JPH08211367A - Liquid crystal display - Google Patents

Abstract

(57) Abstract: To provide a gradation voltage generation circuit of a liquid crystal display device capable of low power consumption and high image quality display. A liquid crystal display device for generating a multi-gradation gray scale voltage applied to a liquid crystal layer by dividing a gray scale reference voltage of a plurality of gray scale reference voltages by a series resistance voltage dividing circuit, The resistance value between the terminals to which each gradation reference voltage is applied in the resistance voltage dividing circuit is set to a resistance value that is substantially proportional to the potential difference between each gradation reference 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 display device used for a personal computer, a workstation, etc., and more particularly to a grayscale voltage generation circuit for a liquid crystal display device capable of displaying a plurality of grayscales.

[0002]

2. Description of the Related Art An example of a TFT liquid crystal display device capable of multi-color display, for example, 64-gradation multi-color display is described in Document I below.

I "Low-Power 6-bit C"
"Olven Driver AMLCDs" (issued in June 1994, SID 94 DIJEST P.
351-354).

FIG. 8 shows the TF described in the above-mentioned document I.
It is a block diagram showing a schematic structure of a T liquid crystal display device.

In FIG. 8, a liquid crystal display panel (TFT-
The LCD) is composed of 800 × 3 × 600 pixels Pix.

An equivalent circuit of the pixel Pix of the TFT liquid crystal display panel is shown in FIG.

ITO is a pixel electrode, COM is a counter electrode,
A liquid crystal display element (not shown) is formed by ITO, COM, and a liquid crystal layer.

The liquid crystal display element can be represented by an electrostatic capacitance CLC when represented by an equivalent circuit.

The liquid crystal display element is made of ITO as shown in FIG.
Since the light transmissivity changes according to the voltage applied between COM and COM, a grayscale voltage is applied to the pixel electrode ITO, in which a voltage is determined for each of a plurality of display grayscales with reference to the voltage applied to COM. This allows multi-gradation display.

Dn is a drain line or a video signal line, and a gradation voltage is applied from the drain driver 11 to a plurality of drain lines Dn.

TFT is a thin film transistor, and ITO
It has a source S and a drain D electrically connected to Dn and a gate G, and the voltage applied to the gate G controls electrical conduction and non-conduction between Dn and ITO.

Gn is a gate line or a scanning line, and Gn
Since n is connected to the gate G of the TFT of the corresponding pixel Pix, the pixel electrode I that applies the gradation voltage by Gn
You can select TO.

Cadd is a holding capacitance, Cn is a capacitance line, and C
add can hold the grayscale voltage applied to the ITO until the next grayscale voltage is applied to the ITO.

FIG. 10 is a diagram showing the timing of the voltage waveform applied to the pixel shown in FIG.

In the figure, (1) shows the waveform of the gate line Gn,
(2) is a waveform of the counter electrode COM and the capacitance line Cn, (3)
Shows the waveform of the drain line Dn. When applying the gradation voltage to the pixel electrode ITO, the gate voltage waveform (1) is Gate.
It is turned on and the TFT source and drain are electrically connected. The drain voltage waveform (3) and the counter electrode voltage waveform (2) have inverted phases, and the difference voltage between the drain voltage waveform (3) and the counter electrode voltage waveform (2) is applied to the liquid crystal display element CLC. To be done. The voltage applied to the liquid crystal display element CLC has a gate voltage waveform (1), a counter electrode voltage waveform (2), and a drain voltage such that the positive polarity application timing and the negative polarity application timing alternate. Since the waveform (3) is set, no direct current component is applied to the liquid crystal display element CLC, and there is no problem of shortening the life of the TFT liquid crystal display panel, image sticking, and afterimage.

The characteristic of the liquid crystal display device using the TFT is that T
Since a grayscale voltage is applied to the pixel electrode ITO through a switching element called FT, there is no crosstalk between the pixels Pix, and a special driving method for preventing crosstalk is used as in a simple matrix liquid crystal display device. There is no need, and it is possible to perform multi-gradation display.

Further, as shown in FIG. 8, the drain driver 11 is provided on one side of the liquid crystal display panel (TFT-LCD).
Is connected to the drain line of the thin film transistor (TFT) to supply a voltage for driving the liquid crystal to the thin film transistor (TFT).

A liquid crystal display panel (TFT-LCD)
A gate driver 12 is disposed on the side surface of the thin film transistor (TFT) and connected to the gate line of the thin film transistor (TFT).
te On voltage is supplied.

The display control device 10 receives the display data and the display control signal from the main body computer from the interface connector, and based on this, the drain driver 1
1, to drive the gate driver 12.

