Charging drive circuit with leakage protection and corresponding charging method

Abstract

This invention provides a charging drive circuit with leakage protection, comprising a charging gun, a relay switch, a handshake signal generator, a power supply, a zero-current transformer, a leakage protection circuit, and a microcontroller unit. The charging gun detects the vehicle load; the relay switch controls the charging gun to supply power to the vehicle's charging port; the handshake signal generator generates a PWM handshake signal; the power supply generates a power signal; a first switch is provided between the power supply and the charging gun; the zero-current transformer collects the charging current between the power supply and the charging gun; a second switch is provided between the zero-current transformer and the charging gun or between the zero-current transformer and ground; the leakage protection circuit controls the relay switch based on the charging current; and the microcontroller unit controls the connected components. This invention also discloses a method for charging a vehicle using the above-described charging drive circuit.

Description

Technical Field

[0001] This invention relates to the field of circuits, and in particular to a charging drive circuit with leakage protection function. Background Technology

[0002] With the development of new energy vehicle technology, people's demand for fast and stable charging of new energy vehicles is also increasing. If a charging station is used for a long time, it may cause leakage in the corresponding charging drive circuit, thereby affecting the safety of charging new energy vehicles.

[0003] Existing charging stations are equipped with corresponding leakage detection circuits to detect leakage, but this is usually done during the charging process, by which time the leakage may have already caused some damage to the charging station or the new energy vehicle.

[0004] Therefore, it is necessary to provide a charging drive circuit with leakage protection function and a corresponding charging method to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention provides a charging drive circuit and a corresponding charging method for detecting leakage current in a charging drive circuit based on a handshake signal, in order to solve the technical problem that existing leakage current detection methods may damage charging piles or new energy vehicles.

[0006] This invention provides a charging drive circuit with leakage protection function, comprising:

[0007] A charging gun, connected to the car's charging port, is used to detect the car's load.

[0008] A relay switch is used to control the charging gun to supply power to the car charging port;

[0009] A handshake signal generator is used to generate a PWM handshake signal and is connected to the charging gun;

[0010] A power source, used to generate a power signal, is connected to the charging gun; wherein a first switch is provided between the power source and the charging gun.

[0011] The zero-current transformer is disposed between the power source and ground or between the power source and the charging gun, and is used to collect the charging current between the power source and the charging gun; a second switch is provided between the zero-current transformer and the charging gun or between the zero-current transformer and ground.

[0012] A leakage current protection circuit is connected to both the zero-current transformer and the relay switch, and is used to control the relay switch based on the charging current; and

[0013] The microcontroller unit is connected to the first switch, the second switch, the handshake signal generator, and the leakage protection circuit, respectively, and is used to control the connected components.

[0014] In the charging drive circuit with leakage protection function in this embodiment of the invention, the handshake signal generator includes:

[0015] A PWM signal generator is used to generate PWM pulse signals; and

[0016] A handshake signal generation circuit is used to convert the PWM pulse signal into a handshake signal with a set voltage, and output the handshake signal to the charging gun.

[0017] In the charging drive circuit with leakage protection function in this embodiment of the invention, the handshake signal generation circuit includes a handshake signal generating NPN transistor and a handshake signal generating PNP transistor. The base of the handshake signal generating NPN transistor is connected to the PWM signal generator, the collector of the handshake signal generating NPN transistor is connected to the first power supply, and the emitter of the handshake signal generating NPN transistor is connected to the charging gun.

[0018] The base of the PNP transistor that generates the handshake signal is connected to the PWM signal generator, the collector of the PNP transistor that generates the handshake signal is connected to the second power supply, and the emitter of the PNP transistor that generates the handshake signal is connected to the charging gun. The voltage of the first power supply is higher than the voltage of the second power supply.

[0019] In the charging drive circuit with leakage protection function in this embodiment of the invention, the leakage protection circuit includes:

[0020] A leakage current detection chip is used to generate a leakage current action level based on the pin voltage difference of the zero current transformer; an input level conversion circuit is used to convert the leakage current action level into a first leakage current latching level.

[0021] A leakage state latching circuit is used to convert the first leakage latching level to a second leakage latching level; and based on a control signal, a level latching capacitor is used to latch the high-level state of the second leakage latching level.

[0022] The output level conversion circuit is used to convert the second leakage latch level into a leakage action level;

[0023] A relay drive circuit is used to control the relay switch based on the leakage current operating level; and

[0024] The leakage current release circuit is used to release the charge of the level latch capacitor and reset the level latch capacitor.

[0025] In the charging drive circuit with leakage protection function in this embodiment of the invention, the input level conversion circuit includes:

[0026] An input level conversion comparator is provided, with the leakage current operating level input to its positive input and a first reference level input to its inverting input. The output of the input level conversion comparator is connected to an input level conversion NPN transistor.

[0027] An input level shifting NPN transistor is provided, wherein the base of the input level shifting NPN transistor is connected to the output of the input level shifting comparator, the emitter of the input level shifting NPN transistor is grounded, and the collector of the input level shifting NPN transistor is connected to the driving power supply; and

[0028] The input level conversion output terminal is connected to the collector of the input level conversion NPN transistor and is used to output the first leakage latch level.

