Phase leading input current compensation in digitally controlled critical mode boost PFC

In this paper, a digital control method to compensate a phase leading input current in a critical mode (CRM) boost power factor corrector (PFC) is proposed. In a constant on-time CRM boost PFC, the power factor (PF) decreases both as the input voltage increases and as the output power decreases because of phase leading input current caused by input filter capacitor. However, conventional researches to obtain a high PF in a CRM boost PFC did not concentrate on this phenomenon. Therefore, a new control method to compensate the phase leading input current of a CRM boost PFC is proposed in this paper. Since the proposed control compensates the current in the input filter capacitor, the phase leading input current is effectively reduced. The cause of the phase leading input current, its tendency, the concept of the proposed control and its implementation are discussed. Finally, the proposed control is experimentally verified with a 60Hz 90-230V_rms input and 395V/0.5A output prototype.