An efficient common-mode hybrid EMI filter used in switch-mode power supply

After the study of electromagnetic interference (EMI) mechanisms in switching mode power system (SMPS) and the soft switch, this paper proposes a novel hybrid filter (HEF) to suppress commend mode EMI in SMPS. The HEF consists of a passive filter and an active filter. Matching network, which can reduce impedance mismatching effects, is introduced in passive part. A feed-forward active filter is adopted as active part. The simulation and experiment results show that the EMI depressing of HEF is good. And the HEF is smaller and lighter than traditional passive filter.