EP0243948B1 - Control circuit for an arc lamp - Google Patents

Control circuit for an arc lamp Download PDF

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Publication number
EP0243948B1
EP0243948B1 EP87106228A EP87106228A EP0243948B1 EP 0243948 B1 EP0243948 B1 EP 0243948B1 EP 87106228 A EP87106228 A EP 87106228A EP 87106228 A EP87106228 A EP 87106228A EP 0243948 B1 EP0243948 B1 EP 0243948B1
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EP
European Patent Office
Prior art keywords
switch
current
switch arrangement
control circuit
arc lamp
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EP87106228A
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German (de)
French (fr)
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EP0243948A2 (en
EP0243948A3 (en
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Michael Dipl.-Ing. Schmidt
Wilfried Dipl.-Ing. Brauckmann
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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
    • H05B41/288—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices and specially adapted for lamps without preheating electrodes, e.g. for high-intensity discharge lamps, high-pressure mercury or sodium lamps or low-pressure sodium lamps
    • H05B41/292—Arrangements for protecting lamps or circuits against abnormal operating conditions

Definitions

  • the invention relates to a control circuit for an arc lamp with two terminals for connecting a DC voltage, a switch arrangement of four switches connected in the manner of a bridge, the first diagonal connection points of which are connected in series with a choke inductance which limits the current intensity and the arc lamp is located between the second diagonal connection points , with a control arrangement which alternately switched through or opens the switches located opposite in the bridge, and with a current regulator connected upstream of the switch arrangement.
  • the arc lamp glows as a result of the formation of a plasma between the two electrodes of the arc lamp.
  • the arc lamps must be subjected to a constantly changing current direction, the alternating frequency being between 50 and 200 Hz. It is known to operate the arc lamp directly with the AC line voltage, the current rise resulting from the plasma formation being limited by a choke inductor connected in series with the arc lamp.
  • Such a control circuit requires a relatively large choke coil, which takes up a relatively large amount of space and contributes to a relatively high weight of the ballast.
  • Another disadvantage of the known control circuit is that due to the constantly changing direction of current through the inductor, the current rise speed becomes very low, so that the plasma formed between the electrodes of the arc lamp cools down and has to be ignited practically anew with each current change. As a result, the service life of the arc lamp is severely impaired.
  • Another disadvantage is that with this control strong light dips are observed in time with the mains frequency, which lead to the fact that when using such a lamp for filming a synchronization with the arc lamp must be carried out so as not to insufficiently expose partial images of the film .
  • a control circuit of the type mentioned is known.
  • This control circuit is operated with direct voltage, with the choke inductor always having a direct current flowing through it, ie with the same current direction.
  • the change in current direction is carried out by the switch arrangement exclusively for the arc lamp and can be carried out with a clock frequency. It follows from this that a smaller inductor can be used, so that the current rise rate can be chosen to be sufficiently large to prevent the cooling of the plasma when the current direction changes in the arc lamp below a critical value, so that the plasma is always kept hot remains. This significantly extends the life of the Uchtbogen lamp. Due to the smaller inductor, the weight and the space required for the control circuit can be significantly reduced.
  • the operation of the known control circuit is based on the fact that in the bridge arrangement of the switches the diagonally opposite switches are closed or opened together and that the other two switches are opened or closed accordingly in the same cycle. Two alternating current paths are formed by the respective switch pairs.
  • the switch arrangement therefore acts as a changeover switch, so that one or the other current path is always conductive. Due to the semiconductor switches usually used, the transition from the renting state to the blocking state and vice versa does not occur suddenly, since charge carrier accumulations are broken down in a similar time. There is therefore a certain overlap of the (still or already) conductive states of semiconductor switches lying next to one another in the bridge, as a result of which a short circuit is caused. This closing of the course is not serious for the control of low electrical outputs, because the current regulator reacts to this. However, regulation with the current regulator is problematic for higher electrical outputs.
  • the invention has for its object to provide a control circuit of the type mentioned in such a way that a short circuit between the diagonal connection points is reliably avoided, so that higher electrical powers can also be switched.
  • the inventive insertion of a line break in the switch arrangement ensures that a short circuit between the diagonal connection points is avoided. Since the current control drives current into the switch arrangement during this line break, this is buffered by the additional circuit with the storage capacitor.
  • the resistor connected in parallel with the diode which is polarized in the current direction ensures a gradual discharge of the storage capacitor when the switch arrangement is again conductive.
  • an electronically controllable switch is arranged at an end of the series circuit comprising a choke inductor and a switch arrangement, a free-wheeling diode connecting the connection point between the switch and the series circuit to the other connection terminal.
  • the electronically controllable switch is switched on or off at a high frequency.
  • this circuit of the electronic switch takes place depending on the current flowing in the series circuit instead.
  • the control of the electronic switch can also be determined empirically - that is to say without a control circuit working with a current sensor.
  • the choke inductance is formed by at least two coils which are connected on both sides of the switch arrangement.
  • the smoothing of the current regulated by the switch in the series circuit can be further improved by the fact that the coils on both sides of the switch arrangement are divided into several partial coils and that the associated connection points on both sides of the switch arrangement are connected to one another by smoothing capacitors.
  • the control circuit shown in FIG. 1 has two terminals 1, 2 to which a direct voltage U1 can be applied.
  • a series connection of several coils L i , L i ', L i n' is connected to terminal 1, the free end of which is connected to a connection point 3 of a switch arrangement 4.
  • the other end of the switch arrangement is formed by a connection point 5 to which the series connection of further coils L 2 , L 2 '... L 2 n ' is connected, the other end of which is connected to the second connection terminal 2 via an electronically controlled switch S5 .
  • the connection point between the switch S5 and the first coil L 2 connected to it is connected to the first connection terminal 1 via a free-wheeling diode D5.
  • the connection points between the sub-coils L1, L1 '..., L2, L2' are each connected to one another via a smoothing capacitor C '...
  • the switch arrangement 4 has four transistor switches S1, S2, S3, S4, which are connected in the manner of a bridge. With the connection point 3 two of the transistor switches S1, S2 are connected in parallel, the other ends of which lie at the two ends of an arc lamp 6, which can be a metal vapor arc discharge lamp (HMI lamp). The two ends of the arc lamp 6 form two connection points 7, 8 of the bridge arrangement, to which two further transistor switches S3, S4 are connected, which are connected to one another at connection point 5 of the switch arrangement 4.
  • Each of the transistor switches S1 ... S4 is connected with a free-wheeling diode D1, D2, D3, D4 anti-parallel - that is, against the current direction specified by the connection terminals 1, 2.
  • connection in series of a diode D6 which is passed in the normal current direction and a charging capacitor C1 is also connected to the connection points 3, 5, the diode D6 being bridged by a resistor R1.
  • a galvanically isolated current sensor 9 which surrounds the conductor and inductively measures the current intensity, is arranged within the series arrangement formed by the coil L 1 ... L 2 ... Inductively forming a choke.
  • the current sensor 9 also preferably detects the conductor located between the resistor R1 and the connection point 3 of the switch arrangement 4.
  • the circuit part behind the connection terminals 1, 2 with the current sensor 9, the partial coils Li, Li ', etc., L 2 L 2 ', etc., the smoothing capacitor C ', the freewheeling diode D5 and the switch S5 forms a high-frequency current regulator 10.
  • Switch arrangement 4 is switched over at intervals of 50 to 200 Hz. Starting from the state described above, the switches S1, S4 are opened and the switches S2, S3 are closed, so that the current from connection point 3 now via the switch S2 through the arc lamp in FIG. 1 from right to left and through the switch S3 to Connection point 5 flows.
  • the commutation of the current direction by the arc lamp accordingly does not lead to a commutation of the current direction by the sub-coils Li, Li ', L2, L2', which form the choke inductance. so that excessive cooling of the plasma within the arc lamp 6 can be prevented.
  • the freewheeling diodes D1 to D4 allow the flow of a freewheeling current through the arc lamp 6 in the short period in which all four switching transistors S1 to S4 are blocked. This current is driven by inductances of the connecting lines of the arc lamp.
  • control circuit The function of the control circuit according to the invention can be illustrated using the schematic illustration in FIG. 2:
  • the mains voltage is rectified in a rectifier 11, so that the voltage U 1 is present at the output of the rectifier.
  • the above-described direct current controller 10 regulates the current through the arc lamp 6, which is changed in its direction by the inverter 4 at a relatively low frequency.
  • the control of the switch S5 in the direct current controller 10 as well as the switches S1 to S4 in the switch arrangement 4 serving as an inverter and possibly the rectifier 11 are controlled by a common regulating and control unit 12.
  • the regulating and control unit 12 receives the signal from the current sensor 9, which determines the current strength in the load circuit for the arc lamp 6.
  • the switch S5 can be switched on when the current falls below a lower level and can be switched off when an upper current is exceeded.
  • the switching frequency is variable.
  • the switch S5 can also be switched in a constant frequency grid, the current sensor 9 determining the switch-on time, ie the pulse width.
  • a combination of both methods is also possible. It is advantageous to lower the switching frequency when a pulse width control is carried out after a minimum switch-on time has been reached in order to further reduce the nominal current. After reaching a maximum switch-on time within the specified frequency grid, the switching frequency is reduced in order to achieve a further increase in current.
  • the nominal frequency which can be, for example, 20 kHz, is used between the minimum pulse width and the maximum pulse width.

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  • Circuit Arrangements For Discharge Lamps (AREA)

Description

Die Erfindung betrifft eine Steuerschaltung für eine Lichtbogenlampe mit zwei Anschlußklemmen zum Anschluß einer Gleichspannung, einer Schalteranordnung aus vier nach Art einer Brücke geschalteten Schaltern, deren erste diagonale Anschlußpunkte in Serie mit einer die Stromstärke begrenzenden Drosselinduktivität geschaltet sind und zwischen deren zweiten diagonalen Anschlußpunkten die Lichtbogenlampe liegt, mit einer Steueranordnung, die abwechselnd die in der Brücke gegenüberliegenden Schalter durchschaltete bzw. öffnet, und mit einem der Schalteranordnung vorgeschalteten Stromregler.The invention relates to a control circuit for an arc lamp with two terminals for connecting a DC voltage, a switch arrangement of four switches connected in the manner of a bridge, the first diagonal connection points of which are connected in series with a choke inductance which limits the current intensity and the arc lamp is located between the second diagonal connection points , with a control arrangement which alternately switched through or opens the switches located opposite in the bridge, and with a current regulator connected upstream of the switch arrangement.

Das Leuchten von Lichtbogenlampe entsteht durch die Ausbildung eines Plasmas zwischen den beiden Elektroden der Lichtbogenlampe. Zur Vermeidung einseitiger Abnutzungen der Elektroden müssen die Lichtbogenlampen mit einer ständig wechselnden Stromrichtung beaufschlagt werden, wobei die Wechselfrequenz zwischen 50 und 200 Hz liegt. Es ist bekannt, die Lichtbogenlampe direkt mit der Netzwechselspannung zu betreiben, wobei der durch die Plasmaausbildung entstehende Stromanstieg durch eine in Serie mit der Lichtbogenlampe geschaltete Drosselinduktivität begrenzt wird.The arc lamp glows as a result of the formation of a plasma between the two electrodes of the arc lamp. To avoid one-sided wear of the electrodes, the arc lamps must be subjected to a constantly changing current direction, the alternating frequency being between 50 and 200 Hz. It is known to operate the arc lamp directly with the AC line voltage, the current rise resulting from the plasma formation being limited by a choke inductor connected in series with the arc lamp.

Eine derartige Steuerschaltung benötigt eine relativ große Drosselspule, die relativ viel Platz benötigt und zu einem relativ hohen Gewicht des Vorschaltgeräts beiträgt. Ein weiterer Nachteil der bekannten Steuerschaltung besteht darin, daß durch die ständig wechselnde Stromrichtung durch die Drosselspule die Stromanstiegsgeschwindigkeit sehr gering wird, so daß sich bei jedem Stromwechsel das zwischen den Elektroden der Lichtbogenlampe ausgebildete Plasma abkühlt und praktisch neu gezündet werden muß. Hierdurch wird die Lebensdauer der Lichtbogenlampe stark beeinträchtigt. Eine weiterer Nachteil besteht darin, daß bei dieser Ansteuerung starke Lichteinbrüche im Takt der Netzfrequenz zu beobachten sind, die dazu führen, daß bei der Verwendung einer derartigen Lampe für Filmaufnahmen eine Synchronisation mit der Lichtbogenlampe vorgenommen werden muß, um nicht Teilbilder des Filmes unzureichend zu belichten.Such a control circuit requires a relatively large choke coil, which takes up a relatively large amount of space and contributes to a relatively high weight of the ballast. Another disadvantage of the known control circuit is that due to the constantly changing direction of current through the inductor, the current rise speed becomes very low, so that the plasma formed between the electrodes of the arc lamp cools down and has to be ignited practically anew with each current change. As a result, the service life of the arc lamp is severely impaired. Another disadvantage is that with this control strong light dips are observed in time with the mains frequency, which lead to the fact that when using such a lamp for filming a synchronization with the arc lamp must be carried out so as not to insufficiently expose partial images of the film .

Aus der DE-A-29 04 393 ist eine Steuerschaltung der eingangs erwähnten Art bekannt. Diese Steuerschaltung wird mit Gleichspannung betrieben, wobei die Drosselinduktivität immer von einem Gleichstrom, also mit derselben Stromrichtung, durchflossen wird. Die Änderung der Stromrichtung wird durch die Schalteranordnung ausschließlich für die Lichtbogenlampe durchgeführt und kann mit eienr Taktfrequenz erfolgen. Hieraus ergibt sich, daß eine kleinere Drosselinduktivität verwendet werden kann, so daß die Stromanstiegsgeschwindigkeit ausreichend groß gewählt werden kann, um die Abkühlung des Plasmas beim Wechsel der Stromrichtung in der Lichtbogenlampe unter einen kritischen Wert zu verhindern, so daß das Plasma immer im heißen Zustand erhalten bleibt. Hierdurch wird die Lebensdauer der Uchtbogenlampe entscheidend verlängert. Durch die kleinere Drosselinduktivität läßt sich das Gewicht und der Platzbedarf für die Steuerschaltung wesentlich verringern.From DE-A-29 04 393 a control circuit of the type mentioned is known. This control circuit is operated with direct voltage, with the choke inductor always having a direct current flowing through it, ie with the same current direction. The change in current direction is carried out by the switch arrangement exclusively for the arc lamp and can be carried out with a clock frequency. It follows from this that a smaller inductor can be used, so that the current rise rate can be chosen to be sufficiently large to prevent the cooling of the plasma when the current direction changes in the arc lamp below a critical value, so that the plasma is always kept hot remains. This significantly extends the life of the Uchtbogen lamp. Due to the smaller inductor, the weight and the space required for the control circuit can be significantly reduced.

Die Funktionsweise der bekannten Steuerschaltung beruht darauf, daß in der Brückenanordnung der Schalter die diagonal gegenüber liegenden Schalter gemeinsam geschlossen bzw. geöffnet werden und daß im gleichen Takt die beiden anderen Schalter entsprechend geöffnet bzw. geschlossen werden. Durch die jeweiligen Schalterpaare werden zwei alternierende Strompfade gebildet. Die Schalteranordnung wirkt daher als Umschalter, so daß immer der eine oder der andere Strompfad leitend ist. Aufgrund der üblicherweise verwendeten Halbleiterschalter geht der Übergang von dem lietenden Zustand in den sperrenden Zustand und umgekehrt dabei nicht schlagartig vor sich, da Ladungsträgeransammlungen in ähnlicher Zeit abgebaut werden. Es kommt daher zu gewissen Überlappungen der (noch bzw. bereits) leitenden Zustände von in der Brücke nebeneinanderliegenden Halbleiterschaltern, wodurch ein Kurzschluß verursacht wird. Dieser Kurszchluß ist für die Steuerung niedriger elektrischer Leistungen nicht gravierend, weil der Stromregler hierauf reagiert. Für höhere elektrische Leistungen ist jedoch die Regelung mit dem Stromregler problematisch.The operation of the known control circuit is based on the fact that in the bridge arrangement of the switches the diagonally opposite switches are closed or opened together and that the other two switches are opened or closed accordingly in the same cycle. Two alternating current paths are formed by the respective switch pairs. The switch arrangement therefore acts as a changeover switch, so that one or the other current path is always conductive. Due to the semiconductor switches usually used, the transition from the renting state to the blocking state and vice versa does not occur suddenly, since charge carrier accumulations are broken down in a similar time. There is therefore a certain overlap of the (still or already) conductive states of semiconductor switches lying next to one another in the bridge, as a result of which a short circuit is caused. This closing of the course is not serious for the control of low electrical outputs, because the current regulator reacts to this. However, regulation with the current regulator is problematic for higher electrical outputs.

Der Erfindung liegt die Aufgabe zugrunde, eine Steuerschaltung der eingangs erwähnten Art so auszubilden, daß ein Kurzschluß zwischen den diagonalen Anschlußpunkten sicher vermieden wird, so daß auch höhere elektrische Leistungen geschaltet werden können.The invention has for its object to provide a control circuit of the type mentioned in such a way that a short circuit between the diagonal connection points is reliably avoided, so that higher electrical powers can also be switched.

Diese Aufgabe wird bei einer Steuerschaltung der eingangs erwähnten Art dadurch gelöst, daß parallel zu den ersten diagonalen Anschlußpunkten der Schalteranordnung ein Speicherkondensator in Serie mit einer in Stromflußrichtung gepolten Diode liegt, zu der ein Widerstand parallelgeschaltet ist.This object is achieved in a control circuit of the type mentioned in the introduction in that, parallel to the first diagonal connection points of the switch arrangement, there is a storage capacitor in series with a diode which is polarized in the direction of current flow and to which a resistor is connected in parallel.

Durch die erfindungsgemäße Einfügung einer Leitungspause der Schalteranordnung wird sichergestgellt, daß ein Kurzschluß zwischen den diagonalen Anschlußpunkten vermieden wird. Da die Stromregelung in dieser Leitungspause Strom in die Schalteranordnung treibt, wird diese durch den Zusatzkreis mit dem Speicherkondensator gepuffert. Der der in Stromrichtung gepolten Diode parallelgeschaltete Widerstand sorgt für eine almähliche Entladung des Speicherkondensators, wenn die Schalteranordnung wieder leitend ist.The inventive insertion of a line break in the switch arrangement ensures that a short circuit between the diagonal connection points is avoided. Since the current control drives current into the switch arrangement during this line break, this is buffered by the additional circuit with the storage capacitor. The resistor connected in parallel with the diode which is polarized in the current direction ensures a gradual discharge of the storage capacitor when the switch arrangement is again conductive.

In einer bevorzugten Ausführungsform der erfindungsgemäßen Steuerschaltung ist an einem anschlußklemmenseitigen Ende der Serienschaltung aus Drosselinduktivität und Schalteranordnung ein elektronisch steuerbarer Schalter angeordnet, wobei eine Freilaufdiode den Verbindungspunkt zwischen dme Schalter und der Serienschaltung mit der anderen Anschlußklemme verbindet.In a preferred embodiment of the control circuit according to the invention, an electronically controllable switch is arranged at an end of the series circuit comprising a choke inductor and a switch arrangement, a free-wheeling diode connecting the connection point between the switch and the series circuit to the other connection terminal.

Hierdurch läßt sich eine dosierte Steuerung des durch die Lichtbogenlampe fließenden Stromes erreichen, wodurch gleichzeitig die Möglichkeit eröffnet wird, die Lichtbogenlampe zu dimmen. Hierzu wird der elektronisch steuerbare Schalter hochfrequent ein- bzw. ausgeschaltet. In einer bevorzugten Ausführungsform findet diese Schaltung des elektronischen Schalters in Abhängigkeit von dem in der Serienschaltung fließenden Strom statt. Wenn der Schalter ausgeschaltet wird, wird die Serienschaltung durch die Freilaufdiode zu einem geschlossenen Kreis, in dem weiterhin ein durch die Drosselinduktivität getriebener Strom fließt. Bevor dieser Strom zu stark abfällt, wird der elektronische Schalter wieder geöffnet. Neben der vorzugsweise angewendeten Messung des Stromes in der Serienschaltung läßt sich die Steuerung des elektronischen Schalters auch empirisch - also ohne eine mit einem Stromsensor arbeitende Regelschaltung - ermitteln.As a result, metered control of the current flowing through the arc lamp can be achieved, which at the same time opens up the possibility of dimming the arc lamp. For this purpose, the electronically controllable switch is switched on or off at a high frequency. In a preferred embodiment, this circuit of the electronic switch takes place depending on the current flowing in the series circuit instead. When the switch is turned off, the series connection through the freewheeling diode becomes a closed circuit in which a current driven by the inductor continues to flow. Before this current drops too much, the electronic switch is opened again. In addition to the preferably used measurement of the current in the series circuit, the control of the electronic switch can also be determined empirically - that is to say without a control circuit working with a current sensor.

