Earth leakage protection circuit and method

Abstract

The invention discloses a leakage protection circuit and method, and relates to the field of grounding fault protection, and the method comprises the steps: detecting grounding faults of a live wire and a neutral wire in real time through the circuit, and judging whether to drive a controllable switch module to cut off the power supply of a power grid or not according to the size of a sampling voltage, thereby protecting the personal safety; the self-checking module sends a simulation fault signal in the positive half cycle of a live wire to simulate a neutral line grounding fault, generated fault current generates sampling voltage in the electric leakage detection module, and when the value of the sampling voltage is larger than first threshold voltage, it is determined that a system electric leakage detection part is normal; and then the self-checking module sends a switching signal in the negative half cycle of the live wire to simulate and drive the controllable switch module, and if a test passing signal is returned, it is determined that the leakage protection system is in a good detection state, and the occurrence of a grounding fault can be dealt with in real time.

Description

Technical Field

[0001] The present invention relates to the field of ground fault protection, and in particular to a leakage protection circuit and method. Background Art

[0002] When the load is connected to the circuit, the live wire and the neutral wire in the three-phase line are connected to the load to supply power to the load, and the ground wire is connected to the load housing as a protective line. When a ground fault occurs in the load, the load housing is energized, and people can easily touch the housing of large electrical appliances. A ground fault may cause a load failure or even affect the life and health of the user, so it is very important to detect ground faults in high-voltage lines. The leakage protection circuit can respond to ground faults when the internal components are normal, but when the internal components of the leakage protection circuit fail, it will not be able to respond to ground faults. Summary of the invention

[0003] The object of the present invention is to provide a leakage protection circuit and method, which can avoid the leakage protection circuit being unable to detect and protect against ground faults in a timely manner due to internal device failures by simulating fault self-detection.

[0004] In order to solve the above technical problems, the present invention provides a leakage protection circuit, comprising:

[0005] A controllable switch module, wherein the first end and the second end of the controllable switch module are both arranged on the live wire, the third end and the fourth end of the controllable switch module are both arranged on the neutral wire, the first end of the controllable switch module is connected to the second end, and the third end is connected to the fourth end when no ground fault occurs, the controllable switch module is used to disconnect the first end from the second end when its control end receives a control signal in the positive half cycle of the live wire, and disconnect the third end from the fourth end when its control end receives a control signal in the positive half cycle of the live wire, so as to cut off the power supply of the live wire and the neutral wire, test its own switch function when receiving the control signal in the negative half cycle of the live wire, maintain the connection state when no ground fault occurs, and return a test pass signal to the self-test module if its own switch function is normal;

[0006] A leakage detection module, wherein the output end of the leakage detection module is connected to the second end of the self-test module, the leakage detection module is used to sample the grounding faults existing in the live wire and the neutral wire and generate a sampling voltage, and when the absolute value of the sampling voltage reaches a first threshold voltage, output a judgment signal to the second end of the self-test module, and the sampling voltage is related to the difference between the current on the live wire and the current on the neutral wire;

[0007] A fault simulation module, wherein the control end of the fault simulation module is connected to the third end of the self-test module, the first end of the fault simulation module is connected to the neutral line of the load end, and the second end is grounded, and is used to connect the first end of the module to the second end when the control end receives a simulated fault signal to simulate a neutral line grounding fault;

[0008] The self-test module, the first end of which is connected to the live wire, is used to detect the phase of the power grid. After sending a simulated fault signal through the third end in the positive half cycle of the live wire, if the judgment signal is received at its second end, then in the negative half cycle of the live wire, a control signal is sent to the controllable switch module through the fourth end. If the test pass signal is received, it is determined that the leakage protection circuit is working normally.

[0009] On the other hand, the controllable switch module includes a first controllable switch, a solenoid and a mechanical device;

[0010] The control end of the first controllable switch is connected to the fourth end of the self-test module, the second end of the first controllable switch is grounded, the first end of the first controllable switch is connected to the first end of the solenoid, the second end of the solenoid is connected to the live wire, the fixed end of the mechanical device is arranged at one end breakpoint of the live wire and one end breakpoint of the neutral wire, and the movable end of the mechanical device is arranged at the other end breakpoint of the live wire and the other end breakpoint of the neutral wire;

[0011] The first controllable switch is used to be turned on when the control end receives a control signal so as to form a current loop from the live wire, the solenoid, the first controllable switch to the ground. The solenoid is used to be turned on during the positive half cycle of the live wire to control the fixed end of the mechanical device to be disconnected from the active end. It cannot be turned on during the negative half cycle of the live wire, and the fixed end of the mechanical device cannot be controlled to be disconnected from the active end.

[0012] On the other hand, the leakage detection module includes a live wire to ground leakage detection module, and the live wire to ground leakage detection module includes a first mutual inductor, a sampling resistor and a first amplifier;

[0013] The live wire and the neutral wire pass through the first mutual inductor, the first end of the first mutual inductor is connected to the first end of the sampling resistor, the first end of the leakage detection module and the first input end of the first amplifier, the second end of the first mutual inductor is connected to the second end of the sampling resistor and the second end of the first amplifier, and the output end of the first amplifier serves as the fourth end of the leakage detection module;

[0014] The first transformer is used to sense the difference between the current on the live line and the current on the neutral line, and then sampled by the sampling resistor after reducing it by a preset multiple, and send a sampling signal to the first amplifier. The first amplifier is used to generate a control signal when the absolute value of the sampling signal is greater than a threshold voltage and send the control signal to the second end of the self-test module.

