EP0047692B1 - Method of generating control signals for a plasma panel, and plasma panel controlled by signals generated according to this method - Google Patents

Description

The present invention relates to a method for generating the control signals of an alternating type plasma panel. It also relates to plasma panels of the alternative type controlled by signals developed by this process.

Plasma panels of the alternative type are well known in the prior art, in particular by patent document FR-A-2417848, in the name of THOMSON-CSF and by the article published in the "THOMSON-CSF Technical Review", June 1978, volume 10, N ° 2, pages 249 to 275.

These panels include a large number of cells arranged in a matrix form. Each cell is constituted by the gas space located at the intersection of two electrodes belonging to two networks of orthogonal electrodes and is subjected to control signals formed by the difference of the voltages applied to the two electrodes between which it is located.

Among the control signals, mention may be made of the registration signals which cause the cells to ignite, the erasure signals which extinguish the cells and the maintenance signals which keep the cells in their initial state, namely the state off, i.e. the status on.

Unlike the maintenance signals which are applied to all the electrodes of the panel to ensure the visualization of the information entered, the recording and erasing signals are selective signals which must not cause recording and erasing only for the selected cells.

For this purpose, any cell C _x y is only registered if its two electrodes, x and y, receive adequate voltages, V _x and Vy, which make it possible to obtain at the terminals of this cell and of it alone the registration signal.

It is the same to obtain the erasure of the Cxy cell.

By patents US-A-3,909,804, US-A-3,973,253 and US-A-4,097,856, it is known to carry out selective inscriptions and deletions of cells in the same row or in the same column simultaneously.

• - à appliquer à l'une des électrodes de l'un des réseaux une tension dite de sélection et aux autres électrodes de ce réseau une tension dite de non-sélection ;
• - à appliquer simultanément à chaque électrode de l'autre réseau une tension choisie parmi au moins trois tensions dites d'inscription et d'effacement ou d'entretien ;

The present invention relates to a method for generating the control signals of an alternating type plasma panel, these control signals being applied between two electrodes belonging to two networks of orthogonal electrodes and the gas space located at the intersection. of two electrodes belonging to different networks constituting a cell of the panel, characterized in that it consists:

• - applying to one of the electrodes of one of the networks a so-called selection voltage and to the other electrodes of this network a so-called non-selection voltage;
• - simultaneously applying to each electrode of the other network a voltage chosen from at least three so-called recording and erasing or maintenance voltages;

• - la tension de sélection croît linéairement en fonction du temps de 0 à la valeur V₁ puis se stabilise à V₁ avant de revenir à 0 ;
• - la tension de non-sélection est nulle ;
• - la tension d'inscription est négative d'amplitude V₁ ;
• - la tension d'effacement est nulle ;
• - la tension d'entretien est positive d'amplitude V₁.

the form, amplitude and duration of these various voltages being such that the cells receiving on one electrode the selection voltage and on the other electrode the writing, erasing or maintenance voltage are written down, erased or maintained in their initial state, whereas the cells receiving the non-selection voltage on one electrode are all maintained in their initial state whatever the voltage applied to the other electrode and in that:

• - the selection voltage increases linearly as a function of time from 0 to the value V ₁ then stabilizes at V ₁ before returning to 0;
• - the non-selection voltage is zero;
• - the writing voltage is negative with amplitude V ₁ ;
• - the erase voltage is zero;
• - the maintenance voltage is positive with amplitude V ₁ .

• - Les figures 1 et 4, une représentation schématique de quelques cellules d'un panneau à plasma ;
• - Les figures 2a à 2h et 3a à 3h, les tensions qui, selon l'art antérieur, sont appliquées aux électrodes des cellules de la figure 1, et les signaux de commande reçus par ces cellules, pour provoquer respectivement l'inscription et l'effacement de l'une des cellules ;
• - Les figures 5a à 5h, les tensions qui, selon l'invention, sont appliquées aux électrodes des cellules de la figure 4, et les signaux de commande reçus par ces cellules.

Other objects, characteristics and results of the invention will emerge from the following description, given by way of nonlimiting example and illustrated by the appended figures which represent:

• - Figures 1 and 4, a schematic representation of some cells of a plasma panel;
• - Figures 2a to 2h and 3a to 3h, the voltages which, according to the prior art, are applied to the electrodes of the cells of Figure 1, and the control signals received by these cells, to respectively cause the inscription and l 'deletion of one of the cells;
• - Figures 5a to 5h, the voltages which, according to the invention, are applied to the electrodes of the cells of Figure 4, and the control signals received by these cells.

In the different figures, the same references designate the same elements, but, for reasons of clarity, the dimensions and proportions of the various elements are not observed.

FIG. 1 schematically represents four cells C ₁₁ , C ₁₂ , C ₂₁ and C ₂₂ of a plasma panel which are located at the intersections of two horizontal electrodes x ₁ and x ₂ and two vertical electrodes y ₁ and y ₂ .

