GaN Devices Based Integrated Two-Stage DC-DC Converter with Voltage Regulation

A four-switch Buck-Boost (FSBB) + half bridge LLC integrated two-stage DC-DC converter is analyzed and improved in this paper. This converter saves two power switches by half bridge multiplexing (HBM). The phase shift control strategy is proposed to eliminate DC bias magnetic of transformer and asymmetrical current of synchronous rectification MOSFETs caused by HBM. In addition, ZVS is achieved in FSBB stage. The operation principle and characteristics of the presented control strategy are analyzed in details, and verified on a 360V-440V input 24V/400W output experimental prototype. Power density and efficiency get higher by using GaN-based high electron mobility transistor (GaN-HEMT), which are up to 96.2% and 112W/in3 respectively.