CC output voltage self-calibration circuit

Abstract

The utility model provides a CC output voltage self-calibration circuit. The CC output voltage self-calibration circuit comprises a power supply isolation unit used for outputting a first preset voltage value, a self-calibration reference power supply unit and an isolation AD sampling unit. The self-calibration reference power supply unit outputs a second preset voltage value at the first output end of the self-calibration reference power supply unit after acquiring the first preset voltage value; the second preset voltage value serves as CC output voltage at the same time; a second output end of the self-calibration reference power supply unit is connected with a signal voltage of the charging interface after passing through the resistor and the PTC self-recovery insurance unit; a second preset voltage value connected with the signal voltage passes through the divider resistor and then enters the input end of the isolation AD sampling unit, and the output end of the isolation AD sampling unit is connected with an AD acquisition pin of the MCU; and a charging interface input voltage anti-reverse connection protection circuit and an overvoltage protection circuit. According to the technical scheme, high-precision analog quantity acquisition precision can be obtained without a calibration power supply, and the problem of inaccurate low-voltage AD sampling precision caused by PTC impedance value difference is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of charging piles, in particular to a CC output voltage self-calibration circuit. Background Art

[0002] In the field of charging piles, the handshake between the off-board DC charger and the charging interface of new energy vehicles is based on the level state, that is, the CC voltage value. Different levels represent different connection states. In order to ensure the reliable connection judgment between the off-board DC charger and the vehicle charging interface, it is necessary to perform highly accurate analog sampling of the voltage value to judge the connection state.

[0003] In actual applications, since CC circuits may often be damaged by external overvoltage or lightning strikes, reverse voltage and overvoltage capability tests need to be connected to the charging interface during product reliability testing, and bidirectional transient diodes, varistors, anti-reverse diodes, and PTC protection devices need to be connected in parallel. However, since PTC has a certain impedance value, and each PTC resistor is different, the DC test value is different, which affects the AD test accuracy, especially the low-voltage AD value sampling accuracy, and thus affects the unreliability of the connection status determination. Utility Model Content

[0004] In order to overcome the shortcomings of the prior art, an AD sampling self-calibration circuit with input voltage reverse connection protection and overcurrent and overvoltage protection functions, namely, a CC output voltage self-calibration circuit is proposed.

[0005] A CC output voltage self-calibration circuit, comprising:

[0006] A power isolation unit, wherein the power isolation unit is used to output a first preset voltage value;

[0007] A self-calibration reference power supply unit, wherein after obtaining the first preset voltage value, the self-calibration reference power supply unit outputs a second preset voltage value at its first output terminal; the second preset voltage value is also used as the CC output voltage; the second output terminal of the self-calibration reference power supply unit is connected to the signal voltage of the charging interface after passing through a first resistor and a PTC self-recovery insurance unit;

[0008] The isolated AD sampling unit, the second preset voltage value connected to the signal voltage enters the input end of the isolated AD sampling unit after passing through the voltage divider resistor, and the output end of the isolated AD sampling unit is connected to the AD acquisition pin of the sampling MCU.

[0009] Preferably, the power isolation unit is a DC / DC isolation circuit, the DC / DC isolation circuit includes a DC / DC isolation module, the input voltage of the DC / DC isolation module is 5V, and the first preset voltage value is 15V;

[0010] Preferably, the second preset voltage value is 12V;

[0011] Preferably, the first resistor is a 1K ohm resistor;

[0012] Preferably, the isolated AD sampling unit includes an operational amplifier and its auxiliary circuit;

[0013] Preferably, the second preset voltage value is connected to PGND after being connected to an external calibration resistor;

[0014] Preferably, the calibration resistor is a 100 ohm resistor.

[0015] The CC output voltage self-calibration circuit provided by the utility model has the following advantages:

[0016] 1) High-precision analog acquisition accuracy can be obtained without calibrating the power supply.

[0017] 2) The problem of inaccurate low voltage AD sampling accuracy caused by differences in PTC impedance values ​​is solved.

[0018] 3) The production is simple and convenient, and there is no need to calibrate the power supply equipment during the production process.

[0019] 4) The calibration method is simple, and calibration is fast and convenient by sampling MCU instructions.

