational amplifier U4 is connected to one end of the ninth resistor R9, and pin 5 of the operational amplifier U4 is used to connect to a 3.3V DC voltage. The other end of the ninth resistor R9 is connected to pin 42 of the third control chip U3.

[0014] In the aforementioned mains voltage detection circuit, the switching power supply unit further includes an eighth resistor R8, a twelfth resistor R12, a tenth capacitor C10, a thirteenth resistor R13, an eleventh resistor R11, a sixteenth resistor R16, and a reference chip IC2. One end of the eighth resistor R8 and one end of the eleventh resistor R11 are respectively used to connect to a 12V DC voltage. The other end of the eighth resistor R8 is connected to one end of the twelfth resistor R12 and pin 1 of the input terminal of the optocoupler OP1. The other end of the twelfth resistor R12, pin K of the reference chip IC2, and one end of the tenth capacitor C10 are respectively connected to pin 2 of the input terminal of the optocoupler OP1. The other end of the tenth capacitor C10 is connected to one end of the thirteenth resistor R13. The other ends of the eleventh resistor R11 and the other ends of the thirteenth resistor R13 are respectively connected to one end of the sixteenth resistor R16 and pin R of the reference chip IC2. The other end of the sixteenth resistor R16 and pin A of the reference chip IC2 are respectively grounded.

[0015] This utility model also provides a PCB board, on which the power grid voltage detection circuit described above is printed.

[0016] This utility model also provides a controller, which uses any of the above-described power grid voltage detection circuits to achieve operation control.

[0017] Beneficial effects:

[0018] This utility model provides a power grid voltage detection circuit. By introducing a current detection unit to monitor the current in real time to obtain the voltage correction compensation value, and introducing a voltage detection unit to monitor the voltage in real time for real-time calculation and correction of the power grid voltage, the accuracy of power grid voltage measurement can be effectively improved, ensuring that the air conditioning system can operate stably according to changes in the power grid voltage. Furthermore, the power grid voltage monitoring circuit disclosed in this application does not require the addition of an isolation power supply or a complex isolation operational amplifier circuit. It has the advantages of low cost, simple circuit structure and high detection accuracy, significantly enhancing the applicability and compatibility of the circuit, while also helping to reduce the size of the controller and reduce unnecessary redundant design. Attached Figure Description

[0019] Figure 1 A circuit block diagram of the power grid voltage detection circuit provided by this utility model;

[0020] Figure 2 Circuit diagrams of the filtering unit, switching power supply unit, voltage detection unit, current detection unit, and voltage regulation unit provided by this utility model;

[0021] Figure 3The circuit structure diagram of the control unit provided by this utility model.

[0022] Explanation of main component symbols: 1-Filtering unit, 2-Switching power supply unit, 3-Control unit, 4-Voltage detection unit, 5-Current detection unit, 6-Voltage regulation unit. Detailed Implementation

[0023] This utility model provides a power grid voltage detection circuit, PCB board and controller. To make the purpose, technical solution and effect of this utility model clearer and more explicit, the following describes this utility model in further detail with reference to the accompanying drawings and embodiments.

[0024] In the description of this utility model, it should be understood that the terms "installation" and "connection" should be interpreted broadly, and those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0025] Please see Figures 1 to 3 This utility model provides a power grid voltage detection circuit, including a filter unit 1, a switching power supply unit 2, a control unit 3, a voltage detection unit 4, a current detection unit 5, and a voltage regulator unit 6. The input terminal of the filter unit 1 is used to acquire the power grid voltage, and the output terminal of the filter unit 1 is connected to the input terminal of the switching power supply unit 2. The output terminal of the switching power supply unit 2 is connected to the input terminal of the voltage regulator unit 6. The input terminals of the voltage detection unit 4 and the current detection unit 5 are respectively connected to the sampling terminal of the voltage regulator unit 6, and the output terminals of the voltage detection unit 4 and the current detection unit 5 are respectively connected to the input terminal of the control unit 3. The control unit 3 is used to generate protection commands.

