WO2009040305A1 - Scalable led driving with minimized power loss - Google Patents

Scalable led driving with minimized power loss Download PDF

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Publication number
WO2009040305A1
WO2009040305A1 PCT/EP2008/062509 EP2008062509W WO2009040305A1 WO 2009040305 A1 WO2009040305 A1 WO 2009040305A1 EP 2008062509 W EP2008062509 W EP 2008062509W WO 2009040305 A1 WO2009040305 A1 WO 2009040305A1
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WO
WIPO (PCT)
Prior art keywords
voltage
led
circuit arrangement
output signal
regulator
Prior art date
Application number
PCT/EP2008/062509
Other languages
German (de)
French (fr)
Inventor
Matthias Hercht
Jürgen Wenning
Wolfgang Freitag
Daniel Warnicki
Matthias Roppel
Original Assignee
Continental Automotive Gmbh
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.)
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Publication date
Application filed by Continental Automotive Gmbh filed Critical Continental Automotive Gmbh
Publication of WO2009040305A1 publication Critical patent/WO2009040305A1/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]
    • H05B45/30—Driver circuits
    • H05B45/347—Dynamic headroom control [DHC]
    • 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]
    • H05B45/40—Details of LED load circuits
    • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
    • H05B45/46—Details of LED load circuits with an active control inside an LED matrix having LEDs disposed in parallel lines

Definitions

  • the invention relates to an electrical circuit arrangement according to the preamble of claim 1. Furthermore, the invention relates to a method for controlling the electrical circuit arrangement described in the preamble of claim 1.
  • Such circuit arrangements of LEDs in a chain or in a plurality of chains connected in parallel are increasingly being used as backlighting of displays, in particular for use in driver information systems in the automotive sector.
  • the parallel-connected chains are connected to a common voltage source, whereby the efficiency of the circuit deteriorates because the differences between the LED forward voltages are converted into power losses. Because of the large number of LEDs installed in a confined space, the problem here arises of dissipating the heat produced by the power loss in the semiconductor components.
  • the inventive concept of the solution in the features of claim 1 and claim 6 lies in the minimization of the total power loss generated by the semiconductor devices in the parallel-connected LED strings. This task is solved by determining a minimum required operating voltage combined with the control of the common voltage regulator. The starting point is the determination of the minimum required operating voltage for each individual LED chain in the energized state of the LEDs.
  • the circuit arrangement therefore has a regulator unit, to which voltage values measured as input signals are supplied via the respective current sources of the individual LED strings. As a result of the output signal of the voltage regulation, the regulator unit outputs a control signal to the controllable voltage regulator.
  • the controller unit comprises the following
  • Function blocks a measuring unit for measuring the voltage values via the
  • the further processing of the voltage values measured via the current sources takes place in a processing unit according to the invention in such a way that the smallest of these voltages is determined.
  • the processing unit for determining the smallest voltage value can be designed as a hardware circuit or advantageously as a flexible software program on a microprocessor. Subsequently, a regulator output signal is derived from the lowest voltage and a supplied voltage regulator setpoint, and finally the regulator output signal is transformed into a control signal for the controllable voltage regulator for setting the minimum required operating voltage.
  • the invention thus achieves that only the minimum required operating voltage is applied across the parallel connection of the LED chains, that is to say that only a minimal power loss occurs, which in turn leads to a lower heat development.
  • the invention provides by providing usable display housing with small dimensions more degrees of freedom in the installation and thus in the design of the installation environment. As a further advantage, it is possible to resort to cost-effective standard components that make a complicated selection of the components unnecessary.
  • FIG. 1 shows a schematic diagram of the circuit arrangement according to the invention.
  • the circuit consists of n parallel-connected LED chains 2, which in this embodiment each have only one LED 4 per LED chain 2; but it can be provided in an LED chain 2 and a plurality of LEDs 4 connected in series.
  • Each LED chain 2 is fed by a controllable current source 6, wherein in many areas the luminance of the LED 4 is proportional to a forward current I LED .
