Protection circuit of switching electrical apparatus, circuit breaker

Abstract

A protection circuit for a switching electrical appliance, a circuit breaker, and a protection method for the circuit breaker. The protection circuit includes a voltage detection control circuit and at least two controllable switch circuits. The voltage detection control circuit can drive the corresponding controllable switch circuit to disconnect when the power supply voltage meets the threshold. When any controllable switch circuit disconnects, the control circuit of the switching electrical appliance can be powered off. The at least two controllable switch circuits have different voltage thresholds when disconnecting. The protection method of the circuit breaker performs hierarchical protection on the control circuit of the circuit breaker through the protection circuit of the switching electrical appliance. The protection circuit can not only reliably protect the control circuit of the circuit breaker, but also reliably protect itself, preventing other potential safety hazards caused by the failure of the protection circuit itself.

Description

Technical Field

[0001] The present invention relates to the field of low-voltage electrical appliances, and particularly to a protection circuit for a switching electrical appliance, a circuit breaker, and a protection method for a circuit breaker. Background Art

[0002] Intelligence will be the future trend, and the low-voltage electrical appliance industry is no exception. With the construction of smart grids and smart substations in recent years, the intelligence of circuit breaker products has become the main requirement and key technical indicator. In order to meet and realize functions such as intelligent Internet of Things, full state perception, and automatic reclosing, the working state and mode of the circuit breaker have also changed accordingly. For example, the power supply power-taking method has changed from the original outgoing line end to the incoming line end, that is, regardless of whether the circuit breaker body part is in the closed state or the open state, the control circuit can still take power from the front end of the previous circuit breaker body, so that the control circuit is in a normal working state.

[0003] Due to the change in the power-taking method of the circuit breaker, when a voltage fault occurs, such as an overvoltage or lightning strike fault, the circuit breaker can quickly trip. Although it can cut off and disconnect the load end to protect the power equipment and lines at the load end, the internal control circuit of the circuit breaker will still be subjected to the impact and damage of the fault voltage. If the fault phenomenon exists for a long time or persists, it is very likely to damage the circuit breaker itself or cause an accident. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a protection circuit for a switching electrical appliance that can protect the control circuit.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A protection circuit for a switching electrical appliance, which includes a voltage detection control circuit and at least two controllable switch circuits. The voltage detection control circuit can drive the corresponding controllable switch circuit to disconnect when the power supply voltage meets the threshold. When any controllable switch circuit disconnects, the control circuit of the switching electrical appliance can be powered off, and the at least two controllable switch circuits have different voltage thresholds when disconnecting.

[0007] Preferably, one of the controllable switch circuits is a fusing circuit, and the fusing circuit includes a self-resetting fuse FU1 and a discharging circuit. The voltage detection control circuit can control the discharging circuit to conduct, so that the self-resetting fuse FU1 melts.

[0008] Preferably, one of the controllable switch circuits is an electronic switch circuit. The electronic switch circuit includes an electronic switch K1, and the voltage detection control circuit can control the controllable switch element V2 to conduct, so that the electronic switch K1 disconnects.

[0009] Preferably, the at least two controllable switch circuits are respectively an electronic switch circuit and a fuse circuit. The electronic switch circuit and the fuse circuit are respectively arranged at the rear end and the front end of the voltage detection and control circuit, and the voltage threshold value for the electronic switch circuit to disconnect is smaller than the voltage threshold value for the fuse circuit to disconnect.

[0010] Preferably, the discharge circuit includes a controllable switch element V1. When the power supply voltage is higher than the fuse value, the voltage detection and control circuit controls the controllable switch element V1 to conduct, so as to discharge the current.

[0011] Preferably, the voltage detection and control circuit includes a comparator, and the on / off of the controllable switch circuit is respectively controlled by the comparator. When the voltage detection and control circuit detects that the power supply voltage is greater than the disconnection threshold value of the controllable switch circuit, it controls the corresponding controllable switch circuit to disconnect.

