EP3780911A1 - Motor vehicle lighting device - Google Patents

Motor vehicle lighting device Download PDF

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Publication number
EP3780911A1
EP3780911A1 EP19191484.5A EP19191484A EP3780911A1 EP 3780911 A1 EP3780911 A1 EP 3780911A1 EP 19191484 A EP19191484 A EP 19191484A EP 3780911 A1 EP3780911 A1 EP 3780911A1
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Prior art keywords
series
transistor
resistor
voltage
motor vehicle
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German (de)
French (fr)
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Thomas Graf
Georg Hebenstreit
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ZKW Group GmbH
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ZKW Group GmbH
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Priority to EP19191484.5A priority Critical patent/EP3780911A1/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]
    • H05B45/40—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 a motor vehicle lighting device with at least two LED series strings, each strand having several LEDs connected in series and a series transistor with a series resistor assigned to it and the LED series strings being connected to a common supply source.
  • a control circuit for a lighting device with at least two LED series strings, each strand having several LEDs connected in series and a series transistor with a series resistor assigned to it and the LED series strings being connected to a common supply voltage is for example in the DE 199 50 135 A1 shown in which to reduce the control power, the series transistors supply the LED strings with their current in the sense of a master-slave control.
  • a motor vehicle lighting device of the type specified at the outset in which, according to the invention, the series transistor of each strand is connected as a constant current source, the series LEDs forming the load resistance of the transistor and the series resistance of each transistor forming a current sensor, the control electrodes of all series transistors are connected to one another and are supplied with a controlled reference voltage which is applied to the collector-emitter path of a control transistor, whose Working resistance is connected to the common supply voltage, and its control electrode is connected to a voltage divider, one branch of the voltage divider being a resistor and the other branch being the series connection of at least one resistor with at least one reference voltage diode, this series connection being connected to the common supply source, which is an overvoltage detection owns.
  • each series transistor is a bipolar transistor and / or the control transistor is a bipolar transistor, since such transistors are available cheaply, they are reliable and their wiring is simple.
  • a capacitor is connected in parallel with the voltage divider.
  • the starting point of the circuit shown here are four strings S1 to S4 with six or seven LEDs in series, which all have the common reference symbol LED.
  • the number of strings, like the number of LEDs contained in them, is only to be understood as an example.
  • Each string S1 to S4 also has a series transistor T1, T2, T3 and T4 with a series resistor R1, R2, R3 and R4 assigned to it, and the LED series strings are connected to a common supply voltage Uv.
  • the series transistors T1, T2, T3 and T4 are each connected as current sources, each of which has a series resistor R1, R2, R3 and R4, with a capacitor C1, C2, C3 and C4 being connected in parallel to these resistors against HF interference.
  • the control electrodes, here the bases, of all series transistors are connected to each other so that the same voltage is applied to them, which creates the symmetry of the individual ones Strands is ensured.
  • the series transistors T1, T2, T3 and T4 therefore compensate for voltage fluctuations.
  • the control electrodes (bases) of the four transistors are jointly supplied with a load resistor R5 of a control transistor T5, the supply voltage Uv, fed by a supply source Q I , here a current source which supplies a current I and has an overvoltage detection, so that the total current of the four strings corresponds to the set current of the feeding power source.
  • the working path of the control transistor T5 lies between the interconnected base connections of the series transistors T1, T2, T3 and T4 and ground.
  • the failure detection of a string caused by the failure of an LED due to an interruption, causes a voltage reduction at the respective string resistance Rl ... R4 due to the missing string current.
  • the common base voltage is reduced by the base-emitter diode of the corresponding transistor and as a result the remaining strings are no longer supplied with the correct base voltage and the defined current can no longer flow.
  • the supplying power source can no longer drive the current and increases the input voltage.
  • the control transistor T5 becomes conductive and blocks the remaining strings.
  • the operating resistance R5 of the control transistor T5 is of particular importance here, since it essentially defines the voltage Uv that is generated by an external supply current source Q I, which is only indicated.
  • This working resistor R5 is dimensioned in such a way that a current that is less than the sum of all currents through the four transistors of strands S1 to S4 flows through it by the total gain factor of all transistors T1, T2, T3 and T4.
  • the transistor T5 causes all strings to be switched off if only a single strand fails, because if a single strand fails, no strand current can flow through the emitter resistor of the associated series transistor; Only the base current then flows through the emitter resistor.
  • the common base potential drops and the supply current source increases the supply voltage to such an extent that the impressed current could flow.
  • the diodes D1 and D2 become conductive, whereupon the control transistor T5 is activated (conductive) via the base current.
  • the supplying current source Q I must for its part have an overvoltage detection; the LED failure detection only has the effect that all LEDs are switched off.
  • a capacitor C5 in connection with resistors R6, R7 and R8 and the associated time constant lead to a delay in the response in the event of undesired disturbances and also to suppress transient processes of the external power supply source Q I.
  • a resistor R9 at the input of the circuit is used to prevent small leakage currents from being emitted by the LEDs, which, however, is not essential to the invention.
  • two series-connected protective diodes D3 and D4 (suppressor diodes) and a capacitor C7 are also located at the input of the circuit.
  • the individual transistor current sources are connected together by a common control so that they compensate for any voltage change due to dynamic loads without passing this change on to the primary source, while keeping a fixed current value constant between the individual strings.
  • transistor is not restricted here to bipolar transistors, but is also intended to include field effect transistors, for example.
  • working path used is therefore to be understood as meaning the collector-emitter path in bipolar transistors and the gate-source path in field-effect transistors.
  • the control electrode is the base for bipolar transistors and the gate for field-effect transistors
  • LED control devices can be used as drivers, which are designed for low LED voltages but high LED currents, so that dynamic loads can also be operated as a result.
  • Such LED control devices or LED drivers could not previously be used for applications with a large number of low-power LEDs.
  • the invention also offers the possibility of failure detection of LEDs, since if an LED of any branch fails, the current or voltage source, which has an overvoltage detection, indicates the failure by switching the control transistor.

