Duty cycle controller for power factor correction circuit

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 the amplified error signal, and
• a signal generator configured to set an ON time of the switching element based on a comparison between an integrated value of the input voltage signal and the result of the calculation, set an OFF time of the switching element based on a comparison between the result of the calculation and an integrated value of differences between the output voltage signal and the input voltage signal, and provide a pulse string signal specifying the set ON time and OFF time.