The utility model provides a AC -DC conversion circuit, including at least a set of alternating current -direct current conversion module, every group including an at least conversion branch road among the alternating current -direct current conversion module, every the conversion branch road includes: a plurality of change of current subelements correspond three -phase alternating current respectively, a plurality of DCAC translation unit, respectively with the direct current side of change of current subelement perhaps total direct current side that the direct current side is established ties or parallelly connected back constitutes of change of current subelement is connected, the coupling unit will whenever be taken a fancy to the instantaneous power coupling of DCAC translation unit output is eliminated in single -phase mutually instantaneous power's fluctuation, at least one ACDC translation unit, with one or the connection of a plurality of outputs of coupling unit, just same looks is adjacent among the alternating current -direct current conversion module cascade connection between change of current subelement exchanges the interface from whenever taking a fancy to the interchange side of change of current subelement is drawn forth, is connected with the alternating current that corresponds looks. Be applied to power electronic transformer with this AC -DC conversion circuit, can effectively reduce power electronic transformer's volume equally, reduce its cost.