Liquid crystal display device and drive method therefor

• US 9,041,636 B2
• Filed: 01/10/2012
• Issued: 05/26/2015
• Est. Priority Date: 01/14/2011
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Fujioka, Akizumi, Kubota, Akinori
• Primary Examiner(s): PATEL, PREMAL R
• Application Number:
  US13/979,261
• Publication Number:
  US 20130286302A1
• Time in Patent Office: 1,232 Days
• Field of Search: 345/87, 345173-179
• US Class Current: 345/87
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G09G 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

A liquid crystal display devices (1a, 1b) each include a touch panel (2), a liquid crystal panel (3), a touch panel controller (4), a liquid crystal driving controller (timing generator) (5), oscillation circuits (7a, 7b), a correcting circuit (10), and a frequency counter (11). The frequency counter (11) counts a reference clock signal CLK supplied from the oscillation circuit (7a) or (7b). The correcting circuit (10) determines, in accordance with information supplied from the frequency counter (11), whether or not a frequency of the reference clock signal CLK is a predetermined frequency. In a case where the frequency of the reference clock signal CLK is not the predetermined frequency, the correcting circuit (10) corrects (i) a frequency at which the liquid crystal panel (3) is driven or (ii) a frequency at which sensing of the touch panel (2) is carried out.

Claims

1. A liquid crystal display device comprising:

a liquid crystal panel configured to display an image supplied from outside;

a timing generator configured or programmed to drive the liquid crystal panel in accordance with a driving signal;

a capacitive touch sensor configured to detect a change in capacitance, the capacitive touch panel being provided so as to overlap the liquid crystal panel;

a touch panel controller configured or programmed to scan the capacitive touch sensor in accordance with a reference clock signal which is generated by an oscillation circuit provided in the liquid crystal display device;

a frequency counter configured or programmed to count a frequency of the driving signal;

a correcting circuit configured or programmed to determine whether or not the frequency of the driving signal is a predetermined value; and

the correcting circuit configured or programmed to change, in a case where the correcting circuit determines that the frequency of the driving signal is not the predetermined value, a frequency at which the capacitive touch sensor is scanned.

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

the oscillation circuit includes (i) a generating circuit configured or programmed to generate a signal having a predetermined frequency and (ii) a frequency dividing circuit configured or programmed to output, as the reference clock signal, a signal obtained by dividing the predetermined frequency of the signal at a given frequency division ratio; and

the correcting circuit is configured or programmed to change the frequency division ratio of the frequency dividing circuit to a predetermined frequency division ratio so as to change a frequency of the reference clock signal to a predetermined frequency, thereby changing, to a predetermined frequency, the frequency at which the capacitive touch sensor is scanned.

3. A liquid crystal display device as set forth in claim 1, further comprising a power source configured to supply a voltage, wherein:

the oscillation circuit is configured or programmed to generate the reference clock signal in accordance with the voltage supplied from the power source; and

the correcting circuit is configured or programmed to change the voltage, which is supplied from the power source to the oscillation circuit, to a predetermined voltage so as to change a frequency of the reference clock signal to a predetermined frequency, thereby changing, to a predetermined frequency, the frequency at which the capacitive touch sensor is scanned.

4. The liquid crystal display device as set forth in claim 1, wherein:

the frequency counter is configured or programmed to count a frequency of any one of a clock signal, a horizontal synchronization signal, a vertical synchronization signal, a source clock signal, a gate clock signal, a source start pulse, and a gate start pulse, each of which serves as the driving signal.

5. A liquid crystal display device comprising:

a liquid crystal panel configured to display an image supplied from outside;

a timing generator configured or programmed to drive the liquid crystal panel in accordance with a driving signal;

a capacitive touch sensor configured to detect a change in capacitance, the capacitive touch panel being provided so as to overlap the liquid crystal panel;

a touch panel controller configured or programmed to scan the capacitive touch sensor in accordance with a reference clock signal which is generated by an oscillation circuit provided in the liquid crystal display device;

a frequency counter configured or programmed to count a frequency of the reference clock signal;

the correcting circuit configured or programmed to determine whether or not the frequency of the reference clock signal is a predetermined value; and

the correcting circuit configured or programmed to change, in a case where the correcting circuit determines that the frequency of the reference clock signal is not the predetermined value, a frequency at which the liquid crystal panel is driven.

6. A liquid crystal display device as set forth in claim 5, further comprising a receiving circuit configured to receive, as the driving signal, a dot clock signal(s) from outside, wherein:

the correcting circuit is configured or programmed to change, to a predetermined number, (i) the number of the dot clock signal(s) outputted from the receiving circuit to the timing generator or (ii) a frequency of each of the dot clock signal(s), thereby changing, to a predetermined frequency, the frequency of the driving signal at which the liquid crystal panel is driven.

7. The liquid crystal display device as set forth in claim 5, wherein:

the timing generator includes an internal oscillation circuit including (i) a generation circuit configured or programmed to generate a signal having a predetermined frequency and (ii) a frequency dividing circuit configured or programmed to output, as the driving signal, a clock signal obtained by dividing the predetermined frequency of the signal at a given frequency division ratio; and

the correcting circuit is configured or programmed to change the frequency division ratio of the frequency dividing circuit to a predetermined frequency division ratio so as to change a frequency of the clock signal to a predetermined frequency, thereby changing, to a predetermined frequency, the frequency of the driving signal at which the liquid crystal panel is driven.

8. A liquid crystal display device as set forth in claim 5, further comprising a power source configured to supply a voltage, wherein:

the timing generator includes an internal oscillation circuit configured or programmed to generate, as the driving signal, a clock signal in accordance with the voltage supplied from the power source; and

the correcting circuit is configured or programmed to change the voltage, which is supplied from the power source to the internal oscillation circuit, to a predetermined voltage so as to change a frequency of the clock signal to a predetermined frequency, thereby changing the frequency of the driving signal at which the liquid crystal panel is driven.

9. A method for driving a liquid crystal display device,

the liquid crystal display device including:

a liquid crystal panel configured to display an image supplied from outside;

a timing generator configured or programmed to drive the liquid crystal panel in accordance with a driving signal;

a capacitive touch sensor configured to detect a change in capacitance, the capacitive touch panel being provided so as to overlap the liquid crystal panel; and

a touch panel controller configured or programmed to scan the capacitive touch sensor in accordance with a frequency of a reference clock signal which is generated by an oscillation circuit provided in the liquid crystal display device,

the method comprising the steps of;

(a) counting a frequency of the driving signal;

(b) determining whether or not the frequency of the driving signal is a predetermined value; and

(c) changing, in a case where the frequency of the driving signal is determined not to be the predetermined value in the step (b), a frequency at which the capacitive touch sensor is scanned.