Alternating current output end short circuit detection device

Abstract

The embodiment of the invention provides an alternating current output end short circuit detection device. The device comprises a first direct current power supply which is connected with a one-way output current limiting circuit; the one-way output current limiting circuit is connected with the first direct-current power supply and the switching circuit; the switching circuit is connected with the one-way output current limiting circuit, the current limiting and detecting circuit and the MCU; the current limiting and detecting circuit is connected with the switching circuit, the alternating current power supply live wire and the MCU; and the residual voltage detection circuit is connected with the AC power supply live wire, the AC power supply zero line and the MCU. According to the embodiment of the invention, the short-circuit detection of the alternating-current output end is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit detection, and particularly to a short - circuit detection device for an AC output terminal. Background Art

[0002] Most of the existing AC charging piles do not have the function of short - circuit detection at the output terminal before AC output power supply. If the output terminal of the AC charging pile is not subjected to short - circuit detection before power supply, it may cause the output current to be instantaneously too large when the output of the charging pile is closed due to a short - circuit at the output terminal, resulting in the burning of internal components of the charging pile and damage to the charging pile. Summary of the Invention

[0003] An embodiment of the present invention provides a short - circuit detection device for an AC output terminal to achieve short - circuit detection of the AC output terminal.

[0004] The technical solution of the embodiment of the present invention is realized as follows: A short - circuit detection device for an AC output terminal, where the AC output terminal is the output terminal of an AC charging pile. The device includes: a first DC power supply, a unidirectional output current - limiting circuit, a switch circuit, a current - limiting and detection circuit, a residual voltage detection circuit, and a micro - control unit. And there are a live - wire switch and a neutral - wire switch between the AC input terminal and the AC output terminal. Among them: The first DC power supply is connected to the unidirectional output current - limiting circuit and is used for: outputting a DC current; The unidirectional output current - limiting circuit is connected to the first DC power supply at one end and to the switch circuit at the other end, and is used for: blocking the current flowing from the switch circuit to the direction of the first DC power supply and sending the DC current output by the first DC power supply to the switch circuit; The switch circuit is connected to the unidirectional output current - limiting circuit at one end, to the current - limiting and detection circuit at one end, to the AC power - supply neutral wire with the connection point between the neutral - wire switch and the AC output terminal, and to the MCU at the other end, and is used for: disconnecting or closing under the control of the MCU; The current - limiting and detection circuit is connected to the switch circuit at one end, to the AC power - supply live wire with the connection point between the live - wire switch and the AC output terminal, and to the MCU at the other end, and is used for: outputting the short - circuit detection voltage of the AC output terminal to the MCU; The residual voltage detection circuit is connected to the AC power - supply live wire with the connection point between the live - wire switch and the AC output terminal at one end, to the AC power - supply neutral wire with the connection point between the neutral - wire switch and the AC output terminal at the other end, and to the MCU at the other end, and is used for: outputting the residual voltage detection voltage of the AC output terminal to the MCU; The MCU is respectively connected to the switch circuit, the current - limiting and detection circuit, and the residual voltage detection circuit, and is used for: controlling the disconnection and closing of the switch circuit, and determining whether there is a short - circuit at the AC output terminal according to the voltage output by the current - limiting and detection circuit and the voltage output by the residual voltage detection circuit.

[0005] The first DC power supply includes a DC power supply and a first capacitor; one end of the first capacitor is connected to the DC power supply, and the other end is grounded.

[0006] The unidirectional output current limiting circuit includes a first diode and a first resistor; the positive electrode of the first diode is connected to the first DC power supply, and the negative electrode of the first diode is connected to the switch circuit; one end of the first resistor is grounded and shares the ground terminal with the first DC power supply, and the other end is connected to the switch circuit.

[0007] The unidirectional output current limiting circuit further includes a second diode and a fuse; One end of the second diode is connected to the negative electrode of the first diode, and the other end is connected between the first resistor and the switch circuit; the fuse is connected between the first resistor and the switch circuit.

[0008] The switch circuit includes a first switch and a second switch; The first switch is connected between the unidirectional output current limiting circuit and the current limiting and detection circuit; the second switch is connected between the unidirectional output current limiting circuit and the AC power supply neutral line, and the connection point with the AC power supply neutral line is located between the neutral line switch and the AC output terminal.

[0009] The current limiting and detection circuit includes a second resistor, a unidirectional optocoupler and a third resistor, where: The second resistor is connected between the switch circuit and the positive electrode of the primary side of the unidirectional optocoupler; The positive electrode of the primary side of the unidirectional optocoupler is connected to the second resistor, the negative electrode is connected to the AC power supply live wire and the connection point is located between the live wire switch and the AC output terminal; One end of the third resistor is connected to the second DC power supply, and the other end is connected to the positive electrode of the secondary side of the unidirectional optocoupler and the second IO port of the MCU; The negative electrode of the secondary side of the unidirectional optocoupler is grounded.

[0010] The current limiting and detection circuit further includes a sixth resistor, a voltage clamping device, a seventh resistor and a second capacitor; The sixth resistor is connected between the second resistor and the positive electrode of the primary side of the unidirectional optocoupler; the voltage clamping device is connected between the second resistor and the negative electrode of the primary side of the unidirectional optocoupler; the seventh resistor is in parallel with the primary side of the unidirectional optocoupler; one end of the second capacitor is connected to the second IO port of the MCU, and the other end is grounded.

