EP0473679B1 - Entladungsleuchteinheit mit änderlicher lichtintensität - Google Patents

Entladungsleuchteinheit mit änderlicher lichtintensität Download PDF

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Publication number
EP0473679B1
EP0473679B1 EP90908615A EP90908615A EP0473679B1 EP 0473679 B1 EP0473679 B1 EP 0473679B1 EP 90908615 A EP90908615 A EP 90908615A EP 90908615 A EP90908615 A EP 90908615A EP 0473679 B1 EP0473679 B1 EP 0473679B1
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EP
European Patent Office
Prior art keywords
filament
light intensity
discharge lamp
direct current
anode
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
Application number
EP90908615A
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English (en)
French (fr)
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EP0473679A1 (de
Inventor
Jozsef Ladanyi
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Individual
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Individual
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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
    • H05B41/16—Circuit arrangements in which the lamp is fed by DC or by low-frequency AC, e.g. by 50 cycles/sec AC, or with network frequencies
    • H05B41/18—Circuit arrangements in which the lamp is fed by DC or by low-frequency AC, e.g. by 50 cycles/sec AC, or with network frequencies having a starting switch
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/39—Controlling the intensity of light continuously
    • H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
    • H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
    • H05B41/3927—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations by pulse width modulation

Definitions

  • the invention relates to a discharge lamp unit with variable light intensity, especially for light display boards, comprising a discharge lamp having a compact discharge tube with two filaments arranged at two end regions thereof and serving as a cathode and an anode, respectively, an ignition circuit coupled to the lamp, a direct current source coupled to anode and cathode electrodes of the lamp and a light intensity adjusting circuit connected in the anode to cathode path of the lamp.
  • Discharge lamp units with variable light intensity are generally used for large light display boards, in which the basic picture element of the board is made of a gas discharge element of special design, wherein several anodes are arranged in a common envelope opposite to a common heated cathode electrode, and in the interior of the envelope fluorescent layers emitting different colored light are associated with the respective anode regions.
  • a further drawback comes from the limited lifetime of the filament of the discharge tubes used in pulse mode.
  • the emission is uneven along the cathode surface, and the extent of emission starts to decrease in the end regions of the filament even after a shorter use. This desrease slowly moves toward the central portion of the filament. By the time the emission decrease reaches the central portion of the filament, the cathode looses its emission capability and the tube cannot be used any more.
  • US-A-4777409 describes a discharge lamp unit according to the prior art comprising a discharge lamp having a compact discharge tube with two filaments arranged at two end regions thereof, wherein the filaments are connected in series with each other through a bimetall switch.
  • both filaments are heated in the closed state of the bimetall swich, which is opened when the discharge process has started.
  • a DC supply voltage is applied to the discharge tube through a controlled switch, which is regulated by means of a switching regulator such that the current drawn by the lamp is maintained at a substantially constant value.
  • the object of the invention is to provide a discharge lamp unit which can provide an increased cathode lifetime, which has an increased light utilization effectivity and which enables the use of mass-produced discharge lamps.
