NL2002605C2 - Method and electrical circuit for automatically adjusting the light-colour of light emitting diodes. - Google Patents

Method and electrical circuit for automatically adjusting the light-colour of light emitting diodes. Download PDF

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Publication number
NL2002605C2
NL2002605C2 NL2002605A NL2002605A NL2002605C2 NL 2002605 C2 NL2002605 C2 NL 2002605C2 NL 2002605 A NL2002605 A NL 2002605A NL 2002605 A NL2002605 A NL 2002605A NL 2002605 C2 NL2002605 C2 NL 2002605C2
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NL
Netherlands
Prior art keywords
current
led
light
level
light color
Prior art date
Application number
NL2002605A
Other languages
Dutch (nl)
Inventor
Gerard Kroone
Original Assignee
Ledzworld B V
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ledzworld B V filed Critical Ledzworld B V
Priority to NL2002605A priority Critical patent/NL2002605C2/en
Application granted granted Critical
Publication of NL2002605C2 publication Critical patent/NL2002605C2/en

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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

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  • Circuit Arrangement For Electric Light Sources In General (AREA)
  • Led Devices (AREA)

Description

Method and electrical circuit for automatically adjusting the light-colour of light emitting diodes
The invention relates to a method and circuit for automatically adjusting the light-colour of light emitting diodes that collectively emit light at a predefined light-intensity.
The invention further relates to an electrical circuit 5 connected of connectable to a current source and comprising light emitting diodes (LEDS) that in use collectively emit light at a predefined variable light-intensity depending on the level of a feeding-current, supplied by the current source.
A known problem with light that stems from light emit-10 ting diodes is that when the light-intensity of the light emitted by the LEDS is diminished by reason that the level of the current that flows through the LEDS is lowered, the colour of the light does not shift to red in the light-spectrum as occurs with the lowering of conventional light sources such as light 15 bulbs. Due to the fact that the light-colour of such dimmed LEDS remains at its original level the light from dimmed LEDS is experienced as being unnatural or even unpleasant.
It is an object of the invention to improve the natural feeling experienced when illumination is performed by LEDS, 20 particularly by LEDS that are reduced in their level of light-intensity, such that the light that originates from such light emitting diodes shifts then to warmer colours.
To realise the above-mentioned objective the method and electrical circuit of the invention is characterized by one or 25 more of the appended claims.
In a first aspect of the invention the method for automatically adjusting the light-colour of light emitting diodes that collectively emit light, is characterized in that at least a first LED having a first light-colour is applied in combina-30 tion with at least a second LED having a second light-colour, wherein the first light-colour differs from the second light-colour and that the first LED and the second LED receive a first current and second current respectively, wherein the level of said first current and/or said second current is selected de-35 pending on the level of said light-intensity. By a proper choice of the light colours of the at least one first LED and the at least one second LED it is then possible to obtain a mixture of the light stemming from such LEDS that is consistent with what 2 the human eye experiences as a natural shift in colour when the light-intensity of the LEDS is changed.
The method of the invention is advantageously realised by the application of an electrical circuit that is connected or 5 connectable to a current source and which circuit comprises light emitting diodes that in use collectively emit light at a light-intensity that depends on the level of the feeding-current that is supplied by the current source. In accordance with the invention this electrical circuit comprises at least one first 10 LED having a first light-colour and at least one second LED having a second light-colour, wherein the first light-colour differs from the second light-colour, and that it is arranged to distribute the feeding-current, from the current source into a first current for the at least one first LED and a second cur-15 rent for the at least one second LED, and that the level of said first current and/or said second current depends on the level of the feeding-current.
A for its simplicity preferred option to implement the method of the invention is that the level of the first current 20 is kept constant whilst the level of the second current is varied depending on the level of the light-intensity.
A first preferred embodiment of the electrical circuit of the invention has the feature that the at least one first LED and the at least one second LED are electrically in a parallel 25 arrangement, and that the at least one first LED is connected to a control circuit for stabilizing the first current through said at least one first LED. In this way it is substantially only the second current trough the at least one second LED that follows the variation of the feeding-current supplied by the current 30 source. In that situation it is preferable that the at least one first LED has a light-colour which is closer to red in the light-spectrum than the first colour of the at least one second LED. Thus when the feeding current is lowered, the at least one first LED having the warmer light-colour becomes relatively more 35 important in its contribution to the total light that is emitted by the LEDS collectively, than the light that stems from the at least one second LED that is more distant in the spectrum from the red area.