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

Abstract

Eine Kraftfahrzeug-Beleuchtungseinrichtung mit zumindest zwei LED-Seriensträngen, wobei jeder Strang in Serie geschaltet mehrere LEDs sowie einen Serientransistor (T1....T4) mit einem diesem zugeordneten Serienwiderstand (R1....R4) aufweist und die LED-Serienstränge an einer gemeinsamen Versorgungsquelle (Qi) liegen, wobei der Serientransistor (T1....T4) jedes Stranges als Konstantstromquelle geschaltet ist, wobei die in Serie liegenden LEDs den Lastwiderstand jedes Transistors bilden und der Serienwiderstand jedes Transistors einen Stromsensor bildet, die Steuerelektroden aller Serientransistoren miteinander verbunden sind und mit einer gesteuerten Referenzspannung versorgt sind, die an der Arbeitsstrecke eines Steuertransistors (T5) liegt, dessen Arbeitswiderstand (R6) an der gemeinsamen Versorgungsspannung liegt, und dessen Basisanschluss an einem Spannungsteiler liegt, wobei ein Zweig des Spannungsteilers ein Widerstand (R8) ist und der andere Zweig die Serienschaltung zumindest eines Widerstandes (R7, R6) mit zumindest einer Referenzspannungsdiode (D1, D2) ist, wobei diese Serienschaltung an der gemeinsamen Versorgungsquelle (Q<sub>I</sub>) liegt, welche eine Überspannungserkennung besitzt.A motor vehicle lighting device with at least two LED series strings, each strand having several LEDs connected in series and a series transistor (T1 .... T4) with a series resistor (R1 .... R4) assigned to it and the LED series strings on a common supply source (Qi), the series transistor (T1 .... T4) of each strand being connected as a constant current source, the LEDs in series forming the load resistance of each transistor and the series resistance of each transistor forming a current sensor, the control electrodes of all series transistors are connected to one another and are supplied with a controlled reference voltage which is applied to the working path of a control transistor (T5), the working resistance (R6) of which is connected to the common supply voltage, and the base connection of which is connected to a voltage divider, one branch of the voltage divider being a resistor (R8 ) and the other branch is the series connection at least one nes resistor (R7, R6) with at least one reference voltage diode (D1, D2), this series circuit being connected to the common supply source (Q <sub> I </sub>), which has overvoltage detection.

Description

Die Erfindung bezieht sich auf eine Kraftfahrzeug-Beleuchtungseinrichtung mit zumindest zwei LED-Seriensträngen, wobei jeder Strang in Serie geschaltet mehrere LEDs sowie einen Serientransistor mit einem diesem zugeordneten Serienwiderstand aufweist und die LED-Serienstränge an einer gemeinsamen Versorgungsquelle liegen.The invention relates to a motor vehicle lighting device with at least two LED series strings, each strand having several LEDs connected in series and a series transistor with a series resistor assigned to it and the LED series strings being connected to a common supply source.

