Single-phase alternating current charging pile output end short circuit detection circuit

Abstract

This invention relates to the field of electronic circuit technology and discloses a short-circuit detection circuit for the output terminal of a single-phase AC charging pile. The output terminal includes a live wire output terminal (Lout) and a neutral wire output terminal (Nout). An output short-circuit detection relay electrically connects the short-circuit detection branch to the output terminal in the detection state and disconnects it in the non-detection state. A sampling module acquires a sampling signal related to the short-circuit state of the output terminal and outputs a sampling voltage in the detection state. A comparison module compares the sampling voltage with a reference voltage and outputs a short-circuit detection signal. A system processing module includes a microcontroller (MCU) that receives the short-circuit detection signal. A switching module drives the output short-circuit detection relay to switch between the detection state and the non-detection state according to the control signal output by the MCU. In the non-detection state, the detection branch is disconnected from the output terminal and is not connected to the detection circuit, thus forming an on-demand detection structure.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit technology, specifically to a short-circuit detection circuit at the output terminal of a single-phase AC charging pile. Background Technology

[0002] Single-phase AC charging piles are typically used to provide AC power to electric vehicles. Their output side is generally equipped with a live wire output terminal and a neutral wire output terminal, which can be electrically connected to the vehicle through the charging gun cable. To ensure the safety of the power supply on the output side and the reliable operation of the equipment, the charging pile usually needs to have the ability to monitor abnormal conditions at the output terminal. Among them, the output terminal short circuit detection circuit is used to provide short circuit indication information to the control system in the event of a short circuit between the live wire and the neutral wire or a low-resistance abnormal connection at the output terminal, so that corresponding control actions can be taken. In the existing implementation of output terminal short circuit detection, the short circuit detection branch is often connected in parallel at the output terminal for a long time or is in an access state for a long time, and it continues to maintain an electrical connection with the output terminal even during the non-detection phase of the charging pile operation.

[0003] However, in current technology, the short-circuit detection branch remains electrically connected to the output terminal during the non-detection phase, making it impossible for the detection circuit to disconnect as needed. Consequently, it continues to participate in the loop in the non-detection state, generating additional electrical connection occupation and additional power loss, which makes it difficult to meet the requirements of the detection circuit to be switchable and controllable. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a short-circuit detection circuit for the output terminal of a single-phase AC charging pile, which solves the problem that existing short-circuit detection branches remain electrically connected to the output terminal during non-detection phases, causing the detection circuit to be unable to disconnect as needed and generating additional power losses.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a short-circuit detection circuit for the output terminal of a single-phase AC charging pile, comprising: The output terminals include the live wire output terminal Lout and the neutral wire output terminal Nout. The output short-circuit detection relay establishes an electrical connection between the short-circuit detection branch and the output terminal in the detection state, and disconnects the short-circuit detection branch from the output terminal in the non-detection state. The sampling module acquires a sampling signal related to the short-circuit state of the output terminal when the output short-circuit detection relay is in the detection state, and outputs a sampling voltage at the sampling node. The comparison module includes a voltage comparator and a reference voltage generation network for providing a reference voltage. The first input terminal of the voltage comparator receives the sampled voltage, the second input terminal receives the reference voltage, and the output terminal of the voltage comparator outputs a short-circuit detection signal. The system processing module includes a microcontroller (MCU), the input of which is connected to the output of the voltage comparator, for receiving the short-circuit detection signal; The switching module drives the output short-circuit detection relay to switch between detection and non-detection states according to the control signal output by the MCU; When the preset detection conditions are met, the MCU controls the output short-circuit detection relay to enter the detection state, and determines the short-circuit state of the output terminal based on the short-circuit detection signal.

[0006] Preferably, the reference voltage generation network includes a first reference resistor R6 and a second reference resistor R7 connected in series. One end of the first reference resistor R6 is connected to a low-voltage power supply terminal, and one end of the second reference resistor R7 is connected to ground. The connection node of the first reference resistor R6 and the second reference resistor R7 outputs the reference voltage and is connected to the second input terminal of the voltage comparator.

