EP1879171A1 - Organische Elektrolumineszenzanzeige - Google Patents

Organische Elektrolumineszenzanzeige Download PDF

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Publication number
EP1879171A1
EP1879171A1 EP06300786A EP06300786A EP1879171A1 EP 1879171 A1 EP1879171 A1 EP 1879171A1 EP 06300786 A EP06300786 A EP 06300786A EP 06300786 A EP06300786 A EP 06300786A EP 1879171 A1 EP1879171 A1 EP 1879171A1
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EP
European Patent Office
Prior art keywords
voltage
electroluminescent
electroluminescent display
column electrode
amplifier
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP06300786A
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English (en)
French (fr)
Inventor
Philippe Le Roy
David Vaufrey
Christophe Prat
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Thomson Licensing SAS
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Thomson Licensing SAS
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Publication date
Application filed by Thomson Licensing SAS filed Critical Thomson Licensing SAS
Priority to EP06300786A priority Critical patent/EP1879171A1/de
Publication of EP1879171A1 publication Critical patent/EP1879171A1/de
Withdrawn legal-status Critical Current

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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
    • G09G3/3233—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix with pixel circuitry controlling the current through the light-emitting element
    • G09G3/3241—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix with pixel circuitry controlling the current through the light-emitting element the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror
    • G09G3/325—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix with pixel circuitry controlling the current through the light-emitting element the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror the data current flowing through the driving transistor during a setting phase, e.g. by using a switch for connecting the driving transistor to the data driver
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3275—Details of drivers for data electrodes
    • G09G3/3283—Details 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
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2300/00—Aspects of the constitution of display devices
    • G09G2300/04—Structural and physical details of display devices
    • G09G2300/0421—Structural details of the set of electrodes
    • G09G2300/043—Compensation electrodes or other additional electrodes in matrix displays related to distortions or compensation signals, e.g. for modifying TFT threshold voltage in column driver
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2300/00—Aspects of the constitution of display devices
    • G09G2300/08—Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
    • G09G2300/0809—Several active elements per pixel in active matrix panels
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
    • G09G2310/0262—The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0242—Compensation of deficiencies in the appearance of colours
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/029—Improving the quality of display appearance by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
    • G09G2320/0295—Improving 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
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/043—Preventing or counteracting the effects of ageing
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/043—Preventing or counteracting the effects of ageing
    • G09G2320/045—Compensation of drifts in the characteristics of light emitting or modulating elements