[0012] Preferably, the voltage detection and control circuit includes U1A, comparator U1B, resistor R1, resistor R2, resistor R5, resistor R6, resistor R7, resistor R11, resistor R12, capacitor C1 and zener diode VZ1. The comparator U1A and the comparator U1B are respectively used to control the controllable switch element V1 of the fuse circuit and the controllable switch element V2 of the electronic switch circuit. The resistor R1 and the zener diode VZ1 are connected in series and then output a voltage reference source Ref1 to the inverting input terminal of the comparator U1A. The resistor R2, resistor R7 and resistor R11 are connected in series between the L line and the N line. The capacitor C1 is connected in parallel at both ends of the resistor R7 and resistor R11. One end of the resistor R5 is connected between the resistor R2 and the resistor R7, and the other end of the resistor R5 is respectively connected to the non-inverting input terminal of the comparator U1A. The output terminal of the comparator U1A is respectively connected to the control terminal of the controllable switch element V2, one end of the resistor R12 and one end of the resistor R6. The other end of the resistor R6 is connected to the non-inverting input terminal of the comparator U1A. The other end of the resistor R12 is grounded. One end of the resistor R9 is connected between the resistor R7 and the resistor R11, and the other end of the resistor R9 is connected to the non-inverting input terminal of the comparator U1B. The output terminal of the comparator U1B is connected to the control terminal of the controllable switch element V1.

[0013] The protection circuit of the switching electrical appliance of the present invention can cut off the power supply of the control circuit in case of a serious voltage fault. Even if the control circuit is connected to the incoming line end of the switching electrical appliance, it can still effectively prevent the damage and potential safety hazards brought by the voltage fault to the control circuit. It is not only safer in power use, has high application value and market potential, but also realizes hierarchical protection through at least two controllable switch circuits, and the protection function is more reliable.

[0014] The present invention also provides a circuit breaker, which can disconnect the main circuit of the circuit breaker when the power supply circuit reaches the voltage threshold of the circuit breaker voltage protection. It includes a control circuit and a protection circuit of the switching device connected between the incoming line terminal and the control circuit. The protection circuit is the protection circuit including at least two controllable switch circuits of the present invention, and can be disconnected when the power supply voltage of the power supply circuit reaches the voltage threshold for protecting the power supply circuit, providing two different levels of disconnection protection. It should be noted that the voltage threshold for protecting the power supply circuit and the voltage threshold of the circuit breaker voltage protection are different protection thresholds.

[0015] The present invention also provides a protection method for a circuit breaker. When the voltage detection and control circuit detects that the power supply voltage reaches the voltage threshold for disconnecting the electronic switch circuit, it drives the electronic switch circuit to disconnect; when the power supply voltage reaches the voltage threshold for disconnecting the fuse circuit, it drives the fuse circuit to disconnect, and the voltage threshold of the circuit breaker voltage protection < the voltage threshold for disconnecting the electronic switch circuit < the voltage threshold for disconnecting the fuse circuit.

[0016] Preferably, the fuse circuit includes a self - resetting fuse; after the electronic switch circuit is disconnected, when the sampled voltage is lower than the voltage threshold for disconnecting the electronic switch circuit, the voltage detection and control circuit drives the electronic switch circuit to conduct.

[0017] The protection method of the circuit breaker of the present invention provides hierarchical protection through the electronic switch circuit and the fuse circuit. Moreover, the fuse circuit and the electronic switch circuit are respectively at the front end and the rear end of the voltage detection and control circuit. When the electronic switch circuit is disconnected, it can protect the main functional circuit, but the voltage detection and control circuit can still work normally and can quickly drive the electronic switch circuit to resume the working state after the fault is eliminated. When the voltage further increases, the voltage detection and control circuit controls the fuse circuit to disconnect to protect the voltage detection and control circuit. Description of the Drawings

[0018] Figure 1 is a schematic structural diagram of the protection circuit of the switching device in the embodiment of the present invention;

[0019] Figure 2 is a schematic structural diagram of the protection circuit of the switching device in the embodiment of the present invention. Detailed Embodiments

[0020] The following Figures 1 to 2 given embodiments further illustrate the specific implementation manners of the protection circuit of the switching device of the present invention. The protection circuit of the switching device of the present invention is not limited to the descriptions of the following embodiments.

