EP0804052A2 - Control circuit for a discharge lamp - Google Patents

Control circuit for a discharge lamp Download PDF

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Publication number
EP0804052A2
EP0804052A2 EP97106831A EP97106831A EP0804052A2 EP 0804052 A2 EP0804052 A2 EP 0804052A2 EP 97106831 A EP97106831 A EP 97106831A EP 97106831 A EP97106831 A EP 97106831A EP 0804052 A2 EP0804052 A2 EP 0804052A2
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EP
European Patent Office
Prior art keywords
lamp
luminance
control
cold cathode
control according
Prior art date
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EP97106831A
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German (de)
French (fr)
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EP0804052A3 (en
Inventor
Martin Dipl.-Ing. Kurz
Helmut Dipl.-Ing. Habel
Thomas Dipl.-Ing. Eberharter
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Osram GmbH
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Patent Treuhand Gesellschaft fuer Elektrische Gluehlampen mbH
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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
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/39—Controlling the intensity of light continuously
    • H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
    • H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
    • H05B41/3922—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations and measurement of the incident light
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • 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
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/39—Controlling the intensity of light continuously
    • H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
    • H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
    • H05B41/3927—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations by pulse width modulation

Definitions

  • the invention relates to a control of cold cathode lamps, which adjusts the luminance of the lamp as closely as possible to a predetermined value, regardless of the ambient and installation conditions, or which enables the largest possible dimming range while protecting the lamp at the same time.
  • Cold cathode lamps are to be understood as complex components and have a piecewise negative current-voltage characteristic.
  • the luminance and the voltage required to ignite the tube have a large temperature dependency, the life of the lamp decreasing at high ignition voltages.
  • Various possibilities are known for controlling gas discharge lamps (see, for example, patents US 4,920,474, E-0 537 394, US 5,309,350, E-0 058 035, E-0 023 263).
  • the usual version is a resonance converter in a push-pull configuration.
  • Scatter transformers isolated DC controls or so-called “Alternating DC” controls are also known. Scatter transformers are used in high-performance applications, but have the disadvantages of poor efficiency, large design and large input reactive power, considerable noise, and they are difficult to dim.
  • DC controls significantly reduce the lamp life and are mainly used in the laboratory.
  • a better method is the "Alternating DC" control, in which the life of the lamp is not worsened, but there are disadvantages here due to the complex or slow switching of the high voltage and also when dimming, since high-voltage sources with high source impedance are fundamentally difficult to implement.
  • Resonance converters are inexpensive and widespread solutions, whereby the dimmability is possible within small limits by changing the supply voltage.
  • the dimming range can be improved by pulse width modulation and additional current feedback, the largest adjustment range is achieved by pulse packet modulation. Since the lamp is operated continuously with pulse width modulation, the ignition voltage is rarely required and the primary current consumption has low peaks, which means that the lamp and the components used are protected. Furthermore, in this operating mode, a change in the input voltage of the resonance converter can be compensated for by varying the pulse width.
  • the minimum dimming state is determined by the limit amplitude of the lamp current, which results in a minimum possible rms value at which the plasma excited during the ignition process is extinguished, whereby parasitic capacitances against housing parts or other potentials can also only partially excite the gas.
  • the lamp is ignited periodically, the system consisting of a resonance converter with a lamp as an integral component being kept in resonance by a pulse packet during the on-time and decaying after the excitation is switched off at the system's own resonance frequency.
  • the effective value of the lamp current and thus also the emitted luminance can thus be set lower than in the case of pulse width modulation.
  • an oscillator which is in resonance by definition has the lowest losses, although through the periodic ignition, which must be at least 50 Hz, the lamp is subjected to greater stress.
  • the control described in Figure 1 consists of a resonance converter supplied with DC voltage with at least one series connection of reactance 3 and cold cathode lamp 4 in the load circuit and a component referred to below as a control part, which either consist only of controller 2 or additionally interface 1 and / or measured value acquisition 5 included can, the interface being used for communication with the environment, by means of which both setpoint values can be set externally and other parameters, such as the ambient brightness E a, can be detected, thereby enabling the control loop to be adapted to static or changing conditions. Since the luminance of the lamp is strongly dependent on the temperature at a constant current (FIG.
  • the measured value acquisition 5 determines a correction factor which depends on the lamp temperature, which naturally also takes into account the ambient temperature T a , and which determines the current determined by the controller 2 in changed the extent that the predetermined luminance is achieved as accurately as possible. Since the self-heating of the cold cathode tube takes place at a defined lamp current according to a lamp-specific time constant, the lamp temperature can not only be measured but also calculated. The determination of the lamp temperature also makes it possible to detect excess temperatures of the lamp caused by malfunctions and to initiate suitable countermeasures.
  • the lamp current is set in such a way that the measured luminance corresponds to the target value and thus temperature and aging effects relating to the luminance are compensated.
  • the output stage 3 of the present invention is preferably designed as a resonance converter, the current is controlled by varying the amplitude and / or the pulse duty factor (pulse width and / or pulse packet modulation), with a direct ⁇
  • An optimization of the dimming range and the life of the lamp can be achieved by alternative selection of pulse width and pulse packet modulation depending on the lamp current and / or the luminance and by reducing the amplitude of the ignition voltage to a minimum depending on the lamp temperature.
  • the lamp is operated continuously by means of pulse width modulation in the dimming range from maximum to the limit amplitude of the lamp current, at which the plasma excited during the ignition process is extinguished, followed by switching to pulse packet modulation, in which the lamp is periodically ignited with a lower effective value of the lamp current and so that the dimming range is extended downwards.
  • the output can be designed as a switched rectifier, which rectifies the output signal and periodically reverses the polarity to the lamp in order to improve the homogeneity of the luminance on the lamp surface.
  • An advantageous embodiment of the device according to the invention uses a microcontroller in which characteristic diagrams of the cold cathode lamp are stored and are used to determine the optimal lamp input parameters in order to achieve the desired luminance.
  • the microcontroller can also be used to correlate the pulse packet repetition rate with the image refresh rate supplied from the outside, as a result of which interference with LCD backlighting can be avoided.
  • a further advantageous embodiment of the device according to the invention takes into account the ambient brightness in order to adapt the luminance of the lamp to it.
  • the operating temperature of the cold cathode lamp can be optimized by an electrically adjustable external cooling, which improves the efficiency of the overall system.

