Circuit Modeling and Simulation of EMI Filter for High Current Power Converters

This paper shows a circuit model that can accurately simulate the differential-mode and common-mode attenuation characteristics of a three-stage EMI filter connected to high-current power converters. Passive components such as common mode choke coils and capacitors are modeled as high-frequency equivalent circuits based on impedance measurement results. For the coils that exhibited characteristics that are difficult to fit manually, vector fitting is used to derive a highly accurate equivalent circuit. The mutual inductance between input and output loops, which has a significant impact on common mode characteristics, is calculated based on the results of electromagnetic field analysis using a 3D CAD model. The combined circuit simulation model is able to predict the filter attenuation characteristics with an accuracy of less than 10 dB error for both modes.