Charging pile short circuit detection device and method and charging pile

Abstract

The invention relates to a charging pile short circuit detection device and method and a charging pile, and relates to the technical field of short circuit detection. The charging pile short circuit detection device comprises an induction circuit, a differential amplification circuit and a controller. Wherein the induction circuit is connected with a power supply access end and a first output contact and a second output contact of a main relay of the charging pile, and is used for outputting a first induction signal and a second induction signal when the main relay is not closed; the differential amplification circuit is connected with the induction circuit and is used for carrying out differential amplification processing on the first induction signal and the second induction signal to obtain a level signal; and the controller is connected with the differential amplification circuit and is used for obtaining a short circuit detection result according to the level signal. The induction circuit can induce a first induction signal and a second induction signal which are low in amplitude based on a power grid signal accessed by the power supply access end. Therefore, the short-circuit detection of the charging pile is realized without using a switching device, so that the circuit structure for realizing the short-circuit detection of the charging pile can be simplified.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of short circuit detection, in particular to a charging pile short circuit detection device and method. BACKGROUND

[0002] The charging pile is an important infrastructure for electric vehicles, which provides electric energy for electric vehicles to charge. In the working process of the charging pile, the output side of the charging pile needs to be directly connected with the electric vehicle. Due to the complex use scene, it may be affected by various factors such as charging gun or power receiving device of the electric vehicle, and short circuit failure may be caused. If the output side of the charging pile is short-circuited, not only the charging pile will be damaged, but also the charging equipment of the electric vehicle may be damaged. Therefore, in order to ensure the safety of charging, the output side of the charging gun needs to be detected.

[0003] At present, since the charging pile is usually connected with the mains to output several hundred volts of high voltage, and the short circuit detection is usually performed by low voltage of several volts or tens of volts, it is necessary to set a circuit breaker or other switching device to realize the isolation between the high voltage power transmission part and the low voltage detection part, so that the circuit structure of the charging pile short circuit detection is relatively complex. SUMMARY

[0004] The embodiment of the present application provides a charging pile short circuit detection device, which simplifies the circuit structure of the charging pile short circuit detection, so as to at least partially solve the above technical problems.

[0005] In order to achieve the above purpose, according to the first aspect of the present application, a charging pile short circuit detection device is provided, comprising: An induction circuit is connected with a power access end and first and second output contacts of a main relay of the charging pile, and is used for outputting first and second induction signals in a state that the main relay is not closed; A differential amplification circuit is connected with the induction circuit, and is used for performing differential amplification processing on the first and second induction signals to obtain a level signal; A controller is connected with the differential amplification circuit, and is used for obtaining a short circuit detection result according to the level signal.

[0006] Optionally, the power access end comprises a zero line end and a live line end, and the induction circuit comprises: A first induction sub-circuit is connected in parallel between the live line end and the first output contact and is connected with the differential amplification circuit, and is used for obtaining the first induction signal according to a connection state between the first and second output contacts and a signal accessed by the live line end; A second induction sub-circuit is connected in parallel between the zero line end and the second output contact and is connected with the differential amplification circuit, and is used for obtaining the second induction signal according to the connection state and the signal accessed by the zero line end.

[0007] Optionally, the first sensing sub-circuit comprises a first safety capacitor; and the second sensing sub-circuit comprises a second safety capacitor. The first safety capacitor comprises a first end connected to the live terminal and a second end connected to the first output contact and the differential amplification circuit. The second safety capacitor comprises a first end connected to the neutral terminal and a second end connected to the second output contact and the differential amplification circuit.

[0008] Optionally, the main relay further comprises a first input contact connected to the live terminal and the first end of the first safety capacitor, and a second input contact connected to the neutral terminal and the first end of the second safety capacitor.

[0009] Optionally, the differential amplification circuit comprises: a first differential sub-circuit connected to the sensing circuit, for differentially amplifying the first sensing signal and the second sensing signal to obtain a differential signal; a second differential sub-circuit connected to the first differential sub-circuit and the controller, for waveform processing the differential signal to obtain the level signal.