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  • Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
  • Circuit Arrangements For Discharge Lamps (AREA)

Abstract

Die Erfindung betrifft eine Ansteuerung von Kaltkathodenlampen, die die Leuchtdichte der Lampe unabhängig von Umgebungs- und Einbaubedingungen einem vorgegebenen Wert möglichst angleicht und/oder einen optimalen Dimmbereich bei gleichzeitiger Lampenschonung ermöglicht, indem ein von der Lampentemperatur abhängiger Korrekturfaktor ermittelt und/oder die Leuchtdichte der Lampe direkt erfaßt und in Abhängigkeit dieser Werte die Amplitude und/oder das Tastverhältnis des Lampenstroms eingestellt wird, wobei gemäß einer lampenspezifischen Zeitkonstante die Lampentemperatur nicht nur gemessen sondern auch berechnet werden kann, und/oder eine alternative Auswahl von Pulsbreiten- und Pulspaketmodulation in Abhängigkeit des Lampenstroms und/oder der Leuchtdichte erfolgt sowie der Ausgang zusätzlich als geschalteter Gleichrichter ausgeführt werden kann.The invention relates to a control of cold cathode lamps which adjusts the luminance of the lamp to a predetermined value as independently of the ambient and installation conditions as possible and / or enables an optimal dimming range while protecting the lamp at the same time by determining a correction factor which is dependent on the lamp temperature and / or the luminance of the lamp directly detected and depending on these values the amplitude and / or the duty cycle of the lamp current is set, whereby according to a lamp-specific time constant the lamp temperature can not only be measured but also calculated, and / or an alternative selection of pulse width and pulse packet modulation depending on the lamp current and / or the luminance takes place and the output can also be designed as a switched rectifier.

