An apparatus and method of switching a switch of a power supply in response to an input voltage signal are disclosed. According to aspects of the present invention, a power supply controller includes a switch duty cycle controller coupled to receive a feedback signal and a duty cycle adjust signal. The switch duty cycle controller is coupled to generate a drive signal coupled to control switching of a switch, which is coupled to an energy transfer element, to regulate energy delivered from an input of a power supply to an output of the power supply. The power supply controller also includes a gain selector circuit coupled to receive an input voltage signal, which is representative of an input voltage to the power supply, to generate the duty cycle adjust signal received by the switch duty cycle controller. The maximum duty cycle of the drive signal to be varied in response to a plurality of linear functions over a range of values of the input voltage signal.