[0015] On the other hand, the leakage detection module includes a neutral grounding fault detection module, and the neutral grounding fault detection module includes a first capacitor, a second capacitor, a second mutual inductor and a second amplifier;

[0016] The live wire and the neutral wire pass through the first mutual inductor and the second mutual inductor at the same time, the first end of the second mutual inductor is connected to the first end of the first capacitor and the common end of the connection is grounded, the second end of the second mutual inductor is connected to the second end of the first capacitor and the first end of the second capacitor, the second end of the second capacitor is connected to the output end of the second amplifier, the first input end of the second amplifier serves as the first end of the leakage detection module, and the second input end of the second amplifier serves as the second end of the leakage detection module;

[0017] The second amplifier is used to amplify the fault current generated by the neutral grounding fault, the second transformer is used to couple the amplified fault current to the first transformer, the first capacitor is used to generate oscillation, and the second capacitor is used to isolate direct current. When the first amplifier detects that the absolute value of the sampling signal is greater than the first threshold voltage, the control signal is generated to control the second end of the self-test module.

[0018] On the other hand, the fault simulation module includes a fault simulation resistor and a second controllable switch;

[0019] The first end of the fault simulation resistor is connected to the neutral line, the second end of the fault simulation resistor is connected to the first end of the second controllable switch, the second end of the second controllable switch is grounded, and the control end of the second controllable switch is connected to the controller in the self-test module;

[0020] The controller is used to send a simulated fault signal to the second controllable switch according to a grid phase, and the second controllable switch is used to be turned on when receiving the simulated fault signal.

[0021] On the other hand, it also includes a rectifier module, the rectifier module includes a first diode, a second diode, a third diode, a fourth diode, a first resistor, a second resistor, a third resistor, a fourth resistor and a third capacitor;

[0022] The anode of the first diode and the anode of the second diode are both connected to the live wire, the cathode of the first diode, the cathode of the second diode, the anode of the third diode and the anode of the fourth diode are connected, the cathode of the third diode, the cathode of the fourth diode, the first end of the first resistor and the first end of the second resistor are connected, the second end of the first resistor, the second end of the second resistor, the first end of the third resistor and the first end of the fourth resistor are connected, the second end of the third resistor and the second end of the fourth resistor are connected to the power supply end of the leakage protection circuit and the first end of the third capacitor, and the second end of the third capacitor is grounded;

[0023] The first diode, the second diode, the third diode, the fourth diode, the first resistor, the second resistor, the third resistor and the fourth resistor are used for half-wave rectification, and the third capacitor is used for filtering.

[0024] On the other hand, it also includes a delay module;

[0025] The input end of the delay module is connected to the output end of the leakage detection module, and the output end of the delay module is connected to the second end of the self-test module, and is used to send the judgment signal to the second end of the self-test module when the judgment signal is continuously received within a first preset time;

[0026] The self-check module is also used to shield and control the first preset time when sending a simulated fault signal, call the second preset time and the third preset time, and if the judgment signal is received within the third preset time, enter the step of sending a control signal to the controllable switch module through the fourth terminal;

[0027] The second preset time is used to prevent interference signals from causing false triggering of the circuit, and the third preset time is used to protect the negative half cycle of self-test to avoid self-test exceeding the negative half cycle time of the live wire. The second preset time and the third preset time are related to the grid frequency.

[0028] In order to solve the above technical problems, the present invention also provides a leakage protection method, which is applied to the self-test module in the above leakage protection circuit, wherein the leakage protection circuit also includes a leakage detection module, a fault simulation module and a controllable switch module, wherein the output end of the leakage detection module is connected to the second end of the self-test module, and the leakage detection module is used to sample the grounding faults existing in the live line and the neutral line and generate a sampling voltage, and when the absolute value of the sampling voltage reaches a first threshold voltage, a judgment signal is output to the second end of the self-test module, and the sampling voltage is related to the difference between the current on the live line and the current on the neutral line, the control end of the fault simulation module is connected to the third end of the self-test module, and the first end of the fault simulation module is connected to the load The first end of the controllable switch module is connected to the neutral line, the second end is grounded, the fourth end of the self-test module is connected to the control end of the controllable switch module, the first end and the second end of the controllable switch module are both arranged on the live line, the third end and the fourth end of the controllable switch module are both arranged on the neutral line, the controllable switch module is used to disconnect the first end and the second end of the controllable switch module when the control end of the controllable switch module receives a control signal in the positive half cycle of the live line, and disconnect the third end and the fourth end of the controllable switch module to cut off the power supply of the live line and the neutral line, test the switch function of the controllable switch module when the control signal is received in the negative half cycle of the live line, maintain the connection state when no ground fault occurs, and return the test pass signal to the self-test module if the switch function of the controllable switch module is normal. The leakage protection method includes:

[0029] Determine whether the power grid is powered on;

[0030] Determine the phase and the time point of the self-test starting point when the grid is powered on;

[0031] After the time point of the self-check starting point, according to the grid phase in the positive half cycle of the live line, the fault simulation module is controlled to connect its first end with the second end to simulate the occurrence of a neutral line grounding fault;

[0032] Determine whether the second end thereof receives the determination signal returned by the leakage detection module;

[0033] According to the negative half cycle of the grid phase in the live line, sending a control signal to the control end of the controllable switch module according to the judgment signal;

[0034] Determining whether the controllable switch module returns a test pass signal;

[0035] If yes, it is determined that the leakage protection circuit works normally;

[0036] If not, it is determined that there is a device in the leakage protection circuit that is working abnormally, and an alarm is issued.

[0037] On the other hand, the leakage protection circuit further includes a fifth diode and a voltage-dividing resistor, wherein the anode of the fifth diode is connected to the first end of the solenoid in the controllable switch module, the second end of the fifth diode is connected to the first end of the voltage-dividing resistor, and the second end of the voltage-dividing resistor is connected to the first end of the self-test module;

[0038] Determine the time point for the self-check starting point, including:

[0039] Determine whether the voltage detected at the first terminal is greater than a second threshold voltage;

[0040] If it is greater than the second threshold voltage, the current time point is determined to be the time point of the self-check starting point.

