Plug protection circuit and plug

Abstract

The utility model relates to the technical field of plug protection, and discloses a plug protection circuit and a plug, the plug protection circuit comprises a temperature monitoring circuit, a control chip and a switch switching circuit, the temperature monitoring circuit comprises a first thermistor, a first triode, a first resistor, a second resistor, a third resistor and a fourth resistor, one end of the first resistor is connected with a preset voltage source, and the other end of the first resistor is connected with a second triode; the other end of the first resistor is connected with one end of the second resistor and the base electrode of the first triode, the other end of the second resistor is connected with the grounding end, and the third resistor, the first thermistor and the fourth resistor are sequentially connected between a preset voltage source and the grounding end in series. A node between the first thermistor and the fourth resistor is connected with an emitting electrode of the first triode, through the temperature monitoring circuit, the control chip and the switch switching circuit, when the resistance value of the first thermistor changes to a resistance value corresponding to a temperature set value, a plug live wire and zero line loop can be disconnected, and then the temperature protection precision is improved.

Description

Technical Field

[0001] This utility model relates to the field of plug protection technology, and in particular to a plug protection circuit and a plug. Background Technology

[0002] Currently, in related leakage current plug technologies, the main method is to use a current transformer to detect the current difference between the live wire and the neutral wire, and quickly cut off the power supply when leakage occurs, so as to protect the safety of electrical appliances and users.

[0003] However, when there is poor contact between the plug and the socket or a short circuit occurs, the power plug will generate a lot of heat due to the current flowing through it, causing the temperature to rise. At this time, because the leakage current detection cannot identify the abnormality, the power will not be cut off in time, which may cause the plug to burn out, or even endanger the equipment or personal safety connected to the plug, causing fires and other situations, directly threatening the safety of electrical appliances and users.

[0004] In related technologies, a method is proposed to use a thermistor to detect temperature and directly drive a thyristor to control the plug circuit to disconnect. However, due to the significant differences in trigger current among different thyristors and the large influence of ambient temperature changes, the temperature protection accuracy is poor. Utility Model Content

[0005] In view of this, the present invention provides a plug protection circuit and a plug to solve or partially solve the technical problem of poor temperature protection accuracy in the prior art.

[0006] The technical solution proposed by this utility model is as follows:

[0007] In a first aspect, this utility model provides a plug protection circuit, comprising: a temperature monitoring circuit, including a first thermistor, a first transistor, a first resistor, a second resistor, a third resistor, and a fourth resistor; one end of the first resistor is connected to a preset voltage source; the other end of the first resistor is connected to one end of the second resistor and the base of the first transistor; the other end of the second resistor is connected to a ground terminal; the third resistor, the first thermistor, and the fourth resistor are connected in series between the preset voltage source and the ground terminal; the node between the first thermistor and the fourth resistor is connected to the emitter of the first transistor; a control chip, the input terminal of which is connected to the collector of the first transistor; and a switch switching circuit, the input terminal of which is connected to the output terminal of the control chip; when the control chip receives a current signal output from the collector of the first transistor, the control chip outputs an enable signal to the switch switching circuit, so as to control the disconnection of the current loop between the live wire and the neutral wire through the switch switching circuit.

[0008] This utility model's plug protection circuit utilizes a voltage divider between a first resistor and a second resistor to provide a reference voltage. Simultaneously, a third resistor, a first thermistor, and a fifth resistor also perform a voltage divider. When the plug temperature is low, the resistance of the first thermistor is high, and the emitter voltage of the first transistor is low. At this time, the emitter voltage of the first transistor is less than the base voltage, and the first transistor is cut off. When the temperature rises, the resistance of the first thermistor decreases, and the emitter voltage of the first transistor rises. When the temperature reaches a set value, the emitter voltage of the first diode is higher than the base voltage, generating a base current, and the first transistor conducts. At this time, the first transistor outputs a current signal to the control chip, and the control chip outputs an enable signal to the switching circuit. The circuit, composed of the first transistor, the first thermistor, the first resistor, the second resistor, the third resistor, and the fourth resistor, detects the temperature. When the resistance of the first thermistor changes to a value corresponding to a set temperature, the live and neutral wires of the plug are disconnected, thereby improving the accuracy of temperature protection and preventing the plug from burning out due to excessive temperature, or even endangering the connected equipment or personal safety.

