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

Abstract

The utility model discloses a three-phase AC charging pile output end short circuit detection circuit before charging, comprising a three-phase AC power supply circuit, a power connection circuit and a short circuit detection circuit, 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 AC 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 utility model relates to three -phase alternating current charging pile technical field especially relates to a three -phase alternating current charging pile before charging output end short circuit detection circuit. BACKGROUND

[0002] At present, the charging pile short circuit detection scheme needs to configure multiple auxiliary relays, isolation power supply or isolator, configure the protection device between high voltage and low voltage, and the hardware cost is high. Part of the charging pile short circuit detection scheme needs to detect short circuit by measuring the voltage division signal, which is easy to be affected by resistance temperature drift or measurement error. Three -phase circuit needs to detect each group of lines mutually, and the detection procedure needs to switch multiple relays for multiple times, and the detection steps are many;And when the relays fail, there are risks such as short circuit, output end live, misjudgment and the like. UTILITY MODEL CONTENTS

[0003] The utility model solves the technical problem according to prior art's insufficient, provides a three -phase alternating current charging pile before charging output end short circuit detection circuit, the main element of the detection circuit is three groups of detection relays and three isolation photocouplers, and the line is simple, and the hardware cost is low;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 zero line output end of the three -phase alternating current power supply circuit;The detection circuit can detect abnormal signal problems through the first detection point, the second detection point and the third detection point in the case that any one or more of the three groups of detection relays fails, to judge the detection circuit failure to alarm.

[0004] To solve the above technical problems, the utility model technical scheme is as follows: a three -phase alternating current charging pile before charging output end short circuit detection circuit, comprising:

[0005] Three -phase alternating current power supply circuit, the main relay is installed on the three -phase alternating current power supply circuit, and the main relay separates the three -phase alternating current power supply circuit into the first phase line input end, the first phase line output end, the second phase line input end, the second phase line output end, the third phase line input end, the third phase line output end, the zero line input end and the zero line output end;

[0006] The power circuit includes the first current -limiting resistor and the second current -limiting resistor, the first phase line input end, the first current -limiting resistor and the first phase line output end are connected in series;The zero line input end, the second current -limiting resistor and the zero line output end are connected in series;The power circuit is equipped with the first detection relay for controlling the conduction or disconnection of the circuit;

[0007] 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, the first, second and third isolation optocouplers each having 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 connected in series; the connection circuit between the fourth current limiting resistor and the fifth current limiting resistor is further electrically connected with the second phase line output end, and the connection circuit between the sixth current limiting resistor and the seventh current limiting resistor is further electrically connected with the third phase line output end; the connection circuit between the input end of the first isolation optocoupler and the input end of the second isolation optocoupler is provided with a second detection relay for controlling the conduction or disconnection of the circuit; the connection circuit between the input end of the second isolation optocoupler and the input end of the third isolation optocoupler is provided with a third detection relay for controlling the conduction or disconnection of the circuit; the output end of the first isolation optocoupler is connected with a 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 with a 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 with a third optocoupler output circuit, and the third optocoupler output circuit is provided with a third detection point.

[0008] The first, second and third detection relays are all normally open contact relays.

[0009] In the technical scheme, the main relay comprises a first main relay and a second main relay, the first main relay and the second main relay each having two groups of relay switches; one group of relay switches of the first main relay is connected between the third phase line input end and the third phase line output end to control the conduction or disconnection of the third phase line; the other group of relay switches of the first main relay is connected between the second phase line input end and the second phase line output end 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 end and the first phase line output end to control the conduction or disconnection of the first phase line; the other group of relay switches of the second main relay is connected between the zero line input end and the zero line output end to control the conduction or disconnection of the zero line.

[0010] In the above technical solution, the first detection relay has two groups of relay switches; one group of relay switches of the first detection relay is connected in the circuit between the first current-limiting resistor and the first phase line output end, or connected in 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 in the circuit between the second current-limiting resistor and the zero line output end, or connected in the circuit between the zero line input end and the second current-limiting resistor.

[0011] In the above technical solution, the second detection relay has two groups of relay switches; one group of relay switches of the second detection relay is connected in the circuit between the first isolation optocoupler input end and the fourth current-limiting resistor; the other group of relay switches of the second detection relay is connected in the circuit between the fifth current-limiting resistor and the second isolation optocoupler input end.

[0012] In the above technical solution, the third detection relay has two groups of relay switches; one group of relay switches of the third detection relay is connected in the circuit between the second isolation optocoupler input end and the sixth current-limiting resistor; the other group of relay switches of the third detection relay is connected in the circuit between the seventh current-limiting resistor and the third isolation optocoupler input end.

