JPH1075412A - Driving method for liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display the images of different systems on the same liquid crystal display device by simultaneously supplying the same scan signal for each adjacent scan signal line group composed of plural scan signal lines when displaying an NTSC image. SOLUTION: Since high-definition television broadcasting is the interlace scan of 2:1, in an odd-numbered field, a gate driver 4 between gate drivers 4 and 5 successively performs shift operation in every horizontal scanning period but the gate driver 5 is not operated. In an even-numbered field, however, only the gate driver 5 performs shift operation in every horizontal scanning period but the gate driver 4 is not operated. In the case of NTSC broadcasting, adjacent scanning lines are driven while being paired two by two, and the image is displayed at the central part of a display area. Namely, only 485×2=970 effective scanning lines of NTSC are used, non-use areas for 27 lines each are provided on the upside and down-side of a display screen, and the image is horizontally displayed in the area of an aspect ratio 4:3 corresponding to the dimension of 970 scanning lines.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device for displaying high-definition and current NTSC and EDTV images and a driving method thereof.

2. Description of the Related Art Hi-vision broadcasting is based on broadcasting satellites (BS-
The broadcast time was extended by the launch of 3b), 1997
A full-scale broadcast is scheduled for this year. Under these circumstances, development of related equipment such as HDTV receivers
Commercialization is actively taking place. As a high-vision display device, a projection TV using a CRT, a projection TV using a liquid crystal panel, and the like have been commercialized, including a direct-view CRT whose standard is unified to 32 inches and 36 inches. . Also, research on high-definition display using a flat panel display device such as a plasma display is being advanced. However, all of the display devices are dedicated to high-vision display, and cannot display the current NTSC broadcast. On the other hand, a decoder (down-converter), which is a related device, has been developed to display high-definition broadcasting on a current NTSC display device, and it is now possible to enjoy high-definition broadcasting on a CRT in each home. However, it deviates from the original purpose of high-definition display, such as the definition and clarity of the image and the powerful image with a sense of presence. In the future, if high-definition video enters the home due to the enhancement of high-definition broadcasting and the reduction and spread of related equipment, at present,
TVs for NTSC and HDTV are required, which causes problems such as installation space and purchase price. In other words, instead of using a downconverter to display high-definition signals on a display device for NTSC, in the future, high-definition display devices that can enjoy high-definition, realistic and powerful images that are the original purpose of Hi-Vision, It is considered that it is required to display an NTSC video. In addition, CR which is heavy in terms of weight
Instead of a display device using T, it is desired to be lightweight and thin. Here, the difference between the NTSC standard and the Hi-Vision standard will be described. The major difference between the two standards is that
It is the number of vertical scanning lines and the aspect ratio of the screen (the aspect ratio of the TV screen). The number of vertical scanning lines, the number of effective scanning lines, and the aspect ratio of the NTSC standard and the Hi-Vision standard are shown below.・ Aspect ratio: NTSC = 4: 3, HDTV = 16: 9 ・ Number of vertical scanning lines: NTSC = 525 lines, HDTV = 1125 lines ・ Effective scanning lines: NTSC = 485 lines, HDTV = 1,035 Display devices conforming to NT
There are the following problems when displaying an SC video. With regard to the number of vertical scanning lines, the NTSC standard is about half of the HDTV standard,
When a TSC image is displayed, only about one half of the area is displayed in the vertical direction, and nothing is displayed in the other half of the area. In addition, if the NTSC broadcast is displayed in the entire effective display area of the 16: 9 aspect ratio of the Hi-Vision standard due to the difference in the aspect ratio of the screen, the image will be elongated in the horizontal direction. In order to display NTSC video on a display device conforming to the Hi-Vision standard, it is necessary to solve the above problems.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and has been made in view of the above-mentioned drawbacks, and has the same display device and a liquid crystal display device that displays a high-definition image and an NTSC / EDTV image in different systems. A display device and a driving method thereof are provided.

A method of driving a liquid crystal display device according to the present invention comprises a matrix display panel having a plurality of scanning signal lines and a plurality of image signal lines conforming to the Hi-Vision standard, and a scanning signal line of the panel. And a scanning signal driving circuit connected to an image signal line of the panel, and a high-definition image and a current NTSC
A method for driving a liquid crystal display device capable of displaying both images, wherein the same scanning signal is simultaneously supplied to each scanning signal line group including a plurality of adjacent scanning signal lines when displaying an NTSC image. It is. <Operation> According to the liquid crystal display device of the present invention, when displaying a high-definition image, the image is displayed on the entire area of the panel of the liquid crystal display device. By controlling the switching so as to display in a part or the whole of the area, the same liquid crystal display device can display a high-definition video and an NTSC video in different systems.

