a first switch configured such that a first terminal thereof is connectable to an application terminal for the input voltage and that a second terminal thereof is connectable to a first terminal of an inductor;

a second switch configured such that a first terminal thereof is connectable to the first terminal of the inductor and to the second terminal of the first switch, and that a second terminal thereof is connectable to an application terminal for a voltage lower than the input voltage;

a third switch configured such that a first terminal thereof is connectable to the first terminal of the inductor, to the second terminal of the first switch, and to the first terminal of the second switch, and that a second terminal thereof is connectable to a second terminal of the inductor;

a detector configured to detect occurrence, or a sign of occurrence, of an overshoot in the output voltage; and

a controller configured to turn on and off the first, second, and third switches,

wherein the controller is configured to produce, after occurrence, or a sign of occurrence, of an overshoot in the output voltage is detected by the detector until the overshoot in the output voltage settles down, a control state in which the first and second switches are kept off and the third switch is kept on,

the detector is configured to detect also settlement of an overshoot in the output voltage, and

the controller is configured such that, in a period after the detector detects occurrence, or sign of occurrence, of an overshoot in the output voltage until the detector detects settlement of the overshoot in the output voltage, the controller keeps the first switch off when at least the third switch is on, keeps the second switch off when at least the third switch is on, and turns on and off the third switch at a fixed period.