EMI Filter Design Based on High-Frequency Modeling of Common-mode Chokes

Aiming at the bad performance of EMI filter in the high frequency band, the non-ideal factors of common-mode chokes and the limitations of the existing high-frequency model are summarized. Considering the frequency characteristics of core material and the influence of parasitic capacitance, an improved cascaded Foster network model is established, and then the common-mode and differential-mode high-frequency equivalent circuits of EMI filter in 150kHz-30MHz are developed. Furthermore, an EMI filter design method based on the optimization of the impedance characteristics of common- mode chokes is proposed. An experiment is carried out to verify the method by an 1.25kW Boost PFC prototype. Results indicate that the device with the proposed EMI filter can pass the conducted EMI test successfully, and the design scheme can provide effective guidance for the remediation of conducted electromagnetic interference.