EP0152026A1 - Feeding device for controlling the light intensity of at least one discharge lamp, and use of this device - Google Patents

Feeding device for controlling the light intensity of at least one discharge lamp, and use of this device Download PDF

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Publication number
EP0152026A1
EP0152026A1 EP85101029A EP85101029A EP0152026A1 EP 0152026 A1 EP0152026 A1 EP 0152026A1 EP 85101029 A EP85101029 A EP 85101029A EP 85101029 A EP85101029 A EP 85101029A EP 0152026 A1 EP0152026 A1 EP 0152026A1
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EP
European Patent Office
Prior art keywords
lamp
tubes
current
tube
voltage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP85101029A
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German (de)
French (fr)
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EP0152026B1 (en
Inventor
Alberto Tellan
Pierre Desarzens
Philippe Déglon
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.)
Omega Electronics SA
Original Assignee
SSIH Management Services SA
Omega Electronics SA
SSIH EQUIPMENT SA
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Publication of EP0152026A1 publication Critical patent/EP0152026A1/en
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Publication of EP0152026B1 publication Critical patent/EP0152026B1/en
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • 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
    • 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 present invention relates to a supply device for controlling, in response to a setpoint signal, the light intensity of at least one light emitting element comprising at least one discharge lamp and to the use of said device.
  • the system whose operation has just been summarized has the advantage of having an almost instantaneous lighting of the lamp and a good light output.
  • it has the drawback of requiring for each lamp a current stabilizing element called ballast as well as a high cut voltage of the order of 400 volts applied continuously across the terminals of the lamp fitted with its ballast during the periods when it is excited.
  • ballast a current stabilizing element
  • Such a system has the drawback of making it difficult to control the discharge current in the lamp.
  • the same system also has the disadvantage of requiring the use of fluorescent tubes provided with two preheating filaments per tube. This results in the use of an isolation transformer for each of the tubes, which complicates and makes expensive the realization of the whole.
  • Document US-A-3,590,316 describes an apparatus serving as a ballast for a plurality of discharge lamps.
  • this is a very classic ignition system where the ignition and maintenance of the arc are done by means of a single inductance coil.
  • the supply system according to the present invention uses two separate sources of supply, one used for striking the arc and the other for its maintenance and this in order to adjust the brightness of the lamp in a very wide range.
  • the cited patent does not dissociate creation of the arc then maintenance of this arc by two different sources does not allow this extended adjustment and does not allow either to use the system to feed a tube forming part of a point of moving image.
  • US-A-4,132,925 describes a system comprising a starting circuit and a DC ballast for supplying a discharge lamp.
  • the starting circuit becomes inactive and it is the amplitude of the direct current which regulates the brightness of the lamp.
  • US-A-4,219,760 describes a manual system for adjusting the light intensity of a discharge lamp.
  • the power supply which is moreover described very briefly, is by no means a continuous power supply, but a pulsed power supply, which the present invention seeks to avoid.
  • the present invention provides the means which appear in the claims to implement the supply device object of said invention as well as a preferred use of said device.
  • a discharge lamp notably comprises two electrodes to which the control voltages are applied. If the lamp is of the hot cathode type, which is the case for a fluorescent lighting tube, the cathodes are then made of filaments covered with an oxide deposit which promotes the emission of electrons and allows striking an arc between the electrodes if, at the same time, they are subjected to a high voltage pulse. In alternating network lighting technique, this high voltage is created by the opening of a switch (choke) placed at the terminals of the lamp which includes a self (ballast) connected in series in its supply circuit. Once the arc is struck, the supply of filaments is cut and the excitation current in the lamp is maintained to reasonable values using the choke as a current limiter. To this known ignition device, it is possible to add adjustment means also known for adjusting the light intensity emitted by the tube, for example a thyristor, the conduction time of which could be varied.
  • a thyristor the conduction time of which could be varied.
  • the device which has just been described cannot be used to supply one or more discharge lamps where it is desired first to obtain instantaneous ignition and then a large range of variation in brightness. Indeed, on the one hand, the use of the conventional starter causes a delay in ignition and, on the other hand, the conduction periods of a thyristor are limited compared to the power cycle. Tests have also shown that the life of the tube is shortened in fairly large proportions if it is supplied by such an assembly, since the temperature of the electrodes is not sufficient at low light.
  • FIG. 1 is a general diagram which shows the supply device according to the invention of a discharge lamp which is to adjust the light intensity.
  • the discharge lamp 1 is provided with two electrodes 2 and 3.
  • a generator 4 supplies the electrodes, at predetermined periodic intervals T with voltage pulses capable of creating the initiation of the discharge in the lamp.
  • the light intensity emitted by the lamp will depend on the duration of application T c of the current delivered by the source 5 between each voltage pulse delivered by the generator 4.
  • each ignition pulse is followed by a period of application T of a discharge maintenance current, the two signals being synchronous.
  • block 6 symbolizes a synchronization circuit which activates the current source .5 when it has received from generator 4 the information that the voltage pulse has been sent to lamp 1.
  • the light intensity emitted by the lamp will depend on the duration of application of the current from the source 5. This duration is controlled by a setpoint signal imposed by a circuit 7 which interrupts the current from the source 5 as a function of the desired brightness.
  • Figure 2 shows the shape of the voltage at electrodes 2 and 3 of lamp 1 in a first case of very low brightness (figure 2a) and in a second case of brightness close to the maximum (Figure 2b).
  • the pulses 10 from the generator 4 and which are repeated at periodic intervals T are followed by maintaining the arc voltage 11 of very short duration T.
  • the same pulses 10 are followed by a maintenance of the arc voltage 12 whose duration T occupies almost all the space available between two pulses. It can be seen that in this system we are dealing with a duration modulation while the amplitude of the direct current delivered by the source 5 remains substantially constant.
  • the light intensity emitted by the lamp depends on the duration during which a holding current is applied between two ignition pulses and that this duration is controlled by a setpoint signal.
  • This setpoint signal can be given by a simple manual adjustment, for example a potentiometer. It can also be derived from a low frequency signal, for example a musical signal.
  • the present invention however finds its preferred application in the reproduction and display of images or texts whether fixed or animated, in black and white or in color.
  • the setpoint signal can be derived from a video signal.
  • Figure 1 shows a light emitting element composed of a single lamp, preferably a fluorescent tube producing white light.
  • This element and the control device which is linked to it can constitute a light point (pixel) of an image part comprising a group of points.
  • a multiplicity of groups of points can constitute a large-dimensional image as it appears in the giant matrix tables intended for example for stadiums where a large number of spectators are gathered.
  • each light emitting element corresponds a source of holding current 5 so as to be able to vary independently the light intensity produced by the lamp to result in the multiple gradations of light which compose an image. It is then possible to display texts such as sports results, advertising, animated events or resumption of said events by means of cameras, discs or magnetic tapes which carry the set signals in turn controlling the sources of holding current.
  • FIG 3 shows in detail an embodiment of the control device which has been roughly sketched in Figure 1.
  • the element shown in Figure 3 includes three discharge lamps 15, 16 and 17 which are tubes which have been coated l inside the glass walls with different fluorescent substances (phosphor) to obtain three basic colors, for example red, green and blue.
  • three discharge lamps 15, 16 and 17 which are tubes which have been coated l inside the glass walls with different fluorescent substances (phosphor) to obtain three basic colors, for example red, green and blue.
  • Each tube is provided with a cold electrode 18 and a hot electrode 19 which is in the form of a filament.
  • Each filament 19 is permanently supplied by a common power source U 5 .
  • the heating power per tube is of the order of one watt.
  • the filament is covered with emissive oxide and acts as a cathode.
  • FIG. 3 we find the generator 4 already sketched in FIG. 1 and capable of supplying all the tubes at the same time with pulses capable of creating the initiation of the discharge. These pulses appear at terminals S, 0 of generator 4.
  • FIGS. 4 and 5 illustrate two possible embodiments of this generator 4.
  • the generator 4 presented in FIG. 4 essentially consists of a DC voltage source U 4 . a coil 20, an inter switch 21 and a capacitor 22.
  • the energy accumulated in the coil 20 in the form of current during the conduction of the switch 21 is restored in the form of voltage across the terminals of the capacitor 22 during opening. of the switch 21.
  • the value of the accumulated energy is determined by the voltage U 4 , the inductance L of the coil 20 and the accumulation period t 1 - t o , t 0 representing the closing time and t 1 the instant of opening of the switch 21.
  • the accumulated energy can be expressed by the relation
  • a diode 23 is placed in the circuit.
  • the switch 21 is constituted by a transistor of the MOSFET type sized to support the very high voltages which arise at its terminals. We could use for example a part coming from the company Siemens and which bears the symbol BUZ 50 A.
  • the transistor is controlled via line 32 by a block 26 appearing in FIG. 3 and which supplies pulses of predetermined periodic intervals. width t l - t 0 . An example of embodiment of this block is given below.
  • the generator 4 presented in FIG. 5 is a preferred solution for producing this generator when it is a question of priming a very large number of tubes (for example more than thirty tubes). It consists of a direct voltage source U 6 of the order of 900 V and a switch 45. The switch is controlled by the transformer 46 by line 32. When a control pulse is emitted by block 26 (see Figure 3), the switch 45 closes and the high voltage U 6 is transferred to the output terminals S, for a very short time (of the order of 5 ps).
  • the overvoltage pulses emitted by the generator 4 on its terminals S and 0 are applied to the tubes via a diode 24 and a resistor 25.
  • These resistors 25 are intended to limit the arc current in the tube from the moment it is started. This device ensures the lighting of all the lamps by means of a single generator. Otherwise, since the lamps have different starting characteristics, only the lamp requiring the lowest voltage pulse would light up. Indeed, the voltage present at the terminals of the tube once Tare established is significantly lower than the voltage necessary to cause it. An important current would then arise if no precautions were taken. This current would prevent, on the one hand, the priming voltage from reaching sufficient values to ignite the other tubes and could, on the other hand, lead to the destruction of the first primed tube.
  • FIG. 3 there is also found for each of the tubes 15, 16 and 17 a source 5 of direct current for maintaining the discharge, the role of which has been explained in connection with FIG. 1.
  • the current sources 5 are all supplied by a common voltage source U 1 .
  • a current source 5 essentially comprises a cascade of two transistors 26 and 27. The base of transistor 26 is supplied via a resistor 28 by the reference signal from block 29, an exemplary embodiment of which will be given below.
  • the current source 5 delivers a current which is that of the directions of the arrows in the figure and the light intensity of the tubes will depend on the time during which this signal is applied.
  • the current source 5 comprises a safety diode 32 which prevents the destruction of the transistor 26 when said source does not deliver any current.
  • FIG. 3 also shows the mounting of two diodes 24 and 31.
  • the diode 24 prevents the current source 5 from tube feeds another tube via the common line of the surge generator.
  • the diode 31 prevents the overvoltage pulse from the generator 4 from going up to the current source 5.
  • the light emitting element whose operation has just been described generally comprises three fluorescent tubes arranged side by side or nested one inside the other according to arrangements which are the subject of document EP 0 109 671 already cited. It is understood that by measuring the time during which the current is injected into each of the tubes 15, 16 and 17, it is possible to obtain a resultant light, the color of which can be varied over the entire range of visible hues.
  • the additive mixture of the three basic colors can be achieved by a frosted glass which is placed in front of the element. This mixture can also occur naturally if we observe the element with a certain distance.
  • the 32 light tones corresponding to 32 different excitation durations of the tube must find a place between two successive overvoltage pulses. If the sensitivity curve of the eye is taken into account, it should however be noted that the luminance which represents a number of candelas emitted per unit of illuminating surface of the element and which is perceived by the eye is not not a linear function of the tube excitation time. Weber recommends the conversion curve for daytime running light whereas for night lighting we will preferably use the relation advanced by Wyszecky and which is written: where L represents the luminance and S the relative level of excitation of the light source. The present device will make use of the laws given above by assimilating the relative level of excitation to the duration during which the fluorescent tube is supplied.
  • FIG. 6 shows a possible embodiment of the blocks 26 and 29 that are found in FIG. 3. It essentially consists of three circuits 555 well known from the state of the art and referenced 40, 41 and 42.
  • the first circuit 40 is a generator which generates short pulses 50 which are collected on its output 3 and the shape of which is shown in FIG. 7a.
  • the repetition period T r of the pulses depends on the values given to R O + R ' 0 and C 0 . It can be adjusted by varying R0.
  • the pulses 50 in turn control the circuit 41 which is a monostable which engages on the falling edge of the pulse 50 and lengthens said pulse by an amount imposed by the values given to R 1 + R ' 1 and C 1 . It can be adjusted by varying R 1 .
  • the resulting pulse which is also shown in FIG. 7b, is collected at the output 3 of circuit 41 and controls by line 32 either the switch 21 of the generator 4 illustrated in FIG. 4, or the transformer 46 of the generator 4 illustrated in FIG. 5, depending on whether one or the other alternative embodiment is chosen.
  • the block 26 of FIG. 3 is constituted in this embodiment by the circuits 40 and 41 of FIG. 6 to generate the pulse 51 of width t 1 - t 0 .
  • the pulses 51 in turn control the circuit 42 which is also a monostable which engages on the falling edge of the pulse 51 and lengthens said pulse by an amount imposed by the values given to R 2 + R ' 2 and C 2 .
  • the pulse 52 of duration T c which results therefrom, and which is shown in FIG.
  • FIG. 7d shows in addition the voltage which appears at the electrodes of the tube and which is the result of the combination of diagrams 7a, 7b and 7c.
  • the embodiment of Figure 6 allows to vary the light intensity by means of a potentiometric adjustment (R 2 ) which is here the setpoint signal itself. It is clear that this adjustment would be carried out in a completely different manner if the reference signal were to be information delivered by a television camera for example.
  • the camera presents an analog signal at its output which is transformed into a digital signal by a converter.
  • One then finds at the output of the converter 2 32 possible tones corrected according to formulas (1) and (2) given above, one of these tones corresponding to the light intensity of the point analyzed at a precise moment.
  • the digital information is then sent to a counter which will output a signal at its output, the duration of which will correspond to the light intensity analyzed at that time. This signal will finally command a holding current source as explained above.

