JP3347616B2 - Display device drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit of a display device for displaying a plurality of gradations based on a plurality of color data respectively defining a plurality of color components, and more particularly, to a liquid crystal driving device and a plasma display. The present invention relates to a driving circuit suitable for a flat display device such as a device, an EL display device, and a field effect display device (FED).

[0002]

2. Description of the Related Art This type of flat display device generally comprises a main unit and a display unit. The main unit is composed of a computer or the like, and outputs a display data signal, a control signal, and the like to the display unit. The display unit includes a liquid crystal driving device, a plasma display device, an EL display device, a field effect display device, or the like, and performs display based on an output signal from the main unit.

Recently, in particular, computers and the like have been reduced in size and weight, and portable notebook personal computers have been used frequently. The prior art will now be described in more detail on the basis of a computer equipped with a liquid crystal display device that has attracted attention as a display device replacing a conventional CRT.

FIG. 9 shows a configuration of a conventional computer 50. The computer 50 includes a computer main body 51 constituting a main unit and a liquid crystal display device 5 constituting a display unit.
It is roughly divided into two. The computer body 51 includes a CPU 51
a, a memory 51b, a hard disk 51c as an auxiliary storage device, a display control circuit unit 51d, and other peripheral devices.

On the other hand, the liquid crystal display device 52 includes a drive circuit such as a data driver and a gate driver and a display unit (TFT).
(Liquid crystal panel) 100. The details of the liquid crystal display device 52 will be described later.

Now, display data (Data) 13, a clock signal (DCK) 14, and synchronizing signals (Hsync (horizontal synchronizing signal), Vsync (vertical synchronizing signal), etc.) 15 are transmitted from the computer main body 51 to the liquid crystal display device 52. Has been sent.

[0007] The liquid crystal display device 52 receives the display data 13, the clock signal 14, and the synchronization signal 15, and samples the display data 13 based on the synchronization signal 15 and the clock signal 14. The sampled data is supplied to the display unit 100, where it is displayed in multiple colors.

Next, the details of the liquid crystal display device 52 will be described with reference to FIG.
The following describes an example of the matrix type liquid crystal display device shown in FIG.

The liquid crystal display device 52 has a TFT liquid crystal panel 100 as a display unit (display section).
The drive circuit 1 for performing display on the TFT liquid crystal panel 100 includes a data driver 2, a gate driver 300, a voltage signal supply circuit 9, a counter electrode drive circuit 8, and a control circuit 4.

The data driver 2 has a function of driving a pixel by supplying a signal voltage to a signal line, converts serial data into parallel data, and has sufficient driving capability to drive the signal line. I have it. Such a data driver 2 is also called a digital driver because it receives a digital video signal.

FIG. 11 shows an example of a data driver 2 for performing gradation display in accordance with n-bit display data. The data driver 2 includes a sampling data storage unit Ms
mp, output holding means MH, and an output circuit OPC. The operation will be described below.

The sampling data storage means Msmp comprises:
Sampling pulse Tsmp input to CK input terminal
The display data is sampled at the rise of. The sampled data is shifted to the output holding means MH at the rise of the output pulse OP, and the output circuit OP
Input to C. The output circuit OPC is a digital / analog converter that converts n-bit display data into a corresponding voltage, and has a sufficient driving capability to drive a signal line.

FIG. 12 shows a data driver 2 for realizing eight gradation displays corresponding to 3-bit display data.
This data driver 2 is also a sampling data storage unit M
mp, output holding means MH, and an output circuit OPC. The eight gradation voltages V0 to V7 are supplied to the data driver 2 from the voltage signal supply circuit 9 (see FIG. 10). As shown in FIG. 2B, this output circuit OPC
Eight gradation voltages V0 to V corresponding to display data values
7 are connected to the analog switches ASW0 to ASW
7 is turned on, and one of the gradation voltages V0 to V7 is selected and output. For example, when the image data is 3, the analog switch ASW3 is turned on,
The gradation voltage V3 is output. In the actual circuit, the circuits shown in FIGS. 12A and 12B exist as many as the number of data lines.

FIG. 13 shows the relationship among pixels, display data, and sampling pulses. As display data (Data), color data R for defining a red component, color data G for defining a green component, and color data B for defining a blue component are sent in parallel from the computer main body 51, and a clock (DCK) is also transmitted. It is sent to the liquid crystal display device 52.

In the figure, Tsmp (j), Tsmp (j +
1), Tsmp (j + 2),... Are picture elements (pixels)
j, j + 1, j + 2,... are sampling pulses supplied to the circuits respectively corresponding to j, j + 1, j + 2,. Data is sampled at the rising edge of the sampling pulse.

FIG. 14 is a circuit diagram of the digital driver 2 when R, G, and B are regarded as one picture element. This circuit configuration has three bits of R, G and B (R = R
0, R1, R2, G = G0, G1, G2, B = B0, B
1, B2) are simultaneously sampled by the Tsmp signal to realize multi-color display.