[0010] Optionally, the first differential sub-circuit comprises a first operational amplifier, a second operational amplifier, a first resistor, a second resistor, and a third resistor. The first operational amplifier comprises an output end connected to the second differential sub-circuit and a first end of the first resistor, a first input end connected to a second end of the first resistor and a first end of the second resistor, and a second input end connected to the sensing circuit. The second operational amplifier comprises a first input end connected to a second end of the second resistor and a first end of the third resistor, a second input end connected to the sensing circuit, and an output end connected to the second differential sub-circuit and a second end of the third resistor.

[0011] Optionally, the second differential sub-circuit comprises a third operational amplifier, a fourth resistor, a fifth resistor, a sixth resistor, and a seventh resistor. The third operational amplifier comprises a first input end, a second input end, and an output end; and the fourth resistor is connected between the output end of the first operational amplifier and the first input end of the third operational amplifier. The fifth resistor is connected between the first input end and the output end of the third operational amplifier. The sixth resistor is connected between the output end of the second operational amplifier and the second input end of the third operational amplifier. The seventh resistor is connected between the second input terminal of the third operational amplifier and the ground.

[0012] Optionally, further comprising a voltage dividing circuit arranged between the induction circuit and the differential amplification circuit, for adjusting the amplitudes of the first induction signal and the second induction signal.

[0013] Optionally, the voltage dividing circuit comprises a first voltage dividing group and a second voltage dividing group. The first voltage dividing group is connected between the first induction sub-circuit and the differential amplification circuit, and comprises one or a plurality of eighth resistors connected in series. The second voltage dividing group is connected between the second induction sub-circuit and the differential amplification circuit, and comprises one or a plurality of ninth resistors connected in series.

[0014] According to a second aspect of the present application, a charging pile short circuit detection method is provided, based on the charging pile short circuit detection device as described above, the method further comprises: outputting, by the induction circuit, the first induction signal and the second induction signal in a state that the main relay of the charging pile is not closed; differentially amplifying, by the differential amplification circuit, the first induction signal and the second induction signal to obtain a level signal; obtaining a short circuit detection result according to the level signal.

[0015] Optionally, the step of obtaining the short circuit detection result according to the level signal comprises: if the waveform of the level signal is a square wave, the short circuit detection result is that the output end of the main relay is not short-circuited; if the waveform of the level signal is a constant voltage waveform, the short circuit detection result is that the output end of the main relay is short-circuited.

[0016] According to a third aspect of the present application, a charging pile is provided, comprising the charging pile short circuit detection device as described above.

[0017] In summary, in the charging pile short circuit detection device of the embodiments of the present application, the induction circuit is linked with the power access end and the first output contact and the second output contact of the main relay of the charging pile, and can induce the first induction signal and the second induction signal with low amplitudes based on the power grid signal accessed by the power access end, without using a relay switching device to realize isolation between the high-voltage power grid transmission part and the low-voltage detection part. Then, the differential amplification circuit is used to process the first induction signal and the second induction signal to obtain a level signal, and the controller obtains a short circuit detection result according to the level signal. In this way, while realizing the short circuit detection of the charging pile, no switching device is used, so that the circuit structure for realizing the short circuit detection of the charging pile can be simplified.

[0018] Other features and advantages of the present application will be described in the following detailed description of the embodiments. BRIEF DESCRIPTION OF DRAWINGS In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some of the embodiments of the present application, and all other drawings obtained by those skilled in the art without creative effort based on these drawings also belong to the protection scope of the present application.

[0019] In order to more completely understand the present application and its beneficial effects, the following will be described in conjunction with the drawings, wherein the same reference numerals in the following description represent the same parts.

[0020] Figure 1 is a schematic diagram of the charging pile short circuit detection device provided in the exemplary embodiment of the present disclosure; Figure 2 is a circuit connection diagram of the charging pile short circuit detection device provided in the exemplary embodiment of the present disclosure; Figure 3 is an equivalent circuit diagram of the charging pile short circuit detection device in the state that the main relay is not short-circuited in the exemplary embodiment of the present disclosure; Figure 4 is a waveform diagram of the level signal in the state that the main relay is not short-circuited in the exemplary embodiment of the present disclosure; Figure 5 is an equivalent circuit diagram of the charging pile short circuit detection device in the state that the main relay is short-circuited in the exemplary embodiment of the present disclosure; Figure 6 is a waveform diagram of the level signal in the state that the main relay is short-circuited in the exemplary embodiment of the present disclosure.

