EP0965249B1 - DEVICE FOR DETECTING THE RECTIFICATION EFFECT OCCURRiNG IN A GAS DISCHARGE LAMP - Google Patents

DEVICE FOR DETECTING THE RECTIFICATION EFFECT OCCURRiNG IN A GAS DISCHARGE LAMP Download PDF

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Publication number
EP0965249B1
EP0965249B1 EP98912300A EP98912300A EP0965249B1 EP 0965249 B1 EP0965249 B1 EP 0965249B1 EP 98912300 A EP98912300 A EP 98912300A EP 98912300 A EP98912300 A EP 98912300A EP 0965249 B1 EP0965249 B1 EP 0965249B1
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EP
European Patent Office
Prior art keywords
gas discharge
discharge lamp
resistor
circuit arrangement
lamp
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
EP98912300A
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German (de)
French (fr)
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EP0965249A1 (en
Inventor
Siegfried Luger
Thomas Marinelli
Falk Richter
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Tridonic Bauelemente GmbH
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Tridonic Bauelemente GmbH
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Publication of EP0965249A1 publication Critical patent/EP0965249A1/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
    • 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
    • Y10S315/07—Starting and control circuits for gas discharge lamp using transistors

Definitions

  • the present invention relates to an electronic ballast for operation at least one gas discharge lamp according to the preamble of claim 1.
  • ballast is known from the applicant's EP-A1-0 490 329.
  • gas discharge lamps occur due to Signs of wear of the heating coils at the end of the service life of the Gas discharge lamp the effect on the lamp electrodes over time wear unevenly, i.e. the removal of the emission layers on the Lamp electrodes is different. Due to the different wear of the Lamp electrodes produce differences in the emissivity of the two Lamp electrodes.
  • FIG. 5 shows the effects of this effect on the basis of the current i L supplied to the gas discharge lamp. From Fig. 5 it can be seen that a higher current flows in one direction than in the other, so that the time profile i L (t) has an increase of a half-wave (in Fig. 5 the positive half-wave). As a result of the different removal of the two lamp electrodes, asymmetries arise which not only give rise to stronger flickering of light at the end of the life of the gas discharge lamp, but even in extreme cases only allow the gas discharge lamp to be operated during one half-wave (in FIG. 5 during the positive half-wave). In this case, the gas discharge lamp acts like a rectifier, so that the effect described above is referred to as the "rectifying effect".
  • the Work function for the electrons higher than the other electrode On the electrode that has worn out more over time is the Work function for the electrons higher than the other electrode, which is less badly worn.
  • the minimum energy is generally referred to as work function, which is required to make an electron from a metal, in the present case from the Pull out the lamp electrode.
  • the dipole layer on the surface of the metal, i.e. the lamp electrode is an important factor in determining the Work function.
  • the more worn electrode, which has a higher work function for the Has electrons than the less worn electrode therefore heats up Commissioning of the gas discharge lamp stronger than the opposite electrode.
  • the electrode can be heated particularly in the case of lamps with a small diameter become so strong that parts of the lamp glass bulb can melt.
  • the rectification effect manifests itself in an asymmetry of the lamp current i L flowing over the gas discharge path of the lamp.
  • One way of recognizing the rectification effect is therefore to monitor the lamp current flowing over the gas discharge path of the lamp, although with this method emission differences of the lamp electrodes can be recognized directly, however, the evaluation of these emission differences and the implementation of this detection method into an integrated circuit, in particular as Application-specific circuit (ASIC) designed monitoring circuit is problematic.
  • ASIC Application-specific circuit
  • the rectification effect can also be recognized by monitoring the lamp voltage, since the asymmetries occurring in the lamp current are transmitted to the lamp voltage.
  • the gas discharge lamp is switched off.
  • this detection method has the disadvantage that the sensitivity of this method is limited, since in the event of a fault, ie when the rectification effect occurs, the peak value of the lamp voltage detected is only 60% higher than in normal operation.
  • the lamp voltage also changes when the gas discharge lamp is dimmed, so that due to the dimming of the gas discharge lamp and the correspondingly increasing lamp voltage, it is erroneously concluded that the rectification effect is present in the gas discharge lamp. It would also be desirable to use the changing arithmetic mean of the monitored circuit size to detect the rectification effect.
  • Ballast is a first resistor with the primary winding of the heating transformer connected in series.
  • the one flowing through the primary winding and the first resistor Current creates a voltage across the resistor that corresponds to the current through the Heating filaments of the lamp is proportional.
  • the voltage drop across the first Resistance is evaluated by a control and regulating circuit in order to over or To detect undervoltage. A rectification effect detection is however in this Documentation not described.
  • Rectification effect detection is described in US-A-5,023,516.
  • a monitoring circuit is provided which is a series circuit of two Resistors and an inductor, wherein the series circuit in parallel with one gas discharge lamp to be monitored is connected.
  • the inverter of the ballast coupled thyristor At the connection point between the one resistor and the inductance one intervenes with the inverter of the ballast coupled thyristor and thus evaluates the one Resistance falling voltage for rectification effect detection.
  • a certain limit in either of the two polarity directions has reached the Thyristor activated and consequently the inverter switched off.
  • the well-known Monitoring circuit detects the presence of a rectification effect in this way two polarity directions of the voltage drop across the resistor.
  • the invention has for its object the known electronic ballast to be provided with a monitoring circuit with which the rectification effect is also in positive and negative Direction can be detected even if the monitoring circuit cannot process negative input voltages. According to the invention, this object is achieved by an electronic ballast Claim 1 solved.
  • the solution according to the invention thus ensures detection of the Rectification effect in both directions of polarization at the first resistor falling voltage and is therefore highly sensitive.
  • the circuit according to the present invention can easily be such be expanded that two or more flame devices with regard to the occurrence of a Rectification effect in one of the gas discharge lamps can be reliably monitored can.
  • the monitoring of the heating current or to that via the primary winding of the Heating transformer flowing heating current proportional size takes place in particular with the help of such a monitoring circuit, which after detection of the Rectification effect that supplies the gas discharge lamp with an AC voltage Drives the frequency and / or the duty cycle of the To change the AC voltage supplied by the inverter and thus the Gas discharge lamp to reduce the power consumed. This way, a Melting the glass bulb of the gas discharge lamp after the rectification effect occurs reliably prevented.
  • Figure 1 shows a first embodiment of the electronic according to the invention Ballast for operating a gas discharge lamp, the monitored and the Gas discharge lamp inductance connected in parallel through the primary winding of a Heating transformer is formed.
  • the solution according to the invention generally consists in the flowing over an inductance connected in parallel to the gas discharge lamp Evaluate current or a quantity proportional to it, since the in the case of a Rectification effect in the lamp branch asymmetries on the over this Inductance flowing current are transmitted.
  • the electronic ballast shown in FIG. 1 essentially has one Rectifier circuit 1, an inverter 2, a monitoring circuit 3 and a connected to the inverter 2 load circuit, which, among other things operating and to be monitored with regard to the occurrence of the rectification effect Contains gas discharge lamp 10.
  • the rectifier 1 is connected to a mains voltage source connected and converts the mains voltage into a rectified intermediate voltage um, which is fed to the inverter 2.
  • the inverter 2 usually includes two controllable switches (not shown), for example MOS field effect transistors, which are controlled alternately by means of a corresponding control circuit, so that one of the switches is switched on and the other is switched off.
  • the two Inverter switches are connected in series between a supply voltage and Ground connected, being at the common node between the two Inverter switches of the load circuit containing the gas discharge lamp 10 connected.
  • the load circuit includes one Series resonance circuit with a resonance circuit coil 4 and a resonance circuit capacitor 5, which is connected to ground.
  • a coupling capacitor 6 connected, which is connected to one of the lamp filaments of the gas discharge lamp 10 is. Due to the alternately controlled switches of the inverter 2, the rectified intermediate voltage into a "chopped" high-frequency AC voltage converted. This high-frequency AC voltage is via the series resonance circuit supplied to the gas discharge lamp 10.
  • the Lamp electrodes of the gas discharge lamp 10 preheated to the life of the Extend gas discharge lamp.
  • the gas discharge lamp 10 is a Heating transformer with a primary winding 7A and two secondary windings 7B and 7C intended.
  • the primary winding is connected to the series resonance circuit, while the Secondary windings are each connected in parallel to one of the lamp filaments.
  • the frequency of the inverter 2 supplied AC voltage against the resonance frequency of the series resonance circuit changed so that the resonant circuit capacitor 5 and thus the Gas discharge lamp 10 lying voltage no ignition of the gas discharge lamp 10 caused.
  • the lamp electrodes designed as filaments the gas discharge lamp 10 a substantially constant current, whereby the Lamp filaments are preheated.
  • the frequency of the AC voltage supplied by the inverter 2 in the vicinity of the resonance frequency of the series resonance circuit shifted, causing the on the resonance circuit capacitor 5 and the gas discharge lamp 10 voltage applied so that the Gas discharge lamp 10 is ignited.
  • a resistor 9 is connected in series with the primary winding 7A, which is connected to ground. From the connection point between the primary winding 7A and the resistor 9, another resistor 8 leads to the monitoring circuit 3, which in turn is connected to ground.
  • the function of the electronic ballast according to the invention shown in FIG. 1 is described in more detail below with reference to FIG. 2 and FIG. 3.
  • FIG. 2a shows the course over time of the voltage u 3 dropping across the resistor 9 in this case. Due to the different wear of the lamp electrodes due to the aging of the lamp electrodes, over time, as already described at the beginning, there is an increase in the positive half-waves over the negative half-waves in the voltage u 3 falling across the resistor 9 or in the voltage across the Resistor 9 flowing current i 3 .
  • a threshold value U S can be defined via the resistance value of the resistor 9, the exceeding of which detects the presence of the rectifying effect is detected.
  • the monitoring circuit 3 is also connected to ground, so that the monitoring point A of the monitoring circuit 3 cannot assume a more negative potential than the ground potential.
  • FIG. 2b shows the course of the potential u 4 occurring at the monitoring point A. Since the potential u 4 can not have a more negative value than the ground potential, the voltage profile of u 4 only has positive half-waves which correspond to the positive half-waves of u 3 .
  • FIG. 2c additionally shows the current profile of the current i 2 flowing through the further resistor 8. It can be seen from FIG. 2c that the current i 2 only occurs when the voltage u 4 present at the monitoring point A is zero.
  • FIG. 3 shows the corresponding voltage and current profiles in the event that the rectification effect described above occurs in the gas discharge lamp 10 in the opposite direction to the case described with reference to FIG. 2.
  • the current i 3 flowing through the resistor 9 or the voltage u 3 falling through the resistor 9 takes on increasing values in the negative direction, so that the negative half-waves in the voltage or current profile of u 3 or i 3 are excessive compared to the positive half-waves.
  • the positive half-waves disappear completely in the course of time, so that the gas discharge lamp 10 acts as a rectifier in the opposite direction with respect to the direction described with reference to FIG.
  • FIG. 2b FIG.
  • the rectification effect acting in the other direction of the gas discharge lamp 10 can be recognized by monitoring the current i 2 flowing through the resistor 8 when this current i 2 exceeds a predetermined limit value I S.
  • This limit value I S can be varied in particular via the value of the resistor 8.
  • the monitoring circuit 3 Based on the negative current values of the current i 2 shown in FIG. 3c, it can be seen in connection with FIG. 1 that the monitoring circuit 3 actually detects the current i 2 flowing out from the monitoring circuit 3 via the monitoring point A. By simultaneously monitoring u 3 and i 2 , the monitoring circuit 3 can reliably detect the rectification effect, regardless of the direction in which the rectification effect occurs in the gas discharge lamp 10.
  • the monitoring of i 2 and u 3 with regard to the exceeding of the limit value I S or U S is advantageously carried out by conventional current or voltage comparators.
  • the monitoring circuit 3 concludes that the rectification effect is present of the gas discharge lamp 10 and issues a corresponding warning.
  • the monitoring circuit 3 is advantageously connected to the inverter 2 and controls the operating behavior of the inverter 2 after detection of a rectification effect in the gas discharge lamp 10 such that the power consumed by the gas discharge lamp 10 is reduced.
  • the monitoring circuit 3 controls the switching behavior of the alternately switching switches of the inverter 2 such that, for example, the frequency f of the clocked alternating voltage supplied by the inverter 2 increases and / or the pulse duty factor d (i.e. the ratio between the switch-on times of the two controlled switches of the inverter 2 ) the clocked AC voltage is reduced so that the lamp current i L supplied to the gas discharge lamp 10 is reduced. In this way, excessive heating is reliably avoided. prevents melting of parts of the lamp glass bulb. If necessary, the monitoring circuit 3 can also cause the inverter 2 to be switched off.
  • the frequency f of the clocked alternating voltage supplied by the inverter 2 increases and / or the pulse duty factor d (i.e. the ratio between the switch-on times of the two controlled switches of the inverter 2 ) the clocked AC voltage is reduced so that the lamp current i L supplied to the gas discharge lamp 10 is reduced. In this way, excessive heating is reliably avoided. prevents melting of parts of the lamp glass
  • FIG. 4 shows a second embodiment of the electronic according to the invention Ballast, wherein a two-lamp load circuit is shown in Figure 4.
  • the second The lamp circuit is connected in the same way as the first lamp circuit.
  • the second circle of lamps also includes a heating transformer, the primary winding 11A with the Series resonance circuit and its two secondary windings 11B and 11C with the Lamp filaments of a second gas discharge lamp 15 are connected.
  • the primary winding 11A of the second heating transformer has a resistor 13 connected to it is also connected to ground. From the connection point between the Primary winding 11A of the second heating transformer and the resistor 13 carries one Connection via a resistor 12 to the monitoring circuit 3.
  • Die Monitoring circuit 3 has an OR circuit 14, the inputs of which with the Monitoring points A and B and the resistors 8 and 12 are connected.
  • everyone the monitoring points A and B is, as explained with reference to Figures 2 and 3, with respect to Occurrence of a rectification effect in the gas discharge lamp 10 or. 15 monitors.
  • the OR circuit 14 reports the presence of a rectifying effect as soon as the Rectification effect in one of the two gas discharge lamps 10 and 15 by monitoring the monitoring points A and B could be recognized.
  • Figure 1 shown embodiment is also shown in Figure 4 after detection of a Rectification effect of the inverter 2 is controlled accordingly to the Power consumption of the gas discharge lamps 10 connected to the inverter 2 and decrease 15.
  • the monitoring circuit 3 is advantageously as ASIC (Application Specific Integrated Ciruit), i.e. as an application-specific circuit.
  • ASIC Application Specific Integrated Ciruit
  • the circuit proposed according to the invention can be simplified Circuitry measures easily for monitoring two or more Extend gas discharge lamps.