FIG. 15 shows the configuration of the digital driver 2 formed as an LSI. The data driver 2 includes a large number of circuits shown in FIG. 14 and one shift register circuit SR for generating a sampling pulse Tsmp.
When the data driver 2 has 192 output terminals, it means that one data driver 2 can drive 64 picture elements.

The data driver 2 is controlled by at least three signals. The three signals are a data sampling start pulse DSP and a clock signal D
CK and output pulse OP. From the data sampling start pulse DSP and the clock signal DCK in the figure,
The sampling pulse Tsmp output from the shift register SR is generated. Note that R _out (1), G
_out (1), B _out (1) are display data corresponding to the first picture element, and R _out (2), G _out (2), B
_out (2) is display data corresponding to the second picture element.

VGA specification (dot configuration: 640 × RGB)
× 480), since there are 640 picture elements in the horizontal direction, R _out (1), G _out (1), B _out (1) to R _out
The display data of _out (640), G _out (640), and B _out (640) are serially input to the liquid crystal display device 52. To drive 640 picture elements with one LSI, L
Since there is a problem that the SI becomes too large, a plurality of LSIs are currently connected in cascade.

In the case of VGA specification, LS of 240 output terminals
When I is used, 640 × 3/240 = 8 digital drivers are required. In an actual drive circuit, the circuits in FIG. 11 are present by the number of data lines.

[0021]

By the way, when the liquid crystal display device 52 is compatible with color, the display data 13 shown in FIG. 9 includes a plurality of color data respectively defining a plurality of color components. I have. Typically, display data 1
3 includes color data R defining a red component, color data G defining a green component, and color data B defining a blue component. By mixing a red component defined by the color data R, a green component defined by the color data G, and a blue component defined by the color data B at a predetermined ratio, an arbitrary color can be synthesized.

Here, each of the color data R, the color data G and the color data B can be represented by a plurality of bit values. Therefore, signal lines corresponding to these color data are required. For example, when one pixel is to display about 260,000 colors with 6-bit R, G, and B color data, as shown in FIG. 16, a total of 18 signal lines of 6 bits × 3 are used. Color data from the computer main body 51 to the liquid crystal display device 5
2 will be transmitted.

In FIG. 16, R0 to R5 indicate each bit constituting the color data R, G0 to G5 indicate each bit constituting the color data G, and B0 to B5 constitute the color data B. Each bit is shown. Liquid crystal display device 52
A few years ago, for example, 496 bits per color
The color display was exhibited as a prototype at the electronics show, but recently, about 26 bits for each color are used.
Those that display all colors are being mass-produced.

Depending on the application, further multi-color display is desired. For example, when multicolor display of about 16.77 million colors is performed using color data of R, G, and B each of 8 bits, 8 bits × 3
Therefore, color data is transmitted using a total of 24 signal lines, and about 26 bits of color data of 6 bits each for R, G, and B are used.
The number of the six signal lines increases as compared with the case where the multicolor display is performed.

Here, in order to facilitate understanding of the relationship between the color data, the display basic color, and the luminance gradation of each color, a case of displaying 4,096 colors with 4 bits for each color will be described with reference to FIG. In FIG. 17, especially in the case of black and white gradation display, any of (a), (b) and (c) in FIG.
The color data of the R, G, and B bits is the same.

Further, an increase in the color data of each bit of R, G, B (for example, 4 bits each → 6 bits → 8 bits →
..) Increases the circuit configuration on the computer main body 51 and the liquid crystal display device 52 side, resulting in an increase in power consumption.
That is, the computer main body 51 requires a drive circuit corresponding to each bit for outputting a signal corresponding to each bit constituting the color data.
Also in the case of No. 2, it is necessary to add a circuit for processing the color data and the like, so that the power consumption increases accordingly.

In a notebook computer, a laptop computer, a workstation, or the like in which the computer main body 51 and the liquid crystal display device 52 are separated from each other,
When increasing the number of colors that can be displayed, the number of signal lines for transmitting the display data 13 between the computer main body 51 and the liquid crystal display device 52 must be increased. Here, as the number of signal lines increases, electromagnetic interference (EMI) called unnecessary radiation also increases accordingly.

FIG. 18 shows a 6-bit ×
3 shows the timing of transmitting binary digital data using a total of 18 signal lines. This transmission is based on the VGA specification (dot configuration: 640 × RGB × 480).

In FIG. 18, the waveform indicated by Data indicates display data, and each of red, blue and green color data R, G,
B is collectively expressed in this way. Also, in FIG. 18, D1 is the first display data in the horizontal direction, D640
Represents the 640th display data in the horizontal direction, DH1 represents the first display data in the vertical direction, and DH480 represents the period during which the 480th display data in the vertical direction is being output.

In FIG. 18, data within a valid data period is sampled based on a clock signal DCK so that multi-color display can be performed on the display unit 100. There are several methods for dividing the non-valid data period and the valid data period, but the description is omitted here.