Zur Symmetrierung der Steuerschaltung ist es vorteilhaft, wenn die Drosselinduktivität durch wenigsten zwei Spulen gebildet ist, die beiderseits der Schalteranordnung angeschlossen sind.For balancing the control circuit, it is advantageous if the choke inductance is formed by at least two coils which are connected on both sides of the switch arrangement.

Die Glättung des durch den Schalter geregelten Stromes in der Serienschaltung kann dadudrch noch verbessert werden, daß die Spulen auf beiden Seiten der Schalteranordnung in mehrere Teilspulen unterteilt sind und daß die zugehörigen Verbindungspunkte auf beiden Seiten der Schalteranordnung durch Glättungskondensatoren miteinander verbunden sind.The smoothing of the current regulated by the switch in the series circuit can be further improved by the fact that the coils on both sides of the switch arrangement are divided into several partial coils and that the associated connection points on both sides of the switch arrangement are connected to one another by smoothing capacitors.

Die Erfindung soll im folgenden anhand eines in der Zeichnung dargestellten Ausführungsbeispiels näher erläutert werden. Es zeigen:

  • Figur 1 - ein Prinzipschaltbild für eine Steuerschaltung für eine Lichtbogenlampe mit Anschlußklemmen für eine Gleichspannung
  • Figur 2 - ein Blockschaltbild für ein komplettes System zur Ansteuerung einer Lichtbogenlampe
The invention will be explained below with reference to an embodiment shown in the drawing. Show it:
  • Figure 1 - a schematic diagram for a control circuit for an arc lamp with terminals for a DC voltage
  • Figure 2 - a block diagram for a complete system for controlling an arc lamp

Die in Figur 1 dargestellte Steuerschaltung weist zwei Klemmen 1,2 auf, an die eine Gleichspannung U1 anlegbar ist. An die Klemme 1 ist eine Serienschaltung mehrerer Spulen Li, Li', Lin' angeschlossen, deren freies Ende mit einem Anschlußpunkt 3 einer Schalteranordnung 4 verbunden ist. Das andere Ende der Schalteranordnung ist durch einen Anschlußpunkt 5 gebildet, an den die Serienschaltung weiterer Spulen L2,L2' ... L2 n' angeschlossen ist, deren anderes Ende über einen elektronisch gesteuerten Schalter S5 mit der zweiten Anschlußklemme 2 verbunden ist. Der Verbindungspunkt zwischen dem Schalter S5 und der ersten an ihn angeschlossenen Spule L2 ist über eine Freilaufdiode D5 mit der ersten Anschlußklemme 1 verbunden. Die Verbindungspunkte zwischen den Teilspulen L1,L1'...,L2,L2' sind jeweils über einen Glättungskondensator C' ... miteinander verbunden.The control circuit shown in FIG. 1 has two terminals 1, 2 to which a direct voltage U1 can be applied. A series connection of several coils L i , L i ', L i n' is connected to terminal 1, the free end of which is connected to a connection point 3 of a switch arrangement 4. The other end of the switch arrangement is formed by a connection point 5 to which the series connection of further coils L 2 , L 2 '... L 2 n ' is connected, the other end of which is connected to the second connection terminal 2 via an electronically controlled switch S5 . The connection point between the switch S5 and the first coil L 2 connected to it is connected to the first connection terminal 1 via a free-wheeling diode D5. The connection points between the sub-coils L1, L1 '..., L2, L2' are each connected to one another via a smoothing capacitor C '...

Die Schalteranordnung 4 weist vier Transistorschalter S1,S2, S3,S4 auf, die nach Art einer Brücke geschaltet sind. Mit dem Anschlußpunkt 3 sind zwei der Transistorschalter S1,S2 parallel verbunden, die mit ihren anderen Enden an den beiden Enden einer Lichtbogenlampe 6 liegen, die eine Metalldampf-Lichtbogenentladungslampe (HMI-Lampe) sein kann. Die beiden Enden der Lichtbogenlampe 6 bilden zwei Anschlußpunkte 7,8 der Brückenanordnung, an die zwei weitere Transistor schalter S3,S4 angeschlossen sind, die am Anschlußpunkt 5 der Schalteranordnung 4 miteinander verbunden sind. Jeder der Transistorschalter S1...S4 ist mit einer Freilaufdiode D1,D2,D3,D4 anti-parallel - also entgegen der durch die Anschlußklemmen 1,2 vorgegebenen Stromrichtung - geschaltet.The switch arrangement 4 has four transistor switches S1, S2, S3, S4, which are connected in the manner of a bridge. With the connection point 3 two of the transistor switches S1, S2 are connected in parallel, the other ends of which lie at the two ends of an arc lamp 6, which can be a metal vapor arc discharge lamp (HMI lamp). The two ends of the arc lamp 6 form two connection points 7, 8 of the bridge arrangement, to which two further transistor switches S3, S4 are connected, which are connected to one another at connection point 5 of the switch arrangement 4. Each of the transistor switches S1 ... S4 is connected with a free-wheeling diode D1, D2, D3, D4 anti-parallel - that is, against the current direction specified by the connection terminals 1, 2.