[0026] The power grid voltage detection circuit disclosed in this application introduces a current detection unit 5 to monitor the current in real time to obtain the voltage correction compensation value, and introduces a voltage detection unit 4 to monitor the voltage in real time for real-time calculation and correction of the power grid voltage. This can effectively improve the accuracy of power grid voltage measurement and ensure that the air conditioning system can operate stably according to changes in the power grid voltage. Furthermore, the power grid voltage monitoring circuit disclosed in this application does not require the addition of an isolation power supply or a complex isolation operational amplifier circuit. It has the advantages of low cost, simple circuit structure and high detection accuracy, which significantly enhances the applicability and compatibility of the circuit. At the same time, it helps to reduce the size of the controller and reduce unnecessary redundant design.

[0027] Further, please refer to Figure 2The filter unit 1 includes a connector CN1, a fuse FUSE1, a varistor ZNR1, and a common-mode inductor L1. The connector CN1 is used to obtain the mains voltage. Pin 1 of the connector CN1 is connected to one end of the fuse FUSE1. The other end of the fuse FUSE1 is connected to one end of the varistor ZNR1. The varistor ZNR1 is also connected to one end of the common-mode inductor L1. The other end of the common-mode inductor L1 is connected to the input terminal of the switching power supply unit 2, which is connected based on the input terminal of the rectifier bridge QD1.

[0028] In this embodiment, the mains voltage is obtained through connector CN1, facilitating connection to an external power source and improving the controller's versatility and flexibility. Secondly, the introduction of fuse FUSE1 can promptly cut off the current in case of overload or short circuit, protecting other components in the circuit from damage and enhancing circuit safety. Furthermore, the addition of varistor ZNR1 can effectively suppress overvoltage in the mains, preventing overvoltage from impacting the equipment and improving its stability and reliability. Finally, the use of common-mode inductor L1 can effectively filter out common-mode noise in the mains, improving signal purity and ensuring the controller operates normally and stably.

[0029] Further, please refer to Figure 2 and Figure 3 The control unit 3 includes a third control chip U3, pin 42 of which is connected to the output terminal of the current detection unit 5, and pin 41 of which is connected to the output terminal of the voltage detection unit 4.

[0030] In this embodiment, the third control chip U3 is a microcontroller.

[0031] In this embodiment, the control unit 3 further includes a twenty-first resistor R21 and a thirteenth capacitor C13. One end of the twenty-first resistor R21 is used to connect to a 3.3V DC voltage, and the other end of the twenty-first resistor R21 is connected to the NRST pin of the third control chip U3 and one end of the thirteenth capacitor C13, respectively. The other end of the thirteenth capacitor C13 is grounded. The NRST pin is a reset pin used to trigger the reset operation of the third control chip U3.

[0032] Further, please refer to Figure 2The switching power supply unit 2 includes a rectifier bridge QD1, a primary coil of transformer T1, an auxiliary coil of transformer T1, a second control chip U2, and an optocoupler OP1. The input terminal of the rectifier bridge QD1 is connected to the output terminal of the filter unit 1, and the output terminal of the rectifier bridge QD1 is connected to the primary coil of transformer T1. The primary coil of transformer T1 is induced to the input terminal of the voltage regulator unit 6 and the auxiliary coil of transformer T1. The pin 5 of the auxiliary coil of transformer T1 is connected to the pin VCC of the second control chip U2. The input terminal of the optocoupler OP1 is used to connect to a DC power supply device, and the output terminal of the optocoupler OP1 is connected to the pin FB of the second control chip U2.

[0033] Further, please refer to Figure 2 The voltage regulator unit 6 includes a secondary coil of transformer T1 and a first control chip U1. The primary coil of transformer T1 is induced to be connected to its secondary coil. The pin 10 of the secondary coil of transformer T1 is connected to the pin IN of the first control chip U1. The pin OUT of the first control chip U1 is used to output a 3.3V DC voltage.

[0034] In this embodiment, the second control chip U2 is model OB6063 / STR-6063, the first control chip U1 is model AMS1117-3.3 / LD1117-3.3, and the first control chip U1 is a voltage regulator chip.