[0021] Legend of reference numerals: 1, induction circuit; 11, first induction sub-circuit; 12, second induction sub-circuit; 2, differential amplification circuit; 21, first differential sub-circuit; 22, second differential sub-circuit; 3, controller; 4, voltage division circuit; 41, first voltage division group; 42, second voltage division group. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described clearly and completely in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort also belong to the protection scope of the present application.

[0023] According to the first aspect of the present application, with reference toFigure 1 The present disclosure provides a charging pile short circuit detection device, which comprises an induction circuit 1, a differential amplification circuit 2 and a controller 3. The induction circuit 1 is connected with a power access end and the first output contact and the second output contact of the main relay of the charging pile, and is used to output a first induction signal and a second induction signal in the state that the main relay is not closed. The differential amplification circuit 2 is connected with the induction circuit 1, and is used to perform differential amplification processing on the first induction signal and the second induction signal to obtain a level signal. The controller 3 is connected with the differential amplification circuit 2, and is used to obtain a short circuit detection result according to the level signal.

[0024] The power access end is used to access alternating voltage, and comprises a zero line end and a live line end. The zero line end and the live line end are connected with the power grid together. When the power grid is accessed, the live line end obtains alternating voltage from the power grid to transmit electric energy to the charging pile. The zero line end is used as a reference potential to provide a return circuit for the current, so as to form a complete circuit in the charging pile.

[0025] As an example, the main relay of the charging pile is used to form a charging circuit in the charging process. After the charging pile issues a charging start instruction, the short circuit detection phase of the charging pile is entered, and at this time the main relay is in the state of being not closed, so that the induction circuit 1 outputs the first induction signal and the second induction signal. The differential amplification circuit 2 performs differential amplification processing on the first induction signal and the second induction signal to obtain a level signal. Finally, the controller 3 obtains a short circuit detection result according to the level signal. After the short circuit detection is passed, a control signal is output to the control end of the main relay. The control end of the main relay receives the control signal to make the main relay closed. One side of the main relay is connected with the live line and the zero line in the power grid, and the other side is connected with the output end of the charging gun of the charging pile. When the contact of the main relay is closed, the alternating voltage of the power grid can flow to the charging gun through the main relay, thereby charging the electric vehicle and forming a complete charging circuit.

[0026] In the above embodiment, the induction circuit 1 is connected with the power access end and the first output contact and the second output contact of the main relay of the charging pile. The first induction signal and the second induction signal with low amplitude can be induced based on the power grid signal accessed by the power access end, without using a relay switching device to realize the isolation between the high-voltage power transmission part and the low-voltage detection part. Then, the differential amplification circuit 2 processes the first induction signal and the second induction signal to obtain a level signal, and the controller 3 obtains a short circuit detection result according to the level signal. In this way, the short circuit detection of the charging pile is realized without using a switching device, so that the circuit structure for realizing the short circuit detection of the charging pile can be simplified.

[0027] Reference Figure 2In some embodiments, the sensing circuit 1 comprises a first sensing sub-circuit 11 and a second sensing sub-circuit 12. The first sensing sub-circuit 11 is connected in parallel between the live wire end and the first output contact and connected to the differential amplification circuit 2, and is configured to obtain a first sensing signal according to the connection state between the first output contact and the second output contact and the signal input from the live wire end; the second sensing sub-circuit 12 is connected in parallel between the zero wire end and the second output contact and connected to the differential amplification circuit 2, and is configured to obtain a second sensing signal according to the connection state and the signal input from the zero wire end.

[0028] In normal conditions, the connection state between the first output contact and the second output contact is in an open state. When there is foreign matter in the charging gun or the power receiving device of the electric vehicle or the transmission line is exposed, the connection state between the first output contact and the second output contact will be in an abnormal conductive state, thereby causing a short circuit on the output side of the charging pile.

