A 1 MHz eGaN FET based 4-switch buck-boost converter for automotive applications

This paper presents the development of a 1 MHz enhancement mode GaN (eGaN) FET based 4-switch buck-boost converter with bootstrap driver for automotive applications. Conventionally, with Si MOSFETs, it is difficult to optimize the efficiency of a 4-switch buck-boost converter since the high side switches need to switch at high frequency or completely conduct the output/input current in either buck or boost operation mode. GaN FET with much lower Figure of Merit provides the possibility to achieve high efficiency of 4-switch buck-boost converter at MHz switching frequency. This paper investigates the challenges of using bootstrap driver in MHz 4-switch buck-boost converter, and presents associated solutions. A 6-45Vin, 10V/7A, 1 MHz eGaN FET based 4-switch buck-boost converter is built and measured high conversion efficiency confirms the superior performance with GaN FET.