Short circuit detection circuit

Abstract

The utility model relates to a short circuit detection circuit, which is used for detecting the output end of a first relay and comprises a power supply module, a main control module, a detection power supply module, a circuit access module and a signal sampling module, the main control module is provided with a control output end and a signal input end; the detection power supply module is connected with the power supply module to take power and output step-down direct current; the circuit access module comprises a second relay and a relay driving unit, and the relay driving unit switches on and off the second relay according to the control signal output by the main control module; the second relay is provided with a first normally open contact and a second normally open contact, the output end of the detection power supply module is connected with one pole of the output end of the first relay through the first normally open contact, and the other pole of the output end of the first relay is connected with the sampling input end of the signal sampling module through the second contact; the sampling output end of the signal sampling module is connected with the signal input end of the master control module. The charging pile short circuit detection device can reliably detect the charging pile short circuit problem, and is simple in structure and low in cost.

Description

Technical Field

[0001] The utility model relates to the technical field of charging piles, and in particular to a short-circuit detection circuit. Background Art

[0002] As electric vehicles gain increasing market share, charging stations for electric vehicles are becoming increasingly popular. According to national standards, a short-circuit test is required before the AC power supply circuit is turned on. This involves performing a short-circuit test on the back end of the charging station's output relay to prevent electrical accidents caused by a short circuit at the charging station output. The general principle of existing charging station short-circuit detection circuits is to first obtain DC power through an AC / DC converter, then boost this DC power through an isolation transformer and introduce it to one of the terminals at the back end of the relay. The other terminal at the back end of the relay is then tested for voltage or current. If voltage or current is detected, a short circuit is present; otherwise, the circuit is normal and charging can proceed. This detection circuit requires an isolation transformer and its corresponding control circuit, which are relatively expensive and complex. Furthermore, while the short-circuit detection circuit including the isolation transformer can also detect relay adhesion, many current relays are designed with built-in adhesion detection, resulting in redundant functionality. Utility Model Content

[0003] The purpose of the utility model is to provide a short-circuit detection circuit, which can reliably detect the short-circuit problem of a charging pile and has a simple structure and low cost.

[0004] To achieve the above object, the utility model discloses a short circuit detection circuit for detecting the output end of a first relay, which includes a power supply module, a main control module, a detection power supply module, a circuit access module and a signal sampling module;

[0005] The power supply module is used to output direct current;

[0006] The main control module is connected to the power supply module to obtain power, and the main control module has a control output terminal for outputting a control signal and a signal input terminal for receiving a short-circuit detection feedback signal;

[0007] The detection power supply module is connected to the power supply module to take power and output stepped-down DC power;

[0008] The circuit access module includes a second relay and a relay driving unit. The relay driving unit is connected to the power supply module, the coil of the second relay and the control output end of the main control module. The relay driving unit switches the second relay on and off according to the control signal output by the main control module; the second relay has a first normally open contact and a second normally open contact. The output end of the detection power supply module is connected to one end of the first normally open contact, the other end of the first normally open contact is connected to one pole of the output end of the first relay, one end of the second normally open contact is connected to the other pole of the output end of the first relay, and the other end of the second normally open contact is connected to the sampling input end of the signal sampling module, and the sampling output end of the signal sampling module is connected to the signal input end of the main control module.

[0009] Preferably, the detection power supply module includes a diode group and a step-down resistor, the diode group includes at least one first diode, the first diodes are connected in series in sequence, the anode side of the diode group is connected to the power supply module, and the cathode side of the diode group is connected to one end of the first normally open contact through the step-down resistor.

[0010] Preferably, at least one fuse is connected in series in the detection power supply module.

[0011] Preferably, the relay drive unit includes a MOS transistor Q9, a resistor R90, a resistor R99, a diode D15, a capacitor C40, and a capacitor C49. The control output end of the main control module is connected to one end of the resistor R99 and the gate of the MOS transistor Q9 via the resistor R90. The other end of the resistor R99 and the drain of the MOS transistor Q9 are grounded. The source of the MOS transistor Q9 is connected to one end of the capacitor C49, the anode of the diode D15, and one end of the coil of the second relay. The other end of the coil of the second relay is connected to the cathode of the diode D15, the other end of the capacitor C49, one end of the capacitor C40, and the power supply module. The other end of the capacitor C40 is grounded.

