JP2002169512A - Liquid crystal driving circuit and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display circuit capable of emitting light of finely divided luminance and chromaticity. SOLUTION: Four external reference voltages 11, i.e., the reference voltages V0 and V15 directly connected with the output voltages for black display V+ (0) and V- (0), and the reference voltages V7 and V8 directly connected with the output voltages for white display V+ (255) and V- (255), are not connected with an internal input resistance 21 but are made independent. With this constitution, 254 output voltages from (1) through (254) among the output voltages 31 can be set as the voltages for a halftone gradation display area. The halftone gradation display area has a 7.87 mV/piece resolution, and this resolution is improved by a 32% compared with the conventional one 10.4 mV. This resolution can easily satisfy the finely divided luminance and chromaticity required for a liquid crystal display or the like for current flight signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal that generates a multi-gradation voltage by dividing the voltage between a plurality of gradation reference voltages by a series resistance dividing circuit and applying the divided voltage to a liquid crystal layer. The present invention relates to a driving circuit and a liquid crystal display device including the liquid crystal driving circuit.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram showing an external reference power supply 1 and a conventional liquid crystal source driver (liquid crystal drive circuit) 4 connected to the external reference power supply 1. The liquid crystal source driver 4 includes the internal input resistor 2 and supplies a drive voltage to a liquid crystal layer in a liquid crystal display device. In the example of FIG. 2, the external reference voltage 1 is composed of 16 reference voltages identified by reference numerals V0, V1,..., V15. External reference voltage 1
Is supplied from a device equipped with a liquid crystal display device, for example, a personal computer (not shown). The individual reference voltages V0, V1,..., V15 in the external reference voltage 1 are values in accordance with specifications predetermined according to the characteristics of the liquid crystal layer in the liquid crystal display device. The internal input resistance 2 includes voltage dividing resistors R1 and R1 provided on the positive voltage side and the negative voltage side, respectively.
, R255. Voltage dividing resistors R1, R2,.
.., R255 are provided to further subdivide the external reference voltage 1 to generate the output voltage 3.

The output voltage 3 is a voltage guided to the liquid crystal display device, and is represented by V + (0), V + (1),.
(N),..., V + (255) and V− (0), V−
, V- (n), ..., V- (255)
Consisting of individual output voltages identified by n
Is a positive integer from 0 to 255. Here, + in the output voltage V + (n) indicates a positive output voltage, and − in the output voltage V− (n) indicates a negative output voltage. The output voltages V + (n) and V− (n) are paired with each other and have opposite polarities of the same magnitude. V + (0), V + (1),.
.., V + (n),..., V + (255) are 256 positive voltages called positive electrode voltages. V-
(0), V- (1), ..., V- (n), ..., V
− (255) is 256 kinds of negative voltages called negative electrode voltages. The voltage is alternately applied to each voltage line in the liquid crystal display device. The method of alternately arranging the supply lines of the positive electrode voltage and the negative electrode voltage and applying a voltage to the liquid crystal layer reduces power consumption and improves display quality. V + (n) and V
-The number n in parentheses in (n) identifies the output voltage. The smaller the number n, the higher the voltage and the LC
In D, the black side is displayed. Therefore, V + (0) and V- (0) are output voltages for black display, and V + (25)
5) and V− (255) represent output voltages for white display.
The output voltage identified by adding (n) between (0) and (255) corresponds to the lightness of 256 tones ranging from black to white.

[0004]

FIG. 3 shows the relationship between the output voltage and the liquid crystal transmittance when the output voltage of the conventional liquid crystal source driver shown in FIG. 2 is applied to the liquid crystal layer of the liquid crystal display device. However, in FIG. 3 (the same applies to FIG. 4 described later), the output voltage is converted into an LCD voltage and displayed. The LCD voltage is equal to the pair of output voltages V + (n)
And V- (n), ie, (V + (n)-
V− (n)) / 2. The LCD voltage consists of 256 voltages from the LCD voltage (0) to the LCD voltage (255). These 256 LCD voltages correspond to 256 gradations in the liquid crystal display device.

As shown in FIG. 2, in the conventional liquid crystal source driver 4, a reference voltage V0 directly connected to a black display positive output voltage V + (0) and a black display negative output voltage V-
Reference voltage V15 directly connected to (0), reference voltage V7 directly connected to white display positive output voltage V + (255)
And the four external reference voltages V8 directly connected to the white display negative output voltage V- (255), like the other external reference voltages V1... V6 and V9. It is connected to the resistor 2.

