EP1103166B1 - Electronic ballast for at least one low-pressure discharge lamp - Google Patents

Electronic ballast for at least one low-pressure discharge lamp Download PDF

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Publication number
EP1103166B1
EP1103166B1 EP00927002A EP00927002A EP1103166B1 EP 1103166 B1 EP1103166 B1 EP 1103166B1 EP 00927002 A EP00927002 A EP 00927002A EP 00927002 A EP00927002 A EP 00927002A EP 1103166 B1 EP1103166 B1 EP 1103166B1
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EP
European Patent Office
Prior art keywords
lamp
electronic ballast
inverter
voltage
circuit arrangement
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP00927002A
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German (de)
French (fr)
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EP1103166A1 (en
Inventor
Stefan Koch
Günter MARENT
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Tridonicatco GmbH and Co KG
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Tridonicatco GmbH and Co KG
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Priority claimed from DE19934687A external-priority patent/DE19934687A1/en
Application filed by Tridonicatco GmbH and Co KG filed Critical Tridonicatco GmbH and Co KG
Publication of EP1103166A1 publication Critical patent/EP1103166A1/en
Application granted granted Critical
Publication of EP1103166B1 publication Critical patent/EP1103166B1/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
    • 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

Definitions

  • the present invention relates to an electronic ballast for a low pressure discharge lamp after The preamble of claim 1, which is a circuit for detection a lamp change or a lamp defect.
  • a ballast with such a circuit is for Example from European patent application EP 0 146 683 B1 known.
  • the resonant capacitor of the series resonant circuit is between the two electrodes of the discharge lamp arranged, thereby preheating the electrodes before ignition the lamp is enabled.
  • the ballast a bistable switching device with an operating and a switch-off state, the switching device at a non-igniting discharge lamp in the shutdown state tilts and switches off the inverter.
  • the function of this Circuit is based on the fact that the amplitude of the current flowing through the load branch with the lamp when the ignition is not ignited Lamp is significantly larger than when ignited.
  • the bistable switching device On via one of the electrodes of the discharge lamp holding circuit then the bistable switching device lasts so long in this shutdown state until it is replaced by the insertion of a new lamp is interrupted, which automatically restarts the lamp is initiated.
  • a disadvantage of this circuit is that a parallel current through the resonance capacitor even after the lamp has been ignited and over the two filaments of the lamp flows.
  • This parallel current means the in normal operation Lamp lost energy and affects its luminosity or the efficiency.
  • the heating power regardless of the lamp current to regulate what particularly in a dimmed operation the lamp is to be regarded as disadvantageous because of the dimming current reduction caused by the filament heating should be balanced.
  • the invention Ballast is characterized by that for heating the filaments a heating transformer is provided, the Primary winding in series with a switch at the output of the inverter is connected. The current in the primary winding is transferred to two secondary windings, the each form a heating circuit with one of the two coils. The current flowing through the primary winding is included an evaluation circuit that detects in the event of a defect at least one of the two coils or when removing the Lamp or in the case of a further evaluation circuits detected defect of the lamp, switching off the inverter causes.
  • the measurement resistance also depends on the DC voltage supplied to the heating transformer. This can, however - for example due to network fluctuations - change quite easily over time.
  • a second measuring resistor may be provided, wherein the voltage drop across this measuring resistor also is evaluated. A comparison of the two tensions then leaves a statement independent of voltage fluctuations about the condition of the electrodes of the lamp too. this happens for example in that the differential voltage is formed which is then compared to a setpoint. As shown this method allows a very simple one but meaningful analysis of the lamp status.
  • the current profile in the heating transformer can also do this at an earlier point in time Measured value or a reference value can be compared. In this case, only a single measuring resistor would be sufficient either the current in the primary winding or in one of the two secondary windings can be evaluated.
  • EP 0 707 438 A3 The use of a heating transformer is already out of the EP 0 707 438 A3 or from EP 748 146 A1 and DE 295 14 817 U1 is known, with the shutdown also in each case here the filament heating mentioned after igniting the lamp becomes.
  • EP 0 707 438 A3 also sees an evaluation of the Heating current in order to detect possible lamp defects. Indeed is none of those described in these writings Ballasts switching off the inverter and one Detection of lamp replacement provided.
  • the invention is also used for electronic ballasts that have multiple Operate lamps, suitable.
  • the inverter is formed by a half bridge made of two electronic switches S1 and S2 connected in series. These switches S1, S2 can be formed, for example, by two MOS field effect transistors.
  • the base of the half-bridge lies on ground, while the DC voltage U BUS is present at its input, which can be generated, for example, by shaping the usual mains voltage using a combination of radio interference suppressor and rectifier. Alternatively, however, any other DC voltage source can also be present on the half bridge.
  • the load circuit containing the discharge lamp LA is connected.
  • This consists of a series resonance circuit, the consists of a choke coil L1 and a resonance capacitor C2 is composed.
  • the choke coil L1 is a coupling capacitor C1 upstream.
  • At the connection node between the choke coil L1 and resonance capacitor C2 is also the upper one of the two cathodes of the lamp LA connected.
  • the two Cathodes each have two connections, between which one heating coil W1 and one W2 each for heating the cathodes is provided.
  • the lower cathode of the lamp LA is again connected to the output of the resonance capacitor C2 and the common node finally via resistor R1 Ground connected.
  • a heating transformer which consists of a primary winding Tp and two secondary windings Ts1 and Ts2.
  • the secondary windings Ts1 and Ts2 are each connected to a filament W1 and W2 of the lamp LA, so that two separate heating circuits are formed.
  • the primary winding Tp is arranged in the middle of a series circuit which, in addition to the primary winding Tp, has a charge / discharge capacitor C3 and a third controllable switch S3. Like the two switches of the half-bridge S1 and S2, this switch S3 can also consist of a field effect transistor.
  • the second connection of the charge / discharge capacitor C3, like the load circuit, is connected to the node of the two switches S1 and S2, so that this series connection is parallel to the lower branch of the half-bridge.
  • the DC supply voltage U BUS is additionally supplied to the node between the primary winding Tp and the charge / discharge capacitor C3 independently of the inverter via a resistor R2.
  • a measuring resistor to measure the heating current R3 arranged.
  • the voltage drop caused by the current An evaluation circuit is used to measure the measuring resistor R3 M1 measured.
  • Another measuring resistor R4 is arranged in the heating circuit of the lower lamp filament W1, the voltage drop across this measuring resistor R4 and thus the current flow through this heating circuit through the Evaluation circuit M1 can be measured.
  • Positions can be arranged.
  • the first Measuring resistor R3 also between the switch S3 and the primary coil Tp of the heating transformer can be provided or itself the second measuring resistor R4 on the other side of the secondary coil Ts1 are in the heating circuit.
  • this resistor R4 can become a heating circuit also in the heating circuit of the upper coil W2 and the second one Secondary coil Ts2 are located.
  • the amperages needed can be instead the measuring resistors R3 and R4 also other current measuring devices be used.
  • the three switches S1, S2 and S3 are activated by a control circuit, not shown, wherein the preheating the coils W1, W2 and the ignition of the lamp LA in a known manner Way is executed.
  • the third becomes during the preheating Switch S3 permanently closed, so that of the inverter AC voltage also delivered to the heating transformer is fed.
  • the switches S1 and S2 are used an increased compared to the resonance frequency of the load circuit Frequency controlled so that the applied to the lamp LA Voltage does not cause ignition.
  • switch S3 is opened and the heating the coils ended with it, and the ignition of the lamp LA Is initiated. To do this, the AC voltage frequency Control signals for the two switches S1 and S2 of the inverter approximated the resonance frequency until finally the Ignition takes place.
  • the evaluation circuit or other monitoring circuits can be used to check in a known manner whether there is an intact lamp LA in the system. If this is not the case or if a filament breakage or removal of the lamp LA is registered during preheating or during normal operation, the ballast is put into an idle state and the inverter is switched off in order to consume as little energy as possible and to enable the lamp LA to be replaced safely , However, the switch S3 belonging to the filament heating is then clocked at low frequency. Since the primary winding Tp is supplied with the supply voltage U BUS via the resistor R2, an actuation of the switch S3 generates an alternating voltage, which is transmitted through the transformer to the two heating circuits with the coils W1 and W2.
  • Switch S3 is preferably switched with a low clock frequency of approximately 50-100 Hz.
  • the duty cycle of the control signal for the switch S3 is approximately 50%, but neither the choice of the clock frequency nor the duty cycle for the lamp status detection are critical.
  • a current pulse results at the primary coil Tp of the heating transformer due to the discharge of the charge / discharge capacitor C3 and accordingly a voltage pulse U R3 at the measuring resistor R3 .
  • the voltage curve across the measuring resistor R3 depends essentially on whether there is a lamp LA in the system and whether the two filaments W1 and W2 are intact.
  • the transformer transforms the heating voltage downwards towards the lamp, so that the resistances of the two filaments W1 and W2 are in turn transformed upwards towards the primary winding Tp.
  • the behavior of the primary winding Tp is therefore influenced by two parallel resistors which correspond to the two coils W1 and W2. If one of the two filaments is broken or the lamp LA has been removed, the behavior of the primary winding Tp changes and thus the course of the current pulse.
  • FIGS. 2a and 2b A typical voltage signal U R3, which can be tapped at the measuring resistor R3, is shown in FIGS. 2a and 2b.
  • the two graphs show the voltage curve that results after the switch S3 is closed, FIG. 2a for an intact lamp and FIG. 2b for the case that one of the two filaments is broken.
  • the voltage U R3 rises very quickly after closing and then drops again after about 3 ⁇ s.
  • the voltage rise U R3 in the event of a filament break is only about half as large and the subsequent voltage drop takes much longer.
  • the curves shown in the two graphs represent waveforms that result from a commercially available gas discharge lamp.
  • the voltage curve U R4 is therefore additionally detected at the second measuring resistor R4.
  • Typical curves of U R4 are also shown in FIGS. 2a and 2b for an intact lamp and for a lamp in which the upper filament is broken.
  • the voltage signal U R4 at the second measuring resistor R4 differs from the signal U R3 at the first measuring resistor R3 primarily by the amplitude of the voltage pulse.
  • the voltage U R3 also rises very quickly and then drops again somewhat more slowly after about 3 ⁇ s.
  • the signals U R3 and U R4 differ very clearly in the event of a spiral break.
  • the curve ⁇ U i shows the difference signal which results from the two curves shown in FIG. 2a with an intact lamp, while the curve ⁇ U d is obtained in the event of a filament break.
  • the voltage difference ⁇ U i is positive at all times.
  • ⁇ U d temporarily takes on negative values.
  • the difference between ⁇ U i and ⁇ U d is more than 400 mV, as a result of which the two states can also be distinguished with the aid of relatively simple measuring devices. Even deviations from the ideal case, which could lead to heating of the filaments and thus a change in the resistance values, are only so great that a measuring tolerance of almost 100 mV remains in any case.
  • a simple assessment of the lamp status is then carried out by measuring the two voltages U R2 and U R3 in a certain time window or at a fixed point in time - for example 10 ms after the switch S3 has been closed, and by forming the differential voltage DU Comparator located in the evaluation circuit M1 is supplied, which compares the DU with a reference or setpoint.
  • the use of the second measuring resistor R4 also provides information about which of the two filaments of the lamp is broken. If this is the lower coil W1, there is inevitably no voltage at R4 because the lower heating circuit is not closed. This is also the case when the lamp has been completely removed. Thus, by evaluating the two voltage signals U R3 and U R4, all four possible lamp states (intact lamp, broken upper or lower filament, no lamp present) can be distinguished very easily. Voltage measurements on the two measuring resistors R3 and R4 are not the only option. It would also be conceivable to use all other types of current measuring method with which the current pulses in the primary coil Tp and one of the two coils W1 and W2 can be evaluated.
  • Another possibility of recognizing the reinstallation of an intact lamp is to dispense with the second measuring resistor R4 and the measurement of the current through one of the two filament heating circuits and instead to consider only the voltage signal U R3 . If a change occurs with regard to the lamp, for example if a new lamp is used, this will definitely cause a change in the signal U R3 .
  • a voltage value U R3 measured at the measuring resistor R3 at a specific point in time after the switch S3 has been closed or an already known target value can be stored and the later current measured values of U R3 can be compared with the stored value. Again, a simple comparator is required, for example. If an intact lamp is used, this is recognized immediately.
  • the construction of the detection and evaluation circuit M1 is even simplified, since only the measurement on a single resistor has to be carried out. Another possibility of recognizing the reinsertion of a lamp is to dispense with the measuring resistor R3 and instead only to evaluate the voltage drops on one or both secondary windings, for example by means of the voltage signal U R4 .
  • the charge / discharge capacitor C3 does not necessarily have to be in the position shown in FIG. 1.

