Power factor control circuit and power source device

A power source device comprising:

• a power factor control circuit;
• a smoothing capacitor charged by the power factor control circuit;
• and
• a rectifying circuit that rectifies an alternating current voltage and supplies the power factor control circuit with an undulating voltage,
• the power factor control circuit including:
• an inductor;
• a switching element which is connected to one end of the inductor in series, performs a switching operation of repeating an on-state and an off-state when an input voltage which is input to the other end of the inductor is relatively high, continues the on-state when the input voltage is relatively low, and causes an input current to flow through the inductor;
• a constant current element which is connected to the switching element in series and limits the current of the switching element;
• a feedback coil which is magnetically coupled to the inductor, supplies a voltage to a control terminal of the switching element, and controls the switching element;
• and
• a control circuit which controls a constant current value of the constant current element depending on the input voltage.