EP0589081B1 - Circuit for operating a fluorescent lamp with a current measuring circuit - Google Patents

Circuit for operating a fluorescent lamp with a current measuring circuit Download PDF

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Publication number
EP0589081B1
EP0589081B1 EP92116334A EP92116334A EP0589081B1 EP 0589081 B1 EP0589081 B1 EP 0589081B1 EP 92116334 A EP92116334 A EP 92116334A EP 92116334 A EP92116334 A EP 92116334A EP 0589081 B1 EP0589081 B1 EP 0589081B1
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EP
European Patent Office
Prior art keywords
lamp
cathode
current
coil
electrical circuit
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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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EP92116334A
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German (de)
French (fr)
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EP0589081A1 (en
Inventor
Felix Tobler
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Knobel AG Lichttechnische Komponenten
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Knobel AG Lichttechnische Komponenten
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Priority to DE59207908T priority Critical patent/DE59207908D1/en
Priority to EP92116334A priority patent/EP0589081B1/en
Priority to AT92116334T priority patent/ATE147926T1/en
Priority to US08/125,167 priority patent/US5504399A/en
Publication of EP0589081A1 publication Critical patent/EP0589081A1/en
Application granted granted Critical
Publication of EP0589081B1 publication Critical patent/EP0589081B1/en
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • 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
    • Y10S315/02—High frequency starting operation for fluorescent lamp

Definitions

  • the invention relates to a circuit arrangement with the features of the preamble of claim 1, as is known for example from EP 0 490 330 A1.
  • a circuit arrangement is known from DE 37 09 004 A1, in which the brightness of a fluorescent lamp is set by measuring and regulating the lamp current.
  • the lamp current is measured by means of a differential current transformer and its actual value is forwarded to a circuit part in order to regulate the lamp current to a preselected setpoint.
  • the windings of the differential current transformer must be manufactured very precisely, which adversely affects the costs of the circuit arrangement.
  • the object of the invention is therefore to create a more cost-effective circuit arrangement in which the lamp current can be measured over a wide dynamic range.
  • the known circuit arrangement shown in Figure 1 receives a fluorescent lamp LL, the lamp cathodes LK1, LK2 with a coupling capacitor C1, with a resonance capacitor C2, with two windings of the differential current transformer TR2.1, TR2.2, with a resonance choke L1 and with a winding of a feedback transformer Tr1.1 form a series resonance circuit which is connected between a pole of a supply voltage Ub and the output of an inverter operating at this supply voltage.
  • the inverter here consists of two power transistors, which switch the one pole of the series resonance circuit between the poles of the supply voltage Ub with a frequency close to the natural frequency of the series resonance circuit via two control circuits A1, A2 and two windings of the feedback transformer TR1.2, TR1.3.
  • a main circuit HS ensures that the fluorescent lamp is fed correctly after the circuit arrangement has been started up, the lamp cathodes being preheated first, then the fluorescent lamp being ignited and the lamp current being regulated to a predetermined setpoint I should .
  • the actual value of the lamp current I ist is via a third winding Transfer Tr2.3 of the residual current transformer to the main circuit HS.
  • the setpoint I want the lamp current is passed to a set point transmitter Tr3 to the main circuit HS.
  • the lamp cathodes must be continuously heated so that the fluorescent lamp does not age prematurely.
  • the lamp cathodes LK1, LK2 are heated by the cathode heating current I loom , which flows through the resonance capacitor C2 and, in the case of a strongly dimmed lamp, is considerably larger than the lamp current I L. If the total current of a residual current transformer is much larger than the differential current, very high demands are placed on the accuracy of the first two windings Tr2.1, Tr2.2 of the residual current transformer, so that the residual current transformer can work without errors in a larger dynamic range.
  • FIG 2 an embodiment of the circuit arrangement according to the invention is shown schematically.
  • the series resonance circuit is formed with a first winding of a feedback transformer Tr1.1, with a resonance choke L1, with a resonance capacitor C2 and with a first winding of an isolating transformer Tr4.1 and between the output of an inverter working on a supply voltage Ub and a pole of the supply voltage Ub switched.
  • the second winding of the isolating transformer Tr4.2 is connected in parallel with the second lamp cathode LK2.
  • the resulting voltage across the resistor R1 is thus the actual value of the lamp current I is proportional and can allow the main circuit HS which is also provided for regulating the lamp current are supplied. It is obvious to the person skilled in the art that such a solution for measuring the lamp current is considerably less expensive than measuring with a differential current transformer.
  • FIG. Compared to the circuit in FIG. 2, the lamp current is conducted in one half-wave via a series circuit of a first diode D3 with a resistor R1 and in the other half-wave via a second diode D4. This makes it possible to supply the main circuit HS with the already rectified value of the lamp current.
  • Another possibility is to use a simple rectifier / low-pass circuit GT to transmit the value of the lamp cathode voltage Vk to the main circuit.
  • the lamp cathode voltage Vk corresponds to the information about the state of the lamp cathodes in the preheating mode, in normal lamp mode or in the dimming mode of the fluorescent lamp.
  • the lamp cathode voltage Vk is one of the important parameters which, according to the regulations of the lamp manufacturers, must be observed within certain limits so that the service life of the fluorescent lamps is not impaired.
  • FIG. 4 Another embodiment of the circuit arrangement according to the invention is partially shown in FIG. 4, in which the cathode heating current I heating can be detected with the aid of a resistor R2 connected in series with the first winding of the isolating transformer Tr4.1 and a simple rectifier / low-pass circuit GT.
  • the detection of the cathode heating current can be used in preheating mode for optimal setting of the preheating current for the lamp cathodes, in ignition mode for measuring the level of the ignition voltage at a known oscillation frequency and with a known value of the resonance capacitor C2 and in lamp or dimming mode for monitoring the maximum cathode heating current.
  • FIG 5 another embodiment of the invention is partially shown, in which the possibility of regulating the heating power in the lamp cathodes LK1, LK2 by means of a third winding of the isolating transformer Tr4.3 connected in parallel with the first lamp cathode LK1 and one with a control circuit SS operated switch S1, which is connected in parallel to the first winding of the isolating transformer Tr4.1.
  • the switch S1 can be short-circuited periodically when a preselected threshold value is reached and thus prevent further heating of the lamp cathodes in the respective half-period. In this way, the power loss of the circuit arrangement can be minimized and the respective regulations of the lamp manufacturers can be easily complied with.
  • the control of the switch S1 can also be carried out periodically via a threshold value of the cathode heating current I heating , so that the lamp cathodes LK1, LK2 can be heated independently of the size of the total resonance current of the series resonance circuit I res and its frequency.
  • FIG. 6 schematically shows an embodiment of the circuit arrangement according to the invention with a plurality of fluorescent lamps LL1, LL2, LL3 in a shortened form.
  • a switching device U1 can be used to make the same circuit arrangement switchable to different lamp types with different lamp powers and lamp currents.
  • various parallel resistors RP1, RP2, RP3, RP4 are switched on and thus the respective fluorescent lamp is regulated to the lamp current associated with it.
  • Such a switching device can be provided in the circuit for specifying the setpoint of the lamp current instead of in the measurement circuit of the lamp current.

