Papers by Author: Dominique Bergogne

Abstract: Silicon Carbide (SiC) Junction-Field Effect Transistors (JFETs) are attractive devices for power electronics. Their high temperature capability should allow them to operate with a reduced cooling system. However, experiments described in this paper conclude to the existence of runaway conditions in which these transistors will reach destructive temperatures.

Abstract: This paper presents a study on a SiC JFET leg of a 3-leg Voltage Source Inverter (VSI). The switching curves obtained with the JFET working in free wheeling mode are shown to point out drain-to-gate interaction effects. Indeed, during the drain-source voltage variations, the JFET gate-source voltage can have considerable variations, because of the electrical coupling induced by the gate-drain capacitance Cgd. When the gate-source voltage variation becomes too negative, there is a risk of occurrence of the phenomenon of punch-through in the gate-source junction. Conversely, when it is enough positive, the JFET may conduct and lead to a leg short-circuit. To decrease these undesired effects for the JFET legs and consequently for the SiC JFET inverter, an external gate-source capacitor is used. This solution is studied and optimized by simulation on an inverter leg.

Abstract: A novel experimental set-up is developed and validated to characterize high voltage diodes in transient switching mode. Parameters extracted from DMTVCA and OCVD techniques, like ambipolar lifetime, epilayer thickness and doping level, diode area, are validated in a buck converter with resistive load. The experimental set-up allows to measure the current and voltage transient characteristics without noise and influence of high parasitic wiring. Experimental results are compared with device simulations and a good correlation is found.