EP0748146B1 - Circuit arrangement for preheating the electrodes of a discharge lamp - Google Patents

Circuit arrangement for preheating the electrodes of a discharge lamp Download PDF

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Publication number
EP0748146B1
EP0748146B1 EP96108864A EP96108864A EP0748146B1 EP 0748146 B1 EP0748146 B1 EP 0748146B1 EP 96108864 A EP96108864 A EP 96108864A EP 96108864 A EP96108864 A EP 96108864A EP 0748146 B1 EP0748146 B1 EP 0748146B1
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EP
European Patent Office
Prior art keywords
fluorescent lamp
circuit arrangement
lamp
transformer
filaments
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP96108864A
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German (de)
French (fr)
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EP0748146A1 (en
Inventor
Peter Krummel
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Osram GmbH
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Patent Treuhand Gesellschaft fuer Elektrische Gluehlampen mbH
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    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14Circuit arrangements
    • H05B41/26Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14Circuit arrangements
    • H05B41/26Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
    • H05B41/295Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices and specially adapted for lamps with preheating electrodes, e.g. for fluorescent lamps
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S315/00Electric lamp and discharge devices: systems
    • Y10S315/05Starting and operating circuit for fluorescent lamp

Definitions

  • the invention relates to a circuit arrangement for Preheat the filaments of at least one fluorescent lamp according to the preamble of claim 1.
  • Circuit arrangements of the type mentioned are for example known from DE-C2-31 52 951, DE-A-4,013,697 and EP-A-0,602,719.
  • EP-A-0,707,438 is also relevant within the meaning of Art.
  • circuitry In terms of circuitry, there are many options in electronic Ballasts certain functions with appropriate Implement circuitry. For economic But reasons are circuit-intensive embodiments only enforceable on the market.
  • ballasts In the currently most economical circuit design known electronic ballasts is a Load circuit that normally uses a series resonant circuit with lamp choke and ignition capacitor.
  • the load circuit is the electrodes or filaments of the fluorescent lamp - if you are here for the sake of simplicity obtains a 1-lamp ballast - connected in series.
  • An inverter with a half-bridge arrangement drives this load circuit consisting of two semiconductor switches connected in series, whose common connection point is the exit of the Half-bridge arrangement forms.
  • the inverter generates one Half-bridge voltage in the form of a high-frequency rectangular pulse train and passes it on to the load circuit.
  • the switches of the half-bridge arrangement are mostly bipolar Power transistors formed, the inverter is designed so that the two switches alternatively activated with a short switching pause.
  • This inverter drives the load circuit on ignition and in Normal operation and the frequency can be influenced. Frequency changes the half-bridge voltage are to adapt to the certain lamp functions in different operating states, such as preheating, ignition or normal operation.
  • a major disadvantage of this solution discussed here is in that the current in the resonant circuit is directly connected to the voltage applied to the lamp, d. H. while the preheating phase is then the specified preheating current. Around a relatively high preheating current, the prerequisite for a rapid heating of the electrodes of the fluorescent lamp is to obtain is therefore a correspondingly high lamp voltage required. The lamp voltage in turn must be limited to premature during this preheating phase Exclude attempts to ignite the fluorescent lamp. With the described Circuit can therefore only be preheated in of the order of about 1.5 to 2 s.
  • the single lamp load circuit consists of the known circuit in each case a fluorescent lamp, an ignition capacitor and one Stray field transformer.
  • the ignition capacitor is over first connections of the filaments of the fluorescent lamp in parallel switched.
  • a primary winding of the stray field transformer is via a coupling capacitor to which the half-bridge voltage leading output of the inverter and on the other hand connected to ground reference potential.
  • a secondary winding of the Stray field transformer is, with second connections of the filaments connected to the fluorescent lamp, also parallel to this arranged.
  • the leakage inductances of the stray field transformer form together with the capacitance of the ignition capacitor a series resonance circuit of the lamp load circuit, which is close to the high-frequency switching frequency of the inverter is coordinated.
  • each of these lamp load circuits has one such series resonant circuit, the secondary windings the stray field transformers are connected in series so that a direct current path is formed in which the electrodes of the Fluorescent lamps and the secondary windings with each other Series lie.
  • this is DC path via one to be closed during the preheating time Switch and a preheating resistor to the supply voltage of the inverter, usually as an intermediate circuit voltage designated, connected.
  • the switch a timer is assigned, which when the electronic ballast due to the build-up of intermediate circuit voltage is triggered and the switch for the keeps the specified duration of the preheating time closed.
  • the invention is therefore based on the object for Circuit arrangement of the type mentioned another Specify solution with which it is simple and in one inexpensive circuit design is possible, the requirements for a safe and especially fast preheating to create the filaments of the fluorescent lamp.
  • FIG. 1 In the drawing is schematically an AC mains voltage un connected harmonic filter 1 shown that serves as a radio protection filter for repercussions on the supply network limited by high-frequency interference voltages, the due to switching operations in the electronic ballast arise.
  • a rectifier arrangement 2 At the output of this harmonic filter 1 a rectifier arrangement 2 is connected, on the one hand the AC line voltage un into a rectified voltage transformed, on the other hand also a sine correction circuit may contain.
  • the rectifier arrangement 2 thus becomes a corrected ground reference potential referenced DC voltage, the one as an electrolytic capacitor trained support capacitor CE supplied with a further connection on the other hand to ground reference potential lies. In this way, a stabilized, unaffected by AC line voltage modulations DC link voltage UZW for continuous Supply of an inverter 3 generated.
  • inverter 3 is indicated that it is generally a half-bridge arrangement from two often bipolar power transistors encompasses that over their in series Switching distances between the intermediate circuit voltage UZW and Ground reference potential are arranged and controlled so that they are alternatively turned on. At the common Connection point of the switching distances of these two The power transistors of the half-bridge arrangement become one generates high-frequency pulse train, which the output signal of Inverter 3 forms and generally as a half-bridge voltage UHB is called.
  • This half-bridge voltage UHB forms the voltage supply for a lamp load circuit connected to the inverter 3.
  • This is here as a series resonance circuit that is between the output of the inverter 3 and ground reference potential is arranged and a lamp choke LDR, a fluorescent lamp FL and a half-bridge capacitor CHB comprises.
  • Ignition capacitor CZ provided to the filaments E1, E2 of the Fluorescent lamp LL is connected.
  • the inverter 3 controls in cooperation with the connected one Lamp load circuit all operating functions of the Fluorescent lamp in the lamp load circuit. After commissioning the electronic ballast by applying the AC mains voltage un becomes the series resonance circuit of the lamp load circuit for gentle switching on of the fluorescent lamp FL operated during a preheating time at a frequency that is above the resonance frequency. It is said to be a high one Current through the electrodes E1, E2 of the fluorescent lamp FL flow to the emission temperature as quickly as possible to heat up. At the same time, however, the fluorescent lamp FL applied voltage should not be too high to be a to prevent premature ignition. As soon as the electrodes E1, E2 of the fluorescent lamp FL at the end of the preheating time at the emission temperature are brought, the fluorescent lamp FL ignite as immediately as possible.
  • the preheating of the coils E1, E2 Fluorescent lamp FL of interest is in the present.
  • the voltage on the fluorescent lamp FL during this Preheating time does not exceed a defined value in order to early ignition if the heater is not sufficiently heated Exclude spirals. Therefore, the inverter 3 controlled so that it a during the specified preheating Supplies half-bridge voltage UHB with a pulse frequency, which over the resonance frequency of the series resonance circuit in Lamp load circuit is. At this high frequency it works Lamp choke LDR current limiting. With that - through Circuit arrangement in the lamp load circuit requires an upper limit for those that can be fed to the filaments E1, E2 of the fluorescent lamp FL Given heating power, so the preheating time accordingly must be long.
  • the in the Drawing shown embodiment of the already described circuit parts that are assumed to be known per se going beyond the lamp load circuit one during the Preheat time can be activated via the half-bridge voltage UHB assigned internal voltage source assigned.
  • This includes a transformer TR with a primary winding PR, which over a coupling capacitor CK directly to the output of the Inverter 3 is connected.
  • the one from the coupling capacitor CK connection of the primary winding PR is over the switching path of a semiconductor switch HS, for example is designed as a field effect transistor Ground reference potential.
  • a timer 4 is over an adaptation network to the control input of this semiconductor switch HS connected. Parallel to the series connection of coupling capacitor CK and primary winding PR of the transformer TR, a free-wheeling diode FD is connected.
  • the secondary side of the transformer TR is through two in their windings synchronized secondary windings S1, S2 educated.
  • the winding sense of the primary and secondary windings PR or S1, S2 of the transformer TR is in the drawing symbolically clarified.
  • Each of the secondary windings S1 or S2 of the transformer TR is direct with one connection to one of the two electrodes E1 or E2 of the fluorescent lamp FL connected while in the line branch between the other winding end and the second, with the ignition capacitor CZ connected connection of the corresponding helix E1 or E2 a rectifier diode DW1 or DW2 is provided.
  • a switch-on process for the fluorescent lamp FL is normally by applying the mains voltage un triggered on the electronic ballast. there the DC link voltage builds up on the support capacitor CE UZW on and inverter 3 is switched on.
  • the frequency the half-bridge voltage UHB is for the duration of the given Preheating time well above the resonance frequency of the Series resonant circuit in the lamp load circuit, so that at the Fluorescent lamp FL applied voltage much lower than the ignition voltage is.
  • the inverter 3 runs to change lamps automatically without switching off the mains voltage back on and tries to replace the fluorescent lamp ignite. If you route the trigger signal for the timer 4 from a known start / stop circuit for the Inverter 3 or from the corresponding changes in Lamp load circuit at the beginning of the connection process, so this operating function is also clearly taken into account.
  • preheating time less than 0.5 s.
  • the transformer TR is therefore no longer excited on the primary side and heating the filaments E1, E2 of the fluorescent lamp FL has ended.
  • the freewheeling diode FD may residual energy still present in the TR transformer quickly reduced.
  • the inverter 3 becomes the frequency of the half-bridge voltage after the end of the preheating time UHB lowered.
  • the voltage on the fluorescent lamp FL thus increases as long until the ignition voltage is reached and the lamp ignites.
  • the lamp choke limits LDR because of their very much at this operating frequency high reactance due to the fluorescent lamp FL flowing current.
  • rectifier diodes DW1 and DW2 are, because appear for the heating function described they are not absolutely necessary. These rectifier diodes serve to relieve high voltages on the sockets To limit fluorescent lamp FL, on the one hand they prevent it an undesirable swinging of the lamp circuit. On the other hand they serve the operational safety when changing the lamp undervoltage.

