Gate driver circuit with all-magnetic isolation for cascode-connected SiC JFETs in a three-level T-type bridge-leg

This article presents a gate driver circuit with all-magnetic isolation for driving SiC power devices in a three-level T-type bridge-leg. The gate driver circuitry used with SiC devices has to be tolerant of rapid common-mode voltage changes. With respect to the resultant potentially problematic common-mode current paths, an arrangement of transformers is proposed for supplying the power devices with drive signals and power for their local floating gate driver circuits. The high-frequency carrier phase-switching technique is used to reduce the number of transformers. Signal timing and other implementation issues are addressed when using this arrangement with the T-type converter. The circuit is demonstrated in a 540 V bridge-leg constructed around 650 V and 1200 V cascode-connected normally-on SiC JFETs.