WO2012000695A1 - Method for operating an arrangement of light-emitting diodes - Google Patents

Method for operating an arrangement of light-emitting diodes Download PDF

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Publication number
WO2012000695A1
WO2012000695A1 PCT/EP2011/055188 EP2011055188W WO2012000695A1 WO 2012000695 A1 WO2012000695 A1 WO 2012000695A1 EP 2011055188 W EP2011055188 W EP 2011055188W WO 2012000695 A1 WO2012000695 A1 WO 2012000695A1
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Prior art keywords
led
strand
current
determined
voltage
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PCT/EP2011/055188
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German (de)
French (fr)
Inventor
Martin John
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Dilitronics Gmbh
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Application filed by Dilitronics Gmbh filed Critical Dilitronics Gmbh
Priority to EP11711908.1A priority Critical patent/EP2589263A1/en
Publication of WO2012000695A1 publication Critical patent/WO2012000695A1/en

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    • 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]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • H05B45/56—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits involving measures to prevent abnormal temperature of the LEDs
    • 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]
    • H05B45/10—Controlling the intensity of the light
    • 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]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • 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]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • H05B45/58—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits involving end of life detection of LEDs

Definitions

  • the invention relates to a method for operating an arrangement of light-emitting diodes (LED), wherein the arrangement has a plurality of strings connected in parallel, each having at least one LED per strand and a driver and the control of the LED's by means of pulse width modulation, according to the preamble of claim 1.
  • LED light-emitting diodes
  • LED modules are known, which include depending on the module type 4 to 6 mounted on a ceramic, highly efficient semiconductor chips.
  • the ceramic is mounted directly on the aluminum of an insulated metal core plate for optimal heat conduction. Due to the previously known design and construction, the
  • Light source has a very low thermal resistance.
  • the carrier board with a temperature measuring resistor, z. B. to provide an NTC resistor. From this, an approximate temperature monitoring of the LEDs is to be achieved for the purpose of improving the driving method.
  • the temperature measurement and its accuracy depends on the specific arrangement and the thermal coupling of the temperature measuring element with respect to the heat-producing p-n junctions of the corresponding LED's.
  • the characteristic is to be determined to avoid damage to the diodes.
  • detection means are provided for the current through the light-emitting diode arrangement and the voltage drop across the light-emitting diode arrangement.
  • means for determining the number and / or color of the LEDs are necessary. The determination of the number and / or the color of the LEDs should be based on the dynamic resistance of the light emitting diode arrangement and / or the temperature dependence of the UI characteristic curve.
  • WO 2009/000475 A2 also proposes a control unit which is designed in such a way that the diode current and the voltage across the light-emitting diode arrangement can be detected, and wherein at a first temperature of the light-emitting diode arrangement a first current / voltage pair and a second current current differ from it. / Voltage pair determined and then at least a second temperature of the light emitting diode array, a third current / voltage pair and a different fourth current / voltage pair is detected. With the known temperature coefficients, the current temperature of the relevant light-emitting diode should then be calculable from the forward-biased flux voltages measured at the same current flow and at different temperatures.
  • WO 2009/000475 A2 proposes the arrangement of a temperature sensor in the vicinity of the light-emitting diodes.
  • each strand comprising at least one or more LEDs connected in series.
  • the LED's in the strings are controlled by pulse width modulation.