Abstract

The pre-heating circuit is used for the filaments (E1,E2) of at least one fluorescent lamp (FL) operated via an electronic bias circuit with a current regulator (3) inserted between a DC source (2) and earth. A switched voltage source (TR,DW1,DW2,HS) coupled to the output (HBO) of the current regulator is activated during the pre-heating phase, with a pair of outputs connected in parallel to the lamp filaments. Pref. the switched current source has a transformer (TR) coupled to the current regulator with a primary winding (P) connected in series with a controlled switch (4,HS) and a pair of secondary windings (S1,S2) coupled in parallel to respective lamp filaments.

Description

Die Erfindung bezieht sich auf eine Schaltungsanordnung zum Vorheizen der Wendeln von mindestens einer Leuchtstofflampe gemäß dem Oberbegriff des Patentanspruches 1.The invention relates to a circuit arrangement for Preheat the filaments of at least one fluorescent lamp according to the preamble of claim 1.

Schaltungsanordnungen der genannten Art sind beispielsweise aus DE-C2-31 52 951, DE-A-4,013,697 und EP-A-0,602,719 bekannt. Ferner ist EP-A-0,707,438 relevant im Sinne von Art. 54(3) EPÜ. Vielfach ist es in Verbindung mit elektronischen Vorschaltgeräten, von denen die genannte Schaltung einen Teil bildet, üblich, vor dem eigentlichen Lampenstart die Wendeln bzw. Elektroden der anzuschaltenden Leuchtstofflampe auf Emissionstemperatur aufzuheizen und dadurch eine die Leuchtstofflampe schonende Zündung vorzubereiten. Es ist wohl unmittelbar einleuchtend, diese Vorheizphase möglichst kurz zu bemessen, weil ja gerade mit elektronischen Vorschaltgeräten unter anderem angestrebt wird, die Leuchtstofflampe möglichst verzögerungslos mit dem Anlegen der Netzspannung an das Vorschaltgerät zu zünden. Da zum Aufheizen der Wendeln der Leuchtstofflampe auf Emissionstemperatur eine bestimmte Energiemenge notwendig ist, wäre es demnach erforderlich, den Heizstrom möglichst hoch zu bemessen.Circuit arrangements of the type mentioned are for example known from DE-C2-31 52 951, DE-A-4,013,697 and EP-A-0,602,719. EP-A-0,707,438 is also relevant within the meaning of Art. 54 (3) EPC. It is often connected with electronic ballasts, one of which is named Circuit forms a part, usually, before the actual one Lamp start the filaments or electrodes of the to be switched on Heat up fluorescent lamp to emission temperature and thereby prepare an ignition that is gentle on the fluorescent lamp. This preheating phase is probably immediately obvious to be as short as possible, because with electronic ones Ballasts among other things is aimed at, the fluorescent lamp as soon as possible with the creation of the Ignite mains voltage to the ballast. Because to heat up the filaments of the fluorescent lamp to the emission temperature it would be a certain amount of energy necessary to measure the heating current as high as possible.

