Systems and methods for controlling solid state lighting devices and lighting apparatus incorporating such systems and/or methods
First Claim
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1. A lighting apparatus comprising:
- a string of serially-connected light-emitting diodes (LEDs) coupled between first and second terminals and comprising a first set of LEDs providing first light output having a first chromaticity and a second set of LEDs providing second light output having a second chromaticity different from the first chromaticity; and
a control circuit comprising a bypass circuit, coupled to the string, that bypasses at least one LED of at least one of the first and second sets of LEDs and varies a color temperature produced by the string by differentially varying respective currents passing through the first and second sets of LEDs of the string responsive to a variation in a total current passing between the first and second terminals,wherein the bypass circuit comprises a variable resistance circuit configured to continuously and differentially vary the respective currents passing through the first and second sets of LEDs, andwherein the control circuit is configured to provide the color temperature as a fixed color temperature over a first range of brightness levels and to conform the color temperature to the Planckian locus over a second range of brightness levels that is lower than the first range of brightness levels.
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Abstract
A lighting apparatus includes at least two sets of light-emitting devices with overlapping spectra and different chromaticities, such as two sets of blue-shifted yellow (BSY) LEDs producing outputs with different yellow content. The devices may be selectively controlled, e.g., by using selective current bypass circuits, to provide a desired color temperature or other visual performance in response to a dimming control input such that, for example, a light output approximating that of an incandescent lamp may be achieved.
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Citations
33 Claims
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1. A lighting apparatus comprising:
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a string of serially-connected light-emitting diodes (LEDs) coupled between first and second terminals and comprising a first set of LEDs providing first light output having a first chromaticity and a second set of LEDs providing second light output having a second chromaticity different from the first chromaticity; and a control circuit comprising a bypass circuit, coupled to the string, that bypasses at least one LED of at least one of the first and second sets of LEDs and varies a color temperature produced by the string by differentially varying respective currents passing through the first and second sets of LEDs of the string responsive to a variation in a total current passing between the first and second terminals, wherein the bypass circuit comprises a variable resistance circuit configured to continuously and differentially vary the respective currents passing through the first and second sets of LEDs, and wherein the control circuit is configured to provide the color temperature as a fixed color temperature over a first range of brightness levels and to conform the color temperature to the Planckian locus over a second range of brightness levels that is lower than the first range of brightness levels. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 29, 30)
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13. A lighting apparatus comprising:
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a plurality of light-emitting devices comprising at least one red light-emitting device, at least one BSY light-emitting device having a first BSY output and at least one BSY light-emitting device having a second BSY output with a greater yellow content than the first BSY output serially connected in a string of light-emitting devices coupled between first and second terminals; and a control circuit comprising a bypass circuit, coupled to the plurality of light-emitting devices, that bypasses at least one light-emitting device of the plurality of light-emitting devices to cause a color temperature produced by the plurality of light-emitting devices to vary in conformance with the Planckian locus in response to a variation in a total current passing between the first and second terminals, wherein the control circuit is configured to provide a fixed color temperature over a first range of brightness levels and to conform the color temperature to the Planckian locus over a second range of brightness levels that is lower than the first range of brightness levels. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 31)
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21. A lighting apparatus comprising:
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a plurality of serially-coupled light-emitting devices comprising light-emitting devices having at least three different chromaticities and coupled between first and second terminals; and a control circuit comprising a bypass circuit, coupled to the plurality of serially-coupled light-emitting device, that bypasses at least one of the serially-coupled light-emitting devices and is configured to cause a color temperature produced by the plurality of light-emitting devices to vary in response to a variation of a total current between the first and second terminals over a range from 5000K to 2000K while maintaining a color rendering index (CRI) greater than 80%, wherein the control circuit is configured to provide a fixed color temperature over a first range of brightness levels and to conform the color temperature to the Planckian locus over a second range of brightness levels that is lower than the first range of brightness levels. - View Dependent Claims (22, 23, 24, 25, 32)
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26. A lighting apparatus comprising:
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a plurality of light-emitting devices comprising serially connected first and second sets of light-emitting devices having overlapping output spectra and chromaticities falling within respective first and second different chromaticity ranges; and a control circuit operatively coupled to the plurality of light-emitting devices and configured to differentially operate the first and second sets of light-emitting devices in response to a dimming control input, wherein the first and second sets of light-emitting devices are serially connected between first and second terminals, wherein the control circuit is configured to differentially vary current passing through the first and second sets of light-emitting devices responsive to a total current passing between the first and second terminals by controlling a resistance of a variable resistance circuit in a continuous manner responsive to the dimming control input, and wherein the control circuit is configured to provide a fixed color temperature of light emitted by the plurality of light-emitting devices over a first range of brightness levels and to conform a color temperature of light emitted by the plurality of light-emitting devices to the Planckian locus over a second range of brightness levels that is lower than the first range of brightness levels. - View Dependent Claims (27, 28, 33)
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Specification