Method of driving liquid crystal display device

• US 6,590,552 B1
• Filed: 06/25/1999
• Issued: 07/08/2003
• Est. Priority Date: 06/29/1998
• Status: Expired due to Term

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Komiya, Naoaki, Yokoyama, Ryoichi
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): ZAMANI, ALI A
• Application Number:
  US09/340,350
• Time in Patent Office: 1,474 Days
• Field of Search: 345/87, 345/96, 345/206, 345/207, 345/211, 345/208, 345/92, 345/212, 345/213, 345/99, 345/89, 345/94, 345/98, 345/100
• US Class Current: 345/92
• CPC Class Codes: G09G 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• CPC Class Codes: G09G 2320/0219 Reducing feedthrough effects in active matrix panels, i.e. voltage changes on the scan electrode influencing the pixel voltage due to capacitive coupling
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors

Abstract

In a liquid crystal display device where a TFT is connected to each pixel electrode, a storage capacitor voltage V_SC inverted after a fall of a gate voltage V_G is applied to a storage capacitor line provided for each gate line. A pixel voltage V_P retained in a liquid crystal capacitor is influenced by a rise or a fall of the storage capacitor voltage V_SC via the storage capacitor, to then rises or fall. By decreasing the amplitude of a drain voltage V_D and utilizing a direct-current voltage as a common voltage V_com, the device requires less current and power consumption is reduced.

Claims

1. A method of driving a liquid crystal display device comprising a pixel electrode, a switching element connected to said pixel electrode, and a storage capacitor utilizing said pixel electrode as its one electrode, said pixel electrode, said switching element, and said storage capacitor formed for each pixel on a side of a first substrate, a common electrode formed on a side of a second substrate, and liquid crystal provided between said pixel electrode and said common electrode, said method comprising the step of:

applying, to the other electrode of said storage capacitor formed for each pixel, a storage capacitor voltage that changes from a low level to a high level immediately after said switching element is turned off during a period in which a voltage of said pixel electrode to which said switching element is connected is higher than that of said common electrode, and that changes from the high level to the low level immediately after said switching element is turned off during a period in which the voltage of said pixel electrode is lower than that of said common electrode.

2. The method of driving a liquid crystal display device according to claim 1, wherein the voltage of said common electrode is a direct-current voltage.

3. The method of driving a liquid crystal display device according to claim 2, wherein the voltage of said common electrode is set as being lower by a prescribed voltage than a central voltage of a display signal voltage applied to said switching element.

4. The method of driving a liquid crystal display device according to claim 3, wherein a potential difference between the central voltage and the voltage of said common electrode is a potential difference in accordance with an amount of change in the voltage of said pixel electrode connected to said switching element exhibited when said switching element is turned off.

5. A method of driving a liquid crystal display device comprising a pixel electrode, a switching element connected to said pixel electrode, and a storage capacitor utilizing said pixel electrode as its one electrode, said pixel electrode, said switching element, and said storage capacitor formed for each pixel on a side of a first substrate, a common electrode formed on a side of a second substrate, and liquid crystal provided between said pixel electrode and said common electrode, said method comprising the steps of:

applying a direct-current voltage to said common electrode; and

applying, to the other electrode of said storage capacitor formed for each pixel, a storage capacitor voltage, a level of which changes during a period in which said switching element corresponding to said storage capacitor is off.

6. The method of driving a liquid crystal display device according to claim 5, wherein said storage capacitor voltage changes from a low level to a high level during a period in which said switching element is off, and in which the voltage of said pixel electrode is higher than that of said common electrode;

and changes from the high level to the low level during a period in which the voltage of said pixel electrode is lower than that of said common electrode.

7. The method of driving a liquid crystal display device according to claim 6, wherein said storage capacitor voltage changes from the low level to the high level, or from the high level to the low level, immediately after said switching element is turned off.

8. The method of driving a liquid crystal display device according to claim 7, wherein the voltage of said common electrode is set lower than a central voltage of a display signal voltage applied to said switching element by a prescribed voltage.

9. The method of driving a liquid crystal display device according to claim 8, wherein a potential difference between the central voltage and the voltage of said common electrode is a potential difference in accordance with an amount of change in the voltage of said pixel electrode connected to said switching element exhibited when said switching element is turned off.

10. A method of driving a liquid crystal display device comprising a pixel electrode, a switching element connected to said pixel electrode, and a storage capacitor utilizing said pixel electrode as its one electrode, said pixel electrode, said switching element, and said storage capacitor formed for each pixel on a side of a first substrate, a common electrode formed on a side of a second substrate, and liquid crystal provided between said pixel electrode and said common electrode, said method comprising the step of:

applying, to the other electrode of said storage capacitor formed for each pixel, a storage capacitor voltage, a level of which changes during a period in which said switching element corresponding to said storage capacitor is off.