SiC Stacked-Capacitor Converters for Pulse Applications

Pulse power converters demands single high voltage and current pulse shape waveform in high temperature, heavy neutrons, and ions radiation environment, where 50% ~75% voltage derating margin is typically required for the power devices. silicon carbide (SiC) MOSFETs are promising to improve radiation reliability owing to wide band-gap. However, the conventional converters with off-the-shelf commercial SiC MOSFETs cannot provide enough voltage margin accordingly. A stack-capacitor pulse converter topology is proposed to reduce the voltage stress of switching devices and capacitors and improve the voltage derating capability significantly. The main idea is to build high voltage with multiple low voltage stacks instead of single high voltage capacitors, so that SiC MOSFETs can be applied with improved voltage margin. The method is to charge the stack-capacitors in parallel with fast charging speed, and discharge in series for high pulse voltage. The converter operates at higher switching frequency, which reduces the weight and size of the magnetic components. A 300-kHz prototype with 18-28 V input and 1 kV/ 100 A output was built using 650 V SiC devices, demonstrating 75% reduction of the voltage stress of the capacitors and power devices compared with the conventional converters.