A bidirectional isolated DC/DC converter as a core circuit for 3.3-kV/6.6-kV power conversion systems in the next generation

This paper describes a bidirectional isolated DC/DC converter considered as a core circuit for next-generation 3.3-kV/6.6-kV high-power-density power conversion systems. The DC/DC converter is intended to use power switching devices based on SiC and/or GaN, which will be available on the market in the near future. A 350-V, 10-kW, and 20-kHz DC/DC converter is designed, constructed, and tested in this paper. It consists of two single-phase full-bridge converters with the latest trench-gate Si-1GBTs and a 20-kHz transformer with a nano-crystalline soft-magnetic material core and litz wires. The transformer plays an essential role in achieving galvanic isolation between the two full-bridge converters. The overall efficiency from the DC-input to DC-output terminals is accurately measured to be as high as 97%, excluding gate drive circuit and control circuit losses from the whole loss. Moreover, loss analysis is carried out to estimate effectiveness in using SiC-based power switching devices. The loss analysis clarifies that the use of SiC-based power devices may bring a significant reduction in conducting and switching losses to the DC/DC converter. As a result, the overall efficiency may reach 99% or higher. (C) 2008 Wiley Periodicals, Inc.