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Abstract

Method for detecting the rectification effect in at least one gas discharge lamp (10) and electronic ballast for operating at least one gas discharge lamp, which recognises the appearance of the rectification effect in the gas discharge lamp (10). In order to be able to detect the appearance of the rectification effect in the gas discharge lamp (10) simply and with high sensitivity there is monitored the current (i1) flowing via a primary winding (7A), connected parallel to the gas discharge lamp (10), of a heating transformer (7A-C) or a parameter (i2, u3) dependent upon this current (i1) , and in the event that a predetermined limit value is overshot the presence of the rectification effect in the gas discharge lamp (10) is determined.

Description

Die vorliegende Erfindung betrifft ein elektronisches Vorschaltgerät zum Betreiben mindestens einer Gasentladungslampe gemäß dem Oberbegriff des Anspruches 1.The present invention relates to an electronic ballast for operation at least one gas discharge lamp according to the preamble of claim 1.

Ein derartiges Vorschaltgerät ist nach EP-A1-0 490 329 der Anmelderin bekannt.Such a ballast is known from the applicant's EP-A1-0 490 329.

Wie bei anderen Lampen auch, tritt bei Gasentladungslampen aufgrund von Abnutzungserscheinungen der Heizwendeln am Lebensdauerende der Gasentladungslampe der Effekt auf, daß sich die Lampenelektroden mit der Zeit ungleichmäßig abnutzen, d.h. die Abtragung der Emissionsschichten auf den Lampenelektroden unterschiedlich ist. Aufgrund der unterschiedlichen Abnutzung der Lampenelektroden entstehen Unterschiede im Emissionsvermögen der beiden Lampenelektroden.As with other lamps, gas discharge lamps occur due to Signs of wear of the heating coils at the end of the service life of the Gas discharge lamp the effect on the lamp electrodes over time wear unevenly, i.e. the removal of the emission layers on the Lamp electrodes is different. Due to the different wear of the Lamp electrodes produce differences in the emissivity of the two Lamp electrodes.