[0011] The residual voltage detection circuit includes: a fourth resistor, a bidirectional optocoupler and a fifth resistor, where: The fourth resistor is connected between the AC power supply live wire and one end of the primary side of the bidirectional optocoupler, and the connection point of the fourth resistor and the AC power supply live wire is located between the live wire switch and the AC output terminal; The other end of the primary side of the bidirectional optocoupler is connected to the neutral wire of the AC power supply, and the connection point is located between the neutral wire switch and the AC output terminal; One end of the fifth resistor is connected to the third DC power supply, and the other end is connected to the positive pole of the secondary side of the bidirectional optocoupler and the first IO port of the MCU; The negative pole of the secondary side of the bidirectional optocoupler is grounded.

[0012] The residual voltage detection circuit further includes a third capacitor; Wherein, one end of the third capacitor is connected to the first IO port of the MCU, and the other end is grounded.

[0013] The MCU is configured to: when an external load is connected to the AC output terminal, output a disconnection signal to the live wire switch and the neutral wire switch; when it detects that the residual voltage detection voltage output by the residual voltage detection circuit satisfies a set first voltage range, send a closing signal to the switch circuit, and after waiting for a preset time duration, if it detects that the short-circuit detection voltage output by the current limiting and detection circuit satisfies a set second voltage range, determine that there is a short circuit at the AC output terminal.

[0014] In the above embodiments, by adding a switch circuit, the circuit between the first DC power supply and the AC output terminal can be disconnected, improving the reliability of the circuit; by adding a residual voltage detection circuit, the forward and reverse residual voltage detection of the AC output terminal is realized. At the same time, this circuit is also the residual voltage discharge circuit of the AC output terminal, and together with the current limiting and detection circuit, the short-circuit detection of the AC output terminal is realized. Description of the Drawings

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0016] Figure 1 It is a schematic structural diagram of a short-circuit detection device for an AC output terminal provided by an embodiment of the present invention; Figure 2 It is a schematic structural diagram of a short-circuit detection device for an AC output terminal provided by another embodiment of the present invention; Figure 3 It is a schematic structural diagram of a short-circuit detection device for an AC output terminal provided by yet another embodiment of the present invention. Detailed Embodiments

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0018] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present invention and the above accompanying drawings are used to distinguish similar objects and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0019] Figure 1 FIG. is a schematic structural diagram of a short-circuit detection device for an AC output terminal provided in an embodiment of the present invention, where the AC output terminal is the output terminal of an AC charging pile. As Figure 1 shown, the device mainly includes: a first DC power supply, a unidirectional output current-limiting circuit, a switching circuit, a current-limiting and detection circuit, a residual voltage detection circuit, and an MCU (Micro Controller Unit), and there are a live wire switch and a neutral wire switch between the AC input terminal and the AC output terminal. The live wire switch is located on the AC power supply live wire between the AC input and output terminals, and the neutral wire switch is located on the AC power supply neutral wire between the AC input and output terminals, where: 1) The first DC power supply is connected to the unidirectional output current-limiting circuit and is used for: outputting a DC current.

[0020] In practical applications, if the AC output terminal is the output terminal of an AC charging pile, the first DC power supply can share the power generated by the flyback power supply circuit on the power supply board of the AC charging pile, or it can be an additional set of power supplies generated by adding an independent winding to the flyback power supply, or an independent power module can also be used. The first DC power supply is usually designed to be 12V (volts).

[0021] 2) The unidirectional output current-limiting circuit is connected to the first DC power supply at one end and the switching circuit at the other end, and is used for: blocking the current flowing from the switching circuit to the first DC power supply direction and transmitting the DC current output by the first DC power supply to the switching circuit.

[0022] iii) A switch circuit, one end of which is connected to the unidirectional output current-limiting circuit, one end is connected to the current-limiting and detection circuit, one end is connected to the AC power supply neutral line and the connection point is between the neutral line switch and the AC output terminal, and the other end is connected to the MCU, and is used for: disconnecting or closing under the control of the MCU.

[0023] In actual application, the switch circuit is default open.

[0024] iv) A current-limiting and detection circuit, one end of which is connected to the switch circuit, one end is connected to the AC power supply live line and the connection point is between the live line switch and the AC output terminal, and the other end is connected to the MCU, and is used for: outputting the short-circuit detection voltage of the AC output terminal to the MCU.

[0025] v) A residual voltage detection circuit, one end of which is connected to the AC power supply live line and the connection point is between the live line switch and the AC output terminal, one end is connected to the AC power supply neutral line and the connection point is between the neutral line switch and the AC output terminal, and the other end is connected to the MCU, and is used for: outputting the residual voltage detection voltage of the AC output terminal to the MCU.

[0026] vi) The MCU is respectively connected to the switch circuit, the current-limiting and detection circuit, and the residual voltage detection circuit, and is used for: controlling the disconnection and closing of the switch circuit, and determining whether there is a short circuit at the AC output terminal according to the residual voltage detection voltage output by the residual voltage detection circuit and the short-circuit detection voltage output by the current-limiting and detection circuit.

[0027] The MCU is also connected to the live line switch and the neutral line switch, and is used for controlling the disconnection and closing of the live line switch and the neutral line switch.

[0028] Figure 1 The L in in is the AC input live line port, N in is the AC input neutral line port, L out is the AC output live line port, N out is the AC output neutral line port, and the external load is connected through L out and N out When the AC output terminal is the output terminal of the AC charging pile, the external load is usually the on-vehicle charger of the electric vehicle. The live line switch and the neutral line switch can adopt relays.

