EP2645529B1 - Circuit assembly and method for testing a light emitting diode branch of a circuit assembly - Google Patents

Circuit assembly and method for testing a light emitting diode branch of a circuit assembly Download PDF

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Publication number
EP2645529B1
EP2645529B1 EP13161845.6A EP13161845A EP2645529B1 EP 2645529 B1 EP2645529 B1 EP 2645529B1 EP 13161845 A EP13161845 A EP 13161845A EP 2645529 B1 EP2645529 B1 EP 2645529B1
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Prior art keywords
light
emitting diode
current
diode branch
constant
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German (de)
French (fr)
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EP2645529A1 (en
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DIN Dietmar Nocker Facilitymanagement GmbH
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DIN Dietmar Nocker Facilitymanagement GmbH
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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
    • H05B45/52—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits in a parallel array of 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]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits

Definitions

  • the invention relates to a circuit arrangement and a method for testing a light diode branch of a circuit arrangement, in particular emergency lighting, on functionality of its LEDs, the LED branch having a plurality of light-emitting diodes and at least one resistor, in which method the LED branch from its operating state by impressing a constant electric current is converted with at least a first current in a test state under impressing an electric current with a different current, wherein, taking into account at least one direct or indirect measurement of at least one electrical variable of the circuit of the light-emitting diode branch is tested.
  • the EP 1 839 928 A2 shows a vehicle lamp assembly having a plurality of parallel light-emitting diode branches each having a plurality of light-emitting diodes connected in series and measures for reliability or failure detection.
  • the DE10 2006 018 575 A1 shows an error detection of LEDs of emergency lighting.
  • a short circuit of one or more light-emitting diodes can disadvantageously lead to considerable currents in the circuit arrangement, whereby damage to other circuit parts is to be feared.
  • the storage of standard current values for the purpose of a current comparison is relatively complex and also represents a relatively unreliable approach to fault detection - among other reasons, because currents can also change due to aging phenomena of the LEDs.
  • a method for detecting a function failure of a light-emitting diode which is based on the comparison with the standard current value and does not take these circumstances into consideration, can thus fail.
  • the invention achieves the stated object with regard to the method in that the light-emitting diode branch, which has at least two parallel light-emitting diodes, each with a resistor in series, a constant electric current is impressed in the test state and that in the operating and test state as electrical variable depending on a voltage at least is measured over the light-emitting diode branch, wherein the light-emitting diode branch is tested for functionality of its light-emitting diode or light-emitting diodes, taking into account the voltages measured in the operating and test states.
  • the light-emitting diode branch has at least two parallel light-emitting diodes, each with a resistor in series, it may be possible for the functional state of the light-emitting diode branch to be checked reliably and reliably. If, for example, a constant electric current is impressed on the light-emitting diode branch in the test state, it can be avoided, among other things, that in the event of an eventual failure Short circuit of a light emitting diode form unacceptably high currents in the circuit. Thus, damage to the circuitry during the test condition can be easily avoided, which can ensure a safe method of testing functionality.
  • a voltage is measured at least across the light-emitting diode branch, the light-emitting diode branch being tested for functionality of its light-emitting diode or light-emitting diodes, taking into account the voltages measured in the operating and test states, in contrast to the prior art stored standard values are omitted for the purpose of checking the functionality of the light-emitting diode path or the light-emitting diode branch. Namely, only the voltage levels measured in the operating and test states can be sufficient to ensure a reliable and reliable testing of preferably all LEDs of the light-emitting diode branch.
  • aging of the light-emitting diode also has only a slight effect on the method result, because even aged light-emitting diodes lead to a non-linear voltage-current characteristic and thus permit testing of the light-emitting diode or light-emitting diodes according to the invention.
  • the method by the voltage tap on the LED branch almost no dependence on the structural design, so that can result in a very versatile application or a wide range of applications.
  • the method can also be used where the light-emitting diode branch has a plurality of light-emitting diodes connected in series and in parallel, each with a resistor in series.
  • the light-emitting diode branch has a plurality of light-emitting diodes connected in series and in parallel, each with a resistor in series.
  • a comparatively simple procedure can result if the test takes into account a ratio of the voltages measured in the operating and test states. In particular, however, the quotient of the voltage values can contribute to a meaningful result and thus to a reliable test of the light-emitting diode.
  • the risk of electrical damage to the light-emitting diode branch due to overloading can be kept low in the test state. This even if there is already an electrical defect in the light-emitting diode branch.
  • the invention achieves the stated object with regard to the circuit arrangement in that the light-emitting diode branch has at least two parallel light-emitting diodes each having a resistor in series, and in that the constant current source in the producible current intensity is variable with respect to its constant current, the test device for a test state of the light diode branch is connected to the constant current source for generating a constant current of a current produced by the constant current source constant current different current and wherein the test device as a measuring circuit has a voltage measuring circuit with a Meßabgriff over at least the light emitting diode branch for measuring each voltage in its operating and test state.
  • Constructive simplicity may result when using a constant current source that is variably variable in the current that can be generated with respect to its constant current to operate the LED branch in different current states, which LED branch has at least two series-connected parallel light emitting diodes.
  • a constant current source that is variably variable in the current that can be generated with respect to its constant current to operate the LED branch in different current states, which LED branch has at least two series-connected parallel light emitting diodes.
  • one and the same constant current source also to be used for the test state of the light-emitting diode branch.
  • the test device with the constant current source for generating a constant Current to be connected to a constant current produced by the constant current source in the operating state constant current different current.
  • the determination of defects in the light-emitting diode branch can be made particularly reliable if the test device has a voltage measuring circuit with a measuring tap as measuring circuit over at least the light-emitting diode branch for measuring a respective voltage in its operating and test state. Since relatively simple construction can be measured over the entire light-emitting diode branch, thus also simplify the design requirements.
  • the circuit arrangement can advantageously check the operation of the light-emitting diode branch with particular reliability or can also be used there when the light-emitting diode branch has a plurality of light-emitting diodes connected in series and in parallel, each with a resistor in series.
  • test device has a ratio circuit for forming a ratio of the voltages to one another in the operating and test state of the light-emitting diode branch, a comparatively high degree of constructive simplicity can be achieved in the circuit arrangement.
  • the circuit arrangement can be protected against overloads in the test state in that the other current intensity of the constant current is lower than the first current intensity of the constant electrical current.
  • circuit arrangement 1 shown is a light-emitting diode branch 2 with six light-emitting diodes (LED) 3 lying in parallel, each of which a resistor 4 is connected in series.
  • This parallel circuit 5 is connected in series with a further parallel circuit 6, which also has six parallel LEDs 3, each with a resistor 4 in series.
  • the resistors 4 are used to balance the brightness of the light-emitting diodes 3, and are designed the same impedance in their impedance.
  • the light-emitting diode branch 2 is supplied with a constant electric current I 1 or impressed on this light-emitting diode branch in order to supply it with electrical power.
  • a constant current source 7 is used.
  • the constant current intensity for generating the current I 1 can be adjusted, for example, according to the brightness requirements and this constant current intensity can certainly also be adapted to a changing brightness requirement - for example: by dimming.
  • Such a setting of the desired current intensity can also be carried out by a test device 8, which measures the voltage across this resistor 9 via a resistor 9 known in the impedance and regulates the constant current source 7 with regard to the desired constant current intensity.
  • This LED branch 2 is tested or checked for the functionality of its LEDs 3 by the LED branch 2 is transferred from its operating state in a test state.
  • the light-emitting diode branch 2 is charged with an electric current I 2 having a current intensity which differs from the current intensity of the constant current I 1 in the operating state, which is lower here, which protects the light-emitting diode branch 2 against electrical overloading.
  • the constant current source 7 is made variable in the generatable current with respect to their constant current I 1 and I 2 .
  • a test device 8 switches the constant current source 7 from a constant current I 1 to a constant current I 2 , in that the test device 8, which is connected to the constant current source 7 in the control network, actuates a control line 10.
  • the light emitting diodes 3 are now tested for their functionality. Like in the Fig. 1 shown, these voltages U 1 and U 2 are measured at the measuring tap 11 on the light-emitting diode branch 2 in the operating and test condition.
  • Fig. 2 exemplifies the effects of various defects of a circuit arrangement illustrated. If there is no defect of a light-emitting diode 3, the voltage-current characteristic 12 results. If one of the light-emitting diodes 3 is defective in that it leads to a short circuit, a voltage-current characteristic 13 can be observed. If three light-emitting diodes 3 of the light-emitting diode branch 2 are defective in that they have a line break (open), the voltage-current characteristic 14 results.
  • the test device 8 has a voltage measuring circuit 15 with a measuring tap 11 on the light-emitting diode branch 2.
  • the voltage measuring circuit 15 is provided with a ratio circuit 16 expanded.
  • the ratio circuit 16 stores-for example with the aid of a memory-the voltage U 1 measured in the operating state so that it can be compared with the voltage U 2 measured in the test state, for example with the aid of a comparator, which automates the test of the light-emitting diodes 2 facilitated.
  • the cases 13 and 14 differ in their ratios significantly compared to the damage-free case 12.
  • a flawless light-emitting branch 2 is due to the intact non-linear voltage-current characteristics of the light-emitting diodes 3, the ratio against 1.
  • the significant differences can be quickly detected, analyzed and reproducible from it a test result for the functioning of the LED branch 2 are formed.
  • Fig. 3 shows the general principles of the invention. A parallel circuit each of a light-emitting diode 3 in series with a resistor 4 is checked for proper functioning here.
  • Is there such an LED branch 2 an electrically open LED (or LED is high impedance) 3, thus increasing the voltage at the series resistor 4 of the functional other diode 3.
  • the constant current I 1 or I 2 does not have to be divided , This leads to an increased dependence of the voltage characteristic of the resistor 4, since the voltage across the LED changes only slightly due to its non-linear characteristic.
  • the influence of the resistor 4 on the measured voltages U 1 and U 2 as a function of the impressed constant current I 1 or I 2 thus increases, or is thus recognizable and thus accessible to the test.