Abstract

An electronic ballast for at least one low-pressure discharge lamp contains an inverter which is connected to a direct-voltage source (UBUS), a load circuit which is connected to the inverter and contains the lamp (LA) and a series resonant circuit, and an evaluating circuit arrangement (M1) which reacts to different operating states of the lamp (LA) and in the case of a defect or removal of the lamp (LA) generates corresponding signals for switching off the inverter. A heating transformer, for heating the coils (W1, W2), the primary winding (Tp) of which is connected in series with a switch (S3) to the output of the inverter and in any case is connected to the direct-voltage source (UBUS) if the inverter is switched off on account of the heating-coil defect or the removal of the lamp (LA), with the switch (S3) being clocked in this off-phase.

Description

Die vorliegende Erfindung betrifft ein elektronisches Vorschaltgerät für eine Niederdruck-Entladungslampe nach dem Oberbegriff des Anspruchs 1, welches eine Schaltung zum Erkennen eines Lampenwechsels oder eines Lampendefekts aufweist.The present invention relates to an electronic ballast for a low pressure discharge lamp after The preamble of claim 1, which is a circuit for detection a lamp change or a lamp defect.

Ein Vorschaltgerät mit einer derartigen Schaltung ist zum Beispiel aus der europäischen Patentanmeldung EP 0 146 683 B1 bekannt. Der Resonanzkondensator des Serienresonanzkreises ist dabei zwischen den beiden Elektroden der Entladungslampe angeordnet, wodurch ein Vorheizen der Elektroden vor dem Zünden der Lampe ermöglicht wird. Ferner weist das Vorschaltgerät eine bistabile Schalteinrichtung mit einem Betriebs- und einem Abschaltzustand auf, wobei die Schalteinrichtung bei einer nichtzündenden Entladungslampe in den Abschaltzustand kippt und den Wechselrichter abschaltet. Die Funktion dieser Schaltung basiert auf der Tatsache, dass die Amplitude des über den Lastzweig mit der Lampe fließenden Stromes bei ungezündeter Lampe wesentlich größer ist als bei gezündeter. Ein über eine der Elektroden der Entladungslampe geführter Haltestromkreis hält dann die bistabile Schalteinrichtung so lange in diesem Abschaltzustand, bis er durch das Einsetzen einer neuen Lampe unterbrochen wird, wodurch automatisch ein Neustart der Lampe eingeleitet wird.A ballast with such a circuit is for Example from European patent application EP 0 146 683 B1 known. The resonant capacitor of the series resonant circuit is between the two electrodes of the discharge lamp arranged, thereby preheating the electrodes before ignition the lamp is enabled. Furthermore, the ballast a bistable switching device with an operating and a switch-off state, the switching device at a non-igniting discharge lamp in the shutdown state tilts and switches off the inverter. The function of this Circuit is based on the fact that the amplitude of the current flowing through the load branch with the lamp when the ignition is not ignited Lamp is significantly larger than when ignited. On via one of the electrodes of the discharge lamp holding circuit then the bistable switching device lasts so long in this shutdown state until it is replaced by the insertion of a new lamp is interrupted, which automatically restarts the lamp is initiated.

Ein Nachteil dieser Schaltung besteht allerdings darin, dass auch nach dem Zünden der Lampe ein Parallelstrom über den Resonanzkondensator und über die beiden Wendeln der Lampe fließt. Dieser Parallelstrom bedeutet im Normalbetrieb der Lampe verlorene Energie und beeinträchtigt deren Leuchtkraft bzw. den Wirkungsgrad. Ferner ist es bei diesem Vorschaltgerät nicht möglich, die Heizleistung unabhängig vom Lampenstrom zu regeln, was insbesondere in einem gedimmten Betrieb der Lampe als nachteilig anzusehen ist, da die durch das Dimmen hervorgerufene Stromreduzierung durch die Wendelheizung ausgeglichen werden sollte.A disadvantage of this circuit, however, is that a parallel current through the resonance capacitor even after the lamp has been ignited and over the two filaments of the lamp flows. This parallel current means the in normal operation Lamp lost energy and affects its luminosity or the efficiency. Furthermore, it is with this ballast not possible, the heating power regardless of the lamp current to regulate what particularly in a dimmed operation the lamp is to be regarded as disadvantageous because of the dimming current reduction caused by the filament heating should be balanced.

Es ist daher Aufgabe der vorliegenden Erfindung, ein elektronisches Vorschaltgerät für eine Niederdruck-Gasentladungslampe anzugeben, bei dem im abgeschalteten Zustand des Wechselrichters mit möglichst geringem Aufwand der Zustand der Lampe und insbesondere ein Lampenwechsel erfasst wird, und das gegenüber dem Stand der Technik eine bessere Steuerung der Heizung der Lampenwendeln ermöglicht.It is therefore an object of the present invention to provide an electronic Ballast for a low pressure gas discharge lamp to be specified when the inverter is switched off with as little effort as possible the condition of the Lamp and in particular a lamp change is detected, and compared to the prior art, better control enables the heating of the lamp filaments.

