DM EMI noise analysis for critical conduction mode PFC

The critical conduction mode (CRM) power factor correction converters are widely used in low power front-end converters for its high efficiency. Compared to the traditional CCM PFC, the large inductor current ripple in the CRM PFC makes the DM EMI noise a major concern and a large EMI filter is needed. Moreover, uncertainty of the worse case for the EMI noise in the CRM PFC may often lead to an overdesign of the EMI filter, which further increases the size of the system. In this paper, the worst case analysis is carried out based on the proposed mathematical prediction model for the DM EMI noise of the CRM PFC. The design criteria of the DM EMI filter are obtained from the worst case analysis without the need of EMI measurement, which helps to link the EMI filter with the initial system design and make the potential optimization possible. Experimental results validate the proposed model and the worst case analysis.