JP2939897B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simple matrix type liquid crystal display device, and more particularly to a drive power supply circuit suitable for a liquid crystal display device using an STN (Super Twisted Nematic) liquid crystal and its drive power supply circuit. And a liquid crystal display device using the same.

[0002]

2. Description of the Related Art A liquid crystal display substrate provided in a simple matrix type liquid crystal display device extends, for example, in the y-direction to a liquid crystal side surface of one of the transparent glass substrates disposed opposite to each other via a liquid crystal. And data lines arranged in parallel in the x direction are formed, and scanning lines extending in the x direction and arranged in the y direction are formed on the surface of the other glass substrate facing the liquid crystal. Have been.

A pixel region is formed at the intersection of a data line and a scanning line. A binary voltage signal is input to each data line via a data driving circuit, and a pixel voltage is applied to each scanning line. Are configured to receive a so-called selection signal and a non-selection signal via a scan driving circuit.

Further, it is known that a selection signal and a non-selection signal input to a scanning line are converted into AC signals, thereby avoiding the occurrence of so-called defective alignment in pixels.

In addition, a power supply circuit for generating each drive voltage to be supplied to the data drive circuit and the scan drive circuit for forming such signals is required.

[0006] As shown in FIG.
Level voltage can be generated. For this reason, the voltage of the V (LCD) power supply is averaged using a resistor and an operational amplifier, and as shown in FIG.
2, V4 and a scanning signal voltage V1 are formed, and data signal voltages V1 and V3 and a scanning signal voltage V2 are formed with their voltage values inverted (by so-called M signals).

[0007] These prior arts are described in detail in, for example, Japanese Patent Application Laid-Open No. 50-68419.

A simple matrix type liquid crystal display device using an STN (Super Twisted Nematic) liquid crystal has a difference in operation principle from an active liquid crystal display device represented by a liquid crystal display device using a TFT. For example, a phenomenon occurs in which a mouse cursor moved at high speed is difficult to see or loses view. this is,
Compared to the active liquid crystal display element, in which each display pixel portion holds electric charge even during a period in which a fixed voltage is not applied to the scanning line (gate line), the simple matrix type liquid crystal display element has a scanning line and a signal line. This is because, at each intersecting pixel portion, a slight potential difference in the scanning period due to the duty driving determines the display image based on the effective value response.

[0009]

In the above-described conventional simple matrix type liquid crystal display device, the charge / discharge current flowing when the liquid crystal display substrate is driven flows from the highest power supply to the lowest power supply. It has been pointed out that the power consumption increases.

That is, when the voltage of V (LCD) shown in FIG. 5 is 25 V, the charge / discharge current flows at a maximum of 20 mA, and the current consumption is 500 mW.

Therefore, the present invention has been made under such circumstances, and a first object is to provide a simple matrix type liquid crystal display device which can reduce power consumption.

It is a second object of the present invention to provide a simple matrix type liquid crystal display device having improved high-speed response for displaying a moving image which can follow a mouse cursor moving on a screen at a high speed. .

[0013]

In order to achieve the first object, a simple matrix type liquid crystal display device according to the present invention is basically arranged opposite to each other so as to intersect with each other via a liquid crystal layer. A plurality of data lines and a plurality of scanning lines; a data driving circuit for selectively outputting a binary voltage signal to each of the data lines according to display contents; A scan drive circuit that selectively outputs a voltage signal at a predetermined cycle, and a power supply circuit that supplies a drive voltage having each of the values to the scan drive circuit and the data drive circuit, wherein the power supply circuit includes: High or low 2 based on a predetermined voltage between two input power supply voltages
A booster circuit that boosts the voltage to two
Is used as the power supply for the operational amplifier, and
The intermediate voltage of the output voltage is
Allocated as the non-selection signal voltage of the scanning line, the booster circuit
And assigning the boosted voltage as the selection signal voltage of the scanning line.

