EP0422255B1 - Electronic ballast - Google Patents

Electronic ballast Download PDF

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Publication number
EP0422255B1
EP0422255B1 EP89118713A EP89118713A EP0422255B1 EP 0422255 B1 EP0422255 B1 EP 0422255B1 EP 89118713 A EP89118713 A EP 89118713A EP 89118713 A EP89118713 A EP 89118713A EP 0422255 B1 EP0422255 B1 EP 0422255B1
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EP
European Patent Office
Prior art keywords
voltage
fluorescent lamp
circuit
lamp
auxiliary
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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EP89118713A
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German (de)
French (fr)
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EP0422255A1 (en
Inventor
Jürgen Klier
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Siemens AG
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Siemens AG
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Publication date
Priority to DE89118713T priority Critical patent/DE58907133D1/en
Application filed by Siemens AG filed Critical Siemens AG
Priority to EP89118713A priority patent/EP0422255B1/en
Priority to AT89118713T priority patent/ATE102430T1/en
Priority to ES89118713T priority patent/ES2049790T3/en
Priority to US07/592,125 priority patent/US5066894A/en
Priority to JP2269688A priority patent/JPH07101638B2/en
Publication of EP0422255A1 publication Critical patent/EP0422255A1/en
Application granted granted Critical
Publication of EP0422255B1 publication Critical patent/EP0422255B1/en
Priority to HK123395A priority patent/HK123395A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/39—Controlling the intensity of light continuously
    • H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
    • H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
    • H05B41/3925—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations by frequency variation

Definitions

  • the invention relates to an electronic ballast according to the preamble of claim 1.
  • Electronic ballasts of this type are known for example from DE-A1-3709004. If such an electronic ballast is to be used for dimming a fluorescent lamp within wide limits, particular difficulties arise when the positions are ⁇ 10% of the nominal luminous flux.
  • the fluorescent lamps have large tolerances with regard to their electrical properties, are sensitive to changes in temperature and are subject to signs of aging. There is therefore a risk that when the fluorescent lamp is dimmed to low values by tearing off the discharge, the fluorescent lamp goes out.
  • the controller regulates the brightness of the fluorescent lamp via its discharge current.
  • this principle fails at positions ⁇ 10% of the nominal luminous flux, since the differential current transformer required for this would have to be completely free of stray fields. In the 1% dimming position, a leakage flux of the residual current transformer of only 1% of the main flow would falsify the measurement result by approx. 100%.
  • a dimming circuit for high-pressure lamps is known from US-A-3,989,976.
  • this known circuit has an auxiliary control loop.
  • This auxiliary control loop detects a tendency for the lamp arc to go out due to the increasing alternating voltage of the high-pressure lamp.
  • the auxiliary control loop is designed in such a way that the increased alternating burning voltage which occurs during dimming is automatically compensated for by the fact that increased power is supplied to the lamp via the ballast. This is done in such a way that the normal control of the ballast, which is matched to the cycle of the AC line voltage, is deactivated in this critical operating state and the control is instead based on the output signal of a scanning circuit evaluating the lamp lamp voltage.
  • the invention is based on the object of specifying a solution for a dimmable electronic ballast of the type mentioned at the outset, regardless of whether use is made of a discharge current control or a power control of the fluorescent lamp, which, with little additional effort, ensures reliable dimming even at dimming positions below 10 % of the nominal luminous flux down to less than 1%.
  • the invention is based on the finding that when the fluorescent lamp is dimmed, the discharge current mainly changes, while the operating voltage - at least in terms of magnitude - remains the same. This means that the voltage-current ratio, that is, the resistance of the discharge gap with increasing brightness of the fluorescent lamp, becomes ever greater and finally tends towards infinity when the discharge stops.
  • a fluorescent lamp can thus still be operated safely at 1% of its nominal luminous flux if the discharge resistance is also monitored and the control variable derived from this in the sense of a correction of the control variable for the controller in the lower range the brightness control is used.
  • ballast can recognize whether the lamp is on without the need for optoelectronic devices or a differential current transformer for lamp current detection. This can be used, for example, in electronic ballasts provided for warm starts to control the preheating phase of the fluorescent lamp, since premature ignition of the fluorescent lamp can be detected and immediately switched from preheating to operation.
  • the dimmable electronic ballast shown partially in the form of a block diagram in FIG. 1 essentially consists of an inverter WR which is connected on the output side to a load circuit.
  • the load circuit consists of the series connection of a lamp inductor L1 with a fluorescent lamp LL, which is an ignition capacitor C2 in parallel.
  • the inverter WR uses a half-bridge circuit comprising two switches T1, T2, which are connected in series as power transistors, and a half-bridge capacitor C1, to which a discharge resistor R1 is connected in parallel.
  • the common connection point of half-bridge capacitor C1, discharge resistor R1 and one of the electrodes of the fluorescent lamp LL is denoted by A and the connection point of the other electrode to the lamp inductor L1 is denoted by B.
  • the switches T1 and T2 of the half-bridge circuit are controlled by an oscillator O, which in turn is connected via its control input to the output of a controller RR.
  • the control input of the controller RR is preceded by a summer SR having comparator properties, the three inputs of which are supplied with a setpoint SW, an actual value IW and an auxiliary control variable HMG.
  • the correct addition of the actual value IW, the setpoint SW and the auxiliary control variable HMG result in a variable for the control deviation RAG, which is fed from the output of the summer SR to the control input of the controller RR.
  • the setpoint value SW, the actual value IW and the auxiliary control variable HMG are DC voltages, which together result in the control deviation RAG, which also represents a DC voltage.
  • the power supply for the inverter WR usually takes the form of a DC voltage which is obtained from the AC line voltage and is indicated in FIG. 1 as an intermediate circuit DC voltage Uzw.
  • This DC link voltage is due to the series connection of the two switches T1 and T2.
  • the half-bridge capacitor C1 and the discharge resistor R1 are in turn connected to the positive pole of the DC link voltage Uzw.
  • the auxiliary control variable HMG is taken from the tap of a voltage divider formed from resistors R2 and R3, which in turn is connected from the connection point A to the negative pole of the DC link voltage Uzw.
  • the setpoint value SW representing a reference voltage is usually generated by a DC voltage which is adjustable in size and is not shown in FIG. 1 and the other figures.
  • the actual value IW which also represents a DC voltage, is either proportional to the discharge current flowing through the fluorescent lamp LL or else to the lamp power. It can be obtained in a known manner via a differential current transformer or via a current-voltage measurement in the area of the load circuit. The circuitry of such an actual value detection is also omitted in FIG. 1, as in the other figures.
  • half the DC link voltage Uzw is set at the connection point B when the fluorescent lamp LL is lit, superimposed by the alternating voltage of the fluorescent lamp LL.
  • the half-bridge capacitor C1 and the discharge resistor R1 lying parallel to it are usually so large that half the DC link voltage Uzw also occurs at the nominal luminous flux of the fluorescent lamp at the connection point A.
  • the discharge resistor R1 is substantially larger than the discharge resistor of the fluorescent lamp, so that the discharge of the half-bridge capacitor C1 caused by the discharge resistor R1 can be practically neglected.
  • the high-frequency lamp current causes only a small voltage drop across the half-bridge capacitor C1.
  • the discharge resistance of the fluorescent lamp LL becomes so great that the discharge resistor R1 can partially discharge the half-bridge capacitor C1.
  • the potential at connection point A and the auxiliary control variable HMG divided down via voltage divider R2 / R3 at the tap of this voltage divider also increase.
  • the auxiliary control variable HMG thus counteracts a further reduction in the lamp power and prevents the unwanted tearing off of the discharge via the controller RR.
  • the described change in the auxiliary control variable HMG has a noticeable effect only in the immediate vicinity of the lower limit of the brightness control range of the fluorescent lamp LL, because only in this range does the discharge resistance of the fluorescent lamp and thus also the potential at the connection point A increase significantly.
  • This type of derivation of the auxiliary control variable HMG from the size of the discharge resistance of the fluorescent lamp LL by means of a DC voltage measurement presupposes that no rectifier effects per se occur in the fluorescent lamp.
  • Such a rectifier effect can occur, for example, if there are large differences in the emissivity of the electrodes of the fluorescent lamp LL. If the dependency of the DC voltage measurement and thus the generation of the auxiliary control variable HMG on such a rectifier effect is to be excluded, then the auxiliary control variable HMG can also be derived from an AC voltage.
  • a corresponding exemplary embodiment is shown in FIG. 2.
  • the auxiliary control variable HMG is derived by superimposing a low-frequency AC voltage on the fluorescent lamp LL with the high-frequency burning AC voltage.
  • the light-bulb lamp LL is additionally connected to the AC line voltage Un via coupling elements KE1, for example in the form of coupling resistors Rk.
  • the low-frequency component of the AC combustion voltage thus occurring on the fluorescent lamp LL is then fed via further coupling elements KE2, which block the high-frequency component of the AC combustion voltage and also the DC component, to a rectifier GL, which is followed by a filter element SG for smoothing the rectified, low-frequency component of the AC combustion voltage.
  • the voltage divider R2 / R3, which is already known from FIG. 1, is connected in parallel to the output of the filter element SG, and the auxiliary control variable HMG is present at its tap.
  • the coupling elements KE2 consist of the series connection of a filter choke Ls and a filter capacitor Cs.
  • a threshold for example in the form of an additional threshold, can be added to the connection path of the tap of the voltage divider R2 / R3 to the summer SR, as shown in FIG. 3 a Zener diode D1. Only when the auxiliary control variable HMG at the tap of the voltage divider R2 / R3 with a dimming position of, for example, one or two percent of the nominal luminous flux has become so large that the zener diode becomes low-resistance does the additional regulation prevent the discharge from breaking off. The behavior of the controller in The brightness control range above this threshold is then, which is sometimes desirable, not influenced by this additional control.
  • the Zener diode D1 is entered in the circuit diagram of FIG. 3.
  • the circuit according to FIG. 3 represents a further development of the circuit according to FIG. 1.
  • the circuit according to FIG. 3 differs from the circuit according to FIG. 1 an additional circuit ZS.
  • a further auxiliary control variable HMG1 is generated via this additional circuit ZS, which is superimposed on the auxiliary control variable HMG with the same effect. As a result, the control speed of the additional control is significantly increased.
  • the change in the discharge resistance during a dimming process of the fluorescent lamp LL in the direction of decreasing brightness results in a relatively slow change in the potential at the connection point A, because a large time constant of the half-bridge capacitor C1 and the discharge resistor R1 is predetermined by the overall circuit. If the dimensions are unfavorable, control vibrations can occur. However, the dynamic behavior of the controller can be significantly improved by the additional circuit ZS because the influence of this large time constant can be reduced. If the lamp power is greatly reduced to values below 10% of the nominal power, the alternating voltage of the fluorescent lamp LL decreases with the lamp power.
  • the additional circuit ZS takes advantage of this by generating a DC voltage from the AC combustion voltage which is proportional to the AC combustion voltage and is superimposed on the auxiliary control variable HMG with the correct sign in the sense of the desired regulation as a further auxiliary control variable HMG1.
  • FIG. 4 A preferred embodiment of the additional circuit ZS according to FIG. 3 is shown in FIG. 4. It consists between the connection point B and the negative pole of the DC link voltage Uzw from the series connection of the capacitor C3 with a voltage divider R4 / R5 formed from resistors R4 and R5.
  • the divided portion of the AC combustion voltage across the resistor R5 is now rectified via a diode D2 and the rectified AC combustion voltage is fed to the parallel circuit comprising a capacitor C4 and a resistor R6.
  • the change in the rectified AC combustion voltage takes effect on the capacitor C4 and is fed via the capacitor C5 to the resistor R3 of the voltage divider R2 / R3 as the further auxiliary control variable HMG1.