Diese Aufgabe wird durch ein Vorschaltgerät, welches die Merkmale des Anspruchs 1 aufweist, gelöst. Das erfindungsgemäße Vorschaltgerät zeichnet sich dadurch aus, dass zum Beheizen der Wendeln ein Heiztransformator vorgesehen ist, dessen Primärwicklung in Serie mit einem Schalter an den Ausgang des Wechselrichters angeschlossen ist. Der Strom in der Primärwicklung wird auf zwei Sekundärwicklungen übertragen, die jeweils mit einer der beiden Wendeln einen Heizkreis bilden. Dabei wird der durch die Primärwicklung fließende Strom mit einer Auswerteschaltung erfasst, die im Falle eines Defekts zumindest einer der beiden Wendeln oder bei Entfernen der Lampe oder im Falle eines durch weitere Auswerteschaltungen erfassten Defekts der Lampe ein Abschalten des Wechselrichters bewirkt. Dabei wird auch im abgeschalteten Zustand des Wechselrichters die Primärwicklung des Heiztransformators mit einer Gleichspannungsquelle verbunden, in dieser Abschaltphase der in Serie mit der Primärwicklung liegende Schalter getaktet und durch die Auswerteschaltung der durch die Primärwicklung und/oder die Sekundärwicklung(en) des Heiztransformators fließende Strom ausgewertet. Dieser Strom hängt wesentlich davon ab, ob eine Lampe im System ist bzw. ob ihre beiden Wendeln intakt sind. Der Heiztransformator transformiert die Heizspannung zu der Lampe hin stark nach unten, so dass die Wendelwiderstände ihrerseits zur Primärwicklung hin nach oben transformiert werden. Eine Auswertung des Stromverlaufs gibt demnach nicht nur darüber Aufschluss ob eine Lampe eingesetzt ist, sondern zusätzlich auch darüber, ob und falls dies der Fall ist, welche Wendel defekt ist. Wird in der Abschaltphase die defekte Lampe durch eine neue ersetzt, wird dies von der Auswerteschaltung erkannt, die dann automatisch einen Neustart der Lampe einleitet.This task is performed by a ballast, which the Features of claim 1, solved. The invention Ballast is characterized by that for heating the filaments a heating transformer is provided, the Primary winding in series with a switch at the output of the inverter is connected. The current in the primary winding is transferred to two secondary windings, the each form a heating circuit with one of the two coils. The current flowing through the primary winding is included an evaluation circuit that detects in the event of a defect at least one of the two coils or when removing the Lamp or in the case of a further evaluation circuits detected defect of the lamp, switching off the inverter causes. It is also in the switched off state of the Inverter with the primary winding of the heating transformer connected to a DC voltage source in this switch-off phase the switch in series with the primary winding is clocked and by the evaluation circuit by the primary winding and / or the secondary winding (s) of the heating transformer flowing electricity evaluated. This current depends essentially depends on whether there is a lamp in the system or whether their both coils are intact. The heating transformer transforms the heating voltage down towards the lamp, so that the coil resistors in turn go towards the primary winding be transformed upwards. An evaluation of the current flow therefore not only provides information about whether a lamp is used, but also whether and if this is the case which coil is defective. Will in the shutdown phase the defective lamp is replaced by a new one this is recognized by the evaluation circuit, which then automatically initiates a restart of the lamp.

Gegenüber dem Vorschaltgerät der EP 0 146 683 B1 wird ein wesentlich höherer Wirkungsgrad für die Lampe erzielt, da durch öffnen des Schalters die Wendelheizung nach dem Zünden der Lampe vollständig abgeschaltet werden kann und somit keine Verlustströme auftreten. Ferner kann durch ein zeitweiliges Schließen des Schalters die Heizleistung geregelt werden.Compared to the ballast of EP 0 146 683 B1, a becomes essential Achieved higher efficiency for the lamp because open the switch the filament heating after igniting the Lamp can be switched off completely and therefore none Leakage currents occur. Furthermore, a temporary Closing the switch will regulate the heating output.

Weiterbildungen der Erfindung sind Gegenstand der Unteransprüche. So erfolgt die Stromauswertung am einfachsten durch eine Messung des Spannungsabfalls über einen in Serie mit der Primärwicklung geschalteten Messwiderstand. Ferner kann die Serienschaltung aus der Primärwicklung und dem Schalter mit einem Lade-/Entladekondensator verbunden sein, wobei zur Erfassung des Lampenzustands die Amplitude des gemessenen Stroms der sich ergebenen Lade- bzw. Entladekurven in ihrem zeitlichen Verlauf oder zu bestimmten Zeitpunkten ausgewertet wird.Developments of the invention are the subject of the dependent claims. This is the easiest way to evaluate the electricity a measurement of the voltage drop across a series with the Primary winding switched measuring resistor. Furthermore, the Series connection from the primary winding and the switch with be connected to a charge / discharge capacitor, for detection of the lamp state, the amplitude of the measured Current of the resulting charge or discharge curves in their evaluated over time or at certain times becomes.

Der Stromverlauf in dem Heiztransformator bzw. der Spannungsabfall über den Messwiderstand hängt unter anderem auch von der dem Heiztransformator zugeführten Gleichspannung ab. Diese kann sich allerdings - beispielsweise aufgrund von Netzschwankungen - mit der Zeit durchaus leicht ändern. In einer Weiterbildung der Erfindung kann daher in einem aus einer Lampenwendel und der dazugehörigen Sekundärwicklung bestehenden Heizkreis ein zweiter Messwiderstand vorgesehen sein, wobei die über diesen Messwiderstand abfallende Spannung ebenfalls ausgewertet wird. Ein Vergleich der beiden Spannungen lässt dann eine von Spannungsschwankungen unabhängige Aussage über den Zustand der Elektroden der Lampe zu. Dies erfolgt beispielsweise dadurch, dass die Differenzspannung gebildet wird, die dann mit einem Sollwert verglichen wird. Wie gezeigt werden wird, erlaubt dieses Verfahren eine sehr einfache aber aussagekräftige Analyse des Lampenzustands. Alternativ dazu kann aber auch der Stromverlauf in dem Heiztransformator jeweils zu bestimmten Zeitpunkten mit einem früheren Messwert oder einem Referenzwert verglichen werden. In diesem Fall wäre nur ein einzelner Messwiderstand ausreichend, wobei wahlweise der Strom in der Primärwicklung oder in einer der beiden Sekundärwicklungen ausgewertet werden kann.The current profile in the heating transformer or the voltage drop The measurement resistance also depends on the DC voltage supplied to the heating transformer. This can, however - for example due to network fluctuations - change quite easily over time. In a Further development of the invention can therefore be in one of a Existing lamp filament and the associated secondary winding Heating circuit, a second measuring resistor may be provided, wherein the voltage drop across this measuring resistor also is evaluated. A comparison of the two tensions then leaves a statement independent of voltage fluctuations about the condition of the electrodes of the lamp too. this happens for example in that the differential voltage is formed which is then compared to a setpoint. As shown this method allows a very simple one but meaningful analysis of the lamp status. alternative however, the current profile in the heating transformer can also do this at an earlier point in time Measured value or a reference value can be compared. In this In this case, only a single measuring resistor would be sufficient either the current in the primary winding or in one of the two secondary windings can be evaluated.

Die Verwendung eines Heiztransformators ist bereits aus der EP 0 707 438 A3 bzw. aus der EP 748 146 A1 und der DE 295 14 817 U1 bekannt, wobei auch hier jeweils das Abschalten der Wendelheizung nach dem Zünden der Lampe erwähnt wird. Ferner sieht die EP 0 707 438 A3 eine Auswertung des Heizstromes vor, um eventuelle Lampendefekte zu erkennen. Allerdings ist bei keinem der in diesen Schriften beschriebenen Vorschaltgeräte ein Abschalten der Wechselrichters und eine Erkennung des Lampenwechsels vorgesehen. Die Erfindung ist auch zum Einsatz für elektronische Vorschaltgeräte, die mehrere Lampen betreiben, geeignet.The use of a heating transformer is already out of the EP 0 707 438 A3 or from EP 748 146 A1 and DE 295 14 817 U1 is known, with the shutdown also in each case here the filament heating mentioned after igniting the lamp becomes. EP 0 707 438 A3 also sees an evaluation of the Heating current in order to detect possible lamp defects. Indeed is none of those described in these writings Ballasts switching off the inverter and one Detection of lamp replacement provided. The invention is also used for electronic ballasts that have multiple Operate lamps, suitable.

Im folgenden soll die Erfindung anhand der beiliegenden Zeichnung näher erläutert werden. Es zeigen:

Fig. 1
ein Ausführungsbeispiel einer erfindungs- gemäßen Schaltung zum Ansteuern der Lampe und zum Erfassen des Lampenzustands;
Fig. 2a
die Spannungsverläufe an den beiden Messwiderständen bei einer intakten Lampe;
Fig. 2b
die Spannungsverläufe an den beiden Messwiderständen bei einer defekten Lampe;
Fig. 2c
den Verlauf der Differenzspannung bei intakter und bei defekter Lampe;
Fig. 3
eine Alternativschaltung zu dem in Fig. 1 gezeigten Ausführungsbeispiel.
The invention will be explained in more detail below with reference to the accompanying drawing. Show it:
Fig. 1
an embodiment of a circuit according to the invention for controlling the lamp and for detecting the lamp state;
Fig. 2a
the voltage profiles at the two measuring resistors with an intact lamp;
Fig. 2b
the voltage profiles at the two measuring resistors in the case of a defective lamp;
Fig. 2c
the course of the differential voltage when the lamp is intact and defective;
Fig. 3
an alternative circuit to the embodiment shown in Fig. 1.

