WO2008078240A1 - Adjusting a driving signal for solid-state lighting devices - Google Patents
Adjusting a driving signal for solid-state lighting devices Download PDFInfo
- Publication number
- WO2008078240A1 WO2008078240A1 PCT/IB2007/055122 IB2007055122W WO2008078240A1 WO 2008078240 A1 WO2008078240 A1 WO 2008078240A1 IB 2007055122 W IB2007055122 W IB 2007055122W WO 2008078240 A1 WO2008078240 A1 WO 2008078240A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- colour
- lighting device
- point
- temperature
- driving signal
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/20—Controlling the colour of the light
- H05B45/22—Controlling the colour of the light using optical feedback
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/20—Controlling the colour of the light
- H05B45/28—Controlling the colour of the light using temperature feedback
Definitions
- the present patent application relates to solid-state lighting and methods for adjusting a driving signal for lighting devices.
- solid-state lighting devices consist of light emitting diodes (LEDs), organic light emitting diodes (OLEDs) or a mixture of these, and in many application red, green and blue LED arrays are employed.
- LEDs light emitting diodes
- OLEDs organic light emitting diodes
- Such lighting devices are applied in different units, e.g. LCD backlighting or white LED lamps. They provide high efficiency and high colour rendering indices.
- Such a lighting device requires colour control systems to achieve colour point accuracy for illumination.
- Some kinds of these lighting devices use colour coordinates feedback schemes for controlling their light output. These schemes seem to be particular suitable, but they offer colour errors as a function of temperature.
- a method for adjusting a driving signal for a lighting device comprising obtaining a temperature of the lighting device, adjusting at least one parameter of a conversion procedure depending on the obtained temperature, converting a set-point of a desired colour and/or brightness into a set-point of colour sensor coordinates with the conversion procedure, obtaining actual colour values of the lighting device, and adjusting the driving signal depending on a difference between the colour sensor coordinates set-point and the obtained colour values.
- a temperature of the lighting device may be obtained by measuring, whereby the temperature may be a single temperature or an averaged temperature of the lighting device. Based on the temperature at least one parameter of the conversion procedure may be adjusted. This may be used to convert a set-point for a desired colour and/or brightness into a set-point of colour sensor coordinates.
- This set-point of colour sensor coordinates may consist of tristimulus values.
- the emitted light may be given by its luminous flux and its chromaticity coordinates. These values can be easily transferred into tristimulus values. Therefore these values may cause a better result of colour point accuracy than luminous flux individually.
- the set-point of colour sensor coordinates may consist of the raw data of colour sensor readings.
- tristimulus values are converted to raw data of sensor readings as part of the above mentioned conversion procedure.
- This approach has the advantage that raw data of sensor readings can be handled more efficiently than tristimulus values in the feedback loop. Further the actual colour values may be obtained by a colour sensor.
- an error signal may be established.
- This function can be realised for example by a proportional- integral-derivative controller (PID controller).
- PID controller proportional- integral-derivative controller
- the colour and/or brightness vary depending on the temperature of the lighting device.
- the temperature is measured for adjusting the set-point of a desired colour and/or brightness. Because the temperature changes are significantly slower than the changes of the measured light output the adjustment may be made in a feed forward way. This leads to an easy implementation and it does not yield any problems of stability. Instead of this the colour values are led back by a feedback scheme for responding to changes of the measured light output in a sufficient way.
- the temperature of the colour sensor unit is a part of the lighting device and its temperature affects the relation between the raw data of its readings and tristimulus values of the light output of the lighting device.
- both the colour sensor unit and the LEDs are thermally coupled to a heatsink of the lighting device. Then the temperature of the heatsink and the LEDs may be inferred from the temperature of the colour sensor unit. Therefore, the temperature of the colour sensor unit can also be measured, which causes an even better accuracy of a desired colour point.
- Another favourable embodiment according to claim 5 is to calibrate at different temperatures. For all possible temperatures accurate parameters are obtained by this way.
- calibrating data of lighting devices of similar design can be used for calibrating. This reduces the effort and accuracy is maintained in a sufficient manner.
- Some lamps of a production can be calibrated in detail and the remaining lamps will be calibrated with the averaged calibrating data of the exactly calibrated lighting devices. Furthermore, it is possible to calculate numerically the parameters from known features of the used LEDs.