Schaltungsmäßig bestehen zwar viele Möglichkeiten, in elektronischen Vorschaltgeräten bestimmte Funktionen bei entsprechendem Schaltungsaufwand zu realisieren. Aus wirtschaftlichen Gründen sind aber schaltungsaufwendige Ausführungsformen auf dem Markt nur beschränkt durchsetzbar.In terms of circuitry, there are many options in electronic Ballasts certain functions with appropriate Implement circuitry. For economic But reasons are circuit-intensive embodiments only enforceable on the market.

In der derzeit kostengünstigsten schaltungstechnischen Ausgestaltung bekannter elektronischer Vorschaltgeräte wird ein Lastkreis verwendet, der normalerweise einen Serienresonanzkreis mit Lampendrossel und Zündkondensator umfaßt. In diesem Lastkreis sind die Elektroden bzw. Wendeln der Leuchtstofflampe - wenn man sich hier der Einfachheit halber auf ein 1-lampiges Vorschaltgerät bezieht - in Serie geschaltet. Diesen Lastkreis treibt ein Wechselrichter mit einer Halbbrückenanordnung aus zwei in Serie geschalteten Halbleiterschaltern, deren gemeinsamer Verbindungspunkt den Ausgang der Halbbrückenanordnung bildet. Der Wechselrichter erzeugt eine Halbbrückenspannung in Form einer hochfrequenten Rechteckimpulsfolge und gibt diese an den Lastkreis ab. Aus Kostengründen sind die Schalter der Halbbrückenanordnung meist als bipolare Leistungstransistoren ausgebildet, wobei der Wechselrichter so ausgestaltet ist, daß die beiden Schalter alternativ mit einer kurzen Schaltpause aktiviert sind.In the currently most economical circuit design known electronic ballasts is a Load circuit that normally uses a series resonant circuit with lamp choke and ignition capacitor. In this The load circuit is the electrodes or filaments of the fluorescent lamp - if you are here for the sake of simplicity obtains a 1-lamp ballast - connected in series. An inverter with a half-bridge arrangement drives this load circuit consisting of two semiconductor switches connected in series, whose common connection point is the exit of the Half-bridge arrangement forms. The inverter generates one Half-bridge voltage in the form of a high-frequency rectangular pulse train and passes it on to the load circuit. For cost reasons the switches of the half-bridge arrangement are mostly bipolar Power transistors formed, the inverter is designed so that the two switches alternatively activated with a short switching pause.

Dieser Wechselrichter treibt den Lastkreis bei Zündung und im Normalbetrieb und ist in der Frequenz beeinflußbar. Frequenzanderungen der Halbbrückenspannung sind zur Anpassung an die bestimmten Lampenfunktionen bei verschiedenen Betriebszuständen, wie Vorheizen, Zünden oder Normalbetrieb, erforderlich. Ein wesentlicher Nachteil dieser hier diskutierten Lösung besteht darin, daß der Strom im Resonanzkreis direkt mit der an der Lampe anliegenden Spannung verknüpft ist, d. h. während der Vorheizphase dann der vorgegebene Vorheizstrom ist. Um einen relativ hohen Vorheizstrom, der Voraussetzung für ein schnelles Aufheizen der Elektroden der Leuchtstofflampe ist, zu erhalten, ist also zugleich eine entsprechend hohe Lampenspannung erforderlich. Die Lampenspannung ihrerseits muß aber während dieser Vorheizphase begrenzt sein, um vorzeitige Zündversuche der Leuchtstofflampe auszuschließen. Mit der geschilderten Schaltung lassen sich daher Vorheizzeiten nur in der Größenordnung von ca. 1,5 bis 2 s erreichen.This inverter drives the load circuit on ignition and in Normal operation and the frequency can be influenced. Frequency changes the half-bridge voltage are to adapt to the certain lamp functions in different operating states, such as preheating, ignition or normal operation. A major disadvantage of this solution discussed here is in that the current in the resonant circuit is directly connected to the voltage applied to the lamp, d. H. while the preheating phase is then the specified preheating current. Around a relatively high preheating current, the prerequisite for a rapid heating of the electrodes of the fluorescent lamp is to obtain is therefore a correspondingly high lamp voltage required. The lamp voltage in turn must be limited to premature during this preheating phase Exclude attempts to ignite the fluorescent lamp. With the described Circuit can therefore only be preheated in of the order of about 1.5 to 2 s.

Aus EP-A1-0 429 716 ist ein elektronisches Vorschaltgerät zum parallelen Betreiben mehrerer Leuchtstofflampen bekannt, dessen Ausgestaltung einen möglichen Weg aufzeigt, wie die erforderliche Vorheizzeit herabzusetzen ist. Der einzelne Lampenlastkreis besteht bei der bekannten Schaltung jeweils aus einer Leuchtstofflampe, einem Zündkondensator und einem Streufeldtransformator. Dabei ist der Zündkondensator über erste Anschlüsse der Wendeln der Leuchtstofflampe parallel geschaltet. Eine Primärwicklung des Streufeldtransformators ist über einen Koppelkondensator an den die Halbbrückenspannung führenden Ausgang des Wechselrichters und andererseits an Massebezugspotential gelegt. Eine Sekundärwicklung des Streufeldtransformators ist, mit zweiten Anschlüssen der Wendeln der Leuchtstofflampe verbunden, ebenfalls parallel zu dieser angeordnet. Die Streuinduktivitäten des Streufeldtransformators bilden zusammen mit der Kapazität des Zündkondensators einen Serienresonanzkreis des Lampenlastkreises, der annähernd auf die hochfrequente Schaltfrequenz des Wechselrichters abgestimmt ist. Sind mehrere Lampenlastkreise vorgesehen, so besitzt jeder dieser Lampenlastkreise einen derartigen Serienresonanzkreis, wobei die Sekundärwicklungen der Streufeldtransformatoren so in Serie geschaltet sind, daß ein Gleichstrompfad gebildet wird, in dem die Elektroden der Leuchtstofflampen und die Sekundärwicklungen miteinander in Serie liegen.From EP-A1-0 429 716 an electronic ballast for parallel operation of several fluorescent lamps known, the Design shows a possible way, such as the required Preheat time must be reduced. The single lamp load circuit consists of the known circuit in each case a fluorescent lamp, an ignition capacitor and one Stray field transformer. The ignition capacitor is over first connections of the filaments of the fluorescent lamp in parallel switched. A primary winding of the stray field transformer is via a coupling capacitor to which the half-bridge voltage leading output of the inverter and on the other hand connected to ground reference potential. A secondary winding of the Stray field transformer is, with second connections of the filaments connected to the fluorescent lamp, also parallel to this arranged. The leakage inductances of the stray field transformer form together with the capacitance of the ignition capacitor a series resonance circuit of the lamp load circuit, which is close to the high-frequency switching frequency of the inverter is coordinated. Are multiple lamp load circuits provided, each of these lamp load circuits has one such series resonant circuit, the secondary windings the stray field transformers are connected in series so that a direct current path is formed in which the electrodes of the Fluorescent lamps and the secondary windings with each other Series lie.

