JP2002258813A - Liquid crystal drive - Google Patents

Abstract

(57) [Summary] [Problem] To provide a liquid crystal drive device capable of performing normal gradation display and improving color reproducibility by individually setting RGB γ curves. A gamma correction voltage generation circuit for R which receives an R reference voltage and generates an R gradation voltage, and a G gamma voltage which receives a G reference voltage and generates a G gradation voltage. A γ correction voltage generation circuit 103, a B γ correction voltage generation circuit 104 that receives a B reference voltage and generates a B gray scale voltage, and an R analog output of R display data based on the R gray scale voltage A DA converter 111 for converting the voltage into a
A DA converter 121 that converts display data for B into an analog output voltage for G, and converts display data for B into B
And a DA converter 131 for converting the analog output voltage into an analog output voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal driving device for driving a TFT liquid crystal panel by converting digital display data into an analog voltage and driving the TFT liquid crystal panel among liquid crystal driving devices for driving a TFT liquid crystal panel.

[0002]

2. Description of the Related Art FIG. 11 shows a configuration example of a conventional liquid crystal driving device for driving a liquid crystal panel by converting 6-bit digital display data into an analog voltage.

[0003] First, the configuration will be described. 20
Reference numeral 01 denotes a liquid crystal driving device, and reference numeral 2002 denotes a gamma correction voltage generation circuit, which inputs ten reference voltages from the outside of the liquid crystal driving device and outputs 64 gradation voltages. Reference numeral 2011 denotes a DA converter corresponding to the output terminal Y1, to which digital display data and the above-mentioned 64 gradation voltages are input, and an analog output voltage is output. 2012 is a display data latch,
In addition to storing the 6-bit display data, the display data is output as gradation selection data for determining which of the 64 gradation voltages is to be selected. Reference numeral 2013 denotes a gray scale voltage selection circuit, which outputs 6 gray scale signals output from the display data latch 2012.
The bit gradation selection data of 1 bit from 64 gradation voltages
One is selected and output as a display voltage. Reference numeral 2014 denotes an operational amplifier that current-amplifies the input display voltage and outputs the amplified voltage from an output terminal Y1 as an analog output voltage. 20
21 is a DA converter corresponding to the output terminal Y2, 2031 is a DA converter corresponding to the output terminal Y3, 2041 is a DA converter corresponding to the output terminal Y3n-1, and 2051 is a DA converter corresponding to the output terminal Y3n. is there.

Here, the above-mentioned output terminal is a set of three,
(Red, hereinafter referred to as R), G (green, hereinafter referred to as G), B
It is assumed that one pixel (blue, hereinafter referred to as B) is formed.
Here, the output terminal Y1 is R, Y2 is G, and Y3 is B
, Y3n-1 corresponds to G, and Y3n corresponds to B. Further, the display data 1 input to the DA converter 2011 of the output terminal Y1 is the display data corresponding to R, the output terminal Y
2, the display data 2 input to the DA converter 2021 is:
Display data corresponding to G, DA converter 2 of output terminal Y3
Display data 3 input to 031 is display data corresponding to B.

Next, the operation of the liquid crystal driving device will be described.

When ten reference voltages are input to the liquid crystal driving device 2001, the gamma correction voltage generation circuit 2002 divides the voltage between the reference voltages by a method such as resistance division to obtain 64 types of floors. Output as a regulated voltage.

The display data latch 2012 receives display data 1 corresponding to R from outside. The display data 1 is latched and output as gradation selection data.

The gradation voltage selection circuit 2013 selects a gradation voltage selected by the gradation selection data from 64 types of gradation voltages and outputs it as a display voltage.

The selected display voltage is applied to the operational amplifier 201.
4, the signal is output from the output terminal Y1 as an analog output voltage.

Similarly, the display data 2 corresponding to G is DA
The display section 3 converts the display data 3 corresponding to B into the analog voltage by converting the analog data into the analog voltage and outputting the analog data from the output terminal Y2.
The voltage is converted into an analog voltage by the A conversion unit 2031 and output from the output terminal Y3.

[0011]

The above-mentioned conventional liquid crystal driving device has a problem that color reproducibility is poor.
In general, R, G, and B have different γ curves, and therefore, if different correction curves are not used, gradation display of R, G, and B cannot be performed normally. For example, when displaying gray tones from white to black, a certain gray level may be reddish gray and another gray level may be greenish gray.

As described above, in the conventional liquid crystal driving device, R
There is a problem that normal gradation display cannot be performed and color reproducibility deteriorates because the GB can support only the same γ curve.

Accordingly, it is an object of the present invention to provide a liquid crystal driving device capable of performing normal gradation display and improving color reproducibility by individually setting RGB γ curves.

