Improving balance technique for high frequency common mode noise reduction in boost PFC converters

The objective of this paper is to investigate and improve the high frequency noise reduction performance of common mode (CM) noise reduction techniques. Balance technique is chosen as the research object. High frequency model of balanced boost PFC converter is derived and important parasitics and parameters in the model are studied. Effects of coupling coefficient, turns ratio and inductor impedance on high frequency CM noise are discussed in detail. According to the model, high frequency resonance due to serial LC network causes high CM noise peak. Turns ratio has significant impact on the noise peak level. Core and winding structure of boost inductors is another important aspect for high frequency CM noise. Design guidelines for implementing balance are summarized to achieve best high frequency CM noise reduction. Boost PFC prototype with CM EMI filter was built to verify the proposed CM noise model and noise reduction methods. Finally, the effect of grounding point on CM EMI filter performance is also studied.