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  • Circuit Arrangements For Discharge Lamps (AREA)
  • Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
  • Mechanical Treatment Of Semiconductor (AREA)
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  • Furan Compounds (AREA)
  • Discharge Heating (AREA)
  • Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)
  • Organic Insulating Materials (AREA)

Abstract

In electronic ballast having inverter rectifiers for fluorescent lamps, a regulation of the lamp current or of the lamp power is usually used in order to stabilize the lighting current independently of tolerances of the electrical properties of the fluorescent lamp or their aging phenomena. When such a regulation is simultaneously utilized for dimming the fluorescent lamp, difficulties arise at the lower limit of the dimming range at, for example, 1% of the nominal light power. The range of brightness at the lower limit is regulated on the basis of an additional regulation, dependent on the discharge resistance of the fluorescent lamp. An auxiliary measured quantity resulting therefrom is superimposed on the actuating quantity of the regulator that results from a reference/actual value comparison of the current or power regulation for the purpose of stabilizing the lamp current.

Description

Die Erfindung bezieht sich auf ein elektronisches Vorschaltgerät gemäß dem Oberbegriff des Patentanspruches 1.The invention relates to an electronic ballast according to the preamble of claim 1.

Elektronische Vorschaltgeräte dieser Art sind beispielsweise aus DE-A1-3709004 bekannt. Soll ein solches elektronisches Vorschaltgerät zum Dimmen einer Leuchtstofflampe in weiten Grenzen verwendet werden, so ergeben sich besondere Schwierigkeiten bei den Stellungen < 10 % des Nennlichtstroms. Die Leuchtstofflampen haben hinsichtlich ihrer elektrischen Eigenschaften große Toleranzen, reagieren empfindlich auf Temperaturänderungen und unterliegen Alterungserscheinungen. Es besteht deshalb die Gefahr, daß beim Dimmen der Leuchtstofflampe zu niedrigen Werten hin durch Abreißen der Entladung die Leuchtstofflampe erlischt.Electronic ballasts of this type are known for example from DE-A1-3709004. If such an electronic ballast is to be used for dimming a fluorescent lamp within wide limits, particular difficulties arise when the positions are <10% of the nominal luminous flux. The fluorescent lamps have large tolerances with regard to their electrical properties, are sensitive to changes in temperature and are subject to signs of aging. There is therefore a risk that when the fluorescent lamp is dimmed to low values by tearing off the discharge, the fluorescent lamp goes out.