[0014]

According to a first aspect of the present invention, there is provided a liquid crystal driving apparatus comprising: an R gamma correction voltage generating circuit for receiving an R reference voltage to generate an R gray scale voltage; A gamma-correction voltage generation circuit for G that generates a gray-scale voltage for G upon input, and a B that generates a gray-scale voltage for B by receiving a reference voltage for B
Γ correction voltage generating circuit, a DA conversion unit assigned to R for converting R display data into an analog output voltage for R by R gray scale voltage, and G display data by G gray scale voltage Is converted to an analog output voltage for G by a DA converter assigned to G, and a gray scale voltage for B
For DA conversion of display data for B to analog output voltage for B
And a DA conversion unit assigned for use.

According to the liquid crystal driving device of the first aspect,
By having independent gamma correction voltages for R, G, and B,
Different gamma correction can be performed for the G and B gradation characteristics, and gamma correction suitable for the R, G and B gradation characteristics can be performed, and thus a normal optimal gradation display can be performed. And the reproducibility of the display color can be improved.

According to a second aspect of the present invention, there is provided a liquid crystal driving device which receives a reference voltage and generates a first gradation voltage larger than the number of R, G, and B gradations, and a gamma correction voltage generation circuit. Selecting means for selecting, from the first gray scale voltage, a second gray scale voltage having a gray scale number corresponding to the bit number of the display data, and outputting the display data by the second gray scale voltage in an analog manner And a plurality of DA converters for converting the voltage.

According to the liquid crystal driving device of the present invention, different gamma correction can be performed for the R, G, and B gradation characteristics in the same manner as in the first embodiment, and a normal optimum gradation display is performed. Can be performed, and the reproducibility of display colors can be improved. In addition to reducing the number of reference voltage input terminals, the number of gamma correction voltage generation circuits can be reduced.
The circuit can be realized with a circuit having less gray scale voltage output suitable for each γ characteristic of B.

According to a third aspect of the present invention, there is provided a liquid crystal driving device.
In the above, the selection means inputs a selection mode signal from the outside to generate a selection signal and a selection signal decoding circuit, and γ selects a first gradation voltage from the first gradation voltage and generates a second gradation voltage set by the selection signal. And a correction voltage selection circuit.

According to the liquid crystal driving device of the third aspect, in addition to the same effects as those of the second aspect, the gradation voltages assigned to R, G, and B can be switched by setting the selection mode signal.

According to a fourth aspect of the present invention, there is provided a liquid crystal driving device.
A plurality of flip-flops, wherein the selection means shifts the selection data input from outside by a selection data latch clock, and a selection signal decoding circuit for decoding data output from the plurality of flip-flops to generate a selection signal. And a gamma correction voltage selection circuit for selecting a set of the second gradation voltage from the first gradation voltage according to the selection signal.

According to the liquid crystal driving device of the fourth aspect, in addition to the same effects as those of the second aspect, the gradation voltages assigned to R, G, and B can be switched for each gradation. The selectable γ correction voltage can be controlled, and the gradation voltage can be set flexibly, so that it is possible to support liquid crystal panels having different gradation characteristics.

According to a fifth aspect of the present invention, there is provided a liquid crystal driving apparatus having a DA converter for converting display data into an analog output voltage based on a gray scale voltage. Correction voltage generating circuit for generating a first gray scale voltage and a first gray scale voltage output circuit for outputting a second gray scale voltage
And a second circuit connected between every other wiring of the gray scale voltage wiring of the second gray scale voltage and the power supply, and between the remaining wiring and GND, which are arranged adjacently inside the LSI. And a switch circuit, wherein ON / OFF of the second switch circuit is controlled by a control signal.

According to the liquid crystal driving device of the present invention, the R, G, and B γ curves can be individually set by the second gradation voltage, so that normal gradation display is performed and color reproduction is performed. Performance can be improved. Further, by pulling up and pulling down the wiring of the gray scale voltage for each adjacent wiring, if there is a leak between the gray scale voltage wirings, a power supply current leak flows, so that it can be detected at the time of inspection.

According to a sixth aspect of the present invention, there is provided a liquid crystal driving apparatus having a DA converter for converting display data into an analog output voltage by using a gray scale voltage, wherein the first gray scale voltage is inputted by inputting a reference voltage. Correction voltage generating circuit for generating a first gray scale voltage and a first gray scale voltage output circuit for outputting a second gray scale voltage
And a second switch circuit connected between each of the gray scale voltage wirings of the second gray scale voltage and the power supply and the GND, which are arranged adjacent to each other inside the LSI. The on / off of the switch circuit is controlled by a control signal.

