Filter design method for GaN-Buck converter taking into account of the common-mode propagation paths

Since some years, one solution to increase the power density of the power converters consists to use the wide band gap semiconductors like SiC and GaN. These devices allow having power converters that operating with the high switching frequencies. These fast devices induce of very high variations of the voltage (dv/dt) and current (di/dt) during commutations. The direct consequence is the generation of the very high levels of the electromagnetic interferences (EMI) in a wide frequency band. This study is focus only on the conducted emissions induced by a Buck converter using GaN-transistor and SiC-diode. To reduce these emissions and to comply with EMC standards, one solution consists to use an EMI filter. In order to design the EMI filters by simulations, a modeling method based on an electrical equivalent circuit is proposed. This method allows taking into account of additional common mode impedance that correspond to the ground plane often neglected in the design of the filters. The comparison of the simulation results and measurements of the conducted emissions of the Buck-converter without and with the EMI filter confirm the validity of the proposed approach.