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  • Circuit Arrangements For Discharge Lamps (AREA)
  • Measurement Of Current Or Voltage (AREA)

Abstract

A series-resonant circuit having a first winding of a feedback transformer (Tr1.1), having a resonance inductor (L1), having a coupling capacitor (C1), having a first lamp cathode (LK1), having a resonance capacitor (C2) and having a first winding of an isolating transformer (Tr4.1) is formed in the circuit arrangement for supplying a fluorescent lamp (LL) and is connected between the output of an invertor, which operates on a supply voltage (Ub), and one pole of the supply voltage (Ub). The second coupling of the isolating transformer (Tr4.2) is connected in parallel with the second lamp cathode (LK2). As a result of this circuitry of the second lamp cathode (LK2), the same currents Iheat flow through the two lamp cathodes (LK1, LK2) with the same number of windings of the windings of the isolating transformer (Tr4.1, Tr4.2), and in consequence the same heating of the two lamp cathodes (LK1, LK2) is achieved. The parallel circuit formed by the second lamp cathode (LK2) and the second winding of the isolating transformer (Tr4.2) is connected to one terminal of the supply voltage Ub, via a resistor (R1), at a potential. The lamp current IL flows through the resistor (R1). The voltage dropped across the resistor (R1) is thus proportional to the actual value of the lamp current Iact and can thus be supplied to the main circuit (HS), which is also provided for regulating the lamp current. <IMAGE>

Description

Die Erfindung bezieht sich auf eine Schaltungsanordnung mit den Merkmalen des Oberbegriffes des Anspruchs 1, wie sie beispielsweise aus der EP 0 490 330 A1 bekannt ist.The invention relates to a circuit arrangement with the features of the preamble of claim 1, as is known for example from EP 0 490 330 A1.