An die Anschlußpunkte 3,5 ist noch die Serienschaltung einer in der normalen Stromrichtung durchlassenen Diode D6 und eines Ladekondensators C1 angeschlossen, wobei die Diode D6 durch einen Widerstand R1 überbrückt ist.The connection in series of a diode D6 which is passed in the normal current direction and a charging capacitor C1 is also connected to the connection points 3, 5, the diode D6 being bridged by a resistor R1.

Innerhalb des durch die eine Drossel induktiv bildenden Spule L1...L2... und der Schalteranordnung 4 gebildeten Serienanordnung ist ein galvanisch getrennter Stromsensor 9 angeordnet, der den Leiter umgibt und die Stromstärke induktiv mißt. Von dem Stromsensor 9 wird vorzugsweise auch die zwischen dem Widerstand R1 und dem Anschlußpunkt 3 der Schalteranordnung 4 befindliche Leiter erfaßt.A galvanically isolated current sensor 9, which surrounds the conductor and inductively measures the current intensity, is arranged within the series arrangement formed by the coil L 1 ... L 2 ... Inductively forming a choke. The current sensor 9 also preferably detects the conductor located between the resistor R1 and the connection point 3 of the switch arrangement 4.

Der Schaltungsteil hinter den Anschlußklemmen 1,2 mit dem Stromsensor 9, den Teilspulen Li,Li', usw.,L2L2',usw., dem Glättungskondensator C', der Freilaufdiode D5 sowie dem Schalter S5 bildet einen hochfrequenten Stromsteller 10.The circuit part behind the connection terminals 1, 2 with the current sensor 9, the partial coils Li, Li ', etc., L 2 L 2 ', etc., the smoothing capacitor C ', the freewheeling diode D5 and the switch S5 forms a high-frequency current regulator 10.

Die Funktion der beschriebenen Steuerschaltung aus Stromsteller 10, Schalteranordnung 4 und Lichtbogenlampe 6 ist wie folgt:

  • Die an den Klemmen 1,2 anliegende Gleichspannung U1 teilt sich auf in die über die ersten Spulen L1... abfallende Spannung UL1, die über die Lichtbogenlampe 6 abfallende Spannung ULAST und die über den zweiten Spulen L2,L2'... abfallende Spannung UL2. Die Schalter S1 bis S4 der Schalteranordnung 4 seien hierbei so gesteuert, daß S1 und S4 geschlossen sind und S2 und S3 geöffnet sind, so daß der Strom über den Schalter S1 durch die Lichtbogenlampe 6 in der Figur 1 von links nach rechts und durch den Schalter S4 fließen kann. Der Stromsensor 9 detektiert die fließende Stromstärke. Erreicht diese einen oberen Grenzwert, wird der Schalter S5 geöffnet. Die in dem Stromkreis enthaltenen Induktivitäten Li,Ll',L2, L2' usw. treiben einen weiteren Strom durch den Stromkreis, der durch die Freilaufdiode D5 geschlossen ist. Dabei fällt der Strom ab. Erreicht der Strom eine untere zulässige Stromstärke, bewirkt der Stromsensor 9 die Wiedereinschaltung des Schalters S5. Dieser Vorgang geschieht hochfrequent mit einigen 10 bis 100 kHz.
The function of the described control circuit comprising current regulator 10, switch arrangement 4 and arc lamp 6 is as follows:
  • The direct voltage U 1 present at the terminals 1 , 2 is divided into the voltage U L1 dropping across the first coils L 1 ..., the voltage U LAST dropping via the arc lamp 6 and that across the second coils L 2 , L 2 '... falling voltage U L2 . The switches S1 to S4 of the switch arrangement 4 are here controlled so that S1 and S4 are closed and S2 and S3 are open, so that the current through the switch S1 through the arc lamp 6 in FIG. 1 from left to right and through the switch S4 can flow. The current sensor 9 detects the flowing current. If this reaches an upper limit, switch S5 is opened. The inductors L i , Ll ', L 2 , L 2 ' etc. contained in the circuit drive a further current through the circuit, which is closed by the freewheeling diode D5. The current drops. If the current reaches a lower permissible current, the current sensor 9 causes the switch S5 to be switched on again. This process takes place at a high frequency of some 10 to 100 kHz.

Im Takt von 50 bis 200 Hz wird die Schalteranordnung 4 umgeschaltet. Ausgehend von dem oben beschriebenen Zustand werden die Schalter S1,S4 geöffnet und die Schalter S2,S3 geschlossen, so daß der Strom von Anschlußpunkt 3 nunmehr über den Schalter S2 durch die Lichtbogenlampe in der Figur 1 von rechts nach links und durch den Schalter S3 zum Anschlußpunkt 5 fließt. Die Kommutierung der Stromrichtung durch die Lichtbogenlampe führt demgemäß nicht zu einer Kommutierung der Stromrichtung durch die die Drosselinduktivität bildenden Teilspulen Li,Li',L2,L2' usw. Hierdurch wird erreicht, daß der Stromwechsel und der Stromanstieg durch die Lichtbogenlampe sehr schnell erfolgen kann, so daß eine zu starke Abkühlung des Plasmas innerhalb der Lichtbogenlampe 6 verhindert werden kann.Switch arrangement 4 is switched over at intervals of 50 to 200 Hz. Starting from the state described above, the switches S1, S4 are opened and the switches S2, S3 are closed, so that the current from connection point 3 now via the switch S2 through the arc lamp in FIG. 1 from right to left and through the switch S3 to Connection point 5 flows. The commutation of the current direction by the arc lamp accordingly does not lead to a commutation of the current direction by the sub-coils Li, Li ', L2, L2', which form the choke inductance. so that excessive cooling of the plasma within the arc lamp 6 can be prevented.

