EP1081988B1 - Circuit for operating at least one discharge lamp - Google Patents

Circuit for operating at least one discharge lamp Download PDF

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Publication number
EP1081988B1
EP1081988B1 EP20000116153 EP00116153A EP1081988B1 EP 1081988 B1 EP1081988 B1 EP 1081988B1 EP 20000116153 EP20000116153 EP 20000116153 EP 00116153 A EP00116153 A EP 00116153A EP 1081988 B1 EP1081988 B1 EP 1081988B1
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EP
European Patent Office
Prior art keywords
threshold switch
circuit arrangement
voltage
capacitor
bridge
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP20000116153
Other languages
German (de)
French (fr)
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EP1081988A3 (en
EP1081988A2 (en
Inventor
Richard Köppl
Olaf Busse
Martin Grabner
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Osram GmbH
Original Assignee
Patent Treuhand Gesellschaft fuer Elektrische Gluehlampen mbH
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Publication of EP1081988A2 publication Critical patent/EP1081988A2/en
Publication of EP1081988A3 publication Critical patent/EP1081988A3/en
Application granted granted Critical
Publication of EP1081988B1 publication Critical patent/EP1081988B1/en
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Classifications

    • 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
    • H05B41/298—Arrangements for protecting lamps or circuits against abnormal operating conditions
    • H05B41/2981—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions
    • H05B41/2985—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions against abnormal lamp operating conditions
    • 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
    • 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 operating at least one discharge lamp according to the preamble of claim 1.
  • Such a circuit arrangement is, for example, in the German patent application DE 196 19 580 discloses.
  • This document describes a safety shutdown device for a half-bridge inverter, which the occurrence of a Rectification effect is detected in the discharge lamp and the half-bridge inverter switches off in this case.
  • the safety shutdown device is designed such that it was caused by a DC component of the lamp current DC voltage on the half-bridge capacitor responds.
  • the appearance of a pronounced rectification effect in the discharge lamp marks the end of the service life of the discharge lamp and caused on the half-bridge capacitor one that deviates from the setpoint - that is, from half the DC link voltage Voltage drop.
  • This comparatively complex safety shutdown device comprises a threshold switch and a bistable multivibrator, by means of which withdraws the drive signal from a half-bridge inverter transistor can be.
  • the published patent application EP 0 886 460 A 1 discloses a circuit arrangement for Operation of low-pressure discharge lamps with a protective circuit, which is a device for monitoring the rectification effect in the lamp. This The device monitors and cuts off the voltage drop across a half-bridge capacitor (CK) connected to a lamp electrode the operation of the oscillator when the monitored voltage is predetermined Limit values exceeded or fallen below.
  • CK half-bridge capacitor
  • the laid-open specification WO 97/43879 describes a circuit arrangement for Operation of discharge lamps, the means of monitoring an asymmetrical Lamp operation and for detection of the end of life of the lamp. Moreover there is also a timer that turns off the lamp when the asymmetrical Lamp operation lasts longer than a specified time.
  • the invention has Circuit arrangement a first and a second RC element, the are interconnected by a threshold switch, and means for detection of the switching state of the threshold switch.
  • the first RC link is to the Center tap of the half-bridge inverter and the second RC element is connected to the Half-bridge capacitor connected. This forms the capacitor on the first RC element from a DC voltage that is half the DC link voltage, that is, half the supply voltage of the half-bridge inverter, while a DC voltage is present on the capacitor of the second RC element forms, which corresponds to the voltage drop across the half-bridge capacitor.
  • the High-frequency voltage components are generated by the second RC element from the half-bridge capacitor voltage filtered out. If the lamp is working properly the aforementioned DC voltages approximately the same size, so that between the there is no significant potential difference between the two RC elements. A rectifying effect occurs on the at least one discharge lamp, the changes Voltage drop across the half-bridge capacitor and accordingly the DC voltage on the capacitor of the second RC element. Reaches the potential difference the threshold voltage between the capacitors of the two RC elements of the threshold switch, it is switched to the conductive state and a current flows between the two aforementioned capacitors, to compensate for their different state of charge.
  • the switching state of the Threshold switch or the current flow between the capacitors of the two RC elements is from the control device of the half-bridge inverter detected by suitable means to the half-bridge inverter in the event of a fault to be able to switch off.
  • the circuit arrangement according to the invention advantageously has a parallel one to the threshold switch arranged ohmic resistance, which with the resistors of the first and second RC elements forms a voltage divider. With help this additional resistance can be achieved by appropriate dimensioning of the aforementioned Resistors the switching threshold of the monitoring circuit according to the invention to any voltage value above the threshold voltage of the Threshold switch can be set.
  • the invention Circuit arrangement advantageously a parallel to the threshold switch arranged capacitor on the threshold switch after switching on lasts long enough in the conductive state to balance the charges to ensure the capacitors of the first and second RC element.
  • a diac is advantageously used as a threshold switch, since it switches to positive as well as reacting to negative tensions.
  • the switching status of the threshold switch the monitoring circuit according to the invention advantageously has to detect another ohmic resistance, of which the different Balancing charges of the capacitors of the two RC elements Current flows through.
  • This resistor is advantageously a rectifier upstream, so that the aforementioned equalizing current between the capacitors the RC elements on the resistor generate unipolar voltage pulses, their polarity is independent of the current direction of the compensating current.
  • This unipolar Voltage pulses can come from the monitor input of an integrated circuit be used to switch off the half-bridge inverter.
  • the monitoring circuit according to the invention can advantageously be for externally controlled Half-bridge inverters can be used. It is also characterized by this from that it is not susceptible to interference because, except for that of the equalizing current flowed through resistor R4 all components of the invention Monitoring circuit arranged in the high voltage part of the circuit arrangement and the signal line from the rectifier to that of the compensating current flowed through resistance is completed by this low resistance.
