Circuit for detecting output short circuit of alternating current charging pile
By combining the L-line and N-line detection resistor circuits with the isolation optocoupler circuit, the problems of complexity and high cost in AC charging pile short circuit detection are solved. This achieves highly sensitive, safe and reliable short circuit and adhesion detection, meets the requirements of the new national standard, and reduces circuit cost and maintenance difficulty.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHENZHEN ENERGY EFFICIENCY ELECTRIC TECH CO LTD
- Filing Date
- 2025-05-29
- Publication Date
- 2026-06-16
AI Technical Summary
The existing short-circuit detection methods for AC charging piles are complex, rely on manual inspection, and cannot predict short-circuit risks, resulting in high costs, difficult maintenance, and non-compliance with the new national standards.
It employs L-line and N-line detection resistor circuits and isolation optocoupler circuits, and linearizes the voltage signal through a resistor voltage divider network. Combined with optocoupler isolation technology, it separates high and low voltage circuits, resulting in high detection sensitivity and high reliability. It also has short circuit and adhesion detection functions, saving components and space.
It achieves highly sensitive short-circuit detection, meets the requirements of the new national standard, reduces circuit costs and maintenance difficulty, and also has adhesion detection function, thus improving the safety and competitiveness of AC charging piles.
Smart Images
Figure CN224366172U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of AC charging pile technology, specifically to a circuit for detecting short circuits in the output of an AC charging pile. Background Technology
[0002] With the rapid development of the electric vehicle industry, the demand for charging piles, as a core supporting facility, has surged. However, the quality of charging piles on the market varies greatly, and many products do not meet safety requirements. To address this, relevant departments issued mandatory national standards for charging piles GB39752-2024 and GB44263-2024 in 2024. The new national standards require that AC charging piles should not charge when a short circuit occurs in the AC output circuit before energy transmission.
[0003] Traditional detection methods are complex. Early short-circuit detection relied on air switches and residual current devices (RCDs), requiring manual troubleshooting and making it impossible to predict short-circuit risks before charging. Existing technologies use complex relay switching logic (such as multiple relays connected in series), resulting in high circuit costs and difficult maintenance. Utility Model Content
[0004] In view of this, a circuit for detecting short circuits at the output of an AC charging pile is provided, which has high detection sensitivity, is safe and reliable, saves on components, space and cost.
[0005] A circuit for detecting short circuits at the output of an AC charging pile, wherein the AC charging pile has an L line and an N line connected to AC power, the input terminal of the L line has an L line main relay K1, the input terminal of the N line has an N line main relay K2, the L line main relay K1 has an L line input terminal contact and an L line output terminal contact, and the N line main relay K2 has an N line input terminal contact and an N line output terminal contact; characterized in that the circuit for detecting short circuits at the output of the AC charging pile includes at least one of an L line detection resistor circuit and an N line detection resistor circuit, and an isolation optocoupler circuit;
[0006] Each of the L-line detection resistor circuit and the N-line detection resistor circuit includes a detection relay and at least one detection resistor.
[0007] The isolation optocoupler circuit includes a first diode D1 connected to the output terminal contact of the L-line main relay K1, several resistors, an isolation optocoupler U1, and a filter circuit. The first terminal of the primary side of the isolation optocoupler U1 is connected to the negative terminal of the first diode D1, and the second terminal is connected to the output terminal contact of the N-line main relay K2 through at least one resistor. The collector of the secondary side of the isolation optocoupler U1 is connected to the power supply terminal, and the emitter is connected to the sampling pin ADC of a microcontroller U2 after passing through the filter circuit.
[0008] Furthermore, the short-circuit detection circuit for the AC charging pile output includes an L-line detection resistor circuit and an N-line detection resistor circuit; the L-line detection resistor circuit includes an L-line detection relay and several L-line detection resistors; the N-line detection resistor circuit includes an N-line detection relay and several N-line detection resistors.
[0009] Preferably, each detection resistor circuit has multiple detection resistors connected in parallel, and each detection relay is connected in series with the corresponding multiple parallel detection resistors.
[0010] Furthermore, the detection relay and detection resistor in each detection resistor circuit are connected in series and then in parallel between the input and output contacts of the main relay on the corresponding line.
