Leakage protection circuit with lightning protection function and overvoltage protection function

Abstract

The invention discloses a leakage protection circuit with a lightning protection function and an overvoltage protection function, which comprises a live wire current-carrying wire, a null line current-carrying wire and a ground wire current-carrying wire which are respectively connected with a live wire, a null line and a ground wire of a mains supply, and controlled switches are arranged on the live wire current-carrying wire and the null line current-carrying wire. A tripping circuit is connected among the live wire current-carrying wire, the ground wire current-carrying wire and the controlled switch, and an earth leakage protection circuit is connected among the live wire current-carrying wire, the zero wire current-carrying wire and the tripping circuit. A lightning protection circuit used for discharging surge current generated by lightning stroke is connected between the ground wire current-carrying wire, the trip circuit, and the live wire current-carrying wire and the zero wire current-carrying wire at the rear side of the controlled switch. An overvoltage protection circuit used for sending an overvoltage signal to the electric leakage protection circuit to enable the electric leakage protection circuit to control the tripping circuit to work when overvoltage is detected is connected between the live wire current-carrying wire on the rear side of the controlled switch and the electric leakage protection circuit, lightning protection is achieved, the problem that an internal circuit is burnt out or even is short-circuited and ignited is avoided, and the overvoltage protection function is achieved.

Description

[Technical Field]

[0001] This invention relates to a leakage current protection circuit with lightning protection and overvoltage protection functions. [Background Technology]

[0002] The circuits in existing residual current devices (RCDs) only have the function of disconnecting the power connection after detecting leakage current. They do not have lightning protection or overvoltage protection functions. Therefore, when a lightning strike generates surge current, it is easy to cause the internal circuit to burn out or even cause a fire, posing a risk of use. At the same time, when the external input voltage is unstable and the RCD operates under overvoltage, it is easy to cause the circuit to burn out and cause short circuits and fires. [Summary of the Invention]

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

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

[0005] A leakage current protection circuit with lightning protection and overvoltage protection functions is characterized by: including a live wire current-carrying line, a neutral wire current-carrying line, and a ground wire respectively connected to the mains live wire, neutral wire, and ground wire; a controlled switch for controlling the on / off state of the live wire current-carrying line and the neutral wire current-carrying line; a tripping circuit for controlling the power off of the controlled switch connected between the live wire current-carrying line, the ground wire current-carrying line, and the controlled switch; a leakage current protection circuit for controlling the tripping circuit to operate when leakage current is detected connected between the live wire current-carrying line, the neutral wire current-carrying line, and the tripping circuit; a lightning protection circuit for discharging surge current generated by lightning strikes connected between the ground wire current-carrying line, the tripping circuit, and the live wire current-carrying line and the neutral wire current-carrying line located behind the controlled switch; and an overvoltage protection circuit for sending an overvoltage signal to the leakage current protection circuit to control the tripping circuit to operate when overvoltage is detected between the live wire current-carrying line located behind the controlled switch and the leakage current protection circuit.

[0006] The leakage current protection circuit with lightning protection and overvoltage protection functions as described above is characterized in that: a test circuit for outputting a simulated leakage current signal to the leakage current protection circuit is connected between the leakage current protection circuit and the live wire and neutral wire located behind the controlled switch.

[0007] The leakage current protection circuit with lightning protection and overvoltage protection functions as described above is characterized in that: a power fault indication circuit for prompting when no power is detected is connected between the trip circuit and the live wire carrying current located in front of the controlled switch.

[0008] The leakage current protection circuit with lightning protection and overvoltage protection functions as described above is characterized in that: the lightning protection circuit includes a gas discharge tube (GDT), one end of the gas discharge tube GDT is connected to the ground current-carrying line, the other end of the gas discharge tube GDT is connected to one end of varistor MOV3 and one end of varistor MOV2 respectively, the other end of varistor MOV3 is connected to the neutral current-carrying line, one end of varistor MOV1, one end of capacitor CX1 and one end of resistor R10 on the back side of the controlled switch respectively, the other end of varistor MOV2 is connected to one end of fuse FUSE, the other end of varistor MOV1, the other end of capacitor CX1 and the other end of resistor R10 respectively, and the other end of fuse FUSE is connected to the live current-carrying line on the back side of the controlled switch.

