EP0320944B1 - Converter for a discharge lamp - Google Patents
Converter for a discharge lamp Download PDFInfo
- Publication number
- EP0320944B1 EP0320944B1 EP88121019A EP88121019A EP0320944B1 EP 0320944 B1 EP0320944 B1 EP 0320944B1 EP 88121019 A EP88121019 A EP 88121019A EP 88121019 A EP88121019 A EP 88121019A EP 0320944 B1 EP0320944 B1 EP 0320944B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- discharge lamp
- converter
- ballast
- frequency
- operating frequency
- 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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- 239000003990 capacitor Substances 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 4
- 238000004804 winding Methods 0.000 description 3
- 238000013016 damping Methods 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
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Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/26—Circuit arrangements in which the lamp is fed by power derived from DC by means of a converter, e.g. by high-voltage DC
- H05B41/28—Circuit arrangements in which the lamp is fed by power derived from DC by means of a converter, e.g. by high-voltage DC using static converters
- H05B41/295—Circuit arrangements in which the lamp is fed by power derived from DC by means of a converter, e.g. by high-voltage DC using static converters with semiconductor devices and specially adapted for lamps with preheating electrodes, e.g. for fluorescent lamps
- H05B41/298—Arrangements for protecting lamps or circuits against abnormal operating conditions
- H05B41/2981—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions
- H05B41/2983—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions against abnormal power supply conditions
Definitions
- the invention relates to a ballast of the type addressed in the preamble of claim 1.
- the operating frequency of the converter is controlled to such a high value during the preheating period of the heated electrodes of the discharge lamp that the voltage on the discharge lamp is not sufficient to ignite even at high ambient temperatures.
- the saturation transformer has an additional secondary winding that is short-circuited during the preheating period. If, after the preheating period has elapsed, this short circuit is removed and the operating frequency of the converter returns to its normal value, a sufficient voltage occurs at the series resonant circuit for the reliable ignition of the discharge lamp. After the discharge lamp has been ignited, it acts as a damping resistor for the series resonant circuit, so that the operating voltage which is then applied to the discharge lamp is very much lower than the ignition voltage.
- ballasts operating with a series resonant circuit for generating the required ignition voltage have the advantage over other ballasts that work with a capacitive ignition aid arranged in the vicinity of the discharge lamp that the lamp blackening increased by the capacitive ignition aid is reduced.
- ballast for a discharge lamp in which there is a current transformer in the connecting line carrying the lamp current between the converter and the discharge lamp, the output signal of which is used as a control signal is used for a voltage controlled oscillator to change the operating frequency of the converter in order to stabilize the lamp current emitted by it.
- a ballast for a discharge lamp which uses a constant frequency oscillator which drives a pulse width modulator.
- the pulse width of the output signal of the pulse width modulator is changed in accordance with a control voltage which is generated in accordance with an error signal which is derived on the basis of a comparison between the direct current output by the secondary winding of an AC-DC converter and a reference voltage.
- ballasts of this type used in connection with systems in which the capacitive loads in the load circuit, for example, those leading to the discharge lamps Output lines are different, it is difficult to provide a sufficient ignition voltage to the discharge lamps, because the resonance frequency of the series resonant circuit shifts due to the different capacitive loads. If the supply voltage for the converter also fluctuates in conventional ballasts, its operating frequency changes, which not only adversely affects the ignition reliability of the discharge lamp, but also leads to fluctuations in light intensity when the discharge lamp is burning. In order to avoid these disadvantages, known ballasts provide complex electronic stabilization circuits in order to supply the converter with a stabilized supply voltage. This is particularly the case in vehicles such as railroad cars.
- the object of the invention is to develop a ballast of the type mentioned in the preamble of claim 1 in such a way that the respective discharge lamp is provided with a sufficient ignition voltage even if the capacitive loads in the load circuit of the converter are different and the supply voltage fluctuates greatly.
- the operating frequency of the DC-AC converter is changed so that the resonance frequency of the series resonance circuit is achieved either by the fundamental wave of the operating frequency or one of its harmonics even when the resonance frequency is detuned due to different capacitive loads on the series resonance circuit. If the respective resonance frequency is reached, the discharge lamp is given a sufficiently high ignition voltage, which will ignite it safely. Immediately after the discharge lamp has been ignited, the wobbler is switched off, so that the operating frequency of the converter then remains essentially the same.