  • the invention is illustrated below with the aid of a preferred exemplary embodiment explained in more detail.
  • the figure shows a schematic representation of the circuit arrangement according to the preferred embodiment.
  • the circuit arrangement is an externally controlled half-bridge inverter for high-frequency Operation of a fluorescent lamp LP.
  • the half-bridge inverter has two alternating switching field effect transistors T1, T2 and a control device A for these transistors T1, T2.
  • the control device A is partially as Integrated circuit IC, in particular designed as a high-voltage IC.
  • the DC voltage supply of the half-bridge inverter is carried out in the usual way Rectification obtained from the AC mains voltage.
  • the center tap M of the half-bridge inverter and the tap V1 on the half-bridge capacitor CK is arranged as a series resonant circuit load circuit, the essentially formed by the lamp inductor LD and the ignition capacitor CR becomes.
  • the load circuit has two pairs of electrical connections j 1, j2 for the electrode filaments E1, E2 of a fluorescent lamp LP.
  • the fluorescent lamp LP is connected in parallel to the ignition capacitor CR.
  • the circuit arrangement is a heater (not shown) for preheating the Have electrode filaments E1, E2 of the fluorescent lamp LP.
  • the circuit arrangement is also equipped with a monitoring circuit, which is a first RC element R1, C1 and a second RC element R2, C2 and a diac DC.
  • the first RC element R1, C1 is at the center tap M of the half-bridge inverter connected, while the second RC element R2, C2 to the tap V2 of the half-bridge capacitor CK is connected.
  • the capacitors C1, C2 of both RC elements R1, C1, R2, C2 are connected to each other by the diac DC.
  • Parallel an ohmic resistor R3 is connected to the diac DC, which is connected to the resistors R1, R2 of the RC elements forms a voltage divider.
  • the monitoring circuit a capacitor in parallel with the diac DC and in parallel with the resistor R3 C3 on, which keeps the diac DC longer in the conductive after it has been switched through Condition holds.
  • the ground connections of the capacitors C1, C2 are with a rectifier consisting of four diodes D1, D2, D3, D4.
  • the DC voltage output of the rectifier D1, D2, D3, D4 is via a low impedance Resistor R4 connected to ground.
  • the voltage drop across the resistor R4 is through a connecting line between the resistor R4 and a Monitor input of the integrated circuit IC from the control device A of the half-bridge inverter is monitored.
  • the half-bridge capacitor CK charged so that the tap V1 is at an electrical potential, that corresponds to half the supply voltage of the half-bridge inverter. Due to the alternating switching transistors T1, T2 of the half-bridge inverter the load circuit with a high-frequency alternating voltage between approx. 30-50 KHz applied.
  • the capacitors C1 and C2 of the two RC elements R1, C1 and R2, C2 are charged so that a DC voltage is applied to them equal to half the intermediate circuit voltage, that is, equal to half the supply voltage of the half-bridge inverter.
  • the high-frequency AC components are filtered out by the capacitors C1, C2. through a heating device (not shown), the electrode coils E1, E2 Fluorescent lamp to be preheated.
  • the ignition capacitor CR is used to ignite a gas discharge in the Fluorescent lamp LP required ignition voltage provided.
  • the starting capacitor CR is bridged by the discharge gap.
  • a high-frequency alternating current flows through the fluorescent lamp LP is regulated to a constant level by the half-bridge inverter.
  • the lamp current is symmetrical with respect to both half-periods of the high-frequency AC voltage, so that the potential at tap V1 remains unchanged half the supply voltage of the half-bridge inverter corresponds.
  • resistance R3 is therefore normally no voltage drop or at least no significant drop in voltage measurable, the state of charge of the capacitors C1, C2 is approximately the same and the diac DC is locked.
  • the diac DC is switched to the conductive state again and finds it again a charge equalization between the capacitors C1, C2 instead.
  • This process repeats itself periodically.
  • the time interval between the charge balancing described above of the capacitors and thus also the time interval between The current pulses through the diac DC depend on the strength of the rectifying effect from. The greater this potential difference, the shorter the time interval between the current impulses. In other words, the more the voltage across the half-bridge capacitor CK deviates from half the DC link voltage, in all the more The current pulses occur at shorter intervals.
  • the low-resistance resistor R4 and the bridge rectifier D1, D2, D3, D4 convert the charge equalization current impulses between the capacitors C1, C2 into unipolar Voltage pulses of positive polarity. These generated at resistor R4 Voltage pulses are a monitor input of the integrated circuit IC supplied to the control device A of the half-bridge inverter.
  • the control device A is programmed to be the half-bridge inverter switches off after detection of an input voltage at the aforementioned monitor input.
  • Table I gives a dimensioning of the components of the monitoring device of the circuit arrangement according to the invention, which are required for the operation of one or more fluorescent lamps connected in series and for a lamp current of 170 mA is suitable.
  • the monitoring device according to the invention can also be used in circuit arrangements which are used to operate a plurality of discharge lamps connected in series or in parallel.
  • the circuit arrangement according to the invention is not only suitable for operating fluorescent lamps, but can generally be used for operating low-pressure discharge lamps.
  • the monitoring device according to the invention can be used not only with externally controlled half-bridge inverters, but also with freely oscillating half-bridge inverters.
  • the control device A of the half-bridge inverter can also be designed so that it responds in a suitable manner to the voltage pulses across the resistor R4.
  • control device A can be designed such that it only switches off the half-bridge inverter from a certain, predetermined pulse frequency of the voltage pulses detected at the resistor R4.

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  • Circuit Arrangements For Discharge Lamps (AREA)

Abstract

The circuit has a half-bridge converter (T1,T2,A) with a drive device (A) and a load circuit (LD,CR,j1,j2), at least one half-bridge capacitor (CK) connected to the converter, load circuit connections for at least one discharge lamp (LP) and an arrangement for monitoring the voltage drop at the capacitor with two RC elements (R1,C1;R2,C2) connected by a threshold switch (DC). The first RC element is connected to the center tapping of the converter, the second to the capacitor and there is an arrangement for detecting the threshold switch state.

