Design of Half-Bridge Switching Power Module Based on Parallel-Connected SiC MOSFETs for LLC Resonant Converter with Symmetrical Structure and Low Parasitic Inductance

Abstract

SiC MOSFETs are used in many power conversion applications because of their superior characteristics, such as fast switching speed, low on-resistance, and high operating temperature. In certain high-power systems, SiC MOSFETs are connected in parallel to enhance their current capacity and power efficiency. However, compared with Si-based devices, the current imbalance caused by the parasitic inductance difference becomes more severe when driving SiC MOSFETs in parallel, owing to the fast switching speed. Furthermore, the power loop inductance imbalance that occurs when constructing a half-bridge with parallel SiC MOSFETs has rarely been addressed in previous studies. In this study, a half-bridge switching power module based on parallel-connected SiC MOSFETs is proposed to solve the current imbalance through a symmetric structure of the gate and power loops. The effects of the magnitude and imbalance of the gate and power loop inductances in the half-bridge structure based on parallel-connected devices are also explained. A detailed printed circuit board layout of the proposed switching power module is provided, and the inductance symmetry is verified through simulations. A double-pulse test is conducted to verify the current-balancing capability of the proposed switching power module. In addition, an LLC resonant converter is designed using the proposed switching power module, and the power loss between parallel SiC MOSFETs is compared. The experimental results indicate the total power loss error between the parallel-connected SiC MOSFETs of the proposed power module is only 1.94%.