Advanced Gate Driving Techniques and Inverter Design Considerations of Wide-Band-Gap Devices

The continuous demand for higher power density and better efficiency to reduce the global energy consumption, is the driving force to introduce new semiconductor technologies. Wide-band-gap (WBG) material based devices such as gallium nitride high electron mobility transistors (GaN HEMTs) and silicon carbide metal-oxide-semiconductor field-effect transistors (SiC MOSFETs) are considered promising candidates for replacing conventional silicon MOSFETs, mainly because of their capabilities of higher switching frequencies with less switching and conduction losses. Although WBG devices can largely improve the conversion efficiency, the implementation of WBG devices brings in some challenges in power converter design. Firstly, the high voltage changing slew rate of WBG devices introduces a distortion current to the gate through the coupling capacitance of the device. The distortion current may cause mis-trigger or overvoltage breakdown of the device gate. This issue is so-called crosstalk effect. This dissertation proposes a multilevel gate driving profile to address this issue. Secondly, due to the gate-to-substrate voltage bias, the integration of multiple GaN devices suffers from the high on-state resistance. This issue is so-called current collapse or electron trap. This dissertation proposes a gate current injection method to address this issue. By injecting relatively large gate current at specific time period, the on-state resistance is largely improved at both hard-switching and soft-switching scenarios. Thirdly, series connection of switches is an effective way to achieve higher blocking voltage of the device. The serial connection of WBG devices suffers from the dynamic voltage unbalance and short-circuit protection issues. The additional short-circuit scenarios are found in the series-connected devices, which are not covered by the traditional short-circuit protection scheme. Dynamic voltage sharing problem is addressed using porposed current source gate driver. Besides, the short-circuit protection circuit is integrated in the proposed gate driver to cover all the short-circuit scenarios of series-connected devices. Finally, this dissertation uses a practical converter design example to comprehensively elaborate the design considerations of WBG based converters. A 1.5 MHz/ 2 kV/ 80 A commercial burst-mode inverter using SiC MOSFETs is designed for electromagnetic acoustic transducer. This inverter design includes comprehensive fault protection, hardware and controller design.