An electric leakage protection circuit with over-temperature protection and power line breakage protection functions
Patent Information
- Application Number
- CN202521921538.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-08
- Publication Date
- 2026-09-22
- Estimated Expiration
- 2035-09-08
AI Technical Summary
[0002]现有的插头在使用中，经常会出现插头中的插片与插座的插套咬合不够紧密而出现两者接触不良，当过大电流时可能会发生严重发热、熔化，更严重则会出现起火等现象
[0016]本实用新型设有用于检测火线载流线和零线载流线输入端的插头温度并在过温时向供电及脱扣输出电路输出脱扣信号的温度检测电路，用于检测屏蔽线漏电信号并在检测到漏电信号后向供电及脱扣输出电路输出脱扣信号的电源线破损检测电路，实现漏电保护电路的过温保护和电源线破损保护功能；同时，插头温度检测电路中过温保护值可根据需要修改电阻RT和电阻R12参数实现，参考电源电路既为温度检测电路提供一路参考电压，又为温度检测电路中的运放器芯片U5供电，电流消耗较小；另一方面，漏电检测功能，插头温度检测功能，电源线破损检测功能采用同回路驱动螺线管L1，功能相互独立。
Smart Images
Figure CN224790352U_ABST
Abstract
Description
[Technical Field]
[0001] This utility model relates to a leakage protection circuit with over-temperature protection and power cord damage protection functions. [Background Technology]
[0002] In existing plugs, the prongs often fail to mesh tightly with the socket, resulting in poor contact. Under excessive current, this can lead to severe overheating, melting, and even fire. Furthermore, most existing residual current circuit breakers (RCCBs) with prong over-temperature protection rely on a temperature control switch that monitors the combined temperature of the neutral and live prongs, which is not precise enough. On the other hand, RCCBs with power cord protection often use power cords with shielding layers covering the neutral and live wires. These shielding layers are connected to the neutral and live wires via resistors, making them energized. Damage to the power cord poses a risk of electric shock. [Utility Model Content]
[0003] This invention overcomes the shortcomings of the prior art and provides a leakage protection circuit with over-temperature protection and power cord damage protection functions.
[0004] To achieve the above objectives, the present invention adopts the following technical solution:
[0005] A leakage current protection circuit with over-temperature protection and power line damage protection functions is characterized by: including a live wire and a neutral wire connected to the mains live wire and neutral wire respectively; a controlled switch for controlling the on / off state of the live wire and neutral wire is provided on the live wire and neutral wire; a power supply and trip output circuit for power supply and controlling the on / off state of the controlled switch is connected to the live wire and neutral wire; a temperature detection circuit for detecting the temperature of the input terminals of the live wire and neutral wire and outputting a trip signal to the power supply and trip output circuit when the temperature is over-temperature; and a reference power supply circuit for drawing power from the power supply and trip output circuit and supplying power to the temperature detection circuit and providing a reference voltage; a shielding wire is provided on the live wire and neutral wire respectively; a series wire is connected between the two shielding wires; and a power line damage detection circuit for detecting leakage current signal of the shielding wire and outputting a trip signal to the power supply and trip output circuit after detecting the leakage current signal is connected to the live wire, neutral wire, and series wire.
[0006] The leakage protection circuit described above, which has over-temperature protection and power cord damage protection functions, is characterized in that: the power supply and tripping output circuit is connected to a leakage signal detection circuit for detecting leakage signals of the live wire and neutral wire and outputting a tripping signal to the power supply and tripping output circuit after detecting the leakage signal.
[0007] The leakage protection circuit with over-temperature protection and power line damage protection functions as described above is characterized in that: the temperature detection circuit includes a thermistor RT, one end of the thermistor RT is connected to the reference power supply circuit and pin 4 of the operational amplifier U5, the other end of the thermistor RT is connected to pin 1 of the operational amplifier U5 and one end of resistor R12, the other end of resistor R12 is grounded, pin 5 of the operational amplifier U5 is grounded, and pin 3 of the operational amplifier U5 is connected to the power supply and tripping output circuit.
[0008] The leakage protection circuit with over-temperature protection and power line damage protection functions as described above is characterized in that: the over-temperature protection value of the temperature detection circuit is set by the parameters of the thermistor RT and resistor R12.
