AC charging pile charging interface low-impedance short circuit detection circuit and AC charging pile

Abstract

The invention relates to a low-impedance short-circuit detection circuit for a charging interface of an alternating-current charging pile and the alternating-current charging pile, and belongs to the field of charging fault detection. Comprising a detection loop and a signal processing loop, a first divider resistor and a control switch are connected in series in the detection loop, and the control switch is used for connecting a null line and a live line of the AC output port in the detection loop in series when the AC output port is not charged; the signal processing loop is connected with a voltage detection point in the detection loop and is used for outputting a signal for judging whether the zero line and the live wire are short-circuited or not according to potential change of the voltage detection point caused by impedance between the zero line and the live wire, so that short-circuit detection between the zero line and the live wire of the charging pile can be still realized when equipment is idle, and the safety is higher; and the accuracy is better.

Description

Technical Field

[0001] The invention relates to a low-impedance short-circuit detection circuit for a charging interface of an AC charging pile and an AC charging pile, belonging to the field of charging fault detection. Background Art

[0002] AC charging piles are a type of equipment used to charge electric vehicles. They are commonly found in public areas and provide convenience for charging electric vehicles. The input end of the AC charging pile is connected to the AC power grid, and the output end is equipped with a charging gun to charge the electric vehicle.

[0003] The rapid development of electric vehicles has made charging piles more and more common, but due to certain factors, charging piles may have a short circuit between the neutral and live wires of the AC charging pile. Short circuits between the neutral and live wires of the charging pile will cause leakage and other phenomena, which is very dangerous. Therefore, detecting whether the neutral and live wires of the charging pile are short-circuited is the key to solving the problem.

[0004] The Chinese invention patent application publication with application publication number CN116184264A discloses a circuit for detecting a short circuit between the live wire and the neutral wire of a charging gun. The scheme sets a voltage divider circuit between the neutral wire of the charging gun and the ground, and detects the output of the voltage divider circuit through a comparison circuit. When a car is charging, the AC output port outputs AC power. At this time, if there is a short circuit between the live wire and the neutral wire of the charging gun, the current flows from the live wire through the short-circuit point into the neutral wire, and flows into the ground through the voltage divider circuit. The voltage divider circuit outputs a certain voltage value to the outside and is detected by the comparison circuit to realize the judgment of whether the live wire and the neutral wire of the charging pile are short-circuited. The detection circuit is as follows Figure 1 shown.

[0005] This solution has the following disadvantages: 1) It is impossible to detect a short circuit between the neutral and live wires of the charging pile when the charging pile is idle. Detection can only be achieved when the AC output port outputs AC power. 2) The safety is poor. When a short circuit is detected between the neutral and live wires of the charging pile, there is already a 220V AC output in the circuit, which can easily cause a charging accident and cause serious losses. 3) The accuracy is poor. The AC power has fluctuations and peaks and is easily affected by external factors. The detected voltage divider value is not accurate enough. Summary of the invention

[0006] In order to solve the above-mentioned problems in the prior art, the present invention provides a low-impedance short-circuit detection circuit for the charging interface of an AC charging pile, which is used to solve the problem in the prior art that the charging gun output port can only be short-circuited when there is AC output. The AC charging pile provided by the present invention can detect whether the AC output port of the charging pile is short-circuited when the device is idle, thereby improving the safety and reliability of the short-circuit detection circuit.

[0007] To achieve the above object, the solution of the present invention includes: A technical solution of a low-impedance short-circuit detection circuit for a charging interface of an AC charging pile of the present invention comprises a detection circuit with one end connected to a power supply and the other end grounded and a signal processing circuit; a first voltage-dividing resistor and a control switch are connected in series in the detection circuit, and the control switch is used to connect the neutral line and the live line of the AC output port in series into the detection circuit when not charging; the signal processing circuit is connected to a voltage detection point in the detection circuit, and is used to output a signal for judging whether there is a short circuit between the neutral line and the live line according to a change in the potential of the voltage detection point caused by the impedance between the neutral line and the live line.

[0008] Furthermore, the detection loop also includes a filter circuit connected between the voltage detection point and the ground for filtering high-frequency signals, and the filter circuit includes a capacitor and a resistor that are connected in parallel and then in series in the filter circuit.

