JP2657139B2 - Driving method of liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an active matrix type liquid crystal display device in which a plurality of liquid crystal cells are arranged in rows and columns.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal display device used in a liquid crystal television, the number of liquid crystal cell rows extending in the horizontal direction of the display screen is approximately equal to the number of effective horizontal scanning lines for forming an image of one frame of the NTSC system. A display composed of 480 lines has been proposed. When displaying a video signal of the NTSC system by such a liquid crystal display device, interlaced scanning with a frame period of 1/30 second (field period of 1/60 second) is performed. It is.

In a liquid crystal display device, in order to extend the life of a liquid crystal cell, the polarity of a video signal shown in FIG. 8A is inverted for each frame as shown in FIG. .

Accordingly, the period in which the same cell is driven with the same polarity is 1/15 second, that is, 2 frame periods, as shown in FIG. 8 (c). There was a problem.

In view of this, there has been proposed a method (double-speed non-interlaced scanning method) in which two rows of pixels are selectively driven during one horizontal scanning period in a non-interlaced scanning method, instead of the interlaced scanning method (Japanese Patent Laid-Open No. 2002-209,837). 62-113129
[G02F1 / 133]).

In recent years, television broadcasting (H.sub.H) based on a high-definition system in which the number of horizontal scanning lines forming one screen is 1125, which is about twice that of the NTSC system.
DTV) is being put to practical use.

[0007]

However, when a liquid crystal display device compatible with the high-vision system is constructed, if the conventional interlaced scanning is performed, the number of liquid crystal cell rows is about 1000, which is twice that of the conventional case. It is necessary to configure a liquid crystal panel, which causes not only loss of compatibility with the conventional NTSC system but also flicker. If the above-described double-speed line sequential scanning method is adopted, flicker can be suppressed to some extent, but there is a problem that the circuit configuration becomes complicated.

It is an object of the present invention to provide a driving method capable of effectively suppressing flicker when a high definition video signal is displayed on a liquid crystal display device without making a significant change in the circuit configuration. is there.

[0009]

According to the driving method of the liquid crystal display device of the present invention, the number of liquid crystal cell rows extending in the horizontal direction is N.
A driving method for displaying a Hi-Vision video signal for a liquid crystal display device corresponding to the number of horizontal scanning lines (effective horizontal scanning lines: about 480) constituting one frame image of the TSC system. Then, after displaying the video signal on each horizontal scanning line constituting the odd field of the image of the HDTV system in one field period by non-interlaced scanning corresponding to each liquid crystal cell row, the even field following the odd field is displayed. A video signal on each horizontal scanning line is displayed in one field period by non-interlaced scanning in correspondence with each liquid crystal cell row.

[0010]

In the display of the odd field and the even field, each liquid crystal cell row is sequentially driven based on the video signal on each horizontal scanning line, and non-interlaced scanning is performed. At this time, in the odd field and the even field, Video signals on horizontal scanning lines at the same vertical position are displayed on liquid crystal cell rows at the same vertical position.

Therefore, the signal is rewritten in the same cell at a field cycle, that is, a cycle of 1/60 second, and flicker on the screen becomes invisible.

[0012] Even in the case of performing the AC drive in which the polarity is inverted for each frame, as shown in FIG. Therefore, flicker on the screen due to polarity inversion is suppressed.

[0013]

According to the driving method of the liquid crystal display device according to the present invention, as the liquid crystal display device, the number of liquid crystal cell rows extending in the horizontal direction is equal to the number of horizontal scanning lines constituting one frame image of the NTSC system. Using a conventional NTSC-compatible liquid crystal panel that supports the number of effective horizontal scanning lines (about 480 lines), it is possible to display high-definition video signals, so there is no need to change the drive circuit significantly. As described above, flicker can be effectively suppressed.

Since an NTSC-compatible liquid crystal panel can be used, when displaying an NTSC video signal, the display is switched to interlaced scanning and an EDTV (Extende
d Definition TV) When displaying a video signal of the system, by providing a switching means for switching to double-speed non-interlaced scanning, not only NTSC video signal,
EDTV video signals can also be displayed on a common liquid crystal display device.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an entire configuration of a liquid crystal display device. An active matrix type liquid crystal panel (2) in which a plurality of liquid crystal cells are arranged in a matrix has a number of liquid crystal cell rows extending in the horizontal direction in the NTSC system. The number of effective horizontal scanning lines for forming one frame image is 480.

The liquid crystal panel (2) is connected to an X driver (3) serving as a scanning drive circuit, and also connected to a first Y driver (4) and a second Y driver (5) serving as a modulation drive circuit.

As shown in FIG. 2, the X driver (3) has gate terminals G1 to G480 for outputting gate pulses corresponding to 480 liquid crystal cell rows of the liquid crystal panel (2).

As shown in FIG. 1, RGB video signals are connected to the first and second Y drivers (4) and (5) via a polarity inversion circuit (6). The polarity inversion circuit (6) inverts the polarity of the video signal for each frame and outputs it, as is well known.

The synchronization control circuit (1) for supplying a start pulse and a clock pulse to each of the drivers (3), (4) and (5) has a video signal to be displayed on the liquid crystal panel (2).
The operation is switched as described later depending on whether the system is the SC system, the EDTV system, or the Hi-Vision system.

That is, the horizontal synchronizing signal separated from the video signal is supplied to the PLL circuit (7), whereby a timing signal whose phase coincides with the horizontal synchronizing signal is created. A plurality of capacitors are connected to the PLL circuit (7) via switches SW1 to SW3. By switching the switches, the PLL circuit (7) is connected to the NTSC system and the EDTV.
Three different time constants corresponding to the system and the HDTV system are set.

The vertical synchronizing signal separated from the video signal is supplied to a pulse generating circuit (8) together with the timing signal generated by the PLL circuit (7). The pulse generating circuit (8) is configured using, for example, a logic cell array (LCA) manufactured by Xilinx Corporation in the United States, and has three memories (9) (9) connected via switches SW4 to SW6 as shown in the figure.
1) A start pulse and a clock pulse for each system are created based on three types of different connection information corresponding to the NTSC system, the EDTV system, and the Hi-Vision system respectively supplied from (92).

The operation of the above circuit will be described below.
FIG. 3 shows the timing of the gate pulse output from each of the gate terminals G1 to G480 of the X driver (3) shown in FIG. 2 when displaying the video signal of the EDTV system and the high vision system, and shows one field period. Included in 4
In synchronization with 480 horizontal synchronizing signals extracted from 80 effective horizontal scanning lines, 480 gate pulses P _{1 to} P ₄₈₀ are synchronized.
Is produced and supplied to each gate line of the liquid crystal panel (2). As a result, double-speed non-interlace scanning is performed in the case of the EDTV system, and non-interlace by half lines is performed in the case of the high-vision system.

FIG. 4 shows the timing of each gate pulse when an NTSC video signal is displayed. In the odd field period, 240 horizontal synchronization lines extracted from 240 effective horizontal scanning lines are shown. Signal (1H to 240
H), the odd-numbered gate terminals G ₁ , G ₃ ,.
_{From 479} , 240 gate pulses are generated and supplied to each gate line of the liquid crystal panel (2). In the next even-numbered field period, the even-numbered gate terminals G ₂ , G _4, ..., G ₄₈₀ are synchronized with the 240 horizontal synchronization signals (241H to 480H) extracted from the 240 effective horizontal scanning lines. , 240 gate pulses are generated and supplied to each gate line of the liquid crystal panel (2). As a result, interlaced scanning is performed.

FIG. 5 shows non-interlaced scanning using half lines when displaying a video signal of the Hi-Vision system. In an odd field and an even field, video signals on horizontal scanning lines at the same vertical position are displayed at the same vertical position. It will be displayed in the liquid crystal cell row. Therefore,
Since the signal is rewritten to the same cell at a field cycle, that is, a cycle of 1/60 second, flicker on the screen is not noticeable.

[0025] Matazu 6 represents the speed non-interlace scanning in the case of the EDTV system, 1 per field
H, 2H,... 480H video signals are displayed. Flicker is suppressed by this double-speed non-interlace scanning.

FIG. 7 shows interlaced scanning in the case of the NTSC system. In odd fields, 1H, 2H... 240H video signals are displayed in odd-numbered liquid crystal cell rows, and in even fields, even-numbered fields are displayed. 480H video signals are displayed on the liquid crystal cell row.
Note that no video signal is displayed at the position indicated by the broken line in the figure.

According to the above-mentioned liquid crystal display device, flicker is suppressed in the case of the HDTV system and the EDTV system, and the video signals of the three systems including the NTSC system can be switched and displayed using a common liquid crystal panel. I can do it.

The description of the above embodiments is for the purpose of illustrating the present invention and should not be construed as limiting the invention described in the claims or reducing the scope thereof. Further, the configuration of each part of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made within the technical scope described in the claims.

For example, in the above embodiment, the polarity inversion of the video signal is performed in the frame cycle. However, it is also possible to perform the polarity inversion in the field cycle, thereby further reducing the effect of the flicker suppression by the polarity inversion. Can be raised.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a connection state between a gate terminal of an X driver and a liquid crystal cell row of a liquid crystal panel.

FIG. 3 is a timing chart of a gate pulse in the Hibernation system and the EDTV system.

FIG. 4 is a timing chart of a gate pulse in the NTSC system.

FIG. 5 is a diagram illustrating non-interlaced scanning in a high-vision system.

FIG. 6 is a diagram illustrating double-speed non-interlace scanning in the EDTV system.

FIG. 7 is a diagram illustrating interlaced scanning in the NTSC system.

FIG. 8 is a waveform chart of a video signal and an applied voltage for explaining an effect of the present invention.

[Explanation of symbols]

 (1) Synchronous control circuit (2) LCD panel (3) X driver (8) Pulse generation circuit

Claims (2)

(57) [Claims] 1. A liquid crystal display device in which a plurality of liquid crystal cells are arranged in a matrix and the number of liquid crystal cell rows extending in the horizontal direction corresponds to the number of horizontal scanning lines constituting one frame image of the NTSC system. A driving method for displaying a high definition video signal, wherein a video signal on each horizontal scanning line constituting an odd field of the high definition method is displayed in one field period by non-interlace scanning in correspondence with each liquid crystal cell row. After that, a video signal on each horizontal scanning line constituting an even field following the odd field is displayed in one field period by non-interlace scanning in correspondence with each liquid crystal cell row. Method. 2. The liquid crystal display device switches to interlaced scanning when displaying an NTSC video signal.
2. The driving method of a liquid crystal display device according to claim 1, further comprising a switching unit for switching to double-speed non-interlace scanning when displaying a DTV video signal.