• - la tension V_x1 a une amplitude V₁ et une durée t₃-t₁ ;
• - la tension V_X2 a la même amplitude V₁ et une durée t₂-t₁ inférieure à t₃-t₁ ;
• - la tension Vy₁ a une partie négative d'amplitude V₂ inférieure à V₁ et de durée t₃-t₂ suivie par une partie positive d'amplitude V₁ et de durée t₅- t₄ ;
• - enfin, la tension V_y2 a une amplitude V_i et une durée t_s-t₄.

Suppose we want to enter cell C ₁₁ . Figures 2a, b, c, d represent the voltages V _x1 , V _X2 , Vy ,, Vy ₂ , which are applied. according to the prior art, at the electrodes X ₁ , X ₂ , Y ₁ , Y ₂ so that only the cell C ₁₁ is registered:

• - the voltage V _x1 has an amplitude V ₁ and a duration t ₃ -t ₁ ;
• - the voltage V _X2 has the same amplitude V ₁ and a duration t ₂ -t ₁ less than t ₃ -t ₁ ;
• the voltage Vy ₁ has a negative part of amplitude V ₂ less than V ₁ and of duration t ₃ -t ₂ followed by a positive part of amplitude V ₁ and of duration t ₅ - t ₄ ;
• - finally, the voltage V _y2 has an amplitude V _i and a duration t _s -t ₄ .

In Figures 2e, f, g, h, the control signals applied to cells C ₁₁ , C ₁₂ , C ₂₁ , C ₂₂ and which result from the difference in the voltages applied to the two electrodes between which each cell is located.

We note the appearance at the terminals of cell C ₁₁ of t ₂ to t ₃ of a voltage of amplitude V ₁ + V ₂ sufficient to cause the writing of C ₁₁ .

On the contrary on the other cells, the amplitude of the voltage does not exceed V ₁ , which is insufficient to cause their inscription. Only cell C ₁₁ is therefore entered.

It is noted that for the four signals applied to the cells which are represented in FIGS. 2e at 2 h, there is at time t ₁ a rising edge of amplitude V ₁ and at time t ₄ a falling edge at - V ₁ ce which corresponds to the characteristics of the maintenance signals and therefore allows viewing of the information already entered on the panel.

• - la tension V_x1 varie, à partir de l'instant t₄ sensiblement linéairement en fonction du temps de 0 à V₁ puis se stabilise à V₁ et redescend à 0 au temps t_s. L'utilisation d'une telle tension pour effacer une cellule à été décrite dans le FR-A-2 417 848 déjà cité ;
• - la tension V_x2 est constamment nulle ;
• - la tension V_y1 a une partie négative d'amplitude V₁ de t₁ à t₂ suivie par une partie positive d'amplitude V₁ de t₃ à t₄ ;
• - la tension V_y2, ne diffère de V_y1 que par le fait que sa partie positive est plus longue et dure de t₃ à t₅.

Figures 3a, b, c, d represent the voltages V _x1 , V _X2 , V _y1 , V _y2 which are applied according to the prior art, to the electrodes x ₁ , x ₂ , y ₁ , y ₂ so that only cell C ₁₁ is deleted. These tensions will be described with reference to the instants t ₁ to t ₅ which follow one another on the time axis, Ot, in the order t ₁ to t ₅ :

• - the voltage V _x1 varies, from time t ₄ substantially linearly as a function of time from 0 to V _1, then stabilizes at V ₁ and drops back to 0 at time t _s . The use of such a voltage to erase a cell has been described in FR-A-2 417 848 already cited;
• - the voltage V _x2 is constantly zero;
• - the voltage V _y1 has a negative part of amplitude V ₁ from t ₁ to t ₂ followed by a positive part of amplitude V ₁ from t ₃ to t ₄ ;
• - the voltage V _y2 , differs from V _y1 only by the fact that its positive part is longer and lasts from t ₃ to t ₅ .

Figures 3e to 3h show the control signals applied to cells C ₁₁ , C ₁₂ , C ₂₁ , C _22. Only the signal applied to cell C ₁₁ allows erasure thanks to the linear growth part of the voltage of 0 at V ₁ from time t ₄ at time t _s .

It is noted that in this case also the four signals applied to the cells carry out the maintenance of the cells because of the rising edge towards V ₁ existing at time t ₁ and the falling edge towards - V, existing at time t ₃ . Only cell C ₁₁ is deleted, the other cells are maintained in their initial state.

It can be seen that the voltages V _x1 and V _y1 making it possible to obtain the registration of cell C ₁₁ differ from the voltages V _x1 and Vy ₁ making it possible to obtain its erasure. To realize this, it suffices to compare Figures 2a and 3a, and 2c and 3c.

