protection circuit

Abstract

The application provides a protection circuit, comprising a miniature circuit breaker, a surge protector and a tripping control circuit, the tripping control circuit comprising a zero sequence transformer, a first comparison module, a delay module, an analog switch and a tripping drive module, the zero sequence transformer can sense a voltage signal proportional to abnormal current, the voltage signal is compared with a first reference level in the first comparison module to filter out the interference of abnormal current with low amplitude, the delay module filters out transient surge interference, for abnormal current generated by long duration transient overvoltage and leakage, the delay module controls the analog switch to be closed to transmit the voltage signal, the tripping drive module drives the tripper to act according to the voltage signal, so that the miniature circuit breaker trips, the transient surge interference can be effectively inhibited, the miniature circuit breaker can be prevented from tripping frequently, the tripper can be triggered to act when long duration transient overvoltage occurs, and the surge protector can be prevented from being damaged due to transient overvoltage.

Description

Technical Field

[0001] This invention relates to the field of circuits, and in particular to a protection circuit. Background Technology

[0002] SPDs (Surge Protective Devices) for AC power supplies are indispensable devices for lightning protection of electronic equipment. Their main function is to divert lightning current that surges into the power line to the ground, protecting equipment or systems from impact. The core components of an SPD typically consist of MOVs (Metal Oxide Varistors) and GDTs (Gas Discharge Tubes). Additionally, MCBs (Micro Circuit Breakers) generally function primarily to switch power on and off in a circuit. An MCB consists of an operating mechanism, contacts, protective devices (various trip units), and an arc-extinguishing system.

[0003] AC power supplies are prone to generating TOV (Temporary Over Voltage) under conditions such as unbalanced load, neutral line breakage, low-voltage grounding faults, and high-voltage single-phase grounding faults. Transient overvoltages in AC power supplies can cause MOV modules to fail due to their inability to withstand them, and may even lead to fires. Short-duration transient interferences such as surges in AC power supplies can cause miniature circuit breakers to trip frequently, affecting the normal power supply to electronic equipment. Simply combining miniature circuit breakers and surge protectors will result in the above drawbacks. Summary of the Invention

[0004] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0005] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a protection circuit that can effectively suppress transient surge interference, avoid frequent tripping of miniature circuit breakers, and prevent surge protectors from being damaged by transient overvoltage.

[0006] In a first aspect, embodiments of the present invention provide a protection circuit, comprising:

[0007] A miniature circuit breaker includes an AC input terminal, an AC output terminal, and a trip unit connected in series between the AC input terminal and the AC output terminal;

[0008] A surge protector is used to discharge surge current into the ground and is connected between the AC output terminal and the protective ground.

[0009] A trip control circuit includes a zero-sequence current transformer, a first comparison module, a delay module, an analog switch, and a trip drive module for driving the trip unit to operate. The zero-sequence current transformer is disposed on a conductor between the AC output terminal and the surge protector. The output terminal of the zero-sequence current transformer is connected to the first input terminal of the first comparison module and the input terminal of the analog switch. The second input terminal of the first comparison module is used to input a first reference level. The output terminal of the first comparison module is connected to the input terminal of the delay module. The output terminal of the delay module is connected to the control terminal of the analog switch. The output terminal of the analog switch is connected to the trip drive module.

[0010] The protection circuit provided by the embodiments of the present invention has at least the following beneficial effects: By setting a trip control circuit, the zero-sequence current transformer can sense a voltage signal proportional to the abnormal current at the AC output terminal. This voltage signal is compared with a first reference level in a first comparison module to filter out interference from abnormal currents with low amplitudes. If the detected voltage signal is greater than the first reference level, the first comparison module outputs a high level to the delay module. The delay module further filters out transient surge interference; that is, for transient surges with short durations, the analog switch will not close, while for... In the event of prolonged transient overvoltages and abnormal currents caused by leakage, the delay module controls the analog switch to close, outputting the detected voltage signal. The trip drive module then drives the trip unit based on this voltage signal, causing the miniature circuit breaker to trip. Therefore, this protection circuit can effectively suppress transient surge interference, preventing frequent tripping of the miniature circuit breaker. It can also trigger the trip unit to operate when a prolonged transient overvoltage occurs, preventing damage to the surge protector due to transient overvoltage. Furthermore, it can detect abnormal leakage and trigger the miniature circuit breaker to trip, preventing electric shock caused by leakage.