Bei der angegebenen Literaturstelle regelt der Regler die Helligkeit der Leuchtstofflampe über ihren Entladungsstrom. Dieses Prinzip versagt jedoch bei den Stellungen <10 % des Nennlichtstromes, da der hierfür notwendige Differenzstromtransformator völlig streufeldfrei sein müßte. In der Dimmstellung 1 % würde ein Streufluß des Differenzstromtransformators von nur 1 % des Hauptflusses das Meßergebnis um ca. 100 % verfälschen.In the specified literature reference, the controller regulates the brightness of the fluorescent lamp via its discharge current. However, this principle fails at positions <10% of the nominal luminous flux, since the differential current transformer required for this would have to be completely free of stray fields. In the 1% dimming position, a leakage flux of the residual current transformer of only 1% of the main flow would falsify the measurement result by approx. 100%.

An Stelle einer Regelung des Entladungsstroms der Leuchtstofflampe kann auch, wie beispielsweise aus DE-A1-2544364 A1 bekannt ist, die Regelung über die Lampenleistung erfolgen. Dies hat jedoch den Nachteil, daß nur die Summe aus Lampenleistung und Wendelheizleistung geregelt werden kann. Die Wendelheizleistung hängt stark vom toleranzbehafteten Wendelwiderstand ab. Dadurch ist auch diese Art der Regelung bei Dimmstellungen < 10 % der Nennlichtleistung nur bedingt einsetzbar. Beispielsweise in einer Dimmstellung von 1 % der Nennlichtleistung beträgt die zu regelnde Lampenleistung üblicher Leuchtstofflampen etwa 0,5 W, die Heizleistung aber etwa 4 W. Ein befriedigender Gleichlauf zwischen mehreren Leuchtstofflampen ist damit bei dem Stellungen < 10 % auf diese Weise nicht gewährleistbar.Instead of regulating the discharge current of the fluorescent lamp, it is also possible, as is known for example from DE-A1-2544364 A1, to regulate the lamp power. However, this has the disadvantage that only the sum of lamp power and filament heating power can be regulated. The filament heating capacity depends heavily on the filament resistance with tolerance. As a result, this type of control can only be used to a limited extent with dimming settings <10% of the nominal light output. For example, in a dimming setting of 1% of the nominal light output, the lamp output to be regulated for conventional fluorescent lamps is approximately 0.5 W, but the heating output is approximately 4 W. A satisfactory synchronization between several fluorescent lamps cannot be guaranteed in this way at positions <10%.

Weiterhin ist aus US-A-3,989,976 eine Dimmschaltung für Hochdrucklampen bekannt. Neben einem Vorschaltgerät, das allerdings im Gegensatz zu modernen elektronischen Vorschaltgeraten für Niederdrucklampen, wie Leuchtstofflampen, nicht mit Hochfrequenz im Bereich von mehr als 20 kHz sondern mit Netzfrequenz arbeitet, besitzt diese bekannte Schaltung einen Hilfsregelkreis. Dieser Hilfsregelkreis erkennt aufgrund der an der Hochdrucklampe ansteigenden Brennwechselspannung eine Tendenz zum Erloschen des Lampenlichtbogens. Der Hilfsregelkreis ist so ausgebildet, daß die beim Dimmen auftretende erhöhte Brennwechselspannung dadurch automatisch kompensiert wird, daß der Lampe über das Vorschaltgerät erhöhte Leistung zugeführt wird. Das geschieht derart, daß die normale, auf den Zyklus der Netzwechselspannung abgestimmte Ansteuerung des Vorschaltgerätes in diesem kritischen Betriebszustand außer Kraft gesetzt und die Regelung stattdessen auf das Ausgangssignal eines die Lampenbrennspannung auswertenden Abtastkreises bezogen wird.Furthermore, a dimming circuit for high-pressure lamps is known from US-A-3,989,976. In addition to a ballast, which, in contrast to modern electronic ballasts for low-pressure lamps, such as fluorescent lamps, does not work with a high frequency in the range of more than 20 kHz but with a mains frequency, this known circuit has an auxiliary control loop. This auxiliary control loop detects a tendency for the lamp arc to go out due to the increasing alternating voltage of the high-pressure lamp. The auxiliary control loop is designed in such a way that the increased alternating burning voltage which occurs during dimming is automatically compensated for by the fact that increased power is supplied to the lamp via the ballast. This is done in such a way that the normal control of the ballast, which is matched to the cycle of the AC line voltage, is deactivated in this critical operating state and the control is instead based on the output signal of a scanning circuit evaluating the lamp lamp voltage.

Die bekannte Losung ist auf die typische Lichtstrom-Spannungscharakteristik bei Hochdrucklampen abgestimmt, die bei fallendem Lampenlichtstrom stark ansteigt. Bei Niederdrucklampen ist aber die Brennwechselspannung vom Lampenlichtstrom nicht in dieser Weise abhängig. Bei grober Betrachtung ist die Lampenbrennspannung bei diesem Lampentyp nahezu unabhängig vom Lampenlichtstrom, bei genauer Betrachtung aber zeigt sich, daß sie bei abnehmendem Lampenlichtstrom nach Durchlaufen eines Maximums in dem gerade kritischen Bereich kleiner Lampenlichtströme wieder abfällt. Mit einer Rückkopplung der Lampenbrennspannung auf den Regelkreis des elektronischen Vorschaltgerätes kann man daher diesen Regelkreis auch dann nicht stabilisieren, wenn man berücksichtigte, daß man auf eine Verringerung der Lampenbrennspannung abstellen mußte. Dies liegt daran, daß die Lichtstrom-Spannungscharakteristik wegen des bei niedrigen Lichtstromwerten auftretenden Maximums nicht eindeutig ist.The well-known solution is matched to the typical luminous flux voltage characteristic of high-pressure lamps, which increases sharply when the lamp luminous flux falls. In the case of low-pressure lamps, however, the burning voltage is not dependent on the lamp luminous flux in this way. When viewed roughly, the lamp lamp voltage for this type of lamp is almost independent of the lamp luminous flux, but a closer look reveals that when the lamp luminous flux decreases after passing a maximum in the critical area of small lamp luminous flux, it drops again. With a feedback of the lamp voltage on the control circuit of the Electronic ballast can therefore not stabilize this control loop even if you take into account that you had to focus on a reduction in lamp lamp voltage. This is because the luminous flux voltage characteristic is not clear because of the maximum that occurs at low luminous flux values.

