High-Power-Density GaN-Based Single-Phase Online Uninterruptible Power Supply

This paper introduces a new topology suitable for a high-power-density single-phase online uninterruptible power supply (UPS) with a common neutral between its input and output ac ports while avoiding a split dc bus. The proposed topology enables high power density by utilizing half-bridge switch structures compatible with MHz-frequency operation. High efficiency is maintained in this converter by achieving softswitching in rectifier stage with a boundary conduction mode control strategy. A comprehensive design methodology is developed to optimize the design of this converter. A 1-kVA prototype online UPS based on the proposed topology that utilizes GaN transistors and operates at switching frequencies up to 2 MHz is built and tested. The prototyped UPS achieves a power density of 26.4 W/m(3).