Patent ID: 7015654

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 greater than the nominal voltage; a boost converter circuit having an inductor, a charge storage element 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 though the light emitting device; and, control means operatively coupled with the first switch for charging and discharging the inductor and for measuring a time period associated with a discharge cycle of the inductor during which a preselected voltage threshold, indicative of an ability of the power supply to charge the inductor is attained such 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.