Fig. 5 zeigt die Auswirkungen dieses Effekts anhand des der Gasentladungslampe zugeführten Stromes iL. Aus Fig. 5 ist ersichtlich, daß in die eine Richtung ein höherer Strom fließt als in die andere, so daß der zeitliche Verlauf iL(t) eine Überhöhung einer Halbwelle (in Fig. 5 der positiven Halbwelle) aufweist. Durch die unterschiedliche Abtragung der beiden Lampenelektroden entstehen somit Asymmetrien, die nicht nur stärkeres Lichtflimmern am Lebensdauerende der Gasentladungslampe entstehen lassen, sondern sogar im Extremfall einen Betrieb der Gasentladungslampe nur während einer Halbwelle (in Fig. 5 während der positiven Halbwelle) zulassen. In diesem Fall wirkt die Gasentladunglampe wie ein Gleichrichter, so daß der zuvor beschriebene Effekt als "Gleichrichteffekt" bezeichnet wird.FIG. 5 shows the effects of this effect on the basis of the current i L supplied to the gas discharge lamp. From Fig. 5 it can be seen that a higher current flows in one direction than in the other, so that the time profile i L (t) has an increase of a half-wave (in Fig. 5 the positive half-wave). As a result of the different removal of the two lamp electrodes, asymmetries arise which not only give rise to stronger flickering of light at the end of the life of the gas discharge lamp, but even in extreme cases only allow the gas discharge lamp to be operated during one half-wave (in FIG. 5 during the positive half-wave). In this case, the gas discharge lamp acts like a rectifier, so that the effect described above is referred to as the "rectifying effect".

An derjenigen Elektrode, die sich im Laufe der Zeit stärker abgenutzt hat, ist die Austrittsarbeit für die Elektronen höher als an der anderen Elektrode, die sich weniger stark abgenutzt hat. Als Austrittsarbeit wird allgemein die Minimalenergie bezeichnet, die erforderlich ist, um ein Elektron aus einem Metall, im vorliegenden Fall aus der Lampenelektrode, herauszuziehen. Die Dipolschicht an der Oberfläche des Metalls, d.h. der Lampenelektrode, ist dabei ein wichtiger Faktor für die Bestimmung der Austrittsarbeit. Die stärker abgenutzte Elektrode, die eine höhere Austrittsarbeit für die Elektronen aufweist als die weniger stark abgenutzte Elektrode, erhitzt sich folglich bei Inbetriebnahme der Gasentladungslampe stärker als die gegenüberliegende Elektrode. Die Erhitzung der Elektrode kann insbesondere bei Lampen mit geringem Durchmesser so stark werden, daß Teile des Lampenglasskolbens schmelzen können. Um die aus der Erhitzung des Lampenglasskolbens resultierende Unfallgefahr zu vermeiden, muß folglich der Gleichrichteffekt erkannt und ggf. die Gasentladungslampe abgeschaltet oder deren Leistungsaufnahme verringert werden, wobei für die Überwachung der zuvor beschriebenen ungleichmäßigen Emission der Lampenelektroden bereits Normvorschriften existieren.On the electrode that has worn out more over time is the Work function for the electrons higher than the other electrode, which is less badly worn. The minimum energy is generally referred to as work function, which is required to make an electron from a metal, in the present case from the Pull out the lamp electrode. The dipole layer on the surface of the metal, i.e. the lamp electrode is an important factor in determining the Work function. The more worn electrode, which has a higher work function for the Has electrons than the less worn electrode, therefore heats up Commissioning of the gas discharge lamp stronger than the opposite electrode. The electrode can be heated particularly in the case of lamps with a small diameter become so strong that parts of the lamp glass bulb can melt. To the from the Heating of the lamp glass bulb must avoid the resulting risk of accidents consequently, the rectification effect is recognized and, if necessary, the gas discharge lamp is switched off or their power consumption can be reduced, with the monitoring of Non-uniform emission of the lamp electrodes described above Standard regulations exist.

Wie bereits oben beschrieben worden ist, äußert sich der Gleichrichteffekt in einer Unsymmetrie des über die Gasentladungsstrecke der Lampe fließenden Lampenstromes iL. Eine Möglichkeit zur Erkennung des Gleichrichteffekts ist daher die Überwachung des über die Gasentladungsstrecke der Lampe fließenden Lampenstroms, wobei mit dieser Methode zwar Emissionsunterschiede der Lampenelektroden direkt erkannt werden können, jedoch die Auswertung dieser Emissionsunterschiede sowie die Umsetzung dieses Erkennungsverfahrens in eine als integrierte Schaltung, insbesondere als applikationsspezifische Schaltung (ASIC) ausgestaltete Überwachungsschaltung problematisch ist. Alternativ dazu kann der Gleichrichteffekt auch durch Überwachung der Lampenspannung erkannt werden, da die in dem Lampenstrom auftretenden Unsymmetrien auf die Lampenspannung übertragen werden. Überschreitet beispielsweise die überwachte Lampenspannung in Folge der aymmetrischen Emission der Lampenelektroden in einer Richtung einen bestimmten Grenzwert, wird die Gasentladungslampe abgeschaltet. Bei diesem Erkennungsverfahren ist jedoch nachteilig, daß die Sensibilität dieses Verfahrens beschränkt ist, da im Fehlerfall, d.h. bei Auftreten des Gleichrichteffekts, der Scheitelwert der erfaßten Lampenspannung lediglich 60% höher ist als im normalen Betriebsfall. Zudem ändert sich auch beim Dimmen der Gasentladungslampe die Lampenspannung, so daß aufgrund des Dimmens der Gasentladungslampe und der entsprechend dadurch ansteigenden Lampenspannung ggf. irrtümlicherweise auf das Vorliegen des Gleichrichteffekts in der Gasentladungslampe geschlossen wird. Des weiteren wäre wünschenswert, für die Erfassung des Gleichrichteffekts den sich verändernden arithmetischen Mittelwert der überwachten Schaltungsgröße zu verwenden. Diese Möglichkeit ist jedoch bei Überwachung der Lampenspannung nicht gegeben, da sich - wie bereits beschrieben - im Fehlerfall der Scheitelwert der Lampenspannung lediglich um 60% erhöht, so daß die Erhöhung im Mittelwert der Lampenspannung für eine ausreichend genaue Erfassung des Gleichrichteffekts nicht ausreichend ist. Insgesamt ist somit die Erfassung des Gleichrichteffekts mithilfe der Überwachung der Lampenspannung problematisch.As has already been described above, the rectification effect manifests itself in an asymmetry of the lamp current i L flowing over the gas discharge path of the lamp. One way of recognizing the rectification effect is therefore to monitor the lamp current flowing over the gas discharge path of the lamp, although with this method emission differences of the lamp electrodes can be recognized directly, however, the evaluation of these emission differences and the implementation of this detection method into an integrated circuit, in particular as Application-specific circuit (ASIC) designed monitoring circuit is problematic. Alternatively, the rectification effect can also be recognized by monitoring the lamp voltage, since the asymmetries occurring in the lamp current are transmitted to the lamp voltage. If, for example, the monitored lamp voltage exceeds a certain limit value as a result of the asymmetrical emission of the lamp electrodes in one direction, the gas discharge lamp is switched off. However, this detection method has the disadvantage that the sensitivity of this method is limited, since in the event of a fault, ie when the rectification effect occurs, the peak value of the lamp voltage detected is only 60% higher than in normal operation. In addition, the lamp voltage also changes when the gas discharge lamp is dimmed, so that due to the dimming of the gas discharge lamp and the correspondingly increasing lamp voltage, it is erroneously concluded that the rectification effect is present in the gas discharge lamp. It would also be desirable to use the changing arithmetic mean of the monitored circuit size to detect the rectification effect. However, this possibility is not available when monitoring the lamp voltage, since - as already described - the peak value of the lamp voltage only increases by 60% in the event of a fault, so that the increase in the mean value of the lamp voltage is not sufficient for a sufficiently precise detection of the rectification effect. Overall, the detection of the rectification effect with the monitoring of the lamp voltage is therefore problematic.

