Short circuit detection circuit

Abstract

The application discloses a short circuit detection circuit, which comprises a first switch circuit, a second switch circuit, an X capacitor circuit and an optical coupler. The first switch circuit is connected between an input live wire and a light-emitting side first end of the optical coupler, and the second switch circuit is connected between an input zero line and a light-emitting side second end of the optical coupler, so as to ensure controllable on-off of a detection loop. The X capacitor circuit is connected in parallel between the first switch circuit and the second switch circuit, a driving voltage is established between an output live wire and an output zero line when no short circuit occurs, so as to drive a light-emitting diode of the optical coupler to work and realize judgment of a short circuit state. An output side of the optical coupler is connected with a feedback signal end, a level of the feedback signal end changes with a working state of the light-emitting diode, so as to indicate whether there is a short circuit at an output end. The optical coupler blocks a coupling path of a high-voltage signal to a low-voltage control side, avoids high-voltage interference on a low-voltage control circuit, and improves detection reliability.

Description

Technical Field

[0001] This invention relates to the field of circuit testing technology, and in particular to a short-circuit detection circuit. Background Technology

[0002] With the increasing popularity of electric vehicles, the safety performance of charging stations is receiving growing attention. Before charging an electric vehicle, a short-circuit test of the AC output circuit is required to ensure charging safety.

[0003] In existing short-circuit detection solutions, a switch is used to connect the live and neutral wires at the output terminal, and a DC resistor voltage divider circuit is used to detect the equivalent impedance at the output terminal to determine whether a short circuit exists. This solution works normally in conventional detection scenarios.

[0004] However, in the application scenarios of AC charging piles, the input is high-voltage AC power, and the output is connected to the electric vehicle. The detection circuit needs to contact both the high-voltage circuit and the low-voltage control circuit simultaneously. Using a direct resistor voltage divider detection method will cause the high-voltage signal to couple to the low-voltage control side through the detection circuit, interfering with the stable operation of the low-voltage control circuit and potentially damaging the low-voltage components. Summary of the Invention

[0005] This invention provides a short-circuit detection circuit to solve the problem in existing short-circuit detection schemes where high-voltage signals are coupled to the low-voltage control side, causing interference and device damage.

[0006] A short-circuit detection circuit includes a first switching circuit, a second switching circuit, an X-capacitor circuit, and an optocoupler; The first switching circuit is connected between the input live wire and the first terminal of the light-emitting side of the optocoupler; The second switching circuit is connected between the input neutral line and the second terminal of the light-emitting side of the optocoupler; The X capacitor circuit is connected between the first switching circuit and the second switching circuit, and is configured to establish a driving voltage when there is no short circuit between the output live wire and the output neutral wire, so as to drive the light-emitting diode of the optocoupler to work. The output side of the optocoupler is used to connect to the feedback signal terminal. The level of the feedback signal terminal changes with the working state of the light-emitting diode to indicate whether there is a short circuit between the output live wire and the output neutral wire.

[0007] Furthermore, the first switching circuit includes a first switch and a first resistor connected in series, and the second switching circuit includes a second switch and a second resistor connected in series.

[0008] Furthermore, the first switching circuit also includes a rectifier diode connected in series with the first resistor.

[0009] Furthermore, the short-circuit detection circuit also includes a first Y-capacitor circuit, which is connected between the first switching circuit and the ground wire.

[0010] Furthermore, the short-circuit detection circuit also includes a second Y-capacitor circuit, which is connected between the second switching circuit and the ground wire.

[0011] Furthermore, the output side of the optocoupler is connected to the power supply terminal and the feedback signal terminal through a voltage divider resistor network.

[0012] Furthermore, the voltage divider resistor network is connected in series between the third resistor and the fourth resistor between the power supply terminal and the feedback signal terminal; the output terminal of the optocoupler is connected to the connection node between the third resistor and the fourth resistor.

[0013] Furthermore, the short-circuit detection circuit also includes a filter capacitor, one end of which is connected to the connection node between the fourth resistor and the feedback signal terminal, and the other end of which is grounded.

[0014] Furthermore, the equivalent capacitance of the X capacitor circuit is less than or equal to 30μF.

[0015] Furthermore, the short-circuit detection circuit also includes a first current-limiting resistor circuit, a second current-limiting resistor circuit, and a third current-limiting resistor circuit; The first current-limiting resistor circuit is connected in series between the first terminal of the light-emitting side of the optocoupler and the first switching circuit; The second current-limiting resistor circuit is connected in series between the second terminal of the light-emitting side of the optocoupler and the second switching circuit; The third current-limiting resistor circuit is connected in series between the first and second terminals of the light-emitting side of the optocoupler.

