EP1410413B1 - Method of connecting a plasma panel to the electrical power supply therefor in an image display device - Google Patents

Abstract

The invention relates to a device comprising a metallic support plate (1), the front face of which supports a plasma discharge panel which is equipped with a network of pairs of adjacent electrodes (7, 8) and the rear face of which is equipped with a power supply (13') . According to the invention, the connection ends of the electrodes (7, 8) of one electrode pair are located on opposite edges (5, 6) of the panel and the power circuit of each pair of adjacent electrodes (7, 8) forms a current loop that does not surround the metallic plate (1). In this way, electric losses are restricted in said plate and the cells of the panel operate identically along the entire length of the electrodes.

Description

The invention relates to the connection of a plasma display panel to power supply and control means of this panel.

With reference to Figures 1 and 2 attached, the document JP 2000-089723 HITACHI discloses an image display device, in particular for television, comprising a metal support plate 1, generally made of aluminum, supporting, on one side, an alternating plasma discharge panel, and on the other side at least one printed circuit board 2 supporting means 13, 14 for supplying and controlling discharges of said panel.

• d'au moins un premier réseau d'électrodes servant notamment au maintien de décharges par application d'impulsions de tension entre des électrodes adjacentes 7, 8 de deux séries différentes d'électrodes de ce premier réseau
• et d'un second réseau d'électrodes d'adressage des décharges (non représenté), croisant les électrodes du premier réseau de manière à former à leurs intersections et entre les dalles 3, 4 des espaces de décharges.

The plasma panel itself comprises a front plate 3 and a rear panel 4 between them plasma discharge areas, and is equipped, between these slabs:

• at least one first electrode array used in particular for maintaining discharges by applying voltage pulses between adjacent electrodes 7, 8 of two different series of electrodes of this first network;
• and a second network of discharge addressing electrodes (not shown), crossing the electrodes of the first network so as to form at their intersections and between the slabs 3, 4 discharge spaces.

On the slab 3, the connection ends of the electrodes of a series are all located on an edge 5 opposite to that 6 on which are all the connection ends of the electrodes of the other series.

The supply circuit of each pair of adjacent electrodes 7, 8 of two different series forms a current loop from the supply and control means through a first electrode 7 and the second electrode 8 of the pair.

All of these components are inserted in a housing 20.

The rear panel 4 of the plasma panel is fixed on the metal support plate 1 with an adhesive layer 16 of a sufficient thickness to compensate for the difference in the coefficient of thermal expansion between the slab and the plate. ; the adhesive material of this layer 16 is adapted in a manner known per se to ensure the heat transfer of the calories dissipated in the operating panel to the plate 1 which, because it is metallic, has a better thermal coefficient of exchange with the air circulating in the housing 20.

The document JP11-041545 FUJITSU also describes an image display device of this type where, specifically, the printed circuit board 2, which supports the power supply and control means, extends over the entire surface of the panel and is directly bonded to the support plate 1 so as to shorten the connections between the ends of the electrodes on the edges of the panel and the supply and control means on either side of the support plate 1; no transverse conductor is inserted between the panel and the support plate.

Between adjacent electrodes 7, 8 of two different series of electrodes of this first network, there is therefore a succession of holding discharge zones, which generally correspond to a line of pixels or elements of the image to be displayed; this electrode array can also be used for addressing in cooperation with the electrodes of the second network; thus, the electrodes of the first series may be holding and addressing electrodes, and the electrodes of the second series are then electrodes only for maintenance.

These electrodes of the first network are in general coplanar.

This holding network generally has only two sets of electrodes so that the adjacent electrodes 7, 8 of different series are grouped in pairs; according to other variants, the first network can have three series and the coplanar electrodes are then associated by triads.

As shown on Figures 1 to 3 , the holding electrodes 7, 8 of the first network are generally arranged on the internal face of the front plate 3; alternatively, they can be arranged on the inner face of the rear panel 4.