According to the liquid crystal driving device of the sixth aspect, in addition to the same effects as those of the fifth aspect, it is also possible to detect a short-circuit failure depending on the direction of the current.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described by way of embodiments with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram of a liquid crystal drive device according to a first embodiment of the present invention. 101 is a liquid crystal driving device, 102 is R
Γ-correction voltage generation circuit 103, a γ-correction voltage generation circuit 103 for G, and a γ correction voltage generation circuit 104 for B, each of which receives five reference voltages from outside the liquid crystal driving device 101, 64 R gradation voltages, 64 G gradation voltages,
A set of 64 gray scale voltages for B is output. Reference numeral 111 denotes a DA converter of the output terminal Y1, to which R display data and 64 R gradation voltages are input, and an R analog output voltage is output. Reference numeral 121 denotes a DA converter of the output terminal Y2, to which G display data and 64 G gradation voltages are input, and a G analog output voltage is output. Reference numeral 131 denotes a DA conversion unit of the output terminal Y3, which stores display data for B and 64
The B gray scale voltage is input, and the B analog output voltage is output. Reference numeral 141 denotes a DA converter of the output terminal Y3n-1, to which G display data and 64 G gradation voltages are input, and a G analog output voltage is output. 151
Is a DA converter of the output terminal Y3n, to which the display data for B and 64 gradation voltages for B are inputted, and the analog output voltage for B is outputted.

Reference numerals 112, 122 and 132 denote display data latches which store display data and output gradation selection data. Reference numerals 113, 123, and 133 denote gray scale voltage selection circuits that select gray scale voltages and output display voltages based on the gray scale selection data. Reference numerals 114, 124, and 134 denote operational amplifiers, and the gray-scale voltage selection circuits 113, 123, 1
33, the display voltage output from the output terminal 33 is amplified, and the output terminal Y
1 to Y3 are output as analog output voltages.

Next, the operation of the liquid crystal driving device will be described.

A reference voltage for R, G
When the reference voltage for B and the reference voltage for B are input, the γ correction voltage generation circuit 102 for R, the γ correction voltage generation circuit 103 for G,
The B γ correction voltage generation circuit 104 divides each reference voltage between the reference voltages by a method such as resistance division, so that 64 types of R gradation voltages, 64 types of G gradation voltages,
It outputs 64 types of B gradation voltages.

Display data latch 11 of DA converter 111
2, R display data is input from the outside. The display data for R is latched and the gradation selection data is output.

The gradation voltage selection circuit 113 selects a gradation voltage selected by the gradation selection data from a set of 64 types of R gradation voltages and outputs it as a display voltage. The selected display voltage is output by the operational amplifier 114 to the output terminal Y1.
Is output as an analog output voltage for R.

The display data latch 122 of the DA converter 121 receives display data for G from outside. This display data for G is latched and gradation selection data is output.

The gradation voltage selection circuit 123 selects a gradation voltage selected by the gradation selection data from a set of 64 types of G gradation voltages, and outputs it as a display voltage. The selected display voltage is output to the output terminal Y2 by the operational amplifier 124.
Is output as a G analog output voltage.

Further, display data for B is input to the display data latch 122 of the DA converter 131 from outside. This B display data is latched, and gradation selection data is output.

The gray scale voltage selection circuit 133 selects a gray scale voltage selected by the gray scale selection data from a set of 64 types of gray scale voltages for B and outputs it as a display voltage. The selected display voltage is output to the output terminal Y3 by the operational amplifier 134.
Is output as a B analog output voltage.

As described above, since each of the RGB has the γ-correction voltage generating circuits 102 to 104, a gradation characteristic of γ-correction corresponding to RGB can be obtained.

(Second Embodiment) FIG. 2 is a configuration diagram of a liquid crystal drive device according to a second embodiment of the present invention.

Reference numeral 201 denotes a liquid crystal driving device, and 202 denotes a gamma correction voltage generation circuit.
The reference voltages are inputted and 128 gradation voltages are outputted. Reference numeral 211 denotes a DA conversion unit of the output terminal Y1. Among the 128 display voltages for R and the 64 grayscale voltages of the 128 grayscale voltages, 64 grayscale voltages that match the γ characteristic of R are input, and an analog output voltage for R is input. Is output. 221 is the DA of the output terminal Y2.
The conversion unit receives 64 gray scale voltages that match the γ characteristics of G among the display data for G and the 128 gray scale voltages, and outputs an analog output voltage for G. 231 is
It is a DA converter for the output terminal Y3, and 64 of the display data for B and the 128 gray scale voltages suitable for the γ characteristic of B are used.
The gray scale voltage is input, and a B analog output voltage is output. Reference numeral 241 denotes a DA converter of the output terminal Y3n-1. Of the display data for G and the 128 gradation voltages, 64 gradation voltages suitable for the γ characteristic of G are input.
The analog output voltage for G is output. Reference numeral 251 denotes a DA conversion unit of the output terminal Y3n, and the display data for B and the 1
Of the 28 gray scale voltages, 64 gray scale voltages matching the γ characteristics of B are input, and a B analog output voltage is output.

