EP0748146A1 - 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
EP0748146A1
EP0748146A1 EP96108864A EP96108864A EP0748146A1 EP 0748146 A1 EP0748146 A1 EP 0748146A1 EP 96108864 A EP96108864 A EP 96108864A EP 96108864 A EP96108864 A EP 96108864A EP 0748146 A1 EP0748146 A1 EP 0748146A1
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EP
European Patent Office
Prior art keywords
fluorescent lamp
circuit arrangement
lamp
filaments
transformer
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.)
Granted
Application number
EP96108864A
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German (de)
French (fr)
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EP0748146B1 (en
Inventor
Peter Krummel
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Osram GmbH
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Siemens AG
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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
    • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • 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
    • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28—Circuit 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
    • H05B41/295—Circuit 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
    • Y—GENERAL 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S315/00—Electric lamp and discharge devices: systems
    • Y10S315/05—Starting and operating circuit for fluorescent lamp

Definitions

  • the invention relates to a circuit arrangement for preheating the filaments of at least one fluorescent lamp according to the preamble of patent claim 1.
  • Circuit arrangements of the type mentioned are known for example from DE-C2-31 52 951.
  • electronic ballasts of which the circuit mentioned forms a part
  • this preheating phase should be as short as possible, because electronic ballasts, among other things, aim to ignite the fluorescent lamp as soon as possible when the mains voltage is applied to the ballast. Since a certain amount of energy is required to heat the filaments of the fluorescent lamp to the emission temperature, it would therefore be necessary to measure the heating current as high as possible.
  • circuitry there are many options for realizing certain functions in electronic ballasts with the corresponding amount of circuitry. For economic reasons, however, circuit-intensive embodiments can only be implemented to a limited extent on the market.
  • a load circuit which normally comprises a series resonant circuit with a lamp choke and an ignition capacitor.
  • this load circuit are 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.
  • This load circuit is driven by an inverter with a half-bridge arrangement consisting of two semiconductor switches connected in series, the common connection point of which forms the output of the half-bridge arrangement.
  • the inverter generates a half-bridge voltage in the form of a high-frequency square-wave pulse sequence and outputs it to the load circuit.
  • the switches of the half-bridge arrangement are usually designed as bipolar power transistors, the inverter being designed in such a way that the two switches are alternatively activated with a short switching pause.
  • This inverter drives the load circuit during ignition and normal operation and the frequency can be influenced. Frequency changes in the half-bridge voltage are required to adapt to the specific lamp functions in various operating states, such as preheating, ignition or normal operation.
  • a major disadvantage of this solution discussed here is that the current in the resonance circuit is directly linked to the voltage applied to the lamp, i. H. the pre-heating current is then during the preheating phase. In order to obtain a relatively high preheating current, which is a prerequisite for rapid heating of the electrodes of the fluorescent lamp, a correspondingly high lamp voltage is therefore also required. The lamp voltage in turn must be limited during this preheating phase in order to rule out early ignition attempts of the fluorescent lamp. With the circuit described, preheating times can therefore only be achieved in the order of approximately 1.5 to 2 s.
  • EP-A1-0 429 716 discloses an electronic ballast for operating a plurality of fluorescent lamps in parallel, the design of which shows a possible way of reducing the preheating time required.
  • the individual lamp load circuit in each case consists of a fluorescent lamp, an ignition capacitor and a stray field transformer.
  • the ignition capacitor is over first connections of the filaments of the fluorescent lamp connected in parallel.
  • a primary winding of the stray field transformer is connected via a coupling capacitor to the output of the inverter carrying the half-bridge voltage and on the other hand to ground reference potential.
  • a secondary winding of the stray field transformer, connected to second connections of the filaments of the fluorescent lamp, is also arranged parallel to the latter.
  • the stray inductances of the stray field transformer together with the capacitance of the ignition capacitor, form a series resonant circuit of the lamp load circuit, which is approximately matched to the high-frequency switching frequency of the inverter. If several lamp load circuits are provided, each of these lamp load circuits has such a series resonance circuit, the secondary windings of the stray field transformers being connected in series in such a way that a direct current path is formed in which the electrodes of the fluorescent lamps and the secondary windings are in series with one another.
  • this direct current path is connected to the supply voltage of the inverter, usually referred to as an intermediate circuit voltage, via a switch to be closed during the preheating time and a preheating resistor.
  • a timer is assigned to the switch, which is triggered by the intermediate circuit voltage building up when the electronic ballast is switched on and keeps the switch closed for the predetermined duration of the preheating time.
  • the invention is therefore based on the object of specifying a further solution for a circuit arrangement of the type mentioned at the outset, with which it is possible in a simple manner and in a cost-effective circuit implementation for a safe and, in particular, rapid preheating of the filaments of the fluorescent lamp.
  • the cost-effectiveness of the solution according to the invention is of essential importance. Not only is the amount of components required in the solution according to the invention relatively low, but inexpensive components can also be used for this. From a functional point of view, the solution according to the invention allows the filaments of the connected fluorescent lamp to be heated up rapidly to the emission temperature in spite of the lamp voltage which is relatively low during the preheating phase and at high heating current. The solution according to the invention thus offers the possibility of realizing preheating times which are not achievable in conventional solutions in a range of less than 0.5 s.
  • a harmonic filter 1 is shown schematically connected to a mains AC voltage and serves as a radio protection filter to limit repercussions on the supply network due to high-frequency interference voltages that arise due to switching operations in the electronic ballast.
  • a rectifier arrangement 2 is connected to the output of this harmonic filter 1, which on the one hand converts the mains AC voltage into a rectified voltage, and on the other hand also a sine correction circuit may contain.
  • a corrected DC voltage based on a ground reference potential, is thus emitted, which is fed to a support capacitor CE, which is designed as an electrolytic capacitor and, on the other hand, has a further connection to ground reference potential.