- the operating frequency of the converter can also be changed when the discharge lamp is on in order to stabilize the operating voltage for the discharge lamp, i.e. the output voltage of the converter, and thus the lamp current, e.g. the supply voltage of the DC voltage source of the DC-AC converter fluctuates, as is often the case with vehicle electrical systems.
- the ballast shown in FIG. 1 comprises a variable frequency DC-AC converter 1 fed by a DC voltage source, not shown here, which, as indicated, emits a square wave signal to a series resonant circuit 3 comprising an inductor 3a and a capacitor 3b.
- the capacitor 3b, the electrodes of a discharge lamp 4 are connected in parallel, which may comprise a capacitive starting aid 4a in a known manner, but which does not receive a potential that differs from earth potential.
- the electrodes of the discharge lamp 4 are designed as heatable electrodes and receive heating current from the converter 1 via separate lines.
- a wobbler 2 is connected to the converter 1, the output signal of which controls the operating frequency of the converter 1. The wobbler 2 works relatively slowly, for example at a frequency of 2 Hz.
- a current transformer 5 In a connecting line carrying the lamp current, a current transformer 5 is provided, the output signal of which is given via a rectifier diode to a capacitor 8, the output voltage of which is used as a control signal for switching off the wobbler 2 and can be used to control the operating frequency of the converter 1, in order to stabilize the output voltage of the converter 1 and thus the lamp current for the discharge lamp 4 via the operating frequency when the supply voltage of the DC voltage source feeding the converter 1 fluctuates.
- a timer circuit 6 is provided which is started when the converter 1 is switched on.
- This timer circuit 6 keeps the operating frequency of the converter 1, preferably when the wobbler 2 is still switched off, or independently of it, at a value at which the series resonant circuit 3 can resonate neither by the fundamental wave nor by one of its harmonics in order to ignite the To safely prevent discharge lamp 4 even at high ambient temperatures.
- the time circuit monitors a sufficient preheating time for the heatable electrodes of the discharge lamp 4, in order to cause the discharge lamp 4 to ignite only when its electrodes are sufficiently preheated. Early attempts at ignition of the discharge lamp 4 would promote undesired lamp blackening.
- the time circuit 6 releases the changeable operating frequency of the converter 1 or switches on the wobbler 2, so that a certain frequency range of the operating frequency is passed through with it periodically, which is chosen so that the resonance frequency of the series resonant circuit 3 is reached even then is when this is significantly detuned due to capacitive loads on the series resonant circuit 3.
- This resonance frequency can be achieved by the fundamental wave of the output signal of the converter 1 or one of its harmonics.
- FIG. 2 and 3 show second and third exemplary embodiments of the ballast, the second exemplary embodiment having a PTC thermistor 9a instead of the timing circuit 6 shown in FIG. 1, which has a strongly positive temperature coefficient. If the ballast is switched on, sufficient ignition voltage cannot occur at the series resonant circuit 3 during the preheating period for the electrodes of the discharge lamp 4, since this is short-circuited or strongly damped by the resistor 9a, which is highly conductive at room temperature.
- the resistor 9a heats up, causing it to reach a high resistance value due to its strongly positive temperature coefficient, which then no longer plays a role as damping resistor for the series resonant circuit 3, so that it is sufficient for the discharge lamp 4 when the resonance frequency is reached Ignition voltage can provide.
- a thermistor 9b is connected in series in the series resonance circuit 3 of the inductor 3a, which thermally dampens the series resonance circuit 3 at room temperature by a high resistance value so strongly that a sufficient ignition voltage cannot be supplied to the discharge lamp even when the resonance frequency is present.
- the thermistor 9b heats up to such an extent that its resistance becomes negligibly small, so that the series resonant circuit 3 can give the discharge lamp 4 a sufficient ignition voltage when the resonance frequency is reached.
- the wobbler 2 can also be designed such that when the converter 1 is switched on, the low-frequency wobble voltage has such a magnitude that the its controlled operating frequency of the converter 1 has a value which is sufficiently far from the resonant frequency of the series resonant circuit 3. If the wobble frequency of the wobbler 2 is sufficiently low, a sufficient preheating time for the heatable electrodes of the discharge lamp 4 can be ensured solely on the basis of this, in that the operating frequency of the converter 1 only reaches the resonance range of the series resonant circuit 3 after the preheating time has elapsed.
- the resonance frequency is preferably tuned to the third harmonic of the fundamental wave of the output voltage of the converter 1, as a result of which the efficiency of the ballast is improved.
