The high-side switch has one end connected to the input terminal. The low-side switch has one end connected to other end of the high-side switch and other end connected to a ground terminal. The inductor has one end connected to the other end of the high-side switch and other end connected to the output terminal. The capacitor has one end connected to the other end of the inductor and other end connected to the ground terminal. The high-side switch controlling circuit generates and supplies a high-side switch controlling signal based on a target voltage of the output terminal, the output voltage of the output terminal, and a current flowing through the capacitor, to the high-side switch. The low-side switch controlling circuit generates and supplies a low-side switch controlling signal based on the high-side switch controlling signal and a current flowing through the inductor, to the low-side switch.