Research of active EMI filter for Gallium Nitride based high frequency resonant converter

With the increasing switching frequency of Gallium Nitride (GaN) based converters, their EMI issues become more and more serious. In this paper, a novel active EMI filtering method is proposed for a high frequency LLC resonant converter. Firstly, a high frequency model of the GaN based converter is given. Common mode EMI coupling paths are analyzed in detail. Secondly, an improved two-stage active EMI filter topology is proposed. It has the advantages of increasing insertion loss, simplifying the structure and reducing the cost effectively. Finally, a GaN based 1MHz high frequency resonant converter as well as the proposed active EMI filter prototype is built. Simulation and experimental results demonstrate the efficiency of the proposed active filtering method.