- the operating frequency of the converter 1 or its third harmonic swept with the aid of the wobbler 2 passes through the respective resonance frequency of the series resonance circuit 3, then this gives a sufficiently large ignition voltage to the electrodes of the discharge lamp 4 due to the resonance, as a result of which it ignites reliably.
- the lamp current flows through it and the current transformer 5, as a result of which the current transformer 5 comes into play this proportional output signal via the rectifier diode 7 and the capacitor 8 to the wobbler 2 to turn it off.
- the operating frequency of the converter 1 remains essentially unchanged.
- the output signal of the current transformer 5 which is proportional to the lamp current, also reaches the control input for the operating frequency of the transformer 1 in order to change the operating frequency within a certain range for increasing or decreasing the output voltage of the transformer 1.
- the lamp current can be stabilized so that the discharge lamp 4 has a constant illuminance. This is particularly advantageous if, for example in vehicle electrical systems, the supply voltage of the DC voltage source supplying converter 1 fluctuates.
- the series resonant circuit 3 is designed in such a way that, even when it is detuned by capacitive loads in the load circuit, it still delivers a sufficient ignition voltage of approximately 1 KV.
Landscapes
- Circuit Arrangements For Discharge Lamps (AREA)
- Lighting Device Outwards From Vehicle And Optical Signal (AREA)
Abstract
Description
Die Erfindung bezieht sich auf ein Vorschaltgerät der im Oberbegriff des Patentanspruchs 1 angegehenen Art.The invention relates to a ballast of the type addressed in the preamble of claim 1.
Bei einem solchen, aus der DE-PS 31 52 951 bekannten Vorschaltgerät wird mit Hilfe eines Sättigungstransformators, dessen Primärwicklung im Lastkreis des Wandlers liegt, die Betriebsfrequenz des Wandlers während der Vorheizdauer der heizharen Elektroden der Entladungslampe auf einen so hohen Wert gesteuert, daß die Spannung an der Entladungslampe auch bei hoher Umgebungstemperatur nicht zu ihrer Zündung ausreicht. Der Sättigungstransformator hat dabei eine zusätzliche Sekundärwicklung, die während der Vorheizdauer kurzgeschlossen wird. Wenn nach dem Verstreichen der Vorheizdauer dieser Kurzschluß aufgehoben wird und damit die Betriebsfrequenz des Wandlers auf ihren normalen Wert zurückkehrt, tritt am Reihenresonanzkreis eine für die sichere Zündung der Entladungslampe ausreichende Spannung auf. Nach der Zündung der Entladungslampe wirkt diese als Dämpfungswiderstand für den Reihenresonanzkreis, so daß die dann an der Entladungslampe anliegende Brennspannung sehr viel geringer als die Zündspannung ist.In such a ballast known from DE-PS 31 52 951, with the aid of a saturation transformer, the primary winding of which is in the load circuit of the converter, the operating frequency of the converter is controlled to such a high value during the preheating period of the heated electrodes of the discharge lamp that the voltage on the discharge lamp is not sufficient to ignite even at high ambient temperatures. The saturation transformer has an additional secondary winding that is short-circuited during the preheating period. If, after the preheating period has elapsed, this short circuit is removed and the operating frequency of the converter returns to its normal value, a sufficient voltage occurs at the series resonant circuit for the reliable ignition of the discharge lamp. After the discharge lamp has been ignited, it acts as a damping resistor for the series resonant circuit, so that the operating voltage which is then applied to the discharge lamp is very much lower than the ignition voltage.
Diese mit einem Reihenresonanzkreis zum Erzeugen der erforderlichen Zündspannung arbeitenden bekannten Vorschaltgeräte haben gegenüber anderen Vorschaltgeräten, die mit einer in der Nähe der Entladungslampe angeordneten kapazitiven Zündhilfe arbeiten, den Vorteil, daß die durch die kapazitive Zündhilfe verstärkte Lampenschwärzung verringert wird.Known ballasts operating with a series resonant circuit for generating the required ignition voltage have the advantage over other ballasts that work with a capacitive ignition aid arranged in the vicinity of the discharge lamp that the lamp blackening increased by the capacitive ignition aid is reduced.
Aus der US-A-4 700 113 ist ein Vorschaltgerät für eine Entladungslampe bekannt, bei dem in der den Lampenstrom führenden Verbindungsleitung zwischen Wandler und Entladungslampe ein Stromwandler liegt, dessen Ausgangssignal als Steuersignal für einen spannungsgesteuerten Oszillator zum Ändern der Betriebsfrequenz des Wandlers dient, um den von ihm abgegebenen Lampenstrom zu stabilisieren.From US-A-4 700 113 a ballast for a discharge lamp is known, in which there is a current transformer in the connecting line carrying the lamp current between the converter and the discharge lamp, the output signal of which is used as a control signal is used for a voltage controlled oscillator to change the operating frequency of the converter in order to stabilize the lamp current emitted by it.
