A power converter comprising: a first bridge circuit including a first leg and a second leg, the first leg including a first switching element and a second switching element connected in series, the second leg including a third switching element and a fourth switching element connected in series, and the first leg and the second leg being connected in parallel to a first DC part (E1, C1); a second bridge circuit including a third leg and a fourth leg, the third leg including a fifth switching element and a sixth switching element connected in series, the fourth leg including a seventh switching element and an eighth switching element connected in series, and the third leg and the fourth leg being connected in parallel to a second DC part (C2, E2); an insulated transformer connected between the first bridge circuit and the second bridge circuit; a control circuit that controls the first switching element -the eighth switching element, wherein diodes (D1-D8) are connected or formed in antiparallel to the first switching element -the eighth switching element, respectively; for power transfer from the first DC part to the second DC part by stepping down a voltage, the second bridge circuit includes a rectification period; variably control a simultaneous off period of the fifth switching element and the sixth switching element, and variably control a simultaneous off period of the seventh switching element and the eighth switching element, wherein the power converter is characterized in that for power transfer from the first DC part to the second DC part by stepping down a voltage, the first bridge circuit includes a period in which the first DC part (E1, C1) and a primary winding of the insulated transformer conduct and a period in which ends of the primary winding of the insulated transformer are short-circuited in the first bridge circuit, and the control circuit is configured to variably control a phase difference between the first leg (S1, S2) and the second leg (S3, S4). a first bridge circuit including a first leg and a second leg, the first leg including a first switching element and a second switching element connected in series, the second leg including a third switching element and a fourth switching element connected in series, and the first leg and the second leg being connected in parallel to a first DC part (E1, C1); a second bridge circuit including a third leg and a fourth leg, the third leg including a fifth switching element and a sixth switching element connected in series, the fourth leg including a seventh switching element and an eighth switching element connected in series, and the third leg and the fourth leg being connected in parallel to a second DC part (C2, E2); an insulated transformer connected between the first bridge circuit and the second bridge circuit; a control circuit that controls the first switching element -the eighth switching element, wherein diodes (D1-D8) are connected or formed in antiparallel to the first switching element -the eighth switching element, respectively; for power transfer from the first DC part to the second DC part by stepping down a voltage, the second bridge circuit includes a rectification period; variably control a simultaneous off period of the fifth switching element and the sixth switching element, and variably control a simultaneous off period of the seventh switching element and the eighth switching element, wherein the power converter is characterized in that for power transfer from the first DC part to the second DC part by stepping down a voltage, the first bridge circuit includes a period in which the first DC part (E1, C1) and a primary winding of the insulated transformer conduct and a period in which ends of the primary winding of the insulated transformer are short-circuited in the first bridge circuit, and the control circuit is configured to variably control a phase difference between the first leg (S1, S2) and the second leg (S3, S4).