Die vorliegende Ansteuerung ermöglicht außerdem, Fehler des Systems zu erkennen und geeignete Gegenmaßnahmen einzuleiten, die Pulspaketwiederholrate mit Bildwiederholfrequenzen von LC-Schirmen zu korrelieren sowie die Betriebstemperatur der Kaltkathodenlampe durch eine elektrisch verstellbare externe Kühlung zu optimieren und damit den Wirkungsgrad des Gesamtsystems zu verbessern.

Figure imgaf001
The present control also enables system errors to be identified and appropriate countermeasures to be initiated, the pulse packet repetition rate to be correlated with the refresh rates of LC screens, and the operating temperature of the cold cathode lamp to be optimized by means of an electrically adjustable external cooling system, thus improving the efficiency of the overall system.
Figure imgaf001

Description

Die Erfindung betrifft eine Ansteuerung von Kaltkathodenlampen, die die Leuchtdichte der Lampe unabhängig von Umgebungs- und Einbaubedingungen einem vorgegebenen Wert möglichst genau angleicht beziehungsweise einen möglichst großen Dimmbereich bei gleichzeitiger Lampenschonung ermöglicht.The invention relates to a control of cold cathode lamps, which adjusts the luminance of the lamp as closely as possible to a predetermined value, regardless of the ambient and installation conditions, or which enables the largest possible dimming range while protecting the lamp at the same time.

Kaltkathodenlampen sind als komplexe Bauelemente zu verstehen und besitzen eine stückweise negative Strom-Spannungskennlinie. Die Leuchtdichte und die zum Zünden der Röhre notwendige Spannung weisen eine große Temperaturabhängigkeit auf, wobei die Lebensdauer der Lampe bei hohen Zündspannungen sinkt. Es sind unterschiedliche Möglichkeiten bekannt, Gasentladungslampen anzusteuern (siehe z.B. Patente US 4,920,474, E-0 537 394, US 5,309,350, E-0 058 035,E-0 023 263).Cold cathode lamps are to be understood as complex components and have a piecewise negative current-voltage characteristic. The luminance and the voltage required to ignite the tube have a large temperature dependency, the life of the lamp decreasing at high ignition voltages. Various possibilities are known for controlling gas discharge lamps (see, for example, patents US 4,920,474, E-0 537 394, US 5,309,350, E-0 058 035, E-0 023 263).