The display data from the main computer is composed of 18 bits, 6 bits for each color.

As shown in FIG. 11, the drain driver 11 has one gradation voltage generation circuit, and the gradation voltage generation circuit is a nine-value gradation reference voltage input from the internal power supply circuit 13. A gradation voltage for 64 gradations is generated from (V0-V8).

Further, the drain driver 11 uses a shift register to latch the display data latching clock signal CLK1.
In synchronism with the above, 6-bit display data for each color is fetched into the input register by the number of outputs. Next, in response to the output timing control clock signal CLK2, the display data in the input register is taken into the storage register, and the output circuit outputs the gradation voltage for 64 gradations generated by the gradation voltage generating circuit. The grayscale voltage corresponding to the display data is selected from the inside and output to each drain line Dn.

The polarity terminal of the drain driver 11 is provided for controlling the polarity of the voltage output to the drain line Dn, and the carry input and carry output terminals are for coordinating between the plurality of drain drivers 11 in the liquid crystal display device. It is provided in.

FIG. 12 is a diagram showing a grayscale voltage generation circuit of the drain driver 11 shown in FIG.

As shown in FIG.
The gray scale voltage generation circuit of the drain driver 11 shown in FIG.
0-V8) between each gradation reference voltage, the series resistance voltage dividing circuit 1
Is used to generate a gradation voltage for 64 gradations of V00 to V63.

[0026]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As shown in FIG.
Generally, the relationship between the voltage applied to the liquid crystal layer and the transmittance is not linear.
The change in transmittance with respect to the voltage applied to the liquid crystal layer is small,
There is a large change in transmittance at an intermediate point.

Therefore, in a liquid crystal display device capable of multi-color display of 64 gradations, in order to linearly display 64 gradations, the gradation reference voltage value given to the gradation voltage generating circuit of the drain driver 11 is , Not evenly spaced, near the halftone (V
2 to V6), the difference is small, and other than that (V0 to V2, V6
~ V8) must be increased.

However, in the above-mentioned document, it is not mentioned in detail how to set the resistance value of the series resistance voltage dividing circuit 1 of the gradation voltage generating circuit of the drain driver 11 shown in FIG.

Therefore, when the grayscale reference voltages V0 to V8 shown in FIG. 14 which are not evenly spaced are applied to the series resistance voltage dividing circuit 1 of the grayscale voltage generating circuit shown in FIG. There is a problem in that a direct current (DC) current flows through the line that supplies the power and the power consumption increases.

For example, FIG. 12B is a simplified version of FIG. 12A, but the resistance values between the gradation reference voltage applying terminals of the series resistance voltage dividing circuit 1 in the gradation voltage generating circuit are different from each other. When a constant value of 100Ω is set, the gradation reference voltage V0
-V1, between V1-V2, between V6-V7, and between V7-V8 the gradation reference voltage differences between the gradation reference voltages V2-V3, V3.
It becomes twice the gradation reference voltage difference between V4, V4 and V5, and V5 and V6.

Therefore, between the terminals of the series resistance voltage dividing circuit 1 to which the gradation reference voltages V6 and V7 are applied and between the terminals to which the gradation reference voltages V1 and V2 are applied. The flowing current is 10mA (1.0V / 100
Ω = 10 mA) while the series resistance voltage dividing circuit 1
Gradation reference voltages V5, V6 and gradation reference voltage V
The current flowing between the terminals to which the gradation reference voltages of 2 and V3 are applied is 5 mA (0.5 V / 100Ω = 5 mA).

Therefore, current flows from the terminal to which the gradation reference voltage V6 is applied and the terminal to which the gradation reference voltage V2 is applied of the series resistance voltage dividing circuit 1 in which the current value is discontinuous.
Since the current flowing out and flowing to the gradation voltage generation circuit increases,
There is a problem that the power consumption of the drain driver 11 increases.

Further, when currents flow in and out of the lines supplying the gradation reference voltages V1 to V7, there is a problem that the power consumption increases due to the internal resistance of the power supply circuit 13.

FIG. 13 shows the gradation reference voltage V0 of the power supply circuit 13.
It is a figure which shows the production | generation part of -V8.

FIG. 9A shows an example in which the generation unit of the gradation reference voltages V0 to V8 is generated by a resistance voltage dividing circuit. The gradation reference voltages V0 to V8 are set by the ratio of the values of the resistors RR0 to RR9, and the output of the voltage dividing circuit of the resistors RR0 to RR9 is amplified to a sufficient electric power by the buffer circuits OP0 to OP9 and the drain driver 11 outputs the same. It is output to the series resistance voltage dividing circuit 1.

