JPH08137445A - Method and device for driving liquid crystal - Google Patents

Abstract

PURPOSE: To adjust a color video displayed on a color liquid crystal display device to a required color tone without drastic increase in the cost and revising a circuit design. CONSTITUTION: An input signal selection means distributes inputted analog RGB signals to a three-bit A/D conversion means A20 and the three-bit A/D conversion means B21 consisting of two systems by selecting fittingly. An A/D reference voltage generation means 22 generates plural kinds of A/D reference voltages used when the analog RGB signals are digitally converted. Then, a reference voltage selection means 23 selects the reference voltage A/D conversion processing for the RGB signals by a prescribed selective pattern based on a mode specified by a mode switch means 24 to output it to the three-bit A/D conversion means A20 and the three-bit A/D conversion means B21. The three-bit A/D conversion means A20 and the three-bit A/D conversion means B21 digitally convert the inputted analog RGB signals based on the selected reference voltage to liquid-crystal-display them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal driving method and a liquid crystal driving device for performing color display.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices (LCD: Liquid C)
Along with the miniaturization of electronic devices, the rystal display) has been attracting attention as a small display with low power consumption. In this LCD, a drive voltage is selectively applied to a liquid crystal sealed between two glass substrates to control the orientation of liquid crystal molecules, and display characteristics are controlled by changing optical characteristics.

In the conventional liquid crystal drive circuit, the input R
(Red), G (green), B (blue) analog gradation signals A /
Each is converted into a digital gradation signal using a D converter. Generally, a 4-bit (bit) A / D converter is used as a liquid crystal driving A / D converter. For example, as shown in FIG. 4, a 3-bit (bit) A / D converter is used. There is one that uses a D converter to digitally convert an input RGB analog gradation signal.

FIG. 4 shows A / A in a conventional liquid crystal display device.
3 is a block diagram showing the configuration of a D converter 1. FIG. The A / D converter 1 appropriately selects an input analog RGB signal and outputs it to the 3-bit A / D converter A3 and the 3-bit A / D converter B4, and its input signal selection circuit 2. A 3-bit A / D converter A3 that converts the analog RGB signal selected by the input signal selection circuit 2 into a 3-bit digital gradation signal and outputs it to two signal-side drive circuits (not shown).
And a 3-bit A / D conversion B4, an A / D reference voltage generation circuit 5 for generating a reference voltage for A / D conversion necessary for A / D conversion, and the A / D reference voltage generation circuit 5. A reference voltage selection circuit 6 for selecting a required reference voltage from a plurality of generated reference voltages, a clock generation circuit 7 for generating a clock pulse required for driving each part of the A / D converter 1 described above, and the like. It consists of

The operation of the conventional A / D converter 1 is as follows.
The analog RGB signals (FIGS. 5B and 5C) selected by the input signal selection circuit 2 are input to the 3-bit A / D converter A3 and the 3-bit A / D converter B4 for parallel processing. 5 (d) and 5 (e) based on the clock shown in FIG. 5 (a) in each of the 3-bit A / D converters A3 and B4.
Are sampled by the sampling signal at the timing of. In the above-mentioned 3-bit A / D converter A3 and 3-bit A / D converter B4, the
From the D reference voltage generation circuit 5, the reference voltage y is generated for each field.
(RHH1, RLL1) and reference voltage x (RHH2, RL
L2) are selected alternately and a predetermined reference voltage is taken in. The timing of taking in the reference voltage is taken in at the timings shown in (f) and (g) of FIG. 5, and A / D conversion is performed based on the selected reference voltage.

The digital RGB signals thus obtained are applied to the signal drive circuits of two systems to drive the liquid crystal at the timings shown in (h) and (i) of FIG. Is getting

The above-mentioned conventional 3-bit A / D converter A
The characteristics of B3 and B4 are as shown in FIG.
HH2, RLL2) and reference voltage y (RHH1, RLL
In order to perform A / D conversion by switching between 1) and 1) for each field, a reference voltage z (RHH1, RLL2) corresponding to 4 bits is obtained while using a 3 bit A / D converter. Therefore, there is an advantage that the circuit can be simplified and the cost can be reduced without lowering the resolution, and the number of wires from the controller circuit to the driver circuit can be reduced.

