Analysis of the CP circuit principle in the car AC charging pile

This article mainly analyzes the CP circuit of the automobile AC charging pile from the following four aspects: 1. Background introduction 2. Introduction to the simulated vehicle end 3. CP circuit analysis 4. CP detection circuit calculation

1. Background

The new energy industry is very popular now, and new energy vehicles are also very popular. Of course, new energy vehicles are inseparable from charging piles. Today, I will share with you the CP circuit in the car AC charging pile and the circuit principle analysis.

Before sharing the circuit, let me first give you some basic knowledge about the application scenarios, which will help you better understand it.

Car charging piles are divided into AC and DC, among which AC charging piles are called slow charging and DC charging piles are called fast charging.

The pin definitions of the AC charging gun are as follows:

Figure 1 AC charging pile charging gun pin definition

L: Output live wire

N: Output neutral line

CC: Connection detection signal, confirming that the connection between the charging pile and the vehicle is normal.

CP: Control guidance signal.

PE: Earth

Regarding CP signals, I think the following points should be emphasized:

① It is the only communication signal between the car charging pile and the charging car. Whether the communication is normal can only be judged by the CP signal.

② The waveform used for communication between the charging pile and the vehicle-mounted OBC is a 1KHz PWM wave. The size of the charging current is determined by the duty cycle. Different duty cycles represent different charging currents. ③ Since the AC neutral and live wires L and N are close to the CP line in the charging gun, and the charging gun is generally 5m long, the interference of the CP line is coupled to the power line through the charging gun, which can easily cause the radiation to exceed the standard. Therefore, it is recommended to replace the CP line with a shielded line (but the shielded line is expensive, and generally the low-frequency conduction without shielding cannot pass).

④ Generally, the status of the charging pile can be judged based on the voltage difference between the CP signal and PE.

When the voltage is 12V, it indicates an idle state (not connected).

When the voltage is 9V, it indicates it is connected.

When the voltage is 6V, it indicates that it is in charging state.

Figure 2 Different CP voltages represent connected charging states

This article mainly explains the CP circuit part, how the CP voltage is 12V when idle, 9V when connected, and 6V when charged, how the MCU detects the CP voltage, and then controls the main relay to close or open when a fault occurs.