Aus der EP-A-240 312 ist ein Vorschaltgerät für eine Entladungslampe bekannt, das einen Oszillator konstanter Frequenz benutzt, der einen Impulsbreitenmodulator ansteuert. Die Impulsbreite des Ausgangssignals des Impulsbreitenmodulators wird nach Maßgabe einer Steuerspannung verändert, die nach Maßgabe eines Fehlersignals erzeugt wird, das aufgrund eines Vergleichs zwischen dem von der Sekundärwicklung eines Wechselspannungs-Gleichspannungs-Wandlers abgegebenen Gleichstroms mit einer Bezugsspannung abgeleitet wird.From EP-A-240 312 a ballast for a discharge lamp is known which uses a constant frequency oscillator which drives a pulse width modulator. The pulse width of the output signal of the pulse width modulator is changed in accordance with a control voltage which is generated in accordance with an error signal which is derived on the basis of a comparison between the direct current output by the secondary winding of an AC-DC converter and a reference voltage.
Werden derartige Vorschaltgeräte in Verbindung mit Anlagen benutzt, bei denen die kapazitiven Belastungen im Lastkreis z.B. durch die zu den Entladungslampen führenden Ausgangsleitungen unterschiedlich sind, ist es schwierig, eine ausreichende Zündspannung den Entladungslampen zur Verfügung zu stellen, da infolge der unterschiedlichen kapazitiven Belastungen sich die Resonanzfrequenz des Reihenresonanzkreises verlagert. Schwankt außerdem bei herkömmlichen Vorschaltgeräten die Speisespannung für den Wandler, so ändert sich dessen Betriebsfrequenz, was nicht nur die Zündzuverlässigkeit der Entladungslampe nachteilig beeinflußt, sondern auch zu Lichtstärkenschwankungen bei brennender Entladungslampe führt. Um diese Nachteile zu vermeiden, sehen bekannte Vorschaltgeräte aufwendige elektronische Stabilisierungsschaltungen vor, um den Wandler mit einer stabilisierten Speisespannung zu versorgen. Dieses ist insbesondere in Fahrzeugen, wie z.B. Eisenbahnwaggons, der Fall.Are ballasts of this type used in connection with systems in which the capacitive loads in the load circuit, for example, those leading to the discharge lamps Output lines are different, it is difficult to provide a sufficient ignition voltage to the discharge lamps, because the resonance frequency of the series resonant circuit shifts due to the different capacitive loads. If the supply voltage for the converter also fluctuates in conventional ballasts, its operating frequency changes, which not only adversely affects the ignition reliability of the discharge lamp, but also leads to fluctuations in light intensity when the discharge lamp is burning. In order to avoid these disadvantages, known ballasts provide complex electronic stabilization circuits in order to supply the converter with a stabilized supply voltage. This is particularly the case in vehicles such as railroad cars.
Aufgabe der Erfindung ist es, ein Vorschaltgerät der im Oberbegriff des Patentanspruchs 1 genannten Art so weiterzubilden, daß der jeweiligen Entladungslampe auch dann eine ausreichende Zündspannung zur Verfügung gestellt wird, wenn die kapazitiven Belastungen im Lastkreis des Wandlers unterschiedlich sind und die Speisespannung stark schwankt.The object of the invention is to develop a ballast of the type mentioned in the preamble of claim 1 in such a way that the respective discharge lamp is provided with a sufficient ignition voltage even if the capacitive loads in the load circuit of the converter are different and the supply voltage fluctuates greatly.
Bei einem Vorschaltgerät der genannten Art ist diese Aufgabe durch das im kennzeichnenden Teil des Patentanspruchs 1 angegebene Merkmal gelöst.In a ballast of the type mentioned, this object is achieved by the feature specified in the characterizing part of patent claim 1.
