Power input surge protection and isolation device and system

Abstract

The invention discloses a power supply input surge protection and isolation device, which comprises a piezoresistor, a surge decoupling power resistor and a TVS (Transient Voltage Suppressor) tube which are sequentially connected in series, and a self-adaptive surge control circuit which is connected with the surge decoupling power resistor in parallel, when surge overvoltage occurs, the TVS tube is firstly broken down, and transient large current flows through the adaptive surge control circuit; the surge decoupling power resistor is used for enabling the passing surge current to generate relatively large voltage drop after the TVS tube is broken down; the self-adaptive surge control circuit comprises a first MOS tube which is used for conducting transient large current passing through a TVS (Transient Voltage Suppressor) tube; when the voltage drop on the MOS tube is greater than the breakdown voltage of the voltage-regulator tube, the voltage-regulator tube is broken down to trigger the conduction of the triode; when the voltage-regulator tube is broken down, the triode is conducted, so that the GS voltage drop of the first MOS tube is reduced, and the first MOS tube is turned off; when the sum of the clamping voltage of the TVS tube end and the voltage drop of the surge decoupling power resistor exceeds the minimum action voltage of the piezoresistor, the piezoresistor acts, so that high-energy transient interference flows through the piezoresistor, and surge protection is realized. According to the invention, the surge protection and isolation protection functions of the input end of the power supply can be effectively realized, and the use safety and stability of the power supply are ensured.

Description

Technical Field

[0001] The present application relates to the field of power supply protection technology, and in particular to a power supply input surge protection and isolation device and system. Background Art

[0002] The existing surge overvoltage protection measures are mainly aimed at the surge overvoltage protection of the power input end, and do not take into account the surge impact current at power-on startup. If the power-on impact current is not suppressed, the reliability of the power supply operation may be affected: when the voltage across the capacitor is "0", there will be a large impact current at the moment of power-on, which may cause the fuse and air switch at the power input end to malfunction, resulting in power-on failure; transient large current may damage the reverse connection protection diode, MOS tube, or AC power rectifier bridge and other devices at the input end. At the same time, transient large current impact may damage the capacitor at the input end and affect its service life, such as tantalum capacitors smoking and catching fire. Summary of the invention

[0003] The embodiment of the present application provides a power input surge protection and isolation device and system, which solves the defects of the prior art. When a surge voltage occurs, a surge adaptive control circuit is used to limit the current through a power resistor to reduce the surge current passing through the TVS tube, thereby indirectly improving the absorption power of the subsequent surge and better protecting the subsequent circuit.

[0004] The present application provides a power input surge protection and isolation device, comprising a varistor, a surge decoupling power resistor and a TVS tube connected in series in sequence, and an adaptive surge control circuit connected in parallel with the surge decoupling power resistor;

[0005] The TVS tube is connected to the input end of the adaptive surge control circuit. When a surge overvoltage occurs, the TVS tube is first broken down, and a transient large current flows through the adaptive surge control circuit.

[0006] The surge decoupling power resistor is connected to the input end of the TVS tube, and is used to generate a large voltage drop in the surge current passing through the TVS tube after the TVS tube is broken down;

[0007] The adaptive surge control circuit includes a first MOS tube, a voltage regulator tube and a triode. The first MOS tube is connected to the input end of the TVS tube and is used to conduct a transient large current through the TVS tube. The voltage regulator tube is connected in parallel with the first MOS tube. When the voltage drop on the MOS tube is greater than the breakdown voltage of the voltage regulator tube, the voltage regulator tube is broken down, triggering the conduction of the triode. The triode is connected to the voltage regulator tube. When the voltage regulator tube is broken down, the triode is turned on, so that the GS voltage drop of the first MOS tube decreases, thereby turning off the first MOS tube.

[0008] When the sum of the clamping voltage at the TVS tube end and the voltage drop of the surge decoupling power resistor exceeds the minimum operating voltage of the varistor, the varistor operates, allowing large-energy transient interference to flow through the varistor, thereby achieving surge protection.