[0013] In the above technical solution, 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 parallel resistors; the equivalent resistance value of the first current-limiting resistor and the second current-limiting resistor is 60-80 KΩ; the equivalent resistance value of the third current-limiting resistor, the fifth current-limiting resistor and the seventh current-limiting resistor is 40-55 KΩ; and the equivalent resistance value of the fourth current-limiting resistor, the sixth current-limiting resistor and the eighth current-limiting resistor is 15-30 KΩ.

[0014] In the technical scheme, the input ends of the first, second and third isolating light couplings are LEDs respectively, and the output ends of the first, second and third isolating light couplings are photosensitive triodes respectively; the first light coupling output circuit comprises a low-voltage power supply, a ninth resistor, a tenth resistor and a first rectification capacitor, the low-voltage power supply, the ninth resistor and the collector of the photosensitive triode of the first isolating light coupling are electrically connected in sequence, the first detection point, the tenth resistor, the first rectification capacitor and the emitter of the photosensitive triode of the first isolating light coupling are electrically connected in sequence, the connecting circuit between the tenth resistor and the first rectification capacitor further electrically connects the collector of the photosensitive triode of the first isolating light coupling, and the emitter of the photosensitive triode of the first isolating light coupling is grounded; the second light coupling output circuit comprises a low-voltage power supply, an eleventh resistor, a twelfth resistor and a second rectification capacitor, the low-voltage power supply, the eleventh resistor and the collector of the photosensitive triode of the second isolating light coupling are electrically connected in sequence, the second detection point, the twelfth resistor, the second rectification capacitor and the emitter of the photosensitive triode of the second isolating light coupling are electrically connected in sequence, the connecting circuit between the twelfth resistor and the second rectification capacitor further electrically connects the collector of the photosensitive triode of the second isolating light coupling, and the emitter of the photosensitive triode of the second isolating light coupling is grounded; and the third light coupling output circuit comprises a low-voltage power supply, a thirteenth resistor, a fourteenth resistor and a third rectification capacitor, the low-voltage power supply, the thirteenth resistor and the collector of the photosensitive triode of the third isolating light coupling are electrically connected in sequence, the third detection point, the fourteenth resistor, the third rectification capacitor and the emitter of the photosensitive triode of the third isolating light coupling are electrically connected in sequence, the connecting circuit between the fourteenth resistor and the third rectification capacitor further electrically connects the collector of the photosensitive triode of the third isolating light coupling, and the emitter of the photosensitive triode of the third isolating light coupling is grounded.

[0015] In the technical scheme, the resistance values of the ninth, eleventh and thirteenth resistors are 8-12 KΩ, the resistance values of the tenth, twelfth and fourteenth resistors are 0.8-1.2 KΩ, and the capacitance values of the first, second and third rectification capacitors are 100 nF-1 μF.

[0016] In the technical scheme, the first, second and third detection points of the first, second and third light coupling output circuits are electrically connected with the MCU respectively.

