Analysis of a bi-directional DC-DC converter topology for low power application

This paper describes a bidirectional DC-DC converter for use in low power applications. The converter is based on a half-bridge in the primary side and on a current fed push-pull in the secondary of a high frequency isolation transformer. In the presence of the DC mains (provided by the AC mains), the converter essentially operates in the buck mode charging the battery. On failure of DC mains the converter operates in the boost mode and thereby the battery supplies the load power. The simple, low part count, galvanically isolated proposed topology provides an attractive solution for use in battery charge/discharge circuits in a DC UPS. Small signal and steady state analysis of both modes of converter operation is shown. Design guidelines are also presented. The concept is evaluated by an experimental setup and key results are presented.