Design Analysis for Current-transformer Based High-frequency Auxiliary Power Supply for SiC-based Medium Voltage Converter Systems

This paper presents a design of 1 MHz isolated auxiliary power supply system using gallium nitride (GaN) devices with medium voltage insulation reinforcement. The designed power supply is capable to simultaneously supply multiple gate drivers and auxiliary components for 10 kV silicon carbide (SiC) MOSFETs based converter systems with a strong high dv/dt common-mode noise immunity. In the system, a highfrequency soft-switched resonant topology and current-fed switching voltage regulator are applied to the power supplies sending and receiving sides respectively. To achieve medium voltage insulation (PD free) as well as low coupling capacitor (<2 pF) of the system, a current based transformer with single turn on the sending side is designed. This complete auxiliary power supply design is capable of driving more than 6 distributed loads with total power of 120 W under different conditions and it is immune to load failures.