FIG. 7B is a diagram showing an equivalent circuit of FIG. The power supply circuit 13 can be represented by DC voltage sources v0 to v8 and internal resistors r0 to r8. DC voltage source v0
v8 is determined by the output of the voltage dividing circuit of the resistors RR0 to RR9, and the internal resistors r0 to r8 are the buffer circuits OP0 to OP9.
It is considered to be determined by the output impedance of.

Assuming that the internal resistances r0 to r8 are set to 20Ω, 0.5 mW of power will be additionally consumed by the power supply circuit 13 when a current of 5 mA flows through the supply line of the gradation reference voltage V2. Further, since the internal resistance r2 causes a voltage drop of 0.2V, the grayscale reference voltage V2 output to the drain driver 11 also drops by 0.2V, and the target grayscale voltage cannot be output to the liquid crystal display panel, resulting in a correct display. There is also a problem that gradation cannot be obtained.

Further, in the drain driver 11, for the purpose of simplifying the configuration and reducing the chip size of the integrated circuit, as shown in FIG. 11, the output of the gradation voltage generating circuit is applied to all drain lines driven by the drain driver 11. Since they are shared, when the number of drain signal lines that select the same gray scale voltage in one drain driver 11 increases, the current flowing through the resistors R1 to R8 of the gray scale reference voltage generation circuit 1 increases, and each gray scale voltage is changed. Pixels corresponding to different drain lines Dn and Dn + 1 are displayed on the display screen of the halftone display (V2 to V6) which varies depending on the drain driver 11 and in which the change of the transmittance of the liquid crystal layer with respect to the applied voltage is large. There is a problem in that there is a difference in brightness at the boundary of Pix and the display quality is degraded.

That is, in the example shown in FIG. 12, the gradation reference voltage differences V3 (2), V4 (3), V5 (4), V6.
(5) is V1 (0), V2 (1), V7 (6), V8
Although lower than (7), the values of R3 to R6 are R1, R2, R
Since it is the same as the values of 7 and R8, it becomes difficult to flow a sufficient current through the output line of the gradation voltage (V15 to V47) output from the resistance voltage dividing circuit between V2 and V6.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to enable low power consumption and high image quality display in a gradation voltage generating circuit of a liquid crystal display device. Another object of the present invention is to provide a liquid crystal display device.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[0042]

Of the inventions disclosed in the present application, a representative one will be briefly described below.
It is as follows.

(1) A liquid crystal display device for generating a multi-gradation gray scale voltage applied to a liquid crystal layer by dividing a plurality of gray scale reference voltages between gray scale reference voltages by a series resistance voltage dividing circuit,
It is characterized in that a resistance value between terminals of the series resistance voltage dividing circuit to which each gradation reference voltage is applied is set to a resistance value substantially proportional to a potential difference between the gradation reference voltages.

(2) In the means of (1) above, the resistance value between the terminals of the series resistance voltage dividing circuit to which each gradation reference voltage is applied is changed to a resistance value which is substantially proportional to the potential difference between the gradation reference voltages. It is characterized in that it is provided with a switching means for

(3) In the means of (1) above, a plurality of series resistance circuits are provided between the terminals of the series resistance voltage dividing circuit to which each gradation reference voltage is applied, and among the plurality of series resistance circuits, The present invention is characterized by including a selecting means for selecting a series resistance circuit having a resistance value substantially proportional to the potential difference between the gradation reference voltages.

According to each of the above means, in the gradation voltage generating circuit of the liquid crystal display device for generating the gradation voltages of multiple gradations to be applied to the liquid crystal layer, between the gradation reference voltage applying terminals of the series resistance voltage dividing circuit. The resistance value is proportional to the voltage difference between the gradation reference voltages, and the maximum gradation reference voltage and the minimum gradation reference voltage voltage among the gradation reference voltage application terminals of the series resistance voltage divider circuit are The inflow and outflow of current from other than the applied gradation reference voltage application terminal is almost zero, and the power consumption of the drain driver 11 and the power supply circuit 13 can be reduced, and the power consumption of the entire liquid crystal display device is reduced. You can

Further, in the halftone display portion where the change in the transmittance of the liquid crystal layer with respect to the applied voltage is large, in order to reduce the resistance value between the gradation reference voltage application terminals, the drain signal lines that output the same gradation voltage are output. Even if the number of lines is large, the voltage variation of the gray scale voltage of the gray scale voltage generation circuit is small, and it is possible to suppress the occurrence of a brightness difference at the boundary between the pixels Pix with different drain drivers 11, and the liquid crystal display. The display characteristics of the device are improved.

[0048]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a TFT liquid crystal display device to which the present invention is applied will be described below in detail with reference to the drawings.