[0009] The leakage current protection circuit with lightning protection and overvoltage protection functions as described above is characterized in that: the overvoltage protection circuit includes a diode D1, the positive terminal of the diode D1 is connected to the live wire of the controlled switch, the negative terminal of the diode D2 is connected to the negative terminal of the Schottky diode ZD2, one end of the capacitor C9, and one end of the resistor R9 through a resistor R8, the positive terminal of the Schottky diode ZD2 is connected to the leakage current protection circuit, and the other end of the capacitor C9 and the other end of the resistor R9 are grounded respectively.

[0010] The leakage current protection circuit with lightning protection and overvoltage protection functions as described above is characterized in that: the leakage current protection circuit includes a zero-sequence current transformer ZCT sleeved on the live wire and neutral wire of the controlled switch; the test circuit includes a test switch TEST SW and a resistor R1; one end of the test switch TEST SW is connected to the live wire of the controlled switch, and the other end of the test switch TEST SW is connected to one of the analog signal terminals of the zero-sequence current transformer ZCT; one end of the resistor R1 is connected to the neutral wire of the controlled switch, and the other end of the resistor R1 is connected to the other analog signal terminal of the zero-sequence current transformer ZCT.

[0011] The leakage current protection circuit with lightning protection and overvoltage protection functions as described above is characterized in that: the power fault indication circuit includes a fault indicator LED1, the positive terminal of the fault indicator LED1 is connected to the trip circuit and one end of the resistor R16, the other end of the resistor R16 is connected to the negative terminal of the diode D2 through the resistor R11, the positive terminal of the diode D2 is connected to the live wire, and the negative terminal of the fault indicator LED1 is connected to the trip circuit and the neutral wire in front of the controlled switch.

[0012] The leakage current protection circuit described above, which includes lightning protection and overvoltage protection functions, is characterized in that: the leakage current protection circuit includes a ZCT mounted on the live wire and neutral wire of the controlled switch and a control chip U1. Pin 1 of the control chip U1 is connected to one end of resistor R5, one end of capacitor C6, and one end of capacitor C7, respectively. The other end of resistor R5 is connected to one end of resistor R6 and one leakage detection terminal of the zero-sequence transformer ZCT, respectively. The other end of capacitor C6 is grounded, and the other end of capacitor C7 is connected to one end of resistor R7 and one end of the control chip U1, respectively. Pin 2 of the control chip is connected to one end of capacitor C8. The other end of resistor R7 is connected to the other end of resistor R6 and the other leakage detection terminal of the zero-sequence current transformer ZCT. The other end of capacitor C8 is grounded. Pin 3 of the control chip U1 is grounded. Pin 5 of the control chip U1 is grounded through capacitor C5. Pin 6 of the control chip U1 is connected to one end of capacitor C4 and the overvoltage protection circuit. The other end of capacitor C4 is grounded. Pin 7 of the control chip U1 is connected to one end of resistor R4 and the tripping circuit. The other end of resistor R4 is grounded. Pin 8 of the control chip U1 is connected to the tripping circuit.

[0013] The leakage current protection circuit with lightning protection and overvoltage protection functions as described above is characterized in that: the trip circuit includes a trip coil L1 for controlling the power off of the controlled switch and a rectifier DB1. Pin 1 of the rectifier DB1 is connected to one end of the trip coil L1 and the positive terminal of the SCR. The other end of the trip coil L1 is connected to the live wire of the controlled switch. The negative terminal of the SCR is grounded. The control terminal of the SCR is connected to one end of the capacitor C2 and one end of the resistor R3. The other end of the capacitor C2 is grounded. The other end of the resistor R3 is connected to the leakage current protection circuit. Pin 2 of the rectifier DB1 is connected to pin 1 of the optocoupler U2 and one end of the capacitor C1 through the resistor R2. The other end of the capacitor C1 is grounded. Pin 2 of the optocoupler U2 is connected to the positive terminal of the electrolytic capacitor C3 and the leakage current protection circuit. The negative terminal of the electrolytic capacitor C3 is connected. Pin 3 of the rectifier DB1 is connected to the neutral wire of the controlled switch. Pin 4 of the rectifier DB1 is grounded.