Description

Die Erfindung betrifft eine Schaltungsanordnung zum Betrieb mindestens einer Entladungslampe gemäß des Oberbegriffs des Patentanspruchs 1.The invention relates to a circuit arrangement for operating at least one discharge lamp according to the preamble of claim 1.

I. Stand der Technik I. State of the art

Eine derartige Schaltungsanordnung ist beispielsweise in der deutschen Offenlegungsschrift DE 196 19 580 offenbart. Diese Schrift beschreibt eine Sicherheitsabschalteinrichtung für einen Halbbrückenwechselrichter, die das Auftreten eines Gleichrichteffektes in der Entladungslampe detektiert und den Halbbrückenwechselrichter in diesem Fall abschaltet. Die Sicherheitsabschalteinrichtung ist derart ausgeführt, daß sie auf eine durch eine Gleichstromkomponente des Lampenstrom verursachte Gleichspannung am Halbbrückenkondensator anspricht. Das Auftreten eines ausgeprägten Gleichrichteffektes in der Entladungslampe markiert nämlich das Lebensdauerende der Entladungslampe und verursacht an dem Halbbrückenkondensator einen vom Sollwert - das heißt, von der halben Zwischenkreisspannung - abweichenden Spannungsabfall. Diese vergleichsweise aufwendige Sicherheitsabschalteinrichtung umfaßt einen Schwellwertschalter und eine bistabile Kippschaltung, mittels der einem Halbbrückenwechselrichtertransistor das Ansteuerungssignal entzogen werden kann.Such a circuit arrangement is, for example, in the German patent application DE 196 19 580 discloses. This document describes a safety shutdown device for a half-bridge inverter, which the occurrence of a Rectification effect is detected in the discharge lamp and the half-bridge inverter switches off in this case. The safety shutdown device is designed such that it was caused by a DC component of the lamp current DC voltage on the half-bridge capacitor responds. The appearance of a pronounced rectification effect in the discharge lamp marks the end of the service life of the discharge lamp and caused on the half-bridge capacitor one that deviates from the setpoint - that is, from half the DC link voltage Voltage drop. This comparatively complex safety shutdown device comprises a threshold switch and a bistable multivibrator, by means of which withdraws the drive signal from a half-bridge inverter transistor can be.

Die Offenlegungsschrift EP 0 886 460 A 1 offenbart eine Schaltungsanordnung zum Betrieb von Niederdruck-Entladungslampen mit einer Schutzschaltung, die eine Vorrichtung zur Überwachung des Gleichrichteffektes in der Lampe aufweist. Diese Vorrichtung überwacht den Spannungsabfall an einem an einer Lampenelektrode angeschlossenen Halbbrückenkondensator (CK) und unterbricht den Betrieb des Oszillators, wenn die überwachte Spannung vorgegebene Grenzwerte über- bzw. unterschreitet.The published patent application EP 0 886 460 A 1 discloses a circuit arrangement for Operation of low-pressure discharge lamps with a protective circuit, which is a device for monitoring the rectification effect in the lamp. This The device monitors and cuts off the voltage drop across a half-bridge capacitor (CK) connected to a lamp electrode the operation of the oscillator when the monitored voltage is predetermined Limit values exceeded or fallen below.

Die Offenlegungsschrift WO 97/43879 beschreibt eine Schaltungsanordnung zum Betrieb von Entladungslampen, die Mittel zur Überwachung eines asymmetrischen Lampenbetriebs und zur Detektion des Lebensdauerendes der Lampe aufweist. Außerdem ist auch ein Timer vorgesehen, der die Lampe ausschaltet, wenn der asymmetrische Lampenbetrieb länger als eine vorgegebene Zeit andauert.The laid-open specification WO 97/43879 describes a circuit arrangement for Operation of discharge lamps, the means of monitoring an asymmetrical Lamp operation and for detection of the end of life of the lamp. Moreover there is also a timer that turns off the lamp when the asymmetrical Lamp operation lasts longer than a specified time.

