Patent ID: 7116090

Claim:
A switching control circuit for a PFC converter wherein generating a switching signal coupled for switching an inductor for power factor control, comprising: a detection terminal, coupled to the inductor for generating a detection signal in response to the discharge of the inductor; an input terminal, coupled for detecting a switching current signal in accordance with the switching current of the inductor; a ramp generator, producing a ramp signal in response to the switching signal; a program terminal, coupled to the ramp generator for determining the slew rate of the ramp signal and determining the maximum on-time of the switching signal; an error amplifier, coupled to the output of the PFC converter for generating an error signal for regulating the output of the PFC converter; a mix circuit, generating a mixing signal proportional to the ramp signal and the switching current signal; wherein the switching signal is turned on in response to the detection signal; and the switching signal is turned off once the mixing signal is found to be higher than the error signal.