To obtain the compact power supply device by providing and laminating an insulating sheet, wherein magnetic powder is mixed, between a component mounting board and a sheet coil transformer.
This switching power supply device has a component mounting board 11, on which electronic circuit elements 10 are mounted, and a sheet oil transformer 12, which is connected to the electronic circuits 10 on the component mounting board 11. Then, an insulating sheet 13, wherein magnetic powder is mixed, is provided and laminated between at least the component mounting board 11 and the sheet coil transformer 12. Since the sheet coil transformer 12 is used as the transformer constituting the electronic circuit of the switching power supply device, a transformer from the surface of the component mounting board 11 can be omitted. Furthermore, since the insulating sheet 13, wherein the magnetic powder is mixed, is provided between is component mounting board 11 and the sheet coil 12, the magnetic-flux density in the vicinity of the sheet coil transformer 12 is enhanced, and the inductance of the sheet coil 12 is increased.
NISHIYAMA TAKAYOSHI
MATSUMOTO YOSHIHIRO