Die wesentlichen Bestandteile der Erfindung sind in dem Schaltbild in Fig. 1 dargestellt. Der Wechselrichter wird durch eine Halbbrücke aus zwei in Serie geschalteten elektronischen Schaltern S1 und S2 gebildet. Diese Schalter S1, S2 können beispielsweise durch zwei MOS-Feldeffekttransistoren gebildet werden. Der Fußpunkt der Halbbrücke liegt auf Masse, während an ihrem Eingang die Gleichspannung UBUS anliegt, die beispielsweise durch die Formung der üblichen Netzspannung durch eine Kombination aus Funkentstörer und Gleichrichter erzeugt werden kann. Alternativ dazu kann allerdings auch eine beliebige andere Gleichspannungsquelle an der Halbbrücke anliegen.The essential components of the invention are shown in the circuit diagram in FIG. 1. The inverter is formed by a half bridge made of two electronic switches S1 and S2 connected in series. These switches S1, S2 can be formed, for example, by two MOS field effect transistors. The base of the half-bridge lies on ground, while the DC voltage U BUS is present at its input, which can be generated, for example, by shaping the usual mains voltage using a combination of radio interference suppressor and rectifier. Alternatively, however, any other DC voltage source can also be present on the half bridge.

An den gemeinsamen Knotenpunkt der beiden Schalter S1 und S2 ist der die Entladungslampe LA enthaltende Lastkreis angeschlossen. Dieser besteht aus einem Serienresonanzkreis, der sich aus einer Drosselspule L1 und einem Resonanzkondensator C2 zusammensetzt. Der Drosselspule L1 ist ein Koppelkondensator C1 vorgeschaltet. An den Verbindungsknoten zwischen Drosselspule L1 und Resonanzkondensator C2 ist ferner die obere der beiden Kathoden der Lampe LA angeschlossen. Die beiden Kathoden weisen jeweils zwei Anschlüsse auf, zwischen denen jeweils eine Heizwendel W1 bzw. W2 zum Beheizen der Kathoden vorgesehen ist. Die untere Kathode der Lampe LA ist wiederum mit dem Ausgang des Resonanzkondensators C2 verbunden und der gemeinsame Knotenpunkt schließlich über den Widerstand R1 mit Masse verbunden.At the common node of the two switches S1 and S2 the load circuit containing the discharge lamp LA is connected. This consists of a series resonance circuit, the consists of a choke coil L1 and a resonance capacitor C2 is composed. The choke coil L1 is a coupling capacitor C1 upstream. At the connection node between the choke coil L1 and resonance capacitor C2 is also the upper one of the two cathodes of the lamp LA connected. The two Cathodes each have two connections, between which one heating coil W1 and one W2 each for heating the cathodes is provided. The lower cathode of the lamp LA is again connected to the output of the resonance capacitor C2 and the common node finally via resistor R1 Ground connected.

Zum Vorheizen der beiden Wendeln W1 und W2 ist ein Heiztransformator vorgesehen, der aus einer Primärwicklung Tp sowie aus zwei Sekundärwicklungen Ts1 und Ts2 besteht. Die Sekundärwicklungen Ts1 und Ts2 sind jeweils mit einer Wendel W1 bzw. W2 der Lampe LA verbunden, so dass zwei getrennte Heizkreise gebildet werden. Die Primärwicklung Tp ist in der Mitte einer Serienschaltung angeordnet, die zusätzlich zu der Primärwicklung Tp einen Lade-/Entladekondensator C3 und einen dritten steuerbaren Schalter S3 aufweist. Auch dieser Schalter S3 kann wie die beiden Schalter der Halbbrücke S1 und S2 aus einem Feldeffekttransistor bestehen. Der zweite Anschluss des Lade-/Entladekondensators C3 ist ebenso wie der Lastkreis mit dem Knotenpunkt der beiden Schalter S1 und S2 verbunden, so dass diese Serienschaltung parallel zum unteren Zweig der Halbbrücke liegt. Dem Knotenpunkt zwischen der Primärwicklung Tp und dem Lade-/Entladekondensator C3 wird unabhängig von dem Wechselrichter zusätzlich über einen Widerstand R2 die Versorgungsgleichspannung UBUS zugeführt.To preheat the two coils W1 and W2, a heating transformer is provided, which consists of a primary winding Tp and two secondary windings Ts1 and Ts2. The secondary windings Ts1 and Ts2 are each connected to a filament W1 and W2 of the lamp LA, so that two separate heating circuits are formed. The primary winding Tp is arranged in the middle of a series circuit which, in addition to the primary winding Tp, has a charge / discharge capacitor C3 and a third controllable switch S3. Like the two switches of the half-bridge S1 and S2, this switch S3 can also consist of a field effect transistor. The second connection of the charge / discharge capacitor C3, like the load circuit, is connected to the node of the two switches S1 and S2, so that this series connection is parallel to the lower branch of the half-bridge. The DC supply voltage U BUS is additionally supplied to the node between the primary winding Tp and the charge / discharge capacitor C3 independently of the inverter via a resistor R2.

Zwischen dem Schalter S3 und dem Masseanschluss der Serienschaltung ist zum Erfassen des Heizstroms ein Messwiderstand R3 angeordnet. Der durch den Strom hervorgerufene Spannungsabfall über den Messwiderstand R3 wird mit Hilfe einer Auswerteschaltung M1 gemessen. Ein weiterer Messwiderstand R4 ist in dem Heizkreis der unteren Lampenwendel W1 angeordnet, wobei auch der Spannungsabfall über diesen Messwiderstand R4 und damit der Stromfluss durch diesen Heizkreis durch die der Auswerteschaltung M1 gemessen werden kann.Between the switch S3 and the ground connection of the series connection is a measuring resistor to measure the heating current R3 arranged. The voltage drop caused by the current An evaluation circuit is used to measure the measuring resistor R3 M1 measured. Another measuring resistor R4 is arranged in the heating circuit of the lower lamp filament W1, the voltage drop across this measuring resistor R4 and thus the current flow through this heating circuit through the Evaluation circuit M1 can be measured.

Da die beiden Messwiderstände R3, R4 indirekt für Strommessungen verwendet werden, können sie natürlich auch an anderen Positionen angeordnet sein. Beispielsweise kann der erste Messwiderstand R3 auch zwischen dem Schalter S3 und der Primärspule Tp des Heiztransformators vorgesehen sein oder sich der zweite Messwiderstand R4 auf der anderen Seite der Sekundärspule Ts1 in dem Heizkreis befinden. Alternativ zu dem unteren Heizkreis kann sich dieser Widerstand R4 allerdings auch in dem Heizkreis der oberen Wendel W2 und der zweiten Sekundärspule Ts2 befinden. Da für die Erfassung des Lampenzustands die Stromstärken benötigt werden, können anstelle der Messwiderstände R3 und R4 auch andere strommessende Vorrichtungen verwendet werden.Since the two measuring resistors R3, R4 indirectly for current measurements can of course also be used on others Positions can be arranged. For example, the first Measuring resistor R3 also between the switch S3 and the primary coil Tp of the heating transformer can be provided or itself the second measuring resistor R4 on the other side of the secondary coil Ts1 are in the heating circuit. Alternatively to the lower one However, this resistor R4 can become a heating circuit also in the heating circuit of the upper coil W2 and the second one Secondary coil Ts2 are located. As for the detection of the lamp status the amperages needed can be instead the measuring resistors R3 and R4 also other current measuring devices be used.

Das Ansteuern der drei Schalter S1, S2 und S3 erfolgt durch eine nicht dargestellte Steuerschaltung, wobei das Vorheizen der Wendeln W1, W2 und das Zünden der Lampe LA in bekannter Weise ausgeführt wird. Während des Vorheizens wird der dritte Schalter S3 permanent geschlossen, so dass die von dem Wechselrichter abgegebene Wechselspannung auch dem Heiztransformator zugeführt wird. Dabei werden die Schalter S1 und S2 mit einer gegenüber der Resonanzfrequenz des Lastkreises erhöhten Frequenz angesteuert, so dass die an der Lampe LA anliegende Spannung noch keine Zündung bewirkt. Nach Ablauf einer vorgegebenen Heizzeit wird der Schalter S3 geöffnet und die Heizung der Wendeln damit beendet, und die Zündung der Lampe LA wird eingeleitet. Dazu wird die Wechselspannungsfrequenz der Steuersignale für die beiden Schalter S1 und S2 des Wechselrichters der Resonanzfrequenz angenähert, bis schließlich die Zündung erfolgt.The three switches S1, S2 and S3 are activated by a control circuit, not shown, wherein the preheating the coils W1, W2 and the ignition of the lamp LA in a known manner Way is executed. The third becomes during the preheating Switch S3 permanently closed, so that of the inverter AC voltage also delivered to the heating transformer is fed. The switches S1 and S2 are used an increased compared to the resonance frequency of the load circuit Frequency controlled so that the applied to the lamp LA Voltage does not cause ignition. After a predetermined Heating time, switch S3 is opened and the heating the coils ended with it, and the ignition of the lamp LA Is initiated. To do this, the AC voltage frequency Control signals for the two switches S1 and S2 of the inverter approximated the resonance frequency until finally the Ignition takes place.

