A Low-Profile (1U) Server Level High-Power-Density Online Uninterruptible Power Supply (UPS)

This paper introduces a control architecture and design methodology for a novel low-profile (1U
$\overset{\text{def}}{=} 1.75$
inch height) server-level online Uninterruptible Power Supply (UPS). The novel online UPS 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 soft-switching in rectification and inversion stages with a Triangular Current Mode (TCM) control strategy. A comprehensive design methodology is developed to optimize the design of this converter to achieve low-profile and high-power-density while ensuring low losses. A 1-kVA prototype low-profile (1U) online UPS operating at switching frequencies up to 2MHz is designed, built, and tested. The prototyped online UPS achieves a power density of 60.4 W/in
³
. The inversion stage of the low-profile online UPS achieves a peak efficiency of 98.8%.