[0021] Such as Figures 1 - 2As shown in the figure, the protection circuit of the switching electrical appliance of the present invention includes a voltage detection and control circuit and at least two controllable switch circuits. The voltage detection and control circuit can drive the corresponding controllable switch circuit to disconnect when the power supply voltage meets the threshold value. When any controllable switch circuit disconnects, the control circuit of the switching electrical appliance will be powered off. The at least two controllable switch circuits have different voltage thresholds when disconnecting.

[0022] The protection circuit of the switching electrical appliance of the present invention can cut off the power supply of the control circuit when a voltage fault occurs. Even if the control circuit is connected to the incoming line end of the switching electrical appliance, it can still effectively prevent the damage and potential safety hazards brought by the voltage fault to the control circuit. It is not only safer in power use, has high application value and market potential, but also realizes hierarchical protection through at least two controllable switch circuits, and the protection function is more reliable.

[0023] The switching electrical appliance in this embodiment is a circuit breaker. The protection circuit is arranged at the front end of the control circuit, between the incoming line end of the circuit breaker and the control circuit. The circuit breaker can disconnect the main circuit of the circuit breaker when the power supply circuit reaches the voltage threshold of the voltage protection of the circuit breaker. This is the existing function of the circuit breaker. The improvement of the present invention lies in the protection circuit for protecting the control circuit of the circuit breaker. In the figure, the main function circuit constitutes the control circuit of the circuit breaker. The main function circuit can be a single-chip microcomputer or a microprocessor MCU. The protection circuit includes a voltage detection and control circuit and at least two controllable switch circuits. The number of the controllable switch circuits in the figure is two. The at least two controllable switch circuits are respectively an electronic switch circuit and a fusing circuit. The fusing circuit and the electronic switch circuit are respectively arranged at the front end and the rear end of the voltage detection and control circuit.

[0024] The main function circuit takes power from the main circuit power supply of the circuit breaker body in sequence through the electronic switch circuit, the voltage detection and control circuit and the fusing circuit, that is, takes power from the incoming line end side of the circuit breaker body. When the power supply voltage of the main circuit of the circuit breaker is normal or powered off, the electronic switch circuit and the fusing circuit are respectively in the on state, and the control circuit functions normally.

[0025] When a fault such as overvoltage occurs and the voltage reaches the voltage threshold of the voltage protection of the circuit breaker, the main function circuit drives the actuator to trip the circuit breaker to protect the load connected to the circuit breaker.

[0026] When the power supply voltage of the main circuit reaches the voltage threshold for the electronic switch circuit to disconnect, the voltage detection and control circuit drives the electronic switch circuit to disconnect and stops supplying power to the main function circuit.

[0027] When the power supply voltage of the main circuit reaches the voltage threshold for the fusing circuit to disconnect, the voltage detection and control circuit drives the fusing circuit to disconnect, and the voltage detection and control circuit is powered off.

[0028] The voltage threshold of the circuit breaker voltage protection < the voltage threshold at which the electronic switch circuit disconnects < the voltage threshold at which the fusing circuit disconnects. The voltage threshold of the circuit breaker voltage protection is generally set according to the application or reference standard. The voltage threshold at which the electronic switch circuit disconnects is generally set to the maximum voltage value at which the circuit breaker can operate normally. The voltage threshold at which the fusing circuit disconnects is generally set to the limit voltage value that the circuit breaker can withstand without damage.

[0029] In this embodiment, hierarchical protection is achieved through the electronic switch circuit and the fusing circuit. Moreover, the fusing circuit and the electronic switch circuit are respectively at the front end and the rear end of the voltage detection control circuit. When the electronic switch circuit disconnects, it can protect the main functional circuit, but the voltage detection control circuit can still operate normally and can quickly drive the electronic switch circuit to resume the working state after the fault is eliminated. When the voltage further increases, the voltage detection control circuit controls the fusing circuit to disconnect to protect the voltage detection control circuit. It can be understood that the two controllable switch circuits can also adopt other working principles, or both controllable switch circuits adopt electronic switch circuits, or both controllable switch circuits adopt fusing circuits, which all fall within the protection scope of the present invention.

