Charging pile safe charging circuit

Abstract

The application provides a charging pile safety charging circuit. The charging pile safety charging circuit comprises a charging module, a charging current sampling circuit, a comparator U2A, an NAND gate U4A, a discharge resistor and a switching tube Q2; the charging module is configured to charge a vehicle power battery; the charging current sampling circuit is configured to collect the charging current of the charging module, the output end of the charging current sampling circuit is connected to the first input end of the comparator U2A, the second input end of the comparator U2A is connected with a reference voltage, the output end of the comparator U2A is connected to the first input end of the NAND gate U4A, the second input end of the NAND gate U4A is used to be connected with the charging state feedback end of the vehicle power battery; the output end of the NAND gate U4A is connected to the control end of the switching tube Q2, the first end of the switching tube Q2 is connected to the first output end of the charging module through the discharge resistor, and the second end of the switching tube Q2 is connected to the second output end of the charging module. The application can solve the problem of electric shock risk caused by residual power in the charging module.

Description

Technical Field

[0001] This application relates to the field of charging pile technology, and in particular to a safe charging circuit for charging piles. Background Technology

[0002] Charging stations are devices for charging electric vehicles. When charging is needed, the user inserts the charging gun into the vehicle's charging port, and the charging module inside the charging station charges the electric vehicle's battery. During the charging process, the charging station monitors the voltage, current, and equipment temperature in real time and dynamically adjusts the output power. Because the charging module typically contains energy storage components such as inductors and capacitors, if the charging gun is unplugged immediately after charging is complete, the residual electrical energy inside the inductors and capacitors may cause an electric shock accident. Utility Model Content

[0003] This application provides a safe charging circuit for charging piles to address the risk of electric shock caused by residual electrical energy inside the charging module.

[0004] This application provides a safe charging circuit for a charging pile, including a charging module, a charging current sampling circuit, a comparator U2A, a NAND gate U4A, a discharge resistor, and a switching transistor Q2; The charging module is configured to charge the vehicle's power battery. The charging current sampling circuit is configured to collect the charging current of the charging module. The output terminal of the charging current sampling circuit is connected to the first input terminal of the comparator U2A. The second input terminal of the comparator U2A is connected to the reference voltage. The output terminal of the comparator U2A is connected to the first input terminal of the NAND gate U4A. The second input terminal of the NAND gate U4A is used to connect to the charging status feedback terminal of the vehicle power battery. The output terminal of the NAND gate U4A is connected to the control terminal of the switch Q2. The first terminal of the switch Q2 is connected to the first output terminal of the charging module through the discharge resistor, and the second terminal of the switch Q2 is connected to the second output terminal of the charging module.

[0005] In one embodiment of this application, the safe charging circuit of the charging pile further includes a voltage reference chip U3, a resistor R10, a resistor R12, and a resistor R17. The anode of the voltage reference chip U3 is grounded, the cathode of the voltage reference chip U3 is connected to the first power supply through resistor R10, the reference terminal of the voltage reference chip U3 is connected to the first end of resistor R12, the second end of resistor R12 is grounded through resistor R17, and the second end of resistor R12 serves as the reference voltage.

[0006] In one embodiment of this application, the charging current sampling circuit includes a sampling resistor RS1, an operational amplifier U1A, a resistor R2, and a resistor R1; The sampling resistor RS1 is connected in series in the charging circuit of the charging module. The first end of the sampling resistor RS1 is connected to the non-inverting input of the operational amplifier U1A. The second end of the sampling resistor RS1 is connected to the inverting input of the operational amplifier U1A through the resistor R2. The output of the operational amplifier U1A is fed back to the inverting input of the operational amplifier U1A through the resistor R1. The inverting input of the operational amplifier U1A is the output of the charging current sampling circuit.

[0007] In one embodiment of this application, the safe charging circuit of the charging pile further includes: A switch Q1 and an optocoupler OP1 are provided between the output terminal of the NAND gate U4A and the control terminal of the switch Q2; The control terminal of the switching transistor Q1 is connected to the output terminal of the NAND gate U4A. The first terminal of the switching transistor Q1 is connected to the first input terminal of the optocoupler OP1. The second input terminal of the optocoupler OP1 is connected to a first power supply. The first output terminal of the optocoupler OP1 is connected to a second power supply. The second output terminal of the optocoupler OP1 is connected to the first terminal of the resistor R19. The second terminal of the resistor R19 is connected to the second output terminal of the charging module. The first end of the resistor R19 is connected to the control terminal of the switch Q2.