• des moyens d'alimentation de puissance adaptés pour générer des séries d'impulsions de haute tension électrique, généralement supérieure à 100 V ;
• des moyens de commutation des différentes électrodes (ou « drivers » en langue anglaise) adaptés pour appliquer lesdites impulsions de tension aux électrodes sélectionnées par les moyens de commande.

The means 13, 14 for supplying and controlling discharges generally comprise:

• power supply means adapted to generate series of pulses of high electrical voltage, generally greater than 100 V;
• switching means of the different electrodes (or "drivers" in English language) adapted to apply said voltage pulses to the electrodes selected by the control means.

As the first electrode array 7, 8 serves to maintain the discharges, it is in this network that dissipates most of the electrical power necessary for the visualization of the images, and it is therefore in this network that significant electrical losses can occur.

Referring to Figures 1 and 2A it can be seen that the supply circuit of each pair of electrodes 7, 8 forms a current loop starting from the power supply and control means 13 via a first conductor 11 passing from one side to the other of the support plate 1, a first electrode 7 and, through the succession of discharge zones served by this pair, the second electrode 8 of the pair, a second conductor 12 passing in the opposite direction from one side to the other of the support plate 1, a third conductor 21 passing from one edge to the other opposite of the support plate 1, until closing on the means 13 for supply and control.

Referring to Figures 1 and 2B it can be seen that the supply circuit of each pair of electrodes 7, 8 also forms a current loop in the opposite direction which is closed here on means 14 for supply and control positioned opposite the preceding means 13 on the support plate 1.

During the steps of maintaining discharges during operation of the device, discharges arise between the electrodes of each pair 7, 8 and large currents flow in these loops.

• la boucle de courant formée par le circuit d'alimentation de chaque paire d'électrodes 7, 8 entoure la plaque de support métallique 1 et engendre dans cette plaque des pertes importantes par courants de Foucault ; lorsqu'une boucle de courant englobe une plaque métallique de forts courants induits apparaissent sur les deux faces de cette plaque, le sens du courant étant inversé d'une face à l'autre ; les courants induits dans cette plaque provoquent des pertes, des échauffements locaux et perturbent les circuits électroniques placés à proximité ;
• ce mode de connexion nécessite, de préférence, deux alimentations électriques de puissance différentes 13, 14, positionnés auprès de bords opposés 5, 6 du panneau, ce qui est relativement coûteux.

The classic mode, schematized at the figure 2 connecting the electrodes of the panel located on one face of the support plate 1 to the supply means 13, 14 located on the other face has the following drawbacks:

• the current loop formed by the supply circuit of each pair of electrodes 7, 8 surrounds the metal support plate 1 and generates in this plate significant losses by eddy currents; when a current loop includes a metal plate, strong induced currents appear on both sides of this plate, the direction of the current being reversed from one face to the other; the currents induced in this plate cause losses, local heating and disturb the electronic circuits placed nearby;
• this mode of connection preferably requires two different power supplies of power 13, 14, positioned near opposite edges 5, 6 of the panel, which is relatively expensive.

The transverse conductor 21 passing from one edge to the other opposite of the support plate 1 is located here on the same side of the support plate 1 as the means 13, 14 for supply and control; according to a variant described in the document EP1065694 - SAMSUNG, this transverse conductor can be located on the same internal face of the slab 3 which carries the electrodes, that is to say the opposite side to the means 13, 14 of supply and control with respect to the support plate 1 (see lead 12a 'in FIG. 8 of this document); no transverse conductor is inserted between the panel and the support plate; as taught by this document, this transverse conductor must then be deported outside the light emission zone and positioned on average at a significant distance from the pairs of electrodes. The current loops then have on average a vertical section of large surface area, generate an electromagnetic field having a large horizontal component, and also induce electric currents in the metal support plate, which causes electrical losses and troublesome interference radiation.

It will be noted that, according to these conventional modes of connection of a plasma panel to its supply means, the first conductor 11 and the second conductor 12, which both pass from one side to the other of the plate of 1, are arranged on opposite edges of the panel, since the ends of the electrodes they serve are on opposite edges.