[0009] The leakage protection circuit with over-temperature protection and power line damage protection functions as described above is characterized in that: the reference power supply circuit includes a resistor R10, one end of which is connected to the power supply and trip output circuit, the other end of which is connected to one end of resistor R11A, the negative terminal of thyristor U4, the temperature detection circuit, and one end of capacitor C11, the other end of capacitor C11 is grounded, the control terminal of thyristor U4 is connected to the other end of resistor R11A, one end of resistor R11B, and the power supply and trip output circuit, the other end of resistor R11B is grounded, and the positive terminal of thyristor U4 is grounded.
[0010] The leakage protection circuit described above, which features over-temperature protection and power line damage protection, is characterized in that: the power supply and tripping output circuit includes a rectifier DB1, pin 1 of rectifier DB1 is connected to the live wire, pin 3 of rectifier DB1 is connected to the neutral wire, pin 4 of rectifier DB1 is grounded, pin 3 of rectifier DB1 is connected to one end of resistor R2 and one end of solenoid L1 respectively, the other end of resistor R2 is connected to pin 1 of control and overvoltage protection chip U2 and the drain terminal of MOSFET Q1 respectively, the control terminal of MOSFET Q1 is connected to pin 2 of control and overvoltage protection chip U2, and the source terminal of MOSFET Q1 is connected to the control and overvoltage protection chip U2 respectively. Pin 3 of the protection chip U2, the reference power supply circuit, and one end of resistor R3 are connected. Pin 4 of the control and overvoltage protection chip U2 is grounded. The other end of resistor R3 is connected to the positive terminal of the LED and the power line damage detection circuit. The negative terminal of the LED is connected to the leakage signal detection circuit. The other end of solenoid L1 is connected to the positive terminal of the SCR. The negative terminal of the SCR is grounded. The control terminal of the SCR is connected to one end of capacitor C1, the leakage signal detection circuit, and the output terminal of dual diode Q2. The other end of capacitor C1 is grounded. One input terminal of dual diode Q2 is connected to the temperature detection circuit, and one input terminal of dual diode Q2 is connected to the power line damage detection circuit.
[0011] The leakage protection circuit described above, which has over-temperature protection and power line damage protection functions, is characterized in that: the power line damage detection circuit includes diodes D1 and D2. The negative terminal of diode D1 is connected to the live wire, and the negative terminal of diode D2 is connected to the neutral wire. The positive terminal of diode D1 is connected to the positive terminal of diode D2 and one end of resistor R6. The other end of resistor R6 is connected to pin 1 of optocoupler U3, one end of resistor R7, and one end of capacitor C9. The other end of resistor R7 is connected to the series wire, the other end of capacitor C9, and the negative terminal of Zener diode ZD1. The positive terminal of Zener diode ZD1 is connected to pin 2 of optocoupler U3 through resistor R8. Pin 3 of optocoupler U3 is connected to the power supply and tripping output circuit. Pin 4 of optocoupler U3 is connected to one end of capacitor C10 and the power supply and tripping output circuit through resistor R9. The other end of capacitor C10 is grounded.
[0012] The leakage current protection circuit described above, which features over-temperature protection and power line damage protection, is characterized in that: the leakage current signal detection circuit includes a residual current transformer ZCT mounted on the live wire and the neutral wire; one output terminal of the residual current transformer ZCT is connected to one end of capacitor C4, one end of resistor R4, and one end of resistor R5A; the other output terminal of the residual current transformer ZCT is connected to the other end of capacitor C4, the other end of resistor R4, and one end of resistor R5B; the other end of resistor R5A is connected to one end of capacitor C8, pin 2 of the leakage current detection chip U1, and one end of capacitor C6; the other end of capacitor C6... And, the other end of resistor R5B is connected to the other end of capacitor C8, pin 1 of leakage current detection chip U1, and one end of capacitor C7. The other end of capacitor C7 is grounded. Pin 3 of leakage current detection chip U1 is grounded. Pin 5 of leakage current detection chip U1 is grounded through capacitor C5. Pin 6 of leakage current detection chip U1 is grounded through capacitor C3. Pin 7 of leakage current detection chip U1 is connected to the power supply and trip output circuit. Pin 8 of leakage current detection chip U1 is connected to the negative terminal of electrolytic capacitor C2, the negative terminal of Zener diode ZD2, and the power supply and trip output circuit. The positive terminal of electrolytic capacitor C2 is grounded, and the positive terminal of Zener diode ZD2 is grounded.
