EP0121917A1 - Electronic device for driving fluorescent lamps - Google Patents

Electronic device for driving fluorescent lamps Download PDF

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Publication number
EP0121917A1
EP0121917A1 EP84103849A EP84103849A EP0121917A1 EP 0121917 A1 EP0121917 A1 EP 0121917A1 EP 84103849 A EP84103849 A EP 84103849A EP 84103849 A EP84103849 A EP 84103849A EP 0121917 A1 EP0121917 A1 EP 0121917A1
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EP
European Patent Office
Prior art keywords
current
working
electronic
circuit
voltage
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.)
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Application number
EP84103849A
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German (de)
French (fr)
Inventor
Fred Dr. Ing. Hasemann
Ferdinand Dipl.-Ing. Mertens
Norbert Dipl.-Ing. Wittig
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Trilux GmbH and Co KG
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Trilux Lenze GmbH and Co KG
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Publication of EP0121917A1 publication Critical patent/EP0121917A1/en
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
    • H05B41/282—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
    • H05B41/2825—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 by means of a bridge converter in the final stage

Definitions

  • the invention relates to an electronic ballast for fluorescent lamps, with a push-pull switch arrangement connected to a DC voltage, consisting of two electronic switches connected in series, a working resonant circuit connected to the connection point of the electronic switches, at least one fluorescent lamp whose supply voltage is derived from the voltage drop of the inductance or the capacitance. and with a control circuit that switches the electronic switches depending on the current in the working circuit.
  • Electronic ballasts are known for the operation of fluorescent lamps (DE-OS 29 41 822), which a working resonant circuit from the series connection of a Have inductance and a capacitance.
  • the fluorescent lamp is connected in parallel to the capacitance of the series resonant circuit at which high voltages occur.
  • the working oscillating circuit is triggered by a push-pull switch arrangement comprising two transistors connected in series, which are controlled in opposite directions to one another depending on the current in the working oscillating circuit, so that one end of the working oscillating circuit is alternately connected to positive and negative potential.
  • the push-pull switch arrangement is controlled in such a way that the transistors are respectively opened in the correct half-wave of the oscillating current in order to support and excite the oscillation, but this activation takes place with a delay in which the oscillating current has already reached a considerable size.
  • the transistor that is controlled in the blocking state must switch off a current of considerable size.
  • switching losses are particularly important for heating a transistor or another electronic switch.
  • the transistors require extensive cooling plates because of the high switching losses. The life of these transistors is limited due to the strong heating.
  • the invention has for its object an electronic ballast of the aforementioned. To create a way in which the power loss is reduced.
  • control circuit is designed such that the switching of the electronic switches takes place in the vicinity of the zero crossings of the current of the working resonant circuit.
  • both electronic switches of the push-pull switch arrangement are practically de-energized at the time of the switchover, so that the switchover takes place with almost no power loss.
  • the electronic switches have almost no switch-on and switch-off losses and remain cold.
  • the current that flows through the respective conductive electronic switch does not cause much heat loss due to the low forward resistance.
  • transistors with relatively low power and without cooling devices can be used as electronic switches. This simplifies the electronic and mechanical components of the device. Due to the low load on the electronic switches, their lifespan is increased.
  • Switching the push-pull switch arrangement in the vicinity of the zero crossing of the oscillating current means at the same time that at the time of switching both at the Inductance and the capacitance of the working oscillating circuit each have the maximum voltage present.
  • the switchover therefore takes place at the point in time at which the voltage of the fluorescent lamp also assumes its maximum value. It has been found that the fluorescent lamp is ignited even at lower supply voltages if the switchover time is selected in the manner according to the invention. Fluorescent lamps can be ignited with a DC supply voltage of approx. 30 volts if the switchover takes place at the maximum voltage. With previous ballasts, a higher operating voltage is required for ignition. As a result of the low ignition voltage, the lamp can also be switched on in the more dimmed state.
  • ballast according to the invention can be used unchanged in connection with different types of fluorescent lamps.
  • Argon lamps have a different ignition and operating behavior than krypton lamps.
  • the ignition voltage is approximately 350 volts and the operating current consumption is approximately 350 mA.
  • the ignition voltage for krypton lamps is approximately 850 volts and the operating current consumption is approximately 450 mA.
  • the working circuit is damped more because of the lower resistance.
  • a ballast which is designed to supply a krypton lamp which has a power of 50 W if it is designed in the manner according to the invention, can also supply an argon lamp in unchanged form, but then a power of about 60 W. Through this additional The ballast is not overloaded in the case of an argon lamp.
  • the push-pull switch arrangement is preferably switched over in a phase angle range of ⁇ 10 °, based on the zero crossing of the current of the working resonant circuit, and in particular in a phase angle range of -5 °.
  • an inductive transformer is connected to the work resonant circuit, the primary winding connected in series, whose two oppositely excited Sekundärwicklun - gen each one of the electronic switches control so that the blocking of the previously conducting switch before the zero crossing of the current and the opening of the previously blocked switch takes place after the zero crossing of the current.
  • a switching interval is achieved, so that it is excluded that both electronic switches are in the conductive state at the same time.
  • the fact that the one transistor is blocked and the other transistor is turned on on both sides of the zero current crossing means that the current values during the switching operations are approximately the same and both are very small.
  • the electronic switches are field effect transistors of the same type and that each of the secondary windings is connected at one end to the source connection and at the other end to the control connection of the associated field effect transistor and that the secondary windings are wound or switched in phase opposition to one another. Since field effect transistors have an extremely high input resistance at the control connection, the secondary windings are not loaded by the field effect transistors, so that only a negligibly small current flows in them. The control voltage at each field effect transistor is thus in phase with the oscillating current, ie with the current in the primary winding of the transformer.
  • phase shifter networks which are connected between the secondary coils of the transformers and the control connections of the electronic switches.
  • An electronic ballast in which the switches are switched near the zero crossings has a very low power loss, while almost all of the input power is transferred to the lamp.
  • the lamp resistance must meet certain conditions so that the working circuit is capable of oscillating at all.
  • the capacitance or the inductance of the working oscillating circuit is the primary winding a transformer is connected in parallel, the secondary winding of which is connected to the electrodes of the fluorescent lamp.
  • L is the inductance of the working resonant circuit, C the capacitance, R the lamp resistance and f the resonant frequency of the resonant circuit
  • the condition must be met without using a transformer be fulfilled so that the vibration is maintained. This means that must be so that the pressure under the root does not become negative or zero.
  • the resonant circuit elements L and C can be determined with a predetermined resistance R and a predetermined mains alternating voltage as well as a predetermined lamp power. With a mains voltage of 220 volts and a nominal lamp output of 50 watts, this means that taking into account the mains voltage tolerances of - 10%, the lamp resistance R must be greater than 474 ohms.
  • the fluorescent lamps used in practice generally have a lower resistance during nominal operation.