[0014] The beneficial effects of this invention are:

[0015] This invention incorporates a lightning protection circuit and an overvoltage protection circuit. The lightning protection circuit can discharge surge currents generated by lightning strikes, preventing internal circuits from being burned out or even short-circuited and ignited, thus improving safety. Simultaneously, when the overvoltage protection circuit detects an overvoltage condition, it sends an overvoltage signal to the leakage current protection circuit, causing the leakage current protection circuit to activate the trip circuit and disconnect the power connection, thereby achieving the overvoltage protection function and ensuring that the leakage current protector operates under non-overvoltage conditions. [Image Description]

[0016] Figure 1 This is the circuit schematic diagram of the present invention. [Detailed Implementation]

[0017] The technical solutions in the embodiments of the present invention will now be clearly and completely described in conjunction with the accompanying drawings.

[0018] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of the components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly. Furthermore, descriptions involving "preferred," "second-best," etc., in this invention 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, a feature defined as "preferred" or "second-best" may explicitly or implicitly include at least one of those features.

[0019] like Figure 1 As shown, a leakage current protection circuit with lightning protection and overvoltage protection functions includes a live wire current-carrying line, a neutral wire current-carrying line, and a ground wire current-carrying line connected to the mains live wire, neutral wire, and ground 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 / off state of the circuit. A tripping circuit 2 for controlling the power off of the controlled switch 1 is connected between the live wire current-carrying line, the neutral wire current-carrying line, and the tripping circuit 2. A leakage current protection circuit 3 for controlling the tripping circuit 2 to operate when leakage current is detected is connected between the live wire current-carrying line, the neutral wire current-carrying line, and the tripping circuit 2. A lightning protection circuit 4 for discharging surge current generated by lightning strikes is connected between the ground wire current-carrying line, the tripping circuit 2, and the live wire current-carrying line and the neutral wire current-carrying line located behind the controlled switch 1. An overvoltage protection circuit 5 for sending an overvoltage signal to the leakage current protection circuit 3 to control the tripping circuit 2 to operate when overvoltage is detected is connected between the live wire current-carrying line located behind the controlled switch and the leakage current protection circuit 3. During use, when the leakage protection circuit 3 detects leakage, it drives the trip circuit 2 to work, causing the trip circuit 2 to control the controlled switch 1 to open, thus realizing the leakage protection function. When a lightning strike generates a surge current, the lightning protection circuit 4 discharges the surge current, preventing circuit burnout and short circuit fires, thus realizing the lightning protection function. When the overvoltage protection circuit 5 detects an overvoltage, it sends an overvoltage signal to the leakage protection circuit 3, causing the leakage protection circuit 3 to drive the trip circuit 2 to work, causing the trip circuit 2 to control the controlled switch 1 to open, thus realizing the overvoltage protection function.

[0020] like Figure 1As shown, a test circuit 6 for outputting a simulated leakage current signal to the leakage current protection circuit 3 is connected between the leakage current protection circuit 3 and the live wire and neutral wire located behind the controlled switch 1. When it is necessary to test the leakage current protection function of the leakage current protection circuit, the test circuit 6 outputs a simulated leakage current signal to the leakage current protection circuit 3, thereby triggering the leakage current protection circuit 3 to drive the trip circuit 2 to work, causing the trip circuit 2 to control the controlled switch 1 to open, thereby realizing the leakage current protection detection function.