In the conventional circuit shown in FIG. 2, the LCD voltage for white display and the LCD voltage for black display are optimized to 0.4 V and 6.5 V, respectively, and the L level is applied to the intermediate gradation display area.
The CD voltage is assigned from 1.4V to 3.4V. However, when the liquid crystal display device is driven by applying the conventional circuit shown in FIG. 2, as shown in FIG. 3, the LCD voltages (1) to (3)
In the case of 1), all display black, despite having a mutual potential difference. Also, the LCD voltages (224) to (25)
4) is also all white display. That is, 256
Although there are output sections, 62 of the output sections do not contribute to the gradation. Of the 256 divided voltages, 62 are useless, so that a high-precision and expensive voltage-dividing resistor is unnecessary, and the number of the voltage-dividing resistors, the manufacturing cost, and the required size of the liquid crystal source driver 4 Is extremely inefficient. The LCD voltage that can be set in the halftone display area by this conventional liquid crystal source driver is LC
A total of 192 D voltages (32) to (223), and LC
The resolution for the D voltage is (3.4-1.4) / 192１９
It becomes 10.4 mV. The resolution of an LCD voltage is the minimum voltage difference between one LCD voltage and another adjacent LCD voltage. When there is a change in the LCD voltage exceeding the resolution, the liquid crystal display device displays a new gradation (a gradation different from the gradation before the change) corresponding to the changed LCD voltage.

[0007] The liquid crystal display device is also used as a display device for displaying various aeronautical signals such as the position of the aircraft in a cockpit of an aircraft, for example. The liquid crystal display device for displaying aeronautical signals is required to be capable of emitting light with finely divided luminance and chromaticity for each signal. However, in the liquid crystal display device using the above-described conventional liquid crystal source driver 4 as a driving circuit, an intermediate state is required. Since the resolution of the gradation display area is determined by the manufacturing accuracy of the voltage dividing resistor and the accuracy of the external reference voltage 1, it is difficult to obtain the required luminance / chromaticity. The present invention has been made in view of the above problems, and has as its object to provide a liquid crystal driving circuit that enables light emission of luminance and chromaticity finely divided, and a liquid crystal display device equipped with the liquid crystal driving circuit. I do.

[0008]

The gist of the present invention to achieve the above object lies in the following inventions. [1] In a liquid crystal driving circuit that generates a multi-gradation gray scale voltage by dividing a plurality of gray scale reference voltages between respective gray scale reference voltages by a series resistance dividing circuit and applying the divided voltage to a liquid crystal layer, A liquid crystal driving circuit, wherein a circuit is inserted only in a part of the plurality of gradation reference voltages.

[2] The liquid crystal according to claim 1, wherein the interval between the gray scale reference voltages into which the series resistance dividing circuit is inserted is between gray scale reference voltages corresponding to an intermediate gray scale display area. Drive circuit.

[3] A liquid crystal display device comprising the liquid crystal drive circuit according to [1] or [2].

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a liquid crystal source driver (liquid crystal drive circuit) according to an embodiment of the present invention.
41 and an external reference power supply input to the liquid crystal source driver 41
FIG. 2 is a circuit diagram showing a connection with the circuit 11; V15, V15,..., And V15, which are represented by boxes on the left end of the figure, are external reference voltages 11 and are input according to predetermined specifications from a device equipped with a liquid crystal display device, for example, a personal computer (not shown). Voltage.

The internal input resistor 21 in the liquid crystal source driver 41 is composed of voltage dividing resistors R1, R2,..., R253 provided on the positive voltage side and the negative voltage side, respectively.
The voltage dividing resistors R1, R2,..., R253 are provided to further subdivide the external reference voltage 11 to generate the output voltage 31. The output voltage 31 is a voltage guided to the liquid crystal display device and includes V + (0), V + (1),.
(N),..., V + (255) and V− (0), V−
, V- (n), ..., V- (255)
It becomes. + Of V + (n) indicates the output voltage of the positive electrode as in the conventional case, and − of V− (n) indicates the output voltage of the negative electrode. The number in parentheses of V + (n) also identifies the output voltage as in the prior art. As the number n in () is smaller, V + (n) is a larger voltage value, and the voltage V +
(N) displays a deeper chromaticity (black side) on a liquid crystal display (LCD). Then, V + (0), V + (1),
, V + (n),..., V + (255) are called positive electrode voltages, and V− (0), V− (1),.
(N),..., V− (255) is referred to as a negative electrode voltage, as in the conventional circuit of FIG.