A second preferred embodiment of the electrical circuit 40 of the invention has the feature that the at least one first LED and the at least one second LED are electrically in a series ar- 3 rangement, and that it comprises a control circuit for increasing the share of the first current through the at least one first LED and/or decreasing the share of the second current through the at least one second LED when the level of the feed-5 ing-current is decreased and vice versa.
This can suitably be arranged by having the control circuit connected or connectable to the current source for receiving a current-part of the feeding-current., and an outlet of the control circuit connected at an interconnecting point of the 10 at least one first LED and the at least one second LED, wherein the at least one first LED is connected to earth and wherein the at least one second LED is electrically connected or connectable to the current source for receiving the remainder of the feeding-current .
15 The invention will hereinafter be further elucidated with reference to some exemplary embodiments of the electrical circuit of the invention and with reference to the drawing.
In the drawing: - Fig. 1 shows a first preferred embodiment of the 20 electrical circuit of the invention, and - Fig. 2 shows a second preferred embodiment of the electrical circuit of the invention.
With reference to both Fig. 1 and Fig. 2 an electrical circuit is shown that is connected or connectable to a current 25 source at its connecting points 1 and 2. The circuit comprises light-emitting diodes LD1-LD8 in Fig. 1 and LD1-LD5 in Fig. 2, which LEDS when the electrical circuit is in operation, collectively emit light at a predefined light-intensity that depends on the level of a feeding current supplied by the current source 30 that is connected (or connectable) to the points 1 and 2.
Fig. 1 shows a first embodiment of the electrical circuit of the invention having a series of first LEDS, i.e. at least one LED, indicated with LDl, LD2, LD3 and LD4 that have a first light colour, for instance red. Furthermore, there is a 35 series of second LEDS, LD5, LD6, LD7, LD8 or at least one of those LEDS which has a second light colour, for instance white.
Both series of LEDS are fed by a current originating from a feeding current It, that is supplied by the current source at the points 1 and 2. The feeding current It is distrib-40 uted into a first current Ir, which flows through the series of first LEDS LD1-LD4 and into a second current Iw that flows 4 through the series of second LEDS LD5-LD8.
The series of first LEDS LD1-LD4 is connected to a control circuit R16-U2, which is arranged to stabilize the current Ir though the series of first LEDS LD1-LD4, such that when the 5 feeding current It is varied, the first current Ir through the series of first LEDS LD1-LD4 is maintained at its original level, whereas the variation of the feeding current It directly translates into a corresponding variation of the second current Iw through the series of second LEDS LD5-LD8.
10 Thus, when the level of the feeding current It dimin ishes the comparative contribution of the series of first LEDS LD1-LD4 in the aggregated amount of light that is emitted by the LEDS LD1-LD8 increases, and the light-colour of the aggregated light thus emitted, shifts to the red part of the light spec-15 trum. This pleases the human eye and is experienced as a natural light behaviour when the light-intensity of the aggregated light emitted by the LEDS LD1-LD8 is reduced.
With reference now to Fig. 2 a second embodiment of the electrical circuit of the invention is shown in which at least 20 one first LED LD5 with a first light colour, for instance amber, is placed in series with at least one second LED, in the shown case four LEDS, LD1, LD2, LD3, LD4, having a second light-colour, in particular white. In this second embodiment there is a control circuit A for increasing the share of the first cur-25 rent Ir through the at least one first LED LD5 and/or decreasing the share of the second current Iw through the at least one second LED LD1-LD4, when the level of the feeding current It is decreased or vice versa.
To realise the just-mentioned objective, the control 30 circuit A secures in the case that the feeding current It is at its maximum value that at the interconnecting point 3 at which the at least one first LED LD5 is electrically connected with the at least one second LED, LD1-LD4, no current adds up to the second current Iw that flows through the series of second LEDS, 35 LD1-LD4. This is realized by the application of the Zener-diode D8, which induces that with the maximum feeding current It present and consequently a maximum voltage present at the points 1, 2, transistor Q2 will entertain a current in its emitter and collector lines causing that transistor Q3 is blocked, so that 40 no current will flow in its collector line.
Conversely when the voltage at the points 1, 2 is de- 5 creased and consequently the feeding current It is decreased that feeds the series of LEDS LD1-LD5, this will result in a gradual increase of the current flowing through the emitter and collector line of transistor Q3. Consequently an increasing cur-5 rent will thus flow through the resistor R22 to the interconnecting point 3 that electrically connects to the first LED LD5 with the first colour. A relatively larger amount of the feeding current It will then flow through the resistor R22 to the first LED LD5, which is at the cost of the current Iw that flows 10 through the series of second LEDS LD1-LD4. The relative part of the light emitted by the first LED LD5 then increases as compared to the part that stems from the series of second LEDS LD1-LD4, and the light colour of the aggregated light that stems from all LEDS LD1-LD5, thus shifts to the red part of the light 15 spectrum.