[0009] Furthermore, the temperature monitoring circuit also includes a first diode, which is connected in series in the forward direction between the fourth resistor and the ground terminal.

[0010] In this method, since the emitter junction (from emitter to base) of the first transistor has a voltage drop of 0.5V-0.7V and is affected by changes in ambient temperature, the first diode is connected in series to increase the PN junction for temperature compensation, thereby reducing the impact of changes in ambient temperature on the protection temperature and ensuring the accuracy and consistency of the temperature protection of the first thermistor.

[0011] Furthermore, the temperature monitoring circuit also includes a first capacitor, one end of which is connected to the emitter of the first transistor, and the other end of which is connected to the ground terminal.

[0012] In this method, because the first thermistor needs to detect the temperature of the power supply connector, the wire will be very long, which will introduce interference signals. By setting the first capacitor, the current can be filtered, and the circuit's anti-interference ability can be improved.

[0013] Furthermore, the temperature monitoring circuit also includes a second thermistor, a second transistor, a fifth resistor, and a sixth resistor. The fifth resistor, the second thermistor, and the sixth resistor are connected in series between a preset voltage source and a ground terminal. The node between the first thermistor and the sixth resistor is connected to the emitter of the second transistor. The node between the first resistor and the second resistor is connected to the base of the second transistor. The collector of the second transistor is connected to the input terminal of the control chip.

[0014] In this method, the plug temperature can be monitored through two detection circuits via a second thermistor and the corresponding circuit, thereby improving the reliability of monitoring.

[0015] Furthermore, the temperature monitoring circuit also includes a second diode, which is connected in series in the forward direction between the sixth resistor and the ground terminal.

[0016] In this method, since the emitter junction (from emitter to base) of the second transistor has a voltage drop of 0.5V-0.7V and is affected by changes in ambient temperature, a second diode is connected in series to increase the PN junction for temperature compensation, thereby reducing the impact of changes in ambient temperature on the protection temperature and ensuring the accuracy and consistency of the temperature protection of the first thermistor.

[0017] Furthermore, the temperature monitoring circuit also includes a second capacitor, one end of which is connected to the emitter of the second transistor, and the other end of which is connected to the ground terminal.

[0018] In this method, because the second thermistor needs to detect the temperature of the power supply connector, the wire will be very long, which will introduce interference signals. By setting a second capacitor, the current can be filtered, improving the circuit's anti-interference capability.

[0019] Furthermore, the switching circuit includes a drive unit, a solenoid, and a step-down power supply. A switching mechanism is provided on the neutral and / or live wires of the plug. The input terminal of the drive unit is connected to the output terminal of the control chip, and the output terminal of the drive unit is connected to the solenoid. The input terminal of the step-down power supply is connected to both the live and neutral wires, and the output terminal of the step-down power supply is connected to the solenoid. The step-down power supply is used to convert the voltage between the live and neutral wires into the working voltage of the solenoid. When the drive unit receives an enable signal, it controls the switching mechanism to open through the solenoid.

[0020] In this method, the switching mechanism is controlled by a drive unit, a spiral tube, and a step-down power supply to automatically disconnect the current loops of the live wire and the neutral wire.

[0021] Furthermore, the driving unit includes a thyristor, the spiral tube includes an iron core and a coil wound around the iron core, the control terminal of the thyristor is connected to the output terminal of the control chip, the two output terminals of the thyristor are respectively connected to the two ends of the coil, and the two ends of the coil are also respectively connected to the positive output terminal and the negative output terminal of the step-down power supply.

[0022] In this approach, the use of thyristors and solenoids enables precise control of the switching mechanism, resulting in fast response and low cost.

[0023] Furthermore, the control chip uses a leakage current chip, and the plug protection circuit also includes a current transformer. The current transformer is installed on the live wire and the neutral wire to detect the leakage current between the live wire and the neutral wire. The output terminal of the current transformer is connected to the input terminal of the leakage current chip. When there is a leakage current between the live wire and the neutral wire, the output terminal of the current transformer outputs a leakage current signal to the leakage current chip. The leakage current chip outputs an enable signal to the switch switching circuit, so as to control the current loop of the live wire and the neutral wire to disconnect through the switch switching circuit.