  • a stabilized intermediate circuit voltage UZW which is not impaired by modulations of the AC line voltage, is generated for the continuous supply of an inverter 3.
  • inverter 3 it is indicated that it generally comprises a half-bridge arrangement of two frequently bipolar power transistors, which are arranged over their series switching paths between the intermediate circuit voltage UZW and ground reference potential and are controlled so that they are alternatively switched to be conductive.
  • a high-frequency pulse sequence is generated which forms the output signal of the inverter 3 and is generally referred to as the half-bridge voltage UHB.
  • 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, which is arranged between the output of the inverter 3 and ground reference potential and comprises a lamp inductor LDR, a fluorescent lamp FL and a half-bridge capacitor CHB.
  • an ignition capacitor CZ is provided, lying parallel to the fluorescent lamp FL, which is connected to the filaments E1, E2 of the fluorescent lamp LL.
  • the inverter 3 controls all operating functions of the fluorescent lamp in the lamp load circuit.
  • the series resonant circuit of the lamp load circuit is operated at a frequency which is above the resonance frequency during a preheating period to gently switch on the fluorescent lamp FL.
  • a high current should flow through the electrodes E1, E2 of the fluorescent lamp FL in order to heat them up to the emission temperature as quickly as possible.
  • the voltage applied to the fluorescent lamp FL must not be too high to prevent premature ignition.
  • the fluorescent lamp FL should ignite as directly as possible.
  • This high voltage is generated by lowering the frequency of the half-bridge voltage UHB to such an extent that the series resonant circuit of the lamp load circuit is operated close to its resonant frequency.
  • a high current flows in the lamp load circuit, which is limited by the reactance of the lamp choke LDR.
  • Such an operating circuit for a fluorescent lamp also permits a dimming function in which the fluorescent lamp only emits a predetermined proportion of its nominal luminous flux.
  • the operating frequency of the inverter 3 is raised in a defined manner, so that the effective reactance of the lamp inductor LDR increases. The current through the fluorescent lamp FL is thus limited to such an extent that it only emits the predetermined proportion of its nominal luminous flux.
  • the preheating of the filaments E1, E2 of the fluorescent lamp FL is of particular interest in the present case.
  • the voltage on the fluorescent lamp FL during this Preheating time should not exceed a defined value in order to prevent premature ignition if the filaments are not sufficiently heated. Therefore, the inverter 3 is controlled so that it supplies a half-bridge voltage UHB with a pulse frequency that is above the resonance frequency of the series resonance circuit in the lamp load circuit during the predetermined preheating time.
  • the lamp choke LDR has a current-limiting effect. This is - due to the circuit arrangement in the lamp load circuit - an upper limit for the heating power that can be supplied to the filaments E1, E2 of the fluorescent lamp FL, so that the preheating time must be measured accordingly long.
  • the lamp load circuit is assigned an internal voltage source which can be activated during the preheating time and is supplied via the half-bridge voltage UHB.
  • This comprises a transformer TR with a primary winding PR, which is connected directly to the output of the inverter 3 via a coupling capacitor CK.
  • the connection of the primary winding PR facing away from the coupling capacitor CK is connected to ground reference potential via the switching path of a semiconductor switch HS, which is designed, for example, as a field effect transistor.
  • a timer 4 is connected to the control input of this semiconductor switch HS via an adaptation network.
  • a freewheeling diode FD is connected in parallel with the series connection of coupling capacitor CK and primary winding PR of transformer TR.
  • the secondary side of the transformer TR is formed by two secondary windings S1, S2 synchronized in their winding direction.
  • the sense of winding of the primary and secondary windings PR and S1, S2 of the transformer TR is symbolically illustrated in the drawing.
  • Each of the secondary windings S1 and S2 of the transformer TR is direct with one connection connected to one of the two electrodes E1 or E2 of the fluorescent lamp FL, while a rectifier diode DW1 or DW2 is provided in the line branch between the other end of the winding and the second connection of the corresponding filament E1 or E2 connected to the ignition capacitor CZ.
  • a connection process for the fluorescent lamp FL is normally triggered by applying the mains voltage to the electronic ballast.
  • the DC link voltage UZW builds up on the support capacitor CE and the inverter 3 is switched on.
  • the frequency of the half-bridge voltage UHB is for the duration of the given preheating time far above the resonance frequency of the series resonance circuit in the lamp load circuit, so that the voltage applied to the fluorescent lamp FL is significantly lower than the ignition voltage.
  • the timer 4 is to be triggered in order to switch the semiconductor switch HS to conductive for the duration of the preheating of the filaments E1, E2 of the fluorescent lamp FL.
  • the increase in the intermediate circuit voltage UZW building up on the support capacitor CE or, for example, also the half-bridge voltage UHB can be used, or a current rise in the lamp load circuit can be detected in another way, for example as a voltage drop across a resistor in series in the lamp load circuit.
  • the timer 4 can only be triggered when the inverter 3 also starts to vibrate.
  • the primary winding PR of the transformer TR is turned on and fed by the half-bridge voltage UHB.
  • the output voltages of the transformer TR on the secondary windings S1 and S2 are constant and, rectified via the rectifier diodes DW1 and DW2, are each fed to one of the filaments E1 and E2 of the fluorescent lamp FL.
  • these are at a low temperature and therefore have a low resistance. This results in a high heating current, whereby the heating power supplied is extremely large, since it increases quadratically with the heating current.
  • the filaments E1, E2 of the fluorescent lamp FL are thus heated up rapidly.
  • the filament resistance increases and the heating current and heating power decrease with increasing filament temperature.
  • the semiconductor switch HS is blocked by the reset timer 4.
  • the transformer TR is therefore no longer energized on the primary side and the heating of the filaments E1, E2 of the fluorescent lamp FL is thus ended. Residual energy that may still be present in the transformer TR quickly becomes fast via the freewheeling diode FD reduced.
  • the frequency of the half-bridge voltage UHB is reduced after the end of the preheating time. As described above, the voltage on the fluorescent lamp FL thus rises until the ignition voltage is reached and the lamp ignites. In the burning mode of the fluorescent lamp FL, the lamp choke LDR limits the current flowing through the fluorescent lamp FL due to its very high reactance at this operating frequency.
  • rectifier diodes DW1 or DW2 are provided, because they do not appear to be absolutely necessary for the heating function described.
  • These rectifier diodes serve to limit high voltages at the sockets of the fluorescent lamp FL, on the one hand they prevent the lamp circuit from undesirably starting to oscillate. On the other hand, they serve for operational safety when changing lamps under voltage.