Bei dem aus der EP-A1-0 490 329 der Anmelderin bekannten elektronischen Vorschaltgerät ist mit der Primärwicklung des Heiztransformators ein erster Widerstand in Serie geschaltet. Der durch die Primärwicklung und den ersten Widerstand fließende Strom erzeugt an dem Widerstand eine Spannung, die dem Strom durch die Heizwendeln der Lampe proportional ist. Der Spannungsabfall über dem ersten Widerstand wird von einer Steuer- und Regelschaltung ausgewertet, um Über- oder Unterspannung zu detektieren. Eine Gleichrichteffekterkennung ist jedoch in dieser Druckschrift nicht beschrieben.In the electronic known from the applicant's EP-A1-0 490 329 Ballast is a first resistor with the primary winding of the heating transformer connected in series. The one flowing through the primary winding and the first resistor Current creates a voltage across the resistor that corresponds to the current through the Heating filaments of the lamp is proportional. The voltage drop across the first Resistance is evaluated by a control and regulating circuit in order to over or To detect undervoltage. A rectification effect detection is however in this Documentation not described.

Eine Gleichrichteffekterkennung ist aber in der US-A-5,023,516 beschrieben. Dazu ist eine Überwachungsschaltung vorgesehen, die eine Serienschaltung aus zwei Widerständen und einer Induktivität umfaßt, wobei die Serienschaltung parallel zu einer zu überwachenden Gasentladungslampe angeschlossen ist. An den Verbindungspunkt zwischen dem einen Widerstand und der Induktivität greift ein mit dem Wechselrichter des Vorschaltgeräts gekoppelter Thyristor an und wertet somit die an dem einen Widerstand abfallende Spannung zur Gleichrichteffekterkennung aus. Sobald die an dem einen Widerstand abfallende Spannung, welche zu dem über den einen Widerstand fließenden Strom proportional ist, einen bestimmten Grenzwert in irgendeiner der beiden Polaritätsrichtungen erreicht hat, wird der Thyristor aktiviert und demzufolge der Wechselrichter abgeschaltet. Die bekannte Überwachungsschaltung detektiert das Vorliegen eines Gleichrichteffekts auf diese Weise in beiden Polaritätsrichtungen der an dem Widerstand abfallenden Spannung.Rectification effect detection is described in US-A-5,023,516. Is to a monitoring circuit is provided which is a series circuit of two Resistors and an inductor, wherein the series circuit in parallel with one gas discharge lamp to be monitored is connected. At the connection point between the one resistor and the inductance one intervenes with the inverter of the ballast coupled thyristor and thus evaluates the one Resistance falling voltage for rectification effect detection. Once the on the voltage dropping one resistance, which to that across the one resistance flowing current is proportional, a certain limit in either of the two polarity directions has reached the Thyristor activated and consequently the inverter switched off. The well-known Monitoring circuit detects the presence of a rectification effect in this way two polarity directions of the voltage drop across the resistor.

Der Erfindung liegt die Aufgabe zugrunde, das bekannte elektronische Vorschaltgerät mit einer Überwachungsschaltung zu versehen, mit der der Gleichrichteffekt ebenfalls in positiver und negativer Richtung erfaßt werden kann, selbst wenn die Überwachungsschaltung keine negative Eingangsspannungen verarbeiten kann. Diese Aufgabe wird erfindungsgemäß durch ein elektronisches Vorschaltgerät nach Anspruch 1 gelöst.The invention has for its object the known electronic ballast to be provided with a monitoring circuit with which the rectification effect is also in positive and negative Direction can be detected even if the monitoring circuit cannot process negative input voltages. According to the invention, this object is achieved by an electronic ballast Claim 1 solved.

Die erfindungsgemäße Lösung gewährleistet also eine Detektierung des Gleichrichteffekts in beiden Polarisationsrichtungen der an dem ersten Widerstand abfallenden Spannung und ist damit von hoher Sensibilität.The solution according to the invention thus ensures detection of the Rectification effect in both directions of polarization at the first resistor falling voltage and is therefore highly sensitive.

Die Schaltung gemäß der vorliegenden Erfindung kann auf einfache Weise derart erweitert werden, daß zwei- oder mehrflammige Geräte bezüglich des Auftretens eines Gleichrichteffekts in einer der Gasentladungslampen zuverlässig uberwacht werden können. The circuit according to the present invention can easily be such be expanded that two or more flame devices with regard to the occurrence of a Rectification effect in one of the gas discharge lamps can be reliably monitored can.

Die Überwachung des Heizstroms bzw. der zu dem über die Primärwicklung des Heiztransformators fließenden Heizstrom proportionalen Größe erfolgt insbesondere mithilfe einer derartigen Überwachungsschaltung, die nach Erkennen des Gleichrichteffekts den die Gasentladungslampe mit einer Wechselspannung versorgenden Wechselrichter ansteuert, um die Frequenz und/oder das Tastverhältnis der von dem Wechselrichter gelieferten Wechselspannung zu verändern und somit die von der Gasentladungslampe aufgenommene Leistung zu verringern. Auf diese Weise wird ein Schmelzen des Glaskolbens der Gasentladungslampe nach Auftreten des Gleichrichteffekts zuverlässig verhindert.The monitoring of the heating current or to that via the primary winding of the Heating transformer flowing heating current proportional size takes place in particular with the help of such a monitoring circuit, which after detection of the Rectification effect that supplies the gas discharge lamp with an AC voltage Drives the frequency and / or the duty cycle of the To change the AC voltage supplied by the inverter and thus the Gas discharge lamp to reduce the power consumed. This way, a Melting the glass bulb of the gas discharge lamp after the rectification effect occurs reliably prevented.

Die Unteransprüche geben weitere vorteilhafte Ausgestaltungen der vorliegenden Erfindung an.The subclaims give further advantageous refinements of the present Invention.

Die Erfindung wird nachfolgend anhand bevorzugter Ausführungsbeispiele unter Bezugnahme auf die beigefügte Zeichnung näher beschrieben. Dabei zeigt:

Fig. 1
ein erstes Ausführungsbeispiel des erfindungsgemäßen elektronischen Vorschaltgeräts zum Betreiben einer Gasentladungslampe,
Fig. 2
Spannungs- und Stromverläufe bei einem in positiver Richtung zunehmenden Heizstrom in der in Figur 1 gezeigten Schaltung,
Fig. 3
Spannungs- und Stromverläufe bei einem in negativer Richtung zunehmenden Heizstrom in der in Figur 1 gezeigten Schaltung,
Fig. 4
ein zweites Ausführungsbeispiel des erfindungsgemäßen elektronischen Vorschaltgeräts, und
Fig. 5
den Verlauf des Lampenstroms über die Gasentladungsstrecke einer Gasentladungslampe bei Auftreten des Gleichrichteffekts.
The invention is described below with reference to preferred embodiments with reference to the accompanying drawings. It shows:
Fig. 1
1 shows a first exemplary embodiment of the electronic ballast according to the invention for operating a gas discharge lamp,
Fig. 2
Voltage and current profiles with a heating current increasing in the positive direction in the circuit shown in FIG. 1,
Fig. 3
Voltage and current profiles with a heating current increasing in the negative direction in the circuit shown in FIG. 1,
Fig. 4
a second embodiment of the electronic ballast according to the invention, and
Fig. 5
the course of the lamp current over the gas discharge path of a gas discharge lamp when the rectification effect occurs.

Figur 1 zeigt ein erstes Ausführungsbeispiel des erfindungsgemäßen elektronischen Vorschaltgeräts zum Betreiben einer Gasentladungslampe, wobei die überwachte und der Gasentladungslampe parallelgeschaltete Induktivität durch die Primärwicklung eines Heiztransformators gebildet wird. Die erfindungsgemäße Lösung besteht allgemein darin, den über eine parallel zu der Gasentladungslampe angeschlossene Induktivität fließenden Strom oder eine dazu proportionalen Größe auszuwerten, da die im Falle eines Gleichrichteffekts im Lampenzweig auftretenden Unsymmetrien auf den über diese Induktivität fließenden Strom übertragen werden.Figure 1 shows a first embodiment of the electronic according to the invention Ballast for operating a gas discharge lamp, the monitored and the Gas discharge lamp inductance connected in parallel through the primary winding of a Heating transformer is formed. The solution according to the invention generally consists in the flowing over an inductance connected in parallel to the gas discharge lamp Evaluate current or a quantity proportional to it, since the in the case of a Rectification effect in the lamp branch asymmetries on the over this Inductance flowing current are transmitted.