[0029] As Figure 1 shown, when the external load is connected to the AC output terminal, the MCU will output a disconnection signal to the live line switch on the AC power supply live line and the neutral line switch on the AC power supply neutral line; then, the MCU detects whether the residual voltage detection voltage output by the residual voltage detection circuit meets the set first voltage range. If it meets, a closing signal is sent to the switch circuit, and after waiting for a preset time period, the MCU detects whether the short-circuit detection voltage output by the current-limiting and detection circuit meets the set second voltage range. If it meets, it is determined that there is a short circuit at the AC output terminal.

[0030] Specifically, when an external load is connected to the AC output terminal, there are two cases at the AC output terminal: Case 1, the AC output terminal is short-circuited; Case 2, the AC output terminal is not short-circuited, and due to the presence of safety capacitors on the external load, there is usually a positive residual voltage or a negative residual voltage on the safety capacitor, and the residual voltage of the safety capacitor is the residual voltage of the AC output terminal, that is, for Case 2, there are also two cases, one is that the AC output terminal has a positive residual voltage, and the other is that the AC output terminal has a negative residual voltage. The working process of the device shown below will be described for these three cases respectively: Figure 1 The working process of the device shown is described as follows: Case 1, the AC output terminal is short-circuited, that is, the impedance of the AC output terminal is 0 Ω (ohm). In this case, when the external load is connected to the AC output terminal, the MCU outputs a disconnection signal to the live wire switch on the AC power supply live wire and the neutral wire switch on the AC power supply neutral wire; Since the residual voltage at the AC output terminal is almost 0 V, almost no current flows through the residual voltage detection circuit. When the MCU detects that the residual voltage detection voltage output by the residual voltage detection circuit satisfies the set first voltage range, it sends a closing signal to the switch circuit; After the switch circuit is closed, the DC current output by the first DC power supply forms a current loop through the switch circuit, the current limiting and detection circuit, and the external load. When the MCU detects that the short-circuit detection voltage output by the current limiting and detection circuit satisfies the set second voltage range, it determines that the AC output terminal is short-circuited.

[0031] Case 2, the AC output terminal is not short-circuited (i.e., the AC output terminal has a certain impedance), and the AC output terminal has a positive residual voltage In this case, when the external load is connected to the AC output terminal, the MCU outputs a disconnection signal to the live wire switch on the AC power supply live wire and the neutral wire switch on the AC power supply neutral wire; Since there is a positive residual voltage at the AC output terminal, the positive residual voltage at the AC output terminal will discharge through the residual voltage detection circuit. When the MCU detects that the residual voltage detection voltage output by the residual voltage detection circuit satisfies the set first voltage range, it sends a closing signal to the switch circuit; After the switch circuit is closed, the DC current output by the first DC power supply forms a current loop through the switch circuit, the current limiting and detection circuit, and the external load, thereby charging the safety capacitor on the external load. When the voltage on the safety capacitor approaches the voltage of the first DC power supply, the MCU detects that the short-circuit detection voltage output by the current limiting and detection circuit does not satisfy the set second voltage range, and determines that the AC output terminal is not short-circuited.

[0032] Case 3, the AC output terminal is not short-circuited (i.e., the AC output terminal has a certain impedance), and the AC output terminal has a negative residual voltage In this case, when an external load is connected to the AC output terminal, the MCU outputs a disconnection signal to the live wire switch on the live wire of the AC power supply and the neutral wire switch on the neutral wire of the AC power supply; Since there is a negative residual voltage at the AC output terminal, the negative residual voltage at the AC output terminal will discharge through the residual voltage detection circuit. When the MCU detects that the residual voltage detection voltage output by the residual voltage detection circuit meets the set first voltage range, it sends a closing signal to the switch circuit; After the switch circuit is closed, the DC current output by the first DC power supply forms a current loop through the switch circuit, the current limiting and detection circuit, and the external load, charging the safety capacitor on the external load. When the voltage on the safety capacitor approaches the voltage of the first DC power supply, the MCU detects that the short-circuit detection voltage output by the current limiting and detection circuit does not meet the set second voltage range, and then determines that there is no short circuit at the AC output terminal.

[0033] It can be seen from the above analysis that for the three situations existing at the AC output terminal: there is a short circuit at the AC output terminal, there is no short circuit at the AC output terminal and there is a positive residual voltage at the AC output terminal, there is no short circuit at the AC output terminal and there is a negative residual voltage at the AC output terminal, Figure 1 the shown device can correctly detect them all.

[0034] Figure 1 The shown device improves the reliability of the circuit by adding a switch circuit to disconnect the circuit between the first DC power supply and the AC output terminal; and by adding a residual voltage detection circuit, the positive and negative residual voltage detection of the AC output terminal is realized. At the same time, this circuit is also the residual voltage discharge circuit of the AC output terminal, and together with the current limiting and detection circuit, the short circuit detection of the AC output terminal is realized.

[0035] Figure 2 This is a schematic structural diagram of a short-circuit detection device for an AC output terminal provided by another embodiment of the present invention. As Figure 2 shown: 1) The first DC power supply includes a DC power supply V CC1 and a first capacitor C1.

[0036] Among them, one end of C1 is connected to V CC1 , and the other end is grounded. C1 is the energy storage and filtering capacitor of V CC1 .

[0037] 2) The unidirectional output current limiting circuit includes a first diode D1 and a first resistor R1.