Um nun eine hohe Heizleistung zu erzielen, wird dieser Gleichstrompfad über einen während der Vorheizzeit zu schlieβenden Schalter sowie einen Vorheizwiderstand an die Versorgungsspannung des Wechselrichters, üblicherweise als Zwischenkreisspannung bezeichnet, angeschlossen. Dem Schalter ist ein Zeitschaltglied zugeordnet, das beim Einschalten des elektronischen Vorschaltgeräts durch die sich aufbauende Zwischenkreisspannung ausgelöst wird und den Schalter für die vorgegebene Dauer der Vorheizzeit geschlossen hält. Neben dem Aufwand für einen in der Serienfertigung nicht so ohne weiteres beherrschbaren Streufeldtransformator mit definierten Eigenschaften hat die bekannte Schaltung den Nachteil, daß sie eine galvanische Trennung der Lampenlastkreise erfordert.In order to achieve a high heating output, this is DC path via one to be closed during the preheating time Switch and a preheating resistor to the supply voltage of the inverter, usually as an intermediate circuit voltage designated, connected. The switch a timer is assigned, which when the electronic ballast due to the build-up of intermediate circuit voltage is triggered and the switch for the keeps the specified duration of the preheating time closed. Next to the Effortlessly for one in series production controllable stray field transformer with defined properties the known circuit has the disadvantage that it galvanic isolation of the lamp load circuits is required.

Der Erfindung liegt daher die Aufgabe zugrunde, für eine Schaltungsanordnung der eingangs genannten Art eine weitere Lösung anzugeben, mit der es auf einfache Weise und in einer kostengünstigen Schaltungsausführung möglich ist, die Voraussetzungen für eine sichere und insbesondere schnelle Vorheizung der Wendeln der Leuchtstofflampe zu schaffen.The invention is therefore based on the object for Circuit arrangement of the type mentioned another Specify solution with which it is simple and in one inexpensive circuit design is possible, the requirements for a safe and especially fast preheating to create the filaments of the fluorescent lamp.

Diese Aufgabe wird bei einer Schaltungsanordnung der eingangs genannten Art erfindungsgemäß mit den im Kennzeichen des Patentanspruches 1 beschriebenen Merkmalen gelöst.This task is at the beginning of a circuit arrangement mentioned type according to the invention with the characterizing part of the claim 1 described features solved.

Bei dem heute für die Herstellung elektronischer Vorschaltgeräte bestehenden Kostendruck ist die Wirtschaftlichkeit der erfindungsgemäßen Lösung von wesentlicher Bedeutung. Nicht nur ist der Bauteileaufwand bei der erfindungsgemäßen Lösung verhältnismäßig gering, sondern es können dafür auch kostengünstige Bauteile eingesetzt werden. Funktional gesehen, erlaubt die erfindungsgemäße Lösung trotz der festgelegten, während der Vorheizphase relativ niedrigen Lampenspannung die Wendeln der angeschlossenen Leuchtstofflampe bei hohem Heizstrom rasch auf Emissionstemperatur aufzuheizen. Somit bietet die erfindungsgemäße Lösung die Möglichkeit, bei konventionellen Lösungen nicht erreichbare Vorheizzeiten in einem Bereich von kleiner als 0,5 s zu realisieren.Today's for the production of electronic ballasts Existing cost pressure is the cost effectiveness of Solution of the invention essential. Not only the cost of components in the solution according to the invention relatively low, but it can also be inexpensive Components are used. Functionally, allowed the solution according to the invention despite the fixed, during the preheating phase the lamp voltage is relatively low Filaments of the connected fluorescent lamp with high heating current heat up quickly to emission temperature. Thus offers the solution according to the invention the possibility with conventional Solutions unavailable preheating times in one area of less than 0.5 s.

Ein Ausführungsbeispiel der Erfindung wird im folgenden anhand der Zeichnung näher beschrieben, dabei zeigt die einzige Figur zum Teil als Blockschaltbild ein elektronisches Vorschaltgerät sowie in Schaltungseinzelheiten eine erfindungsgemäß ausgebildete Schaltungsanordnung zum Vorheizen der Wendeln einer Leuchtstofflampe vor dem eigentlichen Zündvorgang.An embodiment of the invention is described below the drawing described in more detail, the only one shows Figure partly as a block diagram of an electronic ballast as well as a circuit details according to the invention trained circuit arrangement for preheating the filaments a fluorescent lamp before the actual ignition process.

In der Zeichnung ist schematisch ein an eine Netzwechselspannung un angeschlossenes Oberwellenfilter 1 dargestellt, das als Funkschutzfilter dazu dient, Rückwirkungen auf das Versorgungsnetz durch hochfrequente Störspannungen zu begrenzen, die aufgrund von Schaltvorgängen im elektronischen Vorschaltgerät entstehen. An den Ausgang dieses Oberwellenfilters 1 ist eine Gleichrichteranordnung 2 angeschlossen, die zum einen die Netzwechselspannung un in eine gleichgerichtete Spannung umformt, zum anderen zusätzlich eine Sinuskorrekturschaltung enthalten kann. Am Ausgang der Gleichrichteranordnung 2 wird somit eine korrigierte, auf ein Massebezugspotential bezogene Gleichspannung abgegeben, die einem als Elektrolytkondensator ausgebildeten Stützkondensator CE zugeführt wird, der mit einem weiteren Anschluß andererseits auf Massebezugspotential liegt. Auf diese Weise wird eine stabilisierte, von Modulationen der Netzwechselspannung un nicht beeinträchtigte Zwischenkreisspannung UZW zur kontinuierlichen Versorgung eines Wechselrichters 3 erzeugt. Für diesen Wechselrichter 3 ist angedeutet, daß er im allgemeinen eine Halbbrückenanordnung aus zwei häufig bipolar ausgebildeten Leistungstransistoren umfaßt, die über ihre in Serie liegenden Schaltstrecken zwischen der Zwischenkreisspannung UZW und Massebezugspotential angeordnet sind und so angesteuert werden, daß sie alternativ leitend geschaltet sind. An dem gemeinsamen Verbindungspunkt der Schaltstrecken dieser beiden .Leistungstransistoren der Halbbrückenanordnung wird so eine hochfrequente Impulsfolge erzeugt, die das Ausgangssignal des Wechselrichters 3 bildet und im allgemeinen als Halbbrückenspannung UHB bezeichnet wird.In the drawing is schematically an AC mains voltage un connected harmonic filter 1 shown that serves as a radio protection filter for repercussions on the supply network limited by high-frequency interference voltages, the due to switching operations in the electronic ballast arise. At the output of this harmonic filter 1 a rectifier arrangement 2 is connected, on the one hand the AC line voltage un into a rectified voltage transformed, on the other hand also a sine correction circuit may contain. At the output of the rectifier arrangement 2 thus becomes a corrected ground reference potential referenced DC voltage, the one as an electrolytic capacitor trained support capacitor CE supplied with a further connection on the other hand to ground reference potential lies. In this way, a stabilized, unaffected by AC line voltage modulations DC link voltage UZW for continuous Supply of an inverter 3 generated. For this inverter 3 is indicated that it is generally a half-bridge arrangement from two often bipolar power transistors encompasses that over their in series Switching distances between the intermediate circuit voltage UZW and Ground reference potential are arranged and controlled so that they are alternatively turned on. At the common Connection point of the switching distances of these two The power transistors of the half-bridge arrangement become one generates high-frequency pulse train, which the output signal of Inverter 3 forms and generally as a half-bridge voltage UHB is called.