[0041] On the other hand, the leakage protection circuit further includes a sixth diode, an anode of the sixth diode is connected to the second end of the voltage-dividing resistor, and a cathode of the sixth diode is connected to the cathode of the fifth diode;

[0042] Determining whether the controllable switch module returns a test pass signal includes:

[0043] Determining whether the voltage at the first end of the self-test module is lower than a third voltage threshold;

[0044] If it is lower than, it is determined that the controllable switch returns a test pass signal.

[0045] The invention discloses a leakage protection circuit and method, which relate to the field of ground fault protection, including: the circuit detects the ground faults existing in the live line and the neutral line in real time, and judges whether to drive a controllable switch module to disconnect the power supply of the power grid according to the size of the sampling voltage to protect personal safety; the self-checking module sends a simulated fault signal in the positive half cycle of the live line to simulate the neutral line ground fault, and the generated fault current generates a sampling voltage in the leakage detection module. When the value is greater than a first threshold voltage, it is determined that the leakage detection part of the system is normal; and then the self-checking module sends a switch signal in the negative half cycle of the live line to simulate driving the controllable switch module. If a test pass signal is returned, it is determined that the leakage protection system is in a good detection state, and the occurrence of the ground fault can be responded to in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0047] Figure 1 A schematic diagram of the structure of a leakage protection circuit provided by the present invention;

[0048] Figure 2 A schematic diagram of the structure of another leakage protection circuit provided by the present invention;

[0049] Figure 3 A schematic structural diagram of a leakage detection module provided by the present invention;

[0050] Figure 4 The present invention provides a flow chart of a leakage protection method. DETAILED DESCRIPTION

[0051] The core of the present invention is to provide a leakage protection circuit and method, which can avoid the leakage protection circuit being unable to detect and protect the grounding fault in time due to internal device failure by simulating fault self-detection.

[0052] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] Figure 1 A schematic diagram of a leakage protection circuit provided by the present invention, the leakage protection circuit comprises:

[0054] A controllable switch module 1, wherein the first end and the second end of the controllable switch module 1 are both arranged on the live wire, the third end and the fourth end of the controllable switch module 1 are both arranged on the neutral wire, the first end of the controllable switch module 1 is connected to the second end, and the third end is connected to the fourth end when no ground fault occurs, the controllable switch module 1 is used to disconnect the first end from the second end when its control end receives a control signal in the positive half cycle of the live wire, and disconnect the third end from the fourth end when its control end receives a control signal in the positive half cycle of the live wire, so as to cut off the power supply of the live wire and the neutral wire, test its own switch function when receiving a control signal in the negative half cycle of the live wire, maintain the connection state when no ground fault occurs, and return a test pass signal to the self-test module 4 if its own switch function is normal;

[0055] A leakage detection module 2, wherein the output end of the leakage detection module 2 is connected to the second end of the self-test module 4, and the leakage detection module 2 is used to sample the grounding faults existing in the live wire and the neutral wire and generate a sampling voltage. When the absolute value of the sampling voltage reaches a first threshold voltage, a judgment signal is output to the second end of the self-test module 4, and the sampling voltage is related to the difference between the current on the live wire and the current on the neutral wire;

[0056] A fault simulation module 3, wherein the control end of the fault simulation module 3 is connected to the third end of the self-test module 4, the first end of the fault simulation module 3 is connected to the neutral line of the load end, and the second end is grounded, and is used to connect the first end of the fault simulation module 3 to the second end when the control end receives a simulated fault signal, so as to simulate a neutral line grounding fault;

[0057] The self-test module 4 has a first end connected to the live wire and is used to detect the phase of the power grid. After sending a simulated fault signal through the third end in the positive half cycle of the live wire, if a judgment signal is received at its second end, a control signal is sent to the controllable switch module 1 through the fourth end in the negative half cycle of the live wire. If a test pass signal is received, it is determined that the leakage protection circuit is working normally.

[0058] Figure 2 A schematic diagram of the structure of another leakage protection circuit provided by the present invention;

[0059] Figure 2 LOAD_HOT is the live wire at the load end, and LOAD_NUETRAL is the neutral wire at the load end.

[0060] When the appliance starts working, if there is no ground fault current Ifault, the current flowing into the live wire is equal to the current flowing back from the neutral wire, and the leakage protection circuit will not take any action; assuming that there is a leakage from the live wire to the ground at this time, generating a leakage current Ifault to the ground wire, then the current flowing back from the neutral wire to the ground will be reduced accordingly Ifault. If it is detected that the sampling voltage generated by this Ifault current is greater than the set first threshold voltage, it is determined that a ground fault has occurred, and the controllable switch module 1 needs to be controlled to disconnect to complete the leakage protection function.

[0061] The above process can only be realized when all the components inside the leakage protection circuit are normal. Since there are damaged components inside the leakage protection circuit, when a ground fault occurs, the controllable switch module 1 cannot respond to the ground fault to complete the leakage protection function. Therefore, the present application sets up a simulated fault module, which can simulate the occurrence of a ground fault. If the leakage protection circuit can detect the simulated fault and test the function of the controllable switch module 1, it means that the working state of the leakage protection circuit is normal.

[0062] Furthermore, the control module in the present application may be a LT6178S chip.

[0063] The test result is prompted, for example, by using the prompt light LED0. The color of the prompt light can be set according to actual needs. For example, a green light is displayed if the test passes, and a red light is displayed if the test fails.