[0029] Referring to Figure 3 , Figure 3 is an equivalent circuit diagram when the connection state between the first output contact and the second output contact is in an open state (the main relay is omitted), at this time, the branch where the first sensing sub-circuit 11 is located and the branch where the second sensing sub-circuit 12 is located are independent of each other, so the first sensing signal and the second sensing signal received by the differential amplification circuit 2 can be sinusoidal signals with different phases, or one of the first sensing signal and the second sensing signal is a sinusoidal signal, and the other is a reference signal. At this time, the differential signal obtained by the differential amplification circuit 2 after subtracting the first sensing signal and the second sensing signal is still a sinusoidal wave, and after conversion processing, a level signal in a square wave form can be obtained, Figure 4 is a waveform diagram of the level signal in a square wave form.

[0030] Referring to Figure 5 , Figure 5 is an equivalent circuit diagram when the connection state between the first output contact and the second output contact is in a conductive state (the main relay is omitted), at this time, the branch where the first sensing sub-circuit 11 is located and the branch where the second sensing sub-circuit 12 are abnormally conductive, so that the power input end, the first sensing sub-circuit 11, the first output contact, the second output contact, the second sensing sub-circuit 12 and the power input end form a complete loop, so that the signal will not flow to the differential amplification circuit 2, at this time, the first sensing signal and the second sensing signal output by the first sensing sub-circuit 11 and the second sensing sub-circuit 12 are constant signals close to zero volts, at this time, the differential signal obtained by the differential amplification circuit 2 after subtracting the first sensing signal and the second sensing signal is still a constant signal close to zero volts, thereby obtaining a level signal in a constant voltage waveform, Figure 6 is a waveform diagram of the level signal in a constant voltage waveform.

[0031] Thus, by the first sensing sub-circuit 11 outputting the first sensing signal and the second sensing sub-circuit 12 outputting the second sensing signal, after differential processing by the differential amplification circuit 2, a level signal distinguishing the connection state between the first output contact and the second output contact can be obtained, so as to obtain a short circuit detection result according to the level signal.

[0032] With reference to Figure 2 In some embodiments, the first sensing sub-circuit 11 includes a first safety capacitor C1, and the second sensing sub-circuit 12 includes a second safety capacitor C2; the first safety capacitor C1 includes a first end connected to the live line end and a second end connected to the first output contact and the differential amplification circuit 2; and the second safety capacitor C2 includes a first end connected to the neutral line end and a second end connected to the second output contact and the differential amplification circuit 2.

[0033] As an example, the first safety capacitor C1 and the second safety capacitor C2 can interact with the parasitic inductance in the circuit, and as the alternating voltage input by the power supply input end changes, even if the main relay is disconnected, the energy stored by the first safety capacitor C1 and the second safety capacitor C2 can interact with the parasitic inductance to generate oscillation, so as to couple out the first sensing signal and the second sensing signal as virtual voltages at the second end of the first safety capacitor C1 and the second end of the second safety capacitor C2, respectively.

[0034] As an example, the first safety capacitor C1 and the second safety capacitor C2 can be double-insulated capacitors with an insulation withstand voltage greater than 5KV and an insulation resistance greater than 10GΩ, and the first safety capacitor C1 and the second safety capacitor C2 are respectively connected in the charging loop; when the alternating voltage of the power grid has transient fluctuations such as surges or voltage spikes, the first safety capacitor C1 and the second safety capacitor C2 can absorb energy, which can to some extent avoid the impact of surges or voltage spikes on the circuit. In the closed state of the main relay, since the working frequency of the alternating voltage of the power grid is relatively low, usually 50Hz, and the reactance of the first safety capacitor C1 and the second safety capacitor C2 at the working frequency is relatively large, the working frequency current passing through is relatively small, so it will not affect the transmission of the alternating signal on the charging loop.

[0035] With reference to Figure 2 In some embodiments, the main relay further includes a first input contact connected to the live line end and the first end of the first safety capacitor C1, and a second input contact connected to the neutral line end and the first end of the second safety capacitor C2.