Eine Ansteuerschaltung für eine Beleuchtungseinrichtung mit zumindest zwei LED-Seriensträngen, wobei jeder Strang in Serie geschaltet mehrere LEDs sowie einen Serientransistor mit einem diesem zugeordneten Serienwiderstand aufweist und die LED-Serienstränge an einer gemeinsamen Versorgungsspannung liegen, ist beispielsweise in der DE 199 50 135 A1 gezeigt, bei welcher zur Reduzierung der Ansteuerleistung die Serientransistoren den LED-Strängen ihren Strom im Sinne einer Master-Slave-Regelung getaktet zuführen.A control circuit for a lighting device with at least two LED series strings, each strand having several LEDs connected in series and a series transistor with a series resistor assigned to it and the LED series strings being connected to a common supply voltage, is for example in the DE 199 50 135 A1 shown in which to reduce the control power, the series transistors supply the LED strings with their current in the sense of a master-slave control.

Bei Kraftfahrzeug-Beleuchtungseinrichtungen versucht man, die maximale Versorgungsspannung niedrig zu halten und daher werden in mehreren Strängen jeweils mehrere LEDs mit gleichen Stromwerten betrieben, wobei die Stränge sozusagen parallel geschaltet sind. Erwünscht ist hier auch ein dynamischer Betrieb der LEDs, mit der Möglichkeit, diese dabei beliebig aus- und einzuschalten. Bei Kraftfahrzeug-Beleuchtungseinrichtungen der eingangs genannten Art mit analog geregelten Serientransistoren ergibt sich das Problem, dass die passiven Komponenten nicht tolerant gegenüber Toleranzen der LEDs sind. Eine dynamische Ansteuerung einzelner LEDs ist nicht möglich, da bei den bekannten Stromversorgungsschaltungen in den anderen Strängen starke Stromschwankungen auftreten und die LEDs nach Spannungen sortiert verbaut werden müssen, sodass ein dynamisches Ein- und Ausschalten nicht möglich ist. Das Ein- und Ausschalten von LEDs durch zu diesen parallel liegenden Überbrückungsschalter ist bekannt und beispielsweise in dem Dokument WO 2017/190172 der Anmelderin beschrieben. Dazu kommt, dass bei bekannten Lösungen die LEDs Spannungs-sortiert verbaut werden müssen, was gleichfalls wegen der Asymmetrie des Ausbaues ein dynamisches Schalten verhindert.In the case of motor vehicle lighting devices, attempts are made to keep the maximum supply voltage low and therefore several LEDs are operated with the same current values in several strings, the strings being connected in parallel, so to speak. Dynamic operation of the LEDs is also desirable here, with the option of switching them on and off at will. In the case of motor vehicle lighting devices of the type mentioned at the beginning with analog regulated series transistors, the problem arises that the passive components are not tolerant of the tolerances of the LEDs. Dynamic control of individual LEDs is not possible, since with the known power supply circuits strong current fluctuations occur in the other strings and the LEDs have to be installed sorted according to voltage, so that dynamic switching on and off is not possible. The switching on and off of LEDs by bridging switches lying parallel to them is known and for example in the document WO 2017/190172 described by the applicant. In addition, in known solutions, the LEDs must be installed in a voltage-sorted manner, which also prevents dynamic switching due to the asymmetry of the expansion.

Es ist eine Aufgabe der Erfindung eine Kraftfahrzeug-Beleuchtungseinrichtung zu schaffen, bei welcher mehrere Stränge mit jeweils mehreren LEDs vorhanden sind und bei dynamischen Veränderungen der Anzahl der LEDs durch Ein- und Ausschalten keine Auswirkung auf je andere Stränge bzw. die Gesamtspannung auftritt.It is an object of the invention to create a motor vehicle lighting device in which there are several strings with several LEDs each and with dynamic changes in the number of LEDs by switching them on and off there is no effect on the other strings or the total voltage.