[0064] The present invention discloses a leakage protection circuit and method, which relates to the field of ground fault protection, including: after the self-checking module 4 sends a simulated fault signal through the third terminal in the positive half cycle of the live wire, the fault simulation module 3 simulates the neutral line ground fault, and the leakage detection module 2 samples the ground fault to generate a sampling voltage. If the sampling voltage is greater than the first threshold voltage, it is determined that the leakage protection circuit can detect the occurrence of this type of ground fault; then the self-checking module 4 sends a test signal to the controllable switch module 1 in the negative half cycle of the live wire, at which time the controllable switch module 1 will detect the switch function and maintain the connection state when no ground fault occurs, and return a test pass signal. The self-checking module 4 receives the test pass signal to confirm that the leakage protection circuit can be powered off after the ground fault occurs. The use of the simulated self-checking method can avoid the situation where the ground fault cannot be detected in time due to the failure of the internal components of the leakage protection circuit.

[0065] Based on the above embodiments:

[0066] Figure 2 A schematic diagram of the structure of another leakage protection circuit provided by the present invention;

[0067] Figure 3 A schematic structural diagram of a leakage detection module provided by the present invention;

[0068] In some embodiments, the controllable switch module 1 includes a first controllable switch Q1 , a solenoid SOL and a mechanical device S1 ;

[0069] The control end of the first controllable switch Q1 is connected to the fourth end of the self-test module 4, the second end of the first controllable switch Q1 is grounded, the first end of the first controllable switch Q1 is connected to the first end of the solenoid SOL, the second end of the solenoid SOL is connected to the live wire, the fixed end of the mechanical device S1 is set at one end breakpoint of the live wire and one end breakpoint of the neutral wire, and the movable end of the mechanical device S1 is set at the other end breakpoint of the live wire and the other end breakpoint of the neutral wire;

[0070] The first controllable switch Q1 is used to be turned on when the control end receives a control signal so as to form a current loop from the live wire, the solenoid SOL, the first controllable switch Q1 to the ground. The solenoid SOL is used to be turned on in the positive half cycle of the live wire to control the fixed end of the mechanical device S1 to be disconnected from the active end. It cannot be turned on in the negative half cycle of the live wire, and the fixed end of the mechanical device S1 cannot be controlled to be disconnected from the active end.

[0071] The first controllable switch Q1 is a thyristor, the K end of the thyristor serves as the first end of the first controllable switch Q1, the A end of the thyristor serves as the second end of the first controllable switch Q1, and the G end of the thyristor serves as the control end of the first controllable switch Q1. When the first amplifier AMP1 detects that the sampling voltage is greater than the first threshold voltage, the K end and the A end of the thyristor are controlled to be turned on, a large current flows through the solenoid SOL, the fixed end and the active end of the mechanical device S1 are disconnected, and then the power supply of the load is disconnected to protect the safety of electricity use. When the first amplifier AMP1 does not detect a fault, the K end and the A end of the thyristor are cut off, the solenoid SOL has no current loop, the fixed end and the active end of the mechanical device S1 are connected, and the power grid normally supplies power to the load.

[0072] The first controllable switch is a thyristor here, but is not limited to a thyristor, and may also be a MOS tube. The solenoid has a breaking capability only in the positive half cycle of the live wire.

[0073] In some embodiments, the leakage detection module 2 includes a live wire to ground leakage detection module, and the live wire to ground leakage detection module includes a first mutual inductor CT1, a sampling resistor R1 and a first amplifier AMP1;

[0074] The live wire and the neutral wire pass through the first transformer CT1, the first end of the first transformer CT1 is connected to the first end of the sampling resistor R1, the first end of the leakage detection module 2, and the first input end of the first amplifier AMP1, the second end of the first transformer CT1 is connected to the second end of the sampling resistor R1 and the second end of the first amplifier AMP1, and the output end of the first amplifier AMP1 serves as the fourth end of the leakage detection module 2;

[0075] The first transformer CT1 is used to sense the difference between the current on the live line and the current on the neutral line, and then samples it by the sampling resistor R1 after reducing it by a preset multiple, and sends the sampling signal to the first amplifier AMP1. The first amplifier AMP1 is used to generate a control signal when the absolute value of the sampling signal is greater than the first threshold voltage and send the control signal to the second end of the self-test module 4.

[0076] If Ifault does not exist, the current flowing into the live wire is equal to the current flowing back from the neutral wire, and the leakage detection module 2 will not take any action; assuming that there is leakage from the live wire to the ground at this time, generating a leakage current of the live wire to the ground wire of Ifault, then the current flowing back from the neutral wire to the ground will be reduced accordingly Ifault, and the first transformer CT1 will detect this Ifault current, and transfer the current Ifault / 1000 to the sampling resistor R1 according to the turns ratio. If the sampling voltage of R1 reaches the first threshold voltage, the self-test module 3 reads the output judgment signal of the leakage detection module 2 and triggers the control signal, thereby controlling the controllable switch module 1 to disconnect.

[0077] In some embodiments, the leakage detection module includes a neutral grounding fault detection module, and the neutral grounding fault detection module includes a first capacitor C1, a second capacitor C2, a second transformer CT2 and a second amplifier AMP2;

[0078] The live wire and the neutral wire pass through the first transformer CT1 and the second transformer CT2 at the same time, the first end of the second transformer CT2 is connected to the first end of the first capacitor C1 and the common end of the connection is grounded, the second end of the second transformer CT2 is connected to the second end of the first capacitor C1 and the first end of the second capacitor C2, the second end of the second capacitor C2 is connected to the output end of the second amplifier AMP2, the first input end of the second amplifier AMP2 serves as the first end of the leakage detection module 2, and the second input end of the second amplifier AMP2 serves as the second end of the leakage detection module 2;

[0079] The second amplifier AMP2 is used to amplify the fault current generated by the neutral grounding fault, the second transformer CT2 is used to couple the amplified fault current to the first transformer CT1, the first capacitor C1 is used to generate oscillation, and the second capacitor C2 is used to isolate direct current. When the first amplifier detects that the absolute value of the sampling signal is greater than the first threshold voltage, it generates a control signal to control the second end of the self-test module 4.

