Patent ID: 8072199

Claim:
A control circuit of a step-down DC-DC converter comprising a main switching transistor corresponding to an NMOS transistor, wherein the step-down DC-DC converter comprises: a MOS transistor, coupled between a gate of the main switching transistor and a ground potential, conducts in accordance with an OFF command of the main switching transistor; a driver driving the gate of the main switching transistor by drive voltage of which high level input to be inputted into the gate of the main switching transistor is higher than input voltage to be inputted into a drain of the main switching transistor; a detection unit detecting that the drive voltage is lower than a predetermined level; and a control unit bringing the MOS transistor into conduction by the OFF command of the main switching transistor in accordance with a detection result of the detection unit, wherein the main switching transistor is turned on by the drive voltage.