EP1964095B1 - Display panel and control method using transient capacitive coupling - Google Patents

Description

The invention relates to active matrix panels for displaying images using light emitter networks, for example light-emitting diodes, or optical valve arrays, for example liquid crystal valves. These emitters or valves are generally divided into rows and columns.

The term "active matrix" designates a substrate which integrates networks of electrodes and circuits able to control and feed emitters or optical valves supported by this substrate. These electrode arrays generally comprise at least one addressing electrode array, a selection electrode array, at least one reference electrode for addressing and at least one base electrode for feeding these emitters. . Sometimes the reference electrode for addressing and the base electrode for power are merged. The panel further comprises at least one upper feed electrode, generally common to all valves or emitters, but which is not integrated with the active matrix. Each valve or emitter is generally interposed between a base supply terminal connected to a base electrode for the supply and the upper supply electrode which generally covers the entire panel.

Each control circuit comprises a control terminal connected to or coupled to an addressing electrode via a selection switch, a selection terminal which corresponds to the control of this switch and which is connected to a selection electrode, and a terminal of reference connected to or coupled to a reference electrode.

Each control circuit therefore comprises a selection switch adapted to transmit to this circuit the addressing signals from an addressing electrode. Closing the selection switch of a circuit corresponds to the selection of this circuit.

Generally, each addressing electrode is connected to or coupled to the control terminals of the control circuits of all the emitters or valves of the same column; each selection electrode is connected to the selection terminals of the control circuits of all the transmitters or all the valves of the same line. The active matrix may also include other row or column electrodes.

The addressing electrodes are used to address to the control circuits control signals, analog voltage or current, or digital; during the transmission periods, each control signal intended for the control circuit of a valve or transmitter is representative of an image datum of a pixel or sub-pixel associated with this valve or transmitter .

In the case of an optical valve panel, each control and power supply circuit comprises a memory element, generally a capacitor able to maintain the control voltage of this valve during the duration of an image frame; this capacitor is connected in parallel directly to this valve. The control voltage of a valve is the potential difference across this valve. In a particularly simple case of control circuit, the control terminal of the circuit is connected to or coupled to one of the terminals of the valve.

In the case of a panel of current-controllable emitters, for example light-emitting diodes, in particular organic diodes, each control and supply circuit generally comprises a current modulator, generally a TFT transistor, provided with two terminals. current flow, a source terminal and a drain terminal, and a gate terminal for voltage control; this modulator is then connected in series with the transmitter to be controlled, this series being itself connected between an electrode (upper) supply and a base electrode for the power supply; generally, it is the drain terminal which is common to the modulator and the emitter, and the source terminal, connected to the base electrode for the supply, is thus at a constant potential; the modulator control voltage is the potential difference between the gate and the source of the modulator; each control circuit comprises means for generating a control voltage of the modulator as a function of the signal addressed to the control terminal of this circuit; each control circuit also comprises, as previously, a holding capacitor adapted to maintain the control voltage of the modulator during the duration of each image or image frame. In a particularly simple case of circuit of command, the control terminal of the circuit corresponds to the gate terminal of the modulator.

There are typically two types of control: voltage control or current control. In the case of a voltage control, the addressing signals are voltage steps; in the case of current control, the addressing signals are current steps.

In the case of current control of transmitter panels, each control circuit is adapted in a manner known per se to "program", from a current signal, a control voltage of the modulator of this circuit. circuit, which is therefore applied to the gate terminal.

The addressing electrodes and the selection electrodes are themselves controlled by means of control ("drivers" in English) arranged at the ends of these electrodes, at the edge of the panel; these means generally comprise controllable switches.

• dans le cas de panneaux de valves optiques, notamment de cristaux liquides, on alterne généralement la tension aux bornes des valves pour éviter d'initier une composante continue de polarisation du cristal liquide ;
• dans le cas de panneaux d'émetteurs de lumière, où les émetteurs sont des diodes électroluminescentes, il peut être avantageux d'inverser régulièrement la tension aux bornes des émetteurs, comme décrit par exemple dans les documents EP1094438 et EP1197943 ; cependant, pendant les périodes où cette tension d'alimentation est inversée, ces émetteurs n'émettent évidemment aucune lumière, les diodes étant alors polarisées en sens inverse ;
• dans le cas de panneaux d'émetteurs pilotables en courant, dont les circuits de commande comprennent un modulateur de courant, où ces modulateurs sont des transistors comprenant des couches actives de silicium amorphe, il peut être avantageux d'inverser régulièrement la tension de commande des modulateurs, notamment pour compenser les dérives de tension de seuil de déclenchement de ce type de transistors : les documents US2003/052614 , WO2005/071648 illustrent une telle situation. Lors de l'affichage des images, on distingue alors, pour chaque circuit de commande, des périodes d'affichage ou d'émission, où le signe de cette tension est adapté pour rendre le modulateur passant, et des périodes dites de dépolarisation, où le signe de cette tension est inversé et ne permet pas de rendre le modulateur passant. Pour le pilotage global du panneau, les périodes d'émission et les périodes de dépolarisation peuvent se chevaucher : pendant que les émetteurs ou valves de certaines ligne émettent de la lumière, les circuits, émetteurs ou valves d'autres lignes peuvent être en cours de dépolarisation. Néanmoins, globalement, l'alternance de ces périodes est préjudiciable à la luminance maximum du panneau, puisque la durée globale disponible pour l'émission des émetteurs est réduite de la durée des périodes de dépolarisation.

To ensure a good image display quality and / or to improve the service life of the panel, it is important to regularly invert the control voltage of the control circuit modulators, and / or the supply voltage of the valves or issuers:

• in the case of optical valve panels, in particular of liquid crystals, the voltage across the valves is generally alternated to avoid initiating a continuous polarization component of the liquid crystal;
• in the case of light emitter panels, where the emitters are light-emitting diodes, it may be advantageous to regularly invert the voltage across the emitters, as described for example in the documents EP1094438 and EP1197943 ; however, during periods when this supply voltage is reversed, these emitters obviously emit no light, the diodes then being polarized in the opposite direction;
• in the case of current-controllable transmitter panels, whose control circuits comprise a current modulator, where these modulators are transistors comprising active layers of amorphous silicon, it may be advantageous to regularly invert the control voltage of the modulators, in particular to compensate for trigger voltage drifts of this type of transistor: the documents US2003 / 052614 , WO2005 / 071648 illustrate such a situation. During the display of the images, there are then, for each control circuit, display or transmission periods, where the sign of this voltage is adapted to make the modulator passing, and so-called periods of depolarization, where the sign of this voltage is reversed and does not allow to make the modulator passing. For the overall control of the panel, the emission periods and the periods of depolarization may overlap: while the emitters or valves of certain lines emit light, the circuits, emitters or valves of other lines may be in the process of depolarization. Nevertheless, overall, the alternation of these periods is detrimental to the maximum luminance of the panel, since the overall duration available for the emission of the transmitters is reduced by the duration of the periods of depolarization.

