Output end short circuit detection circuit and method before charging of three-phase alternating current charging pile

Abstract

The invention discloses a three-phase alternating current charging pile before-charging output end short circuit detection circuit, which comprises a three-phase alternating current power supply circuit, a power connection circuit and a short circuit detection circuit, and is characterized in that the power connection circuit comprises a first current-limiting resistor, a second current-limiting resistor and a first detection relay; the short circuit detection circuit comprises a first isolation optocoupler, a second isolation optocoupler, a third isolation optocoupler, a third current-limiting resistor, a fourth current-limiting resistor, a fifth current-limiting resistor, a sixth current-limiting resistor, a seventh current-limiting resistor, an eighth current-limiting resistor, a second detection relay, a third detection relay and a first optocoupler output circuit. And a second optocoupler output circuit and a third optocoupler output circuit. The circuit is simple, the hardware cost is low, and whether the output end of the three-phase alternating current power supply circuit is short-circuited or not can be accurately detected; under the condition that any one or more of the three groups of detection relays fail, abnormal signals can be detected through the first, second and third detection points so as to judge whether the detection circuit fails or not and give an alarm.

Description

Technical Field

[0001] The present invention relates to the technical field of three-phase AC charging piles, and in particular to a circuit and method for detecting short circuits at output ends of a three-phase AC charging pile before charging. Background Art

[0002] At present, the short-circuit detection scheme for charging piles needs to be equipped with multiple auxiliary relays, isolated power supplies or isolators, and protective devices between high voltage and low voltage, which has high hardware costs. Some short-circuit detection schemes for charging piles need to detect short circuits by measuring voltage-dividing signals, which are easily affected by resistance temperature drift or measurement errors. The three-phase circuit needs to detect each group of lines mutually, and the detection procedure needs to switch multiple relays multiple times, with many detection steps; and when the relay fails, there will be risks such as short circuit, energized output end, and misjudgment. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a short-circuit detection circuit for the output end of a three-phase AC charging pile before charging based on the deficiencies of the prior art. The main components of the detection circuit are three groups of detection relays and three isolation optocouplers, with simple circuits and low hardware costs. The detection circuit can accurately detect whether there is a short circuit problem between the first phase line output end, the second phase line output end, the third phase line output end and the neutral line output end of the three-phase AC power supply circuit. In the event of failure of any one or more of the three groups of detection relays, the detection circuit can detect abnormal signal problems through the first detection point, the second detection point and the third detection point to determine whether the detection circuit is faulty and to alarm. In addition, the present invention also provides a short-circuit detection method for the short-circuit detection circuit.

[0004] In order to solve the above-mentioned first technical problem, the technical solution of the present invention is: a three-phase AC charging pile output end short circuit detection circuit before charging, comprising: A three-phase AC power supply circuit, wherein a main relay is installed on the three-phase AC power supply circuit, and the main relay separates the three-phase AC power supply circuit into a first phase line input end, a first phase line output end, a second phase line input end, a second phase line output end, a third phase line input end, a third phase line output end, a neutral line input end, and a neutral line output end; A power connection circuit, the power connection circuit includes a first current limiting resistor and a second current limiting resistor, the first phase line input terminal, the first current limiting resistor and the first phase line output terminal are connected in series; the neutral line input terminal, the second current limiting resistor and the neutral line output terminal are connected in series; the power connection circuit is provided with a first detection relay for controlling the circuit to be turned on or off; A short circuit detection circuit, the short circuit detection circuit comprising a first isolation optocoupler, a second isolation optocoupler, a third isolation optocoupler, a third current limiting resistor, a fourth current limiting resistor, a fifth current limiting resistor, a sixth current limiting resistor, a seventh current limiting resistor, and an eighth current limiting resistor, wherein the first isolation optocoupler, the second isolation optocoupler, and the third isolation optocoupler respectively have an input end and an output end; the first phase line output end, the third current limiting resistor, the input end of the first isolation optocoupler, the fourth current limiting resistor, the fifth current limiting resistor, the input end of the second isolation optocoupler, the sixth current limiting resistor, the seventh current limiting resistor, the input end of the third isolation optocoupler, the eighth current limiting resistor, and the zero line output end are sequentially connected in series; the connection circuit between the fourth current limiting resistor and the fifth current limiting resistor is also electrically connected to the second phase line output end, and the sixth current limiting resistor The connecting circuit between the current limiting resistor and the seventh current limiting resistor is also electrically connected to the third phase line output terminal; the connecting circuit between the first isolation optocoupler input terminal and the second isolation optocoupler input terminal is provided with a second detection relay for controlling the circuit to be turned on or off; the connecting circuit between the second isolation optocoupler input terminal and the third isolation optocoupler input terminal is provided with a third detection relay for controlling the circuit to be turned on or off; the output end of the first isolation optocoupler is connected to the first optocoupler output circuit, and the first optocoupler output circuit is provided with a first detection point; the output end of the second isolation optocoupler is connected to the second optocoupler output circuit, and the second optocoupler output circuit is provided with a second detection point; the output end of the third isolation optocoupler is connected to the third optocoupler output circuit, and the third optocoupler output circuit is provided with a third detection point.

[0005] In the above technical scheme, the main relay includes a first main relay and a second main relay, and the first main relay and the second main relay respectively have two groups of relay switches; one group of relay switches of the first main relay is connected between the third phase line input terminal and the third phase line output terminal to control the conduction or disconnection of the third phase line; another group of relay switches of the first main relay is connected between the second phase line input terminal and the second phase line output terminal to control the conduction or disconnection of the second phase line; one group of relay switches of the second main relay is connected between the first phase line input terminal and the first phase line output terminal to control the conduction or disconnection of the first phase line; another group of relay switches of the second main relay is connected between the neutral line input terminal and the neutral line output terminal to control the conduction or disconnection of the neutral line.

[0006] In the above technical solution, the first detection relay is a normally open contact relay, and the first detection relay has two groups of relay switches; one group of relay switches of the first detection relay is connected to the circuit between the first current limiting resistor and the first phase line output end, or is connected to the circuit between the first phase line input end and the first current limiting resistor; the other group of relay switches of the first detection relay is connected to the circuit between the second current limiting resistor and the neutral line output end, or is connected to the circuit between the neutral line input end and the second current limiting resistor.