[0008] In one embodiment of this application, the charging pile safety charging circuit further includes a battery depolarization circuit, which includes a switching transistor Q3, an inductor L1, and a resistor R21. The control terminal of the switch Q3 is used to connect to the first signal input terminal of the main control chip. The first terminal of the switch Q3 is connected to the first terminal of the inductor L1. The second terminal of the inductor L1 is used to connect to the positive terminal of the vehicle power battery. The second terminal of the switch Q3 is connected to the negative terminal of the vehicle power battery through the resistor R21.

[0009] In one embodiment of this application, the safe charging circuit of the charging pile further includes a battery voltage sampling circuit, a delay circuit, and a first subtraction circuit; The battery voltage sampling circuit includes a resistor R23, a switch Q4, and a resistor R24. The control terminal of the switch Q4 is connected to the second signal input terminal of the main control chip. The first terminal of the switch Q4 is connected to the positive terminal of the vehicle power battery through the resistor R23. The second terminal of the switch Q4 is connected to the first terminal of the resistor R24. The second terminal of the resistor R24 ​​is connected to the negative terminal of the vehicle power battery. The first terminal of the resistor R24 ​​is the output terminal of the battery voltage sampling circuit and is connected to the first input terminal of the first subtraction circuit. The output of the battery voltage sampling circuit is also connected to the input of the delay circuit, the output of the delay circuit is connected to the second input of the first subtraction circuit, and the output of the first subtraction circuit is connected to the signal input of the main control chip.

[0010] In one embodiment of this application, the delay circuit includes a resistor R25 and a capacitor C11; The first end of the resistor R25 is the input end of the delay circuit, the second end of the resistor R25 is connected to the first end of the capacitor C11, the second end of the capacitor C11 is grounded, and the first end of the capacitor C11 is the output end of the delay circuit.

[0011] In one embodiment of this application, the first subtraction circuit includes resistors R26, R27, and R28, and operational amplifier U5A; The first end of resistor R26 is the first input terminal of the first subtraction circuit, the second end of resistor R26 is connected to the inverting input terminal of operational amplifier U5A, the first end of resistor R27 is the second input terminal of the first subtraction circuit, the second end of resistor R27 is connected to the non-inverting input terminal of operational amplifier U5A, the output terminal of operational amplifier U5A is fed back to the inverting input terminal of operational amplifier U5A through resistor R28, and the output terminal of operational amplifier U5A is the output terminal of the first subtraction circuit.

[0012] The working principle and beneficial effects of the safe charging circuit for charging piles provided in this application embodiment are as follows: In this embodiment of the application, when the charging module charges the vehicle's power battery, the charging current sampling circuit is used to detect the charging current and output a corresponding voltage signal. The output terminal of the charging current sampling circuit is connected to the first input terminal of the comparator U2A and compared with the reference voltage of the second input terminal of the comparator U2A. When the output voltage of the charging current sampling circuit is less than the reference voltage, the comparator U2A outputs a low-level signal, indicating that the charging current is less than the preset current threshold.

[0013] Furthermore, the output of comparator U2A is connected to the first input of NAND gate U4A, and the charging status feedback terminal of the vehicle power battery is connected to the second input of NAND gate U4A. When charging is complete, the charging status feedback terminal of the vehicle power battery is at a low level. At this time, if the output of comparator U2A is also at a low level, NAND gate U4A outputs a high level, and switch Q2 is turned on. The first output terminal of the charging module, the second output terminal of the charging module, and the discharge resistor form a discharge circuit, which discharges the residual energy in the inductor and capacitor inside the charging module in time, thereby avoiding the risk of electric shock.

[0014] In this embodiment, the charging end status is determined by dual verification of the current being less than the current threshold and the charging status feedback terminal of the vehicle's power battery, which can avoid misjudgment of the charging end status. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the safe charging circuit for a charging pile provided in an embodiment of this application; Figure 2 This is a schematic diagram of the battery depolarization circuit provided in the embodiments of this application. Detailed Implementation

[0017] To enable those skilled in the art to better understand this solution, the technical solutions in the embodiments of this solution will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this solution, not all of them. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this solution.

