Analysis the inductive coupling effects on the differential mode EMI in power converter

In this paper, the effects of inductive couplings (between PFC inductors and capacitor, also PCB trace loop) that exist in Boost PFC converter are analyzed and measured. It is obvious that these couplings have significant effects on conducted DM noise. It is concluded that the capacitor should be perpendicular placement to the inductor and keep out-loop smaller when PCB layout, which can reduce the inductive couplings. Then based on the modeling of Boost inductor and capacitor using network analyzer HP4195A and estimating of inductive couplings using Maxwell 3D software, the model of whole circuit is set up. Comparison of simulated voltage gains and measured voltage gains verifies this model.