[0035] Further, please refer to Figure 2 and Figure 3 The voltage detection unit 4 includes a fifteenth resistor R15, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twelfth capacitor C12, and a fourth diode D4. One end of the seventeenth resistor R17 and the negative terminal of the fourth diode D4 are connected to pin 6 of the secondary coil of the transformer T1. One end of the fifteenth resistor R15 is used to connect to a 3.3V DC voltage. The other ends of the fifteenth resistor R15 and the seventeenth resistor R17 are respectively connected to one end of the nineteenth resistor R19 and one end of the eighteenth resistor R18. The positive terminal of the fourth diode D4 is connected to the other end of the nineteenth resistor R19 and one end of the twelfth capacitor C12 through the twentieth resistor R20. The other end of the twelfth capacitor C12 is grounded. The other end of the eighteenth resistor R18 is connected to pin 41 of the third control chip U3.

[0036] Further, please refer to Figure 2 and Figure 3The current detection unit 5 includes a sampling resistor RS1, a seventh resistor R7, a tenth resistor R10, an eighth capacitor C8, a ninth resistor R9, a ninth capacitor C9, and an operational amplifier U4. One end of the sampling resistor RS1 and one end of the tenth resistor R10 are respectively connected to pin 6 of the secondary coil of the transformer T1. One end of the seventh resistor R7 is connected to the other end of the sampling resistor RS1. The other end of the seventh resistor R7 and one end of the eighth capacitor C8 are respectively connected to pin 1 of the operational amplifier U4. The other end of the tenth resistor R10 and the other end of the eighth capacitor C8 are respectively connected to pins 3 and 4 of the operational amplifier U4 and one end of the ninth resistor R9. Pin 4 of the operational amplifier U4 is connected to one end of the ninth resistor R9. Pin 5 of the operational amplifier U4 is used to connect to a 3.3V DC voltage. The other end of the ninth resistor R9 is connected to pin 42 of the third control chip U3.

[0037] In this embodiment, one end of the sampling resistor RS1 and the tenth resistor R10 is connected to pin 6 of the secondary coil of transformer T1. This direct connection makes the acquisition of the current signal more direct and efficient. One end of the seventh resistor R7 is connected to the other end of the sampling resistor RS1, further ensuring stable signal transmission. The addition of the eighth capacitor C8 and the ninth capacitor C9 provides the necessary filtering function for the circuit, effectively reducing noise interference and ensuring signal purity. Pin 1 of the operational amplifier U4 is connected to the seventh resistor R7 and the eighth capacitor C8, and pins 3 and 4 are connected to the tenth resistor R10 and the eighth capacitor C8. This connection allows the operational amplifier to effectively amplify and regulate the current signal. In addition, the high input impedance and low output impedance characteristics of the operational amplifier U4 result in less loss of the current signal during transmission, ensuring high-quality signal transmission.

[0038] Further, please refer to Figure 2The switching power supply unit 2 further includes an eighth resistor R8, a twelfth resistor R12, a tenth capacitor C10, a thirteenth resistor R13, an eleventh resistor R11, a sixteenth resistor R16, and a reference chip IC2. One end of the eighth resistor R8 and one end of the eleventh resistor R11 are respectively used to connect to a 12V DC voltage. The other end of the eighth resistor R8 is connected to one end of the twelfth resistor R12 and pin 1 of the input terminal of the optocoupler OP1. The other end of the twelfth resistor R12, pin K of the reference chip IC2, and one end of the tenth capacitor C10 are respectively connected to pin 2 of the input terminal of the optocoupler OP1. The other end of the tenth capacitor C10 is connected to one end of the thirteenth resistor R13. The other ends of the eleventh resistor R11 and the other ends of the thirteenth resistor R13 are respectively connected to one end of the sixteenth resistor R16 and pin R of the reference chip IC2. The other end of the sixteenth resistor R16 and pin A of the reference chip IC2 are respectively grounded.

[0039] In this embodiment, the specific circuit structure design of the switching power supply unit 2 not only improves the overall performance of the circuit but also ensures the reliability and safety of the controller under various operating conditions. For example, one end of the eighth resistor R8 and the eleventh resistor R11 are respectively connected to a 12V DC voltage, providing a stable input voltage source for the circuit. The other end of the eighth resistor R8 is connected to one end of the twelfth resistor R12 and pin 1 of the optocoupler OP1. This connection method not only realizes voltage division but also effectively protects the circuit from abnormal voltage impacts such as high voltage and surges through the isolation effect of the optocoupler. In addition, the combination of the tenth capacitor C10 and the thirteenth resistor R13 provides the necessary filtering function for the circuit, ensuring the purity and stability of the output voltage. The reference chip IC2 is the AZ431 model. This chip, with its high precision, low temperature coefficient, and low power consumption, provides a stable reference voltage for the circuit, ensuring the stability and accuracy of the output voltage of the switching power supply unit 2. The use of the optocoupler OP1 not only realizes electrical isolation between the input and output but also greatly enhances the anti-interference capability of the circuit, enabling the entire switching power supply unit 2 to maintain stable operation even when facing complex electromagnetic environments.

