Driving device and driving method of liquid crystal display device

• US 6,501,455 B1
• Filed: 07/08/1999
• Issued: 12/31/2002
• Est. Priority Date: 07/14/1998
• 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: Nakamura, Toshihiro
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): Nguyen, Kimnhung
• Application Number:
  US09/349,932
• Time in Patent Office: 1,272 Days
• Field of Search: 345/87, 345/92, 345/94, 345/96, 345/99, 345/211, 345/212, 345/213
• US Class Current: 345/96
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3685 Details of drivers for data electrodes

Abstract

A driving device of a liquid crystal display device includes a liquid crystal panel which is provided with a group of segment electrodes and a group of common electrodes disposed to intersect with the group of segment electrodes and a liquid crystal sandwitched therebetween. The driving device includes a controller which controls a changing period for changing an output level of a segment driving signal which drives the group of segment electrodes in a single scanning period, within a voltage level which is the same polarity with respect to a common driving output which drives the group of common electrodes. The driving device corrects a driving voltage error generated by a change in display data and alternating signal by controlling the changing period. As a result, the driving device improves the display quality of the liquid crystal panel.

Claims

1. A driving device of a liquid crystal display device, comprising:

a group of signal electrodes which are driven by a driving signal that is in accordance with the display data;

a group of scanning electrodes which are disposed so as to intersect with said group of signal electrodes;

a liquid crystal sandwiched between said group of signal electrodes and said group of scanning electrodes;

alternate control means for alternately and inversely driving said liquid crystal by an alternating signal; and

period control means for setting a changing period of a variable length for changing an output level of the driving signal at least once in a single scanning period, and for controlling the length of the changing period based on a change in the driving signal and a change in the alternating signal.

2. The driving device of a liquid crystal display device as set forth in claim 1, wherein:

said period control means includes signal generating means for generating (a) a polarity switching signal which is switched based on the display data and the alternating signal, (b) an output level switching signal in synchronization with a horizontal synchronizing signal, which is switched twice in one period of the horizontal synchronizing signal, and (c) a first correction signal and a second correction signal, which are different from each other and based on a switching timing of the polarity switching signal and a first switching timing of the output level switching signal,

said period control means controlling the length of the changing period using the first correction and the second correction signal.

3. The driving device of a liquid crystal display device as set forth in claim 1, wherein:

said period control means includes signal generating means for generating (a) an output level switching signal in synchronization with a horizontal synchronizing signal, which is switched twice in one period of the horizontal synchronizing signal, and (b) a correction signal which is based on a second switching timing of the output level switching signal,

said period control means controlling the length of the changing period using the correction signal.

4. The driving device of a liquid crystal display device as set forth in claim 1, wherein the driving signal is a pulse, and the changing period is set between a rise and a fall of the driving signal.

5. The driving device of a liquid crystal display device as set forth in claim 1, comprising:

a power source circuit for supplying (a) V_C which is a non-select output level supplied to said group of scanning electrodes during a non-select period, and (b) V_BH1, V_BH2, V_BL2, and V_BL1, which are output levels of the driving signal, supplied to said group of signal electrodes, satisfying a relationship of V_BH1>

V_BH2>

V_C>

V_BL2>

V_BL1.

6. The driving device of a liquid crystal display device as set forth in claim 5, wherein said period control means outputs V_BH2 or V_BL2 with respect to said group of signal electrodes in the changing period, and outputs V_BH1 or V_BL1 with respect to said group of signal electrodes in a non-changing period.

13. The driving device of a liquid crystal display device as set forth in claim 1, wherein said period control means changes a start timing or an end timing of the changing period so as to control the length of the changing period.

17. The driving device of a liquid crystal display device as set forth in claim 6, comprising:

signal generating means for generating a polarity switching signal which outputs a high level and a low level respectively when the driving signal corresponding to the display data becomes High level and Low level according to the alternating signal,

wherein said period control means extends the length of the changing period when a result of exclusive OR operating on the display data, the alternating signal, and the polarity switching signal is at High level, and said period control means shortens the length of the changing period when a result of said exclusive OR is at Low level.

18. The driving device of a liquid crystal display device as set forth in claim 6, comprising:

comparing means for comparing the driving signal with a driving signal of a preceding scanning period,

wherein said period control means shortens the length of the changing period when the driving signals compared by said comparing means are different and when the alternating signal has not been inverted, or when the driving signals compared by said comparing means are the same and when the alternating signal has been inverted.

7. A method for driving a liquid crystal display device for driving a liquid crystal sandwiched between a group of signal electrodes and a group of scanning electrodes which are disposed to intersect with the group of signal electrodes, by a driving potential difference between the group of signal electrodes and the group of scanning electrodes facing each other,

said method comprising the steps of:

(1) providing in a driving signal of the group of signal electrodes a changing period of a variable length for changing an output level of the driving signal at least once in a single scanning period;

(2) controlling the length of the changing period based on a change in the driving signal and a change in an alternating signal; and

(3) correcting, by the control of the length of the changing period, a driving voltage error generated by distortion which is generated on the group of scanning electrodes by the driving signal of the group of signal electrodes.