Bereits während des Vorheizens der Lampe LA kann mit Hilfe der Auswerteschaltung oder anderen (nicht dargestellten) Überwachungsschaltungen in bekannter Weise überprüft werden, ob sich eine intakte Lampe LA im System befindet. Ist dies nicht der Fall oder wird beim Vorheizen oder im Normalbetrieb ein Wendelbruch bzw. ein Entfernen der Lampe LA registriert, wird das Vorschaltgerät in einen Ruhezustand versetzt und der Wechselrichter abgeschaltet, um möglichst wenig Energie zu verbrauchen und ein gefahrloses Auswechseln der Lampe LA zu ermöglichen. Allerdings wird dafür dann der zu der Wendelheizung gehörige Schalter S3 niederfrequent getaktet. Da der Primärwicklung Tp über den Widerstand R2 die Versorgungsspannung UBUS zugeführt wird, wird durch die Betaktung des Schalters S3 eine Wechselspannung erzeugt, welche durch den Transformator auf die beiden Heizkreise mit den Wendeln W1 und W2 übertragen wird. Der Heizstrom durch die Primärwicklung Tp wird dann durch die Auswerteschaltung M1 erfasst, um das Einsetzen einer neuen intakten Lampe festzustellen. Vorzugsweise wird dabei der Schalter S3 mit einer niedrigen Taktfrequenz von ungefähr 50-100Hz geschaltet. Das Tastverhältnis des Steuersignals für den Schalter S3 liegt bei ungefähr 50%, wobei jedoch weder die Wahl der Taktfrequenz noch das Tastverhältnis für die Lampenzustands-Erfassung kritisch sind.Already during the preheating of the lamp LA, the evaluation circuit or other monitoring circuits (not shown) can be used to check in a known manner whether there is an intact lamp LA in the system. If this is not the case or if a filament breakage or removal of the lamp LA is registered during preheating or during normal operation, the ballast is put into an idle state and the inverter is switched off in order to consume as little energy as possible and to enable the lamp LA to be replaced safely , However, the switch S3 belonging to the filament heating is then clocked at low frequency. Since the primary winding Tp is supplied with the supply voltage U BUS via the resistor R2, an actuation of the switch S3 generates an alternating voltage, which is transmitted through the transformer to the two heating circuits with the coils W1 and W2. The heating current through the primary winding Tp is then detected by the evaluation circuit M1 in order to determine the insertion of a new intact lamp. Switch S3 is preferably switched with a low clock frequency of approximately 50-100 Hz. The duty cycle of the control signal for the switch S3 is approximately 50%, but neither the choice of the clock frequency nor the duty cycle for the lamp status detection are critical.

Im folgenden soll anhand der Fig. 2 die Auswertung der an den Messwiderständen R3 und R4 abgegriffenen Spannungssignale UR3 und UR4 näher erläutert werden. Dazu wird davon ausgegangen, dass im abgeschalteten Zustand des Wechselrichters, der obere Schalter S1 permanent geöffnet ist, während hingegen der untere Schalter S2 geschlossen ist. Der Schalter S3 öffnet und schließt mit einer Frequenz von ungefähr 50 Hz. Mit dem Öffnen des Schalters S3 wird der Lade-/Entladekondensator C3 über den Widerstand R2 von der Spannung UBUS geladen. An dem Lade-/Entladekondensator C3 ergibt sich dabei der Spannungsverlauf einer ansteigenden e-Funktion. Wird der Schalter S3 anschließend geschlossen, führt dies zu einer Entladung des Lade-/Entladekondensators C3, wobei die Spannung zeitlich gesehen nun einer abfallenden e-Funktion folgt.The evaluation of the voltage signals U R3 and U R4 tapped at the measuring resistors R3 and R4 will be explained in more detail below with reference to FIG. 2. For this purpose, it is assumed that when the inverter is switched off, the upper switch S1 is permanently open, whereas the lower switch S2 is closed. The switch S3 opens and closes at a frequency of approximately 50 Hz. When the switch S3 is opened, the charging / discharging capacitor C3 is charged by the voltage U BUS via the resistor R2. The voltage curve of an increasing e-function results at the charge / discharge capacitor C3. If the switch S3 is subsequently closed, this leads to a discharge of the charging / discharging capacitor C3, the voltage now following a decreasing e-function in terms of time.

Bei jedem Schließen des Schalters S3 ergibt sich an der Primärspule Tp des Heiztransformators aufgrund der Entladung des Lade-/Entladekondensator C3 ein Strompuls und dementsprechend an dem Messwiderstand R3 ein Spannungspuls UR3. Der Spannungsverlauf an dem Messwiderstand R3 hängt dabei wesentlich davon ab, ob sich in dem System eine Lampe LA befindet und ob die beiden Wendeln W1 und W2 intakt sind. Der Transformator transformiert die Heizspannung zu der Lampe hin stark nach unten, so dass die Widerstände der beiden Wendeln W1 und W2 ihrerseits zur Primärwicklung Tp hin nach oben transformiert werden. Das Verhalten der Primärwicklung Tp wird daher durch zwei Parallelwiderstände beeinflusst, die den beiden Wendeln W1 bzw. W2 entsprechen. Ist eine der beiden Wendeln gebrochen oder wurde die Lampe LA entfernt, verändert sich das Verhalten der Primärwicklung Tp und damit der Verlauf des Strompulses.Each time the switch S3 is closed, a current pulse results at the primary coil Tp of the heating transformer due to the discharge of the charge / discharge capacitor C3 and accordingly a voltage pulse U R3 at the measuring resistor R3 . The voltage curve across the measuring resistor R3 depends essentially on whether there is a lamp LA in the system and whether the two filaments W1 and W2 are intact. The transformer transforms the heating voltage downwards towards the lamp, so that the resistances of the two filaments W1 and W2 are in turn transformed upwards towards the primary winding Tp. The behavior of the primary winding Tp is therefore influenced by two parallel resistors which correspond to the two coils W1 and W2. If one of the two filaments is broken or the lamp LA has been removed, the behavior of the primary winding Tp changes and thus the course of the current pulse.

Ein typisches, an dem Messwiderstand R3 abgreifbares Spannungssignal UR3 ist in den Fig. 2a und 2b gezeigt. Die beiden Graphen zeigen den sich nach dem Schließen des Schalters S3 ergebenden Spannungsverlauf, Fig. 2a für eine intakte Lampe und Fig. 2b für den Fall, dass eine der beiden Wendeln gebrochen ist. Wie Fig. 2a entnommen werden kann, steigt die Spannung UR3 nach dem Schließen kurzfristig sehr schnell an und fällt daraufhin nach ca. 3 µs wieder ab. Im Gegensatz dazu ist der Spannungsanstieg UR3 bei einem Wendelbruch in etwa nur halb so groß und der anschließende Spannungsabfall dauert wesentlich länger. Die in den beiden Graphen gezeigten Kurven stellen Signalverläufe dar, die sich bei einer handelsüblichen Gasentladungslampe ergeben.A typical voltage signal U R3, which can be tapped at the measuring resistor R3, is shown in FIGS. 2a and 2b. The two graphs show the voltage curve that results after the switch S3 is closed, FIG. 2a for an intact lamp and FIG. 2b for the case that one of the two filaments is broken. As can be seen in FIG. 2a, the voltage U R3 rises very quickly after closing and then drops again after about 3 μs. In contrast, the voltage rise U R3 in the event of a filament break is only about half as large and the subsequent voltage drop takes much longer. The curves shown in the two graphs represent waveforms that result from a commercially available gas discharge lamp.

Prinzipiell kann also schon allein anhand des Signals UR3 eine Aussage getroffen werden, ob eine Lampe eingesetzt wurde und ob diese auch intakt ist. Allerdings hängen die Messergebnisse der Spannung UR3 unter anderem auch von der Versorgungsspannung UBUS ab. Schwankungen in UBUS könnten daher möglicherweise zu einer Beeinträchtigung des Messergebnisses und zu einer Falschaussage über den Zustand der Lampe LA führen, wodurch versehentlich ein Neustart der immer noch defekten Lampe versucht werden könnte.In principle, a statement can be made based solely on the signal U R3 as to whether a lamp has been inserted and whether it is also intact. However, the measurement results of the voltage U R3 also depend, inter alia, on the supply voltage U BUS . Fluctuations in the U BUS could therefore lead to an impairment of the measurement result and to a false statement about the state of the lamp LA, which could inadvertently attempt to restart the lamp which is still defective.

