Research On Characteristics Of SiC Power Devices And Their Applications In Buck Converter

The continuous development of improved power semiconductors is a key enabling factor forpropelling the constantly increasing demand for higher system performance in many power electronicapplications, for instance, aviation, electric vehicle and new energy technology. The silicon carbide(SiC) based device technology has the potential to break through many of the current limitationsassociated with silicon electronics, in particular, the limitations of switching speed, junctiontemperature, and power loss.The SiC-based power devices should not be simply considered as high voltage power devices; thereare some differences in characteristics when compared. These differences need to be carefullyaddressed to get maximum benefit from the SiC power devices, especially the differences in switchingcharacteristics. In this paper, the dynamic and static characteristics of SiC schottky barrier diode (SBD)and MOSFET are analysed in detail, and the differences compared to silicon-based power devices arediscussed. Then, on-resistance test circuit and double pulse dynamic test circuit are designed and built,and the main characteristics and parameters of SiC power devices are measured and compared.In an actual converter using the phase-leg configure, high dv/dt during fast switching transient ofone device will affect the operating behavior of its complementary device (crosstalk). This thesisanalyses the mechanism causing crosstalk interference, and expounds the importance of crosstalksuppression considering the special characteristics of SiC MOSFET. Prior reported methods forcrosstalk mitigation are introduced, and they are tested and analysed in SiC MOSFET based doublepulse test circuit. After that, the traditional active miller clamped circuit is optimized andexperimentally verified.In the end, loss analysis of the power devices in Buck converter is investigated in detail, and theefficiency superiority of SiC power devices is indicated when compared to Si counterpart. Then, a1kW Buck converter prototype and the experimental verification are completed. Besides, with thesame efficiency of Buck converter, the decrease in volume/weight of passive components by usingSiC devices is discussed.