EP1771838B1 - Image display device and display device control method - Google Patents

Image display device and display device control method Download PDF

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Publication number
EP1771838B1
EP1771838B1 EP05793298A EP05793298A EP1771838B1 EP 1771838 B1 EP1771838 B1 EP 1771838B1 EP 05793298 A EP05793298 A EP 05793298A EP 05793298 A EP05793298 A EP 05793298A EP 1771838 B1 EP1771838 B1 EP 1771838B1
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EP
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Prior art keywords
emitters
modulator
data
voltage
emitter
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EP05793298A
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German (de)
French (fr)
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EP1771838A1 (en
Inventor
Philippe Le Roy
Dominique Gagnot
Hassane Guermoud
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THOMSON LICENSING
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Thomson Licensing SAS
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    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20Control 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
    • G09G3/22Control 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
    • G09G3/30Control 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
    • GPHYSICS
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    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20Control 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
    • G09G3/22Control 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
    • G09G3/30Control 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
    • G09G3/32Control 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]
    • G09G3/3208Control 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]
    • G09G3/3225Control 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
    • G09G3/3233Control 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
    • GPHYSICS
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    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20Control 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
    • GPHYSICS
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    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20Control 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
    • G09G3/22Control 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
    • G09G3/30Control 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
    • G09G3/32Control 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]
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20Control 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
    • G09G3/22Control 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
    • G09G3/30Control 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
    • G09G3/32Control 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]
    • G09G3/3208Control 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]
    • G09G3/3275Details of drivers for data electrodes
    • G09G3/3283Details of drivers for data electrodes in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20Control 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
    • G09G3/22Control 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
    • G09G3/30Control 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
    • G09G3/32Control 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]
    • G09G3/3208Control 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]
    • G09G3/3275Details of drivers for data electrodes
    • G09G3/3291Details of drivers for data electrodes in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00Electroluminescent light sources
    • H05B33/12Light sources with substantially two-dimensional radiating surfaces
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2300/00Aspects of the constitution of display devices
    • G09G2300/08Active 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
    • G09G2300/0809Several active elements per pixel in active matrix panels
    • G09G2300/0842Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00Control of display operating conditions
    • G09G2320/02Improving the quality of display appearance
    • G09G2320/0233Improving the luminance or brightness uniformity across the screen
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00Control of display operating conditions
    • G09G2320/02Improving the quality of display appearance
    • G09G2320/0285Improving the quality of display appearance using tables for spatial correction of display data
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00Control of display operating conditions
    • G09G2320/02Improving the quality of display appearance
    • G09G2320/029Improving the quality of display appearance by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
    • G09G2320/0295Improving the quality of display appearance by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel by monitoring each display pixel
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00Control of display operating conditions
    • G09G2320/04Maintaining the quality of display appearance
    • G09G2320/043Preventing or counteracting the effects of ageing
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00Control of display operating conditions
    • G09G2320/06Adjustment of display parameters
    • G09G2320/0693Calibration of display systems
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/02Details of power systems and of start or stop of display operation