[0020] 5) It has output terminal input overvoltage protection and reverse connection protection function. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the CC output voltage self-calibration circuit in the embodiment of the utility model;

[0022] Figure 2 This is a schematic diagram of a power isolation unit in an embodiment of the utility model;

[0023] Figure 3 Schematic diagram of a self-calibration reference power supply unit in an embodiment of the utility model;

[0024] Figure 4 Schematic diagram of the isolated AD sampling unit in the embodiment of the utility model. DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] In one embodiment, a CC output voltage self-calibration circuit is provided, and its system framework is as follows: Figure 1 As shown, it mainly includes: power isolation unit, self-calibration reference power unit, isolated AD sampling unit and anti-reverse connection, overvoltage and overcurrent protection unit. Its working principle is: the power isolation unit outputs 15V power, and generates a high-precision 12V power supply through the self-calibration reference power unit, that is, CC output voltage; then outputs 12V connection signal voltage through the first resistor (R225) and the PTC self-recovery fuse (F202); this voltage is input to the input end of the isolated AD sampling unit after the voltage divider resistor, and the output of the isolated AD sampling unit is connected to the AD acquisition input pin of the sampling MCU processor. During calibration, only a 100 ohm calibration resistor is needed to calculate the PTC electrical value through the voltage at this time to form a calibration coefficient.

[0027] Among them, the implementation principle diagram of the power isolation unit is as follows Figure 2 As shown, it includes a DC / DC isolation circuit and its auxiliary circuit, specifically including a DC / DC isolation module U107, the input voltage is VDD5V, and the output first preset voltage value is 15V.

[0028] The schematic diagram of the self-calibration reference power supply unit is as follows Figure 3 As shown, it includes a voltage reference IC (Q108) and its auxiliary circuit. The first output end of the self-calibration reference power supply unit is a 12V voltage, and the second output end is connected to the signal voltage of the charging interface after the first resistor (R225) of 1K ohms and the PTC self-recovery insurance unit (F202) are connected in series. At the same time, the combination of RD202, RZ2, F202, and R225 has an over-current and over-voltage protection function when the test voltage is input to the output terminal to protect the reference circuit from damage; D505 has an anti-reverse polarity function to protect the isolated power supply module from damage.

[0029] The schematic diagram of the isolated AD sampling unit is as follows Figure 4 As shown, the isolated AD sampling unit includes an operational amplifier (U202) and its auxiliary circuit. The output end of the isolated AD sampling unit is connected to the AD acquisition pin of the sampling MCU.

[0030] During calibration, you only need to connect an external 100 ohm calibration resistor, and calculate the PTC value through the voltage at this time to form the calibration coefficient. The specific calibration steps are as follows:

[0031] PTC impedance calculation

[0032] 1) Connect an external 100 ohm resistor to PGND at the CC output voltage.

[0033] 2) The test voltage value is the reference voltage +12V, through the resistor R225, the F202 impedance Rptc and the 100 ohm resistor to the ground. At this time, the CC-VB voltage value U i is calculated by the following formula:

[0034] U i=12 / (R225+Rptc+100)*(Rptc+100)

[0035] The PTC normal temperature resistance value Rptc is calculated from this.

[0036] 3) Calculate voltage compensation. When the sampling MCU measures the voltage value U i < 12V, it indicates that compensation is required.

[0037] The actual test value (that is, CC voltage value) is: U i-(12 / (1000+Rptc))*Rptc.

[0038] The above is an explanation of the CC output voltage self-calibration circuit of the present invention, which is used to help understand the present invention; however, the implementation of the present invention is not limited to the above embodiments, and any changes, modifications, substitutions, combinations, and simplifications made without departing from the principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A CC output voltage self-calibration circuit, characterized in that: include: A power isolation unit, wherein the power isolation unit is used to output a first preset voltage value; A self-calibration reference power supply unit, which outputs a second preset voltage value at its first output terminal after acquiring the first preset voltage value; The second preset voltage value is also used as the CC output voltage; The second output end of the self-calibration reference power supply unit is connected to the signal voltage of the charging interface through the first resistor and the PTC self-recovery insurance unit; The isolated AD sampling unit has a second preset voltage value connected to the signal voltage and enters the input end of the isolated AD sampling unit after passing through a voltage divider resistor, and the output end of the isolated AD sampling unit is connected to the AD acquisition pin of the sampling MCU.

2. The CC output voltage self-calibration circuit according to claim 1, characterized in that: The power isolation unit is a DC / DC isolation circuit, the DC / DC isolation circuit includes a DC / DC isolation module, the input voltage of the DC / DC isolation module is 5V, and the first preset voltage value is 15V.

3. The CC output voltage self-calibration circuit according to claim 2, characterized in that: The second preset voltage value is 12V.

4. The CC output voltage self-calibration circuit according to claim 2, characterized in that: The first resistor is a 1K ohm resistor.

5. The CC output voltage self-calibration circuit according to claim 2, characterized in that: The isolated AD sampling unit includes an operational amplifier and its auxiliary circuit.

6. The CC output voltage self-calibration circuit according to any one of claims 1 to 5, characterized in that: The second preset voltage value is connected to PGND after passing through an external calibration resistor.

7. The CC output voltage self-calibration circuit according to claim 6, characterized in that: The calibration resistor is a 100 ohm resistor.

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