Leakage protection circuit with overvoltage and undervoltage protection function

Abstract

The utility model discloses a kind of leakage protection circuit with overvoltage and undervoltage protection function, including firewire current-carrying line and zero line current-carrying line, controlled switch for controlling on-off is equipped on firewire current-carrying line and zero line current-carrying line, power supply and tripping output circuit for power supply and control controlled switch on-off and when only control controlled switch intercommunication when commercial voltage is in preset range are connected on firewire current-carrying line, zero line current-carrying line and controlled switch, power supply and tripping output circuit is connected with the commercial voltage detection circuit for detecting commercial voltage and outputting overvoltage and undervoltage control signal when commercial voltage is in overvoltage or undervoltage state, commercial voltage detection circuit is connected with overvoltage and undervoltage protection drive circuit for being connected with power supply and tripping output circuit for driving power supply and tripping output circuit to make controlled switch keep off state after receiving overvoltage and undervoltage control signal, guarantee leakage protection circuit in commercial voltage preset stable range work, improve use safety.

Description

[Technical Field]

[0001] This utility model relates to a leakage current protection circuit with overvoltage and undervoltage protection functions. [Background Technology]

[0002] Existing residual current devices (RCDs) typically supply power directly to appliances after power is applied and disconnect the power connection in the event of a leakage. However, due to the instability of mains voltage, continuous operation of the RCD under abnormal voltage conditions (overvoltage or undervoltage) can easily pose a safety risk. [Utility Model Content]

[0003] This invention overcomes the shortcomings of the prior art and provides a leakage protection circuit with overvoltage and undervoltage protection functions.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A leakage current protection circuit with overvoltage and undervoltage protection functions is characterized by: including a live wire current-carrying line and a neutral wire current-carrying line respectively connected to the mains live wire and neutral wire; a controlled switch for controlling the on / off state is provided on the live wire current-carrying line and the neutral wire current-carrying line; a power supply and trip output circuit is connected to the live wire current-carrying line, the neutral wire current-carrying line and the controlled switch for powering on and off the controlled switch, and for controlling the controlled switch to connect only when the mains voltage is within a preset range; a mains voltage detection circuit is connected to the power supply and trip output circuit for detecting the mains voltage and outputting overvoltage or undervoltage control signals when the mains voltage is in an overvoltage or undervoltage state; and an overvoltage and undervoltage protection drive circuit is connected to the power supply and trip output circuit for driving the power supply and trip output circuit to keep the controlled switch in an off state after receiving the overvoltage or undervoltage control signal.

[0006] The leakage protection circuit with overvoltage and undervoltage protection functions as described above is characterized in that: the mains voltage detection circuit is connected to an overvoltage and undervoltage alarm circuit that is connected to the power supply and tripping output circuit and is used to light up an alarm after receiving an overvoltage and undervoltage control signal.

[0007] The leakage protection circuit with overvoltage and undervoltage protection functions as described above is characterized in that: the power supply and trip output circuit is connected to a leakage signal detection circuit for detecting leakage signals of the live wire and neutral wire and outputting a trip signal to the power supply and trip output circuit after detecting the leakage signal.

[0008] The leakage protection circuit with overvoltage and undervoltage protection functions as described above is characterized in that: the controlled switch includes a switch S2 for controlling the on / off state of the live wire current-carrying line; the switch S2 includes a first connection terminal for connecting the live wire current-carrying line and a second connection terminal for disconnecting the live wire current-carrying line; the power supply and tripping output circuit includes a resistor R2; one end of the resistor R2 is connected to the second connection terminal of the switch S2; the other end of the resistor R2 is connected to one end of the capacitor C1, one end of the resistor R1, and pin 3 of the rectifier DB1; the other end of the capacitor C1 is connected to the live wire current-carrying line input terminal, the other end of the resistor R1, and the positive terminal of the diode D1; the negative terminal of the diode D1 is connected to the mains voltage detection circuit and one end of the resistor R4; the other end of the resistor R4 is connected to the positive terminal of the electrolytic capacitor C3, the overvoltage and undervoltage alarm circuit, and one end of the resistor R5; the resistor R... 5. The other end is connected to the leakage current detection circuit, one end of the RESET button, one end of the resistor R7, the emitter of transistor Q2, and one end of the bidirectional transient suppression diode D2. The other end of the bidirectional transient suppression diode D2 and the negative terminal of the electrolytic capacitor C3 are grounded. The other end of the RESET button is grounded. The base of transistor Q2 is connected to the other end of the resistor R7 and the over / under voltage protection drive circuit. The collector of transistor Q2 is connected to the base of transistor Q1 through resistor R6. The emitter of transistor Q1 is grounded. The collector of transistor Q1 is connected to one end of solenoid SOL1. The other end of solenoid SOL1 is connected to the positive terminal of electrolytic capacitor C2 and pin 4 of rectifier DB1. Pin 2 of rectifier DB1 and the negative terminal of electrolytic capacitor C2 are grounded. Pin 1 of rectifier DB1 is connected to the neutral current-carrying input terminal.