[0017] The utility model discloses beneficial effect is: (1) the utility model detection circuit's main element is three groups of detection relay and three isolated optocoupler, and the line is simple, and the hardware cost is low;(2) the utility model detection circuit judges whether the input end of first isolated optocoupler, second isolated optocoupler and third isolated optocoupler exists pressure difference, whether the output end is conducted through according to whether the first detection point, second detection point and third detection point can detect waveform signal and high level, thereby can accurately detect whether the first phase line output end, second phase line output end, third phase line output end and zero line output end of three -phase alternating current supply circuit exist short -circuit problem;(3) when the first detection relay, second detection relay and third detection relay in anyone or more fail to open, can not conduct through the circuit, at least one of first detection point, second detection point and third detection point can not detect waveform signal, can detect high level, therefore, first phase line output end, second phase line output end, third phase line output end and zero line output end are safe and will not misjudge, when the main relay opens and conducts through the circuit, and first detection relay, second detection relay and third detection relay are in the failure and can not close, can not disconnect the circuit condition, because the whole short -circuit detection circuit is in series with first current -limiting resistance, second current -limiting resistance, third current -limiting resistance, fourth current -limiting resistance, fifth current -limiting resistance, sixth current -limiting resistance, seventh current -limiting resistance and eighth current -limiting resistance, therefore, the whole short -circuit detection circuit is controllable, at this time, first detection point, second detection point and third detection point still can detect waveform, and MCU can judge the whole short -circuit detection circuit to appear the fault and alarm;Therefore, the utility model detection circuit can detect abnormal signal problem through first detection point, second detection point and third detection point under the condition that the failure of anyone or more of three groups of detection relays occurs, to judge the detection circuit to appear the fault to alarm, avoids appearing the misjudgment risk. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The utility model discloses beneficial effect is: (1) the utility model detection circuit's main element is three groups of detection relay and three isolated optocoupler, and the line is simple, and the hardware cost is low;(2) the utility model detection circuit judges whether the input end of first isolated optocoupler, second isolated optocoupler and third isolated optocoupler exists pressure difference, whether the output end is conducted through according to whether the first detection point, second detection point and third detection point can detect waveform signal and high level, thereby can accurately detect whether the first phase line output end, second phase line output end, third phase line output end and zero line output end of three -phase alternating current supply circuit exist short -circuit problem;(3) when the first detection relay, second detection relay and third detection relay in anyone or more fail to open, can not conduct through the circuit, at least one of first detection point, second detection point and third detection point can not detect waveform signal, can detect high level, therefore, first phase line output end, second phase line output end, third phase line output end and zero line output end are safe and will not misjudge, when the main relay opens and conducts through the circuit, and first detection relay, second detection relay and third detection relay are in the failure and can not close, can not disconnect the circuit condition, because the whole short -circuit detection circuit is in series with first current -limiting resistance, second current -limiting resistance, third current -limiting resistance, fourth current -limiting resistance, fifth current -limiting resistance, sixth current -limiting resistance, seventh current -limiting resistance and eighth current -limiting resistance, therefore, the whole short -circuit detection circuit is controllable, at this time, first detection point, second detection point and third detection point still can detect waveform, and MCU can judge the whole short -circuit detection circuit to appear the fault and alarm;Therefore, the utility model detection circuit can detect abnormal signal problem through first detection point, second detection point and third detection point under the condition that the failure of anyone or more of three groups of detection relays occurs, to judge the detection circuit to appear the fault to alarm, avoids appearing the misjudgment risk. DETAILED DESCRIPTION

[0019] The structure principle and working principle of the utility model will be further explained in detail in combination with the drawings.

[0020] As Figure 1 shown, the utility model discloses a three -phase alternating current charging pile charges before output end short -circuit detection circuit, including three -phase alternating current supply circuit, and the circuit and short -circuit detection circuit of electricity;

[0021] A 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 the first phase line input terminal L1_IN, the first phase line output terminal L1_OUT, the second phase line input terminal L2_IN, the second phase line output terminal L2_OUT, the third phase line input terminal L3_IN, the third phase line output terminal L3_OUT, the neutral line input terminal N_IN, and the 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.

[0022] 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.

[0023] 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 each have an input terminal and an output terminal. 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, and the neutral line output terminal N_OUT are connected in series. 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 terminal. 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 input terminal of the first isolation optocoupler OC1 and the input terminal of the second isolation optocoupler OC2 is provided with a second detection relay K4 for controlling the circuit to be turned on or off; the connection circuit between the input terminal of the second isolation optocoupler OC2 and the input terminal of the third isolation optocoupler OC3 is provided with a third detection relay K5 for controlling the circuit to be turned on or off; the output terminal 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 terminal 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 terminal 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.

[0024] like Figure 1 As shown, the main relay includes a first main relay K1 and a second main relay K2. Each of the first and second main relays K1 has two sets of relay switches. One set of relay switches for 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. The other set of relay switches for 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 set of relay switches for 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. The other set of relay switches for 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.

[0025] like Figure 1 As shown, the first detection relay K3 is a normally open contact relay. Before charging the three-phase AC charging pile, the system controls the first detection relay K3 to open and conduct the circuit, energizing the short-circuit detection circuit. After the short-circuit detection ends, the first detection relay K3 automatically resets to its initial closed and disconnected state. The first detection relay K3 has two sets of relay switches. One set of relay switches is connected in the circuit between the first current-limiting resistor R1 and the first phase line output terminal L1_OUT, or in the circuit between the first phase line input terminal L1_IN and the first current-limiting resistor R1. The other set of relay switches is connected in the circuit between the second current-limiting resistor R2 and the neutral line output terminal N_OUT, or in the circuit between the neutral line input terminal N_IN and the second current-limiting resistor R2.

