Prediction of the Conducted Electro-magnetic Interference for Critical Conduction Mode Boost Power Factor Correction Converter

Besides continuous conduction mode (CCM) and discontinuous conduction mode (DCM), the boost PFC converter can be operated in critical conduction mode (CRM). Under CRM, the switching frequency varies in a half line cycle, and the conducted electromagnetic interference (EMI) spectra are quite different under different input voltage and load conditions. In this chapter, the conducted EMI of the CRM boost PFC converter, including the common-mode (CM) and differential-mode (DM) noises, are analyzed, and the worst-case CM and DM noises are predicted. Then, the design of the EMI filter is presented. Finally, a 90-W CRM boost PFC converter prototype is fabricated in the lab, and the worst case of the conducted EMI spectrum and the design of the EMI filter are verified by the experimental results.