Research on the design method of high isolation and low parasitic parameters for medium-voltage SiC MOSFET driver power supply using wireless power transfer

For medium-voltage SiC devices, there is a mutual restraint between the isolation capability and the coupling capacitance of the isolated gate drive power supply. It is the major bottleneck for structural compactness and insulation reliability. This paper innovatively proposes a loosely coupled transformer design scheme using wireless power transfer, achieving the collaborative optimization of high isolation performance and low coupling capacitance within a limited space. The research first establishes a theoretical model of coupling capacitance. Through parameter analysis, the key design variables that affect the performance of the isolation unit are identified. At the coil structure design level, the electric field boundary homogenization was introduced, significantly reducing the local electric field stress and solving the problem of electric field concentration at the triplet points. Furthermore, this paper conducts an in-depth comparison of different insulating materials and insulation schemes, and proposes two isolation unit design schemes: local potting and overall potting. After verification through partial discharge tests and coupling capacitor performance tests, it was finally determined that the overall sealing and filling scheme was the optimal design. This scheme achieves a partial discharge inception voltage (PDIV) of 21.5 kV effective value, and a low coupling capacitance of 2.34 pF.