• comme représenté sur la figure 3, la boucle de courant formée par le circuit d'alimentation de chaque paire d'électrodes 7, 8 n'entoure plus la plaque métallique 1 ; on évite ainsi les pertes par courants de Foucault dans cette plaque ;
• une seule alimentation électrique 13' peut, sans inconvénient, servir à toutes les alternances des impulsions de maintien, comme représenté aux figures 3A et 3B.

To avoid the aforementioned drawbacks, the document JP 2000-089723 already cited described, with reference to the figure 3 attached, a circuit where all the electrodes of the holding network are fed at their end at the same edge 5 of the plasma panel, so that:

• as represented on the figure 3 the current loop formed by the supply circuit of each pair of electrodes 7, 8 no longer surrounds the metal plate 1; this avoids the eddy current losses in this plate;
• a single power supply 13 'can, without inconvenience, be used for all the alternations of the holding pulses, as shown in FIG. Figures 3A and 3B .

Note that, according to this other mode of connection and supply of a plasma display panel, the first conductor 11 and the second conductor 12 ', which both pass from one side to the other of the H support plate 1, are arranged here at the same edge 5 of the panel.

This solution, however, has a serious disadvantage: the discharge zones 9 located towards this edge 5 are subjected to an impedance very different from that of the discharge zones 10 located towards the opposite edge 6 of the panel; the difference corresponds to the impedance of the electrode portions 7, 8 included between these zones 9, 10.

Due to this difference in impedance, the operation of the panel cells differs over the entire length of the electrodes 7, 8 and the light characteristics of the discharge areas differ greatly from one edge to the other 6 of the panel, which seriously compromises the quality of visualization of images

The aim of the invention is to simultaneously remedy all the disadvantages of the solution represented in Figures 1 and 2 and to that represented in figure 3 .

• une plaque de support métallique supportant, sur sa face avant, un panneau à décharges de plasma, et, sur sa face arrière, des moyens d'alimentation et de commande des décharges dudit panneau,
• ledit panneau à plasma comprenant lui-même une dalle avant et une dalle arrière ménageant entre elles des zones de décharge de plasma, et, entre ces dalles, au moins un premier réseau d'électrodes servant notamment au maintien de décharges par application d'impulsions de tension entre des électrodes adjacentes de deux séries différentes d'électrodes de ce premier réseau, où les extrémités de connexion des électrodes d'une série débouchent sur un bord opposé du panneau à celui sur lequel débouchent les extrémités de connexion des électrodes de l'autre série, caractérisé en ce que les extrémités de connexion de l'une des séries d'électrodes débouchant sur un bord du panneau sont reliées aux moyens d'alimentation et de commande par l'intermédiaire de conducteurs électriques transversaux qui sont insérés entre ladite dalle arrière et ladite plaque métallique et qui s'étendent, à partir desdites extrémités, jusqu'au bord opposé du panneau.

For this purpose, the subject of the invention is an image display device comprising:

• a metal support plate supporting, on its front face, a plasma discharge panel, and, on its rear face, means for supplying and controlling discharges of said panel,
• said plasma panel itself comprising a front slab and a rear slab leaving between them plasma discharge zones, and, between these slabs, at least a first electrode array used in particular for maintaining discharges by applying pulses voltage between adjacent electrodes of two different sets of electrodes of this first array, wherein the connection ends of the electrodes of a series open on an opposite edge of the panel to that on which the connection ends of the electrodes of the another series, characterized in that the connection ends of one of the series of electrodes opening on an edge of the panel are connected to the supply and control means via transverse electrical conductors which are inserted between said slab rear and said metal plate and extending from said ends to the opposite edge of the panel.

The electrode array located between the slabs is generally disposed on the internal face of one of the slabs, generally the front slab; the electrodes are generally covered with a dielectric layer; instead of being arranged on the inner face, at least one of the series of electrodes can be arranged between the slabs in the thickness of barriers defining the discharge areas of the panel.

According to one variant, several electrodes of the same series are connected to the supply and control means via the same transverse conductor.