[0038] Among them, the positive electrode of D1 is connected to V CC1 , the negative electrode is connected to the switch circuit; one end of R1 is grounded and shares the ground terminal with the first DC power supply, and the other end is connected to the switch circuit. It can be seen from Figure 2 that the other end of R1 is actually connected to K2 in the switch circuit.

[0039] D1 is a unidirectional conduction diode, ensuring that V CC1 has a normal output and no reverse current flows into V CC1 . R1 is the output current-limiting resistor of V CC1 . R1 can be an ordinary resistor or a PPTC (Polymeric Positive Temperature Coefficient) resistor.

[0040] III) The switch circuit includes: a first switch K1 and a second switch K2.

[0041] Among them, K1 is connected between the unidirectional output current-limiting circuit and the current-limiting and detection circuit; K2 is connected between R1 in the unidirectional output current-limiting circuit and the AC power supply neutral line, and the connection point with the AC power supply neutral line is located between the neutral line switch and the AC output terminal.

[0042] K1 and K2 are default-disconnected.

[0043] K1 and K2 are generally relays, and can also be switching devices such as optocouplers.

[0044] IV) The current-limiting and detection circuit includes: a second resistor R2, a unidirectional optocoupler OP1, and a third resistor R3, where: 1) R2 is connected between the switch circuit and the positive pole of the primary side of OP1; As Figure 2 shown, actually, R2 is connected between K1 in the switch circuit and the positive pole of the primary side of OP1; at the same time, it can be seen from Figure 2 that D1 is connected between V CC1 and K1.

[0045] As Figure 2 shown, the primary side of OP1 is the unidirectional diode.

[0046] 2) The positive pole of the primary side of OP1 is connected to the second resistor R2, and the negative pole is connected to the AC power supply live wire and the connection point is located between the live wire switch and the AC output terminal; 3) One end of R3 is connected to the second DC power supply V CC2 , and the other end is connected to the positive pole of the secondary side of OP1 and the second IO port of the MCU; The negative pole of the secondary side of OP1 is grounded. As Figure 2 shown, the secondary side of OP1 is the NPN transistor, where the collector of the NPN transistor is the positive pole of the secondary side, and the emitter is the negative pole of the secondary side.

[0047] V CC2 is the supply voltage of the secondary side of OP1, generally selected as 3.3V; R3 is the pull-up resistor.

[0048] 5) The residual voltage detection circuit includes: a fourth resistor R4, a bidirectional optocoupler OP2, and a fifth resistor R5, where: R4 is connected between the AC power supply live wire and one end of the primary side of OP2, and the connection point of R4 and the AC power supply live wire is located between the live wire switch and the AC output terminal; The other end of the primary side of OP2 is connected to the AC power supply neutral wire, and the connection point is located between the neutral wire switch and the AC output terminal; One end of R5 is connected to the third DC power supply VCC3, and the other end is connected to the positive electrode of the secondary side of OP2 and the first IO port of the MCU; The negative electrode of the secondary side of OP2 is grounded.

[0049] As Figure 2 shown, the primary side of OP2 is a bidirectional diode, and the secondary side of OP2 is an NPN transistor. The collector of the NPN transistor is the positive electrode of the secondary side, and the emitter is the negative electrode of the secondary side.

[0050] R4 and OP2 constitute the forward and reverse discharge paths of the AC output terminal; V CC3 is the supply voltage of the secondary side of OP2, generally selected as 3.3V; R5 is a pull-up resistor.

[0051] The following describes the working process of the device shown respectively for three situations existing at the AC output terminal: Figure 2 as follows: Situation 1: There is a short circuit at the AC output terminal, that is, the impedance of the AC output terminal is 0Ω In this case, when an external load is connected to the AC output terminal, the MCU outputs a disconnection signal to the live wire switch on the AC power supply live wire and the neutral wire switch on the AC power supply neutral wire; Since the residual voltage at the AC output terminal is almost 0V, almost no current flows through R4 and the primary side of OP2, then no current flows through the secondary side of OP2 either, that is, the secondary side of OP2 is disconnected, and the level V RES on the first IO port of the MCU is high level (for example: V RES is greater than the set first voltage threshold); When the MCU detects that V RES is high level, it can be known that: the secondary side of OP2 is disconnected, and thus it can be inferred that: no current passes through the primary side of OP2, and further it can be inferred that: the residual voltage at the AC output terminal is less than the preset safe residual voltage threshold (for example: 50V), and thus a closing signal is sent to K1 and K2 in the switch circuit; After K1 and K2 are closed, V CC1The output DC current forms a current loop through D1, K1, R2, the primary side of OP1, the external load, K2, R1, and C1. Since the impedance of the AC output terminal is very low, generally 0Ω, the DC current continuously flows through the primary side of OP1, then the secondary side of OP1 conducts, and the level V on the second IO port of the MCU DECT is at a low level (e.g., V DECT is less than the set second voltage threshold), then the MCU determines that there is a short circuit at the AC output terminal.

