Silicon carbide junction field effect transistors applied to solid-state power modulators

A new generation of power semiconductor devices is emerging based on the maturation of semiconducting silicon carbide. In this paper, alternatives to the divider resistors are presented using newly available 600-V, 2-A SiC JFETs. Two configurations are possible. The first employs a series combination of JFETs with shorted gate-source terminals operating as current limiting diodes. This allows a greater voltage to be blocked by the IGBT than can be blocked by currently available SiC JFETs. The superior thermal properties of SiC JFETs permit the larger bias currents required to drive the large IGBT gate capacitance at high repetition rates to be sourced. The second configuration is highly efficient and avoids thermal loading of the SiC JFET. The SiC current limiting diodes are replaced by a single SiC JFET switched concurrently with the IGBT. This configuration requires the SiC JFET to block the full voltage blocked by the IGBT, a capability expected in later generations of SiC JFETs. The gate drivers demonstrated in this paper are also applicable to power modulators using large arrays of silicon power MOSFETs. The near-term prospect for very fast SiC JFETs as replacements for silicon MOSFETs in power modulators is also discussed