How to ensure EMC compliance for EPS safety-compliant X/Y capacitors?

The selection of the capacitance value of the safety-compliant X/Y capacitors in EPS is crucial for balancing EMC filtering performance with safety regulations. X capacitors (bridging LN or DC +/-) primarily suppress differential-mode noise; larger capacitance values result in better low-frequency attenuation, but inrush current and size/cost must be considered. Metallized film capacitors are typically chosen. Y capacitors (bridging wire to ground) provide a return path for common-mode noise, and their capacitance value is directly limited by safety leakage current. For example, for Class I equipment, the leakage current to ground is typically required to be less than 3.5mA. The total allowable Y capacitance value under the maximum operating voltage can be calculated using the formula I=2πfCV. In practice, a common approach is to use multiple small-capacity safety-compliant ceramic Y capacitors connected in parallel, for example, using several 2.2nF capacitors distributed across the circuit. This satisfies strict leakage current requirements while providing an effective high-frequency path to ground for broadband common-mode noise.