Definitions

  • the present invention relates to an electroluminescent display of the active matrix type.
  • a display comprises a large number of pixel circuits, each of which comprises an electroluminescent device, such as an OLED (Organic Light Emitting Diode) and a current modulator associated to it, which is programmable to supply its electroluminescent device with a continuous operating current.
  • the current modulator comprises a number of transistors which must be formed on a same substrate with the respective electroluminescent devices and which must be addressable for programming.
  • the transistors and other components of the current modulators occupy substrate space which is not available for the electroluminescent devices.
  • the portion of the display surface occupied by the electroluminescent devices should be as high as possible. Therefore considerable development efforts have been invested in the development of simple and space-saving current modulators.
  • WO 2005/013250 describes a current modulator formed of a switch, a capacitor and a drive transistor which controls the current flowing through an OLED based on a control voltage which is selectively admitted to the storage capacitor and the control electrode of the drive transistor by the switch.
  • This current modulator is simple and space-saving, but the image quality that can be obtained using it is not satisfactory. The reason for this is in the quality of the drive transistor.
  • Display substrates may be based on poly-crystalline silicon (Poly-Si) or hydrogenated amorphous silicon (a-Si:H).
  • Thin film transistors manufactured on a poly-Si substrate tend to have large manufacturing tolerances: crystal borders are distributed stochastically in the different conductivity regions of the transistors, causing performance characteristics of the transistors such as threshold voltage, slope, etc. to vary from one transistor to the next, so that the luminosity of OLEDs may be different although the same programming voltage is applied to their drive transistors.
  • transistors having closely similar performance characteristics can be manufactured, but the inherent meta-stability of the amorphous silicon layer causes these performance characteristics to drift, so that a good image quality cannot be maintained for a long time.
  • the object of the present invention is, therefore, to provide an electroluminescent display device in which locally or temporally variable thresholds of drive transistors of the electroluminescent devices are compensated for without substantially increasing the number of necessary contacts between a substrate on which the electroluminescent devices are formed and peripheral circuitry.
  • an electroluminescent display device comprising a plurality of pixel circuits formed on a substrate and connected to a common electrode, wherein each pixel circuit comprises a drive transistor and an electroluminescent device connected in series between first and second supply potentials via an intermediate node, a voltage storage element connected to a control electrode of said drive transistor, a first switch for connecting and disconnecting said voltage storage element and said column electrode, and a second switch, by the fact that the second switch is arranged to connect and disconnect said intermediate node and said column electrode, and that control means are provided for closing not more than one of said first and second switches at a time.
  • This arrangement allows for using the common column electrode for extracting a voltage at said intermediate node, from which a threshold voltage of the drive transistor can be inferred, whenever the common column electrode is not in use for programming the pixel circuits associated to it.
  • the luminosity is proportional to the intensity of a current flowing in the device.
  • the display preferably further comprises a drive voltage compensator which is controlled by the device current control signal, for determining a first voltage which, when applied to the electroluminescent device of one of said pixel circuits, will cause a current of the desired intensity to flow through said electroluminescent device, and a second voltage corresponding to a voltage between the control electrode and the intermediate node of said pixel circuit in case of a current of the desired intensity flowing through its drive transistor, and outputting, at an output terminal, a sum of said first and second voltages to the control electrode.
  • the first voltage may conveniently be determined based on a voltage/intensity characteristic of the OLED.
  • the drive voltage compensator therefore preferably comprises a memory for storing a definition of such a characteristic.
  • the definition may e. g. be in the form of an algorithm for carrying out by a digital processor or of a lookup table.
  • the definition of the characteristic may be built into the drive voltage compensator at the time of manufacturing, without a need for a later update.
  • a certain aging may be observed, so that for these a possibility of updating the characteristic may be appropriate, as will be further detailed in a later section of the this description.
  • the drive voltage compensator therefore preferably has an input connected to the common electrode for detecting the voltage applied to the OLED. Further, memory means for storing a threshold voltage obtained from the voltage applied to the OLED should be provided.
  • one value of the threshold voltage may be assumed to be appropriate for all drive transistors, and a same storage cell of said memory means may be associated to all pixel circuits of the display.
  • each pixel circuit may have a storage cell of said memory means associated to it for storing therein the threshold voltage of the drive transistor of said pixel circuit.
  • the substrate is a poly-Si substrate manufactured by annealing an amorphous silicon layer by scanning it with a laser beam
  • transistors formed along a scanning line of the laser beam may have rather homogeneous characteristics.
  • storage space may be saved if the pixel circuits are divided into groups, the pixel circuits of a same group being arranged along a same line on the substrate, and a storage cell of said memory means is associated to each said groups for storing the threshold voltage.
  • a charging current should be provided at low impedance.
  • a first amplifier may be provided which has a first input connected to the output port of the voltage compensator for receiving a voltage signal representative of a desired current intensity in the electroluminescent devices and an output coupled to the voltage storage elements.
  • the amplifier is selectively coupled to the voltage storage elements of all pixel circuits associated to a same common column electrode via said common column electrode.
  • the first amplifier may be a differential amplifier which has a second input coupled to the common column electrode. In this way, the first amplifier may operate at unity gain.
  • a second amplifier may be provided, which has an input coupled to the common column electrode and an output coupled to the input of the voltage compensator, for providing the voltage compensator with the voltage present at the intermediate node.
  • This second amplifier may also preferably operate at unity gain, providing a signal at the voltage level of the intermediate node, to which a load may be applied without influencing the voltage at the intermediate node.
  • the output of the first amplifier preferably has a high impedance state. This state can be activated when the voltage at the intermediate node is applied to the input of the second amplifier.
  • the two amplifiers are prevented from influencing each other by implementing them in a same amplifier, which may fulfil the functions of both in a time-multiplexed manner.
  • the first switch is preferably provided between the output of said same amplifier and the common column electrode, and the second switch is provided between the common column electrode and the first input of the amplifier.
  • these devices may have a first electrode connected to the intermediate node and a second electrode connected to the second supply potential by a third switch, and a resistor provided between the first input of the first amplifier and the second supply potential allows to deviate a current flowing through the drive transistor into the resistor in order to estimate its intensity.
  • the electroluminescent devices may have their second electrodes connected together, so that a single third switch connected between these second electrodes and the second supply potential is sufficient for interrupting the current in all of the electroluminescent devices.
