Method and system for feedback and control of a luminaire

• US 7,573,209 B2
• Filed: 10/12/2005
• Issued: 08/11/2009
• Est. Priority Date: 10/12/2004
• Status: Active Grant

• Current Assignee: Philips Lighting BV (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Ashdown, Ian, Robinson, Shane P.
• Primary Examiner(s): Owens; Douglas W
• Assistant Examiner(s): Alemu; Ephrem
• Application Number:
  US10/558,124
• Publication Number:
  US 20070108846A1
• Time in Patent Office: 1,399 Days
• Field of Search: 315/308, 315/307, 315/149, 315/224, 315/291, 315/312, 345 76- 78, 345/102, 362/612, 362/800
• US Class Current: 315/307
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2330/028 Generation of voltages supplied to electrode drivers in a matrix display other than LCD
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/24 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/28 using temperature feedback
• CPC Class Codes: H05B 45/37 Converter circuits
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A method and system for controlling the chromaticity and luminous flux output of a digitally controlled luminaire. The luminaire comprises one or more light-emitting elements and one or more light sensors which can provide optical feedback, wherein this optical feedback is filtered to remove undesired frequencies. The method and system comprises a control system which can sample the filtered signals from the light sensors according to a predetermined feedback sampling frequency scheme, wherein this scheme is specifically configured to provide sufficient iterations of the feedback loop to be performed for adjustment of the chromaticity and luminous flux output of the light-emitting elements, without perceptible visual flicker or momentary chromaticity shifts.

Claims

1. A system for feedback and control of a luminaire including two or more light-emitting elements in two or more colors, each of the two or more light-emitting elements supplied with electrical current to produce light of a desired chromaticity and luminous flux under operating conditions, the system comprising:

a) a feedback system including two or more light sensors for detecting the light and generating color signals, the feedback system generating current values representative of luminous flux and chromaticity of the light from the color signals, the feedback system further including two or more color filters associated with the two or more light sensors for providing the color signals; and

b) a control system operatively integrated with the feedback system, said control system determining an adjustment factor through a correlation of the current values and a desired chromaticity and luminous flux, the control system adjusting the electrical current to one or more of the two or more light-emitting elements in accordance with the adjustment factor, the control system adjusting the electrical current without perceivable visual flicker or momentary chromaticity shifts.

2. The system according to claim 1, wherein the feedback system further comprises an amplification module operatively coupled to the two or more light sensors, the amplification module comprising a means for applying a gain to the color signals.

3. The system according to claim 2, wherein the means for applying a gain is a logarithmic amplifier.

4. The system according to claim 2, wherein the means for applying a gain applies a selectable gain to the color signals, the selectable gain dependent on the color signals.

5. The system according to claim 4, wherein means for applying a gain is a programmable gain amplifier or an amplifier with a digital potentiometer.

6. The system according to claim 2, wherein the two or more light sensors and the amplification module are formed as a single integrated circuit.

7. The system according to claim 1, wherein the feedback system further comprises one or more thermal sensors for generating signals representative of the two or more light-emitting elements temperature.

8. The system according to claim 1, wherein the feedback system further comprises one or more voltage sensors for generating signals representative of the electrical current transmitted to one or more of the two or more light-emitting elements.

9. The system according to claim 1, wherein the one or more light sensors are operatively coupled to a filter system, the filter system for filtering undesired frequencies from the color signals, the undesired frequencies including the control system operational frequency.

10. The system according to claim 1, wherein one or more of the two or more light sensors are broadband sensors.

11. The system according to claim 1, wherein the one or more of the two or more light sensors are narrowband sensors.

12. The system according to claim 1, wherein the two or more light sensors are optically coupled to a filter, the filter defining a wavelength range of the light that interacts with the two or more light sensors.

13. The system according to claim 1, wherein the control system comprises means to adjust the electrical current to the two or more light-emitting elements using pulse width modulation or pulse code modulation, each of the pulse width modulation and pulse code modulation having a pulse cycle.

14. The system according to claim 13, wherein the control system further comprises a means for modulating pulse width for each pulse cycle, thereby increasing control resolution of the two or more light-emitting elements.

15. The system according to claim 14, wherein the means for modulating the pulse width comprises a N-bit adder operatively coupled to a controller, the N-bit adder providing the controller with control signals for controlling the electrical current to the two or more light-emitting elements, the means for modulating the pulse width further comprising a M-bit programmable counter coupled to the N-bit adder, the means to modulate the pulse width thereby providing a control resolution of 2^N+M states.

16. The system according to claim 15, wherein the means for modulating the pulse width further comprises an exception handling circuit operatively connected to the M-bit programmable counter and the N-bit adder.

17. The system according to claim 16, wherein the means for modulating the pulse width further comprises a divide by N counter operatively connected to the M-bit programmable counter, said divide by N counter for resetting the M-bit programmable counter.

18. The system according to claim 1, wherein the feedback system is operated at a sampling frequency greater than or equal to about 240 Hz.

19. The system according to claim 1, wherein the control system is operated at a control frequency greater than or equal to about 20 kHz.

20. A method for controlling a luminaire including two or more light-emitting elements in two or more colors, each of the two or more light-emitting elements supplied with electrical current to produce light of desired chromaticity and luminous flux under operating conditions, the method comprising the steps of:

a) sensing, using two or more light sensors, predetermined fractions of light emitted by the luminaire in each of the two or more colors providing two or more sensed color signals;

b) processing, using two or more color filters associated with the two or more light sensors each of the one or more sensed color signals thereby determining two or more filtered color signals;

c) transforming the one or more filtered color signals directly into control signals representative of the desired chromaticity and luminous flux; and

d) adjusting electrical current supplied to each of the two or more light-emitting elements based on the control signals, wherein the step of adjusting is performed without perceivable visual flicker or momentary chromaticity shifts.