[0007] In the above technical solution, the second detection relay is a normally open contact relay, and the second detection relay has two groups of relay switches; one group of relay switches of the second detection relay is connected to the circuit between the first isolation optocoupler input terminal and the fourth current limiting resistor; the other group of relay switches of the second detection relay is connected to the circuit between the fifth current limiting resistor and the second isolation optocoupler input terminal.

[0008] In the above technical solution, the third detection relay is a normally open contact relay, and the third detection relay has two groups of relay switches; one group of relay switches of the third detection relay is connected to the circuit between the second isolation optocoupler input terminal and the sixth current limiting resistor; the other group of relay switches of the third detection relay is connected to the circuit between the seventh current limiting resistor and the third isolation optocoupler input terminal.

[0009] In the above technical scheme, the first current limiting resistor, the second current limiting resistor, the third current limiting resistor, the fourth current limiting resistor, the fifth current limiting resistor, the sixth current limiting resistor, the seventh current limiting resistor, and the eighth current limiting resistor are respectively parallel resistors, the equivalent resistance of the first current limiting resistor and the second current limiting resistor is 60 to 80 KΩ, the equivalent resistance of the third current limiting resistor, the fifth current limiting resistor and the seventh current limiting resistor is 40 to 55 KΩ, and the equivalent resistance of the fourth current limiting resistor, the sixth current limiting resistor and the eighth current limiting resistor is 15 to 30 KΩ.

[0010] In the above technical scheme, the input ends of the first isolation optocoupler, the second isolation optocoupler and the third isolation optocoupler are respectively LEDs, and the output ends of the first isolation optocoupler, the second isolation optocoupler and the third isolation optocoupler are respectively phototransistors; the first optocoupler output circuit includes a low-voltage power supply, a ninth resistor, a tenth resistor and a first rectifier capacitor, the low-voltage power supply, the ninth resistor and the phototransistor collector of the first isolation optocoupler are electrically connected in sequence, the first detection point, the tenth resistor, the first rectifier capacitor and the phototransistor emitter of the first isolation optocoupler are electrically connected in sequence, the connection circuit between the tenth resistor and the first rectifier capacitor is also electrically connected to the phototransistor collector of the first isolation optocoupler, and the phototransistor emitter of the first isolation optocoupler is grounded; the second optocoupler output circuit includes a low-voltage power supply, an eleventh resistor, a twelfth resistor and a second rectifier capacitor, the low-voltage power supply, the eleventh resistor and the second The phototransistor collector of the isolated optocoupler is electrically connected in sequence, the second detection point, the twelfth resistor, the second rectifying capacitor and the phototransistor emitter of the second isolated optocoupler are electrically connected in sequence, the connection circuit between the twelfth resistor and the second rectifying capacitor is also electrically connected to the phototransistor collector of the second isolated optocoupler, and the phototransistor emitter of the second isolated optocoupler is grounded; the third optocoupler output circuit includes a low-voltage power supply, a thirteenth resistor, a fourteenth resistor and a third rectifying capacitor, the low-voltage power supply, the thirteenth resistor and the phototransistor collector of the third isolated optocoupler are electrically connected in sequence, the third detection point, the fourteenth resistor, the third rectifying capacitor and the phototransistor emitter of the third isolated optocoupler are electrically connected in sequence, the connection circuit between the fourteenth resistor and the third rectifying capacitor is also electrically connected to the phototransistor collector of the third isolated optocoupler, and the phototransistor emitter of the third isolated optocoupler is grounded.

[0011] In the above technical solution, the resistance values ​​of the ninth resistor, the eleventh resistor and the thirteenth resistor are 8-12 KΩ, the resistance values ​​of the tenth resistor, the twelfth resistor and the fourteenth resistor are 0.8-1.2 KΩ, and the capacitance values ​​of the first rectifier capacitor, the second rectifier capacitor and the third rectifier capacitor are 100nF-1μF.

[0012] In the above technical solution, the first detection point of the first optocoupler output circuit, the second detection point of the second optocoupler output circuit and the third detection point of the third optocoupler output circuit are electrically connected to the MCU respectively.

[0013] In order to solve the above second technical problem, the technical solution of the present invention is: a short circuit detection method using the short circuit detection circuit at the output end of the three-phase AC charging pile before charging, including the following detection method: Ⅰ. Before charging the three-phase AC charging pile, the main relay is in a closed disconnected state, and the first detection relay, the second detection relay and the third detection relay are opened and turned on at the same time, so that the first phase line input end, the first current limiting resistor, the first phase line output end, the third current limiting resistor, the first isolation optocoupler input end, the fourth current limiting resistor, the fifth current limiting resistor, the second isolation optocoupler input end, the sixth current limiting resistor, the seventh current limiting resistor, the third isolation optocoupler input end, the eighth current limiting resistor, the zero line output end, the second current limiting resistor and the zero line input end are turned on in sequence and form a loop, the first isolation optocoupler, the second isolation optocoupler and the third isolation optocoupler input ends are respectively driven by micro-current to emit light, the first isolation optocoupler, the second isolation optocoupler and the third isolation optocoupler output ends are all turned on, and the first detection point, the second detection point and the third detection point can detect the waveform signal; it is judged that the first phase line output end, the second phase line output end, the third phase line output end and the zero line output end are safe, and there is no short circuit problem between them; Ⅱ. If there is no voltage difference at the input ends of the first isolation optocoupler, the second isolation optocoupler and the third isolation optocoupler, and the output ends of the first isolation optocoupler, the second isolation optocoupler and the third isolation optocoupler are not conducting, then the first detection point, the second detection point and the third detection point cannot detect the waveform signal, and can only detect the high level; it is concluded that there is a short circuit problem between the first phase line output end and the neutral line output end; III. If (1) there is no voltage difference at the input end of the first isolation optocoupler, the output end of the first isolation optocoupler is not conducting, the first detection point cannot detect the waveform signal, and can only detect a high level; (2) the input ends of the second isolation optocoupler and the third isolation optocoupler are respectively driven by micro-current to emit light, the output ends of the second isolation optocoupler and the third isolation optocoupler are both conducting, and the second detection point and the third detection point can both detect the waveform signal; it is concluded that there is a short circuit problem between the output end of the first phase line and the output end of the second phase line; IV. If (1) there is no voltage difference at the input end of the second isolation optocoupler, the output end of the second isolation optocoupler is not conducting, the second detection point cannot detect the waveform signal, and can only detect a high level; (2) the input ends of the first isolation optocoupler and the third isolation optocoupler are respectively driven by micro-current to emit light, the output ends of the first isolation optocoupler and the third isolation optocoupler are both conducting, and the first detection point and the third detection point can both detect the waveform signal; it is judged that there is a short circuit problem between the output end of the second phase line and the output end of the third phase line; V. If (1) there is no voltage difference between the input ends of the second isolation optocoupler and the third isolation optocoupler, and the output ends of the second isolation optocoupler and the third isolation optocoupler are not conducting, the second detection point and the third detection point cannot detect the waveform signal, and can only detect a high level; (2) the input end of the first isolation optocoupler is driven by a micro-current to emit light, the output end of the first isolation optocoupler is conducting, and the first detection point can detect the waveform signal; it is judged that there is a short circuit problem between the second phase line output end and the neutral line output end; VI. If (1) there is no voltage difference at the input end of the third isolation optocoupler, the output end of the third isolation optocoupler is not conducting, the third detection point cannot detect the waveform signal and can only detect a high level; (2) the input ends of the first isolation optocoupler and the second isolation optocoupler are driven by micro-current to emit light, the output ends of the first isolation optocoupler and the second isolation optocoupler are both conducting, and the first detection point and the second detection point can both detect the waveform signal; it is concluded that there is a short circuit problem between the third phase line output end and the neutral line output end.

