Gate Driver Power Supply for Medium Voltage SiC Mosfets with Air Core Transformer

Medium voltage SiC power MOSFETs have enabled higher efficiency and simplification of implementations for high voltage and high bandwidth applications. Driving these power devices requires gate drive power supplies with high galvanic isolation. Transformers provide the insulation but must have low interwinding capacitance to deal with the high dv/dt of the switching. In this paper, we present two air-core transformer solutions: single-turn primary and toroidal windings on a nonmagnetic former, and primary and secondary winding embedded in the PCB. Both alternatives can keep the interwinding capacitance < 5pF while providing enough coupling to deliver the needed power. High-frequency driving of the transformers results in compact solutions. Series-series compensation of these air core transformers has been designed for efficient power transfer and low voltage drop. Issues related to the design and compensation parameters are addressed in this paper. The performance has been verified experimentally.