  • a multiple current measurement is made in each pulse width modulation cycle. From this, the currently flowing pulse current is determined. When the currently flowing pulse current deviates from a predetermined setpoint current, the operating voltage in the string is readjusted. In addition, the voltage across the LED in the string is measured or the voltage from the readjustment is determined. From a change in the thus measured or determined forward voltage, the instantaneous temperature of the p-n junction of the respective LED is determined using known, type-specific LED characteristics, so that an impending thermal overload can be detected and avoided by intervention in the control.
  • the multiple current measurement takes place in each PWM cycle in the same cycles or time intervals, whereby the respective charge quantity is determined from this and this is integrated for the respective PWM cycle.
  • the result of the integration is the flow in each strand
  • Total amount of charge which is representative of the brightness of the stranded LED.
  • the brightness of the respective LED in the respective strand can be controlled by an integration threshold value of the charges.
  • the current measurements are made indirectly via a shunt per strand, wherein the shunt of the respective LED in the respective strand is connected in series. From the size of the resistance value of the shunt and the voltage drop across the shunt, the flowing current can be determined.
  • Strand is carried out according to the invention a determination of the relative change in temperature of the respective p-n junction of the respective diode.
  • circuit arrangement for operating an arrangement of light-emitting diodes which has been designed according to the invention, is based on the teaching of DE 102006035601 AI, to which reference is made in full in this respect.
  • the measurement of the current through the respective strand takes place for each strand via a measuring resistor connected in series with the respective diode, i. H. a so-called shunt. This way can be a continuous
  • the LEDs of the respective strands are operated in the pulse width modulation method.
  • the current measurement takes place up to 1023-fold per PWM cycle, whereby a charge determination is possible, due to the fact that the time difference between the individual measurement times is kept constant.
  • the total amount of charge can be determined by the respectively connected light emitting diodes of a string.
  • the specification of different thresholds, upon reaching the respective associated strand is turned off.
  • the brightness of the light emitting diodes of each strand can be controlled by the integration threshold, because the amount of charge is exactly the number of elementary charges, which are implemented in the respective light emitting diode by recombination of electrons to photons.
  • the effective pulse width at which a strand operates can vary with each period, allowing a very rapid response to changes in the strand. Also, in the manner described above, the instantaneous pulse current can be determined. If a given instantaneous pulse current is exceeded, it is possible to lower the voltage or switch off the respective strand when using controllable power supplies to the
  • the instantaneous junction temperature of the p-nN junction is of particular importance. By knowing this temperature, overheating of the semiconductor can be detected early and prevent irreversible destruction of the LEDs.
  • the junction temperature becomes indirect, i. H. without specific sensors.
  • the relative forward voltage of the corresponding LED's is used.
  • a corresponding characteristic which shows the course of the relative forward voltage and its changes over the temperature, is usually manufacturer-side available.
  • This datasheet-relevant characteristic curve describes the relative shift of the LED characteristic curves as a function of the respective junction temperature while the current remains the same.
  • the determined changes in the flux voltage are used to deduce the junction temperature and from this a quantity for regulation-side intervention is derived.
  • the pulse current can be determined currently and strand-related, so that the voltage can be readjusted accordingly in the case of a deviation from the desired current.
  • the relevant method ensures a voltage-controlled constant pulse current.

