According to an embodiment, an input-voltage control circuit outputs an input voltage when a control signal is in an enabled state. A backflow prevention circuit includes a first transistor and a first body diode. The first transistor turns on to output the input voltage to the input-voltage control circuit when the control signal is in the enabled state. The first body diode is formed in the first transistor and having an anode connected to the first terminal of the first transistor and a cathode connected to a second terminal of the first transistor. The booster circuit receives the input voltage outputted from the input-voltage control circuit and boosts the input voltage to generates a boosted voltage. The boosted voltage is outputted from the driver circuit and supplied to the control terminal of an external output transistor.