Patent ID: 8487601

Claim:
A power factor correction (PFC) converter, comprising: an energy transfer element coupled to an input of the PFC converter; a power switch coupled to the energy transfer element; and a controller coupled to the power switch, the controller comprising: an integrator coupled to receive a voltage sense signal responsive to a magnitude of an ac voltage source coupled to the input of the PFC converter, the integrator further coupled to receive a current sense signal responsive to a current through the power switch when the power switch is on, wherein the integrator generates an integrator output signal in response to the voltage sense signal and the current sense signal; and on/off logic coupled to drive the power switch on and off to control a transfer of energy through the energy transfer element to an output of the PFC converter, wherein the on/off logic terminates an on time of the power switch when the integrator output signal reaches a threshold value, and wherein a gain of the integrator is adjusted in response to the voltage sense signal such that the threshold value is substantially constant independent of the magnitude of the ac voltage source when a load condition at the output of the PFC converter is constant.