Claims (7)

1. Werkwijze voor het automatisch aanpassen van de lichtkleur van lichtemitterende diodes (LEDS), die gezamenlijk licht uitstralen met een vooraf bepaalde lichtintensiteit, met het kenmerk, dat ten minste een eerste LED met een eerste licht- 5 kleur in combinatie wordt gebruikt met ten minste een tweede LED met een tweede lichtkleur, waarbij de eerste lichtkleur afwijkt van de tweede lichtkleur, en dat de eerste LED en de tweede LED een eerste stroom respectievelijk een tweede stroom ontvangen waarin het niveau van genoemde eerste stroom en/of tweede stroom 10 gekozen is afhankelijk van het niveau van de lichtintensiteit.Method for automatically adjusting the light color of light-emitting diodes (LEDS), which jointly emit light with a predetermined light intensity, characterized in that at least a first LED with a first light color is used in combination with at least at least a second LED with a second light color, the first light color deviating from the second light color, and in that the first LED and the second LED receive a first current and a second current respectively in which the level of said first current and / or second current 10 is selected depends on the light intensity level. 2. Werkwijze volgens conclusie 1, met het kenmerk, dat het niveau van de eerste stroom constant wordt gehouden, terwijl het niveau van de tweede stroom gevarieerd wordt in afhankelijkheid van het niveau van de lichtintensiteit.Method according to claim 1, characterized in that the level of the first current is kept constant, while the level of the second current is varied depending on the level of the light intensity. 3. Schakeling verbonden of verbindbaar met een stroom bron en voorzien van lichtemitterende diodes (LEDS) die tijdens gebruik gezamenlijk licht uitstralen op een vooraf bepaalde variabele lichtintensiteit die afhankelijk is van het niveau van een voedingsstroom die verschaft wordt door de stroombron, met 20 het kenmerk, dat deze ten minste een eerste LED met een eerste lichtkleur en ten minste een tweede LED met een tweede lichtkleur bezit, waarbij de eerste lichtkleur afwijkt van de tweede lichtkleur, en dat deze is ingericht om de voedingsstroom van de stroombron te verdelen in een eerste stroom voor de ten minste 25 ene tweede LED en dat het niveau van genoemde eerste stroom en/of tweede stroom afhankelijk is van het niveau van de voedingsstroom.3. Circuit connected or connectable to a current source and provided with light-emitting diodes (LEDS) which during use collectively emit light at a predetermined variable light intensity which is dependent on the level of a supply current provided by the current source, characterized in that it has at least a first LED with a first light color and at least a second LED with a second light color, the first light color deviating from the second light color, and that it is arranged to divide the supply current from the current source into a first current for the at least one second LED and that the level of said first current and / or second current is dependent on the level of the supply current. 4. Schakeling volgens conclusie 3, met het kenmerk, dat de ten minste ene eerste LED en de ten minste ene tweede LED 30 elektrisch parallel geschakeld zijn en dat de ten minste ene eerste LED verbonden is met een regelschakeling voor het stabiliseren van de eerste stroom door genoemde ten minste ene eerste LED.Circuit according to claim 3, characterized in that the at least one first LED and the at least one second LED 30 are electrically connected in parallel and in that the at least one first LED is connected to a control circuit for stabilizing the first current by said at least one first LED. 5. Schakeling volgens conclusie 3, met het kenmerk, dat 35 de ten minste ene eerste LED en de ten minste ene tweede LED elektrisch in serie zijn geschakeld, en dat deze een regelschakeling omvat voor het verhogen van het aandeel van de eerste stroom door de ten minste ene eerste LED en/of verlagen van het aandeel van de tweede stroom door de ten minste ene tweede LED 5 wanneer het niveau van de voedingsstroom verlaagd wordt, en vice versa.5. A circuit according to claim 3, characterized in that the at least one first LED and the at least one second LED are electrically connected in series, and that it comprises a control circuit for increasing the proportion of the first current through the at least one first LED and / or decreasing the proportion of the second current through the at least one second LED 5 when the level of the supply current is lowered, and vice versa. 6. Schakeling volgens conclusie 5, met het kenmerk, dat de regelschakeling verbonden is of verbindbaar is met de stroombron voor het ontvangen van een stroomdeel van de voe- 10 dingsstroom, en dat een uitgang van genoemde regelschakeling verbonden is met een verbindingspunt van de ten minste ene eerste LED en de ten minste ene tweede LED, waarbij de ten minste ene eerste LED verbonden is met aarde en waarbij de ten minste ene tweede LED elektrisch verbonden of verbindbaar is met de 15 stroombron voor het ontvangen van het overblijvende deel van de voedingsstroom.6. Circuit according to claim 5, characterized in that the control circuit is connected or connectable to the current source for receiving a current part of the supply current, and in that an output of said control circuit is connected to a connection point of the at least one first LED and the at least one second LED, wherein the at least one first LED is connected to ground and wherein the at least one second LED is electrically connected or connectable to the current source for receiving the remaining part of the supply current . 7. Schakeling volgens een der conclusies 4-6, met het kenmerk, dat de ten minste ene eerste LED een lichtkleur heeft, welke in het lichtspectrum dichter bij rood ligt dan de licht- 20 kleur van de ten minste ene tweede LED.7. Circuit as claimed in any of the claims 4-6, characterized in that the at least one first LED has a light color which is closer to red in the light spectrum than the light color of the at least one second LED.
NL2002605A 2009-03-10 2009-03-10 Method and electrical circuit for automatically adjusting the light-colour of light emitting diodes. NL2002605C2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
NL2002605A NL2002605C2 (en) 2009-03-10 2009-03-10 Method and electrical circuit for automatically adjusting the light-colour of light emitting diodes.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL2002605A NL2002605C2 (en) 2009-03-10 2009-03-10 Method and electrical circuit for automatically adjusting the light-colour of light emitting diodes.
NL2002605 2009-03-10