  • the lamp resistance is transformed by the transformer to a value R ', which must be greater than 474 ohms.
  • the value R ' should not be greater than approx. 1000 ohms in order not to make the ignition of the lamp too difficult by the step-down voltage.
  • R ' is preferably in the range from 600 to 700 ohms and in particular in the vicinity of 700 ohms.
  • the supply circuit shown in Fig. 1 has a low-pass filter 10, the input terminals of which are connected to an AC voltage of e.g. 220 V and 50 Hz.
  • the low-pass filter 10 consists, in a known manner, of at least one choke 11 and one transverse capacitor 12.
  • a full-wave rectifier 13 is connected to the output of the low-pass filter, the output terminals of which are connected to a smoothing capacitor 14.
  • a DC voltage U arises at the smoothing capacitor 14 and is supplied to the circuit according to FIG. 2, FIG. 3 or FIG. 5 as an input voltage.
  • the voltage U is applied to the push-pull switch arrangement 15, 16, which consists of two series-connected transistors 15 and 16 of the same type - in the present case npn transistors.
  • the push-pull switch arrangement 15, 16 which consists of two series-connected transistors 15 and 16 of the same type - in the present case npn transistors.
  • the series circuit of the primary coil 18 of the Ubertragers 19 the inductance 20 and the K is apazi- ty 21 connected.
  • the inductance 20 forms, together with the capacitance 21, the working resonant circuit.
  • the fluorescent lamp 22 is connected in parallel with the capacitor 21. One end of the capacitor 21 and the fluorescent lamp 22 is connected via a capacitor 23 to the positive pole of the supply voltage U g .
  • Transistors 15 and 16 are switched in push-pull mode, ie if transistor 15 is conductive, transistor 16 is blocked and if transistor 16 is conductive transistor 15 is blocked. However, overlap the blocking phases of both transistors change slightly, as will be explained below.
  • Transistors 15 and 16 are controlled via two secondary windings 24, 25 of transformer 19. Secondary winding 24, which is inductively coupled to primary winding 18 via a ferrite core, is connected to a control circuit 26, the output of which is connected to the base of transistor 15 is.
  • the second secondary coil 25, which is also inductively coupled to the primary coil 18 of the transmitter 19 via a ferrite core, is connected to a control circuit 27, the output of which is connected to the base of the transistor 16.
  • the two secondary coils 24 and 25 are excited in opposite directions to one another by the primary coil 18, which is indicated by the points shown. For example, the secondary coils 24 and 25 are wound in opposite directions to one another.
  • the control circuits 26 and 27 control the transistors 15 and 16 so that the transistor 15 connecting the connection point 17 to the positive pole of the supply voltage U becomes conductive when the current in the primary coil 18 is at the beginning of the positive half-wave and is blocked when this current is at the end of the positive half wave.
  • the transistor 16, which connects the connection point 17 to the negative pole of the supply voltage U g becomes conductive when the current in the primary coil 18 is at the beginning of the negative half-wave and blocked when this current is at the end of this negative half-wave.
  • I the oscillating current which flows through the working oscillating circuit 21 and thus also through the primary winding 18 of the transformer 19. This oscillating current is almost sinusoidal.
  • the previously conductive transistor 15 Shortly before the zero crossing 28 from the positive to the negative half-wave, the previously conductive transistor 15 is blocked at time t 1 . A short time after the zero crossing 28 of the oscillating current I, the previously blocked transistor 16 becomes conductive at the time t 2 . Between the two times t 1 and t 2 , both transistors 15 and 16 are blocked.
  • the transistor 16 is blocked again at the time t 3 shortly before the positive zero crossing 29 and shortly after the positive zero crossing 29 the transistor 15 becomes conductive at the time t 4 .
  • FIG. 4 also shows the time profiles of the voltage U L at the inductor 20 and the voltage U c at the capacitor 21. These voltages are 90 ° out of phase with the current I and 180 ° out of phase with respect to each other. It can be seen that at the times of the zero crossings 28, 29 of the oscillating current I, the voltages U L and U c each assume their maximum value. Since the voltage U c is also present on the fluorescent lamp 22, the voltage on the fluorescent lamp has approximately the maximum value at the switching times t 1 to t 4 .
  • FIG. 3 differs from that of FIG. 2 only in that field-effect transistors 35, 36 are used as electronic switches, and in that the control switching devices 26 and 27 are omitted.
  • the field effect transistor 35 is connected with its source connection to the connection point 17 and with its drain connection to the positive pole of the supply voltage U g.
  • the field effect transistor 36 is connected with its source connection to the negative pole of the supply voltage U g and with its drain connection with the connection point 17.
  • One end of the secondary winding 24 is connected to the connection point 17 and the other end to the control connection of the field effect transistor 35.
  • One end of the secondary winding 25 is connected to the control connection of the field effect transistor 36 and the other end to the negative pole of the supply voltage U g .
  • FIG. 5 corresponds to that of FIG. 3, so that only the differences are explained below.
  • the fluorescent lamp 22 is not connected in parallel directly to the capacitance 21 of the working resonant circuit 20, 21, but rather via a transformer 39.
  • the primary winding of the transformer 39 is connected with its two ends to the electrodes of the capacitor 21, that is to say connected to the latter in parallel.
  • the electrodes of the fluorescent lamp 22, the heating circuits of which are not shown in the present case, are connected to the ends of the secondary winding 38 of the transformer 39.
  • the resistance of the fluorescent lamp 22 is according to the formula transformed to the primary side, where R is the lamp resistance, w1 the number of turns of the primary winding 37 and w 2 the number of turns of the secondary winding 38. The number of turns is such that the condition is satisfied.
  • L is the
  • the secondary winding 38 has an additional tap 40 which is used when connecting a krypton lamp.
  • the entire secondary winding 38 is used in the argon lamp.
  • the transformer 39 in FIG. 5 it is possible to evaluate the direct voltage generated from the mains voltage in full, i.e. without a voltage-reducing choke, and the entire available voltage by the push-pull switch arrangement 35, 36 which is switched in the zero current crossings becomes practically lossless and without phase gates in a DC voltage and at the same time achieve that the fluorescent lamp consumes exactly the intended nominal power.
  • the fluorescent lamp is therefore not overloaded and the energy losses of the ballast are reduced to the absolutely necessary level.

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Abstract

The electronic device for driving fluorescent lamps has a push-pull switch arrangement consisting of two electronic switches (35, 36) which are controlled by the current of an operating oscillator (20, 21) and connect this operating oscillator alternately to the positive and negative pole of a supply voltage (Ug). The control is carried out by a transformer (19) which has two secondary windings (24, 25). The secondary windings control the switches (35, 36) such that the switching processes take place near the point at which the current in the operating oscillator (20, 21) is passing through zero. This reduces the switch-on and switch-off losses of the electronic switches (35, 36). <IMAGE>

Description

Die Erfindung betrifft ein elektronisches Vorschaltgerät für Leuchtstofflampen, mit einer an einer Gleichspannung liegenden Gegentaktschalteranordnung aus zwei in Reihe geschalteten elektronischen Schaltern, einem an den Verbindungspunkt der elektronischen Schalter angeschlossenen Arbeitsschwingkreis, mindestens einer Leuchtstofflampe deren Versorungsspannung von dem Spannungsabfall der Induktivität oder der Kapazität abgeleitet wird, und mit einer Steuerschaltung, die die elekt-ronischen Schalter in Abhängigkeit von dem Strom im Arbeitsschwingkreis schaltet.The invention relates to an electronic ballast for fluorescent lamps, with a push-pull switch arrangement connected to a DC voltage, consisting of two electronic switches connected in series, a working resonant circuit connected to the connection point of the electronic switches, at least one fluorescent lamp whose supply voltage is derived from the voltage drop of the inductance or the capacitance. and with a control circuit that switches the electronic switches depending on the current in the working circuit.

