Classifications

• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
  • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
  • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
  • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
  • G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
  • G09G3/3233—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix with pixel circuitry controlling the current through the light-emitting element
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
  • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
  • G09G3/3611—Control of matrices with row and column drivers
  • G09G3/3614—Control of polarity reversal in general
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
  • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
  • G09G3/3611—Control of matrices with row and column drivers
  • G09G3/3648—Control of matrices with row and column drivers using an active matrix
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
  • H10K59/10—OLED displays
  • H10K59/12—Active-matrix OLED [AMOLED] displays
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2300/00—Aspects of the constitution of display devices
  • G09G2300/08—Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
  • G09G2300/0809—Several active elements per pixel in active matrix panels
  • G09G2300/0842—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor
  • G09G2300/0852—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor being a dynamic memory with more than one capacitor
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2300/00—Aspects of the constitution of display devices
  • G09G2300/08—Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
  • G09G2300/0876—Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2310/00—Command of the display device
  • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
  • G09G2310/0243—Details of the generation of driving signals
  • G09G2310/0254—Control of polarity reversal in general, other than for liquid crystal displays
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2320/00—Control of display operating conditions
  • G09G2320/04—Maintaining the quality of display appearance
  • G09G2320/043—Preventing or counteracting the effects of ageing

Definitions

• 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.
• 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.
• 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 .
• 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.
• the control terminal of the circuit is connected to or coupled to one of the terminals of the valve.
• 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.
• 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;
• 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.
• control in English
• these means generally comprise controllable switches.
• the voltage across the valves is generally alternated to avoid initiating a continuous polarization component of the liquid crystal
• the emitters are light-emitting diodes
• 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.
• 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 analog voltage control of emitter panels, 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 while this circuit is selected.
• connection by capacitive coupling, and not by conduction, between the addressing electrodes and the control terminals of the circuits 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.
• the other documents US6777888, US6618030 and 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.
• 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.
• the capacitive coupling makes it possible to modify the voltage of a terminal by a voltage jump.
• an algebraic value voltage step signal ⁇ V 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 + ⁇ V.
• This voltage jump is independent of the value V ini of the initial potential (before the jump) of the addressing electrode.
• 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 + ⁇ V ( ⁇ V ⁇ 0) to retain the same sign as V ini , thus to choose
• 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.
• at least depolarization, if not also emission during each driving period of a circuit, at least depolarization, if not also emission:
• this circuit is selected by capacitively coupling the control terminal of this circuit to an addressing electrode and "shimming" the potential of this terminal to the potential V cal of a reference terminal of this circuit, which therefore becomes a stall 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 ;
• 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.
• the value of V ini is thus adapted as in the first modality so that
• 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 ⁇ V.
• the invention therefore relates to a display panel comprising:
• an array 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 series-connected, 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 clamping terminal, where:
• the clamping terminal is connected to the at least one reference electrode, - the control of said first selector switch and the control of said stall switch are connected to a same selection electrode of said first network.
• switches than the stall switch, including the selector switch itself, can be used to connect the voltage stall terminal to the control terminal.
• 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.
• 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.
• 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 circuit 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.
• each of said control circuits of a transmitter comprises a modulator current circuit 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.
• 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.
• said current modulator is a transistor comprising an amorphous silicon semiconductor layer.
• said emitters are electroluminescent diodes, preferably organic.
• said control circuit comprises a second selection switch connecting said control terminal to said addressing electrode without passing through said coupling capacitor.
• two circuit selection means are available:
• said active matrix then comprises a second selection electrode array for controlling said second selection switches.
• the invention also relates to a control method of 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 of at least one control circuit of said panel, wherein, during at least one period, said predetermined voltage V p ro g -d ata -V prog _ pol is applied to the control terminal of each circuit by transient capacitive coupling according to the following steps:
• a stalling step in which, said reference electrode of the panel being brought to a stalling potential, a selection signal is applied to the selection electrode which controls the first selection switch and the chocking switch of said control circuit, this signal being able to close said switches, and during the application of said selection signal, an initial voltage signal V ini is applied. E , V ini . P to the addressing electrode,
• 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.