[0018] The term "comprising" and any other variations thereof in the specification, claims, and accompanying drawings of this invention mean "including but not limited to," and are intended to cover a non-exclusive inclusion, not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order.

[0019] The implementation of this application will be described in detail below with reference to the specific accompanying drawings: Figure 1 This is a schematic block diagram of a safe charging circuit for a charging pile, provided as an embodiment of this application. (Refer to...) Figure 1The safe charging circuit of the charging pile includes a charging module, a charging current sampling circuit, a comparator U2A, a NAND gate U4A, a discharge resistor, and a switching transistor Q2. The charging module is configured to charge the vehicle's power battery; The charging current sampling circuit is configured to collect the charging current of the charging module. The output of the charging current sampling circuit is connected to the first input of comparator U2A. The second input of comparator U2A is connected to the reference voltage. The output of comparator U2A is connected to the first input of NAND gate U4A. The second input of NAND gate U4A is used to connect to the charging status feedback terminal of the vehicle power battery. The output of NAND gate U4A is connected to the control terminal of switch Q2. The first terminal of switch Q2 is connected to the first output terminal of the charging module through a discharge resistor, and the second terminal of switch Q2 is connected to the second output terminal of the charging module.

[0020] In this embodiment, when the charging module charges the vehicle's power battery, the charging current sampling circuit is used to detect the charging current and output a corresponding voltage signal. The output terminal of the charging current sampling circuit is connected to the first input terminal of the comparator U2A and compared with the reference voltage at the second input terminal of the comparator U2A. When the output voltage of the charging current sampling circuit is less than the reference voltage, the comparator U2A outputs a low-level signal, indicating that the charging current is less than the preset current threshold.

[0021] Furthermore, the output of comparator U2A is connected to the first input of NAND gate U4A, and the charging status feedback terminal of the vehicle power battery is connected to the second input of NAND gate U4A. When charging is complete, the charging status feedback terminal of the vehicle power battery is at a low level. At this time, if the output of comparator U2A is also at a low level, NAND gate U4A outputs a high level, and switch Q2 is turned on. The first output terminal of the charging module, the second output terminal of the charging module, and the discharge resistor form a discharge circuit, which discharges the residual energy in the inductor and capacitor inside the charging module in time, thereby avoiding the risk of electric shock.

[0022] In this embodiment, the charging end status is determined by dual verification of the current being less than the current threshold and the charging status feedback terminal of the vehicle's power battery, which can avoid misjudgment of the charging end status.

[0023] Reference Figure 1 In one embodiment of this application, the safe charging circuit of the charging pile further includes a voltage reference chip U3, a resistor R10, a resistor R12 and a resistor R17; The anode of the voltage reference chip U3 is grounded, the cathode of the voltage reference chip U3 is connected to the first power supply through resistor R10, the reference terminal of the voltage reference chip U3 is connected to the first end of resistor R12, the second end of resistor R12 is grounded through resistor R17, and the second end of resistor R12 serves as the reference voltage.

[0024] In this embodiment, the voltage reference chip U3 specifically adopts the TL431, which can provide a stable reference power supply and is low in cost. A voltage divider circuit consisting of resistors R12 and R17 is set at the output terminal of the voltage reference chip U3. The resistance values ​​of resistors R12 and R17 can be adjusted according to the actual operating conditions of the charging module to adjust the preset current threshold. For example, if it is to be set that charging ends when the current sampling is less than 0.1A, the resistance values ​​of R12 and R17 can be adjusted to adjust the judgment threshold to 0.1A.

[0025] Reference Figure 1 In one embodiment of this application, the charging current sampling circuit includes a sampling resistor RS1, an operational amplifier U1A, a resistor R2, and a resistor R1. The sampling resistor RS1 is connected in series in the charging circuit of the charging module. The first end of the sampling resistor RS1 is connected to the non-inverting input of the operational amplifier U1A, and the second end of the sampling resistor RS1 is connected to the inverting input of the operational amplifier U1A through the resistor R2. The output of the operational amplifier U1A is fed back to the inverting input of the operational amplifier U1A through the resistor R1. The inverting input of the operational amplifier U1A is the output of the charging current sampling circuit.