Further, regarding the display data and the screen display,
As shown in FIG. 19, 640 pixels (R, G, B
1 pixel in a pair), 480 pixels in the vertical direction, totaling 307,
200 (640 × 480) pixels are arranged in a matrix.

In the case of a VGA display device, which has been most commonly used for transmitting digital display data, the transfer time of one data is approximately 40 nsec, and the transmission time of one data is approximately 2 nsec.
A transfer clock of 5 MHz is sent to the liquid crystal display device in parallel with the data.

By the way, recently Microsoft's M
With the rapid spread of S-Windows, higher definition of display devices has been developed, and display from a XGA to SXGA has already been generalized in a display device using a cathode ray tube. There is a strong demand for high definition in flat panel display devices. For example, in liquid crystal display devices as well, conventional VGA (dot configuration: 640 × RGB × 480) is replaced by SVGA (800 ×
RGB × 600) and even higher definition XGA (10
24 × RGB × 768), SXGA (1280 × RGB)
× 1024) The situation is shifting to F.

The liquid crystal display device 52 receives the display data serially and supplies the data to the liquid crystal panel in parallel when the data for one line is completed. As the size of the liquid crystal display screen increases and the definition thereof increases, the display data for the lines tends to increase. For this reason, the frequency of the clock pulse DCK for taking in the display data within a predetermined time is also 3 MHz to 8 MHz.
Higher frequencies, such as MHz, have become necessary.

For example, in the case of XGA, about 60 MHz,
In the case of SXGA, a high-speed clock pulse DCK of about 100 MHz is required.

As described above, the display device is improved in definition (VGA →
(SVGA → XGA → SXGA), if binary digital data is transmitted at high speed, electromagnetic interference called unnecessary radiation occurs. Further, as described above, the circuit scales of the computer main body and the display device are increased, which leads to an increase in power consumption.

A liquid crystal display device used as a display device is one type of information processing device, and is subject to the Voluntary Control Council for Interference by Information Processing Devices (VCCI) and the Federal Communications Commission Regulations (F).
CC) and other products subject to unnecessary radiation regulations. Naturally, there are regulations for the electromagnetic interference,
Engineers are forced to work hard and take countermeasures to keep unwanted emissions within officially determined standards.

As a prior art which solves the problem of the unnecessary radiation, JP-A-6-216480 and JP-A-6-216480 disclose conventional techniques.
Japanese Patent Application Laid-Open No. 37478/1994 and Japanese Patent Application Laid-Open No. 6-95618 have proposed.

For example, (a) JP-A-6-216480 states that "in order to suppress unnecessary radiation noise of an integrated circuit, the integrated circuit itself is shielded, and a board on which the shield is mounted or a system frame. Connect to GND. "

(B) In JP-A-6-37478,
It has been proposed that "a metal foil is attached to an input interface signal wiring or a power supply wiring in a mounting board on which a drive IC for driving a liquid crystal display panel is mounted to provide a shield".

(C) In JP-A-6-95618,
It has been proposed that “the number of signal lines of input data is reduced by dividing and transmitting digital display data”.

However, with the above method, the number of signal lines at the time of data transmission cannot be significantly reduced, and it is difficult to suppress unnecessary radiation to a level at which the above regulation can be cleared. Further, there is a limit in reducing the power consumption of the liquid crystal display device. For these reasons, the appearance of a display device capable of coping with higher definition has been urgently required at present.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a drive circuit of a display device which can significantly reduce unnecessary radiation and reduce power consumption.

[0044]

A drive circuit for a display device according to the present invention performs a plurality of gradation displays on a display device based on a plurality of color data respectively specifying a plurality of color components transmitted from a main engine. in the driving circuit of a display device that, main machine
The gradation display data of multiple color components transmitted from the
That if it has a value, the gradation table of a plurality of color components the main unit from different color tone display data with each transmitted as digital data, which is transmitted from the main machine side
When the display data has the same value, black and white gray scale display data is transmitted as digital data from one of the main units as color data to one of the main data.
A plurality of signal line groups each constituted by a plurality of signal lines corresponding to a plurality of bits constituting gradation display data, and one of the signal line groups is provided with black and white color data as color data from the main unit side. When gradation display data is transmitted,
A color data control signal, which is digital data for identifying that the monochrome gradation display data is transmitted to the signal line group, is transmitted from the main unit to the control signal line. Determining means for determining whether or not a data control signal is being transmitted; and determining that the color data control signal is being transmitted to the control signal line by the determining means. Switching means for switching the input color data to black and white gradation display data as color data transmitted to one of the signal line groups, thereby achieving the above object.

[0045] Preferably, said switching means is provided with said signal line.
Gradation display data black and white as the color data transmitted to one of the groups is such that the color data inputted from the other signal line groups, constituting other input path of the signal line groups to switch each Have been.