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  • Circuit Arrangements For Discharge Lamps (AREA)

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 preheating the filaments of at least one fluorescent lamp according to the preamble of patent claim 1.

Schaltungsanordnungen der genannten Art sind beispielsweise aus DE-C2-31 52 951 bekannt. 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 known for example from DE-C2-31 52 951. In connection with electronic ballasts, of which the circuit mentioned forms a part, it is often customary to heat the filaments or electrodes of the fluorescent lamp to be switched on to the emission temperature before the actual lamp start and thereby prepare an ignition which is gentle on the fluorescent lamp. It is obvious that this preheating phase should be as short as possible, because electronic ballasts, among other things, aim to ignite the fluorescent lamp as soon as possible when the mains voltage is applied to the ballast. Since a certain amount of energy is required to heat the filaments of the fluorescent lamp to the emission temperature, it would therefore be 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 for realizing certain functions in electronic ballasts with the corresponding amount of circuitry. For economic reasons, however, circuit-intensive embodiments can only be implemented to a limited extent 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 cost-effective circuit design of known electronic ballasts, a load circuit is used which normally comprises a series resonant circuit with a lamp choke and an ignition capacitor. In this load circuit are 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. This load circuit is driven by an inverter with a half-bridge arrangement consisting of two semiconductor switches connected in series, the common connection point of which forms the output of the half-bridge arrangement. The inverter generates a half-bridge voltage in the form of a high-frequency square-wave pulse sequence and outputs it to the load circuit. For reasons of cost, the switches of the half-bridge arrangement are usually designed as bipolar power transistors, the inverter being designed in such a way that the two switches are alternatively activated with a short switching pause.

