PURPOSE: To suppress effectively the high-frequency noise characteristic of a switching power supply and apply easily a low-frequency magnetic shield to it, by providing a nonmagnetic layer and a ferromagnetic layer in a metallic core board, and by providing the circuit patterns of a rectification-smoothing circuit and a DC-DC converter part on the nonmagnetic layer.
CONSTITUTION: On a metallic core board 30, a rectification-smoothing circuit 10 and a DC-DC converter part 20 adjacent to the circuit 10 are mounted. The rectification-smoothing circuit 10 makes the AC power supply fed from a commercial power supply into a DC power supply. The DC-DC converter part 20 is switched on or off by a switching device 21. The metallic core board has a double structure, whose upper layer is a nonmagnetic layer 31 and whose lower layer is a ferromagnetic layer 32. As the nonmagnetic layer 31, used is a nonmagnetic material such as aluminum or copper, whose electric resistance is low. As the ferromagnetic layer 32, material such as iron, nickel or ferrite, whose electric resistance is high in comparison with the material of the nonmagnetic layer 31 is used. Thereby, the high-frequency noise characteristic of a switching power supply can be suppressed effectively, and a low-frequency magnetic shield can be easily applied to it.
MATSUDA SHUICHI
FUJITA SEIJI
Next Patent: SUPERCONDUCTING MAGNETIC-SHIELDING BODY AND MANUFACTURE THEREOF