In such a conventional liquid crystal display device, when there are variations in chromaticity, film thickness, transmittance, etc. of color filters, even if an effective voltage is applied uniformly to RGB, the color of the displayed image is changed. The taste becomes unnatural. Therefore, RGB
It is necessary to adjust the tint.

Therefore, conventionally, when it is desired to emphasize only a specific primary color signal (for example, R signal), the A / D converter 1 is used.
A controller for controlling the signal level increases the signal level of a specific primary color signal, or separately provides a dedicated reference voltage source for A / D converting a specific primary color signal (for example, an R signal) so that the R signal becomes At the time of D conversion, digital conversion is performed using the reference voltage from this voltage source.

[0010]

However, in such a conventional liquid crystal driving method, as described above, when the signal level of any of RGB is changed by the controller and the signal color is adjusted. However, there is a problem that an external amplifier for changing the signal level by the controller is required.

Further, as described above, in the case of adjusting a predetermined signal color of RGB, an external A / D reference voltage generating circuit dedicated to the signal is provided and a specific voltage is specified based on the reference voltage. There is a problem that the signal color must be adjusted by A / D converting the signal.

As described above, in any of the conventional liquid crystal driving methods, it is necessary to newly add an external circuit to the conventional liquid crystal driving circuit, so that the cost is increased and the circuit design is drastically changed. There was a need.

Therefore, an object of the present invention is to make it possible to freely adjust the tint of a color image displayed on a color liquid crystal display device without significantly increasing the cost or changing the circuit design, thereby making the image more natural. An object of the present invention is to provide a liquid crystal driving method and a liquid crystal driving device that can reproduce colors.

[0014]

In order to solve the above-mentioned problems, the liquid crystal driving method of the present invention, as described in claim 1, provides an analog signal having a plurality of primary color signals with a plurality of primary color signals. In the liquid crystal driving method of converting to a digital gradation signal based on a reference voltage and performing a color liquid crystal display based on the digital gradation signal, the plurality of references used when converting the analog signal to a digital signal. By varying the ratio of the predetermined reference voltage in the voltage, it is possible to selectively adjust the predetermined primary color signal within a predetermined time so that it has a different time ratio from the reference voltage of the other primary colors. The above object is achieved by generating a digital gradation signal and performing color liquid crystal display by the digital gradation signal.

Further, the liquid crystal driving device of the present invention comprises:
As described in, a liquid crystal drive that converts an analog signal having a plurality of primary color signals into a digital gradation signal based on a predetermined reference voltage for each primary color and performs color liquid crystal display based on the gradation signal. In the device, based on a predetermined reference voltage, an analog / digital conversion means for converting each of the primary color signals into a digital signal, a reference voltage generation means for generating a plurality of reference voltages, and the reference voltage generation Reference voltage selecting means for selecting the predetermined reference voltage and a predetermined primary color signal output time from among the plurality of reference voltages generated by the means, and the predetermined primary color signal for the reference voltage selecting means. The above-mentioned object is achieved by including a mode selection unit that holds the selection time of (1) for a plurality of modes and selects a predetermined mode from the plurality of modes.

[0016]

According to the liquid crystal driving method of the present invention, by varying the ratio of the predetermined reference voltage among the plurality of reference voltages used when converting the analog signal to the digital signal, the predetermined reference voltage within a predetermined time can be obtained. The primary color signal is set to have a time ratio different from that of the reference voltage of the other primary colors to generate a selectively adjustable digital gradation signal, and the color liquid crystal display is performed by the digital gradation signal. Therefore, since the predetermined reference voltage is selected for each primary color signal by changing the time ratio of a plurality of reference voltages used when converting an analog signal into a digital signal, the signal level for each primary color can be finely adjusted. This makes it possible to freely adjust the color tone on the drive circuit side, such as adjusting the color tone according to the color tone characteristic of the liquid crystal.

In the liquid crystal driving device according to the second aspect, the analog / digital converting means converts the analog signal into a digital signal for each primary color signal based on a predetermined reference voltage,
A plurality of reference voltages are generated by the reference voltage generating means, and a predetermined reference voltage and a predetermined primary color signal output time are selected from among the plurality of reference voltages generated by the reference voltage generating means by the reference voltage selecting means. A predetermined mode is selected by using the mode selecting means which holds the selection time of the primary color signal for a plurality of modes with respect to the reference voltage selecting means.