[0009] The leakage protection circuit with overvoltage and undervoltage protection functions described above is characterized in that: the mains voltage detection circuit includes a voltage detection chip U2 with a preset mains voltage range value under normal operating conditions; pin 1 of the voltage detection chip U2 is connected to the overvoltage and undervoltage protection drive circuit; pin 4 of the voltage detection chip U2 is connected to the overvoltage and undervoltage alarm circuit; pin 2 of the voltage detection chip U2 is grounded; pin 3 of the voltage detection chip U2 is connected to the positive terminal of electrolytic capacitor C13, one end of resistor R13, and one end of resistor R14, respectively; the other end of resistor R14 and the negative terminal of electrolytic capacitor C13 are grounded, respectively; the other end of resistor R13 is connected to... One end of resistor R15 is connected to the power supply and trip output circuit. The other end of resistor R15 is connected to one end of resistor R16, the negative terminal of transient suppression diode ZD2, and the positive terminal of electrolytic capacitor C12. The positive terminal of transient suppression diode ZD2 and the negative terminal of electrolytic capacitor C12 are grounded. The other end of resistor R16 is connected to one end of resistor R17, the negative terminal of U3, one end of capacitor C14, and pin 5 of voltage detection chip U2. The other end of resistor R17 is connected to one end of resistor R18 and the control electrode of thyristor U3. The other end of resistor R18 and the positive terminal of thyristor U3 and the other end of capacitor C14 are grounded.

[0010] The leakage protection circuit with overvoltage and undervoltage protection functions as described above is characterized in that: the overvoltage and undervoltage protection drive circuit includes a transistor Q3, the emitter of transistor Q3 is grounded, the base of transistor Q3 is connected to the mains voltage detection circuit through resistor R19, and the collector of transistor Q3 is connected to the power supply and tripping output circuit through resistor R21.

[0011] The leakage protection circuit with overvoltage and undervoltage protection functions as described above is characterized in that: the overvoltage and undervoltage alarm circuit includes a transistor Q4, the emitter of transistor Q4 is grounded, the base of transistor Q4 is connected to the mains voltage detection circuit through resistor R20, the collector of transistor Q3 is connected to the negative terminal of the LED lamp, and the positive terminal of the LED lamp is connected to the power supply and tripping output circuit through resistor E22.

[0012] The leakage current protection circuit with overvoltage and undervoltage protection functions as described above is characterized in that: the leakage current signal detection circuit includes a residual current transformer ZCT sleeved on the live wire and the neutral wire; one output terminal of the residual current transformer ZCT is connected to one end of capacitor C11, one end of resistor R10, and one end of resistor R12 respectively; the other end of resistor R12 is connected to pin 2 of leakage current detection chip U1, one end of capacitor C10, and one end of capacitor C9 respectively; the other end of capacitor C9 is grounded; the other end of capacitor C10 is connected to one end of capacitor C8, pin 1 of leakage current detection chip U1, and one end of resistor R11 respectively; the other end of capacitor C8 is grounded; and the other end of resistor R11 is connected to the other end of resistor R10, the other end of capacitor C11, and the other output terminal of residual current transformer ZCT respectively. The output terminals are connected as follows: pin 3 of the leakage current detection chip U1 is grounded; pin 4 of the leakage current detection chip U1 is connected to one end of capacitor C7 and pin 5 of the leakage current detection chip U1 respectively; the other end of capacitor C7 is grounded; pin 6 of the leakage current detection chip U1 is grounded through capacitor C6; pin 7 of the leakage current detection chip U1 is connected to the control terminal of the SCR and one end of capacitor C4 through resistor R8 respectively; the other end of capacitor C4 is connected to the negative terminal of the SCR, the power supply and tripping output circuit respectively; the positive terminal of the SCR is connected to the power supply and tripping output circuit and one end of resistor R9 respectively; the other end of resistor R9 is connected to pin 8 of the leakage current detection chip U1, one end of capacitor C5, and the negative terminal of Zener diode ZD1 respectively; the other end of capacitor C5 and the positive terminal of Zener diode ZD1 are grounded respectively.