Display data latches 212, 222, and 232 store display data and output gradation selection data. Reference numerals 213, 223, and 233 denote gradation voltage selection circuits that select a gradation voltage based on the gradation selection data and output a display voltage. Reference numerals 214, 224, and 234 denote operational amplifiers, which current-amplify the display voltages output from the gradation voltage selection circuits 213, 223, and 233, and output the analog voltages from the output terminals Y1 to Y3.

Next, the operation of the liquid crystal driving device will be described.

When a reference voltage is input to the liquid crystal driving device 201, the γ correction voltage generation circuit 202 divides the voltage between the reference voltages by a method such as resistance division.
It outputs 128 kinds of gradation voltages.

The display data latch 21 of the DA converter 211
2, R display data is input from the outside. Also, from the above-mentioned 128 types of gradation voltages, a set of 64 types of R gradation voltages that match the γ characteristics of R is input.

When the display data for R is input, it is latched by the display data latch 212 and outputs the gradation selection data.

The gradation voltage selection circuit 213 selects a gradation voltage selected by the gradation selection data from a set of 64 types of R gradation voltages and outputs it as a display voltage. The selected display voltage is output by the operational amplifier 214 from the output terminal Y1 as an analog output voltage for R.

The display data latch 22 of the DA converter 221
2, display data for G is input from the outside. Further, from 128 kinds of gradation voltages, 6
A set of four types of G gradation voltages is input.

When the display data for G is input, it is latched by the display data latch 222 and outputs the gradation selection data.

The gradation voltage selection circuit 223 selects a gradation voltage selected by the gradation selection data from a set of 64 types of G gradation voltages and outputs it as a display voltage. The selected display voltage is output from the output terminal Y2 by the operational amplifier 224 as a G analog output voltage.

Display data latch 23 of DA converter 231
2, display data for B is input from the outside. Further, from 128 kinds of gradation voltages, 6
A set of four types of B gradation voltages is input.

When the display data for B is input, it is latched by the display data latch 232 and outputs the gradation selection data.

The gradation voltage selection circuit 233 selects a gradation voltage selected by the gradation selection data from a set of 64 types of B gradation voltages and outputs it as a display voltage. The selected display voltage is output from the output terminal Y3 by the operational amplifier 234 as an analog output voltage for B.

The second embodiment is different from the first embodiment in that the number of reference voltage input terminals can be reduced and the number of gamma correction voltage generation circuits can be reduced. The circuit can be realized with a circuit having less gray scale voltage output suitable for the γ characteristic.

(Third Embodiment) FIG. 3 is a block diagram of a liquid crystal driving device according to a third embodiment of the present invention, and FIG. 4 is a diagram showing the configuration of the third embodiment. R
3 is an embodiment of a gamma correction voltage selection circuit for use.

Reference numeral 301 denotes a liquid crystal driving device, and 302 denotes a gamma correction voltage generating circuit.
The reference voltages are inputted and 128 gradation voltages are outputted. Reference numeral 303 denotes a selection signal decoding circuit which receives a selection mode signal for selecting a combination of gradations and outputs a selection signal for selecting a combination of gradation voltages. Reference numeral 304 denotes an γ correction voltage selection circuit for R, which converts 64 gradation voltages out of the 128 γ correction voltages to 4 by the selection signal.
It is selected from a set of types and output as an R gradation voltage. 3
Reference numeral 05 denotes a gamma correction voltage selection circuit for G, which selects 64 grayscale voltages out of the 128 types of gamma correction voltages from the four types according to the selection signal and outputs the selected grayscale voltages as G grayscale voltages. . Reference numeral 306 denotes a B γ correction voltage selection circuit,
Of the γ correction voltages, 64 gray scale voltages are selected from four types by a selection signal and output as B gray scale voltages.

Reference numeral 311 denotes a DA converter of the output terminal Y1, which inputs the R display data and the R gradation voltage and outputs them as analog output voltages.