Mit Hilfe des Wobblers wird die Betriebsfrequenz des Gleichspannungs-Wechselspannungs-Wandlers so geändert, daß die Resonanzfrequenz des Reihenresonanzkreises entweder durch die Grundwelle der Betriebsfrequenz oder aber eine ihrer Harmonischen auch dann erreicht wird, wenn die Resonanzfrequenz aufgrund unterschiedlicher kapazitiver Belastungen des Reihenresonanzkreises verstimmt ist. Wird die jeweilige Resonanzfrequenz erreicht, erhält die Entladungslampe eine ausreichend hohe Zündspannung, wodurch diese sicher zündet. Unmittelbar nach dem Zünden der Entladungslampe wird der Wobbler abgeschaltet, so daß dann die Betriebsfrequenz des Wandlers im wesentlichen gleich bleibt.With the help of the wobbler, the operating frequency of the DC-AC converter is changed so that the resonance frequency of the series resonance circuit is achieved either by the fundamental wave of the operating frequency or one of its harmonics even when the resonance frequency is detuned due to different capacitive loads on the series resonance circuit. If the respective resonance frequency is reached, the discharge lamp is given a sufficiently high ignition voltage, which will ignite it safely. Immediately after the discharge lamp has been ignited, the wobbler is switched off, so that the operating frequency of the converter then remains essentially the same.
Vorzugsweise kann die Betriebsfrequenz des Wandlers aber auch bei brennender Entladungslampe geändert werden, um die Brennspannung für die Entladungslampe, also die Ausgangsspannung des Wandlers, und damit den Lampenstrom zu stabilisieren, wenn z.B. die Speisespannung der Gleichspannungsquelle des Gleichspannungs-Wechselspannungs-Wandlers schwankt, wie dieses bei Bordnetzen von Fahrzeugen oftmals der Fall ist.Preferably, however, the operating frequency of the converter can also be changed when the discharge lamp is on in order to stabilize the operating voltage for the discharge lamp, i.e. the output voltage of the converter, and thus the lamp current, e.g. the supply voltage of the DC voltage source of the DC-AC converter fluctuates, as is often the case with vehicle electrical systems.
Weitere Ausgestaltungen der Erfindung sind in den Unteransprüchen angegeben.Further embodiments of the invention are specified in the subclaims.
Ein Ausführungsbeispiel der Erfindung werden anhand der Zeichnung erläutert. Im einzelnen zeigt:
- Fig. 1
- ein erstes Ausführungsbeispiel mit einer Zeitschaltung,
- Fig. 2
- ein zweites Ausführungsbeispiel, das anstelle der Zeitschaltung einen Kaltleiter aufweist, und
- Fig. 3
- ein drittes Ausführungsbeispiel, das anstelle der Zeitschaltung einen Heißleiter aufweist
- Fig. 1
- a first embodiment with a timer,
- Fig. 2
- a second embodiment, which has a PTC thermistor instead of the timer, and
- Fig. 3
- a third embodiment which has a thermistor instead of the timer
Das in Fig. 1 dargestellte Vorschaltgerät umfaßt einen von einer hier nicht gezeigten Gleichspannungsquelle gespeisten Gleichspannungs-Wechselspannungs-Wandler 1 änderbarer Frequenz, der, wie angedeutet, ein Rechtecksignal an einen eine Induktivität 3a und einen Kondensator 3b umfassenden Reihenresonanzkreis 3 abgibt. Dem Kondensator 3b sind die Elektroden einer Entladungslampe 4 parallel geschaltet, die in bekannter Weise eine kapazitive Zündhilfe 4a umfassen kann, die jedoch kein sich von Erdpotential unterscheidendes Potential erhält. Die Elektroden der Entladungslampe 4 sind als heizbare Elektroden ausgebildet und erhalten über gesonderte Leitungen Heizstrom von dem Wandler 1. Mit dem Wandler 1 ist ein Wobbler 2 verbunden, dessen Ausgangssignal die Betriebsfrequenz des Wandlers 1 steuert. Der Wobbler 2 arbeitet dabei relativ langsam, z.B. mit einer Frequenz von 2 Hz. In einer den Lampenstrom führenden Verbindungsleitung ist ein Stromwandler 5 vorgesehen, dessen Ausgangssignal über eine Gleichrichterdiode an einen Kondensator 8 gegeben wird, dessen Ausgangsspannung als Steuersignal zum Abschalten des Wobblers 2 und zum Steuern der Betriebsfrequenz des Wandlers 1 benutzbar ist, um die Ausgangsspannung des Wandlers 1 und damit den lampenstrom für die Entladungslampe 4 über die Betriebsfrequenz zu stabilisieren, wenn die Speisespannung der den Wandler 1 speisenden Gleichspannungsquelle schwankt.The ballast shown in FIG. 1 comprises a variable frequency DC-AC converter 1 fed by a DC voltage source, not shown here, which, as indicated, emits a square wave signal to a series