Definitions

  • the present invention relates to a display device, a display control circuit and an image display method.
  • Image display devices are increasingly used in all kinds of applications such as in motor vehicles, digital cameras or mobile phones.
  • OLED Organic Light Emitting Diode
  • passive matrix OLED display devices are already widely commercialized. However, they consume a lot of electrical energy and have a reduced life.
  • Active Matrix OLED displays have built-in electronics, and have many benefits such as reduced power consumption, high resolution, compatibility with video rates, and longer life than OLED display devices passive matrix.
  • these display devices comprise an active matrix formed in particular by a network of light emitters.
  • Each light emitter is linked to a pixel or subpixel of an image to be displayed and is addressed by an array of column electrodes and line electrodes via an addressing circuit.
  • the addressing circuits include current modulators able to control the current flowing through the emitters and therefore the luminance of each pixel or sub-pixel of the display device.
  • these modulators are thin-film transistors, called Thin Film Transistors (TFTs), made of polycrystalline silicon using low-temperature poly-crystalline silicon (LTPS) technology from a silicon layer. amorphous.
  • TFTs Thin Film Transistors
  • LTPS low-temperature poly-crystalline silicon
  • this technology introduces local spatial variations of the trigger threshold voltage between these transistors. These variations are due to the fact that the seals and grain size of silicon are not sufficiently controllable during the step of crystallization of amorphous silicon (Si-a) in polycrystalline silicon (Poly-Si).
  • TFT transistors fed by the same supply voltage and controlled by identical voltages or display currents generate currents of different intensities.
  • the threshold threshold voltages of the thin film transistors may vary inhomogeneously over time.
  • the heterogeneity of the tripping thresholds of these transistors causes non-uniformity of the brightness of the display device comprising such transistors. This results in differences in luminance levels and obvious visual discomfort for the user.
  • the document EP-1 381 019 discloses a display device comprising a compensation circuit comprising an operational amplifier whose output is connected to the gate of a modulator and whose non-inverting input is successively connected to the anode of each emitter of the same column, without going through the modulator associated with said transmitter.
  • this device is extremely complicated. It requires in particular the control of a large number of switches.
  • the object of the present invention is the implementation of a simpler display device.
  • the present invention relates to an active matrix image display device characterized in that one of the non-inverting input and the inverting input of the operational amplifier is connected to said output supply means for forming, with the gate of the modulator connected to the output of the operational amplifier, a feedback loop of the operational amplifier, when one of said transmitters is selected.
  • the input of the operational amplifier is not connected to the common terminal of the emitter-modulator series of each pixel, but at one end of this series.
  • the invention therefore makes it possible to directly control the power supply current of the emitters in each power supply column of the emitters, at least during the addressing phase of these emitters.
  • An advantage of the invention is that this control is performed without measuring this current.
  • Each emitter is periodically addressed to each image to be displayed, or several times for each image, according to the display method used.
  • the device comprises one or more of the following characteristics.
  • One of said ends of each emitter-modulator series of said column which is connected to the output of said supply means, corresponds to the drain or source of said modulators.
  • the output of the operational amplifier 35 then delivers a control signal V c which is a function of the display signal V data 22 , V data 23 and the trigger threshold voltage V th of the modulator 26 connected to the selected transmitter 22. 23, 24.
  • the control signal V c is adapted to charge the capacitor 30.
  • One of the non-inverting input (+) and the inverting input (-) of the operational amplifier connected to the output of said supply means is adapted to receive a signal dependent on the value of the display signal intended to be addressed to a selected transmitter in said column.
  • said power supply means further comprise a control generator which is adapted to successively supply power and discontinue each of the emitters of a column by providing a control signal at one of said ends of a column. the transmitter-modulator series corresponding to said transmitter, said control signal depending on the value of the display signal intended to be addressed to a selected transmitter in said column.
  • the control generator thus supplies one transmitter at a time, and only during its addressing phase.
  • the supply means then generally further comprise a holding generator whose function is to feed the column transmitters out of their addressing phases.
  • This sustain generator is generally able to supply the emitters of all the columns, outside of their addressing phases.
  • Such a device requires switching means adapted to switch the power of the transmitters between the control generator and the sustain generator. In practice, therefore, there are generally two additional switches in each addressing circuit, one for connecting the transmitter-modulator series of this circuit to the addressing generator during the addressing phases, the other for connecting this series. transmitter-modulator to the sustain generator outside the addressing phases.
  • the output of the driving generator is connected to one of the non-inverting input (+) and the inverting input (-) of the operational amplifier. Only during the addressing of an emitter of this column, this same output is also connected, via a closed switch for addressing, to said end of the corresponding emitter-modulator series.
  • Said control generator comprises a display voltage generator and a resistive element connected in series, and the voltage generator is adapted to generate a voltage dependent on the value of the display signal intended to be addressed to a transmitter selected in said column.
  • This resistance may be an internal resistance to the voltage generator.
  • the value of the current flowing in this resistor and therefore in this emitter during its addressing phase is independent of the trigger threshold voltage of the modulator associated with this emitter.
  • the value of the current is then on the one hand proportional to the difference between said value of the display signal and the value of the voltage applied to the other one of the non-inverting input and the inverting input of the operational amplifier. on the other hand inversely proportional to the resistance value of the resistive element.
  • said power supply means comprise a control generator capable of supplying power, and this time continuously, all the emitters of a column by providing the same control signal to one said ends of each emitter-modulator series of a column, said control signal being a function of the sum of the values of the display signal previously addressed and being addressed to all the emitters of the column for a period of time. picture.
  • Said control generator comprises a display voltage generator and a resistive element connected in series, and the voltage generator is adapted to generate a voltage depending on the sum of the values of the display signal previously addressed and being addressed to all the emitters of the column for a duration of image.
  • This resistance may be an internal resistance to the voltage generator. Thanks to this series resistance, the value of the current flowing in this resistor and therefore in this emitter is independent of the tripping threshold voltage of the modulator associated with this emitter. The value of the current is then on the one hand proportional to the difference between said sum of the values of the display signal and the value of the voltage applied to the other one of the non-inverting input and the inverting input of the operational amplifier, on the other hand inversely proportional to the value of the resistance of the resistive element.
  • the addressing circuits of the transmitters are simplified with respect to the first variant, since it is no longer necessary to switch one end of the transmitter-modulator series alternately to two different generators as in the first variant.
  • the output of the driving generator is connected on the one hand to one of the non-inverting input (+) and the inverting input (-) of the operational amplifier, on the other hand, without intermediate switch, to said end of the corresponding emitter-modulator series.
  • Said control means also comprise a reference generator capable of delivering a reference signal to the other from the inverting input (-) and the non-inverting input (+) of the operational amplifier.
  • Each transmitter has particular electrical and / or optical properties and the value of each reference signal is a function of said electrical and / or optical properties.
  • Each transmitter is associated with the illumination of a color, and the reference signal is able to be modulated according to the color assigned to said selected transmitter.
  • a given white shade is classically identified by its trichromatic coordinates. Thanks to the invention, it is possible to easily optimize the chromatic performances of the device and to compensate for the differences in aging between the emitters.
  • the emitters are grouped into pluralities of adjacent emitters adapted to each emit a different color, and, for each plurality, said reference signals are allocated to the different emitters of this plurality so that the addressing of these emitters by the same display signal value generates the emission of said white tint by this plurality.
  • Said control means further comprise data storage means capable of storing the value of the display signal addressed to each transmitter during an image duration.
  • the method comprises the characteristic according to which the control signal is a function of the sum of the values of the display signals addressed to all the emitters of the column during an image duration.
  • the figure 1 represents an image display device according to the invention. This is constituted by an active matrix 1 controlled by control means 2.
  • the active matrix 1 comprises a plurality of addressing circuits 3, 4, 5, 6, each associated with a transmitter (not shown) and distributed along lines and columns.
  • the means 2 for controlling the active matrix comprise a control system 7, a selection control circuit 8 and an addressing control circuit 10.
  • the control system 7 is adapted to receive an image display signal, to process it (for example, to decode and decompress it) and to output a synchronization signal to the selection control circuit 8 and signal signals. display at the addressing control circuit 10.
  • the selection control circuit 8 is connected to a plurality of line electrodes 14, 15, each associated with a line of transmitters. Sure receiving the synchronization signal, the circuit 8 is adapted to generate a selection pulse V select successively at each line electrode 14, to select in turn all the addressing circuits 3, 6 of this line, at a frequency scan corresponding to an image duration.
  • the selection pulse V select is a logical data selection of the transmitters.
  • the addressing control circuit 10 is connected to a plurality of column electrodes 16, 17 and a plurality of driving electrodes 18, 19, each associated with a transmitter column 21A, 21B. It comprises a plurality of addressing control units 20A, 20B, each adapted to address and supply the addressing circuits 3, 4, 5, 6 of a column 21A, 21B via an electrode 16, 17 and a control electrode 18, 19.
  • the row electrodes 14, 15, 16, 17 of the column and control 18, 19 respectively allow to select, address and supply a specific addressing circuit among the set of circuits 3, 4, 5, 6 of the display device.
  • the figure 2 represents light emitters 22, 23, 24 each associated with an addressing circuit 3, 4, 5 of a set of pixels of a column of emitters 21A and the addressing control unit 20A specific to this column of transmitters 21A and the selection control circuit 8 of the addressing circuits 3, 4, 5, 6.
  • the emitters 22, 23, 24 of the display device are organic light emitting diodes. They include an anode and a cathode.
  • the structure of these diodes is "conventional", that is to say that the anodes are in a lower layer, the side of the substrate, and the cathodes in the upper layer.
  • Each transmitter is a pixel elementary. These elementary pixels are of the same nature (emission of identical color) in the case of a monochrome screen or are structured in the form of triplets red, green and blue in the case of a color screen.
  • all emitters 22, 23, 24 of a column are associated with sub-pixels of the same color.
  • the emitters of three adjacent columns are successively associated with the colors red, green and blue.
  • the bias voltages necessary for emitters 22, 23, 24 to be traversed by a current of the same value vary according to the current-voltage characteristics of these emitters, and in particular as a function of the color of the sub-pixels associated with the emitters 22, 23, 24 of each column.
  • This circuit 3 comprises a current modulator 26, a switch 28 formed of a transistor, a storage capacitor 29 and a feed electrode 30.
  • the current modulator 26 and the switch 28 are thin film transistors (Thin Film Transistor), based on a technology using polycrystalline silicon (Poly-Si), amorphous silicon (a-Si) or Microcrystalline silicon ( ⁇ c-Si) deposited in thin layers on a glass substrate.
  • Thin Film Transistor thin film transistors
  • Such components comprise three electrodes: a drain electrode and a source electrode between which flows a modulated current called drain current, and a gate electrode to which the control voltage V c is applied.
  • the source of the modulator 26 is connected to the anode of the emitter 22, so as to connect in series the modulator 26 and the emitter 22.
  • One 31 of the ends of this series, namely here the drain of the modulator 26 is connected to the control electrode 18.
  • the gate of the modulator 26 is connected on the one hand, to a first terminal of the capacitor 29 and on the other hand, to a current passage electrode (drain or source) of the switch 28, via an electrical line 33.
  • the other current-carrying electrode (drain or source) of the switch 28 is connected to the column electrode 16.
  • the gate of the switch 28 is connected to the line electrode 14.
  • the second terminal of each capacitor 29 of the set of circuits 3, 4, 5 of the column 21A is connected to the supply electrode 30.
  • the other end 32 of each series modulator-emitter namely here the cathode of the emitter 22 is connected to a supply electrode 34.
  • the two feed electrodes 30 and 34 can be interconnected at the same potential by a driver not shown.
  • the modulator 26, represented on the figure 2 is of type n, so that, in operation, its drain current flows between its drain and its source. Note that such a device can also be used to drive p-type TFTs, always with conventional structure diodes, as illustrated in FIG. figure 10 .
  • the capacitor 29, arranged between the gate and the source of the modulator 26, is adapted to substantially maintain a constant control voltage at the gate of the modulator 26 during a time interval corresponding to the duration of an image T1, T2 in order to maintain the brightness of the transmitter during this time.
  • the supply electrode 30 is able to provide the voltage necessary to bias the desired potential to one of the terminals of the capacitor 29, as known in the state of the art.
  • the control unit 20A is adapted to compensate, with the feedback loop described hereinafter, the trigger threshold voltage V th of each modulator 26 of the set of addressing circuits 3, 4, 5 of FIG. 21A column and to supply the transmitters 22, 23, 24 of the 21A transmitters column.
  • an operational amplifier 35 having an inverting input -, a non-inverting input + and an output.
  • the output of this amplifier 35 is connected to the column electrode 16 and its non-inverting input + is connected to the control electrode 18 supplying the transmitters of the column via their associated modulator.
  • this non-inverting input + is simultaneously connected to the anode of each emitter 22, 23, 24 of the column 21A via the modulator 26 associated therewith.
  • a feedback loop of the amplifier 35 is formed by the driving electrode 18, the end 31 of the modulator-emitter series, the modulator 26, the line 33 and the column electrode 16. each time a switch 28 of an addressing circuit 3, 4, 5 of the transmitter column 21A is closed. Note that the end 31 of the modulator-transmitter series which is part of the feedback loop corresponds, in the embodiments presented on figures 2 and 10 , to one of the drain or source of the modulator of this series.
  • the amplifier 35 is able to operate in feedback and thus compensate for the trigger threshold voltage V th of each modulator 26 of the addressing circuits 3, 4, 5 of the transmitter column 21A, as will be explained. in the following description.
  • control unit 20A is suitable for addressing and supplying the emitters 22, 23, 24 of the column 21A with the driving current I.
  • This current I depends on the sum of the values of the display voltages V data 22 , V data 23, V data 24 addressed to transmitters 22, 23, 24 of this column 21A.
  • control current generator 36 for this purpose, it comprises a control current generator 36 and a reference voltage generator 38, respectively connected to the non-inverting input + and the inverting input - of the amplifier 35.
  • the current generator 36 is formed by a variable voltage generator 39 connected in series with a resistor 40.
  • the control electrode 18 is connected to the output of the resistor 40, at the node 42, which thus forms one of the outputs of the current generator 36.
  • the generator 39 is a variable voltage generator whose voltage varies as a function of the values of the display signal V data 22 , V data 23 intended to be addressed to the transmitters 22, 23, as will be explained in the following description.
  • the generator 38 is a generator adapted to deliver a reference voltage which is fixed during the settings of the display device and which is specific to each column.
  • a variable voltage generator it is also possible to use a variable voltage generator; the variation of the reference voltage as a function of the column of transmitters 21A addressed will be explained in the following description.
  • the output of the generator 38 is connected to the inverting input - of the amplifier 35, via, optionally, a resistor 44.
  • This resistor 44 is not absolutely necessary for the operation of the control unit 20A. It only has an advantageous function of balancing between the two inputs of the operational amplifier 35.
  • a capacitor 46 is connected between the inverting input - of the amplifier 35 and the output of this amplifier.
  • the Resistor 44 and capacitor 46 constitute a compensation network which advantageously increases the accuracy and stability of the circuit.
  • the control unit 20A also comprises data storage means 48 and a control module 50 of the generators 38 and 39.
  • the storage means 48 comprise a database 52 adapted to store on the one hand the value of the display signal V data 22 , V data 23 addressed to each transmitter 22, 23 of the column 21A during the previous period of time. T1 image and, secondly, an identification or location data of the transmitter 22, 23 to which this value has been addressed.
  • These storage means 48 also comprise a directory 54 adapted to store a reference voltage value to be associated with all the transmitters of the column 21A. This value is a function of the red, green or blue color associated with the emitters 22, 23 of the column 21A.
  • Emitters associated with different colors have different current-voltage characteristics, as can be seen on the figure 12 . Consequently, it is necessary to apply different voltages across a red emitter and across a blue emitter to obtain the same luminance and the same value of the current flowing through these emitters.
  • the reference voltage values of the directories 54 of each column are set here according to the color of the emitters of a column 21A. This operation is performed at the factory, during the settings of the display device that are performed prior to its commissioning. These reference values are set to compensate for the variations between the electrical current-voltage characteristics and / or the luminous characteristics of the different emitters of the device, as will be described later.
  • these characteristics depend mainly on the emission color of the emitters, there will be three different reference voltage values, a first value V ref.R common to all the red emitters of a first column, a second value V ref.G common to all the green emitters of a second column and a third value V ref.B common to all the blue emitters of a third column.
  • these reference voltage values are specific to each column of emitters, so as to compensate for variations in current-voltage electrical characteristics and / or light characteristics between the emitters of different columns, even when they are of the same emission color.
  • a current can flow in a transmitter only if the V data display signal addressed to it is greater than the reference voltage V ref associated therewith.
  • reference voltage values as low as possible will be preferably set while adjusting the display device while achieving the desired compensations.
  • the control module 50 is connected to the storage means 48 for searching and recording information therein.
  • the module 50 is adapted to receive the display signal transmitted by the system 7 and to control the generators 38 and 39 as a function of this signal and the information stored in the storage means 48.
  • circuits 8 and 10 are adapted to address, supply and successively select all the emitters 22, 23, 24 of the matrix 1.
  • step 60 the control unit 20A and the circuit 8 control the lighting of the first transmitter 22 of the column 21A.
  • This step 60 includes steps 62 to 69.
  • step 62 the circuit 8 generates a selection select pulse V 22 at the line electrode 14. This pulse, shown in FIG. figure 4 , is suitable for closing the switch 28.
  • the module 50 interrogates the directory 54 to know the reference voltage associated with the column of the transmitter 22.
  • This reference voltage is in particular a function of the color of the sub-pixels associated with the transmitters 22 , 23, 24 of this column.
  • the module 50 controls the generator 38 so that it delivers the reference voltage V ref 21A for the transmitters of the column 21A whose value is constant and equal V ref a .
  • the module 50 receives from the control system 7 the value V a of the display voltage V data 22 to be addressed to the transmitter 22 as well as the identification or the position of the addressed transmitter 22 associated with this value. Then, the module 50 stores in the database 52 this value V a and the identification of the issuer to which this value is addressed.
  • the module 50 controls the generator 39 so that it generates the value V a of the display voltage V data 22 to be addressed to the transmitter 22, as represented on FIG. the figure 6 .
  • the generator 38 supplies a reference voltage V ref 21A equal to V ref a , to the inverting input - of the amplifier 35.
  • the generator 39 applies a voltage V data to the resistor 40. equal to V a , represented on the figure 6 .
  • the optional resistor 44 does not intervene in the calculation of the current, because no significant current, at least compared to the value of the driving current of I 22 , circulates in this resistance.
  • the potential difference between the inverting input - and the noninverting input + of the amplifier 35 is canceled.
  • the voltage at the node 42 is then equal to V ref a .
  • a compensation of the triggering threshold voltage of the transmitter 22 of the device is obtained directly, without going through a measurement of the current crossing this transmitter.
  • control voltage V c is a function not only of the display signal of the V data transmitter 22 and of the reference voltage V ref associated with this transmitter, but also of the trigger threshold voltage V th of the modulator 26.
  • the control voltage V c applied to the gate of the modulator 26 is adapted and modulated by the amplifier 35 to compensate for the trigger threshold voltage V th of this modulator.
  • control voltage V c at the output of the amplifier 35 is adjusted exactly to the voltage required to address the transmitter 22 with the value V a of the display voltage V data 22 and that whatever the value of the trigger threshold voltage V th of the modulator 26 and this even if it varies over time.
  • This control voltage V c is then maintained at the gate of the modulator 26 by the capacitor 29 for the rest of the image duration, whereas the switch 28 of the circuit 3 is reopened, as is known in the art. state of the art.
  • Step 70 the second emitter 23 of the column 21A is illuminated.
  • Step 70 includes steps 72 to 79.
  • step 72 the circuit 8 outputs a select select pulse 23 , as shown in FIG. figure 5 , at the line electrode 15.
  • the module 50 determines the reference voltage V ref 21A associated with the column of the transmitter 23, by interrogating the storage means 48. As the transmitter 23 is in the same column as the emitter 22 and therefore these emitters are associated with the same color, the value V ref of this reference voltage V ref 21A is identical to the value V ref a of the reference voltage V ref 22 generated during addressing the first transmitter 22.
  • the module 50 controls the reference generator 38, so that it generates the voltage V ref a determined during the step 74.
  • the module 50 receives from the system 7 and records in the database 52, the value V b of the display voltage V data 23 to be sent to the transmitter 23 and represented on the figure 6 as well as the identification or the position of the addressed transmitter 23 associated with this value.
  • the module 50 adds the value V a of the display voltage V data 22 previously sent to the transmitter 22 of the same column at the value V b of the display voltage V data 23 intended to be addressed to the next transmitter 23.
  • the module 50 controls the generator 39 so that it delivers a display voltage equal to the voltage value calculated during the step 78, namely V a + V b .
  • the current I 22 (V data22 - V ref a ) / R necessary for the illumination of the transmitter 22, continues to feed the modulator 26.
  • the same control voltage V c is maintained at the gate of the modulator 26 of the first circuit 3, by the capacitor 29, and not by the amplifier 35 since the switch 28 of the circuit 3 is now open.
  • This voltage Vc controls the intensity of the current supplying the transmitter 22 so that this intensity is equal to the intensity programmed in step 60.
  • the switch 28 of the circuit 4 has been closed in the step 72, the column electrode 16, the amplifier 35, the control electrode 18, the end 31 of the modulator-emitter series, the modulator 26 of the second circuit 4 and the line 33 of the second circuit 4 form a new loop of Again, the control voltage V c coming out of the amplifier 35 compensates, as before, the trigger threshold voltage V th of the modulator 26 of the second circuit 4.
  • step 80 comprises the steps 82 to 89.
  • the module 50 then controls the generator 39 so that it delivers a display voltage equal to the new calculated value of the sum ⁇ not V data . not .
  • a second addressing of the circuit 4 is performed in the same way. After an image duration T2, all the emitters 22, 23, 24 of the column 21A are illuminated as a function of display voltages representative of the new image data to be displayed by these emitters.
  • a value of the reference voltage V ref 22 equal to V ref a has been applied to the inverting input - of the amplifier 35 and a value of the display voltage V data 22 equal to V a has been addressed to the transmitter 22 during the image duration T1. This value of the voltage V a continues to be addressed during the new image duration T2.
  • the value of the display voltage addressed to the transmitter 23 is equal to V b during the first and previous image duration T3 ( figure 6 ), then is zero during the next frame duration T4.
  • this device and this display method make it possible to avoid an initialization phase prior to the programming of the addressing circuits 3, 4, 5.
  • the use of a reference voltage applied to one of the inputs of the amplifier 35 and specific to each column of transmitters, or groups of columns, as here groups of different colors advantageously allows to reduce the consumption of the display device. Indeed, if one chooses the values of the reference voltages not only so as to compensate variations variations of the electrical and / or luminous characteristics of the transmitters of different columns but also so as to obtain a mean value of reference voltage the as low as possible for each column, it is possible to shift the V data values of the display signals by a similar amount and decrease, which reduces the electrical power to be generated by the power generator 39.
  • figure 2 of an OLED display device with a conventional structure it is the anode of the emitters 22, 23 which forms the interface with the active matrix 1 ("conventional" structure diodes): the drain (n-type case) or the source (p-type case) modulators 26, is then connected to the control electrode 18, and the cathode of the emitters 22, 23 is connected to the electrode 34.
  • the control electrode 18 is then connected to the node 42 where join one of the outputs of the power supply means 36 and the non-inverting input + of the amplifier 35.
  • the present invention also applies to display devices with a so-called inverted structure, in which the cathode of the emitters forms the interface with the active matrix: the drain (p type case) or the source (n type case) of the modulators 26 is then connected to the control electrode 18, and the anode of the emitters 22, 23 is connected to the electrode 34.
  • the control electrode 18 is connected to the node 42 where one of the outputs of the supply means 36 and, this time, the inverting input - of the amplifier 35.
  • This circuit being much more stable than that described for conventional structure diodes, advantageously, no resistor 44 nor any capacitor 46 balancing and / or compensation are no longer necessary.
  • the display signals then correspond to negative voltages and the currents of the diodes are "pulled" from the supply electrodes 34.
  • the generator 38 is able to modify the reference voltage as a function of the aging of the emitters or to lower it in a low consumption mode.
  • a reference voltage is associated with each column of transmitters.
  • the storage means 48 comprise a database suitable for storing the values of the reference voltages to be applied to each column of transmitters.
  • the control unit 50 is able to search in this database for the value the reference voltage to be applied to the inverting input - of the amplifier 35 depending on the identification or position of the column of this transmitter.
  • the difference (V ref x - V ref y ) is preferably established so as to compensate for the differences in electrical and / or luminous characteristics of the different columns of the device. transmitters.
  • Part of a display device according to a third embodiment of the invention is illustrated on the figure 13 .
  • This display device comprises addressing circuits 103 connected, on the one hand, to addressing control units 20A by means of electrodes of FIG. column 16 and control electrodes 18 and, secondly, to a selection circuit 8 by line electrodes 14.
  • the circuit 103 is suitable for addressing and supplying a transmitter 22 whose cathode is connected to a supply electrode 34.
  • It comprises a current modulator 26, three switches 28, 106, 108 formed of a transistor, a storage capacitor 29 and a ground electrode 110.
  • the drain of the modulator 26 is connected to the anode of the emitter 22, so as to connect in series the modulator 26 and the emitter 22.
  • the gate of the modulator 26 is connected, on the one hand, to a first terminal of the capacitor 29 and, secondly, a current passage electrode (drain or source) of the switch 28, via an electrical line 33.
  • the other current passage electrode (drain or source) of the switch 28 is connected to the column electrode 16.
  • the gate of the switch 28 is connected to the line electrode 14.
  • the second terminal of the capacitor 29 is connected to the ground electrode 110.
  • the source of the modulator 26 is connected, on the one hand, to the drain of the switch 108 and, on the other hand, to a current flow electrode (drain or source) of the switch 106.
  • the source of the switch 108 is connected to the 110.
  • the gate of the switch 108 is connected to the line electrode 14.
  • the other electrode e current passage (drain or source) of the switch 106 is connected to the control electrode 18.
  • the gate of the switch 106 is connected to the line electrode 14.
  • the control unit 20A has been partially represented. It has the same components as the control unit shown on the figure 2 and works the same way.
  • the control electrode 18 is connected to the inverting input of the operational amplifier 35 and the resistor 40.
  • the column electrode 16 is connected to the output of the operational amplifier 35.
  • the control unit 20A is adapted to successively supply power and discontinue each of the emitters 22 of the addressing circuits 103 of a column 21A by supplying a current I 21 to one of the ends of the series of emitters 22. - modulators 26.
  • the non-inverting input of the operational amplifier 35 is adapted to receive a reference voltage for the emitters 22 of the column 21A and whose value is a function of the color of the sub-pixels associated with the emitters 22 of this column.
  • the display voltage V data to be addressed to the transmitter 22 is applied to the resistor 40. This voltage generates a control current which is applied to the current-pass electrode of the switch 106.
  • the line electrode 14 is set to a logic state O, so that the switches 28 and 106 are closed and the switch 108 is open.
  • the tripping threshold voltage of the gate of the modulator 26 is compensated by the amplifier 35 operating in feedback and this independently of the characteristics of the modulator 26.
  • the voltage at the gate of the modulator 26 is stored in the capacitor 29.
  • the line electrode 14 goes to a logic state 1 and, consequently, the switches 28 and 106 are open and the switch 108 is closed.
  • the voltages at the drain, source and gate electrodes of the modulator 26 have not varied during the transition from the refresh phase to the storage phase, so that the same current flows through the emitter 22 during the transition from the refresh phase to the storage phase.
  • this device makes it possible to finely control the current flowing through the emitter 22, which generates a precise grid scale, uniform brightness and low noise even on high resolution screens.
  • the programming time of this display device is reduced compared to display devices without feedback.
  • this display device allows significant dispersions on the characteristics and in particular on the trigger threshold voltage of the modulator 26.

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Description

La présente invention concerne un dispositif d'affichage, un circuit de commande d'affichage et un procédé d'affichage d'images.The present invention relates to a display device, a display control circuit and an image display method.

En particulier, la présente invention concerne un dispositif d'affichage d'images à matrice active, comprenant :

  • plusieurs émetteurs de lumière formant un réseau d'émetteurs répartis en lignes et en colonnes, chaque émetteur étant propre à être adressé périodiquement par une valeur d'un signal d'affichage représentative d'une donnée d'affichage d'une durée d'image ;
  • un modulateur de courant raccordé en série à chaque émetteur de lumière du réseau pour former des séries émetteurs-modulateurs, ledit modulateur comportant une source, un drain, une grille, ledit modulateur étant apte à être traversé par un courant de drain pour alimenter ledit émetteur, pour une tension entre l'un parmi le drain et la source, et la grille supérieure ou égale à une tension de seuil de déclenchement de ce modulateur ;
  • un condensateur de stockage de charges électriques propre à maintenir une tension de commande à la grille de chaque modulateur pendant ladite durée d'image ;
  • des moyens de sélection aptes à sélectionner les émetteurs d'une même ligne ; et
  • des moyens de pilotage de l'illumination des émetteurs comprenant, pour chaque colonne, des moyens d'alimentation de ces émetteurs comprenant une sortie connectée à l'une des extrémités de chaque série émetteur-modulateur de ladite colonne, et au moins un amplificateur opérationnel de commande des modulateurs correspondants ayant une entrée inverseuse (-), une entrée non-inverseuse (+) et une sortie, ladite sortie de l'amplificateur étant apte à être connectée à la grille de chaque modulateur de cette colonne lorsqu'un émetteur raccordé à ce modulateur est sélectionné, pour appliquer à ladite grille, ladite tension de commande.
In particular, the present invention relates to an active matrix image display device comprising:
  • a plurality of light emitters forming a network of transmitters distributed in rows and columns, each emitter being adapted to be periodically addressed by a value of a display signal representative of a display datum of an image duration ;
  • a current modulator connected in series to each light emitter of the network to form emitter-modulator series, said modulator comprising a source, a drain, a gate, said modulator being able to be traversed by a drain current for supplying said transmitter for a voltage between one of the drain and the source, and the gate greater than or equal to a trigger threshold voltage of that modulator;
  • an electrical charge storage capacitor adapted to maintain a control voltage at the gate of each modulator during said image duration;
  • selection means adapted to select the transmitters of the same line; and
  • means for controlling the illumination of the emitters comprising, for each column, means for supplying these emitters comprising an output connected to one of the ends of each emitter-modulator series of said column, and at least one operational amplifier for controlling corresponding modulators having an inverting input (-), a non-inverting input (+) and an output, said output of the amplifier being able to be connected to the gate of each modulator of this column when a connected emitter to this modulator is selected, to apply to said gate, said control voltage.

