Research On Characteristics And Application Of GaN Device

ABSTRACT:With the advance of power electronic technology, small power switch power supply develops toward high frequency and miniaturization, and demand is growing for high efficiency and high power density. As the new generation semiconductor device, GaN power semiconductor device arises at the historic moment, and has the tendency to replace Si power semiconductor device, which gradually achieve its theoretical limit. Recently, enhancement mode GaN transistors are promoted in the field of power electronics. For this new type of the third generation wide band gap device, its characteristics are similar to the traditional MOSFET of Si material, while there are also some differences. GaN transistors can work at high frequency theoretically and get considerable high efficiency. This paper aims to study characteristics of enhancement mode GaN transistor, compared with Si MOSFET. Finally, with a target of high efficiency and miniaturization, its application characteristics in high frequency circuit LLC resonant converter will be researched, and the effects on circuit which are brought by high frequency and the corresponding solutions will be studied.The main research object of this paper is the monomer enhancement mode GaN transistors by EPC Company. First, the development and current situation of the GaN devices are introduced, whose characteristics and advantages are then summarized. LLC resonant converter is selected as the study topology to research application characteristics of enhancement mode GaN transistor. Second, the static and dynamic characteristics of enhancement mode GaN transistor are studied, compared with Si MOSFET, and the characteristic tests are made. Third, the influence of stray parameters on the high frequency drive circuit is theoretically analyzed. High frequency drive circuit which is suitable for enhancement mode GaN transistor is designed, and the optimization design of PCB layout is carried out. Then device loss analyses in GaN transistors based and MOSFET based200kHz LLC resonant converter are done and output diodes, dead time and main circuit PCB layout are optimized. Finally, to reduce the prototype volume and operate at a higher frequency, a500kHz LLC resonant converter with synchronous rectification based on optimized PCB is designed. Simulation and experiments are made to verify the application characteristics of GaN transistor. To improve circuit efficiency, some optimizing measures, such as optimizing planar transformer structure and dead time are taken, and experiments are done to verify the effectiveness of these measures.