Improvement of light-load efficiency by using a six-arm converter with series-parallel switching

This paper proposes a DAB converter using two transformers as a method to improve the efficiency in the light-load region when the output voltage fluctuates. In the proposed circuit, in addition to the operation mode of the conventional DAB converter, there exist three other operation modes initiated by switching the connection of these transformers as series or parallel. In the proposed circuit, the transformer-applied voltage can be changed and efficiency can be improved by switching between series-parallel, conventional, and parallel operations according to the input/output voltage ratio. The experimental results confirmed that for the input/output voltage ratios of 1.9 and 0.25, the conversion efficiencies were 96%, and 90%, respectively, the phase difference of 30◦ as the light-load condition. © 2020 The Institute of Electrical Engineers of Japan.