Diese Aufgabe wird mit einer Kraftfahrzeug-Beleuchtungseinrichtung der eingangs angegebenen Art gelöst, bei welcher erfindungsgemäß der Serientransistor jedes Stranges als Konstantstromquelle geschaltet ist, wobei die in Serie liegenden LEDs den Lastwiderstand des Transistors bilden und der Serienwiderstand jedes Transistors eine Stromsensor bildet, die Steuerelektroden aller Serientransistoren miteinander verbunden sind und mit einer gesteuerten Referenzspannung versorgt sind, die an der Kollektor-Emitter-Strecke eines Steuertransistors liegt, dessen Arbeitswiderstand an der gemeinsamen Versorgungsspannung liegt, und dessen Steuerelektrode an einem Spannungsteiler liegt, wobei ein Zweig des Spannungsteilers ein Widerstand ist und der andere Zweig die Serienschaltung zumindest eines Widerstandes mit zumindest einer Referenzspannungsdiode ist, wobei diese Serienschaltung an der gemeinsamen Versorgungsquelle liegt, welche eine Überspannungserkennung besitzt.This object is achieved with a motor vehicle lighting device of the type specified at the outset, in which, according to the invention, the series transistor of each strand is connected as a constant current source, the series LEDs forming the load resistance of the transistor and the series resistance of each transistor forming a current sensor, the control electrodes of all series transistors are connected to one another and are supplied with a controlled reference voltage which is applied to the collector-emitter path of a control transistor, whose Working resistance is connected to the common supply voltage, and its control electrode is connected to a voltage divider, one branch of the voltage divider being a resistor and the other branch being the series connection of at least one resistor with at least one reference voltage diode, this series connection being connected to the common supply source, which is an overvoltage detection owns.

Durch die Verwendung von Transistoren, die als Stromquellen eingesetzt werden, wobei hier eine Transistor-Stromquelle pro Strang zum Einsatz kommt und deren Steuerelektroden zusammengeschaltet sind, stellt sich in jedem Strang ein konstanter Strom ein, der sich auch bei dynamischen geschalteten LEDs. Die Gesamt-Spannung des Systems, welches von einer Strom- oder Spannungsquelle gespeist werden kann, wird somit niedrig gehalten, da nicht eine große Anzahl von LEDs in Serie geschaltet ist, sondern diese Anzahl auf mehrere Stränge aufgeteilt wird. Dadurch können auch Stromquellen, welche nicht für geringe Ströme ausgelegt sind solche niedrigen LED-Ströme treiben und auch dynamische Veränderungen bewerkstelligen.Through the use of transistors that are used as current sources, with one transistor current source per strand being used and the control electrodes of which are connected together, a constant current is established in each strand, which is also found in dynamically switched LEDs. The total voltage of the system, which can be fed by a current or voltage source, is thus kept low, since a large number of LEDs are not connected in series, but this number is divided over several strings. As a result, power sources that are not designed for low currents can also drive such low LED currents and also bring about dynamic changes.

Es ist von Vorteil, wenn jeder Serientransistor ein Bipolartransistor ist und/oder der Steuertransistors ein Bipolartransistor ist, da solche Transistoren günstig zur Verfügung stehen, sie verlässlich sind und ihre Beschaltung einfach ist.It is advantageous if each series transistor is a bipolar transistor and / or the control transistor is a bipolar transistor, since such transistors are available cheaply, they are reliable and their wiring is simple.

Es ist weiters zweckmäßig, wenn parallel zu dem Widerstand des Spannungsteilers, der zwischen Basisanschluss des Steuertransistors und seinem Emitteranschluss liegt, ein Kondensator geschaltet ist.It is also useful if a capacitor is connected in parallel to the resistor of the voltage divider, which is located between the base connection of the control transistor and its emitter connection.

Auch kann mit Vorteil vorgesehen sein, dass parallel zu dem Spannungsteiler ein Kondensator geschaltet ist.It can also be advantageously provided that a capacitor is connected in parallel with the voltage divider.

Die Erfindung samt weiterer Vorteile ist im Folgenden an Hand einer beispielsweisen Ausführungsform näher erläutert, die in der Zeichnung veranschaulicht ist. In dieser zeigt die einzige Figur das Schaltbild für die Ansteuerung von vier Strängen, die jeweils mehrere in Serie geschaltete LEDs aufweisen.The invention together with further advantages is explained in more detail below using an exemplary embodiment which is illustrated in the drawing. In this the only figure shows the circuit diagram for the control of four strings, each of which has several LEDs connected in series.

Ausgangspunkt der hier gezeigten Schaltung sind hier vier Stränge S1 bis S4 mit sechs bzw. sieben in Serie liegenden LEDs, die alle gemeinsam das Bezugszeichen LED besitzen. Die Zahl der Stränge ist ebenso wie die Anzahl der in ihnen enthaltenen LEDs lediglich beispielsweise zu verstehen.The starting point of the circuit shown here are four strings S1 to S4 with six or seven LEDs in series, which all have the common reference symbol LED. The number of strings, like the number of LEDs contained in them, is only to be understood as an example.

Jeder Strang S1 bis S4 weist außerdem einen Serientransistor T1, T2, T3 und T4 mit einem diesem zugeordneten Serienwiderstand R1, R2, R3 und R4 auf und die LED-Serienstränge liegen an einer gemeinsamen Versorgungsspannung Uv.Each string S1 to S4 also has a series transistor T1, T2, T3 and T4 with a series resistor R1, R2, R3 and R4 assigned to it, and the LED series strings are connected to a common supply voltage Uv.