Das in Figur 1 gezeigte elektronische Vorschaltgerät weist im wesentlichen eine Gleichrichterschaltung 1, einen Wechselrichter 2, eine Überwachungsschaltung 3 sowie einen mit dem Wechselrichter 2 verbundenen Lastkreis auf, der unter anderem eine zu betreibende und bezüglich des Auftretens des Gleichrichteffekts zu überwachende Gasentladungslampe 10 enthält. Der Gleichrichter 1 ist an eine Netzspannungsquelle angeschlossen und wandelt die Netzspannung in eine gleichgerichtete Zwischenspannung um, die den Wechselrichter 2 zugeführt wird. Der Wechselrichter 2 umfaßt in der Regel zwei (nicht dargestellte) steuerbare Schalter, beispielsweise MOS-Feldeffekttransistoren, die mittels einer entsprechenden Steuerschaltung alternierend angesteuert werden, so daß jeweils einer der Schalter ein- und der andere ausgeschaltet ist. Die beiden Wechselrichterschalter sind in Serienschaltung zwischen einer Versorgungsspannung und Masse angeschlossen, wobei am gemeinsamen Knotenpunkt zwischen den beiden Wechselrichterschaltern der die Gasentladungslampe 10 enthaltende Lastkreis angeschlossen ist. Der Lastkreis umfaßt neben der Gasentladungslampe 10 einen Serienresonanzkreis mit einer Resonanzkreisspule 4 und einem Resonanzkreiskondensator 5, der mit Masse verbunden ist. An dem Verbindungspunkt zwischen dem Resonanzkreiskondensator 5 und der Resonanzkreisspule 4 ist ein Koppelkondensator 6 angeschlossen, der mit einer der Lampenwendeln der Gasentladungslampe 10 verbunden ist. Aufgrund der alternierend angesteuerten Schalter des Wechselrichters 2 wird die gleichgerichtete Zwischenspannung in eine "zerhackte" hochfrequente Wechselspannung umgewandelt. Diese hochfrequente Wechselspannung wird über den Serienresonanzkreis der Gasentladungslampe 10 zugeführt.The electronic ballast shown in FIG. 1 essentially has one Rectifier circuit 1, an inverter 2, a monitoring circuit 3 and a connected to the inverter 2 load circuit, which, among other things operating and to be monitored with regard to the occurrence of the rectification effect Contains gas discharge lamp 10. The rectifier 1 is connected to a mains voltage source connected and converts the mains voltage into a rectified intermediate voltage um, which is fed to the inverter 2. The inverter 2 usually includes two controllable switches (not shown), for example MOS field effect transistors, which are controlled alternately by means of a corresponding control circuit, so that one of the switches is switched on and the other is switched off. The two Inverter switches are connected in series between a supply voltage and Ground connected, being at the common node between the two Inverter switches of the load circuit containing the gas discharge lamp 10 connected. In addition to the gas discharge lamp 10, the load circuit includes one Series resonance circuit with a resonance circuit coil 4 and a resonance circuit capacitor 5, which is connected to ground. At the connection point between the The resonant circuit capacitor 5 and the resonant circuit coil 4 is a coupling capacitor 6 connected, which is connected to one of the lamp filaments of the gas discharge lamp 10 is. Due to the alternately controlled switches of the inverter 2, the rectified intermediate voltage into a "chopped" high-frequency AC voltage converted. This high-frequency AC voltage is via the series resonance circuit supplied to the gas discharge lamp 10.

Vor dem Anlegen der Zündspannung an die Gasentladungslampe 10 werden die Lampenelektroden der Gasentladungslampe 10 vorgeheizt, um die Lebensdauer der Gasentladungslampe zu verlängern. Zum Vorheizen der Gasentladungslampe 10 ist ein Heiztransformator mit einer Primärwicklung 7A und zwei Sekundärwicklungen 7B und 7C vorgesehen. Die Primärwicklung ist mit dem Serienresonanzkreis verbunden, während die Sekundärwicklungen jeweils parallel zu einer der Lampenwendeln geschaltet sind. Auf diese Weise ist es möglich, auch im gezündeten Betrieb die Lampenwendeln mit Energie zu versorgen. Im Vorheizbetrieb wird die Frequenz der von dem Wechselrichter 2 gelieferten Wechselspannung gegenüber der Resonanzfrequenz des Serienresonanzkreises derart verändert, daß die über dem Resonanzkreiskondensator 5 und damit über der Gasentladungslampe 10 liegende Spannung keine Zündung der Gasentladungslampe 10 verursacht. In diesem Fall fließt durch die als Wendeln ausgeführten Lampenelektroden der Gasentladungslampe 10 ein im wesentlichen konstanter Strom, wodurch die Lampenwendeln vorgeheizt werden. Nach Ablauf der Vorheizphase wird die Frequenz der von dem Wechselrichter 2 gelieferten Wechselspannung in die Nähe der Resonanzfrequenz des Serienresonanzkreises verschoben, wodurch sich die an dem Resonanzkreiskondensator 5 und der Gasentladungslampe 10 anliegende Spannung erhöht, so daß die Gasentladungslampe 10 gezündet wird.Before the ignition voltage is applied to the gas discharge lamp 10, the Lamp electrodes of the gas discharge lamp 10 preheated to the life of the Extend gas discharge lamp. For preheating the gas discharge lamp 10 is a Heating transformer with a primary winding 7A and two secondary windings 7B and 7C intended. The primary winding is connected to the series resonance circuit, while the Secondary windings are each connected in parallel to one of the lamp filaments. On in this way it is possible to power the lamp filaments even when ignited to supply. In preheating mode, the frequency of the inverter 2 supplied AC voltage against the resonance frequency of the series resonance circuit changed so that the resonant circuit capacitor 5 and thus the Gas discharge lamp 10 lying voltage no ignition of the gas discharge lamp 10 caused. In this case, it flows through the lamp electrodes designed as filaments the gas discharge lamp 10 a substantially constant current, whereby the Lamp filaments are preheated. After the preheating phase, the frequency of the AC voltage supplied by the inverter 2 in the vicinity of the resonance frequency of the series resonance circuit shifted, causing the on the resonance circuit capacitor 5 and the gas discharge lamp 10 voltage applied so that the Gas discharge lamp 10 is ignited.

Erfindungsgemäß wird vorgeschlagen, den über die Primärwicklung 7A des Heiztransformators fließenden Primärstrom i1 zu überwachen. Zu diesem Zweck wird in Serie mit der Primärwicklung 7A ein Widerstand 9 geschaltet, der mit Masse verbunden ist. Von dem Verbindungspunkt zwischen der Primärwicklung 7A und dem Widerstand 9 führt ein weiterer Widerstand 8 zu der Überwachungsschaltung 3, die ihrerseits an Masse anliegt. Die Funktion des in Figur 1 gezeigten erfindungsgemäßen elektronischen Vorschaltgerätes wird nachfolgend unter Bezugnahme auf Figur 2 und Figur 3 näher beschrieben.According to the invention, it is proposed to monitor the primary current i 1 flowing through the primary winding 7A of the heating transformer. For this purpose, a resistor 9 is connected in series with the primary winding 7A, which is connected to ground. From the connection point between the primary winding 7A and the resistor 9, another resistor 8 leads to the monitoring circuit 3, which in turn is connected to ground. The function of the electronic ballast according to the invention shown in FIG. 1 is described in more detail below with reference to FIG. 2 and FIG. 3.

Wie in Figur 5 gezeigt, kommt es beim Auftreten des eingangs beschriebenen Gleichrichteffekts zu Unsymmetrien in dem über die Gasentladungsstrecke der Gasentladungslampe 10 fließenden Lampenstroms iL. Sobald im Lampenzweig dieser asymmetrische Strom iL auftritt, werden die Unsymmetrien auf den über die Primärwicklung 7A des Heiztransformators fließenden Primärstrom i1 übertragen. Um die in dem Primärstrom i1 auftretenden Unsymmetrien erfassen und auswerten zu können, wird der Primärstrom i1 über den Widerstand 9 der Überwachungsschaltung 3 zugeführt. Dabei ist zwischen zwei verschiedenen Fällen zu unterscheiden, je nachdem ob die in Figur 5 gezeigten Halbwellen des Lampenstroms iL die positiven oder negativen Halbwellen betreffen. Das heißt, es wird erfindungsgemäß zwischen dem in der einen Richtung der Gasentladungslampe 10 auftretenden Gleichrichteffekt und dem in der entgegensetzten Richtung auftretenden Gleichrichteffekt unterschieden. As shown in FIG. 5, when the rectification effect described at the outset occurs, asymmetries occur in the lamp current i L flowing over the gas discharge path of the gas discharge lamp 10. As soon as this asymmetrical current i L occurs in the lamp branch, the asymmetries are transferred to the primary current i 1 flowing through the primary winding 7A of the heating transformer. In order to be able to detect and evaluate the asymmetries occurring in the primary current i 1 , the primary current i 1 is supplied to the monitoring circuit 3 via the resistor 9. A distinction must be made between two different cases, depending on whether the half-waves of the lamp current i L shown in FIG. 5 relate to the positive or negative half-waves. That is to say, according to the invention, a distinction is made between the rectification effect occurring in one direction of gas discharge lamp 10 and the rectification effect occurring in the opposite direction.

