Protection device for misconnection of protection ground wire of single-phase alternating-current input charger with power supply live wire

Abstract

The embodiment of the invention provides a protection device for misconnection of a protection ground wire of a single-phase alternating-current input charger with a power supply live wire, and belongs to the technical field of electrical safety protection. A protection device for misconnection of a single-phase alternating current input charger protection ground wire with a power supply live wire comprises a current detection circuit, a relay, a main control unit circuit, a relay control circuit, a safety Y capacitor and a charger metal shell. The current detection circuit is used for detecting current in an input protection ground wire, and the relay is used for controlling connection and disconnection between the charger metal shell and the input protection ground wire so as to prevent the charger shell from being electrified due to the fact that the protection ground wire is connected with a live wire by mistake. According to the scheme, disconnection and isolation between the charger shell and the alternating-current input live wire, the input zero line and the input protection ground are achieved; the control is simple, the safety of a user and the reliability of surrounding related power distribution equipment are improved to a great extent, and the increased cost is little.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical safety protection, and in particular to a protection device for preventing a protective ground wire of a single-phase AC input charger from being mistakenly connected to a live power wire. Background Art

[0002] At present, for chargers with single-phase AC input in the industry, when the charger casing is a metal casing, the metal plastic casing is usually directly connected to the input protection ground. It is more common that when the input protection ground wire of the charger is mistakenly connected to the power supply live wire, the charger casing will be directly connected to the live wire and carry high voltage electricity. In this case, it is easy to bring the risk of electric shock to the operator. If it is a vehicle-mounted charger, the charger casing is fixed to the metal frame of the engineering vehicle by screws. In this case, the connection of the metal plastic frame to the live wire may cause damage or destruction to other low-voltage power supply control devices on the vehicle. Summary of the invention

[0003] The purpose of the embodiments of the present invention is to provide a protection device for a single-phase AC input charger when the protective ground wire is mistakenly connected to the power supply live wire, so as to at least solve the above-mentioned problem.

[0004] In order to achieve the above-mentioned objectives, the first aspect of the present invention provides a protection device for a single-phase AC input charger whose protective ground wire is mistakenly connected to a power supply live wire. The device comprises: a current detection circuit, a relay, a main control unit circuit, a relay control circuit, a safety Y capacitor and a metal casing of the charger; the current detection circuit is used to detect the current in the input protective ground wire, and the relay is used to control the connection and disconnection between the metal casing of the charger and the input protective ground wire to prevent the charger casing from being energized due to the protective ground wire being mistakenly connected to the live wire.

[0005] Optionally, the relay is a normally open relay, which is connected in series with the input protective ground wire. When it is detected that the protective ground wire is mistakenly connected to the power supply live wire, the relay remains in a disconnected state to prevent the charger housing from being connected to the live wire; the relay is energized after confirming that the input protective ground wire is correctly connected, allowing the charger to enter a normal working state.

[0006] Optionally, the current detection circuit includes a current sensor; one end of the current sensor is connected to the input protection ground wire, and the other end is connected to a contact of the relay; the current detection circuit outputs the detected current signal to the main control unit circuit to determine whether the connection status of the input ground wire is correct.

[0007] Optionally, the main control unit circuit is connected to the current detection circuit to receive the output signal of the current detection circuit and perform calculations on it; when the main control unit circuit determines that the current flowing through the input protective ground wire exceeds a preset safety threshold, it outputs a control signal to the relay control circuit to disconnect the relay, thereby preventing the charger housing and the input protective ground wire from being accidentally connected to the power supply live wire.

[0008] Optionally, the relay control circuit is connected to the relay and the main control unit circuit, and the relay control circuit controls the closing or opening of the relay according to a control signal output by the main control unit circuit.

[0009] Optionally, the safety Y capacitor is arranged between the metal casing of the charger and the input live wire and neutral wire, namely, the safety Y capacitor C2 between the metal casing of the charger and the live wire and the safety Y capacitor C1 between the metal casing and the neutral wire, for safety isolation of the input protection ground. The capacity of the safety Y capacitor is designed based on the leakage current limiting requirements of the input protection ground.

