Analysis and Design of a Partial Power Processing Architecture for High Step-Up Applications

Combining the advantageous features of the traditional two-stage and input-parallel-output-series structure, this article proposes a partial power connection method for step-up applications with the advantages of wide input voltage range, galvanic isolation and partial power voltage regulation. In the proposed structure, the nonisolated dc-dc converter handles a small portion of the total power to regulate the system output voltage by simple pulsewidth modulation control. The latter stage should be a full bridge structure and the partial power processing is realized with different input voltages of the two bridge arms, which is beneficial to reduce the total number and cost of components, and two connection architectures are achieved in this way. The operation characteristics of the two architectures are analyzed in detail in this article, and an optimal structure is obtained from the perspective of fewer components and better partial power processing capacity. Furthermore, an isolated full bridge dc-dc converter with secondary resonance is selected to operate at the unregulated state as an application case to verify the feasibility and advantages of the proposed structure. An experimental prototype with 32-40 V input voltage range and 400 V/ 0.5 A output is built with 1 MHz switching frequency. The peak measured efficiency at 40 V full load is 95.3%.