EP1739649A1 - Passive matrix display with means for compensating resistive losses - Google Patents

Abstract

The electroluminescent display device has a lightning or displaying panel having a network of light transmitters disposed in rows and columns, and a network of column electrodes. A voltage generating unit (2) delivers a supply voltage between two output terminals. The resistance of the column transmitter is defined as the resistance of the column electrode to which the transmitter is connected, where the resistance is taken between a supplying point of the electrode and connection point of the transmitter. A compensating unit (3) compensates the differences between the resistances of each column transmitter. An independent claim is also included for a method for controlling image lightning or displaying device.

Description

The invention relates to passive matrix electroluminescent diode panels for displaying images and a method for controlling these panels. When modulated in time ("PWM" or "Pulse Width Modulation" in English), the diodes of such panels can be controlled current or voltage.

The current control, as described for example in WO03 / 107318 , requires current generators that are economically disadvantageous; this current control method is also penalized by high parasitic capacitance charging times each time a new line of diodes to be addressed is selected, unless a pre-charge device is added, which increases still the cost of the panel.

The voltage control, which is more economical and allows the quasi-instantaneous load parasitic capacitances, requires on the other hand compensations ohmic losses along the supply electrodes.

To compensate for these losses, as well as the dispersion of the electrical characteristics between the different diodes of the panel, the document W02004 / 027743 proposes to add, at the head of each column electrode, a device for controlling injected charges (product of current by duration) which is slaved to a voltage setpoint addressed to a diode of this column, which diode is also selected by a line electrode. The addition of such a load control device and its servocontrol at the head of each column is economically disadvantageous.

An object of the invention is to avoid the aforementioned drawbacks.

• un panneau d'affichage ou d'éclairage qui comporte :
  • a) un réseau d'émetteurs de lumière disposés en lignes et en colonnes,
  • b) un réseau de N électrodes de ligne, et un réseau de P électrodes de colonne,
    .... chaque émetteur étant connecté d'une part à une desdites électrodes de ligne, en un point de connexion de ligne, et d'autre part à une desdites électrodes de colonne, en un point de connexion de colonne, de manière à pouvoir être alimenté entre cette électrode de ligne et cette électrode de colonne,
• des moyens d'alimentation des émetteurs qui comportent :
  • a) au moins un générateur de tension apte à délivrer une tension d'alimentation entre deux bornes de sortie,
  • b) des moyens aptes à sélectionner successivement chaque ligne d'émetteurs, en reliant un point d'alimentation de l'électrode de ligne à laquelle ces émetteurs sont connectés à l'une des bornes de sortie de l'au moins un générateur,
  • c) des moyens aptes à adresser des émetteurs d'une même ligne pour qu'ils émettent de la lumière, en reliant simultanément un point d'alimentation de chacune des électrodes de colonne auxquelles ces émetteurs sont connectés à l'autre borne de sortie de l'au moins un générateur,
  • d) des moyens aptes à compenser au moins partiellement les différences de résistance de connexion des émetteurs,
  caractérisé en ce que, la résistance dite « de colonne » d'un émetteur étant définie comme la résistance de l'électrode de colonne à laquelle cet émetteur est connecté, prise entre le point d'alimentation de cette électrode de colonne et le point de connexion de cet émetteur sur cette électrode de colonne, lesdits moyens de compensation sont aptes à compenser les différences entre les résistances dites « de colonne » des émetteurs de chaque colonne.

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

• a billboard or lighting panel that includes:
  • a) a network of light emitters arranged in rows and columns,
  • b) a network of N row electrodes, and a network of P column electrodes,
    each transmitter being connected firstly to one of said line electrodes, at a line connection point, and secondly to one of said column electrodes, at a column connection point, so as to be able to be fed between this line electrode and this column electrode,
• transmitter power supply means comprising:
  • a) at least one voltage generator capable of delivering a supply voltage between two output terminals,
  • b) means capable of successively selecting each line of emitters, by connecting a feed point of the line electrode to which these emitters are connected to one of the output terminals of the at least one generator,
  • c) means able to send emitters of the same line so that they emit light, by simultaneously connecting a feed point of each of the column electrodes to which these emitters are connected to the other output terminal of the at least one generator,
  • d) means capable of compensating at least partially the differences in connection resistance of the transmitters,
  characterized in that the so-called "column resistance" of an emitter being defined as the resistance of the column electrode to which this emitter is connected, taken between the feed point of this column electrode and the connection of this transmitter on this column electrode, said compensation means are able to compensate for the differences between the so-called "column" resistors of the emitters of each column.

In summary, the subject of the invention is a passive matrix image display or lighting device comprising an array of light emitters, an array of line electrodes and a network of column electrodes for feeding in voltage these emitters, and means able to compensate, without video processing, and at least partially, the differences in connection resistance of these emitters via these electrodes. Preferably, these compensation means are able to compensate for both differences in column resistances and differences in line resistances.

The connection resistance of an emitter is the sum of the resistance between one of the output terminals of the generator able to supply it and the point of connection of this emitter to its line electrode, and of on the other hand, the resistance between the other of the output terminals of this generator and the point of connection of this emitter to its column electrode. Any other definition of the connection resistance of the transmitters can be retained without departing from the invention, as long as it does not change the differences between the connection resistances of these transmitters.

The "point" of line and column connection of a transmitter generally corresponds to a portion of the line electrode and a portion of the column electrode that form two feed electrodes of that emitter.

The "point" of supply of the line electrode and the column electrode generally corresponds to one end of these electrodes.

Preferably, the so-called "line" resistance of a transmitter being defined as the resistance of the line electrode to which this emitter is connected, taken between the supply point of this line electrode and the connection point of the transmitter. this emitter on this line electrode, said compensation means are able to compensate for the differences between the so-called "line" resistors of the emitters of each line.

