PWM (Pulse Width Modulation) output detection circuit for automobile alternating current charging pile

Abstract

A PWM output detection circuit used for an automobile AC charging pile comprises a power supply conversion module, a PWM isolation module, a CP detection isolation module and a microprocessor. The CP detection isolation module comprises a first window comparator, a second window comparator and a threshold comparator; the output ends of the first window comparator, the second window comparator and the threshold comparator are respectively connected with the input detection end of the microprocessor; and the input ends of the first window comparator, the second window comparator and the threshold comparator are connected with the output end of the PWM isolation module. On one hand, the safety is greatly improved through isolation, and the anti-interference capability is improved; and on the other hand, the CP voltage signal is detected by using the three-path optocoupler signal circuit, so that a high-cost isolation digital-to-analog conversion chip can be saved, and the MCU does not need to use an ADC to collect the CP voltage signal.

Description

Technical Field

[0001] The utility model relates to the technical field of AC charging piles, in particular to a PWM output detection circuit for an automobile AC charging pile. Background Art

[0002] With the rapid development of new energy vehicles, car charging piles have also ushered in development opportunities. Before using the charging pile for charging, existing new energy vehicles need to first confirm and detect whether the charging interface is reliably connected, otherwise it is easy to cause electric shock to people; when charging, the charging gun is inserted into the car charging interface, and the charging current is achieved by adjusting the PWM duty cycle. Therefore, when the charging pile is in the idle state, the gun is plugged in, and the charging state, the charging pile needs to generate a CP signal to realize the handshake communication of charging.

[0003] On the one hand, the traditional PWM signal generation circuit involves many devices, such as logic circuits such as NAND gates; on the other hand, the isolation circuit of the existing PWM signal generation circuit has a low safety factor, for example, only an optical coupler isolation chip is used for isolation, and no isolation is performed from the power supply. Furthermore, the MCU needs to use an ADC to collect the CP voltage signal, which is costly and has strict performance requirements. Utility Model Content

[0004] The purpose of the utility model is to overcome the above-mentioned deficiencies of the prior art and to provide a PWM output detection circuit for an automobile AC charging pile with a simple structure and high reliability.

[0005] The technical solution of the utility model is: a PWM output detection circuit for an automobile AC charging pile, comprising a power conversion module, a PWM isolation module, a CP detection isolation module and a microprocessor; the CP detection isolation module comprises a first window comparator, a second window comparator and a threshold comparator; the output ends of the first window comparator, the second window comparator and the threshold comparator are respectively connected to the input detection end of the microprocessor; the input ends of the first window comparator, the second window comparator and the threshold comparator are connected to the output end of the PWM isolation module.

[0006] Furthermore, the first window comparator is a 5V-7V CP signal detection circuit composed of an operational amplifier and its peripheral circuits; the second window comparator is an 8V-10V CP signal detection circuit composed of an operational amplifier and its peripheral circuits; and the threshold comparator is an 11V CP signal detection circuit composed of an operational amplifier and its peripheral circuits.

[0007] Furthermore, the peripheral circuits of the first window comparator and the second window comparator each include at least three voltage-dividing resistors and an optocoupler chip; the peripheral circuit of the threshold comparator includes at least two voltage-dividing resistors and an optocoupler chip; and the output end of the optocoupler chip is connected to the input detection end of the microprocessor.

[0008] Furthermore, the power conversion module includes a 12V to -12V circuit and a 12V to 12V isolation circuit, which are used to power the PWM isolation module and the CP detection isolation module; the 12V DC power supply output by the 12V to 12V isolation circuit serves as the input power supply of the 12V to -12V circuit.

[0009] Furthermore, the PWM isolation module includes an optocoupler isolation chip, a first resistor, a fuse and a protection device; the input end of the optocoupler isolation chip is connected to the output end of the MCU; the power end is connected to the output end of the power conversion module; the output end of the optocoupler isolation chip is connected to the connection socket via the first resistor and the fuse, and connected to the vehicle controller via the connection socket.