[0009] Furthermore, the signal processing circuit includes a comparator composed of an operational amplifier, one of the positive input terminal and the reverse input terminal of the comparator is connected to the voltage detection point, and the other is used to connect to the reference voltage, and the output terminal of the comparator outputs a signal for determining whether there is a short circuit between the neutral wire and the live wire.

[0010] Furthermore, the signal processing circuit also includes a level receiving circuit, which includes a first transistor whose collector and emitter are connected in series between a power supply and a ground; the base of the first transistor is connected to the output end of the comparator; a second voltage-dividing resistor is also connected in series in the level receiving circuit, and a signal output point for outputting a signal to determine whether there is a short circuit between the neutral wire and the live wire is provided between the second voltage-dividing resistor and the first transistor.

[0011] Furthermore, the comparator connected to the reference voltage terminal also includes a filter circuit for filtering high-frequency signals, and the filter circuit includes a capacitor and a resistor which are connected in parallel and then in series in the filter circuit.

[0012] Furthermore, the signal processing loop also includes a voltage follower composed of an operational amplifier; one of the positive input terminal and the reverse input terminal of the comparator that is not connected to the reference voltage is connected to the voltage detection point through the voltage follower.

[0013] Furthermore, it also includes a control circuit, which includes a switch circuit connected in series with the control coil to form a loop, the switch circuit is connected to the control signal output end, the control signal output end is used to output a control signal when the vehicle is charging, the control signal controls the switch circuit to conduct so that the control coil is energized, and the control coil is used to control the control switch to disconnect after being energized; when the control switch is closed, one of the neutral wire and the live wire is connected to the end close to the positive pole in the detection circuit, and the other of the neutral wire and the live wire is connected to the end close to the negative pole in the detection circuit.

[0014] Furthermore, the switching circuit includes a third transistor whose collector and emitter are connected in series between a power supply and a ground, and a second transistor whose collector and emitter are connected in series with a control coil; the third transistor is also connected in series with a third voltage-dividing resistor, and the base of the second transistor is also connected between the third voltage-dividing resistor and the third transistor.

[0015] Furthermore, a capacitor for adjusting the delay of the switch action by charging and discharging is connected in parallel between the base and the emitter of the second transistor.

[0016] Furthermore, a first diode providing a discharge circuit for the control coil is connected in parallel between two ends of the control coil.

[0017] Furthermore, it also includes an abnormal state protection circuit; the abnormal state protection circuit includes a second diode, a third diode and a resistor; the second diode is connected between the control switch and the voltage detection point for reverse protection; the voltage detection point is grounded through the third diode, and the direction of the third diode is from the ground to the voltage detection point; the resistor is connected between the control switch and the ground.

[0018] The beneficial effects of the present invention are as follows: by setting an active detection circuit between the neutral and live wires of the charging pile, short circuit detection between the neutral and live wires can be achieved when the device is idle. When the device is idle, if the impedance between the neutral and live wires of the charging pile is reduced, resulting in a short circuit, the signal processing circuit detects the change in the potential at the voltage detection point in the detection circuit and immediately outputs a signal to inform the charging pile of the short circuit fault, so that the device can still continuously detect the neutral and live wires of the charging pile when it is idle. When a car is charging, the detection circuit is disconnected from the neutral and live wires of the charging pile, and the detection is stopped. In addition, the use of a DC power supply is safer and more accurate.

[0019] A technical solution of an AC charging pile of the present invention includes a low-impedance short-circuit detection circuit for a charging interface of an AC charging pile, wherein the low-impedance short-circuit detection circuit for the charging interface of the AC charging pile includes a detection circuit with one end connected to a power supply and the other end grounded and a signal processing circuit; a first voltage-dividing resistor and a control switch are connected in series in the detection circuit, and the control switch is used to connect the neutral line and the live line of the AC output port in series into the detection circuit when not charging; the signal processing circuit is connected to a voltage detection point in the detection circuit, and is used to output a signal for judging whether there is a short circuit between the neutral line and the live line according to a change in the potential of the voltage detection point caused by the impedance between the neutral line and the live line.

[0020] Furthermore, the detection loop also includes a filter circuit connected between the voltage detection point and the ground for filtering high-frequency signals, and the filter circuit includes a capacitor and a resistor that are connected in parallel and then in series in the filter circuit.