• ledit panneau est à matrice passive ;
• lesdits émetteurs sont des diodes électroluminescentes, notamment, organiques.

Preferably:

• said panel is passive matrix;
• said emitters are electroluminescent diodes, especially organic diodes.

• à l'aide desdits moyens de sélection, on sélectionne successivement, pendant une période de sélection, chaque ligne du panneau, d'une ligne à la suivante adjacente,
• et, lorsqu'une ligne d'émetteurs est sélectionnée, à l'aide desdits moyens d'adressage, on adresse des émetteurs de cette ligne pour qu'ils émettent de la lumière pendant une partie au moins de ladite période de sélection,
  ... et, si i_d est le courant circulant dans un quelconque desdits émetteurs qui émet de la lumière,
• à l'aide desdits moyens de compensation, on incrémente ladite tension d'alimentation d'une valeur V_inc = R_c × i_d lorsque l'on passe d'une ligne quelconque sélectionnée à la suivante adjacente.

The subject of the invention is also a method for controlling an image display or lighting device according to the invention, characterized in that ... if the "column" resistance difference between two transmitters that are connected to the same column electrode and to two adjacent line electrodes of the panel is approximately constant irrespective of the column electrodes and line electrodes considered, and R _c is equal to

• with the aid of said selection means, each line of the panel is successively selected, during a selection period, from one line to the next adjacent one,
• and, when a line of transmitters is selected, using said means addressing, emitters of this line are sent to emit light during at least part of said selection period,
  ... and, if i _d is the current flowing in any one of the emitters that emits light,
• with the aid of said compensating means, said supply voltage is incremented by a value V _inc = R _c × i _d when passing from one selected line to the next adjacent one.

où VAL_A_g = 1 si l'électrode de colonne X_g est connectée à l'autre borne de sortie de l'au moins un générateur à l'aide desdits moyens d'adressage (4) pendant ladite partie de période de sélection, où VAL_A_g = 0 si l'électrode de colonne X_g n'est pas connectée à l'autre borne de sortie de l'au moins un générateur pendant ladite partie de période de sélection.The subject of the invention is also a method for controlling an image display or lighting device according to the invention, characterized in that ... if the "line" resistance difference between two transmitters which are connected to the same row electrode and to two adjacent column electrodes of the panel is approximately constant irrespective of the column electrodes and line electrodes considered, and is worth R _r , ... while addressing transmitters of said selected line, between two adjacent column electrodes X ( _i-1 ), X _i , a voltage increment ΔV _(i-1) approximately equal to C _(i-1) × V ' _inc , where V' _inc = R _r × i _d , where C _(i-1) $=\underset{\mathrm{boy\; Wut}=i}{\overset{\mathrm{boy\; Wut}=P}{\Sigma }}{\mathit{VAL\_A}}_{\mathrm{boy\; Wut}},$

where VAL_A _g = 1 if the column electrode X _g is connected to the other output terminal of the at least one generator by means of said addressing means (4) during said selection period portion, where VAL_A _g = 0 if the column electrode X _g is not connected to the other output terminal of the at least one generator during said selection period portion.

Whatever the emitters of the panel that are powered by the generator, the voltage across each of these emitters is then approximately identical. Thus, without further processing of the video data and with the aid of a very simple and inexpensive method to be implemented, it is possible to compensate globally and in a very efficient manner the differences in connection resistance of the transmitters, whatever the images displayed by the device.

The emitters of the panel can be divided into several sets according to their emission color and / or their electrical characteristics: for example, a first set of emitters of a first type which are able to emit a red light, a second set of emitters emitters of a second type which are able to emit a green light, a third type of emitters of a third type that are able to emit a blue light. Each type of transmitter has different electrical characteristics, including current-voltage characteristics. According to the invention, whatever the group of transmitters of the same set of transmitters of the same type, the compensation means are adapted to ensure an identical voltage between the terminals of each transmitter of this group. Assuming that, within each set, the emitters have the same luminous emission intensity characteristics for this common identical voltage, a very high luminous emission homogeneity is obtained according to the invention over the entire surface of the panel. which, in the case of a billboard, is very favorable to the quality of display of the images.

The documents EP 1439518 and WO 2004/114273 disclose ohmic loss compensation means in the LED connecting electrodes which are essentially applicable to active matrix image display panels, wherein the electrodes of one of the arrays are common to all the diodes and form usually an upper layer of the panel. The electrodes of the other network are integrated into the matrix of the panel, as in the case of passive matrix panels. Consequently, the compensation means described in the documents EP 1439518 and WO 2004/114273 , only compensate the ohmic losses in a single array of electrodes, whereas the invention relates here passive matrix panels with two power supply electrode arrays and allows to compensate the ohmic losses simultaneously for both electrode networks. The documents JP10-112391 and JP07-295509 do not give any teaching on the compensation of the ohmic losses simultaneously for the two networks of electrodes which feed the emitters.

• la figure 1 illustre un premier mode de réalisation de l'invention adapté pour compenser les différences de résistance de colonne,
• la figure 2 illustre un deuxième mode de réalisation de l'invention adapté pour compenser à la fois les différences de résistance de colonne et les différences de résistance de ligne.

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:

• FIG. 1 illustrates a first embodiment of the invention adapted to compensate for differences in column resistance,
• FIG. 2 illustrates a second embodiment of the invention adapted for compensate for both differences in column resistance and differences in line resistance.

The elements common to the two embodiments of the invention will now be described with reference to FIGS. 1 and 2.