Also in the case of current-controllable transmitter panels, in order to avoid this reduction in luminance, the document WO2005 / 073948 proposes a panel where each transmitter has two control circuits and is controlled alternately by one and the other, which requires doubling the address electrode network. Other solutions require, conversely, to add a network of line electrodes.

The document US2003 / 112205 describes a specific solution: by driving the control circuit described in FIG. 6 as indicated in paragraphs 44 and 45 of this document, where a negative voltage Vee is applied to the reference reference electrode (which is also the electrode base for the power supply), during so-called "non-luminescence" periods, a reverse bias is obtained at the transmitter terminals (here, a light emitting diode), and during this reverse bias, the modulator control current Tr2 which is in series with this transmitter is canceled (source and gate of this modulator are at the same potential because of the closing of the switch bypassing the holding capacitor).

Using the solutions described in the documents US2003 / 052614 , WO2005 / 071648 , the control means of the addressing electrodes must then be adapted to transmit addressing signals of opposite signs or polarity; the solution described in the document US2003 / 052614 need to add a "toggle" element in English. the head of each addressing electrode; this adaptation constraint leads to a significant additional cost of the column drivers.

An object of the invention is to avoid this disadvantage.

In the prior art, the addressing signals are generally transmitted to the control circuits by direct conduction between the addressing electrodes and the control terminals of the circuits, via the selection switch: in the case of analogue control in transmitter panel voltage, where the control terminal of the circuit corresponds to the gate terminal of the modulator, this gate voltage of the modulator is then equal to the voltage of the addressing electrode which controls this circuit, at least during that this circuit is selected.

The document US6229506 describes the case where these addressing signals are on the contrary transmitted to the control circuits by capacitive coupling: in the case of voltage control ( figures 3 and 4 of this document), a coupling capacitor (referenced respectively 350 and 450) here provides the connection without direct conduction between the addressing electrode and the control terminal of the circuit. When such a circuit is selected, this arrangement makes it possible to add the voltage jump signal coming from the addressing electrode to a tripping threshold voltage of the modulator previously stored in the circuit. The connection by capacitive coupling, and not by conduction, between the addressing electrodes and the control terminals of the circuits here makes it possible to compensate for the differences in tripping thresholds of the modulators of these circuits, so as to obtain a better uniformity of luminance. screen and better picture display. For the same purpose, the other documents US6777888 , US6618030 , US6885029 describe a capacitive coupling between the addressing electrodes and the control of the current modulators of the emitters.

An essential aspect of the invention consists in using such a capacitive coupling for another purpose, namely for the purpose of inverting the voltages at the terminals of the valves or at the terminals of the emitters, or the control voltages of the modulators of the circuit circuits. control of these transmitters, without having to invert the addressing signals, which avoids resorting to expensive means for controlling the addressing electrodes.

Thus, according to the invention, the voltage signal that is transmitted by capacitive coupling is in particular an addressing signal for the transmission, which is representative of an image data item and / or an addressing signal (likewise sign) for depolarization, in particular for the depolarization of the current modulator of an emitter.

In general, the capacitive coupling makes it possible to modify the voltage of a terminal by a voltage jump. Thus, an algebraic value voltage step signal ΔV transmitted via capacitive coupling by an addressing electrode to a control terminal prior to the potential V _cal , _changes the potential of this terminal from V to V _cal + ΔV. This voltage jump is independent of the value V _ini of the initial potential (before the jump) of the addressing electrode. When it is desired that the potential of the control terminal of a circuit decreases by a value ΔV (ΔV <0) from an initial value V _cal to the point of reaching a potential V _cal + ΔV of inverse sign of the one applied to obtain the emission of the transmitter controlled by this circuit, thanks to the capacitive coupling, it is sufficient, according to the invention, that the initial value V _ini (eg: V _ini > 0) of the potential of the addressing electrode coupled to this terminal is sufficiently high for the algebraic sum V _ini + ΔV (ΔV <0) to retain the same sign as V _ini , thus to choose | V _ini | > | ΔV |.

For control of the panel according to the invention as described in detail below, the control of each control circuit of a transmitter comprises, during the display of each image frame, two periods, a period of emission of this transmitter and a period of depolarization of the modulator of the control circuit of this transmitter.

• 1/ on sélectionne ce circuit en couplant de manière capacitive la borne de commande de ce circuit à une électrode d'adressage et on « cale » le potentiel de cette borne au potentiel V_cal d'une borne de référence de ce circuit, qui devient donc une borne de calage ; pendant cette sélection et ce « calage », on applique à l'électrode d'adressage un potentiel V_ini, sans aucun effet autre que transitoire, à cause de ce calage, sur le potentiel de la borne de commande qui reste à la valeur V_cal ;
• 2/ le circuit étant toujours sélectionné et la borne de commande étant cette fois toujours calée à la borne de calage, on applique à l'électrode d'adressage un signal de saut de tension ΔV qui se répercute par le couplage capacitif à la borne de commande, selon l'invention uniquement de manière transitoire à cause du maintien du calage ; on « accroche » alors le pic transitoire de tension, en supprimant, à l'instant du pic, simultanément le couplage et le calage de l'étape 1 ; la borne de commande du circuit passe ainsi du potentiel V_cal au potentiel V_prog = V_cal + Δ'V, et se maintient à ce dernier potentiel grâce à l'opération d'accrochage.

For control of the panel according to the invention as described below in detail, during each driving period of a circuit, at least depolarization, if not also emission:

• 1 / this circuit is selected by capacitively coupling the control terminal of this circuit to an addressing electrode and "wedge" the potential of this terminal to the potential V _cal of a reference terminal of this circuit, which becomes therefore a wedging terminal; during this selection and this "setting", a potential V _ini is applied to the addressing electrode, without any effect other than transitory, because of this setting, on the potential of the control terminal which remains at the value V _cal ;
• 2 / the circuit being always selected and the control terminal being this time always wedged to the clamping terminal, a voltage jump signal ΔV is applied to the addressing electrode which is reflected by the capacitive coupling to the terminal of control, according to the invention only transiently because of the maintenance of the setting; the "transient voltage peak" is then "hooked" while suppressing, at the instant of the peak, simultaneously the coupling and the stalling of step 1; the control terminal of the circuit thus goes from the potential V _cal to the potential V _prog = V _cal + Δ'V, and remains at this latter potential thanks to the latching operation.