[0030] As Figure 2 shown, one of the controllable switch circuits is a fusing circuit. The fusing circuit includes a self - restoring fuse FU1 and a discharging circuit. The voltage detection control circuit can control the discharging circuit to conduct, causing the self - restoring fuse FU1 to blow. The discharging circuit includes a controllable switch element V1. When the power supply voltage is higher than the fusing value, the voltage detection control circuit controls the controllable switch element V1 to conduct for current discharging.

[0031] Specifically, the fusing circuit includes a self - restoring fuse FU1 and a controllable switch element V1 connected to the self - restoring fuse FU1. When a fault occurs, the voltage detection control circuit can control the controllable switch element V1 to conduct, increasing the current in the self - restoring fuse FU1 and causing the self - restoring fuse FU1 to actively disconnect. After the fault disappears, the self - restoring fuse FU1 can automatically resume operation. Specifically, the fusing circuit includes a self - restoring fuse FU1 connected in series with the L line and a rectifying device D1, as well as a controllable switch element V1 and a resistor R4 connected between the output terminals of the rectifying device D1. The control electrode of the controllable switch element V1 is respectively connected to a resistor R10 and the voltage detection control circuit. The controllable switch element V1 is pulled down to ground through the resistor R10. The controllable switch element V1 is controlled to turn on and off by the voltage detection control circuit. The rectifying device D1 converts the power supply voltage from alternating current to direct current voltage.

[0032] When a fault occurs and the fuse circuit needs to be disconnected, that is, when the voltage threshold for disconnecting the fuse circuit is met, the voltage detection and control circuit controls the controllable switch element V1 to conduct. Through the on-resistance R4 of the controllable switch element V1, a discharge current is formed. The discharge current value is relatively large, which increases the current value passing through the self - resetting fuse FU1, causing the self - resetting fuse FU1 to heat up and turn off, thereby completely cutting off the control circuit from the power supply. When the fault is eliminated, the self - resetting fuse FU1 re - conducts after the temperature drops to supply power to the voltage detection and control circuit and the main function circuit, and the voltage detection and control circuit can re - detect the voltage. The controllable switch element V1 in this embodiment is a thyristor, and other elements such as the described MOS transistor and triode can also be used instead, all of which fall within the protection scope of this invention. The self - resetting fuse FU1 is much more sensitive to the fault voltage range than the electronic switch circuit. After a serious over - voltage fault occurs, through the inherent characteristic delay recovery of the self - resetting fuse FU1, the devices in the electronic switch circuit that have suffered thermal effects or transient breakdown damage due to over - voltage can be restored.

[0033] As Figure 2 shown, one of the controllable switch circuits is an electronic switch circuit. The electronic switch circuit includes an electronic switch K1, and the voltage detection and control circuit can control the controllable switch element V2 to conduct, causing the electronic switch K1 to disconnect.

[0034] Specifically, the electronic switch circuit includes an electronic switch K1 and a controllable switch element V2 for controlling the closing of the electronic switch K1. The electronic switch K1 is a relay. When a fault occurs, the voltage detection and control circuit can control the controllable switch element V2 to conduct, causing the electronic switch K1 to close and the normally - closed contact to disconnect. After the fault disappears, the normally - closed contact of the electronic switch K1 resumes conduction. Specifically, the electronic switch circuit includes an electronic switch K1. The electronic switch K1 includes a normally - closed contact connected in series with the L line. The two ends of the electromagnetic mechanism of the electronic switch K1 are respectively connected to a resistor R3 and a resistor R8. A controllable switch element V2 is connected in parallel across the resistor R8. The control electrode of the controllable switch element V2 is connected to the voltage detection and control circuit, and the on - off of the controllable switch element V2 is controlled by the voltage detection and control circuit.