The device according to the invention conventionally comprises a display panel which is provided with a network of light emitters, here electroluminescent organic diodes, known in themselves, each feedable between two terminals, a network of N row electrodes Y ₁ , Y ₂ , ..., Y _j , ..., Y _N , and a network of P column electrodes X ₁ , X ₂ ,..., X _i ,... X _P , to supply transmitters; the terminals of each transmitter are connected on the one hand to a line electrode, to a line connection point, and on the other hand to a column electrode, to a column connection point. The display panel does not include control circuits for each transmitter: it is therefore a passive matrix panel.

The device comprises supply means which comprise in particular a voltage generator 2 adapted to deliver a voltage V ₀ between two output terminals: only one terminal is shown in the figures, the other terminal being connected to a ground line.

The device also comprises means 5 capable of successively selecting each line of transmitters, by connecting, with the aid of a controllable line-selection switch S ₁ , S ₂ , ..., S _N , a point of supplying the line electrode Y ₁ , Y ₂ ,..., Y _N , to which these emitters are connected to the output terminal of the generator 2 which is connected to a ground line via a common line electrode 55 and another line of mass. The feed points of the line electrodes are located at the ends of these electrodes on the same side of the panel.

The device also comprises means 4 capable of addressing transmitters of the same line so that they emit light, by simultaneously connecting, with the aid of controllable column addressing switches A ₁ , A ₂ , A ₃ , ..., A _P , a feed point of each of the column electrodes X ₁ , X ₂ ,..., X _P , to which these emitters are connected to the other output terminal of the generator 2 via a common column electrode 44. The feed points of the column electrodes are located at the ends of these columns. electrodes on the same side of the panel. The control of the switches A ₁ , A ₂ , A ₃ ,..., A _P is adapted to control, in particular according to video data, the supply duration of the emitters so as to obtain control of the panel by modulation. of duration. This command is referenced "PWM"("Pulse Width Modulation") in the figures.

Controlling the closing of the switches A _i and S _j therefore makes it possible to connect the generator 2 to any emitter E _ij so that it emits light.

• soit R_co la résistance entre l'extrémité d'une électrode de colonne et le premier point de connexion d'un émetteur sur cette électrode ;
• soit R_ro la résistance entre l'extrémité d'une électrode de ligne et le premier point de connexion d'un émetteur sur cette électrode ;
• soit R_c la résistance d'une électrode de colonne entre deux points successifs de connexion d'émetteurs sur cette électrode ; ainsi, la différence de résistance de connexion entre deux émetteurs, qui sont reliés à une même électrode de colonne et à deux électrodes de ligne adjacentes vaut R_c ;
• soit R_r la résistance d'une électrode de ligne entre deux points successifs de connexion d'émetteurs sur cette électrode ; ainsi, la différence de résistance de connexion entre deux émetteurs, qui sont reliés à une même électrode de ligne et à deux électrodes de colonne adjacentes vaut R_r ;

The connection resistance of any emitter E _ij is defined as the sum of the resistance between the output terminal of the generator 2 which is connected to ground and the point of connection of this emitter to its line electrode Y _j , and secondly the resistance between the other output terminal of this generator 2 and the connection point of this transmitter to its column electrode X _i . ;

• let R _{co be} the resistance between the end of a column electrode and the first point of connection of an emitter on this electrode;
• let R _{ro be} the resistance between the end of a line electrode and the first point of connection of a transmitter on this electrode;
• or R _c the resistance of a column electrode between two successive emitter connection points on this electrode; thus, the difference in connection resistance between two emitters, which are connected to the same column electrode and to two adjacent line electrodes is R _c ;
• let R _{r be} the resistance of a line electrode between two successive emitter connection points on this electrode; thus, the difference in connection resistance between two transmitters, which are connected to one and the same row electrode and to two adjacent column electrodes is R _r ;

The connection resistance R _E11 of the emitter E ₁₁ of the first line and of the first column is therefore R _E11 = R _co + R _ro .

The connection resistance R _E12 of the emitter E ₁₂ of the second line and of the first column is therefore R _E12 = R _c + R _co + R _ro .

The connection resistance R _E21 of the emitter E ₂₁ of the first line and the second column is therefore R _E21 = R _r + R _co + R _ro .

By extension, the connection resistance R _Eij of the transmitter E _ij of the line j and the column i is therefore R _Eij = (i-1) × R _r + (j-1) × R _c + R _co + R _ro .

Let R _d and V _{d be} defined in such a way that the relation between the voltage V _E of any diode of the panel and the current i which flows in this diode is such that V _E = V _d + R _d × i _d , this relation being valid in the operating domain of the diode during operation of the panel.

If V _o is the voltage delivered by the generator 2, if integrating the resistance of the column addressing switches A _i and that of the common column electrode 44 to the value of the resistance R _co , if the integrating the resistance of the line selection switches S _j and that of the common line electrode 55 to the value of the resistor R _ro , then, when any single emitter E _ij of the panel is powered by the generator 2, and in the absence of compensation means according to the invention, the current I _ij which passes through this emitter E _ij is then: I _ij = (V _o -V _d ) / (R _d + R _Eij ) = (V _o - V _d ) / [R _d + (i-1) × R _r + (j-1) × R _c + R _co + R _ro ].

It can therefore be seen that, in the absence of compensation means according to the invention, the current flowing through the transmitter depends on the values of i and j, that is to say on the position of this emitter on the panel.

Therefore, according to the invention, the device also comprises means capable of compensating at least partially the differences in connection resistance R _Eij emitters, two embodiments of which will now be described.

^1st embodiment.