[0013] The leakage protection circuit with over-temperature protection and power line damage protection functions as described above is characterized in that: one test terminal of the residual current transformer ZCT is connected to one end of the test switch SW, the other end of the test switch SW is connected to the neutral current-carrying line, the other test terminal of the residual current transformer ZCT is connected to one end of the resistor R1, and the other end of the resistor R1 is connected to the live current-carrying line.
[0014] The leakage protection circuit described above, which has over-temperature protection and power line damage protection functions, is characterized in that a varistor MOV is connected between the neutral wire current-carrying line input terminal and the live wire current-carrying line input terminal.
[0015] The beneficial effects of this utility model are:
[0016] This invention includes a temperature detection circuit for detecting the plug temperature at the input terminals of the live and neutral wires and outputting a trip signal to the power supply and trip output circuit when the temperature is too high; and a power cord damage detection circuit for detecting leakage current in the shielded wire and outputting a trip signal to the power supply and trip output circuit upon detection of leakage current. This achieves over-temperature protection and power cord damage protection functions for the leakage current protection circuit. Simultaneously, the over-temperature protection value in the plug temperature detection circuit can be adjusted by modifying the parameters of resistors RT and R12 as needed. The reference power supply circuit provides a reference voltage for the temperature detection circuit and also powers the operational amplifier chip U5 in the temperature detection circuit, resulting in low current consumption. Furthermore, the leakage current detection function, plug temperature detection function, and power cord damage detection function all use the same drive solenoid L1, and their functions are independent of each other. [Image Description]
[0017] Figure 1 This is a schematic diagram of the present invention;
[0018] Figure 2 This is the circuit diagram of this utility model. [Detailed Implementation]
[0019] The technical solutions in the embodiments of this utility model will now be clearly and completely described in conjunction with the accompanying drawings.
[0020] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this utility model are only used to explain the relative positional relationship and movement of the components in a specific posture (as shown in the attached figure). If the specific posture changes, the directional indication will also change accordingly. Furthermore, descriptions involving "preferred," "second-best," etc., in this utility model are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "preferred" or "second-best" may explicitly or implicitly include at least one of those features.
[0021] like Figure 1-2As shown, a leakage current protection circuit with over-temperature protection and power cord damage protection functions includes a live wire and a neutral wire connected to the mains live wire and neutral wire respectively. A controlled switch 1 is installed on the live wire and neutral wire to control the on / off state of the circuit. A power supply and trip output circuit 2 is connected to the live wire and neutral wire to supply power and control the on / off state of the controlled switch 1. The power supply and trip output circuit 2 is connected to a circuit for detecting the temperature of the input terminals of the live wire and neutral wire and outputting a power supply and trip output when the temperature exceeds the limit. The circuit 2 includes a temperature detection circuit 3 that outputs a trip signal, and a reference power supply circuit 4 that draws power from the power supply and trip output circuit 2 to supply power to the temperature detection circuit 3 and provide a reference voltage. Shielded wires 5 are respectively wrapped on the live wire and the neutral wire. A series wire 6 is connected between the two shielded wires 5. A power line damage detection circuit 7 is connected to the live wire, the neutral wire, and the series wire 6 to detect the leakage signal of the shielded wire 5 and output a trip signal to the power supply and trip output circuit 2 after detecting the leakage signal. After power-on, the power supply and trip output circuit 2 draws power from the live wire and neutral wire and supplies power to the reference power supply circuit 4. The reference power supply circuit 4 supplies power to the temperature detection circuit 3 and provides a reference voltage. When the temperature detection circuit 3 detects that the plug temperature is too high, it outputs a trip signal to the power supply and trip output circuit 2, causing the power supply and trip output circuit 2 to control the controlled switch 1 to disconnect the power connection. After power-on, the power cord damage detection circuit 7 detects in real time whether there is a leakage signal on the shield wire 5. When the power cord is damaged, a leakage signal is generated on the shield wire 5. When the power cord damage detection circuit 7 detects the leakage signal on the shield wire 5, it outputs a trip signal to the power supply and trip output circuit 2, causing the power supply and trip output circuit 2 to control the controlled switch 1 to disconnect the power connection, thus realizing the over-temperature protection and power cord damage protection functions of the leakage protection circuit.