Aus der DE 37 09 004 A1 ist eine Schaltungsanordnung bekannt, bei welcher die Helligkeit einer Leuchtstofflampe über die Messung und Regelung des Lampenstromes eingestellt wird. Dabei wird der Lampenstrom mittels eines Differenzstromwandlers gemessen und sein Istwert an einen Schaltungsteil weitergeleitet, um den Lampenstrom auf einen vorgewählten Sollwert zu regeln. Bei einer Regelung des Lampenstromes über einen grösseren Dynamikbereich müssen die Wicklungen des Differenzstromwandlers sehr genau hergestellt werden, was die Kosten der Schaltungsanordnung ungünstig beeinflusst.A circuit arrangement is known from DE 37 09 004 A1, in which the brightness of a fluorescent lamp is set by measuring and regulating the lamp current. The lamp current is measured by means of a differential current transformer and its actual value is forwarded to a circuit part in order to regulate the lamp current to a preselected setpoint. When regulating the lamp current over a larger dynamic range, the windings of the differential current transformer must be manufactured very precisely, which adversely affects the costs of the circuit arrangement.

Die Aufgabe der Erfindung ist es deshalb, eine kostengünstigere Schaltungsanordnung zu schaffen, bei welcher die Messung des Lampenstromes über einen grossen Dynamikbereich erfolgen kann.The object of the invention is therefore to create a more cost-effective circuit arrangement in which the lamp current can be measured over a wide dynamic range.

Diese Aufgabe wird durch die Merkmale des kennzeichnenden Teils des Anspruchs 1 gelöst.This object is achieved by the features of the characterizing part of claim 1.

Im folgenden wird die Erfindung anhand der Zeichnungen näher erläutert. Es zeigen:

  • Figur 1 eine schematische Darstellung der aus DE 3 709 004 A1 bekannten Schaltungsanordnung zur Speisung einer Leuchtstofflampe,
  • Figur 2 eine schematische Darstellung einer möglichen Ausführung der Schaltungsanordnung gemäss der Erfindung,
  • Figur 3 eine andere Ausführungsform der Schaltungsanordnung gemäss der Erfindung mit Einweggleichrichtung des Lampenstromes und Messung der Kathodenspannung,
  • Figur 4 eine andere Ausführungsform der Schaltungsanordnung gemäss der Erfindung mit Messung des Kathodenheizstromes,
  • Figur 5 eine andere Ausführungsform der Schaltungsanordnung gemäss der Erfindung mit einer Schaltung zur Regelung der Kathodenheizung, und
  • Figur 6 eine andere Ausführungsform der Schaltungsanordnung gemäss der Erfindung mit mehreren Leuchtstofflampen und einer Umschaltvorrichtung zur Umschaltung auf eine bestimmte Art der Leuchtstofflampen.
The invention is explained in more detail below with reference to the drawings. Show it:
  • 1 shows a schematic representation of the circuit arrangement known from DE 3 709 004 A1 for feeding a fluorescent lamp,
  • FIG. 2 shows a schematic illustration of a possible embodiment of the circuit arrangement according to the invention,
  • 3 shows another embodiment of the circuit arrangement according to the invention with one-way rectification of the lamp current and measurement of the cathode voltage,
  • FIG. 4 shows another embodiment of the circuit arrangement according to the invention with measurement of the cathode heating current,
  • Figure 5 shows another embodiment of the circuit arrangement according to the invention with a circuit for regulating the cathode heating, and
  • Figure 6 shows another embodiment of the circuit arrangement according to the invention with a plurality of fluorescent lamps and a switching device for switching to a specific type of fluorescent lamps.