- a method for obtaining the temperature of the lighting device using a current-voltage characteristic of the lighting device is further preferred according to claim 7.
- the use of a temperature sensor may be omitted.
- the current-voltage voltage characteristic of the lighting device is mostly already known within the lighting device and therefore it is not laboriously to get the needed data.
- Another favourable embodiment of the method according to claim 8 is to obtain the actual colour values of the lighting device by sensing with the peak sensitivity in different parts of a visible spectrum.
- the advantage consists of adjusting a desired sensitivity of the visible spectrum.
- the sensed data can be filtered by a low-pass filter to reduce the data.
- the eye sensitivity may be emulated as well.
- the different parts of the visible spectrum can be red, green and blue. These three fundamental colours are sensed by the human eye through its three different kinds of cones whereby every cone can detect one of these colours. Therefore, it is favourable to use these three parts for emulating the human sensitivity of the visible spectrum.
- the filter characteristics of the colour sensors may be tuned such that they are virtually identical to the eye sensitivity functions.
- Compensating ageing of the lighting device by updating its calibration with the integrated sensors of the lighting device is further preferred according to claim 9.
- the parameters are updated. This can be easily done with its own sensors without great costs.
- a further preferred embodiment is to lead the driving signal back, and to rescale the set-point of a desired colour and/or brightness if the driving signal exceeds a predetermined signal threshold. If the driving signal increases this predetermined signal threshold saturation occurs. Leading the driving signal back and rescaling the set-point by limiting the brightness provides avoiding this effect.
- the temperature of the lighting device can be used as an indicator for rescaling as well. Then, the temperature is also led back.
- Another aspect of the patent application is a system for adjusting a driving signal for a lighting device comprising a temperature sensor unit for obtaining a temperature of the lighting device, a conversion procedure unit for converting a set-point of a desired colour and/or brightness into a set-point of colour sensor coordinates, a colour sensor unit for obtaining actual colour values of the lighting device, and a driving unit for adjusting the driving signal depending on a difference between the colour sensor coordinates set-point and the obtained colour values.
- a further aspect is a computer program product tangibly embodied in an information carrier, the computer program product comprising instructions that, when executed, cause at least one processor to perform operations comprising obtaining a temperature of the lighting device, adjusting at least one parameter of a conversion procedure depending on the obtained temperature, converting a set-point of a desired colour and/or brightness into a set-point of colour sensor coordinates with the conversion procedure, obtaining actual colour values of the lighting device, and adjusting the driving signal depending on a difference between the colour sensor coordinates set-point and the obtained colour values.
- Another aspect is a computer program for adjusting a driving signal for a lighting device the program instructions operable to cause a processor to obtain a temperature of the lighting device, adjust at least one parameter of a conversion procedure depending on the obtained temperature, convert a set-point of a desired colour and/or brightness into a set-point of colour sensor coordinates with the conversion procedure, obtain actual colour values of the lighting device, and adjust the driving signal depending on a difference between the colour sensor coordinates set-point and the obtained colour values.
- Fig 1 a system according to an embodiment
- Fig 3 a flowchart illustrating the adjusting of a driving signal for a lighting device
- the present application provides for an improvement of colour control accuracy and a significant reduction of colour errors for solid-state lighting devices.
- a system 100 of a first embodiment is illustrated.
- the system 100 comprises a conversion procedure unit 102 and a driving unit 104 which drives the lighting device 106.
- a driving unit 104 which drives the lighting device 106.
- the set-point of a desired colour and/or brightness 108 and the converted set-point of colour sensor coordinates 112.
- the colour sensor coordinates 116 of the actual values of the lighting device 106 and the built error signal 114 are also represented as the driving signal 118 and the temperature 110.
- Fig.2 shows a system 200 of a further embodiment of the present application.
- the already known units are not mentioned again and they hold the same designations as in Fig.l.
- a rescaling unit 202 is illustrated.
- the lighting device 106 comprises a temperature sensor unit 206 and a colour sensor unit 204. Illustrated is a limited set-point signal 208 as well as a controlling signal 210 of the driving signal 118.
- the temperature 110 is either the measured temperature of a heat sink of the lighting device 106 or the measured temperature of the LEDs or the measured temperature of the colour sensor unit 204 or a combination of these.