In all the drawings for explaining the embodiments, parts having the same function are designated by the same reference numerals, and the repeated description thereof will be omitted.

The structure of the TFT liquid crystal display device to which the present invention is applied is the same as that of the TFT liquid crystal display device shown in FIG.

[Embodiment 1] FIG. 1 is a diagram showing a gradation voltage generating circuit of a drain driver 11 of a liquid crystal display device which is an embodiment (Embodiment 1) of the present invention.

The gray scale voltage generation circuit of the first embodiment is similar to the gray scale voltage generation circuit shown in FIG.
A series resistance voltage dividing circuit 1 divides each of the 9-valued gradation reference voltages (V0-V8) input from 3 into 8 equal parts to generate 64 gradation voltages. is there.

Here, a nine-value gradation reference voltage (V0-V
8) gradation reference voltage Vn and gradation reference voltage Vn-1 (n =
The voltage difference of 1 to 8) is expressed as Vn (n-1), and the gradation reference voltage Vn and the gradation reference voltage Vn-1 of the series resistance voltage dividing circuit 1 are represented.
The combined resistance value between the gradation reference application terminals (n = 1 to 8) is R
Notated as n.

In the gradation voltage generating circuit of the first embodiment, R
8: R7: R6: R5: R4: R3: R2: R1 = V8
(7): V7 (6): V6 (5): V5 (4): V4
(3): V3 (2): V2 (1): V1 (0).

Therefore, the current flowing through the series resistance voltage dividing circuit 1 has a constant current value (Vn (n-1) / Rn = constant current value), and in the gradation voltage generating circuit of the first embodiment, the maximum value. The gradation reference voltage (V0 and V8) of the series resistance voltage dividing circuit 1 to which the gradation reference voltage and the minimum gradation reference voltage are applied is almost zero, and the current is almost 0. It is possible to reduce the power consumption of the driver, and thus it is possible to reduce the power consumption of the liquid crystal display device.

FIG. 2 is a diagram showing an example in which the present invention is implemented by applying a specific resistance value to the series resistance voltage dividing circuit 1 shown in FIG.

The resistance values of the resistors shown in FIG. 2 are obtained by combining the gradation reference voltages V0 to V8 with the voltage transmittance curve shown in FIG. 3 when the liquid crystal having a transmittance of 0 at 3V is used. Here is an example. V0 ′ to V8 ′ shown in FIG. 3 are reference voltages V of FIG.
It corresponds to 0 to V8.

In the specific embodiment shown in FIG. 2, the currents flowing through the resistors R1 to R8 between the gradation reference voltage terminals are all 1.
3 mA, no current flows through the terminals to which the gradation reference voltage other than V0 and V8 is applied, and the power consumed by the series resistance voltage dividing circuit 1 is only due to the current of 1.3 mA and is the lowest. .

In the embodiment shown in FIG. 2, V6
In order to increase the contrast by setting the gradation voltages of V2 and V63 to be high and making the black display more black, the breakdown of the resistor R8 on the side closer to the terminal of the highest voltage V8 is that the values of R88 and R87 are other resistors R81. The resistance value is set to be higher than the resistance value of R86.

Similarly, in the embodiment shown in FIG. 2, V0
In order to set the gradation voltages of 0 and V01 low to make the white display whiter and increase the contrast, the breakdown of the resistance R1 on the side closer to the terminal of the lowest voltage V0 is that the values of R11 and R12 are other resistances R13. Is set higher than the resistance value of R17.

Since V0 'to V8' shown in FIG. 3 are indicated by the voltage applied to the actual liquid crystal layer (not shown), the variation (0.8 V) is different from the reference voltage V0 to V8 in FIG. ) Just shifted.

The reason why the voltage actually applied to the liquid crystal layer shifts as compared with the reference voltages V0 to V8 in FIG. 2 is that the gate voltage waveform jumps into the pixel electrode ITO. As shown in FIG. 9, the actual pixel has a parasitic capacitance Cgs between the gate G and the pixel electrode ITO. When the gate voltage waveform changes from Gate On to Gate Off by the driving method shown in FIG. Since the pulse is applied to the pixel electrode ITO via Cgs, the voltage applied to the liquid crystal layer shifts.

Therefore, the gradation reference voltages V0 to V0 of the power supply circuit 13
When V8 is set, it is necessary to take into consideration the shift of the voltage applied to the liquid crystal layer in advance.