Die in Figur 1 dargestellte bekannte Schaltungsanordnung erhält eine Leuchtstofflampe LL, deren Lampenkathoden LK1, LK2 mit einem Koppelkondensator C1, mit einem Resonanzkondensator C2, mit zwei Wicklungen des Differenzstromwandlers TR2.1, TR2.2, mit einer Resonanzdrossel L1 und mit einer Wicklung eines Rückkopplungstransformators Tr1.1 einen Serieresonanzkreis bilden, der zwischen einem Pol einer Versorgungsspannung Ub und dem Ausgang eines an dieser Versorgungsspannung arbeitenden Wechselrichters angeschlossen ist. Der Wechselrichter besteht hier aus zwei Leistungstransistoren, welche über zwei Ansteuerungsschaltungen A1, A2 und zwei Wicklungen des Rückkopplungstransformators TR1.2, TR1.3 den einen Pol des Serieresonanzkreises zwischen den Polen der Versorgungsspannung Ub mit einer der Eigenfrequenz des Serieresonanzkreises naheliegenden Frequenz schalten. Durch die Verschiebung der Schaltfrequenz des Wechselrichters gegenüber der Eigenfrequenz des Resonanzkreises werden verschiedene Betriebsarten der Leuchtstofflampen, wie Vorheizen der Lampenkathoden, Zünden, Normalbetrieb und Dimmbetrieb eingestellt. Eine Hauptschaltung HS sorgt für den richtigen Ablauf der Speisung der Leuchtstofflampe nach der Inbetriebnahme der Schaltungsanordnung, wobei die Lampenkathoden zuerst vorgeheizt werden, danach die Leuchtstofflampe gezündet und der Lampenstrom auf einen vorgegebenen Sollwert Isoll geregelt wird. Der Istwert des Lampenstromes Iist wird über eine dritte Wicklung Tr2.3 des Differenzstromwandlers an die Hauptschaltung HS übertragen. Der Sollwert Isoll des Lampenstromes wird mit einem Sollwertübertrager Tr3 an die Hauptschaltung HS weitergegeben. Wenn die Leuchtstofflampe LL in einem stark gedimmten Zustand, z.B. bei 1 % des nominellen Lampenstromes betrieben werden soll, müssen die Lampenkathoden ständig geheizt werden, damit es nicht zu einer vorzeitigen Alterung der Leuchtstofflampe kommt. Die Heizung der Lampenkathoden LK1, LK2 erfolgt durch den Kathodenheizstrom Iheiz, der durch den Resonanzkondensator C2 fliesst und bei einer stark gedimmten Lampe wesentlicht grösser als der Lampenstrom IL ist. Wenn bei einem Differenzstromwandsler der Gesamtstrom viel grösser als der Differenzstrom ist, werden sehr hohe Anforderungen an die Genauigkeit der zwei ersten Wicklungen Tr2.1, Tr2.2 des Differenzstromwandlers gestellt, damit der Differenzstromwandler in einem grösseren Dynamikbereich fehlerfrei arbeiten kann.The known circuit arrangement shown in Figure 1 receives a fluorescent lamp LL, the lamp cathodes LK1, LK2 with a coupling capacitor C1, with a resonance capacitor C2, with two windings of the differential current transformer TR2.1, TR2.2, with a resonance choke L1 and with a winding of a feedback transformer Tr1.1 form a series resonance circuit which is connected between a pole of a supply voltage Ub and the output of an inverter operating at this supply voltage. The inverter here consists of two power transistors, which switch the one pole of the series resonance circuit between the poles of the supply voltage Ub with a frequency close to the natural frequency of the series resonance circuit via two control circuits A1, A2 and two windings of the feedback transformer TR1.2, TR1.3. By shifting the switching frequency of the inverter with respect to the natural frequency of the resonance circuit, different operating modes of the fluorescent lamps, such as preheating the lamp cathodes, ignition, normal operation and dimming operation, are set. A main circuit HS ensures that the fluorescent lamp is fed correctly after the circuit arrangement has been started up, the lamp cathodes being preheated first, then the fluorescent lamp being ignited and the lamp current being regulated to a predetermined setpoint I should . The actual value of the lamp current I ist is via a third winding Transfer Tr2.3 of the residual current transformer to the main circuit HS. The setpoint I want the lamp current is passed to a set point transmitter Tr3 to the main circuit HS. If the fluorescent lamp LL is to be operated in a strongly dimmed state, for example at 1% of the nominal lamp current, the lamp cathodes must be continuously heated so that the fluorescent lamp does not age prematurely. The lamp cathodes LK1, LK2 are heated by the cathode heating current I heiz , which flows through the resonance capacitor C2 and, in the case of a strongly dimmed lamp, is considerably larger than the lamp current I L. If the total current of a residual current transformer is much larger than the differential current, very high demands are placed on the accuracy of the first two windings Tr2.1, Tr2.2 of the residual current transformer, so that the residual current transformer can work without errors in a larger dynamic range.