[0010] Optionally, the current detection circuit includes a Hall current sensor, which has an input end and an output end, the input end is connected to the input protection ground wire, and the output end is connected to the main control unit circuit, for detecting the current in the input protection ground wire and outputting a current signal corresponding to the detected current value.

[0011] Optionally, when the input protective ground wire is connected correctly and the AC input voltage is normal, the relay control circuit provides a closure signal to the relay, causing the normally open relay to closure, thereby achieving normal connectivity between the charger metal casing and the input protective ground wire, ensuring the normal working state of the charger, and the relay always remains closure under normal connectivity conditions.

[0012] Optionally, when the input protective ground wire is mistakenly connected to the live wire of the power supply, the input live wire and neutral wire of the charger will be connected to the neutral wire and protective ground wire of the input power supply, the auxiliary power supply inside the charger cannot be started normally, and the relay remains disconnected to ensure that the charger casing is not energized.

[0013] Optionally, the control circuit of the protection device includes a leakage current control module, which is used to limit the leakage current of the input protection ground line to no more than 3.5 mA when the AC input is 465VAC / 50Hz.

[0014] Through the above technical scheme, by connecting a current detection circuit and a normally open relay in series on the protective ground wire inside the charger and effectively controlling the relay, protection is achieved when the input protective ground wire of the charger is mistakenly connected to the power supply live wire, ensuring the isolation and safety of the metal casing of the charger and the power supply live wire. For example, the on-board charger also ensures the safety of other low-voltage power supply control devices on the vehicle; by detecting the current in the protective ground wire, the relay is disconnected in time when the current in the protective ground wire is abnormal, thereby achieving disconnection and isolation between the charger casing and the AC input live wire, input neutral wire and input protective ground; fewer components are added, the control is simpler, and the safety of users and the reliability of surrounding related power distribution equipment are greatly improved, with very little additional cost.

[0015] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings:

[0017] Figure 1 It is a principle block diagram of a protection device for a single-phase AC input charger that protects the ground wire from being mistakenly connected to the live wire of the power supply, provided in one embodiment of the present invention;

[0018] Figure 2 A corresponding embodiment of the present invention provides Figure 1 A circuit diagram of a protection device for protecting a single-phase AC input charger from misconnection of the ground wire to the live wire of the power supply;

[0019] Figure 3 It is a principle block diagram of another protection device for a single-phase AC input charger that protects the ground wire from being mistakenly connected to the live wire of the power supply, provided in one embodiment of the present invention;

[0020] Figure 4 A corresponding embodiment of the present invention provides Figure 3 A circuit diagram of another protection device for protecting a single-phase AC input charger from misconnecting the ground wire to the live wire of the power supply. DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0022] Figure 1 This is a block diagram of a protection device for protecting a single-phase AC input charger from misconnection of the ground wire to the live wire of the power supply, provided in one embodiment of the present invention. Figure 1As shown, an embodiment of the present invention provides a protection device for a single-phase AC input charger when the protective ground wire is mistakenly connected to the live power line. The device includes: a current detection circuit, a relay, a main control unit circuit, a relay control circuit, a safety Y capacitor and a metal casing of the charger; the current detection circuit is used to detect the current in the input protective ground wire, and the relay is used to control the connection and disconnection between the metal casing of the charger and the input protective ground wire to prevent the charger casing from being energized due to the protective ground wire being mistakenly connected to the live power line.

[0023] Specifically, it includes: current detection circuit, relay, main control unit circuit, relay control circuit, safety Y capacitor between input live wire and neutral wire to protection ground, metal shell of charger, other filtering, rectification, PFC, auxiliary power supply, DCDC power conversion processing circuit, etc. Vin_L signal is live wire input, Vin_N signal is neutral wire input, Vin_PE signal is input protection ground, CASE_PE signal is charger shell ground, and CASE_PE signal is connected to charger metal shell.

[0024] Furthermore, the current detection circuit is used to detect the current flowing through the protective ground wire. One end of the current detection circuit is connected to Vin_PE, and the other end of the current detection circuit is connected to a contact of a relay. The output signal of the current detection circuit meets the safety isolation requirements between the protective grounds. The output signal of the current detection circuit is sent to the main control unit circuit, and the other contact of the relay is connected to the casing ground CASE_PE.

