JPH0990907A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption while continuing a display of a liquid crystal panel. SOLUTION: In a normal operation period 112, a shift register 102 fetches successively the display data based on a shift clock 111 inputted from a shift clock input line 104. In a first power save period 113, the frequency of the shift clock signal 111 is reduced to 1/2 based on a clock switch signal inputted from a clock switch signal input line 106, and the shift register 102 fetches the display data of the same contents to two adjacent signal lines 107. In a second power save period 114, the frequency of the shift clock signal 111 is reduced to 1/2 based on the clock switch signal inputted from the clock switch signal input line 106, and the shift register 102 fetches the display data of the same contents each other though different from the display data fetched in the first power save period to two adjacent signal lines 107.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device capable of reducing driving power.

[0002]

2. Description of the Related Art Generally, a signal driver of a liquid crystal display device takes in display data serially input for each pixel based on a shift clock signal, and outputs the taken display data to a liquid crystal panel line-sequentially. The frequency of the shift clock signal for the signal driver to fetch the display data pixel by pixel is determined by the resolution of the liquid crystal panel and the frame frequency. For example, in a screen specification called VGA which is often used for a display of a personal computer, the screen resolution is 640 × 480,
The frame frequency is 60 Hz and the frequency of the shift clock signal is about 25 MHz.

A method of fetching data in the conventional liquid crystal display device will be described below with reference to FIG.

In FIG. 2, 201 is a signal driver, and the signal driver 201 is the shift register 20.
2 and an output unit 203. Further, 204 is a shift clock input line for inputting a shift clock signal to the shift register 202, 205 is a display data input line for inputting display data to the shift register 202, 2
Reference numeral 06 denotes a signal line for outputting the display data taken in the shift register 202 via the output unit 203, 207
Is a scan driver for driving the scan line 208, 209 is a liquid crystal panel for displaying the display data input from the signal line 206, 210 is a shift clock signal, and 211 to 216 are the display data fetched in the shift register 202. Means the contents of the display data 211 to 216.

Shift register 2 of signal driver 201
02, the shift clock signal 210 is input from the shift clock input line 204 and the display data input line 205
When the display data is input from, the shift register 202 sequentially takes in the display data based on the shift clock signal 210. At the final timing of the display data acquisition in one horizontal period, the contents of the shift register 202 are. The display data 216 captured in the shift register 202 for one horizontal period is simultaneously output from the output unit 203 to the liquid crystal panel 209 once in every horizontal period in synchronization with the scan driver 207. Such an output method is called line-sequential driving.

[0006]

As described above, in the conventional liquid crystal display device, the display data is always taken in corresponding to all the pixels regardless of the display content of the screen, so that the display data is always constant. It consumes the drive power of. Since the frequency of the shift clock signal 210 is as high as several tens MHz, the power consumption of the shift register 202 to which the shift clock signal 210 is input from the shift clock input line 204 may occupy more than half of the power consumption of the liquid crystal display device. .

In a battery-driven system used in a portable personal computer or the like, various measures have been taken to save power in order to extend the battery operating time. However, in the conventional liquid crystal display device, the backlight is turned off. Or, the power cannot be reduced unless the liquid crystal panel display is stopped. In order to save power by turning off the screen in this way, the continuous power-saving technique cannot be performed frequently because it interrupts the continuous thinking of the user. There is a problem that there is a limit to the reduction.

In view of the above, it is an object of the present invention to provide a liquid crystal display device capable of reducing power consumption while continuing the display on the liquid crystal panel.

[0009]

In order to achieve the above-mentioned object, a solution means provided by the invention of claim 1 is a liquid crystal display device comprising a plurality of signal lines, a plurality of scanning lines, and a plurality of the plurality of scanning lines. Dot matrix type liquid crystal panel having pixels connected to one signal line and the plurality of scanning lines, a scan driver for sequentially driving the plurality of scanning lines, and based on an input shift clock signal A signal driver that sequentially fetches the display data into the signal line and outputs the fetched display data to the liquid crystal panel line-sequentially.
It is configured to include a control unit that changes the number of signals to one-half and takes in the same display data to the n signal lines for each shift clock signal.

With the above structure, the frequency of the shift clock signal is changed to 1 / n of the normal operation during power saving, and the same display data is taken into the n signal lines for each shift clock signal. During power saving, the frequency of the shift clock signal can be reduced to 1 / n of the normal operation.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the control means adds a configuration in which the combination of the n signal lines for fetching the same display data is periodically changed. is there.

According to a third aspect of the present invention, in addition to the configuration of the first aspect, the control means adds a configuration in which the combination of the n signal lines that fetch the same display data is changed aperiodically. Is.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, 101 is a signal driver, and the signal driver 101 is a shift register 10.
2 and an output unit 103. Further, in FIG. 1, reference numeral 104 denotes a shift clock signal for the shift register 10.
2, a reference numeral 105 is a shift clock input line, 105 is a display data input line for inputting display data to the shift register 102, and 106 is a clock switch for changing the frequency of the shift clock signal input from the shift clock signal line 104. A clock switching signal input line for inputting a signal to the shift register 102, a signal line 107 for outputting the display data fetched in the shift register 102 via the output unit 103, and a scan 108 for driving the scanning line 109. A driver, 110 is a liquid crystal panel for displaying display data input from the signal line 107, 111 is a shift clock signal, 112 is a normal operation period during which power saving driving is not performed, and 113 is a first power saving operation for performing power saving driving. Period 114 is a second power saving operation period for performing power saving driving, 115 to 12 Shows the display data taken in the shift register 102, - the display data 115-1
Means the contents of 26.