The liquid crystal source driver 41 shown in FIG. 1 is different from the conventional liquid crystal source driver 4 shown in FIG. 2 in that a reference voltage V0 directly connected to a black display positive output voltage V + (0) and a black display negative output voltage are provided. Reference voltage V15 directly connected to V- (0), reference voltage V7 directly connected to white display positive output voltage V + (255), and white display negative output voltage V-
That is, the four external reference voltages 11 of the reference voltage V8 directly connected to (255) are not connected to the internal input resistor 21 but are independent. The internal input resistor 21 is connected only between V1 and V6 and between V9 and V14 which are a part of the external reference voltage 11, divides the difference between these voltages, generates a divided voltage, and outputs the divided voltage. It is output as voltage 31. In the liquid crystal source driver 41 shown in FIG. 1, the voltage dividing resistors R1 to R6 connect between the reference voltages V1 to V6.
Divided by 253 voltage-dividing resistors up to 253, the reference voltage V
Similarly, the range from 9 to V14 is divided by 253 voltage-dividing resistors R1 to R253 to generate 254 steps of positive and negative pairs of output voltages. Therefore, the liquid crystal source driver 41 of FIG. 1 outputs the output voltages V + (0), V− (0), and V + directly connected to the external reference voltage.
It has two pairs of output voltages of (255) and V- (255), further has 254 pairs of output voltages by voltage division, and has a total of 256 pairs of output voltages corresponding to 256 gradations. .

FIG. 4 is a graph showing the relationship between the LCD output voltage and the liquid crystal transmittance according to the embodiment of the present invention shown in FIG. When the liquid crystal display device is driven by the liquid crystal source driver 41 of FIG. 1, as shown in FIG. 4, V7 and V8 which are the reference voltages for white display and V0 and V15 which are the reference voltages for black display are respectively set to .0. 4V and 6.5
V corresponding to the halftone display area.
4V to 3.4V external reference voltages (V1 to V6 and V9
To V14) can be divided into 254 stages. External reference voltages V1 to V6 and V9 to V14 corresponding to the halftone display area
(1.4 V to 3.4 V) is connected to the internal input resistor 21 composed of 253 voltage dividing resistors, so that the external reference voltage from 1.4 V to 3.4 V is divided into 254 voltages. You. Therefore, the resolution of the voltage by the liquid crystal source driver 41 is (3.4-1.4) /254≒7.87 mV.

In the present embodiment, as described above, the reference voltage V input to the liquid crystal source driver 41 is used.
The four external reference voltages 11 of 0, V15, V7 and V8 are not connected to the internal input resistor 21 but are made independent. By employing this configuration, a total of 254 pairs of output voltages from V + (1) to V + (254) and V- (1) to V- (254) of the output voltage 31, that is, 254 kinds of LCD voltages are output. It can be set as the voltage of the halftone display area. Accordingly, the resolution of the halftone display area is 7.87 mV, and the resolution of the halftone display area can be improved by 32% compared to the conventional resolution of 10.4 mV. This can easily satisfy the finely divided luminance and chromaticity required for the current liquid crystal display device for aeronautical signals.

[0016]

According to the present invention, as described above in detail with reference to the embodiments, a liquid crystal drive circuit capable of emitting finely divided luminance and chromaticity, and a liquid crystal drive circuit equipped with this liquid crystal drive circuit A liquid crystal display device can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between an external reference power supply and an internal input resistance of a liquid crystal source driver according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an external reference power supply and an internal input resistance of a conventional liquid crystal source driver.

FIG. 3 shows an LC in a configuration of a conventional liquid crystal source driver.
6 is a graph showing a relationship between a D output voltage and a liquid crystal transmittance.

FIG. 4 is a graph showing a relationship between an LCD output voltage and a liquid crystal transmittance in the configuration of the liquid crystal source driver according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... External reference voltage 2 ... Internal input resistance 3 ... Output voltage 4 ... Liquid crystal source driver 11 ... External reference voltage 21 ... Internal input resistance 31 ... Output voltage 41 ... Liquid crystal source driver R1-R255 ... Division resistance V1-V15 ... External Individual external reference voltages V + (0), V + (1),..., V + (n),.
.., V + (255)... Positive output voltage V− (0), V− (1),..., V− (n),.
・, V− (255)… Negative electrode side output voltage

Claims (3)

[Claims] 1. A liquid crystal driving circuit for generating a multi-gradation gradation voltage by dividing a gradation reference voltage among a plurality of gradation reference voltages by a series resistance dividing circuit and applying the divided voltage to a liquid crystal layer. A liquid crystal drive circuit, wherein a resistance dividing circuit is inserted only in a part of the plurality of gradation reference voltages. 2. The liquid crystal drive according to claim 1, wherein the interval between the gray scale reference voltages into which the series resistance dividing circuit is inserted is between gray scale reference voltages corresponding to an intermediate gray scale display area. circuit. 3. A liquid crystal display device comprising the liquid crystal drive circuit according to claim 1.