During the remainder of the period (emission or depolarization) in progress, the potential of the control terminal is maintained at this value by the holding capacitor, as in the prior art.

It can thus be seen that the value of V _ini has no effect on the potential of the control terminal. According to the invention, in the periods of voltage inversion or depolarization, the value of V _ini is thus adapted as in the first modality so that | V _ini | ≥ | ΔV | so that the potential to be applied to the addressing electrode to obtain V _prog on the control terminal does not change sign. It is thus advantageously avoided to resort to expensive means for controlling the addressing electrodes.

The same principle can be applied for the purpose of reversing the voltages across valves or emitter terminals, without having to reverse the polarity between the supply electrodes.

The control method of the panel according to the invention can be used either only during depolarization periods (then conventional conduction addressing is used during transmission periods), or both during the emission and depolarization periods. .

An advantage of this control method is that it makes it possible to send each circuit a specific depolarization signal, and to adapt the depolarization operation to the polarization level of the modulator of each circuit, which level depends in particular on the signal of addressed issue in the previous issue period.

Another advantage of the invention is that, since the selection and stalling operations are always simultaneous, the same electrode can control the selection switch and the stall switch of the circuit; the number of electrodes of the active matrix is thus advantageously reduced with respect to the first embodiment. This second modality requires, on the other hand, a very precise adjustment of the hooking with respect to the application of the voltage jump ΔV.

• un réseau d'émetteurs de lumière ou de valves optiques,
• une matrice active comprenant un réseau d'électrodes pour l'adressage de signaux en tension, un premier réseau d'électrodes de sélection, au moins une électrode de référence pour l'adressage, un réseau de circuits aptes à commander chacun desdits émetteurs ou valves et dotés, chacun, d'une borne de commande en tension apte à être couplée à une électrode d'adressage via un condensateur de couplage et un premier interrupteur de sélection qui sont montés en série, d'une borne de calage en tension apte à être reliée à ladite borne de commande via un interrupteur de calage, et d'un condensateur de maintien monté entre ladite borne de commande et ladite borne de calage, où :

• la borne de calage est reliée à l'au moins une électrode de référence,
• la commande dudit premier interrupteur de sélection et la commande dudit interrupteur de calage sont reliées à une même électrode de sélection dudit premier réseau.

The invention therefore relates to a display panel comprising:

• a network of light emitters or optical valves,
• an active matrix comprising an array of electrodes for addressing voltage signals, a first array of selection electrodes, at least one reference electrode for addressing, a network of circuits able to control each of said transmitters or valves and each having a voltage control terminal adapted to be coupled to an addressing electrode via a coupling capacitor and a first selection switch which are connected in series, to a voltage clamping terminal adapted to be connected to said control terminal via a stall switch, and a holding capacitor mounted between said control terminal and said stall terminal, where:

• the clamping terminal is connected to the at least one reference electrode,
• the control of said first selection switch and the control of said stall switch are connected to a same selection electrode of said first network.

Other switches than the stall switch, including the selector switch itself, can be used to connect the voltage stall terminal to the control terminal.

Preferably, the stall switch is of the same polarity as the selection switch, so that a signal sent to the common control of these two switches induces the same state, of closing or opening, of these switches. Preferably, this common control is directly connected to a selection electrode.

The emitters or valves are capable of being fed between at least two supply electrodes, namely a base electrode for the supply which is generally part of the active matrix, and a so-called electrode. "Superior" supply, which generally covers all transmitters or valves.

The holding capacitor is adapted to maintain an approximately constant voltage on said control terminal during the duration of an image when said first selector switch and said stall switch are open.

Preferably, the panel comprises an array of light emitters able to be supplied between at least one supply base electrode and at least one upper supply electrode, where each of said control circuits of a transmitter comprises a modulator current sensor itself comprising a voltage control electrode forming the control electrode of said circuit and two current-conducting electrodes, which are connected between one of said supply electrodes and a supply electrode of said emitter. Generally, such a modulator is a TFT transistor; the current delivered by the modulator is then a function of the potential difference between the gate terminal and the source terminal of this transistor; this potential difference is generally a function, if not equal to, the potential difference between the control terminal and a reference electrode for the control voltage of the circuit; the reference electrode for the control voltage of the circuit is then formed by the supply base electrode.

Preferably, said current modulator is a transistor comprising an amorphous silicon semiconductor layer.

Preferably, said emitters are electroluminescent diodes, preferably organic.

Preferably, said control circuit comprises a second selection switch connecting said control terminal to said addressing electrode without passing through said coupling capacitor.

• soir par couplage capacitif lorsqu'on utilise le premier interrupteur de sélection ;
• soir par conduction lorsqu'on utilise le deuxième interrupteur de sélection.

Advantageously, two circuit selection means are available:

• by capacitive coupling when using the first selection switch;
• Conductive evening when using the second selection switch.

Preferably, said active matrix then comprises a second selection electrode array for controlling said second selection switches.

• une étape de calage, lors de laquelle, ladite électrode de référence du panneau étant portée à un potentiel de calage, on applique un signal de sélection à l'électrode de sélection qui commande le premier interrupteur de sélection et l'interrupteur de calage dudit circuit de commande, ce signal étant apte à fermer lesdits interrupteurs, et, pendant l'application dudit signal de sélection, on applique un signal initial de tension V_ini-E, V_ini-P à l'électrode d'adressage,
• une étape de programmation du circuit, lors de laquelle, toujours pendant l'application dudit signal de sélection, après l'obtention du calage du potentiel de la borne de commande au potentiel de calage V_cal de la borne de calage reliée à ladite électrode de référence et après l'application dudit signal initial, on applique un signal final de tension V_data, V_pol à ladite électrode d'adressage, ce signal final générant un saut de tension ΔV_data = V_data - V_ini-E, ΔV_pol = V_pol - V_ini-P sur cette électrode d'adressage qui génère lui-même un saut transitoire de tension sur la borne de commande qui est couplée à ladite électrode d'adressage, et, pendant ledit saut transitoire de tension, on met fin audit signal de sélection, les valeurs dudit signal initial V_ini-E, V_ini-P et dudit signal final V_data, V_pol étant adaptées pour obtenir au moment de la fin dudit signal de sélection un saut de tension ΔV_prog-data = V_prog-data - V_cal, ΔV_prog-pol = V_prog-pol-V_cal sur ladite borne de commande qui permette d'obtenir ladite tension prédéterminée V_prog-data, V_prog-pol.