[0022] like Figure 1 As shown, the power supply and trip output circuit 2 is connected to a leakage signal detection circuit 8, which detects leakage signals on the live wire and neutral wire and outputs a trip signal to the power supply and trip output circuit 2 upon detection of a leakage signal. When the leakage current protector is in operation after power-on, the leakage signal detection circuit 8 detects leakage signals on the live wire and neutral wire. Upon detection of a leakage signal, it outputs a trip signal to the power supply and trip output circuit 2, causing the power supply and trip output circuit 2 to control the controlled switch 1 to disconnect the power connection, thus achieving the leakage protection function.
[0023] like Figure 2 As shown, when the input terminals of the live wire and neutral wire are powered on, the AC power supply is rectified by the rectifier DB1 in the power supply and trip output circuit 2 and enters the step-down voltage regulation circuit composed of resistor R2, control and overvoltage protection chip U2, and MOSFET Q1, and outputs DC voltage VDD at the output terminal of pin 3 of control and overvoltage protection chip U2.
[0024] The live wire and neutral wire leakage protection function: The DC voltage VDD in the power supply and trip output circuit 2 supplies power to the leakage protection-dedicated leakage detection chip U1 in the leakage signal detection circuit 8 through resistor R3 and LED. At this time, the LED serves as both a power supply path and a power-on indicator for the whole machine. Zener diode ZD2 and capacitor C2 perform voltage regulation and filtering on the power supply voltage of leakage detection chip U1.
[0025] When the residual current transformer ZCT in the leakage signal detection circuit 8 detects the leakage signal, it outputs to pins 1 and 2 of the leakage detection chip U1. After internal comparison and judgment, pin 7 of the leakage detection chip U1 outputs a high-level pulse, which turns on the thyristor SCR in the power supply and tripping output circuit 2, energizes the solenoid L1, and drives the controlled switch 1 to open, preparing for the next manual reset switch.
[0026] Over-temperature protection function of plug: The DC voltage VDD in the power supply and tripping output circuit 2 supplies power to the thyristor U4 through the resistor R10 in the reference power supply circuit 4. The thyristor U4 provides two voltages. One output is a stable voltage to pin 2 of the inverting input terminal of the operational amplifier U5 in the temperature detection circuit 3. This voltage is used as a constant comparison reference voltage. The other output voltage VCC supplies power to the operational amplifier U5, the thermistor RT, and the resistor R12. The thermistor RT and the resistor R12 form a voltage divider circuit. The output voltage is VR12 = VCC * (R12 / (RT + R12)) and is output to pin 1 of the non-inverting input terminal of the operational amplifier U5. When the temperature decreases, the resistance of the NTC thermistor RT increases, and the voltage VR12 decreases. When this voltage is less than the set value, the voltage VR12 at pin 1 of the non-inverting input terminal of op-amp U5 is less than the constant reference voltage at pin 2 of the inverting input terminal. Op-amp U5 outputs a low level, the diode in dual diode Q2 connected to op-amp U5 is cut off, causing the SCR in the power supply and trip output circuit 2 to be cut off, solenoid L1 is de-energized, and controlled switch 1 remains on. When the temperature increases, the resistance of the NTC thermistor RT decreases, and the voltage VR12 increases. When this voltage is greater than the set value, the voltage VR12 at pin 1 of the non-inverting input terminal of op-amp U5 is greater than the constant reference voltage at pin 2 of the inverting input terminal. Op-amp U5 outputs a high level, the diode in dual diode Q2 connected to op-amp U5 conducts, causing the SCR in the power supply and trip output circuit 2 to conduct, solenoid L1 is energized, and controlled switch 1 is off, preparing for the next manual reset switch.
[0027] Power cord damage protection function: When the shielding wire 5 ages or is damaged, and it comes into contact with the live wire and neutral wire, current flows through the Zener diode ZD1, resistor R8, pin 2 of the input terminal of the optocoupler U3 diode in the power cord damage detection circuit 7. Resistor R7, capacitor C9, resistor R6, diode D1, and diode D2 form a detection circuit. When the detected current reaches the set value, pins 3 and 4 of the output terminal of the optocoupler U3 are triggered to conduct, thereby turning on the diode connected to the optocoupler U3 in the dual diode Q2, turning on the SCR in the power supply and trip output circuit 2, energizing the solenoid L1, and turning off the controlled switch 1, preparing for the next manual reset switch. When the shielding layer 5 is not in contact with the live wire and neutral wire, since there is no current at the input terminal of the optocoupler U3, the output terminal of the optocoupler U3 is cut off, causing the diode connected to the optocoupler U3 in the dual diode Q2 to be cut off. At this time, it does not affect the operation of other circuits.