Die übliche Ausführung sind Resonanzwandler in Push-Pull-Konfiguration. Weiterhin sind Streutransformatoren, vereinzelt DC-Ansteuerungen oder sogenannte "Alternating DC"-Ansteuerungen bekannt. Streutransformatoren werden bei Anwendungen hoher Leistung verwendet, haben aber die Nachteile von schiechtem Wirkungsgrad, großer Bauform und großer Eingangsblindleistung, erheblicher Störgeräusche und sie lassen sich nur schwer dimmen. DC-Ansteuerungen verringern die Lebensdauer der Lampe erheblich und werden hauptsächlich im Labor eingesetzt. Eine bessere Methode ist die "Alternating DC"-Ansteuerung, bei der die Lebensdauer der Lampe nicht verschlechtert wird, sich aber hier Nachteile durch die aufwendige oder langsame Umschaltung der Hochspannung sowie ebenfalls beim Dimmen ergeben, da grundsätzlich Hochspannungsquellen mit hoher Quellimpedanz nur aufwendig zu realisieren sind. Resonanzwandler sind kostengünstige und weit verbreitete Lösungen, wobei die Dimmbarkeit hier in kleinen Grenzen durch Ändern der Versorgungsspannung möglich ist. Der Dimmbereich kann durch Pulsbreitenmodulation und zusätzlich durch Stromgegenkopplung verbessert werden, der größte Verstellbereich wird durch Pulspaketmodulation erzielt. Da die Lampe bei Pulsbreitenmodulation kontinuierlich betrieben wird, wird die Zündspannung nur selten benötigt und die primäre Stromaufnahme weist geringe Spitzen auf, was eine Schonung der Lampe und der verwendeten Bauteile zur Folge hat. Weiterhin läßt sich bei dieser Betriebsart durch Variation der Pulsbreite eine Änderung der Eingangsspannung des Resonanzwandlers kompensieren. Der minimale Dimmzustand wird bestimmt durch die Grenzamplitude des Lampenstroms, wodurch sich ein minimal möglicher Effektivwert ergibt, bei der das beim Zündvorgang angeregte Plasma gelöscht wird, wobei es zusätzlich durch parasitäre Kapazitäten gegen Gehäuseteile oder andere Potentiale zu einer nur partiellen Anregung des Gases kommen kann. Bei Pulspaketmodulation wird die Lampe periodisch gezündet, wobei das System, bestehend aus Resonanzwandler mit Lampe als integrativem Bestandteil, durch ein Pulspaket während der Einschaltdauer in Resonanz gehalten wird und nach Abschalten der Anregung mit der systemeigenen Resonanzfrequenz ausschwingt. Der Effektivwert des Lampenstroms und damit auch der emittierten Leuchtdichte läßt sich somit niedriger einstellen als bei Pulsbreitenmodulation, weiters weist ein in Resonanz befindlicher Oszillator definitionsgemäß die geringsten Verluste auf, wobei allerdings durch die periodische Zündung, die zumindest über 50 Hz liegen muß, die Lampe stärker beansprucht wird.The usual version is a resonance converter in a push-pull configuration. Scatter transformers, isolated DC controls or so-called "Alternating DC" controls are also known. Scatter transformers are used in high-performance applications, but have the disadvantages of poor efficiency, large design and large input reactive power, considerable noise, and they are difficult to dim. DC controls significantly reduce the lamp life and are mainly used in the laboratory. A better method is the "Alternating DC" control, in which the life of the lamp is not worsened, but there are disadvantages here due to the complex or slow switching of the high voltage and also when dimming, since high-voltage sources with high source impedance are fundamentally difficult to implement. Resonance converters are inexpensive and widespread solutions, whereby the dimmability is possible within small limits by changing the supply voltage. The dimming range can be improved by pulse width modulation and additional current feedback, the largest adjustment range is achieved by pulse packet modulation. Since the lamp is operated continuously with pulse width modulation, the ignition voltage is rarely required and the primary current consumption has low peaks, which means that the lamp and the components used are protected. Furthermore, in this operating mode, a change in the input voltage of the resonance converter can be compensated for by varying the pulse width. The minimum dimming state is determined by the limit amplitude of the lamp current, which results in a minimum possible rms value at which the plasma excited during the ignition process is extinguished, whereby parasitic capacitances against housing parts or other potentials can also only partially excite the gas. In the case of pulse packet modulation, the lamp is ignited periodically, the system consisting of a resonance converter with a lamp as an integral component being kept in resonance by a pulse packet during the on-time and decaying after the excitation is switched off at the system's own resonance frequency. The effective value of the lamp current and thus also the emitted luminance can thus be set lower than in the case of pulse width modulation. Furthermore, an oscillator which is in resonance by definition has the lowest losses, although through the periodic ignition, which must be at least 50 Hz, the lamp is subjected to greater stress.

Der gegenständlichen Erfindung liegt die Aufgabe zugrunde, ein Vorschaltgerät für Kaltkathodenlampen bei bestmöglicher Optimierung der Lebensdauer der Lampe zu schaffen, welches eine vorgegebene Leuchtdichte so weit wie möglich unabhängig von Umgebungs- und Einbaubedingungen konstant hält und/oder über einen möglichst großen Dimmbereich einstellbar macht.