II. Darstellung der Erfindung II. Presentation of the invention

Es ist die Aufgabe der Erfindung, für eine gattungsgemäße Schaltungsanordnung eine verbesserte Vorrichtung zur Detektion eines in der mindestens einen Entladungslampe auftretenden Gleichrichteffektes bereitzustellen. Zur Überwachung des Spannungsabfalls am Halbbrückenkondensator weist die erfindungsgemäße Schaltungsanordnung ein erstes und ein zweites RC-Glied, die durch einen Schwellwertschalter miteinander verbunden sind, und Mittel zur Detektion des Schaltzustandes des Schwellwertschalters auf. Das erste RC-Glied ist an den Mittenabgriff des Halbbrückenwechselrichters und das zweite RC-Glied ist an den Halbbrückenkondensator angeschlossen. Dadurch bildet sich am Kondensator des ersten RC-Gliedes eine Gleichspannung aus, die der halben Zwischenkreisspannung, das heißt, der Hälfte der Versorgungsspannung des Halbbrückenwechselrichters entspricht, während sich am Kondensator des zweiten RC-Gliedes eine Gleichspannung ausbildet, die dem Spannungsabfall am Halbbrückenkondensator entspricht. Die hochfrequenten Spannungsanteile werden von dem zweiten RC-Glied aus der Halbbrückenkondensatorspannung heraus gefiltert. Bei fehlerfreiem Lampenbetrieb sind die vorgenannten Gleichspannungen annähernd gleich groß, so daß zwischen den beiden RC-Gliedern keine nennenswerte Potentialdifferenz besteht. Tritt ein Gleichrichteffekt an der mindestens einen Entladungslampe auf, so verändert sich der Spannungsabfall an dem Halbbrückenkondensator und entsprechend auch die Gleichspannung an dem Kondensator des zweiten RC-Gliedes. Erreicht die Potentialdifferenz zwischen den Kondensatoren der beiden RC-Glieder die Schwellenspannung des Schwellwertschalters, so wird dieser in den leitfähigen Zustand geschaltet und es fließt ein Strom zwischen den beiden vorgenannten Kondensatoren, um ihren unterschiedlichen Ladezustand auszugleichen. Der Schaltzustand des Schwellwertschalters bzw. der Stromfluß zwischen den Kondensatoren der beiden RC-Glieder wird von der Ansteuerungsvorrichtung des Halbbrückenwechselrichters durch geeignete Mittel detektiert, um den Halbbrückenwechselrichter im Störungsfall abschalten zu können.It is the object of the invention for a generic circuit arrangement an improved device for detecting a in the at least one discharge lamp to provide occurring rectification effect. To monitor the voltage drop across the half-bridge capacitor, the invention has Circuit arrangement a first and a second RC element, the are interconnected by a threshold switch, and means for detection of the switching state of the threshold switch. The first RC link is to the Center tap of the half-bridge inverter and the second RC element is connected to the Half-bridge capacitor connected. This forms the capacitor on the first RC element from a DC voltage that is half the DC link voltage, that is, half the supply voltage of the half-bridge inverter, while a DC voltage is present on the capacitor of the second RC element forms, which corresponds to the voltage drop across the half-bridge capacitor. The High-frequency voltage components are generated by the second RC element from the half-bridge capacitor voltage filtered out. If the lamp is working properly the aforementioned DC voltages approximately the same size, so that between the there is no significant potential difference between the two RC elements. A rectifying effect occurs on the at least one discharge lamp, the changes Voltage drop across the half-bridge capacitor and accordingly the DC voltage on the capacitor of the second RC element. Reaches the potential difference the threshold voltage between the capacitors of the two RC elements of the threshold switch, it is switched to the conductive state and a current flows between the two aforementioned capacitors, to compensate for their different state of charge. The switching state of the Threshold switch or the current flow between the capacitors of the two RC elements is from the control device of the half-bridge inverter detected by suitable means to the half-bridge inverter in the event of a fault to be able to switch off.

Vorteilhafterweise besitzt die erfindungsgemäße Schaltungsanordnung einen parallel zu dem Schwellwertschalter angeordneten ohmschen Widerstand, der mit den Widerständen des ersten und zweiten RC-Gliedes einen Spannungsteiler bildet. Mit Hilfe dieses zusätzlichen Widerstandes kann durch geeignete Dimensionierung der vorgenannten Widerstände die Schaltschwelle der erfindungsgemäßen Überwachungsschaltung auf jeden beliebigen Spannungswert oberhalb der Schwellenspannung des Schwellwertschalters eingestellt werden. Außerdem weist die erfindungsgemäße Schaltungsanordnung vorteilhafterweise einen parallel zu dem Schwellwertschalter angeordneten Kondensator auf, der den Schwellwertschalter nach dem Einschalten ausreichend lang in dem leitfähigen Zustand hält, um einen Ausgleich der Ladungen der Kondensatoren des ersten und zweiten RC-Gliedes zu gewährleisten. Als Schwellwertschalter dient vorteilhafterweise ein Diac, da dieser sowohl auf positive als auch auf negative Spannungen reagiert. Um den Schaltzustand des Schwellwertschalters zu detektieren, weist die erfindungsgemäße Überwachungsschaltung vorteilhafterweise einen weiteren ohmschen Widerstand auf, der von dem die unterschiedlichen Ladungen der Kondensatoren der beiden RC-Glieder ausgleichenden Strom durchflossen wird. Vorteilhafterweise ist diesem Widerstand ein Gleichrichter vorgeschaltet, so daß der vorgenannte Ausgleichsstrom zwischen den Kondensatoren der RC-Glieder an dem Widerstand unipolare Spannungsimpulse erzeugt, deren Polarität unabhängig von der Stromrichtung des Ausgleichsstroms ist. Diese unipolaren Spannungsimpulse können von dem Monitoreingang eines Integrierten Schaltkreises zur Abschaltung des Halbbrückenwechselrichters verwendet werden.The circuit arrangement according to the invention advantageously has a parallel one to the threshold switch arranged ohmic resistance, which with the resistors of the first and second RC elements forms a voltage divider. With help this additional resistance can be achieved by appropriate dimensioning of the aforementioned Resistors the switching threshold of the monitoring circuit according to the invention to any voltage value above the threshold voltage of the Threshold switch can be set. In addition, the invention Circuit arrangement advantageously a parallel to the threshold switch arranged capacitor on the threshold switch after switching on lasts long enough in the conductive state to balance the charges to ensure the capacitors of the first and second RC element. As A diac is advantageously used as a threshold switch, since it switches to positive as well as reacting to negative tensions. The switching status of the threshold switch the monitoring circuit according to the invention advantageously has to detect another ohmic resistance, of which the different Balancing charges of the capacitors of the two RC elements Current flows through. This resistor is advantageously a rectifier upstream, so that the aforementioned equalizing current between the capacitors the RC elements on the resistor generate unipolar voltage pulses, their polarity is independent of the current direction of the compensating current. This unipolar Voltage pulses can come from the monitor input of an integrated circuit be used to switch off the half-bridge inverter.

Die erfindungsgemäße Überwachungsschaltung kann vorteilhafterweise für fremdgesteuerte Halbbrückenwechselrichter verwendet werden. Sie zeichnet sich auch dadurch aus, daß sie nicht anfällig für Störungen ist, weil mit Ausnahme des vom Ausgleichsstrom durchflossenen Widerstandes R4 alle Komponenten der erfindungsgemäßen Überwachungsschaltung im Hochspannungsteil der Schaltungsanordnung angeordnet sind und die Signalleitung vom Gleichrichter zu dem vom Ausgleichsstrom durchflossenen Widerstand durch diesen niederohmig abgeschlossen ist.The monitoring circuit according to the invention can advantageously be for externally controlled Half-bridge inverters can be used. It is also characterized by this from that it is not susceptible to interference because, except for that of the equalizing current flowed through resistor R4 all components of the invention Monitoring circuit arranged in the high voltage part of the circuit arrangement and the signal line from the rectifier to that of the compensating current flowed through resistance is completed by this low resistance.

