阐述了三电平DC/DC变换器的发展过程,介绍了其研究焦点的变化:从软开关技术和效率方面转变到性能可靠方面.在此基础上,提出了一种三电平DC/DC变换器(three-level DC/DC converter,TLDC),该变换器由2个四开关半桥三电平(half-bridge three-level,HBTL) DC/DC变换器组成,采用交错和输入-并联-输出-并联(input-parallel output-parallel,IPOP)连接结构,并详细分析了(HBTL) DC/DC变换器的拓扑结构、工作原理、运行特点及工作性能.采用IPOP结构可以有效减小变换器中主要功率元件的电流应力,使得所提出的变换器将更适合于更高功率的应用.更重要的是,通过将所提出的变换器拓扑结构与相应的交换调制(periodically swapping modulation,PSM)策略相结合,不仅2个输入电容器电流得到平衡并大幅降低,而且一次侧的开关管功率也得到了平衡,从而提高了变换器的可靠性.最后,仿真和试验结果验证了该变换器的PSM策略的可行性.“,”This paper first discussed the evolution of three-level (TL) DC/DC converters,then introduced the study focus changes from topics of soft switching techniques and the efficiency to the reliability performance of the converter.On this basis,a three-level DC/DC converter (TLDC) consisting of two four-switch half-bridge three-level (HBTL) DC/DC converters with an interleaving and input-parallel output-parallel (IPOP) connection structure was proposed and the topology,operation principle,characteristics,and performances of the proposed converter were analyzed in details.The IPOP structure can effectively reduce the current stresses of main power components,which makes the proposed converter more applicable for higher power applications.More significantly,by combining the proposed topology with a corresponding periodically swapping modulation (PSM) strategy,not only the currents of two input capacitors can be balanced and greatly reduced,but also the currents of primary side power switches can be balanced,thus the reliability performance of the converters can be improved.Finally,both simulation and experimental results were presented to verify the proposed converter with a PSM strategy.