Further, the booster circuit may be constituted by a pair of circuits for boosting the positive polarity side and the negative polarity side at the same boost ratio with reference to the potential assigned as the non-selection signal voltage of the scanning line. Alternatively, the booster circuit may be provided with adjusting means for adjusting a variation in a boost ratio of each of the pair of circuits.

In order to achieve the second object, a simple matrix type liquid crystal display device according to the present invention basically comprises a plurality of data lines and a plurality of data lines which are arranged so as to intersect with each other via a liquid crystal layer. And a data drive circuit for selectively outputting a binary voltage signal to each of the data lines in accordance with display contents, and a ternary AC voltage signal to the scan lines for a predetermined period. And a power supply circuit that supplies the scan drive circuit and the data drive circuit with the drive voltages having the respective values. The power supply circuit includes two input power supplies.
High or low based on a predetermined voltage between the voltages (Vcc and ground)
A booster circuit for boosting the voltage to two voltages;
The voltage is used for the power supply of the operational amplifier, and
Apply the intermediate voltage of the extracted voltage via the above-mentioned operational amplifier.
Allocated as the non-selection signal voltage of the scanning line,
The voltage boosted in the path is assigned as the selection signal voltage of the scanning line, and the frame frequency is driven at least in the vicinity of 150 Hz to 360 Hz.

The size of the screen of the liquid crystal display element is such that the distance connecting the diagonal lines of the screen, which is currently the mainstream of the liquid crystal display element, is 9.4 to 10.4 inches or 11.3 inches.
A (Video Graphic Array) or SVGA (Super Video Graphic A
(rray) as well as 13.0 to 13.8 inch SVGA, which has a small increase in production cost due to large size, and especially CAD, etc. Suitable 16.6 to 17.6 inch XGA
(Extended Graphic Array) is optimal. In this specification, VGA means that the number of scanning lines and the number of signal lines are each 480.
And 640, SVGA refers to a liquid crystal display element in which the number of scanning lines and signal lines are 600 and 800, respectively, and XGA refers to a liquid crystal display element in which the number of scanning lines and signal lines are 768 and 1024, respectively.

[0017]

According to the simple matrix type liquid crystal display device having the structure for achieving the first object as described above, the binary drive voltage to be input to the data line uses a logic power supply. Even if these values are inverted by the AC conversion, the potential difference is only about 4V.

This means that the charge / discharge current of the liquid crystal is 20 mA.
, Most of them flow between the potential differences (18 mA).

The ternary drive voltage to be input to the scanning line is obtained by boosting the logic power supply by five times, and is assigned as the non-selection signal voltage, and the other remaining binary voltages are used. Each is assigned as a selection signal voltage to be converted to AC. The current supplied from these two values is 2 mA
It will be a little less.

From these, power consumption is as follows.

5 V × (18 mA + 2 mA × 5) = 140 mW Therefore, the power consumption is reduced to １ ／ as compared with the conventional case.
It can be:

Further, at the above-mentioned high frame frequency, the charge / discharge current of the liquid crystal increases in proportion to the frequency, so that the power consumption increases. For example, if the current at a frame frequency of 120 Hz is 20 mA, the current is tripled to 60 mA at a frame frequency of 360 Hz.
Therefore, the power consumption is tripled in the simple calculation. But,
According to the configuration for achieving the above-mentioned second object, even if the frame frequency becomes three times as large as the frame frequency for driving the conventional liquid crystal, the power consumption can be suppressed to approximately the same as the conventional system. .

[0023]

FIG. 1 is a circuit diagram showing one embodiment of a power supply circuit provided in a simple matrix liquid crystal display device according to the present invention, and FIG. 2 is a schematic diagram showing one embodiment of a simple matrix liquid crystal display device according to the present invention. It is a block diagram.

In FIG. 2, there is a liquid crystal display substrate 21,
The liquid crystal display substrate 21 includes glass substrates disposed to face each other with a liquid crystal interposed therebetween.

