Condition monitoring of SiC MOSFETs on LLC resonant converter

Abstract

Silicon carbide (SiC) MOSFETs are widely acknowledged for low loss, fast switching and remarkable thermal conductivity compared to silicon (Si) counterparts. SiC-based power electronic converters, therefore, are optimal when operated at medium voltage to high voltage in high switching frequency applications, which results in a much higher power density than Si-based power converters. The reliability of SiC devices, however, remains a significant hindrance to their wide adoption in power electronics in transportation, industry and military applications. Real-time condition monitoring of SiC devices in SiC-based power converters addresses the reliability issues by providing an early sign of potential failure. Since one of the most consistent failure precursors of a degraded SiC MOSFET is an increase of gate leakage current, a circuitry is developed to track and estimate the on-state gate leakage current of the device during operation. To demonstrate the functionality of the proposed method, an LLC full-bridge resonant converter that operates at a medium voltage and high switching frequency was designed and used to obtain the experimental results. This converter will operate at various duty ratios, DC-link voltages, switching frequencies and output loads to show the consistency and accuracy of the proposed condition monitoring method. With proper calibration, this cost-effective method obtains an accurate gate leakage estimation which opens opportunities to perform prognostic and health monitoring of SiC devices.