Patent ID: 7408388
Filing Date: 2008-08-05
Classification: H02M

Abstract:
1. A switching power supply device comprising: an inductor; a capacitor provided between the output side of the inductor and a ground potential; a first power MOSFET supplying an electric current from an input voltage to the input side of the inductor; a second power MOSFET turned on when the first power MOSFET is off and allowing the input side of the inductor to be of a predetermined potential; and a control circuit which uses a first feedback signal corresponding to an output voltage obtained from the output side of the inductor and a second feedback signal corresponding to an electric current flowed to the first power MOSFET to form a PWM signal and forms a control signal supplied to the gates of the first and second power MOSFETs so that the output voltage is a predetermined voltage, wherein the first power MOSFET has plural cells of a vertical type MOS construction, and wherein a detection MOSFET having cells of the vertical type MOS construction in which the number of cells is 1/N of that of the first power MOSFET and the gate and the drain or the source are shared with the first power MOSFET over the same semiconductor substrate is provided to form the second feedback signal based on an electric current flowed to the detection MOSFET.