Input Differential-Mode EMI of CRM Boost PFC Converter

In this paper, the differential-mode (DM) electromagnetic interference (EMI) noise of a single-phase boost power factor correction converter operating in critical current mode was analyzed. The DM noise spectra are calculated based on the mathematical model of EMI receiver and the required corner frequencies of DM filter are obtained. It can be seen that the minimum corner frequencies are determined by the maximum noises at 150 kHz. With the relation between the magnitude of the inductor current ripple and the DM noise, the characteristics of noise at 150 kHz are obtained by analyzing the current ripple magnitude at 150 kHz; thus, the worst conditions which have the maximum noise value are figured out. Meanwhile, the maximum noises at 150 kHz for different input voltages are identical, so the DM filter can be designed based on one worst spectrum at one input voltage without testing the spectra in other conditions.