Patent ID: 7394211

Claim:
A light emitting device driver circuit, comprising: power supply means for accepting a direct current from a power supply having a nominal voltage; an active light emitting device having a forward bias voltage less than the nominal voltage; a converter circuit having an inductor and a unidirectional current blocking element interconnecting the power supply and the light emitting device; a first switch for selectively electrically communicating the inductor to a ground so that the inductor can alternately be charged by the power supply and discharged through the light emitting device; and control means operatively coupled with the first switch for charging and discharging the inductor and for measuring an instantaneous voltage and comparing the instantaneous voltage to a pre-selected voltage threshold, indicative of an ability of the power supply to charge the inductor, so that a charging cycle duration of the inductor is adjusted through the first switch by the control means so as to deliver substantially constant current to the light emitting device regardless of an actual voltage of the power supply.