Fig. 1
beschreibt den Aufbau des gegenständlichen Vorschaltgeräts, wobei die Leuchtdichte der durch die Endstufe 3 angesteuerten Kaltkathodenlampe 4 vom Regler 2 unter Berücksichtigung einer optimierten Lebensdauer der Lampe dem vorgegebenen Sollwert möglichst angeglichen wird.
Fig. 2
zeigt einen typischen normierten Leuchtdichteverlauf L/Lmax über der Temperatur T bei konstantem Strom.
Fig. 3
zeigt den Schaltplan einer möglichen Realisierung der gegenständlichen Erfindung.
Fig. 4
zeigt zusätzlich zu der in Fig. 3 gezeigten Realisierung eine optionale "Alternating DC"-Ansteuerung der Lampe.
The object of the present invention is to provide a ballast for cold cathode lamps with the best possible optimization of the lamp life, which keeps a given luminance as constant as possible, regardless of the ambient and installation conditions, and / or makes it possible to set it over the largest possible dimming range.
Fig. 1
describes the structure of the ballast in question, the luminance of the cold cathode lamp 4 controlled by the output stage 3 being adjusted as far as possible by the controller 2, taking into account an optimized lamp life, to the predetermined target value.
Fig. 2
shows a typical normalized luminance curve L / L max over the temperature T at a constant current.
Fig. 3
shows the circuit diagram of a possible implementation of the present invention.
Fig. 4
shows in addition to the implementation shown in FIG. 3 an optional "alternating DC" control of the lamp.

Die in Figur 1 beschriebene Ansteuerung besteht aus einem mit Gleichspannung versorgten Resonanzwandler mit zumindest einer Serienschaltung von Reaktanz 3 und Kaltkathodenlampe 4 im Lastkreis und einer im folgenden als Steuerteil bezeichneten Komponente, die entweder nur aus Regler 2 bestehen oder aber zusätzlich Interface 1 und/oder Meßwerterfassung 5 enthalten kann, wobei das Interface zur Kommunikation mit der Umwelt dient, mittels dessen sowohl Sollwertvorgaben extern erfolgen als auch andere Parameter, wie z.B. die Umgebungshelligkeit Ea, erfaßt werden können, wodurch eine Adaptierung des Regelkreises an statische oder sich verändernde Bedingungen ermöglicht wird. Da die Leuchtdichte der Lampe bei konstantem Strom stark von der Temperatur abhängig ist (Fig. 2), ermittelt die Meßwerterfassung 5 einen von der Lampentemperatur, die naturgemäß auch die Umgebungstemperatur Ta mit berücksichtigt, abhängigen Korrekturfaktor, der den vom Regler 2 bestimmten Strom in dem Ausmaß verändert, daß die vorgegebene Leuchtdichte möglichst genau erreicht wird. Da die Eigenerwärmung der Kaltkathodenröhre bei einem definierten Lampenstrom gemäß einer lampenspezifischen Zeitkonstante erfolgt, kann die Lampentemperatur nicht nur gemessen sondern auch berechnet werden. Die Ermittlung der Lampentemperatur ermöglicht weiters, störungsbedingte Übertemperaturen der Lampe zu detektieren und geeignete Gegenmaßnahmen einzuleiten.The control described in Figure 1 consists of a resonance converter supplied with DC voltage with at least one series connection of reactance 3 and cold cathode lamp 4 in the load circuit and a component referred to below as a control part, which either consist only of controller 2 or additionally interface 1 and / or measured value acquisition 5 included can, the interface being used for communication with the environment, by means of which both setpoint values can be set externally and other parameters, such as the ambient brightness E a, can be detected, thereby enabling the control loop to be adapted to static or changing conditions. Since the luminance of the lamp is strongly dependent on the temperature at a constant current (FIG. 2), the measured value acquisition 5 determines a correction factor which depends on the lamp temperature, which naturally also takes into account the ambient temperature T a , and which determines the current determined by the controller 2 in changed the extent that the predetermined luminance is achieved as accurately as possible. Since the self-heating of the cold cathode tube takes place at a defined lamp current according to a lamp-specific time constant, the lamp temperature can not only be measured but also calculated. The determination of the lamp temperature also makes it possible to detect excess temperatures of the lamp caused by malfunctions and to initiate suitable countermeasures.