[0026] like Figure 1As shown, the second detection relay K4 is a normally open contact relay with two sets of relay switches. One set of relay switches is connected to the circuit between the input terminal of the first isolation optocoupler OC1 and the fourth current-limiting resistor R4; the other set of relay switches is connected to the circuit between the fifth current-limiting resistor R5 and the input terminal of the second isolation optocoupler OC2. The third detection relay K5 is a normally open contact relay with two sets of relay switches. One set of relay switches is connected to the circuit between the input terminal of the second isolation optocoupler OC2 and the sixth current-limiting resistor R6; the other set of relay switches is connected to the circuit between the seventh current-limiting resistor R7 and the input terminal of the third isolation optocoupler OC3. 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, thus connecting the short-circuit detection circuit. After the short-circuit detection ends, the second detection relay K4 and the third detection relay K5 automatically reset to their initial closed and disconnected state.

[0027] 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 all parallel resistors. 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; 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 15-30 KΩ, preferably 23.5 KΩ.

[0028] like Figure 1As shown, the input terminals of the first isolation optocoupler OC1, the second isolation optocoupler OC2, and the third isolation optocoupler OC3 are LEDs, and the output terminals 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 connected in sequence. 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 sequentially electrically connected. 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. 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 emitter of the first isolation optocoupler OC1 are connected in sequence. The phototransistor collector of the second isolation optocoupler OC2 is sequentially electrically connected. 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 sequentially electrically connected. 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. 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, and a fourteenth resistor... The phototransistor collector of the third isolation optocoupler OC3 is sequentially connected to resistor R14 and the third rectifier capacitor C3. The phototransistor emitter of the third detection point D3, the fourteenth resistor R14, the third rectifier capacitor C3, and the third isolation optocoupler OC3 is sequentially connected to resistor R14 and the third rectifier capacitor C3. The connection circuit between the fourteenth resistor R14 and the third rectifier capacitor C3 is also electrically connected to the phototransistor collector of the third isolation optocoupler OC3. The phototransistor emitter of the third isolation optocoupler OC3 is grounded.

[0029] like Figure 1 As shown, the resistance values ​​of the ninth resistor R9, the eleventh resistor R11, and the thirteenth resistor R13 are 8 to 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 to 1.2 KΩ, preferably 1 KΩ; and the capacitance values ​​of the first rectifier capacitor C1, the second rectifier capacitor C2, and the third rectifier capacitor C3 are 100 nF to 1 μF.

[0030] 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.

[0031] like Figure 1 As shown, the short-circuit detection method using the short-circuit detection circuit at the output terminal of the three-phase AC charging pile before charging includes the following detection methods:

[0032] I. Before charging at a three-phase AC charging station, the main relay is in the off state (closed). Simultaneously, the first detection relay K3, the second detection relay K4, and the third detection relay K5 are opened and connected, causing the following resistors to be connected: 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, and the neutral line output terminal N_OUT. Two current-limiting resistors R2 and the neutral input terminal N_IN are sequentially connected to form a circuit. The input terminals of the first isolation optocoupler OC1, the second isolation optocoupler OC2, and the third isolation optocoupler OC3 are driven by microcurrents 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 connected. Waveform signals can be detected at the first detection point D1, the second detection point D2, and the third detection point D3. It can be concluded 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 output terminal N_OUT are safe and there is no short circuit between them.

[0033] II. If there is no voltage difference at the input terminals of the first isolation optocoupler OC1, the second isolation optocoupler OC2, and the third isolation optocoupler OC3, and their output terminals are not conducting, then the first detection point D1, the second detection point D2, and the third detection point D3 will not detect any waveform signal; only a high level will be detected. Therefore, it is concluded that there is a short circuit between the first phase line output terminal L1_OUT and the neutral line output terminal N_OUT. When there is a short circuit between the first phase line output terminal L1_OUT and 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 neutral line output terminal N_OUT, the second current-limiting resistor R2, and the neutral line input terminal N_IN will sequentially conduct and form a loop.

