An example power supply includes an energy transfer element, a switch, and a controller. The switch is coupled to the energy transfer element to control a transfer of energy from an input to a galvanically isolated output of the power supply. The controller includes a delayed ramp generator, an integrator, an arithmetic operator, and a drive signal generator. The integrator generates a first signal responsive to integrating an input current of the power supply. The arithmetic operator generates a second signal responsive to the first signal and responsive to a ratio of a rectified input voltage to a dc output voltage of the power supply. The drive signal generator generates a drive signal in response to a delayed ramp signal and the second signal to control switching of the switch to provide power factor correction of the power supply and to provide a regulated current at the output.