A digital pulse width modulator leverages clock frequency to achieve very fine duty cycle resolution by using a constant number of time slots for each state of a pulse signal and varying the number of time slots in a switching cycle within acceptable limits for variation of the switching cycle frequency or by using two relatively low frequency clocks of slightly differing frequency and selecting pulse leading and trailing edges in accordance with pulses output therefrom. A fine resolution of duty cycle adjustment can thus be provided corresponding to a much higher effective clock frequency than is actually used; allowing improvement of efficiency of clock and switching circuits, particularly in switching voltage regulator applications.