Diese Halbbrückenspannung UHB bildet die Spannungsversorgung für einen an den Wechselrichter 3 angeschlossenen Lampenlastkreis. Dieser ist hier als ein Serienresonanzkreis, der zwischen dem Ausgang des Wechselrichters 3 und Massebezugspotential angeordnet ist und eine Lampendrossel LDR, eine Leuchtstofflampe FL und einen Halbbrückenkondensator CHB umfaßt. Außerdem ist, parallel zur Leuchtstofflampe FL liegend, ein Zündkondensator CZ vorgesehen, der an die Wendeln E1, E2 der Leuchtstofflampe LL angeschlossen ist.This half-bridge voltage UHB forms the voltage supply for a lamp load circuit connected to the inverter 3. This is here as a series resonance circuit that is between the output of the inverter 3 and ground reference potential is arranged and a lamp choke LDR, a fluorescent lamp FL and a half-bridge capacitor CHB comprises. In addition, lying parallel to the fluorescent lamp FL is on Ignition capacitor CZ provided to the filaments E1, E2 of the Fluorescent lamp LL is connected.

Soweit vorstehend beschrieben, ist die Schaltungsanordnung für elektronische Vorschaltgeräte zum Betreiben mindestens einer Leuchtstofflampe durchaus bekannt, einer detaillierteren Darstellung und Beschreibung bedarf es daher hier nicht. As far as described above, the circuit arrangement for electronic ballasts for operation at least a fluorescent lamp well known, a more detailed one Presentation and description are therefore not required here.

Der Wechselrichter 3 steuert im Zusammenwirken mit dem angeschlossenen Lampenlastkreis alle Betriebsfunktionen der Leuchtstofflampe im Lampenlastkreis. Nach Inbetriebnahme des elektronischen Vorschaltgerätes durch Anlegen der Netzwechselspannung un wird der Serienresonanzkreis des Lampenlastkreises zum schonenden Einschalten der Leuchtstofflampe FL während einer Vorheizzeit mit einer Frequenz betrieben, die oberhalb der Resonanzfrequenz liegt. Dabei soll ein hoher Strom über die Elektroden E1, E2 der Leuchtstofflampe FL fließen, um diese möglichst schnell auf Emissionstemperatur aufzuheizen. Zugleich darf aber die dabei an der Leuchtstofflampe FL anstehende Spannung nicht zu hoch sein, um ein vorzeitiges Zünden zu verhindern. Sobald die Elektroden E1, E2 der Leuchtstofflampe FL am Ende der Vorheizzeit auf Emissionstemperatur gebracht sind, soll die Leuchtstofflampe FL möglichst unmittelbar zünden. Dazu ist eine Zündspannung erforderlich, die wesentlich höher als die normale Brennspannung der Leuchstofflampe FL ist. Diese hohe Spannung wird dadurch erzeugt, daß die Frequenz der Halbbrückenspannung UHB soweit abgesenkt wird, daß der Serienresonanzkreis des Lampenlastkreises nahe seiner Resonanzfrequenz betrieben wird. Sobald die Leuchtstofflampe FL gezündet hat, fließt zunächst ein hoher Strom im Lampenlastkreis, der durch den Blindwiderstand-der Lampendrossel LDR begrenzt wird. Eine solche Betriebsschaltung für eine Leuchtstofflampe läßt auch eine Dimmfunktion zu, bei der die Leuchtstofflampe lediglich einen vorgegebenen Anteil ihres Nennlichtstromes abgibt. Dafür wird die Betriebsfrequenz des Wechselrichters in definierter Weise angehoben, so daß sich der wirksame Blindwiderstand der Lampendrossel LDR erhöht. Damit wird der Strom durch die Leuchtstofflampe FL so weit begrenzt, daß diese nur noch den vorgegebenen Anteil ihres Nennlichtstroms abgibt.The inverter 3 controls in cooperation with the connected one Lamp load circuit all operating functions of the Fluorescent lamp in the lamp load circuit. After commissioning the electronic ballast by applying the AC mains voltage un becomes the series resonance circuit of the lamp load circuit for gentle switching on of the fluorescent lamp FL operated during a preheating time at a frequency that is above the resonance frequency. It is said to be a high one Current through the electrodes E1, E2 of the fluorescent lamp FL flow to the emission temperature as quickly as possible to heat up. At the same time, however, the fluorescent lamp FL applied voltage should not be too high to be a to prevent premature ignition. As soon as the electrodes E1, E2 of the fluorescent lamp FL at the end of the preheating time at the emission temperature are brought, the fluorescent lamp FL ignite as immediately as possible. An ignition voltage is required for this, which is much higher than the normal burning voltage the fluorescent lamp is FL. This creates this high tension generates the frequency of the half-bridge voltage UHB is lowered so far that the series resonant circuit of the lamp load circuit is operated near its resonance frequency. As soon as the fluorescent lamp FL has ignited, flows first a high current in the lamp load circuit caused by the reactance Lamp choke LDR is limited. Such an operating circuit for a fluorescent lamp also one Dimming function in which the fluorescent lamp only one emits a predetermined proportion of their nominal luminous flux. For that the operating frequency of the inverter in a defined Way raised so that the effective reactance of the Lamp choke LDR increased. So that the current through the Fluorescent lamp FL limited so far that this only the gives the specified proportion of their nominal luminous flux.

Von den obengenannten Betriebsfunktionen ist im vorliegenden Fall insbesondere die Vorheizung der Wendeln E1, E2 der Leuchtstofflampe FL von Interesse. Wie vorstehend angedeutet, darf die Spannung an der Leuchtstofflampe FL während dieser Vorheizzeit einen definierten Wert nicht überschreiten, um ein vorzeitiges Zünden bei noch nicht ausreichend aufgeheizten Wendeln auszuschließen. Deshalb wird der Wechselrichter 3 so gesteuert, daß er während der vorgegebenen Vorheizzeit eine Halbbrückenspannung UHB mit einer Impulsfrequenz liefert, die über der Resonanzfrequenz des Serienresonanzkreises im Lampenlastkreis liegt. Bei dieser hohen Frequenz wirkt die Lampendrossel LDR strombegrenzend. Damit ist - durch die Schaltungsanordnung im Lampenlastkreis bedingt - eine Obergrenze für die den Wendeln E1, E2 der Leuchtstofflampe FL zuführbare Heizleistung gegeben, so daß die Vorheizzeit entsprechend lang bemessen werden muß.Of the above operational functions is in the present In particular, the preheating of the coils E1, E2 Fluorescent lamp FL of interest. As indicated above, the voltage on the fluorescent lamp FL during this Preheating time does not exceed a defined value in order to early ignition if the heater is not sufficiently heated Exclude spirals. Therefore, the inverter 3 controlled so that it a during the specified preheating Supplies half-bridge voltage UHB with a pulse frequency, which over the resonance frequency of the series resonance circuit in Lamp load circuit is. At this high frequency it works Lamp choke LDR current limiting. With that - through Circuit arrangement in the lamp load circuit requires an upper limit for those that can be fed to the filaments E1, E2 of the fluorescent lamp FL Given heating power, so the preheating time accordingly must be long.

Um nun dieser Schwierigkeit zu begegnen, ist in dem in der Zeichnung dargestellten Ausführungsbeispiel über die bereits beschriebenen, als an sich bekannt vorausgesetzten Schaltungsteile hinausgehend, dem Lampenlastkreis eine während der Vorheizzeit aktivierbare, über die Halbbrückenspannung UHB versorgte interne Spannungsquelle zugeordnet. Diese umfaßt einen Transformator TR mit einer Primärwicklung PR, die über einen Koppelkondensator CK unmittelbar an den Ausgang des Wechselrichters 3 angeschlossen ist. Der von dem Koppelkondensator CK abgewandte Anschluß der Primärwicklung PR ist über die Schaltstrecke eines Halbleiterschalters HS, der beispielsweise als Feldeffekttransistor ausgebildet ist, auf Massebezugspotential gelegt. Ein Zeitschaltglied 4 ist über ein Anpassungsnetzwerk an den Steuereingang dieses Halbleiterschalters HS angeschlossen. Parallel zur Serienschaltung von Koppelkondensator CK und Primärwicklung PR des Transformators TR ist eine Freilaufdiode FD angeschlossen.In order to meet this difficulty, the in the Drawing shown embodiment of the already described circuit parts that are assumed to be known per se going beyond the lamp load circuit one during the Preheat time can be activated via the half-bridge voltage UHB assigned internal voltage source assigned. This includes a transformer TR with a primary winding PR, which over a coupling capacitor CK directly to the output of the Inverter 3 is connected. The one from the coupling capacitor CK connection of the primary winding PR is over the switching path of a semiconductor switch HS, for example is designed as a field effect transistor Ground reference potential. A timer 4 is over an adaptation network to the control input of this semiconductor switch HS connected. Parallel to the series connection of coupling capacitor CK and primary winding PR of the transformer TR, a free-wheeling diode FD is connected.

Die sekundäre Seite des Transformators TR ist durch zwei in ihrem Wicklungssinn synchronisierte Sekundärwicklungen S1, S2 gebildet. Der Wicklungssinn der Primär- und Sekundärwicklungen PR bzw. S1, S2 des Transformators TR ist in der Zeichnung symbolisch verdeutlicht. Jede der Sekundärwicklungen S1 bzw. S2 des Transformators TR ist mit einem Anschluß unmittelbar an eine der beiden Elektroden E1 bzw. E2 der Leuchtstofflampe FL angeschlossen, während in dem Leitungszweig zwischen dem anderen Wicklungsende und dem zweiten, mit dem Zündkondensator CZ verbundenen Anschluß der entsprechenden Wendel E1 bzw. E2 eine Gleichrichterdiode DW1 bzw. DW2 vorgesehen ist.The secondary side of the transformer TR is through two in their windings synchronized secondary windings S1, S2 educated. The winding sense of the primary and secondary windings PR or S1, S2 of the transformer TR is in the drawing symbolically clarified. Each of the secondary windings S1 or S2 of the transformer TR is direct with one connection to one of the two electrodes E1 or E2 of the fluorescent lamp FL connected while in the line branch between the other winding end and the second, with the ignition capacitor CZ connected connection of the corresponding helix E1 or E2 a rectifier diode DW1 or DW2 is provided.

