Analysis and filter design of differential mode EMI noise for GaN-based interleaved MHz critical mode PFC converter

Power factor correction (PFC) converter consumes a large part of volume of power supply. Typical switching frequency of commercial PFC converter is usually not higher than several hundred kHz. Increasing the switching frequency of PFC converter to MHz by using GaN devices can greatly reduce the size and increase power density of power supply. In order to eliminate the high turn-on loss of cascode GaN device, critical conduction mode (CRM) is applied. However, when operating on CRM, PFC converter has large inductor current ripple and variable switching frequency. This makes the differential mode (DM) noise a serious issue for CRM PFC converter. This paper provides a more accurate model to calculate the switching frequency and DM noise of MHz CRM PFC converter. Based on the model and experiment result, interleaving impact of DM noise for MHz CRM PFC converter is analyzed. DM noise filter is designed and it demonstrates that increasing the switching frequency of PFC converter to MHz can greatly increase the corner frequency of DM filter and reduce the filter size significantly.