The subject of the invention is also a method for controlling a panel according to the invention, which comprises a succession of periods during which a predetermined voltage V _prog-data , V _prog-pol is applied and maintained at the control terminal. at least one control circuit of said panel, in which, during at least one period, said predetermined voltage V _prog-data , V _prog-pol is applied to the control terminal of each circuit by transient capacitive coupling according to the steps following:

• a stalling step, in which, said panel reference electrode being brought to a stalling potential, a selection signal is applied to the selection electrode which controls the first selection switch and the stall switch of said circuit command, this signal being able to close said switches, and, during the application of said selection signal, an initial voltage signal V _ini-E , V _ini-P is applied to the addressing electrode,
• a programming step of the circuit, during which, still during the application of said selection signal, after obtaining the setting of the potential of the control terminal at the setting potential V _cal of the _clamping terminal connected to said electrode of reference and after the application of said initial signal, applying a final voltage signal V _data , V _pol to said addressing electrode, this final signal generating a voltage jump ΔV _data = V _data - V _ini-E , ΔV _pol = V _pol - V _ini-P on this addressing electrode which itself generates a transient voltage jump on the control terminal which is coupled to said addressing electrode, and, during said transient voltage jump, is set at the end of said selection signal, the values of said initial signal V _ini-E , V _ini-P and of said final signal V _data , V _pol being adapted to obtain at the moment of the end of said selection signal a voltage jump ΔV _prog-data = V _prog-data - V _cal , ΔV _prog-pol = V _prog-pol -V _cal on said control terminal which makes it possible to obtain said predetermined voltage V _prog-data , V _prog-pol .

In practice, during periods of emission or depolarization, a predetermined emission or depolarization voltage is generally applied and maintained at the control terminal of each of said control circuits of said panel.

Control of the panel is generally intended for displaying a succession (or sequence) of images; each emitter or valve of the panel, then corresponds to a pixel or sub-pixel of the images to be displayed; during certain so-called transmission periods, at each emitter or valve of the panel, is associated a predetermined transmission voltage to be applied to the control terminal of the circuit which controls this emitter or valve, this voltage being adapted to obtain the display of said pixel or subpixel by this emitter or valve; alternatively, between any two emission periods, a period of depolarization of the transmitter, the valve, and / or the control circuit is interposed; during each depolarization period, each emitter or valve of the panel is associated with a predetermined depolarization voltage, this voltage being adapted to depolarize said emitter, said valve and / or said circuit.

• à ce que l'émetteur ou la valve du panneau qui est commandée par ce circuit émette un pixel ou sous-pixel de l'image à afficher,
• ou/et à ce que l'émetteur ou la valve du panneau, ou le circuit de commande, ou, le cas échéant, le modulateur de courant de ce circuit, soit dépolarisé, au moins partiellement.

Thus, the predetermined voltage to be applied and maintained at the control terminal of the control circuits of said panel is intended:

• the emitter or valve of the panel which is controlled by this circuit emits a pixel or subpixel of the image to be displayed,
• or / and that the emitter or valve of the panel, or the control circuit, or, where appropriate, the current modulator of this circuit, is depolarized, at least partially.

The end of the selection signal simultaneously opens the first selection switch and the setting switch of the control circuit. At this time, the voltage of the control terminal is equal to said predetermined voltage, and is maintained at approximately this value for the remainder of the duration of the period by means of the holding capacitor to which this terminal is connected.

The transient voltage jump obtained at the control terminal is transient in the sense that, in the absence of interruption by the end of the selection signal, the voltage at the control terminal would return to the stall potential.

The obtaining of said predetermined voltage from the control terminal thus results from a voltage jump caused to this terminal by coupling. transient capacitive to the addressing electrode itself subjected to a tenson jump; of this predetermined voltage, it is possible to deduce the voltage jump to be obtained at the control terminal by difference with the potential of the reference electrode to which this terminal has been previously wedged; from this jump of voltage to be obtained at the control terminal, it is possible to deduce the voltage jump to be generated at the addressing electrode, as a function, in particular, of the coupling level with the control terminal and as a function of the time interval T between this voltage jump and the end of the selection signal.

Preferably, the time interval T between said voltage jump to the addressing electrode and the end of said selection signal is adapted so that the voltage jump obtained at the control terminal is approximately maximum. This optimizes the coupling between this control terminal and the addressing electrode.

alors, l'intervalle de temps T entre ledit saut de tension à l'électrode d'adressage et la fin dudit signal de sélection est tel que l'on a : T₀ ≤ T ≤ 1,1 T₀. De préférence, les dites périodes comprennent des périodes d'émission et des périodes de dépolarisation ; en outre, la tension prédéterminée dite de dépolarisation V_prog-pol à appliquer et à maintenir à la borne de commande d'un circuit de commande pendant une période de dépolarisation est de polarité opposée à la tension prédéterminée dite d'émission V_prog-data à appliquer et à maintenir à la borne de commande du même circuit pendant une période d'émission, tension d'émission qui est obtenue par l'application de signaux dits d'émission à l'électrode d'adressage à laquelle ladite borne de commande est apte à être couplée ; en outre, l'au moins une période d'application de tension par couplage capacitif transitoire comprend lesdites périodes de dépolarisation, et, pour chacune desdites périodes de dépolarisation et pour l'application par couplage capacitif transitoire d'une tension prédéterminée de dépolarisation V_prog-pol à la borne de commande à chaque circuit de commande dudit panneau, on choisit ledit signal initial de tension V_ini-P et ledit signal final de tension V_pol de manière à ce qu'ils présentent la même polarité que lesdits signaux d'émission.Preferably, if C _C and C _S denote the capacitance values respectively of the coupling capacitors and the holding capacitors, if R4 denotes the electrical resistance of the selection switch when it is closed, if R 3 denotes the electrical resistance of the stall switch when it is closed,
... if we define T ₀ by the equation: ${\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="imgf0002.png"\; state="\{\{state\}\}">T</figure-callout>}}_0=\frac{\left(R3\times {\mathrm{VS}}_{\mathrm{VS}}\right)\mathrm{.}\left(R4\times {\mathrm{VS}}_S\right)}{\left(R3\times {\mathrm{VS}}_{\mathrm{VS}}\right)-\left(R4\times {\mathrm{VS}}_S\right)}\mathit{Ln}\left(\frac{R3\times {\mathrm{VS}}_{\mathrm{VS}}}{R4\times {\mathrm{VS}}_S}\right),$

then, the time interval T between said voltage jump to the addressing electrode and the end of said selection signal is such that there is: T ₀ ≤ T ≤ 1.1 T ₀ . Preferably, the said periods comprise emission periods and periods of depolarization; in addition, the predetermined _prog-pol depolarization voltage V to be applied and maintained at the control terminal of a control circuit during a depolarization period is of opposite polarity to the predetermined transmission voltage V _prog-data to apply and maintain at the control terminal of the same circuit during a transmission period, transmission voltage which is obtained by the application of so-called transmission signals to the addressing electrode to which said control terminal is able to be coupled; in addition, the at least one transient capacitive coupling voltage application period comprises said depolarization periods, and for each of said depolarization periods and for application by transient capacitive coupling of a predetermined _prog-pol depolarization voltage V to the control terminal to each control circuit of said panel, said initial voltage signal V _ini-P and said final voltage signal V _pol are chosen so that they have the same polarity as said transmission signals.