[0013] The leakage protection circuit with overvoltage and undervoltage protection functions as described above is characterized in that a test switch SW and a resistor R3 are connected in series between the neutral wire current-carrying input terminal and the live wire current-carrying output terminal.

[0014] The leakage protection circuit with overvoltage and undervoltage protection functions as described above is characterized in that: a varistor MOV is connected between the neutral current-carrying line input terminal and the live current-carrying line input terminal.

[0015] The beneficial effects of this utility model are:

[0016] This invention features an overvoltage and undervoltage protection circuit comprised of a mains voltage detection circuit and an overvoltage / undervoltage protection drive circuit. After the leakage current device (RCD) is powered on, the overvoltage / undervoltage protection circuit takes over the leakage current protection circuit. When the mains voltage detection circuit detects overvoltage or undervoltage, it drives the power supply and trip output circuit via the overvoltage / undervoltage protection drive circuit to keep the controlled switch de-energized, preventing the leakage current protection circuit from operating and related drive outputs. Simultaneously, an LED alarm is activated to ensure the leakage current protection circuit operates within a preset stable mains voltage range, preventing continuous operation under abnormal voltage conditions and avoiding safety risks. [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 overvoltage and undervoltage protection functions includes a live wire current-carrying line and a neutral wire current-carrying line connected to the mains live wire and neutral wire respectively. A controlled switch 1 is provided on the live wire current-carrying line and the neutral wire current-carrying line to control the on and off of power. A power supply and trip output circuit 2 is connected to the live wire current-carrying line, the neutral wire current-carrying line and the controlled switch 1 to supply power and control the controlled switch 1 to turn on only when the mains voltage is within a preset range. The power supply and trip output circuit 2 is connected to a mains voltage detection circuit 3 to detect the mains voltage and output overvoltage and undervoltage control signals when the mains voltage is in an overvoltage or undervoltage state. The mains voltage detection circuit 3 is connected to an overvoltage and undervoltage protection drive circuit 4 connected to the power supply and trip output circuit 2 to drive the power supply and trip output circuit 2 to keep the controlled switch 1 in an off state after receiving the overvoltage and undervoltage control 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 mains voltage detection circuit 3, enabling the mains voltage detection circuit 3 to operate. At this time, the mains voltage detection circuit 3 detects the mains voltage input to the power supply and trip output circuit 2. When the detected mains voltage is within the preset range, the power supply and trip output circuit 2 activates the controlled switch 1 to power on the leakage current protector; when the detected mains voltage is overvoltage or undervoltage, the mains voltage detection circuit 3 drives the power supply and trip output circuit 2 through the overvoltage and undervoltage protection drive circuit 4 to keep the controlled switch 1 de-energized, preventing the leakage current protector from operating.

[0022] like Figure 1 As shown, the mains voltage detection circuit 3 is connected to the power supply and trip output circuit 2, which is used to provide an over / under voltage alarm circuit 5 that illuminates upon receiving an over / under voltage control signal. When an over / under voltage is detected, the mains voltage detection circuit 3 controls the over / under voltage alarm circuit 5 to activate and provide an illuminated alarm.