[0014] The beneficial effects of the present invention are: (1) The main components of the detection circuit of the present invention are three groups of detection relays and three isolation optocouplers, with simple circuits and low hardware costs; (2) The detection circuit of the present invention determines whether there is a voltage difference at the input end of the first isolation optocoupler, the second isolation optocoupler and the third isolation optocoupler and whether the output end is turned on according to whether the first detection point, the second detection point and the third detection point can detect the waveform signal and the high level, so as to accurately detect whether there is a short circuit problem between the first phase line output end, the second phase line output end, the third phase line output end and the neutral line output end of the three-phase AC power supply circuit; (3) When any one or more of the first detection relay, the second detection relay and the third detection relay fail to open and cannot turn on the circuit, at least one of the first detection point, the second detection point and the third detection point will not detect the waveform signal and will detect a high level, so the first phase line output end, the second phase line output end and the neutral line output end will not be misjudged. The output terminal, the third phase line output terminal and the neutral line output terminal are safe; when the main relay is turned on and the circuit is turned on, and the first detection relay, the second detection relay and the third detection relay are in a state of failure and cannot be closed or disconnected, since the entire short-circuit detection circuit is connected in series with the first current limiting resistor, the second current limiting resistor, the third current limiting resistor, the fourth current limiting resistor, the fifth current limiting resistor, the sixth current limiting resistor, the seventh current limiting resistor and the eighth current limiting resistor, the entire short-circuit detection circuit is controllable. At this time, the first detection point, the second detection point and the third detection point can still detect the waveform, and the MCU can determine that the entire short-circuit detection circuit has a fault and alarm; it can be seen that the detection circuit of the present invention can detect abnormal signal problems through the first detection point, the second detection point and the third detection point when any one or more of the three groups of detection relays fail, so as to determine that the detection circuit has a fault and alarm, thereby avoiding the risk of misjudgment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the circuit structure diagram of the output short-circuit detection circuit of the three-phase AC charging pile before charging. DETAILED DESCRIPTION

[0016] The structural principle and working principle of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0017] like Figure 1As shown, the present invention is a short-circuit detection circuit for the output end of a three-phase AC charging pile before charging, comprising a three-phase AC power supply circuit, a power connection circuit and a short-circuit detection circuit; The three-phase AC power supply circuit includes a first phase line, a second phase line, a third phase line and a neutral line. A main relay is installed on the three-phase AC power supply circuit. The main relay divides the three-phase AC power supply circuit into a first phase line input terminal L1_IN, a first phase line output terminal L1_OUT, a second phase line input terminal L2_IN, a second phase line output terminal L2_OUT, a third phase line input terminal L3_IN, a third phase line output terminal L3_OUT, a neutral line input terminal N_IN and a neutral line output terminal N_OUT. By controlling the main relay, the conduction and disconnection of the first phase line, the second phase line, the third phase line and the neutral line can be controlled; The power connection circuit includes a first current limiting resistor R1 and a second current limiting resistor R2, the first phase line input terminal L1_IN, the first current limiting resistor R1 and the first phase line output terminal L1_OUT are connected in series; the neutral line input terminal N_IN, the second current limiting resistor R2 and the neutral line output terminal N_OUT are connected in series; the power connection circuit is provided with a first detection relay K3 for controlling the circuit to be turned on or off; The short circuit detection circuit includes a first isolation optocoupler OC1, a second isolation optocoupler OC2, a third isolation optocoupler OC3, a third current limiting resistor R3, a fourth current limiting resistor R4, a fifth current limiting resistor R5, a sixth current limiting resistor R6, a seventh current limiting resistor R7, and an eighth current limiting resistor R8. The first isolation optocoupler OC1, the second isolation optocoupler OC2, and the third isolation optocoupler OC3 respectively have an input end and an output end; the first phase line output end L1_OUT, the third current limiting resistor R3, the input end of the first isolation optocoupler OC1, the fourth current limiting resistor R4, the fifth current limiting resistor R5, the input end of the second isolation optocoupler OC2, the sixth current limiting resistor R6, the seventh current limiting resistor R7, the input end of the third isolation optocoupler OC3, the eighth current limiting resistor R8, and the zero line output end N_OUT are connected in series in sequence; the connection circuit between the fourth current limiting resistor R4 and the fifth current limiting resistor R5 is also electrically connected to the second phase line output end L2_OUT, the connection circuit between the sixth current limiting resistor R6 and the seventh current limiting resistor R7 is also electrically connected to the third phase line output terminal L3_OUT; the connection circuit between the first isolation optocoupler OC1 input terminal and the second isolation optocoupler OC2 input terminal is provided with a second detection relay K4 for controlling the circuit to be turned on or off; the connection circuit between the second isolation optocoupler OC2 input terminal and the third isolation optocoupler OC3 input terminal is provided with a third detection relay K5 for controlling the circuit to be turned on or off; the output end of the first isolation optocoupler OC1 is connected to the first optocoupler output circuit, and the first optocoupler output circuit is provided with a first detection point D1; the output end of the second isolation optocoupler OC2 is connected to the second optocoupler output circuit, and the second optocoupler output circuit is provided with a second detection point D2; the output end of the third isolation optocoupler OC3 is connected to the third optocoupler output circuit, and the third optocoupler output circuit is provided with a third detection point D3.