[0029] In the charging drive circuit with leakage protection function in this embodiment of the invention, the leakage state latching circuit includes:

[0030] A leakage state latching PNP transistor is provided, wherein the base of the leakage state latching PNP transistor is input with the leakage latching level; the emitter of the leakage state latching PNP transistor is connected to the driving power supply; and the collector of the leakage state latching PNP transistor is connected to the level latching capacitor.

[0031] The level latching capacitor has its first terminal connected to the collector of the leakage-state latching PNP transistor, and its second terminal grounded; and

[0032] The leakage state latch amplifier has its input terminal connected to the collector of the leakage state latch PNP transistor, and its output terminal outputs the second leakage latch level.

[0033] In the charging drive circuit with leakage protection function in this embodiment of the invention, the output level conversion circuit includes:

[0034] An output level conversion NPN transistor is provided, wherein the base of the output level conversion NPN transistor is input to the leakage latch level; the emitter of the output level conversion NPN transistor is grounded; and the collector of the output level conversion NPN transistor is connected to the driving power supply.

[0035] The output level conversion output terminal is connected to the collector of the output level conversion NPN transistor and is used to output the leakage current action level.

[0036] In the charging drive circuit with leakage protection function in this embodiment of the invention, the relay drive circuit includes:

[0037] The AND operator has the leakage current action level input at its first input terminal and a PWM pulse signal input at its second input terminal; the output terminal of the AND operator is connected to a relay-driven NPN transistor.

[0038] The relay drives an NPN transistor, the base of which is connected to the output of the arithmetic unit, the emitter of which is grounded, the collector of which is connected to the driving power supply, and the collector of which outputs the control signal of the relay switch.

[0039] In the charging drive circuit with leakage protection function in this embodiment of the invention, the leakage state release circuit includes:

[0040] A leakage state release NPN transistor is provided, with its emitter grounded, its collector connected to the first terminal of the level latching capacitor, and its base connected to the microcontroller unit for receiving leakage state release signals.

[0041] The present invention also provides a method for charging an automobile using the above-described charging drive circuit, wherein the method includes:

[0042] The microcontroller unit detects the connection signal between the charging gun and the car charging port.

[0043] Based on the connection signal, the microcontroller turns on the first switch and controls the handshake signal generator to send a PWM handshake signal with a first set voltage.

[0044] The microcontroller unit detects whether the PWM handshake signal voltage changes to a second preset voltage based on changes in the vehicle load.

[0045] When the PWM handshake signal voltage changes to the second set voltage, the microcontroller controls the handshake signal generator to send a PWM handshake signal with a third set voltage.

[0046] The microcontroller controls the first switch to open and the second switch to open; the power supply generates a power signal; and the leakage protection circuit performs a leakage self-test on the charging current.

[0047] If the leakage current self-test passes, the microcontroller controls the second switch to open and the first switch to open, and the power supply outputs power to the car charging port through the charging gun; if the leakage current self-test fails, the microcontroller controls the second switch to open and prompts that the leakage current self-test has failed.

[0048] Compared with the prior art, the charging drive circuit and corresponding charging method of the present invention can trigger leakage detection based on the handshake signal communication loop corresponding to the handshake signal generator, which effectively avoids leakage during the charging operation and thus avoids damage to the charging pile and new energy vehicle caused by leakage; effectively solves the technical problem that existing leakage detection may cause damage to the charging pile or new energy vehicle. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the charging drive circuit with leakage protection function according to the present invention.

[0050] Figure 2 This is a circuit diagram of a first embodiment of the charging drive circuit with leakage protection function of the present invention.

[0051] Figure 3 This is a schematic diagram of the leakage detection chip in the leakage protection circuit of the charging drive circuit with leakage protection function of the present invention.

[0052] Figure 4 This is a schematic diagram of the input level conversion circuit of the leakage protection circuit of the charging drive circuit with leakage protection function of the present invention.

[0053] Figure 5 This is a schematic diagram of the leakage state latching circuit of the leakage protection circuit of the charging drive circuit with leakage protection function of the present invention.

[0054] Figure 6 This is a schematic diagram of the output level conversion circuit of the leakage protection circuit of the charging drive circuit with leakage protection function of the present invention.

[0055] Figure 7 This is a schematic diagram of the relay drive circuit of the leakage protection circuit of the charging drive circuit with leakage protection function of the present invention.

[0056] Figure 8 This is a schematic diagram of the leakage state release circuit of the leakage protection circuit of the charging drive circuit with leakage protection function of the present invention.

[0057] Figure 9 This is a circuit diagram of a second embodiment of the charging drive circuit with leakage protection function of the present invention.

[0058] Figure 10 This is a flowchart illustrating an embodiment of the vehicle charging method of the present invention. Detailed Implementation

[0059] 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 embodiments of the present invention, and not all embodiments. 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.

[0060] In the diagram, units with similar structures are represented by the same labels.

