Patent ID: 8587280

Claim:
A power supply arrangement, comprising: a power factor correction (PFC) converter coupled to receive a rectified ac output from a diode bridge; an LLC converter coupled to receive an output voltage from the PFC converter; a control unit coupled to generate a control signal to control a duty cycle of a PWM (Pulse Width Modulation) signal coupled to control the PFC converter, wherein the control unit comprises: a PWM converter coupled to generate the PWM signal in response to an output voltage error signal that is responsive to the output voltage of the PFC converter; a switching circuit coupled to switch in response to the PWM signal a current representing an input current of the PFC converter; a circuit coupled to generate the control signal in response to the current switched by the switching circuit in response to the PWM signal; and an amplifier coupled to receive at an input a current sense signal, the amplifier further coupled to 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 variable offset signal as an offset current coupled to offset the current sense signal received at the input of the amplifier.