[0026] In this embodiment, the sampling resistor RS1 is connected in series in the charging circuit of the charging module. The charging current can be obtained by detecting the voltage across the sampling resistor RS1. Specifically, the operational amplifier U1A, resistor R2, and resistor R1 constitute a second subtraction circuit. The two ends of the sampling resistor RS1 are connected to the two input terminals of the subtraction circuit, respectively. The voltage across the resistor RS1 can be obtained at the output terminal of the second subtraction circuit. This voltage is directly proportional to the charging current, so the charging current can be obtained from this voltage.

[0027] Reference Figure 1 In one embodiment of this application, the safe charging circuit of the charging pile further includes: A switching transistor Q1 and an optocoupler OP1 are provided between the output terminal of the NAND gate U4A and the control terminal of the switching transistor Q2; The control terminal of switch Q1 is connected to the output terminal of NAND gate U4A. The first terminal of switch Q1 is connected to the first input terminal of optocoupler OP1. The second input terminal of optocoupler OP1 is connected to the first power supply. The first output terminal of optocoupler OP1 is connected to the second power supply. The second output terminal of optocoupler OP1 is connected to the first terminal of resistor R19. The second terminal of resistor R19 is connected to the second output terminal of the charging module. The first end of resistor R19 is connected to the control terminal of switch Q2.

[0028] In this embodiment, a switch Q1 and an optocoupler OP1 are provided between the output terminal of the NAND gate U4A and the control terminal of the switch Q2. When the NAND gate U4A outputs a high level, the switch Q1 is turned on, the optocoupler OP1 is turned on, the resistor R19 is connected to the second power supply, and the voltage across the resistor R19 is applied to the control terminal of the switch Q2, so the switch Q2 is turned on.

[0029] As can be seen from the above, in this embodiment, the switch Q1 plays the role of signal amplification, which can realize the reliable conduction of the switch Q2. The optocoupler OP1 plays the role of electrical isolation, which can prevent interference signals from the switch Q2 side from entering the NAND gate U4A, thereby ensuring the reliable operation of the NAND gate U4A.

[0030] Reference Figure 2 In one embodiment of this application, the charging pile safety charging circuit further includes a battery depolarization circuit, which includes a switching transistor Q3, an inductor L1, and a resistor R21. The control terminal of the switching transistor Q3 is used to connect to the first signal input terminal of the main control chip. The first terminal of the switching transistor Q3 is connected to the first terminal of the inductor L1. The second terminal of the inductor L1 is used to connect to the positive terminal of the vehicle power battery. The second terminal of the switching transistor Q3 is connected to the negative terminal of the vehicle power battery through the resistor R21.

[0031] In this embodiment, during battery charging, the electrode reaction rate and ion migration rate are not synchronized, which can easily cause the electrode potential to deviate from the equilibrium potential. This phenomenon is called battery polarization. Battery polarization can lead to artificially high voltage, decreased charging efficiency, and reduced capacity.

[0032] To solve the above problems, this embodiment is equipped with a battery depolarization circuit. In the final stage of charging (obtained through the battery management system), the main control chip outputs a control signal to the control terminal of the switch Q3. The switch Q3, inductor L1 and resistor R21 form a discharge circuit to discharge the vehicle power battery, thereby eliminating the battery polarization phenomenon.

[0033] Reference Figure 2 In one embodiment of this application, the safe charging circuit of the charging pile further includes a battery voltage sampling circuit, a delay circuit, and a subtraction circuit; The battery voltage sampling circuit includes resistor R23, switch Q4, and resistor R24. The control terminal of switch Q4 is connected to the second signal input terminal of the main control chip. The first terminal of switch Q4 is connected to the positive terminal of the vehicle power battery through resistor R23. The second terminal of switch Q4 is connected to the first terminal of resistor R24. The second terminal of resistor R24 ​​is connected to the negative terminal of the vehicle power battery. The first terminal of resistor R24 ​​is the output terminal of the battery voltage sampling circuit and is connected to the first input terminal of the subtraction circuit. The output of the battery voltage sampling circuit is also connected to the input of the delay circuit. The output of the delay circuit is connected to the second input of the subtraction circuit, and the output of the subtraction circuit is connected to the signal input of the main control chip.

[0034] In this embodiment, the battery voltage sampling circuit is used to detect the voltage of the vehicle's power battery. By sending a pulse signal PWM2 to the control terminal of the switching transistor Q4 through the main control chip, the battery voltage sampling circuit can be controlled to work periodically and periodically collect the voltage of the vehicle's power battery.