Die Serientransistoren T1, T2, T3 und T4 sind je als Stromquellen geschaltet, die je einen Serienwiderstand R1, R2, R3 und R4 aufweisen, wobei diesen Widerständen ein Kondensator C1, C2, C3 und C4 gegen HF-Einstreuungen parallel geschaltet ist. Die Steuerelektroden, hier die Basen, aller Serientransistoren sind miteinander verbunden, sodass an ihnen die gleiche Spannung liegt, wodurch die Symmetrie der einzelnen Stränge sichergestellt ist. Daher gleichen die Serientransistoren T1, T2, T3 und T4 Spannungsschwankungen aus.The series transistors T1, T2, T3 and T4 are each connected as current sources, each of which has a series resistor R1, R2, R3 and R4, with a capacitor C1, C2, C3 and C4 being connected in parallel to these resistors against HF interference. The control electrodes, here the bases, of all series transistors are connected to each other so that the same voltage is applied to them, which creates the symmetry of the individual ones Strands is ensured. The series transistors T1, T2, T3 and T4 therefore compensate for voltage fluctuations.

Die Steuerelektroden (Basen) der vier Transistoren sind mit einem Arbeitswiderstand R5 eines Steuertransistors T5 gemeinsam versorgt, wobei sich die Versorgungsspannung Uv, gespeist von einer Versorgungsquelle QI, hier eine Stromquelle, welche einen Strom I liefert und eine Überspannungserkennung besitzt, so einstellt, dass der Summenstrom der vier Stränge dem eingestellten Strom der speisenden Stromquelle entspricht. Die Arbeitsstrecke des Steuertransistors T5 liegt zwischen den miteinander verbundenen Basisanschlüssen der Serientransistoren T1, T2, T3 und T4 und Masse. Die Ausfallserkennung eines Stranges, hervorgerufen durch den Ausfall einer LED durch Unterbrechung, bewirkt eine Spannungsreduktion an dem jeweiligen Strangwiderstand Rl...R4 durch den fehlenden Strangstrom. Durch die Basis-Emitter-Diode des entsprechenden Transistors wird die gemeinsame Basisspannung reduziert und dadurch werden die verbleibenden Stränge nicht mehr mit der richtigen Basisspannung versorgt und somit kann der definierte Strom nicht mehr fließen. Die versorgende Stromquelle kann den Strom nicht mehr treiben und erhöht die Eingangsspannung. Wenn die versorgende Stromquelle den Spannungsschwellwert, eingestellt durch zwei Referenzspannungdioden D1, D2 und ein Widerstandsnetzwerk R6, R7 und R8, erreicht hat, wird der Steuertransistor T5 leitend und sperrt die verbleibenden Stränge.The control electrodes (bases) of the four transistors are jointly supplied with a load resistor R5 of a control transistor T5, the supply voltage Uv, fed by a supply source Q I , here a current source which supplies a current I and has an overvoltage detection, so that the total current of the four strings corresponds to the set current of the feeding power source. The working path of the control transistor T5 lies between the interconnected base connections of the series transistors T1, T2, T3 and T4 and ground. The failure detection of a string, caused by the failure of an LED due to an interruption, causes a voltage reduction at the respective string resistance Rl ... R4 due to the missing string current. The common base voltage is reduced by the base-emitter diode of the corresponding transistor and as a result the remaining strings are no longer supplied with the correct base voltage and the defined current can no longer flow. The supplying power source can no longer drive the current and increases the input voltage. When the supplying current source has reached the voltage threshold value, set by two reference voltage diodes D1, D2 and a resistor network R6, R7 and R8, the control transistor T5 becomes conductive and blocks the remaining strings.

Dies beiden Referenzspannungdioden D1, D2 definieren den Spannungswert, der für die LED-Ausfallserkennung maßgeblich ist. Diese Spannung muss höher sein als die Summe der Flussspannungen des LED-Stranges mit der größten Anzahl an LEDs plus der Spannung an dem zugehörigen Serientransistor.These two reference voltage diodes D1, D2 define the voltage value which is decisive for the LED failure detection. This voltage must be higher than the sum of the forward voltages of the LED string with the largest number of LEDs plus the voltage on the associated series transistor.