[0011] Secondly, embodiments of the present invention also provide a protection circuit, comprising:

[0012] A miniature circuit breaker includes an AC input terminal, an AC output terminal, and a trip unit connected in series between the AC input terminal and the AC output terminal;

[0013] A surge protector is used to discharge surge current into the ground and is connected between the AC output terminal and the protective ground.

[0014] A trip control circuit includes a zero-sequence current transformer, a microcontroller, and a trip drive module for driving the trip unit. The zero-sequence current transformer is disposed on a conductor between the AC output terminal of the miniature circuit breaker and the surge protector. The output terminal of the zero-sequence current transformer is connected to the input terminal of the microcontroller, and the output port of the microcontroller is connected to the trip drive module via an optocoupler. The microcontroller performs the following operations:

[0015] The voltage signal detected by the zero-sequence current transformer is compared with the first reference level;

[0016] When the voltage signal detected by the zero-sequence current transformer is greater than the first reference level, the microcontroller compares the duration of the voltage signal detected by the zero-sequence current transformer with a first preset time.

[0017] When the duration of the voltage signal detected by the zero-sequence current transformer is greater than a first preset time, the output port of the microcontroller outputs an action signal to activate the tripping drive module through the optocoupler.

[0018] The protection circuit provided by the embodiments of the present invention has at least the following beneficial effects: by setting a trip control circuit, the zero-sequence current transformer can sense a voltage signal proportional to the abnormal current at the AC output terminal. After the voltage signal is sent to the microcontroller, it is compared with the first reference level to filter out the interference of abnormal current with low amplitude. If the voltage signal is greater than the first reference level, the duration of the voltage signal is further compared with the first preset time to filter out transient surge interference. That is, for transient surges with short duration, the output port of the microcontroller does not output an action signal, while for transient overvoltages and abnormal currents generated by leakage with long duration, the output port of the microcontroller outputs an action signal to activate the trip drive module through the optocoupler, causing the miniature circuit breaker to trip. Therefore, the protection circuit can effectively suppress transient surge interference, avoid frequent tripping of the miniature circuit breaker, trigger the trip unit to act when a transient overvoltage with long duration occurs, avoid damage to the surge protector due to transient overvoltage, and detect leakage abnormalities to trigger the miniature circuit breaker to trip, avoiding electric shock to the human body caused by leakage.

[0019] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0020] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.

[0021] Figure 1 This is a circuit diagram of a protection circuit provided in one embodiment of the present invention;

[0022] Figure 2 This is a circuit diagram of a protection circuit provided in another embodiment of the present invention;

[0023] Figure 3 This is a circuit diagram of a protection circuit provided in one embodiment of the present invention;

[0024] Figure 4 This is an operation curve diagram of a protection circuit provided in an embodiment of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] It should be noted that although functional modules are divided in the device schematic diagram and a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the device or the order in the flowchart. The terms "first," "second," etc., in the specification, claims, and the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0027] This invention provides a protection circuit that can effectively suppress transient surge interference, prevent frequent tripping of miniature circuit breakers, and prevent surge protectors from being damaged by transient overvoltages.

[0028] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0029] like Figure 1 As shown, Figure 1 This is a schematic diagram of a protection circuit provided in one embodiment of the present invention.

