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US 7,015,654 B1Granted
Light emitting diode driver circuit and method
AssigneeLaughing Rabbit, Inc.
InventorsKurt A. Kuhlmann, David M. Allen
Life of this patent
Estimating the term…
Abstract
A mirco-controller and boost converter circuit provide constant current to light emitting diode array. A micro-controller operatively coupled with a semiconductor switch and the boost converter circuit measure the ability of a DC power supply to change the inductor. Duty cycles of the semiconductor switch are modified according to the measurement so as to supply substantially constant current to the LED array through an inductor regardless of actual battery voltage.
Claims16
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.
3 more elements
A method for driving a light emitting diode, comprising the steps of:
- closing a first switch so as to connect an inductor and a direct current power supply having a nominal voltage less than a forward bias voltage of a light emitting diode to be driven to ground so as to charge the inductor;
- opening the first switch so as to direct current from the inductor though a blocking diode to the light emitting diode and a smoothing capacitor;
- measuring a time period in which the inductor discharges to a pre-determined voltage threshold indicative of an ability of the power supply to charge the inductor;
- and, adjusting a closed time of the first switch so as to provide substantially constant current to the light emitting diode regardless of an actual voltage of the power supply.
1 more element
Dependencies are inferred from the claim text.