Then, n data lines extending in the y direction and juxtaposed in the x direction are formed on the liquid crystal side surface of one of the glass substrates, and each of these data lines is a data driver (data driving circuit). ) 22 to receive a data signal. This data signal has two values.

Further, x is applied to the surface of the other glass substrate on the liquid crystal side.
The m scanning lines extending in the direction and being arranged in the y direction are formed, and a scanning signal is inputted from a scanning driver (scan driving circuit) 23 to each of these scanning lines. This scanning signal has three values.

Each pixel area of the liquid crystal display substrate 21 is formed at the intersection of a data line and a scanning line, so that the liquid crystal display substrate 21 has n × m pixels. Then, the data driver 22 and the scanning driver 2
3 is supplied with a driving voltage for forming a data signal and a scanning signal which are outputs from the power supply circuit 24.

The power supply circuit 24 has a logic power supply V (c
c) have voltages V1, V2,
V3, V4, and V5 are generated, and the voltages V2, V4
Are supplied to the data driver 22, and the voltages V1, V3, V
5 is supplied to the scanning driver 23.
The configuration of the power supply circuit 24 will be described later in detail.

On the other hand, the video information from the computer 25 is input to the data driver 22 via the liquid crystal panel control device 26.
Then, the driving voltages V2 and V4 are set to 2 based on the video information.
The data signal is formed as a value.

That is, as is apparent from FIG. 3 showing the configuration of the data drive 22, the drive voltages V2 and V4 are input to the data lines via separate MOS transistors, respectively. One of the MOS transistors is turned on.

The liquid crystal panel control device 26 sends the FLM
The scanning driver 23 receives the FLM signal as a start signal, the CL1 signal as a shift signal, and sets the driving voltages V1, V3, and V5 to three values. Is formed. That is, as is apparent from FIG. 3 showing the configuration of the scanning driver 23, the driving voltages V1, V3,
V5 are input to the scanning lines via separate MOS transistors, respectively.
One of the OS transistors is turned on.

Further, the data signal in the data driver 22 and the scanning signal in the scanning driver 23 are AC-converted by the M signal output from the AC signal generating circuit 27.

That is, as is apparent from FIG. 3, in both the data driver 22 and the scanning driver 23, the M signal is input to the logic circuit, and the information input to the logic circuit is inverted. .

FIG. 1 is a circuit diagram showing a specific configuration of power supply circuit 24 shown in FIG.

In the figure, a logic power supply V (cc) is adapted to take out a voltage V2 via a transistor Tr and a voltage V4 from its ground.

The transistor Tr, together with a variable resistor R1 for adjusting the current flowing through its base, adjusts the display contrast of the liquid crystal display substrate.

The logic power supply V (cc) via the transistor Tr is supplied to a complementary switch. This bi-complementary switch consists of pMOS and nMO
S, and a pulse signal P is input to those gates. Then, a voltage pulse is supplied to the primary winding of the booster circuit 30 by alternately switching the bi-complementary switch by inputting the pulse signal P to each MOS.

The booster circuit 30 is composed of a pair of circuits having a common intermediate tap of the secondary winding, and each circuit is boosted at a boost ratio of (1: (a-1) / 2 + Δ), The voltage V1 and the voltage V5 are taken out via a rectifying / smoothing circuit composed of D and a capacitor C.

Here, a = √N + 1, where N is the number of time divisions. Thereby, the optimum bias ratio a formed by the voltage averaging method is used. Δ is a correction term of the step-up ratio, and generates a voltage in consideration of the voltage drop of the diode D.

The potential of the intermediate tap of the secondary winding of the booster circuit 30 is taken via an operational amplifier (OPamp1).
V3 can be extracted via an operational amplifier (OPamp2) .

Here, resistors R2, R4, and R3 are provided, and among them, the resistor R4 is a variable resistor so that the relationship of R2 = R4 + R3 is established.

With this configuration, the voltage V3 can be adjusted so as to be equal to half the voltage V2 or V4 which can be extracted from the logic power supply.