  • a discharge lamp unit with variable light intensity has been provided especially for light display boards, which comprises:a discharge lamp having a compact discharge tube with two filaments arranged at two end regions thereof, both ends of the first filament being connected to terminals of a heating source, said first filament being permanently heated during operation and serving as a cathode, said second filament being left unheated and serving as an anode; a direct current source with a positive and a negative terminal, the negative terminal being connected to the heating source; a light intensity adjusting circuit coupled between the positive terminal of the direct current source and the second filament, said light intensity adjusting circuit comprising a controlled switch periodically enabling or disabling at least a major portion of the current corresponding to maximum light intensity to pass therethrough with an on-off ratio that corresponds to the required light intensity; and an ignition circuit coupled to the lamp.
  • the compact discharge tube with two filaments can be exposed to pulse control mode, and if one of the cathodes looses its emission or gets broken, then the tube can be inserted in opposite position into its socket, whereby the filament which was used previously as an anode will thereafter be used as a cathode. This possibility doubles the lifetime of the compact discharge tube.
  • a further increase in lifetime comes from the use of an alternative current heating source i. e. a heating transformer, wherein the end terminals of the first filament are connected to the secondary winding of the heating transformer, and the negative terminal of the direct current source is connected to central tap point of the secondary winding.
  • an alternative current heating source i. e. a heating transformer, wherein the end terminals of the first filament are connected to the secondary winding of the heating transformer, and the negative terminal of the direct current source is connected to central tap point of the secondary winding.
  • both end terminals of the second filament which forms the anode electrode are interconnected and they are coupled directly or through a resistor to the controlled switch and through the switch to positive terminal of the direct current source.
  • the pulse control can be solved in an easier way if a second resistor is connected between the positive terminal and the anode with a resistance value being by at least one order of magnitude higher than that of the resistor in the switched path.
  • the display board has preferably in each picture point three discharge lamp units, and every one of these lamp triplets comprises compact discharge tubes emitting red, green and blue light, respectively.
  • Fig. 1 shows the control circuit of a compact discharge tube 1.
  • Filament 2 of the compact discharge tube 1 is coupled to source 3 which provides a constant filament voltage, while the tube has a second filament 4 which, in operation, serves as an anode and it is not heated.
  • the source 3 is formed by heater transformer coupled to the mains network, the transformer has a secondary winding that provides a 7 V heating voltage for the tube 1 and a central tap point 9 is lead out from the secondary winding.
  • the central tap point 9 is coupled to negative terminal V- of a DC power supply which forms an earth point.
  • the positive terminal V+ of the power supply is connected to a first resistor R1 and to a series member consisting of a controlled switch 5 and a second resistor R2.
  • the other ends of the resistors R1 and R2 are interconnected and coupled through wire 10 to both terminals of filament 4 which is arranged in an end region of the compact discharge tube 1. This end region lies opposite to the one in which the filament 2 that forms the cathode is arranged.
  • the controlled switch 5 has a control input which receives rectangular pulses with adjustable width. During the on periods of these pulses the controlled switch 5 is in conducting state, whereby the resistors R1 and R2 are connected in parallel. During the off periods of the pulses the controlled switch 5 is in non-conducting state, therefore between the positive terminal V+ and the filament 4 the current can flow only through the resistor R1.
  • the ignition of the compact discharge tube 1 is enabled by a capacitive ignition electrode 6 covering a portion of the envelope of the tube 1.
  • the ignition electrode 6 is connected through pulse transformer 7 to pulse generator 8 which provides ignition pulses in 1.5 ⁇ 2 second intervals.
  • a matrice-like light display board 11 shown in Fig. 2 is obtained with pixel points formed by respective single compact discharge tubes.
  • a color display board is obtained if each pixel element is formed by three compact discharge tubes la, lb and lc having red, blue and green colors.
