PURPOSE: To achieve compactness and to reduce cost by enabling a first secondary coil, first and second primary coils, and second secondary coil to share one core.

CONSTITUTION: A second secondary coil 38 is connected to terminals 24 and 25 and is wound at the outer periphery of a connection beam 15 between these. A first primary coil 35 is connected to a terminal 20 and a terminal 21 and is wound at the outer periphery of the connection beam 15 between these and on the upper layer of the second secondary coil 38. A second primary coil 36 is connected to the terminals 21 and 25 and is wound at the outer periphery of the connection beams 15 between these and on the upper layer of the first primary coil 35. Also, a first secondary coil 37 is connected to the terminals 23 and 24 and is wound at the outer periphery of the connection beams 15 between these and on the upper layer of the second primary coil 36. Then, an insulation tape 39 is wound between the second primary coil 36 and the first secondary coil 37.