A step-down circuit includes a first transistor of N-type having a channel between an input terminal and a first node, and a gate to which a reference voltage that is lower than a peak value of an AC voltage applied to the input terminal is applied, a second transistor of P-type having a channel between the input terminal and a second node, and a gate to which the reference voltage is applied, a third transistor of N-type having a channel between the first node and an output terminal, and a gate to which the AC voltage is applied, a fourth transistor of P-type having a channel between the second node and the output terminal, and a gate to which the AC voltage is applied, a first capacitor connected between the first node and the second node, and a second capacitor connected between the output terminal and a reference potential terminal.