A DA converter 321 of the output terminal Y2 receives the G display data and the G gradation voltage, and outputs a G analog output voltage. A DA converter 331 of the output terminal Y3 receives the B display data and the B gray scale voltage, and outputs the B analog output voltage. 341 is
This is a DA converter of the output terminal Y3n-1, which inputs G display data and G gradation voltage, and outputs a G analog output voltage. A DA converter 351 of the output terminal Y3n receives the B display data and the B gradation voltage, and outputs a B analog output voltage. 312, 322, and 332 are display data latches that store display data and output gradation selection data. Reference numerals 313, 323, and 333 denote gray scale voltage selection circuits that select a gray scale voltage based on the gray scale selection data and output a display voltage. 314, 324, 334
Are operational amplifiers, and gray scale voltage selection circuits 313 and 32
3, the display voltage output from the 333 is current amplified and output from the output terminal as an analog output voltage.

FIG. 4 shows an embodiment of the R gamma correction voltage selection circuit. Here, reference numerals 401 to 408 denote switch circuits, which select the R gradation voltage KV (64: 1) from the γ correction voltage V (128: 1) by the selection signal SEL (4: 1). Here, when SEL1 is active and other selection signals are inactive, the R gradation voltage KV1
Γ correction voltage V (1) is selected, and the γ correction voltage V (125) is selected as the R gradation voltage KV64. In FIG. 4, a set of V (1) to V (4) and V (125) to V (125)
The set between the sets of (128) is, for example, basically V (2)
V (5), V (3) to V (6), V (4) to V (7)
... V (123) to V (126), V (125) to V
A combination such as (128) can be used. The same applies to FIG. 6 described later. Note that a combination as shown in FIG. 9 is also possible.

Next, the operation of the liquid crystal driving device will be described.

When a reference voltage is input to the liquid crystal driving device 301, the γ correction voltage generation circuit 302 divides the voltage between the reference voltages by a method such as resistance division.
It outputs 128 kinds of gradation voltages.

In the selection signal decoding circuit 303, when two selection mode signals are input, one of the four selection signals is activated. In accordance with the selection signal SEL (4: 1), the R γ correction voltage selection circuit 304 selects one gradation voltage from four types of gradation voltages for each gradation from the γ correction voltage, and selects 64 gradation gradation voltages. Select the R gradation voltage. Similarly, the γ correction voltage selection circuit for G 305 selects the G gradation voltage for 64 gradations by the selection signal, and the γ correction voltage selection circuit for B 306 selects the B gradation for 64 gradations by the selection signal. Select the gradation voltage.

As described above, in the DA converters 311 to 351, the input display data of each color is converted into an analog output by the DA converters 311 to 351 in the same manner as in the second embodiment. It is converted into a voltage and output from terminals Y1 to Yn. As described above, the set of gradation voltages can be switched by setting the terminals according to different liquid crystal panel characteristics, and the liquid crystal driving device can be used without being changed.

(Fourth Embodiment) FIG. 5 is a configuration diagram of a liquid crystal driving device according to a fourth embodiment of the present invention, and FIG. 5 shows the fourth embodiment. Is an embodiment of the γ correction voltage selection circuit for R in FIG.

Reference numeral 501 denotes a liquid crystal driving device; 502, a gamma correction voltage generating circuit;
The reference voltages are inputted and 128 gradation voltages are outputted. Reference numeral 504 denotes an γ correction voltage selection circuit for R, which inputs selection data input from the outside in accordance with a selection data latch clock, and selects 12 for each gradation in accordance with the selection data.
By selecting 64 gray scale voltages from the eight gamma correction voltages, the gray scale voltages are output as R gray scale voltages. 505 is γ for G
A correction voltage selection circuit, and a γ correction voltage selection circuit 50 for R
As in the case of No. 4, by selecting 64 gray scale voltages from the 128 gamma correction voltages, the gray scale voltages are output as G gray scale voltages. Reference numeral 506 denotes a γ correction voltage selection circuit for B,
Similarly to the correction voltage selection circuit 504, 64 gray scale voltages are selected from the 128 gamma correction voltages and output as B gray scale voltages. Reference numeral 511 denotes a DA converter of the output terminal Y1, which inputs R display data and R gradation voltage,
Output as analog output voltage.

Reference numeral 521 denotes a DA converter of the output terminal Y2, which inputs the G display data and the G gradation voltage, and outputs the G analog output voltage. 531 is D of output terminal Y3
The A conversion unit receives the display data for B and the gray scale voltage for B, and outputs an analog output voltage for B. Reference numeral 541 denotes a DA conversion unit of the output terminal Y3n-1, which inputs the G display data and the G gradation voltage, and outputs the G analog output voltage. Reference numeral 551 denotes a DA converter for the output terminal Y3n,
Display data and a gray scale voltage for B, and an analog output voltage for B is output. Reference numerals 512, 522, and 532 denote display data latches that store display data and output gradation selection data. Reference numerals 513, 523, and 533 denote gray scale voltage selection circuits that select a gray scale voltage based on the gray scale selection data and output a display voltage. Reference numerals 514, 524, and 534 denote operational amplifiers.
The display voltage output from 33 is current-amplified and output from an output terminal as an analog output voltage.