[0061] The charging drive circuit of this invention can be installed in a corresponding charging pile for charging new energy vehicles. The circuit includes a first switch between the power supply and the charging gun, and a second switch between the zero-current transformer and the charging gun, or between the zero-current transformer and ground. This allows leakage detection to be triggered based on the handshake signal communication loop corresponding to the handshake signal generator. If the leakage self-test passes, the charging pile outputs power to the new energy vehicle; if the self-test fails, the charging pile stops charging the new energy vehicle, effectively preventing leakage during the charging process and thus avoiding damage to the charging pile and the new energy vehicle.

[0062] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the charging drive circuit with leakage protection function of the present invention. The charging drive circuit 10 of this embodiment includes a charging gun 11, a relay switch 12, a handshake signal generator 13, a power supply 14, a zero current transformer 15, a leakage protection circuit 16, and a microcontroller unit 17.

[0063] The charging gun 11 is connected to the car charging port 18 to detect the car load. The relay switch 12 is connected to the charging gun 11 to control the charging gun 11 to supply power to the car charging port 18. The handshake signal generator 13 is connected to the charging gun 11 to generate a PWM (Pulse Width Modulation) handshake signal. The power supply 14 is connected to the charging gun 11 to generate a power signal; a first switch 19 is provided between the power supply 14 and the charging gun 11. The power supply 14 can be an AC-DC converter to ensure normal operation under different power supply modes. A zero-current transformer 15 is located between the power supply 14 and ground or between the power supply 14 and the charging gun 11 to collect the charging current between the power supply 14 and the charging gun 11. A second switch 1A is provided between the zero-current transformer 15 and the charging gun 11 or between the zero-current transformer 15 and ground. The zero-current transformer 15 is located at the input terminal of the charging drive circuit, which effectively detects leakage current in the charging drive circuit, ensuring comprehensive leakage protection. The leakage current protection circuit 16 is connected to the zero-current transformer 15 and the relay switch 12, respectively, and is used to control the relay switch 12 based on the charging current collected by the zero-current transformer 15. The microcontroller unit 17 is connected to the first switch 19, the second switch 1A, the handshake signal generator 13, and the leakage current protection circuit 16, respectively, and is used to control the connected components. The first switch 19 and the second switch 1A can be relays, contactors, thyristor switching circuits, or electronic switches, etc.

[0064] Please refer to Figure 2 , Figure 2 This is a circuit diagram of a first embodiment of the charging drive circuit with leakage protection function of the present invention. The handshake signal generator 13 in this embodiment includes a PWM signal generator 131 and a handshake signal generation circuit. The PWM signal generator 131 is used to generate PWM pulse signals; the handshake signal generation circuit is used to convert the PWM pulse signals into handshake signals with a set voltage and output the handshake signals to the charging gun 11.

[0065] In this embodiment, the handshake signal generation circuit includes a handshake signal generating NPN transistor 132 and a handshake signal generating PNP transistor 133. The base of the handshake signal generating NPN transistor 132 is connected to the PWM signal generator 131, the collector of the handshake signal generating NPN transistor 132 is connected to the first power supply, and the emitter of the handshake signal generating NPN transistor 133 is connected to the charging gun 11.

[0066] The base of the PNP transistor 133 that generates the handshake signal is connected to the PWM signal generator 131, the collector of the PNP transistor 133 that generates the handshake signal is connected to the second power supply, and the emitter of the PNP transistor 133 that generates the handshake signal is connected to the charging gun 11. The voltage of the first power supply is higher than the voltage of the second power supply.

[0067] The handshake signal generation circuit in this embodiment can generate a handshake signal with any set voltage that is lower than the first power supply voltage and higher than the second power supply voltage by adjusting the ratio of the high-level pulse width and the low-level pulse width of the PWM pulse signal, thus facilitating the generation of handshake signals with different set voltages. If it is necessary to increase the voltage of the handshake signal, the proportion of the high-level pulse width is increased; if it is necessary to decrease the voltage of the handshake signal, the proportion of the low-level pulse width is increased.

[0068] The leakage protection circuit 16 in this embodiment includes a leakage detection chip 161, an input level conversion circuit 162, a leakage state latching circuit 163, an output level conversion circuit 164, a relay drive circuit 165, and a leakage state release circuit 166.

[0069] The leakage current detection chip 161 is used to generate a leakage current action level S1 based on the pin voltage difference set in the zero current transformer; the input level conversion circuit 162 is used to convert the leakage current action level S1 into a first leakage current latch level S2; the leakage current state latch circuit 163 is used to convert the first leakage current latch level S2 into a second leakage current latch level S3; and based on the control signal, the level latch capacitor is used to latch the high-level state of the second leakage current latch level S3; the output level conversion circuit 164 is used to convert the second leakage current latch level S3 into a leakage current drive level S4; the relay drive circuit 165 is used to control the relay switch of the electrical drive circuit based on the leakage current drive level S4; and the leakage current state release circuit 166 is used to release the charge of the level latch capacitor and reset the level latch capacitor.