[0007] Preferably, an output resistor R8 is connected in series between the output terminal of the voltage comparator and the input terminal of the MCU, and an output filter capacitor C3 is connected between the input terminal of the MCU and ground.

[0008] Preferably, the sampling module includes a filter capacitor C1 connected between the sampling node and the ground terminal, and the sampling module also includes a clamping protection device connected between the sampling node and the ground terminal.

[0009] Preferably, the clamping protection device includes a Zener diode D2 and a transient suppression diode DT1, both of which are connected between the sampling node and ground.

[0010] Preferably, the switching module includes a switching transistor Q1, a coil of an output short-circuit detection relay, and a freewheeling diode D3 connected in anti-parallel to the coil; One end of the coil is connected to the DC power supply, and the other end is connected to the ground via the switch Q1. The control terminal of the switch Q1 is connected to the output terminal of the MCU.

[0011] Preferably, the output short-circuit detection relay is a dual-contact linkage relay, including a first contact KA3-1 and a second contact KA3-2. The first contact KA3-1 and the second contact KA3-2 close simultaneously when the relay is energized and open simultaneously when the relay is released.

[0012] Preferably, the sampling module includes a first resistor R1, a first diode D1, a second resistor R2, a third resistor R3, a fourth resistor R4, a current-limiting resistor R5, a filter capacitor C1, a Zener diode D2, and a transient suppression diode DT1, wherein: One end of the first resistor R1 is connected to the low-voltage power supply terminal, and the other end is connected to the first terminal of the first diode D1; the second terminal of the first diode D1 is connected to the sampling node through the current-limiting resistor R5. The first contact KA3-1 is connected in series between the first diode D1 and the second resistor R2, and the other end of the second resistor R2 is connected to the live wire output terminal Lout; The neutral output terminal Nout is connected to the ground terminal in sequence through the third resistor R3, the second contact KA3-2 and the fourth resistor R4; The filter capacitor C1, the Zener diode D2, and the transient suppression diode DT1 are all connected between the sampling node and the ground.

[0013] Preferably, the sampling node is connected to the first input terminal of the voltage comparator.

[0014] Preferably, the MCU is used to read the short-circuit detection signal after a preset sampling delay after controlling the output short-circuit detection relay to enter the detection state, and output a protection control signal when the short-circuit detection signal indicates a short circuit so that the charging main relay remains open or changes from a closed state to an open state.

[0015] Working Principle: The short-circuit detection circuit at the output terminal of the single-phase AC charging pile operates under the control of the MCU. When the preset detection conditions are met, the MCU drives the output short-circuit detection relay from the non-detection state to the detection state through the switching module, so that the short-circuit detection branch is connected to the output terminals Lout and Nout. In this detection state, the sampling module generates a sampling signal related to the short-circuit state based on the electrical connection state of Lout and Nout, and outputs a sampling voltage at the sampling node. This sampling node is equipped with a filter capacitor C1 and a clamping protection device composed of a Zener diode D2 and a transient suppression diode DT1 to filter the sampling voltage. The protection and comparison module uses a reference voltage generation network (R6 and R7 divide the voltage to generate a reference voltage) to provide a reference voltage to the voltage comparator. The voltage comparator compares the sampled voltage with the reference voltage and outputs a short-circuit detection signal. This short-circuit detection signal is shaped by the output resistor R8 and the output filter capacitor C3 and then input to the MCU. The MCU reads the short-circuit detection signal after the relay enters the detection state and after a preset sampling delay, and completes the short-circuit state determination. When the short-circuit detection signal indicates a short circuit, the MCU outputs a protection control signal to keep the charging main relay open or change it from closed to open, thereby completing the closed-loop process of detection and protection control.

[0016] This invention provides a short-circuit detection circuit for the output terminal of a single-phase AC charging pile. It has the following advantages: 1. This invention controls the connection / disconnection of the detection branch by output short-circuit detection relay. The relay is driven by the MCU through the switching module. In the non-detection state, the detection branch is disconnected from the output terminal and is not connected to the detection circuit, thus forming a detection structure that can be activated on demand.

