JPH07121137A - Display device - Google Patents

Abstract

PURPOSE:To obtain the display device which is reducible in power consumption without spoiling the quality of a display image at a display part so much. CONSTITUTION:This device is provided with a memory 14 which stores an image signal, supplied to a liquid crystal display panel 8 as the display part, by one field, a comparator 15 which compares an image signal of a previous field read out of this memory 14 with an image signal of a current field supplied to the liquid crystal display panel 8 and discriminates between a still picture display and a moving picture display, and a controller 16 which makes the source voltage supplied from a power source 12 for the panel to the liquid crystal display panel 8 lower than at the time of the moving picture display once the comparator 15 decides a still picture by the comparison.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is particularly useful as a display device for portable information equipment, communication equipment, video equipment, game equipment and the like, and as display equipment for equipment mounted on moving bodies such as ships and automobiles. It is suitable for use.

[0002]

2. Description of the Related Art Conventionally, for example, a display device such as a portable personal computer used as a display unit uses a liquid crystal display panel of a TFT active matrix type in which a plurality of pixels are arranged in a matrix in horizontal and vertical directions. The liquid crystal display panel is supplied with a power supply voltage from a battery to be driven by a driver, in this case, a source and a gate driver, to display an image.

Specifically, in this liquid crystal display panel, as shown in FIG. 4, a plurality of signal electrodes 1, scanning electrodes 2, TFTs 3 and pixel electrodes 4 are formed in a matrix on one insulating substrate (not shown) side. At the same time, the common electrode 5 is formed on the other insulating substrate (not shown) side opposite to the common electrode 5, and the display by each pixel constituted by the liquid crystal layer interposed between the common electrode 5 and each pixel electrode 4 is displayed. The line-sequential scanning is performed by each signal electrode 1 and the scanning electrode 2.

For example, when a scanning voltage is applied from the gate driver 6 to the scanning electrode 2 of the first line, each TFT 3 of the first line connected thereto becomes conductive, and each pixel electrode 4 of the first line. The signal electrodes 1 are connected to the respective pixels, and a signal voltage (that is, an image signal) is applied from the source driver 7 to each pixel on the first line.
Therefore, an image signal for one field can be displayed on the liquid crystal display panel by repeating such an application operation (scan operation) sequentially from the first line in a horizontal cycle for each line. The image is reproduced by repeating every field, that is, in the vertical cycle. It is assumed that the signal voltage is polarity-reversed line by line and field by field so that no DC component is applied to the liquid crystal display panel.

[0005]

By the way, the liquid crystal driving voltage in such a display device is becoming higher due to the necessity of high duty, and the power supply voltage supplied to the liquid crystal display panel is set relatively high. ing. As a result, power consumption during image display increases, which is a problem for a display device such as a portable device having a limited power supply capacity such as a battery.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a display device capable of reducing power consumption without deteriorating the quality of a display image in the display section to the left. It is what

[0007]

In order to achieve the above-mentioned object, the present invention provides a display device in which a power supply voltage is supplied to the display unit to display an image signal. Storage means for storing an image signal, a comparison means for comparing the image signal read from the storage means with the image signal supplied to the display section to determine whether to display a still image or an operating image, and to the comparison means. And a control means for lowering the power supply voltage to the display unit when compared with the static image display compared to when the operation image is displayed. Specifically, the storage means stores one field of the image signal supplied to the display section, and the comparison means stores the image signal of the previous field read from the storage means and the current field supplied to the display section. It is to compare with the image signal of the field. Further, the display unit is a liquid crystal display panel, and the storage unit is a non-volatile memory.

[0008]

According to this structure, while the moving image is displayed with motion, the power supply voltage to the display section is normally increased to reproduce a high-definition image so that the moving image can be easily seen. is doing. Since there is no movement during the display of a still image, it is not necessary to have a higher definition as far to the left.Therefore, the power supply voltage to the display unit can be made lower than that of the operation image display, and the minimum voltage required for the image display Power consumption is reduced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A display device of a personal computer using a liquid crystal display panel will be described below as an embodiment of the present invention with reference to the drawings. In this embodiment, the power supply voltage is normally supplied to the liquid crystal display panel during the operation image display,
While still images are being displayed, the operating voltage is lower than that at the time of displaying the operating images so that the voltage is kept at the minimum voltage required for displaying images. It is designed to be compatible with the display.

Specifically, it is constructed as shown in FIG. 1, and 8 is a plurality of pixels in the horizontal and vertical directions (in this case, 48 pixels).
(0 × 640 pixels) is a TFT active matrix type liquid crystal display panel, and 9 is a driver for driving the liquid crystal display panel 8 line-sequentially based on a timing signal from the controller 10 to display an image. It is composed of a gate driver that sequentially selects lines 480 to 480, and a source driver that applies an image signal to each pixel on the line selected by the gate driver, that is, 640 pixels.

Reference numeral 11 denotes a CPU on the personal computer side for controlling the image display on the liquid crystal display panel 8, and by controlling the timing signal output from the controller 10 in response to the operation key input on the keyboard side. It is designed to control the image display on. Reference numeral 12 is a panel power supply for supplying a power supply voltage to the liquid crystal display panel 8 and the driver 9 for displaying an image, and 13 is a memory 1 for extracting an image signal supplied from the personal computer side to the liquid crystal display panel 8.
4 is a controller for storing in this memory 14
Is a non-volatile memory such as EEPROM or FRAM which does not require a special battery backup device, and stores the image signal supplied to the liquid crystal display panel 8 for one field.