[0052] Case 2: There is no short circuit at the AC output terminal (i.e., the AC output terminal has a certain impedance), and there is a positive residual voltage at the AC output terminal In this case, when the external load is connected to the AC output terminal, the MCU outputs a disconnection signal to the live wire switch on the AC power supply live wire and the neutral wire switch on the AC power supply neutral wire; Since there is a positive residual voltage at the AC output terminal, the positive residual voltage at the AC output terminal discharges through R4 in the residual voltage detection circuit and the primary side of OP2, then the secondary side of OP2 conducts, and V RES gradually decreases. When V RES decreases to a set voltage value, the secondary side of OP2 disconnects, and thus V RES increases. The MCU detects that V RES is at a high level (e.g., V RES is greater than the set first voltage threshold), then sends a closing signal to K1 and K2 in the switch circuit; among them, when the MCU detects that V RES is at a high level, it can be known that: the secondary side of OP2 disconnects, and thus it can be inferred that: there is no current passing through the primary side of OP2, and further it can be inferred that: the residual voltage at the AC output terminal is less than the preset safe residual voltage threshold (e.g., 50V), and thus sends a closing signal to K1 and K2 in the switch circuit; After K1 and K2 close, V CC1 The output DC current forms a current loop through D1, K1, R2, the primary side of OP1, the external load, K2, R1, and C1, and V CC1 charges the safety capacitor of the external load; After K1 and K2 are closed for a period of time, the voltage on the safety capacitor of the external load approaches the voltage of V CC1 , then there is no current flowing through the primary side of OP1, and the secondary side of OP1 disconnects, and thus V DECT is at a high level (e.g., V DECT is greater than or equal to the set second voltage threshold), and the MCU determines that the AC output terminal is in a non - short - circuit state.

[0053] Case 3: There is no short circuit at the AC output terminal (i.e., the AC output terminal has a certain impedance), and there is a negative residual voltage at the AC output terminal In this case, when an external load is connected to the AC output terminal, the MCU outputs a disconnection signal to the live wire switch on the AC power supply live wire and the neutral wire switch on the AC power supply neutral wire; Since there is a negative residual voltage at the AC output terminal, the negative residual voltage at the AC output terminal will discharge through R4 and the primary side of OP2 in the residual voltage detection circuit, and then the secondary side of OP2 conducts, and V RES gradually decreases. When V RES decreases to a set voltage value, the secondary side of OP2 disconnects, so that V RES increases. When the MCU detects that V RES is at a high level (e.g., V RES is greater than the set first voltage threshold), it sends a closing signal to K1 and K2 in the switching circuit; among them, when the MCU detects that V RES is at a high level, it can be known that: the secondary side of OP2 disconnects, so it can be inferred that: there is no current passing through the primary side of OP2, and further it can be inferred that: the residual voltage at the AC output terminal is less than the preset safe residual voltage threshold (e.g., 50V), so a closing signal is sent to K1 and K2 in the switching circuit; After K1 and K2 close, the DC current output by V CC1 forms a current loop through D1, K1, R2, the primary side of OP1, the external load, K2, R1, C1, so V CC1 charges the safety capacitor of the external load; at the same time, the negative residual voltage quickly discharges through N out , K2, R1, C1, D1, K1, R2, the primary side of OP1, L out ; After K1 and K2 are closed for a period of time, the voltage on the safety capacitor of the external load approaches the voltage of V CC1 , so there is no current flowing through the primary side of OP1, and the secondary side of OP1 disconnects, so that V DECT is at a high level (e.g., V DECT is greater than or equal to the set second voltage threshold), and the MCU determines that the AC output terminal is in a non-short-circuit state.

[0054] From the above analysis, it can be seen that for the three situations existing at the AC output terminal: the AC output terminal has a short circuit, the AC output terminal has no short circuit and there is a positive residual voltage at the AC output terminal, and the AC output terminal has no short circuit and there is a negative residual voltage at the AC output terminal, Figure 2 the device shown can correctly detect them.

[0055] Figure 2In the shown device, K1 and K2 are default to be disconnected, thus defaultly disconnecting the circuit between the first DC power supply and the AC output terminal, improving the reliability of the circuit; and the residual voltage detection circuit realizes the detection of the positive and negative residual voltages at the AC output terminal. This circuit is also the residual voltage discharge circuit at the AC output terminal. When the MCU detects that the residual voltage detection voltage output by the residual voltage detection circuit is at a high level, it can determine that the residual voltage at the AC output terminal is less than the set safe residual voltage threshold, and then perform the short-circuit detection action before AC output, which can avoid the risk of large impact current that may exist at the moment when the current limiting and detection circuit is turned on, greatly reducing the withstand voltage power of the resistors in the device. Thus, ordinary resistors can be selected for the device, reducing the size and cost of the device and improving the reliability of the device.

[0056] Figure 3 This is a schematic structural diagram of the short-circuit detection device at the AC output terminal provided by another embodiment of the present invention. As Figure 3 shown, its device compared with the device shown in Figure 2 is as follows: 1) The unidirectional output current limiting circuit further includes a second diode D2.

[0057] Among them, one end of D2 is connected to the negative pole of D1, and the other end is connected between R1 and the switch circuit.

[0058] As Figure 3 shown, the other end of D2 is actually connected between R1 and K2 in the switch circuit.

[0059] D2 can provide a discharge loop for the negative residual voltage on the external load to reduce the influence of the negative residual voltage of the external load on V CC1 .

[0060] 2) The unidirectional output current limiting circuit further includes a fuse F1.

[0061] Among them, F1 is connected between R1 and the switch circuit.

[0062] As Figure 3 shown, F1 is actually connected between R1 and K2 in the switch circuit.

[0063] F1 can be a protective resistor. If an accidental overcurrent occurs, F1 will disconnect to protect other devices.

[0064] 3) The current limiting and detection circuit further includes a sixth resistor R6 and a voltage clamping device D3.