[0017] 2. This invention uses a voltage comparator as the core comparison element to compare the sampled voltage output by the sampling module with the reference voltage provided by the reference voltage generation network. The voltage comparator directly outputs a short-circuit detection signal and sends it to the MCU input terminal, making the short-circuit indication signal formation path more direct and facilitating timely judgment and processing. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a short-circuit detection circuit at the output terminal of a single-phase AC charging pile according to the present invention. Figure 2 This is a schematic diagram of a short-circuit detection circuit at the output terminal of a single-phase AC charging pile according to the present invention. Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see the appendix Figure 1 and attached Figure 2 This invention provides a short-circuit detection circuit for the output terminal of a single-phase AC charging pile, comprising: The output terminals include the live wire output terminal Lout and the neutral wire output terminal Nout. The output short-circuit detection relay establishes an electrical connection between the short-circuit detection branch and the output terminal in the detection state, and disconnects the short-circuit detection branch from the output terminal in the non-detection state. The sampling module acquires a sampling signal related to the short-circuit state at the output terminal when the output short-circuit detection relay is in the detection state, and outputs the sampling voltage at the sampling node. The comparison module includes a voltage comparator and a reference voltage generation network for providing a reference voltage. The first input of the voltage comparator receives the sampled voltage, the second input receives the reference voltage, and the output of the voltage comparator outputs a short-circuit detection signal. The system processing module includes a microcontroller (MCU). The input of the MCU is connected to the output of a voltage comparator to receive short-circuit detection signals. The switching module drives the output short-circuit detection relay to switch between detection and non-detection states based on the control signal output by the MCU; When the preset detection conditions are met, the MCU controls the output short-circuit detection relay to enter the detection state, and determines the short-circuit state of the output terminal based on the short-circuit detection signal.

[0021] Specifically, a short-circuit detection circuit for the output terminal of a single-phase AC charging pile is installed on the output side of the charging pile. The detection object is the output terminal, which includes a live wire output terminal Lout and a neutral wire output terminal Nout. To detect the short-circuit state of the output terminal, an output short-circuit detection relay is installed between Lout, Nout and the detection circuit. The switching module drives the output short-circuit detection relay to switch between detection and non-detection states under the control of the microcontroller MCU. When entering the detection state, the output short-circuit detection relay establishes an electrical connection between the short-circuit detection branch and the output terminal. When entering the non-detection state, the output short-circuit detection relay disconnects the short-circuit detection branch from the output terminal, so that the short-circuit detection branch is connected to the output terminal only when detection is required. When the output short-circuit detection relay is in the detection state, the short-circuit detection branch and the sampling module form a sampling path for the output state. The sampling module is used to acquire the sampling signal related to the short-circuit state of the output and output the sampling voltage at its sampling node. Specifically, after the relay is connected to the output, the sampling module makes the sampling node voltage correspond to the conduction / short-circuit state of the output: when the output is in a non-short-circuit state, the sampling node maintains the voltage level corresponding to the state. When a short circuit occurs at the output or a low-impedance abnormal connection occurs, the sampling node voltage will change accordingly, thereby providing input for subsequent judgment. To convert the aforementioned sampling node voltages into discrimination signals that are easy for the system to process, a comparison module is set up. The comparison module includes a voltage comparator and a reference voltage generation network for providing a reference voltage. The first input terminal of the voltage comparator receives the sampling voltage, the second input terminal receives the reference voltage, and the output terminal of the voltage comparator outputs a short-circuit detection signal. That is, the reference voltage is used as a threshold reference. The voltage comparator is used to compare the magnitude relationship between the sampling voltage and the reference voltage, and outputs a short-circuit detection signal corresponding to the logic state to indicate whether the output terminal is in a short-circuit state or a non-short-circuit state. The short-circuit detection signal is sent to the system processing module, which includes a microcontroller (MCU). Its input is connected to the output of a voltage comparator to receive the short-circuit detection signal. When the preset detection conditions are met, the MCU sends a control signal to the switching module through its output to drive the output short-circuit detection relay into the detection state. This allows the short-circuit detection branch to be connected to the output and complete sampling and comparison. The MCU then determines the short-circuit state of the output based on the received short-circuit detection signal. After completing one detection, the MCU can also control the output short-circuit detection relay to exit the detection state through the switching module, disconnecting the short-circuit detection branch from the output to end the detection process and return the detection circuit to the non-detection state. Through the above structure and process, a complete link is formed from the relay input output terminal, the sampling node forming the sampling voltage, comparing with the reference voltage to output the short circuit detection signal, the MCU receiving and judging, to controlling the relay to exit or maintain the detection state, so that each module works collaboratively within the same detection closed loop.