[0040] The mains voltage detection circuit disclosed in this application rectifies the mains voltage Vac input through connector CN1 to obtain a high-voltage DC +VDC. Then, transformer T1 converts the +VDC into a low-voltage AC voltage. A sample is taken from the output of the secondary coil, and after rectification by the fourth diode D4, a low-voltage negative voltage V0 is obtained. Since V0 is approximately negative tens of volts, while the operating voltage of the third control chip U3 is +3.3V, V0 needs further processing. Specifically, the negative voltage V0 is divided by resistors R17 and R19 to obtain an even lower negative voltage Vf = V0 * R19 / (R17 + R19). Then, a voltage V1 of +3.3V is applied to this negative voltage Vf through resistor R15 to cancel the negative voltage, thus obtaining a positive voltage Vo_Vale (0V-3.3V). =Vf+V1=V0*R19 / (R17+R19)+V1; If the grid voltage increases or decreases, +VDC=√2*Vac will also increase or decrease linearly accordingly; Since the turns ratio of transformer T1 is fixed, there is a linear relationship between the secondary coil and the primary coil, so the detected voltage Vo_Vale will change linearly with the grid voltage; However, the magnitude of the load current will affect the value of Vo_Vale, so the value of Vo_Vale cannot be directly used for grid voltage conversion; In order to accurately determine the change of grid voltage, it is also necessary to obtain the corresponding correction compensation voltage V_Adjust according to the different detected load currents I_Vale; The third control chip U3 determines the change of grid voltage according to the magnitude of voltage Vo_Vale+V_Adjust and executes corresponding control, such as undervoltage protection, overvoltage protection, etc.

[0041] This utility model also provides a PCB board, on which the power grid voltage detection circuit described above is printed.

[0042] This utility model also provides a controller, which uses any of the above-described power grid voltage detection circuits to achieve operation control.

[0043] It is understood that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of this utility model, and all such substitutions or changes should fall within the protection scope of this utility model.

Claims

1. A power grid voltage detection circuit, characterized in that, It includes a filtering unit, a switching power supply unit, a control unit, a voltage detection unit, a current detection unit, and a voltage regulator unit. The input terminal of the filtering unit is used to acquire the mains voltage, and the output terminal of the filtering unit is connected to the input terminal of the switching power supply unit. The output terminal of the switching power supply unit is connected to the input terminal of the voltage regulator unit. The input terminals of the voltage detection unit and the current detection unit are respectively connected to the sampling terminal of the voltage regulator unit, and the output terminals of the voltage detection unit and the current detection unit are respectively connected to the input terminal of the control unit. The control unit is used to generate protection commands.

2. The power grid voltage detection circuit according to claim 1, characterized in that, The filtering unit includes a connector CN1, a fuse FUSE1, a varistor ZNR1, and a common-mode inductor L1. The connector CN1 is used to obtain the mains voltage. Pin 1 of the connector CN1 is connected to one end of the fuse FUSE1. The other end of the fuse FUSE1 is connected to one end of the varistor ZNR1. The varistor ZNR1 is also connected to one end of the common-mode inductor L1. The other end of the common-mode inductor L1 is connected to the input terminal of the switching power supply unit.

3. The power grid voltage detection circuit according to claim 1, characterized in that, The control unit includes a third control chip U3, pin 42 of which is connected to the output terminal of the current detection unit, and pin 41 of which is connected to the output terminal of the voltage detection unit.