Description

Die Erfindung betrifft eine Schaltungsanordnung und ein Verfahren zum Testen eines Leuchtdiodenzweigs einer Schaltungsanordnung, insbesondere von einer Notbeleuchtung, auf Funktionstüchtigkeit seiner Leuchtdioden, wobei der Leuchtdiodenzweig mehrere Leuchtdioden und mindestens einen Widerstand aufweist, bei welchem Verfahren der Leuchtdiodenzweig von seinem Betriebszustand unter Einprägung eines konstanten elektrischen Stroms mit wenigstens einer ersten Stromstärke in einen Testzustand unter Einprägung eines elektrischen Stroms mit einer anderen Stromstärke übergeführt wird, wobei unter Berücksichtigung mindestens einer direkten oder indirekten Messung wenigstens einer elektrischen Größe der Schaltungsanordnung der Leuchtdiodenzweig getestet wird.The invention relates to a circuit arrangement and a method for testing a light diode branch of a circuit arrangement, in particular emergency lighting, on functionality of its LEDs, the LED branch having a plurality of light-emitting diodes and at least one resistor, in which method the LED branch from its operating state by impressing a constant electric current is converted with at least a first current in a test state under impressing an electric current with a different current, wherein, taking into account at least one direct or indirect measurement of at least one electrical variable of the circuit of the light-emitting diode branch is tested.

Die EP 1 839 928 A2 zeigt eine Fahrzeugleuchtenanordnung mit mehreren parallel geordneten Leuchtdiodenzweigen mit jeweils mehreren in Serie geschalteten Leuchtdioden und mit Maßnahmen zur Ausfallsicherheit bzw. Ausfallserkennung.The EP 1 839 928 A2 shows a vehicle lamp assembly having a plurality of parallel light-emitting diode branches each having a plurality of light-emitting diodes connected in series and measures for reliability or failure detection.

Die DE10 2006 018 575 A1 zeigt eine Fehlererkennung von Leuchtdioden einer Notbeleuchtung.The DE10 2006 018 575 A1 shows an error detection of LEDs of emergency lighting.