[0012] Preferably, the signal sampling module includes a diode D13, an optocoupler PH3, a resistor R54, a resistor R69, a resistor R70 and a capacitor C34, the anode of the diode D13 is connected to one end of the second normally open contact, the cathode of the diode D13 is connected to the anode of the light emitter of the optocoupler PH3 via the resistor R54, the cathode of the light emitter of the optocoupler PH3 is grounded, the collector of the light receiver of the optocoupler PH3 is connected to the power supply end of the main control module, the emitter of the light receiver of the optocoupler PH3 is connected to one end of the resistor R69, one end of the resistor R70 and one end of the capacitor C34, the other end of the resistor R69 is connected to the signal input end of the main control module, and the other end of the resistor R70 and the other end of the capacitor C34 are grounded.

[0013] Preferably, the main control module includes a chip U2 and a power access unit, the power access unit includes an inductor L5, a capacitor C25, a capacitor C26, a capacitor C29 and a capacitor C31, one end of the inductor L5 and one end of the capacitor C25 are connected to the power supply module, the other end of the inductor L5 is connected to one end of the capacitor C26, one end of the capacitor C29, one end of the capacitor C31, the VDD pin of the chip U2 and the collector of the photoreceiver of the optocoupler PH3, the other end of the capacitor C25, the other end of the capacitor C26, the other end of the capacitor C29 and the other end of the capacitor C31 are grounded.

[0014] Preferably, the power supply module is connected to the input end of the first relay to obtain power.

[0015] Preferably, the power supply module includes an AC / DC unit and a step-down unit, the input end of the AC / DC unit is connected to the input end of the first relay to take power and output DC power, the step-down unit is connected to the output end of the AC / DC unit and outputs stepped-down DC power; the main control module is connected to the output end of the step-down unit to take power; the detection power supply module and the relay drive unit are connected to the output end of the AC / DC unit to take power.

[0016] Preferably, it also includes a main control circuit module and a relay drive module, the main control circuit module includes two first relays, namely relay K1 and relay K2; the relay drive module includes a chip U8, a resistor B1, a resistor B2, a resistor R18, a resistor R27, a resistor R44, a resistor R51, a resistor R125, a resistor R135, a resistor C8C, a resistor R8C, a capacitor C74, a capacitor C72, a MOS tube Q8, a MOS tube QA, a MOS tube QB and an inductor L11, the main control module also has a drive control end, the drive control end is connected to one end of the resistor R135 and the gate of the MOS tube Q8 through the resistor R8C, the other end of the resistor R135 and the source of the MOS tube Q8 are connected to the power supply end of the main control module, the drain of the MOS tube Q8 is connected to one end of the resistor C8C and the IN pin of the chip U8 through the resistor R51, and the other end of the resistor C8C is connected to the C pin of the chip U8 The OM pin is grounded; the output end of the power supply module is connected to one end of the inductor L11 and one end of the capacitor C74. The other end of the inductor L11 is connected to one end of the capacitor C72 and the VCC pin of the chip U8. The other end of the capacitor C72 and the other end of the capacitor C74 are grounded. The OUT1 pin of the chip U8 is connected to one end of the resistor R44 and the gate of the MOS transistor QA via the resistor R18. The drain of the MOS transistor QA is connected to one end of the coil of the relay K1 via the resistor B1. The other end of the coil of the relay K1 is connected to the output end of the power supply module. The other end of the resistor R44 and the source of the MOS transistor QA are grounded. The OUT2 pin of the chip U8 is connected to one end of the resistor R27 and the gate of the MOS transistor QB via the resistor R125. The drain of the MOS transistor QB is connected to one end of the coil of the relay K2 via the resistor B2. The other end of the coil of the relay K2 is connected to the output end of the power supply module. The other end of the resistor R27 and the source of the MOS transistor QB are grounded.

[0017] Preferably, the coils of the relay K1 and the relay K2 are both connected in parallel with a peak absorption unit, the peak absorption unit includes a second diode and a first capacitor, the second diode is connected in parallel with the first capacitor, and the cathode of the second diode is connected to the output end of the power supply module.

