Silicon Carbide High-Voltage Switch

January 1, 2018

North Carolina State University, Raleigh, North Carolina

High-voltage wide bandgap (WBG) semiconductor devices like 15-kV silicon carbide (SiC) MOSFETs have attracted attention because of potential applications in high-voltage and high-frequency power converters. These devices, however, are not commercially available, and their high cost due to expensive material growth and fabrication may limit their widespread adoption in the future.

A high-voltage and high-frequency SiC power switch was developed that could cost much less than similarly rated SiC power switches for applications in the power industry, especially in power converters like medium-voltage drives, solid-state transformers, and high-voltage transmissions and circuit breakers.

Wide bandgap semiconductors show tremendous potential for use in medium-and high-voltage power devices because of their capability to work more efficiently at higher voltages. Currently, though, their high cost impedes their widespread adoption over the prevailing workhorse and industry standard — insulated-gate bipolar transistors (IGBT) made from silicon — which generally works well, but incurs large energy losses when they are turned on and off.

The new SiC power switch could cost approximately one-half the estimated cost of conventional high-voltage SiC solutions. Besides the lower cost, the high-power switch maintains the SiC device’s high efficiency and high switching speed characteristics. In other words, it doesn’t lose as much energy when it is turned on or off.

The power switch, called the FREEDM Super-Cascode, combines 12 smaller SiC power devices in series to reach a power rating of 15 kilovolts (kV) and 40 amps (A). It requires only one gate signal to turn it on and off, making it simple to implement and less complicated than IGBT series connection-based solutions. The power switch is also able to operate over a wide range of temperatures and frequencies due to its proficiency in heat dissipation, a critical factor in power devices.

For more information, contact Alex Huang at This email address is being protected from spambots. You need JavaScript enabled to view it.; 919-513-7387.