Les dispositifs d'affichage d'images sont de plus en plus utilisés dans toutes sortes d'applications telles que dans des véhicules automobiles, des appareils photos numériques ou des téléphones portables.Image display devices are increasingly used in all kinds of applications such as in motor vehicles, digital cameras or mobile phones.

Il est connu des dispositifs d'affichage dans lesquels les émetteurs de lumière sont formés à partir de cellules organiques électroluminescentes tels que les dispositifs d'affichage de type OLED (Organic Light Emitting Diode).There are known display devices in which the light emitters are formed from electroluminescent organic cells such as OLED (Organic Light Emitting Diode) type display devices.

En particulier, les dispositifs d'affichage OLED à matrice passive sont déjà largement commercialisés. Cependant, ils consomment beaucoup d'énergie électrique et ont une durée de vie réduite.In particular, passive matrix OLED display devices are already widely commercialized. However, they consume a lot of electrical energy and have a reduced life.

Les dispositifs d'affichage OLED à matrice active comportent une électronique intégrée, et présentent de nombreux avantages tels qu'une consommation réduite, une haute résolution, une compatibilité avec les cadences vidéos et une durée de vie plus longue que les dispositifs d'affichage OLED à matrice passive.Active Matrix OLED displays have built-in electronics, and have many benefits such as reduced power consumption, high resolution, compatibility with video rates, and longer life than OLED display devices passive matrix.

Classiquement, ces dispositifs d'affichage comprennent une matrice active formée notamment par un réseau d'émetteurs de lumière. Chaque émetteur de lumière est lié à un pixel ou à un sous pixel d'une image à visualiser et est adressé par un réseau d'électrodes de colonne et d'électrodes de ligne, via un circuit d'adressage.Conventionally, these display devices comprise an active matrix formed in particular by a network of light emitters. Each light emitter is linked to a pixel or subpixel of an image to be displayed and is addressed by an array of column electrodes and line electrodes via an addressing circuit.

Les circuits d'adressage comprennent notamment des modulateurs de courant aptes à piloter le courant traversant les émetteurs et donc la luminance de chaque pixel ou sous pixel du dispositif d'affichage.The addressing circuits include current modulators able to control the current flowing through the emitters and therefore the luminance of each pixel or sub-pixel of the display device.

Dans une matrice active, ces modulateurs sont des transistors à couches minces, appelés transistors TFT (Thin Film Transistor), fabriqués en Silicium poly-cristallin selon la technologie du Silicium poly-cristallin basse température (LTPS) à partir d'une couche de silicium amorphe. Cependant, cette technologie introduit des variations spatiales locales de la tension de seuil de déclenchement entre ces transistors. Ces variations sont dues au fait que les joints et les dimensions des grains du Silicium ne sont pas suffisamment maîtrisables pendant l'étape de cristallisation du Silicium amorphe (Si-a) en Silicium poly-cristallin (Poly-Si).In an active matrix, these modulators are thin-film transistors, called Thin Film Transistors (TFTs), made of polycrystalline silicon using low-temperature poly-crystalline silicon (LTPS) technology from a silicon layer. amorphous. However, this technology introduces local spatial variations of the trigger threshold voltage between these transistors. These variations are due to the fact that the seals and grain size of silicon are not sufficiently controllable during the step of crystallization of amorphous silicon (Si-a) in polycrystalline silicon (Poly-Si).

En conséquence, les transistors TFT alimentés par la même tension d'alimentation et commandés par des tensions ou des courants d'affichage identiques génèrent des courants d'intensités différentes. De plus, les tensions de seuil de déclenchement des transistors à couches minces sont susceptibles de varier de façon inhomogène au cours du temps.As a result, TFT transistors fed by the same supply voltage and controlled by identical voltages or display currents generate currents of different intensities. In addition, the threshold threshold voltages of the thin film transistors may vary inhomogeneously over time.

Or, comme un émetteur émet une intensité lumineuse directement proportionnelle au courant qui le traverse, l'hétérogénéité des seuils de déclenchement de ces transistors entraîne une non uniformité de la brillance du dispositif d'affichage comprenant de tels transistors. Il en résulte des différences entre les niveaux de luminance et un inconfort visuel manifeste pour l'utilisateur.However, as a transmitter emits a light intensity directly proportional to the current flowing through it, the heterogeneity of the tripping thresholds of these transistors causes non-uniformity of the brightness of the display device comprising such transistors. This results in differences in luminance levels and obvious visual discomfort for the user.

Afin de limiter cet inconfort, divers circuits de compensation de la tension de seuil de déclenchement, ont été proposés.In order to limit this discomfort, various compensation circuits for the triggering threshold voltage have been proposed.

Par exemple, le document EP-1 381 019 décrit un dispositif d'affichage comportant un circuit de compensation comprenant un amplificateur opérationnel dont la sortie est raccordée à la grille d'un modulateur et dont l'entrée non inverseuse est raccordée successivement à l'anode de chaque émetteur d'une même colonne, sans passer par le modulateur associé audit émetteur.For example, the document EP-1 381 019 discloses a display device comprising a compensation circuit comprising an operational amplifier whose output is connected to the gate of a modulator and whose non-inverting input is successively connected to the anode of each emitter of the same column, without going through the modulator associated with said transmitter.

Toutefois, ce dispositif est extrêmement compliqué. Il nécessite notamment la commande d'un grand nombre d'interrupteurs.However, this device is extremely complicated. It requires in particular the control of a large number of switches.

Le but de la présente invention est la mise en oeuvre d'un dispositif d'affichage plus simple.The object of the present invention is the implementation of a simpler display device.

A cet effet, la présente invention a pour objet un dispositif d'affichage d'images à matrice active caractérisé en ce que l'une parmi l'entrée non-inverseuse et l'entrée inverseuse de l'amplificateur opérationnel est connectée à ladite sortie des moyens d'alimentation pour former, avec la grille du modulateur raccordée à la sortie de l'amplificateur opérationnel, une boucle de contre-réaction de l'amplificateur opérationnel, lorsqu'un desdits émetteurs est sélectionné.For this purpose, the present invention relates to an active matrix image display device characterized in that one of the non-inverting input and the inverting input of the operational amplifier is connected to said output supply means for forming, with the gate of the modulator connected to the output of the operational amplifier, a feedback loop of the operational amplifier, when one of said transmitters is selected.

Ainsi, contrairement aux circuits de pixel décrits dans le document EP-1 381 019 déjà cité, l'entrée de l'amplificateur opérationnel n'est pas reliée à la borne commune de la série émetteur-modulateur de chaque pixel, mais à l'une des extrémités de cette série.So unlike the pixel circuits described in the document EP-1 381 019 already mentioned, the input of the operational amplifier is not connected to the common terminal of the emitter-modulator series of each pixel, but at one end of this series.

L'invention permet donc de contrôler directement le courant d'alimentation des émetteurs dans chaque colonne d'alimentation des émetteurs, au moins pendant la phase d'adressage de ces émetteurs. Un avantage de l'invention est que ce contrôle est effectué sans mesure de ce courant.The invention therefore makes it possible to directly control the power supply current of the emitters in each power supply column of the emitters, at least during the addressing phase of these emitters. An advantage of the invention is that this control is performed without measuring this current.

Chaque émetteur est adressé périodiquement, à chaque image à afficher, ou plusieurs fois pour chaque image, selon le procédé d'affichage utilisé.Each emitter is periodically addressed to each image to be displayed, or several times for each image, according to the display method used.

Suivant des modes particuliers de réalisation, le dispositif comporte une ou plusieurs des caractéristiques suivantes.According to particular embodiments, the device comprises one or more of the following characteristics.

Une desdites extrémités de chaque série émetteur-modulateur de ladite colonne, qui est connectée à la sortie desdits moyens d'alimentation, correspond au drain ou à la source desdits modulateurs.One of said ends of each emitter-modulator series of said column, which is connected to the output of said supply means, corresponds to the drain or source of said modulators.

La sortie de l'amplificateur opérationnel 35 délivre alors un signal de commande Vc fonction du signal d'affichage Vdata 22, Vdata 23 et de la tension de seuil de déclenchement Vth du modulateur 26 raccordé à l'émetteur sélectionné 22, 23, 24. Le signal de commande Vc est propre à charger le condensateur 30.The output of the operational amplifier 35 then delivers a control signal V c which is a function of the display signal V data 22 , V data 23 and the trigger threshold voltage V th of the modulator 26 connected to the selected transmitter 22. 23, 24. The control signal V c is adapted to charge the capacitor 30.

L'une parmi l'entrée non-inverseuse (+) et l'entrée inverseuse (-) de l'amplificateur opérationnel connectée à la sortie desdits moyens d'alimentation est propre à recevoir un signal dépendant de la valeur du signal d'affichage destinée à être adressée à un émetteur sélectionné dans ladite colonne.One of the non-inverting input (+) and the inverting input (-) of the operational amplifier connected to the output of said supply means is adapted to receive a signal dependent on the value of the display signal intended to be addressed to a selected transmitter in said column.

Selon une première variante, lesdits moyens d'alimentation comprennent en outre un générateur de pilotage qui est adapté pour alimenter en puissance et en discontinu successivement chacun des émetteurs d'une colonne par fourniture d'un signal de pilotage à l'une desdites extrémités de la série émetteur-modulateur correspondant audit émetteur, ledit signal de pilotage dépendant de la valeur du signal d'affichage destinée à être adressée à un émetteur sélectionné dans ladite colonne.According to a first variant, said power supply means further comprise a control generator which is adapted to successively supply power and discontinue each of the emitters of a column by providing a control signal at one of said ends of a column. the transmitter-modulator series corresponding to said transmitter, said control signal depending on the value of the display signal intended to be addressed to a selected transmitter in said column.

Le générateur de pilotage alimente donc un émetteur à la fois, et uniquement pendant sa phase d'adressage.The control generator thus supplies one transmitter at a time, and only during its addressing phase.

Les moyens d'alimentation comprennent alors généralement en outre un générateur de maintien qui a pour fonction d'alimenter les émetteurs de la colonne en dehors de leurs phases d'adressage. Ce générateur de maintien est généralement apte à alimenter les émetteurs de toutes les colonnes, en dehors de leurs phases d'adressage. Un tel dispositif nécessite des moyens de commutation adaptés pour faire basculer l'alimentation des émetteurs entre le générateur de pilotage et le générateur de maintien. En pratique, on trouve donc en général deux interrupteurs supplémentaires dans chaque circuit d'adressage, l'un pour connecter la série émetteur-modulateur de ce circuit au générateur d'adressage pendant les phases d'adressage, l'autre pour connecter cette série émetteur-modulateur au générateur de maintien en dehors des phases d'adressage.The supply means then generally further comprise a holding generator whose function is to feed the column transmitters out of their addressing phases. This sustain generator is generally able to supply the emitters of all the columns, outside of their addressing phases. Such a device requires switching means adapted to switch the power of the transmitters between the control generator and the sustain generator. In practice, therefore, there are generally two additional switches in each addressing circuit, one for connecting the transmitter-modulator series of this circuit to the addressing generator during the addressing phases, the other for connecting this series. transmitter-modulator to the sustain generator outside the addressing phases.

Comme mentionné précédemment, la sortie du générateur de pilotage est connectée à l'une parmi l'entrée non-inverseuse (+) et l'entrée inverseuse (-) de l'amplificateur opérationnel. Uniquement pendant l'adressage d'un émetteur de cette colonne, cette même sortie est également connectée, via un interrupteur fermé pour l'adressage, à ladite extrémité de la série correspondante émetteur-modulateur.As mentioned previously, the output of the driving generator is connected to one of the non-inverting input (+) and the inverting input (-) of the operational amplifier. Only during the addressing of an emitter of this column, this same output is also connected, via a closed switch for addressing, to said end of the corresponding emitter-modulator series.

Ledit générateur de pilotage comprend un générateur de tension d'affichage et un élément résistif raccordés en série, et le générateur de tension est adapté pour générer une tension dépendant de la valeur du signal d'affichage destinée à être adressée à un émetteur sélectionné dans ladite colonne.Said control generator comprises a display voltage generator and a resistive element connected in series, and the voltage generator is adapted to generate a voltage dependent on the value of the display signal intended to be addressed to a transmitter selected in said column.

Cette résistance peut être une résistance interne au générateur de tension.This resistance may be an internal resistance to the voltage generator.

Grâce à cette résistance en série, la valeur du courant qui circule dans cette résistance et donc dans cet émetteur pendant sa phase d'adressage est indépendante de la tension de seuil de déclenchement du modulateur associé à cet émetteur. La valeur du courant est alors d'une part proportionnelle à la différence entre ladite valeur du signal d'affichage et la valeur de la tension appliquée à l'autre parmi l'entrée non-inverseuse et l'entrée inverseuse de l'amplificateur opérationnel, d'autre part inversement proportionnelle à la valeur de la résistance de l'élément résistif.Due to this series resistance, the value of the current flowing in this resistor and therefore in this emitter during its addressing phase is independent of the trigger threshold voltage of the modulator associated with this emitter. The value of the current is then on the one hand proportional to the difference between said value of the display signal and the value of the voltage applied to the other one of the non-inverting input and the inverting input of the operational amplifier. on the other hand inversely proportional to the resistance value of the resistive element.

Selon une deuxième variante préférentielle, lesdits moyens d'alimentation comprennent un générateur de pilotage apte à alimenter en puissance et, cette fois, en continu l'ensemble des émetteurs d'une colonne par fourniture d'un même signal de pilotage à l'une desdites extrémités de chaque série émetteur-modulateur d'une colonne ledit signal de pilotage étant fonction de la somme des valeurs du signal d'affichage préalablement adressées et en cours d'adressage à l'ensemble des émetteurs de la colonne pendant une durée d'image.According to a second preferred variant, said power supply means comprise a control generator capable of supplying power, and this time continuously, all the emitters of a column by providing the same control signal to one said ends of each emitter-modulator series of a column, said control signal being a function of the sum of the values of the display signal previously addressed and being addressed to all the emitters of the column for a period of time. picture.

Avantageusement, il n'y a donc pas besoin de générateur supplémentaire de maintien, comme dans la première variante.Advantageously, there is therefore no need for additional maintenance generator, as in the first variant.

Ledit générateur de pilotage comprend un générateur de tension d'affichage et un élément résistif raccordés en série, et le générateur de tension est adapté pour générer une tension dépendant de la somme des valeurs du signal d'affichage préalablement adressées et en cours d'adressage à l'ensemble des émetteurs de la colonne pendant une durée d'image.Said control generator comprises a display voltage generator and a resistive element connected in series, and the voltage generator is adapted to generate a voltage depending on the sum of the values of the display signal previously addressed and being addressed to all the emitters of the column for a duration of image.