[0018] like Figure 1 As shown, the main relay includes a first main relay K1 and a second main relay K2, and the first main relay K1 and the second main relay K2 respectively have two groups of relay switches; one group of relay switches of the first main relay K1 is connected between the third phase line input terminal L3_IN and the third phase line output terminal L3_OUT to control the conduction or disconnection of the third phase line; another group of relay switches of the first main relay K1 is connected between the second phase line input terminal L2_IN and the second phase line output terminal L2_OUT to control the conduction or disconnection of the second phase line; one group of relay switches of the second main relay K2 is connected between the first phase line input terminal L1_IN and the first phase line output terminal L1_OUT to control the conduction or disconnection of the first phase line; another group of relay switches of the second main relay K2 is connected between the neutral line input terminal N_IN and the neutral line output terminal N_OUT to control the conduction or disconnection of the neutral line.

[0019] like Figure 1As shown, the first detection relay K3 is a normally open contact relay. Before the three-phase AC charging pile is charged, the system controls the first detection relay K3 to open and conduct the circuit, so that the short-circuit detection circuit is energized, and after the short-circuit detection is completed, the first detection relay K3 automatically resets to the initial closed and disconnected circuit state; the first detection relay K3 has two groups of relay switches; one group of relay switches of the first detection relay K3 is connected to the circuit between the first current limiting resistor R1 and the first phase line output terminal L1_OUT, or connected to the circuit between the first phase line input terminal L1_IN and the first current limiting resistor R1; the other group of relay switches of the first detection relay K3 is connected to the circuit between the second current limiting resistor R2 and the zero line output terminal N_OUT, or connected to the circuit between the zero line input terminal N_IN and the second current limiting resistor R2.

[0020] like Figure 1 As shown, the second detection relay K4 is a normally open contact relay, and the second detection relay K4 has two groups of relay switches; one group of relay switches of the second detection relay K4 is connected to the circuit between the first isolation optocoupler OC1 input end and the fourth current limiting resistor R4; another group of relay switches of the second detection relay K4 is connected to the circuit between the fifth current limiting resistor R5 and the second isolation optocoupler OC2 input end. The third detection relay K5 is a normally open contact relay, and the third detection relay K5 has two groups of relay switches; one group of relay switches of the third detection relay K5 is connected to the circuit between the second isolation optocoupler OC2 input end and the sixth current limiting resistor R6; another group of relay switches of the third detection relay K5 is connected to the circuit between the seventh current limiting resistor R7 and the third isolation optocoupler OC3 input end. Before charging the three-phase AC charging pile, the system controls the second detection relay K4 and the third detection relay K5 to open and conduct the circuit, so that the short-circuit detection circuit is connected, and after the short-circuit detection is completed, the second detection relay K4 and the third detection relay K5 automatically reset to the initial state of closing and disconnecting the circuit; like Figure 1 As shown, the first current limiting resistor R1, the second current limiting resistor R2, the third current limiting resistor R3, the fourth current limiting resistor R4, the fifth current limiting resistor R5, the sixth current limiting resistor R6, the seventh current limiting resistor R7 and the eighth current limiting resistor R8 are parallel resistors respectively, and the equivalent resistance of the first current limiting resistor R1 and the second current limiting resistor R2 is 60-80 KΩ, preferably 70.5 KΩ; the equivalent resistance of the third current limiting resistor R3, the fifth current limiting resistor R5 and the seventh current limiting resistor R7 is 40-55 KΩ, preferably 47 KΩ; the equivalent resistance of the fourth current limiting resistor R4, the sixth current limiting resistor R6 and the eighth current limiting resistor R8 is 15-30 KΩ, preferably 23.5 KΩ.

[0021] like Figure 1 As shown, the input ends of the first isolation optocoupler OC1, the second isolation optocoupler OC2 and the third isolation optocoupler OC3 are LEDs, and the output ends of the first isolation optocoupler OC1, the second isolation optocoupler OC2 and the third isolation optocoupler OC3 are phototransistors; the first optocoupler output circuit includes a low-voltage power supply VCC, a ninth resistor R9, a tenth resistor R10 and a first rectifier capacitor C1, the low-voltage power supply VCC, the ninth resistor R9 and the collector of the phototransistor of the first isolation optocoupler OC1 are electrically connected in sequence, and the first detection point D1, the tenth resistor R10, the first rectifier capacitor C1 and the phototransistor emitter of the first isolation optocoupler OC1 are electrically connected in sequence, the connection circuit between the tenth resistor R10 and the first rectifier capacitor C1 is also electrically connected to the phototransistor collector of the first isolation optocoupler OC1, and the phototransistor emitter of the first isolation optocoupler OC1 is grounded; the second optocoupler output circuit includes a low-voltage power supply VCC, an eleventh resistor R11, a twelfth resistor R12 and a second rectifier capacitor C2, the low-voltage power supply VCC, the eleventh resistor R11 and The phototransistor collector of the second isolation optocoupler OC2 is electrically connected in sequence, the second detection point D2, the twelfth resistor R12, the second rectifier capacitor C2, and the phototransistor emitter of the second isolation optocoupler OC2 are electrically connected in sequence, the connection circuit between the twelfth resistor R12 and the second rectifier capacitor C2 is also electrically connected to the phototransistor collector of the second isolation optocoupler OC2, and the phototransistor emitter of the second isolation optocoupler OC2 is grounded; the third optocoupler output circuit includes a low-voltage power supply VCC, a thirteenth resistor R13, a fourteenth resistor C2, and a second detection point D2. The low-voltage power supply VCC, the thirteenth resistor R13 and the phototransistor collector of the third isolation optocoupler OC3 are electrically connected in sequence, the third detection point D3, the fourteenth resistor R14, the third rectification capacitor C3 and the phototransistor emitter of the third isolation optocoupler OC3 are electrically connected in sequence, the connection circuit between the fourteenth resistor R14 and the third rectification capacitor C3 is also electrically connected to the phototransistor collector of the third isolation optocoupler OC3, and the phototransistor emitter of the third isolation optocoupler OC3 is grounded.