In Figur 2 ist eine Ausführungsform der Schaltungsanordnung gemäss der Erfindung schematisch dargestellt. Dabei wird der Serieresonanzkreis mit einer ersten Wicklung eines Rückkopplungstransformators Tr1.1, mit einer Resonanzdrossel L1, mit einem Resonanzkondensator C2 und mit einer ersten Wicklung eines Trenntransformators Tr4.1 gebildet und zwischen den Ausgang eines an einer Versorgungsspannung Ub arbeitenden Wechselrichters und einen Pol der Versorgungsspannung Ub geschaltet. Die zweite Wicklung des Trenntransformators Tr4.2 ist parallel mit der zweiten Lampenkathode LK2 geschaltet. Mit dieser Beschaltung der zweiten Lampenkathode LK2 werden bei gleichen Wicklungszahlen der Wicklungen des Trenntransformators Tr4.1, Tr4.2 durch die beiden Lampenkathoden LK1, LK2 die gleichen Ströme Iheiz fliessen und dadurch wird die gleiche Beheizung der beiden Lampenkatho5 den LK1, LK2 erreicht. Die Parallelschaltung der zweiten Lampenkathode LK2 mit der zweiten Wicklung des Trenntransformators Tr4.2 ist an einem Potential über einen Widerstand R1 mit einem Pol der Versorgungsspannung Ub verbunden. Durch den Widerstand R1 fliesst der Lampenstrom IL. Die über dem Widerstand R1 entstehende Spannung ist somit dem Istwert des Lampenstromes Iist proportional und kann damit der Hauptschaltung HS, die auch zur Regelung des Lampenstromes vorgesehen ist, zugeführt werden. Für den Fachmann ist es ersichtlich, dass eine solche Lösung zur Messung des Lampenstromes wesentlich kostengünstiger als die Messung mit einem Diferenzstromwandler ist.In Figure 2, an embodiment of the circuit arrangement according to the invention is shown schematically. The series resonance circuit is formed with a first winding of a feedback transformer Tr1.1, with a resonance choke L1, with a resonance capacitor C2 and with a first winding of an isolating transformer Tr4.1 and between the output of an inverter working on a supply voltage Ub and a pole of the supply voltage Ub switched. The second winding of the isolating transformer Tr4.2 is connected in parallel with the second lamp cathode LK2. With this wiring of the second lamp cathode LK2, the same currents I heat flow through the two lamp cathodes LK1, LK2 with the same number of windings of the windings of the isolating transformer Tr4.1, Tr4.2 , and thereby the same heating of the two lamp cathodes 5, LK1, LK2 is achieved. The parallel connection of the second lamp cathode LK2 with the second winding of the isolating transformer Tr4.2 is at a potential above one Resistor R1 connected to a pole of the supply voltage Ub. The lamp current I L flows through the resistor R1. The resulting voltage across the resistor R1 is thus the actual value of the lamp current I is proportional and can allow the main circuit HS which is also provided for regulating the lamp current are supplied. It is obvious to the person skilled in the art that such a solution for measuring the lamp current is considerably less expensive than measuring with a differential current transformer.

In Figur 3 ist eine andere Ausführungsform der erfindungsgemässen Schaltungsanordnung gezeichnet. Dabei wird gegenüber der Schaltung in Figur 2 der Lampenstrom in einer Halbwelle über eine Serieschaltung einer ersten Diode D3 mit einem Widerstand R1 und in der anderen Halbwelle über eine zweite Diode D4 geleitet. Damit ist es möglich, der Hauptschaltung HS den bereits gleichgerichteten Wert des Lampenstromes zuzuführen. Eine weitere Möglichkeit ist, mit Hilfe einer einfachen Gleichrichter-/Tiefpasschaltung GT den Wert der Lampenkathodenspannung Vk der Hauptschaltung zu übermitteln. Die Lampenkathodenspannung Vk entspricht der Information über den Zustand der Lampenkathoden im Vorheizbetrieb, im normalen Lampenbetrieb oder im Dimmbetrieb der Leuchtstofflampe. Die Lampenkathodenspannung Vk ist wie der Vorheizstrom, der Lampenstrom und der Kathodenheizstrom einer der wichtigen Parameter, die gemäss der Vorschriften der Lampenhersteller in bestimmten Grenzen eingehalten werden müssen, damit die Lebensdauer der Leuchtstofflampen nicht beeinträchtigt wird.Another embodiment of the circuit arrangement according to the invention is shown in FIG. Compared to the circuit in FIG. 2, the lamp current is conducted in one half-wave via a series circuit of a first diode D3 with a resistor R1 and in the other half-wave via a second diode D4. This makes it possible to supply the main circuit HS with the already rectified value of the lamp current. Another possibility is to use a simple rectifier / low-pass circuit GT to transmit the value of the lamp cathode voltage Vk to the main circuit. The lamp cathode voltage Vk corresponds to the information about the state of the lamp cathodes in the preheating mode, in normal lamp mode or in the dimming mode of the fluorescent lamp. The lamp cathode voltage Vk, like the preheating current, the lamp current and the cathode heating current, is one of the important parameters which, according to the regulations of the lamp manufacturers, must be observed within certain limits so that the service life of the fluorescent lamps is not impaired.