Cette résistance peut être une résistance interne au générateur de tension. Grâce à cette résistance en série, la valeur du courant qui circule dans cette résistance et donc dans cet émetteur est indépendante de la tension de seuil de déclenchement du modulateur associé à cet émetteur. La valeur du courant est alors d'une part proportionnelle à la différence entre ladite somme des valeurs du signal d'affichage et la valeur de la tension appliquée à l'autre parmi l'entrée non-inverseuse et l'entrée inverseuse de l'amplificateur opérationnel, d'autre part inversement proportionnelle à la valeur de la résistance de l'élément résistif.This resistance may be an internal resistance to the voltage generator. Thanks to this series resistance, the value of the current flowing in this resistor and therefore in this emitter is independent of the tripping threshold voltage of the modulator associated with this emitter. The value of the current is then on the one hand proportional to the difference between said sum of the values of the display signal and the value of the voltage applied to the other one of the non-inverting input and the inverting input of the operational amplifier, on the other hand inversely proportional to the value of the resistance of the resistive element.

Il ne comprend aucun moyen de commutation entre ladite sortie des moyens d'alimentation et chacune des extrémités des séries émetteur-modulateur de la colonne.It does not include any switching means between said output of the supply means and each of the ends of the transmitter-modulator series of the column.

Avantageusement, les circuits d'adressage des émetteurs sont simplifiés par rapport à la première variante, puisqu'il n'est plus nécessaire de commuter l'une des extrémités des séries émetteur-modulateur alternativement vers deux générateurs différents comme dans la première variante.Advantageously, the addressing circuits of the transmitters are simplified with respect to the first variant, since it is no longer necessary to switch one end of the transmitter-modulator series alternately to two different generators as in the first variant.

La sortie du générateur de pilotage est connectée d'une part à l'une parmi l'entrée non-inverseuse (+) et l'entrée inverseuse (-) de l'amplificateur opérationnel, d'autre part, sans interrupteur intermédaire, à ladite extrémité de la série correspondante émetteur-modulateur.The output of the driving generator is connected on the one hand to one of the non-inverting input (+) and the inverting input (-) of the operational amplifier, on the other hand, without intermediate switch, to said end of the corresponding emitter-modulator series.

Le générateur de tension est raccordé à l'élément résistif pour délivrer un courant de pilotage obtenu à partir de la relation suivante : I = n = 1 p V data n - V ref n R

Figure imgb0001

  • dans laquelle R est l'élément résistif,
  • Vref n est une tension référence associée à l'émetteur n, et
  • Vdata n est la valeur de la tension d'affichage adressée à l'émetteur n, et
  • p est le nombre total d'émetteurs dans une colonne.
The voltage generator is connected to the resistive element to deliver a driving current obtained from the following relation: I = Σ not = 1 p V data n - V ref n R
Figure imgb0001
  • in which R is the resistive element,
  • V ref n is a reference voltage associated with the transmitter n, and
  • V data n is the value of the display voltage addressed to the transmitter n, and
  • p is the total number of emitters in a column.

Lesdits moyens de pilotage comprennent en outre un générateur de référence apte à délivrer un signal de référence à l'autre parmi l'entrée inverseuse (-) et l'entrée non-inverseuse (+) de l'amplificateur opérationnel.Said control means also comprise a reference generator capable of delivering a reference signal to the other from the inverting input (-) and the non-inverting input (+) of the operational amplifier.

Chaque émetteur présente des propriétés électriques et/ou optiques particulières et la valeur de chaque signal de référence est fonction desdites propriétés électriques et/ou optiques.Each transmitter has particular electrical and / or optical properties and the value of each reference signal is a function of said electrical and / or optical properties.

Chaque émetteur est associé à l'illumination d'une couleur, et le signal de référence est apte à être modulé en fonction de la couleur affectée audit émetteur sélectionné.Each transmitter is associated with the illumination of a color, and the reference signal is able to be modulated according to the color assigned to said selected transmitter.

Une teinte blanche donnée est repérée classiquement par ses coordonnées trichromatiques. Grâce à l'invention, on peut optimiser facilement les performances chromatiques du dispositif et compenser les différences de vieillissement entre les émetteurs.A given white shade is classically identified by its trichromatic coordinates. Thanks to the invention, it is possible to easily optimize the chromatic performances of the device and to compensate for the differences in aging between the emitters.

Les émetteurs sont groupés en pluralités d'émetteurs adjacents adaptés pour émettre chacun une couleur différente, et, pour chaque pluralité, lesdits signaux de référence sont attribués aux différents émetteurs de cette pluralité de manière à ce que l'adressage de ces émetteurs par une même valeur de signal d'affichage engendre l'émission de ladite teinte blanche par cette pluralité.The emitters are grouped into pluralities of adjacent emitters adapted to each emit a different color, and, for each plurality, said reference signals are allocated to the different emitters of this plurality so that the addressing of these emitters by the same display signal value generates the emission of said white tint by this plurality.

Lesdits moyens de pilotage comprennent en outre des moyens de stockage de données propres à stocker la valeur du signal d'affichage adressée à chaque émetteur pendant une durée d'image.Said control means further comprise data storage means capable of storing the value of the display signal addressed to each transmitter during an image duration.

L'invention a également pour objet un procédé pour dispositif d'affichage d'images à matrice active, comprenant plusieurs émetteurs de lumière formant un réseau d'émetteurs répartis en lignes et en colonnes, chaque émetteur étant propre à être adressé périodiquement pendant une durée d'image par une valeur d'un signal d'affichage représentative d'une donnée d'affichage ; un modulateur de courant comportant une source, un drain, une grille, l'un parmi le drain ou la source de chaque modulateur étant raccordé en série à un émetteur du réseau pour former une série émetteur-modulateur comprenant deux extrémités ; des moyens de sélection aptes à sélectionner les émetteurs d'une ligne ; un condensateur de stockage de charges électriques propre à maintenir une tension de commande à la grille du ou de chaque modulateur pendant ladite durée d'image ; et des moyens de pilotage de l'illumination des émetteurs d'une colonne comprenant au moins un amplificateur opérationnel ayant une entrée inverseuse, une entrée non-inverseuse et une sortie, le procédé comprenant les étapes suivantes

  • transmission par les moyens de sélection, d'un signal de sélection (Vselect) à une ligne d'émetteurs ;
  • application par les moyens de pilotage, d'un signal de pilotage (I) à l'une des extrémités de chaque série émetteur-modulateur d'une colonne; et
  • application par les moyens de pilotage, d'un signal de commande (Vc) à la grille de chaque modulateur raccordée à l'émetteur sélectionné ;
caractérisé en ce qu'il comporte en outre l'étape suivante:
  • sélection d'une ligne d'émetteurs pour former une boucle de contre-réaction de l'amplificateur opérationnel avec la grille du modulateur raccordée à la sortie de l'amplificateur opérationnel et avec l'une parmi l'entrée non-inverseuse et l'entrée inverseuse de l'amplificateur opérationnel raccordée à ladite sortie des moyens d'alimentation de ces émetteurs.
The subject of the invention is also a method for an active matrix image display device, comprising a plurality of light emitters forming a network of transmitters distributed in rows and columns, each emitter being able to be addressed periodically for a period of time. image by a value of a display signal representative of a display data; a current modulator comprising a source, a drain, a gate, one of the drain or the source of each modulator being connected in series with a transmitter of the network to form a transmitter-modulator series comprising two ends; selection means adapted to select the transmitters of a line; an electrical charge storage capacitor adapted to maintain a control voltage at the gate of the or each modulator during said image duration; and means for controlling the illumination of the emitters of a column comprising at least one operational amplifier having an inverting input, a non-inverting input and an output, the method comprising the following steps
  • transmission by the selection means of a selection signal (V select ) to a line of transmitters;
  • application by the control means of a control signal (I) at one end of each transmitter-modulator series of a column; and
  • application by the control means of a control signal (V c ) to the gate of each modulator connected to the selected transmitter;
characterized in that it further comprises the following step:
  • selecting an emitter line to form a feedback loop of the operational amplifier with the modulator gate connected to the output of the operational amplifier and with one of the non-inverting input and the an inverting input of the operational amplifier connected to said output of the power supply means of these emitters.

Suivant un mode particulier de réalisation, le procédé comporte la caractéristique selon laquelle le signal de pilotage est fonction de la somme des valeurs des signaux d'affichage adressées à l'ensemble des émetteurs de la colonne pendant une durée d'image.According to a particular embodiment, the method comprises the characteristic according to which the control signal is a function of the sum of the values of the display signals addressed to all the emitters of the column during an image duration.

L'invention sera mieux comprise à la lecture de la description qui va suivre, donnée uniquement à titre d'exemple et faite en se référant aux dessins annexés, sur lesquels :

  • la figure 1 est un schéma synoptique d'un dispositif d'affichage selon l'invention ;
  • la figure 2 est un schéma synoptique d'une partie du dispositif d'affichage représenté sur la figure 1 ;
  • la figure 3 est un diagramme représentant schématiquement quelques étapes du procédé de commande selon l'invention ;
  • la figure 4 est un graphe représentant l'évolution temporelle d'une tension de sélection appliquée à une électrode de sélection d'un premier circuit d'adressage du dispositif d'affichage selon l'invention ;
  • la figure 5 est un graphe représentant l'évolution temporelle d'une tension de sélection appliquée à une électrode de sélection d'un deuxième circuit d'adressage du dispositif d'affichage selon l'invention ;
  • la figure 6 est un graphe représentant l'évolution temporelle d'une tension d'affichage générée par un générateur de pilotage pour adresser successivement les différents circuits d'adressage d'une même colonne du dispositif d'affichage selon l'invention, notamment le premier et le deuxième circuit ;
  • la figure 7 est un graphe représentant l'évolution temporelle d'un courant de drain circulant dans un modulateur du premier circuit d'adressage ;
  • la figure 8 est un graphe représentant l'évolution temporelle d'un courant de drain circulant dans un modulateur du deuxième circuit d'adressage du dispositif d'affichage selon l'invention ;
  • la figure 9 est un graphe représentant l'évolution temporelle d'un courant de pilotage généré par une unité de pilotage du dispositif d'affichage selon l'invention ;
  • la figure 10 est un schéma synoptique d'une première variante de réalisation de la partie du dispositif d'affichage représentée sur la figure 2 ;
  • la figure 11 est un schéma synoptique d'une deuxième variante de réalisation de la partie du dispositif d'affichage représentée sur la figure 2 ;
  • la figure 12 est un graphe comportant des courbes représentant le courant traversant différents émetteurs du dispositif d'affichage selon l'invention, en fonction de la tension appliquée à leurs bornes ; et
  • la figure 13 est un schéma synoptique d'une troisième variante de réalisation d'une partie du dispositif d'affichage représenté sur la figure 2.
The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the appended drawings, in which:
  • the figure 1 is a block diagram of a display device according to the invention;
  • the figure 2 is a block diagram of a portion of the display device shown on the figure 1 ;
  • the figure 3 is a diagram schematically showing some steps of the control method according to the invention;
  • the figure 4 is a graph representing the time evolution of a selection voltage applied to a selection electrode of a first addressing circuit of the display device according to the invention;
  • the figure 5 is a graph representing the time evolution of a selection voltage applied to a selection electrode of a second addressing circuit of the display device according to the invention;
  • the figure 6 is a graph representing the time evolution of a display voltage generated by a control generator for successively addressing the different addressing circuits of the same column of the display device according to the invention, in particular the first and the second circuit;
  • the figure 7 is a graph representing the time evolution of a drain current flowing in a modulator of the first addressing circuit;
  • the figure 8 is a graph representing the time evolution of a drain current flowing in a modulator of the second addressing circuit of the display device according to the invention;
  • the figure 9 is a graph representing the time evolution of a driving current generated by a control unit of the display device according to the invention;
  • the figure 10 is a block diagram of a first embodiment of the portion of the display device shown in FIG. figure 2 ;
  • the figure 11 is a block diagram of a second alternative embodiment of the portion of the display device shown in FIG. figure 2 ;
  • the figure 12 is a graph comprising curves representing the current flowing through different emitters of the display device according to the invention, as a function of the voltage applied to their terminals; and
  • the figure 13 is a block diagram of a third alternative embodiment of a portion of the display device shown in FIG. figure 2 .

La figure 1 représente un dispositif d'affichage d'images selon l'invention. Celui-ci est constitué par une matrice active 1 pilotée par des moyens de commande 2.The figure 1 represents an image display device according to the invention. This is constituted by an active matrix 1 controlled by control means 2.

De façon connue en soi, la matrice active 1 comprend une pluralité de circuits d'adressage 3, 4, 5, 6, chacun associé à un émetteur (non représenté) et répartis selon des lignes et des colonnes.In a manner known per se, the active matrix 1 comprises a plurality of addressing circuits 3, 4, 5, 6, each associated with a transmitter (not shown) and distributed along lines and columns.

Les moyens 2 de commande de la matrice active comprennent un système de commande 7, un circuit de commande de sélection 8 et un circuit de commande d'adressage 10.The means 2 for controlling the active matrix comprise a control system 7, a selection control circuit 8 and an addressing control circuit 10.

Le système de commande 7 est propre à recevoir un signal d'affichage d'images, à le traiter (par exemple, le décoder et le décompresser) et à délivrer un signal de synchronisation au circuit de commande de sélection 8 et des signaux d'affichage au circuit de commande d'adressage 10.The control system 7 is adapted to receive an image display signal, to process it (for example, to decode and decompress it) and to output a synchronization signal to the selection control circuit 8 and signal signals. display at the addressing control circuit 10.

Le circuit de commande de sélection 8 est raccordé à une pluralité d'électrodes de ligne 14, 15, chacune associée à une ligne d'émetteurs. Sur réception du signal de synchronisation, le circuit 8 est adapté pour générer une impulsion de sélection Vselect successivement à chaque électrode de ligne 14, pour sélectionner tour à tour l'ensemble des circuits d'adressage 3, 6 de cette ligne, à une fréquence de balayage correspondant à une durée d'image. L'impulsion de sélection Vselect est une donnée logique de sélection des émetteurs.The selection control circuit 8 is connected to a plurality of line electrodes 14, 15, each associated with a line of transmitters. Sure receiving the synchronization signal, the circuit 8 is adapted to generate a selection pulse V select successively at each line electrode 14, to select in turn all the addressing circuits 3, 6 of this line, at a frequency scan corresponding to an image duration. The selection pulse V select is a logical data selection of the transmitters.

Le circuit de commande d'adressage 10 est raccordé à une pluralité d'électrodes de colonne 16, 17 et une pluralité d'électrodes de pilotage 18, 19, chacune associée à une colonne d'émetteurs 21A, 21B. Il comprend une pluralité d'unités de pilotage d'adressage 20A, 20B, chacune propre à adresser et à alimenter les circuits d'adressage 3, 4, 5, 6 d'une colonne 21A, 21B par l'intermédiaire d'une électrode de colonne 16, 17 et d'une électrode de pilotage 18, 19.The addressing control circuit 10 is connected to a plurality of column electrodes 16, 17 and a plurality of driving electrodes 18, 19, each associated with a transmitter column 21A, 21B. It comprises a plurality of addressing control units 20A, 20B, each adapted to address and supply the addressing circuits 3, 4, 5, 6 of a column 21A, 21B via an electrode 16, 17 and a control electrode 18, 19.

Les électrodes de ligne 14, 15, de colonne 16, 17 et de pilotage 18, 19 permettent respectivement de sélectionner, d'adresser et d'alimenter un circuit d'adressage spécifique parmi l'ensemble des circuits 3, 4, 5, 6 du dispositif d'affichage.The row electrodes 14, 15, 16, 17 of the column and control 18, 19 respectively allow to select, address and supply a specific addressing circuit among the set of circuits 3, 4, 5, 6 of the display device.

Ainsi, en sélectionnant la seule électrode de ligne 14 du dispositif d'affichage et en activant l'unité de pilotage 20A propre à transmettre une tension de commande Vc à l'électrode 16 et un courant de pilotage I à l'électrode 18 de la colonne 21A, le circuit 3 au croisement de l'électrode de cette ligne 14 et des électrodes 16 et 18 de cette colonne d'émetteurs 21A est activé, alors qu'aucun des autres circuits 4, ..., 5 de cette même colonne n'est activé.Thus, by selecting the only line electrode 14 of the display device and by activating the control unit 20A capable of transmitting a control voltage Vc to the electrode 16 and a control current I to the electrode 18 of the column 21A, the circuit 3 at the crossing of the electrode of this line 14 and the electrodes 16 and 18 of this column of emitters 21A is activated, whereas none of the other circuits 4, ..., 5 of this same column is enabled.