[0022] like Figure 1 As shown, the resistance values ​​of the ninth resistor R9, the eleventh resistor R11 and the thirteenth resistor R13 are 8-12 KΩ, preferably 10 KΩ; the resistance values ​​of the tenth resistor R10, the twelfth resistor R12 and the fourteenth resistor R14 are 0.8-1.2 KΩ, preferably 1 KΩ; the capacitance values ​​of the first rectifier capacitor C1, the second rectifier capacitor C2 and the third rectifier capacitor C3 are 100nF-1μF.

[0023] like Figure 1As shown, the first detection point D1 of the first optocoupler output circuit, the second detection point D2 of the second optocoupler output circuit and the third detection point D3 of the third optocoupler output circuit are electrically connected to the MCU respectively.

[0024] like Figure 1 As shown, the short-circuit detection method using the short-circuit detection circuit at the output end of the three-phase AC charging pile before charging includes the following detection methods: Ⅰ. Before charging the three-phase AC charging pile, the main relay is in a closed disconnected state, and the first detection relay K3, the second detection relay K4 and the third detection relay K5 are opened and turned on at the same time, so that the first phase line input terminal L1_IN, the first current limiting resistor R1, the first phase line output terminal L1_OUT, the third current limiting resistor R3, the input terminal of the first isolation optocoupler OC1, the fourth current limiting resistor R4, the fifth current limiting resistor R5, the input terminal of the second isolation optocoupler OC2, the sixth current limiting resistor R6, the seventh current limiting resistor R7, the input terminal of the third isolation optocoupler OC3, the eighth current limiting resistor R8, the neutral line output terminal N_OUT, the The two current-limiting resistors R2 and the neutral line input terminal N_IN are turned on in sequence to form a loop, the input terminals of the first isolation optocoupler OC1, the second isolation optocoupler OC2 and the third isolation optocoupler OC3 are respectively driven by micro-current to emit light, the output terminals of the first isolation optocoupler OC1, the second isolation optocoupler OC2 and the third isolation optocoupler OC3 are all turned on, and the first detection point D1, the second detection point D2 and the third detection point D3 can all detect waveform signals; it is judged that the first phase line output terminal L1_OUT, the second phase line output terminal L2_OUT, the third phase line output terminal L3_OUT and the neutral line output terminal N_OUT are safe, and there is no short circuit problem between them; Ⅱ. If there is no voltage difference at the input ends of the first isolation optocoupler OC1, the second isolation optocoupler OC2 and the third isolation optocoupler OC3), and the output ends of the first isolation optocoupler OC1, the second isolation optocoupler OC2 and the third isolation optocoupler OC3 are not conducting, then the first detection point D1, the second detection point D2 and the third detection point D3 cannot detect the waveform signal, and can only detect a high level; it is judged that there is a short circuit problem between the first phase line output terminal L1_OUT and the neutral line output terminal N_OUT; when the first phase line output terminal L1_OUT and the neutral line output terminal N_OUT are short-circuited, the first phase line input terminal L1_IN, the first current limiting resistor R1, the first phase line output terminal L1_OUT, the neutral line output terminal N_OUT, the second current limiting resistor R2 and the neutral line input terminal N_IN are turned on in sequence and form a loop; III. If (1) there is no voltage difference at the input end of the first isolation optocoupler OC1, the output end of the first isolation optocoupler OC1 is not conducting, the first detection point D1 cannot detect the waveform signal, and can only detect a high level; (2) the input ends of the second isolation optocoupler OC2 and the third isolation optocoupler OC3 are respectively driven by micro-current to emit light, the output ends of the second isolation optocoupler OC2 and the third isolation optocoupler OC3 are both conducting, and the second detection point D2 and the third detection point D3 can both detect the waveform signal; it is concluded that there is a voltage difference between the first phase line output end L1_OUT and the second phase line output end L2_OUT Short circuit problem; when the first phase line output terminal L1_OUT is short-circuited with the second phase line output terminal L2_OUT, the first phase line input terminal L1_IN, the first current limiting resistor R1, the first phase line output terminal L1_OUT, the second phase line output terminal L2_OUT, the fifth current limiting resistor R5, the input terminal of the second isolation optocoupler OC2, the sixth current limiting resistor R6, the seventh current limiting resistor R7, the input terminal of the third isolation optocoupler OC3, the eighth current limiting resistor R8, the neutral line output terminal N_OUT, the second current limiting resistor R2 and the neutral line input terminal N_IN are turned on in sequence and form a loop; IV. If (1) there is no voltage difference at the input end of the second isolation optocoupler OC2, the output end of the second isolation optocoupler OC2 is not conducting, the second detection point D2 cannot detect the waveform signal and can only detect a high level; (2) the input ends of the first isolation optocoupler OC1 and the third isolation optocoupler OC3 are respectively driven to emit light with micro-current, the output ends of the first isolation optocoupler OC1 and the third isolation optocoupler OC3 are both conducting, and the first detection point D1 and the third detection point D3 can both detect the waveform signal; it is concluded that there is a short circuit problem between the second phase line output end L2_OUT and the third phase line output end L3_OUT; when the first When the two-phase line output terminal L2_OUT and the third phase line output terminal L3_OUT are short-circuited, the first phase line input terminal L1_IN, the first current limiting resistor R1, the first phase line output terminal L1_OUT, the third current limiting resistor R3, the input terminal of the first isolation optocoupler OC1, the fourth current limiting resistor R4, the second phase line output terminal L2_OUT, the third phase line output terminal L3_OUT, the seventh current limiting resistor R7, the input terminal of the third isolation optocoupler OC3, the eighth current limiting resistor R8, the neutral line output terminal N_OUT, the second current limiting resistor R2 and the neutral line input terminal N_IN are sequentially turned on and form a loop; V. If (1) there is no voltage difference between the input terminals of the second isolation optocoupler OC2 and the third isolation optocoupler OC3, and the output terminals of the second isolation optocoupler OC2 and the third isolation optocoupler OC3 are not conducting, the second detection point D2 and the third detection point D3 cannot detect the waveform signal, and can only detect a high level; (2) the input terminal of the first isolation optocoupler OC1 is driven by a micro-current to emit light, the output terminal of the first isolation optocoupler OC1 is conducting, and the first detection point D1 can detect the waveform signal; it is judged that the second phase line output terminal L2_OUT There is a short circuit problem between the second phase line output terminal L2_OUT and the neutral line output terminal N_OUT; when the second phase line output terminal L2_OUT is short-circuited with the neutral line output terminal N_OUT, the first phase line input terminal L1_IN, the first current limiting resistor R1, the first phase line output terminal L1_OUT, the third current limiting resistor R3, the input terminal of the first isolation optocoupler OC1, the fourth current limiting resistor R4, the second phase line output terminal L2_OUT, the neutral line output terminal N_OUT, the second current limiting resistor R2 and the neutral line input terminal N_IN are sequentially turned on and form a loop; VI. If (1) there is no voltage difference at the input end of the third isolation optocoupler OC3, the output end of the third isolation optocoupler OC3 is not conducting, the third detection point D3 cannot detect the waveform signal, and can only detect a high level; (2) the input ends of the first isolation optocoupler OC1 and the second isolation optocoupler OC2 are driven by micro-current to emit light, the output ends of the first isolation optocoupler OC1 and the second isolation optocoupler OC2 are both conducting, and the first detection point D1 and the first detection point D2 can both detect the waveform signal; it is judged that there is a short circuit between the third phase line output end L3_OUT and the neutral line output end N_OUT Problem: When the third phase line output terminal L3_OUT and the neutral line output terminal N_OUT are short-circuited, the first phase line input terminal L1_IN, the first current limiting resistor R1, the first phase line output terminal L1_OUT, the third current limiting resistor R3, the input terminal of the first isolation optocoupler OC1, the fourth current limiting resistor R4, the fifth current limiting resistor R5, the input terminal of the second isolation optocoupler OC2, the sixth current limiting resistor R6, the third phase line output terminal L3_OUT, the neutral line output terminal N_OUT, the second current limiting resistor R2 and the neutral line input terminal N_IN are turned on in sequence and form a loop; It should be noted that in the above detection methods I, II, III, IV, V and VI, the main relay of the three-phase AC power supply circuit is required to be in a closed disconnected state.

