A method of regulating an output voltage of a switched mode power supply having a variable input voltage and at least one power switch is provided. The method includes generating a control signal for the at least one power switch of the switched mode power supply based at least in part on a control voltage, the control signal having a duty cycle. The method also includes generating a reference voltage based at least in part on the duty cycle of the control signal and a maximum duty cycle, and generating the control voltage based at least in part on the reference voltage and the output voltage.