EMI Study for the Interleaved Multi-Channel PFC

For high power application the interleaved multichannel PFC is becoming more and more popular. It can effectively reduce the input ripple current due to the ripple cancellation effect. It is generally believed that the reduced input ripple current will lower down the DM EMI noise magnitude, which will make the DM Alter smaller. However, for most of today´s PFC, running in the frequency range of 75 kHz ~ 150 kHz, the conventional 2-channel interleaving technique cannot help to reduce the EMI filter size at all. In this switching frequency range, the EMI filter design is based on the 2^nd order harmonic, which cannot be reduced by the conventional interleaving. In this paper, a 2-channel PFC operating with 90 degree phase shift is introduced. It can cancel the 2^nd order harmonic and reduce the 3^rd order harmonic, and the EMI filter size can be reduced. This novel interleaving strategy can be further extended to other switching frequency range and other multi-channel interleaved PFC.