Active matrix type display and a driving method thereof

• US 7,002,541 B2
• Filed: 10/04/2001
• Issued: 02/21/2006
• Est. Priority Date: 10/06/2000
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Kumada, Kouji, Yanagi, Toshihiro, Ohta, Takashige, Mizukata, Katsuya
• Primary Examiner(s): NGUYEN, CHANH DUY
• Application Number:
  US09/974,297
• Publication Number:
  US 20020041281A1
• Time in Patent Office: 1,601 Days
• Field of Search: 345/87, 345/90, 345/92, 345/94, 345/98, 345/99, 345/100, 345/204, 345/205, 345/211, 349/33, 349/34, 349/37, 349/38, 349/39, 349 46- 47
• US Class Current: 345/92
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

In an active matrix type display device, a signal voltage is applied from a signal line driving circuit via an active element such as a TFT to display electrodes on a matrix substrate, and a common voltage is applied to a counter electrode on a facing substrate so that the common voltage is shared by respective display cells. A level of the common voltage is switched in every refresh period of a different length. Thus, it is possible to appropriately set a value of the common voltage which is a reference for specifying an effective voltage of positive polarity and an effective voltage of negative polarity according to the refresh periods. As a result, even when the refresh periods of a different length exist in a mixed manner, it is possible to equalize the effective voltage of positive polarity and the effective voltage of negative polarity so as to suppress an occurrence of a flicker.

Claims

1. A driving method of an active matrix display device which includes plural display electrodes provided in a matrix manner, a counter electrode which is provided so that the counter electrode faces the display electrodes and a common voltage is applied to the counter electrode, an active element for applying a signal voltage to the display electrodes when a scanning line is selected, a storage capacitor for storing a driving voltage which is determined by the signal voltage applied to the display electrodes and the common voltage applied to the counter electrode, wherein

a level of the common voltage is varied according to a length of an applying-storing period for applying the signal voltage and storing the driving voltage, such that a lower common voltage is applied during a shorter applying-storing period, and a higher common voltage is applied during a longer applying-storing period.

2. The driving method of the active matrix display device set forth in claim 1, wherein plural d.c. voltages are used as the common voltage so as to switch the d.c. voltages in every applying-storing period of a different length.

3. The driving method of the active matrix display device set forth in claim 1, wherein an a.c. voltage is used as the common voltage so as to vary a level of a mean potential of an amplitude of the a.c. voltage in every applying-storing period of a different length.

4. The driving method of the active matrix display device set forth in claim 1, wherein an a.c. voltage is used as the common voltage so as to vary an amplitude of the a.c. voltage in every applying-storing period of a different length.

5. The driving method of the active matrix display device set forth in claim 1, wherein after a scanning period in which the signal voltage is applied to the display electrodes of one screen, a non-scanning period, longer than the scanning period, in which the signal voltage is not applied is provided.

6. The driving method of the active matrix display device set forth in claim 1, wherein said active matrix type display device is a reflecting active matrix type display device including reflecting electrodes in the display electrodes.

7. A driving method of an active matrix display device which includes plural display electrodes provided in a matrix manner, a counter electrode which is provided so that the counter electrode faces the display electrodes and a common voltage is applied to the counter electrode, an active element for applying a signal voltage to the display electrodes when a scanning line is selected, a storage capacitor for storing a driving voltage which is determined by the signal voltage applied to the display electrodes and the common voltage applied to the counter electrode, wherein

a level of the signal voltage is varied according to a length of an applying-storing period for applying the signal voltage and storing the driving voltage, such that a lower common voltage is applied during a shorter applying-storing period, and a higher common voltage is applied during a longer applying-storing period.

8. The driving method of the active matrix display device set forth in claim 7, wherein plural d.c. voltages are used as the signal voltage so as to switch the d.c. voltages in every applying-storing period of a different length.

9. The driving method of the active matrix display device set forth in claim 7, wherein a level of a signal voltage is varied with respect to only one of the polarities of the signal voltage which are reversed in every adjacent applying-storing period.