Der Erfindung liegt die Aufgabe zugrunde, bei einem dimmfähigen elektronischen Vorschaltgerät der eingangs genannten Art unabhängig davon, ob von einer Entladungsstrom- oder einer Leistungsregelung der Leuchtstofflampe Gebrauch gemacht wird, eine Lösung anzugeben, die bei geringem Mehraufwand ein sicheres Dimmen auch bei Dimmstellungen unterhalb von 10 % des Nennlichtstromes bis herab zu weniger als 1 % ermöglicht.The invention is based on the object of specifying a solution for a dimmable electronic ballast of the type mentioned at the outset, regardless of whether use is made of a discharge current control or a power control of the fluorescent lamp, which, with little additional effort, ensures reliable dimming even at dimming positions below 10 % of the nominal luminous flux down to less than 1%.

Diese Aufgabe wird gemäß der Erfindung durch die im Kennzeichen des Patentanspruches 1 angegebenen Merkmale gelöst.This object is achieved according to the invention by the features specified in the characterizing part of patent claim 1.

Der Erfindung liegt die Erkenntnis zugrunde, daß sich beim Dimmen einer Leuchtstofflampe hauptsächlich der Entladungsstrom ändert, während die Brennspannung - zumindest von der Größenordnung her - gleich bleibt. Das bedeutet, daß das Spannungs-Strom-Verhältnis, also der Widerstand der Entladungsstrecke bei abnehmender Helligkeit der Leuchtstofflampe immer größer wird und schließlich gegen unendlich strebt, wenn die Entladung abreißt.The invention is based on the finding that when the fluorescent lamp is dimmed, the discharge current mainly changes, while the operating voltage - at least in terms of magnitude - remains the same. This means that the voltage-current ratio, that is, the resistance of the discharge gap with increasing brightness of the fluorescent lamp, becomes ever greater and finally tends towards infinity when the discharge stops.

Unabhängig davon, von welcher Regelung der Leuchtstofflampe Gebrauch gemacht wird, läßt sich somit eine Leuchtstofflampe auch noch sicher bei 1 % ihres Nennlichtstroms betreiben, wenn zusätzlich der Entladungswiderstand überwacht wird und die hiervon abgeleitete Regelgröße im Sinne einer Korrektur der Steuergröße für den Regler im unteren Bereich der Helligkeitsregelung herangezogen wird.Regardless of which control of the fluorescent lamp is used, a fluorescent lamp can thus still be operated safely at 1% of its nominal luminous flux if the discharge resistance is also monitored and the control variable derived from this in the sense of a correction of the control variable for the controller in the lower range the brightness control is used.

Diese zusätzliche Regelung in Abhängigkeit von dem Entladungswiderstand der Leuchtstofflampe hat darüber hinaus beachtliche Vorteile. Wie sich zeigt, haben Argonlampen und Kryptonlampen gleicher Länge, bei sonst unterschiedlichen elektrischen Eigenschaften, bei Dimmstellungen um 1 % des Nennlichtstromes etwa den gleichen Entladungswiderstand. Eine Anpassung dieser speziellen Regelung an den Lampentyp ist also nicht erforderlich.This additional regulation depending on the discharge resistance of the fluorescent lamp also has considerable advantages. As can be seen, argon lamps and krypton lamps of the same length, with otherwise different electrical properties, with dimming settings around 1% of the nominal luminous flux have approximately the same discharge resistance. It is therefore not necessary to adapt this special regulation to the lamp type.

Ein weiterer Vorteil dieser Regelung in Abhängigkeit von dem Entlaoungswiderstand besteht darin, daß das Vorschaltgerät erkennen kann, ob die Lampe brennt, ohne hierfür optoelektronische Einrichtungen oder einen Differenzstromtransformator zur Lampenstromerfassung zu benötigen. Dies läßt sich beispielsweise bei für Warmstart vorgesehenen elektronsichen Vorschaltgeräten zur Steuerung der Vorheizphase der Leuchtstofflampe nutzen, da ein vorzeitiges Zünden der Leuchtstofflampe erkannt und sofort von Vorheizen auf Betrieb umgeschaltet werden kann.Another advantage of this regulation depending on the drain resistance is that the ballast can recognize whether the lamp is on without the need for optoelectronic devices or a differential current transformer for lamp current detection. This can be used, for example, in electronic ballasts provided for warm starts to control the preheating phase of the fluorescent lamp, since premature ignition of the fluorescent lamp can be detected and immediately switched from preheating to operation.

Zweckmäßige Ausgestaltungen des Gegenstandes nach dem Patentanspruch 1 sind in den weiteren Patentansprüchen 2 bis 10 angegeben.Expedient embodiments of the subject matter according to claim 1 are specified in the further claims 2 to 10.

Ausführungsbeispiele der Erfindung werden im folgenden anhand der Zeichnung im einzelnen beschrieben, dabei bedeuten die der näheren Erläuterung der Erfindung dienenden Figuren:

Fig. 1
ein erstes Ausführungsbeispiel eines in weiten Grenzen dimmfähigen elektronsichen Vorschaltgerätes, bei dem die vom Entladungswiderstand der Leuchtstofflampe abhängige Hilfsregelgröße vom Potential einer Lampenelektrode gewonnen ist,
Fig. 2
ein weiteres bevorzugtes Ausführungsbeispiel für ein in weiten Grenzen dimmfähiges elektronisches Vorschaltgerät, bei dem die vom Entladungswiderstand der Leuchtstofflampe abhängige Hilfsregelgröße aus einem niederfrequenten Anteil der Brennwechselspannung der Leuchtstofflampe gewonnen ist,
Fig. 3
eine Weiterbildung der Ausführungsform nach Fig. 1,
Fig. 4
eine Ausführungsform der in der Schaltung nach Fig. 3 verwendeten Zusatzschaltung.
Exemplary embodiments of the invention are described in detail below with reference to the drawing, the figures used to explain the invention in more detail:
Fig. 1
1 shows a first exemplary embodiment of an electronic ballast which is dimmable within wide limits, in which the auxiliary control variable which is dependent on the discharge resistance of the fluorescent lamp is obtained from the potential of a lamp electrode,
Fig. 2
another preferred exemplary embodiment of an electronic ballast which is dimmable within wide limits, in which the auxiliary control variable dependent on the discharge resistance of the fluorescent lamp is obtained from a low-frequency component of the alternating voltage of the fluorescent lamp,
Fig. 3
a development of the embodiment of FIG. 1,
Fig. 4
an embodiment of the additional circuit used in the circuit of FIG. 3.

Das in Fig.1 teilweise in Form eines Blockschaltbildes dargestellte dimmfähiger elektronischer Vorschaltgerät besteht im wesentlichen aus einem Wechselrichter WR, der ausgangsseitig mit einem Lastkreis verbunden ist. Der Lastkreis besteht dabei aus der Reihenschaltung einer Lampendrossel L1 mit einer Leuchtstofflampe LL, der ein Zündkondensator C2 parallel liegt. Der Wechselrichter WR verwendet eine Halbbrückenschaltung aus zwei in Reihe geschalteten, als Leistungstransistoren ausgebildeten Schaltern T1, T2 und einem Halbbrückenkondensator C1, dem ein Entladewiderstand R1 parallel geschaltet ist.The dimmable electronic ballast shown partially in the form of a block diagram in FIG. 1 essentially consists of an inverter WR which is connected on the output side to a load circuit. The load circuit consists of the series connection of a lamp inductor L1 with a fluorescent lamp LL, which is an ignition capacitor C2 in parallel. The inverter WR uses a half-bridge circuit comprising two switches T1, T2, which are connected in series as power transistors, and a half-bridge capacitor C1, to which a discharge resistor R1 is connected in parallel.