[0011] Specifically, when there is an L-line detection resistor circuit, the L-line detection resistor circuit includes an L-line detection relay K3 and three L-line detection resistors R1, R2, and R3; when there is an N-line detection resistor circuit, the N-line detection resistor circuit includes an N-line detection relay K4 and three N-line detection resistors R8, R9, and R10.
[0012] Furthermore, the isolation optocoupler circuit is provided with a second diode D2 connected in reverse parallel to the primary side of the isolation optocoupler U1.
[0013] Furthermore, the first terminal of the primary side of the isolation optocoupler U1 is connected to the negative terminal of the first diode D1 through a fourth voltage divider resistor R4.
[0014] Furthermore, the second primary end of the isolation optocoupler U1 is connected to the N-line output contact of the N-line main relay K2 via at least one resistor.
[0015] Furthermore, the filtering circuit includes a pull-down resistor R7 and a first filtering capacitor C1, which are connected in parallel. One end of the parallel connection is connected to the emitter of the secondary side of the isolation optocoupler U1, and the other end is grounded.
[0016] Furthermore, each of the detection relays is also connected to a corresponding control signal pin of the microcontroller U2. During detection, the corresponding control signal pin of the microcontroller U2 gives an instruction to close the corresponding detection relay to perform short circuit detection.
[0017] In the aforementioned AC charging pile output short-circuit detection circuit, a resistor divider network and isolated sampling are used to linearize the voltage signal, improving detection sensitivity. Simultaneously, optocoupler isolation technology is employed to separate high and low voltage circuits, ensuring system anti-interference capabilities and making the detection results safer and more reliable. Furthermore, this circuit shares the adhesion detection circuit of the L / N main relay, reducing the number of detection circuit components and saving space and cost. Additionally, since this circuit is connected between the two contacts of the L and N main relays, it can also perform adhesion detection on the L / N main relays, combining short-circuit detection and adhesion detection functions into one circuit, further saving space and cost, and making it widely applicable in various AC charging piles. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the circuit for detecting short circuits at the output of an AC charging pile, provided in Embodiment 1 of this utility model.
[0019] Figure 2 This is a schematic diagram of the circuit for detecting short circuits at the output of an AC charging pile, provided in Embodiment 2 of this utility model.
[0020] Figure 3 This is a schematic diagram of the circuit for detecting short circuits at the output of an AC charging pile, provided in Embodiment 3 of this utility model. Detailed Implementation
[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.
[0022] Please see Figure 1 This illustration shows a circuit for short-circuit detection of an AC charging pile output according to Embodiment 1 of the present invention. The AC charging pile has an L line and an N line connected to AC power. The input end of the L line has an L line main relay K1, and the input end of the N line has an N line main relay K2. The L line main relay K1 has two contacts, namely an L line input contact and an L line output contact. The N line main relay K2 has two contacts, namely an N line input contact and an N line output contact. The circuit for short-circuit detection of the AC charging pile output includes at least one of an L line detection resistor circuit and an N line detection resistor circuit, as well as an isolation optocoupler circuit. Figure 1 The circuit shown includes an L-line detection resistor circuit.
[0023] like Figure 1As shown, the L-line detection resistor circuit or the N-line detection resistor circuit each includes a detection relay and at least one detection resistor. Specifically, the isolation optocoupler circuit includes a first diode D1 connected to the output terminal contact of the L-line main relay K1, several resistors, an isolation optocoupler U1, and a filter circuit. The primary side of the isolation optocoupler U1 has its first terminal connected to the negative terminal of the first diode D1, and its second terminal connected to the output terminal contact of the N-line main relay K2 through at least one resistor. The collector of the secondary side of the isolation optocoupler U1 is connected to the power supply terminal, and the emitter is connected to the sampling pin ADC of a microcontroller U2 after passing through the filter circuit. The preferred model of the microcontroller (MCU) U2 is the Arteri AT32F413.
[0024] Specifically, the L-line detection resistor circuit includes an L-line detection relay and a plurality of L-line detection resistors. Preferably, each detection resistor circuit has a plurality of detection resistors connected in parallel, and each detection relay is connected in series with the corresponding plurality of parallel-connected detection resistors. Further, the detection relay and detection resistor in each detection resistor circuit are connected in parallel between the input and output contacts of the main relay of the corresponding line. Further, each of the detection relays is also connected to a corresponding control signal pin of the microcontroller U2, and during detection, the corresponding control signal pin of the microcontroller U2 issues a command to close the corresponding detection relay for short-circuit detection.