Für den Betrieb von Leuchtstofflampen sind elektronische Vorschaltgeräte bekannt (DE-OS 29 41 822), die einen Arbeitsschwingkreis aus der Reihenschaltung einer Induktivität und einer Kapazität aufweisen. Die Leuchtstofflampe-wird der Kapazität des Reihenschwingkreises, an der hohe Spannungen auftreten, parallelgeschaltet. Das Anstoßen des Arbeitsschwingkreises erfolgt über eine Gegentaktschalteranordnung aus zwei in Reihe geschalteten Transistoren, die in Abhängigkeit von dem Strom im Arbeitsschwingkreis gegensinnig zueinander gesteuert werden, so daß das eine Ende des Arbeitsschwingkreises abwechselnd an positives und negatives Potential gelegt wird. Die Steuerung der Gegentaktschalteranordnung erfolgt so, daß die Transistoren zwar jeweils in der richtigen Halbwelle des Schwingstromes aufgesteuert werden, um die Schwingung zu unterstützen und anzuregen, daß jedoch diese Aufsteuerung mit einer Verzögerung erfolgt, in der der Schwingstrom schon eine beträchtliche Größe erreicht hat. Derjenige Transistor, der in den Sperrzustand gesteuert wird, muß einen Strom erheblicher Größe abschalten. Für die Erwärmung eines Transistors oder eines anderen elektronischen Schalters sind aber gerade die Schaltverluste bedeutend. Bei den bekannten elektronischen Vorschaltgeräten benötigen die Transistoren wegen der hohen Schaltverluste umfangreiche Kühlbleche. Infolge der starken Erwärmung ist die Lebensdauer dieser Transistoren begrenzt. Der Erfindung liegt die Aufgabe zugrunde, ein elektronisches Vorschaltgerät der eingangs genannten. Art zu schaffen, bei dem die Verlustleistung verringert ist.Electronic ballasts are known for the operation of fluorescent lamps (DE-OS 29 41 822), which a working resonant circuit from the series connection of a Have inductance and a capacitance. The fluorescent lamp is connected in parallel to the capacitance of the series resonant circuit at which high voltages occur. The working oscillating circuit is triggered by a push-pull switch arrangement comprising two transistors connected in series, which are controlled in opposite directions to one another depending on the current in the working oscillating circuit, so that one end of the working oscillating circuit is alternately connected to positive and negative potential. The push-pull switch arrangement is controlled in such a way that the transistors are respectively opened in the correct half-wave of the oscillating current in order to support and excite the oscillation, but this activation takes place with a delay in which the oscillating current has already reached a considerable size. The transistor that is controlled in the blocking state must switch off a current of considerable size. However, switching losses are particularly important for heating a transistor or another electronic switch. In the known electronic ballasts, the transistors require extensive cooling plates because of the high switching losses. The life of these transistors is limited due to the strong heating. The invention has for its object an electronic ballast of the aforementioned. To create a way in which the power loss is reduced.

Die Lösung dieser Aufgabe besteht erfindungsgemäß darin, daß die Steuerschaltung derart ausgebildet ist, daß die Umschaltung der elektronischen Schalter in der Nähe der Nulldurchgänge des Stromes des Arbeitsschwingkreises erfolgt.The solution to this problem is, according to the invention, that the control circuit is designed such that the switching of the electronic switches takes place in the vicinity of the zero crossings of the current of the working resonant circuit.

Da die Umschaltung dann durchgeführt wird, wenn der Schwingstrom einen sehr niedrigen Wert hat bzw. Null ist, sind zum Zeitpunkt der Umschaltung beide elektronischen Schalter der Gegentaktschalteranordnung praktisch stromlos, so daß die Umschaltung nahezu ohne Verlustleistung erfolgt. Dies hat zur Folge, daß die elektronischen Schalter nahezu keine Einschalt- und Ausschaltverluste haben und kalt bleiben. Der Strom, der den jeweils leitenden elektronischen Schalter durchfließt, verursacht infolge des geringen Durchlaßwiderstandes keine große Verlustwärme.Since the switchover is carried out when the oscillating current has a very low value or is zero, both electronic switches of the push-pull switch arrangement are practically de-energized at the time of the switchover, so that the switchover takes place with almost no power loss. As a result, the electronic switches have almost no switch-on and switch-off losses and remain cold. The current that flows through the respective conductive electronic switch does not cause much heat loss due to the low forward resistance.

Bei dem erfindungsgemäßen elektronischen Vorschaltgerät können als elektronische Schalter Transistoren mit relativ kleiner Leistung und ohne Kühleinrichtungen benutzt werden. Hierdurch werden die elektronischen und die mechanischen Komponenten des Gerätes vereinfacht. Infolge der geringen Belastung der elektronischen Schalter wird deren Lebensdauer erhöht.In the electronic ballast according to the invention, transistors with relatively low power and without cooling devices can be used as electronic switches. This simplifies the electronic and mechanical components of the device. Due to the low load on the electronic switches, their lifespan is increased.

Das Umschalten der Gegentaktschalteranordnung in der Nähe des Nulldurchgangs des Schwingstromes bedeutet gleichzeitig, daß im Schaltzeitpunkt sowohl an der Induktivität als auch an der Kapazität des Arbeitsschwingkreises jeweils die maximale Spannung ansteht. Die Umschaltung erfolgt also zu dem Zeitpunkt, an dem auch die Spannung der Leuchtstofflampe ihren Maximalwert einnimmt. Es hat sich herausgestellt, daß das Zünden der Leuchtstofflampe bereits bei niedrigeren Versorgungsspannungen erfolgt, wenn der Umschaltzeitpunkt in der erfindungsgemäßen Weise gewählt wird. Leuchtstofflampen lassen sich bereits mit einer Versorgungsgleichspannung von ca. 30 Volt zünden, wenn die Umschaltung im Spannungsmaximum erfolgt. Bei den bisherigen Vorschaltgeräten ist zum Zünden eine höhere Betriebsspannung erforderlich. Infolge der niedrigen Zündspannung kann man die Lampe auch im stärker gedimmten Zustand einschalten.Switching the push-pull switch arrangement in the vicinity of the zero crossing of the oscillating current means at the same time that at the time of switching both at the Inductance and the capacitance of the working oscillating circuit each have the maximum voltage present. The switchover therefore takes place at the point in time at which the voltage of the fluorescent lamp also assumes its maximum value. It has been found that the fluorescent lamp is ignited even at lower supply voltages if the switchover time is selected in the manner according to the invention. Fluorescent lamps can be ignited with a DC supply voltage of approx. 30 volts if the switchover takes place at the maximum voltage. With previous ballasts, a higher operating voltage is required for ignition. As a result of the low ignition voltage, the lamp can also be switched on in the more dimmed state.