Dieser Wechselrichter treibt den Lastkreis bei Zündung und im Normalbetrieb und ist in der Frequenz beeinflußbar. Frequenzänderungen 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 during ignition and normal operation and the frequency can be influenced. Frequency changes in the half-bridge voltage are required to adapt to the specific lamp functions in various operating states, such as preheating, ignition or normal operation. A major disadvantage of this solution discussed here is that the current in the resonance circuit is directly linked to the voltage applied to the lamp, i. H. the pre-heating current is then during the preheating phase. In order to obtain a relatively high preheating current, which is a prerequisite for rapid heating of the electrodes of the fluorescent lamp, a correspondingly high lamp voltage is therefore also required. The lamp voltage in turn must be limited during this preheating phase in order to rule out early ignition attempts of the fluorescent lamp. With the circuit described, preheating times can therefore only be achieved in the order of approximately 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.EP-A1-0 429 716 discloses an electronic ballast for operating a plurality of fluorescent lamps in parallel, the design of which shows a possible way of reducing the preheating time required. In the known circuit, the individual lamp load circuit in each case consists of a fluorescent lamp, an ignition capacitor and a stray field transformer. The ignition capacitor is over first connections of the filaments of the fluorescent lamp connected in parallel. A primary winding of the stray field transformer is connected via a coupling capacitor to the output of the inverter carrying the half-bridge voltage and on the other hand to ground reference potential. A secondary winding of the stray field transformer, connected to second connections of the filaments of the fluorescent lamp, is also arranged parallel to the latter. The stray inductances of the stray field transformer, together with the capacitance of the ignition capacitor, form a series resonant circuit of the lamp load circuit, which is approximately matched to the high-frequency switching frequency of the inverter. If several lamp load circuits are provided, each of these lamp load circuits has such a series resonance circuit, the secondary windings of the stray field transformers being connected in series in such a way that a direct current path is formed in which the electrodes of the fluorescent lamps and the secondary windings are in series with one another.

Um nun eine hohe Heizleistung zu erzielen, wird dieser Gleichstrompfad über einen während der Vorheizzeit zu schließenden 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 direct current path is connected to the supply voltage of the inverter, usually referred to as an intermediate circuit voltage, via a switch to be closed during the preheating time and a preheating resistor. A timer is assigned to the switch, which is triggered by the intermediate circuit voltage building up when the electronic ballast is switched on and keeps the switch closed for the predetermined duration of the preheating time. In addition to the expense for a stray field transformer with defined properties that is not so easily controllable in series production, the known circuit has the disadvantage that it requires electrical isolation of the lamp load circuits.

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 of specifying a further solution for a circuit arrangement of the type mentioned at the outset, with which it is possible in a simple manner and in a cost-effective circuit implementation for a safe and, in particular, rapid preheating of 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 object is achieved according to the invention in a circuit arrangement of the type mentioned at the outset with the features described in the characterizing part of patent claim 1.

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.In the current cost pressure for the production of electronic ballasts, the cost-effectiveness of the solution according to the invention is of essential importance. Not only is the amount of components required in the solution according to the invention relatively low, but inexpensive components can also be used for this. From a functional point of view, the solution according to the invention allows the filaments of the connected fluorescent lamp to be heated up rapidly to the emission temperature in spite of the lamp voltage which is relatively low during the preheating phase and at high heating current. The solution according to the invention thus offers the possibility of realizing preheating times which are not achievable in conventional solutions in a range 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 in more detail below with reference to the drawing, the single figure showing partly as a block diagram an electronic ballast and in circuit details an inventive circuit arrangement for preheating the filaments of 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, a harmonic filter 1 is shown schematically connected to a mains AC voltage and serves as a radio protection filter to limit repercussions on the supply network due to high-frequency interference voltages that arise due to switching operations in the electronic ballast. A rectifier arrangement 2 is connected to the output of this harmonic filter 1, which on the one hand converts the mains AC voltage into a rectified voltage, and on the other hand also a sine correction circuit may contain. At the output of the rectifier arrangement 2, a corrected DC voltage, based on a ground reference potential, is thus emitted, which is fed to a support capacitor CE, which is designed as an electrolytic capacitor and, on the other hand, has a further connection to ground reference potential. In this way, a stabilized intermediate circuit voltage UZW, which is not impaired by modulations of the AC line voltage, is generated for the continuous supply of an inverter 3. For this inverter 3, it is indicated that it generally comprises a half-bridge arrangement of two frequently bipolar power transistors, which are arranged over their series switching paths between the intermediate circuit voltage UZW and ground reference potential and are controlled so that they are alternatively switched to be conductive. At the common connection point of the switching paths of these two power transistors of the half-bridge arrangement, a high-frequency pulse sequence is generated which forms the output signal of the inverter 3 and is generally referred to as the half-bridge voltage UHB.