[0022] The reference voltage generation network includes a first reference resistor R6 and a second reference resistor R7 connected in series. One end of the first reference resistor R6 is connected to the low-voltage power supply terminal, and one end of the second reference resistor R7 is connected to the ground terminal. The connection node of the first reference resistor R6 and the second reference resistor R7 outputs a reference voltage and is connected to the second input terminal of the voltage comparator.

[0023] Specifically, the reference voltage generation network in the comparison module is implemented using a resistor voltage divider method, which includes a series connection structure of a first reference resistor R6 and a second reference resistor R7. One end of the first reference resistor R6 is connected to the low-voltage power supply terminal, and one end of the second reference resistor R7 is connected to the ground terminal. The connection node of R6 and R7 forms a voltage divider node and outputs a reference voltage Vref. The reference voltage Vref serves as the threshold input of the voltage comparator and is connected to the second input terminal of the voltage comparator. This enables the voltage comparator to output a corresponding short-circuit detection signal for the system processing module to read and determine based on the comparison relationship between the reference voltage and the sampling voltage output by the sampling module. In the above structure, the resistance values ​​of R6 and R7 are used to determine the level position of the reference voltage to adapt to the sampling voltage range formed by the sampling module under different output terminal states. The reference voltage generation network, as part of the comparison module, is electrically connected to the second input terminal of the voltage comparator to ensure that the comparison module can form a stable comparison reference in the short-circuit detection process.

[0024] An output resistor R8 is connected in series between the output of the voltage comparator and the input of the MCU, and an output filter capacitor C3 is connected between the input of the MCU and ground.

[0025] Specifically, to stably transmit the short-circuit detection signal output by the voltage comparator to the system processing module, an output resistor R8 is connected in series between the output of the voltage comparator and the input of the microcontroller (MCU), and an output filter capacitor C3 is connected between the input of the MCU and ground. The output resistor R8 and the output filter capacitor C3 form a signal shaping and filtering network, used to current-limit and filter the signal at the output of the voltage comparator, ensuring that the short-circuit detection signal input to the MCU meets the electrical interface requirements of the MCU input, and suppressing the impact of transient disturbances during signal transmission on the MCU input level recognition.

[0026] The sampling module includes a filter capacitor C1 connected between the sampling node and the ground terminal, and the sampling module also includes a clamping protection device connected between the sampling node and the ground terminal.

[0027] Specifically, the sampling module is equipped with a filtering and protection structure for processing the sampling node signal. Specifically, a filter capacitor C1 is connected between the sampling node and the ground terminal to filter the sampling voltage at the sampling node, so that the sampling node voltage remains stable during short-circuit detection, which facilitates the subsequent comparison module to compare and distinguish the sampling voltage with the reference voltage. Meanwhile, the sampling module also includes a clamping protection device connected between the sampling node and the ground terminal, which is used to clamp and protect the sampling node from abnormal voltages that may occur, so that the sampling signal entering the comparison module is kept within a predetermined electrical range, thereby meeting the electrical withstand conditions of the comparison module input and protecting the sampling node.

[0028] The clamping protection device includes a Zener diode D2 and a transient suppression diode DT1, both of which are connected between the sampling node and ground.