Ein weiterer Vorteil des erfindungsgemäßen Vorschaltgerätes besteht darin, daß es unverändert in Verbindung mit verschiedenartigen Leuchtstofflampen benutzt werden kann. Argon-Lampen haben ein anderes Zünd- und Betriebsverhalten als Krypton-Lampen. Bei Argon-Lampen beträgt die Zündspannung ca. 350 Volt und die Betriebsstromaufnahme ca. 350 mA. Dagegen beträgt bei Krypton-Lampen die Zündspannung ca. 850 Volt und die Betriebsstromaufnahme ca. 450 mA. Bei einer Krypton-Lampe wird der Arbeitsschwingkreis wegen des geringeren Widerstandes stärker bedämpft. Ein Vorschaltgerät, das dazu ausgelegt ist, eine Krypton-Lampe, die eine Leistung von 50 W hat, zu versorgen, kann, wenn es in der erfindungsgemäßen Weise ausgebildet ist, in unveränderter Form auch eine Argon-Lampe versorgen, die dann jedoch eine Leistung von ca. 60 W aufnimmt. Durch diesen zusätzlichen Leistungsbedarf im Falle einer Argon-Lampe wird das Vorschaltgerät nicht überlastet.Another advantage of the ballast according to the invention is that it can be used unchanged in connection with different types of fluorescent lamps. Argon lamps have a different ignition and operating behavior than krypton lamps. With argon lamps, the ignition voltage is approximately 350 volts and the operating current consumption is approximately 350 mA. In contrast, the ignition voltage for krypton lamps is approximately 850 volts and the operating current consumption is approximately 450 mA. With a Krypton lamp, the working circuit is damped more because of the lower resistance. A ballast which is designed to supply a krypton lamp which has a power of 50 W, if it is designed in the manner according to the invention, can also supply an argon lamp in unchanged form, but then a power of about 60 W. Through this additional The ballast is not overloaded in the case of an argon lamp.

Vorzugsweise erfolgt die Umschaltung der Gegentaktschalteranordnung in einem Phasenwinkelbereich von ± 10°, bezogen auf den Nulldurchgang des Stromes des Arbeitsschwingkreises, und insbesondere in einem Phasenwinkelbereich von - 5°.The push-pull switch arrangement is preferably switched over in a phase angle range of ± 10 °, based on the zero crossing of the current of the working resonant circuit, and in particular in a phase angle range of -5 °.

Gemäß einer bevorzugten Weiterbildung der Erfindung ist vorgesehen, daß mit dem Arbeitsschwingkreis die primärwicklung eines induktiven Übertragers in Reihe geschaltet ist, dessen beide gegensinnig erregten Sekundärwicklun- gen je einen der elektronischen Schalter derart steuern, daß die Sperrung des zuvor leitenden Schalters vor dem Nulldurchgang des Stromes und das Aufsteuern des zuvor gesperrten Schalters nach dem Nulldurchgang des Stromes erfolgt. Auf diese Weise wird ein zeitlicher Schaltabstand erzielt, so daß ausgeschlossen ist, daß beide elektronische Schalter gleichzeitig im leitenden Zustand sind. Dadurch, daß das Sperren des einen und das Aufsteuern des anderen Transistors zu beiden Seiten des Stromnulldurchganges erfolgen, wird erreicht, daß die Stromwerte bei den Schaltvorgängen einander etwa gleich und beide sehr klein sind.According to a preferred development of the invention it is provided that an inductive transformer is connected to the work resonant circuit, the primary winding connected in series, whose two oppositely excited Sekundärwicklun - gen each one of the electronic switches control so that the blocking of the previously conducting switch before the zero crossing of the current and the opening of the previously blocked switch takes place after the zero crossing of the current. In this way, a switching interval is achieved, so that it is excluded that both electronic switches are in the conductive state at the same time. The fact that the one transistor is blocked and the other transistor is turned on on both sides of the zero current crossing means that the current values during the switching operations are approximately the same and both are very small.

Bei einer bevorzugten Ausführungsform der Erfindung ist vorgesehen, daß die elektronischen Schalter Feldeffekttransistoren gleichen Typs sind, und daß jede der Sekundärwicklungen mit einem Ende an den Source-Anschluß und mit dem anderen Ende an den Steueranschluß des zugehörigen Feldeffekttransistors angeschlossen ist und daß die Sekundärwicklungen gegenphasig zueinander gewickelt bzw. geschaltet sind. Da Feldeffekttransistoren einen extrem hohen Eingangswiderstand am Steueranschluß haben, werden die Sekundärwicklungen durch die Feldeffekttransistoren nicht belastet, so daß in ihnen nur ein verschwindend kleiner Strom fließt. Die Steuerspannung an jedem Feldeffekttransistor ist somit phasengleich mit dem Schwingstrom, d.h. mit dem Strom in der Primärwicklung des Übertragers.In a preferred embodiment of the invention it is provided that the electronic switches are field effect transistors of the same type and that each of the secondary windings is connected at one end to the source connection and at the other end to the control connection of the associated field effect transistor and that the secondary windings are wound or switched in phase opposition to one another. Since field effect transistors have an extremely high input resistance at the control connection, the secondary windings are not loaded by the field effect transistors, so that only a negligibly small current flows in them. The control voltage at each field effect transistor is thus in phase with the oscillating current, ie with the current in the primary winding of the transformer.

Alternativ ist es auch möglich, die Umschaltung nahe dem Nulldurchgang durch Phasenschiebernetzwerke zu erreichen, die zwischen die Sekundärspulen der Übertrager und die Steueranschlüsse der elektronischen Schalter geschaltet sind.Alternatively, it is also possible to achieve the switchover near the zero crossing through phase shifter networks which are connected between the secondary coils of the transformers and the control connections of the electronic switches.

Ein elektronisches Vorschaltgerät, bei dem die Schalter in der Nähe der Nulldurchgänge umgeschaltet werden, hat eine sehr geringe Verlustleistung, während nahezu die gesamte Eingangsleistung auf die Lampe übertragen wird. Dies führt dazu, daß eine Lampe, die für übliche verlustbehaftete Vorschaltgeräte ausgelegt ist,bzw. eine Lampe, die auch mit einer die Betriebsspannung verringernden Vorschaltdrossel betrieben werden kann, eine zu hohe Spannung erhält und damit auch eine zu hohe Leistung aufnimmt, wenn sie mit einem Vorschaltgerät betrieben wird, dessen Transistoren im Nullzustand geschaltet werden.An electronic ballast in which the switches are switched near the zero crossings has a very low power loss, while almost all of the input power is transferred to the lamp. This means that a lamp that is designed for conventional lossy ballasts, or. a lamp that can also be operated with a ballast choke that reduces the operating voltage, receives a voltage that is too high and thus also consumes too much power when it is operated with a ballast whose transistors are switched in the zero state.

Andererseits muß der Lampenwiderstand bestimmte Bedingungen erfüllen, damit der Arbeitsschwingkreis überhaupt schwingfähig ist. Um den Lampenwiderstand so an das Vorschaltgerät, dessen Transistoren im Nulldurchgang schalten, anzupassen, daß die Lampe die vorgegebene Leistungsaufnahme hat und daß außerdem die Schwingbedingung erfüllt ist, ist gemäß einer bevorzugten Weiterbildung der Erfindung vorgesehen, daß der Kapazität oder der Induktivität des Arbeitsschwingkreises die Primärwicklung eines Transformators parallelgeschaltet ist, dessen Sekundärwicklung an die Elektroden der Leuchtstofflampe angeschlossen ist.On the other hand, the lamp resistance must meet certain conditions so that the working circuit is capable of oscillating at all. In order to adapt the lamp resistance to the ballast whose transistors switch at zero crossing so that the lamp has the specified power consumption and that the oscillation condition is also met, it is provided according to a preferred development of the invention that the capacitance or the inductance of the working oscillating circuit is the primary winding a transformer is connected in parallel, the secondary winding of which is connected to the electrodes of the fluorescent lamp.

Wenn L die Induktivität des Arbeitsschwingkreises, C die Kapazität, R der Lampenwiderstand und f die Resonanzfrequenz des Schwingkreises ist, so muß ohne Verwendung eines Transformators die Bedingung

Figure imgb0001
erfüllt sein, damit die Schwingung aufrechterhalten bleibt. Dies bedeutet, daß
Figure imgb0002
sein muß, damit der Andruck unter der Wurzel nicht negativ bzw., null wird. Bei vorgegebenem Widerstand R und vorgegebener Netzwechselspannung sowie vorgegebener Lampenleistung lassen sich die Schwingkreiselemente L und C bestimmen. Bei einer Netzspannung von 220 Volt und einer Nennleistung der Lampe von 50 Watt bedeutet dies, daß unter Berücksichtigung der Netzspannungstoleranzen von - 10% der Lampenwiderstand R größer sein muß als 474 Ohm. Die in der Praxis verwendeten Leuchtstofflampen haben in der Regel einen niedrigeren Widerstand bei Nennbetrieb.If L is the inductance of the working resonant circuit, C the capacitance, R the lamp resistance and f the resonant frequency of the resonant circuit, the condition must be met without using a transformer
Figure imgb0001
 be fulfilled so that the vibration is maintained. This means that
Figure imgb0002
 must be so that the pressure under the root does not become negative or zero. The resonant circuit elements L and C can be determined with a predetermined resistance R and a predetermined mains alternating voltage as well as a predetermined lamp power. With a mains voltage of 220 volts and a nominal lamp output of 50 watts, this means that taking into account the mains voltage tolerances of - 10%, the lamp resistance R must be greater than 474 ohms. The fluorescent lamps used in practice generally have a lower resistance during nominal operation.

Zur Anpassung des Lampenwiderstandes an den Schwingkreis bzw. das Vorschaltgerät, wird der Lampenwiderstand von dem Transformator auf einen Wert R' transformiert, der größer sein muß als 474 Ohm. Andererseits sollte der Wert R' nicht größer sein als ca. 1000 Ohm, um die Zündung der Lampe nicht durch die heruntertransformierte Spannung zu stark zu erschweren.To adapt the lamp resistance to the resonant circuit or the ballast, the lamp resistance is transformed by the transformer to a value R ', which must be greater than 474 ohms. On the other hand, the value R 'should not be greater than approx. 1000 ohms in order not to make the ignition of the lamp too difficult by the step-down voltage.

Vorzugsweise liegt der Wert von R' im Bereich von 600 bis 700 Ohm und insbesondere in der Nähe von 700 Ohm.The value of R 'is preferably in the range from 600 to 700 ohms and in particular in the vicinity of 700 ohms.

Im folgenden werden unter Bezugnahme auf die Zeichnungen zwei Ausführungsbeispiele der Erfindung näher erläutert.Two exemplary embodiments of the invention are explained in more detail below with reference to the drawings.

Es zeigen:

  • Fig. 1 eine Ausführungsform des Versorgungsteils des elektronischen Vorschaltgerätes,
  • Fig. 2 ein erstes Ausführungsbeispiel der Steuerschaltung für den Arbeitsschwingkreis,
  • Fig. 3 ein zweites Ausführungsbeispiel der Steuerschaltung für den Arbeitsschwingkreis,
  • Fig. 4 eine graphische Darstellung der Strom- und Spannungsverläufe im Arbeitsschwingkreis, und
  • Fig. 5 ein Ausführungsbeispiel mit einem Transformator zur Transformation des Lampenwiderstandes .
Show it:
  • 1 shows an embodiment of the supply part of the electronic ballast,
  • 2 shows a first exemplary embodiment of the control circuit for the working resonant circuit,
  • 3 shows a second exemplary embodiment of the control circuit for the working resonant circuit,
  • Fig. 4 is a graphical representation of the current and voltage profiles in the working circuit, and
  • Fig. 5 shows an embodiment with a transformer for transforming the lamp resistance.

Die in Fig. 1 dargestellte.Versorgungsschaltung weist ein Tiefpassfilter 10 auf, dessen Eingangsklemmen an eine Wechselspannung von z.B. 220 V und 50 Hz gelegt werden. Das Tiefpassfilter 10 besteht in bekannter Weise aus mindestens einer Drossel 11 und einem Querkondensator 12. An den Ausgang des Tiefpassfilters ist ein Doppelweggleichrichter 13 angeschlossen, dessen Ausgangsklemmen mit einem Glättungskondensator 14 verbunden sind. Am Glättungskondensator 14 entsteht eine Gleichspannung U , die der Schaltung nach Fig. 2, Fig. 3 oder nach Fig. 5 als Eingangsspannung zugeführt wird.The supply circuit shown in Fig. 1 has a low-pass filter 10, the input terminals of which are connected to an AC voltage of e.g. 220 V and 50 Hz. The low-pass filter 10 consists, in a known manner, of at least one choke 11 and one transverse capacitor 12. A full-wave rectifier 13 is connected to the output of the low-pass filter, the output terminals of which are connected to a smoothing capacitor 14. A DC voltage U arises at the smoothing capacitor 14 and is supplied to the circuit according to FIG. 2, FIG. 3 or FIG. 5 as an input voltage.

Gemäß Fig. 2 wird die Spannung U an die Gegentaktschalteranordnung 15, 16 gelegt, die aus zwei in Reihe geschalteten Transistoren 15 und 16 von gleichem Typ - im vorliegenden Fall npn-Transistoren - besteht. An den Verbindungspunkt 17 der beiden Transistoren 15 und 16 ist die Reihenschaltung aus der Primärspule 18 des Ubertragers 19, der Induktivität 20 und der Kapazi- tät 21 angeschlossen. Die Induktivität 20 bildet zusammen mit der Kapazität 21 den Arbeitsschwingkreis.2, the voltage U is applied to the push-pull switch arrangement 15, 16, which consists of two series-connected transistors 15 and 16 of the same type - in the present case npn transistors. To the junction 17 of the two transistors 15 and 16, the series circuit of the primary coil 18 of the Ubertragers 19, the inductance 20 and the K is apazi- ty 21 connected. The inductance 20 forms, together with the capacitance 21, the working resonant circuit.