[0009] According to the power input surge protection and isolation device, the first MOS tube is connected in parallel with the surge decoupling power resistor, wherein the first MOS tube is in an off state when powered on, and its on-resistance is large, and the gate of the first MOS tube is connected to at least one charging capacitor through at least one charging resistor, and the gate-source voltage Vgs of the first MOS tube is gradually increased by charging the charging capacitor, so that the on-resistance of the first MOS tube is gradually reduced from infinity to 0.

[0010] According to the power input surge protection and isolation device, it also includes a DC / DC isolation module, the input end of the DC / DC isolation module is connected to the output end of the TVS tube, the DC / DC isolation module includes an isolation branch, and the isolation branch includes a high-frequency isolation transformer and a feedback optocoupler connected in series, wherein the electrical insulation index of the isolation branch is AC3000V-4000V.

[0011] According to the power input surge protection and isolation device, the electrical insulation index of the power output to the casing ground PE in the DC / DC isolation module is AC1500V-3000V.

[0012] According to the power input surge protection and isolation device, it also includes a fuse, which is connected to one side of the output end of the adaptive surge control circuit and is used to cut off the circuit when the circuit is overloaded to protect circuit components.

[0013] According to the power input surge protection and isolation device, the first MOS tube is connected to at least one overcurrent detection setting resistor for detecting overcurrent conditions.

[0014] According to the power input surge protection and isolation device, it also includes an anti-return circuit, the output end of the anti-return circuit is connected to the input end of the varistor, which is used to ensure that current can only flow in one direction to prevent damage caused by incorrect connection of the positive / negative poles of the power supply.

[0015] The present application also provides a power input surge protection and isolation system, comprising the power input surge protection and isolation device described in any one of the above items.

[0016] The power input surge protection and isolation device and system provided by the present invention have the following advantages over the prior art:

[0017] (1) Through the fast response and low clamping voltage of the TVS tube, the subsequent circuit is better protected. When a surge voltage occurs, the power resistor is used to limit the current, reducing the surge current passing through the TVS tube, indirectly improving the absorption power of the subsequent surge, and through the slow-start impedance characteristics of the MOS tube in the adaptive surge control circuit, the power-on impact current of the power input is reduced to avoid transient overcurrent damage to the components at the power input end, or cause the early short-circuit protection measures of the equipment to malfunction, affecting the power-on of the system; and through the front-stage varistor, high-voltage, high-energy surges and overvoltages are resisted, the number of varistor actions is reduced, and its service life is increased. The present invention can enhance the surge protection effect of the isolated switching power supply, extend the service life of the surge protection circuit, avoid the removal / installation of protection components during the power withstand voltage test, and reduce maintenance costs. At the same time, the suppression of differential mode surge overvoltage and power-on impact current is strengthened to better protect the switching power supply. The power input surge protection and isolation device can effectively realize the surge protection and isolation protection functions of the power input end, ensuring the safety and stability of power supply use.

[0018] (2) By increasing the insulation strength of the isolating switch power supply, the transient overvoltage discharge path is effectively cut off to avoid common-mode interference to sensitive circuits. At the same time, the breakdown voltage of the common-mode protection device is improved, avoiding the problem of frequent disassembly and assembly of the protection device due to power supply withstand voltage testing. The present invention utilizes the insulation withstand voltage characteristics of the isolating switch power supply to achieve common-mode surge overvoltage protection and reduce the number of common-mode protection components. For example, frequent operation of common-mode protection components affects the reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The technical solution and other beneficial effects of the present application will be made apparent by describing in detail the specific implementation methods of the present application in conjunction with the accompanying drawings.

[0020] Figure 1 One of the structural schematic diagrams of an optional power input surge protection and isolation device provided in an embodiment of the present application.

[0021] Figure 2 A schematic diagram of the structure of an optional power surge overvoltage isolation protection provided in an embodiment of the present application.

[0022] Figure 3 The second structural schematic diagram of an optional power input surge protection and isolation device provided in an embodiment of the present application.

[0023] Figure 4 A schematic diagram of the structure of a power input surge protection and isolation system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0025] With the rapid development of power electronics, communications, and industrial control industries, the power supply requirements in various industries are getting higher and higher. In order to ensure the stability and anti-interference of the system, the isolated switching power supply came into being. The block diagram of the isolated switching power supply is shown below: The isolated switching power supply is mainly composed of a high-frequency isolation transformer L1, a PWM controller, a MOS tube P1, an output rectifier diode, an input filter circuit, an output filter circuit, a feedback optocoupler, etc.

