Investigations on a Semiconductor Switching Array Based on COTS SiC MOSFET Devices

We report on the development of a switching array based on commercially off-the-shelf (COTS) silicon-carbide (SiC) MOSFET devices. In the first step, preparatory investigations for series and parallel arrangement of the SiC MOSFETs were carried out. A switching module consisting of ten SiC MOSFETs of type C3M0075120K by Wolfspeed in series with an inductive galvanic isolation between the gate driver and SiC MOSFETs was designed and built. Each one of the ten SiC MOSFETs has its own gate control circuit to minimize turn-on time. It was successfully tested up to a switching voltage of 10.0 kV, reaching a current turn-on time of 20 ns at a drain current of 39.7 A. The studies on parallel arrangement dealt with the question of how many SiC MOSFETs per gate driver constitute a good compromise between switching speed and technological complexity. The realized switch consisted of 12 Wolfspeed C3M0075120K SiC MOSFETs in parallel, grouped in units of four per gate driver. The switch was successfully tested up to a charging voltage of 0.81 kV on a resistive load of
$0.8~\Omega $
. The resulting switch current was 1.01 kA; the turn-on time was 11 ns. The next step was the development of a test board, which could be equipped with up to 12 MOSFETs in series and 12 MOSFETs in parallel. Hence, the maximum possible number of SiC MOSFETs would be 144, arranged in a (
$12\times12$
) array. The principle of implementation of the inductive galvanic isolation, now placed between the gate control circuit and gate driver, and of the dedicated power supply solution for the gate driver will be discussed. Equipped with 40 Wolfspeed C3M0075120K SiC MOSFETs in a (
$10\times4$
) array, a drain current of 416 A was switched at 10.4-kV charging voltage. The current rise time was 42 ns. Furthermore, the scalability to higher switching voltages was investigated. Two test boards were stacked to a 20-kV switching module, which required further adaptation of the power supply of the gate driver. The switch was tested up to 20.9 kV. The turn-on time was 17 ns at a drain current of 20 A. Finally, a second 20-kV switching module was built, and the now available two modules were used as closing switches for a two-stage semiconductor Marx generator. The Marx reached an output voltage of 28 kV and a voltage rise time of 27 ns at a load current of 60 A.