[0034] III. If (1) there is no voltage difference at the input terminal of the first isolation optocoupler OC1, the output terminal of the first isolation optocoupler OC1 is not conducting, the first detection point D1 cannot detect the waveform signal, and can only detect the high level; (2) the input terminals of the second isolation optocoupler OC2 and the third isolation optocoupler OC3 are driven to emit light by microcurrents respectively, the output terminals 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 terminal L1_OUT and the second phase line output terminal L2_OUT. Short circuit problem: When there is a short circuit between the first phase line output terminal L1_OUT and 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 sequentially turned on and form a loop;

[0035] IV. If (1) there is no voltage difference at the input terminal of the second isolation optocoupler OC2, the output terminal of the second isolation optocoupler OC2 is not conducting, the second detection point D2 cannot detect the waveform signal, and can only detect the high level; (2) the input terminals of the first isolation optocoupler OC1 and the third isolation optocoupler OC3 are driven to emit light by microcurrents respectively, the output terminals 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 output terminal L2_OUT of the second phase line and the output terminal L3_OUT of the third phase line; when the first phase line output terminal L2_OUT of the third phase line is short-circuited ... When there is a short circuit between the output terminals L2_OUT and L3_OUT of the second phase line, the input terminal L1_IN of the first phase line, the first current-limiting resistor R1, the output terminal L1_OUT of the first phase line, the third current-limiting resistor R3, the input terminal of the first isolation optocoupler OC1, the fourth current-limiting resistor R4, the output terminal L2_OUT of the second phase line, the output terminal L3_OUT of the third phase line, the seventh current-limiting resistor R7, the input terminal of the third isolation optocoupler OC3, the eighth current-limiting resistor R8, the output terminal N_OUT of the neutral line, the second current-limiting resistor R2, and the input terminal N_IN of the neutral line are sequentially turned on and form a loop.

[0036] V. If (1) there is no voltage difference at 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, then the second detection point D2 and the third detection point D3 cannot detect the waveform signal, and can only detect the high level; (2) the micro-current drives the light emission at the input terminal of the first isolation optocoupler OC1, and the output terminal of the first isolation optocoupler OC1 is conducting, then the first detection point D1 can detect the waveform signal; therefore, the judgment is: the output terminal L2_OUT of the second phase line. There is a short circuit problem between the second phase line output terminal L2_OUT and the neutral line output terminal N_OUT; when there is a short circuit between the second phase line output terminal L2_OUT and 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;

[0037] VI. If (1) there is no voltage difference at the input terminal of the third isolation optocoupler OC3, the output terminal of the third isolation optocoupler OC3 is not conducting, the third detection point D3 cannot detect the waveform signal, and can only detect the high level; (2) the micro-current drives the light emission at the input terminals of the first isolation optocoupler OC1 and the second isolation optocoupler OC2, the output terminals 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 concluded that there is a short circuit between the third phase line output terminal L3_OUT and the neutral line output terminal N_OUT. Problem: When there is a short circuit between the third phase line output terminal L3_OUT and 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 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 sequentially turned on and form a loop.

[0038] It should be noted that in the above-mentioned testing methods I, II, III, IV, V, and VI, the main relay of the three-phase AC power supply circuit is required to be in the off state.

[0039] The present invention has the following technical advantages: (1) The main components of the detection circuit of the present invention are three sets of detection relays and three isolation optocouplers. 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 judges 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 conducting based on whether the waveform signal and high level can be detected at the first detection point D1, the second detection point D2, and the third detection point D3, so as to accurately detect whether there is a short circuit 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 fails to open or 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 the high level. Therefore, it will not misdetect the waveform signal. The system determines that 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 open and the circuit is conducting, 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 from the circuit, the entire short-circuit detection circuit is controllable because it is connected in series with the first, second, third, fourth, fifth, sixth, seventh, and eighth current-limiting resistors. At this time, the first detection point D1, the second detection point D2, and the third detection point D3 can still detect waveforms, and the MCU can determine that the entire short-circuit detection circuit has failed and issue an alarm. Therefore, it can be seen that the detection circuit of this utility model can detect abnormal signals through the first detection point D1, the second detection point D2, and the third detection point D3 in the event of failure of any one or more of the three sets of detection relays, so as to determine that the detection circuit has failed and issue an alarm, avoiding the risk of misjudgment.

[0040] The above are merely preferred embodiments of this utility model. Any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical solution of this utility model shall fall within the scope of the technical solution of this utility model.

Claims

1. A short-circuit detection circuit at the output terminal of a three-phase AC charging pile before charging, characterized in that, include: A three-phase AC power supply circuit is provided, wherein a main relay is installed on the three-phase AC power supply circuit, and 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). 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 equipped with a first detection relay (K3) for controlling the circuit to be turned on or off. A 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) each have an input terminal and an output terminal. 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 neutral 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) is as follows. The circuit is also electrically connected to the output terminal of the second phase line (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 output terminal of the third phase line (L3_OUT); the connection circuit between the input terminal of the first isolation optocoupler (OC1) and the input terminal of the second isolation optocoupler (OC2) is provided with a second detection relay (K4) for controlling the circuit to be turned on or off; the connection circuit between the input terminal of the second isolation optocoupler (OC2) and the input terminal of the third isolation optocoupler (OC3) is provided with a third detection relay (K5) for controlling the circuit to be turned on or off; the output terminal 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 terminal 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 terminal 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). The first detection relay (K3), the second detection relay (K4), and the third detection relay (K5) are all normally open contact relays.

