Bidirectional Isolated Hexamode DC-DC Converter

The proposedisolated buck-boost series resonant dc-dc converter contains two full-bridge hybrid switching cells capable of half-bridge operation. This feature is regarded as topology morphing control. Voltage buck regulation requires special modulations applied to the primary-side hybrid switching cell. In contrast, voltage boost regulation requires special modulations for the secondary-side hybrid switching cell. Combining the topology morphing control with the buck-boost regulation capability, a novel dc-dc converter operating in six different modes was derived. Moreover, the converter is capable of bidirectional operation. This article describes the influence of the topology morphing control on the dc voltage gain of the converter, which results in three boost and three buck modes. The six modes are described, and equations for the converter's dc voltage gain are provided. Based on the selected design guidelines for the power part and the control system, a 350-W prototype was designed and built. Experimental results confirm the theoretical expressions for the converter's dc voltage gain. Experimental efficiency is provided in a wide input voltage range for both energy transfer directions. Operating points with the highest thermal stress of components are analyzed with corresponding power loss breakdown calculations, confirming the measured thermal results.