[0018] The utility model has the following beneficial effects:

[0019] 1. In this utility model, when the first relay is not closed, the main control module controls the second relay to close. Simultaneously, the detection power module draws power from the power supply module and provides a DC voltage to one of the first relay output terminals (the L terminal). If the first relay output terminal short-circuits, the signal sampling module connected to the other terminal (the N terminal) of the first relay output terminal can collect the DC voltage output by the power supply module and feed it back to the main control module, thereby reliably detecting short circuits. Furthermore, this utility model has a simple structure and low cost.

[0020] 2. The diode group set in the detection power module can prevent the second relay from being mis-conducted and causing current to flow back into the power supply module. In addition, the setting of the voltage-dropping resistor can prevent the diode group from being broken down when the second relay is mis-conducted.

[0021] 3. The signal sampling module is built based on optocouplers, which can play a good feedback role. At the same time, it can also play an isolation role to prevent the second relay from being misconnected and damaging the main control module. In addition, the cost of optocouplers is also low. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the AC / DC unit.

[0023] Figure 2 This is a schematic diagram of the main control module.

[0024] Figure 3 This is a schematic diagram of the relay driver module.

[0025] Figure 4 Schematic diagram of the main control line module.

[0026] Figure 5 Schematic diagram of the detection power module, circuit access module and signal sampling module.

[0027] Description of main components symbols:

[0028] AC / DC unit 11 , step-down unit 12 , main control module 20 , relay drive module 30 , main control circuit module 40 , detection power module 50 , circuit access module 60 , signal sampling module 70 . DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0030] like Figures 1 to 5 As shown, the utility model discloses a short-circuit detection circuit for detecting whether the output end of a first relay is short-circuited. In this case, two first relays are provided, namely relay K1 and relay K2. Relay K1 is used to control the L pole of the power supply line, and relay K2 is used to control the N pole of the power supply line. That is, the utility model is used to detect whether the L pole and the N pole of the output end of the first relay are short-circuited.

[0031] The utility model includes a power supply module, a main control module 20 , a detection power supply module 50 , a circuit access module 60 , a signal sampling module 70 , a main control circuit module 40 and a relay drive module 30 .

[0032] The power supply module is used to output DC power. It includes an AC / DC unit 11 and a step-down unit 12. The input end of the AC / DC unit 11 is connected to the input end of the first relay (i.e., the L and N poles on one side of the first relay input end are connected) to draw power and output DC power Vdc+ (+15V). The step-down unit 12 is connected to the output end of the AC / DC unit 11 and outputs a stepped-down DC power Vcc (+5V). The AC / DC unit 11 and the step-down unit 12 are existing mature technologies and can be referenced. Figure 1 , no more details.

[0033] Main control module 20 includes chip U2 and a power supply unit. The power supply unit includes inductor L5, capacitors C25, C26, C29, and C31. Chip U2 is BAT32G135-S LFQFP32. One end of inductor L5 and one end of capacitor C25 are connected to the power supply module (Vcc). The other end of inductor L5 is connected to one end of capacitor C26, one end of capacitor C29, one end of capacitor C31, the VDD pin of chip U2, and the collector of the photodetector of optocoupler PH3. The other ends of capacitors C25, C26, C29, and C31 are connected to ground. Pin 11 of chip U2 is the drive control terminal (KG-11) for controlling the on / off of the first relay. Pin 14 is the control output terminal (K3-shout) for outputting control signals. Pin 15 is the signal input terminal (Out-short) for receiving short-circuit detection feedback signals.

