JPS62169126A - Liquid-crystal color panel driving circuit - Google Patents

Abstract

PURPOSE:To reduce the power consumption of a liquid-crystal panel driving circuit and miniaturize the device, by providing low-pass filters having different delay times before three sequences of video signal lines. CONSTITUTION:Three primary color signals impressed upon video signal input terminals 101-103 are supplied to sample holding circuit groups 114-116 through low-pass filters 104-109. The side shift register 113 simultaneously selects one sample holding circuit from each sample holding circuit group 114-116 and supplied sample-held video signals to a picture-element transistor matrix 117. Since video signals of three picture element quantities are simultaneously sample-held in such way, the shifting frequency of the X-side shift register 113 can be reduced to 1/3 and, as a result, this liquid-crystal panel driving circuit can be reduced in power consumption and the device can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a drive circuit for a liquid crystal color panel used as an image display device.

[Summary of the invention]

In the liquid crystal color panel drive circuit, the present invention reduces the number of pixel selections in one horizontal scan by installing low-pass filters with different delay times in front of five video signal lines for transmitting five primary color signals. Since the number of pixels can be reduced to 1/3 of the actual number of pixels in the horizontal scanning direction, the operating frequency of the O [Conventional technology ] Liquid crystal panels have basically been developed to display grayscale images, that is, black and white images.

Regarding the conventional LCD panel driving method, active φ
As for the matrix type, it was a driving method similar to that seen in [Active Panel J with a wide viewing angle using a guest-host type liquid crystal (Nippon & Electronics 1981゜2.16.).

As shown in Figure 2, the switch transistors of all pixels are connected to a single video signal line, and the structure is such that only the video signal from a single signal source is displayed. When displaying a color image on a color panel with the above structure, the three primary color signals are transferred in a time-division manner onto a single video signal line.At this time, the order of time-division transfer of the three primary color signals is determined by the arrangement of the color filters. It's getting exciting.

[Problem that the invention seeks to solve]

In conventional technology, in order to time-divisionally transfer the three primary color signals to a single video signal line, it was necessary to time-division multiplex the three primary color signals at the pixel selection period, and the signal switching circuit required high speed. Furthermore, the shift register inside the X driver used for horizontal scanning of the liquid crystal panel also required a speed that could operate at the pixel selection period.

Assuming that the number of horizontal pixels of the liquid crystal panel is 240 (80 pixels for each of the three primary colors), the pixel selection period is approximately 200.
ns, the time division period of the three primary color signals and the shift period of the X driver are approximately 200no.

Since liquid crystal panels are usually used as low-power display elements, their peripheral circuits are also required to be low-power.Therefore, peripheral drive circuits are implemented as much as possible using 0M03-C. CM'3''S logic circuits have the characteristic that power consumption increases in proportion to operating frequency (clock frequency), so in order to promote power reduction, it is essential to reduce the speed of the entire circuit. .

Furthermore, the LCD panel is not suitable for portable devices (particularly blurry TV).
In this case, harmonic interference (in-flight interference) from the liquid crystal panel drive circuit to the receiver has become a problem. In order to reduce this harmonic interference,
It is effective to reduce the clock frequency of the shift register in the X driver, which is the source.

The present invention was proposed to solve these problems, and its purpose is to reduce the power consumption of the drive circuit by using a slower lock signal than before when driving a liquid crystal color panel. The purpose of the present invention is to provide a liquid crystal color panel drive circuit that is easy to integrate as it can be driven even by slower logic circuits, and further reduces internal interference caused by harmonics generated by the drive circuit. Means for Solving the Problems] 1) The liquid crystal color panel drive circuit of the present invention has three mutually independent video signal lines for transmitting three primary color signals, and each of the three video signal lines has a It is characterized by having low-pass filters with different delay times in front, and supplying the three primary color signals to the video signal lines through the low-pass filters. Regarding the pass filter, the delay time difference between the first low pass filter and the second low pass filter and the delay time difference between the second low pass filter and the third low pass filter are set to −pixel selection time, respectively. Features.

[For production]

According to the above configuration of the present invention, the three primary color signals applied to the three video signal lines are delayed by the difference in pixel selection time by the low-pass filters placed in front of the respective video signal lines, so that the three primary color signals are delayed by the difference in pixel selection time. It becomes possible to simultaneously select as many X-side electrodes as X (Ell 1!), and the clock frequency of the shift register in the X driver for pole selection is lowered to 14 compared to the conventional one.

〔Example〕

The present invention will be described in detail below using the drawings.

FIG. 1 is a diagram showing the configuration of the present invention.