[0029] Specifically, the clamping protection device of the sampling module consists of a Zener diode D2 and a transient suppression diode DT1. Both the Zener diode D2 and the transient suppression diode DT1 are connected between the sampling node and the ground. In this way, when the voltage change of the sampling node exceeds the preset range, the Zener diode D2 and the transient suppression diode DT1 are used to clamp and suppress the voltage of the sampling node, respectively, to protect the sampling node and the input terminal of the comparison module connected to it, and to ensure that the signal level at the sampling node meets the input conditions for subsequent comparison and discrimination.

[0030] The switching module includes a switching transistor Q1, a coil of an output short-circuit detection relay, and a freewheeling diode D3 connected in anti-parallel to the coil; One end of the coil is connected to the DC power supply, and the other end is connected to the ground via the switching transistor Q1. The control terminal of the switching transistor Q1 is connected to the output terminal of the MCU.

[0031] Specifically, the switching module is used to convert the control signals of the microcontroller (MCU) into driving actions for the output short-circuit detection relay. It includes a switching transistor Q1, the coil of the output short-circuit detection relay, and a freewheeling diode D3 connected in anti-parallel to the coil. One end of the coil is connected to the DC power supply, and the other end of the coil is connected to ground via the switching transistor Q1. The control terminal of the switching transistor Q1 is connected to the output terminal of the MCU, so that the MCU can control the coil to switch on and off by controlling the switching transistor Q1, thereby driving the output short-circuit detection relay to switch between detection and non-detection states. In the above structure, the freewheeling diode D3 is connected in anti-parallel across the coil to provide a release path for the coil current when the switch Q1 is turned off, thereby limiting the influence of the reverse voltage generated during the coil de-energization process on the switch Q1 and related circuits.

[0032] The output short-circuit detection relay is a dual-contact linkage relay, including a first contact KA3-1 and a second contact KA3-2. The first contact KA3-1 and the second contact KA3-2 close simultaneously when the relay is energized and open simultaneously when the relay is released.

[0033] Specifically, the output short-circuit detection relay is implemented using a dual-contact linkage relay, which includes a first contact KA3-1 and a second contact KA3-2. The structure of the dual-contact linkage relay allows the first contact KA3-1 and the second contact KA3-2 to operate synchronously and close simultaneously when the relay coil is energized, thereby establishing the corresponding electrical connection between the short-circuit detection branch and the output terminal within the same detection sequence. When the relay coil is de-energized and released, the first contact KA3-1 and the second contact KA3-2 operate synchronously and open simultaneously, thereby simultaneously releasing the electrical connection between the short-circuit detection branch and the output terminal, causing the short-circuit detection branch to exit the detection state. Thus, the short-circuit detection branch maintains synchronous switching when connected and disconnected, facilitating consistent sampling of the output terminal state by the subsequent sampling module.

[0034] The sampling module includes a first resistor R1, a first diode D1, a second resistor R2, a third resistor R3, a fourth resistor R4, a current-limiting resistor R5, a filter capacitor C1, a Zener diode D2, and a transient suppression diode DT1, wherein: One end of the first resistor R1 is connected to the low-voltage power supply terminal, and the other end is connected to the first terminal of the first diode D1; the second terminal of the first diode D1 is connected to the sampling node through the current-limiting resistor R5. The first contact KA3-1 is connected in series between the first diode D1 and the second resistor R2, and the other end of the second resistor R2 is connected to the live wire output terminal Lout. The neutral output terminal Nout is connected to the ground terminal in sequence through the third resistor R3, the second contact KA3-2 and the fourth resistor R4; The filter capacitor C1, the Zener diode D2, and the transient suppression diode DT1 are all connected between the sampling node and the ground.

