Method of driving liquid crystal display and liquid crystal display using the driving method

• US 20030164813A1
• Filed: 03/04/2003
• Published: 09/04/2003
• Est. Priority Date: 03/04/2002
• Status: Active Grant

• Current Assignee: Beihai HKC Optoelectronics Technology Company Limited
• Original Assignee: NEC Corporation
• Inventors: Fujii, Gen
• Granted Patent: US 7,071,929 B2
• Time in Patent Office: Days
• US Class Current: 345/101
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

In a method of driving an active matrix liquid crystal display according to pulse width modulation driving system using a thin-film transistor for a switching device, the variation of the temperature of a liquid crystal display panel is monitored. Particularly, the panel temperature detecting means of the liquid crystal display panel is provided, and gate-on voltage or data signal pulse width and a frequency of a reference clock signal are corrected according to the temperature of the panel. The corrected quantity of gate-on voltage according to the polarity of write data or the corrected quantity of data signal pulse width is determined according to the temperature of the panel. The higher the temperature of the panel is, to the lower value the positive or negative gate-one voltage is set and the lower the temperature of the panel is, to the higher value the positive or negative gate-on voltage is set. Positive gate-on voltage is set so that it is always higher than negative gate-on voltage.

Claims

1. A method of driving an active matrix liquid crystal display for driving a liquid crystal display panel provided with plural thin-film transistors for switching connected to plural pixel electrodes according to a pulse width modulation driving system, wherein:

the positive gate-on voltage (V_GONP) and the negative gate-on voltage (V_GONN) of the thin-film transistor are set based upon the temperature of the liquid crystal display panel.

2. A method of driving a liquid crystal display according to claim 1, wherein:

the positive gate-on voltage (V_GONP) is set so that it is higher than the negative gate-on voltage (V_GONN) ; and

as the temperature of the panel rises, both the positive gate-on voltage (V_GONP) and the negative gate-on voltage (V_GONN) are set so that they are lower than those before the rise of the panel temperature, maintaining the relation.

3. A method of driving a liquid crystal display according to claim 1, wherein:

the pulse width modulation driving system is a driving system for modulating the pulse width of a data signal.

4. A method of driving a liquid crystal display according to claim 3, comprising:

a circuit for setting the positive gate-on voltage (V_GONP) and the negative gate-on voltage (V_GONN) of the thin-film transistor for switching so that the ON-state current (I_ON) Of the thin-film transistor for switching is fixed independent of the temperature of the panel.

5. A method of driving a liquid crystal display according to claim 3, wherein:

in a method of driving an active matrix liquid crystal display for driving a liquid crystal display panel provided with plural thin-film transistors for switching connected to plural pixel electrodes according to a data signal pulse width modulation driving system, a thin-filmtransistor for monitoring formed at the same time as the thin-film transistor for switching is provided to the liquid crystal display panel; and

a circuit using the thin-film transistor for monitoring for setting the positive gate-on voltage (V_GONP) and the negative gate-on voltage (V_GONN) of the thin-film transistor for switching so that the ON-state current (I_ON) of the thin-film transistor for switching is fixed independent of the temperature of the panel is provided.

6. A method of driving a liquid crystal display according to claim 3, wherein:

the positive data pulse width (T_WP) of the data signal in all displayed gradation is set so that it is longer than the negative data pulse width (T_WN); and

as the temperature of the panel rises, the positive gate-on voltage (V_GONP) and the negative gate-on voltage (V_GONN) of the thin-film transistor are set so that they are lower.

7. A method of driving a liquid crystal display according to claim 3, wherein:

the positive data pulse width (T_WP) and the negative data pulse width (T_WN) of the data signal allocated to each displayed gradation are set according to the temperature of the liquid crystal display panel.

8. A method of driving a liquid crystal display according to claim 3, wherein:

the positive data pulse width (T_WP) of the data signal in all displayed gradation is set so that it is longer than the negative data pulse width (T_WN); and

as the temperature of the liquid crystal display panel rises, both the positive data pulse width (T_WP) and the negative data pulse width (T_WN) are set so that they are shorter than those before the rise of the panel temperature, maintaining the relation.

9. A method of driving a liquid crystal display according to claim 3, wherein:

each displayed gradation is represented by the number of clocks;

a reference clock signal is counted by a counter;

gradation data and the output of the counter are compared and the pulse width (T_W) of the data signal is set; and

temperature detecting means is provided and a frequency of the reference clock signal is variable according to the temperature of the liquid crystal display panel.

10. A method of driving a liquid crystal display according to claim 3, wherein:

each displayed gradation is represented by the number of clocks;

a reference clock signal is counted by a counter;

gradation data and the output of the counter are compared and the pulse width (T_W) of the data signal is set; and

a frequency of the reference clock signal is set using a thin-film transistor for monitoring formed at the same time as the thin-film transistor for switching so that the frequency is proportional to the ON-state current (I_ON) of the thin-film transistor for monitoring.

11. A method of driving a liquid crystal display according to claim 9, wherein:

the positive gate-on voltage (V_GONP) is set so that it is higher than the negative gate-on voltage (V_GONN)

12. A method of driving a liquid crystal display according to claim 10, wherein:

the positive gate-on voltage (V_GONP) is set so that it is higher than the negative gate-on voltage (V_GONN)

13. A method of driving a liquid crystal display according to claim 4, wherein:

the positive data pulse width (T_WP) of the data signal in all displayed gradation is set so that it is longer than the negative data pulse width (T_WN)

14. A method of driving a liquid crystal display according to claim 5, wherein:

the positive data pulse width (T_WP) of the data signal in all displayed gradation is set so that it is longer than the negative data pulse width (T_WN).

15. A method of driving a liquid crystal display according to claim 9, wherein:

the positive data pulse width (T_WP) of the data signal in all displayed gradation is set so that it is longer than the negative data pulse width (T_WN)

16. A method of driving a liquid crystal display according to claim 10, wherein:

the positive data pulse width (T_WP) of the data signal in all displayed gradation is set so that it is longer than the negative data pulse width (T_WN)

17. A method of driving a liquid crystal display according to claim 1, wherein:

as the temperature of the panel rises, the center (V_COM center) of common voltage supplied to a common electrode of the liquid crystal display panel is made higher.

18. A liquid crystal display, wherein:

the liquid crystal display is driven by the driving method according to claim 1.