Um einen Ausfall einer Leuchtdiode (LED) zu erkennen, ist es aus dem Stand der Technik bekannt ( DE102009029930B3 ), einen Leuchtdiodenzweig von einem Betriebszustand, in dem seine Leuchtdioden mit Strom einer Konstantstromquelle betrieben wird, in einen Testzustand überzuführen. Im Testzustand werden nun Messungen von elektrischen Größen der Schaltungsanordnung vorgenommen, wobei mit Hilfe dieser Messdaten auf Betriebsparameter der Leuchtdioden des Leuchtdiodenzweigs rückgeschlossen wird. So wird vorgeschlagen, die Schaltungsanordnung im Testzustand mit einer Konstantspannungsquelle zu verbinden und in diesem Zustand die Stromstärke zu messen, wonach die gemessenen Stromstärken im Vergleich zu einem gespeicherten Normstromwert beurteilt werden. Ein Kurzschluss einer oder mehrere Leuchtdioden kann jedoch nachteilig zu erheblichen Stromstärken in der Schaltungsanordnung führen, wodurch Beschädigungen anderer Schaltungsteile zu befürchten ist. Außerdem ist die Speicherung von Normstromwerten zum Zwecke eines Stromstärkenvergleichs verhältnismäßig aufwändig und stellt auch einen vergleichsweise unzuverlässigen Ansatz für eine Fehlererkennung dar - unter anderem deshalb, weil sich Stromstärken auch durch Alterungserscheinungen der Leuchtdioden ändern können. Ein Verfahren zur Erkennung eines Funktionsversagens einer Leuchtdiode, das auf den Vergleich mit dem Normstromwert beruht und diese Umstände nicht berücksichtigt, kann somit scheitern.In order to detect a failure of a light-emitting diode (LED), it is known from the prior art ( DE102009029930B3 ), to convert a light-emitting diode branch from an operating state in which its light emitting diodes are operated with current of a constant current source to a test state. In the test state, measurements of electrical variables of the circuit arrangement are now made, with the aid of these measurement data being used to infer the operating parameters of the light-emitting diodes of the light-emitting diode branch. So it is proposed the circuit arrangement in the test state to connect to a constant voltage source and to measure the current in this state, after which the measured currents are judged in comparison to a stored standard current value. A short circuit of one or more light-emitting diodes, however, can disadvantageously lead to considerable currents in the circuit arrangement, whereby damage to other circuit parts is to be feared. In addition, the storage of standard current values for the purpose of a current comparison is relatively complex and also represents a relatively unreliable approach to fault detection - among other reasons, because currents can also change due to aging phenomena of the LEDs. A method for detecting a function failure of a light-emitting diode, which is based on the comparison with the standard current value and does not take these circumstances into consideration, can thus fail.

Es ist daher die Aufgabe der Erfindung, ausgehend vom eingangs geschilderten Stand der Technik, ein Verfahren zu schaffen, durch das die Funktionstüchtigkeit von Leuchtdioden sicher und zuverlässig getestet werden kann.It is therefore an object of the invention, starting from the above-described prior art, to provide a method by which the functionality of light-emitting diodes can be tested safely and reliably.

Die Erfindung löst die gestellte Aufgabe hinsichtlich des Verfahrens dadurch, dass dem Leuchtdiodenzweig, der mindestens zwei parallele Leuchtdioden mit je einem Widerstand in Serie aufweist, im Testzustand ein konstanter elektrischer Strom eingeprägt wird und dass im Betriebs- und Testzustand als elektrische Größe je eine Spannung zumindest über dem Leuchtdiodenzweig gemessen wird, wobei der Leuchtdiodenzweig unter Berücksichtigung der im Betriebs- und Testzustand gemessenen Spannungen auf Funktionstüchtigkeit seiner Leuchtdiode bzw. Leuchtdioden getestet wird.The invention achieves the stated object with regard to the method in that the light-emitting diode branch, which has at least two parallel light-emitting diodes, each with a resistor in series, a constant electric current is impressed in the test state and that in the operating and test state as electrical variable depending on a voltage at least is measured over the light-emitting diode branch, wherein the light-emitting diode branch is tested for functionality of its light-emitting diode or light-emitting diodes, taking into account the voltages measured in the operating and test states.