Der Kapazität 21 ist die Leuchtstofflampe 22 parallelgeschaltet. Ein Ende der Kapazität 21 und der Leuchtstofflampe 22 ist über einen Kondensator 23 mit dem positiven Pol der Versorgungsspannung Ug verbunden.The fluorescent lamp 22 is connected in parallel with the capacitor 21. One end of the capacitor 21 and the fluorescent lamp 22 is connected via a capacitor 23 to the positive pole of the supply voltage U g .

Die Transistoren 15 und 16 werden im Gegentakt geschaltet, d.h. wenn Transistor 15 leitend ist, ist Transistor 16 gesperrt und wenn Transistor 16 leitend ist ist Transistor 15 gesperrt. Allerdings überschneiden sich die Sperrphasen beider Transistoren geringfügig, wie nachfolgend noch erläutert wird. Die Steuerung der Transistoren 15 und 16 erfolgt über zwei Sekundärwicklungen 24, 25 des Übertragers 19. Die Sekundärwicklung 24, die mit der Primärwicklung 18 über einen Ferritkern induktiv gekoppelt ist, ist an eine Steuerschaltung 26 angeschlossen, deren Ausgang mit der Basis des Transistors 15 verbunden ist. Die zweite Sekundärspule 25, die ebenfalls über einen Ferritkern induktiv mit der Primärspule 18 des Ubertragers 19 gekoppelt ist, ist mit einer Steuerschaltung 27 verbunden, deren Ausgang mit der Basis des Transistors 16 verbunden ist. Die beiden Sekundärspulen 24 und 25 werden von der Primärspule 18 gegensinnig zueinander erregt, was durch die eingezeichneten Punkte angedeutet ist. Beispielsweise sind die Sekundärspulen 24 und 25 zueinander gegensinnig gewickelt.The transistors 15 and 16 are switched in push-pull mode, ie if transistor 15 is conductive, transistor 16 is blocked and if transistor 16 is conductive transistor 15 is blocked. However, overlap the blocking phases of both transistors change slightly, as will be explained below. Transistors 15 and 16 are controlled via two secondary windings 24, 25 of transformer 19. Secondary winding 24, which is inductively coupled to primary winding 18 via a ferrite core, is connected to a control circuit 26, the output of which is connected to the base of transistor 15 is. The second secondary coil 25, which is also inductively coupled to the primary coil 18 of the transmitter 19 via a ferrite core, is connected to a control circuit 27, the output of which is connected to the base of the transistor 16. The two secondary coils 24 and 25 are excited in opposite directions to one another by the primary coil 18, which is indicated by the points shown. For example, the secondary coils 24 and 25 are wound in opposite directions to one another.

Die Steuerschaltungen 26 und 27 steuern die Transistoren 15 bzw. 16 so an,daß der den Verbindungspunkt 17 mit dem positiven Pol der Versorgungsspannung U verbindende Transistor 15 leitend wird, wenn der Strom in der Primärspule 18 sich am Anfang der positiven Halbwelle befindet und gesperrt wird, wenn dieser Strom sich am Ende der positiven Halbwelle befindet. Dagegen wird der Transistor 16, der den Verbindungspunkt 17 mit dem negativen Pol der Versorgungsspannung Ug verbindet, leitend, wenn der Strom in der Primärspule 18 sich am Anfang der negativen Halbwelle befindet und gesperrt, wenn dieser Strom sich am Ende dieser negativen Halbwelle befindet. Dies ist in Fig. 4 dargestellt. Hier ist der Schwingstrom, der durch den Arbeitsschwingkreis 21 und somit auch durch die Primärwicklung 18 des Übertragers 19 fließt, mit I bezeichnet. Dieser Schwingstrom ist nahezu sinusförmig. Kurz vor dem Nulldurchgang 28 von der positiven zur negativen Halbwelle, wird der zuvor leitende Transistor 15 zum Zeitpunkt t1 gesperrt. Kurze Zeit nach dem Nulldurchgang 28 des Schwingstromes I wird zum Zeitpunkt t2 der zuvor gesperrte Transistor 16 leitend. Zwischen den beiden Zeitpunkten t1 und t2 sind beide Transistoren 15 und 16 gesperrt.The control circuits 26 and 27 control the transistors 15 and 16 so that the transistor 15 connecting the connection point 17 to the positive pole of the supply voltage U becomes conductive when the current in the primary coil 18 is at the beginning of the positive half-wave and is blocked when this current is at the end of the positive half wave. In contrast, the transistor 16, which connects the connection point 17 to the negative pole of the supply voltage U g , becomes conductive when the current in the primary coil 18 is at the beginning of the negative half-wave and blocked when this current is at the end of this negative half-wave. This is shown in FIG. 4. Here the oscillating current which flows through the working oscillating circuit 21 and thus also through the primary winding 18 of the transformer 19 is denoted by I. This oscillating current is almost sinusoidal. Shortly before the zero crossing 28 from the positive to the negative half-wave, the previously conductive transistor 15 is blocked at time t 1 . A short time after the zero crossing 28 of the oscillating current I, the previously blocked transistor 16 becomes conductive at the time t 2 . Between the two times t 1 and t 2 , both transistors 15 and 16 are blocked.

Am Ende der negativen Halbwelle wird zum Zeitpunkt t3 kurz vor dem positiven Nulldurchgang 29 der Transistor 16 wieder gesperrt und kurz nach dem positiven Nulldurchgang 29 wird zum Zeitpunkt t4 der Transistor 15 leitend.At the end of the negative half-wave, the transistor 16 is blocked again at the time t 3 shortly before the positive zero crossing 29 and shortly after the positive zero crossing 29 the transistor 15 becomes conductive at the time t 4 .

In Fig. 4 sind außerdem die zeitlichen Verläufe der Spannung UL an der Induktivität 20 und der Spannung Uc an der Kapazität 21 dargestellt. Diese Spannungen sind gegenüber dem Strom I um 90° phasenverschoben und relativ zueinander um 180° phasenverschoben. Man erkennt, daß zu den Zeitpunkten der Nulldurchgänge 28, 29 des Schwingstromes I die Spannungen UL und Uc jeweils ihren Maximalwert einnehmen. Da die Spannung Uc auch an der Leuchtstofflampe 22 ansteht, hat die Spannung an der Leuchtstofflampe zu den Schaltzeitpunkten t1 bis t4 jeweils annähernd den Maximalwert.4 also shows the time profiles of the voltage U L at the inductor 20 and the voltage U c at the capacitor 21. These voltages are 90 ° out of phase with the current I and 180 ° out of phase with respect to each other. It can be seen that at the times of the zero crossings 28, 29 of the oscillating current I, the voltages U L and U c each assume their maximum value. Since the voltage U c is also present on the fluorescent lamp 22, the voltage on the fluorescent lamp has approximately the maximum value at the switching times t 1 to t 4 .