[0080] When a neutral grounding fault occurs, the fault current value generated is small, and the sampling voltage generated by the first transformer CT1 detecting the fault current does not reach the first voltage threshold. The first amplifier AMP1 does not work and cannot trigger the controllable switch module 1 to disconnect. Therefore, the present application uses the first capacitor C1 and the second transformer CT2 to generate oscillations, and the current generated by the neutral grounding fault is amplified by the second amplifier AMP2, and the amplified current is coupled to the first transformer CT1 through the second transformer CT2. After multiple cycles of oscillation amplification, the first amplifier AMP1 detects that the sampling voltage reaches the first voltage threshold, thereby controlling the controllable switch module 1 to disconnect.

[0081] A loop composed of the first mutual inductor, the second mutual inductor and the second amplifier forms a self-excited positive feedback circuit, the fault current is continuously amplified, and a sampling signal is generated by the sampling resistor.

[0082] In some embodiments, the fault simulation module 3 includes a fault simulation resistor R13 and a second controllable switch in the control module;

[0083] A first end of the fault simulation resistor R13 is connected to the load end neutral line, a second end of the fault simulation resistor R13 is connected to a first end of a second controllable switch, a second end of the second controllable switch is grounded, and a control end of the second controllable switch is connected to a controller in the self-test module 4;

[0084] The controller is used to send a simulated fault signal to the second controllable switch according to the phase of the power grid, and the second controllable switch is used to be turned on when receiving the simulated fault signal.

[0085] When a neutral grounding fault occurs, the fault grounding resistance is ≤10Ω, which means that the insulation characteristics between the neutral line and the ground line of the large machine are broken, and the electrical casing will serve as part of the load current loop. The electrical standard requires a grounding resistance of 4Ω. Since the human safety voltage is 36V, and the power upper limit of commonly used 220V / AC power supply appliances is basically around 2kW, that is, a working current of 10A. 36V / 10A=3.6Ω, this is the origin of the national standard 4Ω contact resistance. The contact resistance refers to the equivalent resistance of the neutral line flowing from the load end of the appliance to the ground, but no wire material will have a zero resistance characteristic. The third end of the self-test module, the GNTST pin, short-circuits the fault simulation resistor R13, and connects the neutral line through the first transformer CT1 and the second transformer CT2 to simulate the neutral line grounding resistance R NG =4Ω. Under this condition, the closed loop composed of CT1, CT2 and AMP2 forms a negative damping oscillator, R NG As the load of the negative resistance oscillator, the oscillation frequency is determined by the first capacitor C1, the second capacitor C2, and the inductance L2 of the second transformer CT2. NG When it is greater than 8Ω, the negative resistance is insufficient to maintain the oscillator operation and cannot handle this level of neutral grounding fault.

[0086] In some embodiments, a rectifier module is further included, the rectifier module includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4 and a third capacitor C3;

[0087] The anode of the first diode D1 and the anode of the second diode D2 are both connected to the live wire, the cathode of the first diode D1, the cathode of the second diode D2, the anode of the third diode D3 and the anode of the fourth diode D4 are connected, the cathode of the third diode D3, the cathode of the fourth diode D4, the first end of the first resistor R1 and the first end of the second resistor R2 are connected, the second end of the first resistor R1, the second end of the second resistor R2, the first end of the third resistor R3 and the first end of the fourth resistor R4 are connected, the second end of the third resistor R3 and the second end of the fourth resistor R4 are connected to the power supply end of the leakage protection circuit and the first end of the third capacitor C3, and the second end of the third capacitor C3 is grounded;

[0088] The first diode D1 , the second diode D2 , the third diode D3 , the fourth diode D4 , the first resistor R1 , the second resistor R2 , the third resistor R3 and the fourth resistor R4 are used for half-wave rectification, and the third capacitor C3 is used for filtering.

[0089] A half-wave rectifier circuit is formed between the diodes and the resistors. Four diodes and four resistors are used because of redundant design. Based on the above connection relationship, the function of the circuit will not be affected if any of the four diodes and the four resistors is open or short-circuited.

[0090] In some embodiments, a delay module is also included;

[0091] The input end of the delay module is connected to the output end of the leakage detection module 2, and the output end of the delay module is connected to the second end of the self-test module 4, and is used to send the judgment signal to the second end of the self-test module 4 when the judgment signal is continuously received within the first preset time;

[0092] The self-check module 4 is also used to shield the first preset time when sending the simulated fault signal, call the second preset time and the third preset time, and if the judgment signal is received within the third preset time, enter the step of sending the control signal to the controllable switch module 1 through the fourth terminal;

[0093] The second preset time is used to prevent interference signals from causing false triggering of the circuit. The third preset time is used to protect the negative half cycle of self-test and avoid self-test exceeding the negative half cycle time of the live wire. The second preset time and the third preset time are related to the grid frequency.

[0094] The simulation of ground fault can be selected in the positive half cycle or the negative half cycle. The positive half cycle is selected to use the time of the positive half cycle of the live wire to perform calculations, so that the entire negative half cycle can be used to detect the switch function; if the negative half cycle simulates the ground fault, it will take 2-3ms for the self-test module to detect the judgment signal, so the time left for the negative half cycle to self-test the controllable switch function will be compressed and shortened. If the function of the controllable switch module 1 is directly detected in the positive half cycle of the live wire, it will directly cause the mechanical device S1 to be disconnected, which will affect the normal operation of the electrical appliance, because the ground fault is a self-test simulation rather than an actual ground fault. Therefore, the present application simulates the occurrence of ground fault in the positive half cycle of the live wire, the self-test module 4 latches the detected ground fault signal, and detects the function of the controllable switch module 1 in the negative half cycle of the live wire. Due to the negative half cycle of the live wire, even if the controllable switch module 1 is controlled to work, it is impossible to provide a current loop for the solenoid SOL, so it is impossible to control the fixed end and the active end of the mechanical device S1 to disconnect, so setting the function of the controllable switch module 1 to be detected in the negative half cycle of the live wire does not affect the normal use of the load electrical appliance.