[0070] The leakage protection circuit 16 in this embodiment can be connected to the zero current transformer 15 on the charging drive circuit 10. The zero current transformer 15 can detect the leakage current on the charging drive circuit 10. If the leakage current on the electrical drive circuit 10 is too large (the voltage difference between the two pins of the zero current transformer 15 is greater than the preset value), the leakage detection chip 161 will output the leakage action level S1.

[0071] Subsequently, the input level conversion circuit 162 converts the leakage action level S1 into the first leakage latch level S2. Since the voltage values ​​of the leakage action level S1 output by the leakage detection chip 161 on the market are not consistent, it is necessary to use the input level conversion circuit 162 to convert the different leakage action levels into a unified first leakage latch level S2 (low level when there is leakage, high level when it is normal) so that the high level state of the second leakage latch level S3 can be latched by the level latch capacitor.

[0072] Then, the leakage current state latching circuit 163 converts the first leakage current latching level S2 to the second leakage current latching level S3, and uses a level latching capacitor to latch the high level state of the second leakage current latching level S3 based on the control signal of the microcontroller unit 17, that is, to keep the leakage current disconnected state of the leakage protection circuit 16, so as to prevent the leakage current disconnected state of the leakage protection circuit 16 from being reset when the leakage current fluctuates or disappears, thereby causing the leakage current protection circuit 16 to repeatedly switch states.

[0073] Since the leakage current drive level S4 of relay switch 12 will be set differently depending on the relay drive circuit 165, the output level conversion circuit 164 will convert the second leakage current latch level S3 into leakage current drive level S4 of different specifications so as to effectively control the relay switch 12 in the future.

[0074] Finally, the relay drive circuit 165 receives the leakage current drive level S4 and controls the relay switch 12 of the charging drive circuit 10 based on the leakage current drive level S4 to disconnect the charging drive circuit 10.

[0075] Because of the high-level latching of the second leakage latching level S3 on the leakage state latching circuit 163, the leakage disconnection state of the leakage protection circuit 16 cannot be automatically reset. Only when the leakage state release circuit 166 receives the control signal from the microcontroller unit 17, which can be sent by software or hardware (the user can set it), can the charge of the level latching capacitor be released through the leakage state release circuit 166, thereby resetting the level latching capacitor.

[0076] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the leakage detection chip in the leakage protection circuit of the charging drive circuit with leakage protection function of the present invention.

[0077] In this embodiment, the leakage current detection chip 161 uses the FM2152 from Fudan Microelectronics. The RCI1 and RCI2 pins of the leakage current detection chip 161 are connected to a zero current transformer. If the voltage difference between the two pins exceeds 5mV and the duration exceeds 4ms, leakage protection will be triggered, and the TRIG pin will generate a leakage current action level.

[0078] Please refer to Figure 4 , Figure 4 This is a schematic diagram of the input level conversion circuit of the leakage protection circuit of the charging drive circuit with leakage protection function of the present invention.

[0079] The input level conversion circuit 162 in this embodiment includes an input level conversion comparator 1621, an input level conversion NPN transistor 1622, and an input level conversion output terminal 1623.

[0080] The input level conversion comparator 1621 is used to convert the voltage value of the leakage current action level S11 in order to effectively drive the input level conversion NPN transistor 1622. The non-inverting input of the input level conversion comparator 1621 receives the leakage current action level S1, the inverting input receives the first reference level REF1, and the output of the input level conversion comparator 1621 is connected to the input level conversion NPN transistor 1622.

[0081] The input level shifting NPN transistor 1622 is used to reverse the polarity of the leakage current action level S1 to generate the first leakage current latch level S2. The base of the input level shifting NPN transistor 1622 is connected to the output of the input level shifting comparator 1621, the emitter of the input level shifting NPN transistor 1622 is grounded, and the collector of the input level shifting NPN transistor 1622 is connected to the drive power supply VCC.

[0082] Finally, the first leakage latch level S2 output from the collector of the input level conversion NPN transistor 1622 is output to the leakage state latch circuit 163 through the input level conversion output terminal 1623.

[0083] Please refer to Figure 5 , Figure 5 This is a schematic diagram of the leakage state latching circuit of the leakage protection circuit of the charging drive circuit with leakage protection function of the present invention.

[0084] The leakage state latching circuit 163 of this embodiment includes a leakage state latching PNP transistor 1631, a level latching capacitor 1632, and a leakage state latching amplifier 1633.

[0085] The leakage state latching PNP transistor 1631 is used to generate the second leakage latch level S3. The base of the leakage state latching PNP transistor 1631 is input to the first leakage latch level S2. The emitter of the leakage state latching PNP transistor 1631 is connected to the driving power supply VCC1. The collector of the leakage state latching PNP transistor 1631 is connected to the level latching capacitor 1632.

[0086] The level latch capacitor 1632 is used to store the input charge of the drive power supply to generate the second leakage latch level S3. The first terminal of the level latch capacitor 1632 is connected to the collector of the leakage state latching PNP transistor 1631, and the second terminal of the level latch capacitor 1632 is grounded.