[0026] Surge overvoltage is one of the main factors that affect the stable operation or service life of power supply. The main causes of power input surge are induced lightning strike and transient overvoltage in operation.

[0027] Operation transient overvoltage: related to the start and stop of equipment and power supply network failures within the power system. Within the power system, due to changes in internal states such as circuit breaker operation, load input and removal, or system failures, system parameters change, causing electromagnetic energy conversion or transmission electromagnetic disturbance within the power system. The surge within the system mainly comes from the impact of the internal power load within the system, accounting for about 80%. The causes of internal overvoltage in the power system can be roughly divided into:

[0028] 1) Input and removal of large power loads;

[0029] 2) Input and output of inductive loads;

[0030] 3) Input and removal of power factor compensation capacitors;

[0031] 4)Short circuit fault.

[0032] Surges can have adverse effects on electrical equipment, especially computers, communication equipment, monitoring equipment and other microelectronic devices connected to the power grid. Even if there is no permanent damage to the equipment, abnormal operation and suspension of the system will have serious consequences.

[0033] The present application provides a power input surge protection and isolation device, Figure 1 One of the schematic diagrams of the structure of a power input surge protection and isolation device provided in an embodiment of the present application is as follows: Figure 1As shown, the device includes a varistor, a surge decoupling power resistor and a TVS tube connected in series in sequence, and an adaptive surge control circuit connected in parallel with the surge decoupling power resistor; the adaptive surge control circuit includes: a first MOS tube, a voltage regulator tube and a triode.

[0034] The TVS tube is connected to the input end of the adaptive surge control circuit. When a surge overvoltage occurs, the TVS tube is first broken down, and a transient large current flows through the adaptive surge control circuit.

[0035] The surge decoupling power resistor (surge decoupling power resistor) is connected to the input end of the TVS tube to produce a large voltage drop in the surge current after the TVS tube is broken down;

[0036] The first MOS tube is connected to the input end of the TVS tube and is used to conduct the transient large current through the TVS tube;

[0037] The voltage regulator tube is connected in parallel with the first MOS tube. When the voltage drop on the MOS tube is greater than the breakdown voltage of the voltage regulator tube, the voltage regulator tube is broken down, triggering the conduction of the triode.

[0038] The triode is connected to the voltage regulator tube. When the voltage regulator tube is broken down, the triode is turned on, so that the GS voltage drop of the first MOS tube decreases, thereby turning off the first MOS tube.

[0039] When the sum of the clamping voltage at the TVS tube end and the voltage drop of the surge decoupling power resistor exceeds the minimum operating voltage of the varistor, the varistor operates, allowing large-energy transient interference to flow through the varistor.

[0040] Specifically, when a surge overvoltage occurs, the TVS tube has an extremely fast reaction speed and is broken down first. At this time, a transient large current will flow through the adaptive surge control circuit. Surge decoupling The surge decoupling power resistor is connected to the input end of the TVS tube. When the TVS tube is broken down, the surge current passing through the TVS tube will inevitably flow through the surge decoupling power resistor. Due to the characteristics of the resistor, a large voltage drop will be generated when the surge current passes through the surge decoupling power resistor. The first MOS tube is connected to the input end of the TVS tube, and its main function is to conduct the transient large current through the TVS tube.

[0041] The voltage regulator tube and the triode work together, and the voltage regulator tube is connected in parallel with the first MOS tube. When the voltage drop on the first MOS tube is greater than the breakdown voltage of the voltage regulator tube, the voltage regulator tube is broken down. The triode is connected to the voltage regulator tube. When the voltage regulator tube is broken down, the triode is turned on. Due to the conduction of the triode, the GS voltage drop of the first MOS tube decreases, so that the first MOS tube is turned off, which plays a role in limiting the further increase of the current.