[0030] like Figure 1As shown, the protection circuit includes a miniature circuit breaker 100, a trip control circuit 200, and a surge protector 300. The miniature circuit breaker 100 includes an AC input terminal, an AC output terminal, and a trip unit 110 connected in series between the AC input terminal and the AC output terminal. The surge protector 300 is used to discharge surge current to ground and is connected between the AC output terminal and the protective ground. The surge protector 300 includes a first varistor 310, a second varistor 320, a third varistor 330, and a gas discharge tube 340. The live wire of the AC output terminal is connected to one end of the first varistor 310 and one end of the second varistor 320, respectively. The neutral wire of the AC output terminal is connected to the other end of the first varistor 310 and one end of the third varistor 330, respectively. The other ends of the second varistor 320 and the third varistor 330 are connected... One end of the gas discharge tube 340 is connected to the gas discharge tube 340, and the other end of the gas discharge tube 340 is grounded; the trip control circuit 200 includes a zero-sequence current transformer 210, a first comparison module 220, a delay module 230, an analog switch 240, and a trip drive module 250 for driving the trip unit 110 to operate. The zero-sequence current transformer 210 is disposed on the conductor between the AC output terminal and the surge protector 300. The output terminal of the zero-sequence current transformer 210 is connected to the first input terminal of the first comparison module 220 and the input terminal of the analog switch 240, respectively. The second input terminal of the first comparison module 220 is used to connect to the first reference level Vref1. The output terminal of the first comparison module 220 is connected to the input terminal of the delay module 230. The output terminal of the delay module 230 is connected to the control terminal of the analog switch 240. The output terminal of the analog switch 240 is connected to the trip drive module 250.

[0031] In this embodiment, by setting the trip control circuit 200, the zero-sequence transformer 210 can sense a voltage signal proportional to the abnormal current at the AC output terminal. This voltage signal is compared with the first reference level Vref1 in the first comparison module 220 to filter out interference from abnormal currents with low amplitudes. If the detected voltage signal is greater than the first reference level Vref1, the first comparison module 220 outputs a high level to the delay module 230. The delay module 230 further filters out transient surge interference. That is, for transient surges with short durations, the analog switch 240 will not close, while for transient surges with longer durations... The delay module 230 controls the analog switch 240 to close in response to abnormal currents caused by overvoltage and leakage, so as to output the detected voltage signal. The trip drive module 250 drives the trip unit 110 to operate according to the voltage signal, so that the miniature circuit breaker 100 trips. Therefore, this protection circuit can effectively suppress transient surge interference and avoid frequent tripping of the miniature circuit breaker 100. It can also trigger the trip unit 110 to operate when there is a transient overvoltage of a long duration, so as to avoid damage to the surge protector 300 due to transient overvoltage. It can also detect abnormal leakage and trigger the miniature circuit breaker 100 to trip, so as to avoid electric shock to the human body caused by leakage.

[0032] Reference Figure 1 In one embodiment, the trip control circuit 200 further includes an amplifier circuit 260 and an absolute value detector circuit 270. The input terminal of the amplifier circuit 260 is connected to the output terminal of the zero-sequence current transformer 210, and the absolute value detector circuit 270 is connected to the output terminal of the amplifier circuit 260 to convert the zero-sequence current into a positive voltage signal. The output terminal of the absolute value detector circuit 270 is connected to the input terminals of the first comparison module 220 and the analog switch 240, respectively.

[0033] In this embodiment, by setting an amplifier circuit 260 and an absolute value detector circuit 270 in the trip control circuit 200 to preprocess the voltage signal detected by the zero-sequence current transformer 210 that is proportional to the abnormal current at the AC output terminal, the subsequent modules can obtain a signal with a large amplitude and a positive value.

[0034] Reference Figure 2 In one embodiment, the amplifier circuit 260 is a differential amplifier, and the absolute value detector circuit 270 is an active bridge rectifier circuit or a passive bridge rectifier circuit. The induced output of the zero-sequence transformer 210 is amplified by the differential amplifier and then converted into a positive voltage signal by the active bridge rectifier circuit or the passive bridge rectifier circuit. Furthermore, to improve the detection sensitivity, the active bridge rectifier circuit or the passive bridge rectifier circuit can be implemented using metal-oxide-semiconductor field-effect transistors or operational amplifiers.