[0025] Furthermore, the relay is a normally open relay, which is used to connect and disconnect the charger housing grounding with the input protective grounding wire.

[0026] Furthermore, the main control unit circuit performs calculation and judgment processing on the output signal of the current detection circuit transmitted, and the main control unit circuit outputs a control signal to the relay control circuit. When the main control unit circuit determines that the current signal is too large, the main control unit circuit outputs a control signal to disconnect the relay to the relay control circuit;

[0027] Furthermore, the relay control circuit controls the closing or opening of the relay connected in series to the protective ground wire according to the relay control signal output by the main control unit circuit.

[0028] Furthermore, a total equivalent safety Y capacitor C2 is connected between the chassis ground CASE_PE and the live line input Vin_L, and a total equivalent safety Y capacitor C1 is connected between the chassis ground CASE_PE and the neutral line input Vin_N.

[0029] Furthermore, the live line input Vin_L and the neutral line input Vin_N are processed by other filtering, rectification, auxiliary power supply, PFC, DCDC power conversion and other circuits for power conversion to realize the relevant functions of the charger.

[0030] Furthermore, since the protection ground wire is not a fixed connection method, in order to better achieve fault isolation and improve safety performance, it is necessary to ensure that the AC input part has a safety Y capacitor for the protection ground wire ( Figure 2 The safety Y capacitors C1 and C2 shown in the figure, C1 and C2 are the total equivalent capacitance of the charger input Vin_N and Vin_L lines to Vin_PE respectively. The total capacity should not be too large. It is best that the leakage current to ground is less than 3.5mA at AC 465VAC / 50HZ to ensure the safety of leakage current to people.

[0031] Further, the control and protection principle of the present invention is described as follows:

[0032] When the input protection ground wiring of the charger is connected correctly and the AC input voltage is normal, the internal auxiliary power supply of the charger will start normally, and the relay control short circuit, current detection circuit and main control unit circuit will be powered normally. When the current detection circuit detects that the current flowing through the protection ground wire is within the normal range, the main control unit circuit will give a control signal of attracting the relay to the relay control circuit, thereby attracting the relay and connecting the casing protection ground CASE_PE with the power supply protection ground Vin_PE. When the current detection circuit detects that the current flowing through the protection ground wire is abnormally large, the main control unit circuit quickly gives a control signal of disconnecting the relay to the relay control circuit, thereby quickly disconnecting the relay.

[0033] When the charger's input protection ground connection is connected to the power supply live wire, the charger's original input live wire and neutral wire must be connected to the input power supply neutral wire and protection ground wire, so there is no actual input voltage between the charger's original input live wire L and neutral wire N, and there is no AC input inside the charger, and the auxiliary power supply cannot start and work normally. Therefore, the control circuit of the relay cannot work normally due to the lack of normal power supply, and the relay continues to maintain the disconnected state. Therefore, the protection ground and casing inside the charger remain disconnected from the power supply live wire. In this case, it is ensured that the charger casing is not charged, and it will not cause abnormal damage to the internal circuit of the charger; after the power input line is reconnected correctly, the charger can work normally.

[0034] Furthermore, since the protection ground wire is not a fixed connection method, in order to better achieve fault isolation and improve safety performance, it is necessary to ensure that the safety Y capacitor capacity of the AC input part to the protection ground wire is not too large. It is best to have a ground leakage current less than 3.5mA when the AC input is 465VAC / 50HZ, that is, it is required that all safety Y capacitors of the AC input to the protection ground ( Figure 2The C1 and C2 shown in the figure are safety Y capacitors. C1 and C2 are the total equivalent capacitance of the charger input Vin_N and Vin_L lines to the chassis protection ground CASE_PE, that is, the total capacity should not exceed 24nF to ensure that the leakage current safety requirements for the protection ground are met when the AC input is 465VAC / 50HZ.

[0035] Furthermore, the live line input Vin_L and the neutral line input Vin_N are processed by other filtering, rectification, PFC, DCDC power conversion and detection control processing circuits to realize the relevant functions of the charger.