La figure 2 représente des émetteurs de lumière 22, 23, 24 chacun associé à un circuit d'adressage 3, 4, 5 d'un ensemble de pixels d'une colonne d'émetteurs 21A ainsi que l'unité de pilotage d'adressage 20A propre à cette colonne d'émetteurs 21A et le circuit de commande de sélection 8 des circuits d'adressage 3, 4, 5, 6.The figure 2 represents light emitters 22, 23, 24 each associated with an addressing circuit 3, 4, 5 of a set of pixels of a column of emitters 21A and the addressing control unit 20A specific to this column of transmitters 21A and the selection control circuit 8 of the addressing circuits 3, 4, 5, 6.

Les émetteurs 22, 23, 24 du dispositif d'affichage sont des diodes électroluminescentes organiques. Ils comprennent une anode et une cathode. La structure de ces diodes est « classique », c'est à dire que les anodes sont en couche inférieure, du côté du substrat, et les cathodes en couche supérieure.The emitters 22, 23, 24 of the display device are organic light emitting diodes. They include an anode and a cathode. The structure of these diodes is "conventional", that is to say that the anodes are in a lower layer, the side of the substrate, and the cathodes in the upper layer.

Ces émetteurs émettent une intensité lumineuse directement proportionnelle au courant qui les traverse. Chaque émetteur constitue un pixel élémentaire. Ces pixels élémentaires sont de même nature (émission de couleur identique) dans le cas d'un écran monochrome ou sont structurés sous la forme de triplets rouge, vert et bleu dans le cas d'un écran couleur.These emitters emit a luminous intensity directly proportional to the current passing through them. Each transmitter is a pixel elementary. These elementary pixels are of the same nature (emission of identical color) in the case of a monochrome screen or are structured in the form of triplets red, green and blue in the case of a color screen.

Dans le cadre de l'invention, l'ensemble des émetteurs 22, 23, 24 d'une colonne est associé à des sous-pixels d'une même couleur. Les émetteurs de trois colonnes adjacentes sont associés successivement aux couleurs rouge, vert et bleu. Les tensions de polarisation nécessaires pour que des émetteurs 22, 23, 24 soient traversés par un courant de même valeur varient en fonction des caractéristiques courant-tension de ces émetteurs, et notamment en fonction de la couleur des sous-pixels associés aux émetteurs 22, 23, 24 de chaque colonne.In the context of the invention, all emitters 22, 23, 24 of a column are associated with sub-pixels of the same color. The emitters of three adjacent columns are successively associated with the colors red, green and blue. The bias voltages necessary for emitters 22, 23, 24 to be traversed by a current of the same value vary according to the current-voltage characteristics of these emitters, and in particular as a function of the color of the sub-pixels associated with the emitters 22, 23, 24 of each column.

Comme les circuits d'adressage 3, 4, 5 de la matrice active 1 sont identiques, seul le circuit 3 sera décrit de manière détaillée.Since the addressing circuits 3, 4, 5 of the active matrix 1 are identical, only the circuit 3 will be described in detail.

Ce circuit 3 comprend un modulateur de courant 26, un interrupteur 28 formé d'un transistor, un condensateur de stockage 29 et une électrode d'alimentation 30.This circuit 3 comprises a current modulator 26, a switch 28 formed of a transistor, a storage capacitor 29 and a feed electrode 30.

Le modulateur de courant 26 et l'interrupteur 28 sont des transistors en couches minces (Thin Film Transistor en anglais), basés sur une technologie utilisant du Silicium poly-cristallin (Poly-Si), du Silicium amorphe (a-Si) ou du Silicium micro-cristallin (µc-Si) déposé en couches minces sur un substrat de verre. De tels composants comprennent trois électrodes : une électrode de drain et une électrode de source entre lesquelles circule un courant modulé appelé courant de drain, et une électrode de grille à laquelle est appliquée la tension de commande Vc.The current modulator 26 and the switch 28 are thin film transistors (Thin Film Transistor), based on a technology using polycrystalline silicon (Poly-Si), amorphous silicon (a-Si) or Microcrystalline silicon (μc-Si) deposited in thin layers on a glass substrate. Such components comprise three electrodes: a drain electrode and a source electrode between which flows a modulated current called drain current, and a gate electrode to which the control voltage V c is applied.

La source du modulateur 26 est reliée à l'anode de l'émetteur 22, de manière à raccorder en série le modulateur 26 et l'émetteur 22. L'une 31 des extrémités de cette série, à savoir ici le drain du modulateur 26, est raccordée à l'électrode de pilotage 18. La grille du modulateur 26 est raccordée d'une part, à une première borne du condensateur 29 et d'autre part, à une électrode de passage de courant (drain ou source) de l'interrupteur 28, via une ligne électrique 33. L'autre électrode de passage de courant (drain ou source) de l'interrupteur 28 est raccordée à l'électrode de colonne 16. La grille de l'interrupteur 28 est raccordée à l'électrode de ligne 14. La seconde borne de chaque condensateur 29 de l'ensemble des circuits 3, 4, 5 de la colonne 21A est connectée à l'électrode d'alimentation 30. Enfin, l'autre extrémité 32 de chaque série modulateur-émetteur, à savoir ici la cathode de l'émetteur 22 est raccordée à une électrode d'alimentation 34. Les deux électrodes d'alimentation 30 et 34 peuvent être reliées entre elles au même potentiel par un conducteur non représenté.The source of the modulator 26 is connected to the anode of the emitter 22, so as to connect in series the modulator 26 and the emitter 22. One 31 of the ends of this series, namely here the drain of the modulator 26 is connected to the control electrode 18. The gate of the modulator 26 is connected on the one hand, to a first terminal of the capacitor 29 and on the other hand, to a current passage electrode (drain or source) of the switch 28, via an electrical line 33. The other current-carrying electrode (drain or source) of the switch 28 is connected to the column electrode 16. The gate of the switch 28 is connected to the line electrode 14. The second terminal of each capacitor 29 of the set of circuits 3, 4, 5 of the column 21A is connected to the supply electrode 30. Finally, the other end 32 of each series modulator-emitter, namely here the cathode of the emitter 22 is connected to a supply electrode 34. The two feed electrodes 30 and 34 can be interconnected at the same potential by a driver not shown.

Le modulateur 26, représenté sur la figure 2, est de type n, de sorte que, en fonctionnement, son courant de drain circule entre son drain et sa source. On notera qu'un tel dispositif peut aussi être utilisé pour piloter des TFT de type p, toujours avec des diodes à structure classique, comme illustré à la figure 10.The modulator 26, represented on the figure 2 , is of type n, so that, in operation, its drain current flows between its drain and its source. Note that such a device can also be used to drive p-type TFTs, always with conventional structure diodes, as illustrated in FIG. figure 10 .

Le condensateur 29, disposé entre la grille et la source du modulateur 26, est adapté pour maintenir sensiblement une tension de commande constante à la grille du modulateur 26 pendant un intervalle de temps correspondant à la durée d'une image T1, T2 afin de maintenir la brillance de l'émetteur pendant cette durée.The capacitor 29, arranged between the gate and the source of the modulator 26, is adapted to substantially maintain a constant control voltage at the gate of the modulator 26 during a time interval corresponding to the duration of an image T1, T2 in order to maintain the brightness of the transmitter during this time.

L'électrode d'alimentation 30 est propre à fournir la tension nécessaire pour polariser au potentiel désiré l'une des bornes du condensateur 29, comme cela est connu dans l'état de la technique.The supply electrode 30 is able to provide the voltage necessary to bias the desired potential to one of the terminals of the capacitor 29, as known in the state of the art.

L'unité de pilotage 20A est adaptée pour compenser, avec la boucle de contre-réaction décrite ci-après, la tension de seuil de déclenchement Vth de chaque modulateur 26 de l'ensemble des circuits d'adressage 3, 4, 5 de la colonne 21A et pour alimenter les émetteurs 22, 23, 24 de la colonne d'émetteurs 21A.The control unit 20A is adapted to compensate, with the feedback loop described hereinafter, the trigger threshold voltage V th of each modulator 26 of the set of addressing circuits 3, 4, 5 of FIG. 21A column and to supply the transmitters 22, 23, 24 of the 21A transmitters column.

A cette fin, elle comprend un amplificateur opérationnel 35 ayant une entrée inverseuse -, une entrée non inverseuse + et une sortie. La sortie de cet amplificateur 35 est connectée à l'électrode de colonne 16 et son entrée non inverseuse + est raccordée à l'électrode de pilotage 18 assurant l'alimentation des émetteurs de la colonne via leur modulateur associé. Ainsi, cette entrée non inverseuse + est reliée simultanément à l'anode de chaque émetteur 22, 23, 24 de la colonne 21A via le modulateur 26 qui lui est associé.To this end, it includes an operational amplifier 35 having an inverting input -, a non-inverting input + and an output. The output of this amplifier 35 is connected to the column electrode 16 and its non-inverting input + is connected to the control electrode 18 supplying the transmitters of the column via their associated modulator. Thus, this non-inverting input + is simultaneously connected to the anode of each emitter 22, 23, 24 of the column 21A via the modulator 26 associated therewith.

En conséquence, une boucle de contre-réaction de l'amplificateur 35 est formée par l'électrode de pilotage 18, l'extrémité 31 de la série modulateur-émetteur, le modulateur 26, la ligne 33 et l'électrode de colonne 16 à chaque fois qu'un interrupteur 28 d'un circuit d'adressage 3, 4, 5 de la colonne d'émetteurs 21A est fermé. A noter que l'extrémité 31 de la série modulateur-émetteur qui fait partie de la boucle de contre-réaction correspond, dans les modes de réalisation présentés sur les figures 2 et 10, à l'un parmi le drain ou la source du modulateur de cette série.Accordingly, a feedback loop of the amplifier 35 is formed by the driving electrode 18, the end 31 of the modulator-emitter series, the modulator 26, the line 33 and the column electrode 16. each time a switch 28 of an addressing circuit 3, 4, 5 of the transmitter column 21A is closed. Note that the end 31 of the modulator-transmitter series which is part of the feedback loop corresponds, in the embodiments presented on figures 2 and 10 , to one of the drain or source of the modulator of this series.

L'amplificateur 35 est propre à fonctionner en contre-réaction et à compenser ainsi la tension de seuil de déclenchement Vth de chaque modulateur 26 des circuits d'adressage 3, 4, 5 de la colonne d'émetteurs 21A, comme cela sera explicité dans la suite de la description.The amplifier 35 is able to operate in feedback and thus compensate for the trigger threshold voltage V th of each modulator 26 of the addressing circuits 3, 4, 5 of the transmitter column 21A, as will be explained. in the following description.

De plus, l'unité de pilotage 20A est propre à adresser et à alimenter les émetteurs 22, 23, 24 de la colonne 21A par le courant de pilotage I. Ce courant I dépend de la somme des valeurs des tensions d'affichage Vdata 22, Vdata 23, Vdata 24 adressées aux émetteurs 22, 23, 24 de cette colonne 21A.In addition, the control unit 20A is suitable for addressing and supplying the emitters 22, 23, 24 of the column 21A with the driving current I. This current I depends on the sum of the values of the display voltages V data 22 , V data 23, V data 24 addressed to transmitters 22, 23, 24 of this column 21A.

A cet effet, elle comprend un générateur de courant de pilotage 36 et un générateur 38 de tension de référence, raccordés respectivement à l'entrée non inverseuse + et à l'entrée inverseuse - de l'amplificateur 35.For this purpose, it comprises a control current generator 36 and a reference voltage generator 38, respectively connected to the non-inverting input + and the inverting input - of the amplifier 35.

Le générateur de courant 36 est formé par un générateur de tension variable 39 raccordé en série à une résistance 40. L'électrode de pilotage 18 est raccordée à la sortie de la résistance 40, au noeud 42, qui forme donc l'une des sorties du générateur de courant 36.The current generator 36 is formed by a variable voltage generator 39 connected in series with a resistor 40. The control electrode 18 is connected to the output of the resistor 40, at the node 42, which thus forms one of the outputs of the current generator 36.

Le générateur 39 est un générateur de tension variable dont la tension varie en fonction des valeurs du signal d'affichage Vdata 22, Vdata 23 destinées à être adressées aux émetteurs 22, 23, comme cela sera explicité dans la suite de la description.The generator 39 is a variable voltage generator whose voltage varies as a function of the values of the display signal V data 22 , V data 23 intended to be addressed to the transmitters 22, 23, as will be explained in the following description.

Le générateur 38 est un générateur adapté pour délivrer une tension de référence qui est fixée lors des réglages du dispositif d'affichage et qui est propre à chaque colonne. En variante, on peut également utiliser un générateur de tension variable ; la variation de la tension de référence en fonction de la colonne d'émetteurs 21A adressée sera explicitée dans la suite de la description.The generator 38 is a generator adapted to deliver a reference voltage which is fixed during the settings of the display device and which is specific to each column. Alternatively, it is also possible to use a variable voltage generator; the variation of the reference voltage as a function of the column of transmitters 21A addressed will be explained in the following description.

La sortie du générateur 38 est reliée à l'entrée inverseuse - de l'amplificateur 35, via, optionnellement, une résistance 44. Cette résistance 44 n'est pas absolument nécessaire au fonctionnement de l'unité de pilotage 20A. Elle a uniquement une fonction avantageuse d'équilibrage entre les deux entrées de l'amplificateur opérationnel 35.The output of the generator 38 is connected to the inverting input - of the amplifier 35, via, optionally, a resistor 44. This resistor 44 is not absolutely necessary for the operation of the control unit 20A. It only has an advantageous function of balancing between the two inputs of the operational amplifier 35.

Optionnellement également, un condensateur 46 est raccordé entre l'entrée inverseuse - de l'amplificateur 35 et la sortie de cet amplificateur. La résistance 44 et le condensateur 46 constituent un réseau de compensation qui permet d'accroître avantageusement la précision et la stabilité du circuit.Optionally also, a capacitor 46 is connected between the inverting input - of the amplifier 35 and the output of this amplifier. The Resistor 44 and capacitor 46 constitute a compensation network which advantageously increases the accuracy and stability of the circuit.

L'unité de pilotage 20A comprend également des moyens de stockage de données 48 et un module de commande 50 des générateurs 38 et 39.The control unit 20A also comprises data storage means 48 and a control module 50 of the generators 38 and 39.

Les moyens de stockage 48 comprennent une base de données 52 adaptée pour stocker d'une part la valeur du signal d'affichage Vdata 22, Vdata 23 adressée à chaque émetteur 22, 23 de la colonne 21A au cours de la précédente durée d'image T1 et, d'autre part une donnée d'identification ou de localisation de l'émetteur 22, 23 auquel cette valeur a été adressée.The storage means 48 comprise a database 52 adapted to store on the one hand the value of the display signal V data 22 , V data 23 addressed to each transmitter 22, 23 of the column 21A during the previous period of time. T1 image and, secondly, an identification or location data of the transmitter 22, 23 to which this value has been addressed.

Ces moyens de stockage 48 comprennent également un répertoire 54 adapté pour stocker une valeur de tension de référence à associer à l'ensemble des émetteurs de la colonne 21A. Cette valeur est fonction de la couleur rouge, vert ou bleu associée aux émetteurs 22, 23 de la colonne 21A.These storage means 48 also comprise a directory 54 adapted to store a reference voltage value to be associated with all the transmitters of the column 21A. This value is a function of the red, green or blue color associated with the emitters 22, 23 of the column 21A.

Les émetteurs associés à des couleurs différentes présentent des caractéristiques courant-tension différentes, comme visible sur la figure 12. En conséquence, il est nécessaire d'appliquer des tensions différentes aux bornes d'un émetteur rouge et aux bornes d'un émetteur bleu pour obtenir la même luminance et la même valeur du courant traversant ces émetteurs.Emitters associated with different colors have different current-voltage characteristics, as can be seen on the figure 12 . Consequently, it is necessary to apply different voltages across a red emitter and across a blue emitter to obtain the same luminance and the same value of the current flowing through these emitters.

Les valeurs de tension de référence des répertoires 54 de chaque colonne sont fixées ici en fonction de la couleur des émetteurs d'une colonne 21A. Cette opération est réalisée en usine, lors des réglages du dispositif d'affichage qui sont effectués préalablement à sa mise en service. Ces valeurs de référence sont établies pour compenser les variations entre les caractéristiques électriques courant-tension et/ou des caractéristiques lumineuses des différents émetteurs du dispositif, comme cela sera décrit ultérieurement.The reference voltage values of the directories 54 of each column are set here according to the color of the emitters of a column 21A. This operation is performed at the factory, during the settings of the display device that are performed prior to its commissioning. These reference values are set to compensate for the variations between the electrical current-voltage characteristics and / or the luminous characteristics of the different emitters of the device, as will be described later.