[0034] The relay driver module 30 includes a chip U8, a resistor B1, a resistor B2, a resistor R18, a resistor R27, a resistor R44, a resistor R51, a resistor R125, a resistor R135, a resistor C8C, a resistor R8C, a capacitor C74, a capacitor C72, a MOS transistor Q8, a MOS transistor QA, a MOS transistor QB and an inductor L11. The model of the chip U8 is NSG44273, SOT23-5. The drive control terminal (KG-11) of the main control module 20 is connected to one end of the resistor R135 and the gate of the MOS transistor Q8 via the resistor R8C. The other end of the resistor R135 and the source of the MOS transistor Q8 are connected to the power supply terminal (VDD) of the main control module 20. The drain of the MOS transistor Q8 is connected to one end of the resistor C8C and the IN pin of the chip U8 via the resistor R51. The other end of the resistor C8C and the COM pin of the chip U8 are grounded. The output terminal (Vdc+) of the power supply module is connected to one end of the inductor L11 and one end of the capacitor C74. The other end of the inductor L11 is connected to one end of the capacitor C72 and the VCC pin of the chip U8. The other end of the capacitor C72 and the other end of the capacitor C74 are grounded. The OUT1 pin of chip U8 is connected to one end of resistor R44 and the gate of MOS transistor QA via resistor R18. The drain of MOS transistor QA is connected to one end of the coil of relay K1 via resistor B1. The other end of the coil of relay K1 is connected to the output end (Vdc+) of the power supply module. The other end of the resistor R44 and the source of MOS transistor QA are grounded. The OUT2 pin of chip U8 is connected to one end of resistor R27 and the gate of MOS transistor QB via resistor R125. The drain of MOS transistor QB is connected to one end of the coil of relay K2 via resistor B2. The other end of the coil of relay K2 is connected to the output end (Vdc+) of the power supply module. The other end of the resistor R27 and the source of MOS transistor QB are grounded.

[0035] The coils of relays K1 and K2 are both connected in parallel with spike absorption units. Taking relay K1 as an example, its corresponding spike absorption unit includes a second diode D2 and a first capacitor C2A. The second diode D2 is connected in parallel with the first capacitor C2A. The cathode of the second diode D2 is connected to the output terminal (Vdc+) of the power supply module, and the anode of the second diode D2 is connected to the resistor B1.

[0036] Chip U8 draws power from Vdc+. The main control module 20 outputs a high level to control the MOS tube Q8 to turn on, thereby providing an output command for chip U8. At this time, the OUT1 and OUT2 pins of chip U8 output a high level, MOS tube QA and MOS tube QB are turned on, the coils of relays K1 and K2 are energized and turned on, and relays K1 and K2 can be closed.

[0037] The circuit access module 60 includes a second relay K3 and a relay driver unit. The relay driver unit is connected to the power supply module, the coil of the second relay K3, and the control output of the main control module 20. The relay driver unit switches the second relay K3 on and off according to the control signal output by the main control module 20. Specifically, the relay driver unit includes a MOS transistor Q9, a resistor R90, a resistor R99, a diode D15, a capacitor C40, and a capacitor C49. The control output (K3-shout) of the main control module 20 is connected to one end of the resistor R99 and the gate of the MOS transistor Q9 via the resistor R90. The other end of the resistor R99 and the drain of the MOS transistor Q9 are grounded. The source of the MOS transistor Q9 is connected to one end of the capacitor C49, the anode of the diode D15, and one end of the coil of the second relay K3. The other end of the coil of the second relay K3 is connected to the cathode of the diode D15, the other end of the capacitor C49, one end of the capacitor C40, and the power supply module (Vdc+). The other end of the capacitor C40 is grounded. The control output terminal (K3-shout) of the main control module 20 outputs a high level, the MOS tube Q9 is turned on, the coil of the second relay K3 is energized, and K3 is closed.

[0038] The second relay K3 has a first normally open contact and a second normally open contact. The output of the detection power module 50 is connected to one end of the first normally open contact, and the other end of the first normally open contact is connected to one of the output terminals (Lout) of the first relay. The detection power module 50 includes a diode group, a voltage-dropping resistor R55, and at least one fuse. The diode group includes at least one first diode, which are connected in series. In this embodiment, the diodes are first diodes D11 and D8. The anode of the first diode group D11 is connected to the power supply module (Vdc+), and the cathode of the first diode group D11 is connected to the anode of the first diode group D8. The cathode of the first diode group D8 is connected to one end of the first normally open contact of K3 via the voltage-dropping resistor R55 and the fuse FR1.