[0021] Furthermore, the signal processing circuit includes a comparator composed of an operational amplifier, one of the positive input terminal and the reverse input terminal of the comparator is connected to the voltage detection point, and the other is used to connect to the reference voltage, and the output terminal of the comparator outputs a signal for determining whether there is a short circuit between the neutral wire and the live wire.

[0022] Furthermore, the signal processing circuit also includes a level receiving circuit, which includes a first transistor whose collector and emitter are connected in series between a power supply and a ground; the base of the first transistor is connected to the output end of the comparator; a second voltage-dividing resistor is also connected in series in the level receiving circuit, and a signal output point for outputting a signal to determine whether there is a short circuit between the neutral wire and the live wire is provided between the second voltage-dividing resistor and the first transistor.

[0023] Furthermore, the comparator connected to the reference voltage terminal also includes a filter circuit for filtering high-frequency signals, and the filter circuit includes a capacitor and a resistor which are connected in parallel and then in series in the filter circuit.

[0024] Furthermore, the signal processing loop also includes a voltage follower composed of an operational amplifier; one of the positive input terminal and the reverse input terminal of the comparator that is not connected to the reference voltage is connected to the voltage detection point through the voltage follower.

[0025] Furthermore, it also includes a control circuit, which includes a switch circuit connected in series with the control coil to form a loop, the switch circuit is connected to the control signal output end, the control signal output end is used to output a control signal when the vehicle is charging, the control signal controls the switch circuit to conduct so that the control coil is energized, and the control coil is used to control the control switch to disconnect after being energized; when the control switch is closed, one of the neutral wire and the live wire is connected to the end close to the positive pole in the detection circuit, and the other of the neutral wire and the live wire is connected to the end close to the negative pole in the detection circuit.

[0026] Furthermore, the switching circuit includes a third transistor whose collector and emitter are connected in series between a power supply and a ground, and a second transistor whose collector and emitter are connected in series with a control coil; the third transistor is also connected in series with a third voltage-dividing resistor, and the base of the second transistor is also connected between the third voltage-dividing resistor and the third transistor.

[0027] Furthermore, a capacitor for adjusting the delay of the switch action by charging and discharging is connected in parallel between the base and the emitter of the second transistor.

[0028] Furthermore, a first diode providing a discharge circuit for the control coil is connected in parallel between two ends of the control coil.

[0029] Furthermore, it also includes an abnormal state protection circuit; the abnormal state protection circuit includes a second diode, a third diode and a resistor; the second diode is connected between the control switch and the voltage detection point for reverse protection; the voltage detection point is grounded through the third diode, and the direction of the third diode is from the ground to the voltage detection point; the resistor is connected between the control switch and the ground.

[0030] The beneficial effects of the present invention are as follows: by setting the circuit as described above between the neutral wire and the live wire of the charging pile, if the neutral wire and the live wire of the charging gun muzzle of the charging pile are short-circuited due to the frequent plugging and unplugging of the charging gun and the fact that the charging gun is usually exposed to the environment, dirt is easily hidden on the surface, and dew is easily condensed when the temperature difference between morning and evening is large, the signal processing circuit detects the change in potential at the voltage detection point in the detection circuit and immediately outputs a signal to inform the charging pile of the short-circuit fault, so that the charging pile can still achieve continuous detection of the neutral wire and the live wire of the charging pile when it is idle, and the use of a DC power supply is safer and more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a circuit diagram for detecting a short circuit between a live wire and a neutral wire of a charging gun in the background technology; Figure 2 It is a circuit diagram of a low-impedance short-circuit detection circuit for an AC charging pile charging interface provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail in a clear and complete manner in conjunction with the accompanying drawings and embodiments.

[0033] The concept of the present invention is to connect the neutral wire and the live wire of the AC output port to an active detection circuit, wherein a section of the detection circuit connected to the positive pole of the power supply and a section connected to the negative pole are respectively connected to the neutral wire and the live wire, and the impedance between the neutral wire and the live wire of the AC output port changes due to a short circuit, thereby obtaining different voltage division values ​​at the detection points in the detection circuit, and judging whether the AC output port is short-circuited by detecting the voltage division values.

