A reliable voltage clamping submodule based on SiC MOSFET for solid state switch

The electron cyclotron resonance heating system is one of the most effective plasma heating systems for controlled nuclear fusion. The key part of the system called gyrotron is driven by a high voltage power supply with a rated output power of hundreds of kilowatts. When the system is in operation, breakdowns frequently occur in the gyrotron. During breakdowns, the gyrotron will endure a large volume of energy and may be damaged. A solid-state switch is required to protect it by blocking high voltage (∼40 kV) within 10 microseconds and limiting energy within a few joules. Compared with Si IGBT/MOSFET, SiC MOSFET with higher switching speed is more suitable for the switch. However, rapid switching speed exacerbates the voltage imbalance. To solve the problems, a reliable module named Advanced Chopper Sub-Model based on SiC MOSFETs for a solid-state switch is proposed. The module adopts a voltage-clamped circuit to achieve the capabilities of rapid switching-off speed, as well as low overvoltage and good voltage balancing. In addition, modules connected in series can tolerate large driver time delay. The SPICE simulation and the double-pulse test are used to validate the effectiveness of the proposed module. The protection performance test was also conducted by using a spark gap to simulate the breakdown fault. Finally, the switch that consists of 64 series-connected modules has been tested at 30 kV/6 A. The turn-off time is ∼5 µs, and the energy during the turn-off transition is 0.283 J. The results show that the switch has good performance.