Dadurch dass der Leuchtdiodenzweig mindestens zwei parallele Leuchtdioden mit je einem Widerstand in Serie aufweist kann es möglich werden, dass der Funktionszustand des Leuchtdiodenzweigs sicher und zuverlässig geprüft werden kann. Wird nämlich dem Leuchtdiodenzweig im Testzustand ein konstanter elektrischer Strom eingeprägt, kann unter anderem vermieden werden, dass sich bei einem eventuellen Kurzschluss einer Leuchtdiode unzulässig hohe Stromstärken in der Schaltungsanordnung ausbilden. Somit können Beschädigungen der Schaltungsanordnung während des Testzustands auf einfache Weise vermieden werden, was ein sicheres Verfahren zum Testen der Funktionstüchtigkeit gewährleisten kann. Wird weiter im Betriebs- und Testzustand als elektrische Größe je eine Spannung zumindest über dem Leuchtdiodenzweig gemessen, wobei der Leuchtdiodenzweig unter Berücksichtigung der im Betriebs- und Testzustand gemessenen Spannungen auf Funktionstüchtigkeit seiner Leuchtdiode bzw. Leuchtdioden getestet wird, kann im Gegensatz zum Stand der Technik auf gespeicherte Normwerte zum Zwecke einer Überprüfung der Funktionstüchtigkeit der Leuchtdiodenstrecke bzw. des Leuchtdiodenzweigs verzichtet werden. Es können nämlich einzig die im Betriebs- und Testzustand gemessenen Spannungshöhen ausreichen, um für eine sichere und zuverlässige Überprüfung vorzugsweise aller Leuchtdioden des Leuchtdiodenzweigs zu sorgen. Mit diesem erfindungsgemäßen Funktionstest der Leuchtdiode bzw. Leuchtdioden kann nun größere Sicherheit darüber gewonnen werden, ob der Leuchtdiodenzweig innerhalb der geplanten Rahmenbedingungen funktioniert bzw. ob bestimmte Eigenschaften vorliegen oder nicht. Über die Höhe der Spannungen kann nämlich Auskunft erhalten werden, ob diese noch von einer nichtlinearen Spannungs-Stromkennlinie der Leuchtdiode geprägt werden, was im bejahenden Fall für eine funktionstüchtige Leuchtdiode bzw. Leuchtdioden sprechen würde - denn auch unterschiedlich hohe konstante Stromstärken führen auf Grundlage der Nichtlinearität der Spannungs-Stromkennlinie einer Leuchtdiode zu vergleichsweise ähnlich hohen Spannungen. Hingegen kann bei einem Fehler an wenigstens einer Leuchtdiode, sei es im Falle eines Kurzschlusses oder auch eines Leitungsbruchs, mit deutlich differierenden Spannungshöhen gerechnet werden. In diesem Fall kommt die Nichtlinearität der Spannungs-Stromkennlinie einer Leuchtdiode nicht mehr zum Tragen, wodurch die Widerstände zu erhöhten Spannungsverschiebungen beitragen. Dies kann sich insbesondere aus der Parallelschaltung der Leuchtdioden mit deren Serienwiderstand ergeben. Gegenüber dem Stand der Technik kann daher ein vergleichsweise einfaches Verfahren zur Überprüfung der Funktionsweise einer Leuchtdiode geschaffen werden. Hinzu kommt, dass das erfindungsgemäße Verfahren auch vergleichsweise robust ist. Beispielsweise wirkt sich auch eine Alterung der Leuchtdiode nur geringfügig auf das Verfahrensergebnis aus, weil selbst gealterte Leuchtdioden eine nichtlineare Spannungs-Stromkennlinie führen und so ein erfindungsgemäßes Testen der Leuchtdiode bzw. der Leuchtdioden ermöglichen können. Außerdem weist das Verfahren durch den Spannungsabgriff über dem Leuchtdiodenzweig nahezu keine Abhängigkeit von dessen konstruktivem Aufbau auf, so dass sich eine äußerst vielseitige Anwendungsmöglichkeit bzw. ein breites Anwendungsspektrum ergeben kann.Because the light-emitting diode branch has at least two parallel light-emitting diodes, each with a resistor in series, it may be possible for the functional state of the light-emitting diode branch to be checked reliably and reliably. If, for example, a constant electric current is impressed on the light-emitting diode branch in the test state, it can be avoided, among other things, that in the event of an eventual failure Short circuit of a light emitting diode form unacceptably high currents in the circuit. Thus, damage to the circuitry during the test condition can be easily avoided, which can ensure a safe method of testing functionality. If, in the operating and test state, a voltage is measured at least across the light-emitting diode branch, the light-emitting diode branch being tested for functionality of its light-emitting diode or light-emitting diodes, taking into account the voltages measured in the operating and test states, in contrast to the prior art stored standard values are omitted for the purpose of checking the functionality of the light-emitting diode path or the light-emitting diode branch. Namely, only the voltage levels measured in the operating and test states can be sufficient to ensure a reliable and reliable testing of preferably all LEDs of the light-emitting diode branch. With this functional test of the light-emitting diode or light-emitting diodes according to the invention, greater certainty can now be gained as to whether the light-emitting diode branch functions within the planned framework conditions or whether certain properties are present or not. In fact, information about the magnitude of the voltages can be obtained as to whether these are still characterized by a non-linear voltage-current characteristic of the light-emitting diode, which in the affirmative case would speak for a functioning light-emitting diode or light-emitting diodes - because different levels of constant current lead on the basis of nonlinearity the voltage-current characteristic of a light-emitting diode to comparatively similar high voltages. On the other hand, in the event of a fault on at least one light-emitting diode, be it in the case of a short circuit or even a line break, significantly different voltage levels can be expected. In this case, the non-linearity of the voltage-current characteristic of a light emitting diode no longer applies, whereby the resistors contribute to increased voltage shifts. This can result in particular from the parallel connection of the light-emitting diodes with their series resistance. Compared to the prior art, therefore, a comparatively simple method for checking the operation of a light-emitting diode can be provided. In addition, the inventive Method is also relatively robust. For example, aging of the light-emitting diode also has only a slight effect on the method result, because even aged light-emitting diodes lead to a non-linear voltage-current characteristic and thus permit testing of the light-emitting diode or light-emitting diodes according to the invention. In addition, the method by the voltage tap on the LED branch almost no dependence on the structural design, so that can result in a very versatile application or a wide range of applications.

Vorteilhaft kann das Verfahren auch dort angewendet werden, wo der Leuchtdiodenzweig mehrere in Serie und parallel geschaltete Leuchtdioden mit je einem Widerstand in Serie aufweist. So kann beispielsweise selbst ein Kurzschluss einer Leuchtdiode bei sechs parallel geschalteten Leuchtdioden reproduzierbar erkannt werden. Der schadhafte Strompfad über die kurzgeschlossene Leuchtdiode und seinem in Serie geschalteten Widerstand führte nämlich zu einer erheblichen Spannungsverschiebung zwischen Betriebs- und Testzustand.Advantageously, the method can also be used where the light-emitting diode branch has a plurality of light-emitting diodes connected in series and in parallel, each with a resistor in series. For example, even a short circuit of a light-emitting diode can be detected reproducibly in the case of six light-emitting diodes connected in parallel. The faulty current path via the short-circuited LED and its series-connected resistor led namely to a significant voltage shift between operating and test condition.

Ein vergleichsweise einfaches Verfahren kann sich ergeben, wenn der Test ein Verhältnis der im Betriebs- und Testzustand gemessenen Spannungen berücksichtigt. Besonders aber kann der Quotient der Spannungswerte zu einem aussagekräftigen Ergebnis und damit zu einem sicheren Test der Leuchtdiode beitragen.A comparatively simple procedure can result if the test takes into account a ratio of the voltages measured in the operating and test states. In particular, however, the quotient of the voltage values can contribute to a meaningful result and thus to a reliable test of the light-emitting diode.

Wird anhand des Quotienten der gemessenen Spannungen getestet, ob eine oder mehrere Leuchtdiode bzw. Leuchtdioden des Leuchtdiodenzweigs funktionsuntüchtig sind, kann eine einfache Verfahrensvorschrift zur Detektion von Fehlern im Leuchtdiodenzweig ermöglicht werden, über die sowohl ein Kurzschluss als auch ein Leitungsbruch erkannt werden kann. Eventuelle Parameterschwankungen im Leuchtdiodenzweig können ausgeglichen werden, wenn dabei ein Schwellwert berücksichtigt wird.If it is tested on the basis of the quotient of the measured voltages whether one or more light emitting diodes or light emitting diodes of the light emitting diode branch are inoperative, a simple procedure for detecting faults in the light emitting diode branch can be made possible, by which both a short circuit and a line break can be detected. Possible parameter fluctuations in the LED branch can be compensated if a threshold value is taken into account.