[0065] Among them, R6 is connected between the positive pole of the primary side of R2 and OP1; D3 is connected between the negative pole of the primary side of R2 and OP1.

[0066] D3 can be a zener diode or other voltage clamping devices. As Figure 3As shown, D3 uses a zener diode. At this time, the negative electrode of D3 is connected to R2, and the positive electrode is connected to the negative electrode of the primary side of OP1.

[0067] 4) The current limiting and detection circuit further includes a seventh resistor R7.

[0068] Among them, R7 is connected in parallel with the primary side of OP1.

[0069] 5) The current limiting and detection circuit further includes a second capacitor C2.

[0070] Among them, one end of C2 is connected to the second IO port of the MCU, and the other end is grounded. C2 is a high-frequency filtering capacitor.

[0071] 6) The residual voltage detection circuit further includes a third capacitor C3.

[0072] Among them, one end of C3 is connected to the first IO port of the MCU, and the other end is grounded. C3 is a high-frequency filtering capacitor.

[0073] The following describes the working process of the Figure 3 shown device for three situations existing at the AC output end respectively: Situation 1: There is a short circuit at the AC output end, that is, the impedance of the AC output end is 0Ω In this case, when an external load is connected to the AC output end, the MCU outputs a disconnection signal to the live wire switch on the AC power supply live wire and the neutral wire switch on the AC power supply neutral wire; Since the residual voltage at the AC output end is almost 0V and almost no current flows through R4 and the primary side of OP2, no current flows through the secondary side of OP2 either, that is, the secondary side of OP2 is disconnected, then the level V RES on the first IO port of the MCU is high level (for example: V RES is greater than the set first voltage threshold); When the MCU detects that V RES is high level, it can be known that: the secondary side of OP2 is disconnected, and thus it can be inferred that: no current passes through the primary side of OP2, and further it can be inferred that: the residual voltage at the AC output end is less than the preset safe residual voltage threshold (for example: 50V), and thus a closing signal is sent to K1 and K2 in the switch circuit; After K1 and K2 are closed, the DC current output by V CC1 forms a current loop through D1, K1, R2, R6, R7, D3, the primary side of OP1, the external load, K2, F1, R1, C1. Since the impedance of the AC output end is very low, generally 0Ω, the DC current continuously flows through the primary side of OP1, then the secondary side of OP1 conducts, and the level V DECT on the second IO port of the MCU is low level (for example: V DECTIf it is less than the set second voltage threshold), the MCU determines that there is a short circuit at the AC output terminal.

[0074] Among them, R2 and D3 form a voltage clamping circuit, clamping the voltage of the circuit composed of the primary side of R6, R7, and OP1 at a lower voltage value. R6 is the current limiting resistor for the total current of the primary side of OP1 and R7. Since the forward conduction voltage of the primary side of OP1 remains unchanged around a fixed voltage (e.g., 1.4V), the value of R6 will determine the maximum value of the total current of the primary side of OP1 and R7. R7 is connected in parallel with the primary side of OP1, and R7 will bypass a part of the current flowing through R6. Generally, the current flowing through R7 is 3~15 mA (milliamperes).

[0075] Case 2: There is no short circuit at the AC output terminal (i.e., there is a certain impedance at the AC output terminal), and there is a positive residual voltage at the AC output terminal Among them, when the AC output terminal is the output terminal of an AC charging pile, the impedance range of the AC output terminal is generally 100Ω~10MΩ (megaohms).

[0076] In this case, when an external load is connected to the AC output terminal, the MCU outputs a disconnection signal to the live wire switch on the AC power supply live wire and the neutral wire switch on the AC power supply neutral wire; Since there is a positive residual voltage at the AC output terminal, the positive residual voltage at the AC output terminal will discharge through R4 and the primary side of OP2 in the residual voltage detection circuit, then the secondary side of OP2 conducts, and V RES gradually decreases. When V RES decreases to a set voltage value, the secondary side of OP2 disconnects, so that V RES increases. The MCU detects that V RES is at a high level (e.g., V RES is greater than the set first voltage threshold), and then sends a closing signal to K1 and K2 in the switch circuit; Among them, when the MCU detects that V RES is at a high level, it can be known that: the secondary side of OP2 disconnects, and thus it can be inferred that: there is no current passing through the primary side of OP2, and further it can be inferred that: the residual voltage at the AC output terminal is less than the preset safety residual voltage threshold (e.g., 50V), and thus a closing signal is sent to K1 and K2 in the switch circuit; After K1 and K2 are closed, the DC current output by VCC1 forms a current loop through D1, K1, R2, R6, R7, D3, the primary side of OP1, the external load, K2, F1, R1, and C1, and VCC1 charges the safety capacitor of the external load. Among them, R2 and D3 constitute a voltage clamping circuit, clamping the voltage of the circuit composed of R6, R7, and the primary side of OP1 at a lower voltage value. R6 is the current limiting resistor for the total current of the primary side of OP1 and R7. Since the forward conduction voltage of the primary side of OP1 remains unchanged around a fixed voltage (e.g., 1.4V), the resistance value of R6 will determine the maximum value of the total current of the primary side of OP1 and R7. R7 is connected in parallel with the primary side of OP1, and R7 will bypass a part of the current flowing through R6. Generally, the current flowing through R7 is 3 - 15mA; After K1 and K2 are closed for a period of time (generally 2 - 5 seconds), the voltage on the safety capacitor of the external load approaches the voltage of V CC1 . The current basically flows through R7, and no current flows through the primary side of OP1. Then the secondary side of OP1 disconnects, so that V DECT is at a high level (e.g., V DECT is greater than or equal to the set second voltage threshold), and the MCU determines that the AC output terminal is in a non - short - circuit state. Among them, the larger the current flowing through R7 within a certain range, the less current will flow through the primary side of OP1, thus shortening the time for V RES to change from low level to high level and reducing the detection time of the MCU.