III. Beschreibung des bevorzugten Ausführungsbeispiels III. Description of the preferred embodiment

Nachstehend wird die Erfindung anhand eines bevorzugten Ausführungsbeispiels näher erläutert. Die Figur zeigt eine schematische Darstellung der Schaltungsanordnung gemäß des bevorzugten Ausführungsbeispiels.The invention is illustrated below with the aid of a preferred exemplary embodiment explained in more detail. The figure shows a schematic representation of the circuit arrangement according to the preferred embodiment.

Bei der Schaltungsanordnung gemäß des bevorzugten Ausführungsbeispiels handelt es sich um einen fremdgesteuerten Halbbrückenwechselrichter zum hochfrequenten Betrieb einer Leuchtstofflampe LP. Der Halbbrückenwechselrichter weist zwei alternierend schaltende Feldeffekttransistoren T1, T2 und eine Ansteuerungsvorrichtung A für diese Transistoren T1, T2 auf. Die Ansteuerungsvorrichtung A ist teilweise als Integrierter Schaltkreis IC, insbesondere als Hochvolt-IC ausgeführt. Die Gleichspannungsversorgung des Halbbrückenwechselrichters wird in üblicher Weise durch Gleichrichtung aus der Netzwechselspannung gewonnen. Zwischen dem Mittenabgriff M des Halbbrückenwechselrichters und dem Abgriff V1 am Halbbrückenkondensator CK ist ein als Serienresonanzkreis ausgebildeter Lastkreis angeordnet, der im wesentlichen von der Lampendrossel LD und dem Zündkondensator CR gebildet wird. Außerdem weist der Lastkreis zwei Paare von elektrischen Anschlüssen j 1, j2 für die Elektrodenwendeln E1, E2 einer Leuchtstofflampe LP auf. Die Leuchtstofflampe LP ist parallel zu dem Zündkondensator CR geschaltet. Außerdem kann die Schaltungsanordnung eine Heizvorrichtung (nicht abgebildet) zur Vorheizung der Elektrodenwendeln E1, E2 der Leuchtstofflampe LP aufweisen. Die Schaltungsanordnung ist ferner mit einer Überwachungsschaltung ausgestattet, die ein erstes RC-Glied R1, C1 und ein zweites RC-Glied R2, C2 sowie einen Diac DC besitzt. Das erste RC-Glied R1, C1 ist an den Mittenabgriff M des Halbbrückenwechselrichters angeschlossen, während das zweite RC-Glied R2, C2 an den Abgriff V2 des Halbbrückenkondensators CK angeschlossen ist. Die Kondensatoren C1, C2 beider RC-Glieder R1, C1, R2, C2 sind durch den Diac DC miteinander verbunden. Parallel zum Diac DC ist ein ohmscher Widerstand R3 geschaltet, der mit den Widerständen R1, R2 der RC-Glieder einen Spannungsteiler bildet. Außerdem weist die Überwachungsschaltung parallel zum Diac DC und parallel zum Widerstand R3 einen Kondensator C3 auf, der den Diac DC nach seinem Durchschalten länger im leitfähigen Zustand hält. Die masseseitigen Anschlüsse der Kondensatoren C1, C2 sind mit einem aus vier Dioden D1, D2, D3, D4 bestehenden Gleichrichter verbunden. Der Gleichspannungsausgang des Gleichrichters D1, D2, D3, D4 ist über einen niederohmigen Widerstand R4 mit Masse verbunden. Der Spannungsabfall am Widerstand R4 wird durch eine Verbindungsleitung zwischen dem Widerstand R4 und einem Monitoreingang des Integrierten Schaltkreises IC von der Ansteuerungsvorrichtung A des Halbbrückenwechselrichters überwacht. In the circuit arrangement according to the preferred embodiment it is an externally controlled half-bridge inverter for high-frequency Operation of a fluorescent lamp LP. The half-bridge inverter has two alternating switching field effect transistors T1, T2 and a control device A for these transistors T1, T2. The control device A is partially as Integrated circuit IC, in particular designed as a high-voltage IC. The DC voltage supply of the half-bridge inverter is carried out in the usual way Rectification obtained from the AC mains voltage. Between the center tap M of the half-bridge inverter and the tap V1 on the half-bridge capacitor CK is arranged as a series resonant circuit load circuit, the essentially formed by the lamp inductor LD and the ignition capacitor CR becomes. In addition, the load circuit has two pairs of electrical connections j 1, j2 for the electrode filaments E1, E2 of a fluorescent lamp LP. The fluorescent lamp LP is connected in parallel to the ignition capacitor CR. Besides, can the circuit arrangement is a heater (not shown) for preheating the Have electrode filaments E1, E2 of the fluorescent lamp LP. The circuit arrangement is also equipped with a monitoring circuit, which is a first RC element R1, C1 and a second RC element R2, C2 and a diac DC. The first RC element R1, C1 is at the center tap M of the half-bridge inverter connected, while the second RC element R2, C2 to the tap V2 of the half-bridge capacitor CK is connected. The capacitors C1, C2 of both RC elements R1, C1, R2, C2 are connected to each other by the diac DC. Parallel an ohmic resistor R3 is connected to the diac DC, which is connected to the resistors R1, R2 of the RC elements forms a voltage divider. In addition, the monitoring circuit a capacitor in parallel with the diac DC and in parallel with the resistor R3 C3 on, which keeps the diac DC longer in the conductive after it has been switched through Condition holds. The ground connections of the capacitors C1, C2 are with a rectifier consisting of four diodes D1, D2, D3, D4. The DC voltage output of the rectifier D1, D2, D3, D4 is via a low impedance Resistor R4 connected to ground. The voltage drop across the resistor R4 is through a connecting line between the resistor R4 and a Monitor input of the integrated circuit IC from the control device A of the half-bridge inverter is monitored.