[0035] Reference Figure 2 In one embodiment, the delay module 230 includes a first resistor R1, a first capacitor C1, and a second comparison module 231. The output terminal of the first comparison module 220 is connected to one end of the first resistor R1, and the other end of the first resistor R1 is connected to one end of the first capacitor C1 and the non-inverting input terminal of the second comparison module 231, respectively. The other end of the first capacitor C1 is grounded, and the inverting input terminal of the second comparison module 231 is connected to the second reference level Vr.

[0036] In this embodiment, since the output of the first comparison module 220 is a constant high level, the delay time t1 of the delay module 230 is independent of the peak value of the abnormal current at the AC output terminal. The delay module 230 shields transient surges with a duration shorter than the delay time t1. The delay time t1 of the delay module 230 is determined by the first resistor R1 and the first capacitor C1, and is generally in the millisecond range.

[0037] Reference Figure 2 In one embodiment, the delay module 230 further includes a first diode D1 connected in reverse parallel across the first resistor R1.

[0038] In this embodiment, by connecting a first diode D1 in reverse parallel across the first resistor R1, once the abnormal current at the AC output terminal disappears, that is, when the output of the absolute value detection circuit 270 is zero, the first diode D1 can quickly release the charge on the first capacitor C1, thereby ensuring the dynamic response of the delay module 230.

[0039] Reference Figure 1 and Figure 2 In one embodiment, the trip control circuit 200 further includes a first filter circuit 280 connected between the output terminal of the absolute value detector circuit 270 and the input terminal of the analog switch 240. The first filter circuit 280 includes a second resistor R2 and a second capacitor C2. The output terminal of the absolute value detector circuit 270 is connected to one end of the second resistor R2, and the other end of the second resistor R2 is connected to the input terminal of the analog switch 240 and one end of the second capacitor C2, respectively. The other end of the second capacitor C2 is grounded.

[0040] In this embodiment, by setting a first filter circuit 280 between the output terminal of the absolute value detector circuit 270 and the input terminal of the analog switch 240, the harmonic components of the voltage signal induced by the zero-sequence transformer 210 that are proportional to the abnormal current can be effectively filtered out before being sent to the analog switch 240.

[0041] Reference Figure 2 In one embodiment, the first filter circuit 280 further includes a second diode D2 connected in reverse parallel across the second resistor R2.

[0042] In this embodiment, by connecting a second diode D2 in reverse parallel across the two ends of the second resistor R2, once the abnormal current at the AC output terminal disappears, that is, when the output of the absolute value detection circuit 270 is zero, the second diode D2 can quickly release the charge on the second capacitor C2, thereby ensuring the dynamic response of the first filter circuit 280.

[0043] Reference Figure 2 In one embodiment, the trip control circuit 200 further includes a second filter circuit 290 and a third comparison module 291 connected between the output terminal of the analog switch 240 and the trip drive module 250. The second filter circuit 290 includes a third resistor R3 and a third capacitor C3. The output terminal of the analog switch 240 is connected to one end of the third resistor R3. The other end of the third resistor R3 is connected to one end of the third capacitor C3 and the non-inverting input terminal of the third comparison module 291. The inverting input terminal of the third comparison module 291 is connected to the third reference level Vref3.

[0044] In this embodiment, if the voltage signal induced by the zero-sequence transformer 210, which is proportional to the abnormal current, is greater than the first reference level Vref1 and the duration of the abnormal current is greater than the delay time t1, the analog switch 240 outputs the voltage signal to the second filter circuit 290. After the interference is filtered out by the second filter circuit 290, it is compared with the third reference level Vref3 to further filter out the interference. Finally, the trip drive module 250 generates a drive current to control the trip unit 110 to operate, causing the miniature circuit breaker 100 to trip. The main contacts of the miniature circuit breaker 100 disconnect from the circuit, thereby preventing the surge protector 300 from tripping and even burning out due to prolonged heating time; the third reference level Vref3 serves as... The anti-interference threshold level for triggering the trip drive module 250 can filter out unnecessary tripping interference. For transient overvoltage, the surge protector 300 is generally not damaged for more than several hundred milliseconds. Since the delay time t1 is several milliseconds, as long as the total delay of the delay time t1, the second filter circuit 290, and the trip drive module 250 driving the trip unit 110 to trip is within 100 milliseconds, the surge protector 300 will not be damaged due to the excessive heat time of the transient overvoltage. The second filter circuit 290 is functionally an integrator circuit, and its output is a voltage signal that is proportional to the product of the transient current and time. That is, the larger the transient current, the shorter the time for the main contacts of the miniature circuit breaker 100 to open.