Therefore, when the analog signal is converted into the digital signal, only by selecting a predetermined mode, the time ratio of the plurality of reference voltages is changed while selecting the reference voltage used for each primary color signal. The signal level of can be finely adjusted, and the tint can be freely adjusted on the drive circuit side.

[0019]

EXAMPLES The present invention will be described below based on examples.
1 to 3 are views for explaining a liquid crystal driving method according to the present invention and a liquid crystal driving device using the method. First, the configuration will be described. FIG. 1 is a block diagram showing the configuration of the liquid crystal display device 11 of this embodiment. A feature of the present invention is that a plurality of types of reference voltages used when digitally converting an analog video signal input to the A / D converter 18 shown in FIG. 1 are used, and different reference voltages are used for RGB primary color signals. Is selected and A / D converted, and the frequency of processing is changed according to the selection pattern of the reference voltage, thereby changing the ratio of the signal levels among R, G, and B to adjust to a desired color tone. There is a point.

The liquid crystal display device 11 shown in FIG. 1 includes a liquid crystal display panel 12, signal side drive circuits 13 and 14, a scan side drive circuit 15, a synchronization processing circuit 16, a controller 17, and an A / D.
It is composed of a converter 18 and the like.

As the liquid crystal display panel 12, a simple matrix liquid crystal display panel is used here, and a scanning electrode and a signal electrode sandwich a liquid crystal layer inside a glass substrate opposed to each other with a fine interval. They are arranged in a matrix. Although not shown, the liquid crystal panel 12
The signal electrodes arranged at are alternately extended in the vertical direction, and display signals are supplied from the upper signal side drive circuit 13 and the lower signal side drive circuit 14, respectively. The plurality of scan electrodes extending from the scan side drive circuit 15 are brought into a selected state by the scan signals sequentially supplied, and the liquid crystal of each pixel on the selected horizontal scan line is driven to form a liquid crystal display screen. There is. In this embodiment, since the color liquid crystal display device is used, the minimum unit pixel (hereinafter, referred to as a picture element) that displays one color is R (red), G (green), and B.
It is composed of three (blue) primary color pixels, and an RGB color filter is provided in each RGB primary color pixel area. By changing the ratio of the three primary colors that pass through this, multicolor display is achieved. It is carried out.

The signal side drive circuits 13 and 14 are drivers for supplying liquid crystal display signals based on image data to the signal electrodes formed of transparent electrodes such as ITO to drive the liquid crystal.

The scanning side driving circuit 15 is a driver which is composed of a transparent electrode such as ITO, and which sequentially supplies scanning signals to a plurality of scanning electrodes which are arranged to face each other in the direction orthogonal to the signal electrodes to bring them into a selected state. is there.

The synchronization processing circuit 16 extracts the vertical synchronization signal φV and the horizontal synchronization signal φH from the input composite video signal and outputs them to the controller 17, and at the same time, RGB
And outputs the separated analog video signal V to the A / D converter 18.

The A / D converter 18 performs an A / D conversion process on the input RGB analog video signal V by a sampling clock (SCK) input from the controller 17 and a reference voltage for A / D conversion. Here, the display data digitally converted by 3 bits is output to the above-described two systems of signal side drive circuits 13 and 14, respectively. The liquid crystal display device 11 of the present embodiment is characterized by the A / D converter 18, and generates a plurality of types of reference voltages having different voltage values to match the processing timing of the input RGB analog video signal V. The reference voltage to be captured is selected, and A / D conversion processing is performed based on this reference voltage.
It is possible to freely and subtly adjust the individual signal levels of, and it is possible to obtain a more natural color tone by changing the tint of the image.

