Research On Losses Of Wide Bandgap Power Device

Compared with traditional silicon (Si) devices, wide bandgap power semiconductor devices have more excellent performances. The application of silicon carbide (SiC) and gallium nitride (GaN) devices is becoming more and more widely, and they may become the next generation power devices, as an alternative to Si devices. At present, the research on the performance of wide bandgap power devices is not mature, and it is not possible to compare the characteristics of GaN, SiC and Si devices based on datasheet because the values in datasheet of different maufactures are tested under different test conditions while some of the values are not available. The biggest challenge in the application of wide bandgap power devices is that the influence of parasitic parameters on the device characteristics is more significant under high switching speed. In order to analyze the influence of parasitic parameters on the switching characteristics, the analytical model of wide bandgap power devices is needed, but the research of analytical model suitable for a high voltage GaN transistor in cascode configuration is far from mature.In this paper, the SiC MOSFET, GaN transistor and Si devices are tested, compared with each other and analyzed under different conditions from the point of view of power loss. Firstly, the conduction and switching characteristics of SiC MOSFET, GaN transistor and Si devices are tested under different values of driving voltage, gate resistor, current and temperature. Then, the conduction loss and switching loss are calculated and the relationship among driving voltage, gate resistor, current, temperature and power loss is discussed. Additionally, the working conditions of different power devices in the inverter application are analyzed and the total device losses are calculated by means of simulation and experiment. Besides, because the surge voltage of GaN anti-parallel diode is very high when it turns off, and the threshold voltage of GaN transistor is low while the driving loop is sensitive to noise, special care should be taken when GaN transistor is used. Finally, an analytical model of GaN transistor in cascode configuration is presented. Based on the analysis of the PCB and package parasitic inductances and the junction capacitors of the cascode GaN transistor, the time domain expressions of voltage and current in the switching process are illustrated. Moreover, the switching waveforms and energy losses are further obtained accordingly. The accuracy of the proposed model is validated by experimental results.