Characterization of gan transistors and developmentof bi-directional dc/dc converter with half-bridgehaving short circuit protection for parallel switches

Karakaya, Furkan
Wide band-gap semiconductors are superior to Si-based semiconductors with their increased electron mobility and breakdown strength which leads to small package sizes, low parasitics, and increased switching frequency capability. Efficient and dense power converter could be obtained with wide band-gap devices especially GaN transistors. This thesis investigates the GaN HEMTs in terms of their characterization and pplication. The gate charge and output capacitance of GaN HEMTs are characterized by designed experimental setups and they are compared with manufacturer-provided data. The differences between outcomes and the datasheet are highlighted and explained. Based on the characterized elements of GaN HEMTs, their switching performance is studied within a simulation platform and effects of package capacitances, parasitic inductances, temperature, gate resistance are discussed. A half-bridge prototype design is performed where layout optimization is done for a parallel-connected GaN HEMTs. Moreover, a short circuit protection technique is implemented on the same half-bridge board to save GaN HEMTs from overcurrent and increase the reliability. The short circuit protection method is able to detect the fault in 40 ns and can control the short circuit current in 100 ns. Lastly, an example application is realized with GaN HEMT based half-bridges to have a bi-directional DC/DC converter. The bi-directional DC/DC converter has 5.4 kW power rating with 5.24 kW/l power density. This power density is achieved with 450 kHz of switching frequency where zero voltage switching is applied with critical conduction mode switching. The efficiency of the converter is 97.7% at maximum load.


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Citation Formats
F. Karakaya, “Characterization of gan transistors and developmentof bi-directional dc/dc converter with half-bridgehaving short circuit protection for parallel switches,” M.S. - Master of Science, Middle East Technical University, 2020.