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, which is arranged between the output of the inverter 3 and ground reference potential and comprises a lamp inductor LDR, a fluorescent lamp FL and a half-bridge capacitor CHB. In addition, an ignition capacitor CZ is provided, lying parallel to the fluorescent lamp FL, which is connected to the filaments E1, E2 of the fluorescent lamp LL.

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 operating at least one fluorescent lamp is well known, a detailed description and description is 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 3 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.In cooperation with the connected lamp load circuit, the inverter 3 controls all operating functions of the fluorescent lamp in the lamp load circuit. After the electronic ballast has been started up by applying the AC line voltage un, the series resonant circuit of the lamp load circuit is operated at a frequency which is above the resonance frequency during a preheating period to gently switch on the fluorescent lamp FL. A high current should flow through the electrodes E1, E2 of the fluorescent lamp FL in order to heat them up to the emission temperature as quickly as possible. At the same time, however, the voltage applied to the fluorescent lamp FL must not be too high to prevent premature ignition. As soon as the electrodes E1, E2 of the fluorescent lamp FL are brought to the emission temperature at the end of the preheating time, the fluorescent lamp FL should ignite as directly as possible. This requires an ignition voltage that is significantly higher than the normal operating voltage of the fluorescent lamp FL. This high voltage is generated by lowering the frequency of the half-bridge voltage UHB to such an extent that the series resonant circuit of the lamp load circuit is operated close to its resonant frequency. As soon as the fluorescent lamp FL has ignited, a high current flows in the lamp load circuit, which is limited by the reactance of the lamp choke LDR. Such an operating circuit for a fluorescent lamp also permits a dimming function in which the fluorescent lamp only emits a predetermined proportion of its nominal luminous flux. For this purpose, the operating frequency of the inverter 3 is raised in a defined manner, so that the effective reactance of the lamp inductor LDR increases. The current through the fluorescent lamp FL is thus limited to such an extent that it only emits the predetermined proportion of its 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-mentioned operating functions, the preheating of the filaments E1, E2 of the fluorescent lamp FL is of particular interest in the present case. As indicated above, the voltage on the fluorescent lamp FL during this Preheating time should not exceed a defined value in order to prevent premature ignition if the filaments are not sufficiently heated. Therefore, the inverter 3 is controlled so that it supplies a half-bridge voltage UHB with a pulse frequency that is above the resonance frequency of the series resonance circuit in the lamp load circuit during the predetermined preheating time. At this high frequency, the lamp choke LDR has a current-limiting effect. This is - due to the circuit arrangement in the lamp load circuit - an upper limit for the heating power that can be supplied to the filaments E1, E2 of the fluorescent lamp FL, so that the preheating time must be measured accordingly 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 overcome this difficulty, in the exemplary embodiment shown in the drawing, going beyond the circuit parts already described, which are assumed to be known per se, the lamp load circuit is assigned an internal voltage source which can be activated during the preheating time and is supplied via the half-bridge voltage UHB. This comprises a transformer TR with a primary winding PR, which is connected directly to the output of the inverter 3 via a coupling capacitor CK. The connection of the primary winding PR facing away from the coupling capacitor CK is connected to ground reference potential via the switching path of a semiconductor switch HS, which is designed, for example, as a field effect transistor. A timer 4 is connected to the control input of this semiconductor switch HS via an adaptation network. A freewheeling diode FD is connected in parallel with the series connection of coupling capacitor CK and primary winding PR of transformer TR.

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 formed by two secondary windings S1, S2 synchronized in their winding direction. The sense of winding of the primary and secondary windings PR and S1, S2 of the transformer TR is symbolically illustrated in the drawing. Each of the secondary windings S1 and S2 of the transformer TR is direct with one connection connected to one of the two electrodes E1 or E2 of the fluorescent lamp FL, while a rectifier diode DW1 or DW2 is provided in the line branch between the other end of the winding and the second connection of the corresponding filament E1 or E2 connected to the ignition capacitor CZ.