The embodiments shown in FIGS. 2 and 3 show the case where the voltage applied to the liquid crystal has a negative polarity, and shows the case where the shift amount of the voltage is applied to the gradation reference voltage. However, when the voltage applied to the liquid crystal has a positive polarity, the value obtained by subtracting the shift amount of the voltage from the gradation reference voltage becomes the actual voltage applied to the liquid crystal layer, and therefore the gradation reference voltage generation circuit shown in FIG. Two types of positive polarity and negative polarity are required.

Similarly, the gradation voltage generating circuit in the drain driver 11 also has two kinds of series resistance voltage dividing circuits 1 of positive polarity and negative polarity, which are switched according to the polarity signal.

In the gray scale reference voltage generating circuit of the first embodiment, the resistance value between the gray scale reference voltage applying terminals of the series resistance voltage dividing circuit 1 is a resistor which is completely proportional to the potential difference between the gray scale reference voltages. Although it is a value, even if it is not perfectly proportional,
Has a similar effect.

That is, even if the value of Vn (n-1) / Rn does not completely match, if the variation of the value is within the specific range, extra power consumption is required as compared with that outside the specific range. Occurrence can be suppressed.

The series resistance voltage dividing circuit 1 is formed inside a semiconductor integrated circuit. Generally, there is a variation in resistance created in a semiconductor integrated circuit, and when a semiconductor diffused resistor is used as the resistance, the resistance value varies by ± 20%. Although it is possible to select the finished semiconductor integrated circuits and set the resistance values to have a variation of ± 10%, the cost of the drain driver 11 increases because the yield of the semiconductor integrated circuits decreases. Therefore, in the liquid crystal display device using the series resistance voltage dividing circuit 1 shown in FIG. 1, it is ideal that the values of Vn (n-1) / Rn are perfectly matched, but it is not practical.

In the embodiment shown in FIG. 2, considering that the resistance R3, which affects the gradation display most, varies by ± 20%, the value of Vn (n-1) / Rn, that is, the current flowing through R3 is ± 0. It fluctuates by 0.3 mA (± 23%). Since R4 has the same resistance value as R3, the current flowing through R4 also fluctuates by ± 0.3 mA. Considering the case where the difference between the current values flowing through R3 and R4 is the largest, a current of ± 0.6 mA flows through the terminal V3, and the power consumption of the series resistance voltage dividing circuit 1 and the power supply circuit 13 increases.

However, the resistance value of the series resistance voltage dividing circuit 1 is ± 2
Even if there is a variation of 0%, if the present embodiment is applied, V
Since the current flowing from 1 to V7 can be suppressed within the range of ± 0.6 mA, the power consumption of the drain driver 11 and the power supply circuit 13 can be suppressed to be low, and the cost of the drain driver 11 is not high and is practical. .

Further, in the embodiment shown in FIG. 2, if the variation of the series resistance voltage dividing circuit 1 is set to ± 10%, the current flowing through R3 and R4 can be suppressed to a fluctuation of ± 0.2 mA (± 15%). Therefore, considering the case where the difference between the current values flowing through R3 and R4 is the maximum, a current of ± 0.4 mA flows through the terminal V3 and the increase in power consumption of the series resistance voltage dividing circuit 1 and the power supply circuit 13 should be further reduced. Is possible and is most preferable.

In this embodiment, V1 to V7 of the power supply circuit
Since the current flowing through the output terminal of can be kept low,
When the power supply circuit 13 having the configuration shown in FIG. 13 is used, V
The buffer circuits OP1 to OP7 that output 1 to V7 are V
The output impedance may be higher than that of the buffer circuits OP0 to OP8 that output 0 and V8, an inexpensive one can be used, and the cost of the power supply circuit 13 can be reduced.

Further, in the present embodiment, the outputs of V1 to V7 can be directly obtained from the resistance voltage dividing circuit except the buffer circuits OP1 to OP7, and the cost of the power supply circuit 13 can be further reduced.

Further, according to the present embodiment, as shown in FIG. 1, the gradation reference voltage differences V4 (3) and V5 for displaying the halftone are displayed.
In (4), since the voltage difference is small, the resistance values R5 and R4 between the gradation reference voltage applying terminals of the series resistance voltage dividing circuit 1 are also small.

That is, in the concrete example shown in FIG. 2, the gradation reference voltage differences V3 (2), V4 (3), V5.
(4), V6 (5) are V1 (0), V2 (1), V7
(6), lower than V8 (7), but the values of R3 to R6 are R
Since it is sufficiently lower than the values of 1, R2, R7 and R8, V2
The gradation voltage (V15
It is possible to pass a sufficient current through the output line of V47.

As a result, even if the number of drain lines Dn that output the same gray scale voltage increases, the voltage variation of the gray scale voltage output by the gray scale voltage generation circuit becomes small, and the drain drivers 11 are different and inter-pixel. It is possible to suppress the occurrence of a difference in luminance.