FIG. 6 shows an embodiment of the γ correction voltage selection circuit 504 for R. The gamma correction voltage selection circuit 50 for G
5. The γ correction voltage selection circuit 506 for B has the same configuration. Here, 601 to 608 are switch circuits,
A voltage is selected for each gradation from the γ correction voltage V (128: 1) by the selection signals SEL1 (4: 1) to SELn (4: 1). Reference numeral 609 denotes a decoding circuit 1, which generates a selection signal for gradation 1 based on selection data input from the outside. A decoding circuit 610 generates a selection signal for gradation n based on externally input selection data. 611 from 614 are flip-flops, and shift by selection <br/>-option data latch clock to capture the selection data inputted from the outside to the LSI, the decoding circuit n 6 the output from the decoding circuit 1 609
10 and the last shift output is
Output from the correction voltage selection circuit 504.

Next, the operation of the liquid crystal driving device will be described.

When a reference voltage is input to the liquid crystal driving device 501, the γ correction voltage generation circuit 502 divides the voltage between the reference voltages by a method such as resistance division.
It outputs 128 kinds of gradation voltages.

Based on the selected data input and the selected data latch clock, the selected data is converted to the γ correction voltage selection circuit 504 for R,
The shift input is performed to the gamma correction voltage selection circuit 505 for G and the gamma correction voltage selection circuit 506 for B. The shift input selection data is stored in flip-flops 611 to 614. According to the stored data, the decoding circuit 1609
In, one of the selection signals SEL1 (4: 1) becomes active, and the selection signal SEL1 (4: 1) becomes 1
The gray scale voltage is selected and output as the gray scale voltage KV (1). Similarly, in the decoding circuit n610, one of the selection signals SELn (4: 1) becomes active, and one gray scale voltage is selected from the γ correction voltage V (128: 125), and the gray scale is selected. It is output as voltage KV (64). In this way, 64 R gradation voltages are selectively output. Similarly, 64 G gray scale voltages are selectively output from the G gamma correction voltage generation circuit 505, and 64 B gray scale voltages are selectively output from the B gamma correction voltage generation circuit 506.

As described above, in the DA converters 511 to 551, the input display data of each color is converted into an analog output by the DA converters 511 to 551 in the same manner as in the second embodiment. It is converted into a voltage and output from terminals Y1 to Yn.

As described above, by shifting the selection data from the outside, it is possible to control the γ correction voltage which can be selected for each gradation, to enable flexible setting of the gradation voltage, and to support liquid crystal panels having different gradation characteristics. Becomes possible.

(Fifth Embodiment) FIG. 7 shows a liquid crystal driving device according to a fifth embodiment of the present invention, which corresponds to the third or fourth embodiment of the present invention. This is a correction voltage selection circuit. FIG. 8 shows an example of a mask arrangement of the gradation voltage.

Reference numerals 701 to 716 denote switches, and 128 selectable γ correction voltages V are output by four select signals SEL (4: 1).
(128: 1) to 64 gradation voltages KV (64: 1)
Select Here, it is assumed that the selection signals SEL (4: 1) can assume a state where all are inactive or only one of the four becomes active. 720, 7
An Nch channel transistor 22 has a drain connected to the gray scale voltage, a source connected to the GND potential, and ON / OFF controlled by a control signal CON2. 721, 7
Reference numeral 23 denotes a Pch channel transistor whose drain is connected to the gray scale voltage, whose source is connected to the VDD potential, and which is turned on and off by a control signal CON1. FIG. 7 basically shows V (1) to V (4), V (3) to V (6),.
(123) to V (126), V (125) to V (12
The arrangement of combinations as in 8) forms 64 combinations.

The reference numerals 801 to 804 denote gradation voltages KV, respectively.
(1), KV (2), ~ KV (63), KV (64) are wirings in the LSI, and 810 is KV (1) and KV (1)
This indicates a failure in the LSI caused by only a resistance component such as dust existing to connect (2).

Next, the operation of the gamma correction voltage selection circuit of the liquid crystal driving device will be described.

When all of the selection signals SEL (4: 1) become inactive, all the switches 701 to 716 are turned off, and the gray scale voltage KV (64: 1) becomes high impedance. Next, when CON1 is set to L level and CON2 is set to H level, all the transistors 720 to 723 are turned on.

Here, if there is a failure 810 shown in FIG. 8, a current flows from the source power supply of the transistor 721 to the GND of the transistor 720.