  • the current sources 6 are controlled individually via separate control lines S 1I -S 1n from a current control unit 10 in accordance with a preset brightness value 11.
  • a control unit 12 as input signals via the current sources 6 of the respective LCD chain 2 measured voltage drops Ui to U n are supplied. From this, the controller unit generates a control signal S u for a controllable voltage regulator 14, which provides an operating voltage for the parallel-connected LED chains 2.
  • the controller unit 12 comprises a measuring unit 14 which has n inputs for measuring the n voltage values Ui to U n .
  • the n voltage values Ui to U n are then processed in an evaluation unit 16 in such a way that from the n voltage values Ui to U n the smallest voltage value U min is determined and then supplied as an output signal with a reference value U n a controller 18th
  • the controller 18 traces the selected voltage U min to the desired value U so n and forwards a controller output signal S r to a voltage control unit 20, a control signal S u for driving the voltage regulator 14 is provided.
  • the voltage regulator 14 then generates the minimum required operating voltage U B for operating the LED string 2.
  • the method according to the invention and its implementation in the circuit arrangement according to the invention also open up the possibility of detecting short-circuited or broken LED chains 2 by evaluating the measured voltage values U 1 to U n and from this safety and protective measures, such as a shutdown of the respective LED chain. derive.

Abstract

The invention relates to an electrical switch arrangement comprising 1 to n parallel-connected LED chains (2) each having at least one LED (4) and each having a controlled current source (6), wherein the LED chains are operated with an operating voltage at a common controllable voltage regulator (14). The invention furthermore relates to a method for driving the electrical circuit arrangement described. The inventive basic concept of the solution resides in the minimization of the total power loss of the parallel-connected LED chains (2) by determining the minimum required operating voltage of each individual LED chain (2) in the energized state of the LEDs (4) and in the driving of the common voltage regulator (14).

Description

Beschreibungdescription
Skalierbare LED-Ansteuerung mit minimierter VerlustleistungScalable LED control with minimized power loss
Die Erfindung betrifft eine elektrische Schaltungsanordnung gemäß dem Oberbegriff des Anspruchs 1. Weiterhin betrifft die Erfindung gemäß Anspruch 6 ein Verfahren zur Ansteuerung der im Oberbegriff des Anspruchs 1 beschriebenen elektrischen Schaltungsordnung .The invention relates to an electrical circuit arrangement according to the preamble of claim 1. Furthermore, the invention relates to a method for controlling the electrical circuit arrangement described in the preamble of claim 1.
Derartige Schaltungsanordnungen von LEDs in einer Kette oder in mehreren parallel geschalteten Ketten finden zunehmend Verwendung als Hinterleuchtung von Displays, insbesondere für den Einsatz in Fahrerinformationssystemen im Automobilbe- reich. Die parallel geschalteten Ketten liegen an einer gemeinsamen Spannungsquelle, wodurch sich der Wirkungsgrad der Schaltungsanordnung verschlechtert, weil die Unterschiede zwischen den LED-Durchlassspannungen in Verlustleistungen umgesetzt werden. Wegen der Vielzahl der auf engem Raum verbau- ten LEDs stellt sich hier das Problem, die durch die Verlustleistung in den Halbleiterbauelementen entstehende Wärme abzuführen .Such circuit arrangements of LEDs in a chain or in a plurality of chains connected in parallel are increasingly being used as backlighting of displays, in particular for use in driver information systems in the automotive sector. The parallel-connected chains are connected to a common voltage source, whereby the efficiency of the circuit deteriorates because the differences between the LED forward voltages are converted into power losses. Because of the large number of LEDs installed in a confined space, the problem here arises of dissipating the heat produced by the power loss in the semiconductor components.