[0035] The output of the battery voltage sampling circuit is connected to the first input of the first subtraction circuit. Simultaneously, the output of the battery voltage sampling circuit is connected to the second input of the first subtraction circuit after a delay circuit. Due to the delay effect of the delay circuit, there is a time interval between the voltage signals obtained by the first and second inputs of the first subtraction circuit. The first subtraction circuit outputs the voltage difference between the two voltage signals and sends this voltage difference to the main control chip. The main control chip outputs a pulse signal PWM1 with a corresponding duty cycle based on the magnitude of the voltage difference. The pulse signal PWM1 is connected to the control terminal of the switching transistor Q3 to adjust the conduction time of the switching transistor Q3, thereby adjusting the discharge current of the vehicle's power battery.

[0036] Specifically, when the voltage difference output by the first subtraction circuit is greater than the preset voltage threshold, it indicates that the battery voltage in the current sampling period is less than the battery voltage in the previous sampling period, and the battery voltage drops rapidly. In this case, the duty cycle of the pulse signal PWM1 can be kept unchanged to continue discharging. Otherwise, if the voltage difference output by the first subtraction circuit is less than the preset voltage threshold, it indicates that the battery voltage drops slowly. In this case, the duty cycle of the pulse signal PWM1 can be increased, thereby increasing the conduction time of the switching transistor Q3 and increasing the average discharge current.

[0037] As can be seen from the above, this embodiment, by setting up a battery voltage sampling circuit, a delay circuit, and a subtraction circuit, can adjust the discharge current of the vehicle's power battery in a timely manner, thereby ensuring the battery depolarization effect.

[0038] Reference Figure 2 In one embodiment of this application, the delay circuit includes a resistor R25 and a capacitor C11; The first end of resistor R25 is the input terminal of the delay circuit. The second end of resistor R25 is connected to the first end of capacitor C11. The second end of capacitor C11 is grounded. The first end of capacitor C11 is the output terminal of the delay circuit.

[0039] In this embodiment, resistor R25 and capacitor C11 form a delay circuit, which is connected in parallel across resistor R24. During each battery voltage sampling period, when the voltage across resistor R24 ​​changes, the voltage across capacitor C11 remains the same as the voltage of the previous sampling period because the voltage across capacitor C11 cannot change abruptly. This results in a time interval between the output voltage of the battery voltage sampling circuit and the output voltage of the delay circuit.

[0040] Reference Figure 2 In one embodiment of this application, the first subtraction circuit includes resistors R26, R27, and R28, and operational amplifier U5A; The first end of resistor R26 is the first input terminal of the first subtraction circuit, and the second end of resistor R26 is connected to the inverting input terminal of operational amplifier U5A. The first end of resistor R27 is the second input terminal of the first subtraction circuit, and the second end of resistor R27 is connected to the non-inverting input terminal of operational amplifier U5A. The output terminal of operational amplifier U5A is fed back to the inverting input terminal of operational amplifier U5A through resistor R28. The output terminal of operational amplifier U5A is the output terminal of the first subtraction circuit.

[0041] In this embodiment, resistors R26, R27, and R28, along with operational amplifier U5A, constitute the first subtraction circuit, which is used to output the voltage difference between the output voltage of the battery voltage sampling circuit and the output voltage of the delay circuit.

[0042] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A safe charging circuit for a charging pile, characterized in that, Includes a charging module, a charging current sampling circuit, a comparator U2A, a NAND gate U4A, a discharge resistor, and a switching transistor Q2; The charging module is configured to charge the vehicle's power battery. The charging current sampling circuit is configured to collect the charging current of the charging module. The output terminal of the charging current sampling circuit is connected to the first input terminal of the comparator U2A. The second input terminal of the comparator U2A is connected to the reference voltage. The output terminal of the comparator U2A is connected to the first input terminal of the NAND gate U4A. The second input terminal of the NAND gate U4A is used to connect to the charging status feedback terminal of the vehicle power battery. The output terminal of the NAND gate U4A is connected to the control terminal of the switch Q2. The first terminal of the switch Q2 is connected to the first output terminal of the charging module through the discharge resistor, and the second terminal of the switch Q2 is connected to the second output terminal of the charging module.

