An alternating current charging gun temperature detection circuit

Abstract

The utility model discloses an alternating current charging gun temperature detection circuit in the technical field of alternating current charging pile charging gun, which comprises: thermistor PTC, input anti -interference filter circuit and sampling amplification circuit that connect gradually, thermistor PTC is located at charging gun head, and thermistor PTC is connected to input anti -interference filter circuit through wire, and input anti -interference filter circuit is used for filtering the voltage peak interference of wire introduction and the interference caused when charging gun alternating current charges, and the signal transmission of filtering is given sampling amplification circuit, and sampling amplification circuit carries out signal amplification processing to the input signal and then carries out anti -aliasing filter transmission and gives main control CPU analog -to -digital conversion mouth. The alternating current charging gun temperature detection circuit of the utility model can detect the temperature of the alternating current charging pile gun head in time and accurately.

Description

Technical Field

[0001] This utility model relates to a temperature detection circuit for an AC charging gun, belonging to the technical field of AC charging pile charging guns. Background Technology

[0002] In recent years, with the increasing popularity of new energy electric vehicles, more and more residential homes have installed AC charging piles. In addition, the number of charging piles built in parking lots, commercial offices and other areas is also increasing. The charging safety of AC charging piles has become increasingly important. Among them, the safe charging of AC charging guns is very important. When charging with an AC charging gun, the current is around 32 amperes (A). Such a large current will cause the temperature of the AC charging gun head to rise. Real-time monitoring of the AC charging gun head temperature and timely stopping charging when the gun temperature is high is of great significance for the charging safety of AC charging piles. Summary of the Invention

[0003] The technical problem to be solved by this utility model is to overcome the defects of the prior art and provide an AC charging gun temperature detection circuit.

[0004] To solve the above technical problems, this utility model provides an AC charging gun temperature detection circuit, including: a thermistor PTC, an input anti-interference filter circuit, and a sampling amplification circuit connected in sequence; The thermistor PTC is located at the charging gun head, and the thermistor PTC is connected to the input anti-interference filter circuit through a wire. The input anti-interference filter circuit is used to filter out voltage spike interference introduced by the wires and interference caused by AC charging of the charging gun, and transmits the filtered signal to the sampling amplifier circuit. The sampling amplification circuit amplifies the input signal and then performs anti-aliasing filtering before transmitting it to the main control CPU's analog-to-digital converter port.

[0005] Furthermore, the sampling amplification circuit includes a sampling start circuit, a first amplification circuit, a second amplification circuit, and an anti-aliasing filter circuit that are connected in sequence.

[0006] Furthermore, the input anti-interference filter circuit includes a TVS diode T1, an inductor L1, a first capacitor C1, and a second capacitor C2; One end of the thermistor PTC is connected to the negative terminal of TVS transistor T1, one end of first capacitor C1 and one end of inductor L1 through a wire; the other end of the thermistor PTC is connected to the positive terminal of TVS transistor T1, the other end of capacitor C1 and common ground GND through a wire. The other end of inductor L1 is connected to one end of the second capacitor C2 and the input anti-interference filter circuit, respectively. The other end of the second capacitor C2 is connected to the common ground GND.

[0007] Furthermore, the sampling start-up circuit includes a first resistor R1, a second resistor R2, a fourth resistor R4, and a third capacitor C3; One end of the first resistor R1 is connected to the other end of the inductor L1, one end of the third capacitor C3 and the first input terminal of the first amplifier circuit, and the other end of the first resistor R1 is connected to one end of the second resistor R2 and the working voltage VCC. The other end of the second resistor R2 is connected to one end of the fourth resistor R4 and the second input terminal of the first amplifier circuit, respectively. The other end of the fourth resistor R4 and the other end of the third capacitor C3 are connected to the common ground GND.