Zum Beispiel im Wandler 1 selbst ist eine Zeitschaltung 6 vorgesehen, die beim Einschalten des Wandlers 1 gestartet wird. Diese Zeitschaltung 6 hält die Betriebsfrequenz des Wandlers 1, vorzugsweise bei noch abgeschaltetem Wobbler 2, oder aber unabhängig von ihm, auf einem Wert, bei dem der Reihenresonanzkreis 3 weder durch die Grundwelle noch durch eine ihrer Harmonischen in Resonanz gelangen kann, um ein Zünden der Entladungslampe 4 selbst bei hohen Umgebungstemperaturen sicher zu verhindern. Die Zeitschaltung überwacht eine ausreichende Vorheizdauer für die heizbaren Elektroden der Entladungslampe 4, um ein Zünden der Entladungslampe 4 erst dann zu veranlassen, wenn ihre Elektroden ausreichend vorgeheizt sind. Vorzeitige Zündversuche der Entladungslampe 4 würden eine unerwünschte Lampenschwärzung fördern.In the converter 1 itself, for example, a
Nach Ablauf der Vorheizdauer gibt die Zeitschaltung 6 die änderbare Betriebsfrequenz des Wandlers 1 frei bzw. schaltet den Wobbler 2 ein, so daß mit diesem periodisch ein bestimmter Frequenzbereich der Betriebsfrequenz durchfahren wird, der so gewählt ist, daß die Resonanzfrequenz des Reihenresonanzkreises 3 selbst dann erreicht wird, wenn diese aufgrund von kapazitiven Belastungen des Reihenresonanzkreises 3 erheblich verstimmt ist. Diese Resonanzfrequenz kann dabei durch die Grundwelle des Ausgangssignals des Wandlers 1 oder aber einer ihrer Harmonischen erreicht werden.After the preheating period, the
In den Fig. 2 und 3 sind zweite und dritte Ausführungsbeispiele des Vorschaltgerätes gezeigt, wobei das zweite Ausführungsbeispiel anstelle der in Fig. 1 gezeigten Zeitschaltung 6 einen Kaltleiter 9a aufweist, der einen stark positiven Temperaturkoeffizienten hat. Wird das Vorschaltgerät eingeschaltet, so kann während der Vorheizdauer für die Elektroden der Entladungslampe 4 am Reihenresonanzkreis 3 keine ausreichende Zündspannung auftreten, da dieser durch den bei Raumtemperatur stark leitenden Widerstand 9a kurzgeschlossen bzw. stark bedämpft ist. Nach Verstreichen einer bestimmten Zeitdauer heizt sich der Widerstand 9a auf, wodurch dieser aufgrund seines stark positiven Temperaturkoeffizienten einen hohen Widerstandswert erreicht, der als Dämpfungswiderstand für den Reihenresonanzkreis 3 dann keine Rolle mehr spielt, so daß dieser für die Entladungslampe 4 beim Erreichen der Resonanzfrequenz eine ausreichende Zündspannung zur Verfügung stellen kann.2 and 3 show second and third exemplary embodiments of the ballast, the second exemplary embodiment having a
Bei dem in Fig. 3 gezeigten dritten Ausführungsbeispiel ist anstelle des den Elektroden der Entladungslampe 4 parallel geschalteten Kaltleiters 9a im Reihenresonanzkreis 3 der Induktivität 3a ein Heißleiter 9b in Reihe geschaltet, der bei Raumtemperatur den Reihenresonanzkreis 3 durch einen hohen Widerstandswert so stark bedämpft, daß keine ausreichende Zündspannung selbst bei vorliegender Resonanzfrequenz an die Entladungslampe gegeben werden kann. Nach Verstreichen einer ausreichenden Vorheizdauer für die heizbaren Elektroden der Entladungslampe heizt sich der Heißleiter 9b so weit auf, daß sein Widerstand vernachlässigbar klein wird, so daß der Reihenresonanzkreis 3 beim Erreichen der Resonanzfrequenz eine ausreichende Zündspannung an die Entladungslampe 4 geben kann.In the third exemplary embodiment shown in FIG. 3, instead of the
Anstelle der in Fig. 1 gezeigten Zeitschaltung 6 sowie der in den Fig. 2 und 3 gezeigten Kalt- bzw. Heißleiter kann auch der Wobbler 2 so ausgebildet sein, daß beim Einschalten des Wandlers 1 die niederfrequente Wobbelspannung eine solche Größe hat, daß die mit ihr gesteuerte Betriebsfrequenz des Wandlers 1 einen Wert hat, der ausreichend weit von der Resonanzfrequenz des Reihenresonanzkreises 3 entfernt liegt. Wenn die Wobbelfrequenz des Wobblers 2 ausreichend niedrig ist, kann allein aufgrund dieser eine ausreichende Vorheizdauer für die heizbaren Elektroden der Entladungslampe 4 sichergestellt werden, indem die Betriebsfrequenz des Wandlers 1 erst dann in den Resonanzbereich des Reihenresonanzkreises 3 gelangt, nachdem die Vorheizdauer verstrichen ist.Instead of the
Vorzugsweise wird die Resonanzfrequenz auf die dritte Harmonische der Grundwelle der Ausgangsspannung des Wandlers 1 abgestimmt, wodurch der Wirkungsgrad des Vorschaltgerätes verbessert ist.The resonance frequency is preferably tuned to the third harmonic of the fundamental wave of the output voltage of the converter 1, as a result of which the efficiency of the ballast is improved.
