How to suppress EMI in the EPS battery charging and switching circuit?

Circuits in the EPS involving battery charging and switching (such as chargers and battery contactors) generate transient EMI during operation. Suppression measures include:

1. Charger (PFC/DC-DC) filtering: Configure independent EMI filters at the charger's input and output terminals to prevent switching noise from interfering with the battery and power grid.

2. Contactor/relay coil absorption: Connect a freewheeling diode, RC, or TVS absorption circuit in parallel with the control coil of the battery contactor to suppress reverse peak voltage during disconnection.

3. Battery cable shielding and filtering: Use shielding for cables connecting to the battery and ground them at both ends. Install common-mode inductors and X capacitors at the battery port (EPS side) for filtering.

4. Control timing optimization: Ensure smooth transitions between charging, discharging, and switching modes, avoiding drastic voltage and current jumps.

5. Battery internal resistance noise: Changes in battery internal resistance introduce low-frequency noise; low-pass filtering can be added to the sampling circuit.

Suppressing EMI in these circuits helps protect the BMS and improve overall system reliability.