Spectral Shift Control for Dimmable AC LED Lighting
First Claim
1. An apparatus for a solid state light engine, the apparatus comprising:
- a pair of terminals to receive an applied electrical excitation for a load;
a first network in the load, wherein the first network includes a first plurality of light emitting diodes (LEDs) arranged in series connection to form a first current path, the first plurality of LEDs having a first color characteristic;
a second network in the load, wherein the second network includes a second plurality of LEDs arranged in series connection to form a second current path, the second plurality of LEDs having a second color characteristic that is substantially different from the first color characteristic; and
,means for selectively diverting current away from at least one of the first and second networks of LEDs,wherein a color characteristic of the combined light output of the first and second networks varies between the first color characteristic and the second color characteristic as a function of the applied electrical excitation, and wherein a rate of change of intensity for a first peak wavelength is at least 40% higher than a rate of change of intensity for a second peak wavelength as the applied electrical excitation is varied within a limited range that encompasses 80% of rated voltage.
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Abstract
Apparatus and associated methods involve operation of an LED light engine in which a relative intensities of selected wavelengths shift as a function of electrical excitation. In an illustrative example, current may be selectively and automatically diverted substantially away from at least one of a number of LEDs arranged in a series circuit until the current or its associated periodic excitation voltage reaches a predetermined threshold level. The diversion current may be smoothly reduced in transition as the excitation current or voltage rises substantially above the predetermined threshold level. A color temperature of the light output may be substantially changed as a predetermined function of the excitation voltage. For example, some embodiments may substantially increase or decrease a color temperature output by a solid state light engine in response to dimming the AC voltage excitation (e.g., by phase-cutting or amplitude modulation).
121 Citations
22 Claims
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1. An apparatus for a solid state light engine, the apparatus comprising:
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a pair of terminals to receive an applied electrical excitation for a load; a first network in the load, wherein the first network includes a first plurality of light emitting diodes (LEDs) arranged in series connection to form a first current path, the first plurality of LEDs having a first color characteristic; a second network in the load, wherein the second network includes a second plurality of LEDs arranged in series connection to form a second current path, the second plurality of LEDs having a second color characteristic that is substantially different from the first color characteristic; and
,means for selectively diverting current away from at least one of the first and second networks of LEDs, wherein a color characteristic of the combined light output of the first and second networks varies between the first color characteristic and the second color characteristic as a function of the applied electrical excitation, and wherein a rate of change of intensity for a first peak wavelength is at least 40% higher than a rate of change of intensity for a second peak wavelength as the applied electrical excitation is varied within a limited range that encompasses 80% of rated voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification