EP0395776B1 - Electronic ballast - Google Patents

Electronic ballast Download PDF

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Publication number
EP0395776B1
EP0395776B1 EP89107955A EP89107955A EP0395776B1 EP 0395776 B1 EP0395776 B1 EP 0395776B1 EP 89107955 A EP89107955 A EP 89107955A EP 89107955 A EP89107955 A EP 89107955A EP 0395776 B1 EP0395776 B1 EP 0395776B1
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EP
European Patent Office
Prior art keywords
invertor
capacitor
voltage
bridge
output
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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EP89107955A
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German (de)
French (fr)
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EP0395776A1 (en
Inventor
Peter Krummel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
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Siemens AG
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Publication date
Application filed by Siemens AG filed Critical Siemens AG
Priority to DE89107955T priority Critical patent/DE58907116D1/en
Priority to ES89107955T priority patent/ES2049772T3/en
Priority to AT89107955T priority patent/ATE102428T1/en
Priority to EP89107955A priority patent/EP0395776B1/en
Priority to JP2111898A priority patent/JP2690382B2/en
Publication of EP0395776A1 publication Critical patent/EP0395776A1/en
Application granted granted Critical
Publication of EP0395776B1 publication Critical patent/EP0395776B1/en
Priority to HK123195A priority patent/HK123195A/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
    • H05B41/26—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

Definitions

  • the invention relates to an electronic ballast for fluorescent lamps according to the preamble of claim 1.
  • An electronic ballast of this type is known for example from DE-A1-33 19 739.
  • the sine correction capacitor serves the prescribed sine shape of the current drawn by the ballast from the network during operation. As long as the switching frequency of the inverter does not change, the ballast draws constant energy from the grid. This means that the effective operating voltages strongly depend on changes in the mains voltage and / or the load fed by the inverter. This dependency within the device not only requires the electrolytic capacitor supporting the DC supply voltage for the inverter to be designed for a higher voltage value, but also requires special measures for monitoring this DC voltage. If the monitoring detects an excessive internal DC voltage, it either switches off the entire ballast or paralyzes the sine correction function caused by the sine correction capacitor. Both measures have serious operational disadvantages. In the one case, the fluorescent lamp goes out, in the second case the correct current consumption from the network is no longer given, which leads to impermissible harmonics and a deterioration in the power factor.
  • the invention is based on the object of specifying a further solution for an electronic ballast of the type mentioned at the outset which, with the aid of simple circuitry measures, prevents the operating disadvantages described in the event of changes in the mains AC voltage and / or the load of the load circuit.
  • the circuit for the electronic ballast according to FIG. 1 known from DE-A1-33 19 739 consists of an inverter WR, to which the AC line voltage is supplied on the input side via a rectifier circuit GS.
  • the inverter WR consists of a switch bridge arrangement, each having a switch SH and SL in two branches and a capacitor CH and CH 'in two branches.
  • the output of the inverter WR is given by the common connection points on the one hand of the two switches SH, SL and on the other hand the capacitors CH, CH 'and connected to the load circuit LA.
  • the load circuit LA in turn consists of the series connection of the choke L with the parallel connection of the ignition capacitor CZ and the fluorescent tube LL.
  • the switches SH and SL are turned on and off in alternation with a high-frequency oscillation that controls them and is not specified. In this way, the load circuit is subjected to a rectangular alternating voltage in the rhythm of the high-frequency oscillation, the amplitude of which is determined by the charging capacitor voltage UE applied to the inverter input.
  • the rectifier circuit GS has on the input side a rectifier GL for a full-wave rectification, the output connections of which are each connected via a diode DK or DK 'polarized in the direction of the rectified alternating current to the charging capacitor CEL, which supports the rectified mains alternating voltage and at the same time the output of the rectifier circuit GS represents.
  • the inverter WR draws a current from the network during operation, which has the required sinusoidal shape, on the one hand, between the common connection points of one of the output-side connections of the rectifier GL and a diode DK or DK 'and the common connection point of the capacitors CH, CH ', ie the common connection point of the capacitive switch branches of the switch bridge arrangement of the inverter WR, on the other hand, a sine correction capacitor CS or CS' is provided. Furthermore, the inverter WR has free-wheeling diodes DFL and DFH, which are still required for proper switch operation and are connected in parallel to the switches SL and SH realized by power transistors.
  • this known circuit has the property that the inverter WR draws a constant energy from the grid as long as the switching frequency of its switches SH and SL does not change. This results in a strong dependence of the circuit on changes in mains voltage and / or changes in the load of the load circuit LA. If the AC voltage decreases or the load of the load circuit decreases, the charging capacitor voltage UE increases very quickly beyond an allowable limit value, which necessitates protective measures which have the serious operating disadvantages already described.
  • the known circuit according to FIG. 1, which shows a symmetrical structure, can be simplified, without its function undergoing a change, in that on the one hand the diode DK 'and the sine correction capacitor CS' are dispensed with.
  • capacitor CH' since the two capacitors CH and CH 'are electrically parallel to one another, capacitor CH' can be used to double the capacitance value of capacitor CH in the following electrically effective bridge capacitor CH called, are waived.
  • Such a simplified inverter circuit shows the preferred embodiment of an electronic ballast according to the invention in FIG. 2.
  • the circuit of the inverter In contrast to the inverter WR according to FIG. 1, WR is further supplemented by the series connection of two clamp diodes DBL and DBH, which are connected in parallel when the polarity is opposite to the charging capacitor voltage at the charging capacitor CEL. Their common connection point is at the same time that of the load circuit LA and the electrically effective bridge capacitor CH common output connection of the inverter WR.
  • the electrically effective bridge capacitor CH represents the half-bridge capacitor of the switch bridge arrangement.
  • the clamp diodes DBH and DBL ensure that, in the event of fluctuations in the mains voltage and / or changes in the load of the load circuit LA, on the one hand the reference potential GND and on the other hand the intermediate circuit potential UZW and thus the charging capacitor voltage US are kept largely stable. Switching off the entire device or paralyzing the sine correction function to protect against impermissible overvoltages is therefore no longer necessary.
  • the preferred circuit of the electronic ballast circuit according to FIG. 2 also differs from the known circuit according to FIG. 1 in that a charging choke LK is provided in the connection path between the one output-side connection of the rectifier GL and the common connection point of diode DK and sine correction capacitor CS and that, in addition, the AC line voltage un is supplied to the rectifier circuit GS via a harmonic filter FE.
  • the inductance of the charging inductor LK is expediently dimensioned for a value at which the charging inductor LK - in the rhythm of the high-frequency oscillation for the control of the switches SH and SL - is only fully charged when the instantaneous AC alternating current is small, that is to say in the region of its zero crossings.
  • a corresponding time diagram of the charging inductor current ilk is shown in FIG. 3.
  • the inductance of the charging inductor LK must be chosen to be relatively large. If the inductance is small, the harmonic component of the mains current can be reduced, but it will then a greater effort in the area of the harmonic filter FE is required to meet the requirements for adequate radio interference suppression.
  • the high-frequency current modulation still remains within small limits, so that the expenditure for the harmonic filter FE, as indicated in FIG. 2, can be limited to a choke having two windings and a capacitor.
  • the inductance of the charging inductor LK can in principle be varied within wide limits without the limiting action of the clamp diodes DBH and DBL being adversely affected thereby.
  • the electrically effective bridge capacitor CH has a value at which its charging voltage largely follows the high-frequency load circuit current. Furthermore, it is expedient for the capacitance of the sine correction capacitor CS to be substantially larger than the capacitance of the electrically effective bridge capacitor CH to choose.
  • the capacitance ratio of sine correction capacitor CS to the electrically effective bridge capacitor CH expediently has a value between 1.5 and 4, preferably the value 2.
  • FIGS. 4 to 7 For a better understanding of the mode of operation of the circuit according to FIG. 2, this circuit is shown again in FIGS. 4 to 7, together with the most important currents occurring during a mains voltage half-wave, which are dependent on different switch positions of the switches SL and SH within one Period of high-frequency oscillator oscillation that controls the switch occurs.
  • a switching period has four different switching phases.
  • the first switching phase in which the switch SL is closed and the switch SH is open, is shown in FIG. 4.
  • the following, second switching phase is shown in FIG. 5, in which both switches SH and SL are open.
  • the intermediate circuit potential UZW is equal to the bridge capacitor voltage UH, that the sine correction capacitor CS is uncharged and the electrically effective bridge capacitor CH , in the following briefly half-bridge capacitor CH called, is charged.
  • the charging choke LK should have a charge and the choke L of the load circuit should have no charge.
  • the half-bridge capacitor now becomes CH discharged by the current ih via the load circuit and the switch SL.
  • the sine correction capacitor CS charged by the current ik, which also flows through the charging choke LK and discharges it.
  • the charging choke LK discharges into the sine correction capacitor CS until the corrected rectified AC mains voltage UK becomes smaller than the rectified AC mains voltage UN.
  • the charging choke LK is charged until the half-bridge capacitor CH is fully discharged.
  • the current ib1 starts through the clamp diode DBL, the circuit of which also closes via the switch SL. This current ensures that the half-bridge capacitor CH cannot charge in the opposite direction.
  • the sine correction capacitor CS is further charged via the charging inductor LK until the corrected rectified AC mains voltage UK becomes greater than the rectified AC mains voltage UN.
  • the switch SL opens, the inductor L of the load circuit charged in the first switching phase is discharged on the one hand via the clamp diode current ib1 flowing through the clamp diode DBL and on the other hand via the sine correction capacitor CS flowing current ik, which takes its way via the freewheeling diode DFH and also flows through the charging choke LK, which is now discharged.
  • the total current flowing through the load circuit from the clamp diode current ib1 and the sine correction capacitor current ik goes towards the value zero.
  • the half-bridge capacitor CH and the inductor L is charged by the bridge capacitor current ih2 and the sine correction capacitor current ik2.
  • the sine correction capacitor CS is also charged by the sine correction capacitor current ik2.
  • the sine correction capacitor current ik2 stops flowing and thus ends the charging of the sine correction capacitor CS.
  • the diode DK which becomes transparent as soon as UK + UH> UE causes the sine correction capacitor current ik1 to flow.
  • the sine correction capacitor current ik1 and the bridge capacitor current ih2 close across the load circuit and cause a further charging of the inductor L.
  • the sine correction capacitor C3 is discharged by the now flowing sine correction capacitor current ik1.
  • the charging choke LK is also partially discharged.
  • the bridge capacitor current ih2 charges the bridge capacitor CH further on. As soon as the bridge capacitor voltage UH becomes larger than the charging capacitor voltage UE, the clamp diode current ibh begins to flow. In this way, a recharge of the sine correction capacitor CS in the opposite direction is prevented, ie its charge assumes the value zero.
  • the inductor L of the load circuit discharges via the clamp diode current ibh which continues to flow.
  • the charging inductor LK partially discharges through the charging inductor current ilk, the circuit of which closes via the charging capacitor CEL.

Abstract

In electronic ballasts, having invertors to which the mains AC voltage is fed via a rectifier voltage, use is made of at least one additional sine-wave correction capacitor. Known circuits of this type show a high dependency of the charge capacitor voltage to changes in the mains AC voltage and/or changes in the load of the load circuit, which result in serious operating disadvantages. It is proposed significantly to reduce this dependency of the charge capacitor voltage on mains AC voltage changes and/or load changes in that two clamping diodes (DBL, DBH), which are connected in series and whose polarity is opposite to that of the rectified AC voltage (UN), are connected in parallel with the invertor input, the common connecting point of which clamping diodes is likewise the output-side termination of the invertor (WR) which is common to the load circuit (LA) and the electrically effective bridging capacitor (CH). <IMAGE>

Description

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

Ein elektronisches Vorschaltgerät dieser Art ist beispielsweise aus DE-A1-33 19 739 bekannt. Der Sinus-Korrekturkondensator dient dabei der vorgeschriebenen Sinusform des im Betrieb vom Vorschaltgerät aus dem Netz aufgenommenen Stromes. Solange sich die Schaltfrequenz des Wechselrichters nicht ändert, nimmt das Vorschaltgerät eine konstante Energie aus dem Netz auf. Dies bedingt eine starke Abhängigkeit der wirksamen Betriebsspannungen von Änderungen der Netzspannung und/oder der vom Wechselrichter gespeisten Last. Diese Abhängigkeit erfordert geräteintern nicht nur eine Auslegung des die Versorgungs-Gleichspannung für den Wechselrichter stützenden Elektrolytkondensators für einen höheren Spannungwert, sondern macht auch besondere Maßnahmen zur Überwachung dieser Gleichspannung erforderlich. Erkennt die Überwachung eine zu hohe interne Gleichspannung, so schaltet sie entweder das ganze Vorschaltgerät ab oder legt die durch den Sinus-Korrekturkondensator bewirkte Sinus-Korrekturfunktion lahm. Mit beiden Maßnahmen sind gravierende Betriebsnachteile verbunden. In dem einen Falle erlischt die Leuchtstofflampe, im zweiten Falle ist die vorschriftsmäßige Stromaufnahme aus dem Netz nicht mehr gegeben, was zu unzulässigen Oberschwingungen und einer Leistungsfaktorverschlechterung führt.An electronic ballast of this type is known for example from DE-A1-33 19 739. The sine correction capacitor serves the prescribed sine shape of the current drawn by the ballast from the network during operation. As long as the switching frequency of the inverter does not change, the ballast draws constant energy from the grid. This means that the effective operating voltages strongly depend on changes in the mains voltage and / or the load fed by the inverter. This dependency within the device not only requires the electrolytic capacitor supporting the DC supply voltage for the inverter to be designed for a higher voltage value, but also requires special measures for monitoring this DC voltage. If the monitoring detects an excessive internal DC voltage, it either switches off the entire ballast or paralyzes the sine correction function caused by the sine correction capacitor. Both measures have serious operational disadvantages. In the one case, the fluorescent lamp goes out, in the second case the correct current consumption from the network is no longer given, which leads to impermissible harmonics and a deterioration in the power factor.

Der Erfindung liegt die Aufgabe zugrunde, für ein elektronisches Vorschaltgerät der einleitend erwähnten Art eine weitere Lösung anzugeben, die mit Hilfe einfacher schaltungstechnischer Maßnahmen die geschilderten Betriebsnachteile bei Änderungen der Netzwechselspannung und/oder der Last des Lastkreises unterbindet.The invention is based on the object of specifying a further solution for an electronic ballast of the type mentioned at the outset which, with the aid of simple circuitry measures, prevents the operating disadvantages described in the event of changes in the mains AC voltage and / or the load of the load circuit.

Diese Aufgabe wird gemäß der Erfindung durch die im Kennzeichendes 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.

Zweckmäßige Ausgestaltungen des Gegenstandes nach dem Patentanspruch 1 sind in den weiteren Patentansprüchen 2 bis 6 angegeben.Expedient embodiments of the subject matter according to claim 1 are specified in the further claims 2 to 6.

Ein Ausführungsbeispiel der Erfindung wird im folgenden anhand der Zeichnung näher erläutert, dabei bedeuten die Figuren:

Fig. 1
eine bekannte Ausführungsform eines von Sinus-Korrekturkondensatoren Gebrauch machenden elektronischen Vorschaltgerätes,
Fig. 2
eine bevorzugte Ausführungsform des elektronischen Vorschaltgerätes nach der Erfindung,
Fig. 3
ein Zeitdiagramm des Stroms durch die Ladedrossel der Gleichrichterschaltung des Vorschaltgerätes nach Fig. 2,
Figuren 4 - 7
die Schaltung nach Fig. 2 mit hierin eingezeichneten Strömen bei den verschiedenen Schaltphasen des Wechselrichters.
An exemplary embodiment of the invention is explained in more detail below with the aid of the drawing, in which the figures mean:
Fig. 1
a known embodiment of an electronic ballast using sine correction capacitors,
Fig. 2
a preferred embodiment of the electronic ballast according to the invention,
Fig. 3
3 shows a time diagram of the current through the charging inductor of the rectifier circuit of the ballast according to FIG. 2,
Figures 4 - 7
the circuit of FIG. 2 with currents shown here in the different switching phases of the inverter.

Die Schaltung für das aus DE-A1-33 19 739 bekannte elektronische Vorschaltgerät nach Fig. 1 besteht aus einem Wechselrichter WR, dem die Netzwechselspannung un über eine Gleichrichterschaltung GS eingangsseitig zugeführt ist. Der Wechselrichter WR besteht aus einer Schalterbrückenanordnung, die in zwei Zweigen jeweils einen Schalter SH und SL und in zwei Zweigen einen Kondensator CH und CH' aufweist. Der Ausgang des Wechselrichters WR ist durch die gemeinsamen Verbindungspunkte einerseits der beiden Schalter SH, SL und andererseits der Kondensatoren CH, CH' gegeben und an den Lastkreis LA angeschaltet. Der Lastkreis LA besteht seinerseits aus der Reihenschaltung der Drossel L mit der Parallelschaltung aus dem Zündkondensator CZ und der Leuchtstoffröhre LL. Die Schalter SH und SL werden im Wechsel einer sie steuernden, nicht angegebenen Hochfrequenzschwingung auf- und zugesteuert. Auf diese Weise wird der Lastkreis im Rhythmus der Hochfrequenzschwingung mit einer rechteckigen Wechselspannung beaufschlagt, deren Amplitude durch die am Wechselrichtereingang anliegende Ladekondensatorspannung UE bestimmt ist.The circuit for the electronic ballast according to FIG. 1 known from DE-A1-33 19 739 consists of an inverter WR, to which the AC line voltage is supplied on the input side via a rectifier circuit GS. The inverter WR consists of a switch bridge arrangement, each having a switch SH and SL in two branches and a capacitor CH and CH 'in two branches. The output of the inverter WR is given by the common connection points on the one hand of the two switches SH, SL and on the other hand the capacitors CH, CH 'and connected to the load circuit LA. The load circuit LA in turn consists of the series connection of the choke L with the parallel connection of the ignition capacitor CZ and the fluorescent tube LL. The switches SH and SL are turned on and off in alternation with a high-frequency oscillation that controls them and is not specified. In this way, the load circuit is subjected to a rectangular alternating voltage in the rhythm of the high-frequency oscillation, the amplitude of which is determined by the charging capacitor voltage UE applied to the inverter input.

Die Gleichrichterschaltung GS weist eingangsseitig einen Gleichrichter GL für eine Doppelweggleichrichtung auf, dessen Ausgangsanschlüsse jeweils über eine in Richtung des gleichgerichteten Wechselstroms gepolte Diode DK bzw. DK' mit dem Ladekondensator CEL verbunden sind, der die gleichgerichtete Netzwechselspannung stützt und zugleich den Ausgang der Gleichrichterschaltung GS darstellt. Damit der Wechselrichter WR im Betrieb einen Strom aus dem Netz entnimmt, der die geforderte Sinusform aufweist, ist jeweils zwischen den gemeinsamen Verbindungspunkten eines der ausgangsseitigen Anschlusse des Gleichrichters GL und einer Diode DK bzw. DK' einerseits und dem gemeinsamen Verbindungspunkt der Kondensatoren CH, CH', d.h. dem gemeinsamen Verbindungspunkt der kapazitiven Schalterzweige der Schalterbrückenanordnung des Wechselrichters WR andererseits je ein Sinus-Korrekturkondensator CS bzw. CS' vorgesehen. Weiterhin weist der Wechselrichter WR für den einwandfreien Schalterbetrieb noch erforderliche Freilaufdioden DFL und DFH auf, die den durch Leistungstransistoren verwirklichten Schaltern SL und SH parallel geschaltet sind.The rectifier circuit GS has on the input side a rectifier GL for a full-wave rectification, the output connections of which are each connected via a diode DK or DK 'polarized in the direction of the rectified alternating current to the charging capacitor CEL, which supports the rectified mains alternating voltage and at the same time the output of the rectifier circuit GS represents. So that the inverter WR draws a current from the network during operation, which has the required sinusoidal shape, on the one hand, between the common connection points of one of the output-side connections of the rectifier GL and a diode DK or DK 'and the common connection point of the capacitors CH, CH ', ie the common connection point of the capacitive switch branches of the switch bridge arrangement of the inverter WR, on the other hand, a sine correction capacitor CS or CS' is provided. Furthermore, the inverter WR has free-wheeling diodes DFL and DFH, which are still required for proper switch operation and are connected in parallel to the switches SL and SH realized by power transistors.

Wie bereits darauf hingewiesen wurde, hat diese bekannte Schaltung die Eigenschaft, daß der Wechselrichter WR aus dem Netz eine konstante Energie aufnimmt, solange sich die Schaltfrequenz seiner Schalter SH und SL nicht ändert. Daraus resultiert eine starke Abhängigkeit der Schaltung von Netzspannungsänderungen und/oder Änderungen der Last des Lastkreises LA. Bei abnehmender Wechselspannung oder abnehmender Last des Lastkreises erhöht sich die Ladekondensatorspannung UE sehr rasch über einen zulässigen Grenzwert hinaus, was Schutzmaßnahmen bedingt, die die bereits geschilderten gravierenden Betriebsnachteile aufweisen.As already pointed out, this known circuit has the property that the inverter WR draws a constant energy from the grid as long as the switching frequency of its switches SH and SL does not change. This results in a strong dependence of the circuit on changes in mains voltage and / or changes in the load of the load circuit LA. If the AC voltage decreases or the load of the load circuit decreases, the charging capacitor voltage UE increases very quickly beyond an allowable limit value, which necessitates protective measures which have the serious operating disadvantages already described.

Die bekannte Schaltung nach Fig. 1, die einen symmetrischen Aufbau zeigt, läßt sich, ohne daß ihre Funktion eine Änderung erfährt, dadurch vereinfachen, daß einerseits auf die Diode DK' und den Sinus-Korrekturkondensator CS' verzichtet wird. In gleicher Weise kann, da die beiden Kondensatoren CH und CH' in ihrer elektrischen Wirksamkeit einander parallel liegen, auf den Kondensator CH' bei gleichzeitiger Verdoppelung des Kapazitätswertes des Kondensators CH im folgenden elektrisch wirksamer Brückenkondensator CH genannt, verzichtet werden.The known circuit according to FIG. 1, which shows a symmetrical structure, can be simplified, without its function undergoing a change, in that on the one hand the diode DK 'and the sine correction capacitor CS' are dispensed with. In the same way, since the two capacitors CH and CH 'are electrically parallel to one another, capacitor CH' can be used to double the capacitance value of capacitor CH in the following electrically effective bridge capacitor CH called, are waived.

Eine solche vereinfachte Wechselrichterschaltung zeigt die bevorzugte Ausführungsform eines elektronischen Vorschaltgerätes nach der Erfindung in Fig. 2. Die Schaltung des Wechselrichters WR ist, im Unterschied zum Wechselrichter WR nach Fig. 1, weiterhin durch die Reihenschaltung zweier Klammerdioden DBL und DBH ergänzt, die bei gegensinniger Polung zur Ladekondensatorspannung am Ladekondensator CEL, diesem parallel angeschaltet sind. Dabei ist ihr gemeinsamer Verbindungspunkt zugleich der dem Lastkreis LA und dem elektrisch wirksamen Brückenkondensator CH gemeinsame ausgangsseitige Anschluß des Wechselrichters WR. Der elektrisch wirksame Brückenkondensator CH stellt dabei den Halbbrückenkondensator der Schalterbrückenanordnung dar.Such a simplified inverter circuit shows the preferred embodiment of an electronic ballast according to the invention in FIG. 2. The circuit of the inverter In contrast to the inverter WR according to FIG. 1, WR is further supplemented by the series connection of two clamp diodes DBL and DBH, which are connected in parallel when the polarity is opposite to the charging capacitor voltage at the charging capacitor CEL. Their common connection point is at the same time that of the load circuit LA and the electrically effective bridge capacitor CH common output connection of the inverter WR. The electrically effective bridge capacitor CH represents the half-bridge capacitor of the switch bridge arrangement.

Durch die Klammerdioden DBH und DBL wird dafür gesorgt, daß bei auftretenden Netzspannungsschwankungen und/oder Änderungen der Last des Lastkreises LA einerseits das Bezugspotential GND und andererseits das Zwischenkreispotential UZW und damit die Ladekondensatorspannung US weitestgehend stabil gehalten werden. Ein Abschalten des kompletten Gerätes oder aber ein Lahmlegen der Sinus-Korrekturfunktion zum Schutz vor unzulässigen Überspannungen ist daher nicht mehr erforderlich.The clamp diodes DBH and DBL ensure that, in the event of fluctuations in the mains voltage and / or changes in the load of the load circuit LA, on the one hand the reference potential GND and on the other hand the intermediate circuit potential UZW and thus the charging capacitor voltage US are kept largely stable. Switching off the entire device or paralyzing the sine correction function to protect against impermissible overvoltages is therefore no longer necessary.

Die bevorzugte Schaltung des elektronischen Vorschaltkreises nach Fig. 2 unterscheidet sich von der bekannten Schaltung nach Fig. 1 weiterhin dadurch, daß im Verbindungsweg zwischen dem einen ausgangsseitigen Anschluß des Gleichrichters GL und dem gemeinsamen Verbindungspunkt von Diode DK und Sinus-Korrekturkondensator CS eine Ladedrossel LK vorgesehen ist und daß darüberhinaus die Netzwechselspannung un der Gleichrichterschaltung GS über ein Oberwellenfilter FE zugeführt wird.The preferred circuit of the electronic ballast circuit according to FIG. 2 also differs from the known circuit according to FIG. 1 in that a charging choke LK is provided in the connection path between the one output-side connection of the rectifier GL and the common connection point of diode DK and sine correction capacitor CS and that, in addition, the AC line voltage un is supplied to the rectifier circuit GS via a harmonic filter FE.

Zweckmäßig ist die Induktivität der Ladedrossel LK für einen Wert bemessen, bei dem die Ladedrossel LK-im Rhythmus der Hochfrequenzschwingung für die Steuerung der Schalter SH und SL - nur bei kleinen Werten des augenblicklichen Netzwechselstromes, also im Bereich seiner Nulldurchgänge, voll umgeladen wird. Ein entsprechendes Zeitdiagramm des Ladedrosselstromes ilk zeigt Fig. 3. Die Induktivität der Ladedrossel LK muß hierzu relativ groß gewählt werden. Bei kleiner Induktivität läßt sich zwar der Oberschwingungsanteil des Netzstromes verringern, jedoch wird dann ein größerer Aufwand im Bereich des Oberwellenfilters FE erforderlich, um die Forderungen an eine ausreichende Funkentstörung zu erfüllen. Bei der angegebenen Bemessung der Induktivität der Ladedrossel LK bleibt die hochfrequente Strommodulation noch in kleinen Grenzen, so daß der Aufwand für das Oberwellenfilter FE, wie in Fig. 2 angedeutet ist, sich auf eine zwei Wicklungen aufweisende Drossel und einen Kondensator beschränken läßt.The inductance of the charging inductor LK is expediently dimensioned for a value at which the charging inductor LK - in the rhythm of the high-frequency oscillation for the control of the switches SH and SL - is only fully charged when the instantaneous AC alternating current is small, that is to say in the region of its zero crossings. A corresponding time diagram of the charging inductor current ilk is shown in FIG. 3. The inductance of the charging inductor LK must be chosen to be relatively large. If the inductance is small, the harmonic component of the mains current can be reduced, but it will then a greater effort in the area of the harmonic filter FE is required to meet the requirements for adequate radio interference suppression. With the specified dimensioning of the inductance of the charging choke LK, the high-frequency current modulation still remains within small limits, so that the expenditure for the harmonic filter FE, as indicated in FIG. 2, can be limited to a choke having two windings and a capacitor.

Der Vollständigkeit halber soll aber nicht unerwähnt bleiben, daß die Induktivität der Ladedrossel LK grundsätzlich in weiten Grenzen variiert werden kann, ohne daß hierdurch die Begrenzerwirkung der Klammerdioden DBH und DBL eine Beeinträchtigung erfährt.For the sake of completeness, it should not go unmentioned that the inductance of the charging inductor LK can in principle be varied within wide limits without the limiting action of the clamp diodes DBH and DBL being adversely affected thereby.

Für eine optimale Begrenzerfunktion der Klammerdioden DBH und DBL ist es wesentlich, daß der elektrisch wirksame Brückenkondensator CH einen Wert hat, bei dem seine Ladespannung dem hochfrequenten Lastkreisstrom weitgehend folgt. Weiterhin ist es zweckmäßig, die Kapazität des Sinus-Korrekturkondensators CS wesentlich größer als die Kapazität des elektrisch wirksamen Brückenkondensators CH zu wählen. Das Kapazitätsverhältnis von Sinus-Korrekturkondensator CS zum elektrisch wirksamen Brückenkondensator CH hat zweckmäßig einen Wert zwischen 1,5 und 4, vorzugsweise den Wert 2.For an optimal limiter function of the clamp diodes DBH and DBL, it is essential that the electrically effective bridge capacitor CH has a value at which its charging voltage largely follows the high-frequency load circuit current. Furthermore, it is expedient for the capacitance of the sine correction capacitor CS to be substantially larger than the capacitance of the electrically effective bridge capacitor CH to choose. The capacitance ratio of sine correction capacitor CS to the electrically effective bridge capacitor CH expediently has a value between 1.5 and 4, preferably the value 2.

Zum besseren Verständnis der Wirkungsweise der Schaltung nach Fig. 2 ist diese Schaltung in den Fig. 4 bis 7 jeweils noch einmal dargestellt und zwar zusammen mit den wichtigsten während einer Netzspannungshalbwelle auftretenden Strömen, die in Abhängigkeit von unterschiedlichen Schalterstellungen der Schalter SL und SH innerhalb einer Periode der hochfrequenten, die Schalter steuernden Oszillatorschwingung auftreten. Eine solche Schaltperiode weist vier voneinander zu unterscheidende Schaltphasen auf. Die erste Schaltphase, bei der der Schalter SL geschlossen und der Schalter SH geöffnet ist, ist in Fig. 4 dargestellt. Die folgende, zweite Schaltphase zeigt Fig. 5, bei der beide Schalter SH und SL geöffnet sind. In der dritten Schaltphase ist der Schalter SL geöffnet und der Schalter SH geschlossen und in der vierten, in Fig. 7 dargestellten Schaltphase sind wiederum, entsprechend der zweiten Schaltphase nach Fig. 5, beide Schalter SH und SL geöffnet.For a better understanding of the mode of operation of the circuit according to FIG. 2, this circuit is shown again in FIGS. 4 to 7, together with the most important currents occurring during a mains voltage half-wave, which are dependent on different switch positions of the switches SL and SH within one Period of high-frequency oscillator oscillation that controls the switch occurs. Such a switching period has four different switching phases. The first switching phase, in which the switch SL is closed and the switch SH is open, is shown in FIG. 4. The following, second switching phase is shown in FIG. 5, in which both switches SH and SL are open. In the third switching phase is the Switch SL opened and switch SH closed and in the fourth switching phase shown in FIG. 7, in turn, corresponding to the second switching phase according to FIG. 5, both switches SH and SL are open.

Die in den Fig. 4 - 7 beschriebenen Ströme gelten natürlich nur für einen bestimmten momentanen Wert der Netzwechselspannung un. Nur der Vollständigkeit halber sei erwähnt, daß im Nulldurchgang der Netzwechselspannung un weder über die Ladedrossel LK noch über den Sinus-Korrekturkondensator CS Strom fließt. Der Betriebsstrom für die Leuchtstoffröhre LL im Lastkreis wird ausschließlich dem Ladekondensator CEL und dem elektrisch wirksamen Brückenkondensator CH entnommen.The currents described in FIGS. 4-7 of course only apply to a specific instantaneous value of the AC line voltage un. For the sake of completeness, it should be mentioned that in the zero crossing of the AC line voltage un current neither flows via the charging inductor LK nor via the sine correction capacitor CS. The operating current for the fluorescent tube LL in the load circuit is exclusively the charging capacitor CEL and the electrically effective bridge capacitor CH taken.

In allen Figuren 4 bis 7 sind neben der Ladekondensatorspannung UE weitere Spannungen eingetragen und zwar sind die gleichgerichtete Netzwechselspannung UN am Ausgang des Gleichrichters, und die korrigierte gleichgerichtete Netzwechselspannung UK am gemeinsamen Verbindungspunkt der Ladedrossel LK und der Diode DK gegen das Bezugspotential GND angegeben. Weiterhin sind noch die Brückenkondensatorspannung UH am elektrisch wirksamen Brückenkondensator CH, die Sinus-Korrekturkondensatorspannung US am Sinus-Korrekturkondensator CS und die Wechselrichterspannung UW vom gemeinsamen Verbindungspunkt der Schalter SH und SL gegen das Bezugspotential GND angegeben.In addition to the charging capacitor voltage UE, further voltages are entered in all FIGS. 4 to 7, namely the rectified AC mains voltage UN at the output of the rectifier and the corrected rectified AC mains voltage UK at the common connection point of the charging choke LK and the diode DK against the reference potential GND. Furthermore, the bridge capacitor voltage UH is still on the electrically effective bridge capacitor CH , the sine correction capacitor voltage US at the sine correction capacitor CS and the inverter voltage UW from the common connection point of the switches SH and SL against the reference potential GND.

Bei der in Fig. 4 dargestellten ersten Schaltphase sei angenommen, daß im Zeitpunkt des Schließens des Schalters SL das Zwischenkreispotential UZW gleich der Brückenkondensatorspannung UH ist, daß der Sinus-Korrekturkondensator CS ungeladen und der elektrisch wirksame Brückenkondensator CH, im folgenden kurz Halbbrückenkondensator CH genannt, aufgeladen ist. Die Ladedrossel LK soll eine Ladung und die Drossel L des Lastkreises keine Ladung aufweisen.In the first switching phase shown in FIG. 4, it is assumed that at the time the switch SL closes, the intermediate circuit potential UZW is equal to the bridge capacitor voltage UH, that the sine correction capacitor CS is uncharged and the electrically effective bridge capacitor CH , in the following briefly half-bridge capacitor CH called, is charged. The charging choke LK should have a charge and the choke L of the load circuit should have no charge.

Mit dem Schließen des Schalters SL wird nun der Halbbrückenkondensator CH durch den Strom ih über den Lastkreis und den Schalter SL entladen. Zugleich wird der Sinus-Korrekturkondensator CS durch den Strom ik aufgeladen, der auch durch die Ladedrossel LK fließt und diese entlädt. Die Ladedrossel LK entlädt sich in den Sinus-Korrekturkondensator CS so lange, bis die korrigierte gleichgerichtete Netzwechselspannung UK kleiner wird als die gleichgerichtete Netzwechselspannung UN. Anschließend wird die Ladedrossel LK aufgeladen, bis der Halbbrückenkondensator CH voll entladen ist. Nunmehr setzt der Strom ib1 durch die Klammerdiode DBL ein, dessen Stromkreis sich ebenfalls über den Schalter SL schließt. Dieser Strom sorgt dafür, daß sich der Halbbrückenkondensator CH nicht in Gegenrichtung aufladen kann. Zugleich wird der Sinus-Korrekturkondensator CS über die Ladedrossel LK weiter aufgeladen, bis die korrigierte gleichgerichtete Netzwechselspannung UK größer wird als die gleichgerichtete Netzwechselspannung UN.When the switch SL is closed, the half-bridge capacitor now becomes CH discharged by the current ih via the load circuit and the switch SL. At the same time, the sine correction capacitor CS charged by the current ik, which also flows through the charging choke LK and discharges it. The charging choke LK discharges into the sine correction capacitor CS until the corrected rectified AC mains voltage UK becomes smaller than the rectified AC mains voltage UN. Then the charging choke LK is charged until the half-bridge capacitor CH is fully discharged. Now the current ib1 starts through the clamp diode DBL, the circuit of which also closes via the switch SL. This current ensures that the half-bridge capacitor CH cannot charge in the opposite direction. At the same time, the sine correction capacitor CS is further charged via the charging inductor LK until the corrected rectified AC mains voltage UK becomes greater than the rectified AC mains voltage UN.

Wenn sich nunmehr, wie das die zweite Schaltphase nach Fig. 5 zeigt, der Schalter SL öffnet, entlädt sich die in der ersten Schaltphase aufgeladene Drossel L des Lastkreises einerseits über den die Klammerdiode DBL durchfließenden Klammerdiodenstrom ib1 und andererseits über den durch den Sinus-Korrekturkondensator CS fließenden Strom ik, der hierbei seinen Weg über die Freilaufdiode DFH nimmt und auch die Ladedrossel LK durchfließt, die sich nunmehr entlädt. Der den Lastkreis durchfließende Summenstrom aus dem Klammerdiodenstrom ib1 und dem Sinus-Korrekturkondensatorstrom ik geht dabei gegen den Wert Null.If, as the second switching phase according to FIG. 5 shows, the switch SL opens, the inductor L of the load circuit charged in the first switching phase is discharged on the one hand via the clamp diode current ib1 flowing through the clamp diode DBL and on the other hand via the sine correction capacitor CS flowing current ik, which takes its way via the freewheeling diode DFH and also flows through the charging choke LK, which is now discharged. The total current flowing through the load circuit from the clamp diode current ib1 and the sine correction capacitor current ik goes towards the value zero.

Sobald nunmehr entsprechend der dritten Schaltphase nach Fig. 6 der Schalter SH schließt, werden der Halbbrückenkondensator CH und die Drossel L durch den Brückenkondensatorstrom ih2 und den Sinus-Korrekturkondensatorstrom ik2 aufgeladen. Durch den Sinus-Korrekturkondensatorstrom ik2 wird der Sinus-Korrekturkondensator CS ebenfalls aufgeladen.As soon as the switch SH closes in accordance with the third switching phase according to FIG. 6, the half-bridge capacitor CH and the inductor L is charged by the bridge capacitor current ih2 and the sine correction capacitor current ik2. The sine correction capacitor CS is also charged by the sine correction capacitor current ik2.

Sobald der Halbbrückenkondensator CH soweit aufgeladen ist, daß die Summe aus der Sinus-Korrekturkondensatorspannung US und der Brückenkondensatorspannung UH größer als die Ladekondensatorspannung UE wird, beginnt ein dritter Strom, nämlich der Brückenkondensatorstrom ih1 zu fließen.Once the half-bridge capacitor CH to the extent that the sum of the sine correction capacitor voltage US and the bridge capacitor voltage UH becomes greater than the charge capacitor voltage UE, a third current, namely the bridge capacitor current ih1, begins to flow.

Zugleich hört der Sinus-Korrekturkondensatorstrom ik2 auf zu fließen und beendet damit die Aufladung des Sinus-Korrekturkondensators CS.At the same time, the sine correction capacitor current ik2 stops flowing and thus ends the charging of the sine correction capacitor CS.

Die Diode DK, die durchlässig wird, sobald UK + UH > UE

Figure imgb0001
Figure imgb0002
 werden, bewirkt das Fließen des Sinus-Korrekturkondensatorstromes ik1. Der Sinus-Korrekturkondensatorstrom ik1 und der Brückenkondensatorstrom ih2 schließen sich über den Lastkreis und bewirken eine weitere Aufladung der Drossel L. Der Sinus-Korrekturkondensator C3 wird durch den nunmehr fließenden Sinus-Korrekturkondensatorstrom ik1 entladen. Zugleich wird auch die Ladedrossel LK teilweise entladen.The diode DK, which becomes transparent as soon as UK + UH> UE
Figure imgb0001
Figure imgb0002
 causes the sine correction capacitor current ik1 to flow. The sine correction capacitor current ik1 and the bridge capacitor current ih2 close across the load circuit and cause a further charging of the inductor L. The sine correction capacitor C3 is discharged by the now flowing sine correction capacitor current ik1. At the same time, the charging choke LK is also partially discharged.

Der Brückenkondensatorstrom ih2 lädt den Brückenkondensator CH weiter auf. Sobald die Brückenkondensatorspannung UH größer als die Ladekondensatorspannung UE wird, beginnt der Klammerdiodenstrom ibh zu fließen. Auf diese Weise wird eine Umladung des Sinus-Korrekturkondensators CS in entgegengesetzter Richtung unterbunden, d.h. seine Ladung nimmt den Wert Null an.The bridge capacitor current ih2 charges the bridge capacitor CH further on. As soon as the bridge capacitor voltage UH becomes larger than the charging capacitor voltage UE, the clamp diode current ibh begins to flow. In this way, a recharge of the sine correction capacitor CS in the opposite direction is prevented, ie its charge assumes the value zero.

Öffnet nun der Schalter SH wiederum entsprechend der vierten Schaltphase nach Fig. 7, dann entlädt sich die Drossel L des Lastkreises über den weiterhin fließenden Klammerdiodenstrom ibh. Die Ladedrossel LK entlädt sich dabei teilweise über den Ladedrosselstrom ilk, dessen Stromkreis sich über den Ladekondensator CEL schließt.If the switch SH now opens again in accordance with the fourth switching phase according to FIG. 7, the inductor L of the load circuit discharges via the clamp diode current ibh which continues to flow. The charging inductor LK partially discharges through the charging inductor current ilk, the circuit of which closes via the charging capacitor CEL.

Ein neuer Zyklus beginnt nun mit dem erneuten Schließen des Schalters SL entsprechend der ersten Schaltphase nach Fig. 4, die bereits erläutert wurde.A new cycle now begins with the closing of the switch SL in accordance with the first switching phase according to FIG. 4, which has already been explained.

Claims (6)

  1. Electronic ballast for fluorescent lamps, having a rectifying circuit (GS) which is fed from an AC supply voltage (un) and has a rectifying bridge (GL), a charging inductor (LK) connected to the positive terminal of said rectifying bridge, and, in series with said inductor, a coupling diode (DK) polarized in the forward direction for the rectified AC supply, as well as a charging capacitor (CEL) in parallel with both their outlets, having a radio-frequency invertor (WR) in a half-bridge arrangement, in which invertor two alternatively controllable switches (SH, SL) are provided arranged between one of the outputs of the rectifying circuit (GS) and a first invertor output, and having at least one load circuit (LA) comprising a fluorescent lamp (LL) with a firing capacitor (CZ) connected in parallel and a lamp inductor (L) connected in series with the fluorescent lamp, the lamp inductor being connected to the first invertor output and the free lamp terminal being connected to the second invertor output, characterized in that in the invertor (WR) two series-connected clamping diodes (DBH, DBL) whose common tie point forms a second invertor output are, in addition, connected between the outputs of the rectifier circuit (GS) in a manner inversely polarized relative to the rectified AC supply voltage, and in that in the invertor (WR) a half-bridge capacitor (CH) is, moreover, arranged between the output of the rectifier circuit (GS), which output is at frame potential, and the second invertor output, and in that, finally, there is provided in the invertor (WR) a sine correction capacitor (CS) which is connected, on the one hand, to the tie point of the charging inductor and coupling diode of the rectifier circuit and, on the other hand, to the second invertor output.
  2. Electronic ballast according to Claim 1, characterized in that the charging inductor (LK) is selected so large that it completely reverses its charge in the rhythm of the radio-frequency switching rate of the invertor (WR) only in the region of the zero crossings of the AC supply.
  3. Electronic ballast according to one of the preceding claims, characterized in that a harmonic filter (FE) is connected upstream of the rectifier circuit (GS).
  4. Electronic ballast according to one of the preceding claims, characterized in that the magnitude of the bridge capacitor (CH) of the invertor (WR) has a value at which its charging voltage largely follows the radio-frequency load circuit current.
  5. Electronic ballast according to Claim 4, characterized in that the capacitance of the bridge capacitor (CH) of the invertor (WR) is substantially smaller than the capacitance of the sine correction capacitor (CS).
  6. Electronic ballast according to Claim 5, characterized in that the capacitance ratio of the sine correction capacitor (CS) to the bridge capacitor (CH) has a value of between 1.5 and 4, preferably the value of 2.
EP89107955A 1989-05-02 1989-05-02 Electronic ballast Expired - Lifetime EP0395776B1 (en)