Das Ausführungsbeispiel von Fig. 3 unterscheidet sich von demjenigen der Fig. 2 nur dadurch, daß als elektronische Schalter Feldeffekttransistoren 35, 36 verwendet werden, und daß die Steuerschalturigen 26 und 27 entfallen. Der Feldeffekttransistor 35 ist mit seinem Source-Anschluß an den Verbindungspunkt 17 und mit seinem Drain-Anschluß mit dem positiven Pol der Versorgungsspannung U g verbunden. Der Feldeffekttransistor 36 ist mit seinem Source-Anschluß an den negativen Pol der Versorgungsspannung Ug und mit seinem Drain-Anschluß mit dem Verbindungspunkt 17 verbunden. Das eine Ende der Sekundärwicklung 24 ist mit dem Verbindungspunkt 17 verbunden und das andere Ende mit dem Steueranschluß des Feldeffekttransistors 35. Das eine Ende der Sekundärwicklung 25 ist mit dem Steueranschluß des Feldeffekttransistors 36 und das andere Ende mit dem negativen Pol der Versorgungsspannung Ug verbunden. Infolge der hohen Eingangswiderstände an den Steueranschlüssen der Feldeffekttransistoren werden die Sekundärwicklungen 24 und 25 praktisch nicht belastet, so daß die an ihnen anstehenden Spannungen gleichphasig mit dem Schwingstrom I sind. In Verbindung mit dem Schaltverhalten der Feldeffekttransistoren entstehen die in Fig. 4 dargestellten und oben erläuterten Schaltvorgänge zu den Zeiten t1 bis t4 jeweils in der Nähe eines Nulldurchgangs 28 bzw. 29 des Schwingstromes I.The embodiment of FIG. 3 differs from that of FIG. 2 only in that field-effect transistors 35, 36 are used as electronic switches, and in that the control switching devices 26 and 27 are omitted. The field effect transistor 35 is connected with its source connection to the connection point 17 and with its drain connection to the positive pole of the supply voltage U g. The field effect transistor 36 is connected with its source connection to the negative pole of the supply voltage U g and with its drain connection with the connection point 17. One end of the secondary winding 24 is connected to the connection point 17 and the other end to the control connection of the field effect transistor 35. One end of the secondary winding 25 is connected to the control connection of the field effect transistor 36 and the other end to the negative pole of the supply voltage U g . Due to the high input resistances at the control connections of the field effect transistors, the secondary windings 24 and 25 are practically not loaded, so that the voltages applied to them are in phase with the oscillating current I. In connection with the switching behavior of the field effect transistors, the switching processes shown in FIG. 4 and explained above occur at times t 1 to t 4 in the vicinity of a zero crossing 28 and 29 of the oscillating current I.

Das Ausführungsbeispiel der Fig. 5 entsprechend demjenigen der Fig. 3, so daß nachfolgend nur die Unterschiede erläutert werden. Gemäß Fig. 5 ist die Leuchtstofflampe 22 nicht direkt der Kapazität 21 des Arbeitsschwingkreises 20, 21 parallelgeschaltet, sondern über einen Transformator 39. Die Primärwicklung des Transformators 39 ist mit ihren beiden Enden an die Elektroden des Kondensators 21 angeschlossen, diesem also parallelgeschaltet. An die Enden der Sekundärwicklung 38 des Transformators 39 sind die Elektroden der Leuchtstofflampe 22 angeschlossen,deren Heizstromkreise im vorliegenden Fall nicht dargestellt sind. Durch den Transformator 39 wird der Widerstand der Leuchtstofflampe 22 nach der Formel

Figure imgb0003
auf die Primärseite transformiert, wobei R der Lampenwiderstand, w1 die Windungszahl der Primärwicklung37 und w2 die Windungszahl der Sekundärwicklung 38 ist. Die Windungszahlen sind so bemessen, daß die Bedingung
Figure imgb0004
erfüllt ist. Hierbei ist L dieThe embodiment of FIG. 5 corresponds to that of FIG. 3, so that only the differences are explained below. 5, the fluorescent lamp 22 is not connected in parallel directly to the capacitance 21 of the working resonant circuit 20, 21, but rather via a transformer 39. The primary winding of the transformer 39 is connected with its two ends to the electrodes of the capacitor 21, that is to say connected to the latter in parallel. The electrodes of the fluorescent lamp 22, the heating circuits of which are not shown in the present case, are connected to the ends of the secondary winding 38 of the transformer 39. Through the transformer 39, the resistance of the fluorescent lamp 22 is according to the formula
Figure imgb0003
 transformed to the primary side, where R is the lamp resistance, w1 the number of turns of the primary winding 37 and w 2 the number of turns of the secondary winding 38. The number of turns is such that the condition
Figure imgb0004
 is satisfied. Here L is the

Induktivität und C die Kapazität des Arbeitsschwingkreises 20, 21.Inductance and C the capacitance of the working circuit 20, 21.

Da Argon-Lampen einen größeren Widerstand R haben als Krypton-Lampen, weist die Sekundärwicklung 38 einen zusätzlichen Abgriff 40 auf, der beim Anschluß einer Krypton-Lampe benutzt wird. Beim Anschluß einerSince argon lamps have a greater resistance R than krypton lamps, the secondary winding 38 has an additional tap 40 which is used when connecting a krypton lamp. When connecting one

Argon-Lampe wird dagegen die gesamte Sekundärwicklung 38 benutzt.In contrast, the entire secondary winding 38 is used in the argon lamp.

Durch den Transformator 39 in Fig. 5 ist es möglich, die aus der Netzspannung erzeugte Gleichspannung in voller Höhe, also ohne eine spannungsvermindernde Drossel, auszuwerten und die gesamte zur Verfügung stehende Spannung durch die Gegentaktschalteranordnung 35, 36, die in den --Stromnulldurchgängen geschaltet wird, praktisch verlustlos und ohne Phasenanschnitte in eine Gleichspannung umzusetzen und dabei gleichzeitig zu erreichen, daß die Leuchtstofflampe exakt die vorgesehene Nennleistung aufnimmt. Die Leuchtstofflampe wird also nicht überlastet und die Energieverluste des Vorschaltgerätes werden auf das unbedingt erforderliche Maß reduziert.By means of the transformer 39 in FIG. 5, it is possible to evaluate the direct voltage generated from the mains voltage in full, i.e. without a voltage-reducing choke, and the entire available voltage by the push-pull switch arrangement 35, 36 which is switched in the zero current crossings becomes practically lossless and without phase gates in a DC voltage and at the same time achieve that the fluorescent lamp consumes exactly the intended nominal power. The fluorescent lamp is therefore not overloaded and the energy losses of the ballast are reduced to the absolutely necessary level.

