A power factor correction circuit includes an error signal generation unit configured to output an error signal obtained by amplifying a difference between an output voltage and a referential voltage. A pulse width modulation unit is configured to receive the error signal to generate a pulse width modulation signal to control an on-time of a switching element. An input interruption detection unit is configured to detect an interruption state of an AC input voltage. When the input interruption detection unit detects an input interruption state, the input interruption detection unit causes the pulse width modulation unit to shorten the on-time of the switching element.