Liquid crystal panel driving device

• US 7,764,260 B2
• Filed: 06/19/2006
• Issued: 07/27/2010
• Est. Priority Date: 03/13/2002
• Status: Active Grant

• Current Assignee: Bishop Display Tech LLC (IP Edge LLC)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Nishi, Kazuyoshi, Date, Yoshito
• Primary Examiner(s): Eisen, Alexander
• Assistant Examiner(s): YEUNG, MATTHEW M
• Application Number:
  US11/454,852
• Publication Number:
  US 20060232542A1
• Time in Patent Office: 1,499 Days
• Field of Search: None
• US Class Current: 345/98
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/023 using energy recovery or conservation
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

A switching-controlling section turns ON one of a transfer gate for high voltages or a transfer gate for low voltages and subsequently turns ON the other one of the transfer gates according to the outputs from the data latches only when the outputs from data latches are different from each other. Source lines are sequentially connected to a capacitor element for high voltages or a capacitor element for low voltages. For those source lines in which applied voltages change in a previous period and a subsequent period, an electric charge is stored and supplied effectively and power consumption is reduced, whereas for those source lines in which the applied voltages do not change, retained voltages do not vary so power is not consumed when subsequent voltages are applied. Power consumption in a liquid crystal panel driving device is reduced, and the time required for storing and supplying an electric charge is shortened. The circuit scale is also reduced.

Claims

1. A liquid crystal panel driving device for a liquid crystal display device comprising source lines, pixel switches, pixel electrodes connected to the source lines through the pixel switches, and an opposing electrode opposed to the pixel electrodes, the liquid crystal panel driving device applying to the pixel electrodes voltages corresponding to image data for pixels through the source lines, the liquid crystal panel driving device comprising:

a charge-reusing means for reusing an electric charge of the source lines;

a charge-reusing means-connecting means for connecting and disconnecting the source lines and the charge-reusing means; and

a controlling means for controlling the charge-reusing means-connecting means such that the source lines are connected to the charge-reusing means after applying a first voltage to a previous set of the pixel electrodes but before applying a second voltage to a subsequent set of the pixel electrodes when the voltage difference between the first voltage and the second voltage is equal to or greater than a predetermined difference.

2. The liquid crystal panel driving device according to claim 1, wherein:

the charge-reusing means comprises a plurality of charge-storing means for storing an electric charge; and

the controlling means controls the charge-reusing means-connecting means such that, after applying a first voltage to a previous set of the pixel electrodes but before applying a second voltage to a subsequent set of the pixel electrodes, the source lines are connected at first timing to one of the plurality of charge-storing means selected according to the first voltage, and thereafter the source lines are connected at second timing to another one of the plurality of charge-storing means selected according to the second voltage.

3. The liquid crystal panel driving device according to claim 2, wherein:

the image data are multi-level image data;

the plurality of charge-storing means are provided so as to correspond to voltage groups, respectively, each of the voltage groups including voltages that are applied to the pixel electrodes corresponding to the multi-level image data and are grouped together into at least one kind of voltage; and

the controlling means controls the charge-reusing means-connecting means such that the source lines are connected at the first timing to the charge-storing means that corresponds to the voltage group that includes the first voltage, and the source lines are connected at the second timing to the charge-storing means that corresponds to the voltage group that includes the second voltage.

4. (Withdrawn-Previously presented) The liquid crystal panel driving device according to claim 2, wherein:

the image data are binary level image data;

the plurality of charge-storing means comprises a charge-storing means for high voltages and a charge-storing means for low voltages that correspond to voltages applied to the pixel electrodes corresponding to the binary level image data;

the controlling means controls the charge-reusing means-connecting means such that the source lines are connected at the first timing to the charge-storing means for high voltages or the charge-storing means for low voltages corresponding to the first voltage, and the source lines are connected at the second timing to the charge-storing means for high voltages or the charge-storing means for low voltages corresponding to the second voltage.

5. The liquid crystal panel driving device according to claim 1, wherein:

the charge-reusing means comprises a first source line-connecting line and a second source line-connecting line, each connecting the source lines to one another;

the charge-reusing means-connecting means comprises;

a first connecting line-connecting means for selectively connecting and disconnecting the source lines and the first source line-connecting line; and

a second connecting line-connecting means for selectively connecting and disconnecting the source lines and the second source line-connecting line; and

the controlling means controls the first connecting line-connecting means and the second connecting line-connecting means such that, after applying a first voltage to a previous set of the pixel electrodes but before applying a second voltage to a subsequent set of the pixel electrodes, among the source lines grouped into at least a first group and a second group, the source lines of the first group are connected to the first source line-connecting line when the first voltage is higher than a predetermined voltage but are connected to the second source line-connecting line when the first voltage is lower than the predetermined voltage, and the source lines of the second group are connected to the first source line-connecting line when the first voltage is lower than the predetermined voltage but are connected to the second source line-connecting line when the first voltage is higher than the predetermined voltage.

6. The liquid crystal panel driving device according to claim 1, wherein:

the charge-reusing means comprises a source line-connecting line that connects the source lines to one another.

7. A liquid crystal panel driving device for a liquid crystal display device comprising source lines, pixel switches, pixel electrodes connected to the source lines through the pixel switches, and an opposing electrode opposed to the pixel electrodes, the liquid crystal panel driving device applying to the pixel electrodes voltages corresponding to image data for pixels through the source lines, the liquid crystal panel driving device comprising:

a charge-reusing line for reusing an electric charge of the source lines;

charge-reusing line-connecting switches for connecting and disconnecting the source lines and the charge-reusing line; and

a controller for controlling the charge-reusing line-connecting switches such that the source lines are connected to the charge-reusing line after applying a first voltage to a previous set of the pixel electrodes but before applying a second voltage to a subsequent set of the pixel electrodes when the voltage difference between the first voltage and the second voltage is equal to or greater than a predetermined difference.

8. The liquid crystal panel driving device according to claim 7, wherein:

the charge-reusing line connects the source lines to one another.