[0025] like Figure 2 In the illustrated embodiment, specifically, the L-line detection resistor circuit includes one L-line detection relay K3 and three L-line detection resistors R1, R2, and R3; the three L-line detection resistors R1, R2, and R3 are connected in parallel and in series with the L-line detection relay K3. The two ends of the entire L-line detection resistor circuit are respectively connected in parallel between the input and output contacts of the main L-line relay, that is, connected in parallel with the main L-line relay K1 at the input of the L-line.
[0026] Furthermore, the isolation optocoupler circuit includes a second diode D2 connected in reverse parallel to the primary side of the isolation optocoupler U1. Further, the first terminal of the primary side of the isolation optocoupler U1 is connected to the cathode of the first diode D1 through a fourth voltage-dividing resistor R4. Specifically, the primary side of the isolation optocoupler circuit includes a photodiode, the anode of which is connected to the second terminal of the fourth voltage-dividing resistor R4, the cathode of the second diode D2 is connected to the second terminal of the fourth voltage-dividing resistor R4, and the first terminal of the fourth voltage-dividing resistor R4 is connected to the cathode of the first diode D1.
[0027] Furthermore, the second terminal of the primary side of the isolation optocoupler U1 is connected to the N-line output contact of the N-line main relay K2 via at least one resistor, and this at least one resistor is connected in series between the primary side of the isolation optocoupler U1 and the N-line output contact of the N-line main relay K2. Figure 1 In the illustrated embodiment, the second terminal of the primary side of the isolation optocoupler U1 is connected to the N-line output contact of the N-line main relay K2 via the fifth voltage divider resistor R5 and the sixth voltage divider resistor R6. The fifth voltage divider resistor R5 and the sixth voltage divider resistor R6 are connected in series. Specifically, the negative terminal of the photodiode and the positive terminal of the second diode D2 in the primary side of the isolation optocoupler circuit are respectively connected to one end of the sixth voltage divider resistor R6.
[0028] Specifically, such as Figure 1 As shown, the secondary side of the isolation optocoupler U1 preferably has a photosensitive element, such as a silicon phototransistor, whose substrate is the light receiving end. The emitter of the photosensitive element is connected to the sampling pin ADC of the microcontroller U2 after passing through a filtering circuit. The filtering circuit includes a pull-down resistor R7 and a first filtering capacitor C1, which are connected in parallel. One end of the parallel connection is connected to the emitter of the secondary side of the isolation optocoupler U1, and the other end is grounded. The collector of the secondary side of the isolation optocoupler U1 is connected to a power supply terminal, for example, to an auxiliary power supply or to a 3.3V voltage provided by the microcontroller U2.
[0029] Please see Figure 2 This illustration shows a circuit for short-circuit detection of the output of an AC charging pile according to Embodiment 2 of this utility model. The circuit for short-circuit detection of the output of the AC charging pile in Embodiment 2 is basically the same as that in Embodiment 1, the main difference being that the circuit for short-circuit detection of the output of the AC charging pile includes an N-line detection resistor circuit. This can be understood as the N-line detection resistor circuit replacing the L-line detection resistor circuit in Embodiment 1. Other circuit components are basically the same. The N-line detection resistor circuit includes several N-line detection resistors. The circuit structure of Embodiment 2, which is basically the same as that in Embodiment 1, will not be described again here. Specifically, the N-line detection resistor circuit includes one N-line detection relay K4 and three N-line detection resistors R8, R9, and R10. The three N-line detection resistors R8, R9, and R10 are connected in parallel and in series with the N-line detection relay K4. The two ends of the entire N-line detection resistor circuit are connected in parallel between the input and output contacts of the main N-line relay, that is, connected in parallel with the main N-line relay K2 at the input of the N-line.