[0042] The action of the varistor is to further protect the varistor in the circuit. When the sum of the clamping voltage at the TVS tube end and the voltage drop of the surge decoupling power resistor exceeds the minimum action voltage of the varistor, the varistor starts to act, and a large amount of transient interference will flow through the varistor, thereby protecting other components in the circuit from damage caused by surge overvoltage.

[0043] Based on the contents of the above embodiments, as an optional embodiment, in the power input surge protection and isolation device provided by the present invention, a first MOS tube is connected in parallel with the surge decoupling power resistor, wherein the first MOS tube is in an off state when powered on, and its on-resistance is large, and the gate of the first MOS tube is connected to at least one charging capacitor through at least one charging resistor, and the gate-source voltage Vgs of the first MOS tube is gradually increased by charging the charging capacitor, so that the on-resistance of the first MOS tube is gradually reduced from infinity to 0.

[0044] The MOS tube slow start specifically includes: the first MOS tube is connected in parallel with the surge decoupling power resistor. When powered on, the first MOS tube is in an off state, and its on-resistance is large. The gate of the first MOS tube is connected to at least one charging capacitor through at least one charging resistor. During the power-on process, the gate-source voltage Vgs of the first MOS tube is gradually increased by charging the charging capacitor. As the Vgs voltage rises, the on-resistance of the first MOS tube is gradually reduced from infinity to 0, thereby realizing the slow start function and avoiding the large current shock at the moment of power-on.

[0045] Based on the content of the above embodiment, as an optional embodiment, the power input surge protection and isolation device provided by the present invention further includes a DC / DC isolation module connected to the output end of the TVS tube. The DC / DC isolation module includes an isolation branch, and the isolation branch includes a high-frequency isolation transformer and a feedback optical coupler connected in series.

[0046] Among them, the electrical insulation index of this isolation branch is AC3000V-4000V, which can effectively prevent low-frequency electromagnetic disturbance below this insulation value at the power input end from coupling to the output end.

[0047] Furthermore, Figure 2 A schematic diagram of a power surge overvoltage isolation protection structure provided in an embodiment of the present application is shown in FIG. Figure 2 As shown in the figure, the electrical insulation index from the power output to the chassis ground PE in the DC / DC isolation module is AC1500V-3000V, which can prevent the low-frequency electromagnetic disturbance at the power input end that is lower than this withstand voltage value from being converted into electromagnetic interference.

[0048] By adopting, for example, high-frequency isolation transformers, optocouplers, creepage distances, electrical clearances, and insulating materials, the insulation withstand voltage strength of the switching power supply input and output, and the power supply input and chassis ground PE, i.e., the insulation withstand voltage strength, can be enhanced. This can make the insulation withstand voltage strength higher than the residual voltage after the protection device is activated, effectively controlling the transient overvoltage discharge path to avoid interference with sensitive circuits; or make the insulation withstand voltage strength higher than the transient overvoltage that is not sufficient to activate the surge protection circuit, cutting off the electromagnetic coupling path to avoid interference caused by transient overvoltage.

[0049] Increase the breakdown voltage of the protective device, that is, apply the insulation withstand voltage required for equipment testing between the power input terminal and the chassis ground PE, so that the protective device will not fail the withstand voltage test due to excessively high operating voltage (such as breakdown, spark discharge, etc.), and avoid disassembly / installation of the protective device due to the power withstand voltage test.

[0050] Frequent on-site operations can easily cause transient overvoltages to frequently cause protective devices to operate. Improving the breakdown voltage of protective devices can prevent damage to protective devices caused by high energy and low voltage. At the same time, reducing the number of protective device operations is conducive to extending the service life of surge protection circuits.

[0051] By increasing the insulation strength of the isolated switching power supply, the coupling path of such transient overvoltage electromagnetic disturbance to the switching power supply is cut off, preventing it from being converted into interference and damaging the switching power supply module and its subsequent load circuit. Therefore, the "insulation isolation strength + protection device" improved lightning surge protection solution of the present invention can not only provide effective surge protection for the isolated power supply, but also extend the service life of the surge protection circuit. In addition, it can also avoid the removal / installation of protection devices due to power withstand voltage testing.