[0095] The delay module is used to delay the triggering of the ground fault signal on the live wire and the neutral wire. When the ground fault signal persists and maintains the set delay time, the delay module transmits the output control signal of the leakage detection module 2 to the second end (judgment end) of the self-test module 4. If the ground fault signal is generated by the fault simulation module 3, the self-test module 4 will shield the first preset time and uniformly call the second preset time inside the chip. The second preset time is generated by the self-test module grid adaptively, and the 50Hz grid corresponds to 1.2ms and the 60Hz grid corresponds to 1ms; there is also a third preset time, 50Hz corresponds to 6ms, and 60Hz corresponds to 5ms;

[0096] For example, in actual situations: for a complete machine produced by a customer, the first preset time corresponds to the segmentation level of the product, ranging from 25ms to 500ms; the second preset time is basically around 1ms, which is prepared for self-test;

[0097] The delay time is determined by the fourth capacitor C4 and the fifth capacitor C5 connected to the two pins DLY and OA; the setting of the delay module can meet the needs of various disconnection levels; by increasing the delay time, the anti-interference performance of the circuit can be greatly improved and the false triggering rate of the leakage protection circuit can be reduced.

[0098] Figure 4 This is a flow chart of a leakage protection method provided by the present invention. The leakage protection method is applied to the self-check module 4 in the above-mentioned leakage protection circuit. The leakage protection circuit also includes a leakage detection module 2, a fault simulation module 3 and a controllable switch module 1. The output end of the leakage detection module 2 is connected to the second end of the self-test module 4. The leakage detection module 2 is used to sample the grounding faults existing in the live line and the neutral line and generate a sampling voltage. When the absolute value of the sampling voltage reaches the first threshold voltage, the judgment signal is output to the second end of the self-test module 4. The sampling voltage is related to the difference between the current on the live line and the current on the neutral line. The control end of the fault simulation module 3 is connected to the third end of the self-test module 4. The first end of the fault simulation module 3 is connected to the neutral line of the load end, and the second end is grounded. The fourth end of the self-test module 4 is connected to the control end of the controllable switch module 1. The first end and the second end of the controllable switch module 1 are both arranged on the live line, and the third end and the fourth end of the controllable switch module 1 are both arranged on the neutral line. The controllable switch module 1 is used to disconnect the connection between the first end and the second end of itself when its control end receives a control signal in the positive half cycle of the live line, and disconnect the connection between the third end and the fourth end of itself, so as to cut off the power supply of the live line and the neutral line; when receiving the control signal in the negative half cycle of the live line, the switch function of itself is tested, and the connection state when no grounding fault occurs is maintained. If the switch function of itself is normal, the test pass signal is returned to the self-test module 4. Leakage protection methods include:

[0099] S11: Determine whether the grid is powered on; if so, proceed to step S12;

[0100] S12: Determine the grid phase and the time point of the self-test starting point when the grid is powered on;

[0101] S13: After the time point of the self-check starting point, the fault simulation module is controlled to connect its first end with its second end according to the grid phase in the positive half cycle of the live line to simulate a neutral line grounding fault;

[0102] S14: Determine whether the second end of the device receives the determination signal returned by the leakage detection module; if so, proceed to step S15;

[0103] S15: sending a control signal to a control terminal of the controllable switch module according to a judgment signal according to the negative half cycle of the grid phase in the live line;

[0104] S16: Determine whether the controllable switch module returns a test pass signal; if so, proceed to step S17; if not, proceed to step S18;

[0105] S17: Determine that the leakage protection circuit works normally;

[0106] S18: Determine whether there is a device with abnormal operation in the leakage protection circuit and issue an alarm.

[0107] In fact, there are three signs of a successful self-test, none of which can be missing, namely, power-on self-test, simulation of ground fault in the positive half cycle and the ability to detect the ground fault, and pass of the negative half cycle detection switch function. Therefore, first, a power-on self-test will be performed on the power supply part, that is, to detect whether the power grid is powered on. If the power grid is not powered on, there will be no leakage problem, and there is no need for self-test. If the power grid is powered on, the self-test module simulates the occurrence of a ground fault according to the power grid phase, successfully detects the ground fault signal in the positive half cycle of the live wire, and successfully detects the function of the controllable switch module 1 in the negative half cycle of the live wire, indicating that the devices in the leakage protection circuit are working normally. If any of the self-test links fail, it means that there is a faulty device that causes inadequate detection or inadequate control, and the user needs to be prompted for subsequent processing.

[0108] In some embodiments, the leakage protection circuit further includes a fifth diode D5 and a voltage-dividing resistor R10, wherein the anode of the fifth diode D5 is connected to the first end of the solenoid SOL in the controllable switch module 1, the second end of the fifth diode D5 is connected to the first end of the voltage-dividing resistor R10, and the second end of the voltage-dividing resistor R10 is connected to the fourth end of the self-test module;

[0109] Determine the time point for the self-check starting point, including:

[0110] Determine whether the voltage detected at the first terminal is greater than a second threshold voltage;

[0111] If it is greater than the second threshold voltage, the current time point is determined to be the time point of the self-check starting point.