4. The power grid voltage detection circuit according to claim 3, characterized in that, The switching power supply unit includes a rectifier bridge QD1, a primary coil of transformer T1, an auxiliary coil of transformer T1, a second control chip U2, and an optocoupler OP1. The input terminal of the rectifier bridge QD1 is connected to the output terminal of the filter unit, and the output terminal of the rectifier bridge QD1 is connected to the primary coil of transformer T1. The primary coil of transformer T1 is induced to the input terminal of the voltage regulator unit and the auxiliary coil of transformer T1. Pin 5 of the auxiliary coil of transformer T1 is connected to pin VCC of the second control chip U2. The input terminal of the optocoupler OP1 is used to connect to a DC power supply device, and the output terminal of the optocoupler OP1 is connected to pin FB of the second control chip U2.

5. The power grid voltage detection circuit according to claim 4, characterized in that, The voltage regulator unit includes a secondary coil of transformer T1 and a first control chip U1. The primary coil of transformer T1 is induced to be connected to its secondary coil. Pin 10 of the secondary coil of transformer T1 is connected to pin IN of the first control chip U1. Pin OUT of the first control chip U1 is used to output a 3.3V DC voltage.

6. The power grid voltage detection circuit according to claim 5, characterized in that, The voltage detection unit includes a fifteenth resistor R15, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twelfth capacitor C12, and a fourth diode D4. One end of the seventeenth resistor R17 and the negative terminal of the fourth diode D4 are connected to pin 6 of the secondary coil of the transformer T1. One end of the fifteenth resistor R15 is used to connect to a 3.3V DC voltage. The other ends of the fifteenth resistor R15 and the seventeenth resistor R17 are respectively connected to one end of the nineteenth resistor R19 and one end of the eighteenth resistor R18. The positive terminal of the fourth diode D4 is connected to the other end of the nineteenth resistor R19 and one end of the twelfth capacitor C12 through the twentieth resistor R20. The other end of the twelfth capacitor C12 is grounded. The other end of the eighteenth resistor R18 is connected to pin 41 of the third control chip U3.

7. The power grid voltage detection circuit according to claim 6, characterized in that, The current detection unit includes a sampling resistor RS1, a seventh resistor R7, a tenth resistor R10, an eighth capacitor C8, a ninth resistor R9, a ninth capacitor C9, and an operational amplifier U4. One end of the sampling resistor RS1 and one end of the tenth resistor R10 are respectively connected to pin 6 of the secondary coil of the transformer T1. One end of the seventh resistor R7 is connected to the other end of the sampling resistor RS1. The other end of the seventh resistor R7 and one end of the eighth capacitor C8 are respectively connected to pin 1 of the operational amplifier U4. The other end of the tenth resistor R10 and the other end of the eighth capacitor C8 are respectively connected to pins 3 and 4 of the operational amplifier U4 and one end of the ninth resistor R9. Pin 4 of the operational amplifier U4 is connected to one end of the ninth resistor R9. Pin 5 of the operational amplifier U4 is used to connect to a 3.3V DC voltage. The other end of the ninth resistor R9 is connected to pin 42 of the third control chip U3.

8. The power grid voltage detection circuit according to claim 4, characterized in that, The switching power supply unit further includes an eighth resistor R8, a twelfth resistor R12, a tenth capacitor C10, a thirteenth resistor R13, an eleventh resistor R11, a sixteenth resistor R16, and a reference chip IC2. One end of the eighth resistor R8 and one end of the eleventh resistor R11 are respectively used to connect to a 12V DC voltage. The other end of the eighth resistor R8 is connected to one end of the twelfth resistor R12 and pin 1 of the input terminal of the optocoupler OP1. The other end of the twelfth resistor R12, pin K of the reference chip IC2, and one end of the tenth capacitor C10 are respectively connected to pin 2 of the input terminal of the optocoupler OP1. The other end of the tenth capacitor C10 is connected to one end of the thirteenth resistor R13. The other ends of the eleventh resistor R11 and the other ends of the thirteenth resistor R13 are respectively connected to one end of the sixteenth resistor R16 and pin R of the reference chip IC2. The other end of the sixteenth resistor R16 and pin A of the reference chip IC2 are respectively grounded.

9. A PCB board, characterized in that, The PCB board is printed with a power grid voltage detection circuit as described in any one of claims 1-8.

10. A controller, characterized in that, The controller uses the power grid voltage detection circuit as described in any one of claims 1-8 to achieve operation control.