[0052] Based on the content of the above embodiment, as an optional embodiment, the power input surge protection and isolation device provided by the present invention further includes a fuse, which is connected to one side of the output end of the adaptive surge control circuit, and is used to cut off the circuit when the circuit is overloaded to protect the circuit components. When the circuit is overloaded, the fuse can cut off the circuit in time, thereby protecting the various components in the circuit from damage by excessive current.

[0053] Based on the contents of the above embodiments, as an optional embodiment, in the power input surge protection and isolation device provided by the present invention, the first MOS tube is connected to at least one overcurrent detection setting resistor for detecting overcurrent conditions.

[0054] Specifically, the first MOS tube is connected to at least one overcurrent detection resistor for detecting overcurrent in the circuit. When overcurrent occurs in the circuit, the overcurrent detection resistor can detect this situation, providing a basis for subsequent protection measures.

[0055] Based on the content of the above embodiment, as an optional embodiment, the power input surge protection and isolation device provided by the present invention is also equipped with an anti-return circuit, whose output end is connected to the input end of the varistor. The anti-return circuit can ensure that the current can only flow in one direction, prevent the circuit from being damaged due to the wrong connection of the positive / negative poles of the power supply, and ensure the safety of the circuit when connected to the power supply.

[0056] Through the coordinated work of the above-mentioned components, the power input surge protection and isolation device can effectively realize surge protection, isolation protection and other related protection functions for the power input end, ensuring the safety and stability of power supply use.

[0057] Figure 3 The second schematic diagram of the structure of a power input surge protection and isolation device provided in an embodiment of the present application is as follows: Figure 3 As shown, the working principle of the above power input surge protection and isolation device is as follows:

[0058] The principle of the MOS tube slow start circuit mainly depends on the characteristics of the MOS tube and the design of the external circuit components to achieve the slow start of the power supply and avoid instantaneous large current impact or voltage mutation. As shown in the figure above: when powered on, the MOS tube Q15 is turned off (the on-resistance is large), and the input terminal voltage can only be charged to the downstream capacitor through the surge decoupling power resistor to suppress the surge start impact current when powered on. At the same time, the capacitor R854 is slowly charged through the resistor R852. The Vgs (fence voltage) voltage of the MOS tube Q15 gradually rises to its turn-on voltage, and the impedance of the MOS tube Q15 gradually decreases from infinity to 0. The voltage regulator D33 is connected to the relevant circuit of the first MOS tube. When the voltage drop on the first MOS tube is greater than the breakdown voltage of the voltage regulator D33, the voltage regulator D33 is broken down.

[0059] At the same time, an over-current detection setting resistor FR9 is set to detect over-current conditions.

[0060] When a surge overvoltage occurs, the TVS tube with the fastest reaction speed breaks down, and a large transient current flows through the power MOS tube Q15 (including the resistor FR9 used for current detection). When the voltage drop is greater than the breakdown voltage of the voltage regulator tube, the transistor Q1 is turned on, and the GS voltage drop of the MOS tube Q15 decreases, thereby shutting down. The surge current passing through the TVS tube can only pass through the surge decoupling power resistor R855 and produce a large voltage drop. The clamping voltage at the TVS end + the voltage drop of the power resistor eventually exceeds the action threshold (minimum action voltage) of the varistor RV4, and the varistor RV4 starts to act, and a large energy transient interference flows through the varistor RV4. When the surge overvoltage is low, the TVS tube can also act as a voltage regulator tube, and together with the power resistor, it forms a voltage stabilization circuit to power the subsequent load.

[0061] Furthermore, the present application also provides another power input surge protection and isolation system, such as Figure 4 As shown, Figure 4 A schematic diagram of the structure of a power input surge protection and isolation system provided in an embodiment of the present application. The power input surge protection and isolation system includes a varistor, a surge decoupling power resistor, a TVS tube, a filter circuit and a DC / DC isolation module connected in series, and an adaptive surge control circuit connected in parallel with the surge decoupling power resistor.

[0062] In summary, the present invention provides a more effective and stable power input surge protection and isolation device and system, which can enhance the surge protection effect of the isolated switching power supply, extend the service life of the surge protection circuit, avoid the disassembly / installation of protection components during power withstand voltage testing, and reduce maintenance costs. At the same time, it strengthens the suppression of differential mode surge overvoltage and power-on impact current, and better protects the switching power supply.