[0039] One end of the second normally open contact of K3 is connected to the other pole (Nout) of the first relay output end, and the other end of the second normally open contact is connected to the sampling input end of the signal sampling module 70. The sampling output end of the signal sampling module 70 is connected to the signal input end of the main control module 20. Specifically, the signal sampling module 70 includes a diode D13, an optocoupler PH3, a resistor R54, a resistor R69, a resistor R70 and a capacitor C34. The anode of the diode D13 is connected to one end of the second normally open contact as the sampling input end of the signal sampling module 70, the cathode of the diode D13 is connected to the anode of the light emitter of the optocoupler PH3 via the resistor R54, the cathode of the light emitter of the optocoupler PH3 is grounded, the collector of the light receiver of the optocoupler PH3 is connected to the power supply end (VDD) of the main control module 20, the emitter of the light receiver of the optocoupler PH3 is connected to one end of the resistor R69, one end of the resistor R70 and one end of the capacitor C34, the other end of the resistor R69 is connected to the signal input end (Out-short) of the main control module 20 as the sampling output end of the signal sampling module 70, and the other end of the resistor R70 and the other end of the capacitor C34 are grounded.

[0040] When relays K1 and K2 are disconnected, main control module 20 outputs a high level, turning on MOS transistor Q9 and closing second relay K3. If outputs Lout and Nout are short-circuited, optocoupler PH3 of signal sampling module 70 will conduct, and main control module 20 will sample a high level, indicating a short circuit. If outputs Lout and Nout are not short-circuited, optocoupler PH3 will not conduct, and main control module 20 will detect a low level. When relays K1 and K2 are closed, if second relay K3 accidentally closes, first diode D11 and first diode D8 prevent current from flowing back into AC / DC unit 11. Simultaneously, high-power resistor R55 reduces the 220V voltage to a tolerable level for the circuit, providing protection. Fuse FR1 further enhances this protection. Optocoupler PH3 acts as a barrier to signal sampling module 70, preventing high voltage from damaging the main control module 20 chip.

[0041] The above is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited to this. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed in the present invention should be covered by the protection scope of the present invention.

Claims

1. A short circuit detection circuit for detecting an output terminal of a first relay, characterized in that: It includes power supply module, main control module, detection power supply module, circuit access module and signal sampling module; The power supply module is used to output direct current; The main control module is connected to the power supply module to obtain power, and the main control module has a control output terminal for outputting a control signal and a signal input terminal for receiving a short-circuit detection feedback signal; The detection power supply module is connected to the power supply module to take power and output stepped-down DC power; The circuit access module includes a second relay and a relay driving unit. The relay driving unit is connected to the power supply module, the coil of the second relay and the control output end of the main control module. The relay driving unit switches the second relay on and off according to the control signal output by the main control module; the second relay has a first normally open contact and a second normally open contact. The output end of the detection power supply module is connected to one end of the first normally open contact, the other end of the first normally open contact is connected to one pole of the output end of the first relay, one end of the second normally open contact is connected to the other pole of the output end of the first relay, and the other end of the second normally open contact is connected to the sampling input end of the signal sampling module, and the sampling output end of the signal sampling module is connected to the signal input end of the main control module.

2. The short-circuit detection circuit according to claim 1, wherein: The detection power supply module includes a diode group and a voltage-dropping resistor. The diode group includes at least one first diode, which is connected in series in sequence. The anode side of the diode group is connected to the power supply module, and the cathode side of the diode group is connected to one end of the first normally open contact through the voltage-dropping resistor.

3. The short-circuit detection circuit according to claim 2, wherein: At least one fuse is also connected in series in the detection power supply module.

4. The short-circuit detection circuit according to claim 1, wherein: The relay drive unit includes a MOS transistor Q9, a resistor R90, a resistor R99, a diode D15, a capacitor C40, and a capacitor C49. The control output end of the main control module is connected to one end of the resistor R99 and the gate of the MOS transistor Q9 via the resistor R90. The other end of the resistor R99 and the drain of the MOS transistor Q9 are grounded. The source of the MOS transistor Q9 is connected to one end of the capacitor C49, the anode of the diode D15, and one end of the coil of the second relay. The other end of the coil of the second relay is connected to the cathode of the diode D15, the other end of the capacitor C49, one end of the capacitor C40, and the power supply module. The other end of the capacitor C40 is grounded.