[0087] The leakage state latch amplifier 1633 acts as a signal follower, maintaining the charge in the level latch capacitor 1632 to prevent it from being released. The input of the leakage state latch amplifier 1633 is connected to the collector of the leakage state latch PNP transistor 1631, and the output of the leakage state latch amplifier 1632 outputs a second leakage latch level S3. The output voltage of the second leakage latch level S3 is determined by the drive power supply VCC1.

[0088] Please refer to Figure 6 , Figure 6 This is a schematic diagram of the output level conversion circuit of the leakage protection circuit of the charging drive circuit with leakage protection function of the present invention.

[0089] The output level conversion circuit 164 in this embodiment includes an output level conversion NPN transistor 1641 and an output level conversion output terminal 1642.

[0090] The output level conversion NPN transistor 1641 is used to convert the second leakage latch level S3 to generate different types of leakage drive levels S4. The base of the output level conversion NPN transistor 1641 is input to the second leakage latch level S3, the emitter of the output level conversion NPN transistor 1641 is grounded, and the collector of the output level conversion NPN transistor 1641 is connected to the drive power supply VCC2. The output voltage of the leakage drive level S4 is determined by the drive power supply VCC2.

[0091] The collector of the NPN transistor 1641 outputs the corresponding leakage drive level S4 through the output level conversion output terminal 1642.

[0092] Please refer to Figure 7 , Figure 7 This is a schematic diagram of the relay drive circuit of the charging drive circuit with leakage protection function of the present invention. The relay drive circuit 165 in this embodiment includes an arithmetic unit 1651 and a relay drive NPN transistor 1652.

[0093] The AND unit 1651 is used to integrate the leakage drive level signal of the hardware and the leakage drive level signal of the software. The AND unit 1651 outputs a high-level signal only when both the leakage drive level signal of the hardware (leakage drive signal S4) and the leakage drive level signal of the software (PWM pulse signal PWM) are high-level signals; otherwise, the AND unit 1651 outputs a low-level signal.

[0094] The first input terminal of the arithmetic unit 1651 receives the leakage current drive level S4, the second input terminal of the arithmetic unit 1651 receives the PWM pulse signal PWM, and the output terminal of the arithmetic unit 1651 is connected to the relay drive NPN transistor 1652.

[0095] The relay-driven NPN transistor 1652 is used to convert the output signal of the arithmetic logic unit 1651 into a control signal for the relay switch 12. The base of the relay-driven NPN transistor 1652 is connected to the output terminal of the arithmetic logic unit 1651, the emitter of the relay-driven NPN transistor 1652 is grounded, and the collector of the relay-driven NPN transistor 1652 is connected to the drive power supply VCC3. The collector of the relay-driven NPN transistor 1652 outputs the control signal for the relay switch 12. The control signal voltage for the relay switch 12 is determined by the drive power supply VCC3.

[0096] Please refer to Figure 8 , Figure 8 This is a schematic diagram of the leakage state release circuit of the leakage protection circuit of the charging drive circuit with leakage protection function of the present invention. The leakage state release circuit 166 in this embodiment includes a leakage state release NPN transistor 1661.

[0097] The emitter of the leakage-state-release NPN transistor 1661 is grounded, the collector of the leakage-state-release NPN transistor 1661 is connected to the first terminal of the level latch capacitor 1632, and the base of the leakage-state-release NPN transistor 1661 receives the control signal MCU_CTL from the microcontroller unit 17 to control whether to perform a reset operation on the level latch capacitor 1632.

[0098] The specific working principle of the charging drive circuit 10 in this embodiment is as follows: When the charging gun 11 is connected to the car charging port 18, the microcontroller unit 17 will detect the connection signal between the charging gun 11 and the car charging port 18. At this time, the microcontroller unit 17 turns on the first switch 19, and the PWM signal generator 131 of the handshake signal generator 13 generates a first PWM pulse signal. The handshake signal generation circuit converts the first PWM pulse signal into a PWM handshake signal with a first set voltage and sends it to the car charging port 18 through the charging gun 11.

[0099] After receiving a PWM handshake signal with a first set voltage, the car charging port 18 adjusts the car load so that the PWM handshake signal changes to a second set voltage. When the microcontroller unit 17 detects that the PWM handshake signal has changed to the second set voltage, the microcontroller unit 17 controls the PWM signal generator 131 to generate a second PWM pulse signal. The handshake signal generation circuit converts the second PWM pulse signal into a PWM handshake signal with a third set voltage and sends it to the car charging port 18 so that the car charging port 18 is ready to receive charging current.

[0100] Subsequently, the microcontroller unit 17 controls the first switch 19 to turn off and the second switch 1A to turn on. At this time, the power supply 14 generates a power signal, the zero current transformer 15 detects the charging current on the entire charging drive circuit 10, and the leakage protection circuit 16 performs a leakage self-test on the charging drive circuit 10 based on the charging current.

[0101] If the leakage current self-test fails, the microcontroller unit 17 disconnects the first switch 19 and the second switch 1A, and the leakage current protection circuit 16 controls the relay switch 12 to disconnect, preventing the power supply 14 from outputting power to the car charging port 18, and indicating that the leakage current self-test has failed. If the leakage current self-test passes, the microcontroller unit 17 controls the second switch 1A to disconnect, controls the first switch 19 to conduct, the leakage current protection circuit 16 controls the relay switch 12 to conduct, and the power supply 14 outputs power to the car charging port 18 through the charging gun 11.

