Characterizations and Converter Design Using the Latest 6.5 kV Silicon Carbide MOSFETs

In this work, comprehensive static and dynamic characterizations were conducted for the latest 6.5 kV silicon carbide (SiC) MOSFETs from room temperature to 175°C. A custom clamped inductive load test setup is developed to evaluate the switching performance and losses for the medium voltage (MV) SiC devices. Grounding paths due to the parasitic capacitances in the test setup are analyzed and reduced to mitigate impacts to drain current sensing during the switching period. In addition, using these latest 6.5 kV SiC MOSFETs, a 25 kW all SiC series-resonant converter (SRC) is proposed to enable a single stage dc-to-dc conversion from 3 kV to 540 V (± 270 V) aiming at applications on future electric aircraft with onboard MVDC distribution. The proposed SRC consists of a 2-level half-bridge stage using 6.5 kV discrete SiC MOSFETs on the primary side, a full-bridge converter using 900 V SiC MOSFET modules on the secondary side and a high frequency transformer. Compared to a 3-level neutral-point-clamped converter using 3.3 kV discrete SiC MOSFETs, the efficiency and power density of the 2-level 6.5 kV SiC devices based converter are increased. To validate the effectiveness of the proposed SRC design, a converter prototype is developed and comprehensive experimental studies are conducted.