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Abstract

The invention relates to a method for operating an arrangement of light-emitting diodes (LEDs), wherein the arrangement has a plurality of parallel-connected sections respectively comprising at least one LED per section and also a driver, and the LEDs are driven by means of pulse width modulation (PWM). According to the invention, for each section per PWM cycle a multiple current measurement is performed and the instantaneously flowing pulsed current is determined therefrom in order to readjust the voltage in the section in the event of deviation from the desired current. Furthermore, a measurement of the voltage across the LED in the section is carried out and the instantaneous temperature of the p-n junction of the respective LED is determined from a change in the forward voltage measured in this way or determined from the readjustment, with use being made of the typical LED characteristic curve, with the result that an imminent thermal overloading can be identified and avoided.

Description

Verfahren zum Betreiben einer Anordnung von lichtemittierenden Dioden  A method of operating an array of light emitting diodes
Beschreibung description
Die Erfindung betrifft ein Verfahren zum Betreiben einer Anordnung von lichtemittierenden Dioden (LED), wobei die Anordnung mehrere parallel geschaltete Stränge mit jeweils mindestens einer LED je Strang sowie einen Treiber aufweist und die Ansteuerung der LED's mittels Pulsweitenmodulation erfolgt, gemäß Oberbegriff des Patentanspruches 1. The invention relates to a method for operating an arrangement of light-emitting diodes (LED), wherein the arrangement has a plurality of strings connected in parallel, each having at least one LED per strand and a driver and the control of the LED's by means of pulse width modulation, according to the preamble of claim 1.
Aus der Appliaktionsschrift OSTAR-Lightning der Opto Semiconductors, Mai 2006, sind LED-Module bekannt, welche je nach Modultyp 4 bis 6 auf eine Keramik montierte, hocheffiziente Halbleiterchips umfassen. Die Keramik ist zur optimalen Wärmeleitung direkt auf das Aluminium einer isolierten Metallkernplatte montiert. Durch das vorbekannte Design und den Aufbau weist die From the application paper OSTAR-Lightning of Opto Semiconductors, May 2006, LED modules are known, which include depending on the module type 4 to 6 mounted on a ceramic, highly efficient semiconductor chips. The ceramic is mounted directly on the aluminum of an insulated metal core plate for optimal heat conduction. Due to the previously known design and construction, the
Lichtquelle einen sehr geringen Wärmewiderstand auf. Darüber hinaus besteht die Möglichkeit, das Trägerboard mit einem Temperaturmesswiderstand, z. B. einem NTC-Widerstand zu versehen. Hieraus soll in Näherung eine Temperaturüberwachung der LED's zum Zweck der Verbesserung des Ansteuerungsver- fahrens erreicht werden. Dabei ist jedoch die Temperaturmessung und deren Genauigkeit abhängig von der konkreten Anordnung und der thermischen Kopplung des Temperaturmesselementes bezüglich der wärmeproduzierenden p- n-Übergänge der entsprechenden LED's. Light source has a very low thermal resistance. In addition, it is possible, the carrier board with a temperature measuring resistor, z. B. to provide an NTC resistor. From this, an approximate temperature monitoring of the LEDs is to be achieved for the purpose of improving the driving method. However, the temperature measurement and its accuracy depends on the specific arrangement and the thermal coupling of the temperature measuring element with respect to the heat-producing p-n junctions of the corresponding LED's.
Aus der WO 2009/000475 A2 ist ein System und ein Verfahren zur Erfassung der Kennlinien von lichtemittierenden Dioden (LED's) vorbekannt.  From WO 2009/000475 A2 a system and a method for detecting the characteristics of light-emitting diodes (LED's) is already known.