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NL2002605C2 true NL2002605C2 (en) 2010-09-13

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Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1318701A2 (en) * 2001-12-05 2003-06-11 Audi Ag Apparatus and method for driving a plurality of Leds
WO2006018604A1 (en) * 2004-08-20 2006-02-23 E-Light Limited Lighting system power adaptor
WO2007078091A1 (en) * 2005-12-30 2007-07-12 Seoul Semiconductor Co., Ltd. Light emitting apparatus
WO2008041151A2 (en) * 2006-10-06 2008-04-10 Philips Intellectual Property & Standards Gmbh Light element array with controllable current sources and method of operation
WO2008108468A1 (en) * 2007-03-08 2008-09-12 Rohm Co., Ltd. Led illumination device and its drive method
US20080224631A1 (en) * 2007-03-12 2008-09-18 Melanson John L Color variations in a dimmable lighting device with stable color temperature light sources
WO2008120166A1 (en) * 2007-04-02 2008-10-09 Koninklijke Philips Electronics N.V. Driving light emitting diodes
US20080252197A1 (en) * 2007-04-13 2008-10-16 Intematix Corporation Color temperature tunable white light source
WO2008149294A1 (en) * 2007-06-08 2008-12-11 Koninklijke Philips Electronics N.V. Driving circuit for driving a plurality of light sources arranged in a series configuration
WO2009013676A2 (en) * 2007-07-23 2009-01-29 Nxp B.V. Led arrangement with bypass driving

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1318701A2 (en) * 2001-12-05 2003-06-11 Audi Ag Apparatus and method for driving a plurality of Leds
WO2006018604A1 (en) * 2004-08-20 2006-02-23 E-Light Limited Lighting system power adaptor
WO2007078091A1 (en) * 2005-12-30 2007-07-12 Seoul Semiconductor Co., Ltd. Light emitting apparatus
WO2008041151A2 (en) * 2006-10-06 2008-04-10 Philips Intellectual Property & Standards Gmbh Light element array with controllable current sources and method of operation
WO2008108468A1 (en) * 2007-03-08 2008-09-12 Rohm Co., Ltd. Led illumination device and its drive method
US20080224631A1 (en) * 2007-03-12 2008-09-18 Melanson John L Color variations in a dimmable lighting device with stable color temperature light sources
WO2008120166A1 (en) * 2007-04-02 2008-10-09 Koninklijke Philips Electronics N.V. Driving light emitting diodes
US20080252197A1 (en) * 2007-04-13 2008-10-16 Intematix Corporation Color temperature tunable white light source
WO2008149294A1 (en) * 2007-06-08 2008-12-11 Koninklijke Philips Electronics N.V. Driving circuit for driving a plurality of light sources arranged in a series configuration
WO2009013676A2 (en) * 2007-07-23 2009-01-29 Nxp B.V. Led arrangement with bypass driving

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Effective date: 20150401