  • Fig. 1 is a block diagram of a display device according to the present invention. It comprises a large number of pixel circuits 1 arranged in a pattern of rows and columns on a silicon thin film substrate made of amorphous or polycrystalline silicon. In the drawing, only two rows and two columns are illustrated, but it is obvious a skilled person that an arbitrary number of rows and columns may be provided. All pixel circuits 1 belonging to a same column are connected to a common column electrode 2. All pixel circuits 1 that belong to a same row are connected to a same row selection circuit 17 by common first and second row select lines 3, 4.
  • the first row select line 3 is connected to a gate of a first thin film transistor (TFT) 5, which has one of its current electrodes connected to the common column electrode 2 and its other current electrode to a first plate of a storage capacitor 6 and to a gate of a drive transistor 7.
  • TFT thin film transistor
  • the drive transistor 7 has its drain connected to the other plate of the storage capacitor 6 and to a positive supply potential Vdd, whereas its source is connected to the anode of an OLED 8 via an intermediate node 9.
  • the cathode of the OLED 8 is connected to ground GND.
  • the second row select line 4 is connected to a gate of a second TFT 10 in each pixel circuit.
  • Current electrodes of the second TFT are connected to the column electrode 2 of the pixel circuit 1, on the one hand, and to the intermediate node 9 thereof, on the other.
  • a controller circuit 11 has an input terminal 12 for receiving a video signal VIDEO of arbitrary conventional type which specifies a desired luminosity of each of the OLEDs 8, and a plurality of output terminals 13, each of which is coupled to an associated one of the common column electrodes 2 by a first operational amplifier 14.
  • the operational amplifier 14 has its output terminal connected to an inverting input terminal, so as to provide unity gain.
  • the controller circuit 11 further has a plurality of feedback input terminals 15, one per column, each of which is coupled to the common column electrode 2 associated to it by a second operational amplifier 16.
  • the amplifiers 16, too have their output terminals connected to respective inverting input terminals, so as to provide unity gain.
  • the controller circuit 11 Based on desired intensity information it extracts from the input video signal VIDEO for a given row of pixel circuits 1, the controller circuit 11 derives a programming voltage V data for each pixel circuit 1 of that row, which is representative of the desired luminosity of the OLED 8 of that pixel circuit.
  • the first amplifier 14 outputs the programming voltages V data to each column electrode 2.
  • the row selection circuit 17 of the row to which the output programming voltages V data correspond controls the first TFTs 5 of that row to be conductive, whereas the second TFTs 10 of that row and first and second TFTs of all other rows are kept non-conductive.
  • the programming voltage V data is applied to the first plate of the storage capacitor 6 and to the gate of drive transistor 7. After a short time, the first TFT 5 is made non-conductive again, so that the programming voltage V data remains stored in the storage capacitor 6 and continues to be applied to the gate of drive transistor 7.
  • V GS voltage at intermediate node 9
  • V data -V GS V OLED .
  • the luminosity of each OLED 8 is directly proportional to the current I OLED flowing through it, and the current I OLED is a function of V OLED which varies very little during the lifetime of the OLED.
  • the controller circuit 11 determines the programming voltage V data for each pixel circuit 1 as follows: based on the desired luminosity of the OLED 8, an appropriate OLED current I OLED is determined. Based on the current/voltage characteristic of the OLEDs, which may be represented in a memory 18 of control circuit 11 in the form of a look-up table or of an algorithm, the controller circuit 11 determines an appropriate OLED voltage V OLED . In order to provide this voltage at the intermediate node, the programming voltage V data output by controller circuit 11 must compensate the gate-source voltage drop V GS of drive transistor 7, i. e.
  • V data V GS + V OLED must hold.
  • the controller circuit 11 is able to provide a programming voltage V data that will yield correct luminosity values for the OLED of each pixel circuit 1, regardless of variations of the threshold voltage between the drive transistor 7 of different pixel circuits 1.
  • the threshold voltages of said drive transistors 7 are obtained in an initialisation procedure which will be described in the following.
  • the initialisation procedure does not have to be carried out at the frame rate or image rate of the input video signal VIDEO; it is sufficient to carry it out e.g. whenever the display is switched on.
  • each pixel circuit 1 Upon initialisation, each pixel circuit 1 is first supplied with a programming voltage V data of arbitrary value.
  • V data has been stored in storage capacitor 6 of a given pixel circuit 1, and its first TFT 5 has become non-conductive
  • amplifier 14 associated to the common column electrode 2 of that pixel circuit is controlled to assume a high impedance state at its output, and row selection circuit 17 activates second row select line 4, causing second TFT 10 to become conductive, whereby the voltage V OLED at intermediate node 9 is output to common column electrode 2.
  • Vth V GS - Id / K
  • the threshold voltage Vth is written into storage cells of a memory 19 for each drive transistor 7.
  • the above-described initialisation can be shortened if the drive transistors 7 are formed along laser scanning lines on a poly-Si substrate obtained by laser annealing of an amorphous silicon layer.
  • annealing conditions are homogeneous along a scanning line, performance characteristics of a group of transistors formed along a same scanning line are closely similar, so that it is sufficient to determine the threshold voltage only for one of these transistors and to use the obtained threshold voltage later for driving all transistors of the group.
  • threshold voltages of the drive transistor 7 are likely to be closely similar to one another, but they tend to drift over the lifetime of the display. In that case, the initialisation may be reduced to determining the threshold voltage Vth of just one of the drive transistors 7, so that during normal operation the programming voltage V data is calculated based on this threshold voltage Vth for all drive transistors 7 of the display.
  • Fig. 2 shows the controller circuit 11 and circuitry connecting it to a common column electrode 2 according to a second embodiment of the invention.
  • the structure of the pixel circuits 1 and the row selection circuits 17 in this second embodiment is the same as in the first one and is not shown and described again.
  • the two operational amplifiers 14, 16 are replaced by a single operational amplifier 20 and first and second switches 21, 22, of which the first one 21 is provided between an output terminal of operational amplifier 20 and the common column electrode 2, and the second one 22 is provided between the common column electrode 2 and a non-inverting input terminal of amplifier 20.
  • the output terminal of amplifier 20 is further directly connected to feedback input terminal 15 of controller circuit 11.
  • switch 21 is closed and switch 22 is open, causing the operational amplifier 20 to assume the functions of first amplifier 14 of Fig. 1.
  • switch 22 is closed, and switch 21 is open, causing amplifier 20 to assume the functions of second amplifier 16 of Fig. 1. Since the two amplifiers 14, 16 of Fig. 1 must not operate simultaneously anyway, the embodiment of Fig. 2 very conveniently reduces hardware complexity without reducing the performance of the display.
  • Fig. 3 illustrates a third embodiment of the display in a block diagram analogous to Fig. 1.
  • a resistor 24 is provided between each common column electrode 2 and the ground potential, and all OLEDs 8 have a common cathode 25 which is formed by a transparent thin metal layer extending all over the substrate, which is coupled to ground by a fourth switch 26 controlled by controller circuit 11.
  • controller circuit 11 When the third switch 23 is open and the fourth switch 26 is closed, the display of Fig. 3 is capable of operating just as described with respect to Fig. 1.
  • Vth can be reliably obtained for every drive transistor (7) regardless of a possible drift of the current-voltage characteristic of the OLEDs 8.
  • Fig. 3 may be simplified in analogy to Fig. 2 by substituting a single operational amplifier 20 and first and second switches 21, 22 for the two amplifiers 14, 16 of Fig. 3. It should be noted that in this embodiment, there are no more third switches 23, either, since in the circuit design of Fig. 4, in programming operation mode, with switch 21 closed and switch 22 open, switch 22 separates resistor 25 from column electrode 2, so that no drain current Id from drive transistor 7 is lost to resistor 25, and the entire drain current Id passes OLED 8 instead.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
EP06300786A 2006-07-10 2006-07-10 Organische Elektrolumineszenzanzeige Withdrawn EP1879171A1 (de)