The three primary color signals applied to the video signal input terminals (101) to (103) are passed through low-pass filters (104) to (109).
Three independent video signal systems Ifj! (11
0) to (112) to the sample/hold circuit group (11
4) to (116). The X-side shift register includes a group of sample-hold circuits (114) to (116).
One sample-hold circuit from each circuit group is selected at the same time, and the sampled and held video signal is supplied to the pixel transistor matrix (117). (117) for vertical scanning @ low-pass filters (104) to (109), if the delay time is selected for the unit pixel selection period, sample and hold times M groups (114) to (116) The video signals added to the original signal are 5τ, 2τ, and τ(
τ is the unit pixel selection period). Therefore, if these three delayed video signals are sampled and held at the same time, the three video signals before being delayed will be delayed by 3τ, This is equivalent to sequentially holding samples at intervals of 2τ and τ. However, in this configuration, only the video signal for the king pixel is sampled and held at the same time, so the number of sample and hold operations is 1/1 compared to the case where the color pixel sample and hold operation is performed.
It becomes 3.

In other words, within the same horizontal scanning period, the number of shifts in the Unnecessary out-of-band components included in the signal can be removed.

FIG. 3 shows a specific example of the area around the pixel transistor matrix (117) in the case of the configuration shown in FIG.

Here, it can be seen that video signals are simultaneously supplied to the X-side electrodes (316) of two adjacent pixels.

The low pass filters (504)-(306) have their delay times selected as described above.

Examples of color filters used in combination with the configuration of FIG. 3 are shown in FIGS. 4 and 5. First, when using the color filter of FIG. 5, three systems of video signal lines (307) to ( 509), the three primary color signals R, G, and B are applied in this order over the entire effective scanning period. Therefore, the three primary color signals are fixedly applied to the video signal input terminals (501) to (503). It's good.

Next, looking at the color filter in Figure 4, the three primary colors are lined up in the order of R, G, and B in the horizontal direction, and the colors are similarly arranged in the vertical direction in the order of R, G, and B. has been done. Therefore, three video signal lines (!107) to (30
9) requires that the three primary color signals be supplied in a different order for each horizontal scanning period. For example, if one horizontal scanning line is R, G, and B in that order, then the next scanning line is G, B, R, and the next scanning line is B,
R.

In order to achieve this, the video signal to be supplied is switched such as G.
3 matrix circuits can be placed in the path of the three primary color signals and switched for each horizontal scan. Figures 6, 7, and 8 show examples of the components of the low-pass filters (104) to (109). .

Figure 7 is a two-stage combination of Figure 6.
It can be realized as shown in FIG. 8 even with only passive elements.

In either case, the delay elements (low-pass filters) shown in the figure are used in multiple stages to obtain the required bandwidth and delay time. Since the configuration is such that the three primary color signals are supplied to the three video signal lines through low-pass filters with different delay times, the number of pixel selections in one horizontal scan is 1/1 of the actual number of horizontal pixels. 3 - The clock frequency of the x-side shift register can be lowered to 115, and time-division transfer of the three primary color signals is no longer necessary, making it possible to reduce the power consumption of the liquid crystal panel drive circuit and facilitate circuit integration. , and also reduces interference due to harmonics, which has the effect of promoting the miniaturization and weight reduction of devices using liquid crystal color/mono channels.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of the liquid crystal color panel drive circuit of the present invention, FIG. 2 is a conventional example, FIG. 3 is a specific example of the area around the pixel transistor matrix in FIG. 1, and FIGS. 4 and 5 are Example of color arrangement of color filters: Figures 6, 7, and 8 are diagrams showing examples of low-pass filters. (101) to (103)...Video signal input terminal (10
4) ~ (109)...Low pass filter (110) ~ (
112)...Video signal line (113)...X side shift register (114) to (116)...Sample/hold circuit group (117)...Pixel transistor matrix (1
18)...Y side shift register (201)...X
Side clock signal line (202)...X side data signal input terminal (203)
...X side shift register (204)...Video signal line (205)...Sample e-hold circuit (2Q6)...
...Y side data signal input terminal (207)...Y side lock signal line (208)...Y side shift register (209)...
・Pixel transistor (210)...Pixel capacitor (211)...X side electrode (212)...Y side electrode (301) to (303)...Video signal input terminal (5O
,S)~(SO6)...Low pass filter (307)~
(309)...Video signal line (310)...Sample hold circuit (!111)...X side clock signal line (312)...X side shift register (313)...
・X side data signal input terminal (314)...Y side lock signal line (315)...Y side shift register (316)...
・Y side data signal input terminal (317)...Y side electrode (31B)...Pixel transistor (319)...Pixel capacitor (320)...X side electrode (61) (71) ( 81)...Input terminal (62)
・(72)・(82)・・・Output terminal or more

Claims (1)

[Scope of Claims] i) A liquid crystal color panel drive circuit that supplies video signals to a liquid crystal color panel, which has three systems of video signal lines independent of each other for transmitting three primary color signals; A low-pass filter with a different delay time is installed in front of the line, and the three video signal lines are connected to the video signal line through this low-pass filter.
A liquid crystal color panel drive circuit characterized by supplying primary color signals. ii) Regarding the low-pass filters installed in front of the above three systems of video signal lines, the delay time difference of the second low-pass filter with respect to the first low-pass filter and the delay time difference of the third low-pass filter with respect to the second low-pass filter 2. The liquid crystal color panel drive circuit according to claim 1, wherein each delay time difference is set to one pixel selection period.