Dem Stand der Technik entsprechend wird dieses Problem durch zusätzliche Wärmeabfuhrmaßnahmen gelöst. Dazu zählen dasAccording to the prior art, this problem is solved by additional heat removal measures. These include that
Verbauen von großflächigen Kühlkörpern oder eine erzwungene Konvektion durch Lüfter. Auch durch Selektion von LEDs mit schmalen Toleranzbereichen in den elektrischen Kenndaten oder durch die Verwendung von CCFL-Röhren (CoId Cathode Fluores- cent Lamp) kann die Verlustleistung gesenkt werden.Installation of large heat sinks or forced convection by fans. Also, by selecting LEDs with narrow tolerance ranges in the electrical characteristics or by using CCFL tubes (CoId Cathode Fluorescent Lamp), the power loss can be reduced.
Diese bekannten Maßnahmen weisen jedoch den Nachteil auf, dass sie entweder zu viel Bauraum beanspruchen, wie im Fall der Kühlkörper und der Lüfter, da dieser in aller Regel stark begrenzt ist oder die Lösung zu kostspielig, wie im Fall der Verwendung selektierter Bauteile. Der Erfindung liegt daher die Aufgabe zu Grunde, bei einer Schaltungsanordnung der eingangs beschriebenen Art die Verlustleistung weiter zu reduzieren, sodass zusätzliche aufwändige Wärmeabfuhrmaßnahmen entfallen können. Diese Aufgabe wird durch die kennzeichnenden Merkmale in Anspruch 1 in Verbindung mit den kennzeichnenden Merkmalen in Anspruch 6 gelöst.However, these known measures have the disadvantage that they either take up too much space, as in the case of the heat sink and the fan, as this is usually very limited or the solution too costly, as in the case of the use of selected components. The invention is therefore based on the object to further reduce the power loss in a circuit arrangement of the type described above, so that additional complex heat removal measures can be omitted. This object is solved by the characterizing features in claim 1 in conjunction with the characterizing features in claim 6.
Der erfinderische Grundgedanke der Lösung in den Merkmalen des Anspruchs 1 und des Anspruchs 6 liegt in der Minimierung der von den Halbleiterbauelementen in den parallel geschalteten LED-Ketten erzeugten Gesamtverlustleistung. Gelöst wird diese Aufgabe durch die Bestimmung einer minimal erforderlichen Betriebsspannung verbunden mit der Ansteuerung des ge- meinsamen Spannungsreglers. Ausgangspunkt ist dabei die Ermittlung der für jede einzelne LED-Kette im bestromten Zustand der LEDs minimal erforderlichen Betriebsspannung.The inventive concept of the solution in the features of claim 1 and claim 6 lies in the minimization of the total power loss generated by the semiconductor devices in the parallel-connected LED strings. This task is solved by determining a minimum required operating voltage combined with the control of the common voltage regulator. The starting point is the determination of the minimum required operating voltage for each individual LED chain in the energized state of the LEDs.
Die Schaltungsanordnung weist daher eine Reglereinheit auf, der als Eingangssignale über den jeweiligen Stromquellen der einzelnen LED-Ketten gemessene Spannungswerte zugeführt werden. Als resultierendes Ausgangssignal der Spannungsregelung gibt die Reglereinheit ein Steuersignal an den steuerbaren Spannungsregler aus.The circuit arrangement therefore has a regulator unit, to which voltage values measured as input signals are supplied via the respective current sources of the individual LED strings. As a result of the output signal of the voltage regulation, the regulator unit outputs a control signal to the controllable voltage regulator.