The controller 17 includes the liquid crystal display panel 12
Is for controlling the overall timing and signal processing operation in the case of display control. For example, the controller 17 supplies the sampling clock SCK synchronized with the vertical and horizontal synchronization signals φV and φH supplied from the synchronization processing circuit 16 to the A / D converter 18, and the signal side drive circuits 13 and 14 as well. And scanning side drive circuit 15
A timing signal for synchronously driving is supplied. In addition, the liquid crystal display device of the present embodiment has the above-mentioned A / D
RGB analog video signal V input to the converter 18
Select the reference voltage selection pattern for A / D conversion processing
A plurality of modes are provided in the / D converter 18, and a mode signal for selecting a specific pattern is output from the controller 17 according to an instruction from the operator.

FIG. 2 is a block diagram showing the configuration of the A / D converter 18 of FIG. 1 according to this embodiment. In FIG.
The A / D converter 18 includes an input signal selection means 19, a 3-bit A / D conversion means A20, and a 3-bit A / D conversion means B2.
1, A / D reference voltage generation means 22, reference voltage selection means 2
3, a mode switching means 24, a clock generating means 25 and the like.

The input signal selecting means 19 is the synchronization processing circuit 1.
Select the analog RGB signal input from 6 as appropriate and 2
The signals to be output to the 3-bit A / D conversion means A20 and the 3-bit A / D conversion means B21, which are systems, are selected.

The 3-bit A / D conversion means A20 converts the analog RGB signal input from the input signal selection means 19 into 3 bits.
It is converted into a bit digital gradation signal and output to the signal side drive circuit 13.

The 3-bit A / D conversion means B21 converts the analog RGB signal input from the input signal selection means 19 into 3 bits.
It is converted into a bit digital gradation signal and output to the signal side drive circuit 14.

The A / D reference voltage generating means 22 generates a plurality of A / D conversion reference voltages used when digitally converting the analog RGB signals. Here, as shown in FIG. 2, y ( RHH1, RLL1) and x (RHH
2 and RLL2) are generated.

The reference voltage selection means 23 is generated by the A / D reference voltage generation means 22 at a predetermined timing based on the clock pulse of the clock generation means 25 synchronized with the input synchronizing signal C (C.Sync). By performing a selection process for switching the plurality of reference voltages thus made, various reference voltages are supplied to the 3-bit A / D conversion means A20 and the 3-bit A / D conversion means B21.

The mode switching means 24 has a plurality of selection patterns for selecting a reference voltage at a predetermined timing with respect to the reference voltage selecting means 23, and a desired selection pattern can be obtained only by the operator designating the mode. A reference voltage is selected based on the A / D conversion process is performed,
The RGB signal levels are individually and finely adjusted. The clock generating means 25 creates a basic clock pulse and supplies it to the above-mentioned respective parts.

FIG. 3 is a timing chart of various signals from field 1 to field 5 when converting analog data into digital data in the A / D converter 18 of FIG.

FIG. 3A is a waveform diagram showing the basic clock input from the clock generation means 25, and the A / D conversion operation is performed based on this clock timing. FIG. 3B shows an analog R selected by the input signal selection means 19 and input to the 3-bit A / D conversion means A20.
It is a figure which shows GB data, and the figure (c) is a figure which shows the analog RGB data input into the 3-bit A / D conversion means B21 from the input signal selection means 19.

FIG. 3 (d) is a diagram showing the timing of the reference voltage selected by the reference voltage selecting means 23 and taken into the 3-bit A / D converting means A20 and the type of the reference voltage. 1) than the primary color signal to be A / D converted shown in FIG.
/ The reference voltage is taken in at the timing of two cycles before, and A /
D conversion processing is performed.

FIG. 3 (e) is a diagram showing the timing of the reference voltage selected by the reference voltage selecting means 23 and taken into the 3-bit A / D converting means B21 and the type of the reference voltage. 1) than the primary color signal to be A / D converted shown in FIG.
/ The reference voltage is taken in at the timing of two cycles before, and A /
D conversion processing is performed.

FIG. 3 (f) is a diagram showing a reference voltage selection signal when A / D converting the R signal, and FIG. 3 (g) shows G.
It is a figure which shows the reference voltage selection signal at the time of A / D-converting a signal, and the figure (h) is a figure which shows the reference voltage selection signal at the time of A / D-converting a B signal.

Next, the operation will be described. First, in the synchronization processing circuit 16 of FIG. 1, the vertical synchronization signal φV and the horizontal synchronization signal φH are extracted from the input composite video signal and output to the controller 17, and the video signal V is A / D.
It is output to the conversion circuit 18.