Généralement, comme ces caractéristiques dépendent principalement de la couleur d'émission des émetteurs, on aura trois valeurs différentes de tension de référence, une première valeur Vref.R commune à l'ensemble des émetteurs rouges d'une première colonne, une deuxième valeur Vref.G commune à l'ensemble des émetteurs verts d'une deuxième colonne et une troisième valeur Vref.B commune à l'ensemble des émetteurs bleus d'une troisième colonne. Selon une variante plus complexe, ces valeurs de tension de référence sont spécifiques à chaque colonne d'émetteurs, de manière à compenser les variations des caractéristiques électriques courant-tension et/ou des caractéristiques lumineuses entre les émetteurs de différentes colonnes, même lorsqu'ils sont de même couleur d'émission.Generally, since these characteristics depend mainly on the emission color of the emitters, there will be three different reference voltage values, a first value V ref.R common to all the red emitters of a first column, a second value V ref.G common to all the green emitters of a second column and a third value V ref.B common to all the blue emitters of a third column. According to a more complex variant, these reference voltage values are specific to each column of emitters, so as to compensate for variations in current-voltage electrical characteristics and / or light characteristics between the emitters of different columns, even when they are of the same emission color.

Un courant ne peut circuler dans un émetteur que si le signal d'affichage Vdata qui lui est adressé est supérieur à la tension de référence Vref qui lui est associée. Pour éviter d'avoir à utiliser des signaux d'affichage de valeurs trop élevées, on établira de préférence, lors des réglages du dispositif d'affichage, des valeurs de tension de référence aussi faibles que possible tout en obtenant les compensations souhaitées.A current can flow in a transmitter only if the V data display signal addressed to it is greater than the reference voltage V ref associated therewith. In order to avoid having to use too high value display signals, reference voltage values as low as possible will be preferably set while adjusting the display device while achieving the desired compensations.

Le module de commande 50 est raccordé aux moyens de stockage 48 pour rechercher et enregistrer des informations dans ceux-ci.The control module 50 is connected to the storage means 48 for searching and recording information therein.

De plus, le module 50 est propre à recevoir le signal d'affichage transmis par le système 7 et à commander les générateurs 38 et 39 en fonction de ce signal et des informations stockées dans les moyens de stockage 48.In addition, the module 50 is adapted to receive the display signal transmitted by the system 7 and to control the generators 38 and 39 as a function of this signal and the information stored in the storage means 48.

En fonctionnement, les circuits 8 et 10 sont propres à adresser, à alimenter et à sélectionner successivement l'ensemble des émetteurs 22, 23, 24 de la matrice 1.In operation, the circuits 8 and 10 are adapted to address, supply and successively select all the emitters 22, 23, 24 of the matrix 1.

Lors de la mise en route, au début d'une première trame d'image T1, au cours d'une étape 60, représentée sur la figure 3, l'unité de pilotage 20A et le circuit 8 commandent l'éclairage du premier émetteur 22 de la colonne 21A. Cette étape 60 comprend des étapes 62 à 69.During start-up, at the beginning of a first image frame T1, during a step 60, represented on the figure 3 , the control unit 20A and the circuit 8 control the lighting of the first transmitter 22 of the column 21A. This step 60 includes steps 62 to 69.

Au cours de l'étape 62, le circuit 8 génère une impulsion de sélection Vselect 22 à l'électrode de ligne 14. Cette impulsion, représentée sur la figure 4, est propre à fermer l'interrupteur 28.In step 62, the circuit 8 generates a selection select pulse V 22 at the line electrode 14. This pulse, shown in FIG. figure 4 , is suitable for closing the switch 28.

Parallèlement, au cours d'une étape 64, le module 50 interroge le répertoire 54 pour connaître la tension de référence associée à la colonne de l'émetteur 22. Cette tension de référence est notamment fonction de la couleur des sous pixels associés aux émetteurs 22, 23, 24 de cette colonne.At the same time, during a step 64, the module 50 interrogates the directory 54 to know the reference voltage associated with the column of the transmitter 22. This reference voltage is in particular a function of the color of the sub-pixels associated with the transmitters 22 , 23, 24 of this column.

Pendant une étape 66, le module 50 commande le générateur 38 afin que celui-ci délivre la tension de référence Vref 21A destinée aux émetteurs de la colonne 21A dont la valeur est constante et égale Vref a.During a step 66, the module 50 controls the generator 38 so that it delivers the reference voltage V ref 21A for the transmitters of the column 21A whose value is constant and equal V ref a .

Parallèlement, au cours d'une étape 68, le module 50 reçoit du système de commande 7 la valeur Va de la tension d'affichage Vdata 22 à adresser à l'émetteur 22 ainsi que l'identification ou la position de l'émetteur adressé 22 associé à cette valeur. Puis, le module 50 enregistre dans la base de données 52 cette valeur Va et l'identification de l'émetteur auquel cette valeur est adressée.At the same time, during a step 68, the module 50 receives from the control system 7 the value V a of the display voltage V data 22 to be addressed to the transmitter 22 as well as the identification or the position of the addressed transmitter 22 associated with this value. Then, the module 50 stores in the database 52 this value V a and the identification of the issuer to which this value is addressed.

En même temps, au cours de l'étape 69, le module 50 commande le générateur 39 pour que celui-ci génère la valeur Va de la tension d'affichage Vdata 22 à adresser à l'émetteur 22, telle que représentée sur la figure 6.At the same time, during step 69, the module 50 controls the generator 39 so that it generates the value V a of the display voltage V data 22 to be addressed to the transmitter 22, as represented on FIG. the figure 6 .

En conséquence, le générateur 38 fournit une tension de référence Vref 21A égale à Vref a, à l'entrée inverseuse - de l'amplificateur 35. En même temps, le générateur 39 applique à la résistance 40, une tension Vdata 22 égale à Va, représentée sur la figure 6. Cette tension Va, génère un courant de pilotage I = I22, qui est introduit dans le drain du modulateur 26, par l'intermédiaire de l'électrode de pilotage 18. Ce courant de pilotage I = I22, représenté sur la figure 7, est défini par la relation suivante : I 22 = V a - V ref a R

Figure imgb0002
dans laquelle Va est la valeur de la tension d'affichage Vdata 22 générée par le générateur 39, Vref a est la valeur de la tension de référence générée par le générateur 38, et R est la valeur de la résistance 40. A noter que la résistance optionnelle 44 n'intervient pas dans le calcul du courant, car aucun courant significatif, du moins au regard de la valeur du courant de pilotage de I22, ne circule dans cette résistance.Consequently, the generator 38 supplies a reference voltage V ref 21A equal to V ref a , to the inverting input - of the amplifier 35. At the same time, the generator 39 applies a voltage V data to the resistor 40. equal to V a , represented on the figure 6 . This voltage V a , generates a control current I = I 22 , which is introduced into the drain of the modulator 26, via the control electrode 18. This driving current I = I 22 , represented on the figure 7 , is defined by the following relation: I 22 = V at - V ref R
Figure imgb0002
in which V a is the value of the display voltage V data 22 generated by the generator 39, V ref a is the value of the reference voltage generated by the generator 38, and R is the value of the resistor 40. A note that the optional resistor 44 does not intervene in the calculation of the current, because no significant current, at least compared to the value of the driving current of I 22 , circulates in this resistance.

En considérant que le modulateur 26 du circuit 3 raccordé en série au premier émetteur 22 fonctionne dans son mode de saturation (Vgs - Vth < Vds), le courant de drain le traversant est égal au courant de pilotage I et la relation suivante est vérifiée : I = I 22 = k V gs - V th 2 = V a - V ref a R

Figure imgb0003
dans laquelle I22 est le courant de drain traversant le modulateur 26, Vgs est la tension entre la grille et la source du modulateur 26, k est une constante qui dépend des caractéristiques intrinsèques du modulateur 26, Vth est la tension de seuil de déclenchement du modulateur 26 et Vds est la tension entre le drain et la source du modulateur 26.Considering that the modulator 26 of the circuit 3 connected in series with the first transmitter 22 operates in its saturation mode (V gs -V th <V ds ), the drain current passing through it is equal to the driving current I and the following relation is verified: I = I 22 = k V gs - V th 2 = V at - V ref R
Figure imgb0003
where I 22 is the drain current flowing through the modulator 26, V gs is the voltage between the gate and the source of the modulator 26, k is a constant which depends on the intrinsic characteristics of the modulator 26, V th is the threshold voltage of tripping of the modulator 26 and V ds is the voltage between the drain and the source of the modulator 26.

En raison de la boucle de contre-réaction selon l'invention, la différence de potentiel entre l'entrée inverseuse - et l'entrée non inverseuse + de l'amplificateur 35 s'annule. La tension au noeud 42 est alors égale à Vref a. L'amplificateur 35 délivre donc à la grille du modulateur 26 une tension de commande Vc qui s'ajuste automatiquement à une valeur telle que le modulateur 26 et l'émetteur 22 en série soient traversés par un courant I = (Va-Vref a)/R qui est donc indépendant de la tension de seuil de déclenchement Vth du modulateur 26. On obtient ainsi directement une compensation de la tension de seuil de déclenchement de l'émetteur 22 du dispositif, sans passer par une mesure du courant traversant cet émetteur.Due to the feedback loop according to the invention, the potential difference between the inverting input - and the noninverting input + of the amplifier 35 is canceled. The voltage at the node 42 is then equal to V ref a . The amplifier 35 thus delivers to the gate of the modulator 26 a control voltage V c which automatically adjusts to a value such that the modulator 26 and the emitter 22 in series are traversed by a current I = (V a -V ref a ) / R which is therefore independent of the trigger threshold voltage V th of the modulator 26. Thus, a compensation of the triggering threshold voltage of the transmitter 22 of the device is obtained directly, without going through a measurement of the current crossing this transmitter.

De la valeur de la tension de commande Vc, se déduit automatiquement une valeur Vgs.From the value of the control voltage V c , a value V gs is automatically deduced.

La valeur de la tension de commande Vc est fonction, non seulement du signal d'affichage de l'émetteur Vdata 22 et de la tension de référence Vref a associée à cet émetteur, mais aussi de la tension de seuil de déclenchement Vth du modulateur 26.The value of the control voltage V c is a function not only of the display signal of the V data transmitter 22 and of the reference voltage V ref associated with this transmitter, but also of the trigger threshold voltage V th of the modulator 26.

Comme la valeur Va de la tension d'affichage Vdata 22 est imposée par le générateur 39, que la tension Vref a est imposée par le générateur 38, que la tension de seuil de déclenchement Vth est intrinsèque aux caractéristiques de construction du modulateur 26, la tension de commande Vc appliquée à la grille du modulateur 26 est adaptée et modulée par l'amplificateur 35 pour compenser la tension de seuil de déclenchement Vth de ce modulateur.Since the value V a of the display voltage V data 22 is imposed by the generator 39, the voltage V ref a is imposed by the generator 38, the trigger threshold voltage V.sub.th is intrinsic to the design characteristics of the generator. modulator 26, the control voltage V c applied to the gate of the modulator 26 is adapted and modulated by the amplifier 35 to compensate for the trigger threshold voltage V th of this modulator.

En conséquence, la tension de commande Vc à la sortie de l'amplificateur 35 s'ajuste exactement à la tension nécessaire pour adresser l'émetteur 22 avec la valeur Va de la tension d'affichage Vdata 22 et cela quelle que soit la valeur de la tension de seuil de déclenchement Vth du modulateur 26 et cela même si celle-ci varie dans le temps.Consequently, the control voltage V c at the output of the amplifier 35 is adjusted exactly to the voltage required to address the transmitter 22 with the value V a of the display voltage V data 22 and that whatever the value of the trigger threshold voltage V th of the modulator 26 and this even if it varies over time.

Cette tension de commande Vc est ensuite maintenue à la grille du modulateur 26 par le condensateur 29 pendant tout le reste de la durée d'image, alors que l'interrupteur 28 du circuit 3 est ré-ouvert, comme cela est connu dans l'état de la technique.This control voltage V c is then maintained at the gate of the modulator 26 by the capacitor 29 for the rest of the image duration, whereas the switch 28 of the circuit 3 is reopened, as is known in the art. state of the art.

Au cours d'une étape 70, le deuxième émetteur 23 de la colonne 21A est éclairé. L'étape 70 comprend des étapes 72 à 79.During a step 70, the second emitter 23 of the column 21A is illuminated. Step 70 includes steps 72 to 79.

Au cours de l'étape 72, le circuit 8 délivre une impulsion de sélection Vselect 23, telle que représentée sur la figure 5, à l'électrode de ligne 15.In step 72, the circuit 8 outputs a select select pulse 23 , as shown in FIG. figure 5 , at the line electrode 15.

Au cours d'une étape 74, le module 50 détermine la tension de référence Vref 21A associée à la colonne de l'émetteur 23, par interrogation des moyens de stockage 48. Comme l'émetteur 23 est dans la même colonne que l'émetteur 22 et que par conséquent ces émetteurs sont associés à la même couleur, la valeur Vref a de cette tension de référence Vref 21A est identique à la valeur Vref a de la tension de référence Vref 22 générée lors de l'adressage du premier émetteur 22.During a step 74, the module 50 determines the reference voltage V ref 21A associated with the column of the transmitter 23, by interrogating the storage means 48. As the transmitter 23 is in the same column as the emitter 22 and therefore these emitters are associated with the same color, the value V ref of this reference voltage V ref 21A is identical to the value V ref a of the reference voltage V ref 22 generated during addressing the first transmitter 22.

Au cours d'une étape 76, le module 50 commande le générateur de référence 38, afin que celui-ci génère la tension Vref a, déterminée pendant l'étape 74.During a step 76, the module 50 controls the reference generator 38, so that it generates the voltage V ref a determined during the step 74.

Parallèlement, au cours d'une étape 77, le module 50 réceptionne du système 7 et enregistre dans la base de données 52, la valeur Vb de la tension d'affichage Vdata 23 à adresser à l'émetteur 23 et représentée sur la figure 6, ainsi que de l'identification ou la position de l'émetteur adressé 23 associé à cette valeur.At the same time, during a step 77, the module 50 receives from the system 7 and records in the database 52, the value V b of the display voltage V data 23 to be sent to the transmitter 23 and represented on the figure 6 as well as the identification or the position of the addressed transmitter 23 associated with this value.

Au cours d'une étape 78, le module 50 additionne la valeur Va de la tension d'affichage Vdata 22 préalablement adressée à l'émetteur 22 de la même colonne à la valeur Vb de la tension d'affichage Vdata 23 destinée à être adressée au prochain émetteur 23.During a step 78, the module 50 adds the value V a of the display voltage V data 22 previously sent to the transmitter 22 of the same column at the value V b of the display voltage V data 23 intended to be addressed to the next transmitter 23.

Puis, au cours d'une étape 79, le module 50 commande le générateur 39 pour que celui-ci délivre une tension d'affichage égale à la valeur de tension calculée pendant l'étape 78, à savoir Va + Vb.Then, during a step 79, the module 50 controls the generator 39 so that it delivers a display voltage equal to the voltage value calculated during the step 78, namely V a + V b .

En conséquence, le nouveau courant de pilotage devient I = I23 + I22, représenté sur la figure 9, circulant dans la résistance R et l'électrode de pilotage 18 dont le point commun est relié à l'entrée non inverseuse + de l'amplificateur 35, est défini par la relation suivante : I = I 22 + I 23 = V data 22 + V data 23 - V ref a R

Figure imgb0004
As a result, the new driving current becomes I = I 23 + I 22 , represented on the figure 9 , flowing in the resistor R and the control electrode 18 whose common point is connected to the non-inverting input + of the amplifier 35, is defined by the following relation: I = I 22 + I 23 = V data 22 + V data 23 - V ref R
Figure imgb0004

Le courant I22 = (Vdata22 - Vref a)/R nécessaire à l'illumination de l'émetteur 22, continue à alimenter le modulateur 26. En effet, la même tension de commande Vc est maintenue à la grille du modulateur 26 du premier circuit 3, par le condensateur 29, et non par l'amplificateur 35 puisque l'interrupteur 28 du circuit 3 est maintenant ouvert. Cette tension Vc contrôle l'intensité du courant alimentant l'émetteur 22 pour que cette intensité soit égale à l'intensité programmée au cours de l'étape 60.The current I 22 = (V data22 - V ref a ) / R necessary for the illumination of the transmitter 22, continues to feed the modulator 26. In fact, the same control voltage V c is maintained at the gate of the modulator 26 of the first circuit 3, by the capacitor 29, and not by the amplifier 35 since the switch 28 of the circuit 3 is now open. This voltage Vc controls the intensity of the current supplying the transmitter 22 so that this intensity is equal to the intensity programmed in step 60.