[0112] Specifically, when the grid is powered on, the function of the fifth diode D5 is to prevent the PHASE pin level from being pulled down by the grid in the negative half cycle of the live line. The voltage obtained by dividing the voltage through the voltage divider resistor R10 can determine the grid voltage. The fifth diode D5 is used for zero detection of the self-test module when forward conducting; when reversely cut off, it is mainly used for reverse isolation during self-test to ensure that no current flows when the live line negative half cycle self-tests the controllable switch module;

[0113] In some embodiments, the leakage protection circuit further includes a sixth diode D6, an anode of the sixth diode D6 is connected to the second end of the voltage-dividing resistor R10, and a cathode of the sixth diode D6 is connected to the cathode of the fifth diode D5;

[0114] Determining whether the controllable switch module 1 returns a test pass signal includes:

[0115] Determine whether the voltage at the first end of the self-test module 4 is lower than a third voltage threshold;

[0116] If it is lower than that, it is determined that the controllable switch returns a test pass signal.

[0117] In the negative half cycle of the live wire, the current mirror inside the chip provides a stable voltage to the first end of the self-test module. If the first controllable switch in the controllable switch module 1 is turned on, the voltage at the first end of the self-test module 4 will be pulled down. The current mirror often outputs a 5V voltage, which will eventually be pulled down to below 3.5V due to the voltage drop when the first controllable switch is turned on.

[0118] R10 is a resistor with a relatively large resistance value, and is used for current limiting protection. In the negative half cycle of the live line, the fifth diode D5 is reversely cut off and does not provide a current loop, and the current flows through the sixth diode D6. The sixth diode D6 is used to conduct in the negative half cycle of the live line to test the function of the controllable switch module 1.

[0119] For an introduction to the leakage protection method provided in the present application, please refer to the above embodiments, which will not be repeated here.

[0120] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0121] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0122] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A leakage protection circuit, characterized in that: include: A controllable switch module, wherein the first end and the second end of the controllable switch module are both arranged on the live wire, the third end and the fourth end of the controllable switch module are both arranged on the neutral wire, the first end of the controllable switch module is connected to the second end, and the third end is connected to the fourth end when no ground fault occurs, the controllable switch module is used to disconnect the first end from the second end when its control end receives a control signal in the positive half cycle of the live wire, and disconnect the third end from the fourth end when its control end receives a control signal in the positive half cycle of the live wire, so as to cut off the power supply of the live wire and the neutral wire, test its own switch function when receiving the control signal in the negative half cycle of the live wire, maintain the connection state when no ground fault occurs, and return a test pass signal to the self-test module if its own switch function is normal; A leakage detection module, wherein the output end of the leakage detection module is connected to the second end of the self-test module, the leakage detection module is used to sample the grounding faults existing in the live wire and the neutral wire and generate a sampling voltage, and when the absolute value of the sampling voltage reaches a first threshold voltage, output a judgment signal to the second end of the self-test module, and the sampling voltage is related to the difference between the current on the live wire and the current on the neutral wire; A fault simulation module, wherein the control end of the fault simulation module is connected to the third end of the self-test module, the first end of the fault simulation module is connected to the neutral line of the load end, and the second end is grounded, and is used to connect the first end of the module to the second end when the control end receives a simulated fault signal to simulate a neutral line grounding fault; The self-test module, the first end of which is connected to the live wire, is used to detect the phase of the power grid. After sending a simulated fault signal through the third end in the positive half cycle of the live wire, if the judgment signal is received at its second end, then in the negative half cycle of the live wire, a control signal is sent to the controllable switch module through the fourth end. If the test pass signal is received, it is determined that the leakage protection circuit is working normally.

2. The leakage protection circuit according to claim 1, characterized in that: The controllable switch module includes a first controllable switch, a solenoid and a mechanical device; The control end of the first controllable switch is connected to the fourth end of the self-test module, the second end of the first controllable switch is grounded, the first end of the first controllable switch is connected to the first end of the solenoid, the second end of the solenoid is connected to the live wire, the fixed end of the mechanical device is arranged at one end breakpoint of the live wire and one end breakpoint of the neutral wire, and the movable end of the mechanical device is arranged at the other end breakpoint of the live wire and the other end breakpoint of the neutral wire; The first controllable switch is used to be turned on when the control end receives a control signal so as to form a current loop from the live wire, the solenoid, the first controllable switch to the ground. The solenoid is used to be turned on during the positive half cycle of the live wire to control the fixed end of the mechanical device to be disconnected from the active end. It cannot be turned on during the negative half cycle of the live wire, and the fixed end of the mechanical device cannot be controlled to be disconnected from the active end.

3. The leakage protection circuit according to claim 1, characterized in that: The leakage detection module includes a live wire to ground leakage detection module, and the live wire to ground leakage detection module includes a first mutual inductor, a sampling resistor and a first amplifier; The live wire and the neutral wire pass through the first mutual inductor, the first end of the first mutual inductor is connected to the first end of the sampling resistor, the first end of the leakage detection module and the first input end of the first amplifier, the second end of the first mutual inductor is connected to the second end of the sampling resistor and the second end of the first amplifier, and the output end of the first amplifier serves as the fourth end of the leakage detection module; The first transformer is used to sense the difference between the current on the live line and the current on the neutral line, and then sampled by the sampling resistor after reducing it by a preset multiple, and send a sampling signal to the first amplifier. The first amplifier is used to generate a control signal when the absolute value of the sampling signal is greater than a threshold voltage and send the control signal to the second end of the self-test module.

4. The leakage protection circuit according to claim 3, characterized in that: The leakage detection module includes a neutral grounding fault detection module, and the neutral grounding fault detection module includes a first capacitor, a second capacitor, a second mutual inductor and a second amplifier; The live wire and the neutral wire pass through the first mutual inductor and the second mutual inductor at the same time, the first end of the second mutual inductor is connected to the first end of the first capacitor and the common end of the connection is grounded, the second end of the second mutual inductor is connected to the second end of the first capacitor and the first end of the second capacitor, the second end of the second capacitor is connected to the output end of the second amplifier, the first input end of the second amplifier serves as the first end of the leakage detection module, and the second input end of the second amplifier serves as the second end of the leakage detection module; The second amplifier is used to amplify the fault current generated by the neutral grounding fault, the second transformer is used to couple the amplified fault current to the first transformer, the first capacitor is used to generate oscillation, and the second capacitor is used to isolate direct current. When the first amplifier detects that the absolute value of the sampling signal is greater than the first threshold voltage, the control signal is generated to control the second end of the self-test module.