Gemäß der dortigen Lehre soll zur Vermeidung von Schäden an den Dioden deren Charakteristik ermittelt werden. Hierfür sind Erfassungsmittel für den Strom durch die Leuchtdiodenanordnung sowie den Spannungsabfall über der Leuchtdiodenanordnung vorgesehen. Weiterhin sind Mittel zur Ermittlung der Anzahl und/oder Farbe der Leuchtdioden notwendig. Die Ermittlung der Anzahl und/oder der Farbe der Leuchtdioden soll anhand des dynamischen Widerstan- des der Leuchtdiodenanordnung und/oder der Temperaturabhängigkeit der U-I- Kennlinie erfolgen. According to the teaching there, the characteristic is to be determined to avoid damage to the diodes. For this purpose, detection means are provided for the current through the light-emitting diode arrangement and the voltage drop across the light-emitting diode arrangement. Furthermore, means for determining the number and / or color of the LEDs are necessary. The determination of the number and / or the color of the LEDs should be based on the dynamic resistance of the light emitting diode arrangement and / or the temperature dependence of the UI characteristic curve.
Die WO 2009/000475 A2 schlägt auch eine Steuereinheit vor, die so ausgelegt ist, dass der Diodenstrom und die Spannung über der Leuchtdiodenanordnung erfassbar ist, und wobei bei einer ersten Temperatur der Leuchtdiodenanordnung ein erstes Strom-/Spannungspaar und ein davon verschiedenes zweites Strom-/Spannungspaar ermittelt und danach bei zumindest einer zweiten Temperatur der Leuchtdiodenanordnung ein drittes Strom-/Spannungspaar und ein davon verschiedenes viertes Strom-/Spannungspaar erfasst wird. Mit dem bekannten Temperaturkoeffizienten soll dann aus bei gleichem Stromfluss und unterschiedlichen Temperaturen gemessenen Flussspannungen die aktuelle Temperatur der betreffenden lichtemittierenden Diode berechenbar sein. WO 2009/000475 A2 also proposes a control unit which is designed in such a way that the diode current and the voltage across the light-emitting diode arrangement can be detected, and wherein at a first temperature of the light-emitting diode arrangement a first current / voltage pair and a second current current differ from it. / Voltage pair determined and then at least a second temperature of the light emitting diode array, a third current / voltage pair and a different fourth current / voltage pair is detected. With the known temperature coefficients, the current temperature of the relevant light-emitting diode should then be calculable from the forward-biased flux voltages measured at the same current flow and at different temperatures.
Zusätzlich schlägt die WO 2009/000475 A2 die Anordnung eines Temperatursensors in der Nähe der lichtemittierenden Dioden vor. In addition, WO 2009/000475 A2 proposes the arrangement of a temperature sensor in the vicinity of the light-emitting diodes.
Bei Steuerschaltungen auf der Basis von Konstantstromtreibern ist die in der WO 2009/000475 A2 dargelegte Lehre der Ermittlung von Strom-/Spannungs- paaren und dem Ableiten der LED-Temperatur relativ einfach umsetzbar. Dies ist jedoch dann nicht ohne Weiteres übertragbar auf Treiberschaltungen, die auf eine spannungsgesteuerte Lösung zurückgreifen. In the case of control circuits based on constant-current drivers, the teaching set forth in WO 2009/000475 A2 of determining pairs of current / voltage and deriving the LED temperature is relatively simple to implement. However, this is then not readily transferable to driver circuits that rely on a voltage-controlled solution.
Aus dem Vorgenannten ist es daher Aufgabe der Erfindung, ein weiterentwickeltes Verfahren zum Betreiben einer Anordnung von lichtemittierenden Dioden anzugeben, wobei die Anordnung mehrere parallel geschaltete Stränge mit jeweils mindestens einer LED je Strang sowie einen Treiber aufweist und die Ansteuerung der LED's mittels Pulsweitenmodulation erfolgt. Dabei soll mit dem zu schaffenden Verfahren ein sicherer Betrieb der LED's ohne Überhitzung realisiert werden und die Bereitstellung ansonsten notwendiger spezifischer Sensorik zur Temperaturmessung entfallen. From the foregoing, it is therefore an object of the invention to provide a further developed method for operating an array of light-emitting diodes, wherein the arrangement comprises a plurality of strings connected in parallel, each having at least one LED per strand and a driver and the control of the LED's by means of pulse width modulation. In this case, a safe operation of the LED's without overheating should be realized with the method to be created and the provision of otherwise necessary specific sensors for temperature measurement omitted.