[0008] Furthermore, the first amplifier circuit includes a third resistor R3, a fifth resistor R5, a sixth resistor R6, a fifth capacitor C5, and a first operational amplifier D1A; One end of the third resistor R3 is connected to one end of the first resistor R1, and the other end of the third resistor R3 is connected to the non-inverting input of the first operational amplifier D1A. One end of the fifth resistor R5 is connected to the other end of the second resistor R2. The other end of the fifth resistor R5 is connected to the inverting input terminal of the first operational amplifier D1A, one end of the sixth resistor R6, and one end of the fifth capacitor C5. The output terminal of the first operational amplifier D1A is connected to the other end of the sixth resistor R6, the other end of the fifth capacitor C5, and the input terminal of the second amplifier circuit, respectively. The positive power supply terminal of the first operational amplifier D1A is connected to the operating voltage VCC, and the negative power supply terminal of the first operational amplifier D1A is connected to the common ground GND.

[0009] Furthermore, the positive power supply terminal of the first operational amplifier D1A is also connected to the common ground GND through the fourth capacitor C4.

[0010] Furthermore, the second amplifier circuit includes a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a sixth capacitor C6, and a second operational amplifier D1B; One end of the seventh resistor R7 is connected to the output terminal of the first operational amplifier D1A, and the other end of the seventh resistor R7 is connected to the non-inverting input terminal of the second operational amplifier D1B. The inverting input of the second operational amplifier D1B is connected to one end of the eighth resistor R8, one end of the ninth resistor R9, and one end of the sixth capacitor C6, respectively. The other end of the eighth resistor R8 is connected to the common ground GND. The output of the second operational amplifier D1B is connected to the other end of the ninth resistor R9, the other end of the sixth capacitor C6, and the input of the anti-aliasing filter circuit.

[0011] Furthermore, the anti-aliasing filter circuit includes a tenth resistor R10, a seventh capacitor C7, and an eighth capacitor C8; One end of the tenth resistor R10 is connected to the output terminal of the second operational amplifier D1B; The other end of the tenth resistor R10 is connected to one end of the seventh capacitor C7, one end of the eighth capacitor C8, and the analog-to-digital converter port of the main control CPU; The other end of the seventh capacitor C7 and the other end of the eighth capacitor C8 are connected to the common ground GND.

[0012] The beneficial effects achieved by this utility model are: The AC charging gun temperature detection circuit of this utility model can promptly filter out interference and accurately detect the temperature value representing the AC charging gun head, and send this temperature value to the main control CPU. When the gun head temperature exceeds the rated value, the main control CPU can promptly issue a command to stop charging for the AC charging pile, thus ensuring the charging safety of the AC charging gun and the electric vehicle, and guaranteeing the charging stability of the AC charging pile. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the AC charging gun temperature detection circuit of this utility model. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0015] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0016] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0017] like Figure 1 As shown, this embodiment provides an AC charging gun temperature detection circuit, including: a thermistor PTC, an input anti-interference filter circuit, and a sampling amplification circuit connected in sequence; The thermistor PTC is located at the charging gun head, and the thermistor PTC is connected to the input anti-interference filter circuit through a wire. The input anti-interference filter circuit is used to filter out voltage spike interference introduced by the wires and interference caused by AC charging of the charging gun, and transmits the filtered signal to the sampling amplifier circuit. The sampling amplification circuit amplifies the input signal and then performs anti-aliasing filtering before transmitting it to the main control CPU's analog-to-digital converter port.

[0018] The thermistor PTC is a positive temperature coefficient thermistor. The resistance of a positive temperature coefficient thermistor increases with increasing temperature. The thermistor PTC is placed at the head of the AC gun and its two ends are connected to the sampling amplification circuit through insulated wires. In one embodiment of the present invention, the sampling amplification circuit includes a sampling start circuit, a first amplification circuit, a second amplification circuit, and an anti-aliasing filter circuit that are connected in sequence.

[0019] In one embodiment of the present invention, the input anti-interference filter circuit includes a TVS diode T1, an inductor L1, a first capacitor C1, and a second capacitor C2; one end of the thermistor PTC is connected to the negative terminal of the TVS diode T1, one end of the first capacitor C1, and one end of the inductor L1 via a wire; the other end of the thermistor PTC is connected to the positive terminal of the TVS diode T1, the other end of the capacitor C1, and the common ground GND via a wire; the other end of the inductor L1 is connected to one end of the second capacitor C2 and the input anti-interference filter circuit, and the other end of the second capacitor C2 is connected to the common ground GND.