[0036] Other filtering, rectification, PFC, auxiliary power supply, DCDC power conversion processing and other circuits and main control unit circuits involved in the solution of the present invention belong to the more conventional power conversion technology and detection operation control technology in the industry and will not be elaborated here.

[0037] Embodiment 1:

[0038] like Figure 4 The circuit as a whole includes current detection circuit, relay, main control unit circuit, relay control circuit, safety Y capacitor between input live wire and neutral wire to protective ground, metal casing of charger, other filtering, rectification, PFC, auxiliary power supply, DCDC power conversion processing and other circuits.

[0039] Specifically, Vin_L signal is live wire input, Vin_N signal is neutral wire input, Vin_PE signal is input protection grounding, CASE_PE signal is charger housing grounding, and CASE_PE signal is connected to the charger housing;

[0040] Specifically, a total equivalent safety Y capacitor C2 is connected between the chassis ground CASE_PE and the live line input Vin_L, and a total equivalent safety Y capacitor C1 is connected between the chassis ground CASE_PE and the neutral line input Vin_N;

[0041] Specifically, the live line input Vin_L and the neutral line input Vin_N are processed by other filtering, rectification, auxiliary power supply, PFC, DCDC power conversion and other circuits to realize the relevant functions of the charger;

[0042] Specifically, the AC input is used as the input of the auxiliary power output after filtering, rectification or pre-stabilization, and the output of the auxiliary power output is used as the power supply for the relay control circuit and the main control unit circuit;

[0043] Specifically, the 3rd and 4th pins of the Hall current sensor D1 are connected to the input protection ground Vin_PE, the 1st and 2nd pins of the Hall current sensor D1 are connected to a contact of the normally open relay K1, the other contact of the normally open relay K1 is connected to the chassis ground CASE_PE, the 5th pin of the Hall current sensor D1 is connected to the working ground GNDS_A, the 6th pin of the Hall current sensor D1 is connected to one end of the capacitor C5 to generate a current reference signal VREF_ISE, the 7th pin of the Hall current sensor D1 is connected to one end of the capacitor C6 to generate a current signal ISE2_DSC, the other end of the capacitor C5 and the other end of the capacitor C6 are connected to the working ground GNDS_A, the current reference signal VREF_ISE and the current signal ISE2_DSC are sent to the main control unit circuit, and the main control unit circuit outputs the control signal K1_DRV of the normally open relay K1;

[0044] Specifically, one end of the control coil of the normally open relay K1 is connected to the anode of the diode VD1 and the collector of the NPN transistor VT1, the other end of the control coil of the normally open relay K1 is connected to the cathode of the diode VD1 and the positive end VCC of the power supply, the base of the NPN transistor VT1 is connected to one end of the resistor R1, one end of the resistor R2 and one end of the capacitor C3, the other end of the resistor R2, the other end of the capacitor C3 and the emitter of the NPN transistor VT1 are connected to the working ground GND_D, the other end of the resistor R1 is connected to the normally open relay control signal K1_DRV, the working ground GND_A and the working ground GND_D are respectively the analog ground and the digital ground short-circuited in the main control unit circuit.

[0045] The principle of this embodiment is specifically described as follows:

[0046] When the charger's input protective ground wiring is connected correctly and the AC input voltage is normal, the auxiliary power supply will start normally, the relay control short circuit, the current detection circuit and the main control unit circuit are powered normally, the Hall current sensor in the current detection circuit detects the protective ground current, and outputs the current reference signal VREF_ISE and the current signal ISE2_DSC to the main control unit circuit. The main control unit circuit calculates the current reference signal VREF_ISE and the current signal ISE2_DSC to form a current detection signal for the protective ground. This current detection signal is compared with the preset current value. When the current detection signal is less than the set current value, it is determined that current is flowing through the protective ground. It is normal, and the control signal K1_DRV outputted by the normally open relay K1 is high level, thereby attracting the relay K1, so that the protective ground CASE_PE of the charger is normally connected with the protective ground Vin_PE of the power supply, and the normal working mode is entered; when the current detection signal is greater than or equal to the set current value, it is determined that the current flowing through the protective ground line is abnormal, and the main control unit circuit quickly outputs the control signal K1_DRV of the normally open relay K1 as a low level, and quickly disconnects the relay K1, so that the relay continues to be disconnected during the initial power-on. If the charger has been working normally, the connection between the protective ground CASE_PE of the charger and the protective ground Vin_PE of the power supply will be quickly disconnected.

