Reducing lumen variability over a range of color temperatures of an output of tunable-white LED lighting devices

• US 8,928,249 B2
• Filed: 08/21/2013
• Issued: 01/06/2015
• Est. Priority Date: 08/25/2011
• Status: Active Grant

• Current Assignee: ABL IP Holding LLC (Acuity Brands, Inc.)
• Original Assignee: ABL IP Holding LLC (Acuity Brands, Inc.)
• Inventors: Raj, Rashmi K., Rogers, Jason W.
• Primary Examiner(s): VU, DAVID HUNG
• Application Number:
  US13/972,341
• Publication Number:
  US 20140035472A1
• Time in Patent Office: 503 Days
• Field of Search: 362/230, 362/231, 362/227, 362/84, 250/216, 250/227.11, 250/206, 315/307, 315/308, 315/291, 315/312, 315/149, 315/159, 315/157, 315/156, 315/153, 315/158
• US Class Current: 315/291
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback

Abstract

A system provides white light having a selectable spectral characteristic (e.g. a selectable color temperature, delta uv, and intensity) using a combination of sources (e.g. LEDs) emitting light of three, four, five, or six different characteristics, for example, one or more white LEDs, and one or more LEDs of each of three primary colors, plus cyan and royal blue. A controller maintains a desired spectral characteristic, e.g. for white light at a selected point on or within a desired range of the black body curve. In addition, the controller provides selectable adjustments for values of the spectral characteristics, while maintaining substantially constant overall output intensity for the light output of White LEDs, thereby achieving Maximum Utilization.

Claims

1. A tunable lighting system comprising:

a white light emitting semiconductor device and a first non-white color light emitting semiconductor device;

a first driver for applying a first controllable drive current to the white light emitting semiconductor device and a separately controllable portion of the first drive current to the first non-white color light emitting semiconductor device;

a second non-white color light emitting semiconductor device, the second non-white color different from the first non-white color;

a second driver for applying a second controllable drive current to the second non-white color light emitting semiconductor device;

an input for receiving user selections of values related to a spectral characteristic of white combined light output of the tunable lighting system; and

a controller connected to control the first driver and the second driver;

wherein the controller is configured to;

control the first driver to maintain application of full drive current to the white light emitting semiconductor device responsive to all of the received input values related to the spectral characteristic; and

in response to the user selecting a range of values related to the spectral characteristic of the white light output, selectively operate the drivers to;

adjust the controllable drive current provided to the first non-white color light emitting semiconductor device and adjust the controllable drive current provided to the second non-white color light emitting semiconductor device, in a manner causing combined light output from the white and non-white light emitting semiconductor devices to exhibit the selected values for the spectral characteristic, while maintaining substantially constant overall output intensity for the combined light output over the selected values.

2. The tunable lighting system of claim 1 wherein:

the controller is configured to determine a correlated color temperature (CCT) value, in response to the user selecting a value related to the spectral characteristic of the white light output; and

the controller includes first and second control channels for operating, respectively, the first driver and the second driver;

wherein the first control channel is configured to provide (a) the first controllable drive current at substantially full drive, and (b) the separately controllable portion of the first drive current at a scaled value based on the CCT value determined by the controller; and

the second control channel is configured to provide the second controllable drive current.

3. The tunable lighting system of claim 1 wherein:

the white light emitting semiconductor device includes multiple white light emitters connected in series, and

the first non-white color light emitting semiconductor device includes multiple first non-white color light emitters connected in series.

4. The tunable lighting system of claim 3 wherein:

the series connected white light emitters and the series connected first non-white color light emitters are connected in series.

5. The tunable lighting system of claim 1 wherein:

the first non-white color is one of red, amber and orange; and

the second non-white color is one of green and blue.

6. The tunable lighting system of claim 1 wherein:

the first non-white color is green; and

the second non-white color is one of (a) either red, amber, or orange and (b) blue.

7. The tunable lighting system of claim 1 further including:

a third non-white color light emitting semiconductor device, the third non-white color different from the first and second non-white colors; and

a third driver for applying a third controllable drive current to the third non-white color light emitting semiconductor device.

8. The tunable lighting system of claim 7 wherein:

the controller is configured to determine a correlated color temperature (CCT) value, in response to the user selecting a value related to the spectral characteristic of the white light output; and

the controller includes first, second and third control channels for operating, respectively, the first, second and third drivers;

the first control channel is configured to provide (a) the first controllable drive current at substantially full drive, and (b) the separately controllable portion of the first drive current at a scaled value based on the CCT value determined by the controller;

the second control channel is configured to provide the second controllable drive current; and

the third control channel is configured to provide the third controllable drive current.

9. The tunable lighting system of claim 8 wherein:

the first non-white color is one of red, amber and orange;

the second non-white color is one of green and blue; and

the third non-white color is the other one of green and blue.

10. The tunable lighting system of claim 8 wherein:

the first non-white color is green;

the second non-white color is one of (a) either red, amber, or orange and (b) blue; and

the third non-white color is the other one of (a) either red, amber, or orange and (b) blue.

11. The tunable lighting system of claim 8 wherein:

the separate portion of the first controllable drive current, and the second and third controllable drive currents include three first values defining a first triangle in a color space;

the first triangle forms a first boundary about the spectral characteristics of the white light output; and

the three first values of the first triangle drive the spectral characteristics of the non-white light emitting semiconductor devices, at a first time.

12. The tunable lighting system of claim 11 wherein:

the controller is configured to modify at least one of the three first values to form a second three values defining a second triangle in the color space;

the second three values of the second triangle drive the non-white light emitting semiconductor devices, at a second time; and

the second time follows the first time.

13. The tunable lighting system of claim 12 wherein:

the controller is configured to compute the second three values of the second triangle to form a second boundary about the spectral characteristics of the white light output.

14. A substantially white luminaire comprising:

at least one light emitting diode (LED) configured to produce a white light;

at least one LED configured to produce a first non-white light;

at least one LED configured to produce a second non-white light;

at least one LED configured to produce a third non-white light;

a first channel driver coupled to both (a) the at least one LED configured to produce white light and (b) the at least one LED configured to produce the first non-white light;

a second channel driver coupled to the at least one LED configured to produce the second non-white light; and

a third channel driver coupled to the at least one LED configured to produce the third non-white light;

wherein the first channel driver controls intensity of the white light and intensity of the first non-white light, and

the intensity of the first non-white light is set to a scalable percentage of the intensity of lighting output from the LED configured to produce white light.

15. The luminaire of claim 14 wherein:

the first non-white color is one of red, amber and orange;

the second non-white color is one of green and blue; and

the third non-white color is the other one of green and blue.

16. The luminaire of claim 14 wherein:

the first non-white color is green;

the second non-white color is one of (a) either red, amber, or orange and (b) blue; and

the third non-white color is the other one of (a) either red, amber, or orange and (b) blue.

17. The luminaire of claim 14 further comprising:

a controller for determining spectral characteristics of the white light, in response to a user selection corresponding to a correlated color temperature (CCT) value;

wherein the controller;

computes spectral characteristics of the first, second and third non-white colors about the spectral characteristics of the white light, and

modifies the spectral characteristics of at least one of the first, second and third non-white colors, in response to the selected CCT value.

18. The luminaire of claim 14 wherein:

the first channel driver includes two digital to analog converters (DACs) for producing a signal controlling intensity of the white light and the first non-white color of light; and

the second and third channels include, respectively, second and third DACs for producing signal controlling intensities of the second and third non-white colors of light.

19. The luminaire of claim 14 wherein

the scalable percentage of the intensity of the non-white light to the white light is modifiable by the first channel driver, over a continuous range of values spanning from ON to OFF.

20. The luminaire of claim 14 wherein

the scalable percentage of the intensity of the non-white light to the white light is modifiable by the first channel driver, over discrete ranges of values spanning from ON to OFF.