FIG. 1 is a block diagram showing the configuration of an image display device according to the present invention. The liquid crystal display device shown in the same figure has an effective display portion with an aspect ratio of 1 in accordance with the Hi-Vision standard.
6: 9, about 1000 scanning signal lines and 14 video signal lines
Data drivers 2 and 3 for supplying video signals to the liquid crystal panel 1 having the number of 00 to 1920, and TFTs in the liquid crystal panel 1
Gate drivers 4 and 5 for controlling (thin film transistor)
And a high-definition or NTSC video signal processing circuit 6
And a timing signal generation circuit 7 for controlling the driver. The operation of each block when a high-definition image is displayed on the liquid crystal display device of FIG. Since HDTV broadcasts use 2: 1 interlaced scanning,
Of the gate drivers 4 and 5, in the odd-numbered fields, 4 sequentially shifts every horizontal scanning period, but 5 does not operate. Similarly, in the even field, only 5 performs the shift operation every horizontal scanning period, but 4 does not operate. Further, the data drivers 2 and 3 sample and hold the video signal by the output pulse of the shift register operating at the frequency f obtained by the following <Equation 1>, and synchronize the shift operation of the gate driver with the liquid crystal panel. Supply video data.

(Equation 1) The video signal processing circuit 6 amplifies the Hi-Vision video signal and performs an AC inversion process required for driving the liquid crystal panel. FIG. 2 shows a timing chart of each signal supplied to the liquid crystal display device. Here, the timing signal generating circuit 7 includes start signals STV1 and STV2 for starting the shift operation of the left and right gate drivers and a shift clock C.
KV1 and CKV2 are generated alternately for each field. Further, a clock signal and a start signal of the data driver having the operating frequency determined by the above-described <Equation 1> are also generated. FIG. 3 shows a display area of a high-definition image in the liquid crystal display device of the present invention. FIG. 9A shows that the number of pixels in the horizontal direction is temporarily set to 1920 in accordance with the HDTV standard.
Dot (length 160cm), number of vertical pixels 1024
An effective display area of the display panel when dots (90 cm in length) are set is shown, and FIG. 2B shows a display area when a high-definition broadcast is displayed. FIG. 4 shows NTSC (ED
5 shows a display area in the case of broadcasting (including TV). FIG.
FIG. 3 shows an example in which adjacent scanning signal lines are driven in pairs every two lines, and an image is displayed in the center of the display area in FIG. That is, the number of effective scanning lines of NTSC is 485 × 2
= 970 lines only, unused areas are provided above and below the display surface in 27 lines each, and images are displayed in an area having an aspect ratio of 4: 3 in the horizontal direction according to the dimensions of 970 scanning lines. . The left and right non-display areas are N
From the difference between the aspect ratios of the TSC standard and the high-definition standard, that is, the difference between 4: 3 (12: 9) and 16: 9, 1/8 in the horizontal direction is provided as an unused area that is not displayed on the left and right of the display area. I just need. The horizontal image display dimensions and the dimensions of the left and right unused areas are calculated by the following equations. 90 cm × (970/1024) × (4/3) = 113.67 cm (160 cm−113.67 cm) /2=23.165 cm By providing a region having this width, an NT having an aspect ratio of 4: 3 is provided.
SC / EDTV video is obtained. That is, an NTSC image is displayed at the center of the screen, and non-display areas are provided on the left and right of the display. This unused area may display an arbitrary background color such as black display. Next, NTSC / EDT is performed using the entire area of the display panel shown in FIG.
An example in which a V image is displayed in overscan will be described. In the horizontal direction, 1920 dots (160c
m) use all, NTS in one vertical direction
Since the aspect ratio of C / EDTV is 4: 3, the display size is 160 cm × 3/4 = 120 cm, and NTS
If 364 (485 × 90 cm / 120 cm) of the 485 effective scanning lines of the C / EDTV are displayed in the entire area of the display panel, an NTSC / EDTV image can be displayed. On the other hand, in the case of performing NTSC / EDTV display using all 1024 pixels in the vertical direction, the same scanning signal is supplied to three adjacent scanning signal lines and overscanning is performed. Is possible. FIG. 4C shows the case where the entire area of the display panel is used and NT
This is an example in which SC / EDTV broadcasting is displayed on four different channels, for example, images of companies A, B, C, D, etc. of commercial broadcasting. Since the number of scanning lines for one channel display is 485 lines, two screens can be displayed in the vertical direction. The horizontal direction is set according to the aspect ratio 4: 3. The multi-channel display for displaying the images of the plurality of channels on the same screen is not limited to four channels. FIG. 5 shows a timing chart in the EDTV system when FIG. 4A is driven. As shown in FIG. 5, in order to make the first 27 lines in FIG. 4A an unused area, the start signal STV in the vertical direction is set earlier by 27 horizontal scanning periods (27 Hs) than the start of the effective scanning line. I have. That is, the start signal STV1 of the odd row driver on the left is 14 Hs before the effective scanning line, and the start signal STV2 of the even row driver on the right is 13 Hs before the effective scanning line.
, The first image is displayed on lines 28 and 29 of the display panel. On the other hand, in the horizontal direction, the entire effective display period of about 52 μs
What is necessary is just to sample with a dot (113.67 cm x 1920/160 cm). In this case, the frequency of the shift clock of the data driver arranged above and below is basically 13 MHz according to the following equation. 1364 dots / 52 μs / 2 ≒ 13 MHz FIG. 6A is a timing chart showing a driving example of FIG. 4B. In this case, the display is overscanned, contrary to the above-described FIG. In order to supply the same scanning signal to three adjacent lines without displaying the first 72 lines of video data on the display, the scanning signal lines 1, 2, 3 (G1, G2, G3 in the figure) of the display panel May be turned on on the 73rd line after the start of effective scanning. Then, G4, G5, and G6 may be sequentially shifted on the 74th line, and G7, G8, and G9 may be sequentially shifted on the 75th line. The same applies to the 76th line and thereafter. When supplying the same scanning signal to these three adjacent lines, the gate driver needs a latch function and an output control function. However, the number of lines supplying the same scanning signal is not limited to three. It is also possible to enlarge and display four lines, six lines, or the like. In that case, the display period in the horizontal direction may be changed according to the number of vertical display lines and the aspect ratio. FIG. 6B shows a display period in the horizontal direction. In other words, 3
The display period in the horizontal direction corresponding to the display of 41 × 3 = 1024 dots is 48.8 μs, and the shift clock 1
9.7 MHz. Here, a typical operation of the above-described latch function will be described. For example, in consideration of interlaced scanning with a gate driver on one side, the output of the gate driver needs to be a signal for each output. In this case, a latch circuit is required. That is,
The shift register performs a shift operation sequentially, and its output is converted one by one by a latch circuit. FIG. 7 shows a timing chart thereof. In the figure, the latch circuit enters the through mode when LAT is High, and LA
When T = Low, the latch mode is set. The input of the latch circuit is the output signal of the shift register circuit. LAT is Hi
In the case of gh, the latch output outputs the output signal of the shift register through, and when the LAT is Low, the output is held. That is, by supplying the LAT signal at twice the cycle of the shift clock (CKV), a signal shifted for each line can be output. In the case of simultaneous driving of three lines by arranging both sides of the gate driver, the control method is somewhat complicated, but basically the above-described latch operation is required. As described above, the liquid crystal display device capable of switching the display between the high-definition video and the current NTSC video or EDTV has a high definition and clarity, which is the purpose of the high-definition display, and has a powerful and realistic feeling. At the same time that an image can be obtained, the current NTSC video can be displayed on the same display device without using a new display device. Further, since the liquid crystal display device is light and thin, it is very effective in terms of installation space and weight.