As described above, when there is a failure 810 in the resistance component between the wirings of the gradation voltage, the current flows,
Failure can be detected.

(Sixth Embodiment) FIG. 9 shows a gamma correction voltage selection circuit of a liquid crystal driving device according to a sixth embodiment of the present invention. FIG. 10 shows an example of a mask arrangement of the gradation voltage.

Reference numerals 901 to 916 denote switches,
128 γ-correction voltages V with the selection signal SEL (4: 1)
(128: 1) to 64 gradation voltages KV (64: 1)
Select Here, it is assumed that the selection signals SEL (4: 1) can assume a state where all are inactive or only one of the four becomes active. 920, 9
Reference numeral 22 denotes a Pch channel transistor whose drain is connected to the gray scale voltage, whose source is connected to the VDD potential, and whose control is turned on and off by a control signal CON3. 921,
Reference numeral 923 denotes a Pch channel transistor having a drain connected to the gradation voltage, a source connected to the VDD potential,
ON and OFF are controlled by the control signal CON1. 93
Reference numerals 0 and 932 denote Nch channel transistors whose drains are connected to the gradation voltage, whose sources are connected to the GND potential, and whose control is turned on and off by the control signal CON4. 9
31 and 933 are Nch channel transistors,
The drain is connected to the gradation voltage, the source is connected to the GND potential, and ON / OFF control is performed by the control signal CON3.

The reference numerals 1001 to 1004 denote gradation voltages K, respectively.
V (1), KV (2), KV (63), and KV (64) are wirings in the LSI, and 1010 is a wiring of KV (1) and KV (1).
A failure having diode characteristics connected to (2) is shown.

Next, the operation of the gamma correction voltage selection circuit of the liquid crystal driving device will be described.

When all of the selection signals SEL (4: 1) become inactive, all the switches 901 to 916 are turned off, and the gray scale voltage KV (64: 1) becomes high impedance. Next, when CON1 is at L level, CON2 is at L level, CON3 is at H level, and CON4 is at H level, transistors 921, 923, 930, 931 are turned on, and transistors 931, 933, 920, 922 are turned off. become.

Here, even if there is a fault 1010 shown in FIG. 10, since the diode is only biased in the reverse direction, no current flows and the fault cannot be detected.

Next, CON1 is set at H level and CON2 is set at H level.
When the level, CON3 is L level, and CON4 is L level, the transistors 921, 923, 930, 931 are turned off, and the transistors 931, 933, 920, 922 are turned on.

With this setting, if there is a failure 1010, the diode becomes forward, a current flows, and the failure can be detected.

As described above, by adopting the configuration as in the sixth embodiment, it is possible to detect a fault having not only a resistance component but also a diode component.

[0087]

According to the liquid crystal driving device of the first aspect,
By having independent gamma correction voltages for R, G, and B,
Different gamma correction can be performed for the G and B gradation characteristics, and gamma correction suitable for the R, G and B gradation characteristics can be performed, and thus a normal optimal gradation display can be performed. And the reproducibility of the display color can be improved.

According to the liquid crystal driving device of the present invention, different gamma correction can be performed for the gradation characteristics of R, G, and B in the same manner as in the first embodiment, and a normal optimum gradation display is performed. Can be performed, and the reproducibility of display colors can be improved. In addition to reducing the number of reference voltage input terminals, the number of gamma correction voltage generation circuits can be reduced.
The circuit can be realized with a circuit having less gray scale voltage output suitable for each γ characteristic of B.

According to the liquid crystal driving device of the third aspect, in addition to the same effects as those of the second aspect, the gradation voltages assigned to R, G, and B can be switched by setting the selection mode signal.

According to the liquid crystal driving device of the fourth aspect, in addition to the same effects as those of the second aspect, the gradation voltages assigned to R, G, and B can be switched for each gradation. The selectable γ correction voltage can be controlled, and the gradation voltage can be set flexibly, so that it is possible to support liquid crystal panels having different gradation characteristics.

According to the liquid crystal driving device of the fifth aspect, the γ curves of R, G, and B can be individually set by the second gradation voltage, so that normal gradation display is performed and color reproduction is performed. Performance can be improved. Further, by pulling up and pulling down the wiring of the gray scale voltage for each adjacent wiring, if there is a leak between the gray scale voltage wirings, a power supply current leak flows, so that it can be detected at the time of inspection.

According to the liquid crystal driving device of the sixth aspect, in addition to the same effects as those of the fifth aspect, it is possible to detect even a short-circuit failure dependent on the direction of the current.