Für den Fall, daß aufgrund des in der Gasentladungslampe 10 auftretenden Gleichrichteffekts über den Widerstand 9 ein sich in positiver Richtung verändernder Strom i3 fließt, wird erfindungsgemäß der Gleichrichteffekt durch Überwachen der an dem Widerstand 9 abfallenden Spannung u3 erfaßt. Figur 2a zeigt den zeitlichen Verlauf der in diesem Fall an dem Widerstand 9 abfallenden Spannung u3. Aufgrund der durch die Alterung der Lampenelektroden auftretenden unterschiedlichen Abnutzung der Lampenelektroden kommt es im Laufe der Zeit, wie bereits eingangs beschrieben, zu einer Überhöhung der positiven Halbwellen gegenüber den negativen Halbwellen in der über den Widerstand 9 abfallenden Spannung u3 bzw. in den über dem Widerstand 9 fließenden Strom i3. Im Extremfall verschwinden mit zunehmender Zeit die negativen Halbwellen im Spannungs- und Stromverlauf von u3 bzw. i3 vollständig, so daß die Gasentladungslampe 10 als Gleichrichter wirkt. Über den Widerstandswert des Widerstands 9 ist ein Schwellenwert US definierbar, bei dessen Überschreiten das Vorliegen des Gleichrichteffekts erkannt wird. Zur Überwachung der an dem Widerstand 9 abfallenden Spannung u3 ist auch die Überwachungsschaltung 3 an Masse gelegt, so daß der Überwachungspunkt A der Überwachungsschaltung 3 kein negativeres Potential als das Massepotential annehmen kann. Figur 2b zeigt den Verlauf des an dem Überwachungspunkt A auftretenden Potentials u4. Da das Potential u4 keinen negativeren Wert als das Massepotential annehmen kann, weist der Spannungsverlauf von u4 nur positive Halbwellen auf, die den positiven Halbwellen von u3 entsprechen. Überschreitet eine dieser Halbwellen den vordefinierten Schwellenwert US, so legt dies die Überwachungsschaltung 3 als Auftreten des Gleichrichteffekts in der Gasentladungslampe 10 aus. Figur 2c zeigt ergänzend den Stromverlauf des über den weiteren Widerstand 8 fließenden Strom i2. Aus Figur 2c ist ersichtlich, daß der Strom i2 nur dann auftritt, wenn die an dem Überwachungspunkt A anliegende Spannung u4 Null ist.In the event that, due to the rectification effect occurring in the gas discharge lamp 10, a current i 3 flowing in the positive direction flows through the resistor 9, the rectification effect is detected according to the invention by monitoring the voltage u 3 dropping across the resistor 9. FIG. 2a shows the course over time of the voltage u 3 dropping across the resistor 9 in this case. Due to the different wear of the lamp electrodes due to the aging of the lamp electrodes, over time, as already described at the beginning, there is an increase in the positive half-waves over the negative half-waves in the voltage u 3 falling across the resistor 9 or in the voltage across the Resistor 9 flowing current i 3 . In the extreme case, the negative half-waves in the voltage and current profile of u 3 and i 3 disappear completely with increasing time, so that the gas discharge lamp 10 acts as a rectifier. A threshold value U S can be defined via the resistance value of the resistor 9, the exceeding of which detects the presence of the rectifying effect is detected. To monitor the voltage u 3 dropping across the resistor 9, the monitoring circuit 3 is also connected to ground, so that the monitoring point A of the monitoring circuit 3 cannot assume a more negative potential than the ground potential. FIG. 2b shows the course of the potential u 4 occurring at the monitoring point A. Since the potential u 4 can not have a more negative value than the ground potential, the voltage profile of u 4 only has positive half-waves which correspond to the positive half-waves of u 3 . If one of these half-waves exceeds the predefined threshold value U S , the monitoring circuit 3 interprets this as the occurrence of the rectification effect in the gas discharge lamp 10. FIG. 2c additionally shows the current profile of the current i 2 flowing through the further resistor 8. It can be seen from FIG. 2c that the current i 2 only occurs when the voltage u 4 present at the monitoring point A is zero.

Figur 3 zeigt die entsprechenden Spannungs- und Stromverläufe für den Fall, daß in der Gasentladungslampe 10 der zuvor beschriebene Gleichrichteffekt in entgegengesetzter Richtung zu dem bezüglich Figur 2 beschriebenen Fall auftritt. In diesem Fall nimmt der über den Widerstand 9 fließende Strom i3 bzw. die über den Widerstand 9 abfallende Spannung u3 in negativer Richtung steigende Werte an, so daß in dem Spannungs- bzw. Stromverlauf von u3 bzw. i3 die negativen Halbwellen gegenüber den positiven Halbwellen überhöht sind. Im Extremfall verschwinden im Laufe der Zeit die positiven Halbwellen vollständig, so daß die Gasentladungslampe 10 in bezüglich der anhand Figur 2 beschriebenen Richtung entgegengesetzter Richtung als Gleichrichter wirkt. Wie Figur 2b zeigt auch Figur 3b, daß das an dem Überwachungspunkt A auftretende Potential u4 aufgrund der Verbindung der Überwachungsschaltung 3 mit Masse nur positive Werte annehmen kann, so daß mit der Zeit die Spannung u4 mit dem Verschwinden der positiven Halbwellen der an dem Widerstand 9 abfallenden Spannung u3 den Wert Null annimmt. Um in diesem Fall trotzdem das Vorliegen des Gleichrichteffekts in der Gasentladungslampe 10 erkennen zu können, wird erfindungsgemäß vorgeschlagen, in diesem Fall den über den Widerstand 8 fließenden Strom i2 auszuwerten. Der Strom i2 kann nur dann über den Widerstand 8 fließen, wenn die an dem Überwachungspunkt A auftretende Spannung u4 den Wert Null annimmt. Aus diesem Grunde kann ab dem Zeitpunkt, zu dem die Spannung u4 vollständig verschwindet, der Strom i2 kontinuierlich von der Überwachungsschaltung 3 überwacht werden. Der Verlauf des Stroms i2 verändert sich dabei in Übereinstimmung mit den in negativer Richtung ansteigenden Halbwellen der Spannung u3.FIG. 3 shows the corresponding voltage and current profiles in the event that the rectification effect described above occurs in the gas discharge lamp 10 in the opposite direction to the case described with reference to FIG. 2. In this case, the current i 3 flowing through the resistor 9 or the voltage u 3 falling through the resistor 9 takes on increasing values in the negative direction, so that the negative half-waves in the voltage or current profile of u 3 or i 3 are excessive compared to the positive half-waves. In the extreme case, the positive half-waves disappear completely in the course of time, so that the gas discharge lamp 10 acts as a rectifier in the opposite direction with respect to the direction described with reference to FIG. Like FIG. 2b, FIG. 3b also shows that the potential u 4 occurring at the monitoring point A can only assume positive values due to the connection of the monitoring circuit 3 to ground, so that over time the voltage u 4 with the disappearance of the positive half-waves at the Resistor 9 falling voltage u 3 assumes the value zero. In order to nevertheless be able to recognize the presence of the rectification effect in the gas discharge lamp 10 in this case, it is proposed according to the invention to evaluate the current i 2 flowing through the resistor 8 in this case. The current i 2 can only flow through the resistor 8 if the voltage u 4 occurring at the monitoring point A assumes the value zero. For this reason, the current i 2 can be continuously monitored by the monitoring circuit 3 from the point in time at which the voltage u 4 completely disappears. The course of the current i 2 changes in accordance with the half-waves of the voltage u 3 rising in the negative direction.

Aus diesem Grund kann der in die andere Richtung der Gasentladungslampe 10 wirkende Gleichrichteffekt durch Überwachen des über den Widerstand 8 fließenden Stroms i2 erkannt werden, wenn dieser Strom i2 einen vorgegebenen Grenzwert IS überschreitet. Dieser Grenzwert IS ist insbesondere über den Wert des Widerstands 8 variierbar. Aufgrund der in Figur 3c dargestellten negativen Stromwerte des Stroms i2 ist im Zusammenhang mit Figur 1 ersichtlich, daß tatsächlich von der Überwachungsschaltung 3 der von der Überwachungsschaltung 3 über den Überwachungspunkt A herausfließende Strom i2 erfaßt wird. Durch gleichzeitiges Überwachen von u3 sowie i2 kann somit die Überwachungsschaltung 3 - unabhängig von der Richtung, in welcher der Gleichrichteffekt in der Gasentladungslampe 10 auftritt - den Gleichrichteffekt zuverlässig erkennen.For this reason, the rectification effect acting in the other direction of the gas discharge lamp 10 can be recognized by monitoring the current i 2 flowing through the resistor 8 when this current i 2 exceeds a predetermined limit value I S. This limit value I S can be varied in particular via the value of the resistor 8. Based on the negative current values of the current i 2 shown in FIG. 3c, it can be seen in connection with FIG. 1 that the monitoring circuit 3 actually detects the current i 2 flowing out from the monitoring circuit 3 via the monitoring point A. By simultaneously monitoring u 3 and i 2 , the monitoring circuit 3 can reliably detect the rectification effect, regardless of the direction in which the rectification effect occurs in the gas discharge lamp 10.

Die Überwachung von i2 und u3 hinsichtlich des Überschreitens des Grenzwertes IS bzw. US erfolgt vorteilhafterweise durch übliche Strom- bzw. Spannungskomparatoren.The monitoring of i 2 and u 3 with regard to the exceeding of the limit value I S or U S is advantageously carried out by conventional current or voltage comparators.

Sobald die Überwachungsschaltung 3 erkannt hat, daß die an dem Überwachungspunkt A anliegende Spannung u4 den vorgegebenen Grenzwert US bzw. über den Überwachungspunkt A fließende Strom i2 den vorgegebenen Grenzwert IS überschritten hat, schließt die Überwachungsschaltung 3 auf das Vorhandensein des Gleichrichteffekts in der Gasentladungslampe 10 und gibt eine entsprechende Warnung aus. Vorteilhafterweise ist die Überwachungsschaltung 3 mit dem Wechselrichter 2 verbunden und steuert das Betriebsverhalten des Wechselrichters 2 nach Erkennen eines Gleichrichteffekts in der Gasentladungslampe 10 derart, daß sich die von der Gasentladungslampe 10 aufgenommene Leistung verringert. Insbesondere steuert die Überwachungsschaltung 3 das Schaltverhalten der alternierend schaltenden Schalter des Wechselrichters 2 derart, daß beispielsweise die Frequenz f der von dem Wechselrichter 2 gelieferten getakteten Wechselspannung erhöht und/oder das Tastverhältnis d (d.h. das Verhältnis zwischen den Einschaltzeiten der beiden angesteuerten Schalter des Wechselrichters 2) der getakteten Wechselspannung verringert wird, so daß sich der der Gasentladungslampe 10 zugeführte Lampenstrom iL reduziert. Auf diese Weise wird zuverlässig eine übermäßige Erhitzung bwz. ein Schmelzen von Teilen des Lampenglaskolbens verhindert. Gegebenenfalls kann die Überwachungsschaltung 3 auch ein Abschalten des Wechselrichters 2 bewirken.As soon as the monitoring circuit 3 has recognized that the voltage u 4 present at the monitoring point A has exceeded the predetermined limit value U S or current i 2 flowing through the monitoring point A has exceeded the predetermined limit value I S , the monitoring circuit 3 concludes that the rectification effect is present of the gas discharge lamp 10 and issues a corresponding warning. The monitoring circuit 3 is advantageously connected to the inverter 2 and controls the operating behavior of the inverter 2 after detection of a rectification effect in the gas discharge lamp 10 such that the power consumed by the gas discharge lamp 10 is reduced. In particular, the monitoring circuit 3 controls the switching behavior of the alternately switching switches of the inverter 2 such that, for example, the frequency f of the clocked alternating voltage supplied by the inverter 2 increases and / or the pulse duty factor d (i.e. the ratio between the switch-on times of the two controlled switches of the inverter 2 ) the clocked AC voltage is reduced so that the lamp current i L supplied to the gas discharge lamp 10 is reduced. In this way, excessive heating is reliably avoided. prevents melting of parts of the lamp glass bulb. If necessary, the monitoring circuit 3 can also cause the inverter 2 to be switched off.

Figur 4 zeigt ein zweites Ausführungsbeispiel des erfindungsgemäßen elektronischen Vorschaltgerätes, wobei in Figur 4 ein Zweilampen-Lastkreis dargestellt ist. Der zweite Lampenkreis ist analog zu dem ersten Lampenkreis verschaltet. Der zweite Lampenkreis umfaßt ebenfalls einen Heiztransformator, dessen Primärwicklung 11A mit dem Serienresonanzkreis und dessen beiden Sekundärwicklungen 11B und 11C mit den Lampenwendeln einer zweiten Gasentladungslampe 15 verbunden sind. In Serie mit der Primärwicklung 11A des zweiten Heiztransformators ist ein Widerstand 13 geschaltet, der zudem an Masse angeschlossen ist. Von dem Verbindungspunkt zwischen der Primärwicklung 11A des zweiten Heiztransformators und dem Widerstand 13 führt eine Verbindung über einen Widerstand 12 zu der Überwachungsschaltung 3. Die Überwachungsschaltung 3 weist eine ODER-Schaltung 14 auf, deren Eingänge mit den Überwachungspunkten A und B sowie den Widerständen 8 und 12 verbunden sind. Jeder der Überwachungspunkte A und B wird, wie anhand Figur 2 und 3 erläutert, bezüglich des Auftretens eines Gleichrichteffekts in der Gasentladungslampe 10 bwz. 15 überwacht. Die ODER-Schaltung 14 meldet das Vorhandensein eines Gleichrichteffekts sobald der Gleichrichteffekt in einer der beiden Gasentladungslampen 10 und 15 durch Überwachung der Überwachungspunkte A und B erkannt werden konnte. Wie bei dem in Figur 1 gezeigten Ausführungsbeispiel wird auch gemäß Figur 4 nach Erkennen eines Gleichrichteffekts der Wechselrichter 2 entsprechend angesteuert, um die Leistungsaufnahme der an den Wechselrichter 2 angeschlossenen Gasentladungslampen 10 und 15 zu verringern.Figure 4 shows a second embodiment of the electronic according to the invention Ballast, wherein a two-lamp load circuit is shown in Figure 4. The second The lamp circuit is connected in the same way as the first lamp circuit. The second circle of lamps also includes a heating transformer, the primary winding 11A with the Series resonance circuit and its two secondary windings 11B and 11C with the Lamp filaments of a second gas discharge lamp 15 are connected. In series with the The primary winding 11A of the second heating transformer has a resistor 13 connected to it is also connected to ground. From the connection point between the Primary winding 11A of the second heating transformer and the resistor 13 carries one Connection via a resistor 12 to the monitoring circuit 3. Die Monitoring circuit 3 has an OR circuit 14, the inputs of which with the Monitoring points A and B and the resistors 8 and 12 are connected. Everyone the monitoring points A and B is, as explained with reference to Figures 2 and 3, with respect to Occurrence of a rectification effect in the gas discharge lamp 10 or. 15 monitors. The OR circuit 14 reports the presence of a rectifying effect as soon as the Rectification effect in one of the two gas discharge lamps 10 and 15 by monitoring the monitoring points A and B could be recognized. As with that in Figure 1 shown embodiment is also shown in Figure 4 after detection of a Rectification effect of the inverter 2 is controlled accordingly to the Power consumption of the gas discharge lamps 10 connected to the inverter 2 and decrease 15.

Die Überwachungsschaltung 3 ist vorteilhafterweise als ASIC (Application Specific Integrated Ciruit), d.h. als applikationsspezifische Schaltung, ausgebildet.The monitoring circuit 3 is advantageously as ASIC (Application Specific Integrated Ciruit), i.e. as an application-specific circuit.