According to the present invention, high-definition and NTSC / NTSC / HDTV can be realized on a single display device without impairing the high-definition, realistic and powerful image which is the original purpose of HDTV.
It is possible to display images of different systems called EDTV, and even if high-definition television spreads to each home in the future, not only will it be possible to display television of each system without requiring a plurality of display devices, It becomes a lightweight and thin display device.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a liquid crystal display device targeted by the present invention.

FIG. 2 is a timing chart when a high-definition display is performed by the liquid crystal display device.

FIG. 3 is a diagram showing a display area of an image in each mode.

FIG. 4 is a timing chart in the EDTV mode.

FIG. 5 is a timing chart illustrating a driving example.

FIG. 6 is a timing chart illustrating a driving example.

FIG. 7 is a timing chart illustrating a latch function.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 Data driver 3 Data driver 4 Gate driver 5 Gate driver 6 Video signal processing circuit 7 Timing signal generation circuit

Claims (1)

[Claims] 1. A matrix display panel comprising a plurality of scanning signal lines and a plurality of image signal lines conforming to the Hi-Vision standard, a scanning signal driving circuit connected to the scanning signal lines of the panel, and an image signal of the panel. With image signal drive circuit connected to the line, HDTV video and current NTS
In a method of driving a liquid crystal display device capable of displaying both C images, when displaying an NTSC image, the same scanning signal is simultaneously supplied to each scanning signal line group including the plurality of adjacent scanning signal lines. A method for driving a liquid crystal display device, comprising: