A bidirectional dc-dc converter topology for low power application

This paper presents a bidirectional de-de converter for use in low power ap plications. 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 isola tion transformer. Achieving bidirectional flow of power using the same powe r components provides a simple, efficient and galvanically isolated topolog y that is specially attractive for use in battery charge/discharge circuits in de UPS. The de mains (provided by the ac mains), when presented, powers the down stream load converters and the bidirectional converter which esse ntially operates in the buck mode to charge the battery to a nominal value of 48 V,On failure of the de mains (derived from the ac mains), the convert er operation is comparable to that of a boost and the battery regulates the bus voltage and thereby provides power to the downstream Converters. Small signal and steady state analyzes are presented for this specific applicati on. The design of a laboratory prototype is included, Experimental results from the prototype, under different operating conditions, validate and eval uate the proposed topology An efficiency of 86.6% is achieved in the batter y charging mode and 90% when the battery provides load power, The converter exhibits good transient response under load variations and switchover from one mode of operation to another.