5. The short-circuit detection circuit according to claim 1, wherein: The signal sampling module includes a diode D13, an optocoupler PH3, a resistor R54, a resistor R69, a resistor R70 and a capacitor C34. The anode of the diode D13 is connected to one end of the second normally open contact, the cathode of the diode D13 is connected to the anode of the light emitter of the optocoupler PH3 via the resistor R54, the cathode of the light emitter of the optocoupler PH3 is grounded, the collector of the light receiver of the optocoupler PH3 is connected to the power supply end of the main control module, the emitter of the light receiver of the optocoupler PH3 is connected to one end of the resistor R69, one end of the resistor R70 and one end of the capacitor C34, the other end of the resistor R69 is connected to the signal input end of the main control module, and the other end of the resistor R70 and the other end of the capacitor C34 are grounded.

6. The short-circuit detection circuit according to claim 5, wherein: The main control module includes a chip U2 and a power access unit. The power access unit includes an inductor L5, a capacitor C25, a capacitor C26, a capacitor C29 and a capacitor C31. One end of the inductor L5 and one end of the capacitor C25 are connected to the power supply module, and the other end of the inductor L5 is connected to one end of the capacitor C26, one end of the capacitor C29, one end of the capacitor C31, the VDD pin of the chip U2 and the collector of the light receiver of the optocoupler PH3. The other end of the capacitor C25, the other end of the capacitor C26, the other end of the capacitor C29 and the other end of the capacitor C31 are grounded.

7. The short-circuit detection circuit according to claim 1, wherein: The power supply module is connected to the input end of the first relay to obtain power.

8. The short-circuit detection circuit according to claim 1, wherein: The power supply module includes an AC / DC unit and a step-down unit. The input end of the AC / DC unit is connected to the input end of the first relay to obtain power and output DC power. The step-down unit is connected to the output end of the AC / DC unit and outputs stepped-down DC power. The main control module is connected to the output end of the step-down unit to obtain power. The detection power supply module and the relay drive unit are connected to the output end of the AC / DC unit to obtain power.

9. The short-circuit detection circuit according to claim 1, wherein: It also includes a main control circuit module and a relay drive module. The main control circuit module includes two first relays, namely relay K1 and relay K2; the relay drive module includes chip U8, resistor B1, resistor B2, resistor R18, resistor R27, resistor R44, resistor R51, resistor R125, resistor R135, resistor C8C, resistor R8C, capacitor C74, capacitor C72, MOS transistor Q8, MOS transistor QA, MOS transistor QB and inductor L11. The main control module also has a drive control end, which is connected to one end of resistor R135 and the gate of MOS transistor Q8 through resistor R8C, the other end of resistor R135 and the source of MOS transistor Q8 are connected to the power supply end of the main control module, the drain of MOS transistor Q8 is connected to one end of resistor C8C and the IN pin of chip U8 through resistor R51, and the other end of resistor C8C is connected to the COM pin of chip U8. The output end of the power supply module is connected to one end of the inductor L11 and one end of the capacitor C74, the other end of the inductor L11 is connected to one end of the capacitor C72 and the VCC pin of the chip U8, and the other end of the capacitor C72 and the other end of the capacitor C74 are grounded; the OUT1 pin of the chip U8 is connected to one end of the resistor R44 and the gate of the MOS transistor QA via the resistor R18, the drain of the MOS transistor QA is connected to one end of the coil of the relay K1 via the resistor B1, the other end of the coil of the relay K1 is connected to the output end of the power supply module, and the other end of the resistor R44 and the source of the MOS transistor QA are grounded; the OUT2 pin of the chip U8 is connected to one end of the resistor R27 and the gate of the MOS transistor QB via the resistor R125, the drain of the MOS transistor QB is connected to one end of the coil of the relay K2 via the resistor B2, the other end of the coil of the relay K2 is connected to the output end of the power supply module, and the other end of the resistor R27 and the source of the MOS transistor QB are grounded.

10. The short-circuit detection circuit according to claim 9, wherein: The coils of the relay K1 and the relay K2 are both connected in parallel with a peak absorption unit, and the peak absorption unit includes a second diode and a first capacitor. The second diode is connected in parallel with the first capacitor, and the cathode of the second diode is connected to the output end of the power supply module.

Images