In Figur 4 ist eine andere Ausführungsform der erfindungsgemässen Schaltungsanordnung teilweise dargestellt, bei welcher der Kathodenheizstsrom Iheiz mit Hilfe eines zu der ersten Wicklung des Trenntransformators Tr4.1 in Serie geschalteten Widerstandes R2 und einer einfachen Gleichrichter-/Tiefpasschaltung GT erfasst werden kann. Die Erfassung des Kathodenheizstromes kann im Vorheizbetrieb zur optimalen Einstellung des Vorheizstromes für die Lampenkathoden, im Zündbetrieb für die Messung der Höhe der Zündspannung bei bekannter Schwingfrequenz und bei bekanntem Wert des Resonanzkondensators C2 und im Lampen- oder Dimmbetrieb zur Ueberwachung des maximalen Kathodenheizstromes benützt werden.Another embodiment of the circuit arrangement according to the invention is partially shown in FIG. 4, in which the cathode heating current I heating can be detected with the aid of a resistor R2 connected in series with the first winding of the isolating transformer Tr4.1 and a simple rectifier / low-pass circuit GT. The detection of the cathode heating current can be used in preheating mode for optimal setting of the preheating current for the lamp cathodes, in ignition mode for measuring the level of the ignition voltage at a known oscillation frequency and with a known value of the resonance capacitor C2 and in lamp or dimming mode for monitoring the maximum cathode heating current.

In Figur 5 ist eine weitere Ausführungsform der Erfindung teilweise dargestellt, bei welcher die Möglichkeit zur Regelung der Heizleistung in den Lampenkathoden LK1, LK2 mit Hilfe einer parallel zu der ersten Lampenkathode LK1 geschalteten, dritten Wicklung des Trenntransformators Tr4.3 und eines mit einer Steuerschaltung SS betriebenen Schalters S1 besteht, der parallel zu der ersten Wicklung des Trenntransformators Tr4.1 angeschlossen ist. Der Schalter S1 kann z.B. in Abhängigkeit der über ihn liegenden Lampenkathodenspannung periodisch beim Erreichen eines vorgewählten Schwellwertes kurzgeschlossen werden und damit die weitere Beheizung der Lampenkathoden in der jeweiligen Halbperiode verhindern. Dadurch kann man die Verlustleistung der Schaltungsanordnung minimalisieren und die jeweiligen Vorschriften der Lampenhersteller problemlos einhalten. Die Ansteuerung des Schalters S1 kann auch über einen Schwellwert des Kathodenheizstromes Iheiz oder periodisch erfolgen, so dass die Beheizung der Lampenkathoden LK1, LK2 unabhängig von der Grösse des gesamten Resonanzstromes des Serieresonanzkreises Ires und seiner Frequenz erfolgen kann.In Figure 5, another embodiment of the invention is partially shown, in which the possibility of regulating the heating power in the lamp cathodes LK1, LK2 by means of a third winding of the isolating transformer Tr4.3 connected in parallel with the first lamp cathode LK1 and one with a control circuit SS operated switch S1, which is connected in parallel to the first winding of the isolating transformer Tr4.1. Depending on the lamp cathode voltage above it, the switch S1 can be short-circuited periodically when a preselected threshold value is reached and thus prevent further heating of the lamp cathodes in the respective half-period. In this way, the power loss of the circuit arrangement can be minimized and the respective regulations of the lamp manufacturers can be easily complied with. The control of the switch S1 can also be carried out periodically via a threshold value of the cathode heating current I heating , so that the lamp cathodes LK1, LK2 can be heated independently of the size of the total resonance current of the series resonance circuit I res and its frequency.