In einer Weiterbildung wird daher zusätzlich der Spannungsverlauf UR4 an dem zweiten Messwiderstand R4 erfasst. Typische Kurven von UR4 sind ebenfalls in den Fig. 2a und 2b für eine intakte Lampe bzw. für eine Lampe, in der die obere Wendel gebrochen ist, gezeigt. Bei einer intakten Lampe unterscheidet sich das Spannungssignal UR4 an dem zweiten Messwiderstand R4 von dem Signal UR3 an dem ersten Messwiderstand R3 in erster Linie durch die Amplitude des Spannungspulses. Der zeitliche Verlauf ist allerdings ähnlich. Die Spannung UR3 steigt ebenfalls sehr schnell an und fällt dann nach ca. 3 µs wieder etwas langsamer ab. Im Gegensatz dazu unterscheiden sich die Signale UR3 und UR4 bei einem Wendelbruch sehr deutlich. Die Spannung UR4 steigt nämlich nach wie vor anfangs sehr stark an und kann dabei sogar deutlich höhere Werte als UR3 erreichen. Anschließend fällt das Signal UR4 aber schneller als UR3 ab und erreicht nach einer gewissen Zeit wieder niedrigere Werte als UR3.In a further development, the voltage curve U R4 is therefore additionally detected at the second measuring resistor R4. Typical curves of U R4 are also shown in FIGS. 2a and 2b for an intact lamp and for a lamp in which the upper filament is broken. In the case of an intact lamp, the voltage signal U R4 at the second measuring resistor R4 differs from the signal U R3 at the first measuring resistor R3 primarily by the amplitude of the voltage pulse. However, the course over time is similar. The voltage U R3 also rises very quickly and then drops again somewhat more slowly after about 3 μs. In contrast, the signals U R3 and U R4 differ very clearly in the event of a spiral break. This is because the voltage U R4 continues to rise very sharply initially and can even reach values significantly higher than U R3 . Subsequently, the signal U R4 drops faster than U R3 and, after a certain time, reaches lower values again than U R3 .

Um nun eine von Schwankungen in der Versorgungsspannung UBUS unabhängige Aussage über den Zustand der Lampe machen zu können, werden die Messergebnisse an den Messwiderständen R3 und R4 zueinander im Verhältnis betrachtet. In einfachster Weise geschieht dies dadurch, dass die Differenzspannung ΔU = UR3 - UR4 gebildet und ausgewertet wird. Das Ergebnis der Differenzbildung ist in Fig. 2c dargestellt. Die Kurve ΔUi zeigt dabei das Differenzsignal, das sich aus den beiden in Fig. 2a gezeigten Kurven bei einer intakten Lampe ergibt, während die Kurve ΔUd im Falle eines Wendelbruchs erhalten wird. Diese Kurven sind nun von Schwankungen in der Versorgungsspannung UBUS unabhängig und erlauben somit, in einfacher Weise eine eindeutige Aussage über den Zustand der Lampe zu treffen. Ist die Lampe intakt, ist die Spannungsdifferenz ΔUi zu jedem Zeitpunkt positiv. Ist jedoch die obere Wendel W2 gebrochen, nimmt ΔUd kurzfristig negative Werte an. Beispielsweise bis zu 15µs nach dem Schließen des Schalters S3 beträgt die Differenz zwischen ΔUi und ΔUd mehr als 400 mV wodurch die beiden Zustände auch mit Hilfe relativ einfacher Messvorrichtungen unterscheidbar sind. Selbst Abweichungen vom Idealfall, die durch eine Erwärmung der Wendeln und damit zu einer Veränderung in den Widerstandswerten führen könnten, sind nur so groß, dass in jedem Fall eine Messtoleranz von nahezu 100 mV verbleibt. Eine einfache Beurteilung des Lampenzustands erfolgt dann dadurch, dass die beiden Spannungen UR2 und UR3 in einem bestimmten Zeitfenster bzw. zu einem festen Zeitpunkt - beispielsweise 10 ms nach dem Schließen des Schalters S3 - gemessen werden, die Differenzspannung DU gebildet wird und diese einem in der Auswerteschaltung M1 befindlichen Komparator zugeführt wird, der DU mit einem Referenz- oder Sollwert vergleicht.In order to be able to make a statement about the state of the lamp that is independent of fluctuations in the supply voltage U BUS , the measurement results at the measuring resistors R3 and R4 are considered in relation to one another. In the simplest way, this happens because the differential voltage ΔU = U R3 - U R4 is formed and evaluated. The result of the difference formation is shown in Fig. 2c. The curve ΔU i shows the difference signal which results from the two curves shown in FIG. 2a with an intact lamp, while the curve ΔU d is obtained in the event of a filament break. These curves are now independent of fluctuations in the supply voltage U BUS and thus allow a simple statement to be made about the state of the lamp. If the lamp is intact, the voltage difference ΔU i is positive at all times. However, if the upper helix W2 is broken, ΔU d temporarily takes on negative values. For example, up to 15µs after the switch S3 is closed, the difference between ΔU i and ΔU d is more than 400 mV, as a result of which the two states can also be distinguished with the aid of relatively simple measuring devices. Even deviations from the ideal case, which could lead to heating of the filaments and thus a change in the resistance values, are only so great that a measuring tolerance of almost 100 mV remains in any case. A simple assessment of the lamp status is then carried out by measuring the two voltages U R2 and U R3 in a certain time window or at a fixed point in time - for example 10 ms after the switch S3 has been closed, and by forming the differential voltage DU Comparator located in the evaluation circuit M1 is supplied, which compares the DU with a reference or setpoint.

Die Verwendung des zweiten Messwiderstandes R4 gibt ferner darüber Auskunft, welche der beiden Wendeln der Lampe gebrochen ist. Handelt es sich nämlich dabei um die untere Wendel W1, so tritt an R4 zwangsläufig gar keine Spannung auf, da der untere Heizkreis nicht geschlossen ist. Dies ist ebenfalls der Fall, wenn die Lampe vollständig entfernt wurde. Somit können durch Auswertung der beiden Spannungssignale UR3 und UR4 sehr einfach alle vier möglichen Lampenzustände (intakte Lampe, obere oder untere Wendel gebrochen, keine Lampe vorhanden) unterschieden werden. Spannungsmessungen an den beiden Messwiderständen R3 und R4 sind jedoch nicht die einzige Möglichkeit. Denkbar wäre auch die Anwendung aller anderen Arten von Strommessverfahren, mit denen die Strompulse in der Primärspule Tp und einer der beiden Wendeln W1 bzw. W2 ausgewertet werden können.The use of the second measuring resistor R4 also provides information about which of the two filaments of the lamp is broken. If this is the lower coil W1, there is inevitably no voltage at R4 because the lower heating circuit is not closed. This is also the case when the lamp has been completely removed. Thus, by evaluating the two voltage signals U R3 and U R4, all four possible lamp states (intact lamp, broken upper or lower filament, no lamp present) can be distinguished very easily. Voltage measurements on the two measuring resistors R3 and R4 are not the only option. It would also be conceivable to use all other types of current measuring method with which the current pulses in the primary coil Tp and one of the two coils W1 and W2 can be evaluated.

Eine weitere Möglichkeit, das Wiedereinsetzen einer intakten Lampe zu erkennen, liegt darin, auf den zweiten Messwiderstand R4 und die Messung des Stromes durch einen der beiden Wendel-Heizkreise zu verzichten und statt dessen nur das Spannungssignal UR3 zu betrachten. Wenn bezüglich der Lampe eine Änderung eintritt, wenn also beispielsweise eine neue Lampe eingesetzt wird, so bewirkt dies auf jeden Fall eine Änderung an dem Signal UR3. Es kann nun ein zu einem bestimmten Zeitpunkt nach dem Schließen des Schalters S3 gemessener Spannungswert UR3 an dem Messwiderstand R3 oder ein bereits bekannter Sollwert gespeichert und die späteren aktuellen Messwerte von UR3 mit dem gespeicherten Wert verglichen werden. Wiederum wird dazu beispielsweise ein einfacher Komparator benötigt. Wird eine intakte Lampe eingesetzt, wird dies unmittelbar erkannt. Der Aufbau der Erfassungs- und Auswerteschaltung M1 wird sogar noch vereinfacht, da nur die Messung an einem einzigen Widerstand durchgeführt werden muss. Eine weitere Möglichkeit, das Wiedereinsetzen einer Lampe zu erkennen, liegt darin, auf den Messwiderstand R3 zu verzichten und statt dessen nur die Spannungsabfälle an einer oder beiden Sekundärwicklung(en), beispielsweise durch das Spannungssignal UR4, auszuwerten.Another possibility of recognizing the reinstallation of an intact lamp is to dispense with the second measuring resistor R4 and the measurement of the current through one of the two filament heating circuits and instead to consider only the voltage signal U R3 . If a change occurs with regard to the lamp, for example if a new lamp is used, this will definitely cause a change in the signal U R3 . A voltage value U R3 measured at the measuring resistor R3 at a specific point in time after the switch S3 has been closed or an already known target value can be stored and the later current measured values of U R3 can be compared with the stored value. Again, a simple comparator is required, for example. If an intact lamp is used, this is recognized immediately. The construction of the detection and evaluation circuit M1 is even simplified, since only the measurement on a single resistor has to be carried out. Another possibility of recognizing the reinsertion of a lamp is to dispense with the measuring resistor R3 and instead only to evaluate the voltage drops on one or both secondary windings, for example by means of the voltage signal U R4 .