[0021] like Figure 1 As shown, a power fault indicator circuit 7 is connected between the trip circuit 2 and the live wire located in front of the controlled switch 1 to indicate when no power is detected. When a fault occurs inside the circuit, causing no power, the power fault indicator circuit 7 illuminates to indicate this.

[0022] like Figure 1 As shown, the working principle of the leakage current protection function is as follows: When a leakage current signal is generated in the live wire L or the neutral wire N, the zero-sequence transformer ZCT of the leakage current protection circuit 3 detects the leakage current signal. The two leakage detection terminals of the zero-sequence transformer ZCT output the leakage current signal and send it to the control chip U1 from pin 1 and pin 2 through resistors R5, R6, and R7. At this time, a high level is output to the trip circuit 2 through pin 7 of the control chip U1, which triggers the control terminal of the SCR in the trip circuit 2 and turns on the SCR, thereby energizing the trip coil L1, controlling the controlled switch 1 to open, and stopping the leakage current protector from supplying power to the load, thus realizing the leakage current protection function.

[0023] like Figure 1 As shown, the working principle of the lightning protection function is as follows: When the voltage between the neutral current-carrying line N and the ground current-carrying line PE exceeds the breakdown voltage of the gas discharge tube GDT in the lightning protection circuit 4, the gas inside the gas discharge tube GDT instantly ionizes into a conductive channel, leading the surge current to the varistor MOV3. The varistor MOV3 quickly clamps the voltage to a safe value and discharges the remaining surge current to the ground current-carrying line PE. After the surge current disappears, the gas discharge tube GDT automatically disconnects because the voltage is lower than the holding voltage, and the varistor MOV3 also returns to a high-resistance state, and the lightning protection circuit 4 returns to normal.

[0024] When the voltage between the live wire (L) and the ground wire (PE) exceeds the breakdown voltage of the gas discharge tube (GDT), the gas inside the GDT instantly ionizes, forming a conductive channel that directs the surge current to the varistor (MOV2). The varistor (MOV2) quickly clamps the voltage to a safe value and discharges the remaining surge current to the ground wire (PE). After the surge current disappears, the gas discharge tube (GDT) automatically disconnects because the voltage is lower than the holding voltage, and the varistor (MOV2) returns to a high-resistance state, thus restoring the surge protection circuit 4 to normal operation.

[0025] When the voltage surge between the live wire (L) and the neutral wire (N) exceeds the operating voltage of the varistor MOV1, the resistance of the varistor MOV1 will drop sharply, clamping the voltage and discharging the surge current. Capacitor CX1 is connected between the live and neutral wires to filter out high-frequency interference, while resistor R10 is connected in parallel with capacitor CX1 to discharge the residual charge in capacitor CX1. Fuse is connected in series with the varistor and the gas discharge tube GDT. When the varistor is subjected to an abnormally large current, fuse FUSE will blow to prevent the varistor from overloading and catching fire or causing a short circuit.

[0026] like Figure 1 As shown, the working principle of the overvoltage protection function is as follows: When the voltage applied to resistor R9 in the overvoltage protection circuit 5 is greater than the voltage regulated by Schottky diode ZD2, Schottky diode ZD2 is reverse-broken down. The voltage flows through Schottky diode ZD2 from pin 6 of control chip U1 in leakage protection circuit 3 into control chip U1. After comparison and judgment inside control chip U1, a high level is output from pin 7 of control chip U1, which serves as the trip signal output pin. This triggers the control terminal of the thyristor SCR in trip circuit 2, causing it to conduct, energizing trip coil L1, opening the controlled switch 1, and stopping the leakage current protector from supplying power to the load, thus providing protection.

[0027] like Figure 1 As shown, the working principle of the test function is as follows: Test circuit 6 is used to verify whether the leakage protection function of the leakage current protector is normal. When the leakage protection function is normal, when the test switch TEST SW of test circuit 6 is pressed, part of the current flows directly from the live wire L through resistor R1 and through the zero-sequence current transformer ZCT back to the neutral wire N; while part of the current flows back from the live wire L to the neutral wire N through the zero-sequence current transformer ZCT. At this time, there is a difference between the current returning to the neutral wire N through the zero-sequence current transformer ZCT and the total current returning to the neutral wire N, generating a simulated leakage current. After the simulated leakage current is detected by the zero-sequence current transformer ZCT, it will trigger the trip circuit 2 through the control chip U1, causing the controlled switch 1 to open and cut off the power supply.