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 function of the circuit arrangement described is explained below. A connection process for the fluorescent lamp FL is normally triggered by applying the mains voltage to the electronic ballast. The DC link voltage UZW builds up on the support capacitor CE and the inverter 3 is switched on. The frequency of the half-bridge voltage UHB is for the duration of the given preheating time far above the resonance frequency of the series resonance circuit in the lamp load circuit, so that the voltage applied to the fluorescent lamp FL is significantly lower than the ignition voltage. At the beginning of the preheating time, the timer 4 is to be triggered in order to switch the semiconductor switch HS to conductive for the duration of the preheating of the filaments E1, E2 of the fluorescent lamp FL. There are various possibilities for generating a corresponding trigger signal for the timer 4 during the start-up of the electronic ballast. For this purpose, the increase in the intermediate circuit voltage UZW building up on the support capacitor CE or, for example, also the half-bridge voltage UHB can be used, or a current rise in the lamp load circuit can be detected in another way, for example as a voltage drop across a resistor in series in the lamp load circuit. In any case, it is advantageous if the timer 4 can only be triggered when the inverter 3 also starts to vibrate. This case, shown schematically in the drawing, takes into account that the inverter in some of the known electronic ballasts is shut down in an error state in which the connected fluorescent lamp is unwilling or even unable to ignite, but without the mains voltage having to be switched off. After a lamp change, the inverter 3 runs on these ballasts without switching off the mains voltage and tries to ignite the replaced fluorescent lamp. If one derives the trigger signal for the timer 4 from a known start / stop circuit for the inverter 3 or from the corresponding changes in the lamp load circuit at the start of the connection process, 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.When the semiconductor switch HS is switched on by the time switching element 4, the primary winding PR of the transformer TR is turned on and fed by the half-bridge voltage UHB. The output voltages of the transformer TR on the secondary windings S1 and S2 are constant and, rectified via the rectifier diodes DW1 and DW2, are each fed to one of the filaments E1 and E2 of the fluorescent lamp FL. At the beginning of the preheating time, these are at a low temperature and therefore have a low resistance. This results in a high heating current, whereby the heating power supplied is extremely large, since it increases quadratically with the heating current. The filaments E1, E2 of the fluorescent lamp FL are thus heated up rapidly. The filament resistance increases and the heating current and heating power decrease with increasing filament temperature. This ensures that the filaments are not overheated. It is therefore easy to determine, in particular by selecting the transformation ratio of the transformer TR, the output voltages on the secondary windings S1 and S2 and thus to adjust the heating power and, as a result, to achieve a correspondingly short preheating time. In this way, preheating times of less than 0.5 s can be achieved.

Nach Ablauf der vorgegebenen Vorheizzeit wird der Halbleiterschalter HS über das rückgesetzte 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 is blocked by the reset timer 4. The transformer TR is therefore no longer energized on the primary side and the heating of the filaments E1, E2 of the fluorescent lamp FL is thus ended. Residual energy that may still be present in the transformer TR quickly becomes fast via the freewheeling diode FD reduced. According to the operating function of the electronic ballast, in particular of the inverter 3, the frequency of the half-bridge voltage UHB is reduced after the end of the preheating time. As described above, the voltage on the fluorescent lamp FL thus rises until the ignition voltage is reached and the lamp ignites. In the burning mode of the fluorescent lamp FL, the lamp choke LDR limits the current flowing through the fluorescent lamp FL due to its very high reactance at this operating frequency.

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.The above functional description does not immediately explain why the rectifier diodes DW1 or DW2 are provided, because they do not appear to be absolutely necessary for the heating function described. These rectifier diodes serve to limit high voltages at the sockets of the fluorescent lamp FL, on the one hand they prevent the lamp circuit from undesirably starting to oscillate. On the other hand, they serve for operational safety when changing lamps under voltage.

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 exemplary embodiment of the invention described above, only a single lamp circuit is connected to the electronic ballast. An expansion of the circuit arrangement described to a plurality of lamp circuits is possible without further changes to the circuit arrangement described. For multi-lamp electronic ballasts, the number of secondary windings of the transformer must be multiplied according to the number of electrodes to be heated for two or three fluorescent lamps. If the circuit is basically identical, only the number of secondary windings of the transformer and, accordingly, the number of rectifier diodes to be arranged in the heating circuit increase for multi-lamp electronic ballasts. Since multi-lamp electronic ballasts are well known, it is probably necessary to describe such an embodiment the invention with more than one fluorescent lamp operated via an electronic ballast does not have its own graphic representation.

Claims (7)