[0010] Furthermore, the first window comparator includes operational amplifiers U8.1 and U8.2, and the power supply is divided by a first voltage-dividing resistor, a second voltage-dividing resistor and a third voltage-dividing resistor; the non-inverting input terminal of the operational amplifier U8.1 is connected between the first voltage-dividing resistor and the second voltage-dividing resistor; the inverting input terminal of U8.1 is connected to the output terminal of the PWM isolation module via a resistor; the inverting input terminal of U8.2 is connected between the second voltage-dividing resistor and the third voltage-dividing resistor, and the non-inverting input terminal of U8.2 is connected to the inverting input terminal of U8.1; the output terminals of U8.1 and U8.2 are connected to the input terminal of the optocoupler chip, and the output terminal of the optocoupler chip is connected to the input detection terminal of the microprocessor.

[0011] Furthermore, the circuit structure of the second window comparator is the same as that of the first window comparator, and the resistance values ​​of the three voltage-dividing resistors are different from those of the first window comparator.

[0012] Furthermore, the threshold comparator includes an operational amplifier U9.1, an inverting input terminal of the operational amplifier U9.1 is connected between two voltage-dividing resistors, and a non-inverting input terminal is connected to an output terminal of the PWM isolation module via a resistor.

[0013] Furthermore, input ends of the first window comparator, the second window comparator and the threshold comparator are all connected between the first resistor and the fuse of the PWM isolation module.

[0014] Furthermore, after the output ends of the operational amplifiers U8.1 and U8.2 are connected, one path is connected to the positive power supply through a pull-up resistor, and the other path is connected to the anode of the light-emitting diode of the optocoupler chip through a resistor; the cathode of the light-emitting diode is connected to the negative power supply; one path of the output end of the optocoupler chip is connected to 3.3V through a pull-up resistor, and the other path is connected to the input detection end of the microprocessor.

[0015] The beneficial effects of the utility model are as follows: on the one hand, by setting up a power conversion module and a PWM isolation module, the main control end is isolated from the charging high-voltage end, which greatly improves safety and anti-interference ability; on the other hand, by setting up a CP detection isolation module and using a three-way optocoupler signal circuit to detect the CP voltage signal, a high-cost isolation digital-to-analog conversion chip can be saved, and the MCU does not need to use an ADC to collect the CP voltage signal, and can use ordinary IO to obtain the 12V, 9V and 6V states of the CP, without requiring the performance of the ADC module of the main control chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the circuit principle of the utility model embodiment;

[0017] Figure 2 This is a schematic diagram of the circuit principle of the PWM isolation module of the utility model embodiment;

[0018] Figure 3 This is a schematic diagram of the principle of a 12V to -12V circuit according to an embodiment of the utility model;

[0019] Figure 4 This is a schematic diagram of the principle of the 12V to 12V isolation circuit of the utility model embodiment;

[0020] Figure 5 This is a schematic diagram of the circuit principle of the first window comparator of the embodiment of the utility model;

[0021] Figure 6 This is a schematic diagram of the circuit principle of the second window comparator of the embodiment of the utility model;

[0022] Figure 7 It is a schematic diagram of the circuit principle of the threshold comparator of the embodiment of the utility model. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0024] like Figure 1 As shown: A PWM output detection circuit for an automobile AC charging pile is connected between the main control end and the charging high voltage end; the detection circuit includes a power conversion module, a PWM isolation module, a CP detection isolation module and an MCU (microprocessor); the power conversion module includes a 12V to -12V circuit and a 12V to 12V isolation circuit. The PWM isolation module inputs the MCU signal, outputs the PWM signal to the CP detection isolation module, and outputs the CP signal to the MCU of the main control end through the CP detection isolation module; and the 12V to 12V isolation circuit, the PWM isolation module and the CP detection isolation module are all used to isolate the main control end from the charging high voltage end.