Zweckmäßigerweise umfasst die Reglereinheit die folgendenConveniently, the controller unit comprises the following
Funktionsblöcke : eine Messeinheit zur Messung der Spannungswerte über denFunction blocks: a measuring unit for measuring the voltage values via the
Stromquellen, eine Auswerteeinheit, die die gemessenen Spannungswerte verarbeitet und ein Ausgangssignal bereitstellt, einen Regler, der eingangsseitig mit dem Ausgangssignal der Auswerteeinheit und einem Sollwert-Eingangssignal verbunden ist und ein Reglerausgangssignal ausgibt, eine Kontrolleinheit, die aus dem Reglerausgangssignal ein Steuersignal für den steuerbaren Spannungsregler erzeugt. Mit der erfindungsgemäßen Schaltungsanordnung wird ein ebenfalls erfindungsgemäßes Verfahren realisiert, das darauf beruht, dass für einen verlustleistungsoptimierten Betrieb der Schaltungsanordnung die minimal erforderliche Betriebsspan- nung bestimmt wird. Die Bestimmung erfolgt derart, dass zunächst im bestromten Zustand der LEDs die Spannungswerte über den Stromquellen der jeweiligen LED-Kette gemessen werden. Die weitere Verarbeitung der über den Stromquellen gemessenen Spannungswerte geschieht in einer Verarbeitungseinheit erfin- dungsgemäß in der Weise, dass die kleinste dieser Spannungen bestimmt wird. Dabei kann die Verarbeitungseinheit zur Ermittlung des kleinsten Spannungswertes als Hardware-Schaltung oder in vorteilhafter Weise flexibel als Software-Programm auf einem Mikroprozessor ausgeführt sein. Anschließend wird aus der kleinsten Spannung und einem zugeführten Spannungsregler-Sollwert ein Reglerausgangssignal abgeleitet und schließlich wird das Reglerausgangssignal in ein Steuersignal für den steuerbaren Spannungsregler zur Einstellung der minimal erforderlichen Betriebsspannung transformiert.Current sources, an evaluation unit which processes the measured voltage values and provides an output signal, a controller, which is the input side of the evaluation unit and a setpoint input signal and outputs a controller output signal, a control unit, from the controller output signal, a control signal for the controllable voltage regulator generated. With the circuit arrangement according to the invention, a likewise inventive method is realized, which is based on the fact that the minimum required operating voltage is determined for a loss-performance optimized operation of the circuit arrangement. The determination is carried out in such a way that, initially in the energized state of the LEDs, the voltage values are measured via the current sources of the respective LED chain. The further processing of the voltage values measured via the current sources takes place in a processing unit according to the invention in such a way that the smallest of these voltages is determined. In this case, the processing unit for determining the smallest voltage value can be designed as a hardware circuit or advantageously as a flexible software program on a microprocessor. Subsequently, a regulator output signal is derived from the lowest voltage and a supplied voltage regulator setpoint, and finally the regulator output signal is transformed into a control signal for the controllable voltage regulator for setting the minimum required operating voltage.
Mit der Erfindung wird somit erreicht, dass nur die minimal benötigte Betriebsspannung über der Parallelschaltung der LED-Ketten anliegt, also auch nur eine minimale Verlustleistung entsteht, die wiederum zu einer geringeren Wärmeentwick- lung führt.The invention thus achieves that only the minimum required operating voltage is applied across the parallel connection of the LED chains, that is to say that only a minimal power loss occurs, which in turn leads to a lower heat development.
Hieraus ergeben sich erhebliche Vorteile hinsichtlich des erforderlichen Platzbedarfs. Wenn überhaupt notwendig, werden nur sehr kleine Kühlkörper benötigt, sodass auf den Einsatz von Zwangskonvektion verzichtet werden kann. Insgesamt gesehen bietet also die Erfindung durch die Bereitstellung einsetzbarer Display-Gehäuse mit kleinen Abmessungen mehr Freiheitsgrade beim Verbau und damit bei der Gestaltung der Einbauumgebung . Als weiterer Vorteil kann auf kostengünstige Standardbauelemente zurückgegriffen werden, die eine aufwändige Selektion der Bauelemente entbehrlich machen.This results in considerable advantages in terms of the required space. If necessary, only very small heatsinks are required, so that the use of forced convection can be dispensed with. Overall, therefore, the invention provides by providing usable display housing with small dimensions more degrees of freedom in the installation and thus in the design of the installation environment. As a further advantage, it is possible to resort to cost-effective standard components that make a complicated selection of the components unnecessary.