[0030] Please see Figure 3This illustration shows a circuit for detecting short circuits at the output of an AC charging pile according to Embodiment 3 of the present invention. The circuit for detecting short circuits at the output of the AC charging pile in Embodiment 3 is basically the same as that in Embodiments 1 or 2, with the main difference being that the circuit for detecting short circuits at the output of the AC charging pile includes an L-line detection resistor circuit and an N-line detection resistor circuit. Therefore, the detection resistor circuits from Embodiments 1 and 2 can also be combined, using the same isolation optocoupler circuit. The L-line detection resistor circuit and the N-line detection resistor circuit correspond to the circuits with the same names in Embodiments 1 and 2, respectively, and their structures are basically the same.
[0031] Specifically, the L-line detection resistor circuit in this embodiment includes one L-line detection relay K3 and three L-line detection resistors R1, R2, and R3; the three L-line detection resistors R1, R2, and R3 are connected in parallel and in series with the L-line detection relay K3. The two ends of the entire L-line detection resistor circuit are connected in parallel between the input and output contacts of the main L-line relay, i.e., connected in parallel with the main L-line relay K1 at the input of the L-line. The N-line detection resistor circuit includes one N-line detection relay K4 and three N-line detection resistors R8, R9, and R10. The three N-line detection resistors R8, R9, and R10 are connected in parallel and in series with the N-line detection relay K4. The two ends of the entire N-line detection resistor circuit are connected in parallel between the input and output contacts of the main N-line relay, i.e., connected in parallel with the main N-line relay K2 at the input of the N-line.
[0032] Taking Example 3 as an example, the specific application process involves short-circuit detection before charging: After receiving the charging start command (e.g., card swiping, App click, scheduled charging, plug-and-charge, etc.), microcontroller U2 controls the N-line main relay K2 and L-line detection relay K3 to close. When the AC charging pile output is short-circuited (on the gun head side, i.e., L_out to N_out), the ADC I / O port of microcontroller U2 samples that the voltage to ground on the secondary side of the isolation optocoupler U1 is 0V. At this time, microcontroller U2 determines that the AC charging pile output is short-circuited. When the AC charging pile output is not short-circuited (on the gun head side), after closing relays K2 and K3, there is voltage at the AC charging pile output. The isolation optocoupler U1 conducts during the positive half-cycle of the AC power, and a square wave signal is generated on the secondary side resistor R7. When the ADC sampling I / O port of microcontroller U2 samples a voltage greater than the judgment value (e.g., 0.8V), it is determined that the AC charging pile output is normal and there is no short circuit, and the normal charging process begins.
[0033] Similarly, the short-circuit detection circuit is set on the other path, namely the N-line side (for example, only...). Figure 2In the circuit shown, short-circuit detection is performed before charging: After receiving the start charging command, microcontroller U2 controls the L-line main relay K1 and the N-line detection relay K4 to close. When the AC charging pile output is short-circuited (on the charging head side, i.e., L_out to N_out), the ADC I / O port of microcontroller U2 samples that the voltage to ground on the secondary side of the isolation optocoupler U1 is 0V. At this time, microcontroller U2 determines that the AC charging pile output is short-circuited. When the AC charging pile output is not short-circuited (on the N-line side), after closing relays K1 and K4, there is voltage at the AC charging pile output. The isolation optocoupler U1 conducts during the positive half-cycle of the AC power, and a square wave signal is generated on the secondary side resistor R7. When the ADC sampling I / O port of microcontroller U2 samples a voltage greater than the judgment value (e.g., 0.8V), it is determined that the AC charging pile output is normal and there is no short circuit, and the normal charging process begins.
[0034] Additionally, by sequentially closing main relays K1 and K2, the sticking detection of the L / N line main relays can also be achieved using the detection circuit of D1, D2, R4, R5, R6, R7, U1, U2, and C1. For example, when the AC terminal output is not short-circuited (i.e., there is no short circuit), open main relays K1 and K2, then close the L line main relay K1 first, without closing the N line main relay K2. If the N line main relay K2 sticks, it is equivalent to the N line main relay K2 being conductive. Then, the isolation optocoupler U1 is conductive, and the ADC IO port of the microcontroller U2 samples a voltage, thus determining that the N line main relay K2 is sticking. Similarly, it is also possible to determine whether the L line main relay K1 is sticking. Therefore, while meeting the requirements of mandatory national standards GB39752-2024 and GB44263-2024, the entire circuit also achieves pre-start short-circuit detection and L / N line main relay adhesion detection with a minimal circuit structure and a small number of components, thereby improving the market competitiveness of AC charging pile products.