- the heatsink of the lighting device 106 is not illustrated.
- Fig.3 illustrates a flowchart 300 for adjusting a driving signal 118 for a lighting device 106.
- the parameters of the conversion procedure unit 102 have to be obtained by calibrating. There exist several methods for calibrating which are not illustrated in the flowchart 300. After the calibration a user sets a desired colour and/or brightness set-point 108 in a first step 302.
- step 304 it is checked, if the controlling signal 210 surpasses a predetermined signal threshold.
- the set-point of a desired colour and/or brightness 108 is limited in its brightness by the rescaling unit 202. This has to be done for avoiding a saturation of the driving signal 118. Otherwise the set-point of a desired colour and/or brightness 108 is forwarded to the conversion procedure unit 102 without limiting the brightness.
- the conversion occurs from the set-point of a desired colour and/or brightness 108 or the limited set-point signal 208 to a set-point of a colour sensor coordinates 112. Therefore, the temperature 110 of the lighting device 106 is sensed by a temperature sensor unit 206.
- the temperature 110 of the colour sensor unit 204 can be sensed by the temperature sensor unit 206 as well.
- the temperature 110 is directed to the conversion procedure unit 102 in a feed forward manner. Based on the temperature 110 and on an accurate previous calibration the set- points 108, 208 are converted into the set-point of a colour sensor coordinates 112.
- the next step 308 includes adjusting the driving signal 118 for the lighting device 106.
- the colour values of the actual light output are obtained by a colour sensor unit 204 and the sensed colour sensor coordinates 116 are directed in a feedback way. This signal 116 is subtracted from the set-point of the colour sensor coordinates 112 with the result of an error signal 114.
- the driving unit 104 generates a driving signal 118 for driving the lighting device 106.
- the lighting device 106 emits light with high accuracy of a desired colour point.
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP07849500A EP2095687A1 (en) | 2006-12-20 | 2007-12-14 | Adjusting a driving signal for solid-state lighting devices |
JP2009542321A JP2010514128A (en) | 2006-12-20 | 2007-12-14 | Driving signal adjustment for solid-state lighting devices |
CN2007800478098A CN101569237B (en) | 2006-12-20 | 2007-12-14 | Adjusting a driving signal for solid-state lighting devices |
US12/519,391 US20100045188A1 (en) | 2006-12-20 | 2007-12-14 | Adjusting a driving signal for solid-state lighting devices |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP06126680 | 2006-12-20 | ||
EP06126680.5 | 2006-12-20 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2008078240A1 true WO2008078240A1 (en) | 2008-07-03 |
Family
ID=39321428
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB2007/055122 WO2008078240A1 (en) | 2006-12-20 | 2007-12-14 | Adjusting a driving signal for solid-state lighting devices |
Country Status (6)
Country | Link |
---|---|
US (1) | US20100045188A1 (en) |
EP (1) | EP2095687A1 (en) |
JP (1) | JP2010514128A (en) |
CN (1) | CN101569237B (en) |
TW (1) | TW200843549A (en) |
WO (1) | WO2008078240A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2009017724A1 (en) * | 2007-07-31 | 2009-02-05 | Cree, Inc. | Correction of temperature induced color drift in solid state lighting displays |
US7969097B2 (en) | 2006-05-31 | 2011-06-28 | Cree, Inc. | Lighting device with color control, and method of lighting |
US8866410B2 (en) | 2007-11-28 | 2014-10-21 | Cree, Inc. | Solid state lighting devices and methods of manufacturing the same |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102016207727A1 (en) | 2016-05-04 | 2017-11-09 | Bayerische Motoren Werke Aktiengesellschaft | lighting device |
DE102016207728A1 (en) * | 2016-05-04 | 2017-11-09 | Bayerische Motoren Werke Aktiengesellschaft | lighting device |
CN107205303B (en) * | 2017-06-30 | 2023-06-20 | 欧普照明股份有限公司 | Color sensor module, intelligent lighting device and intelligent lighting control method |