[0045] The following is combined Figure 2 This paper describes the response status of the protection circuit provided in the embodiments of the present invention to various situations in practical applications.

[0046] Under normal conditions, the first varistor 310, the second varistor 320, the third varistor 330, and the gas discharge tube 340 in the surge protector 300 are in a high-resistance state. The L-phase current and the N-phase current of the AC power supply are equal in magnitude and opposite in direction. The induced output of the zero-sequence transformer 210 is zero. After passing through the first comparison module 220, the delay module 230, and the analog switch 240, the trip drive module 250 has no current output. The trip unit 110 of the miniature circuit breaker 100 does not operate, and the main contacts of the miniature circuit breaker 100 are in the closed state.

[0047] When a short-duration transient interference such as a surge occurs, the surge protector 300 is in a low-resistance state, clamping the surge in the power grid to a certain amplitude and discharging it through the ground. At this time, the L-phase current and N-phase current of the AC power supply are no longer equal in magnitude and opposite in direction. The zero-sequence transformer 210 induces a voltage signal proportional to the abnormal current. This voltage signal is differentially amplified by the amplifier circuit 260 and then converted into a positive voltage signal by an active bridge rectifier circuit or a passive bridge rectifier circuit. In order to improve the detection sensitivity, the active bridge rectifier circuit or the passive bridge rectifier circuit can be implemented by a MOSFET or an operational amplifier. The positive voltage signal output by the active or passive bridge rectifier circuit is divided into two paths: one path passes through the first filter circuit 280, which consists of the second resistor R2, the second capacitor C2, and the second diode D2, and is output to the analog switch 240. Once the abnormal voltage disappears, that is, when the output of the active or passive bridge rectifier circuit is zero, the second diode D2 can quickly release the charge on the second capacitor C2, ensuring the dynamic response of the first filter circuit 280; the other path passes through the first comparison module 220, where the first reference level Vref1 is the trigger level for transient overvoltage and leakage detection. The delay time t1 of the delay module 230 is determined by the first resistor R1 and the first capacitor C1, and is also in the millisecond range. The first diode D1 can quickly release the charge on the first capacitor C1, ensuring the dynamic response of the delay module 230. Although the discharge current of the surge protector 300 is generally large, the output of the first comparison module 220 is a constant high level, which ensures that the delay time t1 is independent of the peak value of the surge current. After passing through the delay module 230, short-duration signals such as surges are shielded. The output of the first comparison module 220 controls the output of the analog switch 240 to connect to the ground, that is, the output of the analog switch 240 is zero volts, the trip drive module 250 has no current output, and the main contacts of the miniature circuit breaker 100 are in the closed state.