  • the U-shaped design of conventional compact discharge tubes and their standard width of 25 mm enable the formation of a display board 11, in which the pixel size is about 60-70 mm.
  • the compact tubes were shown at the first pixel point only, and all other points have similar design.
  • Fig. 3 in which the operational voltage between the filaments 2 and 4 is shown as a function of time.
  • a nominal heating voltage i. e. an AC voltage of 50 Hz frequency and 7 V effective value
  • the zero line of the direct current supply voltage will vary as shown in Fig. 3.
  • the heating voltage of 7V is symmetrical to the zero line of the DC voltage only therefore because the heating source 3 supplies a voltage which is symmetrical to the ground potential.
  • the AC voltage of 7 V applied to the two ends of the filament 2 is evenly distributed along the filament.
  • the filament 4 which serves as an anode
  • curve 2a shows the potential of the first end of the filament 2
  • curve 2b shows the potential of the second end of the filament 2
  • the zero axis designated as 2c shows the potential of the central point of the filament 2.
  • the potentials of the two ends of the filament 2 with respect to the anode correspond to waveforms, in which respective AC voltages of ⁇ 3.5 V are superimposed on the DC anode voltage.
  • the voltage required for maintaining gas discharge is between about 33 ⁇ 35 V. If a ground Potential is provided at the central point of the filament 2 as suggested by the present invention, then the filament 2 will always have an at least 50 % long section which has a potential with respect to the opposite filament 4, i.e. to the anode, that is at least as high as the voltage of the V+ terminal or higher, and this section is sufficient for maintaining the discharge process.
  • the DC voltage V+ can thus be adjusted to correspond to 33 ⁇ 35 V. If the point of the filament 2 is considered as the momentary maximum of the current emission which is the most negative compared to the anode, then in view of the curves of Fig.
  • Firing pulses are coupled to the ignition electrode 6 through the pulse transformer 7. Although the discharge process can be started by a single ignition pulse, these pulses are repeated in 1 ⁇ 2 second long periods in order to ensure the ignited state of the compact discharge tube 1 also in cases if the anode current has broken due to any accidental reason.
  • the value of the discharge current is determined by the state of the controlled switch 5.
  • the resistors R1 and R2 are connected in parallel, and their values are chosen so that they ensure a tube current of about 150 mA. In that case the tube lights with maximum intensity.
  • a minimum current of 1 ⁇ 1.5 mA is allowed by the resistor R1 to flow through the tube which is just sufficient for maintaining the discharge process, whereby noticeable light is not generated.
  • the maintained discharge process ensures that the current of the tube can be increased instantaneously i.e. without any delay.
  • the light intensity is determined by the ratio of the on and off times of the pulses coupled to the control input of the controlled switch 5 and this ratio can be changed easily.
  • any required color and up to a maximum any intensity can be adjusted by the appropriate control of the tubes from which respective different colored triplets are arranged in these points.
  • the speed of this control can be higher than the time resolution of the human eye, whereby moving inscriptions and moving pictures can also be displayed.
  • the advantages of the invention lie first in the increased lifetime of the compact discharge tube 1 owing to the suggested way of heating, second in the interchangeability of the filaments 2 and 4 because if the heated filament gets broken or looses its emission, the tube can be inserted in an opposite position in the socket and the positions of the filaments 2 and 4 get interchanged, and the filament 4 which was used previously as an anode can be used as cathode and the filament 2 can serve as the anode even in broken form or if it has no emission any more. By this possibility the increased lifetime can be doubled. The decrease of the operational DC voltage spares energy.
  • a further substantial advantage comes from the possibility of using mass produced, commercially available compact discharge tubes for forming elements of the display board 11, since this reduces manufacturing costs by a significant extent.