Citations (8)
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WO2002047438A2 (en) * | 2000-12-07 | 2002-06-13 | Koninklijke Philips Electronics N.V. | Led luminary system |
US6411046B1 (en) * | 2000-12-27 | 2002-06-25 | Koninklijke Philips Electronics, N. V. | Effective modeling of CIE xy coordinates for a plurality of LEDs for white LED light control |
WO2003037042A1 (en) * | 2001-10-22 | 2003-05-01 | Koninklijke Philips Electronics N.V. | Led control apparatus |
WO2006011108A1 (en) | 2004-07-23 | 2006-02-02 | Koninklijke Philips Electronics N.V. | System for temperature prioritised colour controlling of a solid-state lighting unit |
US20060091826A1 (en) * | 2004-10-28 | 2006-05-04 | Chen Cheng F | LED controller and control method thereof |
US20060245174A1 (en) * | 2004-10-12 | 2006-11-02 | Tir Systems Ltd. | Method and system for feedback and control of a luminaire |
WO2006126124A2 (en) * | 2005-05-25 | 2006-11-30 | Koninklijke Philips Electronics N.V. | Describing two led colors as a single, lumped led color |
WO2007049180A1 (en) * | 2005-10-26 | 2007-05-03 | Koninklijke Philips Electronics N.V. | Led luminary system |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2006126151A2 (en) * | 2005-05-27 | 2006-11-30 | Koninklijke Philips Electronics N.V. | Controlling an arrangement of semiconductors emitting light of distinct colors |
TWI293543B (en) * | 2005-12-07 | 2008-02-11 | Ind Tech Res Inst | Illumination brightness and color control system and method thereof |
-
2007
- 2007-12-14 WO PCT/IB2007/055122 patent/WO2008078240A1/en active Application Filing
- 2007-12-14 JP JP2009542321A patent/JP2010514128A/en not_active Abandoned
- 2007-12-14 US US12/519,391 patent/US20100045188A1/en not_active Abandoned
- 2007-12-14 EP EP07849500A patent/EP2095687A1/en not_active Withdrawn
- 2007-12-14 CN CN2007800478098A patent/CN101569237B/en not_active Expired - Fee Related
- 2007-12-17 TW TW096148254A patent/TW200843549A/en unknown
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2002047438A2 (en) * | 2000-12-07 | 2002-06-13 | Koninklijke Philips Electronics N.V. | Led luminary system |
US6411046B1 (en) * | 2000-12-27 | 2002-06-25 | Koninklijke Philips Electronics, N. V. | Effective modeling of CIE xy coordinates for a plurality of LEDs for white LED light control |
WO2003037042A1 (en) * | 2001-10-22 | 2003-05-01 | Koninklijke Philips Electronics N.V. | Led control apparatus |
WO2006011108A1 (en) | 2004-07-23 | 2006-02-02 | Koninklijke Philips Electronics N.V. | System for temperature prioritised colour controlling of a solid-state lighting unit |
US20060245174A1 (en) * | 2004-10-12 | 2006-11-02 | Tir Systems Ltd. | Method and system for feedback and control of a luminaire |
US20060091826A1 (en) * | 2004-10-28 | 2006-05-04 | Chen Cheng F | LED controller and control method thereof |
WO2006126124A2 (en) * | 2005-05-25 | 2006-11-30 | Koninklijke Philips Electronics N.V. | Describing two led colors as a single, lumped led color |
WO2007049180A1 (en) * | 2005-10-26 | 2007-05-03 | Koninklijke Philips Electronics N.V. | Led luminary system |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7969097B2 (en) | 2006-05-31 | 2011-06-28 | Cree, Inc. | Lighting device with color control, and method of lighting |
WO2009017724A1 (en) * | 2007-07-31 | 2009-02-05 | Cree, Inc. | Correction of temperature induced color drift in solid state lighting displays |
US8866410B2 (en) | 2007-11-28 | 2014-10-21 | Cree, Inc. | Solid state lighting devices and methods of manufacturing the same |
US9491828B2 (en) | 2007-11-28 | 2016-11-08 | Cree, Inc. | Solid state lighting devices and methods of manufacturing the same |
Also Published As
Publication number | Publication date |
---|---|
TW200843549A (en) | 2008-11-01 |
JP2010514128A (en) | 2010-04-30 |
EP2095687A1 (en) | 2009-09-02 |
CN101569237B (en) | 2011-04-27 |
US20100045188A1 (en) | 2010-02-25 |
CN101569237A (en) | 2009-10-28 |
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