Active Thermal Balancing Strategy for Direct Parallel Connection of SiC MOSFETs

Abstract

silicon carbide (SiC) mosfets are increasingly favored in high-power density applications due to their superior thermal and electrical performance compared to Si-IGBTs. However, current ratings of individual SiC mosfet dies are limited, requiring multiple devices in parallel to meet high-current demands, as is typical in traction applications. Parallel operation introduces current and thermal imbalances related to parameter mismatches and layout asymmetries, which degrade reliability and efficiency. This article presents the extensive investigation of a new active thermal balancing control strategy that dynamically adjusts device duty cycles using case temperature feedback. Experimental validation demonstrates significant enhancements in thermal equilibrium and robust performance of parallel-connected SiC mosfets under switching transients at the limit of the device safe operating area. Results confirm effective switching loss redistribution without impacting overall efficiency. Consequently, the strategy removes thermal imbalance as a limiting factor in parallel SiC mosfet operation, mitigating localized thermal overstress, promoting uniform device utilization across the parallel set, and improving long-term reliability by preventing persistent temperature gradients caused by parameter dispersion and commutation-loop asymmetries.