Wird schließlich festgestellt, dass sich wieder eine intakte Lampe in dem System befindet, kann von der Auswerteschaltung M1 ein entsprechendes Signal an die Steuerschaltung übertragen werden um einen automatischen Neustart zu veranlassen.Finally it is found that there is again an intact Lamp located in the system can be used by the evaluation circuit M1 transmit a corresponding signal to the control circuit to initiate an automatic restart.

Abschließend soll noch eine Alternative zu der in Fig. 1 gezeigten Schaltung erwähnt werden. Der Lade-/Entladekondensators C3 muss sich nämlich nicht zwingend an der in Fig. 1 gezeigten Position befinden. Um dennoch eine Lade- bzw. Entladekurve zu erhalten, kann entsprechend der in Fig. 3 gezeigten Alternativschaltung der Lade-/Entladekondensator C3 beispielsweise auch an einem Ende mit dem Knotenpunkt der beiden Schalter S1 und S2 des Wechselrichters und mit dem anderen Ende direkt mit Masse verbunden sein. Da der Lade-/Entladekondensator C3 im abgeschalteten Zustand des Wechselrichters bei der oben angegebenen Betriebsweise, in der der Schalter S1 permanent geöffnet und der Schalter S2 permanent geschlossen ist, kurzgeschlossen wäre (UC3 = 0), müssen die Schalter S1 und S2 bei Verwendung der in Fig. 3 als Ausführungsbeispiel abgebildeten Schaltung permanent geöffnet bleiben, um einen ordnungsgemäßen Betrieb der Schaltung zu gewährleisten. Finally, an alternative to the circuit shown in FIG. 1 should be mentioned. The charge / discharge capacitor C3 does not necessarily have to be in the position shown in FIG. 1. In order nevertheless to obtain a charge or discharge curve, in accordance with the alternative circuit shown in FIG. 3, the charge / discharge capacitor C3 can, for example, also at one end with the node of the two switches S1 and S2 of the inverter and at the other end directly with ground be connected. Since the charge / discharge capacitor C3 would be short-circuited (U C3 = 0) when the inverter is switched off and in the above-mentioned operating mode, in which the switch S1 is permanently open and the switch S2 is permanently closed, the switches S1 and S2 must be used of the circuit shown as an exemplary embodiment in FIG. 3 remain permanently open in order to ensure proper operation of the circuit.

BezugszeichenlisteLIST OF REFERENCE NUMBERS

Nr.No. Merkmal bzw. KomponenteFeature or component C1C1 Koppel kondensator in Serie zur Drosselspule L1Coupling capacitor in series with the choke coil L1 C2C2 Resonanzkondensator eines Serienresonanzkreises, bestehend aus der Drosselspule mit der Induktivität L1, dem Koppel kondensator mit der Kapazität C1 und dem Resonanzkondensator mit der Kapazität C2Resonance capacitor of a series resonance circuit, consisting of the inductor with the inductance L1, the coupling capacitor with the capacitance C1 and the resonance capacitor with the capacitance C2 C3C3 mit dem Verbindungsknoten der beiden Leistungsschalter S1 und S2 verbundener Lade-/Entladekondensator, der entweder in Serie zu der parallel zum Lastkreis liegenden Serienschaltung des Schalters S3 und der Primärwicklung Tp des Heiztransformators geschaltet ist (vgl. Fig. 1 oder parallel zur Serienschaltung aus S3 und Tp direkt mit dem Masseanschluss verbunden ist (vgl. Fig. 3)with the connection node of the two circuit breakers S1 and S2 connected charging / discharging capacitor, which is either connected in series to the series circuit of switch S3 parallel to the load circuit and the primary winding Tp of the heating transformer (see Fig. 1 or parallel to the series circuit from S3 and Tp is connected directly to the ground connection (see Fig. 3) L1L1 Drosselspule zur Begrenzung des Vorheizstroms für die Wendeln W1 und W2 der Niederdruck-Gasentladungslampe LAChoke coil for limiting the preheating current for the filaments W1 and W2 of the low-pressure gas discharge lamp LA LALA Niederdruck-GasentladungslampeLow-pressure gas discharge lamp M1M1 Mess- und Auswerteschaltung zur Bildung und Auswertung der Differenzspannung ΔU aus den an R3 bzw. R4 abfallenden Spannungen UR3 und UR4 (ΔU = UR3 - UR4)Measuring and evaluation circuit for forming and evaluating the differential voltage ΔU from the voltages U R3 and U R4 dropping at R3 and R4 (ΔU = U R3 - U R4 ) R1R1 Widerstand zur Verbindung des gemeinsamen Knotenpunkts zwischen dem Messwiderstand R4 und der ersten Wendel W1 der Niederdruck-Gasentladungslampe LA mit dem MasseanschlussResistor for connecting the common node between the measuring resistor R4 and the first filament W1 of the low-pressure gas discharge lamp LA to the ground connection R2R2 Widerstand zur Verbindung der Gleichspannungsquelle mit dem Knotenpunkt zwischen der Primärwicklung Tp des Heiztransformators und dem Lade-/Entladekondensator C3Resistor for connecting the DC voltage source to the node between the primary winding Tp of the heating transformer and the charge / discharge capacitor C3 R3R3 Messwiderstand in Serie zu der parallel zum Lastkreis liegenden Serienschaltung des Schalters S3 und der Primärwicklung Tp des Heiztransformators zum Messen der Spannung UR3 Measuring resistor in series with the series connection of switch S3 lying parallel to the load circuit and the primary winding Tp of the heating transformer for measuring the voltage U R3 R4R4 Messwiderstand in Serie zur zweiten Sekundärwicklung Ts2 des Heiztransformators und der ersten Wendel W1 der Nieder- Measuring resistor in series with the second secondary winding Ts2 of the heating transformer and the first coil W1 of the low druck-Entladungslampe LA zum Messen des Stroms durch den Heizkreis der ersten Wendel W1pressure discharge lamp LA for measuring the current through the heating circuit of the first filament W1 S1S1 erster elektronisch gesteuerter Leistungsschalter (realisiert als MOS-Feldeffekttransistor) als Teil eines Wechselrichters (DC/AC-Wandlers), bestehend aus den zwei zu einer Halbbrücke in Serie geschalteten Leistungsschaltern S1 und S2first electronically controlled circuit breaker (realized as a MOS field effect transistor) as part of an inverter (DC / AC converter), consisting of two circuit breakers S1 and S2 connected in series to form a half bridge S2S2 zweiter elektronisch gesteuerter Leistungsschalter (realisiert als MOS-Feldeffekttransistor) als Teil dieses Wechselrichters (DC/AC-Wandlers)second electronically controlled circuit breaker (realized as a MOS field effect transistor) as part of this inverter (DC / AC converter) S3S3 dritter elektronisch gesteuerter Leistungsschalter (realisiert als MOS-Feldeffekttransistor) in Serie zur Primärwicklung Tp des Heiztransformators am Ausgang des Wechselrichtersthird electronically controlled circuit breaker (realized as a MOS field effect transistor) in series with the primary winding Tp of the heating transformer at the output of the inverter Tptp Primärwicklung eines Heiztransformators für die Wendeln W1 und W2 der Niederdruck-Entladungslampe LAPrimary winding of a heating transformer for filaments W1 and W2 of the low-pressure discharge lamp LA Ts1Ts1 erste Sekundärwicklung des Heiztransformatorsfirst secondary winding of the heating transformer Ts2ts2 zweite Sekundärwicklung des Heiztransformatorssecond secondary winding of the heating transformer UBUS U BUS Gleichspannung einer Gleichspannungsquelle zur Stromversorgung der Niederdruck-Gasentladungslampe LADC voltage of a DC voltage source for supplying power to the low-pressure gas discharge lamp LA UR3 U R3 am Messwiderstand R3 abfallende Spannungvoltage drop across the measuring resistor R3 UR4 U R4 am Messwiderstand R4 abfallende Spannungvoltage drop across the measuring resistor R4 ΔU.DELTA.U von einer Auswerteschaltung gebildete und ausgewertete Differenzspannung aus den an R3 bzw. R4 abfallenden Spannungen UR3 und UR4 (ΔU : = UR3 - UR4)Differential voltage formed and evaluated by an evaluation circuit from the voltages U R3 and U R4 dropping at R3 and R4 (ΔU: = U R3 - U R4 ) ΔUd ΔU d Differenzsignal, das sich aus den beiden in Fig. 2b gezeigten Zeitverläufen der Spannungen UR3 und UR4 bei einem Defekt einer der beiden Wendeln W1 oder W2 der Niederdruck-Entladungslampe LA ergibtDifferential signal that results from the two time profiles of the voltages U R3 and U R4 shown in FIG. 2b in the event of a defect in one of the two filaments W1 or W2 of the low-pressure discharge lamp LA ΔUi ΔU i Differenzsignal, das sich aus den beiden in Fig. 2a gezeigten Zeitverläufen der Spannungen UR3 und UR4 bei intakten Wendeln W1 und W2 der Niederdruck-Entladungslampe LA ergibtDifferential signal that results from the two time profiles of the voltages U R3 and U R4 shown in FIG. 2a with intact filaments W1 and W2 of the low-pressure discharge lamp LA W1W1 erste Wendel der Niederdruck-Entladungslampe LAfirst filament of the low-pressure discharge lamp LA W2W2 zweite Wendel der Niederdruck-Entladungslampe LAsecond filament of the low-pressure discharge lamp LA