[0025] The present invention has the following technical advantages: (1) The main components of the detection circuit of the present invention are three groups of detection relays and three isolation optocouplers, and the cost of other resistors and capacitors is low, which makes the structure of the entire circuit simple and the hardware cost low; (2) The detection circuit of the present invention determines whether there is a voltage difference at the input end of the first isolation optocoupler, the second isolation optocoupler and the third isolation optocoupler and whether the output end is turned on according to whether the first detection point D1, the second detection point D2 and the third detection point D3 can detect the waveform signal and the high level, so as to accurately detect whether there is a short circuit problem between the first phase line output end, the second phase line output end, the third phase line output end and the neutral line output end of the three-phase AC power supply circuit; (3) When any one or more of the first detection relay K3, the second detection relay K4 and the third detection relay K5 fail to open and cannot conduct the circuit, at least one of the first detection point D1, the second detection point D2 and the third detection point D3 will not detect the waveform signal and will detect a high level, so the first detection point D1 will not be misjudged. The first phase line output terminal, the second phase line output terminal, the third phase line output terminal and the neutral line output terminal are safe; when the main relay is turned on and the circuit is turned on, and the first detection relay K3, the second detection relay K4 and the third detection relay K5 are in a state of failure and cannot be closed or disconnected, since the entire short-circuit detection circuit is connected in series with the first current limiting resistor, the second current limiting resistor, the third current limiting resistor, the fourth current limiting resistor, the fifth current limiting resistor, the sixth current limiting resistor, the seventh current limiting resistor and the eighth current limiting resistor, the entire short-circuit detection circuit is controllable. At this time, the first detection point D1, the second detection point D2 and the third detection point D3 can still detect the waveform, and the MCU can determine that the entire short-circuit detection circuit has a fault and alarm; it can be seen that the detection circuit of the present invention can detect abnormal signal problems through the first detection point D1, the second detection point D2 and the third detection point D3 when any one or more of the three groups of detection relays fail, so as to determine that the detection circuit has a fault and alarm, thereby avoiding the risk of misjudgment.

[0026] The above are only preferred implementations of the present invention. Any slight modifications, equivalent changes and modifications made to the above implementations according to the technical solutions of the present invention are within the scope of the technical solutions of the present invention.

Claims

1. A three-phase AC charging pile output short circuit detection circuit before charging, characterized in that: include: A three-phase AC power supply circuit, wherein a main relay is installed on the three-phase AC power supply circuit, and the main relay separates the three-phase AC power supply circuit into a first phase line input terminal (L1_IN), a first phase line output terminal (L1_OUT), a second phase line input terminal (L2_IN), a second phase line output terminal (L2_OUT), a third phase line input terminal (L3_IN), a third phase line output terminal (L3_OUT), a neutral line input terminal (N_IN) and a neutral line output terminal (N_OUT); A power connection circuit, the power connection circuit comprising a first current limiting resistor (R1) and a second current limiting resistor (R2), the first phase line input terminal (L1_IN), the first current limiting resistor (R1) and the first phase line output terminal (L1_OUT) are connected in series; the neutral line input terminal (N_IN), the second current limiting resistor (R2) and the neutral line output terminal (N_OUT) are connected in series; the power connection circuit is provided with a first detection relay (K3) for controlling the circuit to be turned on or off; A short circuit detection circuit, the short circuit detection circuit comprising a first isolation optocoupler (OC1), a second isolation optocoupler (OC2), a third isolation optocoupler (OC3), a third current limiting resistor (R3), a fourth current limiting resistor (R4), a fifth current limiting resistor (R5), a sixth current limiting resistor (R6), a seventh current limiting resistor (R7), and an eighth current limiting resistor (R8), the first isolation optocoupler (OC1), the second isolation optocoupler (OC2), and the third isolation optocoupler (OC3) respectively having an input end and an output end; the first phase The line output terminal (L1_OUT), the third current limiting resistor (R3), the input terminal of the first isolation optocoupler (OC1), the fourth current limiting resistor (R4), the fifth current limiting resistor (R5), the input terminal of the second isolation optocoupler (OC2), the sixth current limiting resistor (R6), the seventh current limiting resistor (R7), the input terminal of the third isolation optocoupler (OC3), the eighth current limiting resistor (R8) and the zero line output terminal (N_OUT) are connected in series in sequence; the connection between the fourth current limiting resistor (R4) and the fifth current limiting resistor (R5) The circuit is also electrically connected to the second phase line output end (L2_OUT), and the connection circuit between the sixth current limiting resistor (R6) and the seventh current limiting resistor (R7) is also electrically connected to the third phase line output end (L3_OUT); the connection circuit between the first isolation optocoupler (OC1) input end and the second isolation optocoupler (OC2) input end is provided with a second detection relay (K4) for controlling the circuit to be turned on or off; the connection circuit between the second isolation optocoupler (OC2) input end and the third isolation optocoupler (OC3) input end is provided with a third detection relay (K5) for controlling the circuit to be turned on or off; the output end of the first isolation optocoupler (OC1) is connected to a first optocoupler output circuit, and the first optocoupler output circuit is provided with a first detection point (D1); the output end of the second isolation optocoupler (OC2) is connected to a second optocoupler output circuit, and the second optocoupler output circuit is provided with a second detection point (D2); the output end of the third isolation optocoupler (OC3) is connected to a third optocoupler output circuit, and the third optocoupler output circuit is provided with a third detection point (D3).