[0028] like Figure 1As shown, the working principle of the power fault indicator is as follows: When the circuit is closed, the live wire signal of the live wire L enters the rectifier DB1 through the trip coil L1 of the trip circuit 2 for rectification. The rectified electrical signal returns to the neutral wire N through the resistor R2, optocoupler U2, control chip U1, and rectifier DB1 to form a loop. At this time, the optocoupler U2 is turned on, and the output terminal of the optocoupler U2 short-circuits the LED1 in the power fault indicator circuit 7, so the LED1 does not work. Conversely, when the circuit is closed, no signal passes through the rectifier DB1, and the optocoupler U2 cannot form a loop, so the optocoupler U2 is not turned on. At this time, the live wire signal of the live wire L returns to the neutral wire N through the diode D2, resistor R11, resistor R16, and LED1 to form a loop, so that the LED1 has voltage and the LED1 lights up as an indicator.

[0029] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct or indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A leakage current protection circuit with lightning protection and overvoltage protection functions, characterized in that: It includes a live wire, a neutral wire, and a ground wire, which are respectively connected to the mains live wire, neutral wire, and ground wire. A controlled switch (1) is provided on the live wire and the neutral wire to control the on / off state. A trip circuit (2) for controlling the power off of the controlled switch (1) is connected between the live wire, the ground wire, and the controlled switch (1). A leakage current circuit is connected between the live wire, the neutral wire, and the trip circuit (2) to control the trip circuit (2) to operate when leakage current is detected. The protection circuit (3), the ground current-carrying line, the trip circuit (2), and the live current-carrying line and the neutral current-carrying line located behind the controlled switch (1) are connected to a lightning protection circuit (4) for discharging the surge current generated by lightning strikes. The live current-carrying line located behind the controlled switch and the leakage protection circuit (3) are connected to an overvoltage protection circuit (5) for sending an overvoltage signal to the leakage protection circuit (3) to make the leakage protection circuit (3) control the trip circuit (2) to work.

2. The leakage current protection circuit with lightning protection and overvoltage protection functions according to claim 1, characterized in that: A test circuit (6) for outputting a simulated leakage signal to the leakage protection circuit (3) is connected between the leakage protection circuit (3) and the live wire and neutral wire located behind the controlled switch (1).

3. A leakage current protection circuit with lightning protection and overvoltage protection functions according to claim 1, characterized in that: A power fault indication circuit (7) is connected between the trip circuit (2) and the live wire in front of the controlled switch (1) to indicate when no power is detected.

4. A leakage current protection circuit with lightning protection and overvoltage protection functions according to claim 1, characterized in that: The lightning protection circuit (4) includes a gas discharge tube (GDT). One end of the gas discharge tube (GDT) is connected to the ground current-carrying line. The other end of the gas discharge tube (GDT) is connected to one end of the varistor MOV3 and one end of the varistor MOV2. The other end of the varistor MOV3 is connected to the neutral current-carrying line behind the controlled switch (1), one end of the varistor MOV1, one end of the capacitor CX1, and one end of the resistor R10. The other end of the varistor MOV2 is connected to one end of the fuse FUSE, the other end of the varistor MOV1, the other end of the capacitor CX1, and the other end of the resistor R10. The other end of the fuse FUSE is connected to the live current-carrying line behind the controlled switch (1).

5. A leakage current protection circuit with lightning protection and overvoltage protection functions according to claim 1, characterized in that: The overvoltage protection circuit (5) includes a diode D1. The positive terminal of the diode D1 is connected to the live wire of the controlled switch (1). The negative terminal of the diode D2 is connected to the negative terminal of the Schottky diode ZD2, one end of the capacitor C9, and one end of the resistor R9 through the resistor R8. The positive terminal of the Schottky diode ZD2 is connected to the leakage protection circuit (3). The other end of the capacitor C9 and the other end of the resistor R9 are grounded.