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  • Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Circuit Arrangements For Discharge Lamps (AREA)

Abstract

Le dispositif permet de commander un élément émetteur de lumière comportant au moins un tube à décharge (1). L'amorçage du tube est réalisé par un générateur (4) qui fournit à intervalles périodiques prédéterminés (Tr) des impulsions de tension. L'intensité lumineuse du tube est commandée par une source de courant continu (5) qui permet d'appliquer au tube un courant de maintien de la décharge dont la durée d'application (Tc) dépend d'un signal de consigne (7). Un circuit (6) permet l'application du courant de maintient en synchronisme avec l'impulsion de tension. Le dispositif trouve son application dans les tableaux d'affichage matriciel.The device makes it possible to control a light emitting element comprising at least one discharge tube (1). The priming of the tube is carried out by a generator (4) which supplies voltage pulses at predetermined periodic intervals (Tr). The light intensity of the tube is controlled by a direct current source (5) which makes it possible to apply a discharge maintenance current to the tube, the duration of application (Tc) of which depends on a set signal (7). . A circuit (6) allows the application of the holding current in synchronism with the voltage pulse. The device finds its application in the matrix display boards.

Description

La présente invention est relative à un dispositif d'alimentation pour commander, en réponse à un signal de consigne, l'intensité lumineuse d'au moins un élément émetteur de lumière comprenant au moins une lampe à décharge et à l'utilisation dudit dispositif.The present invention relates to a supply device for controlling, in response to a setpoint signal, the light intensity of at least one light emitting element comprising at least one discharge lamp and to the use of said device.

Plusieurs systèmes ont déjà été proposés pour régler la luminosité d'une lampe à décharge comme un tube fluorescent, en agissant par exemple sur une commande manuelle qui commande à son tour la conduction d'un thyristor pendant un laps de temps donné. Si l'intensité lumineuse de la lampe à décharge doit être réglée automatiquement, par exemple pour former une image animée composée d'une multiplicité de lampes à partir d'un signal vidéo, on pourrait faire appel à la technique qui consiste à alimenter chaque lampe par un générateur à haute fréquence comme cela est décrit dans la demande de brevet EP 0 109 671. Dans cette technique, le courant transver- sant la lampe est constitué par la juxtaposition de périodes de référence comportant chacune une pluralité d'alternances. On varie l'intensité de lumière émise au moyen d'un élément situé en série dans l'alimentation de la lampe qui permet de contrôler son temps d'allumage par inhibition d'un nombre variable d'alternances contenues dans ladite période de référence.Several systems have already been proposed for adjusting the brightness of a discharge lamp such as a fluorescent tube, for example by acting on a manual control which in turn controls the conduction of a thyristor for a given period of time. If the light intensity of the discharge lamp is to be adjusted automatically, for example to form an animated image composed of a multiplicity of lamps from a video signal, the technique of feeding each lamp could be used. by a high frequency generator as described in patent application EP 0 109 671. In this technique, the current passing through the lamp is formed by the juxtaposition of reference periods each comprising a plurality of alternations. The intensity of the light emitted is varied by means of an element located in series in the power supply of the lamp which makes it possible to control its lighting time by inhibiting a variable number of alternations contained in said reference period.

Le système dont on vient de résumer le fonctionnement a l'avantage de présenter un allumage quasi instantané de la lampe et un bon rendement de lumière. Il présente cependant l'inconvénient de nécessiter pour chaque lampe un élément stabilisateur de courant appelé ballast de même qu'une haute tension découpée de l'ordre de 400 volts appliquée en permancence aux bornes de la lampe munie de son ballast pendant les périodes où elle se trouve excitée. Un tel système présente l'inconvénient de rendre difficile le contrôle du courant de décharge dans la lampe.The system whose operation has just been summarized has the advantage of having an almost instantaneous lighting of the lamp and a good light output. However, it has the drawback of requiring for each lamp a current stabilizing element called ballast as well as a high cut voltage of the order of 400 volts applied continuously across the terminals of the lamp fitted with its ballast during the periods when it is excited. Such a system has the drawback of making it difficult to control the discharge current in the lamp.

