DM EMI Noise Prediction for Constant On-Time, Critical Mode Power Factor Correction Converters

Critical conduction mode (CRM) power factor correction (PFC) converters are widely used in industries. For CRM PFC converters, high inductor current ripples generate high differential mode (DM) electromagnetic interference (EMI) noise, which calls for big EMI filters. On the other hand, the switching frequency varies during a half line cycle. The characteristics of the EMI in CRM PFC converters have not been carefully investigated and the worst case DM EMI noise has not been identified. The design of an EMI filter is difficult. In this paper, a mathematical model based on the principle of quasi-peak noise detection is proposed to predict the EMI noise in CRM PFC converters. The developed model is verified by experimental results. Based on this model, the worst case DM EMI noise can be predicted. This will greatly help in the design of EMI filters for CRM PFC converters.