Schaltungsanordnung zum Vorheizen der Wendeln (E1, E2) von mindestens einer Leuchtstofflampe (FL), die mit einem elektronischen Vorschaltgerät betrieben wird, in dem zwischen einer Gleichspannungsquelle (2) und einem Massebezugspotential ein Wechselrichter (3) angeordnet ist, an dessen Ausgang, an dem eine Halbbrückenspannung (VHB) in Form einer hochfrequenten Impulsfolge abgegeben wird, ein andererseits an dem Massebezugspotential liegender Lastkreis mit einer Lampendrossel (LDR), der mindestens einen Leuchtstofflampe (FL), einem Zündkondensator (CZ) und einem Halbbrückenkondensator (CHB) angeschlossen ist, gekennzeichnet durch eine während einer vorgegebenen Vorheizzeit der Wendeln (E1, E2) aktivierbare, an den Ausgang (HBO) des Wechselrichters (3) angeschlossene, schaltbare Spannungsquelle (TR, DW1, DW2, HS, 4) mit paarweise ausgebildeten Ausgängen, denen jeweils eine der Wendeln (E1 bzw. E2) der Leuchtstofflampe (FL) parallel geschaltet ist.Circuit arrangement for preheating the filaments (E1, E2) of at least one fluorescent lamp (FL), which is operated with an electronic ballast, in which an inverter (3) is arranged at its output between a DC voltage source (2) and a ground reference potential to which a half-bridge voltage (VHB) is emitted in the form of a high-frequency pulse sequence, on the other hand a load circuit lying at the ground reference potential with a lamp inductor (LDR) connected to at least one fluorescent lamp (FL), an ignition capacitor (CZ) and a half-bridge capacitor (CHB), characterized by a switchable voltage source (TR, DW1, DW2, HS, 4) which can be activated during a predetermined preheating time of the filaments (E1, E2) and is connected to the output (HBO) of the inverter (3), with outputs in pairs, each of which has one the filaments (E1 or E2) of the fluorescent lamp (FL) is connected in parallel. Schaltungsanordnung nach Anspruch 1, dadurch gekennzeichnet, daß die schaltbare Spannungsquelle einen Transformator (TR) umfaßt, dessen Primärwicklung (PR) zwischen dem Ausgang des Wechselrichters (3) und dem Massebezugspotential angeordnet ist und der über ihren Wicklungssinn synchronisierte Sekundärwicklungen (S1, S2) besitzt, deren Anschlüsse jeweils einen der paarweise ausgebildeten Ausgänge der schaltbaren Spannungsquelle bilden, denen je eine der Wendeln (E1 bzw. E2) der Leuchtstofflampe (FL) parallel geschaltet ist.Circuit arrangement according to Claim 1, characterized in that the switchable voltage source comprises a transformer (TR), the primary winding (PR) of which is arranged between the output of the inverter (3) and the ground reference potential and which has secondary windings (S1, S2) synchronized via its winding direction , whose connections each form one of the paired outputs of the switchable voltage source, to which one of the filaments (E1 or E2) of the fluorescent lamp (FL) is connected in parallel. Schaltungsanordnung nach Anspruch 2, dadurch gekennzeichnet, daß in Serie zu der Primärwicklung (PR) des Transformators (TR) liegend ein zeitabhängig gesteuertes Schaltglied (HS, 4) zum Aktivieren der schaltbaren Spannungsquelle während der vorgegebenen Vorheizzeit vorgesehen ist.Circuit arrangement according to claim 2, characterized in that in series with the primary winding (PR) of the transformer (TR) a time-dependent controlled switching element (HS, 4) is provided for activating the switchable voltage source during the predetermined preheating time. Schaltungsanordnung nach Anspruch 3, dadurch gekennzeichnet, daß das zeitabhängig gesteuerte Schaltglied (HS, 4) als Kaltleiter ausgebildet ist.Circuit arrangement according to Claim 3, characterized in that the switching element (HS, 4) which is controlled as a function of time is designed as a PTC thermistor. Schaltungsanordnung nach Anspruch 3, dadurch gekennzeichnet, daß das zeitabhängige Schaltglied (HS, 4) einen Halbleiterschalter (HS) besitzt, dessen Schaltstrecke in Serie zu der Primärwicklung (PR) des Transformators (TR) liegend angeordnet ist und an dessen Steuereingang der Ausgang eines Zeitschaltgliedes (4) zum Aktivieren des Halbleiterschalters (HS) während der vorgegebenen Vorheizzeit angeschlossen ist.Circuit arrangement according to claim 3, characterized in that the time-dependent switching element (HS, 4) has a semiconductor switch (HS), the switching path of which is arranged in series with the primary winding (PR) of the transformer (TR) and at the control input of which the output of a time switching element (4) for activating the semiconductor switch (HS) during the specified preheating time. Schaltungsanordnung nach einem der Ansprüche 2 bis 5, dadurch gekennzeichnet, daß zu den Sekundärwicklungen (S1, S2) des Transformators (TR) in Reihe liegend jeweils eine Gleichrichterdiode (DW1 bzw.DW2) vorgesehen ist.Circuit arrangement according to one of Claims 2 to 5, characterized in that a rectifier diode (DW1 or DW2) is provided in series with the secondary windings (S1, S2) of the transformer (TR). Schaltungsanordnung nach einem der Ansprüche 2 bis 6, dadurch gekennzeichnet, daß parallel zu der Primärwicklung (PR) des Transformators (TR) eine Freilaufdiode (FD) angeordnet ist.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)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19520999 1995-06-08
DE19520999A DE19520999A1 (en) 1995-06-08 1995-06-08 Circuit arrangement for filament preheating of fluorescent lamps