Therefore, by using the gradation voltage generating circuit of the first embodiment, it becomes possible to construct a liquid crystal display device with high image quality and low power consumption.

[Embodiment 2] FIGS. 4 and 5 are diagrams showing a gray scale voltage generation circuit of a drain driver of a liquid crystal display device according to another embodiment (Embodiment 2) of the present invention.

Generally, the voltage transmittance characteristics shown in FIG. 14 differ depending on the material of the liquid crystal layer.

Therefore, the gradation reference voltage of the power supply circuit 13 is set in accordance with the voltage transmittance characteristic of the liquid crystal layer, and the gradation voltage generation circuit in the drain driver 11 must also be set in accordance with the voltage transmittance characteristic. , Drain driver 1
However, there is a problem that the cost of the liquid crystal display device is increased because the drain driver 11 must be used for each liquid crystal display panel.

The second embodiment is a more specific embodiment of the first embodiment, and easily changes the set value of the grayscale voltage of the grayscale voltage generation circuit of the drain driver 11 according to the liquid crystal display panel. This is a possible embodiment.

In the gray scale reference voltage generating circuit of the second embodiment, as shown in FIG. 4 in the semiconductor manufacturing stage, the gray scale reference voltage applying terminals of the respective gray scale reference voltages (V1 to V7) are connected to the series resistance voltage dividing circuit. 1 to several points (A, B, C) via a fuse 32.

In this case, the points A, B and C are selected so as to have the partial pressure values which may be actually used.

The gradation reference voltage generating circuit of the second embodiment is
When a predetermined gradation reference voltage is applied as each gradation reference voltage (V0 to V8) during actual use, a current is supplied to the fuse 32 connected to the resistance value proportional to the voltage difference between the gradation reference voltages. It does not flow and the fuse 32 is not blown.

However, a current flows through the other fuses 32, and the fuses 32 are blown.
The resistance value between the gradation reference voltage applying terminals of the series resistance voltage dividing circuit 1 becomes a resistance value proportional to the voltage difference between the gradation reference voltages.

Further, as shown in FIG. 5, on the side to which the output switch 3 of the series resistance voltage dividing circuit 1 is connected, similarly, each gradation voltage output terminal 4 is connected via the fuse 2 to the series resistance voltage dividing terminal 4. Connect to several points (D, E, F) of circuit 1.

After selecting a predetermined gradation, for example, the gradation V62, based on the display data, the gradation reference voltages V8 and V7 are selected.
A predetermined voltage is applied to the gradation reference voltage applying terminal and the gradation voltage output terminal 4.

At this time, the gradation voltage output terminal 4 is set to the resistance value at the point where the fuse 2 which is not desired to be blown is connected, for example, the voltage (0.8 × V8 (7)) corresponding to the point E. Apply.

As described above, in the grayscale voltage generation circuit of the second embodiment, when the fuse 2 on the side to which the output switch 3 is connected is blown, only the voltage difference between the grayscale reference voltages corresponds to the value in actual use. The absolute value shall be higher than that in actual use.

As a result, in the gradation voltage generating circuit of the second embodiment, it is possible to flow a current that does not blow the fuse 2 during actual use.

As described above, in the second embodiment,
It is possible to give the drain driver 11 versatility,
Similar to the first embodiment, it is possible to easily realize a liquid crystal display device having high image quality and low power consumption, corresponding to various characteristics of the liquid crystal display panel.

[Third Embodiment] FIG. 6 is a diagram showing a gray scale voltage generation circuit of a drain driver of a liquid crystal display device according to another embodiment (third embodiment) of the present invention.

The third embodiment is also a more specific embodiment of the first embodiment, and easily changes the set value of the grayscale voltage of the grayscale voltage generation circuit of the drain driver 11 according to the liquid crystal display panel. This is a possible embodiment.

The gradation voltage generating circuit according to the third embodiment includes several kinds of series resistance circuits between the gradation reference voltage application terminals of the gradation reference voltages (V0-V8) of the series resistance voltage dividing circuit 1. (101, 102, 103) are provided, and the series resistance circuit (101, 102, 103) having a resistance ratio close to the ratio of the voltage difference of each gradation reference voltage is selected by the switching signal in actual use.

Similarly, the changeover switch 5 is changed over by the changeover signal to change the series resistance circuits (101, 10).
2, 103) is output to each gradation voltage output terminal 4.

At this time, the switching signal is the display control device 10
Each drain driver 11 is supplied from the internal register, EPROM, or a dedicated input terminal of an interface connector connected to a computer.

