LIGHTING SYSTEMS WITH UNIFORM LED BRIGHTNESS
First Claim
1. A lighting system, comprising:
- a plurality of light emitting diodes (LEDs) serially connected in a string;
a plurality of switches, each switch connected across a different set of the LEDs in the string; and
a controller configured to selectively activate the switches in effort to provide a brightness that appears uniform to a human.
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Accused Products
Abstract
Solid state lighting systems are disclosed for providing uniform brightness of LEDs serially connected in a string. In some embodiments, the LEDs can be powered directly from the mains such that no switch-mode power supply or the output storage elements associated therewith are needed. In some such cases, a linear regulator and switches can be used to control the current through the LEDs to provide uniform brightness. Other embodiments can be used with a switch-mode based driver topology and/or storage elements coupled in parallel with clusters of the LEDs. In any such cases, control logic (e.g., microcontroller or other suitable controller) can be used to control the switches accordingly to provide uniform brightness, and in some cases, to mitigate the implications of having no SMPS output storage element. In some embodiments, the switching pattern provided by the control logic is random, although other switching patterns can be used.
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Citations
21 Claims
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1. A lighting system, comprising:
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a plurality of light emitting diodes (LEDs) serially connected in a string; a plurality of switches, each switch connected across a different set of the LEDs in the string; and a controller configured to selectively activate the switches in effort to provide a brightness that appears uniform to a human. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A lighting system, comprising:
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a plurality of light emitting diodes (LEDs) serially connected in a string; a plurality of switches, each switch connected across a different set of the LEDs in the string; and a microcontroller configured to selectively activate the switches in effort to provide a brightness that appears uniform to a human, and wherein the microcontroller selectively activates the switches so that the LED string has a forward voltage drop that is within 20% or less of a line voltage powering the system. - View Dependent Claims (18, 19)
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20. A lighting system, comprising:
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a plurality of light emitting diodes (LEDs) serially connected in a string; a plurality of switches, each switch connected across a different set of the LEDs in the string; a linear regulator in series with the LEDs; and a microcontroller configured to selectively activate the switches in effort to provide a brightness that appears uniform to a human, wherein each of the switches is associated with one or more of the LEDs to provide a switchable LED cluster, and the controller is further configured to turn on as many clusters as possible so as to reduce losses in the linear regulator.
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21-23. -23. (canceled)
Specification