Im folgenden wird die Funktion der beschriebenen Schaltungsanordnung erläutert. Ein Anschaltvorgang für die Leuchtstofflampe FL wird im Normalfall durch Anlegen der Netzspannung un an das elektronische Vorschaltgerät ausgelöst. Dabei baut sich am Stützkondensator CE die Zwischenkreisspannung UZW auf und der Wechselrichter 3 wird eingeschaltet. Die Frequenz der Halbbrückenspannung UHB liegt für die Dauer der gegebenen Vorheizzeit weit oberhalb der Resonanzfrequenz des Serienresonanzkreises im Lampenlastkreis, so daß die an der Leuchtstofflampe FL anstehende Spannung wesentlich geringer als die Zündspannung ist. Mit Beginn der Vorheizzeit soll das Zeitschaltglied 4 ausgelöst werden, um den Halbleiterschalter HS für die Dauer der Vorheizung der Wendeln E1, E2 der Leuchtstofflampe FL leitend zu schalten. Es gibt verschiedene Möglichkeiten, während des Anlaufens des elektronischen Vorschaltgerätes ein entsprechendes Auslösesignal für das Zeitschaltglied 4 zu erzeugen. So kann dafür der Anstieg der sich am Stützkondensator CE aufbauenden Zwischenkreisspannung UZW oder beispielsweise auch die Halbbrückenspannung UHB herangezogen bzw. auf andere Weise ein Stromanstieg im Lampenlastkreis detektiert, etwa als Spannungsabfall an einem seriell im Lampenlastkreis liegenden Widerstand abgegriffen werden. Von Vorteil ist es jedenfalls, wenn das Zeitschaltglied 4 nur ausgelöst werden kann, wenn auch der Wechselrichter 3 anschwingt. Dieser in der Zeichnung schematisch dargestellte Fall berücksichtigt, daß der Wechselrichter bei einem Teil der bekannten elektronischen Vorschaltgeräte in einem Fehlerzustand stillgesetzt wird, bei dem die angeschlossene Leuchtstofflampe zündunwillig bzw. sogar zündunfähig ist, ohne daß aber die Netzspannung abgeschaltet werden müßte. Nach einem Lampenwechsel läuft der Wechselrichter 3 bei diesen Vorschaltgeräten ohne Abschalten der Netzspannung automatisch wieder an und versucht die ausgewechselte Leuchtstofflampe zu zünden. Leitet man das Auslösesignal für das Zeitschaltglied 4 von einer an sich bekannten Start/Stop-Schaltung für den Wechselrichter 3 bzw. aus den entsprechenden Veränderungen im Lampenlastkreis zu Beginn des Anschaltvorganges ab, so wird auch dieser Betriebsfunktion eindeutig Rechnung getragen.The following is the function of the circuit arrangement described explained. A switch-on process for the fluorescent lamp FL is normally by applying the mains voltage un triggered on the electronic ballast. there the DC link voltage builds up on the support capacitor CE UZW on and inverter 3 is switched on. The frequency the half-bridge voltage UHB is for the duration of the given Preheating time well above the resonance frequency of the Series resonant circuit in the lamp load circuit, so that at the Fluorescent lamp FL applied voltage much lower than the ignition voltage is. With the start of the preheating time, that should Timer 4 are triggered to the semiconductor switch HS for the duration of the preheating of the coils E1, E2 Fluorescent lamp FL to switch on. There are different Possibilities while starting the electronic ballast a corresponding trigger signal for the timer 4 to generate. So can the increase in itself DC link voltage UZW building up on the support capacitor CE or, for example, the half-bridge voltage UHB is also used or in another way a current increase in the lamp load circuit detected, for example as a voltage drop on a serial resistance in the lamp load circuit can be tapped. In any case, it is advantageous if the timer 4 only can be triggered when the inverter 3 also swings. This is shown schematically in the drawing Case takes into account that the inverter is part of the known electronic ballasts in an error state is stopped at which the connected fluorescent lamp is unwilling to ignite or even incapable of igniting without but the mains voltage would have to be switched off. After one With these ballasts, the inverter 3 runs to change lamps automatically without switching off the mains voltage back on and tries to replace the fluorescent lamp ignite. If you route the trigger signal for the timer 4 from a known start / stop circuit for the Inverter 3 or from the corresponding changes in Lamp load circuit at the beginning of the connection process, so this operating function is also clearly taken into account.

Mit dem Einschalten des Halbleiterschalters HS durch das Zeitschaltglied 4 wird die Primärwicklung PR des Transformators TR leitend geschaltet und durch die Halbbrückenspannung UHB gespeist. Die Ausgangsspannungen des Transformators TR an den Sekundärwicklungen S1 bzw. S2 sind konstant und werden, über die Gleichrichterdioden DW1 bzw. DW2 gleichgerichtet, jeweils einer der Wendeln E1 bzw. E2 der Leuchtstofflampe FL zugeführt. Diese sind zu Beginn der Vorheizzeit auf niedriger Temperatur und daher niederohmig. Dies hat einen hohen Heizstrom zur Folge, wobei die zugeführte Heizleistung extrem groß ist, da sie quadratisch mit dem Heizstrom steigt. Somit werden die Wendeln E1, E2 der Leuchtstofflampe FL rasch aufgeheizt. Dabei steigt der Wendelwiderstand und Heizstrom wie Heizleistung sinken mit steigender Wendeltemperatur. Somit ist sichergestellt, daß die Wendeln nicht überheizt werden. Somit hat man es auf einfache Weise in der Hand, insbesondere durch die Wahl des Übersetzungsverhältnisses des Transformators TR die Ausgangsspannungen an den Sekundärwicklungen S1 bzw. S2 festzulegen und damit die Heizleistung einzustellen und daraus resultierend eine entsprechend kurze Vorheizzeit zu erzielen. Auf diese Weise lassen sich Vorheizzeit von kleiner als 0,5 s erreichen.With the switching on of the semiconductor switch HS by the Timer 4 becomes the primary winding PR of the transformer TR switched on and by the half-bridge voltage UHB powered. The output voltages of the transformer TR on the secondary windings S1 and S2 are constant and rectified via the rectifier diodes DW1 or DW2, one of the filaments E1 and E2 of the fluorescent lamp FL fed. These are lower at the start of the preheating time Temperature and therefore low resistance. This has a high heating current result, the heating power supplied extremely is large because it increases quadratically with the heating current. Consequently the filaments E1, E2 of the fluorescent lamp FL are rapidly heated. The spiral resistance and heating current increase as Heating output decrease with increasing coil temperature. Consequently ensures that the filaments are not overheated. So you have it in your hand, especially by choosing the transformation ratio of the transformer TR the output voltages on the secondary windings S1 or S2 and thus set the heating output and the result is a correspondingly short preheating time to achieve. In this way, preheating time of less than 0.5 s.

Nach Ablauf der vorgegebenen Vorheizzeit wird der Halbleiterschalter HS über das zurückgesetzte Zeitschaltglied 4 gesperrt. Der Transformator TR wird damit primärseitig nicht mehr erregt und die Heizung der Wendeln E1, E2 der Leuchtstofflampe FL ist damit beendet. Über die Freilaufdiode FD wird eventuell im Transformator TR noch vorhandene Restenergie schnell abgebaut. Entsprechend der Betriebsfunktion des elektronischen Vorschaltgerätes, insbesondere des Wechselrichters 3 wird nach dem Ende der Vorheizzeit die Frequenz der Halbbrückenspannung UHB abgesenkt. Wie vorstehend beschrieben, steigt damit die Spannung an der Leuchtstofflampe FL solange an, bis die Zündspannung erreicht wird und die Lampe zündet. Im Brennbetrieb der Leuchtstofflampe FL begrenzt die Lampendrossel LDR aufgrund ihres bei dieser Betriebsfrequenz sehr hohen Blindwiderstandes den durch die Leuchtstofflampe FL fließenden Strom.After the specified preheating time, the semiconductor switch HS locked via the reset timer 4. The transformer TR is therefore no longer excited on the primary side and heating the filaments E1, E2 of the fluorescent lamp FL has ended. The freewheeling diode FD may residual energy still present in the TR transformer quickly reduced. According to the operational function of the electronic Ballast, in particular the inverter 3 becomes the frequency of the half-bridge voltage after the end of the preheating time UHB lowered. As described above, the voltage on the fluorescent lamp FL thus increases as long until the ignition voltage is reached and the lamp ignites. When the fluorescent lamp FL is burning, the lamp choke limits LDR because of their very much at this operating frequency high reactance due to the fluorescent lamp FL flowing current.

