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EP0488516A2 - Méthode et dispositif pour afficher des niveaux de gris - Google Patents

Méthode et dispositif pour afficher des niveaux de gris Download PDF

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Publication number
EP0488516A2
EP0488516A2 EP91309733A EP91309733A EP0488516A2 EP 0488516 A2 EP0488516 A2 EP 0488516A2 EP 91309733 A EP91309733 A EP 91309733A EP 91309733 A EP91309733 A EP 91309733A EP 0488516 A2 EP0488516 A2 EP 0488516A2
Authority
EP
European Patent Office
Prior art keywords
gray
switches
scale levels
scale
selection
Prior art date
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Withdrawn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
EP91309733A
Other languages
German (de)
English (en)
Other versions
EP0488516A3 (en
Inventor
Terazawa Sadahiro
Yamaguchi Hidefumi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
International Business Machines Corp
Original Assignee
International Business Machines Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by International Business Machines Corp filed Critical International Business Machines Corp
Publication of EP0488516A2 publication Critical patent/EP0488516A2/fr
Publication of EP0488516A3 publication Critical patent/EP0488516A3/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/2007—Display of intermediate tones
    • G09G3/2011—Display of intermediate tones by amplitude modulation
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3685—Details of drivers for data electrodes
    • G09G3/3688—Details of drivers for data electrodes suitable for active matrices only
    • 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
    • G09G2310/0264—Details of driving circuits
    • G09G2310/027—Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters

Definitions

  • the present invention relates to improvements in an active matrix-type liquid crystal display (thereafter abbreviated LCD), more particularly to improvements for displaying multi gray-scale levels.
  • LCD active matrix-type liquid crystal display
  • An active matrix LCD has scan bus lines and data bus lines which perpendicularly intersect each other and liquid crystal cells are connected, through switching elements such as thin-film transistors,to respective intersections of the scan bus lines and the data bus lines. Gray-scale levels are displayed by varying a data voltage under the on-off control of the switching elements.
  • a data driver generates a drive voltage corresponding to digital data indicating a gray-scale level to be displayed.
  • the drive voltage is selected by turning analog switches and needs more analog switches than gray-scale levels to be displayed. If the number of gray-scale levels (digital data) is N and polarity is reversed for each frame by analog switches, then 2 N+1 analog switches are needed for each output. In this case, 2 N+1 DC voltage sources, connected to the data driver, are needed as voltage sources for driving the liquid crystals. Also, if polarity is reversed for each frame by external voltage sources, 2 N analog switches are needed for each output. In this case, 2 N voltage sources for driving the liquid crystals, with the capability of reversing polarity for each frame, are needed.
  • An object of the present invention is to solve the above problem, that is, to provide an economical LCD by decreasing analog switches, voltage sources for driving liquid crystals, and the inputs of data driver which are needed to display gray-scale levels.
  • a method for operating a matrix display device having cells which display a range of gray-scale levels, plural voltage sources and plural switches for selecting said voltage sources to apply drive voltages to the cells in accordance with the gray-scale levels, the method comprising applying the drive voltages through switches which are selected by a selector which translates each gray-scale selection into a selection of one or a combination of the switches, each selection of one or more switches, presenting a drive voltage different from that presented by every other selection whereby the number of voltage sources and switches to operate a cell is less than the number of gray scale values for the cell.
  • a matrix display device having cells which display a range of gray-scale levels, plural voltage sources and plural switches for selecting said voltage sources to apply drive voltages to the cells in accordance with the gray-scale levels, the display device incorporating a selector to translate each gray-scale selection for a cell into a selection of one or a combination of the switches, each selection of one or more switches presenting a drive voltage different from that presented by every other selection of the switches whereby the number of voltage sources and switches to operate a cell is less than the number of gray-scale values for the cell.
  • FIG.1 shows a main circuit of the data driver of a display device according to the present invention.
  • FIG.2 is a table showing the relationship between input data and voltages applied to the data line in the embodiment according to the present invention of Figure 1.
  • FIG.3 shows the outline of the construction of a typical liquid crystal display panel.
  • FIG.4 is a diagram showing a main circuit of the data driver constructed for conventional display of gray-scale levels.
  • FIG.3 shows the outline of a conventional general active matrix LCD constructed so that an intermediate gray-scale level among multi gray-scale levels is displayed.
  • voltage sources 2 for driving liquid crystal are connnected, through liquid crystal driving voltage source buses, to a data driver 1.
  • the data driver 1 is connected to m data lines DL1 to DLm.
  • a scan line driver 3 is connected to n scan lines GL1 to GLn.
  • Each of the data lines DL1 to DLm is connected to respective source electrodes of n thin film transistors (thereafter abbreviated TFTs) 4.
  • Each of the scan lines GL1 to GLn is connected to respective gate electrodes of m TFTs 4. Drainelectrode of each TFT 4 is connected to respective liquid crystal cell 5.
  • a liquid crystal panel 6 is comprised of m n TFTs 4 and the liquid crystal cells 5.
  • FIG.4 is a diagram showing a main circuit of the data driver shown in FIG.3.
  • each of voltages corresponding to eight gray-scale levels can be applied to each data line.
  • liquid crystal driving source buses are connected to eight respective external voltage sources V0 to V7 for driving liquid crystals.
  • the liquid crystal driving source buses are connected to respective analog switches SW0 to SW7.
  • the Switch On resistances of the analog switches SW0 to SW7 are R0 to R7, respectively.
  • the respective ends of the switches (Switch On resistances R0 to R7 in the figure) are connected to a common line and a voltage outputted to the common line is applied to each data line DL.
  • Three-bit input data D1 to D2 are inputted to a selector 11 connected, through eight selection lines, to the eight analog switches SW0 to SW7, respectively.
  • the scan line driver 3 sequentially applies a pulse voltage to the scan lines GL1 to GLn.
  • the TFT 4 when the pulse voltage is applied, will be turned on.
  • one of eight voltages obtained from selecting the analog switches and the source voltages for driving liquid crystals in the data driver in accordance with a predetermined gray-scale levels are applied to display one of eight gray-scale levels. For example, if the input data D0, D1, and D2 are 0, 1, and 0, respectively, in FIG.4, then the selector 11 turns the analog switch SW1 on, other analog switches SW0 and SW2 to SW7 remain turned off, and thus the voltage source V1 is selected and applied to one of the data lines.
  • the selector 11 turns the analog switch SW5 on, other analog switches SW0 to SW4, SW6, and SW7 remain turned off, and thus the voltage source V5 is selected and applied to one of the data lines.
  • the source voltages to be applied to the data lines are varied to realize the display of gray-scale levels.
  • Polarity of a source voltage applied to a data line is usually reversed for each frame.
  • FIG.1 shows a main circuit of a data driver of an embodiment according to the present invention.
  • FIG.2 is a table showing the relationship between input data and a voltage applied to a data line.
  • FIG.1 is the same as FIG.4 except that the number of voltage sources and the number of analog switches is decreased from eight to five.
  • FIG.2 The relationship, which is obtained if data other than above example is inputted, between the states of the analog switches and the voltages applied to the data line is shown in FIG.2.
  • the voltages thus obtained for each data line are applied to respective data lines DL1 to DLm shown in FIG.3.
  • the TFTs 4 are sequentially scanned by the scan line driver 3 synchronously with the application of the voltages to the data lines to sequentially turn on the TFTs 4.
  • a voltage corresponding to a gray-scale level is applied, as described above, to display eight gray-scale levels.
  • liquid crystal driving voltages for displaying two different gray-scale levels are applied to a data line simultaneously to produce an intermediate voltage between the above voltages and display an intermediate gray-scale level between the two gray-scale levels.
  • one driving voltage level or at least two driving voltage levels are supplied to an output to display plural gray-scale levels far each pixel.
  • the present invention has the advantage that by simultaneously applying driving voltages of two levels through two analog switches turned on simultaneously, the number of analog switches, driving sources, and inputs in the data driver are decreased to K/2+1, where K gray scales are required.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Liquid Crystal (AREA)
  • Liquid Crystal Display Device Control (AREA)
EP19910309733 1990-11-28 1991-10-22 Method and apparatus for displaying gray-scale levels Withdrawn EP0488516A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP323432/90 1990-11-28
JP32343290A JPH04194896A (ja) 1990-11-28 1990-11-28 階調表示方法及び装置

