JP2002099252A - Liquid crystal driver and liquid crystal display device using the driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of display irregularity generated between driver ICs as a result of dispersion in output characteristics caused by the dispersion generated during the production of the driver ICs in a conventional liquid crystal display device. SOLUTION: A pair of transistors TR1 and TR2 are serially connected between a gate ON voltage 26 and a gate OFF voltage 27. An output buffer outputs the voltages 26 and 27. The output of a level shifter circuit 33 is adjusted by a differential operational amplifier 36 whose output value is adjusted by the control signals inputted from an external adjustment terminal 37. The adjusted outputs are respectively inputted to the bases of the pair of transistors TR1 and TR2 which constitute the output buffer and the gate ON voltage and the gate OFF voltage outputted by the output buffer are adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thin film transistor (hereinafter, referred to as a TFT).
active matrix type liquid crystal display device (hereinafter referred to as LCD: liquid crystal)
al display) and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art A conventional method of driving a TFT-LCD will be described. FIG. 5 is a configuration diagram showing a general conventional liquid crystal driving device. Reference numeral 1 denotes a liquid crystal panel, which includes a plurality of gate lines 2a, 2b...
A plurality of source lines 3a, 3b,
.. 3n. Reference numeral 4 denotes a TFT formed at the intersection of a gate line group and a source line group which intersect with each other in a matrix, and 5 denotes a pixel provided corresponding to each TFT. Each pixel 5 has a liquid crystal layer 8 and a storage capacitor 9 sandwiched between a common electrode 6 and each pixel electrode 7. 1
0 is the gate electrode of each TFT 4 and the corresponding gate line 2
a, 2b... 2m. 11 is TFT4
Source electrodes 3a, 3b,.
n. A drain electrode 12 of the TFT 4 is connected to the pixel electrode 7 of the corresponding pixel 5.

A gate driver IC 14 is connected to a group of gate lines and turns on the gate of the TFT 4 in accordance with vertical scanning. A source driver IC 15 is connected to a group of source lines and converts display pixel data into a liquid crystal driving voltage. The gate driver IC 14 and the source driver IC 15 are arranged according to the number of lines. For example, in the case of a liquid crystal panel having the number of pixels called XGA, the number of source lines is one.
3072 lines in 024 × RGB. The number of gate lines is 76
The number of outputs is 384 for each source driver IC 15 and 25 for each gate driver IC 14.
When six ICs are used, the source driver IC 15 uses eight ICs and the gate driver IC 14 uses three ICs per panel. The number of used ICs in the case of the XGA is an example, and the number of driver ICs to be used depends on the number of pixels of the panel. Generally, a plurality of driver ICs are used per panel.

[0004] Reference numeral 16 denotes a timing controller (hereinafter, referred to as TCON) for controlling the timing of the gate driver IC 14 and the source driver IC 15. Reference numeral 17 denotes a liquid crystal driving voltage generation circuit that supplies a liquid crystal driving voltage (Vref) to the source driver IC 15, reference numeral 18 denotes a DC / DC converter that generates various voltages, and reference numerals 16 to 18 constitute a control circuit. 19 is an input signal input to the TCON 16 from an external computer or the like, and 20 is an input voltage input to the DC / DC converter 18.

[0005] 21 is a source driver I from the TCON 16.
Sampling CLK (clock) output to C15,
22, DATA which is display data output from the TCON 16 to the source driver IC 15;
Are output to the source driver IC 15 to control the output of the source driver IC 15. 24
Is a shift CLK output from the TCON 16 to the gate driver IC 14, and 25 is a shift start signal output from the TCON 16 to the gate driver IC 14. 26 is a DC / DC converter 18 to a gate driver IC 14
Is output to the gate ON voltage (VDDG), 27 is DC
A gate OFF voltage (VEEG) output from the / DC converter 18 to the gate driver IC 14. 28 is a liquid crystal drive voltage generation circuit 1 from the DC / DC converter 18
7 and a liquid crystal driving power supply (VDDA) output to the source driver IC 15, and a liquid crystal driving voltage (VD) output from the liquid crystal driving voltage generation circuit 17 to the source driver IC 15.
ref). Reference numeral 30 denotes a logic power supply (VDDD) output from the DC / DC converter 18 to the source driver IC 15 and the gate driver IC 14. 31 is D
This is a common voltage (VCOM) output from the C / DC converter 18 and applied to the common electrode 6. FIG. 6 is a timing chart showing a conventional liquid crystal driving method.