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DE89107955T DE58907116D1 (en) 1989-05-02 1989-05-02 Electronic ballast.
ES89107955T ES2049772T3 (en) 1989-05-02 1989-05-02 ELECTRONIC ADAPTER.
AT89107955T ATE102428T1 (en) 1989-05-02 1989-05-02 ELECTRONIC BALLAST.
EP89107955A EP0395776B1 (en) 1989-05-02 1989-05-02 Electronic ballast
JP2111898A JP2690382B2 (en) 1989-05-02 1990-05-01 Electronic auxiliary equipment for fluorescent lamps
HK123195A HK123195A (en) 1989-05-02 1995-07-27 Electronic ballast

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EP0395776B1 true EP0395776B1 (en) 1994-03-02

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EP0488478A2 (en) * 1990-11-27 1992-06-03 Matsushita Electric Works, Ltd. Inverter device
EP0585077A1 (en) * 1992-08-25 1994-03-02 General Electric Company Power supply circuit with power factor correction
EP0606665A1 (en) * 1993-01-12 1994-07-20 Koninklijke Philips Electronics N.V. Circuit arrangement
EP0606664A1 (en) * 1993-01-12 1994-07-20 Koninklijke Philips Electronics N.V. Ballast circuit
GB2256099B (en) * 1990-08-31 1994-10-19 Siew Ean Wong Improvements in electronic ballasts
EP0757420A1 (en) 1995-08-04 1997-02-05 Siemens Aktiengesellschaft Electric ballast with inrush current limitation and overvoltage protection
US5610479A (en) * 1992-11-13 1997-03-11 Patent-Treuhand-Gesellschaft Fur Elektrische Gluhlampen Mbh Circuit arrangement for operating low-pressure discharge lamps
EP0831677A2 (en) * 1996-09-24 1998-03-25 Mass Technology (H.K.) Ltd. Electronic ballast for fluorescent lamp
US5798617A (en) 1996-12-18 1998-08-25 Pacific Scientific Company Magnetic feedback ballast circuit for fluorescent lamp
US5866993A (en) 1996-11-14 1999-02-02 Pacific Scientific Company Three-way dimming ballast circuit with passive power factor correction
US5925986A (en) 1996-05-09 1999-07-20 Pacific Scientific Company Method and apparatus for controlling power delivered to a fluorescent lamp
US5955841A (en) 1994-09-30 1999-09-21 Pacific Scientific Company Ballast circuit for fluorescent lamp
US5982111A (en) 1994-09-30 1999-11-09 Pacific Scientific Company Fluorescent lamp ballast having a resonant output stage using a split resonating inductor
US6037722A (en) 1994-09-30 2000-03-14 Pacific Scientific Dimmable ballast apparatus and method for controlling power delivered to a fluorescent lamp

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DE4237262A1 (en) * 1992-11-04 1994-05-05 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Circuit arrangement for high-frequency operation of a consumer
CN1050493C (en) * 1993-01-16 2000-03-15 浙江照明电器总公司 High power factor electronic lamp with protector for abnormal condition
CN1054726C (en) * 1993-01-30 2000-07-19 皇家菲利浦电子有限公司 Circuit arrangement
CN1049553C (en) * 1993-01-30 2000-02-16 皇家菲利浦电子有限公司 Ballast circuit
EP0885550A1 (en) * 1996-03-06 1998-12-23 Tecninter Ireland Limited An electronic ballast for a compact fluorescent lamp
US6107753A (en) * 1998-12-18 2000-08-22 Philips Electronics North America Corporation Radio frequency electronic ballast with integrated power factor correction stage
CN2515919Y (en) * 2001-12-05 2002-10-09 马士科技有限公司 Adjustable light fluorescent lamp device using mached with silicon controlled PM light modulator
US7122972B2 (en) 2003-11-10 2006-10-17 University Of Hong Kong Dimmable ballast with resistive input and low electromagnetic interference
EP2104402A1 (en) * 2008-03-17 2009-09-23 Chuan Shih Industrial Co., Ldt. Electronic ballast for fluorescent lamps

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Publication number Priority date Publication date Assignee Title
GB2256099B (en) * 1990-08-31 1994-10-19 Siew Ean Wong Improvements in electronic ballasts
EP0488478A3 (en) * 1990-11-27 1992-10-14 Matsushita Electric Works, Ltd. Inverter device
EP0488478A2 (en) * 1990-11-27 1992-06-03 Matsushita Electric Works, Ltd. Inverter device
EP0585077A1 (en) * 1992-08-25 1994-03-02 General Electric Company Power supply circuit with power factor correction
US5610479A (en) * 1992-11-13 1997-03-11 Patent-Treuhand-Gesellschaft Fur Elektrische Gluhlampen Mbh Circuit arrangement for operating low-pressure discharge lamps
EP0606665A1 (en) * 1993-01-12 1994-07-20 Koninklijke Philips Electronics N.V. Circuit arrangement
EP0606664A1 (en) * 1993-01-12 1994-07-20 Koninklijke Philips Electronics N.V. Ballast circuit
US5955841A (en) 1994-09-30 1999-09-21 Pacific Scientific Company Ballast circuit for fluorescent lamp
US5982111A (en) 1994-09-30 1999-11-09 Pacific Scientific Company Fluorescent lamp ballast having a resonant output stage using a split resonating inductor
US6037722A (en) 1994-09-30 2000-03-14 Pacific Scientific Dimmable ballast apparatus and method for controlling power delivered to a fluorescent lamp
EP0757420A1 (en) 1995-08-04 1997-02-05 Siemens Aktiengesellschaft Electric ballast with inrush current limitation and overvoltage protection
US5925986A (en) 1996-05-09 1999-07-20 Pacific Scientific Company Method and apparatus for controlling power delivered to a fluorescent lamp
EP0831677A2 (en) * 1996-09-24 1998-03-25 Mass Technology (H.K.) Ltd. Electronic ballast for fluorescent lamp
AU737784B2 (en) * 1996-09-24 2001-08-30 Mass Technology (H.K.) Ltd. An electronic ballast for a fluorescent lamp
US5866993A (en) 1996-11-14 1999-02-02 Pacific Scientific Company Three-way dimming ballast circuit with passive power factor correction
US5798617A (en) 1996-12-18 1998-08-25 Pacific Scientific Company Magnetic feedback ballast circuit for fluorescent lamp

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JP2690382B2 (en) 1997-12-10
EP0395776A1 (en) 1990-11-07
HK123195A (en) 1995-08-04
JPH02304896A (en) 1990-12-18
DE58907116D1 (en) 1994-04-07
ES2049772T3 (en) 1994-05-01
ATE102428T1 (en) 1994-03-15

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