[0020] The positive temperature coefficient thermistor PTC placed at the gun head is connected to the two ends of the input anti-interference filter tube T1 via wires. The voltage spike interference introduced by the wires is filtered out by the TVS tube T1. Then, the interference caused by AC charging is filtered out by the π-type filter circuit composed of the first capacitor C1, the inductor L1 and the second capacitor C2 before being connected to the sampling starting circuit.

[0021] In one embodiment of the present invention, the sampling start-up circuit includes a first resistor R1, a second resistor R2, a fourth resistor R4, and a third capacitor C3; One end of the first resistor R1 is connected to the other end of the inductor L1, one end of the third capacitor C3, and the first input terminal of the first amplifier circuit. The other end of the first resistor R1 is connected to one end of the second resistor R2 and the operating voltage VCC. The other end of the second resistor R2 is connected to one end of the fourth resistor R4 and the second input terminal of the first amplifier circuit. The other end of the fourth resistor R4 and the other end of the third capacitor C3 are connected to the common ground GND.

[0022] After the interference caused by AC charging is filtered out by the π-type filter circuit composed of the first capacitor C1, the first inductor L1 and the first capacitor C2, it is connected to the two ends of the third capacitor C3 at the sampling starting point circuit V1, and the high-frequency interference is further filtered out by the third capacitor C3.

[0023] In one embodiment of the present invention, the first amplification circuit includes a third resistor R3, a fifth resistor R5, a sixth resistor R6, a fifth capacitor C5, and a first operational amplifier D1A; one end of the third resistor R3 is connected to one end of the first resistor R1, and the other end of the third resistor R3 is connected to the non-inverting input terminal of the first operational amplifier D1A; one end of the fifth resistor R5 is connected to the other end of the second resistor R2, and the other end of the fifth resistor R5 is connected to the inverting input terminal of the first operational amplifier D1A, one end of the sixth resistor R6, and one end of the fifth capacitor C5; the output terminal of the first operational amplifier D1A is connected to the other end of the sixth resistor R6, the other end of the fifth capacitor C5, and the input terminal of the second amplification circuit; the positive power supply terminal of the first operational amplifier D1A is connected to the operating voltage VCC, and the negative power supply terminal of the first operational amplifier D1A is connected to the common ground GND; the positive power supply terminal of the first operational amplifier D1A is also connected to the common ground GND through a fourth capacitor C4 to filter out power supply interference.

[0024] The second amplifier circuit includes a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a sixth capacitor C6, and a second operational amplifier D1B. One end of the seventh resistor R7 is connected to the output terminal of the first operational amplifier D1A, and the other end of the seventh resistor R7 is connected to the non-inverting input terminal of the second operational amplifier D1B. The inverting input terminal of the second operational amplifier D1B is connected to one end of the eighth resistor R8, one end of the ninth resistor R9, and one end of the sixth capacitor C6, respectively. The other end of the eighth resistor R8 is connected to the common ground GND. The output terminal of the second operational amplifier D1B is connected to the other end of the ninth resistor R9, the other end of the sixth capacitor C6, and the input terminal of the anti-aliasing filter circuit, respectively.