6. A leakage current protection circuit with lightning protection and overvoltage protection functions according to claim 2, characterized in that: The leakage protection circuit (3) includes a zero-sequence current transformer ZCT mounted on the live wire and neutral wire of the controlled switch (1). The test circuit (6) includes a test switch TEST SW and a resistor R1. One end of the test switch TEST SW is connected to the live wire of the controlled switch (1), and the other end of the test switch TEST SW is connected to one of the analog signal terminals of the zero-sequence current transformer ZCT. One end of the resistor R1 is connected to the neutral wire of the controlled switch (1), and the other end of the resistor R1 is connected to the other analog signal terminal of the zero-sequence current transformer ZCT.

7. A leakage current protection circuit with lightning protection and overvoltage protection functions according to claim 3, characterized in that: The power fault indication circuit (7) includes a fault indicator LED1. The positive terminal of the fault indicator LED1 is connected to the trip circuit (2) and one end of the resistor R16. The other end of the resistor R16 is connected to the negative terminal of the diode D2 through the resistor R11. The positive terminal of the diode D2 is connected to the live wire current-carrying line. The negative terminal of the fault indicator LED1 is connected to the trip circuit (2) and the neutral wire current-carrying line in front of the controlled switch (1).

8. A leakage current protection circuit with lightning protection and overvoltage protection functions according to claim 1, characterized in that: The leakage protection circuit (3) includes a ZCT mounted on the live wire and neutral wire behind the controlled switch (1) and a control chip U1. Pin 1 of the control chip U1 is connected to one end of resistor R5, one end of capacitor C6, and one end of capacitor C7, respectively. The other end of resistor R5 is connected to one end of resistor R6 and one leakage detection terminal of the zero-sequence transformer ZCT, respectively. The other end of capacitor C6 is grounded. The other end of capacitor C7 is connected to one end of resistor R7, pin 2 of control chip U1, and one end of capacitor C8, respectively. The other end of resistor R7 is connected to... One end is connected to the other end of resistor R6 and the other leakage detection end of zero-sequence transformer ZCT respectively. The other end of capacitor C8 is grounded. Pin 3 of control chip U1 is grounded. Pin 5 of control chip U1 is grounded through capacitor C5. Pin 6 of control chip U1 is connected to one end of capacitor C4 and overvoltage protection circuit (5) respectively. The other end of capacitor C4 is grounded. Pin 7 of control chip U1 is connected to one end of resistor R4 and trip circuit (2) respectively. The other end of resistor R4 is grounded. Pin 8 of control chip U1 is connected to trip circuit (2).

9. A leakage current protection circuit with lightning protection and overvoltage protection functions according to claim 1, characterized in that: The trip circuit (2) includes a trip coil L1 that controls the power off of the controlled switch (1) and a rectifier DB1. Pin 1 of the rectifier DB1 is connected to one end of the trip coil L1 and the positive terminal of the SCR. The other end of the trip coil L1 is connected to the live wire of the controlled switch (1). The negative terminal of the SCR is grounded. The control terminal of the SCR is connected to one end of the capacitor C2 and one end of the resistor R3. The other end of the capacitor C2 is grounded. The other end of the resistor R3 is connected to the leakage protection circuit (3). Pin 2 of the rectifier DB1 is connected to pin 1 of the optocoupler U2 and one end of the capacitor C1 through the resistor R2. The other end of the capacitor C1 is grounded. Pin 2 of the optocoupler U2 is connected to the positive terminal of the electrolytic capacitor C3 and the leakage protection circuit (3). The negative terminal of the electrolytic capacitor C3 is connected. Pin 3 of the rectifier DB1 is connected to the neutral wire of the controlled switch (1). Pin 4 of the rectifier DB1 is grounded.

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