Während des Stromwechsels, also des Umschaltens der Schalter S1,S4 bzw. S2,S3 ist es erforderlich, daß für eine sehr kurze Zeit alle Schalter gesperrt sind, um keine Kurzschlußströme durch noch teilweise geöffnete Transistorschalter S1 und S3 bzw. S2,S4 zu produzieren. Während der kurzen Zeit, in der alle Schalter Z1 bis S4 gesperrt sind, fließt der Strom von Anschlußpunkt 3 über die Diode D6 in den Ladekondensator Cl , der dadurch aufgeladen wird. Beim Abfall der Spannung zwischen den Anschlußpunkten 3 und 5 kann sich der Kondensator C1 über den Widerstand R1 entladen, indem ein entsprechender Strom in die Anschlußpunkte 3 und 5, und somit in die Lichtbogenlampe 6, eingespeist wird.During the current change, i.e. the switching of the switches S1, S4 or S2, S3, it is necessary that all switches are blocked for a very short time in order not to produce short-circuit currents through transistor switches S1 and S3 or S2, S4 that are still partially open . During the short time in which all switches Z1 to S4 are blocked, the current from connection point 3 flows via diode D6 into charging capacitor Cl, which is thereby charged. When the voltage between the connection points 3 and 5 drops, the capacitor C1 can discharge via the resistor R1 by feeding a corresponding current into the connection points 3 and 5, and thus into the arc lamp 6.

Die Freilaufdioden D1 bis D4 ermöglichen in der kurzen Zeitspanne, in der alle vier Schalttransistoren S1 bis S4 gesperrt sind, das Fließen eines Freilaufstromes über die Lichtbogenlampe 6. Dieser Strom wird durch Induktivitäten der Anschlußleitungen der Lichtbogenlampe getrieben.The freewheeling diodes D1 to D4 allow the flow of a freewheeling current through the arc lamp 6 in the short period in which all four switching transistors S1 to S4 are blocked. This current is driven by inductances of the connecting lines of the arc lamp.

Die Funktion der erfindungsgemäßen Steuerschaltung kann anhand der schematischen Darstellung in Figur 2 verdeutlicht werden:The function of the control circuit according to the invention can be illustrated using the schematic illustration in FIG. 2:

Die Netzspannung wird in einem Gleichrichter 11 gleichgerichtet, so daß am Ausgang des Gleichrichters die Spannung U1 ansteht. Der oben beschriebene Gleichstromsteller 10 regelt den Strom durch die Lichtbogenlampe 6, der durch den Wechselrichter 4 in seiner Richtung relativ niederfrequent geändert wird. Die Steuerung des Schalters S5 in dem Gleichstromsteller 10 sowie der Schalter S1 bis S4 in der als Wechselrichter dienenden Schalteranordnung 4 und ggf. der Gleichrichter 11 werden durch eine gemeinsame Regel- und Steuereinheit 12 gesteuert. Die Regel- und Steuereinheit 12 erhält das Signal von dem Stromsensor 9, der die Stromstärke in dem Lastkreis für die Lichtbogenlampe 6 feststellt.The mains voltage is rectified in a rectifier 11, so that the voltage U 1 is present at the output of the rectifier. The above-described direct current controller 10 regulates the current through the arc lamp 6, which is changed in its direction by the inverter 4 at a relatively low frequency. The control of the switch S5 in the direct current controller 10 as well as the switches S1 to S4 in the switch arrangement 4 serving as an inverter and possibly the rectifier 11 are controlled by a common regulating and control unit 12. The regulating and control unit 12 receives the signal from the current sensor 9, which determines the current strength in the load circuit for the arc lamp 6.

Für die Steuerung oder Regelung des Gleichstromstellers 10, also das Ein- und Ausschalten des Schalters S5 sind verschiedene Verfahren möglich.Various methods are possible for controlling or regulating the DC chopper 10, that is to say switching the switch S5 on and off.

Der Schalter S5 kann bei Unterschreiten einer unteren Stromstärke eingeschaltet und bei Überschreiten einer oberen Stromstärke abgeschaltet werden. Dabei ist die Schaltfrequenz variabel.The switch S5 can be switched on when the current falls below a lower level and can be switched off when an upper current is exceeded. The switching frequency is variable.

Der Schalter S5 kann aber auch in einem konstanten Frequenz raster geschaltet werden, wobei der Stromsensor 9 die Einschaltzeit, also die Impulsbreite, bestimmt.The switch S5 can also be switched in a constant frequency grid, the current sensor 9 determining the switch-on time, ie the pulse width.

