EP0152026B1 - Feeding device for controlling the light intensity of at least one discharge lamp, and use of this device - Google Patents

Description

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.

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-A-0 109 671. In this technique, the current crossing 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.

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.

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 it expensive to produce the entire assembly.

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 calls upon two distinct sources of supply, one serving 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. 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.

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.

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 DC source, but rather a voltage source. 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.

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.

• 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.

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 then consist of filaments covered with an oxide deposit which promotes the emission of electrons and allows the striking of 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 has been struck, the supply of filaments is cut off and the excitation current in the lamp is kept at reasonable values by using the inductor 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.

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. because the temperature of the electrodes is not sufficient in low light.

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 _r, 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 _c of a discharge maintenance current, the two signals being synchronous. In FIG. 1, the block 6 symbolizes a synchronization circuit which activates the current source 5 when it has received from the generator 4 the information that the voltage pulse has been sent to the lamp 1. It has already been 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.

FIG. 2 shows the shape of the voltage at the electrodes 2 and 3 of the lamp 1 in a first case of very low brightness (FIG. 2a) and in a second case of brightness close to the maximum (FIG. 2b). In the first case, the pulses 10 from the generator 4 and which are repeated at periodic intervals T _r are followed by maintaining the arc voltage 11 of very short duration T _c . In the second case, the same pulses 10 are followed by maintaining the arc voltage 12 whose duration T _c 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 luminosity is that where the duration of application T _c of the voltage 11 is zero (FIG. 2a) and that the case of maximum luminosity is that where T _c = T _r (FIG. 2b).

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.

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 repeats of said events by means of cameras, discs or magnetic tapes which carry the set signals in turn controlling the sources. holding current.

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.

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.

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.

Reference will now be made to FIGS. 4 and 5 which illustrate two possible embodiments of this generator 4.

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

et que le transfert d'énergie impose E_acc =Erest, on trouve pour la valeur de la surtension

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.The generator 4 presented in FIG. 4 essentially consists of a DC voltage source U ₄ , a coil 20, a 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 when the switch 21 is opened. 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, - t _o , t _o representing the closing time and t, the opening time of the switch 21. The accumulated energy can be expressed by relationship

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

and that the energy transfer imposes E _acc = Erest, we find for the value of the overvoltage

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.

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.

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, - t _o . 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, Ø for a very short time (of the order of 5 us).

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 the arc is 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.

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 _t . 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 apply this signal. 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.

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 luminosity emitted by the group of tubes to the ambient light.

It will also be mentioned that a supply voltage U ₁ of 60 V DC makes it possible 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 a 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 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 ⁵ = 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.

alors que pour l'éclairage nocturne on utilisera de préférence la relation avancée par Wyszecky et qui s'écrit :

où 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

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.

It remains to say a word on the periodicity of the overvoltage pulses. In the particular case where the device described finds its application in the reproduction of animated images resulting from a video signal for example, it will be understood that an image point (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 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 the flashing of the image which is reduced by the interleaving process.

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 Ro + R ' _o and C _o . It can be adjusted by varying R _o . 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, + R ' _i and Ci. It can be adjusted by varying R _i . 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 Figure 3 is constituted in this embodiment by the circuits 40 and 41 of Figure 6 to generate the pulse 51 of width t, - t _o . 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 a quantity 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 line 33 the switching on of the broker generator 5 supplying the tube 15 , as can be 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 embodiment of the 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 the three tubes 15, 16 and 17 of the light emitting element presented in FIG. 3 with holding current, 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 the other two generators 5 via lines 34 and 35.

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.

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.

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 ⁵ = 32 possible tones corrected according to the 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. Energizing arrangement for controlling, in response to at least one instruction signal, the luminous intensity of at least one light emitting element having at least one discharge lamp (1), characterized by the fact that it comprises a generator (4) providing voltage pulses (10) at predetermined periodic intervals (T_r) in order to start the discharge in the lamp and a direct current source (5) of essentially constant amplitude adapted to provide the lamp with a discharge maintenance current in synchronism with each voltage pulse, the duration (T_c) of said maintenance current being determined by said instruction signal.

2. Energizing arrangement as set forth in claim 1, characterized by the fact that the voltage pulse generator (4) comprises a low voltage source (U₄) a coil (20) and a switch (21) arranged in series, the terminals (18, 19) of the lamp being connected to the switch terminals so as to subject the lamp to a voltage pulse at each switch opening.

3. Energizing arrangement as set forth in claim 2, characterized by the fact that the voltage pulse generator further includes a capacitor (22) arranged at the switch terminals in order to limit the voltage pulse amplitude to a controllable value.

4. Energizing arrangement as set forth in claim 1, characterized by the fact that the voltage pulse generator (4) comprises a high voltage source (U₆) and a switch (45) in series therewith arranged so as to subject the lamp to a voltage pulse at each switch closing.

5. Energizing arrangement as set forth in claim 2 or in claim 4, characterized by the fact that the terminals of the lamp are connected to the voltage pulse generator (4) terminals (S, 0) via a resistance (25) arranged in series therewith so as to limit the current in the lamp.

6. Energizing arrangement as set forth in claim 1, characterized by the fact that the maintenance current is applied after each voltage pulse over a time period (T_c) not exceeding the time interval (T_r) separating said pulses, said period having at least thirty two different values.

7. Energizing arrangement as set forth in claim 1, characterized by the fact that the interval (T_r) separating said pulses is less than 20 ms.

8. Energizing arrangement as set forth in claim 1, characterized by the fact that it is adapted to control a group of light emitting elements, each element including a fluorescent discharge tube (1) emitting white light, and that it comprises as many maintenance current sources (5) as there are tubes in order to control independently the luminous intensity emitted by each tube.

9. Energizing arrangement as set forth in claim 1, characterized by the fact that it is adapted to control a light emitting element comprising at least three fluorescent discharge tubes (15, 16, 17) each emitting light of a different primary colour, and that it comprises as many maintenance current sources (5) as there are tubes in order to control independently the luminous intensity emitted by each tube thereby to obtain a resultant light output the colour of which may be varied over the entire visible spectmm.

10. Energizing arrangement as set forth in claim 1, characterized by the fact that it is adapted to control a group of light emitting elements each including at least three fluorescent discharge tubes (15, 16, 17), each emitting light of a different primary colour, and that it comprises as many maintenance current sources (5) as there are tubes, in order to control independently the luminous intensity emitted by each tube, thereby to obtain a matrix of points the colour of which may be varied over the entire visible spectrum.

11. Energizing arrangement as set forth in claims 8 to 10, characterized by the fact that the discharge fluorescent tubes are each provided with a single active filament (19). with all filaments permanently energized from a common source (U₅).

12. Energizing arrangement as set forth in claims 8 to 10, characterized by the fact that it comprises one voltage pulse generator (4) only common to all tubes.

13. Energizing arrangement as set forth in claims 8 to 10, characterized by the fact that it comprises as many maintenance current sources as there are tubes, each maintenance current (5) source having means for manually adjusting the amplitude of the current flowing in the tube associated therewith.

14. Energizing arrangement as set forth in claims 8 to 10, characterized by the fact that the maintenance current sources (5) are provided with common means (U₃) for simultaneously adjusting the current amplitude in all the tubes energized by said sources.

15. Energizing arrangement as set forth in claims 8 to 10, characterized by the fact that the maintenance current sources (5) are energized by a common voltage source (U_l).

16. Energizing arrangement as set forth in claims 8 to 10, characterized by the fact that each tube has associated therewith a first diode (24) connected in series between the voltage pulse generator (4) and an electrode (18) of the tube and a second diode (31) connected in series between the maintenance current source (5) and said electrode (18).

17. Utilization of the energizing arrangement as set forth in claims 1 to 16 in a matrix display board.

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