• the predetermined voltage to be applied and maintained at the control terminal of the control circuits of said panel is intended: - that the emitter or the valve of the panel which is controlled by this circuit emits a pixel or sub-pixel of the image to be displayed, or / and that the transmitter or the valve of the panel, or the control circuit, or, if 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.
• 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.
• 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.
• C c and C s denote the capacitance values respectively of the coupling capacitors and the holding capacitors
• R4 denotes the electrical resistance of the selection switch when it is closed
• R 3 denotes the electrical resistance of the stall switch when it is closed
• the time interval T between said jump of tension to the addressing electrode and the end of said selection signal is such that there is: T 0 ⁇ T ⁇ 1, 1 T 0 .
• the said periods comprise emission periods and periods of depolarization; in addition, the predetermined voltage called depolarization V prog . pol to apply and maintain at the control terminal of a control circuit during a depolarization period is of opposite polarity to the predetermined transmission voltage V prog .
• 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 voltage depolarization V p ro g - p oi a ' a control terminal to each control circuit of said panel, one chooses said initial voltage signal V ini . P and said final voltage signal V pol so that they have the same polarity as said transmission signals.
• 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.
• a reference electrode for the control voltage of the circuits it may be in particular a base electrode for powering transmitters or valves.
• FIG. 3 is a timing diagram of the signals applied during a succession of periods and frames for controlling the circuit of FIG. 2 while driving the panel of FIG. 2 (logic signals V YA , V YB , addressing signals Vx 0 ); this timing diagram also illustrates the evolution of the control potential of the modulator V G of this circuit, and the intensity l 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.
• the active matrix of the panel according to this first embodiment comprises:
• 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.
• 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 C of the circuit control terminal is coupled to an address electrode X D via a select 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.
• 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 the selection switch T 4.
• the setting terminal R is connected to the 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.
• V cal , Vdd and Vss are respectively applied to the reference electrodes P R , supply P A and P B respectively.
• Further references for the control voltage of the circuit can be envisaged without departing from the invention
• the duration of each image frame is decomposed then in six steps.
• the duration of this step is sufficiently high to obtain the stabilization of the potentials, and in particular so that the potential of the gate G remains at the value V cal .
• Step 2 of programming the circuit during the transmission period The duration of this step is particularly critical for addressing the panel as described below.
• the selection switch T4 and the calibration switch T3 are simultaneously opened by applying to the selection electrode Y s an appropriate 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.
• 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 for maintaining the circuit during the emission period During the next transmission period of this diode 2 during this image frame, the selection switch T4 and the calibration 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 is
• 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 select switch is closed T4 and the clamping switch T3 by applying to the selection electrode Y S an appropriate 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 1n ⁇ p 4 whose value will be established later.
• Step 5 of programming the circuit during the depolarization period is also particularly critical for addressing the panel as described below.
• the voltage of the addressing electrode never changes sign and can advantageously use conventional and economical means for controlling the addressing electrodes.
• the modulator T2 begins to be depolarized in proportion to the value of V pnJg ⁇ 1 . ! .
• Step 6 of maintaining the circuit during the depolarization period During the subsequent depolarization period of this diode 2 during this image frame, the selection switch T4 and the calibration switch T3 are kept open; the control circuit 1 "is therefore no longer selected During this step, the capacitor C s keeps the voltage of the control terminal C at a constant value, and the modulator T2 therefore continues to be depolarized in proportion to the value from V p108- P 014 .
• 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.
• the duration T of the programming steps 2 and 4 is therefore particularly critical.
• C c and C s denote as previously the capacitance values respectively of the coupling capacitors and the holding capacitors
• R4 denotes the electrical resistance of the selection switch T4 when it is closed
• R3 denotes the electrical resistance of T3 when closed
• 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.
• C s 0.5 pF
• C c 3 pF
• T 0 1 ⁇ s.
• 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 ⁇ V prog .
• K (t) Kx (the ⁇ ).
• K C c / (C c + C s ), C c and C s here denoting the capacitance values respectively of the coupling capacitors and of the holding capacitors,
• ⁇ 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.
• the duration of this step be at least equal to 5 ⁇ ⁇ . .
• control voltage of modulator T2 undergoes a slight drop - ⁇ V prog . data . horn between step 2 and step 3, - ⁇ V 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 + ⁇ V prog . data . cor , + ⁇ V prog . pol . cor to the target value V prog . data-the "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 FIG. 2, the panel then comprises two selection electrode arrays Y SE and Y SP , the first network serving during the transmission periods, and the second network during the depolarization periods; each control circuit 1 '"is different 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 so as 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. 3. For the control of each control circuit 1 '"
• step 1 - steps 1, 2 of the transmission 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 respectively 2, 3, 4 and 5.
• 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 selecting switch is turned to the T1 transmission by applying to the selection electrode Y S an appropriate 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 M ⁇ X ⁇ -I 0 M 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.
• 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.
• the selection switch for the transmission therefore remains open.
• Step 4 programming the circuit during the depolarization period: see previous step 5.
• 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.

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