[0034] Circuit Example 1: In the present embodiment, a low-impedance short-circuit detection circuit for the charging interface of an AC charging pile is provided. When the neutral wire and the live wire of the AC power are connected to the detection circuit, the impedance between the neutral wire and the live wire of the AC output port changes, and the detection point obtains a different voltage division value. When the voltage division value of the detection point exceeds the limited voltage, the controller is informed after signal processing that the charging pile is in a short-circuit fault state.

[0035] like Figure 2What is shown is a schematic diagram of a low-impedance short-circuit detection circuit of an AC charging pile charging interface provided by an embodiment of the present invention. The low-impedance short-circuit detection circuit of the AC charging pile charging interface includes a detection circuit and a signal processing circuit.

[0036] Figure 2 The first voltage-dividing resistor R166, the control switch K3 for controlling the AC output port to be connected to the cut-out detection circuit, and the third resistor R187 are connected in series to form a detection circuit. One end of the first voltage-dividing resistor R166 is connected to a 12V DC power supply, and the other end is connected to contact 5 of the control switch K3. One end of the third resistor R187 is connected to contact 2 of the control switch K3, and the other end is grounded. The control switch K3 can be controlled to connect its contact 5 and its contact 4 inside it, and at the same time connect its contact 2 and its contact 3 inside it, and the contact 2 and contact 3 of the control switch K3 are respectively connected to the neutral wire and the live wire of the AC output port (that is, the AC output port is connected to the detection circuit, that is, the neutral wire and the live wire of the AC output port are connected in series to the detection circuit). The voltage detection point is Figure 2 At point A of the AC output terminal. When the neutral and live wires are connected to the detection circuit, if there is no impedance between the neutral and live wires, the detection circuit cannot be turned on, and a corresponding potential is generated at the voltage detection point A. If there is impedance between the neutral and live wires due to a short circuit, the detection circuit is turned on, and a different potential is generated at the voltage detection point A. The corresponding potential is detected by the signal processing circuit, thereby realizing the detection of the short circuit of the AC output port.

[0037] In order to reduce the influence of high-frequency signals on the detection loop, as an optional implementation, a filter circuit is connected near the detection point A. The second resistor R167 and the first capacitor C42 are connected in parallel to form a filter circuit, one end of the filter circuit is grounded, and the other end is connected to the detection loop.

[0038] The first voltage-dividing resistor R166 and the third resistor R187 are both 510R resistors with a precision of 1%, the second resistor R167 is a 360R resistor with a precision of 1%, and the first capacitor C42 is a capacitor with a capacitance of 4.7μF and a withstand voltage of 25V. Modifying the values ​​of the first voltage-dividing resistor R166, the second resistor R167, and the third resistor R187 can change the corresponding potential during short-circuit detection, and can be used to adjust the impedance between the charging interfaces to be considered as a short circuit.

[0039] The signal processing circuit includes a comparator. The comparator is composed of an operational amplifier. Specifically, the positive input terminal 5 of the operational amplifier is connected to the voltage detection point A, and the reverse input terminal 6 is connected to the +12V power supply through the fourth resistor R171 to provide a reference voltage to the comparator; the potential change at the voltage detection point A is measured by the reference voltage, so as to determine whether a short circuit occurs in the charging interface through the output level of the comparator.

[0040] In order to avoid the detection deviation caused by the interference of the comparator output, as another embodiment, the signal processing circuit also includes a level receiving circuit, and the level receiving circuit includes a first transistor Q20. The base of the first transistor Q20 is connected to the output end of the comparator, the collector is connected to the positive electrode of the 3.3V DC power supply through the voltage dividing resistor R176, and the emitter is grounded. Specifically, the potential obtained at the voltage detection point A in the detection circuit is compared with the reference voltage through the comparator. If the potential at the voltage detection point A is higher than the reference voltage, the comparator outputs a high level, the base voltage of the first transistor Q20 is higher than the emitter, the collector and the emitter are turned on, and the level of the signal output point OUT SC is pulled down, indicating that the charging pile is normal; if the voltage at the voltage detection point is lower than the reference voltage, the comparator outputs a low level, the base voltage of the first transistor Q20 is lower than the emitter, the first transistor Q20 is turned off, and the level of the signal output point OUT SC increases, indicating that the charging pile is short-circuited abnormally.

[0041] In order to reduce the influence of high-frequency signals on the detection circuit, as an optional implementation, a filter circuit is connected between the fourth resistor R171 and the comparator. The filter resistor R172 and the filter capacitor C31 are connected in parallel to form a filter circuit, one end of the filter circuit is grounded, and the other end is connected to the detection circuit.

