A ZVS Branch-Sharing Partial Power Converter with Bipolar Voltage Regulation Capability

The isolated input-parallel-output-series (IPOS) partial power converter (PPC), which is composed of a dc transformer (DCX) cell and a voltage regulation (VR) cell, is regarded as a promising solution for dc distribution power systems for only a partial power is delivered by the VR cell under different voltage conditions. In this paper, a branch-sharing IPOS-PPC with bipolar voltage regulation capability is proposed, which is composed of two cells: 1) A half-bridge LLC resonant cell works at fixed switching frequency as a DCX with desired performance to realize isolation and main power conversion. 2) An auxiliary full-bridge/push-pull (FB/PP) cell is applied to realize the bipolar voltage regulation and the rest partial power conversion. Two cells share the lagging-leg of FB/PP cell to guarantee zero voltage switching (ZVS) in the whole load range from zero to full load. Compared with the traditional unipolar voltage regulation VR cell, the FB/PP cell can not only reduce the power processed by itself within the same voltage regulation range, but also reduce the component count and achieve a compact structure. Finally, a 180-300 V/ 48 V/ 1 kW experimental prototype is built to verify the feasibility and advantages of the proposed converter.