[Brief description of the drawings]

FIG. 1 is a block diagram of a liquid crystal driving device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a liquid crystal driving device according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a liquid crystal driving device according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram of an γ correction voltage selection circuit for R according to a third embodiment of the present invention.

FIG. 5 is a block diagram of a liquid crystal driving device according to a fourth embodiment of the present invention.

FIG. 6 is a block diagram of an R γ correction voltage selection circuit according to a fourth embodiment of the present invention.

FIG. 7 is a circuit diagram of a gamma correction voltage selection circuit according to a fifth embodiment of the present invention.

FIG. 8 is a mask layout diagram of a gray scale voltage signal for explaining the operation of the fifth embodiment of the present invention.

FIG. 9 is a circuit diagram of a gamma correction voltage selection circuit according to a sixth embodiment of the present invention.

FIG. 10 is a mask layout diagram of a gray scale voltage signal for explaining the operation of the sixth embodiment of the present invention.

FIG. 11 is a block diagram of a conventional liquid crystal driving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Liquid crystal drive device 102 R gamma correction voltage generation circuit 103 G gamma correction voltage generation circuit 104 B gamma correction voltage generation circuit 111 Y1 DA converter 121 Y2 DA converter 131 Y3 DA converter 141 Y3n-1 DA conversion unit 151 Y3n DA conversion unit 112, 122, 132 Display data latch 113, 123, 133 Gray scale voltage selection circuit 114, 124, 134 Operational amplifier

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H093 NA58 NA61 NC28 NC90 ND06 ND17 5C006 AA11 AA22 AF46 AF82 AF85 BB16 BC11 BC16 BF06 BF25 FA42 FA43 5C080 AA10 BB05 CC03 DD01 EE29 FF11 JJ02 JJ03

Claims (6)

[Claims] An R gamma correction voltage generating circuit for receiving an R reference voltage and generating an R gradation voltage, and a G gamma voltage for receiving a G reference voltage and generating a G gradation voltage. a gamma correction voltage generating circuit, a gamma correction voltage generating circuit for b for generating a gray scale voltage for b by inputting a reference voltage for b, and an analog output voltage for r based on the gray scale voltage for r. A D / A conversion unit assigned for R for D / A conversion, and the G display data to the G analog output voltage by the G gradation voltage.
A liquid crystal drive device comprising: a D / A converter assigned to G for conversion; and a D / A converter assigned to B for D / A conversion of display data for B to an analog output voltage for B by the gray scale voltage for B. . 2. A gamma correction voltage generating circuit for receiving a reference voltage and generating a first gray scale voltage larger than the number of gray scales of R, G and B, and a gamma correction voltage generation circuit provided corresponding to each output terminal. Selecting means for selecting, from one gray scale voltage, a second gray scale voltage having a gray scale number corresponding to the bit number of display data, and a plurality of converting means for converting the display data into an analog output voltage by the second gray scale voltage A liquid crystal driving device comprising a DA converter. 3. A selection signal decoding circuit for generating a selection signal by inputting a selection mode signal from the outside,
3. A gamma correction voltage selection circuit for selecting a set of a second gradation voltage from a first gradation voltage according to the selection signal.
The liquid crystal driving device as described in the above. 4. The selecting means includes: a plurality of flip-flops for shifting selected data input from the outside by a selected data latch clock; and a selection unit for decoding data output from the plurality of flip-flops to generate a selection signal. 3. The liquid crystal driving device according to claim 2, further comprising: a signal decoding circuit; and a gamma correction voltage selection circuit that selects a set of a second gradation voltage from a first gradation voltage according to the selection signal. 5. A liquid crystal drive device having a DA converter for converting display data into an analog output voltage based on a gray scale voltage, wherein a γ generates a first gray scale voltage by inputting a reference voltage.
A correction voltage generating circuit, a first switch circuit for receiving the first gray scale voltage and outputting a second gray scale voltage, and an LSI
A second switch circuit connected between every other wiring of the grayscale voltage wiring of the second grayscale voltage and a power supply, and between the remaining wiring and GND, which are arranged to be adjacent to each other inside; A liquid crystal driving device, wherein ON / OFF of the second switch circuit is controlled by a control signal. 6. A liquid crystal driving device having a DA converter for converting display data into an analog output voltage based on a gray scale voltage, wherein a γ generating a first gray scale voltage by inputting a reference voltage.
A correction voltage generating circuit, a first switch circuit for receiving the first gray scale voltage and outputting a second gray scale voltage, and an LSI
A second switch circuit connected between a power supply and GND, and each of the grayscale voltage wirings of the second grayscale voltage arranged to be adjacent to each other inside; A liquid crystal driving device characterized in that turning off and turning off are controlled by a control signal.