[0042] The fourth resistor R171 is a resistor with an accuracy of 1% and a resistance value of 10K, the voltage-dividing resistor R176 is a resistor with an accuracy of 5% and a resistance value of 4.7K, the filter resistor R172 is a resistor with an accuracy of 1% and a resistance value of 4.7K, and the filter capacitor C31 is a capacitor with a capacitance of 4.7μF and a withstand voltage of 25V.

[0043] Circuit Example 2: On the basis of Example 1, in order to avoid the influence of the subsequent circuit on the voltage detection point A, a voltage follower composed of an operational amplifier is connected between the voltage detection point A and the comparator. The positive input terminal of the operational amplifier is connected to the voltage detection point A through the fifth resistor R165, the reverse input terminal is connected to the output terminal through the sixth resistor R169, and the output terminal is connected to the positive input terminal of the comparator through the seventh resistor R175. The power supply terminal of the operational amplifier is connected to a 12V DC power supply, and the other power supply terminal is grounded. In order to reduce the influence of high-frequency signals on the voltage follower circuit, a grounded second capacitor C33 is connected to the power supply terminal for filtering.

[0044] Among them, the fifth resistor R165, the sixth resistor R169, and the seventh resistor R175 are all resistors with a precision of 1% and a resistance of 1K, and the second capacitor C33 is a capacitor with a capacitance of 0.1 μF and a withstand voltage of 50V.

[0045] Circuit Example 3: On the basis of Example 1, when a car comes to charge, the AC relay is closed, and the neutral line and the live line of the AC output port are respectively connected to the 220V mains. At this time, if the AC output port is connected to the detection circuit, the detection circuit will be easily damaged. When charging is required, the control switch K3 is switched to cut the AC output port out of the detection circuit. The operation is troublesome and unreliable. In order to avoid damage to the detection circuit, a control circuit is added at the control switch K3.

[0046] The closing or opening of the control switch K3 can control the AC output port to connect or disconnect the detection circuit. Figure 2 The third triode Q19, the second triode Q18 and the control coil for controlling the control switch K3 to be closed or disconnected constitute the control loop of the control switch K3, which controls the action of the control switch K3. The base of the third triode Q19 is connected to the control signal output terminal PE3_JDQ_N, the collector is connected to the 3.3V DC power supply through the eighth resistor R168, and the emitter is grounded. The base of the second triode Q18 is connected to the 3.3V DC power supply through the eighth resistor R168, the collector is connected to the 12V DC power supply through the control coil, and the emitter is grounded. In order to avoid excessive current damaging the third triode Q19, the ninth resistor R185 and the tenth resistor R186 are connected in series in front of its base for current limiting. At the same time, in order to avoid the influence of high-frequency signals on the control loop, as an optional implementation method, the third capacitor C38 and the fourth capacitor C39 are connected to the 3.3V DC power supply through the eighth resistor R168 at one end, and the other end is grounded. Specifically, when a car is charging at the charging pile, the control signal output terminal PE3_JDQ_N outputs a low-level signal, and the base of the third transistor Q19 receives the low-level signal. At this time, the base voltage of the third transistor Q19 is lower than the emitter, and the collector of the third transistor Q19 is disconnected from the emitter, and then the base of the second transistor Q18 is divided into a high voltage, and the collector and the emitter of the second transistor Q18 are connected. After the control coil is energized, the control switch K3 is disconnected, and the AC output port cuts out the detection loop. When there is no car charging at the charging pile, the control signal output terminal PE3_JDQ_N outputs a high-level signal, and the base of the third transistor Q19 receives a high-level signal. The base voltage of the third transistor Q19 is higher than the emitter, and the collector and the emitter are connected, thereby lowering the base voltage of the second transistor Q18. At this time, the collector and the emitter of the third transistor Q19 cannot be connected, the control coil loses power, and the control switch K3 is closed, and the neutral wire and the live wire of the AC power supply are connected to the detection loop.

[0047] At the same time, in order to prevent the self-inductance potential generated by the power failure of the relay from causing an impact on the circuit, as an implementable method, a first diode D20 is connected at both ends of the control coil to provide a discharge circuit for the self-inductance electromotive force, so that the current discharges smoothly and protects the previous circuit.