[0048] When a transient overvoltage occurs, the surge protector 300 is in a low-resistance state, clamping the transient voltage in the power grid to a certain amplitude and discharging it through the ground. At this time, the L-phase current and N-phase current of the AC power supply are no longer equal in magnitude and opposite in direction. The zero-sequence transformer 210 induces a voltage signal proportional to the transient current. This voltage signal is differentially amplified by the amplifier circuit 260 and then split into two paths: one path is output to the analog switch 240 through the first filter circuit 280, and the other path is output to the first comparison module 220. The first reference level Vref1 is the trigger level for transient overvoltage and leakage current detection, which is then extended... After a delay of t1, the time module 230 controls the connection between the output and input terminals of the analog switch 240. That is, the output of the analog switch 240 is a voltage signal proportional to the transient current. After the interference is filtered out by the second filter circuit 290, it is compared with the third reference level Vref3. The third reference level Vref3 is the anti-interference threshold level. Finally, the trip drive module 250 controls the trip unit 110 of the miniature circuit breaker 100 to operate. The main contacts of the miniature circuit breaker 100 disconnect the main circuit, thereby avoiding the risk of tripping failure or even burning out of the surge protector 300 due to long heating time. For transient overvoltages, the surge protector 300 is generally not damaged for more than several hundred milliseconds. Since the delay time t1 is several milliseconds, as long as the total delay of the delay time t1, the second filter circuit 290, and the trip unit 110 is within 100ms, the surge protector 300 will not be damaged due to the prolonged heating time of the transient overvoltage. The second filter circuit 290 is composed of the third resistor R3 and the third capacitor C3. Functionally, it is an integrating circuit. Its output is a voltage signal that is proportional to the product of the transient current and time. That is, the larger the transient current, the shorter the time for the main contacts of the miniature circuit breaker 100 to open, ensuring that the AC power supply of the miniature circuit breaker 100 is cut off before the surge protector 300 is damaged.

[0049] When a leakage current abnormality occurs, the first varistor 310, the second varistor 320, the third varistor 330 and the gas discharge tube 340 in the surge protector 300 are in a high resistance state, and the leakage current flows into the ground through the AC power supply, equipment and human body. At this time, the L-phase current and N-phase current of the AC power supply are no longer equal in magnitude and opposite in direction. The zero-sequence transformer 210 induces a voltage signal proportional to the leakage current. This voltage signal is differentially amplified by the amplifier circuit 260 and then split into two paths: one path is output to the analog switch 240 through the first filter circuit 280, and the other path is output to the analog switch 240 through the first comparison module 220. The first reference level Vref1 is the transient overvoltage and leakage current detection trigger level. After a delay of t1 by the delay module 230, the output and input terminals of the analog switch 240 are connected. That is, the output of the analog switch 240 is a voltage signal proportional to the leakage current. After filtering out interference by the second filter circuit 290, it is compared with the third reference level Vref3. The third reference level Vref3 is the anti-interference threshold level. Finally, the trip drive module 250 controls the trip unit 110 of the miniature circuit breaker 100 to operate. The main contacts of the miniature circuit breaker 100 disconnect the main circuit, thereby avoiding the risk of electric shock to the human body due to leakage current. Since the delay time t1 is several milliseconds, and the total delay of the delay time t1, the second filter circuit 290, and the trip unit 110 is within 100ms, it meets the relevant leakage protection standard requirements.

[0050] Reference Figure 3 Another embodiment of the present invention also provides a protection circuit, comprising:

[0051] Miniature circuit breaker 100 includes an AC input terminal, an AC output terminal, and a trip unit 110 connected in series between the AC input terminal and the AC output terminal;

[0052] The surge protector 300 is used to discharge surge current into the ground and is connected between the AC output terminal and the protective ground.

[0053] The trip control circuit 200 includes a zero-sequence current transformer 210, a microcontroller 400, and a trip drive module 250 for driving the trip unit 110. The zero-sequence current transformer 210 is disposed on a conductor between the AC output terminal of the miniature circuit breaker 100 and the surge protector 300. The output terminal of the zero-sequence current transformer 210 is connected to the input terminal of the microcontroller 400. The output port of the microcontroller 400 is connected to the trip drive module 250 through an optocoupler 500. The microcontroller 400 performs the following operations:

[0054] The voltage signal detected by the zero-sequence current transformer 210 is compared with the first reference level Vref1;

[0055] When the voltage signal detected by the zero-sequence current transformer 210 is greater than the first reference level Vref1, the microcontroller 400 compares the duration of the voltage signal detected by the zero-sequence current transformer 210 with the first preset time.

[0056] When the duration of the voltage signal detected by the zero-sequence transformer 210 is greater than the first preset time, the output port of the microcontroller 400 outputs an action signal to activate the trip drive module 250 through the optocoupler 500.