Le même système présente encore l'inconvénient d'obliger l'emploi de tubes fluorescents munis de deux filaments de préchauffage par tube. Cela a pour conséquence la mise en oeuvre d'un transformateur d'isolation pour chacun des tubes, ce qui complique et rend onéreuse la réalisation de tout l'ensemble.The same system also has the disadvantage of requiring the use of fluorescent tubes provided with two preheating filaments per tube. This results in the use of an isolation transformer for each of the tubes, which complicates and makes expensive the realization of the whole.

Les documents cités dans le rapport de recherche vont faire maintenant l'objet d'une brève analyse.The documents cited in the research report will now be briefly analyzed.

Le document US-A-3 590 316 décrit un appareil servant de ballast à une pluralité de lampes à décharge. Il s'agit cependant là d'un système d'allumage très classique où l'amorçage et l'entretien de l'arc se font au moyen d'une seule bobine à inductance. Au contraire de cela, et comme cela apparaîtra par la suite, le système d'alimentation selon la présente invention fait appel à deux sources distinctes d'alimentation, l'une servant à l'amorçage de l'arc et l'autre à son entretien et ceci dans le but de régler la luminosité de la lampe dans une gamme très étendue. Le brevet cité ne dissociant pas création de l'arc puis maintien de cet arc par deux sources différentes ne permet pas ce réglage étendu et ne permet pas non plus d'utiliser le système pour alimenter un tube faisant partie d'un point d'une image mouvante.Document US-A-3,590,316 describes an apparatus serving as a ballast for a plurality of discharge lamps. However, this is a very classic ignition system where the ignition and maintenance of the arc are done by means of a single inductance coil. On the contrary, and as will appear later, the supply system according to the present invention uses two separate sources of supply, one used for striking the arc and the other for its maintenance and this in order to adjust the brightness of the lamp in a very wide range. The cited patent does not dissociate creation of the arc then maintenance of this arc by two different sources does not allow this extended adjustment and does not allow either to use the system to feed a tube forming part of a point of moving image.

Le brevet US-A-4 132 925 décrit un système comprenant un circuit de démarrage et un ballast à courant continu pour l'alimentation d'une lampe à décharge. Dans ce système, dès que la décharge est amorcée, le circuit de démarrage devient inactif et c'est l'amplitude du courant continu qui règle la luminosité de la lampe. On a donc affaire là à un réglage d'intensité lumineuse par variation de l'amplitude du courant et non pas par variation de la durée d'un courant restant constant comme c'est le cas dans la présente invention. Dans cette dernière, il s'agit principalement d'utiliser le tube comme composant matriciel d'une image vidéo et pour cela il est nécessaire de rafraîchir les points lumineux composant cette image à périodes prédéterminées, ce qui ne peut pas être réalisé dans le dispositif du brevet cité.US-A-4,132,925 describes a system comprising a starting circuit and a DC ballast for supplying a discharge lamp. In this system, as soon as the discharge is initiated, the starting circuit becomes inactive and it is the amplitude of the direct current which regulates the brightness of the lamp. We are therefore dealing here with a light intensity adjustment by varying the amplitude of the current and not by varying the duration of a current remaining constant as is the case in the present invention. In the latter, it is mainly a question of using the tube as a matrix component of a video image and for this it is necessary to refresh the light points composing this image at predetermined periods, which cannot be achieved in the device. of the cited patent.

Le brevet US-A-4 219 760 décrit un système manuel de réglage d'intensité lumineuse d'une lampe à décharge. On s'aperçoit cependant que l'alimentation, par ailleurs décrite fort sommairement, n'est nullement une alimentation continue, mais une alimentation pulsée, ce que justement cherche à éviter la présente invention.US-A-4,219,760 describes a manual system for adjusting the light intensity of a discharge lamp. However, it can be seen that the power supply, which is moreover described very briefly, is by no means a continuous power supply, but a pulsed power supply, which the present invention seeks to avoid.

Enfin, le brevet FR-A-2 397 768 (= US-A-4 158 793) ne montre pas non plus d'impulsions d'amorçage périodiques ou de rafraîchissement comme cela a été dit ci-dessus. On n'y trouve pas non plus de source de courant continu mais bien plutôt une source de tension. De plus, aucun moyen n'est mis en oeuvre pour régler indépendamment l'intensité lumineuse de chacun des trois tubes représentés qui sont tous réglés en même temps au moyen d'une seule source de réglage.Finally, patent FR-A-2,397,768 (= US-A-4,158,793) also does not show periodic priming or refresh pulses as has been said above. There is also no source of direct current but rather a source of voltage. In addition, no means is used to independently adjust the light intensity of each of the three tubes shown, which are all adjusted at the same time by means of a single adjustment source.

Pour remédier aux inconvénients énumérés, la présente invention propose les moyens qui apparaissent dans les revendications pour mettre en oeuvre le dispositif d'alimentation objet de ladite invention ainsi qu'une utilisation préférée dudit dispositif.To remedy the drawbacks listed, the present invention provides the means which appear in the claims to implement the supply device object of said invention as well as a preferred use of said device.

L'invention sera comprise maintenant à l'aide de la description qui va suivre et pour l'intelligence de laquelle on se référera, à titre d'exemple, au dessin dans lequel :

  • La figure 1 est un schéma général qui montre le dispositif d'alimentation d'une lampe à décharge selon l'invention.
  • La figure 2 montre l'allure de la tension aux électrodes de la lampe quand elle est alimentée au moyen du dispositif montré en figure 1.
  • La figure 3 est un schéma de détail d'alimentation d'un élément émetteur de lumière comprenant trois tubes fluorescents.
  • Les figures 4 et 5 montrent chacune un schéma de réalisation possible du générateur de surtension 4 qui apparaît en figure 3.
  • La figure 6 est un schéma de réalisation possible des blocs 26 et 29 illustrés en figure 3.
  • La figure 7 présente les divers signaux formés par le circuit de la figure 6 ainsi que l'allure de la tension aux bornes de la lampe résultant de la combinaison desdits signaux.
The invention will now be understood with the aid of the description which follows and for the understanding of which reference will be made, by way of example, to the drawing in which:
  • Figure 1 is a general diagram showing the device for supplying a discharge lamp according to the invention.
  • FIG. 2 shows the shape of the voltage at the electrodes of the lamp when it is supplied by means of the device shown in FIG. 1.
  • FIG. 3 is a detailed diagram of the supply of a light emitting element comprising three fluorescent tubes.
  • FIGS. 4 and 5 each show a possible embodiment diagram of the overvoltage generator 4 which appears in FIG. 3.
  • FIG. 6 is a possible embodiment diagram of the blocks 26 and 29 illustrated in FIG. 3.
  • Figure 7 shows the various signals formed by the circuit of Figure 6 as well as the shape of the voltage across the lamp resulting from the combination of said signals.

Une lampe à décharge comprend notamment deux électrodes auxquelles sont appliquées les tensions de commande. Si la lampe est du type à cathodes chaudes, ce qui est le cas pour un tube d'éclairage fluorescent, les cathodes sont alors constituées de filaments recou- verts d'un dépôt d'oxyde qui favorise l'émission d'électrons et permet l'amorçage d'un arc entre les électrodes si, en même temps on les soumet à une impulsion à haute tension. En technique de l'éclairage sur réseau alternatif, cette haute tension est créée par l'ouverture d'un interrupteur (starter) disposé aux bornes de la lampe laquelle comporte une self (ballast) montée en série dans son circuit d'alimentation. Une fois l'arc amorcé, on coupe l'alimentation des filaments et on maintient le courant d'excitation dans la lampe à des valeurs raisonnables en se servant de la self comme limiteur de courant. A ce dispositif d'allumage connu, on pourrait adjoindre des moyens de réglage également connus pour régler l'intensité lumineuse émise par le tube, par exemple un thyristor dont on pourrait varier le temps de conduction.A discharge lamp notably comprises two electrodes to which the control voltages are applied. If the lamp is of the hot cathode type, which is the case for a fluorescent lighting tube, the cathodes are then made of filaments covered with an oxide deposit which promotes the emission of electrons and allows striking an arc between the electrodes if, at the same time, they are subjected to a high voltage pulse. In alternating network lighting technique, this high voltage is created by the opening of a switch (choke) placed at the terminals of the lamp which includes a self (ballast) connected in series in its supply circuit. Once the arc is struck, the supply of filaments is cut and the excitation current in the lamp is maintained to reasonable values using the choke as a current limiter. To this known ignition device, it is possible to add adjustment means also known for adjusting the light intensity emitted by the tube, for example a thyristor, the conduction time of which could be varied.

