In this paper, an interleaved buck-integrated branch-sharing modular multilevel DC transformer (DCT) combining the features of the dual-active-bridge (DAB) converter is proposed. The branch-sharing modular multilevel converter (BS-MMC) structure is adopted on the medium voltage dc (MVDC) side, which can be thought as the primary side of DAB. While on the low voltage dc (LVDC) side, there is only an interleaved buck cell with four multiplexed switches as the secondary full bridge of DAB. With the interleaved buck cell, the proposed converter can achieve wide voltage range regulation, as well as the voltage matching between the primary and secondary sides of DAB all the time. Moreover, the zero-voltage-switching (ZVS) for all switches are realized in full operation range. In addition, the input inductor effectively suppresses the detrimental effect of short-circuit faults on the MVDC side.