[0057] In this embodiment, by setting a trip control circuit 200, the zero-sequence current transformer 210 can sense a voltage signal proportional to the abnormal current at the AC output terminal. After this voltage signal is sent to the microcontroller 400, it is compared with the first reference level Vref1 to filter out interference from abnormal currents with low amplitudes. If the voltage signal is greater than the first reference level Vref1, the duration of the voltage signal is further compared with a first preset time to filter out transient surge interference. That is, for transient surges with short durations, the output port of the microcontroller 400 does not output an action signal, while for transient surges with long durations... In the event of prolonged transient overvoltage and abnormal current caused by leakage, the output port of the microcontroller 400 outputs an action signal to activate the trip drive module 250 via the optocoupler 500, causing the miniature circuit breaker 100 to trip. Therefore, this protection circuit can effectively suppress transient surge interference, prevent the miniature circuit breaker 100 from tripping frequently, and trigger the trip unit 110 to operate when a prolonged transient overvoltage occurs, preventing the surge protector 300 from being damaged by transient overvoltage. It can also detect abnormal leakage and trigger the miniature circuit breaker 100 to trip, preventing electric shock caused by leakage.

[0058] Reference Figure 3 In one embodiment, the trip control circuit 200 further includes an amplifier circuit 260 and an absolute value detector circuit 270. The input terminal of the amplifier circuit 260 is connected to the output terminal of the zero-sequence current transformer 210, and the absolute value detector circuit 270 is connected to the output terminal of the amplifier circuit 260 to convert the zero-sequence current into a positive voltage signal. The output terminal of the absolute value detector circuit 270 is connected to the microcontroller 400.

[0059] In this embodiment, by setting an amplifier circuit 260 and an absolute value detector circuit 270 in the trip control circuit 200 to preprocess the voltage signal detected by the zero-sequence current transformer 210, which is proportional to the abnormal current at the AC output terminal, the microcontroller 400 can obtain a signal with a large amplitude and a positive value. It is understood that the microcontroller 400 internally includes an analog-to-digital converter module, i.e., an ADC module, which can convert the analog signal obtained from the absolute value detector circuit 270 into a digital signal for subsequent digital logic operations.

[0060] Additionally, refer to Figure 4Curve A is the power frequency current non-damage curve of surge protector 300. Miniature circuit breaker 100 can set curve B as its own main contact disconnection curve according to the power frequency current non-damage curve of surge protector 300 and store it in the microcontroller 400. This determines the disconnection time of miniature circuit breaker 100 under abnormal conditions, which can improve the protection effect of surge protector 300 and avoid frequent damage to surge protector 300 caused by transient overvoltage.

[0061] Furthermore, since the microcontroller 400 is introduced to implement the logic judgment, this embodiment can also have an automatic reclosing function: after the main switch of the miniature circuit breaker 100 is disconnected, after a certain predetermined time, the main switch is closed again. If the fault disappears at this time, the AC load continues to be powered, thereby reducing the number of times manual on-site reclosing is required; if the fault still exists at this time, after a certain number of preset attempts, the main switch is disconnected and no further attempts are made, waiting for maintenance personnel to come to the site to troubleshoot the fault.

[0062] It should be noted that the miniature circuit breaker 100, trip control circuit 200 and surge protector 300 can be assembled into an integrated DIN rail module. On-site, simply replacing the conventional miniature circuit breaker 100 and surge protector 300 can achieve surge protection, transient overvoltage protection and leakage protection functions.

[0063] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of the present invention.