Le dispositif qui vient d'être décrit est inutilisable pour alimenter une ou plusieurs lampes à décharge où l'on désire obtenir d'abord un allumage instantané et ensuite un grand domaine de variation de luminosité. En effet, d'une part, l'emploi du starter classique provoque un retard à l'allumage et, d'autre part, les périodes de conduction d'un thyristor sont limitées par rapport au cycle d'alimentation. Des essais ont également montré que la durée de vie du tube est raccourcie dans d'assez fortes proportions s'il est alimenté par un tel montage, car la température des électrodes n'est pas suffisante à faible luminosité.The device which has just been described cannot be used to supply one or more discharge lamps where it is desired first to obtain instantaneous ignition and then a large range of variation in brightness. Indeed, on the one hand, the use of the conventional starter causes a delay in ignition and, on the other hand, the conduction periods of a thyristor are limited compared to the power cycle. Tests have also shown that the life of the tube is shortened in fairly large proportions if it is supplied by such an assembly, since the temperature of the electrodes is not sufficient at low light.

La figure 1 est un schéma général qui montre le dispositif d'alimentation selon l'invention d'une lampe à décharge dont il s'agit de régler l'intensité lumineuse. La lampe à décharge 1 est pourvue de deux électrodes 2 et 3. Un générateur 4 fournit aux électrodes, à intervalles périodiques prédéterminés T des impulsions de tension aptes à créer l'amorçage de la décharge dans la lampe. On trouve également une source de courant continu 5 branchée aux mêmes électrodes. Dans ce système l'intensité lumineuse émise par la lampe va dépendre de la durée d'application Tc du courant délivré par la source 5 entre chaque impulsion de tension délivrée par le générateur 4. Ainsi, chaque impulsion d'amorçage est suivie par une période d'application T d'un courant de maintien de la décharge, les deux signaux étant synchrones. Dans la figure 1, le bloc 6 symbolise un circuit de synchronisation qui active la source de courant .5 quand il a reçu du générateur 4 l'information que l'impulsion de tension a été envoyée à la lampe 1. On l'a déjà dit, l'intensité lumineuse émise par la lampe va dépendre de la durée d'application du courant issu de la source 5. Cette durée est contrôlée par un signal de consigne imposé par un circuit 7 qui interrompt le courant de la source 5 en fonction de la luminosité désirée.Figure 1 is a general diagram which shows the supply device according to the invention of a discharge lamp which is to adjust the light intensity. The discharge lamp 1 is provided with two electrodes 2 and 3. A generator 4 supplies the electrodes, at predetermined periodic intervals T with voltage pulses capable of creating the initiation of the discharge in the lamp. There is also a direct current source 5 connected to the same electrodes. In this system the light intensity emitted by the lamp will depend on the duration of application T c of the current delivered by the source 5 between each voltage pulse delivered by the generator 4. Thus, each ignition pulse is followed by a period of application T of a discharge maintenance current, the two signals being synchronous. In FIG. 1, block 6 symbolizes a synchronization circuit which activates the current source .5 when it has received from generator 4 the information that the voltage pulse has been sent to lamp 1. We already have it said, the light intensity emitted by the lamp will depend on the duration of application of the current from the source 5. This duration is controlled by a setpoint signal imposed by a circuit 7 which interrupts the current from the source 5 as a function of the desired brightness.

La figure 2 montre l'allure de la tension aux électrodes 2 et 3 de la lampe 1 dans un premier cas de luminosité très faible (figure 2a) et dans un second cas de luminosité proche du maximum (figure 2b). Dans le premier cas, les impulsions 10 issues du générateur 4 et qui se répètent à intervalles périodiques T sont suivies par un maintien de la tension d'arc 11 de très courte durée T . Dans le second cas, les mêmes impulsions 10 sont suivies par un maintien de la tension d'arc 12 dont la durée T occupe presque tout l'espace disponible entre deux impulsions. On s'aperçoit que dans ce système on a affaire à une modulation de durée alors que l'amplitude du courant continu délivré par la source 5 reste sensiblement constante. On remarquera que le cas de luminosité la plus faible est celui où la durée d'application T de la tension 11 est nulle (figure 2a) et que le cas de luminosité maximum est celui où Tc = T (figure 2b).Figure 2 shows the shape of the voltage at electrodes 2 and 3 of lamp 1 in a first case of very low brightness (figure 2a) and in a second case of brightness close to the maximum (Figure 2b). In the first case, the pulses 10 from the generator 4 and which are repeated at periodic intervals T are followed by maintaining the arc voltage 11 of very short duration T. In the second case, the same pulses 10 are followed by a maintenance of the arc voltage 12 whose duration T occupies almost all the space available between two pulses. It can be seen that in this system we are dealing with a duration modulation while the amplitude of the direct current delivered by the source 5 remains substantially constant. It will be noted that the case of lowest brightness is that where the duration of application T of the voltage 11 is zero (FIG. 2a) and that the case of maximum luminosity is that where T c = T (FIG. 2b).

On a vu que l'intensité lumineuse émise par la lampe dépend de la durée pendant laquelle on applique un courant de maintien entre deux impulsions d'amorçage et que cette durée est contrôlée par un signal de consigne. Ce signal de consigne peut être donné par un simple réglage manuel, par exemple un potentiomètre. Il peut également être dérivé d'un signal à basse fréquence par exemple musical. La présente invention trouve cependant son application privilégiée dans la reproduction et l'affichage d'images ou de textes qu'ils soient fixes ou animés, en noir et blanc ou en couleur. Dans ce cas, le signal de consigne peut être dérivé d'un signal vidéo.We have seen that the light intensity emitted by the lamp depends on the duration during which a holding current is applied between two ignition pulses and that this duration is controlled by a setpoint signal. This setpoint signal can be given by a simple manual adjustment, for example a potentiometer. It can also be derived from a low frequency signal, for example a musical signal. The present invention however finds its preferred application in the reproduction and display of images or texts whether fixed or animated, in black and white or in color. In this case, the setpoint signal can be derived from a video signal.

La figure 1 montre un élément émetteur de lumière composé d'une seule lampe, de préférence un tube fluorescent produisant une lumière blanche. Cet élément et le dispositif de commande qui lui est lié peut constituer un point lumineux (pixel) d'une partie d'image comportant un groupe de points. A leurs tours, une multiplicité de groupes de points peut constituer une image à grande dimension comme cela apparaît dans les tableaux matriciels géants destinés par exemple à des stades où un grand nombre de spectateurs sont rassemblés. Pour cette application, on comprendra qu'à chaque élément émetteur de lumière correspond une source de courant de maintien 5 de façon à pouvoir varier indépendamment l'intensité lumineuse produite par la lampe pour aboutir aux multiples dégradés de lumière qui composent une image. Il est alors possible d'afficher des textes comme des résultats sportifs, de la réclame, des événements animés ou des reprises desdits évènements au moyen de caméras, de disques ou de bandes magnétiques qui sont porteurs des signaux de consigne contrôlant à leur tour les sources de courant de maintien.Figure 1 shows a light emitting element composed of a single lamp, preferably a fluorescent tube producing white light. This element and the control device which is linked to it can constitute a light point (pixel) of an image part comprising a group of points. In their turn, a multiplicity of groups of points can constitute a large-dimensional image as it appears in the giant matrix tables intended for example for stadiums where a large number of spectators are gathered. For this application, it will be understood that to each light emitting element corresponds a source of holding current 5 so as to be able to vary independently the light intensity produced by the lamp to result in the multiple gradations of light which compose an image. It is then possible to display texts such as sports results, advertising, animated events or resumption of said events by means of cameras, discs or magnetic tapes which carry the set signals in turn controlling the sources of holding current.

La figure 3 montre en détail un exemple de réalisation du dispositif de commande qui a été sommairement esquissé en figure 1. L'élément présenté en figure 3 comporte cependant trois lampes à décharge 15, 16 et 17 qui sont des tubes dont on a revêtu l'intérieur des parois de verre avec des substances fluorescentes (phos- phor) différentes pour obtenir trois couleurs fondamentales, par exemple le rouge, le vert et le bleu.Figure 3 shows in detail an embodiment of the control device which has been roughly sketched in Figure 1. The element shown in Figure 3, however, includes three discharge lamps 15, 16 and 17 which are tubes which have been coated l inside the glass walls with different fluorescent substances (phosphor) to obtain three basic colors, for example red, green and blue.