Nach dem Einschalten der Schaltungsanordnung wird der Halbrückenkondensator CK aufgeladen, so daß der Abgriff V1 sich auf einem elektrischen Potential befindet, das der Hälfte der Versorgungsspannung des Halbbrückenwechselrichters entspricht. Durch die alternierend schaltenden Transistoren T1, T2 des Halbbrückenwechselrichters wird der Lastkreis mit einer hochfrequenten Wechselspannung zwischen ca. 30-50 KHz beaufschlagt. Die Kondensatoren C1 und C2 der beiden RC-Glieder R1, C1 und R2, C2 werden aufgeladen, so daß an ihnen eine Gleichspannung anliegt, die gleich der halben Zwischenkreisspannung, das heißt, gleich der Hälfte der Versorgungsspannung des Halbbrückenwechselrichters ist. Die hochfrequenten Wechselstromanteile werden dabei von den Kondensatoren C1, C2 heraus gefiltert. Mittels einer Heizvorrichtung (nicht abgebildet) können die Elektrodenwendeln E1, E2 der Leuchtstofflampe vorgeheizt werden. Mittels der Methode der Resonanzüberhöhung wird an dem Zündkondensator CR die zur Zündung einer Gasentladung in der Leuchtstofflampe LP erforderliche Zündspannung bereitgestellt. Nach dem Ausbilden einer Gasentladung zwischen den Elektrodenwendeln E1, E2 der Leuchtstofflampe LP wird der Zündkondensator CR durch die Entladungsstrecke überbrückt. Durch die Leuchtstofflampe LP fließt ein hochfrequenter Wechselstrom, der von dem Halbbrückenwechselrichter auf ein konstantes Niveau geregelt wird. Im Idealfall ist der Lampenstrom symmetrisch bezüglich beider Halbperioden der hochfrequenten Wechselspannung, so daß das Potential am Abgriff V1 unverändert der halben Versorgungsspannung des Halbbrückenwechselrichters entspricht. Am Widerstand R3 ist daher im Normalfall kein oder zumindest kein nennenswerter Spannungsabfall meßbar, der Ladezustand der Kondensatoren C1, C2 ist annähernd gleich und der Diac DC ist gesperrt.After switching on the circuit arrangement, the half-bridge capacitor CK charged so that the tap V1 is at an electrical potential, that corresponds to half the supply voltage of the half-bridge inverter. Due to the alternating switching transistors T1, T2 of the half-bridge inverter the load circuit with a high-frequency alternating voltage between approx. 30-50 KHz applied. The capacitors C1 and C2 of the two RC elements R1, C1 and R2, C2 are charged so that a DC voltage is applied to them equal to half the intermediate circuit voltage, that is, equal to half the supply voltage of the half-bridge inverter. The high-frequency AC components are filtered out by the capacitors C1, C2. through a heating device (not shown), the electrode coils E1, E2 Fluorescent lamp to be preheated. Using the method of increasing the resonance the ignition capacitor CR is used to ignite a gas discharge in the Fluorescent lamp LP required ignition voltage provided. After training a gas discharge between the electrode filaments E1, E2 of the fluorescent lamp LP, the starting capacitor CR is bridged by the discharge gap. A high-frequency alternating current flows through the fluorescent lamp LP is regulated to a constant level by the half-bridge inverter. in the Ideally, the lamp current is symmetrical with respect to both half-periods of the high-frequency AC voltage, so that the potential at tap V1 remains unchanged half the supply voltage of the half-bridge inverter corresponds. With resistance R3 is therefore normally no voltage drop or at least no significant drop in voltage measurable, the state of charge of the capacitors C1, C2 is approximately the same and the diac DC is locked.