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Application Number Priority Date Filing Date Title
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2081177A3 (de) * 2008-01-21 2009-12-16 Samsung Mobile Display Co., Ltd. Organische lichtemittierende Anzeige und Verfahren zu ihrem Antrieb
JP2011170313A (ja) * 2010-02-19 2011-09-01 Samsung Mobile Display Co Ltd 表示装置及びその駆動方法
CN104361861A (zh) * 2014-11-20 2015-02-18 昆山国显光电有限公司 一种有机电致发光装置
WO2024139025A1 (zh) * 2022-12-26 2024-07-04 惠科股份有限公司 像素驱动电路、电阻补偿方法以及显示面板

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040046719A1 (en) * 2002-08-16 2004-03-11 Wen-Chun Wang Active organic light emitting diode drive circuit
FR2857146A1 (fr) * 2003-07-03 2005-01-07 Thomson Licensing Sa Dispositif d'affichage d'images a matrice active
WO2005109389A1 (en) * 2004-05-06 2005-11-17 Thomson Licensing Circuit and control method for a light-emitting display
US20060139253A1 (en) * 2004-12-24 2006-06-29 Choi Sang M Pixel and light emitting display

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040046719A1 (en) * 2002-08-16 2004-03-11 Wen-Chun Wang Active organic light emitting diode drive circuit
FR2857146A1 (fr) * 2003-07-03 2005-01-07 Thomson Licensing Sa Dispositif d'affichage d'images a matrice active
WO2005109389A1 (en) * 2004-05-06 2005-11-17 Thomson Licensing Circuit and control method for a light-emitting display
US20060139253A1 (en) * 2004-12-24 2006-06-29 Choi Sang M Pixel and light emitting display

Cited By (7)

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