In practice, the difference ΔV _pol = V _pol -V _{ini-P is} first chosen in order to obtain the predetermined depolarization voltage V _prog-pol , in a manner known per se, to compensate for the polarization, for example the derives from the trip threshold voltage of a current modulator that has occurred during a previous transmission period; a sufficiently high value of V _ini-P , of the same polarity as that of the transmission signals, is then chosen so that the value of V _pol-1 , resulting from the said difference ΔV _pol , is of the same polarity as V _ini-P and that the emission signals. Preferably, when the value of ΔV _pol allows it, one chooses V _ini-P = 0.

The polarity of the signals is evaluated with respect to a reference electrode for the control voltage of the circuits; it may be in particular a base electrode for powering transmitters or valves.

Thus, the voltage of the addressing electrode never changes sign and can advantageously use conventional and economical means for controlling the addressing electrodes.

• les figures 1 et 2 décrivent deux modes de réalisation de circuits de commande de panneaux selon l'invention ;
• la figure 3 est un chronogramme des signaux appliqués pendant une succession de périodes et de trames pour la commande du circuit de la figure 2 lors du pilotage du panneau de la figure 2 (signaux logiques V_YA, V_YB, signaux d'adressage V_XD); ce chronogramme illustre également l'évolution du potentiel de commande du modulateur V_G de ce circuit, et de l'intensité I_dd du courant circulant dans la diode que ce circuit commande ;

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 Figures 1 and 2 describe two embodiments of panel control circuits according to the invention;
• the figure 3 is a timing diagram of the signals applied during a succession of periods and frames for the control of the circuit of the figure 2 when piloting the panel of the figure 2 (logic signals V _YA , V _YB , addressing signals V _XD ); this timing diagram also illustrates the evolution of the control potential of the modulator V _G of this circuit, and the intensity I _dd of the current flowing in the diode that this circuit controls;

Figures representing chronograms do not take into account scale of values to better reveal certain details that would not be apparent if the proportions had been respected.

In order to simplify the description, identical references are used for the elements that provide the same functions.

The embodiments presented below relate to image display panels where the emitters are organic electroluminescent diodes deposited on an active matrix incorporating control circuits and power supply of these diodes. These emitters are arranged in line and in column.

• un réseau d'électrodes d'adressage disposées en colonnes de manière à ce que tous les circuits commandant les diodes d'une même colonne soient desservis par la même électrode d'adressage X_D ;
• un réseau d'électrodes de sélection Y_S disposées en lignes de manière à ce que tous les circuits commandant les diodes d'une même ligne soient desservis par la même électrode ;
• une électrode de référence P_R commune à tous les circuits ;
• une électrode de base d'alimentation P_B commune à tous les circuits ;

We will now describe a first embodiment of the invention. With reference to the figure 1 which describes a control circuit and supply 1 "of a diode and its connections to the electrodes of the panel, the active matrix of the panel according to this first embodiment comprises:

• an array of addressing electrodes arranged in columns so that all the circuits controlling the diodes of the same column are served by the same address electrode X _D ;
• an array of selection electrodes Y _S arranged in lines so that all the circuits controlling the diodes of the same line are served by the same electrode;
• a reference electrode P _R common to all the circuits;
• a basic supply electrode P _B common to all circuits;

The active matrix also comprises a control circuit 1 "and supply for each diode 2.

The panel also comprises an upper supply electrode P _A common to all the diodes.

• un modulateur de courant T2 comprenant deux bornes de courant, à savoir une borne de drain D et une borne de source S, et une borne de grille G, qui correspond ici à la borne de commande C du circuit.
• un condensateur de maintien C_S branché entre ladite grille G et une borne de calage R du circuit.

The circuit 1 for controlling and feeding each diode 2 comprises:

• a current modulator T2 comprising two current terminals, namely a drain terminal D and a source terminal S, and a gate terminal G, which corresponds here to the control terminal C of the circuit.
• a holding capacitor C _S connected between said gate G and a clamping terminal R of the circuit.

The control terminal C of the circuit is coupled to an addressing electrode X _D via a selection switch T4 and a coupling capacitor C _C , which are connected in series; there is no connection here by electrical conduction between this control terminal C and this address electrode X _D. Preferably, this coupling capacitor C _C is common to all the control circuits served by this addressing electrode. The selection switch T4 is controlled by a selection electrode Y _S.

The circuit 1 "also comprises a stall switch T3 adapted to connect the control terminal C to the clamping terminal R of the circuit, here via the switch T4 or optionally directly, this stall switch T3 is controlled by the same electrode. selection Y _S as selector switch T 4. Stall terminal R is connected to reference electrode P _R.

The current modulator T2 is connected in series with the diode 2: the drain terminal D is thus connected to the cathode of the diode 2. This series is connected between two supply electrodes: the source terminal S is connected to the supply base electrode P _B and the anode of diode 2 is connected to the upper supply electrode P _A.

We will now describe the operation of the panel according to this first embodiment.

The potentials V _cal , Vdd and Vss are respectively applied to the reference electrodes P _R , supply P _A and P _B respectively. Here, the potential Vss of the supply base electrode P _B is zero and serves as a reference for the control voltage of the circuit 1 ", which corresponds here to the difference V _G -V _S = V _G -V _SS = V _G. other references for the control voltage of the circuit may be envisaged without departing from the invention.

For the control of each control circuit 1 "of a diode 2, the duration of each frame of picture is then decomposed in six steps.

Step 1 of setting the circuit during the emission period : this step marks the beginning of the emission period of the diode during this image or image frame.

The selection switch T4 and the clamping switch T3 are simultaneously closed by applying to the selection electrode Y _S a suitable logic signal; the closing of T4 has the effect of selecting the control circuit 1 "of the diode 2 by coupling, via the capacitor C _C , the control terminal C to the address electrode X _D; the simultaneous closing of the switches T3 and T4 has the effect, despite the coupling, of setting the potential of the control terminal C to the setting potential V _cal applied to the clamping electrode P _R ; during this stalling step, the potential of the addressing electrode is raised to the value V _ini-E = 0. The duration of this step is sufficiently high to obtain the stabilization of the potentials, and in particular for the potential of the grid G remains at the value V _cal

Step 2 programming the circuit during the emission period :

The duration of this step is particularly critical for addressing the panel as described below.

While maintaining at the beginning of this step the same logic signal to the selection electrode Y _S - which has the effect of keeping the calibration switch T3 and the selection switch T4 closed - the potential of the addressing electrode at the value V _data-1 , which thus undergoes a jump of potential ΔV _data-1 = V _data-1 -V in _-E = V _data-1 - By transient capacitive coupling via the coupling capacitor C _C , the potential of the control terminal C then undergoes a transient (positive) peak from the value V _cal of the stall potential.

At a time T evaluated with respect to the instant of application of the potential jump ΔV _data-1 to the addressing electrode X _D , the selection switch T4 and the calibration switch T3 are simultaneously opened by applying at the selection electrode Y _S a suitable logic signal; the instant T is chosen as close as possible to the instant of the peak of the transient peak, as described below in more detail.

Thus "hooks" the potential V _G of the control terminal C to a value V _prog-data-1 ; the voltage jump ΔV _prog-data-1 = V _prog-data-1 -V _cal is proportional to ΔV _data-1 ; the value of V _data-1 is set so that the control voltage of the modulator V _G -V _S = V _prog-data-1 -Vss = V _prog-data-1 is proportional to the image data at display by the diode 2 during this frame of image.

At this stage, the diode 2 begins to emit a luminance proportional, with said correction, to the image data of the pixel or subpixel associated with it during this image frame.

It should be noted that the voltage of the control terminal C would return to the value V _cal if one chose T too long.

Step 3 of maintaining the circuit during the emission period :

During the remainder of the emission period of this diode 2 during this image frame, the selection switch T4 and the blocking switch T3 remain open; the control circuit 1 "is therefore no longer selected During this step, the capacitor C _S maintains a constant value the voltage of the control terminal C, and the diode 2 continues to emit a luminance proportional to the data image of the pixel or subpixel associated with it During this step 3, steps 1 and 2 above are applied to the control circuits of the diodes of the other lines so as to display the entire image.

Step 4 of calibration of the modulator control during the depolarization period :

The beginning of this step marks the end of the emission period of the diode and the beginning of the depolarization period of the modulator T2.

The selection switch T4 and the clamping switch T3 are simultaneously closed by applying to the selection electrode Y _S a suitable logic signal; the closing of T4 has the effect of selecting the control circuit 1 of the diode 2 by coupling, via the capacitor C _C , the control terminal C of the modulator T2 to the address electrode X _D ; the simultaneous closing of the switches T3 and T4 has the effect, despite the coupling, of setting the potential V _G of the control terminal C to the setting potential V _cal applied to the reference electrode P _R ; during the simultaneous closing of these switches, the potential of the addressing electrode is raised to the value V _ini-P-1 , the value of which will be established later. The duration of this step is sufficiently high to obtain the stabilization of the potentials, in particular so that the potential of the control terminal C remains at the value V _cal .

Step 5 programming the circuit during the depolarization period :

The duration of this step is also particularly critical for addressing the panel as described below.

While maintaining at the beginning of this step the same logic signal to the selection electrode Y _S - which has the effect of keeping the T3 blocking switch closed and the selection switch T4 -on carries the potential of the addressing electrode at the value V _pol-1 , which therefore undergoes a potential jump ΔV _pol-1 = V _pol-1 V _ini-P . By transient capacitive coupling via the coupling capacitor C _C , the potential of the control terminal C then undergoes a transient (positive) potential peak from the value V _cal of the stall potential.

At a time T evaluated with respect to the instant of application of the potential jump ΔV _pol-1 to the addressing electrode X _D , the selection switch T4 and the calibration switch T3 are simultaneously opened by applying at the selection electrode Y _S a suitable logic signal; the instant T is chosen as close as possible to the instant of the peak of the peak of potential, as described below in more detail.

• critère 1 : la différence ΔV_pol-1 est adaptée pour obtenir une tension (négative) de commande de dépolarisation du modulateur V_G-V_S = V_prog-pol-1 - Vss = V_prog-pol-1 de valeur adaptée, d'une manière connue en elle-même, pour compenser la dérive de la tension de seuil de déclenchement du modulateur qui s'est produite pendant la période d'émission précédente ;
• critère 2 : V_ini-P-1 est suffisamment élevé pour que V_pol-1, défini selon le critère 1, soit positif ou nul. De préférence, lorsque la valeur de ΔV_pol-1 le permet, on choisit V_ini-P-1 =0

Thus the potential V _G of the control terminal C is connected to a value V _prog-pol-1 ; the potential jump ΔV _prog-pol-1 = V _prog-pol-1 -V _cal is proportional to ΔV _pol-1 = V _pol-1 -V _ini-P-1 ; according to the invention, the values of V _ini-P-1 and V _pol-1 are chosen according to a double criterion:

• criterion 1: the difference ΔV _pol-1 is adapted to obtain a (negative) depolarization control voltage of the modulator V _G -V _S = V _prog-pol-1 - Vss = V _prog-pol-1 of suitable value, d a manner known per se to compensate for the drift of the modulator trip threshold voltage which occurred during the previous transmission period;
• criterion 2: V _ini-P-1 is sufficiently high for V _pol-1 , defined according to criterion 1, to be positive or zero. Preferably, when the value of ΔV _pol-1 allows it, V _ini-P-1 = 0 is chosen.

Thus, the voltage of the addressing electrode never changes sign and can advantageously use conventional and economical means for controlling the addressing electrodes.

At this point, the modulator T2 begins to be depolarized in proportion to the value of V _prog-pol-1 .

Step 6 of maintaining the circuit during the depolarization period :

During the remainder of the depolarization period of this diode 2 during this image frame, the selection switch T4 and the setting switch T3 are kept open; the control circuit 1 "is therefore no longer selected During this step, the capacitor C _S maintains a constant value the voltage of the control terminal C, and the modulator T2 continues to be depolarized in proportion to the value of V _prog-pol-1 .

During this step 6, steps 4 and 5 above are applied to the control circuits of the other diode lines so as to depolarize the modulators of all the control circuits of the panel.

The end of this step marks the end of the depolarization period of the modulator T2 and the beginning of a new transmission period of the diode 2, during a new image frame.