[0016] This invention provides a short-circuit detection circuit, which includes a first switching circuit, a second switching circuit, an X-capacitor circuit, and an optocoupler. The first switching circuit is connected between the input live wire and the first terminal of the optocoupler's light-emitting side, and the second switching circuit is connected between the input neutral wire and the second terminal of the optocoupler's light-emitting side to ensure controllable switching of the detection loop. The X-capacitor circuit is connected between the first and second switching circuits to establish a driving voltage when no short circuit occurs between the output live wire and the output neutral wire, thereby driving the light-emitting diode of the optocoupler to operate and realizing the judgment of the short circuit state. The output side of the optocoupler is connected to a feedback signal terminal, and the level of the feedback signal terminal changes with the operating state of the light-emitting diode to indicate whether there is a short circuit at the output terminal. The optocoupler blocks the coupling path of the high-voltage signal to the low-voltage control side, avoiding high-voltage interference from affecting the low-voltage control circuit and improving detection reliability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of a short-circuit detection circuit in one embodiment of the present invention.

[0019] In the diagram: 1. First switch circuit; 11. First switch; 12. First resistor; 13. Rectifier diode; 2. Second switch circuit; 21. Second switch; 22. Second resistor; 3. X capacitor circuit; 4. Optocoupler; 5. First Y capacitor circuit; 6. Second Y capacitor circuit; 7. Voltage divider resistor network; 71. Third resistor; 72. Fourth resistor; 8. Filter capacitor; 91. First current limiting resistor circuit; 92. Second current limiting resistor circuit; 93. Third current limiting resistor circuit. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be understood that the invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0022] To fully understand this invention, detailed structures and steps will be presented in the following description to illustrate the technical solution proposed by this invention. Preferred embodiments of the invention are described in detail below; however, in addition to these detailed descriptions, the invention may have other embodiments.

[0023] This embodiment provides a short-circuit detection circuit, such as Figure 1 As shown, it includes a first switching circuit 1, a second switching circuit 2, an X-capacitor circuit 3, and an optocoupler 4.

[0024] As an example, the first switching circuit 1 is connected between the input live wire L_in and the first terminal of the light-emitting side of the optocoupler 4, that is, the first switching circuit 1 is connected between the input live wire L_in and the anode of the light-emitting diode of the optocoupler 4. Specifically, the first switching circuit 1 includes a first switch 11 and a first resistor 12 connected in series, and the first resistor 12 is connected between the first switch 11 and the input live wire L_in.

[0025] As an example, the second switching circuit 2 is connected between the input neutral line N_in and the second terminal of the light-emitting side of the optocoupler 4, that is, the second switching circuit 2 is connected between the input neutral line N_in and the cathode of the light-emitting diode of the optocoupler 4. Specifically, the second switching circuit 2 includes a second switch 21 and a second resistor 22 connected in series, and the second resistor 22 is connected between the second switch 21 and the input neutral line N_in.

[0026] In this embodiment, the first switching circuit 1 further includes a rectifier diode 13 connected in series with the first resistor 12 to prevent reverse current.

[0027] As an example, the X-capacitor circuit 3 is connected between the first switch circuit 1 and the second switch circuit 2. Specifically, one end of the X-capacitor circuit 3 is connected between the first switch 11 and the first terminal of the light-emitting side of the optocoupler 4, and the other end is connected between the second switch 21 and the second terminal of the light-emitting side of the optocoupler 4.

[0028] As an example, this short-circuit detection circuit is used in an AC charging station. The input live wire L_in and input neutral wire N_in are used to connect to the AC power grid, and the output live wire L_out and output neutral wire N_out are used to connect to the electric vehicle. Before the charging station outputs energy, the first switch 11 and the second switch 21 are closed to perform short-circuit detection.

[0029] This embodiment also includes a first current-limiting resistor circuit 91, a second current-limiting resistor circuit 92, and a third current-limiting resistor circuit 93. The first current-limiting resistor circuit 91 is connected in series between the first terminal of the light-emitting side of the optocoupler 4 and the first switching circuit 1; the second current-limiting resistor circuit 92 is connected in series between the second terminal of the light-emitting side of the optocoupler 4 and the second switching circuit 2; the third current-limiting resistor circuit 93 is connected in series between the first and second terminals of the light-emitting side of the optocoupler 4, and is used to limit the current flowing through the light-emitting diode of the optocoupler 4 to protect the light-emitting diode.

[0030] This embodiment also includes a first Y-capacitor circuit 5 and a second Y-capacitor circuit 6. The first Y-capacitor circuit 5 is connected between the first switching circuit 1 and the ground line GND, specifically at the node between the first switch 11 and the first terminal of the optocoupler 4 (light-emitting side); the second Y-capacitor circuit 6 is connected between the second switching circuit 2 and the ground line GND, specifically at the node between the second switch 21 and the second terminal of the optocoupler 4 (light-emitting side). The first Y-capacitor circuit 5 and the second Y-capacitor circuit 6 are used to filter out common-mode interference.

[0031] As an example, the output side of optocoupler 4, i.e., the collector of the phototransistor, is connected to the power supply terminal VCC and the feedback signal terminal FB through a voltage divider resistor network 7. The voltage divider resistor network 7 includes a third resistor 71 and a fourth resistor 72 connected in series between the power supply terminal VCC and the feedback signal terminal FB. The output terminal of optocoupler 4, i.e., the collector of the phototransistor, is connected to the connection node between the third resistor 71 and the fourth resistor 72.