[0028] In this case, the over-temperature protection value in the temperature detection circuit 3 for detecting the plug temperature can be achieved by modifying the parameters RT and R12 as needed. The reference power supply circuit 4 provides a reference voltage for the plug temperature detection circuit and also powers the operational amplifier U5, with relatively low current consumption. Meanwhile, the leakage current detection function, plug temperature detection function, and shielded wire damage detection function in this case all use the same circuit driving solenoid L1, and their functions are independent of each other.
[0029] The above are merely preferred embodiments of this utility model and do not limit the patent scope of this utility model. Any equivalent structural transformations made based on the inventive concept of this utility model and the contents of this utility model specification and drawings, or direct or indirect applications in other related technical fields, are included within the patent protection scope of this utility model.
Claims
1. A leakage current protection circuit with over-temperature protection and power cord damage protection functions, characterized in that: It includes a live wire and a neutral wire connected to the mains live wire and neutral wire respectively. A controlled switch (1) is installed on the live wire and neutral wire to control the on / off state of the power supply. A power supply and trip output circuit (2) for powering on and controlling the on / off state of the controlled switch (1) is connected to the live wire and neutral wire. A temperature detection circuit (3) is connected to the power supply and trip output circuit (2) to detect the temperature at the input terminals of the live wire and neutral wire and output a trip signal to the power supply and trip output circuit (2) when the temperature is too high. A reference power supply circuit (4) is used to supply power to the temperature detection circuit (3) and provide a reference voltage after drawing power from the power supply and trip output circuit (2). Shielded wires (5) are respectively wrapped on the live wire and the neutral wire. A series wire (6) is connected between the two shielded wires (5). A power line damage detection circuit (7) is connected to the live wire, the neutral wire and the series wire (6) to detect the leakage signal of the shielded wire (5) and output a trip signal to the power supply and trip output circuit (2) after detecting the leakage signal.
2. The leakage protection circuit with over-temperature protection and power line damage protection functions according to claim 1, characterized in that: The power supply and trip output circuit (2) is connected to a leakage signal detection circuit (8) for detecting leakage signals of the live wire and neutral wire and outputting a trip signal to the power supply and trip output circuit (2) after detecting the leakage signal.
3. A leakage current protection circuit with over-temperature protection and power line damage protection functions according to claim 1, characterized in that: The temperature detection circuit (3) includes a thermistor RT. One end of the thermistor RT is connected to the reference power supply circuit (4) and the pin 4 of the op-amp U5. The other end of the thermistor RT is connected to the pin 1 of the op-amp U5 and one end of the resistor R12. The other end of the resistor R12 is grounded. The pin 5 of the op-amp U5 is grounded. The pin 3 of the op-amp U5 is connected to the power supply and trip output circuit (2).
4. A leakage current protection circuit with over-temperature protection and power line damage protection functions according to claim 3, characterized in that: The over-temperature protection value of the temperature detection circuit (3) is set by the parameters of the thermistor RT and resistor R12.
5. A leakage current protection circuit with over-temperature protection and power line damage protection functions according to claim 1, characterized in that: The reference power supply circuit (4) includes a resistor R10. One end of the resistor R10 is connected to the power supply and trip output circuit (2). The other end of the resistor R10 is connected to one end of the resistor R11A, the negative terminal of the thyristor U4, the temperature detection circuit (3), and one end of the capacitor C11. The other end of the capacitor C11 is grounded. The control terminal of the thyristor U4 is connected to the other end of the resistor R11A, one end of the resistor R11B, and the power supply and trip output circuit (2). The other end of the resistor R11B is grounded, and the positive terminal of the thyristor U4 is grounded.