Die Lösung der Aufgabe der Erfindung erfolgt durch die Lehre des Verfahrens gemäß Patentanspruch 1, wobei die Unteransprüche mindestens zweckmäßige Ausgestaltungen und Weiterbildungen darstellen. Bei dem erfindungsgemäßen Verfahren beim Betreiben einer Anordnung von lichtemittierenden Dioden (LED) wird zunächst von einer Vielzahl parallel geschalteter Stränge ausgegangen, wobei jeder Strang mindestens eine oder mehrere in Serie geschaltete LED's umfasst. Die Ansteuerung der LED's in den Strängen erfolgt durch Pulsweitenmodulation. The object of the invention is achieved by the teaching of the method according to claim 1, wherein the dependent claims represent at least expedient refinements and developments. In the method according to the invention when operating an arrangement of light-emitting diodes (LED), a plurality of parallel-connected strands is initially assumed, each strand comprising at least one or more LEDs connected in series. The LED's in the strings are controlled by pulse width modulation.
Für jeden Strang wird in jedem Pulsweitenmodulations-Zyklus eine mehrfache Strommessung vorgenommen. Hieraus wird der momentan fließende Pulsstrom ermittelt. Beim Abweichen des momentan fließenden Pulsstromes von einem vorgegebenen Sollstrom wird die Betriebsspannung im Strang nachgeregelt. Zusätzlich erfolgt eine Messung der Spannung über der LED im Strang oder es wird die Spannung aus der Nachregelung ermittelt. Aus einer Änderung der derart gemessenen oder ermittelten Vorwärtsspannung wird unter Nutzung bekannter, typspezifischer LED-Kennlinien die momentane Temperatur des p-n- Übergangs der jeweiligen LED bestimmt, so dass eine drohende thermische Überlastung erkannt und durch Eingriff in die Regelung vermieden werden kann. For each string, a multiple current measurement is made in each pulse width modulation cycle. From this, the currently flowing pulse current is determined. When the currently flowing pulse current deviates from a predetermined setpoint current, the operating voltage in the string is readjusted. In addition, the voltage across the LED in the string is measured or the voltage from the readjustment is determined. From a change in the thus measured or determined forward voltage, the instantaneous temperature of the p-n junction of the respective LED is determined using known, type-specific LED characteristics, so that an impending thermal overload can be detected and avoided by intervention in the control.
Ausgestaltend erfolgt die mehrfache Strommessung in jedem PWM-Zyklus in gleichen Takten oder Zeitabständen, wobei hieraus die jeweilige Ladungsmenge bestimmt und diese für den jeweiligen PWM-Zyklus integriert wird. Im Ergebnis der Integration stellt sich die im jeweiligen Strang fließende The multiple current measurement takes place in each PWM cycle in the same cycles or time intervals, whereby the respective charge quantity is determined from this and this is integrated for the respective PWM cycle. The result of the integration is the flow in each strand
Gesamtladungsmenge dar, die für die Helligkeit der im Strang befindlichen LED repräsentativ ist. Total amount of charge, which is representative of the brightness of the stranded LED.
Die Helligkeit der jeweiligen LED im jeweiligen Strang lässt sich durch ein Integrationsschwellwert der Ladungen steuern. The brightness of the respective LED in the respective strand can be controlled by an integration threshold value of the charges.
Der vorstehend erläuterte Integrationsprozess beginnt mit jedem PWM-Zyklus erneut. The integration process explained above starts again with each PWM cycle.
In einer Weiterbildung der Erfindung werden die Strommessungen indirekt über einen Shunt je Strang vorgenommen, wobei der Shunt der jeweiligen LED im jeweiligen Strang in Serie geschalten ist. Aus der Größe des Widerstandswertes des Shunts und der über dem Shunt abfallenden Spannung ist der fließende Strom bestimmbar. In one embodiment of the invention, the current measurements are made indirectly via a shunt per strand, wherein the shunt of the respective LED in the respective strand is connected in series. From the size of the resistance value of the shunt and the voltage drop across the shunt, the flowing current can be determined.