Next, the operation will be described. The source driver IC 15 receives the data supplied from the TCON 16
22 is sampled and held by the sampling CLK 21 for one gate line (for example, for the gate line 2a). Further, a liquid crystal drive voltage 29 is supplied from the liquid crystal drive voltage generation circuit 17. The data for the gate line 2a is
After being held by the source driver IC 15, the TCON 16
The gate driver IC 14 outputs in response to the shift start signal 25 and the shift CLK 24 from the
A voltage is applied to the gate electrodes 10 of all the TFTs 4 connected to a, and the gates are turned on. Immediately after that, TC
In response to the output control signal 23 of the ON 16, all the source driver ICs 15 output, and all the source lines 3 a, 3 a
b ... DATA22 sampled earlier in 3n
Of the TFT 4 of the gate line 2a whose gate electrode 10 is turned on.
The voltage is supplied to the drain electrode 12 and the pixel electrode 7 via 1, and the voltage is accumulated in the liquid crystal layer 8 and the storage capacitor 9. In the above operation, after the source driver IC 15 converts the sampled DATA 22 to the liquid crystal drive voltage 29, the source driver IC 15 controls the TCON 16 to control the DAT of the next gate line, for example, the gate line 2b.
A22 sampling is started. These operations are as shown in FIG. Thereafter, by repeating the above operation, display data of an input signal from a computer or the like is displayed favorably.

FIG. 7 is a configuration diagram showing an output section of a conventional liquid crystal drive driver IC. In FIG. 7, reference numeral 32 denotes an internal logic, 33 denotes a level shifter circuit receiving an output of the internal logic 32, and 34 denotes a transistor having an npn structure.
R1 and R35 are pnp transistors TR2, and TR1 and TR2 constitute an output buffer. FIG.
Has been described with respect to the gate driver IC 14 for the sake of explanation, but the source driver IC 15 has the same configuration. In the driver IC having the output section as shown in FIG. 7, a base voltage for activating the npn structure TR1 is supplied from the level shifter circuit 33 to output the gate ON voltage (VDDG) 26. Gate OFF voltage (VEEG) 2
7 is supplied from the level shifter circuit 33 to the base voltage for activating the pnp-structure TR2.

[0008]

In the TFT-LCD which operates as described above, a technical development has been rapidly made in recent years to a large screen, a high definition and a multi-gradation display. As a result, the number of driver ICs used increases due to the increase in the number of pixels,
As the pixel charging time is shortened, process variations in manufacturing driver ICs cause variations in output characteristics, and as a result, display unevenness between driver ICs occurs. In addition, when one of the plurality of driver ICs has a defect, for example, only one of the driver ICs may be replaced. In this case, the influence of the lot-to-lot variation of the driver ICs may appear as display unevenness. There is. Furthermore, in recent years,
When the market for TFT-LCDs expands, it may be difficult to obtain driver ICs. In some cases, driver ICs from a plurality of companies are used for the same panel.
Display unevenness appears due to output characteristic variation between C.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its first object to obtain a liquid crystal drive device in which output variations between driver ICs are eliminated. A second object is to obtain a liquid crystal display device using such a liquid crystal driving device.

[0010]

In a liquid crystal driving device according to the present invention, a differential operational amplifier whose output value is adjusted by an externally input adjustment signal, and a liquid crystal panel controlled by an output of the differential operational amplifier, An output unit having a pair of transistors configured to output a driving voltage for driving is provided. The adjustment signal is
Each transistor is formed so as to be individually controlled.

A resistor whose resistance value is changed by an adjustment signal input from the outside, and a first voltage controlled by the change of the resistance value of the resistor and configured to output a driving voltage for driving a liquid crystal panel. And a second transistor to which the second voltage is input. Furthermore, the resistor is arranged on the input side of the first voltage of the first transistor. Further, the resistor is arranged on the input side of the second voltage of the second transistor. Further, the resistor is disposed on the output side of the output section.

[0012] Furthermore, an output unit having a plurality of transistor pairs each having a different driving capability and outputting a drive voltage for driving the liquid crystal panel is provided, and the output unit is provided with a plurality of transistor pairs according to an externally input adjustment signal. The drive voltage value is adjusted by selecting one of the above. In addition, a plurality of output stages are constituted by the plurality of transistor pairs, and an output unit for outputting a driving voltage for driving the liquid crystal panel is provided. The number of output stages is adjusted by an adjustment signal input from the outside. Thus, the driving voltage value is adjusted.

