A controller for a power converter is disclosed. An example circuit controller according to aspects of the present invention includes an input voltage sensor to be coupled to receive an input signal representative of an input voltage of the power converter. A current sensor is also included and is to be coupled to sense a current flowing in a power switch. A drive signal generator is to be coupled to drive the power switch into an on state for an on time period and an off state for an off time period. The controller is coupled to adjust a switching cycle period of the power switch to be proportional to a value of the input signal multiplied by a time period. The time period is the time it takes for the current flowing in the power switch to change between two current values when the power switch is in the on state.