Weitere zweckmäßige Ausgestaltungsmerkmale werden an Hand eines bevorzugten, in der Zeichnung veranschaulichten Ausführungsbeispiels erläutert. Dabei zeigt die Figur ein Prinzipschaltbild der erfindungsgemäßen Schaltungsanordnung.Further expedient design features will be explained with reference to a preferred, illustrated in the drawing embodiment. The figure shows a schematic diagram of the circuit arrangement according to the invention.
Die Schaltung besteht aus n parallel geschalteten LED-Ketten 2, die in diesem Ausführungsbeispiel jeweils nur eine LED 4 pro LED-Kette 2 aufweisen; es können aber in einer LED-Kette 2 auch mehrere in der Reihe geschaltete LEDs 4 vorgesehen werden. Jede LED-Kette 2 wird durch eine steuerbare Strom- quelle 6 gespeist, wobei in weiten Bereichen die Leuchtdichte der LED 4 proportional zu einem Durchlassstrom ILED ist. Angesteuert werden die Stromquellen 6 individuell über separate Steuerleitungen S1I - S1n von einer Strom-Kontrolleinheit 10 nach Vorgabe eines Helligkeits-Sollwertes 11.The circuit consists of n parallel-connected LED chains 2, which in this embodiment each have only one LED 4 per LED chain 2; but it can be provided in an LED chain 2 and a plurality of LEDs 4 connected in series. Each LED chain 2 is fed by a controllable current source 6, wherein in many areas the luminance of the LED 4 is proportional to a forward current I LED . The current sources 6 are controlled individually via separate control lines S 1I -S 1n from a current control unit 10 in accordance with a preset brightness value 11.
Aus dem Prinzipschaltbild geht hervor, dass einer Reglereinheit 12 als Eingangssignale über den Stromquellen 6 der jeweiligen LCD Kette 2 gemessene Spannungsabfälle Ui bis Un zugeführt werden. Die Reglereinheit erzeugt daraus ein Steuer- signal Su für einen steuerbaren Spannungsregler 14, der eine Betriebsspannung für die parallel geschalteten LED-Ketten 2 bereitstellt .From the block diagram it appears that a control unit 12 as input signals via the current sources 6 of the respective LCD chain 2 measured voltage drops Ui to U n are supplied. From this, the controller unit generates a control signal S u for a controllable voltage regulator 14, which provides an operating voltage for the parallel-connected LED chains 2.
Die Reglereinheit 12 umfasst eine Messeinheit 14, die n Ein- gänge zur Messung der n Spannungswerte Ui bis Un aufweist. Die n Spannungswerte Ui bis Un werden anschließend in einer Auswerteeinheit 16 derart verarbeitet, dass aus den n Spannungswerte Ui bis Un der kleinste Spannungswert Umin ermittelt und als Ausgangssignal zusammen mit einem Sollwert Uson einem Regler 18 zugeführt wird. Der Regler 18 führt die ausgewählte Spannung Umin dem Sollwert Uson nach und leitet ein Reglerausgangssignal Sr an eine Spannungs-Kontrolleinheit 20 weiter, die ein Steuersignal Su zur Ansteuerung des Spannungsreglers 14 bereitgestellt. Der Spannungsregler 14 erzeugt dann die zum Betrieb der LED-Kette 2 minimale erforderliche Betriebsspannung UBmin-The controller unit 12 comprises a measuring unit 14 which has n inputs for measuring the n voltage values Ui to U n . The n voltage values Ui to U n are then processed in an evaluation unit 16 in such a way that from the n voltage values Ui to U n the smallest voltage value U min is determined and then supplied as an output signal with a reference value U n a controller 18th The controller 18 traces the selected voltage U min to the desired value U so n and forwards a controller output signal S r to a voltage control unit 20, a control signal S u for driving the voltage regulator 14 is provided. The voltage regulator 14 then generates the minimum required operating voltage U B for operating the LED string 2.