[0102] The leakage protection circuit 16 performs a leakage self-test on the charging drive circuit 10, which includes the following steps: When the leakage detection chip 161 detects the absence of pin voltage difference in the zero current transformer 15, the leakage detection chip 161 does not generate a leakage action level S1. Subsequently, the output of the input level conversion comparator 1621 outputs a low first reference level REF1 to the base of the input level conversion NPN transistor 1622, the input level conversion NPN transistor 1622 is turned off, the drive power supply VCC maintains a high level at the base of the leakage state latching PNP transistor 1631, the leakage state latching PNP transistor 1631 is turned off, the level latching capacitor 1632 does not store any charge, and therefore a high second leakage latching level S3 is not generated.

[0103] In this way, the output level conversion NPN transistor 1641 is also in the off state. The high voltage of the drive power supply VCC2 is input to the first input terminal of the arithmetic unit 1651, and the high level is output from the output terminal of the arithmetic unit 1651 to the base of the relay-driven NPN transistor 1652. The relay-driven NPN transistor 1652 turns on, and the collector of the relay-driven NPN transistor 1652 outputs a low level signal to the relay switch 12, and the relay maintains its working state.

[0104] If the leakage current detection chip 161 detects the presence of the zero current transformer 15 and generates a high-level leakage current action level S1, and the leakage current action level S1 at the positive input terminal of the input level conversion comparator 1621 is higher than the first reference level REF1, then the output terminal of the input level conversion comparator 1621 outputs a high-level leakage current action level S1.

[0105] The base of the leakage state latching PNP transistor 1631 is connected to the collector of the input level conversion NPN transistor 1622. At this time, the input level conversion NPN transistor 1622 is turned on, so the base of the leakage state latching PNP transistor 1631 is input with a low level first leakage latching level S2, and the leakage state latching PNP transistor 1631 is turned on.

[0106] The drive power supply VCC1 charges the level latching capacitor 1632 through the leakage state latching PNP transistor 1631 to form the second leakage latching level S3. At the same time, the level latching capacitor 1632 locks the high level of the second leakage latching level S3.

[0107] Subsequently, the second leakage latch level S3 is output to the base of the output level conversion NPN transistor 1641 through the leakage state latch amplifier 1633. The output level conversion NPN transistor 1641 is turned on, and the collector of the output level conversion NPN transistor 1641 outputs a low-level leakage drive level S4 to the AND unit 1651.

[0108] Meanwhile, the software part of the leakage protection circuit 16 will also set the PWM pulse signal to zero based on the leakage action level S1 of the leakage detection chip 161, and the arithmetic unit 1651 will output a low-level signal to the base of the relay-driven NPN transistor 1652 under the action of the low-level leakage drive level S1 or the zeroed PWM pulse signal.

[0109] The relay drives the NPN transistor 1652 to disconnect, and the power supply VCC3 outputs the control signal for the relay switch 12 to disconnect the relay switch 12.

[0110] Subsequently, after the high-level leakage current action level S1 is eliminated, the high-level second leakage current latch level S3 will not be eliminated due to the presence of the level latch capacitor 1632. If the microcontroller unit 17 determines that the leakage phenomenon has been eliminated, it can send a high-level control signal MCU_CTL to the base of the leakage state release NPN transistor 1661, so that the leakage state release NPN transistor 1661 is turned on. In this way, the charge of the level latch capacitor 1632 can be released through the leakage state release NPN transistor 1661, realizing the reset of the level latch capacitor 1632 and the entire leakage protection circuit 16.

[0111] This leakage current protection circuit can effectively maintain the open state of the relay switch by locking the high-level second leakage current latch level. At the same time, the hardware and software parts of the leakage current protection circuit can control the relay switch simultaneously. When the software part of the leakage current protection circuit fails, the hardware part of the leakage current protection circuit can still output the control signal of the relay switch to open the relay switch.

[0112] In this embodiment, the zero-current transformer of the charging drive circuit is set between the power supply and the charging gun. When the handshake signal generator and the new energy vehicle communicate with the handshake signal, the leakage detection circuit can simultaneously detect the leakage of the charging drive circuit through the handshake signal communication loop. If the leakage detection fails, the handshake signal result is not processed, and the device alarm is triggered when necessary, which improves the efficiency of leakage detection.

[0113] Please refer to Figure 9 , Figure 9 This is a circuit diagram of a second embodiment of the charging drive circuit with leakage protection function of the present invention.

[0114] Based on the first embodiment, the zero current transformer 25 of the charging drive circuit in this embodiment is set between the power supply 24 and the ground. This scheme defaults to the first switch 29 being turned on and the second switch 2A being turned off. When a leakage self-test is performed, the first switch 29 is turned off and the second switch 2A is turned on.