In the A / D converter 18, as shown in FIG. 2, the input RGB analog video signal V is separated by the input signal selection means 19 so as to be supplied to the drivers of two systems, and is separated as R data as serial data. , B, G are sequentially input to the 3-bit A / D conversion means A20 at the timing shown in FIG. 3 (b), and at the same time as shown in FIG. 3 (c).
It is given to the D conversion means B21.

On the other hand, the A / D reference voltage generating means 22 shown in FIG.
Then, y (RHH1, RLL1) and x (RHH2, RL
L2) two types of reference voltages are generated, and the reference voltages x and y are generated by the R reference voltage selection signal, the G reference voltage selection signal, and the B reference voltage selection signal output from the reference voltage selection means 23. Are selected, and the selected reference voltages are the 3-bit A / D conversion means A20 and the 3-bit A, respectively.
It is output to the / D conversion means B21.

On the A / D conversion means A20, B21 side, immediately before sampling the analog RGB data (here, as shown in (d) and (c) of FIG. 3, 1/2 cycle before).
Then, a desired reference voltage (x or y) corresponding to each primary color signal is captured, and A / D conversion processing is performed based on the captured reference voltage. For example, in field 3 of FIG. 3B, “R signal” and “B signal” are shown in FIG.
A / D conversion is performed on the basis of the “reference voltage x” and the “reference voltage y” that are taken in at the timing of ½ cycle before. As described above, in the present embodiment, each of the R, G, and B components that are always A / D converted during the fields 1 to 5 in FIG.
The reference voltage for A / D converting the primary color signal is taken in 1/2 cycle before the input timing of the primary color signal.

In the above-mentioned reference voltage selecting means 23, the selection pattern of the reference voltage is determined according to the mode designated by the mode switching means 24, and RGB is selected according to the designated mode.
The reference voltage selection signal of is output.

Therefore, in FIG. 3, the fetch period of the reference voltage y is once every three fields (field 1 and field 4) by the reference voltage selection signal for R shown in FIG.
By this, an example of a timing chart for emphasizing the tint of the R signal is shown. Then, the remaining reference voltages of the G signal and the B signal are fetched in the same manner as the conventional reference voltage by the G reference voltage selection signal and the B reference voltage selection signal shown in FIGS. x and y are switched for each field.

FIGS. 3D and 3E show a 3-bit A / D.
It shows a state in which the reference voltage is taken in 1/2 cycle before the timing of each primary color signal input to the conversion means A20 and the 3-bit A / D conversion means B21. 3 (f), (g), and (h) show R,
It is a reference voltage selection signal for G and B, and the reference voltage “y” is taken in the case of “High” and the reference voltage “x” is taken in the case of “Low”.

When a reference voltage selection pattern other than the above is adopted, mode 1 (MODE 1) to mode 3 (MODE 3) for the mode switching means 24 shown in FIG.
By specifying, the acquisition cycle of the reference voltage “y” can be freely changed so that the acquisition cycle is once every three fields, once every four fields, or once every five fields. can do. As a result, the frequency of A / D conversion processing by the predetermined reference voltage (here, the reference voltage y) differs between the G signal and the B signal with respect to the R signal, so the degree of emphasis of the signal level may be slightly changed. Since it is possible to adjust the tint individually and delicately, it is possible to perform a more natural color display by adjusting the tint according to the tint characteristics of each liquid crystal display panel.

On the other hand, as a general method, the reference voltage may be lowered, or the reference voltage may be relatively lowered by amplifying the analog RGB data to emphasize the tint. However, according to this method, when a high voltage such as the analog input voltage Va shown in FIG. 6 is input, for example, the level of digital data after A / D conversion becomes a high value of 111B. On the high voltage side, the problem that no resolution can be obtained occurs.

In this respect, according to the liquid crystal driving method of the above-described embodiment, the reference voltage is individually set according to RGB, and the A / D is set.
Since it is converted, the high analog input voltage V as described above
Even if a is input, the resolution will not be lost at all and will be reflected in the output data to a large extent, so that it is possible to prevent a significant deterioration in image quality.

