Liquid crystal panel driving device

• US 20060232542A1
• Filed: 06/19/2006
• Published: 10/19/2006
• Est. Priority Date: 03/13/2002
• Status: Active Grant

• Current Assignee: Bishop Display Tech LLC (IP Edge LLC)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Nishi, Kazuyoshi, Date, Yoshito
• Granted Patent: US 7,764,260 B2
• Time in Patent Office: Days
• 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 alternately applying to the pixel electrodes through the source lines high voltages and low voltages that are respectively higher and lower than a predetermined voltage, both of the voltages corresponding to image data for pixels, the liquid crystal panel driving device comprising:

a charge-storing means for storing an electric charge;

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

an opposing electrode-connecting means for connecting and disconnecting the source lines and the opposing electrode; and

a controlling means for controlling the charge-storing means-connecting means and the opposing electrode-connecting means such that, after applying one of the high voltage and the low voltage to a set of the pixel electrodes but before applying the other one of the voltages to a subsequent set of the pixel electrodes, the source lines are connected to the electric charge-storing means and subsequently the source lines are connected to the opposing electrode.

2-3. -3. (canceled)

4. 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 alternately applying to the pixel electrodes through the source lines high voltages and low voltages that are respectively higher and lower than a predetermined voltage, both of the voltages corresponding to image data for pixels, the liquid crystal panel driving device comprising:

a charge-storing means for storing an electric charge;

a charge-storing means-connecting means for selectively connecting and disconnecting the source lines to one of terminals of the charge-storing means or the other one of the terminals thereof; and

a controlling means for controlling the charge-storing means-connecting means such that, after applying one of the high voltages and the low voltages to the pixel electrodes but before applying the other one of the voltages to the pixel electrodes, the source lines are connected to one of the terminals of the charge-storing means at first timing, and thereafter, the source lines are connected to the other one of the terminals of the charge-storing means at second timing.

5. (canceled)

6. 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-utilizing means for utilizing an electric charge of the source lines;

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

a controlling means for controlling the charge-utilizing means-connecting means based on at least one of the first voltage and the second voltage 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.

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

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

the controlling means controls the charge-utilizing 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 the plurality of charge-storing means selected according to the second voltage.

8. The liquid crystal panel driving device according to claim 7, 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-utilizing 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.

9. The liquid crystal panel driving device according to claim 7, 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-utilizing 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.

10. The liquid crystal panel driving device according to claim 7, wherein the controlling means controls whether or not the source lines are connected to one of the charge storing means at the first timing and the second timing according to the first voltage and the second voltage.

11. The liquid crystal panel driving device according to claim 10, wherein the controlling means controls the charge-utilizing means-connecting means such that the source lines are connected to one of the charge storing means at the first timing and the second timing when the voltage difference between the first voltage and the second voltage is equal to or greater than a predetermined difference.

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

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

the charge-utilizing 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.

13. The liquid crystal panel driving device according to claim 12, wherein the controlling means controls whether or not the source lines are connected to the first source line-connecting line or the second source line-connecting line according to the first voltage and the second voltage.

14. The liquid crystal panel driving device according to claim 13, wherein the controlling means controls the charge-utilizing means-connecting means such that the source lines are connected to the first source line-connecting line or the second source line-connecting line when the voltage difference between the first voltage and the second voltage is equal to or greater than a predetermined difference.

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

the charge-utilizing means comprises a source line-connecting line that connects the source lines one another; and

the controlling means controls the charge-utilizing 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 to the source line-connecting line according to the first voltage and the second voltage.

16. The liquid crystal panel driving device according to claim 15, wherein the controlling means controls the charge-utilizing means-connecting means such that the source lines are connected to the source line-connecting line when the voltage difference between the first voltage and the second voltage is equal to or greater than a predetermined difference.