Analysis of overcurrent protection circuit of electric vehicle on-board charger

Further, according to an embodiment of the utility model, as shown in FIG5 , the overcurrent protection unit 20 may also include: an amplifier A2, a second capacitor C2, a seventh resistor R7, and a third capacitor C3. Among them, the positive input terminal of the amplifier A2 is connected to the other end of the fifth resistor R5 and one end of the sixth resistor R6, respectively, the negative input terminal of the amplifier A2 is connected to the output terminal of the amplifier A2, and the power supply terminal of the amplifier A2 is connected to the first preset power supply VCC2. One end of the second capacitor C2 is connected to the power supply terminal of the amplifier, and the other end of the second capacitor C2 is grounded. One end of the seventh resistor R7 is connected to the output terminal of the amplifier A2, and the other end of the seventh resistor R7 is connected to the control unit 30. One end of the third capacitor C3 is connected to the other end of the seventh resistor R7, and the other end of the third capacitor C3 is grounded.

Specifically, the model of amplifier A2 can be LMV842, and amplifier A2 can be used as a voltage follower. C2 is used to stabilize the 5V power supply, and its size can be 100nF. R7 and C3 are used for filtering, R7 can be 51Ω, and C3 can be 22nF. Further, according to an embodiment of the utility model, as shown in Figure 5, the overcurrent protection unit 20 can also include: a first clamping diode D1 and a second clamping diode D2. Among them, the anode of the first clamping diode D1 is grounded. The anode of the second clamping diode D2 is connected to the cathode of the first clamping diode D2, and there is a second node Q2 between the anode of the second clamping diode D2 and the cathode of the first clamping diode D1, and the cathode of the second clamping diode Q2 is connected to the first preset power supply VCC2, and the second node Q2 is connected to the other end of the seventh resistor R7.

Specifically, the first clamping diode D1 and the second clamping diode D2 are used to control the level of the overcurrent protection signal within a preset range, and the signal exceeding the preset range will be discarded to prevent the overcurrent protection signal from being too strong to damage the control unit 30. As shown in Figures 4 and 5, when the current detection value is greater than the preset current threshold, the overcurrent protection unit 20 will output an overcurrent protection signal to the control unit 30. The control unit 30 receives the overcurrent protection signal and turns off the control signal output channel of the SiC switch tube to stop the AC/DC converter 40 and the DC/DC converter 50 from working, thereby realizing the overcurrent protection function of the on-board charger.

The overcurrent protection circuit of the vehicle charger of the utility model combines software and hardware. The software configures the interrupt in advance. When the hardware detects an overcurrent fault, the overcurrent protection can be triggered immediately, which shortens the action time of the protection circuit and improves the safety of the vehicle charger.

In summary, according to the overcurrent protection circuit of the on-board charger of the utility model, the current detection unit outputs the current detection value by detecting the output current of the DC/DC converter, and the overcurrent protection unit outputs the overcurrent protection signal when the current detection value is greater than the preset current threshold value, and the control unit closes the control signal output channel of the SiC switch tube when receiving the overcurrent protection signal, so that the AC/DC converter and the DC/DC converter stop working. Therefore, the overcurrent protection circuit can quickly trigger the overcurrent protection function when an overcurrent fault occurs in the on-board charger, thereby improving the safety of the on-board charger. At the same time, the on-board charger adopts the SiC switch tube, which can improve the charging rate of the on-board charger and reduce the control difficulty and cost.

The utility model also proposes a vehicle charger, which includes the above-mentioned vehicle charger overcurrent protection circuit. The vehicle charger of the utility model detects the output current of the DC/DC converter through the current detection unit of the above-mentioned vehicle charger overcurrent protection circuit to output the current detection value, and outputs the overcurrent protection signal through the overcurrent protection unit when the current detection value is greater than the preset current threshold, and closes the control signal output channel of the SiC switch tube through the control unit when receiving the overcurrent protection signal, so that the AC/DC converter and the DC/DC converter stop working. As a result, the vehicle charger can quickly trigger the overcurrent protection function when an overcurrent fault occurs, thereby improving the safety of the vehicle charger. At the same time, the vehicle charger adopts the SiC switch tube, which can improve the charging rate of the vehicle charger and reduce the control difficulty and cost.

In addition, the utility model also provides an electric vehicle, which includes the above-mentioned on-board charger.

The electric vehicle of the utility model can quickly trigger the overcurrent protection function when an overcurrent fault occurs in the on-board charger through the above-mentioned on-board charger, thereby improving the safety of the on-board charger. At the same time, the on-board charger adopts a SiC switch tube, which can increase the charging rate of the electric vehicle and reduce the control difficulty and cost.

The CH704150CT chip mentioned in the article is an isolated integrated current sensor chip with the advantages of high precision, enhanced insulation withstand voltage, high reliability, and low power consumption. The CH704 series products are isolated integrated current sensor chips developed specifically for large current detection applications. They have a built-in primary conductor resistance of 0.1mΩ, which effectively reduces chip heating and supports large current detection: ±50A, ±100A, ±150A, ±200A. It integrates a unique temperature compensation circuit to achieve good consistency of the chip in the full temperature range of -40 to 150°C. This chip is a product that meets automotive-grade standards and fills a domestic gap.

Features are as follows:

• Isolation voltage: 4800VRMS

• AEC-Q100 automotive qualified (CH704A)

• Power supply: 4.5-5.5V

• Output voltage is proportional to current: +/-50A, +/-100A, +/-150A, +/-200A

• Bandwidth: 120kHz

• Response time: 2us

• Wide temperature range: -40°C to 150°C

• High-resolution offset and sensitivity adjustment using EEPROM

• Wire resistance: 0.1 mΩ

• Integrated digital temperature compensation circuit

• Almost zero hysteresis

• Ratiometric output of supply voltage

• Resistant to external magnetic fields

Key applications include:

• Automotive electronics: automotive OBC, DC-DC, EPS motor, etc.

• Industrial control: uninterruptible power supply (UPS), welding machine/mobile communication equipment, etc.

• High-power motors: balance car/unicycle controller, heat pump/ice maker, etc.

• Energy: process control, battery testing, energy measurement, etc.