Claims (15)

  1. Electronic ballast for at least one low-pressure discharge lamp, having
    an inverter which is connected to a direct-voltage source (UBUS),
    a load circuit which is connected to the inverter and contains the lamp (LA) and a series resonant circuit (L1, C1 and C2), and
    an evaluating circuit arrangement (M1) which reacts to different operating states of the lamp (LA) and in the case of a defect or removal of the lamp (LA) generates corresponding signals which are used to switch off the inverter,
    characterised by
    a heating transformer for the coils (W1, W2) of the lamp (LA), the primary winding (Tp) of which transformer is connected in series with a switch (S3) to the output of the inverter and in any case is then connected to the direct-voltage source (UBUS) if the inverter is switched off on account of a heating-coil defect or the removal of the lamp (LA), with the switch (S3) being clocked in this off-phase and the evaluating circuit arrangement (M1) evaluating the current that flows through the primary winding (Tp) and/or through the secondary winding(s) (Ts1 and/or Ts2) of the heating transformer.
  2. Electronic ballast according to claim 1,
    characterised in that,
    the series circuit arrangement consisting of the switch (S3) and the primary winding (Tp) is additionally connected to the direct-voltage source (UBUS) independently of the inverter.
  3. Electronic ballast according to claim 1 or 2,
    characterised in that,
    a charging/discharging capacitor (C3) is connected to the series circuit arrangement consisting of the switch (S3) and the primary winding (Tp), with the evaluating circuit arrangement (M1) evaluating the amplitude of the measured current in its time characteristic or at a specific instant in order to identify a lamp change or lamp defect.
  4. Electronic ballast according to claim 3,
    characterised in that,
    the charging/discharging capacitor (C3) is connected in series with the series circuit arrangement consisting of the switch (S3) and the primary winding (Tp), and in that this extended series circuit arrangement is connected in parallel with the load circuit.
  5. Electronic ballast according to claim 3,
    characterised in that,
    the charging/discharging capacitor (C3) is connected to the output of the inverter, and in that the charging/discharging capacitor (C3) and the series circuit arrangement consisting of the switch (S3) and the primary winding (Tp) are connected in parallel with each other and in parallel with the load circuit.
  6. Electronic ballast according to claim 2 and any of claims 3 to 5,
    characterised in that,
    a nodal point between the primary winding (Tp) and the charging/discharging capacitor (C3) is connected by way of a resistor (R2) to the direct-voltage source (UBUS).
  7. Electronic ballast according to any preceding claim,
    characterised in that,
    a measuring resistor (R3) is connected in series with the series circuit arrangement consisting of the switch (S3) and the primary winding (Tp), and in that the evaluating circuit arrangement (M1) evaluates the voltage (UR3) that is generated at the measuring resistor (R3) by the current flowing through the latter.
  8. Electronic ballast according to any preceding claim,
    characterised in that,
    for the purpose of measuring the current through one of the two heating circuits, this heating circuit contains a further measuring resistor (R4), and in that the voltage (UR4) that drops across this further measuring resistor (R4) is fed to the evaluating circuit arrangement (M1).
  9. Electronic ballast according to claim 7 and 8,
    characterised in that,
    the evaluating circuit arrangement (M1) forms a differential voltage (DU) from the two voltages (UR3, UR4) that drop across the two measuring resistors (R3, R4) and evaluates it.
  10. Electronic ballast according to claim 9,
    characterised in that,
    the evaluating circuit arrangement (M1) contains a comparator to which the differential voltage (DU) is fed, and in that this comparator compares the differential voltage (DU) with a desired value.
  11. Electronic ballast according to any of claims 7 to 10,
    characterised in that,
    the evaluating circuit arrangement (M1) contains a comparator which compares the voltage (UR3 or UR4) dropping across the respective measuring resistor (R3 or R4) with a desired value at predetermined instants or in specific windows of time.
  12. Electronic ballast according to claim 11,
    characterised in that,
    the desired value is a voltage value (UR3 or UR4) that is measured at the respective measuring resistor (R3 or R4) at an earlier instant.
  13. Electronic ballast according to any preceding claim,
    characterised in that,
    it contains a rectifier that is connected to the mains and which generates the direct voltage (UBUS) that is to be fed to the inverter.
  14. Electronic ballast according to any preceding claim,
    characterised in that,
    the inverter contains a half-bridge consisting of two electronic switches (S1, S2) which are connected in series, and in that the load circuit containing the lamp (LA) is connected in parallel with one of the two electronic switches (S1, S2).
  15. Electronic ballast according to any preceding claim,
    characterised in that,
    the load circuit contains an inductance coil (L1), which is connected in series with the lamp (LA), and a resonant capacitor (C2) which is connected in parallel with the lamp (LA).
EP00927002A 1999-05-25 2000-04-19 Electronic ballast for at least one low-pressure discharge lamp Expired - Lifetime EP1103166B1 (en)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
DE19923946 1999-05-25
DE19923946 1999-05-25
DE19934687 1999-07-23
DE19934687A DE19934687A1 (en) 1999-05-25 1999-07-23 Electronic ballast for at least one low-pressure discharge lamp
PCT/EP2000/003572 WO2000072642A1 (en) 1999-05-25 2000-04-19 Electronic ballast for at least one low-pressure discharge lamp

Publications (2)

Publication Number Publication Date
EP1103166A1 EP1103166A1 (en) 2001-05-30
EP1103166B1 true EP1103166B1 (en) 2003-07-16

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP00927002A Expired - Lifetime EP1103166B1 (en) 1999-05-25 2000-04-19 Electronic ballast for at least one low-pressure discharge lamp

Country Status (6)

Country Link
US (1) US6433490B2 (en)
EP (1) EP1103166B1 (en)
AT (1) ATE245337T1 (en)
AU (1) AU761360B2 (en)
BR (1) BR0007013A (en)
WO (1) WO2000072642A1 (en)

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DE10126011A1 (en) * 2001-05-28 2002-12-05 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Procedure for starting a discharge lamp
DE10200053A1 (en) * 2002-01-02 2003-07-17 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Operating device for discharge lamps with preheating device
DE10345610A1 (en) * 2003-09-29 2005-05-12 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Method for operating at least one low-pressure discharge lamp
DE102004044180A1 (en) * 2004-09-13 2006-03-16 Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH Electronic ballast with pumping circuit for discharge lamp with preheatable electrodes
DE102005018761A1 (en) * 2005-04-22 2006-10-26 Tridonicatco Gmbh & Co. Kg Intelligent flyback heater
US7586268B2 (en) * 2005-12-09 2009-09-08 Lutron Electronics Co., Inc. Apparatus and method for controlling the filament voltage in an electronic dimming ballast
WO2009126472A1 (en) * 2008-04-11 2009-10-15 Osram Sylvania, Inc. Stand alone lamp filament preheat circuit for ballast
US7839094B2 (en) * 2008-05-02 2010-11-23 General Electric Company Voltage fed programmed start ballast
US8232727B1 (en) 2009-03-05 2012-07-31 Universal Lighting Technologies, Inc. Ballast circuit for a gas-discharge lamp having a filament drive circuit with monostable control
ATE523948T1 (en) * 2009-04-07 2011-09-15 Osram Gmbh CONVERSION DEVICE AND CORRESPONDING CONVERSION METHOD
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
US20100327759A1 (en) * 2009-06-24 2010-12-30 Koninklijke Philips Electronics N.V. Electronic ballast for a fluorescent lamp
AT12060U1 (en) * 2010-01-28 2011-09-15 Tridonic Gmbh & Co Kg OPERATING DEVICE FOR GAS DISCHARGE LAMPS
DE102010029511B4 (en) * 2010-05-31 2014-10-09 Osram Gmbh Circuit arrangement for operating a discharge lamp
US8922131B1 (en) 2011-10-10 2014-12-30 Universal Lighting Technologies, Inc. Series resonant inverter with capacitive power compensation for multiple lamp parallel operation
DE102011085659A1 (en) 2011-11-03 2013-05-08 Tridonic Gmbh & Co. Kg Clocked heating circuit for control gear for lamps
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Also Published As

Publication number Publication date
ATE245337T1 (en) 2003-08-15
US20010007410A1 (en) 2001-07-12
AU4553500A (en) 2000-12-12
AU761360B2 (en) 2003-06-05
WO2000072642A1 (en) 2000-11-30
EP1103166A1 (en) 2001-05-30
US6433490B2 (en) 2002-08-13
BR0007013A (en) 2001-07-03

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