HIGHLY EFFICIENT PFC CIRCUIT AND CONTROL METHOD THEREOF

摘要

A PFC circuit includes: a switching circuit having a power switch; an on time control circuit for controlling an on time period of the power switch; a first off time control circuit; a second off time control circuit; and a logic circuit selectively controls the power switch working under CCM or DCM; when working under CCM, the first off time control circuit controls an off time period of the power switch and when working under DCM, the second off time control circuit controls the off time period of the power switch.

主权项

1. A Power Factor Correction (PFC) circuit comprising:
a switching circuit comprising a power switch, the switching circuit having an input terminal configured to receive an input voltage, the switching circuit further having an output terminal configured to provide an output voltage for supplying a load; an on time control circuit configured to provide an on time control signal for controlling an on time period of the power switch; a first off time control circuit configured to provide a first off time control signal; a second off time control circuit configured to provide a second off time control signal; and a logic circuit configured to selectively control the power switch working under a Continuous Conduction Mode (CCM) or a Discontinuous Conduction Mode (DCM) based on a load condition of the load, and wherein the logic circuit is configured to receive the on time control signal, the first off time control signal and the second off time control signal, and to generate a switching control signal that is coupled to the power switch; wherein when working under CCM, the first off time control signal is configured to control an off time period of the power switch; and when working under DCM, the second off time control signal is configured to control the off time period of the power switch.