Der gemeinsame Verbindungspunkt von Halbbrückenkondensator C1, Entladewiderstand R1 und einer der Elektroden der Leuchtstofflampe LL ist mit A und der Verbindungspunkt der anderen Elektrode mit der Lampendrossel L1 ist mit B bezeichnet. Die Schalter T1 und T2 der Halbbrückenschaltung werden von einem Oszillator O angesteuert, der seinerseits über seinen Steuereingang mit dem Ausgang eines Reglers RR verbunden ist.The common connection point of half-bridge capacitor C1, discharge resistor R1 and one of the electrodes of the fluorescent lamp LL is denoted by A and the connection point of the other electrode to the lamp inductor L1 is denoted by B. The switches T1 and T2 of the half-bridge circuit are controlled by an oscillator O, which in turn is connected via its control input to the output of a controller RR.

Dem Steuereingang des Reglers RR ist ein Vergleichereigenschaften aufweisender Summierer SR vorgeordnet, dessen drei Eingängen ein Sollwert SW, ein Istwert IW und eine Hilfsregelgröße HMG zugeführt sind. Die vorzeichenrichtige Addition des Istwertes IW, des Sollwertes SW und der Hilfsregelgröße HMG ergeben eine Größe für die Regelabweichung RAG, die vom Ausgang des Summierers SR dem Steuereingang des Reglers RR Zugeführt wird. Beim Ausführungsbeispiel nach Fig. 1 sind der Sollwert SW, der Istwert IW sowie die Hilfsregelgröße HMG Gleichspannungen, die gemeinsam die ebenfalls eine Gleichspannung darstellende Regelabweichung RAG ergeben.The control input of the controller RR is preceded by a summer SR having comparator properties, the three inputs of which are supplied with a setpoint SW, an actual value IW and an auxiliary control variable HMG. The correct addition of the actual value IW, the setpoint SW and the auxiliary control variable HMG result in a variable for the control deviation RAG, which is fed from the output of the summer SR to the control input of the controller RR. In the exemplary embodiment according to FIG. 1, the setpoint value SW, the actual value IW and the auxiliary control variable HMG are DC voltages, which together result in the control deviation RAG, which also represents a DC voltage.

Die Stromversorgung für den Wechselrichter WR erfolgt üblicherweise in Form einer Gleichspannung, die aus der Netzwechselspannung gewonnen und in Fig. 1 als Zwischenkreisgleichspannung Uzw angegeben ist. Diese Zwischenkreisgleichspannung liegt an der Reihenschaltung der beiden Schalter T1 und T2. Der Halbbrückenkondensator C1 und der Entladewiderstand R1 sind ihrerseits an den positiven Pol der Zwischenkreisgleichspannung Uzw angeschaltet. Die Hilfsregelgröße HMG wird am Abgriff eines aus Widerständen R2 und R3 gebildeten Spannungsteilers abgenommen, der seinerseits vom Verbindungspunkt A gegen den negativen Pol der Zwischenkreisgleichspannung Uzw geschaltet ist.The power supply for the inverter WR usually takes the form of a DC voltage which is obtained from the AC line voltage and is indicated in FIG. 1 as an intermediate circuit DC voltage Uzw. This DC link voltage is due to the series connection of the two switches T1 and T2. The half-bridge capacitor C1 and the discharge resistor R1 are in turn connected to the positive pole of the DC link voltage Uzw. The auxiliary control variable HMG is taken from the tap of a voltage divider formed from resistors R2 and R3, which in turn is connected from the connection point A to the negative pole of the DC link voltage Uzw.

Der eine Bezugsspannung darstellende Sollwert SW ist üblicherweise von einer in ihrer Größe einstellbaren Gleichspannung erzeugt, die in Fig. 1 und den übrigen Figuren nicht dargestellt ist. Der ebenfalls eine Gleichspannung darstellende Istwert IW ist entweder dem durch die Leuchtstofflampe LL fließenden Entladestrom oder aber der Lampenleistung proportional. Er kann in bekannter Weise über einen Differenzstromtransformator bzw. über eine Strom-Spannungsmessung im Bereich des Lastkreises gewonnen werden. Auf die schaltungstechnische Darstellung einer solchen Istwerterkennung ist in Fig. 1, wie auch in den übrigen Figuren, ebenfalls verzichtet.The setpoint value SW representing a reference voltage is usually generated by a DC voltage which is adjustable in size and is not shown in FIG. 1 and the other figures. The actual value IW, which also represents a DC voltage, is either proportional to the discharge current flowing through the fluorescent lamp LL or else to the lamp power. It can be obtained in a known manner via a differential current transformer or via a current-voltage measurement in the area of the load circuit. The circuitry of such an actual value detection is also omitted in FIG. 1, as in the other figures.

Bei der üblicherweise symmetrischen Ansteuerung der Schalter T1 und T2 der Halbbrücke stellt sich am Verbindungspunkt B bei brennender Leuchtstofflampe LL die halbe Zwischenkreisgleichspannung Uzw, überlagert durch die Brennwechselspannung der Leuchtstofflampe LL ein. Üblicherweise sind der Halbbrückenkondensator C1 sowie der ihm parallel liegende Entladewiderstand R1 so groß, daß sich beim Nennlichtstrom der Leuchtstofflampe am Verbindungspunkt A ebenfalls die halbe Zwischenkreisgleichspannung Uzw einstellt. Mit anderen Worten, in dieser Betriebssituation ist der Entladewiderstand R1 wesentlich größer als der Entladewiderstand der Leuchtstofflampe, so daß die durch den Entladewiderstand R1 bewirkte Entladung des Halbbrückenkondensators C1 praktisch vernachlässigt werden kann. Der hochfrequente Lampenstrom bewirkt nur einen geringen Spannungsabfall am Halbbrückenkondensator C1.With the usually symmetrical activation of the switches T1 and T2 of the half-bridge, half the DC link voltage Uzw is set at the connection point B when the fluorescent lamp LL is lit, superimposed by the alternating voltage of the fluorescent lamp LL. The half-bridge capacitor C1 and the discharge resistor R1 lying parallel to it are usually so large that half the DC link voltage Uzw also occurs at the nominal luminous flux of the fluorescent lamp at the connection point A. In other words, in this operating situation, the discharge resistor R1 is substantially larger than the discharge resistor of the fluorescent lamp, so that the discharge of the half-bridge capacitor C1 caused by the discharge resistor R1 can be practically neglected. The high-frequency lamp current causes only a small voltage drop across the half-bridge capacitor C1.