Publications (2)

Publication Number Publication Date
EP0488516A2 true EP0488516A2 (fr) 1992-06-03
EP0488516A3 EP0488516A3 (en) 1992-10-28

Family

ID=18154615

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19910309733 Withdrawn EP0488516A3 (en) 1990-11-28 1991-10-22 Method and apparatus for displaying gray-scale levels

Country Status (2)

Country Link
EP (1) EP0488516A3 (fr)
JP (1) JPH04194896A (fr)

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0478386A2 (fr) * 1990-09-28 1992-04-01 Sharp Kabushiki Kaisha Circuit de commande d'un dispositif d'affichage
EP0478371A2 (fr) * 1990-09-28 1992-04-01 Fujitsu Limited Circuit de commande pour un dispositif d'affichage à cristaux liquides
EP0600499A1 (fr) * 1992-12-02 1994-06-08 Nec Corporation Circuit de commande d'un affichage à cristaux liquides
EP0600609A1 (fr) * 1992-10-30 1994-06-08 Sharp Kabushiki Kaisha Circuit de commande pour un dispositif d'affichage
EP0620543A1 (fr) * 1993-04-14 1994-10-19 International Business Machines Corporation Appareil d'affichage à cristaux liquides
EP0631394A1 (fr) * 1993-06-24 1994-12-28 International Business Machines Corporation Dispositif d'affichage à cristaux liquides
EP0707306A3 (fr) * 1994-10-14 1996-07-24 Sharp Kk Circuit d'attaque avec niveaux de gris pour un appareil d'affichage et appareil d'affichage à cristaux liquides qui l'utilise
US5574475A (en) * 1993-10-18 1996-11-12 Crystal Semiconductor Corporation Signal driver circuit for liquid crystal displays
US5583531A (en) * 1991-05-21 1996-12-10 Sharp Kabushiki Kaisha Method of driving a display apparatus
US5621426A (en) * 1993-03-24 1997-04-15 Sharp Kabushiki Kaisha Display apparatus and driving circuit for driving the same
US5703617A (en) * 1993-10-18 1997-12-30 Crystal Semiconductor Signal driver circuit for liquid crystal displays
GB2326013A (en) * 1997-05-31 1998-12-09 Lg Semicon Co Ltd Gate driver circuit for LCD
US6064363A (en) * 1997-04-07 2000-05-16 Lg Semicon Co., Ltd. Driving circuit and method thereof for a display device
US6124840A (en) * 1997-04-07 2000-09-26 Hyundai Electronics Industries Co., Ltd. Low power gate driver circuit for thin film transistor-liquid crystal display (TFT-LCD) using electric charge recycling technique
US6151006A (en) * 1994-07-27 2000-11-21 Sharp Kabushiki Kaisha Active matrix type display device and a method for driving the same

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3560957A (en) * 1966-01-26 1971-02-02 Hitachi Ltd Signal conversion systems with storage and correction of quantization error
EP0391655A2 (fr) * 1989-04-04 1990-10-10 Sharp Kabushiki Kaisha Dispositif de commande d'un appareil d'affichage matriciel à cristaux liquides

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2646523B2 (ja) * 1984-10-26 1997-08-27 旭硝子株式会社 画像表示装置

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3560957A (en) * 1966-01-26 1971-02-02 Hitachi Ltd Signal conversion systems with storage and correction of quantization error
EP0391655A2 (fr) * 1989-04-04 1990-10-10 Sharp Kabushiki Kaisha Dispositif de commande d'un appareil d'affichage matriciel à cristaux liquides

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
IBM TECHNICAL DISCLOSURE BULLETIN. vol. 33, no. 6B, November 1990, NEW YORK US pages 384 - 385; 'Driving method for TFT/LCD gray scale' *
PATENT ABSTRACTS OF JAPAN vol. 12, no. 402 (E-673)25 October 1988 *