Durchläuft die mit Hilfe des Wobblers 2 gewobbelte Betriebsfrequenz des Wandlers 1 bzw. ihre dritte Harmonische die jeweilige Resonanzfrequenz des Reihenresonanzkreises 3, so gibt dieser aufgrund der Resonanz eine ausreichend große Zündspannung an die Elektroden der Entladungslampe 4, wodurch diese sicher zündet. Nach dem Zünden der Entladungslampe fließt durch diese und den Stromwandler 5 der Lampenstrom, wodurch der Stromwandler 5 ein diesem proportionales Ausgangssignal über die Gleichrichterdiode 7 und den Kondensator 8 an den Wobbler 2 gibt, um diesen abzuschalten. Nach dem Abschalten des Wobblers 2 bleibt die Betriebsfrequenz des Wandlers 1 im wesentlichen unverändert. Andererseits gelangt das dem Lampenstrom proportionale Ausgangssignal des Stromwandlers 5 auch an den Steuereingang für die Betriebsfrequenz des Wandlers 1, um die Betriebsfrequenz innerhalb eines bestimmten Bereiches zum Erhöhen oder Erniedrigen der Ausgangsspannung des Wandlers 1 zu ändern. Dadurch kann der Lampenstrom stabilisiert werden, so daß die Entladungslampe 4 eine konstante Beleuchtungsstärke hat. Dieses ist insbesondere dann von Vorteil, wenn z.B. bei Bordnetzen von Fahrzeugen die Speisespannung der den Wandler 1 speisenden Gleichspannungsquelle schwankt.If the operating frequency of the converter 1 or its third harmonic swept with the aid of the
Der Reihenresonanzkreis 3 ist so ausgelegt, daß er auch im durch kapazitive Belastungen im Lastkreis verstimmten Zustand noch eine ausreichende Zündspannung von etwa 1 KV abgibt.The series
Claims (8)
- Ballast for a discharge lamp (4) which, together with a series resonant circuit (3), forms the load circuit of a direct- or alternating-voltage/alternating-voltage converter (1) of variable operating frequency which is fed by a direct- or alternating-voltage source, the capacitor (3b) of the series resonant circuit (3) being located between the electrodes of the discharge lamp (4), characterised in that the converter (1) is connected to a sweep frequency generator (2) with which a particular frequency range of the operating frequency of the converter (1) is periodically swept, which range is selected so that the resonant frequency of the series resonant circuit (3) is reached when the discharge lamp (4) is to be ignited.
- Ballast according to Claim 1, characterised in that in the connecting line carrying the lamp current between converter (1) and discharge lamp (4), a current transformer (5) is located, the output signal of which is used as control signal for switching off the sweep frequency generator (2) and for changing the operating frequency of the converter (1) in order to stabilise the lamp current delivered by it when the feed voltage is fluctuating.
- Ballast which supplies the heatable electrodes of the discharge lamp with heating current, according to Claim 1 or 2, characterised in that a thing circuit (6) is provided which, after the converter (1) has been switched on, keeps its operating frequency, during the preheating period, at a value which is sufficiently different with respect to the resonant frequency of the series resonant circuit (3) to prevent an ignition of the discharge lamp (4) even with high ambient temperatures.
- Ballast according to Claim 3, characterised in that the timing circuit (6) switches the sweep frequency generator (2) on after the preheating period has elapsed.
