Patent ID: 8116052

Claim:
A power supply control circuit, comprising: an output transistor coupled between a power supply line and an output terminal to be coupled to a load; a first overvoltage protection circuit including a first clamping circuit and a first switch, the first clamping circuit and the first switch being coupled in series between the power supply line and a control terminal of the output transistor, the first switch coupling between the first clamping circuit and the control terminal of the output transistor in relation to a back electromotive voltage from the load and disconnecting between the first clamping circuit and the control terminal of the output transistor in relation to both a first surge voltage and a second surge voltage applied to the power supply line, the second surge voltage being greater than the first surge voltage; and a second overvoltage protection circuit including a second clamping circuit, a second switch and a pull-down device, the second clamping circuit and the second switch being coupled in series between the power supply line and the control terminal of the output transistor, the second switch coupling between the second clamping circuit being and the control terminal of the output transistor in relation to the second surge voltage, and the pull-down device maintaining the second switch inoperative in relation to both the back electromotive voltage from the load and the first surge voltage.