Im Fall einer direkten Rückführung der Leuchtdichte wird der Lampenstrom in der Art eingestellt, daß die gemessene Leuchtdichte dem Sollwert entspricht und somit die Leuchtdichte betreffende Temperatur- als auch Alterungseffekte kompensiert werden.In the case of a direct feedback of the luminance, the lamp current is set in such a way that the measured luminance corresponds to the target value and thus temperature and aging effects relating to the luminance are compensated.

Die Endstufe 3 der gegenständlichen Erfindung ist vorzugsweise als Resonanzwandler ausgeführt, die Stromsteuerung erfolgt dabei durch Variation von Amplitude und/oder des Tastverhältnisses (Pulsbreiten- und/oder Pulspaketmodulation), wobei bei Pulspaketmodulation eine direkte ∫|i(t)| dt-(Lampenstrom-Zeitflächen)-Gegenkopplung verwendet werden kann.The output stage 3 of the present invention is preferably designed as a resonance converter, the current is controlled by varying the amplitude and / or the pulse duty factor (pulse width and / or pulse packet modulation), with a direct ∫ | i (t) | in pulse packet modulation dt (lamp current time areas) negative feedback can be used.

Eine Optimierung des Dimmbereichs als auch der Lebensdauer der Lampe läßt sich durch alternative Auswahl von Pulsbreiten- und Pulspaketmodulation in Abhängigkeit des Lampenstroms und/oder der Leuchtdichte sowie durch Reduktion der Amplitude der Zündspannung auf ein Minimum in Abhängigkeit der Lampentemperatur erzielen. Die Lampe wird mittels Pulsbreitenmodulation im Dimmbereich von Maximum bis zur Grenzamplitude des Lampenstroms, bei der das beim Zündvorgang angeregte Plasma gelöscht wird, kontinuierlich betrieben, anschließend erfolgt die Umschaltung auf Pulspaketmodulation, bei der eine periodische Zündung der Lampe bei jedoch niedrigerem Effektivwert des Lampenstroms erfolgt und damit der Dimmbereich nach unten erweitert wird.An optimization of the dimming range and the life of the lamp can be achieved by alternative selection of pulse width and pulse packet modulation depending on the lamp current and / or the luminance and by reducing the amplitude of the ignition voltage to a minimum depending on the lamp temperature. The lamp is operated continuously by means of pulse width modulation in the dimming range from maximum to the limit amplitude of the lamp current, at which the plasma excited during the ignition process is extinguished, followed by switching to pulse packet modulation, in which the lamp is periodically ignited with a lower effective value of the lamp current and so that the dimming range is extended downwards.

Zusätzlich zur beschriebenen Lösung kann der Ausgang als geschalteter Gleichrichter ausgeführt sein, der das Ausgangssignal gleichrichtet und periodisch verpolt an die Lampe legt, um die Homogenität der Leuchtdichte an der Lampenoberfläche zu verbessern.In addition to the solution described, the output can be designed as a switched rectifier, which rectifies the output signal and periodically reverses the polarity to the lamp in order to improve the homogeneity of the luminance on the lamp surface.

Sämtliche dargestellten Lösungen können zum Großteil auch für alle anderen Formen von Gasentladungslampen als Kaltkathodenlampen angewendet werden. Eine Realisierungsmöglichkeit des beschriebenen Systems ist in den Schaltplänen in Fig. 3 und Fig. 4 ersichtlich.Most of the solutions shown can also be used for all other forms of gas discharge lamps than cold cathode lamps. One possible implementation of the system described can be seen in the circuit diagrams in FIGS. 3 and 4.