[0025] like Figure 3 As shown: In this embodiment, the PWM isolation module includes an optocoupler isolation chip U2, a resistor R2 and a fuse F1, and a protection device, namely a bidirectional TVS tube D4, is also provided. Specifically, the model of the optocoupler isolation chip U2 is TLP2745, and its pin 1 is connected to a 3.3V power supply via a resistor R1; pin 3 is connected to the output end of the MCU for generating a PWM signal; pin 6 is connected to a +12V DC power supply, and pin 4 is connected to a -12V DC power supply; pin 5 (output end) is connected to a connector CN1 via a resistor R2 and a fuse F1, and is connected to a car controller via a connector CN1. One end of the bidirectional TVS tube D4 is connected between the resistor R2 and the fuse F1, and the other end is grounded.

[0026] The working principle of the above-mentioned PWM isolation module is as follows: the CP signal of the AC charging pile realizes the handshake communication of charging through the PWM signal duty cycle and the PWM level. The PWM waveform is a 1KHz rectangular wave according to the national standard requirements, and the charging current is realized by adjusting the PWM duty cycle. When the charging pile is in an idle state, the MCU outputs a 3.3V high-level signal to pin 3 of the optocoupler isolation chip U2. At this time, the optocoupler outputs +12V, and outputs a +12V high-level signal to the outside through R2 and F1. When the charging gun is connected to the car, the MCU detects the gun insertion signal (9V), and the MCU generates a 1KHzPWM, outputs a ±12V high-level signal through the optocoupler isolation chip U2, and generates a ±9V PWM (CP) signal at the connector CN1 through resistor R2 and fuse F1. The car controller of the charging car determines the charging current that the charging pile can provide through the PWM duty cycle. In the charging state, as with the principle of adding the charging gun mentioned above, a ±6V PWM (CP) signal is generated at the connector CN1.

[0027] In this embodiment, the input end of the 12V to 12V isolation circuit can convert the AC220V input into DC12V through other isolation power modules, and the output end is used to power the PWM isolation module and the CP detection isolation module.

[0028] like Figure 3 As shown: the 12V to 12V isolation circuit includes a power voltage regulator chip U5, the positive pole of the power input terminal of U5 is connected to a +12V DC power supply, the negative pole is grounded, and a capacitor C5 is connected between the positive and negative poles of the power input terminal; the power output terminal of U5 outputs a +12V DC power supply, which is connected to pin 6 of the optocoupler isolation chip U2 on the one hand, and serves as the input power supply of the 12V to -12V circuit on the other hand. It can be understood that the 12V DC power supply output by the power output terminal of U5 can also be used as the power supply for each operational amplifier of the CP detection isolation module. By setting a 12V to 12V isolation circuit, this embodiment can isolate the main control end from the charging high-voltage end, thereby improving anti-interference ability and safety.

[0029] like Figure 4 As shown: the 12V to -12V circuit includes a power chip U21, and the model is preferably MD7660. The BOOST pin of the power chip U21 is connected to the +12V DC power output by the power output terminal of U5 through the resistor R197, and the VDD terminal is also connected to the +12V DC power supply; the external capacitors C61 and C62 are connected between the pins CAP+ and CAP-; the output terminal VOUT outputs a -12V DC power supply, and the output terminal VOUT is also grounded after passing through the parallel circuit of capacitors C21, C19 and bidirectional TVS tube D7. Through the power chip U21, the +12V DC power supply can be converted into a -12V DC power supply to power the PWM isolation module, that is, the output terminal VOUT of the 12V to -12V circuit is connected to pin 4 of the optocoupler isolation chip U2, and is also connected to each operational amplifier of the CP detection isolation module.

[0030] In this embodiment, the CP detection isolation module includes a first window comparator, a second window comparator and a threshold comparator. Among them, operational amplifiers U8.1, U8.2 and their peripheral circuits constitute a first window comparator of 5V-7V; operational amplifiers U7.1, U7.2 and their peripheral circuits constitute a second window comparator of 8V-10V; operational amplifier U9.1 and its peripheral circuits constitute an 11V threshold comparator, and CP1_IE, CP2_IE, and CP3_IE in the figure are MCU input detection pins. The output ends of the 12V to 12V isolation circuit are respectively connected to the first window comparator, the second window comparator and the threshold comparator.

