Patent ID: 8138737

Claim:
A power factor correction circuit comprising: a first rectifier configured to rectify and convert an AC voltage into a DC voltage; a series circuit connected to an output o the first rectifier and including a step-up reactor and a switching element; a rectifying-smoothing circuit connected to both ends of the switching element and including a second rectifier and a smoothing capacitor; an input voltage detector configured to detect an output voltage of the first rectifier and provide an input voltage signal representing the detected voltage; an output voltage detector configured to detect a voltage across the smoothing capacitor and provide an output voltage signal representing the detected voltage; an error amplifier configured to amplify an error between the output voltage signal and a reference voltage and provide an amplified error signal; and a controller configured to determine an ON/OFF duty ration of the switching element, wherein the controller includes, an operation unit configured to provide the result of a calculation carried out on the input voltage signal and output voltage signal, and a signal generator configured to set an ON time of the switching element in proportion to the amplified error signal, set an OFF time of the switching element based on a comparison between the result of the calculation and the amplified error signal, and provide a pulse string signal specifying the set ON time and OFF time.