In Figur 6 ist eine Ausführungsform der erfindungsgemässen Schaltungsanordnung mit mehreren Leuchtstofflampen LL1, LL2, LL3 schematisch in einer verkürzten Form dargestellt. Dabei sind die jeweils benachbarten Lampenkathoden LK3; LK4; LK5; LK6 in Serie geschaltet, jede solche Serieschaltung ist parallel zu einer zweiten Wicklung eines jeweils zusätzlichen Trenntransformators Tr5.2, Tr6.2 und die jeweils zugehörige erste Wicklung des Trenntransformators Tr5.1, Tr6.1 ist in Serie zu dem Serieresonanzkreis geschaltet. Bei der jeweils gleichen Wicklungszahl der ersten und der zweiten Wicklungen der Trenntransformatoren sind alle Lampenkathodenströme gleich dem Kathodenheizstrom Iheiz und alle Lampenkathoden gleichmässig beheizt.FIG. 6 schematically shows an embodiment of the circuit arrangement according to the invention with a plurality of fluorescent lamps LL1, LL2, LL3 in a shortened form. The adjacent lamp cathodes LK3; LK4; LK5; LK6 connected in series, each such series connection is parallel to a second winding of an additional isolating transformer Tr5.2, Tr6.2 and the associated first winding of the isolating transformer Tr5.1, Tr6.1 is in series with that Series resonance circuit switched. With the same number of windings of the first and the second windings of the isolating transformers, all lamp cathode currents are equal to the cathode heating current I heating and all lamp cathodes are heated uniformly.

Eine Umschaltvorrichtung U1 kann dazu verwendet werden, die gleiche Schaltungsanordnung umschaltbar auf verschiedene Lampentypen mit unterschiedlichen Lampenleistungen und Lampenströmen zu gestalten. Dabei werden z.B. für die verschiedenen Lampentypen zum Messwiderstand R1 verschiedene Parallelwiderstände RP1, RP2, RP3, RP4 zugeschaltet und damit die jeweilige Leuchtstofflampe auf den ihr zugehörigen Lampenstrom geregelt. Eine solche Umschaltvorrichtung kann anstatt in der Messchaltung des Lampenstromes in der Schaltung für die Sollwertvorgabe des Lampenstromes vorgesehen werden.A switching device U1 can be used to make the same circuit arrangement switchable to different lamp types with different lamp powers and lamp currents. Here, e.g. for the different lamp types to the measuring resistor R1, various parallel resistors RP1, RP2, RP3, RP4 are switched on and thus the respective fluorescent lamp is regulated to the lamp current associated with it. Such a switching device can be provided in the circuit for specifying the setpoint of the lamp current instead of in the measurement circuit of the lamp current.

Claims (11)

