Characteristics of SiC MOSFET and its application in a phase-shift full-bridge converter

With the outstanding advantages of SiC MOSFET, which has lower junction capacitance, low-on-state resistor and high junction operating temperature compared to a Si devices, the converter can achieve a high-frequency and high-efficiency. This increases the power density with smaller volume of passive components and reduced cooling requirements. However, in the phase-leg configuration, high dv/dt will worsen the interference between the two devices during a switching transient (i.e., crosstalk). Unfortunately, SiC power devices are more easily affected by crosstalk than Si devices due to their intrinsic properties. To utilize the full potential of fast SiC devices, a novel and cost-effective gate assist circuit for crosstalk supression is proposed in this paper. Besides, with the increase of power density, the thermal design is increasingly becoming the key factor that affects the reliability of converters. Thus, the thermal model of the phase-shift full-bridge converter (PSFBC) is established. The simulation and experimental results are in good agreement, which testifies the accuracy of thermal model. The efficiency of 2kW PSFBC based on Si and SiC MOSFETs under different loads is also measured and compared in this paper.