[0013] In addition, in the liquid crystal display device according to the present invention, a liquid crystal panel for displaying an image, a control circuit for generating a control signal based on image data input from the outside, and a control circuit for generating the control signal. It is provided with a liquid crystal driving device for driving a liquid crystal panel by a signal.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a configuration diagram showing an output unit of a liquid crystal drive driver IC according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 26 denotes DC /
A gate ON voltage (VDDG) output from the DC converter 18 to the gate driver IC 14, and 27 is the DC ON voltage of FIG.
A gate OFF voltage (VEEG) output from the / DC converter 18 to the gate driver IC 14. Reference numeral 32 denotes an internal logic constituted by a shift register or the like which receives the shift CLK 24 and the shift start signal 25 output from the TCON 16 and shifts the output of the gate driver IC 14, and 33 denotes a level shifter circuit which receives a logic signal output from the internal logic 32. , Converts the logic signal output from the internal logic 32 into a voltage level at which the gates of the transistors TR1 and TR2 can be turned on and off. 34
Is an npn transistor TR1 and 35 is a pn transistor
TR2 which is a p-type transistor, and TR1 and T
R2 constitutes an output buffer. Numeral 36 denotes a differential operational amplifier arranged on the output side of the level shifter circuit 33. The output of the differential operational amplifier 36 is a transistor TR1 or TR
2 is input to the base. An external adjustment terminal 37 receives an external adjustment signal.

Next, the operation will be described. Differential operational amplifier 3 to which the output of level shifter circuit 33 is input to one side
6 is connected to the external adjustment terminal 3 of the driver IC.
7, the output transistors TR1 and T1
The base voltage applied to the base electrode serving as the control electrode of R2 can be arbitrarily set. As a result, the output characteristics of the output transistors TR1 and TR2 can be arbitrarily set, and output variations can be eliminated. That is, the differential operational amplifier 36 is disposed on the output side of the level shifter circuit 33, and the output transistor TR1,
By controlling the base voltage of TR2, the output characteristics of transistors TR1 and TR2 can be arbitrarily set.

According to the first embodiment, output variations among a plurality of driver ICs mounted on a liquid crystal panel can be eliminated, and display unevenness caused by the output variations can be eliminated. Therefore, even when several driver ICs have some problem and repair and replacement are necessary, the repair can be performed without concern for the output variation of the driver ICs. Further, it becomes possible to mount driver ICs of a plurality of companies on the same liquid crystal panel.

Embodiment 2 FIG. FIG. 2 is a configuration diagram showing an output unit of a liquid crystal drive driver IC according to Embodiment 2 of the present invention. In FIG. 2, reference numerals 26, 27, and 32 to 36 are the same as those in FIG. An external adjustment terminal 37 is connected to an input of one side of a differential operational amplifier 36 connected to the transistor TR1 in the output section, and receives an adjustment signal. A reference numeral 38 is one side of the differential operational amplifier 36 connected to the transistor TR2 in the output section. And an external adjustment terminal to which an adjustment signal is input.

Next, the operation will be described. One input of the differential operational amplifier 36 connected to the transistor TR1 is used as an external adjustment terminal 37 of the driver IC, and one input of the differential operational amplifier 36 connected to the transistor TR2 is used as the external adjustment terminal 38 of the driver IC. , The base voltages of the output transistor TR1 and the transistor TR2 can be set independently and arbitrarily.

According to the second embodiment, it is possible to arbitrarily set the output characteristics of the output transistor TR1 and the output transistor TR2 separately, and it is possible to eliminate output variations.

Embodiment 3 FIG. 3 is a configuration diagram showing an output unit of a liquid crystal drive driver IC according to Embodiment 3 of the present invention. 3, reference numeral 26 denotes a gate ON voltage (VDDG) which is a first voltage output from the DC / DC converter 18 of FIG. 5 to the gate driver IC 14, and 27 denotes a gate ON voltage from the DC / DC converter 18 of FIG.
14 is a gate-off voltage (VEEG), which is a second voltage output to 14. Reference numeral 32 denotes an internal logic constituted by a shift register or the like which receives the shift CLK 24 and the shift start signal 25 output from the TCON 16 and shifts the output of the gate driver IC 14, and 33 denotes a level shifter circuit which receives a logic signal output from the internal logic 32. , Converts the logic signal output from the internal logic 32 into a voltage level at which the gates of the transistors TR1 and TR2 can be turned on and off. Reference numeral 34 denotes a first transistor TR1 having an npn structure, and reference numeral 35 denotes a second transistor TR2 having a pnp structure. TR1 and TR2 constitute an output buffer. An external adjustment terminal 37 receives an external adjustment signal. 39 is a transistor TR1, T
A selector 40 arranged on the output side of R2 and controlled by the external adjustment terminal 37 is a resistor having a plurality of resistors having different values selected by the selector 39.

Next, the operation will be described. Selector 3
Since 9 is connected to the external adjustment terminal 37, an arbitrary output resistance can be selected by inputting a signal to the external adjustment terminal 37. As a result, the output resistance can be set arbitrarily, and output variations can be eliminated. Note that the resistor 40 may be configured by a semiconductor element.

In the third embodiment, a plurality of resistors having different values are selected by the selector 39. However, a configuration is also possible in which the resistance of the output section is adjusted by connecting the resistors in parallel. good. Further, the configuration is such that the resistor 40 is arranged at the output unit.
R2 power supply gate ON voltage (VDDG) 26,
The same effect can be obtained even if the same selector 39 and resistor 40 are arranged in the gate OFF voltage (VEEG) 27.

According to the third embodiment, since the resistor is provided on the output side of the output transistor and the resistance value of the resistor is made variable and the output characteristics are set arbitrarily, output variations can be eliminated.

Embodiment 4 FIG. 4 is a configuration diagram showing an output unit of a liquid crystal drive driver IC according to Embodiment 4 of the present invention. In FIG. 4, reference numerals 26, 27 and 32-35 are the same as those in FIG. 37 is an external adjustment terminal to which an adjustment signal is input, and 39 is a selector. 4
1, 42 are transistors TR1 (34) and TR2 (3
5) An npn-structure transistor TR3 and a pnp-structure transistor TR4 constituting an output unit as in 5).
The driving capability is different from the transistors TR1 and TR2.

Next, the operation will be described. Transistors TR3 and TR4 having different driving capabilities from the transistors TR1 and TR2 of the output section are provided, and one of the outputs is selected by a selector 39 controlled by an adjustment signal input to an external adjustment terminal 37. By making the output transistors TR1 and TR2 and the transistors TR3 and TR4 switchable, variations in output characteristics are reduced.

In the fourth embodiment, the output section is provided with two pairs of transistors having different driving capabilities.
More than pairs may be provided. In the fourth embodiment,
Although a configuration is provided in which transistor pairs having different driving capabilities are provided and selected, a plurality of transistor pairs having the same driving capability are provided,
The configuration may be such that the number of stages is increased and the driving capability is adjusted by setting the external adjustment terminal to reduce output variations.

According to the fourth embodiment, the output characteristics can be adjusted and output variations can be eliminated by making the drive capability of the output transistor variable.

[0028]

Since the present invention is configured as described above, it has the following effects. An output unit having a pair of transistors configured to output a drive voltage for driving a liquid crystal panel, which is controlled by an output of the differential operational amplifier and whose output value is adjusted by an adjustment signal input from the outside. With such a configuration, it is possible to eliminate output variations between the liquid crystal driving devices by using a differential operational amplifier. Further, since the adjustment signal is formed so as to control each transistor individually, it is possible to more accurately eliminate the output variation between the liquid crystal driving devices.

Also, a resistor whose resistance value is changed by an adjustment signal input from the outside, and a first voltage controlled by changing the resistance value of the resistor and configured to output a driving voltage for driving the liquid crystal panel. Since the output unit includes the first transistor to which the first voltage is input and the second transistor to which the second voltage is input, it is possible to eliminate the output variation between the liquid crystal driving devices by the resistor. It is. Furthermore, since the resistor is arranged on the input side of the first voltage of the first transistor, the resistor arranged on the input side of the first voltage of the first transistor allows the liquid crystal driving device to be connected. It is possible to eliminate output variations.

Further, since the resistor is disposed on the second voltage input side of the second transistor, the liquid crystal driving is performed by the resistor disposed on the second voltage input side of the second transistor. It is possible to eliminate output variations between devices. Further, since the resistor is arranged on the output side of the output unit, it is possible to eliminate output variations between the liquid crystal driving devices by the resistor arranged on the output side of the output unit.

