How to match parameters for an EPS input EMI filter?

The parameter matching of EPS input EMI filters must be based on input specifications, noise characteristics, and safety requirements. First, determine the input voltage (AC or DC) and maximum input current. Determine the common-mode and differential-mode noise frequency bands to be suppressed through pre-testing or analysis. Matching steps:

1. Common-mode inductor: Select based on the current and impedance curve of the required suppression frequency band. For example, the CML series can be selected for small to medium power applications, while the CMZ series is selected for high power or high impedance requirements. Ensure its saturation current is greater than the peak current.

2. X capacitor: Connected between input lines (LN or DC+/-) to suppress differential-mode noise. Its capacitance value is limited by leakage current and inrush current; a safety-certified film capacitor must be used.

3. Y capacitor: Connected between the input line and protective ground to provide a common-mode noise loop. Its total capacitance value is strictly limited by safety leakage current; a safety-certified ceramic capacitor must be used, typically in the nF range.

Finally, verify the filter's temperature rise and actual attenuation effect under full load.