Hereinafter, the first and second power saving operation periods 11
The frequency of the shift clock signal 111 in 3, 114 is set to the shift clock signal 11 in the normal operation period 112.
A case will be described where the frequency is reduced to one half.

First, in a period in which the clock switching signal input from the clock switching signal input line 106 is off, that is, in the normal operation period 112, the shift register 10 is operated.
Similarly to the conventional example, 2 sequentially fetches the display data based on the shift clock signal 111 input from the shift clock input line 104.

Next, in the first power saving period 113, the frequency of the shift clock signal 111 is reduced to one half based on the clock switching signal input from the clock switching signal input line 106, and the shift register 102 is operated.
For each shift clock signal 111, display data of the same content (for example,
, And) are taken in and the horizontal resolution is halved.

Next, in the second power saving period 114, the frequency of the shift clock signal 111 is reduced to one half based on the clock switching signal input from the clock switching signal input line 106, and the shift register 102 is operated.
Is different from the display data captured in the first power saving period 113 in the two adjacent signal lines 107 for each shift clock signal 111, but the display data having the same content (for example ,,,, and ) Is taken in and the horizontal resolution is halved.

As described above, if the frequency of the shift clock 111 in the first and second power saving periods 113 and 114 is halved, the power consumption by the shift clock 111 can be halved. it can.

In this embodiment, the first and second
The power saving periods 113 and 114 are each one horizontal period. As described above, if the combination of the two signal lines 107 that simultaneously fetch the display data is changed every horizontal period as in the first power saving period 113 and the second power saving period 114, an odd number is obtained. Since the th display data and the even display data are alternately displayed, it is possible to prevent deterioration of the resolution in the visual sense.

When the combination of the two signal lines 107 for fetching the display data is periodically changed, visual discontinuity or unevenness of the screen may periodically occur. By changing the combination of the display data taken in the signal line 107 aperiodically, the discontinuity and unevenness of the screen can be reduced.

Further, in a liquid crystal panel such as STN having a slow response, even if the combination of the signal lines 107 for fetching display data is changed every field period, flicker is not so noticeable. Absent.

Further, in the above-described embodiment, the frequency of the shift clock signal 111 is reduced to half during the power saving period, and the shift register 102 is
Although the display data of the same content is fetched into the two adjacent signal lines 107, the frequency reduction rate and the number of display data of the same content are not limited to these, and when there are a plurality of signal lines, at the time of power saving. The frequency of the shift clock signal can be changed to 1 / n of the normal operation, and the same display data can be taken into the n signal lines for each shift clock signal.

In the above embodiment, the display data 1 is stored in the shift register 102 of the signal driver 101.
However, instead of this, the shift register 102 may generate only the display data fetch timing signal, and the display data may be fetched by the latch unit connected in parallel with the output unit 103. . Even with such a configuration, the effect of reducing the power by reducing the frequency of the shift clock signal 111 can be obtained as in the above-described embodiment.

Further, although the type of the liquid crystal panel is not particularly described in the above embodiment, the type of the liquid crystal panel is not particularly limited in the present invention, and is applied to both active matrix and simple matrix types. Is possible.

[0026]

According to the liquid crystal display device of the first aspect of the present invention, the power for driving the signal driver can be greatly reduced by lowering the frequency of the shift clock signal, so that the liquid crystal panel is consumed while being displayed. It becomes possible to reduce the electric power.

According to the liquid crystal display device of the second aspect of the present invention, the combination of the n signal lines for fetching the same display data can be periodically changed.
It is possible to prevent deterioration of the visual resolution.

According to the liquid crystal display device of the third aspect of the invention, the combination of the n signal lines for taking in the same display data can be changed aperiodically, so that the discontinuity and unevenness of the screen are caused. Can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration and a timing chart of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an overall configuration and a timing chart of a conventional liquid crystal display device.

[Explanation of symbols]

 101 signal driver 102 shift register 103 output unit 104 shift clock input line 106 clock switching signal input line 107 signal line 108 scanning driver 109 scanning line 110 liquid crystal panel

Claims (3)

[Claims] 1. A dot matrix type liquid crystal panel having a plurality of signal lines, a plurality of scanning lines, a pixel connected to each of the plurality of signal lines and the plurality of scanning lines, and the plurality of: A scanning driver that sequentially drives the scanning lines of a book; a signal driver that sequentially captures display data into the signal lines based on an input shift clock signal and outputs the captured display data to the liquid crystal panel line-sequentially; When the power is applied, the frequency of the shift clock signal is changed to 1 / n of that in the normal operation, and the control means for fetching the same display data into the n signal lines for each shift clock signal is provided. Liquid crystal display device. 2. The liquid crystal display device according to claim 1, wherein the control unit periodically changes a combination of the n signal lines that fetch the same display data. 3. The liquid crystal display device according to claim 1, wherein the control unit changes a combination of the n signal lines that fetch the same display data aperiodically.