Adjustable color solid state lighting

• US 7,986,102 B2
• Filed: 09/12/2008
• Issued: 07/26/2011
• Est. Priority Date: 09/12/2008
• Status: Active Grant

• Current Assignee: Savant Technologies, LLC (Savant Systems, LLC)
• Original Assignee: General Electric Company
• Inventors: Roberts, Bruce R.
• Primary Examiner(s): Owens; Douglas W
• Assistant Examiner(s): A; Minh D
• Application Number:
  US12/209,490
• Publication Number:
  US 20100066255A1
• Time in Patent Office: 1,047 Days
• Field of Search: 315/209.R, 315/210, 315/291, 315/307, 315/312, 315/224, 315/302
• US Class Current: 315/209.00R
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices

Abstract

A multi-channel light source has different channels for generating illumination of different channel colors corresponding to the different channels. An electrical power supply selectively energizes the channels using time division multiplexing to generate illumination of a selected time-averaged color.

Claims

1. An adjustable color light source comprising:

a light source having different channels for generating illumination of different channel colors corresponding to the different channels; and

an electrical power supply selectively energizing the channels using time division multiplexing to generate illumination of a selected time-averaged color, the electrical power supply including (i) a power source generating a substantially constant rms drive current on a timescale longer than a period T of the time division multiplexing and (ii) circuitry that time division multiplexes the substantially constant rms drive current into selected ones of the channels.

2. The adjustable color light source as set forth in claim 1, wherein the circuitry drives precisely one of the channels with the substantially constant rms drive current at any given time during operation of the adjustable color light source.

3. The adjustable color light source as set forth in claim 2, further comprising:

a current controller configured to communicate with the power source to adjust a current level of the substantially constant rms drive current.

4. The adjustable color light source as set forth in claim 1, wherein the substantially constant rms drive current is a substantially constant d.c. drive current.

5. The adjustable color light source as set forth in claim 1, further comprising:

a photosensor arranged to measure light from the light source, the photosensor being capable of measuring any of the different channel colors corresponding to the different channels of the light source.

6. The adjustable color light source as set forth in claim 5, wherein the color controller is configured to adjust the time division based on feedback provided by the photosensor compared with a setpoint color.

7. An adjustable color light source comprising:

a light source having different channels for generating illumination of different channel colors corresponding to the different channels;

an electrical power supply selectively energizing the channels using time division multiplexing to generate illumination of a selected time-averaged color;

a photosensor having a spectral response effective to measure any of the channel colors of the light source; and

an optical meter configured to estimate at least ratios of optical energy output by the different channels during the selective energizing based on optical power measured by the photosensor correlated with the time division multiplexing.

8. An adjustable color source comprising:

a light source having different channels for generating illumination of different channel colors corresponding to the different channels, the light source including solid state lighting devices grouped into N channels wherein the solid state lighting devices of each channel are electrically energized together when the channel is selectively energized; and

an electrical power supply selectively energizing the channels using time division multiplexing to generate illumination of a selected time-averaged color, the electrical power supply including (i) switching circuitry arranged to energize a selected one of the N channels and (ii) a color controller causing the switching circuitry to operate over a time interval T in accordance with a selected time division of the time interval T to generate illumination of the selected time-averaged color, wherein the time interval T is shorter than a flicker fusion threshold.

9. The adjustable color light source as set forth in claim 8, wherein the solid state lighting devices include LEDs.

10. The adjustable color light source as set forth in claim 8, wherein the LEDs include at least one shared LED that is a member of an overlapping two or more of the N channels such that the at least one shared LED is energized when any one of the overlapping two or more of the N channels is selectively energized.

11. The adjustable color light source as set forth in claim 8, further comprising:

a broadband photosensor having a detection bandwidth encompassing the channel colors generated by the N channels; and

an optical meter receiving a detection signal from the broadband photosensor during each time division and computing a measured optical energy for each time division based at least on the received detection signals;

wherein the color controller is configured to adjust the time division of the time interval T based on the measured optical energies and a setpoint color.

12. An adjustable color light generation method comprising:

generating a drive electrical current;

energizing a selected channel of a multi-channel light source using the generated drive electrical current;

cycling the energizing amongst channels of the multi-channel light source fast enough to substantially suppress visually perceptible flicker due to the cycling; and

controlling a time division of the cycling to generate a selected time-averaged color.

13. The adjustable color light generation method as set forth in claim 12, wherein the generated drive electrical current has a substantially constant rms current value on a time scale of the cycling.

14. The adjustable color light generation method as set forth in claim 13, wherein the generated drive electrical current has a substantially constant d.c. current value on a time scale of the cycling.

15. The adjustable color light generation method as set forth in claim 13, wherein the generating comprises adjusting the substantially constant rms current value on a time scale substantially larger than the cycling.

16. The adjustable color light generation method as set forth in claim 12, wherein the cycling energizes exactly one of the channels of the multi-channel light source at any point in the cycling.

17. An adjustable color light source comprising:

a plurality of illumination channels for generating illumination of different channel colors; and

an electrical power supply cycling an electrical drive current amongst the plurality of illumination channels to generate illumination of a selected time-averaged color, the cycling being non-overlapping in that exactly one illumination channel is driven by the electrical drive current at any point in the cycling.

18. The adjustable color light source as set forth in claim 17, wherein the electrical drive current is substantially constant on a time scale of the cycling.

19. The adjustable color light source as set forth in claim 17, further comprising:

a photosensor arranged to measure electrical power of any channel of the plurality of illumination channels; and

a color controller configured to adjust the cycling based on a signal received from the photosensor and correlated with the cycling.