Control device of power factor correction circuit, power factor correction circuit and power supply device

A control device, for a power factor correction circuit disposed in a power supply device configured to generate a DC output voltage from an AC voltage applied to a pair of power supply terminals,

• the power factor correction circuit,
• disposed between a full-wave rectifier circuit configured to generate a full-wave rectified voltage by full-wave rectifying an alternating current voltage and an output wiring configured to apply the output voltage, and
• including:
• an inductor inserted between the full-wave rectifier circuit and the output wiring;
• and
• a switching element configured to switch between an on state and an off state to control a current flowing through the inductor,
• the control device is configured to, during a period when the switching element is turned off, control a number of bottoms in a free vibration of a voltage between a first end and a second end of the switching element based on a period from a turn-on of the switching element to a start of the free vibration.