Reference numeral 15 compares the image signal of the current field supplied to the liquid crystal display panel 8 with the image signal of the previous field read from the memory 14 to determine whether the image is an operation image display such as screen scroll or still image display. If the image signal of the current field is not different from the image signal of the previous field, that is, if the image signal is not updated, it is determined that the display is a still image display. For example, it is determined that the operation image is displayed. Reference numeral 16 denotes a controller that controls the panel power supply 12 based on the comparison determination made by the comparator 15, and when the comparison is determined to be a still image display, the power supply voltage from the panel power supply 12 to the liquid crystal display panel 8 is changed. The voltage is reduced to the minimum voltage required for image display.

Therefore, when the image signal of the operation image is supplied to the display device having such a configuration, the image signal of the current field supplied from the driver 9 to the liquid crystal display panel 8 and stored in the memory 14. The image signal of the previous field does not become the same, that is, the image signal is updated for each field, and the comparator 15 makes a comparison determination to be the operation image display. Therefore, in such a case, the power supply voltage supplied to the liquid crystal display panel 8 by the controller 16 is normally set to be relatively high, and an image with high definition can be reproduced so as not to hinder the operation image display. Will be done.

On the contrary, when the image signal of the still image is supplied to the display device, the image signal of the current field supplied from the driver 9 to the liquid crystal display panel 8 and the image of the previous field stored in the memory 14. The signal becomes the same, and the comparator 15 makes a comparison determination to display a still image. Therefore, the controller 1
6, the power supply voltage supplied to the liquid crystal display panel 8 is reduced to the minimum voltage required for image display, and power consumption is reduced.

Next, FIG. 2 is a flow chart for explaining such a power supply control operation. As shown in FIG. 3, a predetermined line number in the vertical (Y) direction of the liquid crystal display panel 8 of 480 × 640 pixels. Ym, horizontal on that line (X)
The predetermined pixel number in the direction is Xn, and for example, step # 5 now
If the image signal of the (i-1) th field is displayed on the liquid crystal display panel 8, the i
The image signal of the -1st field is stored in the memory 14. Then, before the image signal of the next i-th field is displayed on the liquid crystal display panel 8 in step # 20, the image signal of the i-th field is stored in the memory 14 in step # 10. The image signal of the (i-1) th field is compared.

If the two image signals are not the same, for example, the image signal X of the (i-1) th field during the comparison is calculated.
If (i-1) n, Y (i-1) m and the image signals X (i) n, Y (i) m of the i-th field do not match,
Assuming that the image is an operation image, the process proceeds to step # 45 to supply a normal power supply voltage to the liquid crystal display panel 8 to display the image signal of the i-th field in step # 20. On the other hand, if both image signals are the same, it is determined that the image is a still image, the process proceeds to step # 50, the power supply voltage to the liquid crystal display panel 8 is reduced, and the image signal of the i-th field is displayed in step # 20. Let me do it.

Then, in step # 25, the image signal of the i-th field is stored in the memory 14, and the same operation is repeated thereafter. That is, step #
Before the image signal of the next (i + 1) th field is displayed on the liquid crystal display panel 8 in step 35, the i
The image signal of the + 1st field is compared with the image signal of the i-th field stored in the memory 14 in step # 25, and depending on the comparison result, the process proceeds to step # 45 or # 50, and in step # 40. Similarly, the image signal of the (i + 1) th field is stored in the memory 14.

In this embodiment, the liquid crystal display panel has a T
The case of FT has been described, but the case of STN is also acceptable.
In that case, the liquid crystal display panel is driven by the segment driver and the common driver. Further, although the power supply voltage is supplied from the panel power supply to the liquid crystal display panel, it may be supplied from the system power supply such as a controller, in which case the system power supply is controlled. Further, a picture tube may be used as the display unit, and the power supply voltage supplied to the anode side of the picture tube may be lowered when displaying a still image.

[0019]

As described above, according to the display device of the present invention, when the operation image is displayed, the normal power supply voltage is supplied to the liquid crystal display panel so that the operation image display is not hindered. At the same time, when displaying a still image, a power supply voltage lower than that during displaying the operation image is supplied to reduce power consumption. It will be possible.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram for explaining the power supply control operation.

FIG. 3 is a diagram showing predetermined line numbers and pixel numbers of the liquid crystal display panel.

FIG. 4 is a diagram showing an example of driving a conventional liquid crystal display panel.

[Explanation of symbols]

 8 LCD display panel 9 Driver 12 Power supply for panel 14 Memory 15 Comparator 16 Controller

Claims (3)

[Claims] 1. A power supply voltage is supplied to a display unit,
In a display device for displaying an image signal on a display unit, a storage unit for storing an image signal supplied to the display unit and an image signal read from the storage unit and an image signal supplied to the display unit are compared. And comparing means for determining whether to display a still image or operating image, and control means for lowering the power supply voltage to the display unit when the comparing image is compared and determined to be still image display by the comparing means. A display device comprising: 2. A power supply voltage is supplied to the display unit,
In a display device for displaying an image signal on a display unit, a storage unit for storing the image signal supplied to the display unit for one field, and an image signal of the previous field read from this storage unit and supplied to the display unit. Comparing means for comparing the image signal of the current field to determine whether to display a still image or an operating image,
A display device comprising: a control unit that lowers the power supply voltage to the display unit when the comparison unit determines that the display is a still image display, compared to the case where the operation image is displayed. 3. The display device according to claim 1, wherein the display unit is a liquid crystal display panel, and the storage unit is a non-volatile memory.