[0046] Preferably, said switching means is provided with said signal line.
In this configuration, color data produced based on monochrome gradation display data transmitted to one of the groups is switched so as to be input from another signal line group .

Preferably, the determination means determines the presence or absence of the color data control signal according to the "H" level and the "L" level of the color data control signal.

Preferably, the determination means and the switching means include a switch circuit.

Preferably, the determining means and the switching means are constituted by IC circuits.

Preferably, the judgment means and the switching means are constituted by a logic circuit comprising an AND circuit and an OR circuit.

Preferably, the plurality of color data include color data of R, G, and B primary colors.

The operation of the present invention will be described below.

According to the above configuration, for example, when transmitting black-and-white gradation display data from the main unit to the display device, the color data control signal is set to "H" level and only the R color data is transmitted. Becomes possible. In this case, G,
There is no need to transmit the B color data. Therefore, G, B
Signal lines are inactive, and the number of signal lines during color data transfer can be substantially reduced, which eliminates the difficult situation of suppressing unnecessary radiation and reduces the amount of unnecessary radiation. Can be realized.

In this case, on the display device side,
If the read R color data signal is read as G and B color data, the read R color data signal can be used for the G and B color data, so that multi-color display is possible.

Here, for example, a work screen of a word processor using a computer is particularly effective in such a case, since almost all of the screen can be displayed in black and white (monotone) gradation.

Further, as will be understood from the principle of the driving circuit of the display device of the present invention described later, the power consumption of the display device can be greatly reduced.

The above-mentioned determination means and switching means for switching the input path of the color data to the display device between the black and white gradation display and the other gradation display include a switch circuit, an IC, and the like.
It can be easily realized by a circuit and a logic circuit.

[0058]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings.

(Principle of Driving Circuit of Display Device of the Present Invention) First, the principle and effect of the display device of the present invention will be described with reference to FIGS. The drive circuit of the display device of the present invention performs different operations depending on the presence or absence of the color data control signal (BW) transmitted from the computer main body 11.

First, a schematic configuration of a computer 10 to which the present invention is applied will be described with reference to FIG. The computer 10 includes a computer main body 5 constituting a main engine unit.
1 and a liquid crystal display device 12 constituting a display unit. The computer main body 11 includes a CPU 11a, a memory 1
1b, a hard disk 11c as an auxiliary storage device, a display control circuit unit 11d, and other peripheral devices are connected.

The liquid crystal display device 12 has substantially the same configuration as the liquid crystal display device 52 shown in FIG. 10, except for the configuration of the data driver. Therefore, the overlapping description of the common parts will be omitted.

In the computer 10 of the present invention, the display data (Data) 13 and the clock signal (DCK) 1 are transmitted from the computer main body 11 to the liquid crystal display device 12.
4. A synchronization signal (Hsync, Vsync, etc.) 15 and a color data control signal (BW) 16 are transmitted. Here, the color data control signal (BW) 16 is a signal indicating whether or not data transmitted from the computer main body 11 to the liquid crystal display device 12 is monochrome display data.

When transmitting black-and-white gradation display data, the computer main body 11 performs the following transmission operation.
That is, in this case, the clock signal 14, the synchronization signal 15,
Only the color data control signal 16 and the R color data signal are transmitted. Therefore, in this case, the G and B color data signals are not transmitted to the liquid crystal display device 12.

Specifically, for example, when transmitting black and white gradation display data to the liquid crystal display device 12, the color data control signal is set to the “H” level, and only the R color data is transmitted. Further, the G and B signal lines that do not transmit color data are made inoperative by using one of the following three states, thereby substantially reducing the number of signal lines during color data transfer. However, this eliminates a difficult situation for suppressing unnecessary radiation, and realizes a transmission system in which unnecessary radiation is significantly reduced. In addition, low power consumption is achieved.

The three types of states are specifically described as follows: (1) making the signal line of the portion not transmitting color data high impedance; and (2) making the signal line potential of the portion not transmitting color data high. Setting the level (3) Setting the signal line potential of the portion not transmitting color data to the ground level.

At this time, the liquid crystal display device 12, that is, its driving circuit performs the following operations. The state of the color data control signal 16 transmitted from the computer main body 11, that is, its "H" and "L" levels is observed. Then, when it is determined that the color data control signal 16 is at the “H” level and the computer main body 11 transmits the grayscale display data of black and white, for example, the R color data signal is read and read as the G and B color data. That is, in this case, the read R color data signal is also used for the G and B color data.

In the reading operation, more specifically, the display data 13 is sampled based on the synchronization signal 15 and the clock signal 14, and the sampled data is supplied to the display unit 100.

On the other hand, when transmitting gradation display data other than black and white, the computer main body 11 performs the following transmission operation. That is, in this case, the clock signal 14, the synchronization signal 15, the color data control signal 16, and the R, G, B color data signals are transmitted.

Specifically, for example, the color data control signal 1
6 is set to the "L" level, and the R, G, and B color data signals are transmitted.

At this time, the liquid crystal display device 12, that is, its driving circuit performs the following operation. The state of the color data control signal 16 transmitted from the computer main body 11, that is, its "H" and "L" levels is observed. Then, it is determined that the color data control signal 16 is at the “L” level, and when the R, G, and B color data signals are transmitted from the computer main body 11, based on the synchronization signal 15 and the clock signal 14, The display data 13 is sampled. The sampled data is supplied to the display unit 100, where it is displayed in multiple colors.

When the liquid crystal display device 12 supports colors, the display data 13 includes a plurality of color data that respectively define a plurality of color components. Typically,
The display data 13 includes color data R that defines a red component, color data G that defines a green component, and color data B that defines a blue component. It is not limited to R, color data G and color data B. As long as an arbitrary color can be synthesized, the display data 13 may include color data defining an arbitrary color component.

According to the present invention, when transmitting monochrome gradation display data to the liquid crystal display device 12 side, only one color data is transmitted, so that the number of signal lines at the time of color data transfer is substantially reduced. You can do it. For this reason, it is possible to reduce electromagnetic interference called unnecessary radiation, which increases as the number of signal lines increases.

According to the present invention, power consumption can be significantly reduced. The reason will be described below with reference to FIG.
However, FIG. 2 shows ten data drivers 2-1, 2-2,
.. Shows a drive circuit for driving the TFT liquid crystal panel 100 using 2-10, and a control circuit 11d (51d) in the figure is a display control circuit section in the computer main body 11 (51).

First, generally, a capacitor C (here, TFT
The power P consumed when driving the load of the liquid crystal panel 100) has a value represented by the following equation (1).

P = f · C · V ² (1) where f: operating frequency V: power supply voltage As shown in FIG.
When 0 performs a monochrome gradation display operation, ten data drivers 2-bit data of 6 bits each for R, G, and B are used.
TFT liquid crystal panel 1 using 1, 2 ... 2-10
00 is being driven.

Here, in general, the load up to the input of the driver IC is often several PF to 20 PF in the input bus line of one IC.
The case of PF will be described as an example.

As shown in FIG. 2, each bus line for transmitting the R, G, and B color data and the input lines of the ten data drivers 2-1 to 2-10 are connected in parallel. Therefore, for example, the load of one bus line is 1
0 PF × 10 = 100 PF. In the case of 6 bits for each of R, G, and B, 18 bus lines are required, so the total load capacity C is C = 100 PF × 18 = 18
00PF.

In the case of the VGA specification, f = 25 MH
Assuming that z and V = 5V, the power consumption P
= (25 × 10 ⁶ ) × (1800 × 10 ^-12 ) × 5 ² =
1.125 W.

On the other hand, according to the present invention, when the TFT liquid crystal panel 100 performs a monochrome gradation display operation, since only one color is transmitted, the total load capacitance C is smaller than that of the conventional example. It becomes 1/3. This means that the power required to transfer data to the control circuit 11d or the data driver can be reduced to 1/3 from the above equation (1). Therefore, according to the first embodiment, power consumption can be significantly reduced as compared with the above-described conventional example.

As described above, according to the present invention, when the TFT liquid crystal panel 100 performs a monochrome gray scale display operation,
Since electromagnetic interference called unnecessary radiation can be reduced and power consumption can be significantly reduced, for example, a work screen of a word processor using a computer can be used in such a case because most of the screen can be displayed in black and white gradation. Especially effective.

Hereinafter, an embodiment which embodies the driving circuit of the display device of the present invention having the above-described effects will be described.

(Embodiment 1) FIGS. 3 to 5 show Embodiment 1 of the drive circuit of the display device of the present invention.

As shown in FIG. 3, the liquid crystal display device 12
A display data line group 13a for receiving the color data R, a display data line group 13b for receiving the color data G, a display data line group 13c for receiving the color data B, a signal line 14a for receiving the clock signal 14, Synchronous signal 1
5 and a control signal line 16a for receiving the color data control signal 16.

Each of the color data R, the color data G, and the color data B is 6 bits, that is, as shown in FIG.
R5), G (= G0 to G5), and B (= B0 to B5), each of the display data line groups 13a to 13c includes six signal lines.

Here, when the monochrome gradation display is performed in the liquid crystal display device 12, the color data R, the color data G and the color data B have the same value. For example, the values of the color data R, the color data G, and the color data B are all “00000”.
If it is “0”, it indicates that the gray level to be displayed on the liquid crystal display device 12 is “black”. When the values of the color data R, the color data G, and the color data B are all “111111”, it indicates that the gray scale to be displayed on the liquid crystal display device 12 is “white”. When the values of the color data R, the color data G, and the color data B are all “010101”, it indicates that the gray scale to be displayed on the liquid crystal display device 12 is “gray”.

As described above, when the color data R, the color data G, and the color data B have the same value, the computer main body 11 sets the level of the color data control signal 16 to “H” level, "H" level color data control signal 16
Then, only the color data R is transmitted to the liquid crystal display device 12.

The color data transmitted from the computer main body 11 to the liquid crystal display device 12 may be any one of a plurality of color data, and is not limited to the color data R. However, which of the plurality of color data is to be transmitted is determined in advance between the computer main body 11 and the liquid crystal display device 12.

FIG. 4 shows the timing of data transmitted from the computer main body 11 to the liquid crystal display device 12 when the level of the color data control signal 16 is "H" level. This transmission is based on the VGA specification. In FIG. 4, only the color data R of the display data is transmitted from the computer main body 11 to the liquid crystal display device 12 as indicated by the mark *.

When performing color gradation display in the liquid crystal display device 12, the color data R, the color data G, and the color data B do not necessarily have the same value. In this case, transmission from the computer main body 11 to the liquid crystal display device 12 is the same as the above-described conventional transmission. That is, the computer main body 11 transmits the color data R, the color data G, and the color data B to the liquid crystal display device 12. In this case, the computer main body 11 sets the level of the color data control signal 16 to the “L” level and transmits the “L” level color data control signal 16 to the liquid crystal display device 12.

Hereinafter, the operation of the liquid crystal display device 12 will be described with reference to FIG.

The liquid crystal display device 12 receives the color data control signal 16 via the control signal line 16a. The level of the color data control signal 16 is either “H” level or “L” level. The liquid crystal display device 12 determines whether the level of the color data control signal 16 is “H” level. This determination means will be described later.

When the level of the color data control signal 16 is "H" level, the liquid crystal display device 12 transmits a plurality of colors through one of the display data line groups 13a to 13c. Receiving color data of one of the data. Which color data of the plurality of color data is to be received is determined in advance between the computer main body 11 and the liquid crystal display device 12. In the first embodiment, the liquid crystal display device 12 receives only the color data R via the display data line group 13a. In this case, the color data G and the color data B are not transmitted from the computer main body 11 to the liquid crystal display device 12.

Here, that the level of the color data control signal 16 is "H" level means that the color data R, the color data G and the color data B have the same value. The liquid crystal display device 12 creates color data G and color data B having the same value as the color data R based on the color data R received from the computer main body 11. Alternatively, without actually producing the color data G and the color data B, the color data R is supplied to the display unit 100 (see FIG. 1) as the color data G, and the color data R is supplied to the display unit 100 as the color data B. You may make it supply.

On the other hand, when the level of the color data control signal 16 is "L" level, the liquid crystal display device 12 receives the color data R via the display data line group 13a, and receives the color data R via the display data line group 13b. Receives the color data G, and receives the color data B via the display data line group 13c. The color data R, the color data G, and the color data B thus received are supplied to the display unit 100.

As shown in FIG. 5, the liquid crystal display device 12
It has a switch circuit 22. The color data control signal 16 is input to the switch circuit 22. Switch circuit 22
Determines whether the level of the color data control signal 16 is "H" level or "L" level. That is, the switch circuit 22 functions as a means for determining the color data control signal 16. In addition, as described below, it functions as an input signal switching unit.

When the switch circuit 22 determines that the level of the color data control signal 16 is "H" level,
As shown in FIG. 5, the display data line group 13a and the signal line G0
0 to G05 and a display data line group 1
3a and the signal lines B00 to B05 are electrically connected. Here, the signal lines G00 to G05 connect the color data G to the display unit 1.
Used to feed 00. Similarly, the signal line B0
0 to B05 are used to supply the color data B to the display unit 100.

According to this connection state, the display data line group 13
The color data G and the color data B having the same value as the color data R received via the “a” are supplied to the display unit 100. The display data line group 13a includes signal lines R00 to R00.
05 is always electrically connected. As a result, the display unit 100 performs multi-color display based on the color data R, the color data G, and the color data B.

On the other hand, when it is determined that the level of the color data control signal 16 is "L" level, the switch circuit 22
Electrically connects the display data line group 13b to the signal lines G00 to G05, and connects the display data line group 13c to the signal line B
00 to B05 are electrically connected. The display unit 20 performs multi-color display based on the color data R, the color data G, and the color data B. This operation is the same as in the conventional example.

As described above, when the level of the color data control signal 16 is "L" level, the display is performed through a total of 18 signal lines (display data line groups 13a to 13c) of 6 bits × 3. Data is transmitted from the computer main body 11 to the liquid crystal display device 12. On the other hand, when the level of the color data control signal 16 is the “H” level, a total of seven signal lines (display data line group 13 a
The display data is transmitted from the computer main body 11 to the liquid crystal display device 12 via the control signal line 16a). As a result, the number of signal lines at the time of data transfer can be significantly reduced, so that electromagnetic interference called unnecessary radiation can be reduced.

This effect is more effective when the color data R, the color data G, and the color data B are all 6 bits or more (when performing further multicolor display). That is, the number of signal lines during data transfer can be further reduced.