Wird aber, die Leuchtstofflampe LL ausgehend vom Nennlichtstrom zu abnehmender Helligkeit hin bis zu dem Punkt gedimmt, bei dem die Entladung abzureißen droht, dann wird der Entladungswiderstand der Leuchtstofflampe LL derart groß, daß der Entladewiderstand R1 den Halbbrückenkondensator C1 teilweise entladen kann. Dadurch steigt das Potential am Verbindungspunkt A und die über den Spannungsteiler R2/R3 heruntergeteilte Hilfsregelgröße HMG am Abgriff dieses Spannungsteilers ebenfalls. Somit wirkt die Hilfsregelgröße HMG einem weiteren Absenken der Lampenleistung entgegen und verhindert über den Regler RR das unerwünschte Abreißen der Entladung. Die beschriebene Änderung der Hilfregelgröße HMG wirkt sich nennenswert erst in unmittelbarer Nähe der unteren Grenze des Helligkeitsregelbereichs der Leuchtstofflampe LL aus, weil erst in diesem Bereich der Entladungswiderstand der Leuchtstofflampe und damit auch das Potential am Verbindungspunkt A nennenswert ansteigen.However, if the fluorescent lamp LL is dimmed from the nominal luminous flux to decreasing brightness to the point at which the discharge threatens to tear off, then the discharge resistance of the fluorescent lamp LL becomes so great that the discharge resistor R1 can partially discharge the half-bridge capacitor C1. As a result, the potential at connection point A and the auxiliary control variable HMG divided down via voltage divider R2 / R3 at the tap of this voltage divider also increase. The auxiliary control variable HMG thus counteracts a further reduction in the lamp power and prevents the unwanted tearing off of the discharge via the controller RR. The described change in the auxiliary control variable HMG has a noticeable effect only in the immediate vicinity of the lower limit of the brightness control range of the fluorescent lamp LL, because only in this range does the discharge resistance of the fluorescent lamp and thus also the potential at the connection point A increase significantly.

Diese Art der Ableitung der Hilfsregelgröße HMG von der Größe des Entladungswiderstandes der Leuchtstofflampe LL durch eine Gleichspannungsmessung setzt voraus, daß in der Leuchtstofflampe keine an sich möglichen Gleichrichtereffekte auftreten.This type of derivation of the auxiliary control variable HMG from the size of the discharge resistance of the fluorescent lamp LL by means of a DC voltage measurement presupposes that no rectifier effects per se occur in the fluorescent lamp.

Ein solcher Gleichrichtereffekt kann beispielsweise dann auftreten, wenn starke Unterschiede in der Emissionsfähigkeit der Elektroden der Leuchtstofflampe LL vorhanden sind. Soll die Abhängigkeit der Gleichspannungsmessung und damit der Erzeugung der Hilfsregelgröße HMG von einem solchen Gleichrichtereffekt ausgeschlossen werden, dann kann die Hilfsregelgröße HMG auch von einer Wechselspannung abgeleitet werden. Ein entsprechendes Ausführungsbeispiel zeigt Fig. 2.Such a rectifier effect can occur, for example, if there are large differences in the emissivity of the electrodes of the fluorescent lamp LL. If the dependency of the DC voltage measurement and thus the generation of the auxiliary control variable HMG on such a rectifier effect is to be excluded, then the auxiliary control variable HMG can also be derived from an AC voltage. A corresponding exemplary embodiment is shown in FIG. 2.

Die Ableitung der Hilfsregelgröße HMG erfolgt dabei durch Überlagerung einer niederfrequenten Wechselspannung an der Leuchtstofflampe LL mit der hochfrequenten Brennwechselspannung. Hierzu wird die Leichtstofflampe LL über Koppelelemente KE1, beispielsweise in Form von Koppelwiderständen Rk, zusätzlich an die Netzwechselspannung Un angeschaltet. Der hierdurch an der Leuchtstofflampe LL auftretende niederfrequente Anteil der Brennwechselspannung wird dann über weitere Koppelelemente KE2, die den hochfrequenten Anteil der Brennwechselspannung und auch den Gleichanteil sperren, einem Gleichrichter GL zugeführt, dem zur Glättung des gleichgerichteten niederfrequenten Anteils der Brennwechselspannung ein Siebglied SG nachgeschaltet ist. Dem Ausgang des Siebglieds SG ist der aus Fig. 1 bereits bekannte Spannungsteiler R2/R3 parallel geschaltet, an dessen Abgriff die Hilfsregelgröße HMG ansteht. Die Koppelelemente KE2 bestehen aus der Reihenschaltung einer Siebdrossel Ls und eines Siebkondensators Cs.The auxiliary control variable HMG is derived by superimposing a low-frequency AC voltage on the fluorescent lamp LL with the high-frequency burning AC voltage. For this purpose, the light-bulb lamp LL is additionally connected to the AC line voltage Un via coupling elements KE1, for example in the form of coupling resistors Rk. The low-frequency component of the AC combustion voltage thus occurring on the fluorescent lamp LL is then fed via further coupling elements KE2, which block the high-frequency component of the AC combustion voltage and also the DC component, to a rectifier GL, which is followed by a filter element SG for smoothing the rectified, low-frequency component of the AC combustion voltage. The voltage divider R2 / R3, which is already known from FIG. 1, is connected in parallel to the output of the filter element SG, and the auxiliary control variable HMG is present at its tap. The coupling elements KE2 consist of the series connection of a filter choke Ls and a filter capacitor Cs.

Da die Wirksamkeit der Hilfsregelgröße HMG lediglich an der unteren Grenze des Helligkeitsregelbereichs der Leuchtstofflampe LL von Interesse ist, kann in den Verbindungsweg des Abgriffs des Spannungsteilers R2/R3 zum Summierer SR, wie das Fig. 3 zeigt, zusätzlich eine Schwelle, zum Beispiel in Form einer Zenerdiode D1, eingebaut werden. Erst wenn die Hilfsregelgröße HMG am Abgriff des Spannungsteilers R2/R3 bei einer Dimmstellung von beispielsweise ein oder zwei Prozent des Nennlichtstromes so groß geworden ist, daß die Zenerdiode niederohmig wird, setzt schlagartig die das Abreißen der Entladung verhindernde Zusatzregelung ein. Das Verhalten des Reglers im Helligkeitsregelbereich oberhalb dieser Schwelle wird dann, was mitunter erwünscht ist, von dieser Zusatzregelung nicht beeinflußt. Die Zenerdiode D1 ist im Schaltbild nach Fig. 3 eingetragen. Die Schaltung nach Fig. 3 stellt eine Weiterbildung der Schaltung nach Fig. 1 dar. Abgesehen von der Zenerdiode D1 im Verbindungsweg des Abgriffs des Spannungsteilers R2/R3 zum Summierer SR unterscheidet sich die Schaltung nach Fig. 3 von der Schaltung nach Fig. 1 durch eine Zusatzschaltung ZS. Über diese Zusatzschaltung ZS wird eine weitere Hilfsregelgröße HMG1 erzeugt, die der Hilfsregelgröße HMG gleichwirkend überlagert ist. Hierdurch wird die Regelgeschwindigkeit der zusätzlichen Regelung wesentlich erhöht.Since the effectiveness of the auxiliary control variable HMG is only of interest at the lower limit of the brightness control range of the fluorescent lamp LL, a threshold, for example in the form of an additional threshold, can be added to the connection path of the tap of the voltage divider R2 / R3 to the summer SR, as shown in FIG. 3 a Zener diode D1. Only when the auxiliary control variable HMG at the tap of the voltage divider R2 / R3 with a dimming position of, for example, one or two percent of the nominal luminous flux has become so large that the zener diode becomes low-resistance does the additional regulation prevent the discharge from breaking off. The behavior of the controller in The brightness control range above this threshold is then, which is sometimes desirable, not influenced by this additional control. The Zener diode D1 is entered in the circuit diagram of FIG. 3. The circuit according to FIG. 3 represents a further development of the circuit according to FIG. 1. Apart from the Zener diode D1 in the connection path of the tap of the voltage divider R2 / R3 to the summer SR, the circuit according to FIG. 3 differs from the circuit according to FIG. 1 an additional circuit ZS. A further auxiliary control variable HMG1 is generated via this additional circuit ZS, which is superimposed on the auxiliary control variable HMG with the same effect. As a result, the control speed of the additional control is significantly increased.