[0023] like Figure 1 As shown, the power supply and trip output circuit 2 is connected to a leakage signal detection circuit 6, 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. In this case, when the mains voltage is detected to be over-voltage or under-voltage, the controlled switch 1 remains de-energized, and the leakage signal detection circuit 6 does not operate. When the detected mains voltage is within a preset range, the controlled switch 1 is activated, causing the leakage current protector to operate and also activating the leakage signal detection circuit 6 to detect leakage signals on the live wire and neutral wire. Upon detection of a leakage signal, the power supply and trip output circuit 2 drives the controlled switch 1 to trip and disconnect the power connection. This ensures that the mains voltage is detected first upon power-on, thereby guaranteeing that the leakage protection circuit operates within the preset stable range of the mains voltage and preventing the leakage protection circuit from continuously operating under abnormal voltage conditions, thus avoiding safety risks.

[0024] like Figure 2As shown, when the power input terminals of the live wire and neutral wire are powered on, the AC power supply is used to power the solenoid SOL1 through resistor R2, capacitor C1, and rectifier DB1 in the power supply and trip output circuit 2, and after filtering by electrolytic capacitor C2. At the instant transistor Q1 is turned on, solenoid SOL1 generates a large pull-in current, causing switches S1 and S2 of the controlled switch 1 to reliably close, thus connecting the controlled switch 1. At this time, the resistor R2 circuit is open, and solenoid SOL1 is only provided with a holding current by the capacitor C1 and resistor R1 circuit rectified by rectifier DB1. This circuit can provide a large instantaneous pull-in current while consuming a small current during holding, thereby reducing power consumption.

[0025] When the power input terminals of the live wire and neutral wire are powered on, DC power is provided to the LED, SCR, transistor Q1, transistor Q2, leakage current detection chip U1, voltage detection chip U2, etc. through diode D1, resistor R4, electrolytic capacitor C3, and resistor R5.

[0026] Leakage detection function: Resistor R9, Zener diode ZD1, and capacitor C5 in leakage signal detection circuit 6 supply power to leakage detection chip U1, which is dedicated to leakage protection. When the mains voltage is within the preset range, and the residual current transformer ZCT detects a leakage signal and outputs it to leakage detection chip U1, if leakage is determined by the internal comparison of leakage detection chip U1, the drive pin 7 of leakage detection chip U1 outputs a high-level pulse, which turns on the SCR through resistor R8, de-energizing leakage detection chip U1, turning off transistors Q2 and Q1 in power supply and trip output circuit 2, de-energizing solenoid SOL1, and opening switches S1 and S2. This state is maintained continuously. When the manual reset switch RESET is pressed, leakage detection chip U1 returns to normal power supply, transistors Q2 and Q1 turn on, solenoid SOL1 is energized, switches S1 and S2 are energized, and controlled switch 1 is turned on.

[0027] Undervoltage and overvoltage protection function: After the mains power passes through the basic power supply circuit consisting of diode D1, resistor R15 in the power supply and trip output circuit 2, electrolytic capacitor C12 in the mains voltage detection circuit 3, and Zener diode ZD2, it then passes through a low-power precision regulated power supply consisting of resistors R16, R17, R18, thyristor U3, and capacitor C14 to power the voltage detection chip U2 and provide a reference voltage. The mains power then passes through the mains voltage detection circuit consisting of resistors R13, R14, and electrolytic capacitor C13. The voltage detection chip U2 continuously samples, filters, delays, and compares the mains power through pin 3, using different comparison thresholds for overvoltage and undervoltage. When the sampled voltage is higher than the comparison threshold, it indicates mains overvoltage; when it is lower than the comparison threshold, it indicates mains undervoltage. That is, when the mains voltage is not within the preset range, the voltage detection chip U2 outputs two overvoltage or undervoltage signals. One path passes through pin 4 of the voltage detection chip U2, outputting to the power supply circuit consisting of resistor R20, transistor Q4, LED, resistor R22, and electrolytic capacitor C3. When the mains voltage is within the preset range, pin 4 of the voltage detection chip U2 outputs a low level, causing transistor Q4 to be cut off and the LED to turn off. However, when the mains voltage is over-voltage or under-voltage, this pin outputs a high level, causing transistor Q4 to be turned on and the LED to light up as an alarm. Another path outputs through pin 1 of voltage detection chip U2 to a control circuit consisting of resistor R19, transistor Q3, resistor R21, resistor R7, transistor Q2, resistor R6, transistor Q1, and solenoid SOL1. When the mains voltage is within a predetermined range, pin 1 of voltage detection chip U2 outputs a high level, turning on transistors Q3 and Q2. Whether transistor Q1 is turned on depends on whether the reset button RESET is pressed and whether leakage current is generated in the leakage current detection circuit. When the mains voltage is over-voltage or under-voltage, this pin outputs a low level, turning off transistors Q3, Q2, and Q1, de-energizing solenoid SOL1, and opening switches S1 and S2.