Tritt in der Leuchtstofflampe LP ein Gleichrichteffekt auf, der zur Ausbildung einer Vorzugsrichtung für den Lampenstrom führt, so vergrößert oder verringert sich der Spannungsabfall am Halbbrückenkondensator CK, je nach dem, welche Halbwelle des Lampenstroms bevorzugt von der Leuchtstofflampe LP durchgelassen wird. Das Potential am Abgriff V1 wird dementsprechend erhöht oder reduziert und der Kondensator C2 des zweiten RC-Gliedes wird entsprechend umgeladen. Dadurch bildet sich zwischen den Abgriffen M und V1 eine dementsprechend veränderte Potentialdifferenz aus, die sich im Verhältnis der Widerstandswerte auf die Widerstände R1, R2, R3 aufteilt. Erreicht der Spannungsabfall am Widerstand R3 die Schwellenspannung des Diacs DC, die im vorliegenden Fall ± 32 V beträgt, so wird der Diac DC leitend. Dann fließt entweder über die Diode D3 oder über die Diode D2 und durch den Diac DC sowie durch den Widerstand R4 ein Strom, der die unterschiedlichen Ladungen der Kondensatoren C1, C2 ausgleicht. Der Diac DC schaltet erst dann wieder in den sperrenden Zustand, wenn sein Haltestrom unterschritten wird. Der parallel zum Diac DC angeordnete Kondensator C3 ist so dimensioniert, daß er den Diac DC ausreichend lang im leitenden Zustand hält, um einen vollständigen Ausgleich der Ladungen der Kondensatoren C1, C2 zu gewährleisten. Nachdem der Ladungsausgleich zwischen den Kondensatoren C1, C2 erfolgt ist und der Diac DC wieder in den sperrenden Zustand geschaltet hat, baut sich am Kondensator C2 erneut eine Spannung auf, die der halben Zwischenkreisspannung zuzüglich der durch den Gleichrichteffekt verursachten Potentialverschiebung am Abgriff V1 entspricht. Sobald sich am Widerstand R3 erneut die Schwellenspannung des Diacs DC aufgebaut hat, wird der Diac DC wieder in den leitenden Zustand geschaltet und es findet erneut ein Ladungsausgleich zwischen den Kondensatoren C1, C2 statt. Dieser Vorgang wiederholt sich periodisch. Der zeitliche Abstand des oben beschriebenen Ladungsausgleichs der Kondensatoren und damit auch der zeitliche Abstand zwischen den Stromimpulsen durch den Diac DC hängt von der Stärke des Gleichrichteffektes ab. Je größer diese Potentialdifferenz ist, um so kürzer ist der zeitliche Abstand zwischen den Stromimpulsen. Oder anders formuliert, je mehr die Spannung am Halbbrückenkondensator CK von der halben Zwischenkreisspannung abweicht, in um so kürzeren Abständen erfolgen die Stromimpulse. Der niederohmige Widerstand R4 und der Brückengleichrichter D1, D2, D3, D4 wandeln diese den Ladungsausgleich zwischen den Kondensatoren C1, C2 herbeiführenden Stromimpulse in unipolare Spannungsimpulse positiver Polarität um. Diese am Widerstand R4 generierten Spannungsimpulse werden einem Monitoreingang des Integrierten Schaltkreises IC der Ansteuerungsvorrichtung A des Halbbrückenwechselrichters zugeführt. Die Ansteuerungsvorrichtung A ist so programmiert, daß sie den Halbbrückenwechselrichter nach der Detektion einer Eingangsspannung am vorgenannten Monitoreingang abschaltet.If a rectification effect occurs in the fluorescent lamp LP, this leads to the formation of a Preferred direction for the lamp current leads, the increases or decreases Voltage drop across the half-bridge capacitor CK, depending on which half-wave of the lamp current is preferably let through by the fluorescent lamp LP. The The potential at tap V1 is increased or reduced accordingly and the capacitor C2 of the second RC element is reloaded accordingly. This forms between the taps M and V1 there is a correspondingly changed potential difference from the ratio of the resistance values to the resistors R1, Split R2, R3. If the voltage drop across resistor R3 reaches the threshold voltage of the DC dia, which in this case is ± 32 V, becomes the diac DC conductive. Then flows either through the diode D3 or through the diode D2 and through the diac DC and a current through the resistor R4, which the different Balances charges of the capacitors C1, C2. Only then will the Diac DC switch back into the blocking state when its holding current is undershot. The parallel to the diac DC capacitor C3 is dimensioned so that it Diac DC keeps conductive long enough to fully compensate to ensure the charges of the capacitors C1, C2. After charge balancing between the capacitors C1, C2 and the diac DC has switched back to the blocking state, builds up again on the capacitor C2 a voltage which is half the intermediate circuit voltage plus the by corresponds to the rectification effect caused by potential shift at tap V1. As soon as the threshold voltage of the DC DC is built up again at the resistor R3 the diac DC is switched to the conductive state again and finds it again a charge equalization between the capacitors C1, C2 instead. This process repeats itself periodically. The time interval between the charge balancing described above of the capacitors and thus also the time interval between The current pulses through the diac DC depend on the strength of the rectifying effect from. The greater this potential difference, the shorter the time interval between the current impulses. In other words, the more the voltage across the half-bridge capacitor CK deviates from half the DC link voltage, in all the more The current pulses occur at shorter intervals. The low-resistance resistor R4 and the bridge rectifier D1, D2, D3, D4 convert the charge equalization current impulses between the capacitors C1, C2 into unipolar Voltage pulses of positive polarity. These generated at resistor R4 Voltage pulses are a monitor input of the integrated circuit IC supplied to the control device A of the half-bridge inverter. The control device A is programmed to be the half-bridge inverter switches off after detection of an input voltage at the aforementioned monitor input.

Die Tabelle I gibt eine Dimensionierung der Bauteile der Überwachungsvorrichtung der erfindungsgemäßen Schaltungsanordnung an, die für den Betrieb einer oder mehrerer in Reihe geschalteter Leuchtstofflampen und für einen Lampenstrom von 170 mA geeignet ist.Table I gives a dimensioning of the components of the monitoring device of the circuit arrangement according to the invention, which are required for the operation of one or more fluorescent lamps connected in series and for a lamp current of 170 mA is suitable.

Die Erfindung beschränkt sich nicht auf das oben näher erläuterte Ausführungsbeispiel. Beispielsweise kann die erfindungsgemäße Überwachungsvorrichtung auch bei Schaltungsanordnungen, die zum Betrieb von mehreren in Reihe oder parallel geschalteten Entladungslampen dient, verwendet werden. Die erfindungsgemäße Schaltungsanordnung eignet sich nicht nur zum Betrieb von Leuchtstofflampen, sondern kann generell zum Betrieb von Niederdruckentladungslampen verwendet werden. Außerdem kann die erfindungsgemäße Überwachungsvorrichtung nicht nur bei fremdgesteuerten Halbbrückenwechselrichtern, sondern auch bei freischwingenden Halbbrückenwechselrichtern eingesetzt werden. Die Ansteuerungsvorrichtung A des Halbbrückenwechselrichters kann ferner auch so ausgeführt werden, daß sie in geeigneter Weise auf die Spannungsimpulse am Widerstand R4 reagiert. Beispielsweise kann die Ansteuerungsvorrichtung A derart ausgebildet sein, daß sie erst ab einer bestimmten, vorgegebenen Pulsfrequenz der am Widerstand R4 detektierten Spannungsimpulse den Halbbrückenwechselrichter abschaltet. Dimensionierung der Bauteile der erfindungsgemäßen Überwachungsvorrichtung für eine Schaltungsanordnung, die den Lampenstrom auf einen Wert von 170 mA regelt R1, R2 100 kΩ, 10%, 500 V R3 390 kΩ, 5% R4 150 Ω C1, C2 10 nF, 250 V, RM 7,5 C3 47 nF, 50 V D1, D2, D3, D4 Diode-SMD, 75 V-150mA SOD80 DC Diac, 32 V The invention is not limited to the exemplary embodiment explained in more detail above. For example, the monitoring device according to the invention can also be used in circuit arrangements which are used to operate a plurality of discharge lamps connected in series or in parallel. The circuit arrangement according to the invention is not only suitable for operating fluorescent lamps, but can generally be used for operating low-pressure discharge lamps. In addition, the monitoring device according to the invention can be used not only with externally controlled half-bridge inverters, but also with freely oscillating half-bridge inverters. The control device A of the half-bridge inverter can also be designed so that it responds in a suitable manner to the voltage pulses across the resistor R4. For example, the control device A can be designed such that it only switches off the half-bridge inverter from a certain, predetermined pulse frequency of the voltage pulses detected at the resistor R4. Dimensioning of the components of the monitoring device according to the invention for a circuit arrangement which regulates the lamp current to a value of 170 mA R1, R2 100 kΩ, 10%, 500 V R3 390 kΩ, 5% R4 150 Ω C1, C2 10 nF, 250 V, RM 7.5 C3 47 nF, 50 V D1, D2, D3, D4 Diode SMD, 75 V-150mA SOD80 DC Diac, 32 V.