[0032] This embodiment also includes a filter capacitor 8, one end of which is connected to the node between the fourth resistor 72 and the feedback signal terminal FB, and the other end is grounded to stabilize the feedback signal.

[0033] In this embodiment, the equivalent capacitance of the X capacitor circuit 3 is less than or equal to 30μF.

[0034] In this embodiment, the short-circuit detection circuit operates as follows: Before the charging station outputs energy, close the first switch 11 and the second switch 21. If there is no short circuit between the output live wire L_out and the output neutral wire N_out, the AC input voltage forms a loop through the first resistor 12, the first switch 11, the first current-limiting resistor circuit 9, the LED of the optocoupler 4, the second current-limiting resistor circuit 10, the second switch 21, and the second resistor 22, simultaneously charging the X capacitor circuit 3. When the voltage across the X capacitor circuit 3 rises sufficiently to make the LED of the optocoupler 4 light up, the output side of the optocoupler 4 is turned on, and the level of the feedback signal terminal FB is pulled low, thus indicating that the output terminal is normal.

[0035] If there is a short circuit between the output live wire L_out and the output neutral wire N_out, the two ends of the X capacitor circuit 3 are short-circuited and cannot establish a sufficient voltage. The LED of the optocoupler 4 will not light up, the output side of the optocoupler 4 will not be conductive, and the level of the feedback signal terminal FB will be pulled up to a high level, thus indicating that there is a short circuit.

[0036] After the test is completed, disconnect the first switch 11 and the second switch 21, and then close the main power relay to start normal charging.

[0037] This embodiment provides an AC charging pile, including the aforementioned short-circuit detection circuit. Before outputting energy, the AC charging pile detects whether there is a short circuit between the output live wire and the output neutral wire using the short-circuit detection circuit. If a short circuit exists, energy output is prohibited, and an alarm signal is issued; if there is no short circuit, energy is output normally.

[0038] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A short-circuit detection circuit, characterized in that, It includes a first switching circuit, a second switching circuit, an X-capacitor circuit, and an optocoupler; The first switching circuit is connected between the input live wire and the first terminal of the light-emitting side of the optocoupler; The second switching circuit is connected between the input neutral line and the second terminal of the light-emitting side of the optocoupler; The X capacitor circuit is connected between the first switching circuit and the second switching circuit, and is configured to establish a driving voltage when there is no short circuit between the output live wire and the output neutral wire, so as to drive the light-emitting diode of the optocoupler to work. The output side of the optocoupler is used to connect to the feedback signal terminal. The level of the feedback signal terminal changes with the working state of the light-emitting diode to indicate whether there is a short circuit between the output live wire and the output neutral wire.

2. The short-circuit detection circuit according to claim 1, characterized in that, The first switching circuit includes a first switch and a first resistor connected in series, and the second switching circuit includes a second switch and a second resistor connected in series.

3. The short-circuit detection circuit according to claim 2, characterized in that, The first switching circuit also includes a rectifier diode connected in series with the first resistor.

4. The short-circuit detection circuit according to claim 1, characterized in that, The short-circuit detection circuit further includes a first Y-capacitor circuit, which is connected between the first switching circuit and the ground wire.

5. The short-circuit detection circuit according to claim 1, characterized in that, The short-circuit detection circuit further includes a second Y-capacitor circuit, which is connected between the second switching circuit and the ground wire.

6. The short-circuit detection circuit according to claim 1, characterized in that, The output side of the optocoupler is connected to the power supply terminal and the feedback signal terminal through a voltage divider resistor network.

7. The short-circuit detection circuit according to claim 6, characterized in that, The voltage divider resistor network is connected in series between the third resistor and the fourth resistor between the power supply terminal and the feedback signal terminal; the output terminal of the optocoupler is connected to the connection node between the third resistor and the fourth resistor.

8. The short-circuit detection circuit according to claim 6, characterized in that, The short-circuit detection circuit also includes a filter capacitor, one end of which is connected to the connection node between the fourth resistor and the feedback signal terminal, and the other end of which is grounded.

9. The short-circuit detection circuit according to claim 1, characterized in that, The equivalent capacitance of the X capacitor circuit is less than or equal to 30μF.

10. The short-circuit detection circuit according to claim 1, characterized in that, The short-circuit detection circuit further includes a first current-limiting resistor circuit, a second current-limiting resistor circuit, and a third current-limiting resistor circuit. The first current-limiting resistor circuit is connected in series between the first terminal of the light-emitting side of the optocoupler and the first switching circuit; The second current-limiting resistor circuit is connected in series between the second terminal of the light-emitting side of the optocoupler and the second switching circuit; The third current-limiting resistor circuit is connected in series between the first and second terminals of the light-emitting side of the optocoupler.

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