Auch eröffnet das erfindungsgemäße Verfahren und dessen Implementierung in der erfindungsgemäßen Schaltungsanordnung die Möglichkeit, durch Auswertung der gemessenen Spannungswerte Ui bis Un kurzgeschlossene oder unterbrochene LED-Ketten 2 zu erkennen und daraus Sicherungs- und Schutzmaßnahmen, wie z.B. eine Abschaltung der jeweiligen LED-Kette, abzuleiten. The method according to the invention and its implementation in the circuit arrangement according to the invention also open up the possibility of detecting short-circuited or broken LED chains 2 by evaluating the measured voltage values U 1 to U n and from this safety and protective measures, such as a shutdown of the respective LED chain. derive.

Claims

Patentansprüche claims
1. Schaltungsanordnung bestehend aus 1 bis n parallel geschalteten LED-Ketten mit jeweils mindestens einer LED und mit jeweils einer gesteuerten Stromquelle, wobei die LED- Ketten an einem gemeinsamen steuerbaren Spannungsregler mit einer Betriebsspannung betrieben werden, dadurch gekennzeichnet, dass über den jeweiligen Stromquellen (6) der einzelnen LED-Ketten (2) gemessene Spannungswerte (Ui bis Un) als Eingangssignale einer Reglereinheit (12) zugeführt werden und diese ein Steuersignal (Su) an den steuerbaren Spannungsregler (14) ausgibt.1. Circuit arrangement consisting of 1 to n parallel LED chains with at least one LED and each with a controlled current source, the LED chains are operated on a common controllable voltage regulator with an operating voltage, characterized in that on the respective power sources ( 6) of the individual LED chains (2) measured voltage values (Ui to U n ) are supplied as inputs to a control unit (12) and this outputs a control signal (S u ) to the controllable voltage regulator (14).
2. Schaltungsanordnung nach Anspruch 1, dadurch gekennzeichnet, dass die Reglereinheit (12) folgende Funktionsblöcke aufweist: eine Messeinheit (14) zur Messung der Spannungswerte (Ui bis Un) über den Stromquellen (6), eine Auswerteeinheit (16), die die gemessenen Spannungswerte (Ui bis Un) verarbeitet und ein Ausgangssignal (Umin ) bereitstellt, einen Regler (18), der eingangsseitig mit dem Ausgangssignal (Um1n) der Auswerteeinheit (16) und einem Sollwert- Eingangssignal (Uson) verbunden ist und ein Reglerausgangssignal (Sr) ausgibt, eine Spannungs-Kontrolleinheit (20), die aus dem Reglerausgangssignal (Sr) ein Steuersignal (Su) für den steuerbaren Spannungsregler (14) erzeugt.2. Circuit arrangement according to claim 1, characterized in that the control unit (12) has the following functional blocks: a measuring unit (14) for measuring the voltage values (Ui to U n ) over the current sources (6), an evaluation unit (16), the processed voltage values (Ui to U n ) and an output signal (U min ) provides, a controller (18), the input side to the output signal (Um 1n ) of the evaluation unit (16) and a setpoint input signal (U so n) is connected and a regulator output signal (Sr) outputs, a voltage control unit (20) which generates from the regulator output signal (S r ) a control signal (S u ) for the controllable voltage regulator (14).
3. Schaltungsanordnung nach Anspruch 2, dadurch gekennzeichnet , dass die Auswerteeinheit (16) als Hardware-Schaltung ausgeführt ist.3. Circuit arrangement according to claim 2, characterized in that the evaluation unit (16) is designed as a hardware circuit.
4. Schaltungsanordnung nach Anspruch 2, dadurch gekennzeichnet , dass die Auswerteeinheit (16) flexibel als Software-Programm auf einem Mikroprozessor implementiert ist.4. Circuit arrangement according to claim 2, characterized in that the evaluation unit (16) is flexibly implemented as a software program on a microprocessor.
5. Schaltungsanordnung nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass eine Strom-Kontrolleinheit (10) über separate Steuerleitungen (S1I - S1n) mit den jeweiligen Stromquellen (6) der einzelnen LED-Ketten (2) verbunden ist.5. Circuit arrangement according to one of claims 1 to 4, characterized in that a current control unit (10) via separate control lines (S 1I - S 1n ) with the respective current sources (6) of the individual LED chains (2) is connected.