Ist die andere bzw. zweite Stromstärke des konstanten elektrischen Stroms geringer als die erste Stromstärke des konstanten elektrischen Stroms, kann im Testzustand die Gefahr einer elektrischen Beschädigung am Leuchtdiodenzweig durch Überlastung gering gehalten werden. Dies auch dann, wenn bereits ein elektrischer Defekt im Leuchtdiodenzweig vorliegt.If the other or the second current intensity of the constant electrical current is less than the first current intensity of the constant electrical current, the risk of electrical damage to the light-emitting diode branch due to overloading can be kept low in the test state. This even if there is already an electrical defect in the light-emitting diode branch.

Es ist weiter die Aufgabe der Erfindung, ausgehend vom eingangs geschilderten Stand der Technik eine konstruktiv einfache Schaltungsanordnung zu schaffen, deren Leuchtdiodenzweig auf defekte und/oder der Art der Defekte von Leuchtdioden sicher getestet werden kann.It is a further object of the invention to provide, starting from the above-described prior art, a structurally simple circuit arrangement whose LED branch can be safely tested for defects and / or the nature of the defects of LEDs.

Die Erfindung löst die gestellte Aufgabe hinsichtlich der Schaltungsanordnung dadurch, dass der Leuchtdiodenzweig mindestens zwei parallele Leuchtdioden mit je einem Widerstand in Serie aufweist, und dass die Konstantstromquelle in der erzeugbaren Stromstärke hinsichtlich ihres konstanten Stroms variabel ausgeführt ist, wobei die Testeinrichtung für einen Testzustand des Leuchtdiodenzweigs mit der Konstantstromquelle zur Erzeugung eines konstanten Stroms einer zum im Betriebszustand von der Konstantstromquelle erzeugten konstanten Strom unterschiedlichen Stromstärke verbunden ist und wobei die Testeinrichtung als Messschaltung eine Spannungsmessschaltung mit einem Messabgriff über wenigstens dem Leuchtdiodenzweig zur Messung je einer Spannung in ihrem Betriebs- und Testzustand aufweist.The invention achieves the stated object with regard to the circuit arrangement in that the light-emitting diode branch has at least two parallel light-emitting diodes each having a resistor in series, and in that the constant current source in the producible current intensity is variable with respect to its constant current, the test device for a test state of the light diode branch is connected to the constant current source for generating a constant current of a current produced by the constant current source constant current different current and wherein the test device as a measuring circuit has a voltage measuring circuit with a Meßabgriff over at least the light emitting diode branch for measuring each voltage in its operating and test state.

Konstruktive Einfachheit kann sich ergeben, wenn eine Konstantstromquelle verwendet wird, die in der erzeugbaren Stromstärke hinsichtlich ihres konstanten Stroms variabel ausgeführt ist, um den Leuchtdiodenzweig so in unterschiedlichen Stromzuständen zu betreiben, welcher Leuchtdiodenzweig mindestens zwei parallele Leuchtdioden mit je einem Widerstand in Serie aufweist. Dadurch kann auch ermöglicht werden, dass ein und dieselbe Konstantstromquelle auch für den Testzustand des Leuchtdiodenzweigs Verwendung finden kann. Zu diesem Zweck kann die Testeinrichtung mit der Konstantstromquelle zur Erzeugung eines konstanten Stroms einer zum im Betriebszustand von der Konstantstromquelle erzeugten konstanten Strom unterschiedlichen Stromstärke verbunden sein. Die Bestimmung von Defekten im Leuchtdiodenzweig kann besonders sicher möglich werden, wenn die Testeinrichtung als Messschaltung eine Spannungsmessschaltung mit einem Messabgriff über wenigstens dem Leuchtdiodenzweig zur Messung je einer Spannung in seinem Betriebs- und Testzustand aufweist. Da verhältnismäßig konstruktiv einfach über den gesamten Leuchtdiodenzweig gemessen werden kann, können sich damit auch die konstruktiven Voraussetzungen vereinfachen.Constructive simplicity may result when using a constant current source that is variably variable in the current that can be generated with respect to its constant current to operate the LED branch in different current states, which LED branch has at least two series-connected parallel light emitting diodes. As a result, it can also be made possible for one and the same constant current source also to be used for the test state of the light-emitting diode branch. For this purpose, the test device with the constant current source for generating a constant Current to be connected to a constant current produced by the constant current source in the operating state constant current different current. The determination of defects in the light-emitting diode branch can be made particularly reliable if the test device has a voltage measuring circuit with a measuring tap as measuring circuit over at least the light-emitting diode branch for measuring a respective voltage in its operating and test state. Since relatively simple construction can be measured over the entire light-emitting diode branch, thus also simplify the design requirements.

Vorteilhaft kann die Schaltungsanordnung die Funktionstüchtigkeit des Leuchtdiodenzweigs besonders sicher überprüfen bzw. auch dort angewendet werden, wenn der Leuchtdiodenzweig mehrere in Serie und parallel geschaltete Leuchtdioden mit je einem Widerstand in Serie aufweist.The circuit arrangement can advantageously check the operation of the light-emitting diode branch with particular reliability or can also be used there when the light-emitting diode branch has a plurality of light-emitting diodes connected in series and in parallel, each with a resistor in series.

Weist die Testeinrichtung eine Verhältnisschaltung zur Ausbildung eines Verhältnisses der Spannungen zueinander im Betriebs- und Testzustand des Leuchtdiodenzweigs auf, kann eine vergleichsweise hohe konstruktive Einfachheit an der Schaltungsanordnung erreicht werden.If the test device has a ratio circuit for forming a ratio of the voltages to one another in the operating and test state of the light-emitting diode branch, a comparatively high degree of constructive simplicity can be achieved in the circuit arrangement.

Die Schaltungsanordnung kann gegenüber Überlastungen im Testzustand geschützt werden, indem die andere Stromstärke des konstanten Stroms geringer ist als die erste Stromstärke des konstanten elektrischen Stroms.The circuit arrangement can be protected against overloads in the test state in that the other current intensity of the constant current is lower than the first current intensity of the constant electrical current.