[0035] Specifically, the sampling module consists of a first resistor R1, a first diode D1, a second resistor R2, a third resistor R3, a fourth resistor R4, a current-limiting resistor R5, a filter capacitor C1, a Zener diode D2, and a transient suppression diode DT1. It is used to form a sampling path and output a sampling voltage at the sampling node when the output short-circuit detection relay is in the detection state. Specifically, one end of the first resistor R1 is connected to the low-voltage power supply terminal, and the other end is connected to the first terminal of the first diode D1; the second terminal of the first diode D1 is connected to the sampling node via the current-limiting resistor R5. Through this connection method, the sampling node can obtain the sampling branch potential from the low-voltage power supply terminal, and the current-limiting resistor R5 is used to limit the current of the sampling branch to meet the working requirements of the sampling module. When the output short-circuit detection relay is energized and enters the detection state, the first contact KA3-1 closes, establishing a series connection between the first diode D1 and the second resistor R2. The other end of the second resistor R2 is connected to the live wire output terminal Lout, thus establishing an electrical connection path between the sampling module and the live wire output terminal Lout. Simultaneously, the neutral wire output terminal Nout is connected to the ground terminal through the third resistor R3, the second contact KA3-2, and the fourth resistor R4 in sequence, establishing a corresponding loop path between the sampling module and the neutral wire output terminal Nout. Thus, in the detection state, the sampling module generates a sampling node voltage based on the electrical connection state between Lout and Nout, making the sampling voltage output by the sampling node correlated with the short-circuit state of the output terminal. In addition, the filter capacitor C1, the Zener diode D2, and the transient suppression diode DT1 are all connected between the sampling node and the ground. The filter capacitor C1 is used to filter the sampling node voltage; the Zener diode D2 and the transient suppression diode DT1 are used to clamp and suppress transients at the sampling node voltage, so that the sampling signal at the sampling node meets the electrical conditions of the input terminal of the subsequent comparison module.

[0036] The sampling node is connected to the first input terminal of the voltage comparator.

[0037] Specifically, the sampling node, which serves as the node for the sampling module to output the sampled voltage, is electrically connected to the first input terminal of the voltage comparator. This allows the sampled voltage generated by the sampling module in the detection state to be directly input to the comparator module. The voltage comparator compares the sampled voltage received at the first input terminal with the reference voltage received at its second input terminal, and outputs a short-circuit detection signal accordingly for the system processing module to receive and process. This enables the sampling module, the comparator module, and the system processing module to achieve signal transmission and state determination within the same detection link.

[0038] The MCU is used to read the short-circuit detection signal after a preset sampling delay after the control output short-circuit detection relay enters the detection state, and outputs a protection control signal when the short-circuit detection signal indicates a short circuit, so that the charging main relay remains open or changes from the closed state to open.

[0039] Specifically, when the microcontroller (MCU) performs short-circuit detection, it first controls the output short-circuit detection relay to enter the detection state via the switching module, establishing an electrical connection between the short-circuit detection branch and the output terminal. To ensure that the sampling voltage output by the sampling module and the short-circuit detection signal output by the comparison module are in a readable state, after the output short-circuit detection relay enters the detection state, the MCU waits for a preset sampling delay according to a pre-set time parameter, and then reads the short-circuit detection signal output by the voltage comparator and makes a judgment. When the short-circuit detection signal indicates that the output terminal is in a short-circuit state, the MCU outputs a protection control signal to the control terminal of the charging main relay, keeping the charging main relay open, or controlling it to switch from a closed state to an open state when it is already in a closed state, thus completing the control processing of the charging main circuit. When the short-circuit detection signal does not indicate a short-circuit state, the MCU ends the detection or enters the next detection cycle according to the detection process. Through the above control, the MCU realizes the timing coordination between the switching of the output short-circuit detection relay state, the reading of the short-circuit detection signal, and the control of the charging main relay.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A short-circuit detection circuit at the output terminal of a single-phase AC charging pile, characterized in that, include: The output terminals include the live wire output terminal Lout and the neutral wire output terminal Nout. The output short-circuit detection relay establishes an electrical connection between the short-circuit detection branch and the output terminal in the detection state, and disconnects the short-circuit detection branch from the output terminal in the non-detection state. The sampling module acquires a sampling signal related to the short-circuit state of the output terminal when the output short-circuit detection relay is in the detection state, and outputs a sampling voltage at the sampling node. The comparison module includes a voltage comparator and a reference voltage generation network for providing a reference voltage. The first input terminal of the voltage comparator receives the sampled voltage, the second input terminal receives the reference voltage, and the output terminal of the voltage comparator outputs a short-circuit detection signal. The system processing module includes a microcontroller (MCU), the input of which is connected to the output of the voltage comparator, for receiving the short-circuit detection signal; The switching module drives the output short-circuit detection relay to switch between detection and non-detection states according to the control signal output by the MCU; When the preset detection conditions are met, the MCU controls the output short-circuit detection relay to enter the detection state, and determines the short-circuit state of the output terminal based on the short-circuit detection signal.

