Patent ID: 7626372

Claim:
A switching control circuit for a power factor correction (PFC) converter, comprising: a PFC-control circuit coupled to a first inductor and the output of the PFC converter to receive a first-inductor signal and a feedback signal for generating a first-switching signal, wherein the first-switching signal is coupled to switch the first inductor for power factor correction, wherein the first-inductor signal is correlated to the demagnetization of the first inductor; a phase-detection circuit coupled to detect the first-switching signal and a second-inductor signal for generating a start signal and a phase-lock signal, wherein the start signal is utilized to enable a second-switching signal, and the second-switching signal is coupled to switch a second inductor, wherein the second-inductor signal is correlated to the demagnetization of the second inductor, the first inductor and the second inductor are coupled to the output of the PFC converter; an on-time-adjust circuit coupled to adjust the on time of the second-switching signal in accordance with the phase-lock signal; and a light-load detection circuit generating an off signal and a range signal in response to the feedback signal, wherein the phase-lock signal is correlated to the period between of the second-inductor signal and the start signal, the off signal is utilized to turn off the second-switching signal, and the range signal is coupled to program the output voltage of the PFC converter.