With the development of DC power distribution technology

DC transformer has attracted enough attention. Its efficiency and power density are the main technical problems at present. Therefore

based on the power electronicpowerconversiontopology

it is necessary to study high frequency and soft switching topology suitable for multioperating and wide voltage range conditions. In this paper

an isolated multi-resonant DC/DC converter based on variable structures and multi-mode operations is proposed. The converter uses auxiliary switches to control the resonant tank for exhibiting adaptive resonance characteristics in different application scenarios. When high voltage gain is needed

the dual transformer multi-resonance converter（MRC）topology is adopted

while a five-element MRC topology is required in rated state to achieve high efficiency. Thanks to the variable structure multi-mode operation topology

the converter has a wide voltage gain range and always maintains a high efficiency. These characteristics make the converter very suitable for DC distribution system applications. Finally

the performance of the prototype is tested. The input voltage is from 80 V to 600 V

and the output voltage stays 400 V constantly. The peak efficiency is97.5% in the whole gain range.