Ausgehend von einer ersten Messung bei Inbetriebnahme des jeweiligen Starting from a first measurement at commissioning of the respective
Strangs erfolgt erfindungsgemäß eine Ermittlung der relativen Temperaturänderung des jeweiligen p-n-Übergangs der jeweiligen Diode. Strand is carried out according to the invention a determination of the relative change in temperature of the respective p-n junction of the respective diode.
Die Erfindung soll nachstehend anhand eines Ausführungsbeispiels näher erläutert werden. The invention will be explained below with reference to an embodiment.
Die Schaltungsanordnung zum Betreiben einer Anordnung von lichtemittierenden Dioden, welche erfindungsgemäß ausgestaltet wurde, geht aus von der Lehre der DE 102006035601 AI, auf die diesbezüglich vollinhaltlich Bezug genommen wird. The circuit arrangement for operating an arrangement of light-emitting diodes, which has been designed according to the invention, is based on the teaching of DE 102006035601 AI, to which reference is made in full in this respect.
Die Messung des Stroms durch den jeweiligen Strang erfolgt für jeden Strang über einen mit der jeweiligen Diode in Serie geschalteten Messwiderstand, d. h. einen sogenannten Shunt. Auf diese Weise kann eine fortlaufende The measurement of the current through the respective strand takes place for each strand via a measuring resistor connected in series with the respective diode, i. H. a so-called shunt. This way can be a continuous
Messung erfolgen, ohne dass ein Abschalten weiterer Kanäle erforderlich ist. Measurement takes place without switching off other channels is required.
Die LED's der jeweiligen Stränge werden im Pulsweitenmodulationsverfahren betrieben. The LEDs of the respective strands are operated in the pulse width modulation method.
Die Strommessung erfolgt bis zu 1023-fach pro PWM-Zyklus, wodurch eine Ladungsbestimmung möglich ist, aufgrund der Tatsache, dass die Zeitdifferenz zwischen den einzelnen Messzeitpunkten konstant gehalten wird. The current measurement takes place up to 1023-fold per PWM cycle, whereby a charge determination is possible, due to the fact that the time difference between the individual measurement times is kept constant.
Durch die Integration, d. h. Summierung aller gemessenen Ladungen innerhalb eines PWM-Zyklus lässt sich die Gesamtladungsmenge durch die jeweils angeschlossenen lichtemittierenden Dioden eines Strangs bestimmen. Für jeden Integrationsvorgang kann mit dem erfindungsgemäßen Steuerverfahren die Vorgabe von unterschiedlichen Schwellwerten erfolgen, bei dessen Erreichen der jeweils zugehörige Strang abgeschalten wird. By integrating, ie summing all measured charges within a PWM cycle, the total amount of charge can be determined by the respectively connected light emitting diodes of a string. For each integration process can be carried out with the control method of the invention, the specification of different thresholds, upon reaching the respective associated strand is turned off.
Die Helligkeit der lichtemittierenden Dioden eines jeweiligen Strangs lässt sich so durch den Integrationsschwellwert steuern, weil die Ladungsmenge exakt der Anzahl der Elementarladungen ist, die in der jeweiligen lichtemittierenden Diode durch Rekombination von Elektronen zu Photonen umgesetzt werden. The brightness of the light emitting diodes of each strand can be controlled by the integration threshold, because the amount of charge is exactly the number of elementary charges, which are implemented in the respective light emitting diode by recombination of electrons to photons.
Mit Beginn eines neuen PWM-Zyklus startet der vorerwähnte Integrationspro- zess erneut. Die effektive Pulsbreite, bei der ein Strang betrieben wird, kann mit jeder Periode variieren, so dass eine sehr schnelle Reaktion auf Änderungen im Strang möglich ist. Auch kann in der vorbeschriebenen Weise der momentane Pulsstrom ermittelt werden. Wird ein vorgegebener momentaner Pulsstrom überschritten, besteht die Möglichkeit, bei dem Einsatz regelbarer Netzteile die Spannung absenken oder den jeweiligen Strang abzuschalten, um die With the beginning of a new PWM cycle, the aforementioned integration process starts again. The effective pulse width at which a strand operates can vary with each period, allowing a very rapid response to changes in the strand. Also, in the manner described above, the instantaneous pulse current can be determined. If a given instantaneous pulse current is exceeded, it is possible to lower the voltage or switch off the respective strand when using controllable power supplies to the