Landscapes

  • Circuit Arrangements For Discharge Lamps (AREA)
  • Discharge Lamp (AREA)
  • Lasers (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)
  • Endoscopes (AREA)
  • Gas-Filled Discharge Tubes (AREA)
  • Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
  • Discharge Lamps And Accessories Thereof (AREA)

Claims (5)

  1. Entladungslampeneinheit mit veränderlicher Lichtintensität, insbesondere für Leuchtanzeigetafeln, mit einer Entladungslampe, die ein Kompaktentladungsrohr (1) mit zwei in dessen zwei Endbereichen angeordneten Glühfäden (2, 4) aufweist, wobei beide Enden des ersten Glühfadens (2) an Anschlüsse einer Heizquelle (3) angeschlossen sind, der erste Glühfaden (2) während des Betriebs dauernd geheizt wird und als Kathode dient, der zweite Glühfaden (4) nicht geheizt ist und als Anode dient; einer Gleichstromquelle mit einem positiven und einem negativen Anschluß (V+ und V-), wobei der negative Anschluß (V-) an die Heizquelle (3) angeschlossen ist; einer zwischen den positiven Anschluß (V+) der Gleichstromquelle und den zweiten Glühfaden (4) eingekoppelten Lichtintensitäts-Einstellschaltung, welche einen gesteuerten Schalter (5) aufweist, von welchem periodisch zugelassen oder nicht zugelassen wird, daß wenigstens ein Hauptteil des der maximalen Lichtintensität entsprechenden Stromes mit einem der erforderlichen Lichtintensität entsprechenden Ein-Aus-Verhältnis durch den Schalter (5) hindurchtritt; und einem an die Lampe (1) gekoppelten Zündkreis.
  2. Entladungslampeneinheit nach Anspruch 1, dadurch gekennzeichnet, daß die Heizquelle (3) einen Heiztransformator aufweist, wobei die Endanschlüsse des ersten Glühfadens an die Sekundärwicklung des Heiztransformators angeschlossen sind, und der negative Anschluß (V-) der Gleichstromquelle an eine Zentralabgriffstelle (9) der Sekundärwiklung angeschlossen ist.
  3. Entladungslampeneinheit nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß beide Endanschlüsse des die Anodenelektrode bildenden zweiten Glühfadens (4) miteinander verbunden sind und über einen Widerstand (R2) unmittelbar an den gesteuerten Schalter (5), und über diesen an den positiven Anschluß (V+) der Gleichstromquelle gekoppelt sind.
  4. Entladungslampeneinheit nach Anspruch 3, dadurch gekennzeichnet, daß ein zweiter Widerstand (R1) zwischen den positiven Anschluß (V+) und die Anode mit einem Widerstandswert geschaltet ist, der wenigstens um eine Größenordnung größer ist als der des Widerstandes (R2) in dem geschalteten Zweig.
  5. Leuchttafel mit drei Entladungslampeneinheiten, jeweils wie im Anspruch 1 oder 2 beansprucht, welche drei Entladungslampeneinheiten in jedem Bildpunkt der Anzeigetafel angeordnet sind, wobei jeder von diesen Lampen-Drillingen Kompaktentladungsrohre (1) aufweist, welche rotes, grünes bzw. blaues Licht emittieren.
EP90908615A 1989-05-25 1990-05-25 Entladungsleuchteinheit mit änderlicher lichtintensität Expired - Lifetime EP0473679B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
HU268189 1989-05-25
HU892681A HU202701B (en) 1989-05-25 1989-05-25 Fluorescent lamp unit of controllable light intensity
PCT/HU1990/000037 WO1990014746A1 (en) 1989-05-25 1990-05-25 Discharge lamp unit with variable light intensity

Publications (2)

Publication Number Publication Date
EP0473679A1 EP0473679A1 (de) 1992-03-11
EP0473679B1 true EP0473679B1 (de) 1995-02-22

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ID=10960610

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Application Number Title Priority Date Filing Date
EP90908615A Expired - Lifetime EP0473679B1 (de) 1989-05-25 1990-05-25 Entladungsleuchteinheit mit änderlicher lichtintensität

Country Status (7)

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EP (1) EP0473679B1 (de)
AT (1) ATE118955T1 (de)
DE (1) DE69017209T2 (de)
ES (1) ES2071098T3 (de)
HU (1) HU202701B (de)
RU (1) RU2095946C1 (de)
WO (1) WO1990014746A1 (de)

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2536563B1 (fr) * 1982-11-23 1985-07-26 Ssih Equipment Sa Element emetteur de lumiere a tube a decharge pour tableau d'affichage matriciel
DE3331996A1 (de) * 1983-09-05 1985-03-21 Siemens AG, 1000 Berlin und 8000 München Hilfseinrichtung zum regulieren der helligkeit von niederspannungs-leuchtstofflampen
US4777409A (en) * 1984-03-23 1988-10-11 Tracy Stanley J Fluorescent lamp energizing circuit
HU201193B (en) * 1988-06-21 1990-09-28 Jozsef Ladanyi Process and switchgear for regulating the light intensity of gas-discharge tubes

Also Published As

Publication number Publication date
ATE118955T1 (de) 1995-03-15
EP0473679A1 (de) 1992-03-11
ES2071098T3 (es) 1995-06-16
RU2095946C1 (ru) 1997-11-10
WO1990014746A1 (en) 1990-11-29
DE69017209T2 (de) 1995-09-28
HU202701B (en) 1991-03-28
DE69017209D1 (de) 1995-03-30

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