6. Verfahren zur Ansteuerung von 1 bis n parallel geschalteten LED-Ketten mit jeweils mindestens einer LED und mit jeweils einer gesteuerten Stromquelle, wobei die LED-Ketten an einem gemeinsamen steuerbaren Spannungsregler mit einer Betriebsspannung betrieben werden, dadurch gekennzeichnet, dass für einen verlustleistungsoptimierten Betrieb der Schaltungsanordnung die minimal erforderliche Betriebsspannung (UBmm) bestimmt wird.6. A method for driving 1 to n parallel LED chains with at least one LED and each having a controlled current source, wherein the LED chains are operated on a common controllable voltage regulator with an operating voltage, characterized in that for a loss-performance optimized operation the circuit arrangement, the minimum required operating voltage (U B mm) is determined.
7. Verfahren nach Anspruch 6, dadurch gekennzeichnet, dass die minimal erforderliche Betriebsspannung (UBmin) durch die7. The method according to claim 6, characterized in that the minimum required operating voltage (U Bm i n ) by the
Signalverarbeitungsschritte a) bis d) bestimmt wird: a) im bestromten Zustand der LEDs werden die Spannungswerte (Ui bis Un) über den Stromquellen (6) der jeweiligen LED- Kette (2) gemessen, b) von den gemessenen Spannungswerten (Ui bis Un) wird die kleinste Spannung (Umin) bestimmt, c) aus der kleinsten Spannung (Umin) und einem zugeführten Spannungsregler-Sollwert (Uson) wird ein Reglerausgangssignal (Sr) abgeleitet, d) das Reglerausgangssignal (Sr) wird in ein Steuersignal (Su) für den steuerbaren Spannungsregler (14) zur Einstellung der minimal erforderlichen Betriebsspannung (UBmin) transfor- miert.A) in the energized state of the LEDs, the voltage values (Ui to U n ) are measured via the current sources (6) of the respective LED chain (2), b) from the measured voltage values (Ui to U n ), the smallest voltage (U min ) is determined, c) a controller output signal (Sr) is derived from the lowest voltage (U min ) and a supplied voltage regulator setpoint (U so n), d) the controller output signal (S r ) is transformed into a control signal (S u ) for the controllable voltage regulator (14) for setting the minimum required operating voltage (U Bm i n ).
8. Verfahren nach Anspruch 6 oder 7, dadurch gekennzeichnet, dass mittels einer Strom-Kontrolleinheit (10) durch Vorgabe eines Helligkeits-Sollwertes (11) die gewünschte Helligkeit über die Steuerleitungen (S1I - S1n) individuell für die einzelnen LED-Ketten (2) eingestellt werden kann.8. The method according to claim 6 or 7, characterized in that by means of a current control unit (10) by specifying a brightness setpoint (11), the desired brightness via the control lines (S 1I - S 1n ) can be set individually for the individual LED chains (2).
9. Verfahren nach einem der Ansprüche 6 bis 8, dadurch gekennzeichnet, dass durch Auswertung der gemessenen Spannungswerte (Ui bis Un) kurzgeschlossene oder unterbrochene LED-Ketten (2) erkannt werden können .9. A method according to any one of claims 6 to 8, characterized in that by evaluating the measured voltage values (Ui to U n) short-circuited or interrupted LED strings (2) can be detected.
10. Verfahren nach Anspruch 9, dadurch gekennzeichnet , dass bei Erkennen einer kurzgeschlossenen oder unterbrochenen LED- Kette (2) Sicherungs- und Schutzmaßnahmen, insbesondere eine Abschaltung der jeweiligen LED-Kette (2) , abgeleitet werden können . 10. The method according to claim 9, characterized in that upon detection of a short-circuited or interrupted LED chain (2) backup and protective measures, in particular a shutdown of the respective LED chain (2) can be derived.
PCT/EP2008/062509 2007-09-25 2008-09-19 Scalable led driving with minimized power loss WO2009040305A1 (en)

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