10. The driving method of the active matrix display device set forth in claim 7, wherein a level of the signal voltage is varied with respect to both polarities of the signal voltage which are reversed in every adjacent applying-storing period.

11. The driving method of the active matrix display device set forth in claim 7, wherein an a.c. voltage is used as the signal voltage so as to vary a level of a mean potential of an amplitude of the a.c. voltage in every applying-storing period of a different length.

12. The driving method of the active matrix display device set forth in claim 7, wherein an a.c. voltage is used as the signal voltage so as to vary an amplitude of the a.c. voltage in every applying-storing period of a different length.

13. The driving method of the active matrix display device set forth in claim 7, wherein after a scanning period in which the signal voltage is applied to the display electrodes of one screen, a non-scanning period, longer than the scanning period, in which the signal voltage is not applied is provided.

14. The driving method of the active matrix display device set forth in claim 7, wherein said active matrix type display device is a reflecting active matrix type display device including reflecting electrodes in the display electrodes.

15. An active matrix display device comprising:

plural display electrodes provided in a matrix manner;

a counter electrode which is provided so that the counter electrode faces the display electrodes and a common voltage is applied to the counter electrode;

an active element for applying a signal voltage to the display electrodes when a scanning line is selected;

a storage capacitor for storing a driving voltage which is determined by the signal voltage applied to the display electrodes and the common voltage applied to the counter electrode; and

level varying means for varying a level of the common voltage according to a length of an applying-storing period in which the signal voltage is applied and the driving voltage is stored, such that a lower common voltage is applied during a shorter applying-storing period, and a higher common voltage is applied during a longer applying-storing period.

16. The active matrix display device set forth in claim 15, wherein said level varying means includes voltage switching means by which plural d.c. voltages as the common voltage are switched in every applying-storing period of a different length.

17. The active matrix display device set forth in claim 16, wherein said voltage switching means is provided so as to correspond itself to the applying-storing period, and includes voltage setting means for setting the d.c. voltages, and applies a current only to a selected voltage setting means.

18. The active matrix display device set forth in claim 15, wherein said level varying means varies a level of a mean potential of an amplitude of an a.c. voltage as the common voltage in every applying-storing period of a different length.

19. The active matrix display device set forth in claim 15, wherein said level varying means includes amplitude varying means which varies an amplitude of an a.c. voltage as the common voltage in every applying-storing period of a different length.

20. An active matrix display device comprising:

plural display electrodes provided in a matrix manner;

a counter electrode which is provided so that the counter electrode faces the display electrodes and a common voltage is applied to the counter electrode;

an active element for applying a signal voltage to the display electrodes when a scanning line is selected;

a storage capacitor for storing a driving voltage which is determined by the signal voltage applied to the display electrodes and the common voltage applied to the counter electrode; and

level varying means for varying a level of the signal voltage according to a length of an applying-storing period in which the signal voltage is applied and the driving voltage is stored, such that a lower common voltage is applied during a shorter applying-storing period, and a higher common voltage is applied during a longer applying-storing period.

21. The active matrix display device set forth in claim 20, wherein said level varying means includes voltage varying means by which plural d.c. voltages as the signal voltage are switched in every applying-storing period of a different length.

22. The active matrix display device set forth in claim 21, wherein said voltage switching means is provided so as to correspond itself to the applying-storing period, and includes voltage setting means for setting the d.c. voltages, and applies a current only to a selected voltage setting means.

23. The active matrix display device set forth in claim 20, wherein said level varying means varies a level of the signal voltage with respect to only one of the polarities of the signal voltage which are reversed in every adjacent applying-storing period.

24. The active matrix display device set forth in claim 20, wherein said level varying means varies a level of the signal voltage with respect to both polarities of the signal voltage which are reversed in every adjacent applying-storing period.

25. The active matrix display device set forth in claim 20, wherein said level varying means varies a level of a mean potential of an amplitude of an a.c. voltage as the signal voltage in every applying-storing period of a different length.

26. The active matrix display device set forth in claim 20, wherein said level varying means includes amplitude varying means which varies an amplitude of an a.c. voltage as the signal voltage in every applying-storing period of a different length.