[0077] Case 3: There is no short - circuit at the AC output terminal (i.e., there is a certain impedance at the AC output terminal), and there is a negative residual voltage at the AC output terminal In this case, when the external load is connected to the AC output terminal, the MCU outputs a disconnection signal to the live - wire switch on the AC power supply live wire and the neutral - wire switch on the AC power supply neutral wire; Since there is a negative residual voltage at the AC output terminal, the negative residual voltage at the AC output terminal will discharge through R4 and the primary side of OP2 in the residual voltage detection circuit, and then the secondary side of OP2 conducts, and V RES gradually decreases. When V RES decreases to a set voltage value, the secondary side of OP2 disconnects, so that V RES rises. The MCU detects that V RES is at a high level (e.g., V RES is greater than the set first voltage threshold), and then sends a closing signal to K1 and K2 in the switching circuit; Among them, when the MCU detects that V RES is at a high level, it can be known that: the secondary side of OP2 disconnects, and thus it can be inferred that: no current passes through the primary side of OP2, and further it can be inferred that: the residual voltage at the AC output terminal is less than the preset safety residual voltage threshold (e.g., 50V), so as to send a closing signal to K1 and K2 in the switching circuit; After K1 and K2 are closed, V CC1 The output DC current forms a current loop through D1, K1, R2, R6, R7, D3, the primary side of OP1, the external load, K2, F1, R1, and C1, then V CC1 charges the safety capacitor of the external load; at the same time, the negative residual voltage quickly discharges through N out , K2, F1, D2, K1, R2, R6, R7, D3, the primary side of OP1, and Lout. Among them, R2 and D3 constitute a voltage clamping circuit, clamping the voltage of the circuit composed of R6, R7, and the primary side of OP1 at a lower voltage value. R6 is the current-limiting resistor for the total current of the primary side of OP1 and R7. Since the forward conduction voltage of the primary side of OP1 remains around a fixed voltage (such as 1.4V) unchanged, the value of R6 will determine the maximum value of the total current of the primary side of OP1 and R7. R7 is connected in parallel with the primary side of OP1, and R7 will bypass a part of the current flowing through R6. Generally, the current flowing through R7 is 3 - 15 mA; After K1 and K2 are closed for a period of time (generally 2 - 5 seconds), the voltage on the safety capacitor of the external load approaches the voltage of V CC1 , and almost all the current flows through R7. No current flows through the primary side of OP1, then the secondary side of OP1 disconnects, so V DECT is at a high level (such as: V DECT is greater than or equal to the set second voltage threshold), and the MCU determines that the AC output terminal is in a non-short-circuit state. Among them, the larger the current flowing through R7 within a certain range, the less current flows through the primary side of OP1, thus shortening the time for V RES to change from a low level to a high level and reducing the detection time of the MCU.

[0078] From the above analysis, it can be seen that for the three situations existing at the AC output terminal: the AC output terminal is short-circuited, the AC output terminal is not short-circuited and there is a positive residual voltage at the AC output terminal, and the AC output terminal is not short-circuited and there is a negative residual voltage at the AC output terminal, Figure 3 the device shown can correctly detect them.

[0079] Figure 3In the device shown, K1 and K2 are defaultly disconnected, thus defaultly disconnecting the circuit between the first DC power supply and the AC output terminal, improving the reliability of the circuit; and the residual voltage detection circuit realizes the detection of the positive and negative residual voltages at the AC output terminal. This circuit is also the residual voltage discharge circuit at the AC output terminal. When the MCU detects that the residual voltage detection voltage output by the residual voltage detection circuit is at a high level, it can be determined that the residual voltage at the AC output terminal is less than the set safe residual voltage threshold, and then the short-circuit detection operation before AC output is performed, which can avoid the risk of large impact current that may exist at the moment when the current limiting and detection circuits are turned on, greatly reducing the withstand power of the resistors and the tolerance power of the voltage regulator components in the device. Therefore, ordinary resistors and voltage regulator components can be selected for the device, reducing the size and cost of the device and improving the reliability of the device.

[0080] Those skilled in the art can understand that the features recited in the various embodiments and / or claims of the present disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly recited in the present application. In particular, without departing from the spirit and teachings of the present application, the features recited in the various embodiments and / or claims of the present application can be combined and / or combined in various ways, and all such combinations and / or combinations fall within the scope disclosed in the present application.

[0081] Specific embodiments are used herein to illustrate the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the core idea of the present invention and does not limit the present application. For those skilled in the art, changes can be made in the specific implementation manners and application scopes according to the ideas, spirits, and principles of the present invention. Any modifications, equivalent replacements, improvements, etc. made by them shall be included within the scope protected by the present application.