[0031] like Figure 5 As shown: Specifically, in the first window comparator, the +12V power supply is divided by the voltage-dividing resistors R14 and R18 to form 7V, the non-inverting input terminal of the operational amplifier U8.1 is connected between the voltage-dividing resistors R14 and R18, and the 7V voltage is input; the inverting input terminal of U8.1 is connected to the CP_1 terminal of the PWM isolation module, that is, between the resistor R2 and the fuse F1, through the resistor R15; Pin 4 and Pin 8 of U8.1 are respectively connected to the -12V and +12V output by the power conversion module. The inverting input of U8.2 is connected between the voltage-dividing resistors R18 and R19, and the 7V power supply is divided into 5V by R18 and R19, so a 5V voltage is input to the inverting input of U8.2; the non-inverting input of U8.2 is connected to the inverting input of U8.1; the outputs (pin 1) of U8.1 and U8.2 are connected and divided into two paths, one path is connected to 12V through resistor R16, and the other path is connected to pin 1 (i.e., the anode of the light-emitting diode) of the optocoupler chip U6 through resistor R201, and pin 2 is connected to the -12V power supply (i.e., the cathode of the light-emitting diode); one path of the output (pin 4) of the optocoupler chip U6 is connected to 3.3V through a pull-up resistor R17, and the other path is CP3_IE, which is connected to the input detection pin of the MCU.

[0032] like Figure 6 As shown: Similarly, the circuit structure of the second window comparator is the same as that of the first window comparator, except that the resistance of the voltage divider resistor is different, that is, the non-inverting input terminal of U7.1 inputs a 10V voltage, and the inverting input terminal of U7.2 inputs an 8V voltage. The specific structure of this embodiment will not be described in detail.

[0033] like Figure 7 As shown: In the threshold comparator, the +12V power supply is divided by the voltage-dividing resistors R7 and R11 to form an 11V voltage, the inverting input terminal of the operational amplifier U9.1 is connected between the voltage-dividing resistors R7 and R11, and the 11V voltage is input, and the non-inverting input terminal of U9.1 is connected to the CP_1 terminal of the PWM isolation module through the resistor R8; the connection structure of the output terminal of U9.1 is the same as the first window comparator mentioned above, and will not be described in detail here. U9.2 is idle and not used.

[0034] In this embodiment, by setting up a CP detection isolation module, the relationship between the vehicle's gun plugging status and the MCU input detection pin status is shown in the following table:

[0035] state CP (PWM) voltage CP1_IE CP2_IE CP3_IE idle +12V Low level High level High level Insert the gun +9V High level 1KHz PWM input High level Charge +6V High level High level 1KHz PWM input

[0036] For example, when in charging state, the inverting input of U8.1 is 6V, and the non-inverting input is 7V; the inverting input of U8.2 is 5V, and the non-inverting input is 6V, and both U8.1 and U8.2 output high level, driving the light-emitting diode of the optocoupler chip U6 to emit light, and the circuit is turned on, so that the detection point inputs 1KHzPWM to the MCU for detection; while the second window comparator and the threshold comparator cannot be turned on, and output high level. Similarly, the principles of the idle state and the gun plugging state are the same, as shown in the table above.

[0037] The CP detection isolation module of this embodiment is a low-cost isolation detection circuit that does not require a main control chip and has a high-performance ADC module.

[0038] In summary, on the one hand, the utility model isolates the main control end from the charging high-voltage end by setting a power conversion module and a PWM isolation module, thereby greatly improving safety and anti-interference ability; on the other hand, by setting a CP detection isolation module and using a three-way optocoupler signal circuit to detect the CP voltage signal, it is possible to save high-cost isolation digital-to-analog conversion chips. The MCU does not need to use ADC to collect the CP voltage signal, and can use ordinary IO to obtain the 12V, 9V and 6V states of the CP, without requiring the performance of the main control chip ADC module.