[0048] Specifically, an auxiliary contact of the AC output relay is connected to the control signal output terminal PE3_JDQ_N for outputting a high level. At the same time, the control signal output terminal PE3_JDQ_N controls the closing or opening of the control switch K3 through the above process, so that the control switch K3 and the AC output relay maintain interlocking control, that is, the control switch K3 remains open during the charging process (when the AC output relay is closed), and the control switch K3 remains closed in the non-charging state (when the AC output relay is open), which can effectively prevent the detection circuit from being damaged when a car comes to charge.

[0049] The ninth resistor R185 and the tenth resistor R186 are both 4.7K resistors with a precision of 5%, the eighth resistor R168 is a 10K resistor with a precision of 5%, and the third capacitor C38 and the fourth capacitor C39 are both 4.7μF capacitors with a withstand voltage of 25V.

[0050] Circuit Example 4: On the basis of Example 3, the eighth resistor R168, the third capacitor C38, the fourth capacitor C39 and the capacitor of the AC output relay control part cooperate with each other through charging and discharging to adjust the action delay of the relay, which can ensure that there is enough dead time between the AC output relay and the action of K3. Specifically, when a car comes to charge, PE3 outputs a low level, the base voltage of the first diode Q19 is lower than the emitter, and the collector and the emitter cannot be turned on. At this time, the 3.3V DC voltage delays the change speed of the base voltage of the third transistor Q18 by charging the third capacitor C38 and the fourth capacitor C39, thereby ensuring that there is enough dead time between the AC output relay and the action of K3.

[0051] Circuit Example 5: On the basis of Example 1, in order to avoid the relay from malfunctioning due to some reason and being unable to close or disconnect, thereby causing damage to the detection circuit, the abnormal state protection circuit is formed by the second diode D15, the third resistor R187 and the third diode D19. The second diode D15 is connected between the voltage detection point A and the contact 5 of the control switch K3. One end of the third diode D19 is connected to the 12V DC power supply through the first voltage-dividing resistor R166, and the other end is grounded. Specifically, when an abnormal situation occurs and causes the AC output relay to close, the control switch K3 contact 5 and contact 4, contact 2 and contact 3 fail to be successfully disconnected, and there is an AC220V AC voltage between the AC output ports AC220Vout_L and AC220Vout_N. In the positive half cycle, due to the reverse cutoff characteristics of the second diode D15, the circuit is blocked, preventing high voltage from entering the detection control circuit. In the negative half cycle, in conjunction with the layout position of the PCB, the current forms a path through GND, the third diode D19, and the second diode D15. The second diode D15 is a TVS diode (Transient Voltage Suppression Diode, used to protect the circuit from overvoltage damage), which can clamp the voltage at the detection point A of the detection circuit to 0.7V, thereby protecting the subsequent circuit. In this process, a large current will be generated, and the previous detection circuit will trigger the overcurrent protection to disconnect the AC output relay. If the previous detection circuit does not respond to the overcurrent fault for a long time, the large current will melt the third diode D19 and the second diode D15 to disconnect the circuit. At this time, the current flows into GND through the third resistor R187. This process will also trigger the previous overcurrent protection to disconnect the AC output relay. If the previous detection circuit does not respond to the overcurrent fault for a long time, the large current will melt the third resistor R187 and completely disconnect the circuit, intercepting the fault in the protection circuit part, and will not cause large-scale damage and serious accidents.

[0052] Charging pile implementation example: An AC charging pile of this embodiment includes a charging gun. The AC charging interface on the charging gun is connected to the charging socket of the vehicle by inserting the charging gun into the vehicle. The charging gun is often plugged in and out and is usually exposed to the environment. The surface is easy to hide dirt. When the temperature difference between morning and evening is large, it is easy to condense dew. Therefore, there is a probability that the impedance between the neutral line and the live line in the AC charging interface is reduced, which may cause a short circuit. If the charging pile does not promptly detect that the impedance between the neutral line and the live line is too low and there may be a short circuit, if a vehicle comes to charge at this time, the AC contactor of the charging pile closes and outputs power, which may cause danger.

[0053] To solve the above problems, the charging pile of this embodiment is equipped with an AC charging pile charging interface low-impedance short-circuit detection circuit as described in circuit embodiments 1 to 5 around the neutral wire and the live wire. The circuit has been described clearly enough in the circuit embodiment and will not be repeated here.