[0024] In this method, by adding a leakage current chip and a current transformer, the plug protection circuit can not only monitor overheating, but also detect leakage current, preventing electric shock accidents and fires caused by leakage, and providing more comprehensive protection.

[0025] Secondly, this utility model provides a plug, including a plug protection circuit as described in any of the first aspects. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of this utility model, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a circuit block diagram of the plug protection circuit according to an embodiment of the present utility model;

[0028] Figure 2 This is a circuit diagram of a temperature monitoring circuit according to an embodiment of the present invention;

[0029] Figure 3 This is a circuit diagram of another temperature monitoring circuit according to an embodiment of the present invention.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1-Temperature monitoring circuit; 2-Control chip; 3-Switch circuit; R1-First resistor; R2-Second resistor; R3-Third resistor; R4-Fourth resistor; R5-Fifth resistor; R6-Sixth resistor; NTC1-First thermistor; NTC2-Second thermistor; D1-First diode; D2-Second diode; Q1-First transistor; Q2-Second transistor; C1-First capacitor; C2-Second capacitor. Detailed Implementation

[0032] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0033] In the description of this utility model, it should be noted that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0035] Furthermore, the technical features involved in the different embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.

[0036] In leakage current plug technology, the main method is to detect the current difference between the live wire and the neutral wire using a current transformer. In the event of a leakage, the power supply is quickly cut off to protect the appliance and the user. However, if the leakage current plug experiences poor contact leading to high temperatures, it may burn out the plug or even endanger the connected equipment or personal safety. Therefore, this invention provides a plug protection circuit that uses a thermistor to detect abnormal high temperatures, causing the leakage current plug to trip in time, thus providing protection.

[0037] like Figure 1 and Figure 2 As shown, the plug protection circuit of this utility model embodiment includes:

[0038] Temperature monitoring circuit 1 includes a first thermistor NTC1, a first transistor Q1, a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4. One end of the first resistor R1 is connected to a preset voltage source, and the other end of the first resistor R1 is connected to one end of the second resistor R2 and the base of the first transistor Q1. The other end of the second resistor R2 is connected to a ground terminal. The third resistor R3, the first thermistor NTC1, and the fourth resistor R4 are connected in series between the preset voltage source and the ground terminal. The node between the first thermistor NTC1 and the fourth resistor R4 is connected to the emitter of the first transistor Q1.

[0039] The input terminal of control chip 2 is connected to the collector of the first transistor Q1;

[0040] The input terminal of the switching circuit is connected to the output terminal of the control chip 2. When the control chip 2 receives the current signal output from the collector of the first transistor Q1, the control chip 2 outputs an enable signal to the switching circuit so as to control the disconnection of the current loop between the live wire and the neutral wire through the switching circuit.

[0041] Specifically, the first thermistor NTC1 is a negative temperature coefficient thermistor (NTC), whose resistance decreases as temperature increases. The setting value of the first thermistor NTC1 is located inside the plug to monitor the temperature of the power connector.

[0042] The first transistor, Q1, is a PNP type transistor.

[0043] The first resistor R1 and the second resistor R2 form a voltage divider circuit, which can set the midpoint voltage of the first resistor R1 and the second resistor R2 as the reference voltage and connect it to the base of the first transistor Q1.

[0044] The third resistor R3, the first thermistor NTC1, and the fourth resistor R4 also form a voltage divider circuit. The third resistor R3 and the first thermistor NTC1 form the upper voltage divider, and the fourth resistor R4 forms the lower voltage divider. The node between the first thermistor NTC1 and the fourth resistor R4 is connected to the emitter of the first transistor Q1. By comparing the emitter junction (emitter to base) of the first transistor Q1 with the reference voltage, when the first thermistor NTC1 detects a lower temperature, its resistance is higher, and the emitter voltage of the first transistor Q1 is lower than its base voltage, so the first transistor Q1 is cut off. When the temperature reaches the set temperature value, the emitter voltage of the first transistor Q1 increases, and the first transistor Q1 generates a base current, turning on the first transistor Q1. At the same time, the first transistor Q1 outputs a current signal to the IC pin of the control chip 2. The input impedance of the IC pin is very high, and a small current is required to raise the voltage, which the control chip 2 recognizes and generates an enable signal to trigger the switching circuit to produce a protection action.

