Modeling and Prediction of Common-Mode Electromagnetic Interference for GaN-Based LLC Resonant Converters

The third generation of power semiconductor devices, such as GaN HEMTs, have been increasingly used in the design of power converters, due to their advantages of low loss, high efficiency, fast switching speed and high operating frequency. However, high dv/dt and di/dt slew rates of GaN devices will generate more electromagnetic interference (EMI) noise in power converters, and GaN devices themselves are more sensitive to EMI noise due to the lower threshold voltage, which leads to more instability and fault factors. In this paper, conducted EMI is analyzed for GaN HEMT-based LLC resonant converter, and the effect of high-frequency transformer is also investigated, which provides the common mode (CM) EMI propagation path. Then, CM EMI equivalent circuit model of LLC resonant converter is proposed to predict the conducted CM EMI noise. Finally, experiments are carried out to verify the effectiveness of the conducted CM EMI modeling method of GaN-based LLC resonant converter.