Single-Gate Driving and Nonisolated Power Supply Technology for Series SiC-MOSFETs in High-Voltage Applications

Series-connection of silicon carbide (SiC)-MOSFETs has significant advantages in simplifying the topology and control of high-voltage converters. However, the challenges of high isolation and signal crosstalk persist in the gate signal transmission and drive power supply. To solve this problem, a new cascade bootstrap circuits-based nonisolated gate drive topology is proposed for high-voltage series-connected SiC-MOSFETs. The cascade bootstrap circuits consist of fundamental diodes, capacitors, and other devices. With this topology, all the gate drivers can be supplied by only a nonisolated power source instead of the highly isolated sources, and only one single-gate signal instead of independent gate signals is needed to drive all the series devices. The electrical connection in the gate signal transmission path is isolated by photocouplers, effectively avoiding crosstalk between gate signals. Furthermore, a snubber circuit is employed to clamp the voltage of each MOSFET and realize automatic capacitor voltage sharing during the turn-on process. A 6 kV-to-24 V single-ended flyback converter with four series-connected SiC-MOSFETs is constructed to verify the proposed topology. The experimental results demonstrate the exceptional driving and switching performance of the proposed topology, as evidenced by achieving a stable 24 V output at an input of 6.05 kV and a switching frequency of 32 kHz.