Liquid crystal display device

• US 20040041773A1
• Filed: 08/01/2003
• Published: 03/04/2004
• Est. Priority Date: 08/02/2002
• Status: Active Grant

• Current Assignee: Vista Peak Ventures LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: NEC LCD Technologies Limited (Tianma Microelectronics Company Limited)
• Inventors: Takeda, Hiroshi, Hirano, Youji
• Granted Patent: US 7,151,516 B2
• Time in Patent Office: Days
• US Class Current: 345/98
• CPC Class Codes: G09G 2330/023 using energy recovery or conservation
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors

Abstract

An active matrix liquid crystal display device operates such that the polarity of a voltage on a common electrode 30 is inverted by row or by frame. A charge collection/resupply circuit includes a switch connected between the common electrode and a common voltage output buffer, a charge collection capacitor, and a switch connected between a connection point of the common electrode and the switch and the charge collection capacitor. The switch control unit is configured to operate such that immediately before a polarity of a common voltage VCOM10 is inverted, the switch 11 is turned off and then the switch 12 is turned on, and further, after inversion of the polarity of the common voltage VCOM, the switch is turned off and then the switch is turned on.

Claims

1. An active matrix liquid crystal display device configured to invert a polarity of a voltage on a common electrode by row or by frame, comprising:

a common voltage supply circuit provided to supply a common voltage VCOM10 to said common electrode; and

a charge collection and resupply circuit connected between said common electrode and said common voltage supply circuit, said charge collection and resupply circuit including;

a first switch connected between said common electrode and said common voltage supply circuit;

a charge collection capacitor;

a second switch connected between a connection point of said common electrode and said first switch and said charge collection capacitor;

a switch control unit provided to control turning on and off of said first and second switches, said switch control unit being configured to operate such that immediately before a polarity of said common voltage VCOM10 is inverted, said first switch is turned off and then said second switch is turned on, and further, after inversion of said polarity of said common voltage VCOM10, said second switch is turned off and then said first switch is turned on.

3. The liquid crystal display device according to claim 1, further comprising a DC level shift circuit provided to invert a polarity of a common voltage and disposed in a stage prior to said charge collection and resupply circuit.

5. The liquid crystal display device according to claim 1, further comprising a DC level shift circuit provided to invert a polarity of a common voltage and disposed in a stage subsequent to said charge collection and resupply circuit.

7. The liquid crystal display device according to claim 5, wherein said DC level shift circuit includes:

a coupling and DC blocking capacitor connected between said charge collection and resupply circuit and said common electrode;

a first bias voltage generation resistor connected between said common electrode and a first power supply; and

a second bias voltage generation resistor connected between said common electrode and a second power supply.

2. An active matrix liquid crystal display device configured to invert a polarity of a voltage on a common electrode by row or by frame, comprising:

a common voltage supply circuit provided to supply a common voltage VCOM10 to said common electrode; and

a charge collection and resupply circuit connected between said common electrode and said common voltage supply circuit, said charge collection and resupply circuit including;

a first switch connected between said common electrode and said common voltage supply circuit;

a positive charge collection capacitor;

a negative charge collection capacitor;

a second switch connected between a connection point of said common electrode and said first switch and said positive charge collection capacitor;

a third switch connected between said connection point and ground;

a fourth switch connected between said connection point and said negative charge collection capacitor; and

a switch control unit provided to control turning on and off of said first through fourth switches, said switch control unit being configured to operate such that immediately before a polarity of said common voltage VCOM10 is inverted from a positive polarity to a negative polarity, said first switch is turned off and then said second switch is turned on and held in an on-state during a specific period of time and then said polarity is inverted while said third switch is being in an on-state during a specific period of time, and subsequently, after said fourth switch is being in an on-state during a specific period of time, said first switch is turned on, and immediately before said common voltage VCOM10 is inverted from a negative polarity to a positive polarity, said first switch is turned off and then said fourth switch is turned on and held in an on-state during a specific period of time, and then, said polarity is inverted while said third switch is being in an on-state during a specific period of time, and thereafter, said second switch is turned on and held in an on-state during a specific period of time and then said first switch is turned on.

4. The liquid crystal display device according to claim 2, further comprising a DC level shift circuit provided to invert a polarity of a common voltage and disposed in a stage prior to said charge collection and resupply circuit.

6. The liquid crystal display device according to claim 2, further comprising a DC level shift circuit provided to invert a polarity of a common voltage and disposed in a stage subsequent to said charge collection and resupply circuit.

8. The liquid crystal display device according to claim 6, wherein said DC level shift circuit includes:

a coupling and DC blocking capacitor connected between said charge collection and resupply circuit and said common electrode;

a first bias voltage generation resistor connected between said common electrode and a first power supply; and

a second bias voltage generation resistor connected between said common electrode and a second power supply.