To perform accurate AC current control where the ripple components of an AC input current is reduced, by connecting bidirectional switching elements each between the contacts of two pieces of capacitors and the input end of multiphase AC.

The series connected body of two capacitors 91 and 92 is arranged at the DC output end of a forward converter, and bidirectional switching elements 81, 82, and 83 are connected between these junctions and the multiphase AC input ends of a forward converter. A comparator 109 generates a drive signal G42' when the input is at a specified value or over, so as to drive a switching element 42, and a comparator 110 generates a drive signal G81' when the absolute value of input is not more than the specified value, so as to drive a bidirectional switching element 81, and a comparator 111 generates a drive signal G41' when the input is at a specified value or under, so as to drive a switching element 41. Hereby, accurate AC current control in which the ripple components of an AC input current are reduced can be performed.