Referring to Figure 1, according to the first embodiment of the invention, the generator 2 are associated with column compensation means 3 able to compensate for differences in connection resistance called "column". The so-called "column" resistance of an emitter is defined as the resistance of the column electrode to which this emitter is connected, taken between the supply point of this column electrode and the point of connection of this emitter on this column electrode; for a transmitter E _ij , this column resistance is therefore R _co + (j-1) × R _c .

• un sommateur 31 doté de deux entrées à additionner et d'une sortie délivrant la somme des signaux d'entrée ; l'un des signaux d'entrée est V_inc, dont la valeur sera définie ultérieurement ;
• une mémoire 32 apte à stocker la valeur délivrée par le sommateur 31 ;
• un multiplexeur « MUX » 33 doté de deux entrées, dont l'une est alimentée par la mémoire 32, l'autre par le signal de tension V_o, et d'une sortie adaptée pour délivrer l'une des deux entrées en fonction d'une donnée de commande. La sortie du multiplexeur 33 est reliée d'une part à l'électrode commune de colonne 44, et d'autre part à l'une des entrées du sommateur 31.

The column compensation means 3 comprise:

• an adder 31 having two inputs to be added and an output delivering the sum of the input signals; one of the input signals is V _inc , the value of which will be defined later;
• a memory 32 able to store the value delivered by the adder 31;
• a multiplexer "MUX" 33 having two inputs, one of which is powered by the memory 32, the other by the voltage signal V _o , and an output adapted to deliver one of the two inputs as a function of a control data. The output of the multiplexer 33 is connected on the one hand to the common column electrode 44, and on the other hand to one of the inputs of the adder 31.

• on sélectionne la première ligne en fermant l'interrupteur S1, et on envoie simultanément un signal de 1^ère ligne (marqué « 1st line » sur la figure) au multiplexeur 33 ; les émetteurs de la première ligne étant alors connectés à la première électrode de ligne Y₁, le multiplexeur 33 délivre une tension V_o à l'électrode commune de colonne 44 ; les interrupteurs A₁, A₂, A₃,..., A_P sont maintenus ouverts ou fermés pendant une durée contrôlée en fonction des données vidéo à adresser aux émetteurs de cette première ligne ; à chaque interrupteur fermé A_i, correspond un émetteur E_i1 qui est alors alimenté par le générateur 2 pour émettre de la lumière ; sur le circuit de chaque émetteur alimenté, on a donc : V_o = (R_co + R_d) i_d + V_d, ou i_d.= (V₀ -V_d)/(R_co + R_d).
• au déclenchement d'un signal de changement de ligne (« line + 1 ») appliqué à la mémoire 22, la somme de la tension V_o délivrée par le multiplexeur 23 et de V_inc est envoyée à l'électrode commune de ligne 44 pour alimenter un deuxième groupe d'émetteurs connectés à la deuxième électrode de ligne Y₂ ; sur le circuit de chaque émetteur alimenté de cette ligne, on a donc : V_o + V_inc = (R_co + R_d + R_c) i'_d + V_d . En prenant V_inc = R_c × i_d, on en déduit que i'_d = i_d. On constate donc que la résistance d'électrode de colonne apportée par le changement de ligne est compensée par l'incrément de tension d'alimentation V_inc, du moment que l'on choisit V_inc = R_c × i_d.

In operation, the device operates as follows:

• the first line is selected by closing the switch S1, and simultaneously sends a signal of one line ^period (labeled "1st line" in the figure) to the multiplexer 33; the emitters of the first line then being connected to the first line electrode Y ₁ , the multiplexer 33 delivers a voltage V _o to the common column electrode 44; the switches A ₁ , A ₂ , A ₃ ,..., A _P are kept open or closed for a controlled duration depending on the video data to be sent to the transmitters of this first line; each closed switch A _i corresponds to a transmitter E _i1 which is then powered by the generator 2 to emit light; on the circuit of each emitter fed, we thus have: V _o = (R _co + R _d ) i _d + V _d , where i _d = (V ₀ -V _d ) / (R _co + R _d ).
• at the triggering of a line-change signal ("line + 1") applied to the memory 22, the sum of the voltage V _o delivered by the multiplexer 23 and of V _inc is sent to the common line electrode 44 for supplying a second group of transmitters connected to the second line electrode Y ₂ ; on the circuit of each emitter supplied with this line, we thus have: V _o + V _inc = (R _co + R _d + R _c ) i ' _d + V _d . Taking V _inc = R _c × i _d , we deduce that i ' _d = i _d . It can therefore be seen that the column electrode resistance provided by the line change is compensated by the supply voltage increment V _inc , as long as V _inc = R _c × i _d is chosen.

The same advantage applies to the other lines of the panel, applying, each time one goes from one line to the next, the same voltage increment V _inc .

• à l'aide des moyens de sélection 5, on sélectionne successivement, pendant une période de sélection, chaque ligne du panneau, d'une ligne à la suivante adjacente,
• et, lorsqu'une ligne d'émetteurs est sélectionnée, à l'aide des moyens d'adressage 4, on adresse des émetteurs de cette ligne pour qu'ils émettent de la lumière pendant une partie de cette période de sélection correspondant à la donnée vidéo à leur adresser,
• et, si i_d est le courant circulant dans un quelconque desdits émetteurs qui émet de la lumière pendant cette partie de période de sélection, à l'aide des moyens de compensation de colonne 3, on incrémente la tension d'alimentation délivrée par le générateur 2 d'une valeur R_c × i_d lorsque l'on passe d'une ligne quelconque sélectionnée à la suivante adjacente.

Thus, overall, the device is piloted as follows:

• using the selection means 5, one selects successively, during a selection period, each line of the panel, from one line to the next adjacent,
• and, when a line of transmitters is selected, using the addressing means 4, transmitters of this line are addressed to emit light during part of this selection period corresponding to the data. video to send them,
• and, if i _d is the current flowing in any one of said emitters which emits light during this selection period portion, using the column compensation means 3, the supply voltage supplied by the generator is incremented 2 of a value R _c × i _d when passing from one selected line to the next adjacent one.

In the case where the panel is trichromatic and has three sets of transmitters, one set for each primary color of emission, it will be necessary to implement column compensation means 3 for each set of transmitters. Generally, each column corresponds to the same primary color, and the columns of different primary colors are alternated.

Such resistance compensation means of the column electrodes are particularly simple and economical to implement and allow the voltage control of the emitters of the panel, which is advantageous because it limits the preload times, which allows to increase by the transmission durations when displaying the images, and thus to improve the luminous performances of the panel. Moreover, this device makes it possible to use economic column control means which integrate globally for the whole panel only three voltage generators according to this device, instead of a current generator by column electrode as in the current drivers of the device. walk. This device is also much simpler and more economical to implement than specific video data processing devices capable of compensating for differences in connection resistance, especially since such video processing often involves a loss of definition of the levels of gray of each color.

^2nd embodiment.

With reference to FIG. 2, according to the second embodiment of the invention, at the same generator 2 are added compensating means that are able to compensate not only the differences in column resistance as before, but also the differences in resistances. say "line". The so-called "line" resistance of a transmitter is defined as the resistance of the line electrode to which this emitter is connected, taken between the supply point of this line electrode and the point of connection of this emitter on this line electrode; for a transmitter E _ij , this line resistance is therefore R _ro + (i-1) × R _r .

A difficulty for the compensation of differences in line resistance comes from the fact that the different resistances R _r between the successive points of connection of transmitters on the same line electrode are generally traversed by different currents, at least when several transmitters of this line are activated simultaneously, ie when the "PWM" command simultaneously closes several addressing switches.

Aux bornes d'une quelconque résistance de ligne R_r sur l'électrode de ligne Y_j, comprise entre deux points de connections de deux émetteurs adjacents E_(i-1)j et E_ij de cette électrode de ligne Y_j, la différence de potentiel vaut ${\mathrm{R}}_{\mathrm{r}}\times \sum _{k=i}^{k=p}{\mathit{VAL\_A}}_k\times i_{\mathrm{ij}}\mathrm{.}$

If VAL_A _k denotes the value 1 or 0 of the command of an address switch of the column electrode X _i (1 = closed and emitter E _kj active, 0 = open and emitter E _kj off) if i _ij denotes the current flowing through each emitter E _ij of the line j which is activated, the total current flowing at the feed point (i.e. the end) of the line electrode Y _j will then be equal to $\underset{i=1}{\overset{i=p}{\Sigma }}{\mathit{VAL\_A}}_i\times i_{\mathit{ij}}\mathrm{.}$

At the terminals of any line resistor R _r on the line electrode Y _j , between two connection points of two adjacent emitters E _{(i-1) j} and E _ij of this line electrode Y _j , the difference potential is worth ${\mathrm{R}}_{\mathrm{r}}\times \underset{k=i}{\overset{k=p}{\Sigma }}{\mathit{VAL\_A}}_k\times i_{\mathrm{ij}}\mathrm{.}$

In the absence of means for compensating the line resistors, for each emitter E _ij , we therefore have the equation: $$\left\{{\mathrm{V}}_0+\left(\mathrm{j}-1\right).{\mathrm{V}}_{\mathrm{i}\mathrm{not}\mathrm{vs}}-{\mathrm{V}}_{\mathrm{d}}\right\}=\left\{{\mathrm{R}}_{\mathrm{vs}\mathrm{o}}+\left(\mathrm{j}-1\right)\times {\mathrm{R}}_{\mathrm{vs}}+{\mathrm{R}}_{\mathrm{d}}\right\}\times {\mathrm{i}}_{\mathrm{i}\mathrm{j}}+\left\{{\mathrm{R}}_{\mathrm{r}\mathrm{o}}\times {\displaystyle {\Sigma }_{k=1}^{k=P}{\mathit{VAL\_A}}_k\times i_{kj}}+{\mathrm{R}}_{\mathrm{r}}\times {\displaystyle {\Sigma }_{k=2}^{k=P}{\mathit{VAL\_A}}_k\times i_{kj}}+{\mathrm{R}}_{\mathrm{r}}\times {\displaystyle {\Sigma }_{k=3}^{k=P}{\mathit{VAL\_A}}_k\times i_{kj}}+...+{\mathrm{R}}_{\mathrm{r}}\times {\displaystyle {\Sigma }_{k=i}^{k=P}{\mathit{VAL\_A}}_k\times i_{kj}}\right\}=\left\{{\mathrm{R}}_{\mathrm{vs}\mathrm{o}}+\left(\mathrm{j}-1\right)\times {\mathrm{R}}_{\mathrm{vs}}+{\mathrm{R}}_{\mathrm{d}}\right\}\times {\mathrm{i}}_{\mathrm{i}\mathrm{j}}+\left\{{\mathrm{R}}_{\mathrm{r}\mathrm{o}}\times {\displaystyle {\Sigma }_{k=1}^{k=P}{\mathit{VAL\_A}}_k\times i_{kj}}+{\mathrm{R}}_{\mathrm{r}}\times {\displaystyle {\Sigma }_{\mathrm{boy\; Wut}=2}^{\mathrm{boy\; Wut}=i}{\displaystyle {\Sigma }_{k=\mathrm{boy\; Wut}}^{k=P}{\mathit{VAL\_A}}_k\times i_{kj}}}\right\}$$

According to the column compensation means described above, there is V _inc = (j-1) × R _c .