With this, it is possible to easily realize a series resistance voltage dividing circuit having a resistance ratio close to the ratio of the voltage difference between the gradation reference voltages in actual use, and the gradation voltage generating circuit of the third embodiment also
It is possible to give the drain driver 11 versatility,
Similar to the first embodiment, it is possible to easily realize a liquid crystal display device having high image quality and low power consumption, corresponding to various characteristics of the liquid crystal display panel.

[Fourth Embodiment] FIG. 7 is a diagram showing a grayscale voltage generation circuit of a drain driver of a liquid crystal display device according to another embodiment (fourth embodiment) of the present invention.

The fourth embodiment is also a more specific embodiment of the first embodiment, and easily changes the set value of the grayscale voltage of the grayscale voltage generation circuit of the drain driver 11 according to the liquid crystal display panel. This is a possible embodiment.

In the gray scale voltage generation circuit of the fourth embodiment, as in the third embodiment, any number of gray scale reference voltage application terminals of the gray scale reference voltages (V0-V8) of the series resistance voltage dividing circuit 1 can be used. A plurality of series resistance circuits (101, 102, 103)
And a series resistance circuit (101, 102, 103) having a resistance ratio close to the ratio of the voltage difference of each gradation reference voltage,
It is selected by changing only the metal wiring layer during the semiconductor manufacturing process.

Similarly, the switching means 6 is switched by changing only the metal wiring layer or the like during the semiconductor manufacturing process, and the grayscale voltage from each series resistance circuit (101, 102, 103) is output to each grayscale voltage output terminal 4. It is designed to be output to.

With this, it is possible to easily realize the series resistance voltage dividing circuit having a resistance ratio close to the ratio of the voltage difference between the gradation reference voltages in actual use, and the gradation voltage generating circuit of the fourth embodiment also
It is possible to give the drain driver 11 versatility,
Similar to the first embodiment, it is possible to easily realize a liquid crystal display device having high image quality and low power consumption, corresponding to various characteristics of the liquid crystal display panel.

In each of the above embodiments, the case where the present invention is applied to a liquid crystal display device has been described, but the present invention is not limited to this, and the present invention can be applied to all liquid crystal display devices such as liquid crystal display modules. Needless to say.

The present invention has been specifically described above based on the embodiments. However, it goes without saying that the present invention is not limited to the above-mentioned embodiments and can be variously modified without departing from the scope of the invention.

[0105]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) According to the present invention, in the gradation voltage generation circuit of the liquid crystal display device for generating the gradation voltages of multiple gradations applied to the liquid crystal layer, each gradation reference voltage of the series resistance voltage dividing circuit 1 is applied. The resistance value between the terminals is proportional to the voltage difference between the gradation reference voltages, and the maximum gradation reference voltage and the minimum gradation reference voltage among the gradation reference voltage application terminals of the series resistance voltage divider circuit. The inflow and outflow of the current from other than the gradation reference voltage applying terminal to which the voltage is applied becomes almost zero, and the power consumption of the drain driver can be reduced, thereby reducing the power consumption of the liquid crystal display device. It becomes possible to do.

(2) According to the present invention, in the halftone display portion where the change in the transmittance of the liquid crystal layer with respect to the applied voltage is large,
Since the resistance value between the gradation reference voltage applying terminals is small, even if the number of drain signal lines that output the same gradation voltage increases, the voltage fluctuation of the gradation voltage of the gradation reference voltage generation circuit becomes small, which is different. It is possible to suppress the occurrence of a brightness difference on the display screen between the drain drivers 11.

[Brief description of drawings]

FIG. 1 is a diagram showing a grayscale voltage generation circuit of a drain driver of a liquid crystal display device which is an embodiment (first embodiment) of the present invention.

FIG. 2 is a diagram in which specific resistance values and grayscale reference voltage values are applied to the grayscale voltage generation circuit of the drain driver of the liquid crystal display device according to one embodiment (first embodiment) of the present invention.

FIG. 3 is a diagram showing the relationship between the gray scale reference voltage shown in FIG. 2 and the transmittance of the liquid crystal display element.

FIG. 4 is a diagram showing a grayscale voltage generation circuit of a drain driver of a liquid crystal display device according to another embodiment (second embodiment) of the present invention.

FIG. 5 is a diagram showing a grayscale voltage generation circuit of a drain driver of a liquid crystal display device according to another embodiment (Embodiment 2) of the present invention.

FIG. 6 is a diagram showing a grayscale voltage generation circuit of a drain driver of a liquid crystal display device according to another embodiment (Embodiment 3) of the present invention.

FIG. 7 is a diagram showing a grayscale voltage generation circuit of a drain driver of a liquid crystal display device according to another embodiment (Embodiment 4) of the present invention.

