System and method for driving LEDs
AssigneeFairchild Semiconductor Corporation
InventorsLajos Burgyan, Francois Prinz
Life of this patent
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Abstract
Embodiments of the invention provide for a system and method for driving LEDs with consistently good illumination and superior efficiency at lower cost and suitable for use with cheaper LEDs or with LEDs having wide component parameter tolerances over wide operating voltages and temperature variations.
Claims41
A system for driving a plurality of light emitting diodes (LEDs) comprising:
- a voltage regulator operable to provide current to the plurality of LEDs;
- a plurality of current regulators, each current regulator connected to a respective LED and operable to regulate the current provided to the respective LED;
- and
- a detector coupled to the plurality of current regulators, the detector operable to detect an occurrence of current starvation at any of the current regulators, the detector further operable to output a signal for adjusting power supplied to the charge pump in response to the detection of an occurrence of current starvation.
A method for driving a plurality of light emitting diodes (LEDs) comprising:
- providing current to the plurality of LEDs using a voltage regulator;
- regulating the current provided to each LED with a respective current regulator;
- detecting an occurrence of current starvation at any of the current regulators;
- and
- adjusting power supplied to the charge pump in response to the detection of an occurrence of current starvation.
A circuit for providing current to a plurality of light emitting diodes (LEDs), the circuit comprising:
- a charge pump terminal operable to supply current to the plurality of LEDs;
- a voltage regulator operable to supply energy to the charge pump;
- a plurality of current regulators, each current regulator operable to control current in a respective one of the LEDs;
- and
- a detector operable to detect a condition of current starvation at any of the current regulators;
- wherein the voltage regulator has an output that is responsive to detection of the condition of current starvation.
A system for driving a plurality of light emitting diodes (LEDs) comprising:
- a charge pump operable to provide current to the plurality of LEDs;
- a detector coupled to the plurality of LEDs, the detector operable to detect an undervoltage condition at any of the LEDs, the detector further operable to output a signal for adjusting power supplied to the charge pump in response to the detection of the undervoltage condition;
- and
- a plurality of current regulators, each current regulator connected to a respective LED and operable to regulate the current provided to the respective LED so that, collectively, the plurality of LEDs are uniformly illuminated.
A method for driving a plurality of light emitting diodes (LEDs) comprising:
- providing current to the plurality of LEDs using a charge pump;
- regulating the current provided to each LED so that, collectively, the plurality of LEDs are uniformly illuminated;
- detecting an undervoltage condition at any of the LEDs;
- and
- adjusting power supplied to the charge pump in response to the detection of the undervoltage condition.
A system for providing power to a plurality of light emitting diodes (LEDs) comprising:
- a multi-mode charge pump operable to provide voltage to the LEDs at a plurality of gain ratios;
- a detector for detecting if a supply voltage for the system is diminishing and for adjusting the gain ratio of the multi-mode charge pump in response to the detection of a diminishing supply voltage;
- and
- a plurality of current regulators, each current regulator coupled to one of the plurality of LEDs for individually adjusting the power supplied to the respective LED.
A method for providing current to a plurality of light emitting diodes (LEDs) comprising:
- regulating current in each of the LEDs to not exceed a desired amount;
- detecting a condition of current starvation in any of the LEDs;
- and
- regulating a voltage supplied to the plurality of LEDs in response to the detecting so that the current starvation is abated.
A system for providing current to a plurality of light emitting diodes (LEDs) comprising:
- means for regulating current in each of the LEDs to not exceed a desired amount;
- means for detecting a condition of current starvation in any of the LEDs;
- and
- means for regulating a voltage supplied to the plurality of LEDs in response to the detecting so that the current starvation is abated.
A detector for regulating power provided to a plurality of light emitting diodes (LEDs) comprising:
- a plurality of diodes, each diode connected to a respective LED at a respective sense terminal, wherein the plurality of diodes operate collectively to provide a signal derived from a lowest of voltage values appearing at the sense terminals;
- and
- an operational amplifier operable to receive the signal provided by the plurality of diodes, the operational amplifier operable to generate a feedback signal for controlling the power supplied to the plurality of LEDs so that the voltage values appearing at the sense terminals are held at an appropriate level.
A method for efficiently powering a plurality of light emitting diodes (LEDs) comprising:
- supplying a voltage for the LEDs, wherein the voltage causes current to flow through each of the LEDs;
- regulating the current in each of the LEDs to not exceed a respective predetermined amount so that the LEDs are uniformly illuminated;
- detecting if any one of the LEDs is receiving insufficient current;
- and
- in response to the detection of insufficient current, adjusting the voltage supplied to the LEDs so that no LED is receiving insufficient current.
Dependencies are inferred from the claim text.