[0028] This solution achieves the following: after power-on, the overvoltage and undervoltage protection circuit takes over the leakage current protection circuit. When overvoltage or undervoltage occurs, the leakage current protection circuit and related drive outputs are disabled, and an alarm LED light is used to indicate this. When the mains voltage is within the set range, the leakage current protection circuit is allowed to work, thus preventing the leakage current protection circuit from continuing to work under abnormal voltage conditions and causing safety risks.

[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 overvoltage and undervoltage protection functions, characterized in that: It includes a live wire current-carrying line and a neutral wire current-carrying line connected to the mains live wire and neutral wire respectively. A controlled switch (1) is provided on the live wire current-carrying line and the neutral wire current-carrying line to control the on and off of the power. A power supply and trip output circuit (2) is connected to the live wire current-carrying line, the neutral wire current-carrying line and the controlled switch (1) to supply power and control the controlled switch (1) to turn on when the mains voltage is within a preset range. A mains voltage detection circuit (3) is connected to the mains voltage to detect the mains voltage and output over- or under-voltage control signals when the mains voltage is in an over- or under-voltage state. A mains voltage detection circuit (3) is connected to the power supply and trip output circuit (2) to drive the power supply and trip output circuit (2) to keep the controlled switch (1) in an off-state after receiving the over- or under-voltage control signal.

2. A leakage current protection circuit with overvoltage and undervoltage protection functions according to claim 1, characterized in that: The mains voltage detection circuit (3) is connected to the power supply and trip output circuit (2), which is used to light up the alarm after receiving the over- or under-voltage control signal.

3. A leakage current protection circuit with overvoltage and undervoltage protection functions according to claim 2, characterized in that: The power supply and trip output circuit (2) is connected to a leakage signal detection circuit (6) 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.

4. A leakage current protection circuit with overvoltage and undervoltage protection functions according to claim 3, characterized in that: The controlled switch (1) includes a switch S2 that controls the on / off state of the live wire current-carrying line. The switch S2 includes a first connection terminal that connects the live wire current-carrying line and a second connection terminal that disconnects the live wire current-carrying line. The power supply and tripping output circuit (2) includes a resistor R2. One end of the resistor R2 is connected to the second connection terminal of the switch S2. The other end of the resistor R2 is connected to one end of the capacitor C1, one end of the resistor R1, and pin 3 of the rectifier DB1. The other end of the capacitor C1 is connected to the live wire current-carrying line input terminal, the other end of the resistor R1, and the positive terminal of the diode D1. The negative terminal of the diode D1 is connected to the mains voltage detection circuit (3) and one end of the resistor R4. The other end of the resistor R4 is connected to the positive terminal of the electrolytic capacitor C3, the over / under voltage alarm circuit (5), and one end of the resistor R5. The other end of the resistor R5 is connected to the leakage signal detection circuit (3). The circuit (6) is connected to one end of the reset button (RESET), one end of the resistor (R7), the emitter of transistor Q2, and one end of the bidirectional transient suppression diode (D2). The other end of the bidirectional transient suppression diode (D2) and the negative terminal of the electrolytic capacitor (C3) are grounded. The other end of the reset button (RESET) is grounded. The base of transistor Q2 is connected to the other end of the resistor (R7) and the over / under voltage protection drive circuit (4). The collector of transistor Q2 is connected to the base of transistor Q1 through the resistor (R6). The emitter of transistor Q1 is grounded. The collector of transistor Q1 is connected to one end of solenoid (SOL1). The other end of solenoid (SOL1) is connected to the positive terminal of electrolytic capacitor (C2) and pin 4 of rectifier (DB1). Pin 2 of rectifier (DB1) and the negative terminal of electrolytic capacitor (C2) are grounded. Pin 1 of rectifier (DB1) is connected to the input terminal of the neutral current-carrying line.

