Capacitively isolated multicell DC-DC transformer for future dc distribution system

Abstract

This paper proposes a new capacitively isolated multicell dc-dc transformer (dcx). The proposed dcx consists of dc-dc cell converters with pairs of isolation capacitors that substitute for high frequency transformers. The capacitively isolated cell converter achieves higher efficiency compared with the conventional inductively isolated dc-dc converter because of no transformers. The multicell approach also accomplishes the various voltage transformation ratios based on the input-series-and-output-parallel and input-parallel-and-output-series connections of the cell converters, overcoming the drawback of the capacively isolated converter with the fixed voltage transformation ratio. The analysis of the isolation voltage-sharing across the capacitors was conducted to show the feasibility of the proposed multicell dcx. The prototype of the 96V-24V, 200W dcx using two 48V-24V, 100W capacitively isolated dc-dc cell converters was also fabricated to confirm the validity of the analysis. The proposed approach contributes to the achievement of highly efficient and scalable power converters to realize future low-carbon societies.