In den Figuren ist der Erfindungsgegenstand beispielsweise dargestellt. Es zeigen

Fig. 1
eine Schaltungsanordnung,
Fig. 2
ein Spannungs-Stromkennliniendiagramm zur Schaltungsanordnung nach Fig. 1 und
Fig. 3
eine Teilausschnitt der Fig. 1.
In the figures, the subject invention is shown, for example. Show it
Fig. 1
a circuit arrangement,
Fig. 2
a voltage-current characteristic diagram according to the circuit arrangement Fig. 1 and
Fig. 3
a partial section of the Fig. 1 ,

In der nach der Fig. 1 beispielsweise dargestellten Schaltungsanordnung 1 wird ein Leuchtdiodenzweig 2 mit sechs parallel liegenden Leuchtdioden (LED) 3 gezeigt, denen je ein Widerstand 4 in Serie geschaltet ist. Diese Parallelschaltung 5 ist mit einer weiteren Parallelschaltung 6, die ebenso sechs parallel liegende Leuchtdioden 3 mit je einem Widerstand 4 in Serie aufweist, in Serie geschaltet. Vorzugsweise werden die Widerstände 4 zum Abgleich der Helligkeit der Leuchtdioden 3 verwendet, und sind in derer Impedanz gleich ausgelegt.In the after the Fig. 1 For example, circuit arrangement 1 shown is a light-emitting diode branch 2 with six light-emitting diodes (LED) 3 lying in parallel, each of which a resistor 4 is connected in series. This parallel circuit 5 is connected in series with a further parallel circuit 6, which also has six parallel LEDs 3, each with a resistor 4 in series. Preferably, the resistors 4 are used to balance the brightness of the light-emitting diodes 3, and are designed the same impedance in their impedance.

Im Allgemeinen wird erwähnt, dass als Grundschaltung des Leuchtdiodenzweigs 2 eine Parallelschaltung von zwei Leuchtdioden 3 mit je einem Widerstand 4 in Serie angesehen werden kann, was nach Fig. 3 näher dargestellt ist.In general, it is mentioned that as a basic circuit of the LED branch 2, a parallel connection of two light-emitting diodes 3, each with a resistor 4 can be viewed in series, which is after Fig. 3 is shown in more detail.

Im Betriebszustand der Leuchtdioden 3 wird dem Leuchtdiodenzweig 2 ein konstanter elektrischer Strom I1 zugeführt bzw. diesem Leuchtdiodenzweig eingeprägt, um diese mit elektrischer Leistung zu versorgen. Zu diesem Zweck wird eine Konstantstromquelle 7 verwendet. Im Allgemeinen wird erwähnt, dass die konstante Stromstärke zur Erzeugung des Stroms I1 beispielsweise nach den Helligkeitsanforderungen eingestellt werden kann und diese konstante Stromstärke durchaus auch einem sich ändernden Helligkeitsbedarf angepasst werden kann - z.B.: durch Dimmen. Solch eine Einstellung der gewünschten Stromstärke kann auch eine Testeinrichtung 8 vornehmen, die über einen in der Impedanz bekannten Widerstand 9 die Spannung über diesen Widerstand 9 misst und die Konstantstromquelle 7 hinsichtlich der gewünschten konstanten Stromstärke regelt.In the operating state of the light-emitting diodes 3, the light-emitting diode branch 2 is supplied with a constant electric current I 1 or impressed on this light-emitting diode branch in order to supply it with electrical power. For this purpose, a constant current source 7 is used. In general, it is mentioned that the constant current intensity for generating the current I 1 can be adjusted, for example, according to the brightness requirements and this constant current intensity can certainly also be adapted to a changing brightness requirement - for example: by dimming. Such a setting of the desired current intensity can also be carried out by a test device 8, which measures the voltage across this resistor 9 via a resistor 9 known in the impedance and regulates the constant current source 7 with regard to the desired constant current intensity.

Dieser Leuchtdiodenzweig 2 wird getestet bzw. auf die Funktionstüchtigkeit seiner Leuchtdioden 3 überprüft, indem der Leuchtdiodenzweig 2 von seinem Betriebszustand in einen Testzustand übergeführt wird. Hierzu wird der Leuchtdiodenzweig 2 mit einem elektrischen Strom I2 mit einer gegenüber der Stromstärke des konstanten Stroms I1 im Betriebszustand unterschiedlichen, hier geringeren, Stromstärke belastet, was den Leuchtdiodenzweig 2 vor elektrischer Überbelastung schützt.This LED branch 2 is tested or checked for the functionality of its LEDs 3 by the LED branch 2 is transferred from its operating state in a test state. For this purpose, the light-emitting diode branch 2 is charged with an electric current I 2 having a current intensity which differs from the current intensity of the constant current I 1 in the operating state, which is lower here, which protects the light-emitting diode branch 2 against electrical overloading.

Um im Falle defekter Leuchtdioden 3, was beispielsweise auch in einem Kurzschluss liegen kann, keine Beschädigungen an anderen Bauteilen der Schaltungsanordnung 1 befürchten zu müssen, wird erfindungsgemäß im Testzustand ebenfalls ein konstanter elektrischer Strom I2 eingeprägt. Zu diesem Zweck ist die Konstantstromquelle 7 in der erzeugbaren Stromstärke hinsichtlich ihres konstanten Stroms I1 bzw. I2 variabel ausgeführt. Eine Testeinrichtung 8 schaltet die Konstantstromquelle 7 von einem konstanten Strom I1 auf einen konstanten Strom I2 um, indem die mit der Konstantstromquelle 7 im Steuerungsverbund stehende Testeinrichtung 8 eine Steuerungsleitung 10 betätigt. Unter Berücksichtigung einer direkten Messung von Spannungen U1 und U2 als elektrische Größen der Schaltungsanordnung 1 werden nun die Leuchtdioden 3 auf ihre Funktionstüchtigkeit getestet. Wie in der Fig. 1 dargestellt, werden diese Spannungen U1 und U2 am Messabgriff 11 über dem Leuchtdiodenzweig 2 im Betriebs- und Testzustand gemessen.In the case of defective light-emitting diodes 3, which may be, for example, in a short circuit, no damage to other components of the circuit arrangement 1 to fear, according to the invention in the test state also a constant electric current I 2 impressed. For this purpose, the constant current source 7 is made variable in the generatable current with respect to their constant current I 1 and I 2 . A test device 8 switches the constant current source 7 from a constant current I 1 to a constant current I 2 , in that the test device 8, which is connected to the constant current source 7 in the control network, actuates a control line 10. Taking into account a direct measurement of voltages U 1 and U 2 as electrical variables of the circuit arrangement 1, the light emitting diodes 3 are now tested for their functionality. Like in the Fig. 1 shown, these voltages U 1 and U 2 are measured at the measuring tap 11 on the light-emitting diode branch 2 in the operating and test condition.