[0045] A preset voltage source is a voltage source with a lower voltage value obtained by converting mains power. For example, the voltage value of the preset voltage source can be 5V, 10V, 12V, etc.

[0046] The control chip 2 can be of models including LT6973S, FM2147, and SMC5147. When the control chip 2 receives the current signal output from the collector of the first transistor Q1, it outputs an enable signal through its output pin.

[0047] The function of a switching circuit is to cut off the current loop between the live wire and the neutral wire when an enable signal is received. This can be achieved using devices such as relays or electromagnetic switches. Specifically, a switch can be installed on either the live wire or the neutral wire to cut off the current loop. Alternatively, two switches can be installed on the live wire and the neutral wire respectively, allowing both wires to be cut off simultaneously.

[0048] This utility model discloses a plug protection circuit that utilizes a voltage divider between a first resistor R1 and a second resistor R2 to provide a reference voltage. Simultaneously, a third resistor R3, a first thermistor NTC1, and a fifth resistor R5 also perform a voltage divider. When the plug temperature is low, the resistance of the first thermistor NTC1 is high, and the emitter voltage of the first transistor Q1 is low. At this time, the emitter voltage of the first transistor Q1 is less than its base voltage, and the first transistor Q1 is cut off. As the temperature rises, the resistance of the first thermistor NTC1 decreases, and the emitter voltage of the first transistor Q1 rises. When the temperature reaches a set value, the emitter voltage of the first diode D1... When the voltage is higher than the base voltage, a base current is generated, and the first transistor Q1 conducts. At this time, the first transistor Q1 outputs a current signal to the control chip 2. The control chip 2 outputs an enable signal to the switching circuit. The circuit composed of the first transistor Q1, the first thermistor NTC1, the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 detects the temperature. When the resistance of the first thermistor NTC1 changes to the resistance value corresponding to a temperature set value, the live wire and neutral wire circuit of the plug can be disconnected, thereby improving the temperature protection accuracy and preventing the plug from burning out when the temperature is too high, or even endangering the equipment or personal safety connected to the plug.

[0049] In some embodiments, the temperature monitoring circuit 1 further includes a first diode D1, which is connected in series in the forward direction between the fourth resistor R4 and the ground terminal.

[0050] Specifically, the positive terminal of the first diode D1 is connected to the low-voltage side of the fourth resistor R4, and the negative terminal of the first diode D1 is connected to the ground terminal. The low-voltage side refers to the terminal with a relatively low voltage when there is current in the circuit.

[0051] Because the emitter junction (from emitter to base) of the first transistor Q1 has a voltage drop of 0.5V-0.7V and is affected by changes in ambient temperature, the temperature compensation of the emitter junction of the first transistor Q1 can be achieved by connecting the first diode D1 in series to increase the PN junction. This can reduce the impact of changes in ambient temperature on the protection temperature and ensure the accuracy and consistency of the temperature protection of the first thermistor NTC1.

[0052] Furthermore, the temperature monitoring circuit 1 also includes a first capacitor C1, one end of which is connected to the emitter of the first transistor Q1, and the other end of which is connected to the ground terminal.

[0053] The main function of the first capacitor C1 is to filter the current. Because the first thermistor NTC1 needs to detect the temperature of the power supply connector, the wire will be very long, which will introduce interference signals. By setting the first capacitor C1, the current can be filtered, improving the circuit's anti-interference ability.

[0054] In some embodiments, the temperature monitoring circuit 1 further includes a second thermistor NTC2, a second transistor Q2, a fifth resistor R5, and a sixth resistor R6. The fifth resistor R5, the second thermistor NTC2, and the sixth resistor R6 are connected in series between a preset voltage source and a ground terminal. The node between the first thermistor NTC1 and the sixth resistor R6 is connected to the emitter of the second transistor Q2. The node between the first resistor R1 and the second resistor R2 is connected to the base of the second transistor Q2. The collector of the second transistor Q2 is connected to the input terminal of the control chip 2.