  1. Electrical circuit with an inverted rectifier connected to a current source, an oscillating circuit (L1, C1) for feeding at least one fluorescent lamp with two lamp cathodes (LK1, LK2), and with a device for measuring the lamp current, characterized in that the oscillating circuit (L1, C1) which comprises the first lamp cathode (LK1) is connected between the outlet of the inverted rectifier and one pole of the current source, that the second lamp cathode (LK2) is coupled via a separating transformer (TR4.2) with the oscillating circuit, and that the device for measuring the lamp current is connected between the second lamp cathode (LK2) and the current source.
  2. Electrical circuit according to claim 1, characterized in that the oscillating circuit is a serial oscillating circuit with a coupling condenser (C1), a resonant condenser (C2), a resonant inductor (L1) and a first coil of a feedback transformer (TR1.1), that a first coil of the separating transformer (TR4.1) is connected in series in the serial oscillating circuit, and that the second coil of the separating transformer (TR4.2) is connected in parallel with the second lamp cathode (LK2).
  3. Electrical circuit according to claim 1 or 2, characterized in that the device for measuring the lamp current comprises a measuring resistance (R1).
  4. Electrical circuit according to claim 1 or 2, characterized in that the device for measuring the lamp current comprises a serial arrangement of a measuring resistance (R1) and a diode (D3), and that a second diode (D4) is connected in parallel to this serial arrangement in such a way that a half-wave of the lamp current flows through the serial arrangement (R1;D3) and the second half-wave through the second diode (D4).
  5. Electrical circuit according to one of claims 1 to 4, characterized by a measuring circuit connected in parallel to the first coil of the separating transformer (TR4.1) for monitoring the tension of the lamp cathode.
  6. Electrical circuit according to one of claims 1 to 5, characterized by a resistance (R2) connected in series to the first coil of the separating transformer (TR4.1) in order to measure the heating current of the cathode.
  7. Electrical circuit according to one of claims 1 to 6, characterized by a third coil of the separating transformer (TR4.3) connected in parallel to the first lamp cathode (LK1), by a switch (S1) connected in parallel to the first coil of the separating transformer (TR4.1), and by a command circuit for commanding this switch (S1).
  8. Electrical circuit according to claim 7, characterized in that the switch (S1) comprises a semiconductor switching element, and that the command circuit reacts to a threshold of the tension of the lamp cathode or to a threshold of the cathode heating current.
  9. Electrical circuit according to one of claims 1 to 8 for operating at least two fluorescent lamps connected in series, characterized in that the mutually neighboring lamp cathodes (LK3; LK4; LK5; LK6) of the fluorescent lamps are arranged in series, that each such serial arrangement is connected in parallel to a second coil of a corresponding, additional separating transformer (TR5.2, TR6.2) and that each corresponding first coil of the separating transformer (TR5.1), TR6.1) is connected in series to the oscillating circuit.
  10. Electrical circuit according to one of claims 1 to 9, characterized by a selector (U1) for selecting a predetermined lamp current.
  11. Electrical circuit according to claim 10, characterized in that the selector (U1) acts on the rated or the actual value of the lamp current.
EP92116334A 1992-09-24 1992-09-24 Circuit for operating a fluorescent lamp with a current measuring circuit Expired - Lifetime EP0589081B1 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
DE59207908T DE59207908D1 (en) 1992-09-24 1992-09-24 Circuit arrangement for operating a fluorescent lamp and for measuring the lamp current
EP92116334A EP0589081B1 (en) 1992-09-24 1992-09-24 Circuit for operating a fluorescent lamp with a current measuring circuit
AT92116334T ATE147926T1 (en) 1992-09-24 1992-09-24 CIRCUIT ARRANGEMENT FOR OPERATING A FLUORESCENT LAMP AND FOR MEASURING THE LAMP CURRENT
US08/125,167 US5504399A (en) 1992-09-24 1993-09-23 Electrical circuit for operating a fluorescent lamp and for measuring the lamp current

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP92116334A EP0589081B1 (en) 1992-09-24 1992-09-24 Circuit for operating a fluorescent lamp with a current measuring circuit

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EP0589081A1 EP0589081A1 (en) 1994-03-30
EP0589081B1 true EP0589081B1 (en) 1997-01-15

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US (1) US5504399A (en)
EP (1) EP0589081B1 (en)
AT (1) ATE147926T1 (en)
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EP1191824A2 (en) * 2000-09-20 2002-03-27 Helvar Oy Ab Electronic ballast for fluorescent lamp

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US7126450B2 (en) * 1999-06-21 2006-10-24 Access Business Group International Llc Inductively powered apparatus
US6232726B1 (en) * 1999-12-28 2001-05-15 Philips Electronics North America Corporation Ballast scheme for operating multiple lamps
US6359387B1 (en) * 2000-08-31 2002-03-19 Philips Electronics North America Corporation Gas-discharge lamp type recognition based on built-in lamp electrical properties
US6501225B1 (en) * 2001-08-06 2002-12-31 Osram Sylvania Inc. Ballast with efficient filament preheating and lamp fault protection
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DE102005047985A1 (en) * 2005-10-06 2007-04-12 Tridonicatco Gmbh & Co. Kg Dynamic coil heater
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US20100102738A1 (en) * 2007-04-23 2010-04-29 Osram Gesellschaft Mit Beschraenkter Haftung Circuit arrangement for operating a vacuum gas discharge lamp
DE102008004399A1 (en) * 2008-01-14 2009-07-16 HÜCO electronic GmbH Electronic ballast with current measuring device, method for its control and lighting device
WO2009089918A1 (en) * 2008-01-18 2009-07-23 Osram Gesellschaft mit beschränkter Haftung Electronic ballast and method for operating at least one gas discharge lamp

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US5656891A (en) * 1994-10-13 1997-08-12 Tridonic Bauelemente Gmbh Gas discharge lamp ballast with heating control circuit and method of operating same
EP1191824A2 (en) * 2000-09-20 2002-03-27 Helvar Oy Ab Electronic ballast for fluorescent lamp

Also Published As

Publication number Publication date
US5504399A (en) 1996-04-02
ATE147926T1 (en) 1997-02-15
DE59207908D1 (en) 1997-02-27
EP0589081A1 (en) 1994-03-30

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