A variable frequency pulse width modulated apparatus and method supplies variable frequency and variable duty cycle power to a load, particularly an electric load of a motor vehicle, and preferably to a filament-type lamp such as a headlight. Which one of the two frequencies are selected is based on a monitored battery parameter, such as a comparison between the current supplied to the battery by an alternator and the current drawn from the battery by a load, with a higher one of the two frequencies being selected when the input current exceeds the output current and the lower frequency being selected when the battery input current is less than the output current. The duty cycle is variably selectable with either first or second pulse width modulated frequency.