[0055] Specifically, the base of the second transistor Q2 and the base of the first transistor are connected together to the midpoint between the first resistor R1 and the second resistor R2. A second thermistor NTC2, a fifth resistor R5, and a sixth resistor R6 are added to form a voltage divider circuit, creating two temperature detection loops. This allows the plug temperature to be monitored through two detection circuits, improving monitoring reliability.

[0056] Furthermore, the temperature monitoring circuit 1 also includes a second diode D2, which is connected in series in the forward direction between the sixth resistor R6 and the ground terminal.

[0057] Because the emitter junction (from emitter to base) of the second transistor Q2 has a voltage drop of 0.5V-0.7V and is affected by changes in ambient temperature, a second diode D2 is connected in series to increase the PN junction for temperature compensation. This reduces the impact of ambient temperature changes on the protection temperature and ensures the accuracy and consistency of the thermistor's temperature protection.

[0058] In a preferred embodiment, to reduce the number of diodes used in the circuit, the second diode D2 and the first diode D1 can also be the same diode, such as... Figure 3 As shown, the positive terminal of the first diode D1 is connected to both the fourth resistor R4 and the sixth resistor R6, while the negative terminal of the first diode D1 is grounded.

[0059] Furthermore, the temperature monitoring circuit 1 also includes a second capacitor C2, one end of which is connected to the emitter of the second transistor Q2, and the other end of which is connected to the ground terminal.

[0060] Specifically, because the second thermistor NTC2 needs to detect the temperature of the power supply connector, the wire will be very long, which will introduce interference signals. By setting the second capacitor C2, the current can be filtered to improve the circuit's anti-interference capability.

[0061] In some embodiments, the switching circuit includes a drive unit, a solenoid, and a step-down power supply. A switching mechanism is provided on the neutral and / or live wires of the plug. The input terminal of the drive unit is connected to the output terminal of the control chip 2, and the output terminal of the drive unit is connected to the solenoid. The input terminal of the step-down power supply is connected to the live wire and the neutral wire respectively, and the output terminal of the step-down power supply is connected to the solenoid. The step-down power supply is used to convert the voltage between the live wire and the neutral wire into the working voltage of the solenoid. When the drive unit receives an enable signal, it controls the switching mechanism to open through the solenoid.

[0062] The switching mechanism is controlled by a drive unit, a spiral tube, and a step-down power supply to automatically disconnect the current loops of the live wire and the neutral wire.

[0063] Specifically, the driving unit includes a thyristor, the spiral tube includes an iron core and a coil wound around the iron core, the control terminal of the thyristor is connected to the output terminal of the control chip 2, the two output terminals of the thyristor are respectively connected to the two ends of the coil, and the two ends of the coil are also respectively connected to the positive output terminal and the negative output terminal of the step-down power supply.

[0064] The switching mechanism is a normally open switch. When the thyristor receives the enable signal, its two output terminals are turned on. At this time, the coil is short-circuited, so the solenoid is de-energized. At this time, the switching mechanism on the neutral wire and / or the live wire is disconnected, that is, the circuit between the neutral wire and the live wire is broken.

[0065] In this embodiment of the invention, precise control of the switching mechanism can be achieved by using a thyristor and a solenoid, resulting in fast response and low cost.

[0066] In some embodiments, the control chip 2 is a leakage current chip, and the plug protection circuit also includes a current transformer. The current transformer is installed on the live wire and the neutral wire to detect the leakage current between the live wire and the neutral wire. The output terminal of the current transformer is connected to the input terminal of the leakage current chip. When there is a leakage current between the live wire and the neutral wire, the output terminal of the current transformer outputs a leakage current signal to the leakage current chip. The leakage current chip outputs an enable signal to the switch switching circuit to control the current loop of the live wire and the neutral wire to disconnect through the switch switching circuit.

[0067] The leakage current chips used include the LT6973S, FM2147 and SMC5147. The leakage current chips have multiple input terminals and can input different signals.

[0068] When no leakage occurs, the current in the live wire and the neutral wire is the same because they form a closed loop. However, when leakage occurs, the current in the live wire and the neutral wire will differ. Therefore, the difference in current between the live wire and the neutral wire is detected by a current transformer. When the leakage current collected by the current transformer is detected, the power supply is quickly cut off to protect the safety of the appliance and the user. This makes the plug protection circuit of this utility model have both temperature protection and leakage protection functions, providing more comprehensive protection.