To obtain the required potential jumps ΔV _prog-data-1 and ΔV _prog-pol-1 on the gate G of the modulator T2, the duration T of the programming steps 2 and 4 is therefore particularly critical.

If C _C and C _S designate as previously the capacitance values respectively of the coupling capacitors and the holding capacitors, if R4 denotes the electrical resistance of the selection switch T4 when it is closed, if R3 denotes the electrical resistance of T3 when closed, it is shown that the potential peak on the gate G is obtained at a time t = T ₀ offset from the instant t = 0 of the application of the voltage jump ΔV _{data -1} and ΔV _pol-1 on the addressing electrode,
or ${\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="imgf0002.png"\; state="\{\{state\}\}">T</figure-callout>}}_0=\frac{\left(R3\times {\mathrm{VS}}_{\mathrm{VS}}\right)\mathrm{.}\left(R4\times {\mathrm{VS}}_S\right)}{\left(R3\times {\mathrm{VS}}_{\mathrm{VS}}\right)-\left(R4\times {\mathrm{VS}}_S\right)}\mathit{Ln}\left(\frac{R3\times {\mathrm{VS}}_{\mathrm{VS}}}{R4\times {\mathrm{VS}}_S}\right)$

As the transistors of the control circuit are in amorphous silicon, the values of R4 and R3 are generally high, of the order of one hundred kiloOhms, which induces time constants R3 x C _C and R4 x C _S relatively high. Taking R3 = R4 = 1 MΩ, C _S = 0.5 pF, C _C = 3 pF, so we have T ₀ = 1 μs.

• où K = C_C / (C_C + C_S), C_C et C_S désignant ici les valeurs des capacités respectivement des condensateurs de couplage et des condensateurs de maintien,
• où τ = R4 x C_S x C_C / (C_C + C_S), où R4 désigne la résistance électrique de l'interrupteur de sélection lorsqu'il est fermé.

Preferably, the value of T should be chosen so that T ₀ ≤ T ≤ 1.1 T ₀ . It has previously been indicated that, in step 2, the potential jump ΔV _prog-data-1 = V _prog-data-1 -V _cal was proportional to ΔV _data-1 = = V _data-1 -V _{init E-1} , and that, in step 5, the voltage jump ΔV _prog-pol-1 = V _prog-pol-1 -V _cal was proportional to ΔV _pol-1 = V _pol-1 -V _{init P-1} , this proportionality depends not only on the duration T of the programming steps 2 and 5, but also on the "coupling factor" between the addressing electrode X _D and the control terminal C. It is shown that the constant K (t) of proportionality, that is to say of coupling, between the jumps of potential on the control terminal C: ΔV _prog-data-1 , ΔV _prog-pol-1 , ΔV _prog-data-2 , and ΔV _prog-pol-2 , and the corresponding potential jumps on the address electrode ΔV _data-1 , ΔV _pol-1 , ΔV _data-2 , and ΔV _pol-2 , which changes as a function of time from of the moment t = 0 at which said jump of potential is applied to the addressing electrode, xprime in the form: $K\left(t\right)=K\times \left(1-e^{-\frac{t}{\mathrm{\tau }}}\right),$

• where K = C _C / (C _C + C _S ), C _C and C _S here denoting the capacitance values respectively of the coupling capacitors and the holding capacitors,
• where τ = R4 x C _S x C _C / (C _C + C _S ), where R4 denotes the electrical resistance of the selection switch when it is closed.

To obtain the stabilization of the potentials and to charge the holding capacitor C _S during an addressing step (step 2 or 5 above), it is preferable that the duration of this step be at least equal to 5 × τ. .

It is possible that the control voltage of the modulator T2 undergoes a slight drop -ΔV _{prog-data-cor} between step 2 and step 3, -ΔV _prog-pol-cor between step 5 and step 6 due to the suppression of the capacitive coupling; so that the depolarization of the modulator is in accordance with the objectives, it is then preferable to provide a correction + ΔV _{prog-data-cor} , + ΔV _prog-pol-cor to the target value V _prog-data-1 , V _{prog-pol -1} .

A second embodiment of the invention will now be described which differs from the first embodiment essentially in that, during transmission periods, the addressing of the circuits is carried out in a conventional manner by conduction between the electrodes. addressing and the terminal circuit control; with reference to the figure 2 the panel then comprises two selection electrode arrays Y _SE and Y _SP , the first network serving during transmission periods, and the second network during depolarization periods; each control circuit 1 "'differs from that 1" of the first embodiment which has just been described in that it further comprises a selection switch for the transmission T1 capable of short-circuiting the coupling capacitor C _C to conditively connect the control terminal C to the addressing electrode X _D ; this switch T1 is controlled by a selection electrode for the emission Y _SE ; the selection switch T4 serves for depolarization only; the control circuits of the emitters therefore each comprise four TFT transistors.

The operation of the panel according to this second embodiment will now be described with reference to FIG. figure 3 .

• les étapes 1, 2 de la période d'émission sont modifiées et remplacées par l'étape 1 ci-dessous ;
• l'étape 3 de la période d'émission et les étapes 4, 5, et 6 de la période de dépolarisation sont inchangées et renumérotées respectivement 2, 3, 4 et 5.

For the control of each control circuit 1 '"of a diode 2, the duration of each picture frame is then divided into five steps: The operation differs from that previously described in that:

• steps 1, 2 of the emission period are modified and replaced by step 1 below;
• step 3 of the emission period and steps 4, 5, and 6 of the depolarization period are unchanged and renumbered 2, 3, 4 and 5 respectively.

The potentials V _cal , Vdd and Vss are respectively applied to the reference electrodes P _R , supply P _A and P _B respectively.

Step 1 addressing the circuit during the transmission period : this step marks the beginning of the emission period of the diode during this image frame; during this period, the selection switches for the depolarization T4 and the stall switch T3 remain open.

The selection switch for the transmission T1 is closed by applying to the selection electrode Y _S a suitable logic signal; the closing of T1 has the effect of selecting the circuit for the transmission by connecting the gate G of the modulator T2 to the addressing electrode X _D ; during this step, the potential of the addressing electrode is raised to the value V _data-1 which is reflected in the control gate G of the modulator T2. The duration of this step is sufficient high to charge the holding capacitor C _S ; the diode 2 begins to emit a luminance proportional to the image data of the pixel or subpixel associated with it during this image frame.

Step 2 of maintaining the circuit during the transmission period : see previous step 3.