2. The short-circuit detection circuit at the output terminal of the three-phase AC charging pile before charging as described in claim 1, characterized in that: The main relays include a first main relay (K1) and a second main relay (K2). Each of the first and second main relays (K1 and K2) has two sets of relay switches. One set of relay switches for 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. The other set of relay switches for 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 set of relay switches for 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. The other set of relay switches for 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.

3. The short-circuit detection circuit at the output terminal of the three-phase AC charging pile before charging as described in claim 1, characterized in that: The first detection relay (K3) has two sets of relay switches; one set of relay switches of the first detection relay (K3) is connected in the circuit between the first current limiting resistor (R1) and the first phase line output terminal (L1_OUT), or in the circuit between the first phase line input terminal (L1_IN) and the first current limiting resistor (R1); the other set of relay switches of the first detection relay (K3) is connected in the circuit between the second current limiting resistor (R2) and the neutral line output terminal (N_OUT), or in the circuit between the neutral line input terminal (N_IN) and the second current limiting resistor (R2).

4. The short-circuit detection circuit at the output terminal of the three-phase AC charging pile before charging as described in claim 1, characterized in that: The second detection relay (K4) has two sets of relay switches; one set of relay switches of the second detection relay (K4) is connected in the circuit between the input terminal of the first isolation optocoupler (OC1) and the fourth current limiting resistor (R4); the other set of relay switches of the second detection relay (K4) is connected in the circuit between the fifth current limiting resistor (R5) and the input terminal of the second isolation optocoupler (OC2).

5. The short-circuit detection circuit at the output terminal of the three-phase AC charging pile before charging as described in claim 1, characterized in that: The third detection relay (K5) has two sets of relay switches; one set of relay switches of the third detection relay (K5) is connected in the circuit between the input terminal of the second isolation optocoupler (OC2) and the sixth current limiting resistor (R6); the other set of relay switches of the third detection relay (K5) is connected in the circuit between the seventh current limiting resistor (R7) and the input terminal of the third isolation optocoupler (OC3).

6. The short-circuit detection circuit at the output terminal of the three-phase AC charging pile before charging as described in 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 all parallel resistors. The equivalent resistance of the first current-limiting resistor (R1) and the second current-limiting resistor (R2) is 60-80 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 40-55 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 15-30 KΩ.

7. The short-circuit detection circuit at the output terminal of the three-phase AC charging pile before charging as described in claim 1, characterized in that: The input terminals of the first isolation optocoupler (OC1), the second isolation optocoupler (OC2), and the third isolation optocoupler (OC3) are LEDs, and the output terminals of the first isolation optocoupler (OC1), the second isolation optocoupler (OC2), and the third isolation optocoupler (OC3) are phototransistors. The output circuit of the first optocoupler 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 phototransistor collectors of the first isolation optocoupler (OC1) are sequentially electrically connected. The first detection point ( The phototransistor emitters of the first optocoupler (OC1), the tenth resistor (R10), the first rectifier capacitor (C1), and the first isolation optocoupler (OC1) are sequentially electrically connected. The connection circuit between the tenth resistor (R10) and the first rectifier capacitor (C1) is also electrically connected to the collector of the phototransistor of the first isolation optocoupler (OC1). The emitter of the phototransistor 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), the twelfth resistor (R12), and the second rectifier capacitor (C2) are connected in sequence. The phototransistor collectors of the second and second isolation optocouplers (OC2) are sequentially connected. 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 sequentially connected. 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). 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), and a fourteenth resistor. The phototransistor collector of the low-voltage power supply (VCC), the thirteenth resistor (R13), and the third isolation optocoupler (OC3) is sequentially electrically connected to the phototransistor collector of the phototransistor. The phototransistor emitter of the phototransistor of the third detection point (D3), the fourteenth resistor (R14), the third rectifier capacitor (C3), and the third isolation optocoupler (OC3) is sequentially electrically connected to the phototransistor collector of the phototransistor. The phototransistor emitter of the phototransistor of the third isolation optocoupler (OC3) is grounded.

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

9. The short-circuit detection circuit at the output terminal of the three-phase AC charging pile before charging as described in 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.

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