Patent ID: 8248051

Claim:
An apparatus comprising: a control unit to generate a control signal to control a duty cycle of a PWM (Pulse Width Modulation) switching signal that controls a switch in a PFC (Power Factor Correction) converter, wherein the control unit comprises: a PWM converter to produce a PWM signal responsive to an output voltage error signal that is responsive to an output voltage of the PFC converter; a switching circuit to switch in response to the PWM signal a current representing an input current of the PFC converter; and a circuit to generate the control signal for the PFC converter in response to the switched current, wherein the control unit further includes an amplifier to receive at an input a current sense signal and provide at an output the current representing the input current of the PFC converter; and an offset unit coupled to the control unit to generate a variable offset signal to offset the control signal or a signal used by the control unit to generate the control signal, wherein the offset unit is coupled to provide the offset signal as an offset current for offsetting a current at the input of the amplifier.