During the remainder of the emission period of this diode 2 during this image frame, the selection switches T1 and T4, and the setting switch T3 remain open; the control circuit 1 "'is thus no longer selected for the emission no more than for the depolarization During this step, the capacitor C _S maintains at a constant value the control voltage of the modulator T2, and the diode 2 continues therefore, to emit a luminance proportional to the image data of the pixel or subpixel associated with it During this step 3, step 1 above is applied to the control circuits of the diodes of the other lines so as to view the entire image.

Step 3 of setting the modulator control during the depolarization period : see previous step 4.

The beginning of this step marks the end of the emission period of the diode and the beginning of the depolarization period of the modulator T2. During the depolarization period, the selection switch for the transmission therefore remains open.

Step 4 programming the circuit during the depolarization period : see previous step 5. Step 5 of maintaining the circuit during the period of depolarization : see previous step 6.

The end of this step marks the end of the depolarization period of the modulator T2 and the beginning of a new transmission period of the diode 2, during a new image frame.

The embodiments described above relate to display panels with organic electroluminescent diodes active matrix; the invention applies more generally to all kinds of active matrix display panels, including current-controllable emitters or optical valves.

Claims (9)

1. Display panel comprising:

   - an array of light emitters or optical valves,

   - an active matrix comprising an array of electrodes (X_D) for addressing voltage-mode signals, a first array of select electrodes (Y_S, Y_SP), at least one reference electrode (P_R) for addressing, an array of circuits each suitable for controlling each of said emitters or valves and each (1 ", 1 "') provided with a voltage-mode control terminal (C) suitable for coupling to an address electrode (X_D) via a coupling capacitor (C_C) and via a first select switch (T4) which are mounted in series, a voltage-mode clamping terminal (R) suitable for connecting to said control terminal (C) via a clamping switch (T3) of the same polarity as the select switch (T4), and a sustain capacitor (C_S) mounted between said control terminal (C) and said clamping terminal (R), where the clamping terminal (R) is linked to the at least one reference electrode (P_R),

   characterized in that the control of said first select switch (T4) and the control of said clamping switch (T3) are directly connected to the same select electrode (Y_S) of said first array.
2. Panel according to Claim 1, comprising an array of light emitters suitable to be powered between at least one base power supply electrode P_B and at least one upper power supply electrode P_A, characterized in that each of said control circuit of an emitter (2) comprises a current modulator (T2) comprising a voltage-mode control electrode (G) forming the control electrode (C) of said control circuit and two current-passing electrodes (D, S) that are connected between one of said power supply electrodes (P_A, P_B) and a power supply electrode of said emitter.
3. Panel according to Claim 2, characterized in that said current modulator is a transistor comprising a semiconductor layer of amorphous silicon.
4. Panel according to Claim 2 or 3, characterized in that said emitters are light-emitting diodes.
5. Panel according to any one of the preceding claims, characterized in that said control circuit (1'") comprises a second select switch (T1) suitable for linking said control terminal (C) to said address electrode (X_D) without passing through said coupling capacitor (C_C).
6. Method of controlling a panel according to any one of the preceding claims, which comprises a succession of periods during which a predetermined voltage (V_prog-data, V_prog-pol) is applied and sustained at the control terminal of at least one control circuit of said panel, in which, in at least one of said periods, said predetermined voltage (V_prog-data, V_prog-pol) is applied to the control terminal (C) of each circuit by transient capacitive coupling according to the following steps:

   - a clamping step, during which, said reference electrode of the panel (P_R) being raised to a clamping potential (V_cal), a select signal is applied to the select electrode (Y_S) that controls the first select switch (T4) and the clamping switch (T3) of said control circuit, this signal being suitable for closing said switches (T4, T3), and, while said select signal is being applied, an initial voltage signal (V_ini-E, V_ini-P) is applied to the address electrode (X_D),

   - a circuit programming step, during which, still while said select signal is being applied, after the clamping of the potential of the control terminal (C) to the clamping potential (V_cal) of the clamping terminal (R) linked to said reference electrode (P_R) has been obtained, and after the application of said initial signal, a final voltage signal (V_data, V_pol) is applied to said address electrode (X_D), this final signal generating a voltage jump (ΔV_data = V_data V_ini-E, ΔV_pol = V_pol - V_ini-P) on this address electrode (X_D) which in turn generates a transient voltage jump on the control terminal (C) that is coupled to said address electrode (X_D), and, during said transient voltage jump, said select signal is ended, the values of said initial signal (V_ini-E, V_ini-P) and of said final signal (V_data, V_pol) being adapted to obtain at the moment when said select signal is ended, a voltage jump (ΔV_prog-data = V_prog-data - V_cal, ΔV_prog-pol = V_prog-pol - V_cal) on said control terminal (C) which makes it possible to obtain said predetermined voltage (V_prog-data, V_prog-pol).
7. Method according to Claim 6, characterized in that the time interval T between said voltage jump at the address electrode (X_D) and the end of said select signal is adapted so that the voltage jump obtained at the control terminal is approximately maximum.
8. Method according to Claim 6 or 7, characterized in that:

   ... if C_C and C_S denote the values of the capacitances respectively of the coupling capacitors and of the sustain capacitors, if R4 denotes the electrical resistance of the select switch (T4) when it is closed, if R3 denotes the electrical resistance of the clamping switch (T3) when it is closed, ... if T₀ is defined by the equation: $T_0=\frac{\left(R3\times C_C\right)\mathrm{.}\left(R4\times C_S\right)}{\left(R3\times C_C\right)-\left(R4\times C_S\right)}\mathit{Ln}\left(\frac{R3\times C_C}{R4\times C_S}\right),$

   

   then, the time interval T between said voltage jump at the address electrode (X_D) and the end of said select signal is such that T₀ = T = 1.1 T₀.
9. Method according to any one of Claims 6 to 8, wherein
   ... the said periods comprises emission periods and depolarization periods,
   ... the predetermined so-called depolarization voltage (V_prog-pol) to be applied and to be sustained at the control terminal of a control circuit during a depolarization period are of a polarity opposite to the predetermined so-called emission voltage (V_prog-data) to be applied and to be sustained at the control terminal of the same circuit during an emission period, this emission voltage being obtained by the application of so-called emission signals to the address electrode (X_D) to which said control terminal is suitable for coupling,
   characterized in that the at least one period of application of voltage by transient capacitive coupling comprises said depolarization periods, and in that, for each of said depolarization periods and for the application by transient capacitive coupling of a predetermined depolarization voltage
   (V_prog-pol) to the control terminal of each control circuit of said panel, said initial voltage signal (V_ini-P) and said final voltage signal (V_pol) are chosen such that they present the same polarity as said emission signals.

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