Patent ID: 8072246

Claim:
A switching power supply device for use in a DC-DC converter, comprising: an input voltage terminal; a midpoint voltage terminal coupled to an inductor having an input-side terminal and an output-side terminal, the input-side terminal being coupled to the midpoint voltage terminal, a ground potential terminal; a high-side MOSFET of the DC-DC converter, whose drain and source are coupled to the input voltage terminal and the midpoint voltage terminal, respectively; a low-side MOSFET of the DC-DC converter, whose drain and source coupled to the midpoint voltage terminal and the ground potential terminal, respectively; a control circuit controlling a gate of the high-side MOSFET and a gate of the low-side MOSFET; a first feedback signal and a second feedback signal being inputted to the control circuit, the control circuit forming a control signal controlling the high-side and low-side MOSFETs; and a detection MOSFET whose gate is coupled to the gate of the high-side MOSFET and whose drain is coupled to the input terminal, wherein the high-side MOSFET comprises a first number of MOSFET cells, wherein the detection MOSFET comprises a second number of MOSFET cells, wherein the first number is greater than the second number, wherein the first feedback signal is obtained from a voltage based on the output-side of the inductor, and wherein the second feedback signal is obtained from an electric current flowing to the detection MOSFET, wherein the high-side MOSFET and the detection MOSFET are disposed in a same semiconductor substrate.