entsprechenden LED's vor Zerstörung zu bewahren. corresponding LEDs to prevent destruction.
Für den Betrieb von lichtemittierenden Dioden ist die momentane Junction- Temperatur des p-nN-Übergangs von besonderer Bedeutung. Durch die Kenntnis dieser Temperatur lässt sich eine Überhitzung des Halbleiters frühzeitig erkennen und eine nicht reversible Zerstörung der LED's verhindern. For the operation of light-emitting diodes, the instantaneous junction temperature of the p-nN junction is of particular importance. By knowing this temperature, overheating of the semiconductor can be detected early and prevent irreversible destruction of the LEDs.
Gemäß dem Ausführungsbeispiel der Erfindung wird die Junction-Temperatur indirekt, d. h. ohne spezifische Sensorik, ermittelt. According to the embodiment of the invention, the junction temperature becomes indirect, i. H. without specific sensors.
Hierbei wird auf die relative Vorwärtsspannung der entsprechenden LED's zurückgegriffen. Eine entsprechende Kennlinie, die den Verlauf der relativen Vorwärtsspannung und deren Änderungen über die Temperatur zeigt, steht üblicherweise herstel lerseitig zur Verfügung. Diese datenblatt-relevante Kennlinie beschreibt die relative Verschiebung der LED-Kennlinien in Abhängigkeit von der jeweiligen Junction-Temperatur bei gleichbleibendem Strom. Erfindungsgemäß wird über die ermittelten Flussspannungsänderungen auf die Junction-Temperatur rückgeschlossen und hieraus eine Größe zum regelungs- seitigen Eingriff abgeleitet. Here, the relative forward voltage of the corresponding LED's is used. A corresponding characteristic, which shows the course of the relative forward voltage and its changes over the temperature, is usually manufacturer-side available. This datasheet-relevant characteristic curve describes the relative shift of the LED characteristic curves as a function of the respective junction temperature while the current remains the same. According to the invention, the determined changes in the flux voltage are used to deduce the junction temperature and from this a quantity for regulation-side intervention is derived.
Bei dem erläuterten PWM-Betriebsverfahren kann der Pulsstrom aktuell und strangbezogen ermittelt werden, so dass bei einer Abweichung vom Sollstrom die Spannung entsprechend nachregelbar ist. Das diesbezügliche Verfahren stellt einen spannungsgeregelten Konstantpulsstrom sicher. Unter Rückgriff auf die bekannte Kennlinie der relativen Vorwärtsspannung über die Temperatur besteht die Möglichkeit, die relative Temperaturänderung seit der ersten Messung abzuleiten. Über die Korrelation von Flussspannung und Temperatur kann mit einer einmaligen Messung des entsprechenden Wertepaares eine Aussage zur jeweils aktuellen, absoluten Temperatur getroffen werden. Diese Aussagen zur jeweiligen Temperatur und Zustand können sehr schnell, d. h. zeitnah gewonnen werden. Verzögerungen, wie bei der Temperaturermittlung durch räumlich entfernt angeordnete Sensoren unvermeidlich, entfallen. In the explained PWM operating method, the pulse current can be determined currently and strand-related, so that the voltage can be readjusted accordingly in the case of a deviation from the desired current. The relevant method ensures a voltage-controlled constant pulse current. By resorting to the known characteristic of the relative forward voltage across the temperature, it is possible to derive the relative temperature change since the first measurement. By means of the correlation between forward voltage and temperature, a statement about the current absolute temperature can be made with a single measurement of the corresponding value pair. These statements about the respective temperature and condition can be very fast, d. H. be obtained promptly. Delays, as in the temperature determination by spatially remote sensors inevitably omitted.