Durch die erfindungsgemäß vorgeschlagene Überwachung des über die Primärwicklungen 7A bzw. 11A der entsprechenden Heiztransformatoren fließenden Heizstromes, dessen Verlauf sich bei Vorliegen eines Gleichrichteffekts in der entsprechenden Gasentladungslampe 10 bzw. 15 stark verändert, kann der Gleichrichteffekt in der Gasentladungslampe 10 bzw. 15 mit großer Genauigkeit und zuverlässig erkannt werden. Die erfindungsgemäß vorgeschlagene Schaltung läßt sich durch einfache schaltungstechnische Maßnahmen leicht für die Überwachung von zwei oder mehr Gasentladungslampen erweitern.Through the monitoring of the primary windings proposed according to the invention 7A or 11A of the corresponding heating transformers flowing heating current, the If there is a rectification effect in the corresponding Gas discharge lamp 10 or 15 changed greatly, the rectification effect in the Gas discharge lamp 10 or 15 can be detected with great accuracy and reliably. The circuit proposed according to the invention can be simplified Circuitry measures easily for monitoring two or more Extend gas discharge lamps.

Claims (10)

  1. Electronic ballast for operating at least one gas discharge lamp (10, 15), having an inverter (2), having a load circuit (4, 5, 6) which is connected to the inverter (2) and to which the gas discharge lamp (10) can be connected, having a filament-heating transformer (7A-C) for preheating the lamp filaments of the gas discharge lamp (10), the primary winding (7A) of which is connected in series with a first resistor (9) in parallel with the gas discharge lamp (10, 15), and having a monitoring circuit arrangement (3) for monitoring the current (i1) flowing by way of the primary winding (7A) of the filament-heating transformer (7A-C) or a variable (i2, u3) that is proportionally dependent upon this current, characterised in that the interconnection point between the primary winding (7A) of the filament-heating transformer (7A-C) and the first resistor (9) is connected to the monitoring circuit arrangement (3) by way of a second resistor (8) so that the voltage (u3) dropping across the first resistor (9) and the current (i2) flowing by way of the second resistor (8) are fed as monitoring variables to the monitoring circuit arrangement (3), and in that the monitoring circuit arrangement (3) assesses the presence of the rectification effect in the gas discharge lamp (10) in the case of a voltage (u3) dropping across the first resistor (9) and increasing in a positive direction or a current (i3) flowing by way of the first resistor (9) and increasing in a positive direction as a function of the voltage (u3) dropping across the first resistor (9) as a monitoring variable, and in that the monitoring circuit arrangement (3) assesses the presence of the rectification effect in the gas discharge lamp (10) in the case of a voltage (u3) dropping across the first resistor (9) and increasing in a negative direction or a current (i3) flowing by way of the first resistor (9) and increasing in a negative direction as a function of the current (i2) flowing by way of the second resistor (8) as a monitoring variable, and in that the monitoring circuit arrangement (3) is designed in such a way that it concludes that the rectification effect is present in the gas discharge lamp (10) if the monitoring variable exceeds a predetermined limiting value (Is, US),
  2. Electronic ballast according to claim 1, characterised in that the limiting value (US) for the detection of the rectification effect in the gas discharge lamp (10) on the basis of the voltage (u3) dropping across the first resistor (9) is determined by the resistance value of the first resistor (9) and can be changed.
  3. Electronic ballast according to claim 1 or 2, characterised in that the limiting value (IS) for the detection of the rectification effect in the gas discharge lamp (10) on the basis of the current (i2) flowing by way of the second resistor (8) is determined by the resistance value of the second resistor (8) and can be changed.
  4. Electronic ballast according to one of claims 1-3, characterised in that the monitoring circuit arrangement (3) and the first resistor (9) are connected to earth.
  5. Electronic ballast according to one of claims 1-4, characterised in that the filament-heating transformer (7A-C) has two secondary windings (7B, 7C) which are, in each case, connected to one of the lamp filaments of the gas discharge lamp (10).
  6. Electronic ballast according to one of claims 1-4, characterised by at least one further filament-heating transformer (11A-C), in which case a series circuit arrangement consisting of the primary winding (11A) of the at least one further filament-heating transformer (11A-C) and a further first resistor (13) is connected in parallel with the series circuit arrangement consisting of the primary winding (7A) of the filament-heating transformer (7A-C) and the first resistor (9), having at least one further gas discharge lamp (15), in which case two secondary windings (11B, 11C) of the at least one further filament-heating transformer (11A-C) are, in each case, connected to one of the lamp filaments of the at least one further gas discharge lamp (15) in such a way that the circuit arrangement consisting of the secondary windings (11B, 11C) of the at least one further filament-heating transformer (11A-C) and the lamp filaments of the at least one further gas discharge lamp (15) is connected in parallel with the circuit arrangement consisting of the secondary windings (7B, 7C) of the filament-heating transformer (7A-C) and the lamp filaments of the gas discharge lamp (10), and at least one further second resistor (12) which is connected between the monitoring circuit arrangement (3) and the interconnection point between the primary winding (11A) of the at least one further filament-heating transformer (11A-C) and the at least one further first resistor (13).
  7. Electronic ballast according to claim 6, characterised in that the monitoring circuit arrangement (3) contains an OR-circuit arrangement (14), the input terminals of which are connected to the second resistors (8, 12) so that the monitoring circuit arrangement (3) concludes that the rectification effect is present in one of the gas discharge lamps (10, 15) if at least one of the variables (i2, u3) fed to the monitoring circuit arrangement (3) by way of the second resistors (8, 12) exceeds a predetermined limiting value (IS, US).
  8. Electronic ballast according to one of claims 1-7, characterised in that the inverter (2) has two alternately activated switches which are connected in series and are supplied with a direct voltage from a direct-voltage source (1), in that the load circuit connected to the inverter (2) contains a series-resonant circuit (4, 5) to which the at least one gas discharge lamp (10, 15) is connected, and in that the monitoring circuit arrangement (3) after identification of the rectification effect in the at least one gas discharge lamp (10, 15) changes the frequency (f) and/or the pulse duty factor (d) of the alternating voltage delivered by the inverter (2) in such a way that the power consumed by the at least one gas discharge lamp (10, 15) is reduced.
  9. Electronic ballast according to claim 8, characterised in that after identification of the rectification effect in the at least one gas discharge lamp (10, 15) the monitoring circuit arrangement (3) increases the frequency (f) of the alternating voltage delivered by the inverter (2) and/or reduces the pulse duty factor (d) thereof.
  10. Electronic ballast according to one of claims 1-9, characterised in that the monitoring circuit arrangement (3) is designed as an ASIC.
EP98912300A 1997-03-04 1998-02-12 DEVICE FOR DETECTING THE RECTIFICATION EFFECT OCCURRiNG IN A GAS DISCHARGE LAMP Expired - Lifetime EP0965249B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19708792 1997-03-04
DE19708792A DE19708792A1 (en) 1997-03-04 1997-03-04 Method and device for detecting the rectification effect occurring in a gas discharge lamp
PCT/EP1998/000791 WO1998039948A1 (en) 1997-03-04 1998-02-12 Method and device for detecting the rectification effect occurring in a gas discharge lamp

Publications (2)

Publication Number Publication Date
EP0965249A1 EP0965249A1 (en) 1999-12-22
EP0965249B1 true EP0965249B1 (en) 2001-05-02

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EP98912300A Expired - Lifetime EP0965249B1 (en) 1997-03-04 1998-02-12 DEVICE FOR DETECTING THE RECTIFICATION EFFECT OCCURRiNG IN A GAS DISCHARGE LAMP

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US (1) US6140771A (en)
EP (1) EP0965249B1 (en)
AT (1) ATE200950T1 (en)
AU (1) AU721988B2 (en)
BR (1) BR9808165B1 (en)
DE (2) DE19708792A1 (en)
WO (1) WO1998039948A1 (en)

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Publication number Publication date
ATE200950T1 (en) 2001-05-15
BR9808165B1 (en) 2012-02-22
AU6719598A (en) 1998-09-22
WO1998039948A1 (en) 1998-09-11
EP0965249A1 (en) 1999-12-22
DE59800669D1 (en) 2001-06-07
US6140771A (en) 2000-10-31
AU721988B2 (en) 2000-07-20
BR9808165A (en) 2000-05-16
DE19708792A1 (en) 1998-09-10

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