[0025] Working principle: One end of the thermistor PTC is connected to the common ground via a wire. The other end of the thermistor PTC is connected to one end of the first sampling resistor R1 via an anti-interference filter circuit to generate a sampling voltage V1. The other end of the first resistor R1 is connected to the working voltage VCC. The sampling voltage V1 is connected to the non-inverting input (+) pin 3 of the first operational amplifier D1A through the third resistor R3. V2 is the voltage at the non-inverting input (+) pin 3 of the first operational amplifier D1A. Since the input impedance of the first operational amplifier D1A is extremely high, it is equivalent to a virtual open circuit. At this time, voltage V2 = voltage V1. According to the principle of resistor voltage division, V1 = [Rptc / (Rptc+R1)]. ×VCC, Rptc is the real-time temperature resistance value of the thermistor PTC. Since the open-loop gain of the first operational amplifier D1A is extremely high, the voltages at its non-inverting input (+) and inverting input (-) tend to be equal, equivalent to a virtual short. At this time, V4 = V2. V4 is the voltage at pin 2 of the inverting input (-) of the first operational amplifier D1A. Therefore, V4 = V1 = [Rptc / (Rptc+R1)] × VCC. According to the principle of voltage division by resistors, voltage V3 = [R4 / (R2+R4)] × VCC. Here, resistors R1 = R2, R3 = R5, and the resistance value of resistor R4 is chosen to be equal to the AC charging gun temperature. The detection temperature range corresponds to the lowest detection temperature of the PTC thermistor. Since the PTC thermistor is a positive temperature coefficient thermistor, its resistance increases with temperature. Thus, during the AC charging pile charging gun temperature detection process, the value of the sampling point voltage V1 is always greater than or equal to the value of voltage V3. Because the input impedance of the inverting input terminal (-)2 of the first operational amplifier D1A is high, it is equivalent to a virtual open circuit. At this time, since it is a DC voltage change, we can get V5 / R6=(V4-V3) / R5. Since V1=V4, V5 / R6=(V1-V3) / R5. Therefore, V5=[(V1-V3) ×R6] / R5. Capacitor C5 can filter out high-frequency noise interference. The change in the voltage value (V1-V3) is the change in the resistance value of the sampling point thermistor PTC, which is the change in the charging gun temperature detected by the thermistor PTC.

[0026] Since the non-inverting input (+)5 of the second operational amplifier D1B has extremely high input impedance, which is equivalent to a virtual open circuit, the voltage V6 = V5. Also, since the open-loop gain of the second operational amplifier D1B is extremely large, the voltages at its non-inverting input (+)5 and inverting input (-)6 tend to be equal, which is equivalent to a virtual short circuit, so the voltage V7 = V6. At this time, V7 = [R8 / (R9+R8)]*V8, V8 = (1+R9 / R8)*V7. Capacitor C6 can further filter out high-frequency noise interference, so V8 = [(1+R9 / R8)*(V1-V3)*R6] / R5.

[0027] In one embodiment of the present invention, the anti-aliasing filter circuit includes a tenth resistor R10, a seventh capacitor C7, and an eighth capacitor C8; one end of the tenth resistor R10 is connected to the output terminal of the second operational amplifier D1B; the other end of the tenth resistor R10 is connected to one end of the seventh capacitor C7, one end of the eighth capacitor C8, and the analog-to-digital converter port of the main control CPU; the other ends of the seventh capacitor C7 and the other ends of the eighth capacitor C8 are connected to the common ground GND.

[0028] Working principle: V8 passes through an anti-aliasing filter composed of the tenth resistor R10, the seventh capacitor C7, and the eighth capacitor C8 before entering the main control CPU's analog-to-digital converter port AD0_Temp for sampling and calculation of the gun temperature. Charging stops when the gun temperature exceeds a specified value to ensure charging safety. The anti-aliasing filter prevents aliasing, which occurs when high-frequency components exceed half the sampling frequency during analog signal sampling, making it impossible to recover the original signal and causing spectral overlap, resulting in errors and distortions. The anti-aliasing filter overcomes the sampling and measurement errors and distortions caused by high-frequency noise, further ensuring the stability of the measured gun temperature.

[0029] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A temperature detection circuit for an AC charging gun, characterized in that, include: The thermistor PTC, the input anti-interference filter circuit, and the sampling amplifier circuit are connected in sequence. The thermistor PTC is located at the charging gun head, and the thermistor PTC is connected to the input anti-interference filter circuit through a wire. The input anti-interference filter circuit is used to filter out voltage spike interference introduced by the wires and interference caused by AC charging of the charging gun, and transmits the filtered signal to the sampling amplifier circuit. The sampling amplification circuit amplifies the input signal and then performs anti-aliasing filtering before transmitting it to the main control CPU's analog-to-digital converter port.