[0047] When the charger's input protection ground Vin_PE is connected to the live wire of the power supply, the original live wire and neutral wire of the charger must be connected to the neutral wire and protective ground wire of the power supply. Therefore, there is no AC input voltage between the original input live wire L and neutral wire N of the charger, and there is no AC input inside the charger. It is also impossible to provide the necessary DC voltage after AC rectification to the auxiliary power supply inside the charger. The auxiliary power supply cannot start and work normally. Therefore, the control circuit of the relay cannot work normally due to the lack of normal power supply, and the relay continues to maintain the disconnected state. Therefore, the protective ground and casing inside the charger remain disconnected from the live wire of the power supply. In this case, it is ensured that the charger casing is not charged, and it will not cause abnormal damage to the internal circuit of the charger. After the power input line is correctly reconnected, the detection signal of the input current detection circuit is judged to be normal, and the charger enters the normal working mode.

[0048] Embodiment 2:

[0049] like Figure 3 As shown: a current detection circuit and a normally open relay are connected in series to the input protection ground wire of the charger. When the protection ground wire is mistakenly connected to the power supply live wire or the current in the detection circuit is abnormally large, the relay remains normally open. When the protection ground wire is connected correctly and the current detected by the current detection circuit is within the normal range, the normally open relay is attracted. In order to achieve the above purpose, this embodiment and technical solution Figure 1The control circuit and principle are basically the same, and the specific scheme will not be repeated. The only difference is the scheme Figure 3 The relay is only used to control the connection or disconnection between the casing and the input protection ground. Since the casing itself is not directly connected to the safety equivalent total capacitors C1 and C2 of the input part, there are no other special requirements for the safety Y capacitor at the input end of the charger. Of course, it is necessary to meet the requirements of the power input safety capacitor for ground leakage current or the specific customer requirements for this indicator.

[0050] like Figure 4 , as a specific implementation method, is suitable for normal single-phase AC input.

[0051] The circuit as a whole includes current detection circuit, relay, main control unit circuit, relay control circuit, safety Y capacitor between input live wire and neutral wire to protective ground, charger metal casing, and other filtering, rectification, PFC, auxiliary power supply, DCDC power conversion processing and other circuits.

[0052] Specifically, the Vin_L signal is the live wire input, the Vin_N signal is the neutral wire input, the Vin_PE signal is the input protection grounding, the CASE_PE signal is the charger casing grounding, and the CASE_PE signal is connected to the charger casing.

[0053] Specifically, a total equivalent safety Y capacitor C2 is connected between the chassis ground CASE_PE and the live line input Vin_L, and a total equivalent safety Y capacitor C1 is connected between the chassis ground CASE_PE and the neutral line input Vin_N.

[0054] Specifically, the live line input Vin_L and the neutral line input Vin_N are processed by other filtering, rectification, auxiliary power supply, PFC, DCDC power conversion and other circuits for power conversion to realize the relevant functions of the charger.

[0055] The AC input is used as the input of the auxiliary power output after filtering, rectification or pre-stage pre-stabilization, and the output of the auxiliary power output is used as the power supply for the relay control circuit and the main control unit circuit.

[0056] The Hall current sensor in the current detection circuit is used to detect the current of the protective ground wire, and generate a current reference signal and a current signal to send to the main control unit circuit. The main control unit circuit performs calculations on the current signal to determine whether the current flowing through the protective ground wire is normal. When the current detection signal is less than the set value, the main control unit circuit outputs a high-level control signal to close the normally open relay, thereby connecting the charger's protective ground CASE_PE with the power supply's protective ground Vin_PE and entering the normal working mode. When the current signal exceeds the set value, the main control unit circuit outputs a low-level control signal to disconnect the relay to ensure safe isolation.

[0057] When the charger's input protection ground Vin_PE is mistakenly connected to the power supply live wire, the charger cannot start due to the lack of actual input voltage, and the relay remains disconnected, ensuring that the charger case is not energized and avoiding damage to the internal circuit.