The supply circuit of each pair of adjacent electrodes of two different series forms a loop of current from the supply and control means via a first electrode and then the second electrode of the pair; thanks to the invention, the current loop of the supply circuit of each pair of the panel does not surround the metal plate, unlike the solutions described in the documents JP 2000-089723 and JP11-041545 ; thus limiting the eddy current losses in the metal plate while obtaining identical impedance discharge areas between the adjacent electrodes along their entire length; thus limiting the losses without degrading the image viewing quality.

The transverse conductors being inserted according to the invention between the rear panel of the panel and the support plate, it is no longer necessary to deport them outside the light emission area as in the document EP1065694 already cited, which allows to position them so as to advantageously limit the vertical section of the current loops of the different pairs of electrodes and the disadvantages relating thereto.

Thanks to the transverse conductors, all the power supply of the electrodes is brought back to the same edge of the panel so that it is then possible, as described in the invention. JP 2000-089723 as represented in figure 3 hereinafter, to connect on the same edge of the panel all the electrodes of said network to the power supply and control means; the advantage of this arrangement is that a single power supply can, without inconvenience, serve all alternations of holding pulses.

These transverse conductors are preferably grouped into several layers of conductors each located at a position corresponding approximately to the average position of the electrodes to which the conductors of this sheet are connected; as these electrodes generally correspond to lines of the panel, this position generally corresponds to a height on the panel; in the case of the use of 3 layers, the first would for example be positioned at 1/6 of the height of the panel, the second for example at half the height, and the third for example at 5/6 of the height .

In the case of the grouping of the transverse conductors into several layers thus spaced from each other, the transverse conductor returning the supply current of a pair of electrodes is therefore not generally located at the same height as this pair of electrodes but slightly offset with respect to this pair, and the corresponding current loop still has a large surface vertical section and generates an electromagnetic field having a large horizontal component; to avoid this disadvantage, on the panel, each transverse conductor connected to a single electrode corresponding to a pair of adjacent electrodes is preferably positioned approximately at the same height as said pair; preferably, these transverse electrical conductors then form a single conductive sheet inserted between the rear slab and the metal plate.

Preferably, this conductive sheet or these conductive sheets also serve as fixing means of the panel on said metal support plate; one can for example use one or plies having two adhesive faces; the thickness of the conductive sheet advantageously makes it possible to damp the differences in thermal expansion between the rear panel slab and the metal support plate.

According to an advantageous variant of the invention, the supply circuit of each pair comprising, at the start of the supply and control means, a pair of supply conductors each of which is connected to an electrode of the pair, the device according to the invention comprises common mode filtering means surrounding each pair of conductors.

The common mode filter is adapted in a manner known per se to reduce the transmission of radio frequency high frequency disturbances from electronic power and control means and transmitted in common mode to the plasma panel.

Preferably, these common mode filtering means comprise a tube of ferromagnetic material surrounding this pair of supply conductors.

During operation of the panel, at the location of this core, the currents flowing in each conductor of the same pair are opposite, which allows this ferromagnetic tube to act as a common mode filter and to reduce the transmission of radio frequency interference from the electronic power supply and control means and transmitted to the plasma panel.

Preferably, said so-called common mode filtering means are located at the edge of the panel where all the electrode supply conductors open out.

Since the ends of the transverse electrical conductors opposite to those of the electrodes of the same series open at the same panel edge as the connection ends of the electrodes of the other series, it is very easy to implant there. the filtering means since the supply conductors of each pair of electrodes are found close to each other and can easily be surrounded by a ferromagnetic filtering tube in common mode.

In general, the plasma panel also comprises a second electrode array for addressing the discharges, crossing the electrodes of the first network at the discharge zones of the panel.

• la figure 1, déjà décrite, représente une vue générale de dessus en coupe d'un dispositif de visualisation d'images ;
• les figures 2A et 2B, déjà décrites, représentent schématiquement les composants et les connexions électriques d'un dispositif selon l'art antérieur, avec, dans la partie supérieure, une vue de face d'une paire d'électrodes de maintien sur la dalle d'un panneau à plasma, et, dans la partie inférieure, une vue en coupe de la plaque de support du panneau et des moyens d'alimentation et de commande des électrodes.
• les figures 3A et 3B, déjà décrites, représentent, de la même façon qu'aux figures 2A et 2B, un autre schéma de connexions tel que décrit dans le document JP 2000-089723 ;
• la figure 4 illustre un schéma de connexion selon un mode préférentiel de réalisation de l'invention, où l'ensemble du dispositif de visualisation est représenté en coupe sauf la dalle avant qui est représentée en perspective pour faire apparaître les deux électrodes de maintien d'une même paire.

The invention will be better understood on reading the description which follows, given by way of nonlimiting example, and with reference to the appended figures in which:

• the figure 1 , already described, represents a general top view in section of an image display device;
• the Figures 2A and 2B , already described, schematically show the components and electrical connections of a device according to the prior art, with, in the upper part, a front view of a pair of holding electrodes on the slab of a panel to plasma, and, in the lower part, a sectional view of the support plate of the panel and means for supplying and controlling the electrodes.
• the Figures 3A and 3B , already described, represent, in the same way as in Figures 2A and 2B , another connection scheme as described in the document JP 2000-089723 ;
• the figure 4 illustrates a connection diagram according to a preferred embodiment of the invention, wherein the entire display device is shown in section except the front plate which is shown in perspective to show the two holding electrodes of the same pair .

In order to simplify the description and to show the differences and advantages that the invention presents with respect to the prior art, identical references are used for the elements that provide the same functions.

• la dalle avant 3 est dotée d'un réseau de paires d'électrodes coplanaires de maintien 7, 8, l'une des électrodes de chaque paire servant également à l'adressage ;
• la dalle arrière 4 est dotée d'un réseau d'électrodes d'adressage 18 ;
• les extrémités de connexion des électrodes 7 d'une paire 7, 8 étant, comme dans l'art antérieur, situées sur un bord 5 du panneau et connectées à l'alimentation 13' par l'intermédiaire des moyens de connexion 11, les extrémités de connexion de l'autre électrode 8 de cette paire 7, 8 sont situées sur le bord opposé 6 du panneau ;
• l'extrémité de connexion de cette électrode 8 débouchant sur le bord 6 du panneau est reliée à l'alimentation 13' par l'intermédiaire de moyens de connexion 12 classiques d'extrémité d'électrodes et d'un conducteur électrique transversal 21' placé entre la face avant dé la plaque métallique 1 et la face externe de la dalle arrière 4 ; ce conducteur 21' s'étend d'un bord 6 à l'autre 5 du panneau.

In addition to the elements already described concerning the front and rear panels 3 and 4 of the plasma panel, the metal support plate 1 and, on the back of this plate, a power supply 13 'serving for the supply and the control of discharges in the panel, referring to the figure 4 :

• the front panel 3 is provided with a network of coplanar holding electrode pairs 7, 8, one of the electrodes of each pair also serving for addressing;
• the rear panel 4 is provided with a network of addressing electrodes 18;
• the connection ends of the electrodes 7 of a pair 7, 8 being, as in the prior art, located on an edge 5 of the panel and connected to the power supply 13 'via the connection means 11, the ends connecting the other electrode 8 of this pair 7, 8 are located on the opposite edge 6 of the panel;
• the connecting end of this electrode 8 opening on the edge 6 of the panel is connected to the supply 13 'via conventional electrode end connection means 12 and a transverse electrical conductor 21' placed between the front face of the metal plate 1 and the outer face of the rear panel 4; this conductor 21 'extends from one edge 6 to the other 5 of the panel.

Thus, for each pair of adjacent electrodes 7, 8, the current loop of the supply circuit of this pair does not surround the metal plate 1.

The device illustrated in figure 4 also includes common mode filtering means surrounding each pair of conductors feeding a pair of electrodes 7, 8, here a tube of ferromagnetic material implanted at the edge 5 of the panel, where all the feed conductors electrodes, namely the end 22 of the transverse conductor 21 'supplying the electrode 8 and the connection means 11 to the electrode 7.