We therefore have as many equations as unknowns. The resolution of such a system generally gives different values for the currents that flow through the activated transmitters of the line j. However, the function of the compensation means is to obtain identical values of these currents.

The compensation means here comprise on the one hand the same column compensation means 3 as those previously described in the first embodiment, but also elements added to the addressing means 4 'which are able to partially compensate for the differences in line resistors, as described below.

As indicated in FIG. 2, the common feed electrode of the columns 44 is interrupted: between the successive connection points of this electrode to a switch controlling the emission duration A ₁ , A ₂ , A ₃ , ..., A _P , there are in this embodiment of voltage generators G ₀ , G ₁ , ..., G _p-1 , which are programmed using commands; each generator G _i is able to deliver a voltage ΔV _i proportional to its control C _i .

In addition, the new elements added to the addressing means 4 'include adders Add0, Add1, ..., Add (p-2), Add (p-1). Each adder Add (i-1) comprises two inputs and an output: one of the inputs is connected to the control (value 1 or 0) of the switch A _i , which is able to connect the common column electrode 44 to the column electrode X _i ; the other input is connected to the output of adders Add (i) of the next column if it exists; the output of this adders Add (i-1) is connected to the input of the adder Add (i-2) of the previous column if it exists, and also forms the command C _(i-1) of the generator G _{( i-1)} which is interposed on the common column electrode between the connection point of the switch A _(i-1) and that of the switch A _i .

We will now explain the operation of the compensation of the differences in line resistances.

For each emitter E _ij , we now have the equation: $$\left\{{\mathrm{V}}_0+\left(\mathrm{j}-1\right).{\mathrm{V}}_{\mathrm{i}\mathrm{not}\mathrm{vs}}-{\mathrm{V}}_{\mathrm{d}}+{\displaystyle {\Sigma }_{\mathrm{boy\; Wut}=0}^{\mathrm{boy\; Wut}=i-1}\Delta V_{\mathrm{boy\; Wut}}}\right\}=\left\{{\mathrm{R}}_{\mathrm{vs}\mathrm{o}}+\left(\mathrm{j}-1\right)\times {\mathrm{R}}_{\mathrm{vs}}+{\mathrm{R}}_{\mathrm{d}}\right\}\times {\mathrm{i}}_{\mathrm{i}\mathrm{j}}+\left\{{\mathrm{R}}_{\mathrm{r}\mathrm{o}}\times {\displaystyle {\Sigma }_{k=1}^{k=P}{\mathit{VAL\_A}}_k\times i_{kj}}+{\mathrm{R}}_{\mathrm{r}}\times {\displaystyle {\Sigma }_{\mathrm{boy\; Wut}=2}^{\mathrm{boy\; Wut}=i}{\displaystyle {\Sigma }_{k=\mathrm{boy\; Wut}}^{k=P}{\mathit{VAL\_A}}_k\times i_{kj}}}\right\}$$

l'équation ci-dessus devient : $$\left({\mathrm{V}}_0+\left(\mathrm{j}-1\right).{\mathrm{V}}_{\mathrm{i}\mathrm{n}\mathrm{c}}-{\mathrm{V}}_{\mathrm{d}}+{\mathrm{R}}_{\mathrm{r}\mathrm{o}}\times {\mathrm{i}}_{\mathrm{d}}\times {\displaystyle {\sum }_{g=1}^{g=P}{\mathit{VAL\_A}}_g}+{\mathrm{R}}_{\mathrm{r}}\times {\mathrm{i}}_{\mathrm{d}}\times {\displaystyle {\sum }_{k=1}^{k=i-1}{\displaystyle {\sum }_{g=k+1}^{g=P}{\mathit{VAL\_A}}_g}}\right)=\left\{{\mathrm{R}}_{\mathrm{c}\mathrm{o}}+\left(\mathrm{j}-1\right)\times {\mathrm{R}}_{\mathrm{c}}+{\mathrm{R}}_{\mathrm{d}}\right\}\times {\mathrm{i}}_{\mathrm{d}}+\left\{{\mathrm{R}}_{\mathrm{r}\mathrm{o}}\times {\displaystyle {\sum }_{k=1}^{k=P}{\mathit{VAL\_A}}_k}\times i_d+{\mathrm{R}}_{\mathrm{r}}\times {\displaystyle {\sum }_{g=2}^{g=i}{\displaystyle {\sum }_{k=g}^{k=P}{\mathit{VAL\_A}}_k}}\times i_d\right\}$$

If, according to the invention, each generator delivers a voltage ΔV _k = C _k × V ' _inc ^, if i _d is the current flowing through each activated transmitter when column and line connection resistances have been compensated, and if V ' _inc = R _r × i _d , and knowing that, from the description of the line compensation means described above, it follows that the command C _k of each generator G _{k is} worth ${\displaystyle {\Sigma }_{\mathrm{boy\; Wut}=k+1}^{\mathrm{boy\; Wut}=P}{\mathit{VAL\_A}}_{\mathrm{boy\; Wut}}},$

the equation above becomes: $$\left({\mathrm{V}}_0+\left(\mathrm{j}-1\right).{\mathrm{V}}_{\mathrm{i}\mathrm{not}\mathrm{vs}}-{\mathrm{V}}_{\mathrm{d}}+{\mathrm{R}}_{\mathrm{r}\mathrm{o}}\times {\mathrm{i}}_{\mathrm{d}}\times {\displaystyle {\Sigma }_{\mathrm{boy\; Wut}=1}^{\mathrm{boy\; Wut}=P}{\mathit{VAL\_A}}_{\mathrm{boy\; Wut}}}+{\mathrm{R}}_{\mathrm{r}}\times {\mathrm{i}}_{\mathrm{d}}\times {\displaystyle {\Sigma }_{k=1}^{k=i-1}{\displaystyle {\Sigma }_{\mathrm{boy\; Wut}=k+1}^{\mathrm{boy\; Wut}=P}{\mathit{VAL\_A}}_{\mathrm{boy\; Wut}}}}\right)=\left\{{\mathrm{R}}_{\mathrm{vs}\mathrm{o}}+\left(\mathrm{j}-1\right)\times {\mathrm{R}}_{\mathrm{vs}}+{\mathrm{R}}_{\mathrm{d}}\right\}\times {\mathrm{i}}_{\mathrm{d}}+\left\{{\mathrm{R}}_{\mathrm{r}\mathrm{o}}\times {\displaystyle {\Sigma }_{k=1}^{k=P}{\mathit{VAL\_A}}_k}\times i_d+{\mathrm{R}}_{\mathrm{r}}\times {\displaystyle {\Sigma }_{\mathrm{boy\; Wut}=2}^{\mathrm{boy\; Wut}=i}{\displaystyle {\Sigma }_{k=\mathrm{boy\; Wut}}^{k=P}{\mathit{VAL\_A}}_k}}\times i_d\right\}$$

By simplifying a first time: $$\left({\mathrm{V}}_0-{\mathrm{V}}_d+{\mathrm{R}}_{\mathrm{r}\mathrm{o}}\times {\mathrm{i}}_{\mathrm{d}}\times {\displaystyle {\Sigma }_{\mathrm{boy\; Wut}=1}^{\mathrm{boy\; Wut}=P}{\mathit{VAL\_A}}_{\mathrm{boy\; Wut}}}+{\mathrm{R}}_{\mathrm{r}}\times {\mathrm{i}}_{\mathrm{d}}\times {\displaystyle {\Sigma }_{k=1}^{k=i-1}{\displaystyle {\Sigma }_{\mathrm{boy\; Wut}=k+1}^{\mathrm{boy\; Wut}=P}{\mathit{VAL\_A}}_{\mathrm{boy\; Wut}}}}\right)=\left\{{\mathrm{R}}_{\mathrm{vs}\mathrm{o}}+{\mathrm{R}}_{\mathrm{d}}+{\mathrm{R}}_{\mathrm{r}\mathrm{o}}\times {\displaystyle {\Sigma }_{k=1}^{k=P}{\mathit{VAL\_A}}_k}+{\mathrm{R}}_{\mathrm{r}}\times {\displaystyle {\Sigma }_{\mathrm{boy\; Wut}=2}^{\mathrm{boy\; Wut}=i}{\displaystyle {\Sigma }_{k=\mathrm{boy\; Wut}}^{k=P}{\mathit{VAL\_A}}_k}}\right\}\times {\mathrm{i}}_{\mathrm{d}}.$$

Simplifying a second time: $$\left({\mathrm{V}}_0-{\mathrm{V}}_{\mathrm{d}}\right)=\left\{{\mathrm{R}}_{\mathrm{vs}\mathrm{o}}+{\mathrm{R}}_{\mathrm{d}}\right\}\times {\mathrm{i}}_{\mathrm{d}}.$$

And, as in the first embodiment, i _d = (V ₀ -V _d ) / (R _co + R _d ).

It is therefore verified that, thanks to the compensation means according to the invention as previously described, this time overall the global transmitter connection resistance variations, that is to say both the column resistances and the resistors, are compensated overall. line resistance, whatever the video data displayed by the device. Advantageously, this result is obtained without additional processing of the video data, unlike the compensation means described in the prior art. The means used for this compensation are particularly simple and economical.

• à l'aide des moyens de sélection 5, on sélectionne successivement, pendant une période de sélection, chaque ligne du panneau, d'une ligne à la suivante adjacente,
• et, lorsqu'une ligne d'émetteurs est sélectionnée, à l'aide des moyens d'adressage 4, on adresse des émetteurs de cette ligne pour qu'ils émettent de la lumière pendant une partie au moins de cette période de sélection,
• et, si i_d est le courant circulant dans un quelconque desdits émetteurs qui émet de la lumière pendant cette partie de période de sélection, pendant qu'on adresse des émetteurs de ladite ligne sélectionnée, entre deux électrodes de colonne adjacentes X(_i-1), X_i, on applique un incrément de tension ΔV_(i-1) égal à ${\mathrm{C}}_{\left(\mathrm{i}-1\right)}\times {{\mathrm{V}}^{\prime }}_{\mathrm{inc}},\mathrm{\hspace{1em}où\hspace{1em}}{{\mathrm{V}}^{\prime }}_{\mathrm{inc}}={\mathrm{R}}_{\mathrm{r}}\times {\mathrm{i}}_{\mathrm{d}},{\mathrm{\hspace{1em}où\hspace{1em}C}}_{\mathrm{k}}=\sum _{g=i}^{g=p}{\mathit{VAL\_A}}_g,$
  
• et, à l'aide des moyens de compensation de colonne 3, on incrémente la tension d'alimentation délivrée par le générateur 2 d'une valeur R_c × i_d lorsque l'on passe d'une ligne quelconque sélectionnée à la suivante adjacente. Quelque soient les émetteurs du panneau qui sont alimentés par le générateur, la tension aux bornes de chacun de ces émetteurs est alors approximativement identique. On parvient ainsi, sans traitement complémentaire des données vidéo et à l'aide d'une méthode très simple et économique à implémenter, à compenser totalement les différences de résistance de connexion des émetteurs, quelques soient les images affichées par le dispositif.

Thus, overall, the device is piloted as follows:

• using the selection means 5, one successively selects, during a selection period, each line of the panel, from one line to the next adjacent,
• and, when an emitter line is selected, using the addressing means 4, transmitters of this line are addressed to emit light during at least part of this selection period,
• and, if i _d is the current flowing in any one of said emitters that emits light during that selection period portion, while emitters of said selected line are addressed between two adjacent column electrodes X ( _i-1 ), X _i , a voltage increment ΔV _(i-1) equal to ${\mathrm{VS}}_{\left(\mathrm{i}-1\right)}\times {{\mathrm{V}}^{\text{'}}}_{\mathrm{Inc.}},\mathrm{or}{{\mathrm{V}}^{\text{'}}}_{\mathrm{Inc.}}={\mathrm{R}}_{\mathrm{r}}\times {\mathrm{i}}_{\mathrm{d}},{\mathrm{where\; C}}_{\mathrm{k}}=\underset{\mathrm{boy\; Wut}=i}{\overset{\mathrm{boy\; Wut}=p}{\Sigma }}{\mathit{VAL\_A}}_{\mathrm{boy\; Wut}},$
  
• and, using the column compensation means 3, the supply voltage supplied by the generator 2 is incremented by a value R _c × i _d when passing from one selected line to the next adjacent one. . Whatever the emitters of the panel that are powered by the generator, the voltage across each of these emitters is then approximately identical. Thus, without further processing of the video data and using a very simple and inexpensive method to implement, it is possible to completely compensate the differences in the connection resistance of the transmitters, whatever the images displayed by the device.

The present invention is applicable to all types of light emitter panels, especially those that are current-controllable like light-emitting diodes.

Claims (6)

An image display or lighting device comprising: - a billboard or lighting panel (1) which comprises: a) a network of light emitters (E _ij ) arranged in lines (1, 2, 3, ...., j, ...., N) and in columns (1, 2, 3, ... ., i, ...., P), b) an array of N row electrodes (Y ₁ , Y ₂ , Y ₃ , ..., Y _j , ..., Y _N ), and an array of P column electrodes (X ₁ , X ₂ ,. .., X _i , ..., X _P ),
each emitter (E _ij ) being connected firstly to one of said line electrodes (Y _j ), at a line connection point, and secondly to one of said column electrodes (X _i ) at a column connection point, so that it can be fed between this line electrode (Y _j ) and this column electrode (X _i ), power supply means for emitters which comprise: a) at least one voltage generator (2) capable of delivering a supply voltage (V ₀ ) between two output terminals, b) means (5) able successively to select each line of emitters (1, 2, 3, ...., j, ...., N), by connecting a feed point of the electrode of line to which these emitters are connected to one of the output terminals of the at least one generator, c) means (4; 4 ') able to send transmitters of the same line so that they emit light, simultaneously connecting a feed point of each of the column electrodes to which these emitters are connected to the other output terminal of the at least one generator, d) means (3; 4 ') able to at least partially compensate for the differences in the connection resistance of the emitters, characterized in that
... the so-called "column" resistance of a transmitter (E _ij ) being defined as the resistance of the column electrode (X _i ) to which this emitter is connected, taken between the supply point of this electrode column and the point of connection of this emitter on this column electrode (X _i ), said compensation means are able to compensate for the differences between the so-called "column" resistors of the emitters of each column. Device according to claim 1, characterized in that the so-called "line" resistance of a transmitter (E _ij ) being defined as the resistance of the line electrode (Y _j ) to which this emitter is connected, taken between the feed point of this line electrode and the connection point of this emitter on this line electrode (Y _j ),
said compensation means are able to compensate for the differences between the so-called "line" resistors of the emitters of each line. Device according to claim 1 or 2 characterized in that said panel is passive matrix. Device according to any one of the preceding claims, characterized in that said emitters are light-emitting diodes. Method for controlling an image display or lighting device according to any one of the preceding claims, characterized in that ... if the "column" resistance difference between two transmitters which are connected to the same adjacent row column and electrode electrode of the panel is approximately constant regardless of the column electrodes (X _i ) and line electrodes (Y _j ) considered, and is worth R _c , with the aid of said selection means (5), each line of the panel is successively selected, during a selection period, from one line to the next adjacent one, and, when a line of transmitters is selected, using said addressing means (4), transmitters of this line are addressed so that they emit light during at least part of said period of time. selection,
... and, if i _d is the current flowing in any one of the emitters that emits light, with the aid of said compensation means, said voltage is incremented supply of a value V _inc = R _c × i _d when passing from one selected line to the next adjacent one. Method for controlling an image display or lighting device according to any one of Claims 2 to 4, characterized in that
... if the "line" resistance difference between two transmitters that are connected to the same row electrode and two adjacent column electrodes of the panel is approximately constant regardless of the column electrodes (X _i ) and the electrodes of line (Y _j ) considered, and is worth R _r ,
while sending transmitters of said selected line between two adjacent column electrodes (X ( _i-1 ), X _i ), a voltage increment ΔV _(i-1) approximately equal to C is applied _{( i-1)} × V ' _inc , where V' _inc = R _r × i _d , where ${\mathrm{VS}}_{\left(\mathrm{i}-1\right)}={\displaystyle {\Sigma }_{\mathrm{boy\; Wut}=i}^{\mathrm{boy\; Wut}=P}{\mathit{VAL\_A}}_{\mathrm{boy\; Wut}}},$

where VAL_A _g = 1 if the column electrode X _g is connected to the other output terminal of the at least one generator by means of said addressing means (4) during said selection period portion, where VAL_A _g = 0 if the column electrode X _g is not connected to the other output terminal of the at least one generator during said selection period portion.

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