An example on time control circuit for use in a power factor correction (PFC) controller includes an amplifier, an integrator, and a comparator. The amplifier generates an error signal that is representative of a difference between a feedback signal and a reference value. The integrator integrates a current sense signal that is representative of a current through the power switch to generate an integrator output signal. A gain of the integrator is varied in response to a voltage sense signal that is representative of a value of an input voltage of the PFC converter. The comparator generates a switch power off signal to terminate the on time of the power switch in response to comparing the integrator output signal with the error signal.