[0035] It should be noted that this utility model is not limited to the above-described embodiments. Based on the inventive spirit of this utility model, those skilled in the art can make other changes, and these changes made based on the inventive spirit of this utility model should be included within the scope of protection claimed by this utility model.
Claims
1. A circuit for short-circuit detection at the output of an AC charging pile, wherein the AC charging pile has an L-line and an N-line connected to AC power, the input terminal of the L-line has an L-line main relay K1, the input terminal of the N-line has an N-line main relay K2, the L-line main relay K1 has an L-line input terminal contact and an L-line output terminal contact, and the N-line main relay K2 has an N-line input terminal contact and an N-line output terminal contact; characterized in that, The short-circuit detection circuit for the AC charging pile output includes at least one of an L-line detection resistor circuit and an N-line detection resistor circuit, as well as an isolation optocoupler circuit. Each of the L-line detection resistor circuit and the N-line detection resistor circuit includes a detection relay and at least one detection resistor. The isolation optocoupler circuit includes a first diode D1 connected to the output terminal contact of the L-line main relay K1, several resistors, an isolation optocoupler U1, and a filter circuit. The first terminal of the primary side of the isolation optocoupler U1 is connected to the negative terminal of the first diode D1, and the second terminal is connected to the output terminal contact of the N-line main relay K2 through at least one resistor. The collector of the secondary side of the isolation optocoupler U1 is connected to the power supply terminal, and the emitter is connected to the sampling pin ADC of a microcontroller U2 after passing through the filter circuit.
2. The circuit for detecting short circuits at the output of an AC charging pile as described in claim 1, characterized in that, The short-circuit detection circuit for the AC charging pile output includes an L-line detection resistor circuit and an N-line detection resistor circuit; the L-line detection resistor circuit includes an L-line detection relay and several L-line detection resistors; the N-line detection resistor circuit includes an N-line detection relay and several N-line detection resistors.
3. The circuit for detecting short circuits at the output of an AC charging pile as described in claim 1, characterized in that, Each sensing resistor circuit has multiple sensing resistors connected in parallel, and each sensing relay is connected in series with the corresponding multiple parallel sensing resistors.
4. The circuit for detecting short circuits at the output of an AC charging pile as described in claim 1, characterized in that, In each sensing resistor circuit, the sensing relay and sensing resistor are connected in series and then in parallel between the input and output contacts of the main relay on the corresponding line.
5. The circuit for detecting short circuits at the output of an AC charging pile as described in claim 1, characterized in that, When there is an L-line detection resistor circuit, the L-line detection resistor circuit includes one L-line detection relay K3 and three L-line detection resistors R1, R2, and R3; when there is an N-line detection resistor circuit, the N-line detection resistor circuit includes one N-line detection relay K4 and three N-line detection resistors R8, R9, and R10.
6. The circuit for detecting short circuits at the output of an AC charging pile as described in claim 1, characterized in that, The isolation optocoupler circuit is provided with a second diode D2 connected in reverse parallel to the primary side of the isolation optocoupler U1.
7. The circuit for detecting short circuits at the output of an AC charging pile as described in claim 1, characterized in that, The primary side of the isolation optocoupler U1 is connected to the negative terminal of the first diode D1 through a fourth voltage divider resistor R4.
8. The circuit for detecting short circuits at the output of an AC charging pile as described in claim 1, characterized in that, The second terminal of the primary side of the isolation optocoupler U1 is connected to the N-line output terminal contact of the N-line main relay K2 through at least one resistor.
9. The circuit for detecting short circuits at the output of an AC charging pile as described in claim 1, characterized in that, The filtering circuit includes a pull-down resistor R7 and a first filtering capacitor C1. The pull-down resistor R7 and the first filtering capacitor C1 are connected in parallel, with one end connected to the emitter of the secondary side of the isolation optocoupler U1 and the other end grounded.
10. The circuit for detecting short circuits at the output of an AC charging pile as described in claim 1, characterized in that, Each of the detection relays is also connected to a corresponding control signal pin of the microcontroller U2. During detection, the corresponding control signal pin of the microcontroller U2 gives an instruction to close the corresponding detection relay to perform short circuit detection.