Chaque tube est muni d'une électrode froide 18 et d'une électrode chaude 19 qui se présente sous la forme d'un filament. Chaque filament 19 est alimenté en permanence par une source d'alimentation commune U5. La puissance de chauffage par tube est de l'ordre de un watt. Le filament est recouvert d'oxyde émissif et fait office de cathode. On pourrait envisager un chauffage indirect d'une cathode isolée du filament de chauffage à l'image des tubes électroniques. On conçoit aisément l'avantage qu'il y a avec le dispositif selon l'invention de ne prévoir qu'un filament chauffé par tube. On comprend en effet que si l'électrode 18 devait être chauffée, il faudrait l'alimenter en courant de chauffage par autant de sources qu'il y a de tubes puisque pour fonctionner selon le principe proposé ici les électrodes 18 et 19 doivent être séparées galvaniquement. Quoiqu'il en soit, l'expérience a montré qu'un seul filament actif était suffisant pour favoriser l'émission d'électrons voulue et assurer l'amorçage de l'arc lors de l'application d'une surtension aux bornes du tube. Si l'on dispose de tubes déjà munis de deux filaments, comme c'est usuellement le cas, on ne chauffera qu'un seul de ces filaments.Each tube is provided with a cold electrode 18 and a hot electrode 19 which is in the form of a filament. Each filament 19 is permanently supplied by a common power source U 5 . The heating power per tube is of the order of one watt. The filament is covered with emissive oxide and acts as a cathode. One could consider indirect heating of a cathode isolated from the heating filament like electronic tubes. It is easy to see the advantage that there is with the device according to the invention of only providing one heated filament per tube. It is in fact understood that if the electrode 18 were to be heated, it would have to be supplied with heating current by as many sources as there are tubes since to operate according to the principle proposed here the electrodes 18 and 19 must be separated galvanically. Anyway, experience has shown that a single active filament is sufficient to promote the desired emission of electrons and ensure the ignition of the arc during the application of an overvoltage at the terminals of the tube. . If there are tubes already provided with two filaments, as is usually the case, only one of these filaments will be heated.

En figure 3, on retrouve le générateur 4 déjà esquissé en figure 1 et susceptible de fournir à tous les tubes en même temps des impulsions aptes à créer l'amorçage de la décharge. Ces impulsions apparaissent aux bornes S, 0 du générateur 4.In FIG. 3, we find the generator 4 already sketched in FIG. 1 and capable of supplying all the tubes at the same time with pulses capable of creating the initiation of the discharge. These pulses appear at terminals S, 0 of generator 4.

On se référera maintenant aux figures 4 et 5 qui illustrent deux réalisations possibles de ce générateur 4.Reference will now be made to FIGS. 4 and 5 which illustrate two possible embodiments of this generator 4.

Le générateur 4 présenté en figure 4 se compose essentiellement d'une source de tension continue U4. d'une bobine 20, d'un interrupteur 21 et d'un condensateur 22. Dans un tel système, l'énergie accumulée dans la bobine 20 sous forme de courant pendant la conduction de l'interrupteur 21 est restituée sous forme de tension aux bornes du condensateur 22 lors de l'ouverture de l'interrupteur 21. La valeur de l'énergie accumulée est déterminée par la tension U4, l'inductance L de la bobine 20 et la période d'accumulation t1 - to, t0 représentant l'instant de fermeture et t1 l'instant d'ouverture de l'interrupteur 21. L'énergie accumulée peut être exprimée par la relation

Figure imgb0001
The generator 4 presented in FIG. 4 essentially consists of a DC voltage source U 4 . a coil 20, an inter switch 21 and a capacitor 22. In such a system, the energy accumulated in the coil 20 in the form of current during the conduction of the switch 21 is restored in the form of voltage across the terminals of the capacitor 22 during opening. of the switch 21. The value of the accumulated energy is determined by the voltage U 4 , the inductance L of the coil 20 and the accumulation period t 1 - t o , t 0 representing the closing time and t 1 the instant of opening of the switch 21. The accumulated energy can be expressed by the relation
Figure imgb0001

En transférant cette énergie magnétique dans un condensateur 22 de capacité C, on peut alors contrôler la valeur de la surtensions US obtenue. Si l'énergie restituée s'exprime par la relation

Figure imgb0002
et que le transfert d'énergie impose Eacc = Erest , on trouve pour la valeur de la surtension
Figure imgb0003
 By transferring this magnetic energy into a capacitor 22 of capacitance C, it is then possible to control the value of the overvoltages U S obtained. If the energy returned is expressed by the relationship
Figure imgb0002
 and that the energy transfer imposes E acc = E rest , we find for the value of the overvoltage
Figure imgb0003

Ainsi, pour prendre un exemple, avec une source U4 de 12 V, une self L de 25 mH, une période de fermeture de l'interrupteur 21 de l'ordre de 100 µs et un condensateur C de 120 pF, la surtension présente aux bornes S, 0 sera de 700 V.So, to take an example, with a 12 V source U 4 , a 25 mH choke L, a closing period of the switch 21 of the order of 100 µs and a 120 pF capacitor C, the overvoltage presents at terminals S, 0 will be 700 V.

Afin d'éviter l'oscillation du circuit LC formé par les éléments 20 et 22, et par là-même la décharge du condensateur 22 dans la source U4, on place dans le circuit une diode 23.In order to avoid oscillation of the LC circuit formed by the elements 20 and 22, and thereby the discharge of the capacitor 22 in the source U 4 , a diode 23 is placed in the circuit.

L'interrupteur 21 est constitué par un transistor du type MOSFET dimensionné pour supporter les très hautes tensions qui prennent naissance à ses bornes. On pourra utiliser par exemple une pièce en provenance de la société Siemens et qui porte le symbole BUZ 50 A. La commande du transistor est assurée via la ligne 32 par un bloc 26 apparaissant en figure 3 et qui fournit à intervalles périodiques prédéterminés des impulsions de largeur tl - t0. Un exemple de réalisation de ce bloc est donné plus bas.The switch 21 is constituted by a transistor of the MOSFET type sized to support the very high voltages which arise at its terminals. We could use for example a part coming from the company Siemens and which bears the symbol BUZ 50 A. The transistor is controlled via line 32 by a block 26 appearing in FIG. 3 and which supplies pulses of predetermined periodic intervals. width t l - t 0 . An example of embodiment of this block is given below.

Le générateur 4 présenté en figure 5 est une solution préférée de réalisation de ce générateur quand il s'agit d'amorcer un très grand nombre de tubes (par exemple plus de trente tubes). Il se compose d'une source de tension continue U6 de l'ordre de 900 V et d'un interrupteur 45. La commande de l'interrupteur est assurée via le transformateur 46 par la ligne 32. Lorsqu'une impulsion de commande est émise par le bloc 26 (voir figure 3), l'interrupteur 45 se ferme et la haute tension U6 est reportée aux bornes de sorties S, pendant un temps très court (de l'ordre de 5 ps).The generator 4 presented in FIG. 5 is a preferred solution for producing this generator when it is a question of priming a very large number of tubes (for example more than thirty tubes). It consists of a direct voltage source U 6 of the order of 900 V and a switch 45. The switch is controlled by the transformer 46 by line 32. When a control pulse is emitted by block 26 (see Figure 3), the switch 45 closes and the high voltage U 6 is transferred to the output terminals S, for a very short time (of the order of 5 ps).

Si l'on revient maintenant à la figure 3, on constate que les impulsions de surtension émises par le générateur 4 sur ses bornes S et 0 sont appliquées aux tubes par l'intermédiaire d'une diode 24 et d'une résistance 25. Ces résistances 25 ont pour but de limiter le courant d'arc dans le tube dès l'instant où il est amorcé. Cet artifice permet d'assurer l'allumage de toutes les lampes au moyen d'un générateur unique. Sans cela, du fait que les lampes présentent des caractéristiques d'amorçage différentes, seule la lampe exigeant l'impulsion de tension la plus faible s'allumerait. En effet, la tension présente aux bornes du tube une fois Tare établi est nettement plus faible que la tension nécessaire à la provoquer. Un courant important prendrait alors naissance si aucune précaution n'était prise. Ce courant empêcherait, d'une part, la tension d'amorçage d'atteindre des valeurs suffisantes pour amorcer les autres tubes et pourrait, d'autre part, entraîner la destruction du premier tube amorcé.Returning now to FIG. 3, it can be seen that the overvoltage pulses emitted by the generator 4 on its terminals S and 0 are applied to the tubes via a diode 24 and a resistor 25. These resistors 25 are intended to limit the arc current in the tube from the moment it is started. This device ensures the lighting of all the lamps by means of a single generator. Otherwise, since the lamps have different starting characteristics, only the lamp requiring the lowest voltage pulse would light up. Indeed, the voltage present at the terminals of the tube once Tare established is significantly lower than the voltage necessary to cause it. An important current would then arise if no precautions were taken. This current would prevent, on the one hand, the priming voltage from reaching sufficient values to ignite the other tubes and could, on the other hand, lead to the destruction of the first primed tube.