Cited By (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0478386A2 (fr) * 1990-09-28 1992-04-01 Sharp Kabushiki Kaisha Circuit de commande d'un dispositif d'affichage
US5686933A (en) * 1990-09-28 1997-11-11 Sharp Kabushiki Kaisha Drive circuit for a display apparatus
EP0478371A3 (en) * 1990-09-28 1992-12-09 Fujitsu Limited Liquid crystal display driver circuitry
US5196738A (en) * 1990-09-28 1993-03-23 Fujitsu Limited Data driver circuit of liquid crystal display for achieving digital gray-scale
US5623278A (en) * 1990-09-28 1997-04-22 Sharp Kabushiki Kaisha Drive circuit for a display apparatus
EP0478371A2 (fr) * 1990-09-28 1992-04-01 Fujitsu Limited Circuit de commande pour un dispositif d'affichage à cristaux liquides
EP0478386A3 (en) * 1990-09-28 1993-07-21 Sharp Kabushiki Kaisha Drive circuit for a display apparatus
US5635950A (en) * 1990-09-28 1997-06-03 Sharp Kabushiki Kaisha Drive circuit for a display apparatus
US5583531A (en) * 1991-05-21 1996-12-10 Sharp Kabushiki Kaisha Method of driving a display apparatus
EP0600609A1 (fr) * 1992-10-30 1994-06-08 Sharp Kabushiki Kaisha Circuit de commande pour un dispositif d'affichage
US5521611A (en) * 1992-10-30 1996-05-28 Sharp Kabushiki Kaisha Driving circuit for a display apparatus
US5534885A (en) * 1992-12-02 1996-07-09 Nec Corporation Circuit for driving liquid crystal device
EP0600499A1 (fr) * 1992-12-02 1994-06-08 Nec Corporation Circuit de commande d'un affichage à cristaux liquides
US5621426A (en) * 1993-03-24 1997-04-15 Sharp Kabushiki Kaisha Display apparatus and driving circuit for driving the same
EP0620543A1 (fr) * 1993-04-14 1994-10-19 International Business Machines Corporation Appareil d'affichage à cristaux liquides
EP0631394A1 (fr) * 1993-06-24 1994-12-28 International Business Machines Corporation Dispositif d'affichage à cristaux liquides
US5574475A (en) * 1993-10-18 1996-11-12 Crystal Semiconductor Corporation Signal driver circuit for liquid crystal displays
US5703617A (en) * 1993-10-18 1997-12-30 Crystal Semiconductor Signal driver circuit for liquid crystal displays
US5719591A (en) * 1993-10-18 1998-02-17 Crystal Semiconductor Signal driver circuit for liquid crystal displays
US5726676A (en) * 1993-10-18 1998-03-10 Crystal Semiconductor Signal driver circuit for liquid crystal displays
US6151006A (en) * 1994-07-27 2000-11-21 Sharp Kabushiki Kaisha Active matrix type display device and a method for driving the same
EP0707306A3 (fr) * 1994-10-14 1996-07-24 Sharp Kk Circuit d'attaque avec niveaux de gris pour un appareil d'affichage et appareil d'affichage à cristaux liquides qui l'utilise
US5923312A (en) * 1994-10-14 1999-07-13 Sharp Kabushiki Kaisha Driving circuit used in display apparatus and liquid crystal display apparatus using such driving circuit
US6064363A (en) * 1997-04-07 2000-05-16 Lg Semicon Co., Ltd. Driving circuit and method thereof for a display device
US6124840A (en) * 1997-04-07 2000-09-26 Hyundai Electronics Industries Co., Ltd. Low power gate driver circuit for thin film transistor-liquid crystal display (TFT-LCD) using electric charge recycling technique
GB2326013A (en) * 1997-05-31 1998-12-09 Lg Semicon Co Ltd Gate driver circuit for LCD
GB2326013B (en) * 1997-05-31 1999-11-24 Lg Semicon Co Ltd A display device

Also Published As

Publication number Publication date
JPH04194896A (ja) 1992-07-14
EP0488516A3 (en) 1992-10-28

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