[0035] When a fault occurs and the electronic switch circuit needs to be disconnected, that is, when the voltage threshold for disconnecting the electronic switch circuit is met, the voltage detection and control circuit controls the controllable switch element V2 to conduct, short-circuits the resistor R8 through the controllable switch element V2, increases the current passing through the electromagnetic mechanism of the electronic switch K1, causes the electromagnetic mechanism to attract and disconnect the normally closed contact, and then disconnects the electronic switch circuit. When the fault is eliminated, the voltage detection and control circuit controls the controllable switch element V2 to turn off, the electromagnetic mechanism releases, the normally closed contact re-closes, and the electronic switch circuit re-conducts to supply power to the main function circuit. The electronic switch K1 is driven by the circuit and is completely controlled by the voltage detection and control circuit. When a fault occurs, it can quickly disconnect the voltage from the main function circuit; when the fault is eliminated, it can quickly connect the power supply of the main function circuit.

[0036] It can be understood that other components can be used to replace the electronic switch K1 in the electronic switch circuit, such as contactors, etc. The electronic switch K1 is not limited to normally closed contacts. In addition, the MOS transistor V2 is a controllable switch element, and other components such as thyristors and triodes can also be used to replace it, which all fall within the protection scope of the present invention.

[0037] As Figure 2 shown, the voltage detection and control circuit includes a comparator, which controls the on / off of the controllable switch circuit through the comparator respectively. When the voltage detection and control circuit detects that the power supply voltage is greater than the disconnection threshold of the controllable switch circuit, it controls the corresponding controllable switch circuit to disconnect.

[0038] Specifically, the voltage detection and control circuit includes two comparators. The two comparators are respectively used to control the controllable switch element V1 of the fuse circuit and the controllable switch element V2 of the electronic switch circuit. The two comparators respectively compare the sampled voltage with the voltage threshold for disconnecting the electronic switch circuit and the voltage threshold for disconnecting the fuse circuit, and conduct the corresponding controllable switch element V1 and controllable switch element V2 when the voltage signal meets the threshold;

[0039] The voltage detection and control circuit includes comparator U1A and comparator U1B that constitute the two comparators, as well as resistor R1, resistor R2, resistor R5, resistor R6, resistor R7, resistor R11, resistor R12, capacitor C1, and zener diode VZ1. Resistor R1 is connected in series with zener diode VZ1 to output voltage reference source Ref1 and is connected to the inverting input terminal of comparator U1A. Resistor R2, resistor R7, and resistor R11 are connected in series between the L line and the N line. Capacitor C1 is connected in parallel across resistor R7 and resistor R11 to form a voltage division circuit. One end of resistor R5 is connected between resistor R2 and resistor R7, and the other end of resistor R5 is respectively connected to the non-inverting input terminal of comparator U1A. The output terminal of comparator U1A is connected to the G pole of controllable switch element V2 serving as the control terminal. The output terminal of comparator U1A is respectively connected to one end of resistor R12 and one end of resistor R6. The other end of resistor R6 is connected to the non-inverting input terminal of comparator U1A. The other end of resistor R12 is pulled down to ground. One end of resistor R9 is connected between resistor R7 and resistor R11, and the other end of resistor R9 is connected to the non-inverting input terminal of comparator U1B. The output terminal of comparator U1B is connected to the gate of controllable switch element V1 serving as the control terminal.