Die mit der Erfindung erzielten Vorteile bestehen insbesondere darin:

  • a) die Leuchtdichte von Kaltkathodenlampen unabhängig von Umgebungsbedingungen einem vorgegebenen Wert möglichst genau anzugleichen
  • b) den Dimmbereich durch Kombination von Pulsbreiten- und Pulspaketmodulation mit optionaler Gleichrichtung und periodischer Verpolung des Ausgangssignals zu maximieren
  • c) durch die Rückführung ein oder mehrerer Ausgangsgrößen, wie zum Beispiel Leuchtdichte und/oder Temperatur und/oder Lampenspannung Fehler des Systems, wie zum Beispiel Alterung, Kurzschluß, Unterbrechung oder sonstige Fehler, zu erkennen
  • d) die Leistung des Systems in Abhängigkeit von der Temperatur zu begrenzen oder die Lampe abzuschalten.
The advantages achieved with the invention are in particular:
  • a) to match the luminance of cold cathode lamps to a predetermined value as closely as possible, regardless of ambient conditions
  • b) to maximize the dimming range by combining pulse width and pulse packet modulation with optional rectification and periodic polarity reversal of the output signal
  • c) to detect errors in the system, such as aging, short-circuit, interruption or other errors, by feeding back one or more output variables, such as, for example, luminance and / or temperature and / or lamp voltage
  • d) limit the performance of the system depending on the temperature or turn off the lamp.

Eine vorteilhafte Ausgestaltung der erfindungsgemäßen Vorrichtung verwendet einen Mikrocontroller, in dem Kennfelder der Kaltkathodenlampe abgelegt sind und dazu verwendet werden, die optimalen Lampeneingangsparameter zur Erzielung der gewünschten Leuchtdichte zu ermitteln. Ebenso kann der Mikrocontroller verwendet werden, um die Pulspaketwiederholrate mit der von außen zugeführten Bildwiederholfrequenz zu korrelieren, wodurch Interferenzen bei LCD-Hinterleuchtung vermieden werden können.An advantageous embodiment of the device according to the invention uses a microcontroller in which characteristic diagrams of the cold cathode lamp are stored and are used to determine the optimal lamp input parameters in order to achieve the desired luminance. The microcontroller can also be used to correlate the pulse packet repetition rate with the image refresh rate supplied from the outside, as a result of which interference with LCD backlighting can be avoided.

Eine weitere vorteilhafte Ausgestaltung der erfindungsgemäßen Vorrichtung berücksichtigt die Umgebungshelligkeit, um die Leuchtdichte der Lampe an diese anzupassen.A further advantageous embodiment of the device according to the invention takes into account the ambient brightness in order to adapt the luminance of the lamp to it.

Weiters kann die Betriebstemperatur der Kaltkathodenlampe durch eine elektrisch verstellbare externe Kühlung optimiert werden, wodurch der Wirkungsgrad des Gesamtsystems verbessert wird.Furthermore, the operating temperature of the cold cathode lamp can be optimized by an electrically adjustable external cooling, which improves the efficiency of the overall system.

Claims (8)