Die Änderung des Entladungswiderstandes bei einem Dimmvorgang der Leuchtstofflampe LL in Richtung abnehmender Helligkeit hat eine relativ langsame Änderung des Potentials am Verbindungspunkt A zur Folge, weil durch die Gesamtschaltung eine große Zeitkonstante von Halbbrückenkondensator C1 und Entladewiderstand R1 vorgegeben ist. Bei ungünstiger Dimensionierung können deshalb Regelschwingungen auftreten. Durch die Zusatzschaltung ZS läßt sich das dynamische Verhalten des Reglers jedoch wesentlich verbessern, weil dadurch der Einfluß dieser großen Zeitkonstante verringert werden kann. Bei stark verringerter Lampenleistung auf Werte unterhalb 10 % der Nennleistung nimmt die Brennwechselspannung der Leuchtstofflampe LL mit der Lampenleistung ab. Dies macht sich die Zusatzschaltung ZS zunutze, indem sie aus der Brennwechselspannung eine Gleichspannung erzeugt, die der Brennwechselspannung proportional ist und als weitere Hilfsregelgröße HMG1 der Hilfsregelgröße HMG im Sinne der gewünschten Regelung vorzeichenrichtig überlagert wird.The change in the discharge resistance during a dimming process of the fluorescent lamp LL in the direction of decreasing brightness results in a relatively slow change in the potential at the connection point A, because a large time constant of the half-bridge capacitor C1 and the discharge resistor R1 is predetermined by the overall circuit. If the dimensions are unfavorable, control vibrations can occur. However, the dynamic behavior of the controller can be significantly improved by the additional circuit ZS because the influence of this large time constant can be reduced. If the lamp power is greatly reduced to values below 10% of the nominal power, the alternating voltage of the fluorescent lamp LL decreases with the lamp power. The additional circuit ZS takes advantage of this by generating a DC voltage from the AC combustion voltage which is proportional to the AC combustion voltage and is superimposed on the auxiliary control variable HMG with the correct sign in the sense of the desired regulation as a further auxiliary control variable HMG1.

Eine bevorzugte Ausführungsform der Zusatzschaltung ZS nach Fig. 3 ist in Fig. 4 dargestellt. Sie besteht zwischen dem Verbindungspunkt B und dem negativen Pol der Zwischenkreisgleichspannung Uzw aus der Reihenschaltung des Kondensators C3 mit einem aus Widerständen R4 und R5 gebildeten Spannungsteiler R4/R5.A preferred embodiment of the additional circuit ZS according to FIG. 3 is shown in FIG. 4. It consists between the connection point B and the negative pole of the DC link voltage Uzw from the series connection of the capacitor C3 with a voltage divider R4 / R5 formed from resistors R4 and R5.

Der heruntergeteilte Anteil der Brennwechselspannung am Widerstand R5 wird nun über eine Diode D2 gleichgerichtet und die gleichgerichtete Brennwechselspannung der Parallelschaltung aus einem Kondensator C4 und einem Widerstand R6 zugeführt. Die Änderung der gleichgerichteten Brennwechselspannung wird am Kondensator C4 wirksam und über den Kondensator C5 dem Widerstand R3 des Spannungsteilers R2/R3 als die weitere Hilfsregelgröße HMG1 zugeführt.The divided portion of the AC combustion voltage across the resistor R5 is now rectified via a diode D2 and the rectified AC combustion voltage is fed to the parallel circuit comprising a capacitor C4 and a resistor R6. The change in the rectified AC combustion voltage takes effect on the capacitor C4 and is fed via the capacitor C5 to the resistor R3 of the voltage divider R2 / R3 as the further auxiliary control variable HMG1.

Claims (9)