Im Weiteren wird nun näher auf Fig. 2 eingegangen, die beispielhaft die Auswirkungen diverser Defekte einer Schaltungsanordnung veranschaulicht. Liegt kein Defekt einer Leuchtdiode 3 vor, so ergibt sich die Spannungs-Stromkennlinie 12. Ist eine der Leuchtdioden 3 defekt, indem diese einen Kurzschluss führt, kann eine Spannungs-Stromkennlinie 13 beobachtet werden. Sind drei Leuchtdioden 3 des Leuchtdiodenzweigs 2 defekt, indem diese einen Leitungsbruch (offen) aufweisen, ergibt sich die Spannungs-Stromkennlinie 14.In the following will now be closer Fig. 2 which exemplifies the effects of various defects of a circuit arrangement illustrated. If there is no defect of a light-emitting diode 3, the voltage-current characteristic 12 results. If one of the light-emitting diodes 3 is defective in that it leads to a short circuit, a voltage-current characteristic 13 can be observed. If three light-emitting diodes 3 of the light-emitting diode branch 2 are defective in that they have a line break (open), the voltage-current characteristic 14 results.

Folgende Spannungen U1 und U2 konnten in diesen Fällen unter Verwendung von I1 mit einer ersten Stromstärke von 60mA und I2 mit einer Stromstärke von 240mA gemessen werden: Fall 12 Fall 13 Fall 14 U1 5,72 Volt 3,73 Volt 5,91 Volt U2 6,80 Volt 6,26 Volt 7,38 Volt The following voltages U 1 and U 2 could be measured in these cases using I 1 with a first current of 60mA and I 2 with a current of 240mA: Case 12 Case 13 Case 14 U 1 5.72 volts 3.73 volts 5.91 volts U 2 6.80 volts 6.26 volts 7.38 volts

Zur Messung der Spannungen U1 und U2 weist die Testeinrichtung 8 eine Spannungsmessschaltung 15 mit einem Messabgriff 11 über dem Leuchtdiodenzweig 2 auf. Insbesondere ist die Spannungsmessschaltung 15 mit einer Verhältnisschaltung 16 erweitert. Die Verhältnisschaltung 16 speichert -beispielsweise mit Hilfe eines Speichers- die im Betriebszustand gemessene Spannung U1, um diese mit der im Testzustand gemessenen Spannung U2 in Verhältnis setzen zu können -beispielsweise mit Hilfe eines Komparators-, was den Test der Leuchtdioden 2 automatisiert und erleichtert.To measure the voltages U 1 and U 2 , the test device 8 has a voltage measuring circuit 15 with a measuring tap 11 on the light-emitting diode branch 2. In particular, the voltage measuring circuit 15 is provided with a ratio circuit 16 expanded. The ratio circuit 16 stores-for example with the aid of a memory-the voltage U 1 measured in the operating state so that it can be compared with the voltage U 2 measured in the test state, for example with the aid of a comparator, which automates the test of the light-emitting diodes 2 facilitated.

Folgende Quotienten U2/U1 bilden sich aus:

  • im Fall 12 (ohne eine defekte Leuchtdiode 3) 1,18
  • im Fall 13 (mit einer kurzgeschlossenen Leuchtdiode 3) 1,68
  • im Fall 14 (mit drei offenen Leuchtdioden 3) 1,25
The following quotients U 2 / U 1 are formed by:
  • in case 12 (without a defective LED 3) 1,18
  • in case 13 (with a short-circuited LED 3) 1.68
  • in case 14 (with three open LEDs 3) 1.25

Die Fälle 13 und 14 unterscheiden sich in ihren Verhältnissen deutlich gegenüber dem schadensfreien Fall 12. Bei einem fehlerlosen Leuchtdiodenzweig 2 geht nämlich aufgrund der intakten nichtlinearen Spannungs-Stromkennlinien der Leuchtdioden 3 das Verhältnis gegen 1. Die deutlichen Unterschiede können schnell detektiert, analysiert und daraus reproduzierbar ein Testergebnis zur Funktionstüchtigkeit des Leuchtdiodenzweigs 2 gebildet werden.The cases 13 and 14 differ in their ratios significantly compared to the damage-free case 12. In a flawless light-emitting branch 2 is due to the intact non-linear voltage-current characteristics of the light-emitting diodes 3, the ratio against 1. The significant differences can be quickly detected, analyzed and reproducible from it a test result for the functioning of the LED branch 2 are formed.

Um erhöhte Testsicherheit zu erreichen, kann noch ein Schwellwert berücksichtigt werden. So ist vorstellbar, erst bei einem Überschreiten eines Schwellwerts von 1,2 von einem Defekt im Leuchtdiodenzweig 2 auszugehen.In order to achieve increased test safety, a threshold value can be taken into account. Thus, it is conceivable to assume a defect in the light-emitting diode branch 2 only when a threshold value of 1.2 is exceeded.

Im Allgemeinen ist auch denkbar, die Größe des Unterschieds des gemessenen Verhältnis U2/U1 zum schadensfreien Verhältnis U2/U1 (Fall 12 ohne Defekt) heranzuziehen, um damit eine Unterscheidung der Art des Schadensfalls - beispielsweise hinsichtlich eines Kurzschlusses oder eines Leitungsbruchs an den Leuchtdioden 3 - vorzunehmen.In general, it is also conceivable to use the magnitude of the difference of the measured ratio U 2 / U 1 to the damage-free ratio U 2 / U 1 (case 12 without defect), in order to distinguish the type of damage event - for example with regard to a short circuit or a line break at the LEDs 3 - make.

Fig. 3 zeigt den allgemeinen Grundgedanken der Erfindung. Eine parallele Schaltung je einer Leuchtdiode 3 in Serie mit einem Widerstand 4 wird hier auf Funktionstüchtigkeit sicher überprüft. Fig. 3 shows the general principles of the invention. A parallel circuit each of a light-emitting diode 3 in series with a resistor 4 is checked for proper functioning here.