Claims

1. A PWM output detection circuit for an automobile AC charging pile, comprising a power conversion module, a PWM isolation module, a CP detection isolation module and a microprocessor; characterized in that: The CP detection isolation module includes a first window comparator, a second window comparator and a threshold comparator; the output ends of the first window comparator, the second window comparator and the threshold comparator are respectively connected to the input detection end of the microprocessor; the input ends of the first window comparator, the second window comparator and the threshold comparator are connected to the output end of the PWM isolation module.

2. The PWM output detection circuit for an automobile AC charging pile according to claim 1, characterized in that: The first window comparator is a 5V-7V CP signal detection circuit composed of an operational amplifier and its peripheral circuits; the second window comparator is an 8V-10V CP signal detection circuit composed of an operational amplifier and its peripheral circuits; and the threshold comparator is an 11V CP signal detection circuit composed of an operational amplifier and its peripheral circuits.

3. The PWM output detection circuit for an automobile AC charging pile according to claim 1 or 2, characterized in that: The peripheral circuits of the first window comparator and the second window comparator each include at least three voltage-dividing resistors and an optocoupler chip; the peripheral circuit of the threshold comparator includes at least two voltage-dividing resistors and an optocoupler chip; the output end of the optocoupler chip is connected to the input detection end of the microprocessor.

4. The PWM output detection circuit for an automobile AC charging pile according to claim 1, characterized in that: The power conversion module includes a 12V to -12V circuit and a 12V to 12V isolation circuit, which are used to power the PWM isolation module and the CP detection isolation module; the 12V DC power supply output by the 12V to 12V isolation circuit serves as the input power supply of the 12V to -12V circuit.

5. The PWM output detection circuit for an automobile AC charging pile according to claim 1, characterized in that: The PWM isolation module includes an optocoupler isolation chip, a first resistor, a fuse and a protection device; the input end of the optocoupler isolation chip is connected to the output end of the MCU; the power end is connected to the output end of the power conversion module; the output end of the optocoupler isolation chip is connected to the connection socket via the first resistor and the fuse, and connected to the automobile controller via the connection socket.

6. The PWM output detection circuit for an automobile AC charging pile according to claim 3, characterized in that: The first window comparator includes operational amplifiers U8.1 and U8.2, and the power supply is divided by a first voltage-dividing resistor, a second voltage-dividing resistor and a third voltage-dividing resistor; the non-inverting input terminal of the operational amplifier U8.1 is connected between the first voltage-dividing resistor and the second voltage-dividing resistor; The inverting input terminal of U8.1 is connected to the output terminal of the PWM isolation module via a resistor; The inverting input terminal of U8.2 is connected between the second voltage-dividing resistor and the third voltage-dividing resistor, and the non-inverting input terminal of U8.2 is connected to the inverting input terminal of U8.1; the output terminals of U8.1 and U8.2 are connected to the input terminals of the optocoupler chip, and the output terminals of the optocoupler chip are connected to the input detection terminals of the microprocessor.

7. The PWM output detection circuit for an automobile AC charging pile according to claim 6, characterized in that: The circuit structure of the second window comparator is the same as that of the first window comparator, and the resistance values ​​of the three voltage-dividing resistors are different from those of the first window comparator.

8. The PWM output detection circuit for an automobile AC charging pile according to claim 3, characterized in that: The threshold comparator comprises an operational amplifier U9.1, an inverting input terminal of the operational amplifier U9.1 is connected between two voltage-dividing resistors, and a non-inverting input terminal is connected to the output terminal of the PWM isolation module via a resistor.

9. The PWM output detection circuit for an automobile AC charging pile according to claim 5, characterized in that: Input terminals of the first window comparator, the second window comparator and the threshold comparator are all connected between the first resistor and the fuse of the PWM isolation module.

10. The PWM output detection circuit for an automobile AC charging pile according to claim 6, characterized in that: After the output ends of the operational amplifiers U8.1 and U8.2 are connected, one path is connected to the positive power supply through a pull-up resistor, and the other path is connected to the anode of the light-emitting diode of the optocoupler chip through a resistor; the cathode of the light-emitting diode is connected to the negative power supply; one path of the output end of the optocoupler chip is connected to 3.3V through a pull-up resistor, and the other path is connected to the input detection end of the microprocessor.

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