Controllable dυ/dt behaviour of the SiC MOSFET/JFET cascode an alternative hard commutated switch for telecom applications

摘要

Switching devices based on SiC offer outstanding performance with respect to operating frequency, junction temperature and conduction losses and enable a significant improvement of the system performance. There, the cascode consisting of a MOSFET and a JFET additionally has the advantage of being a normally off device and offering a simple control via the gate of the MOSFET. Without dv/dt control, however, the transients with hard commutation reach values of up to 45 kV/¿s, which could lead to EMC problems and especially in drive systems to problems related to earth currents (bearing currents) due to parasitic capacitances. Therefore, new dv/dt control methods for the SiC MOSFET/JFET cascode as well as measurement results are presented in this paper. Based on this new concepts the outstanding performance of the SiC devices can be fully utilised without impairing EMC.