Claims

1. A low impedance short circuit detection circuit for an AC charging pile charging interface, characterized in that: It comprises a detection circuit with one end connected to a power supply and the other end grounded, and a signal processing circuit; the detection circuit is connected in series with a first voltage-dividing resistor and a control switch, and the control switch is used to connect the neutral line and the live line of the AC output port in series into the detection circuit when not charging; the signal processing circuit is connected to the voltage detection point in the detection circuit, and is used to output a signal for judging whether there is a short circuit between the neutral line and the live line according to the change of the potential of the voltage detection point caused by the impedance between the neutral line and the live line.

2. The AC charging pile charging interface low impedance short circuit detection circuit according to claim 1, characterized in that: The signal processing circuit includes a comparator composed of an operational amplifier, one of the positive input terminal and the reverse input terminal of the comparator is connected to the voltage detection point, and the other is used to connect to the reference voltage. The output terminal of the comparator outputs a signal for determining whether there is a short circuit between the neutral wire and the live wire.

3. The AC charging pile charging interface low impedance short circuit detection circuit according to claim 2, characterized in that: The signal processing circuit also includes a level receiving circuit, which includes a first transistor with a collector and an emitter connected in series between a power supply and a ground; the base of the first transistor is connected to the output end of the comparator; a second voltage-dividing resistor is also connected in series in the level receiving circuit, and a signal output point for outputting a signal to determine whether there is a short circuit between the neutral line and the live line is provided between the second voltage-dividing resistor and the first transistor.

4. The AC charging pile charging interface low impedance short circuit detection circuit according to claim 3, characterized in that: The comparator connected to one end of the reference voltage also includes a filter circuit for filtering high-frequency signals, and the filter circuit includes a capacitor and a resistor connected in parallel and then in series in the filter circuit; the detection circuit also includes a filter circuit connected between the voltage detection point and the ground for filtering high-frequency signals, and the filter circuit includes a capacitor and a resistor connected in parallel and then in series in the filter circuit.

5. The AC charging pile charging interface low impedance short circuit detection circuit according to claim 2, characterized in that: The signal processing loop also includes a voltage follower composed of an operational amplifier; one of the positive input terminal and the reverse input terminal of the comparator that is not connected to the reference voltage is connected to the voltage detection point through the voltage follower.

6. The AC charging pile charging interface low impedance short circuit detection circuit according to claim 1, characterized in that: It also includes a control circuit, which includes a switch circuit connected in series with the control coil to form a loop, the switch circuit is connected to the control signal output end, the control signal output end is used to output a control signal when the vehicle is charging, the control signal controls the switch circuit to conduct so that the control coil is energized, and the control coil is used to control the control switch to be disconnected after being energized; when the control switch is closed, one of the neutral wire and the live wire is connected to the end of the detection circuit close to the positive electrode, and the other of the neutral wire and the live wire is connected to the end of the detection circuit close to the negative electrode.

7. The AC charging pile charging interface low impedance short circuit detection circuit according to claim 6, characterized in that: The switch circuit includes a third transistor whose collector and emitter are connected in series between a power supply and a ground, and a second transistor whose collector and emitter are connected in series with a control coil; the third transistor is also connected in series with a third voltage-dividing resistor, and the base of the second transistor is also connected between the third voltage-dividing resistor and the third transistor.

8. The AC charging pile charging interface low impedance short circuit detection circuit according to claim 6, characterized in that: A capacitor for adjusting the delay of the control switch action through charging and discharging is connected in parallel between the base and the emitter of the second transistor; and a first diode for providing a discharge circuit for the control coil is connected in parallel at both ends of the control coil.

9. The AC charging pile charging interface low impedance short circuit detection circuit according to claim 1, characterized in that: It also includes an abnormal state protection circuit; the abnormal state protection circuit includes a second diode, a third diode and a resistor; the second diode is connected between the control switch and the voltage detection point for reverse protection; the voltage detection point is grounded through the third diode, and the direction of the third diode is from the ground to the voltage detection point; the resistor is connected between the control switch and the ground.

10. An AC charging pile, characterized in that: It comprises a low impedance short circuit detection circuit for a charging interface of an AC charging pile as described in any one of claims 1 to 9.

Images