  1. Electronic ballast having an inverter (WR) which is constructed in a switching bridge and to which there is connected on the output side at least one load circuit which has a lamp inductor (L1) and, situated in series therewith, a parallel circuit composed of a fluorescent lamp (LL) and an ignition capacitor (C2), and having a controlling system (SR, RR) which drives the inverter and, by means of a desired/actual value comparison and a system deviation (RAG) resulting therefrom permits both continuous operation with stabilized brightness and dicing of the fluorescent lamp as a function of an actual value (IW), which is derived from a measured instantaneous value of the lamp performance or the lamp current, as well as of a corresponding desired value (SW), which is referred to the lamp performance or the lamp current and is of adjustable level, characterized in that there is provided for the purpose of measuring the instantaneous discharge resistance of the fluorescent lamp an auxiliary measuring circuit (Uzw, R1, R2, R3 or Un, KE1, KE2, R2, R3) which derives from this discharge resistance, which increases with decreasing brightness of the fluorescent lamp, an auxiliary controlled variable (HMG) which is superimposed on the system deviation in the controlling system.
  2. Electronic ballast according to Claim 1, characterized in that in addition to a controller (RR), which drives the inverter (WR), the controlling system has a summer (SR) to which the desired value (SW), the actual value (IW) and the auxiliary controlled variable (HMG) are fed in the form of DC voltages and which, adding up these DC voltages correctly in terms of sign, forms as output voltage the superimposed system deviation (RAG) which is fed to the controller as controlled variable.
  3. Electronic ballast according to Claim 1 or 2, in which the inverter (WR) has two controlled switches (T1, T2) which are situated in series with one another and whose common tie point forms the inverter output and is connected via the lamp inductor (L1) to an electrode of the fluorescent lamp (LL), in which this series circuit composed of the controlled switches is connected to an intermediate circuit DC voltage (Uzw) which forms the power supply of the inverter and is derived from an AC supply voltage (Ch), and in which a terminal of this series circuit composed of the controlled switches is connected via a half-bridge capacitor (C1) to the second electrode of the fluorescent lamp (LL), characterized in that the auxiliary measuring circuit (Uzw, R1, R2, R3) comprises a discharge resistor (R1) connected in parallel to the half-bridge capacitor (C1) and a voltage divider (R2/R3) which is formed from two further resistors (R2 and R3, respectively) and which is connected, on the one hand, to the electrode of the fluorescent lamp that is connected to the half-bridge capacitor, and is thus assigned via this capacitor to one terminal (+) of the intermediate circuit voltage, and which is connected, on the other hand, directly to the other terminal (-) of the intermediate circuit voltage and which has a centre tap which forms the output of the auxiliary measuring circuit and is connected to the input of the controlling system (SR, RR).
  4. Electronic ballast according to Claim 3, characterized in that there is provided between the electrode of the fluorescent lamp (LL) that is connected via a common tie point (B) to the lamp inductor (L1) and the other terminal (-) of the intermediate circuit DC voltage (Uzw) an additional circuit (ZS) for forming a further auxiliary controlled variable (HMG1) which is derived in the form of a DC voltage from the AC operating voltage of the fluorescent lamp and fed at the centre tap of the voltage divider (R2/R3) to the auxiliary controlled variable (HMG) derived from the discharge resistance of the fluorescent lamp in such a way that it is superimposed on this auxiliary controlled variable derived from the discharge resistance of the fluorescent lamp and supports the voltage variation thereof in an amplifying manner in the lower range of dimming.
  5. Electronic ballast according to Claim 4, characterized in that the additional circuit (ZS) for measuring the AC operating voltage of the fluorescent lamp (LL) has a series circuit composed of a further capacitor (C3) as well as two further resistors (R4, R5) likewise forming a voltage divider, this series circuit being arranged between the tie point (B) of the lamp inductor (L1) having the assigned electrode of the fluorescent lamp and the other terminal (-) of the intermediate circuit DC voltage (Uzw), and in that there is arranged between a centre tap of this voltage divider (R4/R5) of the additional circuit and the other terminal (-) of the intermediate circuit DC voltage in a manner connected in parallel to the corresponding resistor (R5) of this voltage divider a π four-terminal network which has shunt elements composed of a parallel circuit of a further capacitor (C4) and a further resistor (R6) and has series elements formed from a series circuit of a diode (D2) connected to the centre tap of the voltage divider (R4/R5) and a further capacitor (C5), a component voltage tapped at the centre tap of the voltage divider of the additional circuit and proportional to the AC operating voltage of the fluorescent lamp being rectified and filtered by this π four--terminal network, which outputs it at the free terminal of the series element capacitor (C5) as the further auxiliary controlled variable (HMG1) derived from the AC operating voltage.
  6. Electronic ballast according to one of the preceding claims, characterized in that the value of the discharge resistor (R1) connected in parallel with the half-bridge capacitor (C1) is dimensioned in terms of its order of magnitude in accordance with that value of the discharge resistance of the fluorescent lamp (LL) which occurs at the lower limit of the range of dimming.
  7. Electronic ballast according to Claim 1 or 2, characterized in that for the purpose of deriving the auxiliary controlled variable (HMG) derived from the discharge resistance of the fluorescent lamp (LL), the auxiliary measuring circuit (Un, KE1, KE2) is supplied by a low-frequency AC voltage (Un), and comprises first coupling elements (KE1) for superimposing this low-frequency AC voltage with the high-frequency AC operating voltage of the fluorescent lamp and second coupling elements (KE2) for filtering out a corresponding low-frequency AC voltage signal, as well as a rectifier circuit (GL) for rectifying this filtered-out AC voltage signal, and the voltage divider (R2/R3) of the auxiliary measuring circuit, which outputs the auxiliary controlled variable at its centre tap, is connected to this rectifier circuit with its two resistors.
  8. Electronic ballast according to Claim 7, characterized in that use is made as the low-frequency AC voltage of the AC supply voltage (Un), which is fed to the electrodes of the fluorescent lamp (LL) directly via the first coupling elements (KE1), in that the second coupling elements (KE2), which block both the high-frequency component of the AC operating voltage and a DC voltage component, are connected to one of the electrodes of the fluorescent lamp, and in that a filter (SG) for smoothing the rectified low-frequency AC voltage signal is provided between the rectifier circuit (GL) and the voltage divider (R2/R3) of the auxiliary measuring circuit.
  9. Electronic ballast according to one of the preceding claims, characterized in that at its output the auxiliary measuring circuit (Uzw, R1, R2, R3 or Un, KE1, KE2, R2, R3) has a threshold element (D1) which blocks this output until the auxiliary controlled variable (HMG) derived from the discharge resistance of the fluorescent lamp (LL) overshoots a prescribed threshold value.
EP89118713A 1989-10-09 1989-10-09 Electronic ballast Expired - Lifetime EP0422255B1 (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
EP89118713A EP0422255B1 (en) 1989-10-09 1989-10-09 Electronic ballast
AT89118713T ATE102430T1 (en) 1989-10-09 1989-10-09 ELECTRONIC BALLAST.
ES89118713T ES2049790T3 (en) 1989-10-09 1989-10-09 ELECTRONIC ADAPTER.
DE89118713T DE58907133D1 (en) 1989-10-09 1989-10-09 Electronic ballast.
US07/592,125 US5066894A (en) 1989-10-09 1990-10-03 Electronic ballast
JP2269688A JPH07101638B2 (en) 1989-10-09 1990-10-09 Electronic auxiliary switching device with an inverter configured as a switch bridge
HK123395A HK123395A (en) 1989-10-09 1995-07-27 Electronic ballast

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP89118713A EP0422255B1 (en) 1989-10-09 1989-10-09 Electronic ballast

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EP0422255A1 EP0422255A1 (en) 1991-04-17
EP0422255B1 true EP0422255B1 (en) 1994-03-02

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EP89118713A Expired - Lifetime EP0422255B1 (en) 1989-10-09 1989-10-09 Electronic ballast

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US (1) US5066894A (en)
EP (1) EP0422255B1 (en)
JP (1) JPH07101638B2 (en)
AT (1) ATE102430T1 (en)
DE (1) DE58907133D1 (en)
ES (1) ES2049790T3 (en)
HK (1) HK123395A (en)

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DE102011082245B3 (en) * 2011-09-07 2013-01-17 Osram Ag Electronic ballast and method of operating a discharge lamp
DE102011082239B3 (en) * 2011-09-07 2013-01-17 Osram Ag Electronic ballast and method of operating a discharge lamp
US8878462B2 (en) 2010-07-12 2014-11-04 Osram Gesellschaft Mit Beschraenkter Haftung Circuit arrangement and method for operating at least one discharge lamp

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DE4340604A1 (en) * 1993-08-25 1995-03-02 Tridonic Bauelemente Ges Mbh Electronic ballast for supplying a load, for example a lamp
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US5066894A (en) 1991-11-19
EP0422255A1 (en) 1991-04-17
JPH03138896A (en) 1991-06-13
DE58907133D1 (en) 1994-04-07
JPH07101638B2 (en) 1995-11-01
ATE102430T1 (en) 1994-03-15
ES2049790T3 (en) 1994-05-01
HK123395A (en) 1995-08-04

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