2. The short-circuit detection circuit at the output terminal of a single-phase AC charging pile according to claim 1, characterized in that, The reference voltage generation network includes a first reference resistor R6 and a second reference resistor R7 connected in series. One end of the first reference resistor R6 is connected to the low-voltage power supply terminal, and one end of the second reference resistor R7 is connected to the ground terminal. The connection node of the first reference resistor R6 and the second reference resistor R7 outputs the reference voltage and is connected to the second input terminal of the voltage comparator.

3. The short-circuit detection circuit at the output terminal of a single-phase AC charging pile according to claim 2, characterized in that, An output resistor R8 is connected in series between the output terminal of the voltage comparator and the input terminal of the MCU, and an output filter capacitor C3 is connected between the input terminal of the MCU and ground.

4. The short-circuit detection circuit at the output terminal of a single-phase AC charging pile according to claim 1, characterized in that, The sampling module includes a filter capacitor C1 connected between the sampling node and the ground terminal, and the sampling module also includes a clamping protection device connected between the sampling node and the ground terminal.

5. A short-circuit detection circuit for the output terminal of a single-phase AC charging pile according to claim 4, characterized in that, The clamping protection device includes a Zener diode D2 and a transient suppression diode DT1, both of which are connected between the sampling node and ground.

6. A short-circuit detection circuit for the output terminal of a single-phase AC charging pile according to claim 1, characterized in that, The switching module includes a switching transistor Q1, a coil of an output short-circuit detection relay, and a freewheeling diode D3 connected in anti-parallel to the coil; One end of the coil is connected to the DC power supply, and the other end is connected to the ground via the switch Q1. The control terminal of the switch Q1 is connected to the output terminal of the MCU.

7. A short-circuit detection circuit for the output terminal of a single-phase AC charging pile according to claim 1, characterized in that, The output short-circuit detection relay is a dual-contact linkage relay, including a first contact KA3-1 and a second contact KA3-2. The first contact KA3-1 and the second contact KA3-2 close simultaneously when the relay is energized and open simultaneously when the relay is released.

8. A short-circuit detection circuit for the output terminal of a single-phase AC charging pile according to claim 7, characterized in that, The sampling module includes a first resistor R1, a first diode D1, a second resistor R2, a third resistor R3, a fourth resistor R4, a current-limiting resistor R5, a filter capacitor C1, a Zener diode D2, and a transient suppression diode DT1, wherein: One end of the first resistor R1 is connected to the low-voltage power supply terminal, and the other end is connected to the first terminal of the first diode D1; the second terminal of the first diode D1 is connected to the sampling node through the current-limiting resistor R5. The first contact KA3-1 is connected in series between the first diode D1 and the second resistor R2, and the other end of the second resistor R2 is connected to the live wire output terminal Lout; The neutral output terminal Nout is connected to the ground terminal in sequence through the third resistor R3, the second contact KA3-2 and the fourth resistor R4; The filter capacitor C1, the Zener diode D2, and the transient suppression diode DT1 are all connected between the sampling node and the ground.

9. A short-circuit detection circuit at the output terminal of a single-phase AC charging pile according to claim 8, characterized in that, The sampling node is connected to the first input terminal of the voltage comparator.

10. A short-circuit detection circuit for the output terminal of a single-phase AC charging pile according to claim 1, characterized in that, The MCU is used to read the short-circuit detection signal after a preset sampling delay after controlling the output short-circuit detection relay to enter the detection state, and output a protection control signal when the short-circuit detection signal indicates a short circuit so that the charging main relay remains open or changes from a closed state to an open state.

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