[0115] When the charging gun is connected to the car charging port, the first switch 29 is turned on and the second switch 2A is turned off. The microcontroller unit will detect that the PWM handshake signal voltage jumps from 12V to 9V. At this time, the first switch 29 is turned off and the second switch 2A is turned on. The leakage detection circuit performs a leakage self-test on the charging drive circuit. In this way, the leakage detection circuit and the charging circuit are physically isolated, ensuring that the power supply 24 will not incorrectly output power to the car charging port before the leakage detection circuit completes the leakage detection of the charging drive circuit.

[0116] This invention also provides a method for charging a car using the above-described charging drive circuit, please refer to... Figure 10 , Figure 10 This is a flowchart illustrating an embodiment of the vehicle charging method of the present invention. The vehicle charging method of the present invention specifically includes the following steps:

[0117] Step S1001: After the user connects the charging gun to the car charging port, the microcontroller detects the connection signal between the charging gun and the car charging port.

[0118] In step S1002, the microcontroller unit controls the first switch to be turned on and the second switch to be turned off based on the connection signal, and controls the handshake signal generator to send a PWM handshake signal with a first set voltage (such as a 12V PWM handshake signal) to the car charging port.

[0119] In step S1003, when the new energy vehicle detects the PWM handshake signal with the first set voltage, it loads the vehicle load into the charging drive circuit. At this time, the voltage of the PWM handshake signal changes to the second set voltage (e.g., changes to 6V).

[0120] Step S1004: When the PWM handshake signal voltage changes to the second set voltage, the microcontroller controls the handshake signal generator to send a PWM handshake signal with a third set voltage (such as a 6V PWM handshake signal) to the car charging port.

[0121] In step S1005, after the new energy vehicle receives the PWM handshake signal of the third set voltage (the new energy vehicle is ready to charge), the microcontroller controls the first switch to open and controls the second switch to turn on; the power supply generates a power signal, and when the charging current passes through the zero current transformer, the leakage protection circuit performs a leakage self-check on the charging current.

[0122] In step S1006, if the leakage self-test passes, the microcontroller controls the second switch to open and the first switch to open, allowing the power supply to output power to the car's charging port through the charging gun; if the leakage self-test fails, the microcontroller controls the second switch to open and indicates that the leakage self-test has failed; at the same time, the leakage protection circuit disconnects the relay switch to prevent the power supply from outputting power to the car's charging port through the charging gun.

[0123] This completes the vehicle charging control process of the vehicle charging method in this embodiment.

[0124] The PWM handshake signal generation process in the car charging method of this embodiment is the same as or similar to the working principle of the handshake signal generator in the charging drive circuit described above. The leakage self-test process in the car charging method of this embodiment is the same as or similar to the working principle of the leakage protection circuit in the charging drive circuit described above. For details, please refer to the detailed description in the specific embodiment of the charging drive circuit described above.

[0125] The charging drive circuit and corresponding charging method of this invention can trigger leakage detection based on the handshake signal communication loop corresponding to the handshake signal generator, effectively avoiding leakage during the charging operation and thus preventing damage to the charging pile and new energy vehicle caused by leakage; effectively solving the technical problem that existing leakage detection may cause damage to the charging pile or new energy vehicle.

[0126] In summary, although the present invention has been disclosed above with reference to preferred embodiments, the above preferred embodiments are not intended to limit the present invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope defined in the claims.

Claims

1. A charging drive circuit with leakage protection function, characterized in that, include: A charging gun, connected to the car's charging port, is used to detect the car's load. A relay switch is used to control the charging gun to supply power to the car charging port; A handshake signal generator is used to generate a PWM handshake signal and is connected to the charging gun; A power source, used to generate a power signal, is connected to the charging gun; wherein a first switch is provided between the power source and the charging gun. A zero-current transformer is installed between the power source and ground or between the power source and the charging gun to collect the charging current between the power source and the charging gun; a second switch is installed between the zero-current transformer and the charging gun or between the zero-current transformer and ground. A leakage protection circuit is connected to the zero current transformer and the relay switch respectively, and is used to control the relay switch based on the charging current. as well as The microcontroller unit is connected to the first switch, the second switch, the handshake signal generator, and the leakage protection circuit, respectively, and is used to control the connected components. The microcontroller unit detects the connection signal between the charging gun and the car charging port; Based on the connection signal, the microcontroller turns on the first switch and controls the handshake signal generator to send a PWM handshake signal with a first set voltage. The microcontroller detects whether the PWM handshake signal voltage changes to a second preset voltage based on changes in the vehicle load. When the PWM handshake signal voltage changes to the second set voltage, the microcontroller controls the handshake signal generator to send a PWM handshake signal with a third set voltage. The microcontroller controls the first switch to open and the second switch to open; the power supply generates a power signal; and the leakage protection circuit performs a leakage self-test on the charging current. If the leakage current self-test passes, the microcontroller controls the second switch to open and the first switch to open, and the power supply outputs power to the car charging port through the charging gun; if the leakage current self-test fails, the microcontroller controls the second switch to open and prompts that the leakage current self-test has failed.

2. The charging drive circuit with leakage protection function according to claim 1, characterized in that, The handshake signal generator includes: A PWM signal generator is used to generate PWM pulse signals; and A handshake signal generation circuit is used to convert the PWM pulse signal into a handshake signal with a set voltage, and output the handshake signal to the charging gun.

