A bi-directional DC-DC converter topology for low power application

This paper presents a bi-directional DC-DC converter for use in low power applications. The proposed topology is based on a half-bridge on the primary and a current fed push-pull on the secondary side of a high frequency isolation transformer. Achieving bi-directional flow of power using the same power components provides a simple, efficient and galvanically isolated topology that is specially attractive for use in battery charge/discharge circuits in DC UPS. In the presence of the DC mains (provided by the AC mains), the converter essentially operates in the buck mode to power the load and charge the battery. On failure of the DC mains, operation is comparable to that of a boost converter and the battery supplies the load power. Small signal and steady state analyses are presented for this specific application. Design guidelines for a laboratory prototype are included. Experimental results validate and evaluate the proposed topology.