For the same reason as described above, power consumption can be greatly reduced.

(Embodiment 2) FIGS. 6 and 7 show Embodiment 2 of the drive circuit of the display device of the present invention. The drive circuit according to the second embodiment includes a three-state IC 2 shown by a broken line in FIG.
Nos. 01 to 204 are added to the configuration of the conventional data driver shown in FIG. Therefore, corresponding parts are denoted by the same reference numerals.

In the second embodiment, the three-state ICs 201 to 201 are set according to the color data control signals “H” and “L”.
Reference numeral 204 denotes a configuration for switching the input path of the color data to the liquid crystal display device 12. The operation will be described below.

The three-state IC 201 of the broken line portion A,
202 connects the signal line G to the bus line G 'and the signal line B to the bus line B' when the color data control signal (BW) is at "L" level. On the other hand, the color data control signal (BW)
Are at the "H" level, they are disconnected.

The three-state IC 203 of the broken line portion B,
Reference numeral 204 connects the signal line R to the bus line G 'and the signal line R to the bus line B' when the color data control signal (BW) is at "L" level. On the other hand, when the color data control signal (BW) is at "H" level, these are disconnected.

FIG. 7 shows the relationship between pixels, display data, and sampling pulses according to the second embodiment. j-th, j +
The first picture element performs black and white gradation display. If the color data control signal is at the H level, the gray scale display data of black and white is being transmitted, and only the R color data signal is read and utilized for the G and B color data. G (j),
B (j), G (j + 1), and B (j + 1) indicate that data corresponding to the pixel has not been input to the liquid crystal display device 12.

The j + 2nd picture element shows a display other than monochrome gradation display. Color data evening control signal is "L"
If it is a level, display data other than monochrome gradation is being transmitted, and each color data of R, G, and B is read.

More specifically, when the signals corresponding to the j-th and j + 1-th signals are input, since the color data control signal is at the "H" level, the display data of R is (R0 → G).
0, R1 → G1, R2 → G2), (R0 → B0, R1 →
B1, R2 → B2).

On the other hand, when the signal corresponding to the (j + 2) th signal is inputted, since the color data control signal is at the "L" level, the display data is displayed as usual (R0 → R0, R1).
→ R1, R2 → R2), (G0 → G0, Gl → G1, G
2 → G2), (B0 → B0, R1 → B1, R2 → B2)
Used as

Note that the sampling pulses in the figure are the same as in the prior art.

In the second embodiment, the means for determining the color data control signal and the means for switching the input of color data are as follows.
Although the three-state ICs 201 to 204 are used instead of the switch circuit 22 of the first embodiment, a selector IC may be used instead. .

(Embodiment 3) FIG. 8 shows Embodiment 3 of the drive circuit of the display device of the present invention. The drive circuit according to the third embodiment uses a logic circuit including four AND circuits 211 to 214 and two OR circuits 221 and 222 as a means for determining a color data control signal and a means for switching input of color data. ing.

This logic circuit controls the color data control signal (B
By taking the logical product corresponding to "H" and "L" of W), color data corresponding to monochrome gradation display and other gradation display is captured as in the first and second embodiments.

In the case of 3-bit data for each of R, G, and B, one output means includes 3 × 4 (AND circuit), 3 × 2
(OR circuit) is required.

(Other Embodiments) In the above description, the main body of the computer has been described based on a computer equipped with a liquid crystal display which has attracted attention as a display replacing the conventional CRT. However, the present invention is also applicable to devices and products in which display data is sent from the main machine to the display device.

[0116]

According to the present invention described above, when monochrome display data is transmitted from the main unit to the display device, only one color, for example, R color data is transmitted, and the other color is displayed. For example, since it is not necessary to transmit G and B color data, the G and B signal lines are in a non-operating state, and the number of signal lines during color data transfer can be substantially reduced. Therefore, according to the present invention, electromagnetic interference called unnecessary radiation can be remarkably reduced.

Here, for example, the work screen of a word processor utilizing a computer is sufficient in most of the screen in black and white gradation display, and the present invention is particularly effective in such a case.

Further, according to the present invention, the power required to transfer data to the data driver provided in the display device can be greatly reduced as compared with the conventional example, and as a result, the power consumption of the display device is significantly reduced. Can be reduced.

Therefore, according to the present invention, it is possible to realize a display device which can cope with higher definition.

According to the driving circuit of the display device according to the second or third aspect, if the read color data signal of the display device is read as the G and B color data on the display device side, for example, the reading is performed. The color data signals of R, G,
Since it can also be used for the B color data, it is possible to perform multi-color display on the display device side at the time of gray scale display of black and white.

Further, according to the driving circuit of the display device according to the fifth to seventh aspects, a driving circuit having the above-described effects can be easily realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a computer to which the present invention is applied.

FIG. 2 is a circuit diagram for explaining the reason why power consumption of a display device can be reduced according to the present invention.

