Patent ID: 7940531

Claim:
A DC-DC converter comprising a soft-magnetic, multi-layer substrate provided with a laminated coil constituted by connecting pluralities of conductor lines, and a semiconductor integrated circuit device comprising a switching device and a control circuit, which are mounted on said soft-magnetic, multi-layer substrate, said semiconductor integrated circuit device comprising an input terminal, an output terminal, a first control terminal for controlling the ON/OFF of said switching device, a second control terminal for variably controlling output voltage, and ground terminals; said soft-magnetic, multi-layer substrate comprising first external terminals formed on a first main surface, second external terminals formed on a second main surface, and connecting wires connecting said first external terminals and said second external terminals; terminals of said semiconductor integrated circuit device being connected to said first external terminals on said soft-magnetic, multi-layer substrate; at least part of said first external terminals being electrically connected to said second external terminals through said connecting wires; and said output terminal of said semiconductor integrated circuit device being connected to said second external terminal via said laminated coil, and being connected to other said second external terminal via said connecting wires.