Merits of SiC MOSFETs for high-frequency soft-switched converters, measurement verifications by both electrical and calorimetric methods

ABSTRACT

This paper quantifies the soft switching loss of a 1.2 kV SiC MOSFET module via a calorimetric method in a 78 kW full-bridge resonant inverter switched at approximately 200 kHz. By switching the SiC MOSFET just before the zero crossing of the current during turn-off and at perfect zero voltage during turn-on, this converter yielded an efficiency of roughly 99 %. Then, a simplified laboratory setup, including only a half-bridge series resonant inverter topology with split DC-link capacitors and an LC load, was built such that a real inverter operation was emulated, and thereby, turn-off loss was measured via an electrical method. A discrepancy of approximately 10 % is found between the two loss measurement methods, and the possible source for this difference is discussed. Furthermore, a standard double pulse test was also performed in an inductive clamped buck converter for measuring the hard switching loss. Finally, a comparison of losses obtained from the hard versus resonant topologies at the same load current was accomplished, which verifies the substantial benefits of the latter over the former. Thus, the merits of SiC MOSFETs for high frequency soft switched converters are demonstrated, which is the main contribution of this paper.

KEYWORDS:

• Silicon Carbide (SiC)
• MOSFET
• resonant converter
• conduction losses
• switching losses
• soft switching
• hard switching
• efficiency

Acknowledgments

The authors would like to thank The Research Council of Norway and 6 industry partners who sponsor this project: EFD Induction, Siemens, Eltek, Statkraft, Norwegian Electric Systems, and Vacon.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by The Research Council of Norway, EFD Induction, Siemens, Eltek, Norwegian Electric Systems, and Vacon.

Notes on contributors

S. Tiwari

S. Tiwari pursued her MSc in Electric Power Engineering in 2011 from the Norwegian University of Science and Technology. She started her PhD at the same department from April 2015. Her focus is on Silicon carbide Power Semiconductor Devices in an application level. Before starting her PhD she worked at Wärtsilä Norway AS as a Specialist Engineer at the Department of Power Electronics Development. Her research interests are power electronic converters and designs, gate drivers, snubbers and semiconductor devices.

J. K. Langelid

J. K. Langelid received his MSc in Electric Power Engineering in 1990 from the Norwegian University of Science and Technology. He worked at Akershus Energy Plant ELVA Induction before he started job at R & D department of EFD Induction AS in Skien, Norway. His research interest include power electronics, gate drivers, snubbers and new power semiconductor devices, especially for induction heating applications.

T. M. Undeland

T. M. Undeland is em. Professor at the Department of Electric Power Engineering at the Norwegian University of Science and Technology. He has been a professor at the Department since 1984. He has co-written the book Power Electronics: Converters, Applications, and Design. Dr. Undeland was the Chairman of the EPE 1997 conference, Trondheim, and was Vice President of EPE. He was active as IEEE Power Electronics Society, where he also has been a Distinguished Lecturer. His research interests are power converters, snubbers, and control in power electronics.

O.-M. Midtgård

O.-M. Midtgård is Head of Department at the Department of Electric Power Engineering at the Norwegian University of Science and Technology. He has been a professor at the Department since 2012. Midtgård has broad research interests, which include Smart Grids, PV applications, power electronics, and electromagnetic computations.