FIG. 3 is a diagram illustrating signals transmitted from the computer main body to the liquid crystal display device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing the timing of signals transmitted from the computer main body to the liquid crystal display device according to the first embodiment of the present invention.

FIG. 5 is a circuit diagram illustrating the operation of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 6 is a circuit diagram illustrating a schematic configuration of a digital driver of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a relationship between pixels, display data, and sampling pulses according to a second embodiment of the present invention.

FIG. 8 is a circuit diagram illustrating a main part of a digital driver of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 9 is a block diagram showing a schematic configuration of a conventional computer.

FIG. 10 is a circuit diagram showing a conventional liquid crystal display device.

FIG. 11 is a circuit diagram corresponding to one output of a conventional digital driver that performs gradation display in accordance with n-bit display data.

12A and 12B show a digital driver for realizing eight gradation displays corresponding to 3-bit display data in a liquid crystal display device. FIG. 12A is a schematic circuit diagram showing the entire configuration, and FIG. 12B shows details of an output circuit. FIG.

FIG. 13 is a diagram showing the relationship among pixels, display data, and sampling pulses in a conventional liquid crystal display device.

FIG. 14 is a circuit diagram showing a schematic configuration of a digital driver of a conventional liquid crystal display device.

FIG. 15 is a circuit diagram showing a configuration of an LSI digital driver of a conventional liquid crystal display device.

FIG. 16 is a diagram showing signals transmitted from a conventional computer main body to a liquid crystal display device.

FIG. 17 is a diagram showing a relationship between color data, a display basic color, and a luminance gradation of each color.

FIG. 18 is a diagram showing timings of signals transmitted from a conventional computer main body to a liquid crystal display device.

FIG. 19 is a manpower signal (display data) in the VGA specification.
FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Computer 11 Computer main body 12 Liquid crystal display device 13 Display data 13a, 13b, 13c Display data line group 14 Clock signal 14a Signal line 15 Synchronization signal 15a Signal line 16 Color data control signal 16a Control signal line 22 Switch circuit 100 Display part (TFT) Liquid crystal panel) 201 to 204 Three-state IC 211 to 214 AND circuit 221 and 222 OR circuit MH output holding means Msmp sampling data storage means OPC output circuit

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-123293 (JP, A) JP-A-5-61434 (JP, A) JP-A-3-174585 (JP, A) JP-A-8- 95528 (JP, A) JP-A-8-278479 (JP, A) JP-A-2-120889 (JP, A) JP-A-63-253399 (JP, A) (58) Fields investigated (Int. Cl. ^7, DB name) G09G 3/00 - 5/42 G02F 1/133 505 - 580

Claims (8)

(57) [Claims] 1. A driving circuit of a display device to perform a plurality of grayscale display on the display device based on a plurality of color data defining each a plurality of color components transmitted from the main machine side, it is transmitted from the main machine side Display data of multiple color components
Is the case with different values, together with the gradation display data of different colors from the main unit side are respectively transmitted as digital data, a plurality of color components transmitted from the main machine side
When the gray scale display data has the same value, black and white gray scale display data is transmitted as digital data from the main unit as digital data to one of the gray scale display data. A plurality of signal line groups respectively constituted by a plurality of signal lines corresponding to a plurality of bits constituting display data; Is transmitted, a color data control signal which is digital data for identifying that the monochrome gradation display data is transmitted to the signal line group, a control signal line transmitted from the main unit side, Determining means for determining whether or not the color data control signal is transmitted to the control signal line; and when the determining means determines that the color data control signal is transmitted to the control signal line. The other trust As the color data inputted from the lines, the driving circuit of a display device having a switching means for switching to the gradation display data black and white as the color data transmitted to one of the signal line groups. 2. The switching means according to claim 1, wherein the grayscale display data of black and white as color data transmitted to one of the signal line groups is
The drive circuit for a display device according to claim 1, wherein input signal paths of the other signal lines are switched so that color data input from the other signal lines is input. 3. A configuration in which the switching means switches so that color data created based on black and white gradation display data transmitted to one of the signal line groups is input from another signal line group. The driving circuit for a display device according to claim 1, wherein 4. The display device according to claim 1, wherein said determination means determines the presence or absence of said color data control signal according to the “H” level and “L” level of said color data control signal. Drive circuit. 5. The drive circuit for a display device according to claim 1, wherein the determination unit and the switching unit include a switch circuit. 6. The drive circuit for a display device according to claim 1, wherein the determination unit and the switching unit are configured by an IC circuit. 7. The method according to claim 6, wherein the determining unit and the switching unit are AND.
5. The driving circuit for a display device according to claim 1, wherein the driving circuit comprises a logic circuit comprising a circuit and an OR circuit. 8. The method according to claim 1, wherein the plurality of color data include color data of R, G, and B primary colors.
8. The driving circuit for a display device according to 5, 6, or 7.