Driving method and drive control circuit of liquid crystal display device, and liquid crystal display device including the same

• US 8,432,347 B2
• Filed: 01/11/2008
• Issued: 04/30/2013
• Est. Priority Date: 06/27/2002
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Hiraki, Katsuyoshi, Furukoshi, Yasutake, Katagawa, Koichi, Nishido, Masanori, Kobayashi, Tetsuya
• Primary Examiner(s): Dharia, Prabodh M
• Application Number:
  US12/008,634
• Publication Number:
  US 20080122778A1
• Time in Patent Office: 1,936 Days
• Field of Search: 345/629, 345/690, 345/59, 345/63, 345 87-100, 345204-214, 345/698, 327/563, 358/474, 358/496, 358/497, 348/674
• US Class Current: 345/98
• CPC Class Codes: G09G 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

A drive control circuit includes a timing controller for detecting a change of a horizontal scanning frequency, a gate voltage generating circuit for generating two kinds of gate-on voltages Va and Vb (Va<Vb), and a switch for outputting one of the gate-on voltages Va and Vb from the gate voltage generating circuit in accordance with an output of the timing controller. The timing controller includes a counter for counting the number of clocks for one horizontal period, and a comparator for comparing a count result with a threshold value. When the horizontal scanning frequency is in a normal state, the low gate-on voltage Va is outputted, and when the horizontal scanning frequency exceeds a predetermined threshold value, that is, the count value falls below a threshold value, the high gate-on voltage Vb is outputted.

Claims

1. A method for correcting gradation voltage characteristics of a liquid crystal display device having a reference voltage generating circuit which includes a fixed voltage divider circuit for outputting a predetermined drive voltage from an input power supply for generating a reference voltage, and a gradation voltage generating circuit for generating gradation voltages based on the reference voltage output by the reference voltage generating circuit, said method comprising the step of:

maintaining a substantially constant input power supply to the reference voltage generating circuit;

correcting the predetermined drive voltage output from the fixed voltage divider circuit with a control circuit which varies the resistance in the fixed voltage divider circuit, the control circuit including a pulse width modulation circuit for generating signals with different pulse widths under a predetermined condition, a transistor controlled by the pulse width modulation circuit, and at least a pair of resistors connected in series with the transistor and in parallel with at least one resistor in the fixed voltage divider circuit; and

applying the changed predetermined drive voltage to the gradation voltage generating circuit;

wherein the reference voltage is an applied voltage for black display and/or white display.

2. A method for correcting gradation voltage characteristics of a liquid crystal display device according to claim 1, wherein the level of the reference voltage is changed by pulse width modulation control.

3. A method for correcting gradation voltage characteristics of a liquid crystal display device according to claim 2, wherein the pulse width modulation is performed on the basis of the applied voltage to the liquid crystal and a characteristic of transmissivity.

4. A method for correcting gradation voltage characteristics of a liquid crystal display device according to claim 2, wherein the pulse width modulation is performed on the basis of variations in liquid crystal material and in liquid crystal driving electric components.

5. A method for correcting gradation voltage characteristics of a liquid crystal display device according to claim 1, wherein a variable amount of the level of the reference voltage includes a variation range of contrast.

6. A method for correcting gradation voltage characteristics of a liquid crystal display device according to claim 1, wherein the level of the reference voltage is changed in a part of one display frame.

7. A method for correcting gradation voltage characteristics of a liquid crystal display device according to claim 6, wherein a timing of changing the level of the reference voltage is between turning-ON of a gate electrode of a pixel transistor and application of a gradation voltage to a drain electrode of the pixel transistor.

8. A drive control circuit of a liquid crystal display device, comprising:

a reference voltage generating circuit for generating a reference voltage, said reference voltage generating circuit including a fixed voltage divider circuit for outputting a predetermined drive voltage converted by said reference voltage generating circuit for generating the reference voltage;

a control circuit for correcting the predetermine drive voltage output from the fixed voltage divider circuit by varying the resistance in the fixed voltage divider circuit, the control circuit including a pulse width modulation circuit for generating signals with different pulse widths under a predetermined condition, a transistor controlled by the pulse width modulation circuit, and at least a pair of resistors connected in series with the transistor and in parallel with at least one resistor in the fixed voltage divider circuit; and

a gradation voltage generating circuit for generating gradation voltages based on the reference voltage output by the reference voltage generating circuit;

wherein the reference voltage is an applied voltage for black display and/or white display.

9. A liquid crystal display device comprising a liquid crystal sealed between substrates disposed to be opposite to each other with a predetermined cell gap, further comprising a drive control circuit for driving the liquid crystal according to claim 8.