[0036] As an example, Figure 2L-IN is the live wire end, N-IN is the neutral wire end, L-OUT is the first output contact, and N-OUT is the second output contact. The first input contact and the second input contact can be the movable contacts of the main relay, the first output contact and the second output contact can be the fixed contacts of the main relay, and the first input contact and the first output contact are matched, and when the first input contact and the first output contact are closed, a live wire branch in the charging circuit is formed. The second input contact and the second output contact are matched, and when the second input contact and the second output contact are closed, a neutral wire branch in the charging circuit is formed.

[0037] In the above embodiment, the first input contact and the second input contact of the main relay are connected with the live wire end and the neutral wire end respectively, so that the charging circuit of the main relay and the energy source for the induction circuit 1 to induce the first induction signal and the second induction signal are the same, and the live wire end and the neutral wire end can be multiplexed.

[0038] Referring to Figure 2 In some embodiments, the differential amplification circuit 2 includes a first differential sub-circuit 21 and a second differential sub-circuit 22. The first differential sub-circuit 21 is connected with the induction circuit 1 and is used for differentially amplifying the first induction signal and the second induction signal to obtain a differential signal; and the second differential sub-circuit 22 is connected with the first differential sub-circuit 21 and the controller 3 and is used for waveform processing the differential signal to obtain a level signal.

[0039] In the above embodiment, the first differential sub-circuit 21 is connected with the induction circuit 1 and differentially amplifies the first induction signal and the second induction signal to obtain a differential signal that can represent the difference between the first induction signal and the second induction signal. The second differential sub-circuit 22 waveform processes the differential signal to convert it into a level signal that is convenient for the controller 3 to recognize, so that the controller 3 can detect the short circuit.

[0040] Referring to Figure 2 In some embodiments, the first differential sub-circuit 21 includes a first operational amplifier U1, a second operational amplifier U2, a first resistor R1, a second resistor R2, and a third resistor R3; the first operational amplifier U1 includes an output end connected with the second differential sub-circuit 22 and a first end of the first resistor R1, a first input end connected with a second end of the first resistor R1 and a first end of the second resistor R2, and a second input end connected with the induction circuit 1; the second operational amplifier U2 includes a first input end connected with a second end of the second resistor R2 and a first end of the third resistor R3, a second input end connected with the induction circuit 1, and an output end connected with the second differential sub-circuit 22 and a second end of the third resistor R3.

[0041] As an example, the first operational amplifier U1 and the second operational amplifier U2 constitute a non-inverting differential amplifier, amplify the difference between the first sensing signal and the second sensing signal, and suppress common-mode noise, thereby obtaining a differential signal. The first resistor R1, the second resistor R2, and the third resistor R3 are gain resistors of the non-inverting differential amplifier, and by adjusting the resistance values of the first resistor R1, the second resistor R2, and the third resistor R3, the amplification gain of the first operational amplifier U1 and the second operational amplifier U2 on the difference between the first sensing signal and the second sensing signal can be adjusted. Among them, the resistance values of the first resistor R1 and the third resistor R3 can be the same, and the resistance value of the second resistor R2 is different from the resistance values of the first resistor R1 and the third resistor R3.

[0042] With reference to Figure 2 In some embodiments, the second differential sub-circuit 22 includes a third operational amplifier U3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7; the third operational amplifier U3 includes a first input terminal, a second input terminal, and an output terminal; the fourth resistor R4 is connected between the output terminal of the first operational amplifier U1 and the first input terminal of the third operational amplifier U3; the fifth resistor R5 is connected between the first input terminal and the output terminal of the third operational amplifier U3; the sixth resistor R6 is connected between the output terminal of the second operational amplifier U2 and the second input terminal of the third operational amplifier U3; and the seventh resistor R7 is connected between the second input terminal of the third operational amplifier U3 and the ground.

[0043] As an example, the third operational amplifier U3 can convert the differential signal in a sine waveform into a square waveform, the sixth resistor R6 and the seventh resistor R7 constitute a voltage division structure to provide a reference potential to the second input terminal of the third operational amplifier U3, and the fourth resistor R4 and the fifth resistor R5 are feedback resistors of the third operational amplifier U3, so that the third operational amplifier U3 converts the differential signal in a sine waveform into a square waveform.