- Ballast which supplies the heatable electrodes of the discharge lamp with heating current, according to Claim 1 or 2, characterised in that a resistor (9a) having a highly positive temperature coefficient is connected in parallel with the electrodes of the discharge lamp (4).
- Ballast which supplies the heatable electrodes of the discharge lamp with heating current, according to Claim 1 or 2, characterised in that a resistor (9b) having a highly negative temperature coefficient is connected between the inductance (3a) and the capacitor (3b) within the series resonant circuit (3).
- Ballast according to one of Claims 1 to 6, characterised in that the resonant frequency of the series resonant circuit (3) is tuned to the third harmonic of the operating frequency of the converter (1).
- Ballast according to one of Claims 1 to 7, characterised in that the direct-voltage source is the feed source for the electrical system of a vehicle.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT88121019T ATE79503T1 (en) | 1987-12-17 | 1988-12-15 | BALLAST FOR A DISCHARGE LAMP. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3742921 | 1987-12-17 | ||
| DE19873742921 DE3742921A1 (en) | 1987-12-17 | 1987-12-17 | CONTROL UNIT FOR A DISCHARGE LAMP |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0320944A1 EP0320944A1 (en) | 1989-06-21 |
| EP0320944B1 true EP0320944B1 (en) | 1992-08-12 |
Family
ID=6342896
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP88121019A Expired - Lifetime EP0320944B1 (en) | 1987-12-17 | 1988-12-15 | Converter for a discharge lamp |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0320944B1 (en) |
| AT (1) | ATE79503T1 (en) |
| DE (2) | DE3742921A1 (en) |
| ES (1) | ES2008840A4 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL9300710A (en) * | 1993-04-26 | 1994-11-16 | Nijssen Light Div | Device for controlling a light output of a high or low pressure gas discharge lamp to a desired value. |
| DE102009048562B4 (en) * | 2009-10-07 | 2012-08-30 | Heraeus Noblelight Gmbh | Method and device for operating an electrodeless discharge lamp with a sweep generator |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1326392A (en) * | 1970-11-14 | 1973-08-08 | Dobson Park Ind | Fluorescent lamp and other circuits |
| DE3140175A1 (en) * | 1981-10-08 | 1983-04-28 | Licentia Gmbh | Transistor ballast apparatus |
| DE3149526A1 (en) * | 1981-12-14 | 1983-06-23 | Philips Patentverwaltung | CIRCUIT ARRANGEMENT FOR OPERATING HIGH PRESSURE GAS DISCHARGE LAMPS |
| US4700113A (en) * | 1981-12-28 | 1987-10-13 | North American Philips Corporation | Variable high frequency ballast circuit |
| CH663508A5 (en) * | 1983-09-06 | 1987-12-15 | Knobel Elektro App | ELECTRONIC CONTROLLER FOR FLUORESCENT LAMPS AND METHOD FOR THE OPERATION THEREOF. |
| NZ209570A (en) * | 1983-09-19 | 1988-03-30 | Minitronics Pty Ltd | Switching regulator |
| CA1333408C (en) * | 1984-10-16 | 1994-12-06 | Calvin E. Grubbs | Electronic ballast circuit for fluorescent lamps |
| DE3441992A1 (en) * | 1984-11-16 | 1986-05-22 | Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH, 8000 München | CIRCUIT ARRANGEMENT FOR IGNITING A LOW-PRESSURE DISCHARGE LAMP |
| CA1327991C (en) * | 1986-03-28 | 1994-03-22 | Thomas E. Dean | High frequency ballast for gaseous discharge lamps |
| JPS62233067A (en) * | 1986-03-31 | 1987-10-13 | Toshiba Corp | Stabilized power unit |
-
1987
- 1987-12-17 DE DE19873742921 patent/DE3742921A1/en not_active Withdrawn
-
1988
- 1988-12-15 AT AT88121019T patent/ATE79503T1/en not_active IP Right Cessation
- 1988-12-15 ES ES88121019T patent/ES2008840A4/en active Pending
- 1988-12-15 EP EP88121019A patent/EP0320944B1/en not_active Expired - Lifetime
- 1988-12-15 DE DE8888121019T patent/DE3873708D1/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0320944A1 (en) | 1989-06-21 |
| DE3742921A1 (en) | 1989-06-29 |
| DE3873708D1 (en) | 1992-09-17 |
| ES2008840A4 (en) | 1989-08-16 |
| ATE79503T1 (en) | 1992-08-15 |
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