[0063] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0064] In addition, the terms "first", "second", etc. used in the embodiments of the present invention are only used for descriptive purposes and should not be understood as indicating or implying relative importance, or implicitly indicating the number of technical features indicated in the present embodiment. Therefore, the features defined by the terms "first", "second", etc. in the embodiments of the present invention can explicitly or implicitly indicate that the embodiment includes at least one of the features. In the description of the present invention, the word "multiple" means at least two or two or more, such as two, three, four, etc., unless otherwise clearly and specifically defined in the embodiments.

[0065] In the present invention, unless otherwise clearly specified or limited in the embodiments, the terms "installed", "connected", "connected" and "fixed" etc. in the embodiments should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integrated connection. It can be understood that it can also be a mechanical connection, an electrical connection, etc.; of course, it can also be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements, or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific implementation situation.

[0066] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A power input surge protection and isolation device, comprising a varistor, a surge decoupling power resistor and a TVS tube connected in series in sequence, and an adaptive surge control circuit connected in parallel with the surge decoupling power resistor; The TVS tube is connected to the input end of the adaptive surge control circuit. When a surge overvoltage occurs, the TVS tube is first broken down, and a transient large current flows through the adaptive surge control circuit. The surge decoupling power resistor is connected to the input end of the TVS tube, and is used to generate a large voltage drop in the surge current passing through the TVS tube after the TVS tube is broken down; The adaptive surge control circuit includes a first MOS tube, a voltage regulator tube and a triode. The first MOS tube is connected to the input end of the TVS tube and is used to conduct a transient large current through the TVS tube. The voltage regulator tube is connected in parallel with the first MOS tube. When the voltage drop on the MOS tube is greater than the breakdown voltage of the voltage regulator tube, the voltage regulator tube is broken down, triggering the conduction of the triode. The triode is connected to the voltage regulator tube. When the voltage regulator tube is broken down, the triode is turned on, so that the GS voltage drop of the first MOS tube decreases, thereby turning off the first MOS tube. When the sum of the clamping voltage at the TVS tube end and the voltage drop of the surge decoupling power resistor exceeds the minimum operating voltage of the varistor, the varistor operates, allowing large-energy transient interference to flow through the varistor, thereby achieving surge protection.

2. The power input surge protection and isolation device according to claim 1, characterized in that: The first MOS tube is connected in parallel with the surge decoupling power resistor, wherein the first MOS tube is in an off state when powered on, and its on-resistance is large, and the gate of the first MOS tube is connected to at least one charging capacitor through at least one charging resistor, and the gate-source voltage Vgs of the first MOS tube is gradually increased by charging the charging capacitor, so that the on-resistance of the first MOS tube is gradually reduced from infinity to 0.

3. The power input surge protection and isolation device according to claim 1, characterized in that: It also includes a DC / DC isolation module, the input end of the DC / DC isolation module is connected to the output end of the TVS tube, the DC / DC isolation module includes an isolation branch, and the isolation branch includes a high-frequency isolation transformer and a feedback optical coupler connected in series, wherein the electrical insulation index of the isolation branch is AC3000V-4000V.

4. The power input surge protection and isolation device according to claim 3, characterized in that: The electrical insulation index of the power output from the DC / DC isolation module to the casing ground PE is AC1500V-3000V.

5. The power input surge protection and isolation device according to claim 1, characterized in that: It also includes a fuse, which is connected to one side of the output end of the adaptive surge control circuit and is used to cut off the circuit when the circuit is overloaded to protect circuit components.

6. The power input surge protection and isolation device according to claim 1, characterized in that: The first MOS tube is connected to at least one overcurrent detection setting resistor for detecting overcurrent conditions.

7. The power input surge protection and isolation device according to claim 1, characterized in that: It also includes an anti-return circuit, the output end of which is connected to the input end of the varistor to ensure that current can only flow in from one direction to prevent damage caused by incorrect connection of the positive / negative poles of the power supply.

8. A power input surge protection and isolation system, characterized in that: It comprises a power input surge protection and isolation device as described in any one of claims 1 to 7.

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