Furthermore, an output section for outputting a drive voltage for driving the liquid crystal panel is provided, the output section comprising a plurality of transistor pairs each having a different driving capability, and the output section being provided with a plurality of transistor pairs in response to an externally input adjustment signal. Is selected so that the drive voltage value is adjusted. Therefore, by selecting a transistor pair that outputs a drive voltage, it is possible to eliminate output variations between the liquid crystal drive devices. . In addition, a plurality of output stages are constituted by the plurality of transistor pairs, and an output unit for outputting a driving voltage for driving the liquid crystal panel is provided. The number of output stages is adjusted by an adjustment signal input from the outside. Accordingly, the configuration is such that the drive voltage value is adjusted, so that by adjusting the number of output stages, it is possible to eliminate output variations among the liquid crystal drive devices.

In addition, in the liquid crystal display device according to the present invention, a liquid crystal panel for displaying an image, a control circuit for generating a control signal based on image data input from the outside, and a control circuit for generating the control signal. Since the liquid crystal driving device that drives the liquid crystal panel by a signal is provided, a liquid crystal display device free from display unevenness due to output variations of the liquid crystal driving device can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an output unit of a liquid crystal drive driver IC according to Embodiment 1 of the present invention.

FIG. 2 is a configuration diagram showing an output unit of a liquid crystal drive driver IC according to Embodiment 2 of the present invention.

FIG. 3 is a configuration diagram showing an output unit of a liquid crystal drive driver IC according to Embodiment 3 of the present invention.

FIG. 4 is a configuration diagram showing an output unit of a liquid crystal drive driver IC according to Embodiment 4 of the present invention.

FIG. 5 is a configuration diagram showing a conventional liquid crystal driving device.

FIG. 6 is a timing chart showing a conventional liquid crystal driving method.

FIG. 7 is a configuration diagram showing an output unit of a conventional liquid crystal drive driver IC.

[Explanation of symbols]

1 liquid crystal panel, 14 gate driver IC, 15 source driver IC, 26 gate ON voltage (VDD
G), 27 gate OFF voltage (VEEG), 32 internal logic, 33 level shifter circuit, 34 transistor TR1, 35 transistor TR2, 36 differential operational amplifier, 37, 38 external adjustment terminal, 39 selector, 40 resistor, 41 transistor TR3, 42
Transistor TR4.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/20 624 G09G 3/20 624B F term (Reference) 2H093 NC03 NC05 NC34 NC48 NC62 ND60 NE07 5C006 AF52 BB16 BC03 BC12 BF24 BF25 BF32 BF42 BF46 EB05 FA20 FA22 5C080 AA10 BB05 DD05 DD28 FF11 JJ02 JJ03 JJ04

Claims (9)

[Claims] 1. A differential operational amplifier whose output value is adjusted by an externally input adjustment signal, and a pair of transistors controlled by an output of the differential operational amplifier and configured to output a driving voltage for driving a liquid crystal panel. A liquid crystal driving device comprising an output unit having: 2. The liquid crystal driving device according to claim 1, wherein the adjustment signal is formed so as to control each transistor individually. 3. A resistor whose resistance value is changed by an externally-adjusted adjustment signal, wherein the first resistance value is controlled by changing the resistance value of the resistor and outputs a driving voltage for driving a liquid crystal panel. And a second transistor to which a second voltage is input. 4. The liquid crystal driving device according to claim 3, wherein the resistor is arranged on an input side of the first transistor. 5. The liquid crystal driving device according to claim 3, wherein the resistor is arranged on an input side of the second transistor. 6. The liquid crystal driving device according to claim 3, wherein the resistor is arranged on an output side of the output section. 7. An output unit having a plurality of transistor pairs each having a different driving capability and outputting a drive voltage for driving a liquid crystal panel, wherein the output unit is configured to output the drive voltage by an externally input adjustment signal. A liquid crystal driving device, wherein a driving voltage value is adjusted by selecting one of the pair. 8. A plurality of output stages formed by a plurality of transistor pairs, and an output unit for outputting a drive voltage for driving a liquid crystal panel, wherein the output unit is configured to output the drive voltage by an externally input adjustment signal. A liquid crystal driving device, wherein the driving voltage value is adjusted by adjusting the number of stages. 9. A liquid crystal panel for displaying an image, a control circuit for generating a control signal based on image data input from the outside, and the liquid crystal panel is driven by a control signal generated by the control circuit. Item 10. A liquid crystal display device comprising the liquid crystal driving device according to any one of items 8.