In conclusion and as has already been said in the introduction to the description, it is not possible, according to the prior art, to simultaneously carry out selective recording and erasure of cells having an electrode in common. For example, it is not possible to enter C ₁₁ and simultaneously delete C ₁₂ or C ₂₁ . We have seen the problem that this entailed for producing the display of successive images with plasma panels of the alternative type.

FIG. 4 schematically represents six cells C ₁₁ , C ₁₂ , C ₁₃ , C ₂₁ , C ₂₂ , C ₂₃ of a plasma panel which are located at the intersections of two horizontal electrodes x ₁ and x ₂ and three electrodes vertical y ₁ , y ₂ and y ₃ .

FIGS. 5a to 5e serve to illustrate the method for developing the control signals according to the invention. These figures represent the voltages V _x1 , ^V x ₂ , Vyi, V _y2 and Vy ₃ which are applied to the electrodes x ₁ , x ₂ , y ₁ , y ₂ and y ₃ so as to cause, for example, at at the same time, the inscription of C ₁₁ , the erasure of C ₁₂ and the maintenance in its initial state of C ₁₃ , as well as the maintenance of the other cells C ₂₁ , C ₂₂ and C ₂₃ in their initial state.

FIGS. 5f to 5k represent the resulting voltages obtained at the terminals of cells C11, C12, C13, C ₂₁ , C22, C ₂₃ .

In FIGS. 5a to 5k, the selective part of the voltages has been shown in broken lines, that is to say that which is not identical for all the electrodes and all the cells of the panel and which extends in the 'example chosen from t ₃ to t ₄ . We have located on the time axis, Ot, the instants t ₁ to t ₆ which follow each other in order.

In FIGS. 5a to 5k, the non-selective part of the voltages, which is identical for all the electrodes and all the cells of the panel, and which aims to apply to all the cells a maintenance signal consisting of 'a positive part of amplitude V ₁ and a negative part of amplitude V ₁ .

In the example shown in FIGS. 5a to 5e, the non-selective part is obtained by providing a positive part of amplitude V ₁ from t ₁ to t ₂ for the voltages V _y1 , V _y2 and Vy ₃ and by providing a part positive of amplitude V ₁ from t ₅ to t ₆ for the voltages V _x1 and V _X2 .

It would of course be possible to proceed differently, for example, by providing a negative part of amplitude V ₁ from t ₅ to t ₆ for the voltages V _y1 , V _y2 and V _y3 and by applying a zero voltage between the instants t ₅ and t ₆ for the voltages V _x1 and V _x2 .

• - à appliquer à l'électrode x₁ qui correspond à la ligne sur laquelle on veut réaliser, simultanément et sélectivement, une inscription, un effacement et l'entretien d'une cellule dans son état initial, une tension dite de sélection. Sur la figure 3a, cette tension varie à partir de l'instant t₃ sensiblement linéairement en fonction du temps 0 à V₁ puis se stabilise à V₁ et redescend à 0 au temps t₄ ;
• - à appliquer à l'autre électrode x₂ une tension dite de non-sélection qui sur la figure 5b est nulle de t₃ à t₄ ;
• - à appliquer toujours t₃ à t₄ :
  • sur l'électrode y₁, une tension dite d'inscription de façon à inscrire la cellule C₁₁. Sur la figure 5c, cette tension est négative et d'amplitude V₁ ;
  • sur l'électrode y₂, une tension dite d'effacement de façon à effacer la cellule C₁₂. Sur la figure 5d, cette tension est nulle ;
  • sur l'électrode y₃, une tension dite d'entretien pour entretenir la cellule C₁₃ dans son état initial. Sur la figure 5e, cette tension est positive et d'amplitude V₁.

The method according to the invention consists:

• - To apply to the electrode x ₁ which corresponds to the line on which we want to carry out, simultaneously and selectively, an entry, an erasure and the maintenance of a cell in its initial state, a so-called selection voltage. In FIG. 3a, this voltage varies from instant t ₃ substantially linearly as a function of time 0 to V _1, then stabilizes at V ₁ and drops back to 0 at time t ₄ ;
• - applying to the other electrode x ₂ a so-called non-selection voltage which in FIG. 5b is zero from t ₃ to t ₄ ;
• - always apply t ₃ to t ₄ :
  • on the electrode y ₁ , a so-called registration voltage so as to register the cell C ₁₁ . In FIG. 5c, this voltage is negative and of amplitude V ₁ ;
  • on the electrode y ₂ , a so-called erase voltage so as to erase the cell C ₁₂ . In FIG. 5d, this voltage is zero;
  • on the electrode y ₃ , a so-called maintenance voltage for maintaining the cell C ₁₃ in its initial state. In FIG. 5e, this voltage is positive and of amplitude V ₁ .

