New technique cuts costs of SiC high-voltage switches

Connecting several silicon-carbide MOSFETs in series may be a relatively inexpensive way of fielding high-performance power switches. So say researchers at North Carolina State University’s FREEDM Systems Center.

The topology for the new power switches is called the FREEDM Super-Cascode. It combines 12 smaller SiC power MOSFETs in series to reach a power rating of 15 kV and 40 A. It requires just one gate signal for turn -on and off, making it less complicated than IGBT series connection-based schemes, researchers say. The power switch is also said to operate over a wide range of temperatures and frequencies because it dissipates heat efficiently.

Commercially available SiC devices top out at 1.7 kV. The FREEDM Super-Cascode is expected to help make practical the development of power switches in large quantities with breakdown voltages from 2.4 kV to 15 kV. The findings could lead to early applications in power converters for medium-voltage drives, solid-state transformers and high-voltage circuit breakers.

Researcher Xiaoqing Song, a Ph.D. candidate at the FREEDM Systems Center, described the FREEDM Super-Cascode switch at the IEEE Energy Conversion Congress & Exposition (ECCE 2016) in Milwaukee from Sept. 18-22, 2016.