En figure 3, on retrouve également pour chacun des tubes 15, 16 et 17 une source 5 de courant continu de maintien de la décharge dont le rôle a été expliqué à propos de la figure 1. Ici, il y a autant de sources 5 que de tubes pour permettre de régler indépendamment l'intensité de lumière de chacun d'eux. Les sources de courant 5 sont toutes alimentées par une source de tension commune U1. Une source de courant 5 comprend essentiellement une cascade de deux transistors 26 et 27. La base du transistor 26 est alimentée via une résistance 28 par le signal de consigne issu du bloc 29 dont un exemple de réalisation sera donné ci-après. Quand un signal est présent sur la base du transistor 26, la source de courant 5 débite un courant qui est celui des sens des flèches de la figure et l'intensité lumineuse des tubes va dépendre du temps pendant lequel on va appliquer ce signal. La source de courant 5 comprend une diode de sécurité 32 qui empêche la destruction du transistor 26 lorsque ladite source ne débite aucun courant.In FIG. 3, there is also found for each of the tubes 15, 16 and 17 a source 5 of direct current for maintaining the discharge, the role of which has been explained in connection with FIG. 1. Here, there are as many sources 5 as tubes to allow independent adjustment of the light intensity of each of them. The current sources 5 are all supplied by a common voltage source U 1 . A current source 5 essentially comprises a cascade of two transistors 26 and 27. The base of transistor 26 is supplied via a resistor 28 by the reference signal from block 29, an exemplary embodiment of which will be given below. When a signal is present on the base of transistor 26, the current source 5 delivers a current which is that of the directions of the arrows in the figure and the light intensity of the tubes will depend on the time during which this signal is applied. The current source 5 comprises a safety diode 32 which prevents the destruction of the transistor 26 when said source does not deliver any current.

Il faut indiquer aussi qu'on a prévu la possibilité de régler individuellement le courant débité par chaque source en jouant sur le potentiomètre 30 placé en série dans le circuit de l'émetteur du transistor 27. Ceci permet d'équilibrer entre eux les flux lumineux émis par chacun des tubes quand ils reçoivent un signal de consigne de même durée. De même, il a été prévu de pouvoir régler le courant de toutes les sources d'une quantité égale en même temps. Pour ce faire, on alimente le collecteur du transistor 26 par une source de tension variable U3 commune a toutes les sources de courant 5. Une tension U3 variant entre 3 et 6 volts suffira en général à satisfaire aux besoins qui se présentent et qui consistent entre autres à adapter la luminosité émise par le groupe de tubes à la lumière ambiante.It should also be noted that provision has been made for the possibility of individually adjusting the current delivered by each source by playing on the potentiometer 30 placed in series in the circuit of the emitter of transistor 27. This makes it possible to balance the light fluxes between them emitted by each of the tubes when they receive a setpoint signal of the same duration. Likewise, provision has been made to be able to regulate the current from all sources by an equal quantity at the same time. To do this, the collector of transistor 26 is supplied by a variable voltage source U 3 common to all the current sources 5. A voltage U 3 varying between 3 and 6 volts will generally suffice to satisfy the needs which arise and which These consist, among other things, of adapting the brightness emitted by the group of tubes to the ambient light.

On mentionnera encore qu'une tension d'alimentation U1 de 60 V continu permet dans le dispositif décrit d'assurer une tension d'arc d'environ 40 V dans le tube. Enfin, comme il est nécessaire d'isoler les sources de courant 5 du générateur a impulsions 4, le schéma de la figure 3 montre encore le montage de deux diodes 24 et 31. La diode 24 empêche que la source de courant 5 d'un tube n'alimente un autre tube via la ligne commune du générateur de surtension. La diode 31 interdit à l'impulsion de surtension en provenance du générateur 4 de remonter jusqu'à la source de courant 5.It will also be mentioned that a supply voltage U 1 of 60 V DC allows in the device described to ensure an arc voltage of around 40 V in the tube. Finally, as it is necessary to isolate the current sources 5 of the pulse generator 4, the diagram in FIG. 3 also shows the mounting of two diodes 24 and 31. The diode 24 prevents the current source 5 from tube feeds another tube via the common line of the surge generator. The diode 31 prevents the overvoltage pulse from the generator 4 from going up to the current source 5.

L'élément émetteur de lumière dont on vient de décrire le fonctionnement comprend généralement trois tubes fluorescents disposés côte à côte ou imbriqués les uns dans les autres selon des dispositions qui font l'objet du document EP 0 109 671 déjà cité. On comprend qu'en dosant le temps pendant lequel le courant est injecté dans chacun des tubes 15, 16 et 17 on puisse obtenir une lumière résultante dont la couleur peut être variée sur toute l'étendue des teintes visibles. Le mélange additif des trois couleurs fondamentales peut être réalisé par un verre dépoli que l'on dispose devant l'élément. Ce mélange peut aussi intervenir naturellement si l'on observe l'élément avec un certain recul.The light emitting element whose operation has just been described generally comprises three fluorescent tubes arranged side by side or nested one inside the other according to arrangements which are the subject of document EP 0 109 671 already cited. It is understood that by measuring the time during which the current is injected into each of the tubes 15, 16 and 17, it is possible to obtain a resultant light, the color of which can be varied over the entire range of visible hues. The additive mixture of the three basic colors can be achieved by a frosted glass which is placed in front of the element. This mixture can also occur naturally if we observe the element with a certain distance.

La richesse des coloris ou, si l'on veut, le nombre de couleurs différentes que l'on pourra obtenir d'un tel élément va dépendre du nombre de tons présentés par chacun des tubes formant l'élément. Avec le dispositif préconisé par la présente invention, on peut obtenir au moins 2 = 32 dégradés de lumière par tube. Enfin, si un tube autorise 32 dégradés de lumière, trois tubes de couleurs différentes permettront alors 215 = 32'768 teintes différentes.The richness of the colors or, if you like, the number of different colors that can be obtained from such an element will depend on the number of tones presented by each of the tubes forming the element. With the device recommended by the present invention, it is possible to obtain at least 2 = 32 light gradations per tube. Finally, if a tube allows 32 shades of light, three tubes of different colors will then allow 2 15 = 32,768 different shades.

Dans le dispositif décrit, les 32 tons de lumière correspondant à 32 durées d'excitation différentes du tube doivent trouver place entre deux impulsions de surtension successives. Si l'on tient compte de la courbe de sensibilité de l'oeil, il faut remarquer cependant que la luminance qui représente un nombre de candelas émis par unité de surface éclairante de l'élément et qui est perçue par l'oeil n'est pas une fonction linéaire de la durée d'excitation du tube. Weber préconise pour l'éclairage diurne la courbe de conversion

Figure imgb0004
alors que pour l'éclairage nocturne on utilisera de préférence la relation avancée par Wyszecky et qui s'écrit :
Figure imgb0005
ou L représente la luminance et S le niveau relatif d'excitation de la source lumineuse. Le présent dispositif fera usage des lois données ci-dessus en assimilant le niveau relatif d'excitation à la durée pendant laquelle le tube fluorescent est alimenté.In the device described, the 32 light tones corresponding to 32 different excitation durations of the tube must find a place between two successive overvoltage pulses. If the sensitivity curve of the eye is taken into account, it should however be noted that the luminance which represents a number of candelas emitted per unit of illuminating surface of the element and which is perceived by the eye is not not a linear function of the tube excitation time. Weber recommends the conversion curve for daytime running light
Figure imgb0004
 whereas for night lighting we will preferably use the relation advanced by Wyszecky and which is written:
Figure imgb0005
 where L represents the luminance and S the relative level of excitation of the light source. The present device will make use of the laws given above by assimilating the relative level of excitation to the duration during which the fluorescent tube is supplied.

Reste à dire un mot sur la périodicité les impulsions de surtension. Dans le cas particulier où le dispositif décrit trouve son application dans la reproduction d'images an nées issues d'un signal vidéo par exemple, on comprendra qu'un poin-. image (l'élément émetteur de lumière cité dans les revendications) doit pouvoir être rafraîchi, ou, en d'autres termes, doit pouvoir être capable de recevoir une nouvelle information au moins vous les 1/25 de seconde dans les réseaux à 50 Hz (1/30 de seconde dans les réseaux à 60 Hz), ce qui conduit à une répétition d'impulsifs de surtension toutes les 40 ms. Cependant, cette périodicité sera choisie inférieure à 20 ms pour éviter le clignotement d'image qu'on réduit par le procédé d'entrelaçage.It remains to say a word about the frequency of the overvoltage pulses. In the particular case where the device described finds its application in the reproduction of old images from a video signal for example, it will be understood that a pin. image (the light emitting element cited in the claims) must be able to be refreshed, or, in other words, must be able to receive new information at least you every 1/25 of a second in 50 Hz networks (1/30 of a second in 60 Hz networks), which leads to a repetition of overvoltage pulses every 40 ms. However, this periodicity will be chosen less than 20 ms to avoid image flashing which is reduced by the interleaving process.