[0069] This utility model also provides a plug, including the plug protection circuit as described in any of the above embodiments.

[0070] Although the exemplary embodiments and their advantages have been described in detail, those skilled in the art can make various changes, substitutions and modifications to these embodiments without departing from the spirit and scope of protection of this utility model, and such modifications and variations all fall within the scope defined by the present invention.

Claims

1. A plug protection circuit, characterized in that, include: A temperature monitoring circuit includes a first thermistor, a first transistor, a first resistor, a second resistor, a third resistor, and a fourth resistor. One end of the first resistor is connected to a preset voltage source, and the other end of the first resistor is connected to one end of the second resistor and the base of the first transistor. The other end of the second resistor is connected to a ground terminal. The third resistor, the first thermistor, and the fourth resistor are connected in series between the preset voltage source and the ground terminal. The node between the first thermistor and the fourth resistor is connected to the emitter of the first transistor. The control chip's input terminal is connected to the collector of the first transistor; The switching circuit has its input terminal connected to the output terminal of the control chip. When the control chip receives the current signal output from the collector of the first transistor, the control chip outputs an enable signal to the switching circuit to control the disconnection of the current loop between the live wire and the neutral wire through the switching circuit.

2. The plug protection circuit according to claim 1, characterized in that, The temperature monitoring circuit also includes a first diode, which is connected in series in the forward direction between the fourth resistor and the ground terminal.

3. The plug protection circuit according to claim 1, characterized in that, The temperature monitoring circuit also includes a first capacitor, one end of which is connected to the emitter of the first transistor, and the other end of which is connected to the ground terminal.

4. The plug protection circuit according to claim 1, characterized in that, The temperature monitoring circuit further includes a second thermistor, a second transistor, a fifth resistor, and a sixth resistor. The fifth resistor, the second thermistor, and the sixth resistor are connected in series between the preset voltage source and the ground terminal. The node between the first thermistor and the sixth resistor is connected to the emitter of the second transistor. The node between the first resistor and the second resistor is connected to the base of the second transistor. The collector of the second transistor is connected to the input terminal of the control chip.

5. The plug protection circuit according to claim 4, characterized in that, The temperature monitoring circuit also includes a second diode, which is connected in series in the forward direction between the sixth resistor and the ground terminal.

6. The plug protection circuit according to claim 4, characterized in that, The temperature monitoring circuit also includes a second capacitor, one end of which is connected to the emitter of the second transistor, and the other end of which is connected to the ground terminal.

7. The plug protection circuit according to claim 1, characterized in that, The switching circuit includes a drive unit, a spiral tube, and a step-down power supply. A switching mechanism is provided on the neutral and / or live wires of the plug. The input terminal of the drive unit is connected to the output terminal of the control chip, and the output terminal of the drive unit is connected to the spiral tube. The input terminal of the step-down power supply is connected to both the live and neutral wires, and the output terminal of the step-down power supply is connected to the spiral tube. The step-down power supply is used to convert the voltage between the live and neutral wires into the operating voltage of the spiral tube. When the drive unit receives the enable signal, it controls the switching mechanism to open through the spiral tube.

8. The plug protection circuit according to claim 7, characterized in that, The driving unit includes a thyristor, and the spiral tube includes an iron core and a coil wound around the iron core. The control terminal of the thyristor is connected to the output terminal of the control chip. The two output terminals of the thyristor are respectively connected to the two ends of the coil. The two ends of the coil are also respectively connected to the positive and negative output terminals of the step-down power supply.

9. The plug protection circuit according to claim 1, characterized in that, The control chip uses a leakage current chip, and the plug protection circuit also includes a current transformer. The current transformer is installed on the live wire and the neutral wire to detect the leakage current between the live wire and the neutral wire. The output terminal of the current transformer is connected to the input terminal of the leakage current chip. When there is a leakage current between the live wire and the neutral wire, the output terminal of the current transformer outputs a leakage current signal to the leakage current chip. The leakage current chip outputs an enable signal to the switch switching circuit to control the current loop of the live wire and the neutral wire to disconnect through the switch switching circuit.

10. A plug, characterized in that, Includes the plug protection circuit as described in any one of claims 1 to 9.

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