[0058] Figure 4 The principle and control method of the embodiment are the same as Figure 2 They are basically the same, the difference lies in the specific circuit implementation details and component selection.

[0059] Those skilled in the art will understand that all or part of the steps in the method for implementing the above-mentioned embodiments can be completed by instructing the relevant hardware through a program, and the program is stored in a storage medium, including several instructions for making a single-chip microcomputer, a chip or a processor (processor) perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0060] The optional embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the technical concept of the embodiments of the present invention, the technical scheme of the embodiments of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the embodiments of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the embodiments of the present invention will not further describe various possible combinations.

[0061] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the embodiments of the present invention, they should also be regarded as the contents disclosed in the embodiments of the present invention.

Claims

1. A protection device for a single-phase AC input charger that protects the ground wire from being mistakenly connected to the live wire of the power supply, characterized in that: The device comprises: Current detection circuit, relay, main control unit circuit, relay control circuit, safety Y capacitor and charger metal casing; The current detection circuit is used to detect the current in the input protective ground wire, and the relay is used to control the connection and disconnection between the charger metal casing and the input protective ground wire to prevent the charger casing from being energized due to the protective ground wire being mistakenly connected to the live wire.

2. The protection device according to claim 1, characterized in that: The relay is a normally open relay, which is connected in series to the input protection ground wire. When it is detected that the protection ground wire is mistakenly connected to the power supply live wire, the relay remains in an open state to prevent the charger housing from being connected to the live wire; After confirming that the input protection ground connection is correct, the relay is energized, allowing the charger to enter normal working state.

3. The protection device according to claim 2, characterized in that: The current detection circuit includes a current sensor; One end of the current sensor is connected to the input protection ground wire, and the other end is connected to a contact of the relay; The current detection circuit outputs the detected current signal to the main control unit circuit to determine whether the connection state of the input ground line is correct.

4. The protection device according to claim 3, characterized in that: The main control unit circuit is connected to the current detection circuit, and is used to receive the output signal of the current detection circuit and perform calculation processing on it; When the main control unit circuit determines that the current flowing through the input protective ground wire exceeds the preset safety threshold, it outputs a control signal to the relay control circuit to disconnect the relay to prevent the charger housing and the input protective ground wire from being mistakenly connected to the power supply live wire.

5. The protection device according to claim 4, characterized in that: The relay control circuit is connected to the relay and the main control unit circuit, and the relay control circuit controls the relay to be closed or disconnected according to the control signal output by the main control unit circuit.

6. The protection device according to claim 5, characterized in that: The safety Y capacitor is arranged between the metal casing of the charger and the input live wire and neutral wire, namely, the safety Y capacitor C2 between the metal casing of the charger and the live wire and the safety Y capacitor C1 between the metal casing and the neutral wire, and is used to perform safety isolation on the input protection ground. The capacity of the safety Y capacitor is designed based on the leakage current limit requirement of the input protection ground.

7. The protection device according to claim 6, characterized in that: The current detection circuit includes a Hall current sensor, which has an input end and an output end. The input end is connected to the input protection ground wire, and the output end is connected to the main control unit circuit. The Hall current sensor is used to detect the current in the input protection ground wire and output a current signal corresponding to the detected current value.

8. The protection device according to claim 7, characterized in that: When the input protective ground wire is connected correctly and the AC input voltage is normal, the relay control circuit provides a pull-in signal to the relay, causing the normally open relay to pull in, thereby achieving normal connection between the charger metal casing and the input protective ground wire, ensuring the normal working state of the charger. The relay always remains in the pull-in state under normal connection conditions.

9. The protection device according to claim 8, characterized in that: When the input protective ground wire is mistakenly connected to the live wire of the power supply, the input live wire and neutral wire of the charger will be connected to the neutral wire and protective ground wire of the input power supply, the auxiliary power supply inside the charger cannot start normally, and the relay remains disconnected to ensure that the charger casing is not energized.

10. The protection device according to claim 9, characterized in that: The control circuit of the protection device includes a leakage current control module, which is used to limit the leakage current of the input protection ground line to no more than 3.5 mA when the AC input is 465VAC / 50Hz.

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