Publications (2)

Publication Number Publication Date
EP0748146A1 true EP0748146A1 (en) 1996-12-11
EP0748146B1 EP0748146B1 (en) 2001-08-29

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US (1) US5854538A (en)
EP (1) EP0748146B1 (en)
KR (1) KR100448290B1 (en)
AT (1) ATE205042T1 (en)
CA (1) CA2178443C (en)
DE (2) DE19520999A1 (en)
HK (1) HK1005304A1 (en)
SG (1) SG64387A1 (en)
TW (1) TW415158B (en)

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US6555970B2 (en) 2001-01-22 2003-04-29 Patent-Treuhand-Gesellschaft Fur Elektrische Glucklampen Mbh Ballast for gas discharge lamps with shutdown of the filament heating
EP1675442A2 (en) * 2004-12-27 2006-06-28 Osram-Sylvania Inc. Ballast with filament heating control circuit
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CN101888735A (en) * 2009-05-12 2010-11-17 奥斯兰姆有限公司 Drive the circuit arrangement and the corresponding method of low-pressure gaseous discharge lamp
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Cited By (17)

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EP0707438A3 (en) * 1994-10-13 1997-07-30 Tridonic Bauelemente Ballast for at least one discharge lamp
US6366031B2 (en) 1999-05-25 2002-04-02 Tridonic Bauelemente Gmbh Electronic ballast for at least one low-pressure discharge lamp
US6433490B2 (en) 1999-05-25 2002-08-13 Tridonic Bauelemente Gmbh Electronic ballast for at least one low-pressure discharge lamp
US6555970B2 (en) 2001-01-22 2003-04-29 Patent-Treuhand-Gesellschaft Fur Elektrische Glucklampen Mbh Ballast for gas discharge lamps with shutdown of the filament heating
DE10127135B4 (en) * 2001-06-02 2006-07-06 Insta Elektro Gmbh Dimmable electronic ballast
DE10304544B4 (en) * 2003-02-04 2006-10-12 Hep Tech Co.Ltd. Electronic ballast
US7728528B2 (en) 2004-11-29 2010-06-01 Century Concept Ltd Electronic ballast with preheating and dimming control
EP1675442A3 (en) * 2004-12-27 2007-12-19 Osram-Sylvania Inc. Ballast with filament heating control circuit
EP1675442A2 (en) * 2004-12-27 2006-06-28 Osram-Sylvania Inc. Ballast with filament heating control circuit
WO2007051751A1 (en) * 2005-11-03 2007-05-10 Osram Gesellschaft mit beschränkter Haftung Drive circuit for a switchable heating transformer of an electronic ballast and corresponding method
US7723920B2 (en) 2005-11-03 2010-05-25 Osram Gesellschaft Mit Beschraenkter Haftung Drive circuit for a switchable heating transformer of an electronic ballast and corresponding method
CN101888735A (en) * 2009-05-12 2010-11-17 奥斯兰姆有限公司 Drive the circuit arrangement and the corresponding method of low-pressure gaseous discharge lamp
EP2252133A2 (en) 2009-05-12 2010-11-17 Osram Gesellschaft mit beschränkter Haftung Switching assembly for operating a low pressure gas discharge lamp and method for same
DE102009020849A1 (en) 2009-05-12 2010-11-18 Osram Gesellschaft mit beschränkter Haftung Circuit arrangement for operating a low-pressure gas discharge lamp and corresponding method
CN101888735B (en) * 2009-05-12 2014-06-11 奥斯兰姆有限公司 Circuit arrangement for operating a low-pressure gas discharge lamp and corresponding method
WO2010150151A3 (en) * 2009-06-24 2011-03-24 Koninklijke Philips Electronics N.V. Electronic ballast for a fluorescent lamp
WO2011061053A1 (en) * 2009-11-17 2011-05-26 Osram Gesellschaft mit beschränkter Haftung Electronic ballast and method for operating at least one discharge lamp

Also Published As

Publication number Publication date
TW415158B (en) 2000-12-11
DE59607566D1 (en) 2001-10-04
KR970004974A (en) 1997-01-29
DE19520999A1 (en) 1996-12-12
ATE205042T1 (en) 2001-09-15
KR100448290B1 (en) 2004-11-26
US5854538A (en) 1998-12-29
SG64387A1 (en) 1999-04-27
HK1005304A1 (en) 1998-12-31
CA2178443A1 (en) 1996-12-09
EP0748146B1 (en) 2001-08-29
CA2178443C (en) 2005-04-05

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