Claims (7)

  1. Circuit arrangement for operating at least one discharge lamp, the circuit arrangement having the following features:
    a half-bridge inverter (T1, T2, A) having a drive apparatus (A) and having a downstream load circuit (LD, CR, j1, j2),
    at least one half-bridge capacitor (CK) connected to the load circuit and to the half-bridge inverter, the load circuit (LD, CR, j1, j2) having electrical connections (j1, j2) for at least one discharge lamp (LP), and
    means for monitoring the voltage drop across the at least one half-bridge capacitor (CK), the said means having a first RC element (R1, C1) and a second RC element (R2, C2), which are connected to one another by a threshold switch (DC), so that the threshold switch (DC) is arranged between the capacitors (C1, C2) in these RC elements, one of these RC elements (R2, C2) being connected to the half-bridge capacitor (CK),
    means for detecting the switching state of the threshold switch (DC), characterized in that the other of these RC elements (R1, C1) is connected to the centre tap (M) of the half-bridge inverter (T1, T2, A).
  2. Circuit arrangement according to Claim 1, characterized in that the means for detecting the switching state of the threshold switch (DC) have a non-reactive resistor (R4) which detects the flow of current through the threshold switch (DC).
  3. Circuit arrangement according to Claim 2, characterized in that a rectifier (D1-D4) is connected upstream of the non-reactive resistor (R4).
  4. Circuit arrangement according to Claim 1, characterized in that the threshold switch (DC) has a non-reactive resistor (R3) connected in parallel with it, the said non-reactive resistor forming a voltage divider with the resistors (R1, R2) in the first RC element (R1, C1) and the second RC element (R2, C2).
  5. Circuit arrangement according to Claim 1, characterized in that the threshold switch (DC) has a capacitor (C3) connected in parallel with it.
  6. Circuit arrangement according to Claim 1, characterized in that the threshold switch (DC) is a diac.
  7. Circuit arrangement according to Claim 3, characterized in that the drive apparatus (A) in the half-bridge inverter (T1, T2, A) has an integrated circuit (IC) with a monitor input, the monitor input being connected to the non-reactive resistor (R4) detecting the flow of current through the threshold switch (DC).
EP20000116153 1999-08-30 2000-08-01 Circuit for operating at least one discharge lamp Expired - Lifetime EP1081988B1 (en)

Applications Claiming Priority (2)

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DE19941437 1999-08-30
DE19941437A DE19941437A1 (en) 1999-08-30 1999-08-30 Circuit arrangement for operating at least one discharge lamp

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EP1081988A2 EP1081988A2 (en) 2001-03-07
EP1081988A3 EP1081988A3 (en) 2002-09-11
EP1081988B1 true EP1081988B1 (en) 2004-10-27

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JP (1) JP2001102192A (en)
AT (1) ATE281057T1 (en)
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DE202005013754U1 (en) * 2005-08-31 2005-11-17 Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH Electronic control gear for operating discharge lamp, has measuring device to measure parameter that correlates to increased electrode temperature, and control device to react to temperature by adjustment of operating parameter of gear
WO2013024401A2 (en) * 2011-08-12 2013-02-21 Koninklijke Philips Electronics N.V. Universal voltage converter and inductive power coupling

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DE4406083A1 (en) * 1994-02-24 1995-08-31 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Circuit arrangement for operating at least one low-pressure discharge lamp
US5677602A (en) * 1995-05-26 1997-10-14 Paul; Jon D. High efficiency electronic ballast for high intensity discharge lamps
US5808422A (en) * 1996-05-10 1998-09-15 Philips Electronics North America Lamp ballast with lamp rectification detection circuitry
DE19619580A1 (en) 1996-05-15 1997-11-20 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Safety shutdown with asymmetrical lamp power
US5994847A (en) * 1997-01-31 1999-11-30 Motorola Inc. Electronic ballast with lamp current valley-fill power factor correction
DE69828484T2 (en) * 1997-04-17 2005-08-25 Toshiba Lighting & Technology Corp. DISCHARGE LAMP AND LIGHTING DEVICE
US5770925A (en) * 1997-05-30 1998-06-23 Motorola Inc. Electronic ballast with inverter protection and relamping circuits
FI102347B (en) * 1997-06-18 1998-11-13 Helvar Oy The detection circuit of the lamp direction is provided with an electronic connection device
US5869937A (en) * 1997-12-17 1999-02-09 Motorola Inc. High efficiency electronic ballast

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CA2317310A1 (en) 2001-02-28
US6291947B1 (en) 2001-09-18
EP1081988A3 (en) 2002-09-11
ATE281057T1 (en) 2004-11-15
DE19941437A1 (en) 2001-03-01
JP2001102192A (en) 2001-04-13
EP1081988A2 (en) 2001-03-07
DE50008397D1 (en) 2004-12-02

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