Claims

1. An AC output terminal short-circuit detection device, characterized in that, The AC output terminal is the output terminal of an AC charging pile. The device includes: a first DC power supply, a unidirectional output current limiting circuit, a switching circuit, a current limiting and detection circuit, a residual voltage detection circuit, and a microcontroller unit. There are a live wire switch and a neutral wire switch between the AC input terminal and the AC output terminal. Among them: The first DC power supply, connected to the unidirectional output current limiting circuit, is used for: outputting a DC current; The unidirectional output current limiting circuit, with one end connected to the first DC power supply and the other end connected to the switching circuit, is used for: blocking the current flowing from the switching circuit to the first DC power supply direction, and transmitting the DC current output by the first DC power supply to the switching circuit; The switching circuit, with one end connected to the unidirectional output current limiting circuit, one end connected to the current limiting and detection circuit, one end connected to the AC power supply neutral wire and the connection point is between the neutral wire switch and the AC output terminal, and the other end connected to the MCU, is used for: disconnecting or closing under the control of the MCU; The current limiting and detection circuit, with one end connected to the switching circuit, one end connected to the AC power supply live wire and the connection point is between the live wire switch and the AC output terminal, and the other end connected to the MCU, is used for: outputting the short-circuit detection voltage of the AC output terminal to the MCU; The residual voltage detection circuit, with one end connected to the AC power supply live wire and the connection point is between the live wire switch and the AC output terminal, one end connected to the AC power supply neutral wire and the connection point is between the neutral wire switch and the AC output terminal, and the other end connected to the MCU, is used for: outputting the residual voltage detection voltage of the AC output terminal to the MCU; The MCU, respectively connected to the switching circuit, the current limiting and detection circuit, and the residual voltage detection current, is used for: controlling the disconnection and closing of the switching circuit, and determining whether there is a short circuit at the AC output terminal according to the voltage output by the current limiting and detection circuit and the voltage output by the residual voltage detection circuit.

2. The device according to claim 1, wherein The first DC power supply includes a DC power supply and a first capacitor; among them, one end of the first capacitor is connected to the DC power supply, and the other end is grounded.

3. The device according to claim 1, characterized in that The unidirectional output current limiting circuit includes a first diode and a first resistor; among them, the positive pole of the first diode is connected to the first DC power supply, and the negative pole of the first diode is connected to the switching circuit; one end of the first resistor is grounded and shares the grounding end with the first DC power supply, and the other end is connected to the switching circuit.

4. The device according to claim 2 or 3, characterized in that, The unidirectional output current limiting circuit further includes a second diode and a fuse; Among them, one end of the second diode is connected to the negative pole of the first diode, and the other end is connected between the first resistor and the switching circuit; the fuse is connected between the first resistor and the switching circuit.

5. The device according to claim 1, characterized in that, The switching circuit includes a first switch and a second switch; Among them, the first switch is connected between the unidirectional output current limiting circuit and the current limiting and detection circuit; the second switch is connected between the unidirectional output current limiting circuit and the AC power supply neutral wire, and the connection point with the AC power supply neutral wire is between the neutral wire switch and the AC output terminal.

6. The device according to claim 1, characterized in that, The current limiting and detection circuit includes a second resistor, a unidirectional optocoupler, and a third resistor, among which: The second resistor is connected between the switching circuit and the positive pole of the primary side of the unidirectional optocoupler; The positive pole of the primary side of the unidirectional optocoupler is connected to the second resistor, and the negative pole is connected to the AC power supply live wire and the connection point is between the live wire switch and the AC output terminal; One end of the third resistor is connected to the second DC power supply, and the other end is connected to the positive electrode of the secondary side of the unidirectional optocoupler and the second IO port of the MCU; The negative electrode of the secondary side of the unidirectional optocoupler is grounded.

7. The device according to claim 6, wherein The current limiting and detection circuit further includes a sixth resistor, a voltage clamping device, a seventh resistor and a second capacitor; Among them, the sixth resistor is connected between the second resistor and the positive electrode of the primary side of the unidirectional optocoupler; the voltage clamping device is connected between the second resistor and the negative electrode of the primary side of the unidirectional optocoupler; the seventh resistor is connected in parallel with the primary side of the unidirectional optocoupler; one end of the second capacitor is connected to the second IO port of the MCU, and the other end is grounded.

8. The device according to claim 1, characterized in that, The residual voltage detection circuit includes: a fourth resistor, a bidirectional optocoupler and a fifth resistor, where: The fourth resistor is connected between the AC power supply live wire and one end of the primary side of the bidirectional optocoupler, and the connection point of the fourth resistor and the AC power supply live wire is located between the live wire switch and the AC output terminal; The other end of the primary side of the bidirectional optocoupler is connected to the AC power supply neutral wire and the connection point is located between the neutral wire switch and the AC output terminal; One end of the fifth resistor is connected to the third DC power supply, and the other end is connected to the positive electrode of the secondary side of the bidirectional optocoupler and the first IO port of the MCU; The negative electrode of the secondary side of the bidirectional optocoupler is grounded.

9. The device according to claim 8, wherein The residual voltage detection circuit further includes a third capacitor; Among them, one end of the third capacitor is connected to the first IO port of the MCU, and the other end is grounded.

10. The device according to claim 1, characterized in that, The MCU is configured to: when an external load is connected to the AC output terminal, output a disconnection signal to the live wire switch and the neutral wire switch; when it detects that the residual voltage detection voltage output by the residual voltage detection circuit satisfies a set first voltage range, send a closing signal to the switch circuit, and after waiting for a preset time period, if it detects that the short-circuit detection voltage output by the current limiting and detection circuit satisfies a set second voltage range, determine that there is a short circuit at the AC output terminal.

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