Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-03-02
2003-07-08
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S087000, C345S093000, C345S094000, C345S096000, C345S101000, C349S072000
Reexamination Certificate
active
06590555
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a liquid crystal display (LCD) panel driving circuit and liquid crystal display, particularly to the 1-line and 2-line dot inversion driving mode of the LCD panel data driver, providing a method capable of eliminating the frame flickers in the prior art and/or the odd/even scan line brightness unevenness of the LCD panel driver circuit, thereby improving the frame quality.
2. Description of the Related Art
FIG. 1
is a schematic diagram of a prior art liquid crystal display panel (hereinafter, referred to as a “LCD panel”) and the peripheral driving circuit thereof. As shown in the figure, a LCD panel is formed by interlacing data electrodes (represented on D
1
, D
2
, D
3
, . . . , Dm) and gate electrodes (represented on G
1
, G
2
, G
3
, . . . , Gm), each of interlacing data electrodes and gate electrodes is used to control a display unit. For example, using the interlacing data electrode D
1
and gate electrode G
1
controls the display unit
200
. The equivalent circuit of each display unit comprises thin film transistors (TFT) (Q
11
-Q
1
m
, Q
21
-Q
2
m
, . . . , Qn
1
-Qnm) and storage capacitors (C
11
-C
1
m
, C
21
-C
2
m
, . . . , Cn
1
-Cnm). The gate and drain of TFTs are respectively connected to gate electrodes (G
1
-Gn) and data electrodes (D
1
-Dm). Such a connection can turn on/off all TFTs on the same line (i.e. positioned on the same scan line) using a scan signal of gate electrodes (G
1
-Gn), thereby controlling the video signal of data electrodes to be written into the corresponding display unit. It is noted that a display unit only controls a single pixel brightness on the LCD panel. Accordingly, each display unit responds to a single pixel on a mono-color LCD while each display unit responds to a single subpixel on a color LCD. The subpixel can be red (represented by “R”), blue (represented by “G”), or green (represented by “G”). In other words, a single pixel is formed of a RGB (three display units) combination.
In addition,
FIG. 1
also shows a part of the driving circuit of the LCD panel
1
. Gate driver
10
outputs the scan signals (or referred to as a scan pulse) of each of the gate electrodes G
1
, G
2
, . . . , Gn according to a predetermined sequence. When a scan signal is carried on one gate electrode, the TFTs within all display units on the same row or the same scan line are turned on while the TFTs within all display units on other rows or other scan lines are in a state to be turned off. When a scan line is selected, data driver
20
outputs a video signal (gray value) to the m display units of the respective row through data electrodes D
1
, D
2
, . . . , Dm according to the image data to be displayed. After gate driver
10
scans n rows continuously, the display of a single frame is completed. Thus, repeated scans of each scan line can achieve the purpose of continuously displaying the image. As shown in
FIG. 1
, signal CPV indicates the clock of gate driver
10
, signal CRT indicates the scan control signal received by gate driver
10
, signal LD indicates a data latch signal of data driver
20
, and signal DATA indicates the image signal received by data driver
20
.
Typically, a video signal, which is transferred by the data electrodes D
1
, D
2
, . . . , Dm, is divided into a positive video signal and a negative video signal based on the relationship with the common electrode voltage V
COM
. The positive video signal indicates the signal having a voltage level higher than the voltage V
COM
, and based on the gray value represented, the actually produced potential of the signal ranges between voltages Vp
1
and Vp
2
. In general, the gray value closer to the common electrode voltage V
COM
is lower. On the other hand, the negative video signal indicates the signal having a voltage level lower than the voltage V
COM
, and based on the gray value represented, the actually produced potential of the signal ranges between voltages Vn
1
and Vn
2
. Also, the gray value closer to the common electrode voltage V
COM
is lower. When a gray value is represented, whether in a positive video signal or in a negative video signal, the display effect generally is the same. In order to prevent the liquid crystal molecule from continuously receiving a single-polar bias voltage so as to reduce the liquid crystal molecular life, a display unit respectively receives positive and negative polar video signals corresponding to odd and even frames.
The disposition of the different polar video signal in each display unit can be divided into four driving types: frame inversion, line inversion, column inversion, and dot inversion. In frame inversion driving mode, the polarity of the video signal is the same on the same frame but the opposite on its adjacent frames. In line or column inversion driving mode, the same line or column on the same frame has the same polarity of the video signal but the opposite polarity to its adjacent lines or columns. In dot inversion driving mode, the polarity of the video signal on the same frame is presented in an interlaced form, which will be described in detail later.
In the actual practice using dot inversion, it can be further divided into a 1-line dot inversion and a 2-line dot inversion, described as follows.
FIG. 2
is a schematic diagram of the polarity of the video signal received by display units of a color LCD panel in a prior 1-line dot inversion driving mode. In
FIG. 2
, a coordinate represents a single pixel, e.g. (i,j), (i+1,j), (i,j+1), (i+1,j+1) . . . , the single pixel further including three corresponding subpixels, i.e. red (R), green (G), and blue (B) subpixels, wherein a subpixel corresponds to a single display unit of FIG.
1
. In the 1-line dot inversion driving mode, the video signal polarity of a display unit on the same frame is the opposite to that of its adjacent units, including at the up, down, left, and right positions. The subpixels positioned on the oblique areas of
FIG. 2
(for example, (i,j,R), (i,j,B), (i+1,j,G), (i+2,j,R), (i+2,j,B), . . . , and so on) and the other subpixels (for example, (i,j,G), (i+1,j,R), (i+1,j,B), (i+2,j,G), . . . , and so on) on the same frame receive the opposite polarities. For example, the subpixels positioned on the oblique have the positive polarity of the video signal while the other subpixels have the negative polarity. The inverse operation has the same feature as the above.
Although the slightly display difference between the positive and negative polarity of the video signals exists, the full display effect is not obviously different from the 1-line dot inversion driving mode when viewing a stationary frame. An example of
FIG. 2
, it is assumed that this area is blue (B) color, i.e. light on B, and light off R (red) and G (green). In pixels (i,j), (i,j+2), (i+1,j+1), (i+1,j+3), (i+2,j), (i+2,j+2), . . . of the Nth frame, the B subpixels receive positive polarity video signal, while in pixels (i,j+1), (i,j+3), (i+1,j), (i+1,j+2), . . . of the Nth frame, the B subpixels receive a negative polarity video signal. However, the polarity of the pixels of the N+1th frame is opposite to that of the Nth frame. Either the pixels on the Nth frame or the pixels on the N+1th frame have almost the same display effect, compared to both frames. However, an obvious display difference may happen on some specific frame, for example, the shut-down frame with the Microsoft Windows Operating System (MS OS).
For the shut-down frame with the MS OS, only half pixels of a scan line are selected to be displayed, and pixels selected from two adjacent scan lines are different to each other scan line. For an example of
FIG. 2
, the shutdown frame with Windows OS displays (i,j), (i,j+2), (i+1,j+1), (i+1,j+3), (i+2,j), (i+2,j+2), (i+3,j+1), (i+3,j+3), (i+4,j), (i+4,j+2), (i+5,j+1), (i+5,j+3). Wh
Su Feng-Cheng
Tseng Chun-Chin
Au Optronics Corp.
Darby & Darby
Hjerpe Richard
Lesperance Jean
LandOfFree
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