Design and Analysis of Differential Mode Active EMI Filter for GaN-based Totem Pole PFC Converter

Traditional passive LC filters for EMI mitigation are becoming a bottleneck in achieving high power density in power electronic converters. Their large size, weight, and high cost have driven the search for alternative solutions. Active EMI filters have emerged as a suitable alternative to passive LC filters for providing mitigation. In this work, a differential mode active EMI filter is proposed for a high-frequency GaN-based totem-pole PFC converter. A second-order RC network is used to sense the noise voltage, and an RC network is employed to inject anti-noise to mitigate the DM noise. To address the stability problem caused by the two poles of the sensing network and one pole of the injection network below the 150 kHz range, a type II compensator is implemented. The zero introduced by the type II compensator is properly placed at the pole location of the injection network to mitigate its impact and achieve sufficient phase margin. The proposed method is experimentally verified on a totem-pole PFC converter, achieving 28 dBµV DM noise attenuation.