3. The charging drive circuit with leakage protection function according to claim 2, characterized in that, The handshake signal generation circuit includes a handshake signal generating NPN transistor and a handshake signal generating PNP transistor. The base of the handshake signal generating NPN transistor is connected to the PWM signal generator, the collector of the handshake signal generating NPN transistor is connected to the first power supply, and the emitter of the handshake signal generating NPN transistor is connected to the charging gun. The base of the PNP transistor that generates the handshake signal is connected to the PWM signal generator, the collector of the PNP transistor that generates the handshake signal is connected to the second power supply, and the emitter of the PNP transistor that generates the handshake signal is connected to the charging gun. The voltage of the first power supply is higher than the voltage of the second power supply.

4. The charging drive circuit with leakage protection function according to claim 1, characterized in that, The leakage protection circuit includes: A leakage current detection chip is used to generate a leakage current action level based on the pin voltage difference of the zero current transformer. Input level conversion circuit, used to convert the leakage current action level into a first leakage current latching level. A leakage state latching circuit is used to convert the first leakage latching level to a second leakage latching level; and based on a control signal, a level latching capacitor is used to latch the high-level state of the second leakage latching level. The output level conversion circuit is used to convert the second leakage latch level into a leakage action level; A relay drive circuit is used to control the relay switch based on the leakage current operating level; and The leakage current release circuit is used to release the charge of the level latch capacitor and reset the level latch capacitor.

5. The charging drive circuit with leakage protection function according to claim 4, characterized in that, The input level conversion circuit includes: An input level conversion comparator is provided, with the leakage current operating level input to its positive input and a first reference level input to its inverting input. The output of the input level conversion comparator is connected to an input level conversion NPN transistor. An input level shifting NPN transistor is provided, wherein the base of the input level shifting NPN transistor is connected to the output of the input level shifting comparator, the emitter of the input level shifting NPN transistor is grounded, and the collector of the input level shifting NPN transistor is connected to the driving power supply; and The input level conversion output terminal is connected to the collector of the input level conversion NPN transistor and is used to output the first leakage latch level.

6. The charging drive circuit with leakage protection function according to claim 4, characterized in that, The leakage current state latching circuit includes: A leakage state latching PNP transistor is provided, wherein the base of the leakage state latching PNP transistor is input with the leakage latching level; the emitter of the leakage state latching PNP transistor is connected to the driving power supply; and the collector of the leakage state latching PNP transistor is connected to the level latching capacitor. The level latching capacitor has its first terminal connected to the collector of the leakage-state latching PNP transistor, and its second terminal grounded; and A leakage state latching amplifier, wherein the input terminal of the leakage state latching amplifier is connected to the collector of the leakage state latching PNP transistor, and the output terminal of the leakage state latching amplifier outputs the second leakage latching level.

7. The charging drive circuit with leakage protection function according to claim 4, characterized in that, The output level conversion circuit includes: An output level conversion NPN transistor is provided, wherein the base of the output level conversion NPN transistor is input to the leakage latch level; the emitter of the output level conversion NPN transistor is grounded; and the collector of the output level conversion NPN transistor is connected to the driving power supply. The output level conversion output terminal is connected to the collector of the output level conversion NPN transistor and is used to output the leakage current action level.

8. The charging drive circuit with leakage protection function according to claim 4, characterized in that, The relay drive circuit includes: The AND operator has the leakage current action level input at its first input terminal and a PWM pulse signal input at its second input terminal; the output terminal of the AND operator is connected to a relay-driven NPN transistor. The relay drives an NPN transistor, the base of which is connected to the output of the arithmetic unit, the emitter of which is grounded, the collector of which is connected to the driving power supply, and the collector of which outputs the control signal of the relay switch.

9. The charging drive circuit with leakage protection function according to claim 4, characterized in that, The leakage current release circuit includes: A leakage state release NPN transistor is provided, with its emitter grounded, its collector connected to the first terminal of the level latching capacitor, and its base connected to the microcontroller unit for receiving leakage state release signals.

10. A method for charging an automobile using any one of the charging drive circuits of claims 1-9, characterized in that, The method includes: The microcontroller unit detects the connection signal between the charging gun and the car charging port. Based on the connection signal, the microcontroller turns on the first switch and controls the handshake signal generator to send a PWM handshake signal with a first set voltage. The microcontroller detects whether the PWM handshake signal voltage changes to a second preset voltage based on changes in the vehicle load. When the PWM handshake signal voltage changes to the second set voltage, the microcontroller controls the handshake signal generator to send a PWM handshake signal with a third set voltage. The microcontroller controls the first switch to open and the second switch to open; the power supply generates a power signal; and the leakage protection circuit performs a leakage self-test on the charging current. If the leakage current self-test passes, the microcontroller controls the second switch to open and the first switch to open, and the power supply outputs power to the car charging port through the charging gun; if the leakage current self-test fails, the microcontroller controls the second switch to open and prompts that the leakage current self-test has failed.

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