Desat Protection With Ultrafast Response for High-Voltage SiC MOSFETs With High dv/dt

Abstract

This article presents a desat protection scheme with the ultrafast response for high-voltage (>3.3 kV) SiC MOSFETs. Its working principle is the same as the conventional desat protection designed for high-voltage SiC MOSFETs, yet its blanking time is implemented by fully considering the influence of high negative dv_ds/dt during the fast turn- on transient. With the same circuitry as the conventional desat protection, the proposed protection scheme can significantly shorten the response time of the desat protection when it is used to protect high-voltage SiC MOSFETs. In addition, the proposed protection scheme with ultrafast response features strong noise immunity, low-cost, and simple implementation. By taking advantage of the high dv/dt during the normal turn- on transients, the proposed protection scheme can be even faster when the MOSFET has a faster switching speed. Design details and the response speed analysis under various short circuit faults are presented in detail. A half bridge phase leg based on discrete 10 kV/20 A SiC MOSFETs is built to demonstrate the proposed protection scheme. Experimental results at 6.5 kV validate the ultrafast response (115 ns response time under a hard switching fault, 155 ns response time under a fault under load), and strong noise immunity of the proposed desat protection scheme.