Claims

Patentansprüche claims
1. Verfahren zum Betreiben einer Anordnung von lichtemittierenden Dioden (LED), wobei die Anordnung mehrere parallel geschaltete Stränge mit mindestens jeweils einer LED je Strang sowie einen Treiber aufweist und die Ansteuerung der LED's mittels Pulsweitenmodulation (PWM) erfolgt, dadurch gekennzeichnet, dass 1. A method for operating an arrangement of light emitting diodes (LED), wherein the arrangement comprises a plurality of strings connected in parallel with at least one LED per strand and a driver and the control of the LED's by means of pulse width modulation (PWM), characterized in that
für jeden Strang je PWM-Zyklus eine mehrfache Strommessung vorgenommen und hieraus der momentan fließende Pulsstrom ermittelt wird, um beim Abweichen vom Sollstrom die Spannung im Strang nachzuregeln, weiterhin eine Messung der Spannung über der LED im jeweiligen Strang durchgeführt oder aus der Nachregelung ermittelt und aus einer  For each strand per PWM cycle made a multiple current measurement and from this the currently flowing pulse current is determined to readjust the voltage in the strand when deviating from the desired current, further carried out a measurement of the voltage across the LED in each strand or determined from the readjustment and off one
Änderung der derart gemessenen Vorwärtsspannung unter Nutzung der typspezifischen LED-Kennlinie die momentane Temperatur des p-n- Übergangs der jeweiligen LED bestimmt wird, so dass eine drohende thermische Überlastung erkannt und vermieden werden kann.  Changing the thus measured forward voltage using the type-specific LED characteristic curve, the current temperature of the p-n junction of the respective LED is determined, so that a threat of thermal overload can be detected and avoided.
2. Verfahren nach Anspruch 1, 2. The method according to claim 1,
dadurch gekennzeichnet, dass  characterized in that
die mehrfache Strommessung in jedem PWM-Zyklus in gleichen Takten oder Zeitabständen erfolgt, wobei hieraus die jeweilige Ladungsmenge bestimmt und diese für den jeweiligen PWM-Zyklus integriert wird derart, dass die im jeweiligen Strang fließende Gesamtladungsmenge für die Helligkeit der im Strang befindlichen LED repräsentativ ist.  the multiple current measurement in each PWM cycle takes place in equal cycles or time intervals, from which the respective amount of charge is determined and integrated for the respective PWM cycle such that the total amount of charge flowing in the respective strand is representative of the brightness of the stranded LED ,
3. Verfahren nach Anspruch 2, 3. The method according to claim 2,
dadurch gekennzeichnet, dass  characterized in that
die Helligkeit der jeweiligen LED durch einen Integrationsschwellwert der Ladungen steuerbar ist.  the brightness of the respective LED is controllable by an integration threshold value of the charges.
4. Verfahren nach Anspruch 2 oder 3, 4. The method according to claim 2 or 3,
dadurch gekennzeichnet, dass  characterized in that
der Integrationsprozess mit jedem PWM-Zyklus erneut zu laufen beginnt. Verfahren nach einem der vorangegangenen Ansprüche, dadurch gekennzeichnet, dass the integration process begins to run again with each PWM cycle. Method according to one of the preceding claims, characterized in that
die Strommessungen indirekt über einen Shunt erfolgen, der der jeweiligen LED im jeweiligen Strang in Serie geschalten ist. the current measurements are made indirectly via a shunt which is connected in series to the respective LED in the respective string.
Verfahren nach einem der vorangegangenen Ansprüche, Method according to one of the preceding claims,
dadurch gekennzeichnet, dass characterized in that
ausgehend von einer ersten Messung bei Inbetriebnahme des Strangs eine Ermittlung der relativen Temperaturänderung des p-n-Übergangs der jeweiligen LED erfolgt. Based on a first measurement during startup of the strand, a determination of the relative change in temperature of the p-n junction of the respective LED is performed.
PCT/EP2011/055188 2010-06-29 2011-04-04 Method for operating an arrangement of light-emitting diodes WO2012000695A1 (en)

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DE102010025468.1 2010-06-29
DE102010025468 2010-06-29
DE102011009607.8 2011-01-27
DE102011009607A DE102011009607A1 (en) 2010-06-29 2011-01-27 Method for operating an arrangement of light-emitting diodes

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102006035601A1 (en) 2006-07-27 2008-01-31 Fachhochschule Jena Image projection device
US20080084169A1 (en) * 2004-10-22 2008-04-10 Koninklijke Philips Electronics, N.V. Method for Driving a Led Based Lighting Device
WO2009000475A2 (en) 2007-06-25 2008-12-31 Tridonicatco Schweiz Ag System and method for recording the characteristic curves of light-emitting diodes
WO2009095853A2 (en) * 2008-01-28 2009-08-06 Nxp B.V. System and method for estimating the junction temperature of a light emitting diode
WO2009157763A2 (en) * 2008-06-24 2009-12-30 Eldolab Holding B.V. Control unit for a led assembly and lighting system

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080084169A1 (en) * 2004-10-22 2008-04-10 Koninklijke Philips Electronics, N.V. Method for Driving a Led Based Lighting Device
DE102006035601A1 (en) 2006-07-27 2008-01-31 Fachhochschule Jena Image projection device
WO2009000475A2 (en) 2007-06-25 2008-12-31 Tridonicatco Schweiz Ag System and method for recording the characteristic curves of light-emitting diodes
WO2009095853A2 (en) * 2008-01-28 2009-08-06 Nxp B.V. System and method for estimating the junction temperature of a light emitting diode
WO2009157763A2 (en) * 2008-06-24 2009-12-30 Eldolab Holding B.V. Control unit for a led assembly and lighting system

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
HULETT J ET AL: "Measuring LED Junction Temperature", INTERNET CITATION, July 2008 (2008-07-01), pages 1 - 3, XP002563429, Retrieved from the Internet <URL:http://www.photonics.com/Content/ReadArticle.aspx?ArticleID=34316> [retrieved on 20080701] *

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