Besteht nun in solch einem Leuchtdiodenzweig 2 eine elektrisch offene Leuchtdiode (bzw. LED wird hochohmig) 3, erhöht sich damit die Spannung am Serien-Widerstand 4 der funktionstüchtigen anderen Diode 3. Der konstante Strom I1 bzw. I2 muss sich nämlich nicht aufteilen. Dies führt zu einer erhöhten Abhängigkeit der Spannungskennlinie vom Widerstand 4, da sich die Spannung an der LED durch ihre nichtlineare Kennlinie lediglich geringfügig ändert. Der Einfluss des Widerstands 4 auf die gemessenen Spannungen U1 bzw. U2 in Abhängigkeit vom eingeprägten Konstantstrom I1 bzw. I2 steigt somit, bzw. ist damit erkennbar und so dem Test zugänglich.Is there such an LED branch 2 an electrically open LED (or LED is high impedance) 3, thus increasing the voltage at the series resistor 4 of the functional other diode 3. The constant current I 1 or I 2 does not have to be divided , This leads to an increased dependence of the voltage characteristic of the resistor 4, since the voltage across the LED changes only slightly due to its non-linear characteristic. The influence of the resistor 4 on the measured voltages U 1 and U 2 as a function of the impressed constant current I 1 or I 2 thus increases, or is thus recognizable and thus accessible to the test.

Besteht nun in solch einem Leuchtdiodenzweig 2 eine elektrisch kurzgeschlossene Leuchtdiode 3 (bzw. LED wird niederohmig), dann zieht deren Serien-Widerstand 4 erheblich mehr Strom. Dies ergibt sich durch den geringen elektrischen Widerstand 4 in diesem parallelen Ast. Auch hier steigt somit der Einfluss des Widerstands 4 auf die gemessene Spannung U1 bzw. U2 in Abhängigkeit vom eingeprägten Konstantstrom I1 bzw. I2. Die erhöhte Abhängigkeit der Spannungskennlinie vom Widerstand 4 ist damit erkennbar und so dem Test zugänglich.If there is an electrically short-circuited LED 3 (or LED becomes low-resistance) in such a light-emitting diode branch 2, then its series resistor 4 draws considerably more current. This is due to the low electrical resistance 4 in this parallel branch. In this case as well, the influence of the resistor 4 on the measured voltage U 1 or U 2 increases as a function of the impressed constant current I 1 or I 2 . The increased dependence of the voltage characteristic of the resistor 4 is thus recognizable and thus accessible to the test.

Zusammengefasst lässt sich sagen, dass in beiden Fehlerfällen aufgrund eines steigenden Einflusses der Widerstände die Gesamtspannung in erhöhtem Ausmaß von der Höhe des eingeprägten Konstantstroms abhängiger wird und damit Fehler im Leuchtdiodenzweig erkannt werden können.In summary, it can be said that in both cases of error due to an increasing influence of the resistors, the total voltage becomes more dependent on the level of the impressed constant current and thus errors in the light-emitting diode branch can be detected.

Claims (9)

  1. A method for testing a light-emitting diode branch (2) of a circuit assembly (1), especially of emergency lighting, concerning the functionality of its light-emitting diodes (3), wherein the light-emitting diode branch (2) comprises several light-emitting diodes (3) and at least one resistor (4), in which method the light-emitting diode branch (2) is transferred from its operating state under injection of a constant electrical current (I1) with at least one first current intensity to a test state under injection of an electrical current (I2) with a different current intensity, wherein, by considering at least one direct or indirect measurement, at least one electrical quantity of the circuit arrangement (1) of the light-emitting diode branch (2) is tested, characterized in that in the test state a constant electrical current (I2) is injected into the light-emitting diode branch (2), which comprises at least two parallel light-emitting diodes (3) with one resistor (4) each in series, and that in the operating and test state a respective voltage (U1, U2) is measured at least via the light-emitting diode branch (2) as the electrical quantity, wherein the light-emitting diode branch (2) is tested with respect to functionality of its light-emitting diode (3) or light-emitting diodes (3) by considering the voltages (U1, U2) measured in the operating and test state.
  2. A method according to claim 1, characterized in that the light-emitting diode branch (2) comprises multiple light-emitting diodes (3) switched in series and in parallel and having a respective resistor (4) switched in series.
  3. A method according to claim 1 or 2, characterized in that the test considers a ratio of the voltages (U1, U2) measured in the operating and test state.
  4. A method according to claim 3, characterized in that it is tested on the basis of the quotient of the measured voltages (U1, U2), by optionally considering a threshold value, whether one or several light-emitting diodes (3) of the light-emitting diode branch (2) are inoperative.
  5. A method according to one of the claims 1 to 4, characterized in that the other current intensity of the constant electrical current (I2) is lower than the first current intensity of the constant electrical current (I1).
  6. A circuit assembly, especially for lamps of an emergency lighting, for carrying out the method according to one of the claims 1 to 5 with a light-emitting diode branch (2) which comprises multiple light-emitting diodes (3) and at least one resistor (4), comprising a constant-current source (7) which is electrically connected to the light-emitting diode branch (2) for electrical power supply, and a testing device (8) having a measurement circuit for testing the light-emitting diode branch (2) concerning the functionality of the light-emitting diodes (3), characterized in that the light-emitting diode branch (2) comprises at least two parallel light-emitting diodes (3) with one resistor (4) each in series, and the constant-current source (7) is variably formed in the producible current intensity concerning its constant current (I1 or I2), wherein the testing device (8), for a testing state of the light-emitting diode branch (2), is connected to the constant-current source (7) for generating a constant current (I2) of a current intensity which differs from a constant current (I1) which is produced in the operating state by the constant-current source (7), and wherein the testing device (8) comprises a voltage measurement circuit (15) as the measurement circuit with a measuring pickoff (11) via at least the light-emitting diode branch (2) for measuring one voltage (U1, U2) each in its operating and test state.
  7. A circuit assembly according to claim 6, characterized in that the light-emitting diode branch (2) comprises multiple light-emitting diodes (3) switched in series and in parallel and having a respective resistor (4) switched in series.
  8. A circuit assembly according to claim 6 or 7, characterized in that the testing device (8) comprises a ratio circuit (16) for forming a ratio of the voltages (U1 and U2) in relation to each other in the operating and test state of the light-emitting diode branch (2).
  9. A circuit assembly according to claim 6, 7 or 8, characterized in that the other current intensity of the constant current (I2) is lower than the first current intensity of the constant electrical current (I1).
EP13161845.6A 2012-03-29 2013-03-29 Circuit assembly and method for testing a light emitting diode branch of a circuit assembly Active EP2645529B1 (en)

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JP3450001B1 (en) * 2002-11-21 2003-09-22 株式会社テクノローグ LED deterioration inspection method
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