La figure 6 montre un exemple de réalisation possible des blocs 26 et 29 qu'on trouve à la figure 3. Il se compose essentiellement de trois circuits 555 bien connus de l'état de la technique et référencés 40, 41 et 42. Le premier circuit 40 est un générateur qui engendre de brèves impulsions 50 qu'on recueille sur sa sortie 3 et dont l'allure est montrée en figure 7a. La période de répétition Tr des impulsions dépend des valeurs qu'on donne à RO + R'0 et C0. Elle peut être ajustée en variant R0. Les impulsions 50 commandent à leur tour le circuit 41 qui est un monostable qui s'enclenche sur le flanc descendant de l'impulsion 50 et allonge ladite impulsion d'une quantité imposée par les valeurs données à R1 + R'1 et C1. Elle peut être ajustée en variant R1. L'impulsion qui en résulte et qui est également représentée sur la figure 7b est recueillie à la sortie 3 du circuit 41 et commande par la ligne 32 soit l'interrupteur 21 du générateur 4 illustré en figure 4, soit le transformateur 46 du générateur 4 illustré en figure 5, selon que l'on choisisse l'une ou l'autre variante d'exécution. Ainsi, le bloc 26 de la figure 3 est constitué dans cet exemple de réalisation par les circuits 40 et 41 de la figure 6 pour générer l'impulsion 51 de largeur t1 - t0. Les impulsions 51 commandent à leur tour le circuit 42 qui est également un monostable qui s'enclenche sur le flanc descendant de l'impulsion 51 et allonge ladite impulsion d'une quantité imposée par les valeurs données à R2 + R'2 et C2. L'impulsion 52 de durée Tc qui en résulte, et qu'on a représentée sur la figure 7c, est recueillie à la sortie 3 du circuit 42 et commande par la ligne 33 l'enclenchement du générateur de courtant 5 alimentant le tube 15, comme on le voit en figure 3. L'impulsion 52 n'est autre que le signal de consigne issu du bloc 29 de la même figure 3, ledit bloc 29 étant constitué dans cet exemple de réalisation du circuit 42 de la figure 6, circuit qui fonctionne donc en synchronisme avec le générateur d'amorçage du tube. Il est évident que pour alimenter en courant de maintien les trois tubes 15, 16 et 17 de l'élément émetteur de lumière présenté en figure 3, i1 sera nécessaire de prévoir deux circuits supplémentaires 42 identiques à celui montré en figure 6. Ces deux circuits supplémentaires 42 attaqueront alors les deux autres générateurs 5 par les lignes 34 et 35.FIG. 6 shows a possible embodiment of the blocks 26 and 29 that are found in FIG. 3. It essentially consists of three circuits 555 well known from the state of the art and referenced 40, 41 and 42. The first circuit 40 is a generator which generates short pulses 50 which are collected on its output 3 and the shape of which is shown in FIG. 7a. The repetition period T r of the pulses depends on the values given to R O + R ' 0 and C 0 . It can be adjusted by varying R0. The pulses 50 in turn control the circuit 41 which is a monostable which engages on the falling edge of the pulse 50 and lengthens said pulse by an amount imposed by the values given to R 1 + R ' 1 and C 1 . It can be adjusted by varying R 1 . The resulting pulse, which is also shown in FIG. 7b, is collected at the output 3 of circuit 41 and controls by line 32 either the switch 21 of the generator 4 illustrated in FIG. 4, or the transformer 46 of the generator 4 illustrated in FIG. 5, depending on whether one or the other alternative embodiment is chosen. Thus, the block 26 of FIG. 3 is constituted in this embodiment by the circuits 40 and 41 of FIG. 6 to generate the pulse 51 of width t 1 - t 0 . The pulses 51 in turn control the circuit 42 which is also a monostable which engages on the falling edge of the pulse 51 and lengthens said pulse by an amount imposed by the values given to R 2 + R ' 2 and C 2 . The pulse 52 of duration T c which results therefrom, and which is shown in FIG. 7c, is collected at the output 3 of the circuit 42 and controls by the line 33 the switching on of the broker generator 5 supplying the tube 15 , as seen in FIG. 3. The pulse 52 is none other than the reference signal from block 29 of the same FIG. 3, said block 29 being constituted in this exemplary embodiment of circuit 42 of FIG. 6, circuit which therefore operates in synchronism with the generator for priming the tube. It is obvious that in order to supply holding current to the three tubes 15, 16 and 17 of the light emitting element presented in FIG. 3, it will be necessary to provide two additional circuits 42 identical to that shown in FIG. 6. These two circuits additional 42 will then attack both other generators 5 by lines 34 and 35.

Il faut mentionner encore à propos de la figure 6 la présence du circuit comportant le transistor 60 qui a pour but la remise à zéro du monostable 42 dès qu'apparaît à la sortie 3 du circuit 40 une nouvelle impulsion 50, ceci pour éviter tout chevauchement de l'impulsion 50 sur une impulsion 52 qui ne serait pas terminée.It should also be mentioned in connection with FIG. 6 the presence of the circuit comprising the transistor 60 which aims at resetting the monostable 42 as soon as a new pulse 50 appears at the output 3 of the circuit 40, this to avoid any overlap from pulse 50 to pulse 52 which would not be finished.

Enfin, la figure 7d montre en complément la tension qui appa- rait aux électrodes du tube et qui est le résultat de la combinaison des diagrammes 7a, 7b et 7c. Ainsi, l'impulsion de surtension 10 coïncide avec le flanc descendant de l'impulsion 51 et la tension de modulation 13 (ou de maintien de l'arc) coïncide avec l'impulsion 52.Finally, FIG. 7d shows in addition the voltage which appears at the electrodes of the tube and which is the result of the combination of diagrams 7a, 7b and 7c. Thus, the overvoltage pulse 10 coincides with the falling edge of the pulse 51 and the modulation voltage 13 (or of arc maintenance) coincides with the pulse 52.

Le schéma de réalisation de la figure 6 permet de varier l'intensité de lumière au moyen d'un réglage potentiométrique (R2) qui est ici le signal de consigne à proprement parler. Il est clair que ce réglage serait réalisé de façon toute différente si le signal de consigne devait être une information livrée par une caméra de télévision par exemple. Dans ce cas, la caméra présente à sa sortie un signal analogique qu'on transforme en signal digital par un convertisseur. On trouve alors à la sortie du convertisseur 2 = 32 tons possibles corrigés selon les formules (1) et (2) données plus haut, l'un de ces tons correspondant à l'intensité lumineuse du point analysé à un moment précis. L'information digitale est ensuite envoyée à un compteur qui restituera à sa sortie un signal dont la durée correspondra à l'intensité lumineuse analysée à ce moment. Ce signal commandera enfin une source de courant de maintien comme cela a été expliqué plus haut.The embodiment of Figure 6 allows to vary the light intensity by means of a potentiometric adjustment (R 2 ) which is here the setpoint signal itself. It is clear that this adjustment would be carried out in a completely different manner if the reference signal were to be information delivered by a television camera for example. In this case, the camera presents an analog signal at its output which is transformed into a digital signal by a converter. One then finds at the output of the converter 2 = 32 possible tones corrected according to formulas (1) and (2) given above, one of these tones corresponding to the light intensity of the point analyzed at a precise moment. The digital information is then sent to a counter which will output a signal at its output, the duration of which will correspond to the light intensity analyzed at that time. This signal will finally command a holding current source as explained above.

Claims (17)

1. Dispositif d'alimentation pour commander, en réponse à au moins un signal de consigne, l'intensité lumineuse d'au moins un élément émetteur de lumière comprenant au moins une lampe à décharge (1), caractérisé par le fait qu'il comporte un générateur (4) fournissant à intervalles périodiques prédéterminés (T ) des impulsions de tension (10) aptes à créer l'amorçage de la décharge dans la lampe et une source de courant continu (5) d'amplitude sensiblement constante susceptible de fournir à la lampe, en synchronisme avec chaque impulsion de tension, un courant de maintien de la décharge dont la durée d'application (T ) est fonction dudit signal de consigne.1. Supply device for controlling, in response to at least one setpoint signal, the light intensity of at least one light emitting element comprising at least one discharge lamp (1), characterized in that it comprises a generator (4) supplying at predetermined periodic intervals (T) voltage pulses (10) capable of creating the initiation of the discharge in the lamp and a source of direct current (5) of substantially constant amplitude capable of supplying at the lamp, in synchronism with each voltage pulse, a discharge maintenance current whose duration of application (T) is a function of said setpoint signal. 2. Dispositif selon la revendication 1, caractérisé par le fait que le générateur d'impulsions de tension (4) comporte une source de basse tension (U4), une bobine (20) et un interrupteur (21) disposés en série et que les bornes (18, 19) de la lampe sont connectées aux bornes de l'interrupteur pour soumettre la lampe à une impulsion de tension chaque fois que ledit interrupteur passe de l'état fermé à l'état ouvert.2. Device according to claim 1, characterized in that the voltage pulse generator (4) comprises a low voltage source (U 4 ), a coil (20) and a switch (21) arranged in series and that the terminals (18, 19) of the lamp are connected to the terminals of the switch to subject the lamp to a voltage pulse each time said switch goes from the closed state to the open state. 3. Dispositif selon la revendication 2, caractérisé par le fait que le générateur d'impulsion comporte en outre un condensateur (22) disposé aux bornes de l'interrupteur pour limiter à une valeur contrôlable l'amplitude de l'impulsion de tension.3. Device according to claim 2, characterized in that the pulse generator further comprises a capacitor (22) disposed at the terminals of the switch to limit the amplitude of the voltage pulse to a controllable value. 4. Dispositif selon la revendication 1, caractérisé par le fait que le générateur d'impulsions (4) comporte une source de haute tension (U6) et un interrupteur (45) disposés en série pour sou- mettre la lampe à une impulsion de tension chaque fois que ledit interrupteur est fermé.4. Device according to claim 1, characterized in that the pulse generator (4) comprises a high voltage source (U 6 ) and a switch (45) arranged in series for submitting - the lamp to a pulse of voltage each time said switch is closed. 5. Dispositif selon la revendication 2 ou la revendication 4, caractérisé par le fait que les bornes de la lampe sont connectées aux bornes (S, 0) du générateur d'impulsions (4) par l'intermédiaire d'une résistance (25) interposée en série pour limiter le courant dans la lampe.5. Device according to claim 2 or claim 4, characterized in that the terminals of the lamp are connected to the terminals (S, 0) of the pulse generator (4) via a resistor (25) interposed in series to limit the current in the lamp. 6. Dispositif selon la revendication 1, caractérisé par le fait que le courant de maintien est appliqué après chaque impulsion de tension pendant une période (Tc) n'excédant pas l'intervalle (T ) séparant lesdites impulsions, ladite période pouvant prendre au moins trente-deux valeurs différentes.6. Device according to claim 1, characterized in that the holding current is applied after each voltage pulse for a period (T c ) not exceeding the interval (T) separating said pulses, said period possibly taking at least thirty-two different values. 7. Dispositif selon la revendication 1, caractérisé par le fait que l'intervalle (Tr) séparant lesdites impulsions est inférieur à 20 ms.7. Device according to claim 1, characterized in that the interval (T r ) separating said pulses is less than 20 ms. 8. Dispositif selon la revendication 1, caractérisé par le fait qu'il commande un groupe d'éléments émetteurs de lumière, chaque élément comprenant un tube à décharge (1) fluorescent produisant une lumière blanche et qu'il comporte autant de sources de courant de maintien (5) qu'il y a de tubes pour commander indépendamment l'intensité lumineuse émise par chacun d'entre eux.8. Device according to claim 1, characterized in that it controls a group of light emitting elements, each element comprising a fluorescent discharge tube (1) producing white light and that it comprises as many current sources holding (5) that there are tubes for independently controlling the light intensity emitted by each of them. 9. Dispositif selon la revendication 1, caractérisé par le fait qu'il commande un élément émetteur de lumière composé d'au moins trois tubes à décharge fluorescents (15, 16, 17) produisant chacun une couleur fondamentale et qu'il comporte autant de sources de courant de maintien (5) qu'il y a de tubes pour commander indépendamment l'intensité de lumière émise par chacun d'entre eux pour obtenir une lumière résultante dont la couleur peut être variée sur toute l'étendue des teintes visibles.9. Device according to claim 1, characterized in that it controls a light emitting element composed of at least three fluorescent discharge tubes (15, 16, 17) each producing a fundamental color and that it comprises as many holding current sources (5) that there are tubes for independently controlling the intensity of light emitted by each of them to obtain a resultant light whose color can be varied over the entire range of visible hues. 10. Dispositif selon la revendication 1, caractérisé par le fait qu'il commande un groupe d'éléments émetteurs de lumière composé chacun d'au moins trois tubes à décharge fluorescents (15, 16, 17) produisant chacun une couleur fondamentale et qu'il comporte autant de sources de courant de maintien (5) qu'il y a de tubes pour commander indépendamment l'intensité de lumière émise par chacun d'eux pour obtenir une matrice de points dont la couleur peut être variée sur toute l'étendue des teintes visibles.10. Device according to claim 1, characterized in that it controls a group of light emitting elements each composed of at least three fluorescent discharge tubes (15, 16, 17) each producing a fundamental color and that it includes as many holding current sources (5) as there are tubes for independently controlling the intensity of light emitted by each of them to obtain a matrix of dots whose color can be varied over the entire range visible shades. 11. Dispositif selon l'une quelconque des revendications 8 à 10, caractérisé par le fait que les tubes à décharge fluorescents qu'il commande sont pourvus chacun d'un seul filament actif (19), tous alimentés en permanence à une source d'alimentation commune (U5).11. Device according to any one of claims 8 to 10, characterized in that the fluorescent discharge tubes which it controls are each provided with a single active filament (19), all permanently supplied to a source of common power supply (U 5 ). 12. Dispositif selon l'une quelconque des revendications 8 à 10, caractérisé par le fait qu'il comporte un seul générateur d'impulsions (4) commun à tous les tubes.12. Device according to any one of claims 8 to 10, characterized in that it comprises a single pulse generator (4) common to all the tubes. 13. Dispositif selon l'une quelconque des revendications 8 à 10, caractérisé par le fait que chaque source de courant de maintien (5) est pourvu de moyens (30) pour ajuster manuellement l'amplitude du courant traversant le tube qu'elle alimente.13. Device according to any one of claims 8 to 10, characterized in that each source of holding current (5) is provided with means (30) for manually adjusting the amplitude of the current passing through the tube which it supplies. 14. Dispositif selon l'une quelconque des revendications 8 à 10, caractérisé par le fait que les sources de courant de maintien (5) sont pourvues de moyens communs (U3) pour ajuster simultanément l'amplitude du courant de tous les tubes alimentés par lesdites sources.14. Device according to any one of claims 8 to 10, characterized in that the holding current sources (5) are provided with common means (U 3 ) for simultaneously adjusting the amplitude of the current of all the tubes supplied by said sources. 15. Dispositif selon l'une quelconque des revendications 8 à 10, caractérisé par le fait que les sources de courant de maintien (5) sont alimentées par une source de tension commune (U1).15. Device according to any one of claims 8 to 10, characterized in that the holding current sources (5) are supplied by a common voltage source (U 1 ). 16. Dispositif selon l'une quelconque des revendications 8 à 10, caractérisé par le fait qu'à chaque tube est associée une première diode (25) interposée en série entre le générateur d'impulsions (4) et une électrode (18) du tube et une seconde diode (31) interposée en série entre la source de courant de maintien (5) et ladite électrode (18).16. Device according to any one of claims 8 to 10, characterized in that each tube is associated with a first diode (25) interposed in series between the pulse generator (4) and an electrode (18) of the tube and a second diode (31) interposed in series between the holding current source (5) and said electrode (18). 17. Utilisation du dispositif selon l'une quelconque des revendications 1 à 16 dans un tableau d'affichage matriciel.17. Use of the device according to any one of claims 1 to 16 in a matrix display table.
EP85101029A 1984-02-03 1985-02-01 Feeding device for controlling the light intensity of at least one discharge lamp, and use of this device Expired EP0152026B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8401800A FR2559334B1 (en) 1984-02-03 1984-02-03 POWER SUPPLY DEVICE FOR CONTROLLING THE LIGHT INTENSITY OF AT LEAST ONE DISCHARGE LAMP AND USE OF SAID DEVICE
FR8401800 1984-02-03

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EP0152026A1 true EP0152026A1 (en) 1985-08-21
EP0152026B1 EP0152026B1 (en) 1988-06-29

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EP (1) EP0152026B1 (en)
JP (1) JPS60189196A (en)
KR (1) KR900000669B1 (en)
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CA (1) CA1227528A (en)
DE (1) DE3563584D1 (en)
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SG (1) SG42291G (en)

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EP0288924A1 (en) * 1987-04-29 1988-11-02 Omega Electronics S.A. Power supply device for a discharge lamp
EP0296558A1 (en) * 1987-06-26 1988-12-28 Omega Electronics S.A. Power supply device for a discharge lamp
EP0406116A1 (en) * 1989-06-30 1991-01-02 Thomson-Csf Process and device for dimming a fluorescent lamp of an LCD backlight
EP1115272A1 (en) * 2000-01-07 2001-07-11 Issei Yoshitake Method and system for lighting discharge lamps

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DE19531458A1 (en) * 1995-08-26 1997-02-27 Telefunken Microelectron Operation of fluorescent lamp
JP2007124448A (en) * 2005-10-31 2007-05-17 Pioneer Electronic Corp Speaker unit and speaker mounting bracket

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EP0278468A2 (en) * 1987-02-10 1988-08-17 Sharp Kabushiki Kaisha System for lighting fluorescent lamps
EP0278468A3 (en) * 1987-02-10 1991-01-09 Sharp Kabushiki Kaisha System for lighting fluorescent lamps
EP0288924A1 (en) * 1987-04-29 1988-11-02 Omega Electronics S.A. Power supply device for a discharge lamp
FR2614748A1 (en) * 1987-04-29 1988-11-04 Omega Electronics Sa DEVICE FOR SUPPLYING A DISCHARGE LAMP
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CA1227528A (en) 1987-09-29
KR900000669B1 (en) 1990-02-02
US4649322A (en) 1987-03-10
SG42291G (en) 1991-07-26
FR2559334A1 (en) 1985-08-09
DE3563584D1 (en) 1988-08-04
KR850006296A (en) 1985-10-02
FR2559334B1 (en) 1988-02-26
EP0152026B1 (en) 1988-06-29
JPH0447959B2 (en) 1992-08-05
AU578263B2 (en) 1988-10-20
JPS60189196A (en) 1985-09-26
AU3828785A (en) 1985-08-08

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