The form, amplitude and duration of the various selection, non-selection, registration, erasure or maintenance voltages are chosen so that the cells receiving the selection voltage on an electrode and the other electrode the voltage of registration, erasure or maintenance are registered, erased or maintained in their initial state. On the contrary, the cells receiving on a non-selection voltage on one electrode must be maintained in their initial state whatever the voltage applied to the other electrode of these cells.

This is what happens with the voltages shown in broken lines in FIGS. 5a to 5e which are given only by way of example.

• - que la cellule C_n est inscrite, car elle reçoit entre t₃ et t₄ une tension élevée qui atteint 2V₁ ;
• - que la cellule C₁₂ est effacée, car elle reçoit de t₃ à t₄ une tension qui croît linéairement en fonction du temps de 0 à V₁ ;
• - que les autres cellules C,₃, C₂₁, C₂₂ et C₂₃ sont entretenues dans leur état initial car elles reçoivent des tensions représentées sur les figures 5h à 5k qui sont successivement négatives, d'amplitude V₁ et positives, d'amplitude V₁, mais qui n'atteignent jamais une amplitude suffisante pour permettre l'inscription et ne comportent pas non plus de zone à croissance linéaire de la tension qui permette l'effacement.

We observe indeed by observing Figures 5f to 5k:

• - that cell C _n is registered, because it receives between t ₃ and t ₄ a high voltage which reaches 2V ₁ ;
• - that cell C ₁₂ is deleted, since it receives from t ₃ to t ₄ a voltage which increases linearly as a function of time from 0 to V ₁ ;
• - that the other cells C, ₃ , C ₂₁ , C ₂₂ and C ₂₃ are maintained in their initial state because they receive voltages shown in FIGS. 5h to 5k which are successively negative, of amplitude V ₁ and positive, of amplitude V ₁ , but which never reach a sufficient amplitude to allow registration and also do not include a linear growth zone of the voltage which allows erasure.

• - les électrodes d'un réseau reçoivent une tension dite de sélection ou une tension dite de non-sélection ;
• - les électrodes de l'autre réseau reçoivent une tension dite d'inscription, d'effacement, d'entretien ou toute autre tension mettant la cellule dans un état donné.

It can be seen that with the method according to the invention:

• the electrodes of a network receive a so-called selection voltage or a so-called non-selection voltage;
• - The electrodes of the other network receive a voltage called registration, erasure, maintenance or any other voltage putting the cell in a given state.

One carries out, simultaneously and selectively, for a given row or column, the recording, the deletion and the maintenance of the cells.

In the prior art, on the contrary, the various cycles, for writing and erasing for example, are carried out separately. The electrodes of each network receive, during a given cycle, only two types of voltage, selection or non-selection, specific to this cycle.

As seen in the introduction to the description, the method according to the invention makes it possible to solve the problem of displaying successive images by plasma panel.

If from one image to another, there is no area of the image which remains unchanged, it is not necessary to carry out, simultaneously and selectively, inscriptions, erasures and maintenance of cells in their initial state. It suffices to carry out selective registrations and erasures. The electrodes of one of the networks therefore receive a voltage chosen only from the writing or erasing voltages.

If, on the other hand, from one image to another, certain image zones remain unchanged, it is useful to simultaneously and selectively carry out inscriptions, erasures and maintenance of cells in their initial state.

As regards the control circuits of the plasma panel allowing the implementation of this process, they derive directly from those described by FR-A-2 417 848 already cited.

Claims (2)

1. A method for establishing control signals for a plasma panel of the AC type, these control signals being applied between two electrodes belonging to two families of orthogonal electrodes, and the gas space situated at the intersection zone of two electrodes which belong to different families constituting a panel cell, characterized in :

- that a voltage called selection voltage (V_x1) is applied to one of the electrodes of one of the families and a voltage called non-selection voltage (V_x2) is applied to the other electrodes of this family ;

- simultaneously, a voltage chosen from at least three voltages called write voltage (Vy_i), clear voltage (V_Y2) or maintenance voltage (Vy₃) is applied to each electrode of the other family ; the shape, the amplitude and the duration of these different voltages being such that the cells receiving at one electrode the selection voltage and at the other electrode the write, clear or maintenance voltage are inscribed, cleared or maintained in their initial state, while the cells receiving on one electrode the non-selection voltage are all maintained in their initial state regardless of the type of voltage applied to the other electrode,

- that the selection voltage (V_x1) increases linearily in time from zero to an amplitude V₁, then stabilizes at this amplitude before returning to zero ;

- that the non-selection voltage (V_x2) is zero ;

- that the write voltage (Vy_i) is a negative voltage of an amplitude V₁ ;

- that the clear voltage (Vy₂) is zero ;

- that the maintenance voltage (V_y3) is a positive voltage of an amplitude V₁.

2. A plasma panel of the AC type characterized in that it is controlled by control signals established by means of the method defined in claim 1.

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