Der Arbeitswiderstand R5 des Steuertransistors T5 ist hier von besonderer Bedeutung, da er im Wesentlichen die Spannung Uv definiert, die durch eine nur angedeutete externe Versorgungs-Stromquelle QI erzeugt wird. Diese Arbeitswiderstand R5 wird so dimensioniert, dass durch ihn ein um den Gesamtverstärkungsfaktor aller Transistoren T1, T2, T3 und T4 geringerer Strom fließt, als die Summe aller Ströme durch die vier Transistoren der Stränge S1 bis S4. Der Transistor T5 bewirkt ein Abschalten sämtlicher Stränge bei Ausfall lediglich eines einzigen Stranges, denn bei Ausfall eines einzelnen Stranges kann kein Strangstrom mehr durch den Emitterwiderstand des zugehörigen Serientransistors fließen; durch den Emitterwiderstand fließt dann lediglich der Basisstrom. Dadurch sinkt das gemeinsame Basispotential und die Versorgungsstromquelle erhöht die Versorgungsspannung so weit, dass der eingeprägte Strom fließen könnte. Jedoch werden bei einer solchen Erhöhung der Versorgungsspannung die Dioden D1 und D2 leitend, worauf über den Basisstrom der Steuertransistor T5 aktiviert (leitend) wird. Die versorgende Stromquelle QI muss ihrerseits eine Überspannungserkennung besitzen; die LED-Ausfallserkennung bewirkt nur, dass sämtliche LEDs abgeschaltet werden. Ein Kondensator C5 in Verbindung mit den Widerständen R6, R7 und R8 und die zugehörige Zeitkonstante führen zu einer Verzögerung des Ansprechens bei ungewünschten Störungen und auch, um Einschwingvorgänge der externen Stromversorgungsquelle QI zu unterdrücken.The operating resistance R5 of the control transistor T5 is of particular importance here, since it essentially defines the voltage Uv that is generated by an external supply current source Q I, which is only indicated. This working resistor R5 is dimensioned in such a way that a current that is less than the sum of all currents through the four transistors of strands S1 to S4 flows through it by the total gain factor of all transistors T1, T2, T3 and T4. The transistor T5 causes all strings to be switched off if only a single strand fails, because if a single strand fails, no strand current can flow through the emitter resistor of the associated series transistor; Only the base current then flows through the emitter resistor. As a result, the common base potential drops and the supply current source increases the supply voltage to such an extent that the impressed current could flow. However, with such an increase in the supply voltage, the diodes D1 and D2 become conductive, whereupon the control transistor T5 is activated (conductive) via the base current. The supplying current source Q I must for its part have an overvoltage detection; the LED failure detection only has the effect that all LEDs are switched off. A capacitor C5 in connection with resistors R6, R7 and R8 and the associated time constant lead to a delay in the response in the event of undesired disturbances and also to suppress transient processes of the external power supply source Q I.

Ein Widerstand R9 am Eingang der Schaltung dient dazu, bei kleinen Leckströmen zu verhindern, dass geringes Licht von den LEDs emittiert wird, was jedoch nicht erfindungswesentlich ist. Zum Schutz vor transienten Spannungsimpulsen liegen am Eingang der Schaltung auch einerseits zwei in Serie geschaltete Schutzdioden D3 und D4 (Suppressordioden) und andererseits ein Kondensator C7.A resistor R9 at the input of the circuit is used to prevent small leakage currents from being emitted by the LEDs, which, however, is not essential to the invention. To protect against transient voltage pulses, two series-connected protective diodes D3 and D4 (suppressor diodes) and a capacitor C7 are also located at the input of the circuit.

Wie ersichtlich, sind bei der Erfindung die einzelnen Transistor-Stromquellen durch eine gemeinsame Ansteuerung so zusammen geschaltet, dass diese im Verbund jegliche Spannungsänderung durch dynamische Lasten ausgleichen, ohne der Primärquelle diese Veränderung weiterzugeben, wobei sie einen fixen Stromwert zwischen den einzelnen Strängen konstant halten.As can be seen, in the invention the individual transistor current sources are connected together by a common control so that they compensate for any voltage change due to dynamic loads without passing this change on to the primary source, while keeping a fixed current value constant between the individual strings.