[0044] It should be noted that the specific structure of the differential amplification circuit 2 is not limited to the structure of the first differential sub-circuit 21 and the second differential sub-circuit, as long as it can realize the difference between the first sensing signal and the second sensing signal in a sine waveform and amplify it, and ultimately obtain a level signal in a square waveform.

[0045] In some embodiments, the short circuit detection device of the charging pile further includes a voltage division circuit 4 arranged between the sensing circuit 1 and the differential amplification circuit 2, for adjusting the amplitude of the first sensing signal and the second sensing signal.

[0046] As an example, the voltage dividing circuit 4 includes a first voltage dividing group 41 and a second voltage dividing group 42. The first voltage dividing group 41 is connected between the first induction sub-circuit 11 and the differential amplification circuit 2, and includes one or a plurality of eighth resistors R8 connected in series. The second voltage dividing group 42 is connected between the second induction sub-circuit 12 and the differential amplification circuit 2, and includes one or a plurality of ninth resistors R9 connected in series.

[0047] In the above embodiment, the first induction signal and the second induction signal are respectively divided by the first voltage dividing group 41 and the second voltage dividing group 42, so that the amplitudes of the first induction signal and the second induction signal transmitted to the differential amplification circuit 2 are within a suitable range, so as to obtain a level signal that can be recognized by the controller 3.

[0048] According to a second aspect of the present application, a charging pile short circuit detection method is provided, based on the charging pile short circuit detection device as described above. The method further includes steps S10-S30.

[0049] Step S10: outputting the first induction signal and the second induction signal in a state where the main relay of the charging pile is not closed by the induction circuit 1; Step S20: performing differential amplification processing on the first induction signal and the second induction signal by the differential amplification circuit 2 to obtain a level signal; Step S30: obtaining a short circuit detection result according to the level signal.

[0050] In some embodiments, step S30 can include steps S31-S32.

[0051] Step S31: if the waveform of the level signal is a square wave, the short circuit detection result is that the output end of the main relay is not short-circuited; Step S32: if the waveform of the level signal is a constant voltage waveform, the short circuit detection result is that the output end of the main relay is short-circuited.

[0052] As an example, since the differential amplification circuit itself has a supply voltage, even if the first induction signal and the second induction signal input to the differential amplification circuit are close to zero volts, the level signal output by the differential amplification circuit will still have a certain constant voltage amplitude.

[0053] It should be noted that the charging pile short circuit detection method has all the beneficial effects of the charging pile short circuit detection device described above, and the present disclosure will not be repeated here.

[0054] According to a third aspect of the present application, a charging pile is provided, which includes the charging pile short circuit detection device described above. The charging pile has all the beneficial effects of the charging pile short circuit detection device described above, and the present disclosure will not be repeated here.

[0055] In the description of the application, the terms "first", "second", "third" and the like are used only for the purpose of description, and cannot be understood as indicating or implying relative importance or implying the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more features. In the description of the application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0056] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0057] The embodiments, implementation manners and related technical features of the present application can be combined or replaced with each other without conflict.

[0058] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification made to the above embodiment in accordance with the technical essence of the present application without departing from the technical solution content of the present application still falls within the scope of the technical solution of the present application.

Claims

1. A short-circuit detection device for charging piles, characterized in that, include: The sensing circuit is connected to the power input terminal and the first and second output contacts of the main relay of the charging pile, and is used to output a first sensing signal and a second sensing signal when the main relay is not closed. A differential amplifier circuit, connected to the sensing circuit, is used to differentially amplify the first sensing signal and the second sensing signal to obtain a level signal; The controller, connected to the differential amplifier circuit, is used to obtain the short-circuit detection result based on the level signal.

2. The charging pile short-circuit detection device according to claim 1, characterized in that, The power input terminal includes a neutral wire terminal and a live wire terminal, and the sensing circuit includes: A first sensing sub-circuit is connected in parallel between the live wire terminal and the first output contact and is connected to the differential amplifier circuit. It is used to obtain the first sensing signal based on the connection state between the first output contact and the second output contact and the signal input to the live wire terminal. The second sensing sub-circuit is connected in parallel between the neutral terminal and the second output contact and is connected to the differential amplifier circuit. It is used to obtain the second sensing signal based on the connection state and the signal connected to the neutral terminal.