6. A leakage current protection circuit with over-temperature protection and power line damage protection functions according to claim 2, characterized in that: The power supply and trip output circuit (2) includes a rectifier DB1. Pin 1 of the rectifier DB1 is connected to the live wire current-carrying line, pin 3 of the rectifier DB1 is connected to the neutral wire current-carrying line, pin 4 of the rectifier DB1 is grounded, pin 3 of the rectifier DB1 is connected to one end of resistor R2 and one end of solenoid L1 respectively, the other end of resistor R2 is connected to pin 1 of control and overvoltage protection chip U2 and the drain end of MOSFET Q1 respectively, the control terminal of MOSFET Q1 is connected to pin 2 of control and overvoltage protection chip U2, and the source end of MOSFET Q1 is connected to pin 3 of control and overvoltage protection chip U2, reference power supply circuit (4), and one end of resistor R3 respectively. Connect the control and overvoltage protection chip U2 pin 4 to ground, the other end of resistor R3 is connected to the positive terminal of the LED and the power line damage detection circuit (7) respectively, the negative terminal of the LED is connected to the leakage signal detection circuit (8), the other end of solenoid L1 is connected to the positive terminal of the SCR, the negative terminal of the SCR is grounded, the control terminal of the SCR is connected to one end of capacitor C1, the leakage signal detection circuit (8) and the output terminal of dual diode Q2 respectively, the other end of capacitor C1 is grounded, one input terminal of dual diode Q2 is connected to the temperature detection circuit (3), and one input terminal of dual diode Q2 is connected to the power line damage detection circuit (7).
7. A leakage current protection circuit with over-temperature protection and power line damage protection functions according to claim 1, characterized in that: The power cord damage detection circuit (7) includes diodes D1 and D2. The negative terminal of diode D1 is connected to the live wire and the negative terminal of diode D2 is connected to the neutral wire. The positive terminal of diode D1 is connected to the positive terminal of diode D2 and one end of resistor R6. The other end of resistor R6 is connected to pin 1 of optocoupler U3, one end of resistor R7, and one end of capacitor C9. The other end of resistor R7 is connected to the series wire (6), the other end of capacitor C9, and the negative terminal of Zener diode ZD1. The positive terminal of Zener diode ZD1 is connected to pin 2 of optocoupler U3 through resistor R8. Pin 3 of optocoupler U3 is connected to the power supply and trip output circuit (2). Pin 4 of optocoupler U3 is connected to one end of capacitor C10 and the power supply and trip output circuit (2) through resistor R9. The other end of capacitor C10 is grounded.
8. A leakage current protection circuit with over-temperature protection and power line damage protection functions according to claim 2, characterized in that: The leakage current detection circuit (8) includes a residual current transformer ZCT mounted on the live wire and the neutral wire. One output terminal of the residual current transformer ZCT is connected to one end of capacitor C4, one end of resistor R4, and one end of resistor R5A. The other output terminal of the residual current transformer ZCT is connected to the other end of capacitor C4, the other end of resistor R4, and one end of resistor R5B. The other end of resistor R5A is connected to one end of capacitor C8, pin 2 of the leakage current detection chip U1, and one end of capacitor C6. The other end of capacitor C6 is grounded. The other end of resistor R5B is connected to the other end of capacitor C8. One end of the leakage current detection chip U1 pin 1 and one end of the capacitor C7 are connected, the other end of the capacitor C7 is grounded, the leakage current detection chip U1 pin 3 is grounded, the leakage current detection chip U1 pin 5 is grounded through the capacitor C5, the leakage current detection chip U1 pin 6 is grounded through the capacitor C3, the leakage current detection chip U1 pin 7 is connected to the power supply and trip output circuit (2), the leakage current detection chip U1 pin 8 is connected to the negative terminal of the electrolytic capacitor C2, the negative terminal of the Zener diode ZD2, and the power supply and trip output circuit (2) respectively, the positive terminal of the electrolytic capacitor C2 is grounded, and the positive terminal of the Zener diode ZD2 is grounded.
9. A leakage current protection circuit with over-temperature protection and power line damage protection functions according to claim 8, characterized in that: One test terminal of the residual current transformer ZCT is connected to one end of the test switch SW, and the other end of the test switch SW is connected to the neutral current-carrying line. The other test terminal of the residual current transformer ZCT is connected to one end of the resistor R1, and the other end of the resistor R1 is connected to the live current-carrying line.
10. A leakage current protection circuit with over-temperature protection and power line damage protection functions according to claim 1, characterized in that: A varistor MOV is connected between the neutral current-carrying line input terminal and the live current-carrying line input terminal.