2. The AC charging gun temperature detection circuit according to claim 1, characterized in that, The sampling amplification circuit includes a sampling start circuit, a first amplification circuit, a second amplification circuit, and an anti-aliasing filter circuit that are connected in sequence.

3. The AC charging gun temperature detection circuit according to claim 2, characterized in that, The input anti-interference filter circuit includes a TVS diode T1, an inductor L1, a first capacitor C1, and a second capacitor C2. One end of the thermistor PTC is connected to the negative terminal of TVS transistor T1, one end of first capacitor C1 and one end of inductor L1 through a wire; the other end of the thermistor PTC is connected to the positive terminal of TVS transistor T1, the other end of capacitor C1 and common ground GND through a wire. The other end of inductor L1 is connected to one end of the second capacitor C2 and the input anti-interference filter circuit, respectively. The other end of the second capacitor C2 is connected to the common ground GND.

4. The AC charging gun temperature detection circuit according to claim 3, characterized in that, The sampling start circuit includes a first resistor R1, a second resistor R2, a fourth resistor R4, and a third capacitor C3; One end of the first resistor R1 is connected to the other end of the inductor L1, one end of the third capacitor C3 and the first input terminal of the first amplifier circuit, and the other end of the first resistor R1 is connected to one end of the second resistor R2 and the working voltage VCC. The other end of the second resistor R2 is connected to one end of the fourth resistor R4 and the second input terminal of the first amplifier circuit, respectively. The other end of the fourth resistor R4 and the other end of the third capacitor C3 are connected to the common ground GND.

5. The AC charging gun temperature detection circuit according to claim 4, characterized in that, The first amplifier circuit includes a third resistor R3, a fifth resistor R5, a sixth resistor R6, a fifth capacitor C5, and a first operational amplifier D1A; One end of the third resistor R3 is connected to one end of the first resistor R1, and the other end of the third resistor R3 is connected to the non-inverting input of the first operational amplifier D1A. One end of the fifth resistor R5 is connected to the other end of the second resistor R2. The other end of the fifth resistor R5 is connected to the inverting input terminal of the first operational amplifier D1A, one end of the sixth resistor R6, and one end of the fifth capacitor C5. The output terminal of the first operational amplifier D1A is connected to the other end of the sixth resistor R6, the other end of the fifth capacitor C5, and the input terminal of the second amplifier circuit, respectively. The positive power supply terminal of the first operational amplifier D1A is connected to the operating voltage VCC, and the negative power supply terminal of the first operational amplifier D1A is connected to the common ground GND.

6. The AC charging gun temperature detection circuit according to claim 5, characterized in that, The positive power supply terminal of the first operational amplifier D1A is also connected to the common ground GND through the fourth capacitor C4.

7. The AC charging gun temperature detection circuit according to claim 5, characterized in that, The second amplifier circuit includes a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a sixth capacitor C6, and a second operational amplifier D1B; One end of the seventh resistor R7 is connected to the output terminal of the first operational amplifier D1A, and the other end of the seventh resistor R7 is connected to the non-inverting input terminal of the second operational amplifier D1B. The inverting input of the second operational amplifier D1B is connected to one end of the eighth resistor R8, one end of the ninth resistor R9, and one end of the sixth capacitor C6, respectively. The other end of the eighth resistor R8 is connected to the common ground GND. The output of the second operational amplifier D1B is connected to the other end of the ninth resistor R9, the other end of the sixth capacitor C6, and the input of the anti-aliasing filter circuit.

8. The AC charging gun temperature detection circuit according to claim 7, characterized in that, The anti-aliasing filter circuit includes a tenth resistor R10, a seventh capacitor C7, and an eighth capacitor C8. One end of the tenth resistor R10 is connected to the output terminal of the second operational amplifier D1B; The other end of the tenth resistor R10 is connected to one end of the seventh capacitor C7, one end of the eighth capacitor C8, and the analog-to-digital converter port of the main control CPU; The other end of the seventh capacitor C7 and the other end of the eighth capacitor C8 are connected to the common ground GND.

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