Research On High Speed Switching Characteristics And Application Of Enhanced GaN Devices

At present,traditional silicon(Si)devices cannot meet the rapid development of power electronic converters.The emergence and wide application of wide bandgap power devices have increased the switching frequency of converters to megahertz,thereby increasing efficiency and power density.Among the wide bandgap power devices,the Enhanced-mode Gallium Nitride High Electron Mobility Transistor(Emode GaN HEMT)stands out with its excellent performance,but there are still many problems in practical applications.This article will start from the characteristics of the enhanced GaN HEMT,and conduct related researches on the oscillation problem of its switching process and its application in hard switching and soft switching.First,the on-state characteristics,resistance characteristics and dynamic characteristics of the enhanced GaN HEMT are analyzed,and compared with Si MOSFETs and cascode GaN HEMTs at similar power levels to clarify their specific advantages.Build a dual-pulse experiment platform to further test and study the turnon and turn-off process of the enhanced GaN HEMT.Secondly,based on the analysis of the dynamic characteristics of the enhanced GaN HEMT,the main factors affecting its switching process are systematically studied,and the mechanism of the voltage and current oscillations caused by the parasitic parameters of the drive circuit and power circuit at high frequencies is explained,aiming at different spikes and oscillations.The problem studies optimization schemes and suppression measures,and clarifies the priority of optimizing parasitic parameters in practical applications.Finally,the enhanced GaN HEMT is applied to the hard-switching topology,and the negative voltage turn-off drive design and passive device selection schemes are given according to the design parameters.The analysis model is established to study the loss in the hard-switching,and a synchronous machine is built.The Buck principle prototype verifies the correctness of the design scheme and analysis model,and clarifies that the switching loss accounts for the largest proportion in the hard switching technology,which restricts the converter’s further improvement to high-frequency efficiency.Subsequently,the enhanced GaN HEMT was applied to the soft switching technology of half-bridge LLC resonant converters,and the zero-voltage turn-off drive was optimized.The effectiveness of the measures was verified through experiments.At the same time,the soft switching technology was combined with the enhanced GaN HEMT the efficiency of the converter can be further improved.