Ferner ist eine Kombination aus beiden Verfahren möglich. So ist es vorteilhaft, bei Durchführung einer Pulsbreitensteuerung nach Erreichen einer minimalen Einschaltzeit zur weiteren Reduzierung des Nennstromes die Schaltfrequenz abzusenken. Nach Erreichen einer maximalen Einschaltzeit innerhalb des vorgegebenen Frequenzrasters wird die Schaltfrequenz verringert, um eine weitere Stromerhöhung zu erreichen. Zwischen der minimalen Pulsbreite und der maximalen Pulsbreite wird mit der Nennfrequenz gearbeitet, die beispielsweise bei 20 kHz liegen kann.A combination of both methods is also possible. It is advantageous to lower the switching frequency when a pulse width control is carried out after a minimum switch-on time has been reached in order to further reduce the nominal current. After reaching a maximum switch-on time within the specified frequency grid, the switching frequency is reduced in order to achieve a further increase in current. The nominal frequency, which can be, for example, 20 kHz, is used between the minimum pulse width and the maximum pulse width.

Claims (5)

1. A control circuit for an arc lamp (6) having two connection terminals (1, 2) for connecting a d.c. voltage (Ui), a switch arrangement (4) comprising four switches (S1, S2, S3, S4) which are connected in the manner of a bridge and whose first diagonal connection points (3, 5) are connected in series with a choke inductor (L1, L1', ...L2, L2', ...) limiting the current intensity, and between the second diagonal connection points (7, 8) of which is located the arc lamp (6), having a control arrangement which alternately triggers and opens the switches (S1, S4 or S2, S3) located opposite one another in the bridge, and a current regulator (S5) connected in series with the switch arrangement (4), characterised in that a storage capacitor (C1) is connected in parallel with the first diagonal connection points (3, 5) of the switch arrangement (4) and in series with a forward biassed diode (D6) connected in parallel with a resistor (R1).
2. A control circuit as claimed in claim 1, characterised in that the current regulator is formed by an electronically controllable switch (S5) disposed at one connection terminal end of the series combination comprising the choke inductor (Li, L1', ..., L2, L2', ...) and the switch arrangement (4), that a free- running diode (D5) connects the junction between the switch (S5) and the series combination to the other connection terminal (1), that current sensors (9) are disposed in the series combination comprising choke inductor (L1', L1', ..., L2, L2', ... and switch arrangement (4) on the one hand, and in the circuit formed by diode (D6), resistor (R1) and storage capacitor (C1) on the other hand, the output signals of which current sensors are summatde and applied to a regulating circuit (12) which switches the electronic switch (S5) on and off in dependence upon the total current intensity detected.
3. A control circuit as claimed in claim 1 or 2, characterised in that the choke inductor is formed by at least two coils (L1, L1', ..., L2, L2', ...) which are connected on both sides of the switch arrangement (4).
4. A control circuit as claimed in claim 3, characterised in that the coils at both sides of the switch arrangement (4) are subdivided into a plurality of component coils (L1', L1', ..., L2, L2', ...), and that the associated connection points on both sides of the switch arrangement (4) are interconnected by smoothing capacitors (C').
5. A control circuit as claimed in one of the claims 1 to 4, characterised in that each of the switches (S1 to S4) of the switch arrangement (4) has a respective diode (D1, D2, D3, D4) connected in the opposite direction to the direction of currrent determined by the connection terminals (1, 2).
EP87106228A 1986-04-30 1987-04-29 Control circuit for an arc lamp Expired - Lifetime EP0243948B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3614708 1986-04-30
DE19863614708 DE3614708A1 (en) 1986-04-30 1986-04-30 CONTROL CIRCUIT FOR AN ARC LAMP

Publications (3)

Publication Number Publication Date
EP0243948A2 EP0243948A2 (en) 1987-11-04
EP0243948A3 EP0243948A3 (en) 1988-01-20
EP0243948B1 true EP0243948B1 (en) 1990-09-26

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ID=6299907

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87106228A Expired - Lifetime EP0243948B1 (en) 1986-04-30 1987-04-29 Control circuit for an arc lamp

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EP (1) EP0243948B1 (en)
DE (2) DE3614708A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4301184A1 (en) * 1993-01-19 1994-07-21 B & S Elektronische Geraete Gm Control unit for electrical discharge lamps

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2212995A (en) * 1987-10-23 1989-08-02 Rockwell International Corp Fluorescent lamp dimmer
DE3925654A1 (en) * 1989-08-03 1991-02-07 Schmidt Michael Control unit for discharge lamp(s) - has switches in series connected to DC circuit and diode in parallel in blocking direction
DE4224996A1 (en) * 1992-07-29 1994-02-03 Hella Kg Hueck & Co Ballast for operating high-pressure gas discharge lamps with low-frequency, rectangular voltage in motor vehicles
JP2879514B2 (en) * 1993-01-07 1999-04-05 株式会社小糸製作所 Lighting circuit for vehicle discharge lamps

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1387842A (en) * 1972-02-16 1975-03-19 Thorn Electrical Ind Ltd Ballast circuits for discharge lamps
FR2416617A1 (en) * 1978-02-07 1979-08-31 Signaux Entr Electriques CONVERTER FOR THE POWER SUPPLY OF DISCHARGE LAMPS, AND MORE GENERALLY OF ARC LAMPS, AND ITS APPLICATION TO PROJECTORS FOR SUCH LAMPS

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4301184A1 (en) * 1993-01-19 1994-07-21 B & S Elektronische Geraete Gm Control unit for electrical discharge lamps

Also Published As

Publication number Publication date
EP0243948A2 (en) 1987-11-04
DE3614708A1 (en) 1987-11-19
EP0243948A3 (en) 1988-01-20
DE3765163D1 (en) 1990-10-31

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