Accordingly, it is possible to prevent the occurrence of luminance unevenness of the pixel due to the inversion of the scanning signal.

FIG. 4 shows a data signal and a scanning signal input to the liquid crystal display substrate 21 by the data driver 22 and the scanning driver 23 shown in FIG. 2 based on the respective voltages generated by the power supply circuit thus configured. It is a time chart.

As can be seen from the figure, the difference between the data signals inverted by the M signal is 4 V, similar to the voltage of the logic power supply.

Therefore, as shown in FIG. 6 which is a time chart of the corresponding data signal and scanning signal in the conventional configuration (FIG. 5), the difference between the data signal and the M signal is 2
It turns out that it becomes extremely small as compared with the case of 5V.

As described above, according to the liquid crystal display device of the present embodiment, the binary drive voltage to be input to the data line uses the logic power supply, and therefore, even if those values are inverted by AC conversion, The potential difference is only about 4V.

This means that the charge / discharge current of the liquid crystal is 20 mA.
, Most of them flow between the potential differences (18 mA).

The ternary drive voltage to be input to the scanning line is obtained by boosting the logic power supply by five times, and is assigned as the non-selection signal voltage, and the other remaining binary voltages are used. Each is assigned as a selection signal voltage to be converted to AC. The current supplied from these two values is 2 mA
It will be a little less.

From the above, the power consumption is as follows.

5 V × (18 mA + 2 mA × 5) = 140 mW From this equation, the power consumption can be reduced to １ ／ or less as compared with the conventional case. Generally, at a high frame frequency, the power consumption increases because the charge / discharge current of the liquid crystal increases in proportion to the frequency. For example, if the current at a frame frequency of 120 Hz is 20 mA, the current is tripled to 60 mA at a frame frequency of 360 Hz. Therefore, the power consumption is tripled in the simple calculation. However, according to the present invention, even if the frame frequency is three times as large as the conventional frame frequency for driving the liquid crystal, the power consumption can be suppressed to substantially the same level as the conventional system.

The value of the frame frequency of the liquid crystal display device of the present invention is set to the frame frequency 60 used in the current product.
It is desirable to take a value from twice or more than 60 Hz or 75 Hz to 360 Hz. Experimental data is omitted, but considering a value that satisfies the specification of high-speed response required from practical use, it is around 150 Hz or 180 Hz. It is desirable to set.

As is clear from the above description, according to the simple matrix type liquid crystal display device of the present invention,
A device with low power consumption can be obtained.

The liquid crystal material has the general formula

[0055]

(Equation 2)

It is preferable to add a PCH (Phenyl-Cyclohexane) -based liquid crystal represented by the following formula in the range of 10 to 50% by weight. The twist angle of liquid crystal molecules is 200 degrees or more
270 degree STN (Super Twisted Nematic: Supe
(r Twisted Nematic) In liquid crystal, γ
This is because it is necessary to use a liquid crystal having good characteristics.

[0057]

As is apparent from the above description,
ADVANTAGE OF THE INVENTION According to the simple matrix type liquid crystal display device by this invention, the thing with small power consumption can be obtained even if high-speed response is improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a power supply circuit provided in a simple matrix liquid crystal display device according to the present invention.

FIG. 2 is a circuit diagram showing one embodiment of a simple matrix liquid crystal display device according to the present invention.

FIG. 3 is a circuit diagram illustrating details of a data driver and a scan driver included in a simple matrix liquid crystal display device according to the present invention.

FIG. 4 is a time chart showing a data signal and a scanning signal input to a liquid crystal substrate included in a simple matrix liquid crystal display device according to the present invention.

FIG. 5 is a circuit diagram showing an example of a conventional power supply circuit.

FIG. 6 is a time chart showing a conventional data signal and scanning signal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 21 ... Liquid crystal display board, 22 ... Data driver, 23 ... Scan driver, 24 ... Power supply circuit, 25 ... Computer, 2
6 ... Liquid crystal panel control device, 27 ... AC signal generation circuit,
30 ... Booster circuit.