2. The three-phase AC charging pile pre-charging output short-circuit detection circuit according to claim 1, characterized in that: The main relay comprises a first main relay (K1) and a second main relay (K2), wherein the first main relay (K1) and the second main relay (K2) respectively have two groups of relay switches; one group of relay switches of the first main relay (K1) is connected between a third phase line input terminal (L3_IN) and a third phase line output terminal (L3_OUT) to control the conduction or disconnection of the third phase line; another group of relay switches of the first main relay (K1) is connected between a second phase line input terminal (L2_IN) and a second phase line output terminal (L2_OUT) to control the conduction or disconnection of the second phase line; one group of relay switches of the second main relay (K2) is connected between a first phase line input terminal (L1_IN) and a first phase line output terminal (L1_OUT) to control the conduction or disconnection of the first phase line; another group of relay switches of the second main relay (K2) is connected between a neutral line input terminal (N_IN) and a neutral line output terminal (N_OUT) to control the conduction or disconnection of the neutral line.

3. The three-phase AC charging pile pre-charging output short-circuit detection circuit according to claim 1, characterized in that: The first detection relay (K3) is a normally open contact relay, and the first detection relay (K3) has two groups of relay switches; one group of relay switches of the first detection relay (K3) is connected to the circuit between the first current limiting resistor (R1) and the first phase line output terminal (L1_OUT), or connected to the circuit between the first phase line input terminal (L1_IN) and the first current limiting resistor (R1); the other group of relay switches of the first detection relay (K3) is connected to the circuit between the second current limiting resistor (R2) and the neutral line output terminal (N_OUT), or connected to the circuit between the neutral line input terminal (N_IN) and the second current limiting resistor (R2).

4. The three-phase AC charging pile pre-charging output short-circuit detection circuit according to claim 1, characterized in that: The second detection relay (K4) is a normally open contact relay, and the second detection relay (K4) has two groups of relay switches; one group of relay switches of the second detection relay (K4) is connected to the circuit between the input end of the first isolation optocoupler (OC1) and the fourth current limiting resistor (R4); the other group of relay switches of the second detection relay (K4) is connected to the circuit between the fifth current limiting resistor (R5) and the input end of the second isolation optocoupler (OC2).

5. The three-phase AC charging pile pre-charging output short-circuit detection circuit according to claim 1, characterized in that: The third detection relay (K5) is a normally open contact relay, and the third detection relay (K5) has two groups of relay switches; one group of relay switches of the third detection relay (K5) is connected to the circuit between the input end of the second isolation optocoupler (OC2) and the sixth current limiting resistor (R6); the other group of relay switches of the third detection relay (K5) is connected to the circuit between the seventh current limiting resistor (R7) and the input end of the third isolation optocoupler (OC3).

6. The three-phase AC charging pile pre-charging output short-circuit detection circuit according to claim 1, characterized in that: The first current limiting resistor (R1), the second current limiting resistor (R2), the third current limiting resistor (R3), the fourth current limiting resistor (R4), the fifth current limiting resistor (R5), the sixth current limiting resistor (R6), the seventh current limiting resistor (R7), and the eighth current limiting resistor (R8) are respectively parallel resistors, the equivalent resistance of the first current limiting resistor (R1) and the second current limiting resistor (R2) is 60 to 80 KΩ, the equivalent resistance of the third current limiting resistor (R3), the fifth current limiting resistor (R5) and the seventh current limiting resistor (R7) is 40 to 55 KΩ, and the equivalent resistance of the fourth current limiting resistor (R4), the sixth current limiting resistor (R6) and the eighth current limiting resistor (R8) is 15 to 30 KΩ.

7. The three-phase AC charging pile pre-charging output short-circuit detection circuit according to claim 1, characterized in that: The input ends of the first isolation optocoupler (OC1), the second isolation optocoupler (OC2) and the third isolation optocoupler (OC3) are LEDs, respectively, and the output ends of the first isolation optocoupler (OC1), the second isolation optocoupler (OC2) and the third isolation optocoupler (OC3) are phototransistors, respectively; the first optocoupler output circuit comprises a low-voltage power supply (VCC), a ninth resistor (R9), a tenth resistor (R10) and a first rectifier capacitor (C1); the low-voltage power supply (VCC), the ninth resistor (R9) and the collector of the phototransistor of the first isolation optocoupler (OC1) are electrically connected in sequence; the first detection point ( D1), a tenth resistor (R10), a first rectifier capacitor (C1) and a phototransistor emitter of a first isolation optocoupler (OC1) are electrically connected in sequence, the connection circuit between the tenth resistor (R10) and the first rectifier capacitor (C1) is also electrically connected to the phototransistor collector of the first isolation optocoupler (OC1), and the phototransistor emitter of the first isolation optocoupler (OC1) is grounded; the second optocoupler output circuit includes a low-voltage power supply (VCC), an eleventh resistor (R11), a twelfth resistor (R12) and a second rectifier capacitor (C2), the low-voltage power supply (VCC), the eleventh resistor (R11 ) and the phototransistor collector of the second isolation optocoupler (OC2) are electrically connected in sequence, the second detection point (D2), the twelfth resistor (R12), the second rectifier capacitor (C2) and the phototransistor emitter of the second isolation optocoupler (OC2) are electrically connected in sequence, the connection circuit between the twelfth resistor (R12) and the second rectifier capacitor (C2) is also electrically connected to the phototransistor collector of the second isolation optocoupler (OC2), and the phototransistor emitter of the second isolation optocoupler (OC2) is grounded; the third optocoupler output circuit includes a low voltage power supply (VCC), a thirteenth resistor (R13), a fourteenth resistor (R14) and the third rectifying capacitor (C3), the low-voltage power supply (VCC), the thirteenth resistor (R13) and the photosensitive transistor collector of the third isolation optocoupler (OC3) are electrically connected in sequence, the third detection point (D3), the fourteenth resistor (R14), the third rectifying capacitor (C3) and the photosensitive transistor emitter of the third isolation optocoupler (OC3) are electrically connected in sequence, the connection circuit between the fourteenth resistor (R14) and the third rectifying capacitor (C3) is also electrically connected to the photosensitive transistor collector of the third isolation optocoupler (OC3), and the photosensitive transistor emitter of the third isolation optocoupler (OC3) is grounded.

8. The three-phase AC charging pile pre-charging output short-circuit detection circuit according to claim 7, characterized in that: The resistance values ​​of the ninth resistor (R9), the eleventh resistor (R11) and the thirteenth resistor (R13) are 8 to 12 KΩ, the resistance values ​​of the tenth resistor (R10), the twelfth resistor (R12) and the fourteenth resistor (R14) are 0.8 to 1.2 KΩ, and the capacitance values ​​of the first rectifier capacitor (C1), the second rectifier capacitor (C2) and the third rectifier capacitor (C3) are 100nF to 1μF.

9. The three-phase AC charging pile pre-charging output short-circuit detection circuit according to claim 1, characterized in that: The first detection point (D1) of the first optocoupler output circuit, the second detection point (D2) of the second optocoupler output circuit and the third detection point (D3) of the third optocoupler output circuit are electrically connected to the MCU respectively.

10. A short-circuit detection method using the short-circuit detection circuit at the output end of a three-phase AC charging pile before charging as claimed in any one of claims 1 to 9, characterized in that: The following detection methods are included: Ⅰ. Before charging the three-phase AC charging pile, the main relay is in the off state, and the first detection relay (K3), the second detection relay (K4) and the third detection relay (K5) are opened and turned on at the same time. If the input ends of the first isolation optocoupler (OC1), the second isolation optocoupler (OC2) and the third isolation optocoupler (OC3) are respectively driven by micro-current to emit light, and the output ends of the first isolation optocoupler (OC1), the second isolation optocoupler (OC2) and the third isolation optocoupler (OC3) are all turned on, then the first detection point (D1), the second detection point (D2) and the third detection point (D3) can all detect waveform signals; it is judged that the first phase line output end (L1_OUT), the second phase line output end (L2_OUT), the third phase line output end (L3_OUT) and the neutral line output end (N_OUT) are safe, and there is no short circuit problem between them; Ⅱ. If there is no voltage difference at the input ends of the first isolation optocoupler (OC1), the second isolation optocoupler (OC2) and the third isolation optocoupler (OC3), and the output ends of the first isolation optocoupler (OC1), the second isolation optocoupler (OC2) and the third isolation optocoupler (OC3) are not conducting, then the first detection point (D1), the second detection point (D2) and the third detection point (D3) cannot detect waveform signals, and can only detect high levels; it is concluded that there is a short circuit problem between the first phase line output end (L1_OUT) and the neutral line output end (N_OUT); III. If (1) there is no voltage difference at the input end of the first isolation optocoupler (OC1), the output end of the first isolation optocoupler (OC1) is not conducting, the first detection point (D1) cannot detect the waveform signal, and can only detect a high level; (2) the input ends of the second isolation optocoupler (OC2) and the third isolation optocoupler (OC3) are respectively driven to emit light with a micro current, the output ends of the second isolation optocoupler (OC2) and the third isolation optocoupler (OC3) are both conducting, and the second detection point (D2) and the third detection point (D3) can detect the waveform signal; it is concluded that there is a short circuit problem between the first phase line output end (L1_OUT) and the second phase line output end (L2_OUT); IV. If (1) there is no voltage difference at the input end of the second isolation optocoupler (OC2), the output end of the second isolation optocoupler (OC2) is not conducting, the second detection point (D2) cannot detect the waveform signal and can only detect a high level; (2) the input ends of the first isolation optocoupler (OC1) and the third isolation optocoupler (OC3) are respectively driven to emit light with a micro current, the output ends of the first isolation optocoupler (OC1) and the third isolation optocoupler (OC3) are both conducting, and the first detection point (D1) and the third detection point (D3) can detect the waveform signal; it is concluded that there is a short circuit problem between the second phase line output end (L2_OUT) and the third phase line output end (L3_OUT); V. If (1) there is no voltage difference between the input ends of the second isolation optocoupler (OC2) and the third isolation optocoupler (OC3), the output ends of the second isolation optocoupler (OC2) and the third isolation optocoupler (OC3) are not conducting, the second detection point (D2) and the third detection point (D3) cannot detect the waveform signal, and can only detect a high level; (2) the input end of the first isolation optocoupler (OC1) is driven by a micro-current to emit light, the output end of the first isolation optocoupler (OC1) is conducting, and the first detection point (D1) can detect the waveform signal; it is concluded that there is a short circuit problem between the second phase line output end (L2_OUT) and the neutral line output end (N_OUT); VI. If (1) there is no voltage difference at the input end of the third isolation optocoupler (OC3), the output end of the third isolation optocoupler (OC3) is not conducting, the third detection point (D3) cannot detect the waveform signal and can only detect a high level; (2) the input ends of the first isolation optocoupler (OC1) and the second isolation optocoupler (OC2) are driven by micro-current to emit light, the output ends of the first isolation optocoupler (OC1) and the second isolation optocoupler (OC2) are both conducting, and the first detection point (D1) and the first detection point (D1) can both detect the waveform signal; it is concluded that there is a short circuit problem between the third phase line output end (L3_OUT) and the neutral line output end (N_OUT).

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