[0040] The protection circuit of the switching electrical appliance of the present invention is applicable to protecting the control circuit connected to the incoming line end of the switching electrical appliance, and can effectively protect the switching electrical appliance body and the control circuit when a serious voltage fault occurs. The switching electrical appliance includes an incoming line end, an outgoing line end, a contact mechanism connected between the incoming line end and the outgoing line end, and a control circuit connected to the incoming line end. The protection circuit of the switching electrical appliance of the present invention is connected between the incoming line end and the control circuit. The control circuit obtains power from the incoming line end. When a fault occurs in the circuit, including one or more of undervoltage, overvoltage, short circuit, and leakage, etc., the control circuit triggers the separation of the moving contact and the static contact of the contact mechanism through the actuator, or the protection mechanism of the switching electrical appliance will trigger the separation of the moving contact and the static contact of the contact mechanism, causing the switching electrical appliance to trip and realizing the protection of the equipment at the load end. The protection mechanism of the switching electrical appliance can include one or more of an undervoltage release, an overvoltage release, an overload protection mechanism, a short circuit protection mechanism, or a leakage release, etc. However, the protection mechanism of the switching electrical appliance cannot achieve the protection of the control circuit. The protection circuit of the present invention is used to achieve the protection of the control circuit and realizes hierarchical protection through at least two controllable switch circuits. When a serious voltage fault occurs, the switching electrical appliance can not only disconnect the load end in time, but also cut off the power supply of the control circuit, effectively preventing the damage and potential safety hazards brought by the voltage fault to the switching electrical appliance itself, making the power consumption safer and more reliable.

[0041] The hysteresis comparison circuit is composed of a comparator U1A. The comparator U1A determines whether to turn on and off the electronic switch circuit according to the maximum threshold VHth and the minimum threshold VLth. The on and off threshold voltages of the electronic switch circuit are the minimum threshold VLth and the maximum threshold VHth respectively. The comparator U1A does not act when the sampling voltage is between the maximum threshold VHth and the minimum threshold VLth. In this embodiment, the sampling voltage is the divided voltage value between the resistor R2 and the resistor R7, which prevents the electronic switch circuit from frequently switching near the voltage threshold. When the sampling voltage is higher than the maximum threshold VHth, the comparator U1A outputs a low level to control the controllable switch element V2 to turn off, thereby turning off the electronic switch circuit. When the sampling voltage is lower than the minimum threshold VLth, the comparator U1A outputs a high level to control the controllable switch element V2 to turn on and turn on the electronic switch circuit. It can be understood that the comparator U1A can also judge according to a certain voltage threshold corresponding to the electronic switch circuit. Although it may frequently switch near the threshold, it belongs to the protection scope of the present invention.

[0042] Further, in step S4, the comparator U1B determines whether to disconnect the fuse circuit according to the voltage threshold corresponding to the fuse circuit. When the sampling voltage is higher than the voltage reference source Ref1, in this embodiment, the sampling voltage is the divided voltage value between the resistor R7 and the resistor R11. The comparator U1B outputs a high level to turn on the controllable switch element V1, so that the current in the loop where the self - reset fuse FU1 is located increases, and the fuse circuit is disconnected through the self - reset fuse FU1. After the self - reset fuse FU1 is restored, if the power supply voltage is normal, it starts again from the above step S1.

[0043] In this embodiment, the sampling voltage is obtained from different voltage - dividing resistors and compared with a voltage reference source Ref1 to control the on - off of the electronic switch circuit and the fuse circuit. Of course, it is also possible to compare the same sampling voltage with two different voltage reference sources (i.e., different thresholds) respectively to control the on - off of the electronic switch circuit and the fuse circuit.

[0044] The present invention also provides a protection method for a switch electrical appliance. When the voltage detection and control circuit detects that the power supply voltage reaches the voltage threshold for disconnecting the electronic switch circuit, it drives the electronic switch circuit to disconnect. When the power supply voltage reaches the voltage threshold for disconnecting the fuse circuit, it drives the fuse circuit to disconnect. The voltage threshold for circuit breaker voltage protection < the voltage threshold for disconnecting the electronic switch circuit < the voltage threshold for disconnecting the fuse circuit. The fuse circuit includes a self - reset fuse. After the fuse circuit is disconnected and the fault is eliminated, the self - reset fuse can be re - conducted to supply power to the voltage detection and control circuit and the control circuit. After the electronic switch circuit is disconnected and the sampling voltage is lower than the voltage threshold for disconnecting the electronic switch circuit, the voltage detection and control circuit drives the electronic switch circuit to conduct.

[0045] The above content is a further detailed description of the present invention and creation in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention and creation is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention and creation pertains, without departing from the concept of the present invention and creation, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the protection scope of the present invention and creation.