5. A leakage current protection circuit with overvoltage and undervoltage protection functions according to claim 4, characterized in that: The mains voltage detection circuit (3) includes a voltage detection chip U2 with a preset mains voltage range value. Pin 1 of the voltage detection chip U2 is connected to the over / under voltage protection drive circuit (4), pin 4 of the voltage detection chip U2 is connected to the over / under voltage alarm circuit (5), pin 2 of the voltage detection chip U2 is grounded, pin 3 of the voltage detection chip U2 is connected to the positive terminal of electrolytic capacitor C13, one end of resistor R13, and one end of resistor R14, respectively. The other end of resistor R14 and the negative terminal of electrolytic capacitor C13 are grounded, respectively. The other end of resistor R13 is connected to one end of resistor R15, the power supply and The trip output circuit (2) is connected. The other end of resistor R15 is connected to one end of resistor R16, the negative terminal of transient suppression diode ZD2, and the positive terminal of electrolytic capacitor C12. The positive terminal of transient suppression diode ZD2 and the negative terminal of electrolytic capacitor C12 are grounded respectively. The other end of resistor R16 is connected to one end of resistor R17, the negative terminal of U3, one end of capacitor C14, and pin 5 of voltage detection chip U2 respectively. The other end of resistor R17 is connected to one end of resistor R18 and the control electrode of thyristor U3 respectively. The other end of resistor R18 and the positive terminal of thyristor U3 and the other end of capacitor C14 are grounded respectively.

6. A leakage current protection circuit with overvoltage and undervoltage protection functions according to claim 4, characterized in that: The over / under voltage protection drive circuit (4) includes a transistor Q3. The emitter of transistor Q3 is grounded, the base of transistor Q3 is connected to the mains voltage detection circuit (3) through resistor R19, and the collector of transistor Q3 is connected to the power supply and trip output circuit (2) through resistor R21.

7. A leakage current protection circuit with overvoltage and undervoltage protection functions according to claim 4, characterized in that: The over / under voltage alarm circuit (5) includes a transistor Q4, the emitter of transistor Q4 is grounded, the base of transistor Q4 is connected to the mains voltage detection circuit (3) through resistor R20, the collector of transistor Q3 is connected to the negative terminal of the LED lamp, and the positive terminal of the LED lamp is connected to the power supply and trip output circuit (2) through resistor E22.

8. A leakage current protection circuit with overvoltage and undervoltage protection functions according to claim 4, characterized in that: The leakage current detection circuit (6) 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 C11, one end of resistor R10, and one end of resistor R12. The other end of resistor R12 is connected to pin 2 of the leakage current detection chip U1, one end of capacitor C10, and one end of capacitor C9. The other end of capacitor C9 is grounded. The other end of capacitor C10 is connected to one end of capacitor C8, pin 1 of the leakage current detection chip U1, and one end of resistor R11. The other end of capacitor C8 is grounded. The other end of resistor R11 is connected to the other end of resistor R10, the other end of capacitor C11, and the other output terminal of the residual current transformer ZCT. Pin 3 of the leakage current detection chip U1 is connected to the other end of the residual current transformer ZCT. The leakage current detection chip U1 pin 4 is connected to one end of capacitor C7 and the leakage current detection chip U1 pin 5 respectively. The other end of capacitor C7 is grounded. The leakage current detection chip U1 pin 6 is grounded through capacitor C6. The leakage current detection chip U1 pin 7 is connected to the control terminal of the thyristor SCR and one end of capacitor C4 respectively through resistor R8. The other end of capacitor C4 is connected to the negative terminal of the thyristor SCR and the power supply and trip output circuit (2) respectively. The positive terminal of the thyristor SCR is connected to the power supply and trip output circuit (2) and one end of resistor R9 respectively. The other end of resistor R9 is connected to the leakage current detection chip U1 pin 8, one end of capacitor C5 and the negative terminal of Zener diode ZD1 respectively. The other end of capacitor C5 and the positive terminal of Zener diode ZD1 are grounded respectively.

9. A leakage current protection circuit with overvoltage and undervoltage protection functions according to claim 1, characterized in that: A test switch SW and a resistor R3 are connected in series between the neutral wire current-carrying line input terminal and the live wire current-carrying line output terminal.

10. A leakage current protection circuit with overvoltage and undervoltage 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.

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