FIG. 8 is a block diagram showing a schematic configuration of a TFT liquid crystal display device.

FIG. 9 is a diagram showing an equivalent circuit of a pixel of a TFT liquid crystal display device.

FIG. 10 is a diagram showing a timing relationship of voltages applied to pixels of a TFT liquid crystal display device.

FIG. 11 is a block diagram showing a schematic configuration of a drain driver.

FIG. 12 is a diagram showing a grayscale voltage generation circuit of a conventional drain driver 11.

FIG. 13 is a circuit diagram of a gradation reference voltage generation unit of a power supply circuit.

14 is a diagram showing the relationship between the gray scale reference voltage and the transmittance of the liquid crystal display element shown in FIG.

[Explanation of symbols]

TFT-LCD ... TFT liquid crystal display panel, 1 ... Series resistance voltage dividing circuit, 2, 32 ... Fuse, 3 ... Switch, 4 ... Grayscale voltage output terminal, 5 ... Changeover switch, 6, 7 ... Changeover means, 10 ... Display Controller, 11 ... Drain driver,
12 ... Gate driver, 13 ... Power supply circuit, 101, 10
2, 103 ... Series resistance circuit.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Iwa ▲ Saki ▼ Shinichi 3681 Hayano, Mobara-shi, Chiba Hitachi Device Engineering Co., Ltd.

Claims (7)

[Claims] 1. A liquid crystal display panel in which a plurality of pixels each having a thin film transistor and a pixel electrode electrically connected to a source of the thin film transistor are arranged, and a drain of the thin film transistor is selected from grayscale voltages of a plurality of potentials. A liquid crystal having a drain driver that outputs a voltage, a power supply circuit that outputs a gray scale reference voltage of a plurality of potentials to the drain driver, and a gate driver that outputs a voltage to the gate of the thin film transistor to select the pixel In the display device, the drain driver has a grayscale voltage generation circuit, and the grayscale voltage generation circuit uses a voltage divider circuit in which resistors are connected in series between the potentials of the grayscale reference voltages. To generate the gradation voltages of the plurality of potentials, and the resistance value between the potentials of the gradation reference voltages of the voltage dividing circuit is divided into the gradation reference voltages. The liquid crystal display device, characterized in that set to approximately proportional to the resistance value to a potential difference between the 圧間. 2. A switching means for changing the resistance value between the potentials of the gradation reference voltages of the voltage dividing circuit to a resistance value substantially proportional to the potential difference between the gradation reference voltages. The liquid crystal display device according to claim 1. 3. A plurality of series resistance circuits are provided between the potentials of the gradation reference voltages of the voltage dividing circuit, and a resistance value that is substantially proportional to the potential difference between the gradation reference voltages is selected from the plurality of series resistance circuits. 2. The liquid crystal display device according to claim 1, further comprising selection means for selecting the series resistance circuit. 4. A liquid crystal display panel in which a plurality of pixels each having a thin film transistor and a pixel electrode electrically connected to a source of the thin film transistor are arranged, and a drain of the thin film transistor is selected from gray scale voltages of a plurality of potentials. A liquid crystal having a drain driver that outputs a voltage, a power supply circuit that outputs a gray scale reference voltage of a plurality of potentials to the drain driver, and a gate driver that outputs a voltage to the gate of the thin film transistor to select the pixel In the display device, the drain driver has a grayscale voltage generation circuit, and the grayscale voltage generation circuit uses a voltage divider circuit in which resistors are connected in series between the potentials of the grayscale reference voltages. Of the plurality of potentials to generate the gray scale voltages of the plurality of potentials, and the one gray scale reference voltage Vn and the other gray scale reference voltage Vn-
1 is Vn (n-1), and the combined resistance value between the application terminals of the voltage dividing circuit for the gradation reference voltages Vn and Vn-1 is Rn, Vn (n -1)
A liquid crystal display device, wherein the value of each resistor of the voltage dividing circuit is set so that the value of / Rn is matched within a specific variation range. 5. The Vn (n- for all of the Rn.
5. The liquid crystal display device according to claim 4, wherein the values of the resistors of the voltage dividing circuit are set so that the values of 1) / Rn match within a range of fluctuation of ± 23%. 6. The above Vn (n-
5. The liquid crystal display device according to claim 4, wherein the values of the resistors of the voltage dividing circuit are set so that the values of 1) / Rn match within a range of fluctuation of ± 15%. 7. The Vn (n-
5. The liquid crystal display device according to claim 4, wherein the values of the resistors of the voltage dividing circuit are set so that the values of 1) / Rn completely match.