2. The safe charging circuit for a charging pile as described in claim 1, characterized in that, It also includes voltage reference chip U3, resistor R10, resistor R12 and resistor R17; The anode of the voltage reference chip U3 is grounded, the cathode of the voltage reference chip U3 is connected to the first power supply through resistor R10, the reference terminal of the voltage reference chip U3 is connected to the first end of resistor R12, the second end of resistor R12 is grounded through resistor R17, and the second end of resistor R12 serves as the reference voltage.

3. The safe charging circuit for a charging pile as described in claim 1, characterized in that, The charging current sampling circuit includes a sampling resistor RS1, an operational amplifier U1A, a resistor R2, and a resistor R1; The sampling resistor RS1 is connected in series in the charging circuit of the charging module. The first end of the sampling resistor RS1 is connected to the non-inverting input of the operational amplifier U1A. The second end of the sampling resistor RS1 is connected to the inverting input of the operational amplifier U1A through the resistor R2. The output of the operational amplifier U1A is fed back to the inverting input of the operational amplifier U1A through the resistor R1. The inverting input of the operational amplifier U1A is the output of the charging current sampling circuit.

4. The safe charging circuit for a charging pile as described in claim 1, characterized in that, Also includes: A switch Q1 and an optocoupler OP1 are provided between the output terminal of the NAND gate U4A and the control terminal of the switch Q2; The control terminal of the switching transistor Q1 is connected to the output terminal of the NAND gate U4A. The first terminal of the switching transistor Q1 is connected to the first input terminal of the optocoupler OP1. The second input terminal of the optocoupler OP1 is connected to a first power supply. The first output terminal of the optocoupler OP1 is connected to a second power supply. The second output terminal of the optocoupler OP1 is connected to the first terminal of the resistor R19. The second terminal of the resistor R19 is connected to the second output terminal of the charging module. The first end of the resistor R19 is connected to the control terminal of the switch Q2.

5. The safe charging circuit for a charging pile as described in claim 1, characterized in that, It also includes a battery depolarization circuit, which includes a switching transistor Q3, an inductor L1, and a resistor R21; The control terminal of the switch Q3 is used to connect to the first signal input terminal of the main control chip. The first terminal of the switch Q3 is connected to the first terminal of the inductor L1. The second terminal of the inductor L1 is used to connect to the positive terminal of the vehicle power battery. The second terminal of the switch Q3 is connected to the negative terminal of the vehicle power battery through the resistor R21.

6. The safe charging circuit for a charging pile as described in claim 5, characterized in that, It also includes a battery voltage sampling circuit, a delay circuit, and a first subtraction circuit; The battery voltage sampling circuit includes a resistor R23, a switch Q4, and a resistor R24. The control terminal of the switch Q4 is connected to the second signal input terminal of the main control chip. The first terminal of the switch Q4 is connected to the positive terminal of the vehicle power battery through the resistor R23. The second terminal of the switch Q4 is connected to the first terminal of the resistor R24. The second terminal of the resistor R24 ​​is connected to the negative terminal of the vehicle power battery. The first terminal of the resistor R24 ​​is the output terminal of the battery voltage sampling circuit and is connected to the first input terminal of the first subtraction circuit. The output of the battery voltage sampling circuit is also connected to the input of the delay circuit, the output of the delay circuit is connected to the second input of the first subtraction circuit, and the output of the first subtraction circuit is connected to the signal input of the main control chip.

7. The safe charging circuit for a charging pile as described in claim 6, characterized in that, The delay circuit includes a resistor R25 and a capacitor C11; The first end of the resistor R25 is the input end of the delay circuit, the second end of the resistor R25 is connected to the first end of the capacitor C11, the second end of the capacitor C11 is grounded, and the first end of the capacitor C11 is the output end of the delay circuit.

8. The safe charging circuit for a charging pile as described in claim 6, characterized in that, The first subtraction circuit includes resistors R26, R27, and R28, and operational amplifier U5A; The first end of resistor R26 is the first input terminal of the first subtraction circuit, the second end of resistor R26 is connected to the inverting input terminal of operational amplifier U5A, the first end of resistor R27 is the second input terminal of the first subtraction circuit, the second end of resistor R27 is connected to the non-inverting input terminal of operational amplifier U5A, the output terminal of operational amplifier U5A is fed back to the inverting input terminal of operational amplifier U5A through resistor R28, and the output terminal of operational amplifier U5A is the output terminal of the first subtraction circuit.

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