Aus der vorstehenden Funktionsbeschreibung ergibt sich nicht unmittelbar, warum die Gleichrichterdioden DW1 bzw. DW2 vorgesehen sind, denn für die beschriebene Heizfunktion erscheinen sie nicht unbedingt erforderlich. Diese Gleichrichterdioden dienen dazu, hohe Spannungen an den Fassungen der Leuchtstofflampe FL zu begrenzen, so verhindern sie zum einen ein unerwünschtes Anschwingen der Lampenschaltung. Zum anderen dienen sie dabei der Betriebssicherheit bei einem Lampenwechsel unter Spannung.It does not follow from the functional description above immediately why the rectifier diodes DW1 and DW2 are provided are, because appear for the heating function described they are not absolutely necessary. These rectifier diodes serve to relieve high voltages on the sockets To limit fluorescent lamp FL, on the one hand they prevent it an undesirable swinging of the lamp circuit. On the other hand they serve the operational safety when changing the lamp undervoltage.

In dem vorstehend beschriebenen Ausführungsbeispiel der Erfindung ist an das elektronische Vorschaltgerät lediglich ein einziger Lampenstromkreis angeschlossen. Eine Erweiterung der beschriebenen Schaltungsanordnung auf mehrere Lampenstromkreise ist ohne weiteres möglich, ohne daß sich dabei an der beschriebenen Schaltungsanordnung grundsätzlich etwas ändert. Für mehrlampige elektronische Vorschaltgeräte ist entsprechend der Zahl der zu heizenden Elektroden zweier oder dreier Leuchtstofflampen die Zahl der Sekundärwicklungen des Transformators zu vervielfachen. Bei grundsätzlich identischer Schaltungsausführung erhöht sich somit für mehrlampige elektronische Vorschaltgeräte lediglich die Zahl der Sekundärwicklungen des Transformators sowie entsprechend auch die Zahl der im Heizkreis anzuordnenden Gleichrichterdioden. Da mehrlampige elektronische Vorschaltgeräte durchaus bekannt sind, bedarf es wohl für die Beschreibung eines solchen Ausführungsbeispieles der Erfindung mit mehr als einer über ein elektronisches Vorschaltgerät betriebenen Leuchtstofflampe keiner eigenen zeichnerischen Darstellung.In the embodiment of the invention described above is only a to the electronic ballast only lamp circuit connected. An extension of the described circuit arrangement on several lamp circuits is possible without further ado described circuit arrangement basically changes something. For multi-lamp electronic ballasts is corresponding the number of electrodes to be heated, two or three Fluorescent lamps the number of secondary windings of the transformer to multiply. If fundamentally identical Circuit design thus increases for multi-lamp electronic Ballasts only the number of secondary windings of the transformer as well as accordingly Number of rectifier diodes to be arranged in the heating circuit. There Multi-lamp electronic ballasts are well known are, it is probably necessary for the description of such an embodiment of the invention with more than one over one electronic ballast operated fluorescent lamp no own graphic representation.

Claims (7)

  1. Circuit arrangement for preheating the filaments (E1, E2) of at least one fluorescent lamp (FL), which is operated with an electronic ballast in which there is arranged, between a DC voltage source (2) and an earth reference potential, an invertor (3), to whose output, at which a half-bridge voltage (UHB) is output in the form of a high-frequency pulse train, there is connected a load circuit having a lamp inductor (LDR), the at least one fluorescent lamp (FL), an ignition capacitor (CZ) and a half-bridge capacitor (CHB), which load circuit is connected to the earth reference potential at the other end, characterized by a switchable voltage source (TR, DW1, DW2, HS, 4) which is connected to the output of the invertor (3), is constantly switched on for the entire duration of a predetermined preheating time of the filaments (E1, E2) and is only activated during this preheating time, and has outputs formed in pairs, to which in each case one of the filaments (E1, E2) of the fluorescent lamp (FL) is connected in parallel.
  2. Circuit arrangement according to Claim 1, characterized in that the switchable voltage source comprises a transformer (TR), whose primary winding (PR) is arranged between the output of the invertor (3) and the earth reference potential and which has secondary windings (S1, S2), which are synchronized by way of their winding sense and whose connections each form one of the outputs of the switchable voltage source which are formed in pairs and with which a respective one of the filaments (E1 or E2) of the fluorescent lamp (FL) is connected in parallel.
  3. Circuit arrangement according to Claim 2, characterized in that there is provided, connected in series with the primary winding (PR) of the transformer (TR), a switching element (HS, 4) which is controlled in a time-dependent manner and serves for activating the switchable voltage source during the predetermined preheating time.
  4. Circuit arrangement according to Claim 3, characterized in that the switching element (HS, 4) which is controlled in a time-dependent manner is designed as a PTC thermistor.
  5. Circuit arrangement according to Claim 3, characterized in that the time-dependent switching element (HS, 4) has a semiconductor switch (HS), whose switching path is arranged in series with the primary winding (PR) of the transformer (TR) and to whose control input is connected the output of a time switching element (4) for activating the semiconductor switch (HS) during the predetermined preheating time.
  6. Circuit arrangement according to one of Claims 2 to 5, characterized in that provision is made of a rectifier diode (DW1 and DW2) respectively connected in series with the secondary windings (S1, S2) of the transformer (TR).
  7. Circuit arrangement according to one of Claims 2 to 6, characterized in that a freewheeling diode (FD) is arranged in parallel with the primary winding (PR) of the transformer (TR).
EP96108864A 1995-06-08 1996-06-03 Circuit arrangement for preheating the electrodes of a discharge lamp Expired - Lifetime EP0748146B1 (en)

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DE19520999A DE19520999A1 (en) 1995-06-08 1995-06-08 Circuit arrangement for filament preheating of fluorescent lamps
DE19520999 1995-06-08

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EP0748146B1 true EP0748146B1 (en) 2001-08-29

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US8228000B2 (en) 2009-05-12 2012-07-24 Osram Ag Circuit arrangement for operating a low-pressure gas discharge lamp and corresponding method

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US5854538A (en) 1998-12-29
KR970004974A (en) 1997-01-29
DE59607566D1 (en) 2001-10-04
HK1005304A1 (en) 1998-12-31
SG64387A1 (en) 1999-04-27
TW415158B (en) 2000-12-11
CA2178443C (en) 2005-04-05
DE19520999A1 (en) 1996-12-12
ATE205042T1 (en) 2001-09-15
KR100448290B1 (en) 2004-11-26
CA2178443A1 (en) 1996-12-09
EP0748146A1 (en) 1996-12-11

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