A switching control circuit for multi-phases PFC converters is provided.
It includes a PFC-control circuit coupled to receive a first-inductor
signal and a feedback signal for generating a first-switching signal. The
first-switching signal is utilized to switch the first inductor for power
factor correction. A phase-detection circuit detects the first-switching
signal and a second-inductor signal for generating a start signal and a
phase-lock signal. The start signal is developed to enable a
second-switching signal. The second-switching signal is coupled to switch
a second inductor. An on-time-adjust circuit is coupled to adjust the on
time of the second-switching signal in accordance with the phase-lock
signal. The phase-lock signal is correlated to the period between the end
of the second-inductor signal and the start of the second-switching
signal.