Ansteuerung (Energieversorgung) für Kaltkathodenlampen mit partiell negativer Strom-Spannungskennlinie, bestehend aus einem mit Gleichspannung versorgten Resonanzwandler mit zumindest einer Serienschaltwig von Reaktanz und Kaltkathodenlampe im Lastkreis und Steuerteil, dadurch gekennzeichnet, daß der Regler (2) die Amplitude und/oder das Tastverhältnis (Modulationsarten Pulsbreiten- und/oder Pulspaketsteuerung) des durch die Endstufe (3) generierten Lampenstroms durch Berücksichtigung der gemäß der lampenspezifischen Korrelation mit der Leuchtdichte und dem Lampenstrom bewerteten Temperatur und/oder Leuchtdichte (Fig. 2), wobei die Bestimmung dieser Werte durch Messung oder durch Ermittlung mittels lampenspezifischer Zeitkonstante erfolgt, so einstellt, daß die Leuchtdichte der Kaltkathodenlampe (4) dem vorgegebenen Sollwert entspricht, oder die Modulationsarten Pulsbreiten- und Pulspaketsteuerung abhängig vom Lampenstrom und/oder der Leuchtdichte gewechselt werden.Control (energy supply) for cold cathode lamps with a partially negative current-voltage characteristic, consisting of a resonance converter supplied with direct voltage with at least one series circuit of reactance and cold cathode lamp in the load circuit and control section, characterized in that the controller (2) controls the amplitude and / or the duty cycle ( Modulation types pulse width and / or pulse packet control) of the lamp current generated by the output stage (3) by taking into account the temperature and / or luminance assessed according to the lamp-specific correlation with the luminance and the lamp current (FIG. 2), the determination of these values by measurement or by determining by means of a lamp-specific time constant, set such that the luminance of the cold cathode lamp (4) corresponds to the predetermined target value, or the types of modulation pulse width and pulse packet control are changed depending on the lamp current and / or the luminance. Ansteuerung nach Anspruch 1, dadurch gekennzeichnet, daß der Ausgang als geschalteter Gleichrichter ausgeführt ist, der das Ausgangssignal gleichrichtet und periodisch verpolt an die Lampe legt.Control according to claim 1, characterized in that the output is designed as a switched rectifier, which rectifies the output signal and periodically reverse polarity applied to the lamp. Ansteuerung nach Anspruch 1, dadurch gekennzeichnet, daß der Steuerteil digital ausgeführt ist und die ein- oder mehrdimensionalen Kennfelder der Lampe berücksichtigt.Control according to claim 1, characterized in that the control part is designed digitally and takes into account the one-dimensional or multi-dimensional characteristics of the lamp. Ansteuerung nach Anspruch 1, dadurch gekennzeichnet, daß der Steuerteil digital ausgeführt ist und die Vorgabe des Sollwertes und/oder anderer Parameter über eine Schnittstelle erfolgt.Control according to claim 1, characterized in that the control part is carried out digitally and the specification of the setpoint and / or other parameters takes place via an interface. Ansteuerung nach Anspruch 1, dadurch gekennzeichnet, daß der Steuerteil einen Eingang für die Bildwiederholfrequenz eines LC-Schirms aufweist.Control according to claim 1, characterized in that the control part has an input for the refresh rate of an LC screen. Ansteuerung nach Anspruch 1, dadurch gekennzeichnet, daß Übertemperaturen, die zur Zerstörung der Lampe führen können, detektiert und geeignete Maßnahmen eingeleitet werden können.Control according to Claim 1, characterized in that excess temperatures which can lead to the destruction of the lamp are detected and suitable measures can be initiated. Ansteuerung nach Anspruch 1, dadurch gekennzeichnet, daß der Steuerteil Signale zur Ansteuerung einer elektrisch steuerbaren Kühlung für die Lampe und/oder anderen externen Verbrauchern zur Verfügung stellt.Control according to claim 1, characterized in that the control part provides signals for controlling an electrically controllable cooling for the lamp and / or other external consumers. Ansteuerung nach Anspruch 1, dadurch gekennzeichnet, daß der Sollwert der Leuchtdichte die Umgebungshelligkeit berücksichtigt.Control according to claim 1, characterized in that the nominal value of the luminance takes into account the ambient brightness.
EP97106831A 1996-04-24 1997-04-24 Control circuit for a discharge lamp Withdrawn EP0804052A3 (en)

Applications Claiming Priority (2)

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AT74396A AT407461B (en) 1996-04-24 1996-04-24 CONTROL FOR DISCHARGE LAMP
AT743/96 1996-04-24

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EP0804052A3 EP0804052A3 (en) 1999-04-07

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AT407461B (en) 2001-03-26
ATA74396A (en) 2000-07-15
EP0804052A3 (en) 1999-04-07

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