In addition, according to the liquid crystal driving method of the present embodiment, it is possible to freely make adjustments such as emphasizing or weakening only a specific color tone, and the degree of the adjustment can be adjusted very delicately. A color image closer to a natural color can be obtained by adjusting the liquid crystal display panel according to the subtle difference in the tint characteristics.

Further, according to the liquid crystal driving method of this embodiment described above, for example, the analog input voltage shown in FIG.
Since D conversion is performed to obtain digital data equivalent to 4 bits as A / D conversion output data of 3 bits, if it is assumed that the conventional signal level is 101B on average, 110
Since the data level is increased to about B, the tint can be emphasized. In this case, since the circuit configuration of the A / D converter can be simplified without degrading the resolution, the cost can be reduced and the number of wires from the controller circuit to the driver circuit can be reduced.

In the above embodiment, the case where the R signal is emphasized has been described as an example, but the present invention is not limited to this, and the G signal or the B signal may be individually or, alternatively,
It is possible to freely and easily perform color adjustment by combining these by mode selection.

[0052]

As described above, according to the liquid crystal driving method of the first aspect, the ratio of the plurality of reference voltages used when converting the analog signal into the digital signal is made different so that the predetermined time within the predetermined time is reached. Since the reference voltage of the primary color signal is set to a different time ratio from the reference voltage of other primary colors, the tint can be freely adjusted by finely adjusting the signal level for each primary color signal on the drive circuit side. .

According to the liquid crystal driving device of the second aspect, the analog / digital converting means converts the analog signal into a digital signal for each primary color signal on the basis of a predetermined reference voltage, and the reference voltage generating means makes a plurality of signals. Since the reference voltage is generated and the predetermined reference voltage and the predetermined primary color signal output time are selected by the reference voltage selection means from the plurality of reference voltages generated by the reference voltage generation means, The signal level of can be finely adjusted, and the tint can be freely adjusted on the drive circuit side.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a liquid crystal display device of an embodiment.

FIG. 2 is a block diagram showing the configuration of the A / D converter of FIG. 1 according to the present embodiment.

3 is a timing chart of various signals from field 1 to field 5 when converting analog data into digital data in the A / D conversion means of FIG.

FIG. 4 is a block diagram showing a configuration of an A / D converter in a conventional liquid crystal display device.

FIG. 5 is a timing chart of various signals when performing A / D conversion processing in a conventional A / D converter.

FIG. 6 is a diagram showing a relationship between an analog input voltage for A / D conversion and a digital output.

[Explanation of symbols]

 11 liquid crystal display device 12 liquid crystal display panel 13, 14 signal side driving circuit 15 scanning side driving circuit 16 synchronization processing circuit 17 controller 18 A / D converter 19 input signal selecting means 20 3 bit A / D converting means A 21 3 bit A / D conversion means B 22 A / D reference voltage generation means 23 Reference voltage selection means 24 Mode switching means 25 Clock generation means

Claims (2)

[Claims] 1. An analog signal having a plurality of primary color signals,
A liquid crystal driving method for converting a digital gradation signal based on a plurality of reference voltages for each primary color and performing color liquid crystal display based on the digital gradation signal, which is used when converting the analog signal into a digital signal. , A predetermined primary color signal within a predetermined time is selected so as to have a different time ratio from the reference voltages of the other primary colors by varying the ratio of the predetermined reference voltage among the plurality of reference voltages. A liquid crystal driving method characterized in that a digital gradation signal that can be adjusted dynamically is generated, and a color liquid crystal display is performed by the digital gradation signal. 2. A liquid crystal drive device for converting an analog signal having a plurality of primary color signals into a digital gradation signal based on a predetermined reference voltage for each primary color and performing color liquid crystal display based on the gradation signals. An analog / digital conversion means for converting the analog signal into a digital signal for each of the primary color signals based on a predetermined reference voltage; a reference voltage generation means for generating a plurality of reference voltages; and a reference voltage generation means. Reference voltage selection means for selecting the predetermined reference voltage and a predetermined primary color signal output time from among the plurality of generated reference voltages; and selection of the predetermined primary color signal for the reference voltage selection means. A liquid crystal driving device comprising: a mode selecting unit that holds time for a plurality of modes and selects a predetermined mode from the plurality of modes.