• à éviter que le courant ne circule autour de la plaque de support métallique 1 du panneau et à limiter ainsi les pertes électriques d'alimentation des électrodes ;
• à maintenir un fonctionnement identique pour toutes les cellules du panneau sur toute la largeur du panneau comprise entre les bords opposés 5 et 6 du panneau.

Referring to the figure 4 it can be seen that the current produced by the supply 13 'leaves one of its two terminals, goes through the connection means 11 at the end of the electrode 7, then crosses the panel between the electrodes 7 and 8 of the one pair, to emerge at the other edge 6 of the panel by the connection means 12 at the end of the electrode 8 and returns to the other terminal of the generator 13 'via the transverse connector 21 ', thereby constituting a current loop; to implement the invention in this particular embodiment, the following results in particular:

• to prevent the current from circulating around the metal support plate 1 of the panel and thus to limit the electrical losses of the electrodes;
• to maintain an identical operation for all the cells of the panel over the entire width of the panel between the opposite edges 5 and 6 of the panel.

Preferably, it is sought to minimize the inner surface of the loop of the feed current of the panel in order to minimize the electromagnetic radiation induced by this loop; for this purpose, it is preferable to position each transverse conductor 21 'connected to an electrode 8 corresponding to a pair of adjacent electrodes 7, 8 at approximately the same height as said pair.

The invention is defined by the claims.

Claims (9)

1. Image display device comprising:

   - a metal support plate (1) supporting, on its front face, a plasma discharge panel and, on its rear face, means for supplying and for driving the discharges of said panel:

   - the said plasma panel itself comprising a front tile (3) and a rear tile (4) leaving between them plasma discharge regions (9, 10) and, between these tiles, at least a first array of electrodes serving in particular for sustaining discharges by applying voltage pulses between adjacent electrodes (7, 8) of two different series of electrodes of this first array, in which the connection ends of the electrodes (7) of one series emerge on an opposite edge (5) of the panel to that (6) on which the connection ends of the electrodes (8) of the other series emerge, characterized in that the connection ends of one of the series of electrodes (8) emerging on one edge (6) of the panel are connected to supply and drive means via transverse electrical conductors (21') which are inserted between the said rear tile (4) and the said metal plate (1) and which extend, from the said ends, as far as the opposite edge (5) of the panel.
2. Device according to Claim 1, characterized additionally in that these transverse conductors are grouped together in several ribbons of conductors, each located at a position corresponding approximately to the mean position of the electrodes (8) to which the conductors of this ribbon are connected.
3. Device according to Claim 1, characterized additionally in that each transverse conductor (21') is connected to a single electrode (8) corresponding to one pair of adjacent electrodes (7, 8) and is positioned on the said panel at approximately the same height as the said pair.
4. Device according to Claim 3, characterized additionally in that these transverse electrical conductors (21') form a single conducting ribbon inserted between the rear tile (4) and the metal plate (1).
5. Device according to either of Claims 2 and 4, characterized additionally in that the said conducting ribbons or the said conducting ribbon also serve as a means for fastening the said panel to the said metal support plate (1).
6. Device according to any one of Claims 1 to 5, characterized additionally in that, since the supply circuit for each pair has, at the start of the supply and drive means, a pair of supply conductors, each of which is connected to an electrode (7, 8) of the pair, the said device includes common-mode filtering means (15) surrounding each pair of conductors.
7. Device according to Claim 6, characterized additionally in that the common-mode filtering means (15) comprise a tube made of a ferromagnetic material surrounding the said pair of supply conductors.
8. Device according to either of Claims 6 and 7, characterized additionally in that the said common-mode filtering means (15) are implanted at the edge (5) of the panel on which all the supply conductors for the electrodes emerge.
9. Device according to any one of the preceding claims, characterized additionally in that the said panel also includes a second array of electrodes (18) for addressing the discharges, these intersecting the electrodes of the first array at the said discharge regions (9, 10).

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