3. The charging pile short-circuit detection device according to claim 2, characterized in that, The first sensing sub-circuit includes a first safety capacitor; the second sensing sub-circuit includes a second safety capacitor. The first safety capacitor includes a first end connected to the live wire and a second end connected to the first output contact and the differential amplifier circuit; The second safety capacitor includes a first end connected to the neutral terminal and a second end connected to the second output contact and the differential amplifier circuit.

4. The charging pile short-circuit detection device according to claim 3, characterized in that, The main relay also includes a first input contact connected to the live wire terminal and the first terminal of the first safety capacitor, and a second input contact connected to the neutral wire terminal and the first terminal of the second safety capacitor.

5. The charging pile short-circuit detection device according to claim 1, characterized in that, The differential amplifier circuit includes: A first-stage differential circuit, connected to the sensing circuit, is used to differentially amplify the first sensing signal and the second sensing signal to obtain a differential signal; A second-level differential circuit, connected to the first-level differential circuit and the controller, is used to perform waveform processing on the differential signal to obtain the level signal.

6. The charging pile short-circuit detection device according to claim 5, characterized in that, The first-level differential circuit includes a first operational amplifier, a second operational amplifier, a first resistor, a second resistor, and a third resistor; The first operational amplifier includes an output terminal connected to the first end of the second-order differential numerator circuit and the first resistor, a first input terminal connected to the second end of the first resistor and the first end of the second resistor, and a second input terminal connected to the sensing circuit; The second operational amplifier includes a first input terminal connected to the second terminal of the second resistor and the first terminal of the third resistor, a second input terminal connected to the induction circuit, and an output terminal connected to the second differential numerator circuit and the second terminal of the third resistor.

7. The charging pile short-circuit detection device according to claim 6, characterized in that, The second-order differential numerator circuit includes a third operational amplifier, a fourth resistor, a fifth resistor, a sixth resistor, and a seventh resistor; The third operational amplifier includes a first input terminal, a second input terminal, and an output terminal; The fourth resistor is connected between the output terminal of the first operational amplifier and the first input terminal of the third operational amplifier. The fifth resistor is connected between the first input terminal and the output terminal of the third operational amplifier; The sixth resistor is connected between the output terminal of the second operational amplifier and the second input terminal of the third operational amplifier; The seventh resistor is connected between the second input terminal of the third operational amplifier and ground.

8. The charging pile short-circuit detection device according to claim 1, characterized in that, It also includes a voltage divider circuit disposed between the sensing circuit and the differential amplifier circuit, used to adjust the amplitude of the first sensing signal and the second sensing signal.

9. The charging pile short-circuit detection device according to claim 8, characterized in that, The voltage divider circuit includes a first voltage divider group and a second voltage divider group; The first voltage divider group is connected between the first inductive sub-circuit and the differential amplifier circuit, and includes one or more eighth resistors connected in series. The second voltage divider group is connected between the second inductor circuit and the differential amplifier circuit, and includes one or more ninth resistors connected in series.

10. A method for detecting short circuits in a charging pile, based on the charging pile short circuit detection device as described in any one of claims 1 to 9, characterized in that, The method further includes: The induction circuit outputs the first and second induction signals when the main relay of the charging pile is not closed. The first and second sensed signals are differentially amplified by a differential amplifier circuit to obtain a level signal. The short-circuit detection result is obtained based on the stated level signal.

11. The short-circuit detection method for charging piles according to claim 10, characterized in that: The step of obtaining the short-circuit detection result based on the level signal includes: If the waveform of the level signal is a square wave, then the short circuit detection result is that the output terminal of the main relay is not short-circuited; If the waveform of the level signal is a constant voltage waveform, then the short circuit detection result is that the output terminal of the main relay is short-circuited.

12. A charging pile, characterized in that, It includes the charging pile short circuit detection device according to any one of claims 1 to 9.

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