──────────────────────────────────────────────────続 き Continued on the front page (56) References JP-A-5-297832 (JP, A) JP-A-64-46729 (JP, A) JP-A-7-23384 (JP, U) (58) Field (Int.Cl. ⁶ , DB name) G02F 1/133 G09G 3/36

Claims (8)

(57) [Claims] 1. A liquid crystal display device of a simple matrix type, comprising a plurality of data lines and a plurality of scanning lines which are arranged so as to intersect each other with a liquid crystal layer interposed therebetween, and each of said data lines has a binary value. A data drive circuit for selectively outputting a voltage signal in accordance with display contents; a scan drive circuit for selectively outputting a ternary AC voltage signal to the scan line at a predetermined cycle; And a power supply circuit for supplying a drive voltage having each value to the data drive circuit. The power supply circuit comprises two input power supplies.
Boosts to two high and low voltages based on a predetermined voltage between the voltages
A booster circuit, which supplies the input power supply voltage to an operational amplifier power supply
Between the voltages extracted from the above input power supply voltage
The voltage is applied to the non-selection signal of the scanning line via the operational amplifier.
Allocated as voltage, and the voltage boosted by the booster circuit is
The liquid crystal display device characterized by allocating a selection signal voltage of the scanning line. 2. The booster circuit according to claim 1, wherein said predetermined voltage is a reference.
2. The liquid crystal display device according to claim 1, comprising a pair of circuits for boosting the positive polarity side and the negative polarity side at the same boost ratio. 3. The booster circuit according to claim 1, wherein said booster circuit has a boost ratio of two high and low voltages.
2. The liquid crystal display device according to claim 1 , further comprising: means for adjusting the predetermined voltage according to the variation of the voltage . 4. The liquid crystal display device according to claim 1, wherein a frame frequency, which is a reference for operation of said scan drive circuit and said data drive circuit, is in the range of about 150 Hz to 360 Hz. 5. A liquid crystal material of a liquid crystal layer provided between a plurality of data lines and a plurality of scanning lines arranged opposite to each other is added with a PCH-based liquid crystal represented by the following general formula in a range of 10 to 50 wt%. The liquid crystal display device according to claim 1, wherein (Equation 1) 6. A liquid crystal display device of a simple matrix type, comprising a plurality of liquid crystal layers including a super twisted nematic liquid crystal having a twist angle of 200 to 270 degrees and intersecting each other via a liquid crystal layer including a super twisted nematic liquid crystal. A data line and a plurality of scanning lines, a data driving circuit for selectively outputting a binary voltage signal to each of the data lines in accordance with display contents, and a ternary alternating voltage to the scanning line. A scan drive circuit for selectively outputting a signal at a predetermined cycle; and a power supply circuit for supplying a drive voltage having each of the values to the scan drive circuit and the data drive circuit . Reference to a predetermined voltage between input power supply voltages
And a booster circuit for boosting the voltage to two high and low voltages.
The power supply voltage is used for the power supply of the operational amplifier,
The intermediate voltage of the voltage extracted from the
And assigned as the non-selection signal voltage of the scanning line.
A voltage boosted by the booster circuit is assigned as a selection signal voltage of the scanning line, and a frame frequency serving as a reference for operation of the scan driving circuit and the data driving circuit is 150 Hz.
A liquid crystal display device having a frequency range from near to 360 Hz. 7. The booster circuit according to claim 1, wherein said predetermined voltage is a reference.
7. The liquid crystal display device according to claim 6, comprising a pair of circuits for boosting the positive polarity side and the negative polarity side at the same boost ratio. 8. The booster circuit according to claim 1, wherein said booster circuit has a boost ratio of two high and low voltages.
7. The liquid crystal display device according to claim 6 , further comprising: means for adjusting the predetermined voltage in accordance with a variation in the voltage .