A controller for use in a power factor correction converter, comprising: an integrator (154, 254, 354) coupled to receive a voltage sense signal (159, 259, 359) responsive to a magnitude of an AC voltage source coupled to an input of the power factor correction converter coupled to an energy transfer element coupled to a power switch (118, 218, 818), wherein the voltage sense signal (159, 259, 359) is not representative of the instantaneous input voltage at any instant in time, but rather is a value that typically remains substantially constant over many half cycle periods, the integrator (154, 254, 354) further coupled to receive a current sense signal (164, 264, 364) responsive to a current (134, 234) flowing in the power switch (118, 218) when the power switch (118, 218, 818) is on, the integrator (154, 254, 354) to generate an integrator output signal (157, 257, 357) in response to the voltage sense signal (159, 259, 359) and the current sense signal (164, 264, 364); and an error amplifier (153,253,353) coupled to receive a reference voltage and a feedback signal responsive to the magnitude of a DC output voltage of the power factor correction converter, a comparator (169,269,369) to receive the output value from the error amplifier and the integrator output signal, on/off logic (156, 256) coupled to drive the power switch (118, 218) on and off to control a transfer of energy through the energy transfer element to a load coupled to an output of the power factor correction converter, the on/off logic (156, 256) coupled to the output of the comparator to terminate an on time of the power switch (118, 218) when the integrator output signal (157, 257, 357) reaches a threshold value said threshold being the output value of the error amplifier, wherein a gain of the integrator circuit (154, 254, 354) is adjusted in response to the voltage sense signal (159, 259, 359) such that the threshold value (158, 258, 358) is substantially constant independent of the magnitude of the AC voltage source when a magnitude of the load is constant. an integrator (154, 254, 354) coupled to receive a voltage sense signal (159, 259, 359) responsive to a magnitude of an AC voltage source coupled to an input of the power factor correction converter coupled to an energy transfer element coupled to a power switch (118, 218, 818), wherein the voltage sense signal (159, 259, 359) is not representative of the instantaneous input voltage at any instant in time, but rather is a value that typically remains substantially constant over many half cycle periods, the integrator (154, 254, 354) further coupled to receive a current sense signal (164, 264, 364) responsive to a current (134, 234) flowing in the power switch (118, 218) when the power switch (118, 218, 818) is on, the integrator (154, 254, 354) to generate an integrator output signal (157, 257, 357) in response to the voltage sense signal (159, 259, 359) and the current sense signal (164, 264, 364); and an error amplifier (153,253,353) coupled to receive a reference voltage and a feedback signal responsive to the magnitude of a DC output voltage of the power factor correction converter, a comparator (169,269,369) to receive the output value from the error amplifier and the integrator output signal, on/off logic (156, 256) coupled to drive the power switch (118, 218) on and off to control a transfer of energy through the energy transfer element to a load coupled to an output of the power factor correction converter, the on/off logic (156, 256) coupled to the output of the comparator to terminate an on time of the power switch (118, 218) when the integrator output signal (157, 257, 357) reaches a threshold value said threshold being the output value of the error amplifier, wherein a gain of the integrator circuit (154, 254, 354) is adjusted in response to the voltage sense signal (159, 259, 359) such that the threshold value (158, 258, 358) is substantially constant independent of the magnitude of the AC voltage source when a magnitude of the load is constant.