Claims

1. A protection circuit for a switching electrical appliance, characterized in that: It includes a voltage detection and control circuit and at least two controllable switch circuits. The voltage detection and control circuit can drive the corresponding controllable switch circuit to disconnect when the power supply voltage meets the threshold. When any controllable switch circuit disconnects, it can cut off the power supply to the control circuit of the switching electrical appliance. The at least two controllable switch circuits have different voltage thresholds when disconnecting. Among them, two controllable switch circuits are an electronic switch circuit and a fusing circuit respectively. The electronic switch circuit and the fusing circuit are respectively arranged at the rear end and the front end of the voltage detection and control circuit. The voltage threshold for the electronic switch circuit to disconnect is less than that for the fusing circuit to disconnect. When the voltage detection and control circuit detects that the power supply voltage reaches the voltage threshold for the electronic switch circuit to disconnect, it drives the electronic switch circuit to disconnect. After the electronic switch circuit disconnects, when the power supply voltage is lower than the voltage threshold for the electronic switch circuit to disconnect, the voltage detection and control circuit drives the electronic switch circuit to conduct. When the power supply voltage reaches the voltage threshold for the fusing circuit to disconnect, it drives the fusing circuit to disconnect. The voltage detection and control circuit includes comparator U1A, comparator U1B, resistor R1, resistor R2, resistor R5, resistor R6, resistor R7, resistor R11, resistor R12, capacitor C1 and zener diode VZ1. Comparator U1A and comparator U1B are respectively used to control the controllable switch element V1 of the fusing circuit and the controllable switch element V2 of the electronic switch circuit. The resistor R1 is connected in series with the zener diode VZ1 and then outputs the voltage reference source Ref1 to the inverting inputs of comparator U1A and comparator U1B. Resistor R2, resistor R7 and resistor R11 are connected in series between the L line and the N line. Capacitor C1 is connected in parallel at both ends of resistor R7 and resistor R11. One end of resistor R5 is connected between resistor R2 and resistor R7, and the other end of resistor R5 is respectively connected to the non-inverting input of comparator U1A. The output end of comparator U1A is respectively connected to the control end of the controllable switch element V2, one end of resistor R12 and one end of resistor R6. The other end of resistor R6 is connected to the non-inverting input of comparator U1A. The other end of resistor R12 is grounded. One end of resistor R9 is connected between resistor R7 and resistor R11, and the other end of resistor R9 is connected to the non-inverting input of comparator U1B. The output end of comparator U1B is connected to the control end of the controllable switch element V1.

2. The protection circuit of the switching electrical apparatus according to claim 1, wherein: The fusing circuit includes a self - recovering fuse FU1 and a discharging circuit. The voltage detection and control circuit can control the discharging circuit to conduct, so that the self - recovering fuse FU1 fuses.

3. The protection circuit of the switching electrical appliance according to claim 1, characterized in that: The electronic switch circuit includes an electronic switch K1 and a controllable switch element V2. The control end of the controllable switch element V2 is connected to the voltage detection and control circuit. The voltage detection and control circuit can control the controllable switch element V2 to conduct, so that the electronic switch K1 disconnects.

4. The protection circuit of the switching electrical appliance according to claim 2, characterized in that: The discharging circuit includes a controllable switch element V1. When the power supply voltage is higher than the voltage threshold for the fusing circuit to disconnect, the voltage detection and control circuit controls the controllable switch element V1 to conduct for current discharging.

5. A circuit breaker that can disconnect the main circuit of the circuit breaker when the power supply voltage reaches the voltage threshold for voltage protection of the circuit breaker, characterized in that: It includes a control circuit and a protection circuit of the switching electrical appliance as described in any one of claims 1 - 4 connected between the incoming line end and the control circuit.

6. The circuit breaker according to claim 5, characterized in that: The voltage threshold for the breaker voltage protection < the voltage threshold at which the electronic switch circuit opens < the voltage threshold at which the fuse circuit opens.

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