EV & EV Charging EMI Filter Solutions

A: By using multi-stage EMI filters, proper grounding, shielding, and optimized circuit design.

Applicable EMC and safety standards depend on charger type, charging mode, power level, installation environment, and target market. IEC 61851-21-2 is commonly relevant to EMC requirements for off-board conductive charging systems.

A: Yes, custom EMI filters are often required to match specific power levels, voltages, and system designs.

DC fast chargers typically require EMI filtering on the three-phase AC input, and in some designs additional filtering may also be needed on the high-voltage DC side. The correct filter depends on charger power, input voltage, current, converter topology, switching frequency, grounding, cable layout, and EMC test results.

For high-power systems, a three-phase EMI filter is commonly used at the AC input to reduce conducted common-mode and differential-mode noise generated by AC/DC conversion stages. High-voltage DC EMI filters may also be used where significant noise is present on the DC output or internal DC bus.

Not every EV charger requires EMI filters on both sides. The required filtering configuration depends on where the dominant noise is generated and how it propagates through the system.

The AC input side is usually the primary location for filtering conducted emissions entering or leaving the charger through the mains connection. DC-side filtering may be added when high-frequency noise from DC/DC converters or switching devices propagates onto the DC bus, charging cable, or vehicle interface.

In high-power DC fast charging systems, AC-side and DC-side filtering may be used together when system-level EMC testing shows that a single filter stage is not sufficient.

Start with the electrical requirements of the charging system, including operating voltage, rated current, charger power, number of phases, and DC bus voltage.

Then evaluate the main EMI characteristics, such as switching frequency, converter topology, common-mode and differential-mode noise, cable length, grounding, leakage current limits, and available installation space.

For high-power chargers, it is also important to consider filter current margin, thermal performance, insertion loss, mechanical mounting, and the applicable EMC requirements for the target market.

If EMC test data is available, conducted-emission results can help determine the required attenuation more accurately.

EMI filters can help reduce power-line noise that may contribute to CAN, PLC, or other communication instability, especially when interference is coupled through the power system.

However, communication problems are not always caused only by conducted EMI. Grounding, shielding, cable routing, common-mode current, connector design, and separation between power and signal cables should also be evaluated.

In EV charging systems, the most effective solution often combines appropriate power-line filtering with improved grounding, shielding, and wiring layout.