5. The leakage protection circuit according to claim 1, characterized in that: The fault simulation module includes a fault simulation resistor and a second controllable switch; The first end of the fault simulation resistor is connected to the neutral line, the second end of the fault simulation resistor is connected to the first end of the second controllable switch, the second end of the second controllable switch is grounded, and the control end of the second controllable switch is connected to the controller in the self-test module; The controller is used to send a simulated fault signal to the second controllable switch according to a grid phase, and the second controllable switch is used to be turned on when receiving the simulated fault signal.

6. The leakage protection circuit according to claim 1, characterized in that: Also includes a rectifier module, the rectifier module includes a first diode, a second diode, a third diode, a fourth diode, a first resistor, a second resistor, a third resistor, a fourth resistor and a third capacitor; The anode of the first diode and the anode of the second diode are both connected to the live wire, the cathode of the first diode, the cathode of the second diode, the anode of the third diode and the anode of the fourth diode are connected, the cathode of the third diode, the cathode of the fourth diode, the first end of the first resistor and the first end of the second resistor are connected, the second end of the first resistor, the second end of the second resistor, the first end of the third resistor and the first end of the fourth resistor are connected, the second end of the third resistor and the second end of the fourth resistor are connected to the power supply end of the leakage protection circuit and the first end of the third capacitor, and the second end of the third capacitor is grounded; The first diode, the second diode, the third diode, the fourth diode, the first resistor, the second resistor, the third resistor and the fourth resistor are used for half-wave rectification, and the third capacitor is used for filtering.

7. The leakage protection circuit according to any one of claims 1 to 6, characterized in that: It also includes a delay module; The input end of the delay module is connected to the output end of the leakage detection module, and the output end of the delay module is connected to the second end of the self-test module, and is used to send the judgment signal to the second end of the self-test module when the judgment signal is continuously received within a first preset time; The self-check module is also used to shield the first preset time when sending a simulated fault signal, call the second preset time and the third preset time, and if the judgment signal is received within the third preset time, enter the step of sending a control signal to the controllable switch module through the fourth terminal; The second preset time is used to prevent interference signals from causing false triggering of the circuit, and the third preset time is used to protect the negative half cycle of self-test to avoid self-test exceeding the negative half cycle time of the live wire. The second preset time and the third preset time are related to the grid frequency.

8. A leakage protection method, characterized in that: A self-test module applied to a leakage protection circuit as claimed in any one of claims 1 to 7, wherein the leakage protection circuit further comprises a leakage detection module, a fault simulation module and a controllable switch module, wherein the output end of the leakage detection module is connected to the second end of the self-test module, the leakage detection module is used to sample the grounding faults existing in the live line and the neutral line and generate a sampling voltage, and when the absolute value of the sampling voltage reaches a first threshold voltage, output a judgment signal to the second end of the self-test module, wherein the sampling voltage is related to the difference between the current on the live line and the current on the neutral line, the control end of the fault simulation module is connected to the third end of the self-test module, the first end of the fault simulation module is connected to the neutral line of the load end, and the second The first end and the second end of the controllable switch module are both arranged on the live wire, and the third end and the fourth end of the controllable switch module are both arranged on the neutral wire. The controllable switch module is used to disconnect the first end and the second end thereof when its control end receives a control signal in the positive half cycle of the live wire, and disconnect the third end and the fourth end thereof to cut off the power supply of the live wire and the neutral wire, and test its own switch function when receiving the control signal in the negative half cycle of the live wire, and maintain the connection state when no ground fault occurs. If its own switch function is normal, a test pass signal is returned to the self-test module. The leakage protection method comprises: Determine whether the power grid is powered on; Determine the grid phase and the time point of the self-test starting point when the grid is powered on; After the time point of the self-check starting point, according to the grid phase in the positive half cycle of the live line, the fault simulation module is controlled to connect its first end with the second end to simulate the occurrence of a neutral line grounding fault; Determine whether the second end thereof receives the determination signal returned by the leakage detection module; According to the negative half cycle of the grid phase in the live line, sending a control signal to the control end of the controllable switch module according to the judgment signal; Determining whether the controllable switch module returns a test pass signal; If yes, it is determined that the leakage protection circuit works normally; If not, it is determined that there is a device in the leakage protection circuit that is working abnormally, and an alarm is issued.

9. The leakage protection method according to claim 8, characterized in that: The leakage protection circuit further includes a fifth diode and a voltage-dividing resistor, wherein an anode of the fifth diode is connected to a first end of a solenoid in a controllable switch module, a second end of the fifth diode is connected to a first end of the voltage-dividing resistor, and a second end of the voltage-dividing resistor is connected to a first end of the self-test module; Determine the time point for the self-check starting point, including: Determine whether the voltage detected at the first terminal is greater than a second threshold voltage; If it is greater than the second threshold voltage, the current time point is determined to be the time point of the self-check starting point.

10. The leakage protection method according to claim 8 or 9, characterized in that: The leakage protection circuit further includes a sixth diode, an anode of the sixth diode is connected to the second end of the voltage-dividing resistor, and a cathode of the sixth diode is connected to the cathode of the fifth diode; Determining whether the controllable switch module returns a test pass signal includes: Determining whether the voltage at the first end of the self-test module is lower than a third voltage threshold; If it is lower than, it is determined that the controllable switch returns a test pass signal.

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