Le courant restant I23= I - I22 = Vdata23/ R sur l'électrode de pilotage 18 alimente le modulateur 26 du deuxième circuit 4. Comme l'interrupteur 28 du circuit 4 a été fermé au cours de l'étape 72, l'électrode de colonne 16, l'amplificateur 35, l'électrode de pilotage 18, l'extrémité 31 de la série modulateur-émetteur, le modulateur 26 du deuxième circuit 4 et la ligne 33 du deuxième circuit 4 forment une nouvelle boucle de contre-réaction de l'amplificateur 35. En conséquence, la tension de commande Vc sortant de l'amplificateur 35 compense comme précédemment la tension de seuil de déclenchement Vth du modulateur 26 du deuxième circuit 4.The remaining current I 23 = I - I 22 = V data23 / R on the control electrode 18 supplies the modulator 26 of the second circuit 4. As the switch 28 of the circuit 4 has been closed in the step 72, the column electrode 16, the amplifier 35, the control electrode 18, the end 31 of the modulator-emitter series, the modulator 26 of the second circuit 4 and the line 33 of the second circuit 4 form a new loop of Again, the control voltage V c coming out of the amplifier 35 compensates, as before, the trigger threshold voltage V th of the modulator 26 of the second circuit 4.

Le procédé d'adressage du dispositif d'affichage selon l'invention se poursuit par l'adressage de l'ensemble des émetteurs 22, 23, 24 de la colonne 21A au cours de la même première trame d'image de durée T1, par réalisation d'étapes similaires aux étapes 72 à 79, pour chaque circuit d'adressage 3, 4, 5 de la colonne 21A. En particulier, la base de données 52 contient alors les p valeurs Vdata.n de tension d'affichage adressée à chaque émetteur de la colonne 21A au cours de cette première trame d'image et le module 50 commande le générateur 39 pour que celui-ci délivre une tension d'affichage V = n V data . n .

Figure imgb0005
Le courant de pilotage I traversant l'électrode de pilotage 18 est alors défini par la relation générale suivante : I = n I n = n = 1 p V data n - V ref 21 A R
Figure imgb0006
dans laquelle :

  • I est le courant de pilotage généré par l'unité de pilotage 20A et circulant dans l'électrode de pilotage 18 ;
  • In est le courant circulant dans l'émetteur n ;
  • Vdata n est la valeur de la tension d'affichage d'images adressée à l'émetteur n ;
  • Vref 21A est la valeur de la tension de référence associée aux émetteurs de la colonne 21A ; et
  • p est le nombre d'émetteurs dans la colonne 21A.
The addressing method of the display device according to the invention is continued by addressing all the transmitters 22, 23, 24 of the column 21A during the same first image frame of duration T1, by performing steps similar to steps 72 to 79, for each addressing circuit 3, 4, 5 of column 21A. In particular, the database 52 then contains the p values V data.n of display voltage addressed to each emitter of the column 21A during this first image frame and the module 50 controls the generator 39 so that the it delivers a display voltage V = Σ not V data . not .
Figure imgb0005
The driving current I passing through the control electrode 18 is then defined by the following general relationship: I = Σ not I not = Σ not = 1 p V data n - V ref 21 AT R
Figure imgb0006
in which :
  • I is the control current generated by the control unit 20A and flowing in the control electrode 18;
  • I n is the current flowing in the transmitter n;
  • V data n is the value of the image display voltage addressed to the transmitter n;
  • V ref 21A is the value of the reference voltage associated with the transmitters of the column 21A; and
  • p is the number of emitters in column 21A.

Après une durée d'image T1, l'ensemble des émetteurs 22, 23, 24 de la colonne 21A est illuminé en fonction des tensions d'affichage représentative des données d'image à afficher par ces émetteurs, et le circuit 3 est adressé pour la seconde fois au cours d'une étape 80. Cette étape 80 comprend les étapes 82 à 89.After an image duration T1, all the emitters 22, 23, 24 of the column 21A are illuminated as a function of the display voltages representative of the image data to be displayed by these emitters, and the circuit 3 is addressed to the second time during a step 80. This step 80 comprises the steps 82 to 89.

Les étapes 82, 84, 86, 87, 88 et 89 sont respectivement identiques aux étapes 62, 64, 66, 68 et 69 et ne seront pas décrites une nouvelle fois.Pour ce deuxième adressage du circuit 3, ces étapes sont adaptées pour que le module 50 :

  • réceptionne de la base de données 52 la valeur Va de la tension d'affichage Vdata 22 préalablement adressée à l'émetteur 22 au cours de la trame d'image précédente et réceptionne du système 7 et enregistre dans la base de données 52 la nouvelle valeur V'a de la tension d'affichage V'data 22 à adresser à l'émetteur 22, à la place de l'ancienne valeur Va.
  • soustraie l'ancienne valeur Va de la somme n V data . n
    Figure imgb0007
    et lui additionne la nouvelle valeur V'a.
Steps 82, 84, 86, 87, 88 and 89 are respectively identical to steps 62, 64, 66, 68 and 69 and will not be described again. For this second addressing of circuit 3, these steps are adapted so that the module 50:
  • receives from the database 52 the value V a of the display voltage V data 22 previously sent to the transmitter 22 during the preceding frame of image and receives the system 7 and records in the database 52 the new value V ' a of the display voltage V' data 22 to be sent to the transmitter 22, instead of the old value V a .
  • subtract the old value V a from the sum Σ not V data . not
    Figure imgb0007
    and he adds the new value V ' a .

Le module 50 commande alors le générateur 39 pour que celui-ci délivre une tension d'affichage égale à la nouvelle valeur calculée de la somme n V data . n .

Figure imgb0008
The module 50 then controls the generator 39 so that it delivers a display voltage equal to the new calculated value of the sum Σ not V data . not .
Figure imgb0008

Un deuxième adressage du circuit 4 est effectué de la même façon. Après une durée d'image T2, l'ensemble des émetteurs 22, 23, 24 de la colonne 21A est illuminé en fonction de tensions d'affichage représentative des nouvelles données d'image à afficher par ces émetteurs.A second addressing of the circuit 4 is performed in the same way. After an image duration T2, all the emitters 22, 23, 24 of the column 21A are illuminated as a function of display voltages representative of the new image data to be displayed by these emitters.

Les autres trames d'image succèdent alors aux précédentes comme la trame d'image T2 a succédé à la trame d'image T1.The other image frames then succeed to the previous ones as the image frame T2 has succeeded the image frame T1.

Dans l'exemple de réalisation de l'invention tel qu'illustré sur la figure 6 , une valeur de la tension de référence Vref 22 égale à Vref a a été appliquée à l'entrée inverseuse - de l'amplificateur 35 et une valeur de la tension d'affichage Vdata 22 égale à Va a été adressée à l'émetteur 22 au cours de la durée d'image T1. Cette valeur de la tension Va continue à être adressée au cours de la nouvelle durée d'image T2.In the exemplary embodiment of the invention as illustrated on the figure 6 a value of the reference voltage V ref 22 equal to V ref a has been applied to the inverting input - of the amplifier 35 and a value of the display voltage V data 22 equal to V a has been addressed to the transmitter 22 during the image duration T1. This value of the voltage V a continues to be addressed during the new image duration T2.

En conséquence, la somme n = 1 p V data - n

Figure imgb0009
n'est pas modifiée au cours de la deuxième durée d'image T2 et les charges stockées par le condensateur 29 du circuit 3 au cours de la précédente durée d'image T1 ne sont pas modifiées.As a result, the sum Σ not = 1 p V data - not
Figure imgb0009
is not modified during the second image duration T2 and the charges stored by the capacitor 29 of the circuit 3 during the previous image duration T1 are not modified.

De même, lors de l'étape d'éclairage du deuxième émetteur 23, non représentée sur la figure 3, la valeur de la tension d'affichage adressée à l'émetteur 23 est égale à Vb au cours de la première et précédente durée d'image T3 (figure 6), puis est nulle au cours de la durée d'image suivante T4.Similarly, during the lighting step of the second transmitter 23, not shown on the figure 3 , the value of the display voltage addressed to the transmitter 23 is equal to V b during the first and previous image duration T3 ( figure 6 ), then is zero during the next frame duration T4.

En conséquence, la somme n = 1 p V data - n

Figure imgb0010
est simplement diminuée de la valeur Vdata de sorte que l'ensemble des charges accumulées sur le condensateur 29 du circuit 4 est éliminé et que celui-ci présente un potentiel nul, caractéristique d'une diode éteinte.As a result, the sum Σ not = 1 p V data - not
Figure imgb0010
is simply reduced by the value V data so that all the charges accumulated on the capacitor 29 of the circuit 4 is eliminated and that it has a zero potential, characteristic of an off diode.

Avantageusement, on voit que ce dispositif et ce procédé d'affichage permettent d'éviter une phase d'initialisation préalablement à la programmation des circuits d'adressage 3, 4, 5.Advantageously, it can be seen that this device and this display method make it possible to avoid an initialization phase prior to the programming of the addressing circuits 3, 4, 5.

Avantageusement, l'utilisation d'une tension de référence appliquée à l'une des entrées de l'amplificateur 35 et spécifique à chaque colonne d'émetteurs, ou à des groupes de colonnes comme ici des groupes de couleurs différentes, permet avantageusement de réduire la consommation du dispositif d'affichage. En effet, si l'on choisit les valeurs des tensions de référence non seulement de manière à compenser les variations les variations des caractéristiques électriques et/ou lumineuses des émetteurs de différnets colonnes mais également de manière à obtenir une valeur moyenne de tension de référence la plus faible possible pour chaque colonne, on peut décaler d'autant et diminuer les valeurs Vdata des signaux d'affichage, ce qui diminue la puissance électrique à générer par le générateur d'alimentation 39.Advantageously, the use of a reference voltage applied to one of the inputs of the amplifier 35 and specific to each column of transmitters, or groups of columns, as here groups of different colors, advantageously allows to reduce the consumption of the display device. Indeed, if one chooses the values of the reference voltages not only so as to compensate variations variations of the electrical and / or luminous characteristics of the transmitters of different columns but also so as to obtain a mean value of reference voltage the as low as possible for each column, it is possible to shift the V data values of the display signals by a similar amount and decrease, which reduces the electrical power to be generated by the power generator 39.

Dans le cas de la figure 2 de dispositif d'affichage OLED à structure classique, c'est l'anode des émetteurs 22, 23 qui forme l'interface avec la matrice active 1 (diodes à structure « classique ») : le drain (cas type n) ou la source (cas type p) des modulateurs 26, est alors connecté à l'électrode de pilotage 18, et la cathode des émetteurs 22, 23 est connectée à l'électrode 34. L'électrode de pilotage 18 est alors connectée au noeud 42 où se rejoignent l'une des sorties des moyens d'alimentation 36 et l'entrée non-inverseuse + de l'amplificateur 35.In the case of figure 2 of an OLED display device with a conventional structure, it is the anode of the emitters 22, 23 which forms the interface with the active matrix 1 ("conventional" structure diodes): the drain (n-type case) or the source (p-type case) modulators 26, is then connected to the control electrode 18, and the cathode of the emitters 22, 23 is connected to the electrode 34. The control electrode 18 is then connected to the node 42 where join one of the outputs of the power supply means 36 and the non-inverting input + of the amplifier 35.

Toutefois, comme illustré à la figure 11, la présente invention s'applique également à des dispositifs d'affichage à structure dite inversée, dans lesquels la cathode des émetteurs forme l'interface avec la matrice active : le drain (cas type p) ou la source (cas type n) des modulateurs 26 est alors connecté à l'électrode de pilotage 18, et l'anode des émetteurs 22, 23 est connectée à l'électrode 34. L'électrode de pilotage 18 est connectée au noeud 42 où se rejoignent l'une des sorties des moyens d'alimentation 36 et, cette fois, l'entrée inverseuse - de l'amplificateur 35. Ce circuit étant beaucoup plus stable que celui qui a été décrit pour les diodes à structure classique, avantageusement, aucune résistance 44 ni aucune capacité 46 d'équilibrage et/ou de compensation ne sont plus nécessaires. Les signaux d'affichage correspondent alors à des tensions négatives et les courants des diodes sont « tirés » à partir des électrodes d'alimentation 34.However, as illustrated in figure 11 the present invention also applies to display devices with a so-called inverted structure, in which the cathode of the emitters forms the interface with the active matrix: the drain (p type case) or the source (n type case) of the modulators 26 is then connected to the control electrode 18, and the anode of the emitters 22, 23 is connected to the electrode 34. The control electrode 18 is connected to the node 42 where one of the outputs of the supply means 36 and, this time, the inverting input - of the amplifier 35. This circuit being much more stable than that described for conventional structure diodes, advantageously, no resistor 44 nor any capacitor 46 balancing and / or compensation are no longer necessary. The display signals then correspond to negative voltages and the currents of the diodes are "pulled" from the supply electrodes 34.

En variante, le générateur 38 est propre à modifier la tension de référence en fonction du vieillissement des émetteurs ou à abaisser celle-ci dans un mode de basse consommation.As a variant, the generator 38 is able to modify the reference voltage as a function of the aging of the emitters or to lower it in a low consumption mode.

En variante, une tension de référence est associée à chaque colonne d'émetteurs. Dans ce cas, les moyens de stockage 48 comprennent une base de données propre à stocker les valeurs des tensions de référence à appliquer à chaque colonne d'émetteurs.. L'unité de pilotage 50 est apte à rechercher dans cette base de données la valeur de la tension de référence à appliquer à l'entrée inverseuse - de l'amplificateur 35 en fonction de l'identification ou de la position de la colonne de cet émetteur.Alternatively, a reference voltage is associated with each column of transmitters. In this case, the storage means 48 comprise a database suitable for storing the values of the reference voltages to be applied to each column of transmitters. The control unit 50 is able to search in this database for the value the reference voltage to be applied to the inverting input - of the amplifier 35 depending on the identification or position of the column of this transmitter.

Selon l'invention, lors des réglages préalables à la mise en service du dispositif, on établit alors de préférence la différence (Vref x - Vref y) de manière à compenser les différences de caractéristiques électriques et/ou lumineuses des différentes colonnes d'émetteurs.According to the invention, during the settings prior to the putting into service of the device, the difference (V ref x - V ref y ) is preferably established so as to compensate for the differences in electrical and / or luminous characteristics of the different columns of the device. transmitters.

Une partie d'un dispositif d'affichage selon un troisième mode de réalisation de l'invention est illustrée sur la figure 13.Part of a display device according to a third embodiment of the invention is illustrated on the figure 13 .

Les composants électroniques de ce dispositif d'affichage identiques aux composants électroniques du dispositif d'affichage représentés sur la figure 2, ont été référencés avec les mêmes numéros de référence.The electronic components of this display device are identical to the electronic components of the display device shown on the display. figure 2 , have been referenced with the same reference numbers.

Ce dispositif d'affichage comporte des circuits d'adressage 103 reliés, d'une part, à des unités de pilotage d'adressage 20A par des électrodes de colonne 16 et des électrodes de pilotage 18 et, d'autre part, à un circuit de sélection 8 par des électrodes de ligne 14.This display device comprises addressing circuits 103 connected, on the one hand, to addressing control units 20A by means of electrodes of FIG. column 16 and control electrodes 18 and, secondly, to a selection circuit 8 by line electrodes 14.

Le circuit 103 est propre à adresser et à alimenter un émetteur 22 dont la cathode est reliée à une électrode d'alimentation 34.The circuit 103 is suitable for addressing and supplying a transmitter 22 whose cathode is connected to a supply electrode 34.

Il comprend un modulateur de courant 26, trois interrupteurs 28, 106, 108 formés d'un transistor, un condensateur de stockage 29 et une électrode de masse 110.It comprises a current modulator 26, three switches 28, 106, 108 formed of a transistor, a storage capacitor 29 and a ground electrode 110.