Der Begriff "Transistor" ist hier nicht auf Bipolar-Transistoren eingeschränkt, sondern soll beispielsweise auch Feldeffekttransistoren umfassen. Unter dem verwendeten Begriff "Arbeitsstrecke" ist somit bei Bipolaren Transistoren die Kollektor-Emitter-Strecke zu verstehen, bei Feldeffekttransistoren die Gate-Source-Strecke. Sinngemäß ist die Steuerelektrode bei Bipolartransistoren die Basis und bei Feldeffekttransistoren das GateThe term “transistor” is not restricted here to bipolar transistors, but is also intended to include field effect transistors, for example. The term "working path" used is therefore to be understood as meaning the collector-emitter path in bipolar transistors and the gate-source path in field-effect transistors. Correspondingly, the control electrode is the base for bipolar transistors and the gate for field-effect transistors

Wegen der Strom-Symmetrierung, die der Erfindung zu eigen ist, können LED-Steuergeräte als Treiber eingesetzt werden, welche für niedrige LED-Spannungen aber hohen LED-Ströme ausgelegt sind, sodass dadurch auch dynamische Lasten betrieben werden können. Solche LED-Steuergeräte bzw. LED-Treiber konnten bisher für Anwendungen mit einer hohen Anzahl von Kleinleistungs-LEDs nicht eingesetzt werden.Because of the current balancing, which is inherent in the invention, LED control devices can be used as drivers, which are designed for low LED voltages but high LED currents, so that dynamic loads can also be operated as a result. Such LED control devices or LED drivers could not previously be used for applications with a large number of low-power LEDs.

Der Erfindung bietet auch die Möglichkeit einer Ausfallserkennung von LEDs, da bei Ausfall einer LED irgendeines Zweiges durch Schalten des Steuertransistors die Strom- bzw. Spannungsquelle, welche eine Überspannungserkennung besitzt, den Ausfall anzeigt.The invention also offers the possibility of failure detection of LEDs, since if an LED of any branch fails, the current or voltage source, which has an overvoltage detection, indicates the failure by switching the control transistor.

Liste der BezugszeichenList of reference symbols

C1C1
Kondensatorcapacitor
C2C2
Kondensatorcapacitor
C3C3
Kondensatorcapacitor
C4C4
Kondensatorcapacitor
C5C5
Kondensatorcapacitor
C6C6
Kondensatorcapacitor
C7C7
Kondensatorcapacitor
D1D1
ReferenzspannungdiodeReference voltage diode
D2D2
ReferenzspannungdiodeReference voltage diode
D3D3
SchutzdiodeProtection diode
D4D4
SchutzdiodeProtection diode
II.
Stromelectricity
LEDLED
LEDsLEDs
QI Q I
VersorgungsquelleSupply source
R1...R4R1 ... R4
SerienwiderstandSeries resistance
R5R5
Widerstandresistance
R6R6
Widerstandresistance
R7R7
Widerstandresistance
R8R8
Widerstandresistance
R9R9
Widerstandresistance
S1S1
Strangstrand
S2S2
Strangstrand
S3S3
Strangstrand
S4S4
Strangstrand
T1T1
SerientransistorSeries transistor
T2T2
SerientransistorSeries transistor
T3T3
SerientransistorSeries transistor
T4T4
SerientransistorSeries transistor
T5T5
SteuertransistorControl transistor
UvUv
VersorgungsspannungSupply voltage

Claims (5)

Kraftfahrzeug-Beleuchtungseinrichtung mit zumindest zwei LED-Seriensträngen, wobei jeder Strang in Serie geschaltet mehrere LEDs sowie einen Serientransistor (T1....T4) mit einem diesem zugeordneten Serienwiderstand (R1....R4) aufweist und die LED-Serienstränge an einer gemeinsamen Versorgungsquelle (QI) liegen,
dadurch gekennzeichnet, dass
der Serientransistor (T1....T4) jedes Stranges als Konstantstromquelle geschaltet ist, wobei die in Serie liegenden LEDs den Lastwiderstand jedes Transistors bilden und der Serienwiderstand jedes Transistors einen Stromsensor bildet,
die Steuerelektroden aller Serientransistoren miteinander verbunden sind und mit einer gesteuerten Referenzspannung versorgt sind, die an der Arbeitsstrecke eines Steuertransistors (T5) liegt, dessen Arbeitswiderstand (R6) an der gemeinsamen Versorgungsspannung liegt, und dessen Basisanschluss an einem Spannungsteiler liegt, wobei ein Zweig des Spannungsteilers ein Widerstand (R8) ist und der andere Zweig die Serienschaltung zumindest eines Widerstandes (R7, R6) mit zumindest einer Referenzspannungsdiode (D1, D2) ist, wobei diese Serienschaltung an der gemeinsamen Versorgungsquelle (QI) liegt, welche eine Überspannungserkennung besitzt.Motor vehicle lighting device with at least two LED series strings, each strand connected in series having several LEDs and a series transistor (T1 .... T4) with a series resistor (R1 .... R4) assigned to it and the LED series strings on one common supply source (Q I ),
characterized in that
the series transistor (T1 ... T4) of each string is connected as a constant current source, the LEDs in series forming the load resistance of each transistor and the series resistance of each transistor forming a current sensor,
the control electrodes of all series transistors are connected to one another and are supplied with a controlled reference voltage which is applied to the working path of a control transistor (T5), the working resistor (R6) of which is connected to the common supply voltage and the base connection of which is connected to a voltage divider, one branch of the voltage divider a resistor (R8) and the other branch is the series connection of at least one resistor (R7, R6) with at least one reference voltage diode (D1, D2), this series connection being connected to the common supply source (Q I ), which has an overvoltage detection. Kraftfahrzeug-Beleuchtungseinrichtung nach Anspruch 1, dadurch gekennzeichnet, dass jeder Serientransistor (T1....T4) ein Bipolartransistor ist.Motor vehicle lighting device according to Claim 1, characterized in that each series transistor (T1 .... T4) is a bipolar transistor. Kraftfahrzeug-Beleuchtungseinrichtung nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass der Steuertransistors (T5) ein Bipolartransistor ist.Motor vehicle lighting device according to Claim 1 or 2, characterized in that the control transistor (T5) is a bipolar transistor. Kraftfahrzeug-Beleuchtungseinrichtung nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass parallel zu dem Widerstand (R8) des Spannungsteilers, der zwischen Basisanschluss des Steuertransistors (T5) und seinem Emitteranschluss liegt, ein Kondensator (C6) geschaltet ist.Motor vehicle lighting device according to one of Claims 1 to 3, characterized in that a capacitor (C6) is connected in parallel with the resistor (R8) of the voltage divider, which lies between the base connection of the control transistor (T5) and its emitter connection. Kraftfahrzeug-Beleuchtungseinrichtung nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass parallel zu dem Spannungsteiler (R7, R8) ein Kondensator (C5) geschaltet ist.Motor vehicle lighting device according to one of Claims 1 to 4, characterized in that a capacitor (C5) is connected in parallel with the voltage divider (R7, R8).
EP19191484.5A 2019-08-13 2019-08-13 Motor vehicle lighting device Withdrawn EP3780911A1 (en)

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Application Number Priority Date Filing Date Title
EP19191484.5A EP3780911A1 (en) 2019-08-13 2019-08-13 Motor vehicle lighting device

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Application Number Priority Date Filing Date Title
EP19191484.5A EP3780911A1 (en) 2019-08-13 2019-08-13 Motor vehicle lighting device

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5598068A (en) * 1994-03-18 1997-01-28 Sony/Tektronix Corporation Light emitting apparatus comprising multiple groups of LEDs each containing multiple LEDs
DE19950135A1 (en) 1999-10-18 2001-04-19 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Control circuit for LED array has master string with given number of LEDs in string and control circuit also controls semiconducting switch of slave string
DE10201280A1 (en) * 2001-01-16 2002-09-05 Visteon Global Tech Inc Temperature compensated parallel light emitting diode control circuit for LCD indicator units in motor vehicles, has each LED coupled to separate current source transistor
EP2469980A2 (en) * 2010-12-24 2012-06-27 Lih-Wen Mao Array constant-current multi-driving circuit
EP2749131A1 (en) * 2011-11-23 2014-07-02 Automotive Lighting Italia S.p.A. A Socio Unico Driver circuit and method for vehicle light
WO2017190172A1 (en) 2016-05-06 2017-11-09 Zkw Group Gmbh Motor vehicle illumination device

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5598068A (en) * 1994-03-18 1997-01-28 Sony/Tektronix Corporation Light emitting apparatus comprising multiple groups of LEDs each containing multiple LEDs
DE19950135A1 (en) 1999-10-18 2001-04-19 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Control circuit for LED array has master string with given number of LEDs in string and control circuit also controls semiconducting switch of slave string
DE10201280A1 (en) * 2001-01-16 2002-09-05 Visteon Global Tech Inc Temperature compensated parallel light emitting diode control circuit for LCD indicator units in motor vehicles, has each LED coupled to separate current source transistor
EP2469980A2 (en) * 2010-12-24 2012-06-27 Lih-Wen Mao Array constant-current multi-driving circuit
EP2749131A1 (en) * 2011-11-23 2014-07-02 Automotive Lighting Italia S.p.A. A Socio Unico Driver circuit and method for vehicle light
WO2017190172A1 (en) 2016-05-06 2017-11-09 Zkw Group Gmbh Motor vehicle illumination device

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