Claims (6)

1. Elektronisches Vorschaltgerät für Leuchtstofflampen, mit einer an einer Gleichspannung liegenden Gegentaktschalteranordnung aus zwei in Reihe geschalteten elektronischen Schaltern, mit einem an den Verbindungspunkt der elektronischen Schalter angeschlossenen Arbeitsschwingkreis, mindestens einer Leuchtstofflampe, deren Versorgungsspannung von dem Spannungsabfall der Induktivität oder der Kapazität abgeleitet wird, und mit einer Steuerschaltung, die die elektronischen Schalter in Abhängigkeit von dem Strom im Arbeitsschwingkreis schaltet, dadurch gekennzeichnet, daß die Steuerschaltung derart ausgebildet ist, daß die Umschaltung der elektronischen Schalter in der Nähe der Nulldurchgänge (28,29) des Stromes (I) des Arbeitsschwingkreises (20,21) erfolgt.1.electronic ballast for fluorescent lamps, with a push-pull switch arrangement connected to a direct voltage, consisting of two electronic switches connected in series, with a working resonant circuit connected to the connection point of the electronic switches, at least one fluorescent lamp, the supply voltage of which is derived from the voltage drop of the inductance or the capacitance, and with a control circuit which switches the electronic switches in dependence on the current in the working resonant circuit, characterized in that the control circuit is designed such that the switching of the electronic switches in the vicinity of the zero crossings (28, 29) of the current (I) of the Working oscillating circuit (20,21) takes place. 2. Elektronisches Vorschaltgerät nach Anspruch 1, da-. durch gekennzeichnet, daß die Umschaltung in einem Phasenwinkelbereich von - 10°, vorzugsweise von ± 5°, bezogen auf den Nulldurchgang (28,29) des Stromes (I) des Arbeitsschwingkreises (20,21) erfolgt.2. Electronic ballast according to claim 1, da-. by in that the switchover into a P of hare angle range - 10 °, preferably at the zero-crossing (28,29) is from ± 5 ° with respect of the current (I) of the working oscillating circuit (20,21). 3. Elektronisches Vorschaltgerät nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß mit dem Arbeitsschwingkreis (20,21) die Primärwicklung (18) eines induktiven übertragers (19) in Reihe geschaltet ist, dessen beide gegensinnig erregten Sekundärwicklungen (24,25) je einen der elektronischen Schalter derart steuern, daß die Sperrung des zuvor leitenden Schalters vor dem Nulldurchgang (28,29) des Stromes (I) und das Aufsteuern des zuvor gesperrten Schalters nach dem Nulldurchgang (28,29) des Stromes (I) erfolgt.3. Electronic ballast according to claim 1 or 2, characterized in that with the working resonant circuit (20,21), the primary winding (18) of an inductive transmitter (19) is connected in series, the two oppositely excited secondary windings (24,25) each one control the electronic switch in such a way that the blocking of the previously conductive switch before the zero crossing (28,29) of the current (I) and the opening of the previously blocked switch after the zero crossing (28,29) of the current (I). 4. Elektronisches Vorschaltgerät nach Anspruch 3, dadurch gekennzeichnet, daß die elektronischen Schalter Feldeffekttransistoren (35,36) gleichen Typs sind, daß jede der Sekundärwicklungen (24,25) mit einem Ende an dem Source-Anschluß und mit dem anderen Ende an dem Steueranschluß des zugehörigen Feldeffekttransistors angeschlossen ist und daß die Sekundärwicklungen (24,25) gleichsinnig zueinander angeordnet und mit den Feldeffekttransistoren (35,36) verbunden sind.4. Electronic ballast according to claim 3, characterized in that the electronic switches field effect transistors (35,36) are of the same type that each of the secondary windings (24,25) with one end to the source connection and with the other end to the control connection of the associated field-effect transistor is connected and that the secondary windings (24, 25) are arranged in the same direction as one another and are connected to the field-effect transistors (35, 36). 5. Elektronisches Vorschaltgerät nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß der Kapazität (21) oder der Induktivität (20) des Arbeitsschwingkreises die Primärwicklung (37) eines Transformators (39) parallelgeschaltet ist, dessen Sekundärwicklung (38) an die Elektroden der Leuchtstofflampe (22) angeschlossen ist.5. Electronic ballast according to one of claims 1 to 4, characterized in that the capacitance (21) or the inductance (20) of the working resonant circuit, the primary winding (37) of a transformer (39) is connected in parallel, the secondary winding (38) to the electrodes the fluorescent lamp (22) is connected. 6. Elektronisches Vorschaltgerät nach Anspruch 5, dadurch gekennzeichnet, daß der Transformator (39) derart ausgelegt ist, daß die Bedingung
Figure imgb0005
erfüllt ist, wobei R der Lampenwiderstand L die Induktivität des Arbeitsschwingkreises C die Kapazität des Arbeitsschwingkreises und
Figure imgb0006
 das Windungszahlverhältnis des Transfor- mators
ist.6. Electronic ballast according to claim 5, characterized in that the transformer (39) is designed such that the condition
Figure imgb0005
 is fulfilled, whereby R the lamp resistance L the inductance of the working circuit C the capacity of the working circuit and
Figure imgb0006
 the ratio of turns of the transformer
is.
EP84103849A 1983-04-08 1984-04-06 Electronic device for driving fluorescent lamps Withdrawn EP0121917A1 (en)

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DE19833312574 DE3312574A1 (en) 1983-04-08 1983-04-08 ELECTRONIC CONTROLLER FOR FLUORESCENT LAMPS

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WO1983000271A1 (en) * 1981-07-06 1983-01-20 Zelina, William, B. Line operated fluorescent lamp inverter ballast

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2061037A (en) * 1979-10-16 1981-05-07 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Circuit arrangement for driving low pressure discharge
GB2080652A (en) * 1980-07-21 1982-02-03 Philips Nv Oscillator for supplying an electrodeless discharge lamp
WO1983000271A1 (en) * 1981-07-06 1983-01-20 Zelina, William, B. Line operated fluorescent lamp inverter ballast

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4996462A (en) * 1988-07-27 1991-02-26 Siemens Aktiengesellschaft Electronic ballast for fluoroscent lamps
EP0361706A1 (en) * 1988-09-08 1990-04-04 Hayashibara, Ken Lighting device
EP0361748A1 (en) * 1988-09-26 1990-04-04 General Electric Company Power control circuit for discharge lamp and method of operating same
EP0391679A1 (en) * 1989-04-04 1990-10-10 Aktiebolaget Electrolux Oscillator circuit
US5043680A (en) * 1989-04-04 1991-08-27 Aktiebolaget Electrolux Resonant converter oscillator usable for powering a magnetron
AU626399B2 (en) * 1989-04-04 1992-07-30 Aktiebolaget Electrolux Oscillator circuit
US5434880A (en) * 1992-07-11 1995-07-18 Lumonics Ltd. Laser system
EP0659037A2 (en) * 1993-12-15 1995-06-21 General Electric Company Gas discharge lamp ballast circuit with indicator of ballast operability
EP0659037A3 (en) * 1993-12-15 1997-03-26 Gen Electric Gas discharge lamp ballast circuit with indicator of ballast operability.

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