Design and implementation of a bidirectional isolated Ćuk converter for low-voltage and high-current automotive DC source applications

This paper presents the design guideline of a bidirectional isolated Ćuk converter with an active-snubber circuit, which is used as a cell level tester for multiple automotive dc energy storage devices (ESDs), such as ultracapacitors, Li-ion batteries, and NiMH batteries. The converter interfaces those automotive dc ESD cells with 24-V dc systems, and it realizes bidirectional power flow with two main switches. Based on the ratings of those dc ESD cells, the designed converter operates at a very low voltage range, i.e., from 1.5 to 6 V, with current as high as 300 A. The detailed operation principle and major features, such as soft switching and energy recovery, are analyzed under continuous current mode. Based on the analysis, the design guideline of the dc-dc converter is presented. A 1.2-kW laboratory prototype has been built and tested with full power rating. Both simulation and experimental results are presented to verify the analysis.