Claims

1. A protection circuit, characterized in that, include: A miniature circuit breaker includes an AC input terminal, an AC output terminal, and a trip unit connected in series between the AC input terminal and the AC output terminal; A surge protector is used to discharge surge current into the ground and is connected between the AC output terminal and the protective ground. The trip control circuit includes a zero-sequence current transformer, an amplifier circuit, an absolute value detector circuit, a first comparison module, a delay module, an analog switch, and a trip drive module for driving the trip unit to operate. The zero-sequence current transformer is disposed on a conductor between the AC output terminal and the surge protector. The output terminal of the zero-sequence current transformer is connected to the input terminal of the amplifier circuit. The absolute value detector circuit is connected to the output terminal of the amplifier circuit to convert the zero-sequence current into a positive voltage signal. The output terminal of the absolute value detector circuit is connected to the first input terminal of the first comparison module and the input terminal of the analog switch, respectively. The second input terminal of the first comparison module is used to connect to a first reference level. The delay module includes a first resistor, a first capacitor, and a second comparison module. The output terminal of the first comparison module is connected to one end of the first resistor, and the other end of the first resistor is connected to one end of the first capacitor and the non-inverting input terminal of the second comparison module. The other end of the first capacitor is grounded. The inverting input terminal of the second comparison module is connected to a second reference level. The output terminal of the second comparison module serves as the output terminal of the delay module and is connected to the control terminal of the analog switch. The output terminal of the analog switch is connected to the tripping drive module.

2. The protection circuit according to claim 1, characterized in that, The absolute value detection circuit is an active bridge rectifier circuit or a passive bridge rectifier circuit.

3. The protection circuit according to claim 1, characterized in that, The delay module also includes a first diode connected in reverse parallel across the first resistor.

4. The protection circuit according to claim 1, characterized in that, The tripping control circuit further includes a first filter circuit connected between the output terminal of the absolute value detector circuit and the input terminal of the analog switch. The first filter circuit includes a second resistor and a second capacitor. The output terminal of the absolute value detector circuit is connected to one end of the second resistor, and the other end of the second resistor is connected to the input terminal of the analog switch and one end of the second capacitor, respectively. The other end of the second capacitor is grounded.

5. The protection circuit according to claim 4, characterized in that, The first filter circuit also includes a second diode connected in reverse parallel across the second resistor.

6. The protection circuit according to claim 1, characterized in that, The tripping control circuit further includes a second filter circuit and a third comparison module connected between the output terminal of the analog switch and the tripping drive module. The second filter circuit includes a third resistor and a third capacitor. The output terminal of the analog switch is connected to one end of the third resistor, and the other end of the third resistor is connected to one end of the third capacitor and the non-inverting input terminal of the third comparison module. The inverting input terminal of the third comparison module is connected to a third reference level.

7. A protection circuit, characterized in that, include: A miniature circuit breaker includes an AC input terminal, an AC output terminal, and a trip unit connected in series between the AC input terminal and the AC output terminal; A surge protector is used to discharge surge current into the ground and is connected between the AC output terminal and the protective ground. A trip control circuit includes a zero-sequence current transformer, an amplifier circuit, an absolute value detector circuit, a microcontroller, and a trip drive module for driving the trip unit. The zero-sequence current transformer is disposed on a conductor between the AC output terminal of the miniature circuit breaker and the surge protector. The output terminal of the zero-sequence current transformer is connected to the input terminal of the amplifier circuit. The absolute value detector circuit is connected to the output terminal of the amplifier circuit to convert the zero-sequence current into a positive voltage signal. The output terminal of the absolute value detector circuit is connected to the input terminal of the microcontroller. The output port of the microcontroller is connected to the trip drive module via an optocoupler. The microcontroller performs the following operations: The voltage signal detected by the zero-sequence current transformer is compared with the first reference level; When the voltage signal detected by the zero-sequence current transformer is greater than the first reference level, the microcontroller compares the duration of the voltage signal detected by the zero-sequence current transformer with a first preset time. When the duration of the voltage signal detected by the zero-sequence current transformer is greater than a first preset time, the output port of the microcontroller outputs an action signal to activate the tripping drive module through the optocoupler.

8. The protection circuit according to any one of claims 1 to 7, characterized in that, The surge protector includes a first varistor, a second varistor, a third varistor, and a gas discharge tube. The live wire of the AC output terminal is connected to one end of the first varistor and one end of the second varistor, respectively. The neutral wire of the AC output terminal is connected to the other end of the first varistor and one end of the third varistor, respectively. The other ends of the second varistor and the third varistor are connected to one end of the gas discharge tube, and the other end of the gas discharge tube is grounded.

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