14. The method for driving a liquid crystal display device as set forth in claim 7, wherein a start timing or an end timing of the changing period is changed to control the length of the changing period and thereby control an output level of the driving signal, so as to correct the driving voltage error.

19. The method for driving a liquid crystal display device as set forth in claim 7, wherein:

the driving signal has high level outputs V_BH1 and V_BH2 and low level outputs V_BL1 and V_BL2 which are related by V_BH1>

V_BH2>

V_BL2>

V_BL1, and

the output level of the driving signal becomes V_BH2 or V_BL2 in the changing period, and becomes V_BH1 or V_BL1 in a non-changing period, and

the length of the changing period is varied depending on a result of exclusive OR operating on the display data, the alternating signal, and a signal which becomes High level and Low level respectively when the driving signal corresponding to the display data becomes High level and Low level according to the alternating signal, so that the length of the changing period becomes longer when the result of exclusive OR is at High level and becomes shorter when the result of exclusive OR is at Low level.

8. A method for driving a liquid crystal display device for driving a liquid crystal sandwiched between a group of signal electrodes which are driven by a driving signal in accordance with display data and a group of scanning electrodes which are disposed to intersect with the group of signal electrodes,

said method comprising the steps of:

(1) comparing display data and display data of a preceding scanning period in a signal electrode group side driving circuit which drives the group of signal electrodes; and

(2) correcting, when there is a difference between the display data compared in said step (1), a driving voltage error generated by blunted waveform of the driving signal, by controlling a variable length of a changing period for changing an output level of the driving signal in a single scanning period.

9. The method as set forth in claim 8, wherein:

the liquid crystal is inversely driven by an alternating signal, and

when the display data compared are different while the alternating signal is not inverted, the driving voltage error generated by blunted waveform of the driving signal is corrected by controlling the length of the changing period.

15. The method for driving a liquid crystal display device as set forth in claim 8, wherein a start timing or an end timing of the changing period is changed to control the length of the changing period and thereby control an output level of the driving signal, so as to correct the driving voltage error.

20. The method for driving a liquid crystal display device as set forth in claim 8, wherein:

the driving signal has high level outputs V_BH1 and V_BH2 and low level outputs V_BL1 and V_BL2 which are related by V_BH1>

V_BH2>

V_BL2>

V_BL1, and

the output level of the driving signal becomes V_BH2 or V_BL2 in the changing period, and becomes V_BH1 or V_BL1 in a non-changing period, and

the length of the changing period is made shorter when the display data compared are different.

10. A method for driving a liquid crystal display device for alternately and inversely driving by an alternating signal a liquid crystal sandwiched between a group of signal electrodes which are driven by a driving signal in accordance with display data and a group of scanning electrodes which are disposed to intersect with the group of signal electrodes,

said method comprising the steps of:

(1) comparing display data and display data of a preceding scanning period in a signal electrode group side driving circuit which drives the group of signal electrodes; and

(2) correcting, when the alternating signal has been inverted and when the display data compared in said step (1) are the same, or when the alternating signal has not been inverted and when the display data compared in said step (1) are different, a driving voltage error generated by blunted waveform of the driving signal, by controlling a variable length of a changing period for changing an output level of the driving signal in a single scanning period.

16. The method for driving a liquid crystal display device as set forth in claim 10, wherein a start timing or an end timing of the changing period is changed to control the length of the changing period and thereby control an output level of the driving signal, so as to correct the driving voltage error.

21. The method for driving a liquid crystal display device as set forth in claim 10, wherein:

the driving signal has high level outputs V_BH1 and V_BH2 and low level outputs V_BL1 and V_BL2 which are related by V_BH1>

V_BH2>

V_BL2>

V_BL1, and

the output level of the driving signal becomes V_BH2 or V_BL2 in the changing period, and becomes V_BH1 or V_BL1 in a non-changing period, and

the length of the changing period is made shorter when the alternating signal has been inverted and when the display data compared are the same, or when the alternating signal has not been inverted and when the display data compared are different.

11. A method for driving a liquid crystal display device for driving a liquid crystal sandwiched between a group of signal electrodes and a group of scanning electrodes which are disposed to intersect with the group of signal electrodes, the liquid crystal being driven by a driving signal in accordance with display data, which is outputted to the group of signal electrodes, and by a scanning signal outputted to the group of scanning electrodes,

said method comprising the step of:

setting a changing period for changing an output level of the driving signal in a single scanning period so as to control a start timing of the changing period based on the display data and an inverse driving state and thereby changes a length of the changing period to change the output level of the driving signal.

12. A method for driving a liquid crystal display device for driving a liquid crystal sandwiched between a group of signal electrodes and a group of scanning electrodes which are disposed to intersect with the group of signal electrodes, the liquid crystal being driven by a driving signal in accordance with display data, which is outputted to the group of signal electrodes, and by a scanning signal outputted to the group of scanning electrodes,

said method comprising the step of:

setting a changing period for changing an output level of the driving signal in a single scanning period so as to control an end timing of the changing period based on the display data and an inverse driving state and thereby changes a length of the changing period to change the output level of the driving signal.