Le drain du modulateur 26 est relié à l'anode de l'émetteur 22, de manière à raccorder en série le modulateur 26 et l'émetteur 22. La grille du modulateur 26 est raccordée, d'une part, à une première borne du condensateur 29 et, d'autre part, à une électrode de passage de courant (drain ou source) de l'interrupteur 28, via une ligne électrique 33. L'autre électrode de passage de courant (drain ou source) de l'interrupteur 28 est raccordée à l'électrode de colonne 16. La grille de l'interrupteur 28 est raccordée à l'électrode de ligne 14. La seconde borne du condensateur 29 est raccordée à l'électrode de masse 110. La source du modulateur 26 est raccordée, d'une part, au drain de l'interrupteur 108 et, d'autre part, à une électrode de passage de courant (drain ou source) de l'interrupteur 106. La source de l'interrupteur 108 est raccordée à l'électrode de masse 110. La grille de l'interrupteur 108 est connectée à l'électrode de ligne 14. L'autre électrode de passage de courant (drain ou source) de l'interrupteur 106 est raccordée à l'électrode de pilotage 18. La grille de l'interrupteur 106 est raccordée à l'électrode de ligne 14.The drain of the modulator 26 is connected to the anode of the emitter 22, so as to connect in series the modulator 26 and the emitter 22. The gate of the modulator 26 is connected, on the one hand, to a first terminal of the capacitor 29 and, secondly, a current passage electrode (drain or source) of the switch 28, via an electrical line 33. The other current passage electrode (drain or source) of the switch 28 is connected to the column electrode 16. The gate of the switch 28 is connected to the line electrode 14. The second terminal of the capacitor 29 is connected to the ground electrode 110. The source of the modulator 26 is connected, on the one hand, to the drain of the switch 108 and, on the other hand, to a current flow electrode (drain or source) of the switch 106. The source of the switch 108 is connected to the 110. The gate of the switch 108 is connected to the line electrode 14. The other electrode e current passage (drain or source) of the switch 106 is connected to the control electrode 18. The gate of the switch 106 is connected to the line electrode 14.

L'unité de pilotage 20A a été représentée partiellement. Elle comporte les mêmes composants que l'unité de pilotage représentée sur la figure 2 et fonctionne de la même façon.The control unit 20A has been partially represented. It has the same components as the control unit shown on the figure 2 and works the same way.

L'électrode de pilotage 18 est connectée à l'entrée inverseuse de l'amplificateur opérationnel 35 et à la résistance 40.The control electrode 18 is connected to the inverting input of the operational amplifier 35 and the resistor 40.

L'électrode de colonne 16 est connectée à la sortie de l'amplificateur opérationnel 35.The column electrode 16 is connected to the output of the operational amplifier 35.

L'unité de pilotage 20A est adaptée pour alimenter en puissance et en discontinu successivement chacun des émetteurs 22 des circuits d'adressage 103 d'une colonne 21A par fourniture d'un courant I21 à une des extrémités de la série d'émetteurs 22 - modulateurs 26.The control unit 20A is adapted to successively supply power and discontinue each of the emitters 22 of the addressing circuits 103 of a column 21A by supplying a current I 21 to one of the ends of the series of emitters 22. - modulators 26.

L'entrée non inverseuse de l'amplificateur opérationnel 35 est propre à recevoir une tension de référence destinée aux émetteurs 22 de la colonne 21A et dont la valeur est fonction de la couleur des sous-pixels associés aux émetteurs 22 de cette colonne.The non-inverting input of the operational amplifier 35 is adapted to receive a reference voltage for the emitters 22 of the column 21A and whose value is a function of the color of the sub-pixels associated with the emitters 22 of this column.

La tension d'affichage Vdata à adresser à l'émetteur 22 est appliquée à la résistance 40. Cette tension génère un courant de pilotage qui est appliqué à l'électrode de passage de courant de l'interrupteur 106.The display voltage V data to be addressed to the transmitter 22 is applied to the resistor 40. This voltage generates a control current which is applied to the current-pass electrode of the switch 106.

Au cours d'une phase de rafraîchissement du circuit d'adressage 103, l'électrode de ligne 14 est mise à un état logique O, de sorte que les interrupteurs 28 et 106 sont fermés et l'interrupteur 108 est ouvert.During a refresh phase of the addressing circuit 103, the line electrode 14 is set to a logic state O, so that the switches 28 and 106 are closed and the switch 108 is open.

Une boucle de contre-réaction de l'amplificateur 35 est formée par l'électrode de pilotage 18, l'interrupteur 106, le modulateur 26 et l'interrupteur 28. Cette boucle de contre-réaction permet la stabilisation du courant I21A traversant l'électrode de pilotage 18, de sorte que celui-ci satisfasse la relation suivante : I 21 A = V 21 A - V ref / R .

Figure imgb0011
A feedback loop of the amplifier 35 is formed by the control electrode 18, the switch 106, the modulator 26 and the switch 28. This feedback loop allows the stabilization of the current I 21A passing through the piloting electrode 18, so that it satisfies the following relation: I 21 AT = V 21 AT - V ref / R .
Figure imgb0011

La tension de seuil de déclenchement de la grille du modulateur 26 est compensée par l'amplificateur 35 fonctionnant en contre-réaction et cela indépendamment des caractéristiques du modulateur 26.The tripping threshold voltage of the gate of the modulator 26 is compensated by the amplifier 35 operating in feedback and this independently of the characteristics of the modulator 26.

Puis, la tension à la grille du modulateur 26 est mémorisée dans le condensateur 29.Then, the voltage at the gate of the modulator 26 is stored in the capacitor 29.

Au cours d'une phase de mémorisation du courant I21A, l'électrode de ligne 14 passe à un état logique 1 et, en conséquence, les interrupteurs 28 et 106 sont ouverts et l'interrupteur 108 est fermé.During a storage phase of the current I 21A , the line electrode 14 goes to a logic state 1 and, consequently, the switches 28 and 106 are open and the switch 108 is closed.

Avantageusement, les tensions aux électrodes de drain, de source et de grille du modulateur 26 n'ont pas varié lors du passage de la phase de rafraîchissement à la phase de mémorisation, de sorte que le même courant traverse l'émetteur 22 lors du passage de la phase de rafraîchissement à la phase de mémorisation.Advantageously, the voltages at the drain, source and gate electrodes of the modulator 26 have not varied during the transition from the refresh phase to the storage phase, so that the same current flows through the emitter 22 during the transition from the refresh phase to the storage phase.

Avantageusement, ce dispositif selon le troisième mode de réalisation de l'invention permet de contrôler finement le courant traversant l'émetteur 22, ce qui engendre une échelle de grille précise, une luminosité uniforme et un faible bruit même sur des écrans de haute résolution.Advantageously, this device according to the third embodiment of the invention makes it possible to finely control the current flowing through the emitter 22, which generates a precise grid scale, uniform brightness and low noise even on high resolution screens.

Avantageusement, le temps de programmation de ce dispositif d'affichage est réduit par rapport aux dispositifs d'affichage dépourvus de contre-réaction.Advantageously, the programming time of this display device is reduced compared to display devices without feedback.

Avantageusement, ce dispositif d'affichage autorise d'importantes dispersions sur les caractéristiques et notamment sur la tension de seuil de déclenchement du modulateur 26.Advantageously, this display device allows significant dispersions on the characteristics and in particular on the trigger threshold voltage of the modulator 26.

Claims (16)

  1. Active-matrix image display device (1), comprising:
    - several light emitters (22, 23, 24) forming an array of emitters distributed in rows and columns (21A, 21B), each emitter (22, 23, 24) being designed to be addressed periodically by a voltage (Vdata 22, Vdata 23) of a display signal representative of display data of an image duration (T1, T2, T3, T4); and
    - a current modulator (26) connected in series to each light emitter (22, 23, 24) of the array, so as to form emitter/modulator series, said modulator (26) comprising a source, a drain and a gate, it being possible for a drain current to pass through said modulator so as to supply said emitter (22, 23, 24), for a voltage between either the drain or the source and the gate equal to or greater than a triggering threshold voltage (Vth) of this modulator; and
    - an electric charge storage capacitor (29) designed to maintain a control voltage at the gate of each modulator (26) over said image duration (T1, T2, T3, T4); and
    - select means (8, 14, 15) capable of selecting the emitters (22) of a given row; and
    - drive means (20A, 35, 36, 38, 39, 40, 48) for illuminating the emitters, comprising, for each column (21A), means (36, 39, 40) for supplying these emitters (22, 23, 24) comprising an output (42) connected to one of the terminals (31, 32) of each emitter/modulator series of said column (21A), and at least one operational amplifier (35) for controlling the corresponding modulators (26), said amplifier having an inverting input (-), a non-inverting input (+) and an output, said output of the amplifier (35) being able to be connected to the gate of each modulator (26) of this column (21A) when an emitter (22, 23, 24) connected to this modulator (26) is selected, in order to apply said control voltage to said gate,
    characterized in that either the non-inverting input (+) or the inverting input (-) of the operational amplifier (35) is connected to said output (42) of the power supply means (36, 39, 40) in order to form, with the gate of the modulator (26) connected to the output of the operational amplifier (35), a feedback loop of the operational amplifier (35) when one of said emitters (22, 23, 24) is selected.
  2. Device according to Claim 1, characterized in that one of said terminals (31, 32) of each emitter/modulator series of said column (21A), which is connected to the output (42) of said power supply means (36, 39, 40), corresponds to the drain or to the source of said modulators (26).
  3. Device according to Claim 1 or 2, characterized in that either the non-inverting input (+) or the inverting input (-) of the operational amplifier (35), connected to the output (42) of said power supply means, is designed to receive a signal dependent on the voltage (Vdata 22, Vdata 23) of the display signal intended to be addressed to a selected emitter (22, 23, 24) in said column (21A).
  4. Device according to any one of Claims 1 to 3, characterized in that said power supply means (36, 39, 40) furthermore comprise a drive generator (36, 39, 40) which is designed to supply power discontinuously in succession to each of the emitters (22, 23, 24) of a column (21A) by delivering a drive signal (In) to one of said terminals (31, 32) of the emitter/modulator series corresponding to said emitter, said drive signal (In) being dependent on the voltage (Vdata 22, Vdata 23) of the display signal intended to be addressed to a selected emitter (22, 23, 24) in said column (21A).
  5. Device according to Claim 4, characterized in that said drive generator (36, 39, 40) comprises a voltage generator (39) for generating a display voltage (Vdata 22, Vdata 23) and a resistive element (40) connected in series, and in that the voltage generator (39) is designed to generate a voltage dependent on the voltage of the display signal intended to be addressed to a selected emitter (22, 23, 24) in said column (21A) .
  6. Device according to any one of Claims 1 to 3, characterized in that said power supply means (36, 39, 40) furthermore comprise a drive generator (36, 39, 40) capable of supplying power continuously to all of the emitters (22, 23, 24) of a column (21A) by delivering one and the same drive signal (I) to one of said terminals (31, 32) of each emitter/modulator series of a column (21A), said drive signal (I) being a function of the sum of the voltages (Vdata 22, Vdata 23) of the display signal that are addressed beforehand, and during addressing, to all of the emitters (22, 23) of the column (21A) over an image duration (T1, T2, T3, T4).
  7. Device according to Claim 6, characterized in that said drive generator (36, 39, 40) comprises a voltage generator (39) for generating a display voltage (Vdata 22, Vdata 23) and a resistive element (40) connected in series, and in that the voltage generator (39) is designed to generate a voltage dependent on the sum of the voltages (Vdata 22, Vdata 23) of the display signal that are addressed beforehand, and during addressing, to all of the emitters (22, 23) of the column (21A) over an image duration (T1, T2, T3, T4).
  8. Device according to Claim 7, characterized in that it comprises no means for switching between said output of the power supply means and each of the terminals of the emitter/modulator series of the column.
  9. Device according to either of Claims 7 and 8, characterized in that the voltage generator (39) is connected to the resistive element (40) in order to deliver a drive current (I) obtained from the following equation: I = n = 1 p V data n - V ref n R
    Figure imgb0013

    in which:
    R is the resistance of the resistive element (40);
    Vref n is a reference voltage associated with the emitter n;
    Vdata n is the display voltage addressed to the emitter n; and
    p is the total number of emitters in a column.
  10. Device according to any one of the preceding claims, characterized in that said drive means (20A, 35, 36, 38, 39, 40, 48) furthermore comprise a reference generator (38) capable of delivering a reference signal (Vref) to the other one of either the inverting input (-) or the non-inverting input (+) of the operational amplifier (35).
  11. Device according to Claim 10, characterized in that each emitter (22, 23, 24) has particular electrical and/or optical properties and in that the voltage of each reference signal (Vref) is a function of said electrical and/or optical properties.
  12. Device according to either or Claims 10 and 11, characterized in that each emitter (22, 23, 24) is associated with the illumination with one colour and in that the reference signal (Vref) can be modulated according to the colour assigned to said selected emitter (22, 23, 24).
  13. Device according to either of Claims 10 and 11, characterized in that the emitters (22, 23, 24) are grouped in sets of adjacent emitters (22, 23, 24) each designed to emit a different colour and in that, for each set, said reference signals (Vref) are assigned to the various emitters of this set so that addressing these emitters with the same display signal voltage (Vdata 22, Vdata 23) results in this set emitting white light.
  14. Device according to any one of the preceding claims, characterized in that said drive means (20A, 35, 36, 38, 39, 40, 48) furthermore comprise data storage means (48) designed to store the display signal voltage (Vdata 22, Vdata 23) addressed to each emitter (22, 23) over an image duration (T1, T2, T3, T4).
  15. Method of controlling an active-matrix image display device (1) comprising: several light emitters (22, 23, 24) forming an array of emitters distributed in rows and columns (21A, 21B), each emitter (22, 23, 24) being designed to be addressed periodically by a voltage (Vdata 22, Vdata 23) of a display signal representative of display data over an image duration (T1, T2, T3, T4); a current modulator (26) comprising a source, a drain and a gate, either the drain or the source of each modulator (26) being connected in series to an emitter (22, 23, 24) of the array, so as to form an emitter/modulator series comprising two terminals (31, 32); select means (8, 14, 15) capable of selecting the emitters (22, 23) of a row; an electric charge storage capacitor (29) designed to maintain a control voltage at the gate of the or each modulator (26) over said image duration (T1, T2); and drive means (20A, 35, 36, 38, 39, 40, 48) for illuminating the emitters (22, 23) of a column, comprising, for each column (21A), means (36, 39, 40) for supplying these emitters (22, 23, 24) comprising an output (42) connected to one of the terminals (31, 32) of each emitter/modulator series of said column (21A), and at least one operational amplifier (35) having an inverting input (-), a non-inverting input (+) and an output, the method comprising the following steps:
    - transmission by the select means (8, 14, 15) of a select signal (Vselect) to a row of emitters (22);
    - application by the drive means (20A, 35, 36, 38, 39, 40, 48) of a drive signal (I) to one of the terminals (31, 32) of each emitter/modulator series of a column (21A); and
    - application by the drive means (20A, 35, 36, 38, 39, 40, 48) of a control signal (Vc) to the gate of each modulator (26) connected to the selected emitter (22),
    characterized in that it further includes the following step:
    - selection of a row of emitters in order to form a feedback loop of the operational amplifier (35) with the gate of the modulator (26) connected to the output of the operational amplifier (35) and with either the non-inverting input (+) or the inverting input (-) of the operational amplifier (35), said input being connected to said output (42) of the means (36, 39, 40) for supplying power to these emitters (22, 23).
  16. Method according to Claim 15, characterized in that the drive signal (I) is a function of the sum of the display signal voltages (Vdata 22, Vdata 23) addressed to all of the emitters (22, 23) of the column (21A) over an image duration (T1, T2, T3, T4).
EP05793298A 2004-07-29 2005-07-29 Image display device and display device control method Ceased EP1771838B1 (en)

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EP04292622A EP1622120A1 (en) 2004-07-29 2004-11-04 Active matrix display device and method of driving such a device
PCT/FR2005/002005 WO2006018553A1 (en) 2004-07-29 2005-07-29 Image display device and display device control method
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CN100476937C (en) 2009-04-08
CN101031948A (en) 2007-09-05

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