JP2001331151A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize low power consumption without shortage of an output current ability of a signal electrode driving circuit group. SOLUTION: An output current ability of the signal electrode driving circuit group 16 is increased or decreased according to the analog output voltage levels by arranging a signal level comparison circuit 10, detecting a potential difference between the video signal level outputted from a video signal processing circuit 12 and a counter signal level outputted from a counter electrode driving circuit 11 for a period of transmitting sample-held video signals to signal electrodes, generating an analog output voltage proportional to this potential difference, and supplying this analog output voltage to the signal electrode driving circuit group 16 as an output current ability control signal.

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 useful as a display for video equipment such as a television and information equipment such as a computer.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram of a liquid crystal display device often used in recent years, and FIG. 3 is a block diagram showing a detailed configuration thereof. In FIG. 4, the liquid crystal panel 42
The scanning electrode and the signal electrode are formed in a matrix, a pixel electrode is provided in each pixel where the scanning electrode and the signal electrode intersect, and a liquid crystal layer is provided between the pixel electrode and the counter electrode. Then, the twist angle of the liquid crystal is controlled by the potential difference between the pixel electrode and the counter electrode, and an image is displayed.

The counter electrode driving circuit 11 includes a liquid crystal panel 42
The counter signal S3 is applied to the counter electrode of
It has a function of driving the two counter electrodes.

The video signal processing circuit 12 generates a display image signal S
7 has a function of processing the video signal S2 to be applied to the signal electrode.

[0005] The signal electrode drive circuit group 16 includes the liquid crystal panel 4
2 for driving the two signal electrodes. The video signal is sampled and held in time series during the horizontal scanning period, and the sampled and held video signal is signaled within the next horizontal retrace period. It has a function of sending out to the electrodes, and the output current capability can be changed in an analog manner by an output current capability control signal S1 (described later) externally given.

The scan electrode drive circuit group 41 includes a liquid crystal panel 42
Has the function of driving the scanning electrodes.

The control signal generation circuit 13 has a function of generating a control signal for displaying a video signal as an image on the liquid crystal panel 42. The control signal generation circuit 13 includes a scan electrode drive circuit group 41, a signal electrode drive circuit group 16, and a video signal processing circuit. An electrode drive circuit group control signal S4, a video signal processing circuit control signal S5, and a counter electrode drive circuit control signal S6 are supplied to the circuit 12 and the counter electrode drive circuit 11, respectively.

[0008] The operation of the conventional liquid crystal display device configured as described above will be described below.

In the conventional liquid crystal display device, a scanning electrode and a signal electrode are provided on a liquid crystal panel 42, and a pixel is provided at each intersection. The signal electrode drive circuit group 16 and the scan electrode drive circuit group 41 drive the signal electrode and the scan electrode, respectively.

The signal electrode drive circuit group 16 includes a video signal S
2, an electrode drive circuit group control signal S4, and an output current capability control signal S1 are input, whereby signal electrode signals are generated from the signal electrode drive circuit group 16. The video signal S2 is based on the video signal processing circuit control signal S5 given from the control signal generation circuit 13 and is based on the display image signal S7.
Is processed by the video signal processing circuit 12 into a signal applied to the signal electrode. The electrode drive circuit group control signal S4 is output from the control signal generation circuit 13 to output the signal electrode drive circuit group 1
6 is controlled. The output current capability control signal S1 controls the current capability of the video signal S2 written to the signal electrode.

The scan electrode drive circuit group 41 receives an electrode drive circuit group control signal S4, whereby scan electrode signals are generated from the scan electrode drive circuit group 41. The electrode drive circuit group control signal S4 is output from the control signal generation circuit 13 and controls the scan electrode drive circuit group 41.

Further, a control signal S6 for the counter electrode driving circuit synchronized with the video signal S2 is input to the counter electrode driving circuit 11, and a counter signal S3 synchronized with the video signal S2 is generated. The counter electrode drive circuit control signal S6 is output from the control signal generation circuit 13 to control the counter electrode drive circuit 11.

The control signal generating circuit 13 generates the above-described electrode drive circuit group control signal S4, video signal processing circuit control signal S5, and counter electrode drive circuit control signal S6 in synchronization with the video signal S2. By supplying the video signal processing circuit 12, the counter electrode drive circuit 11, the signal electrode drive circuit group 16, and the scan electrode drive circuit group 41, the video signal is displayed on the liquid crystal panel 42 as an image.

In this way, a display image is displayed on each pixel of the liquid crystal display device by the generated signal electrode signal, scanning electrode signal and counter signal S3.

Here, the flow of signals will be described in more detail with reference to FIG.

In FIG. 3, the signal electrode drive circuit group 16
Is composed of a sampling circuit 14 and an amplifier circuit 15. Further, the pixels 17 constituting the liquid crystal panel include:
It comprises a pixel transistor 18 and a liquid crystal pixel 19. The signal electrode signal S8 is output from the signal electrode drive circuit group 16, and the scan electrode signal S9 is output from the scan electrode drive circuit group 41.

With respect to the operation of the conventional liquid crystal display device configured as described above, a signal flow in a portion for displaying an image which is not touched in the above will be described below.

The signal electrode drive circuit group 16 includes a sampling circuit 14 and an amplifier circuit 15. Then, the video signal S2 output from the video signal processing circuit 12
Is sampled by the sampling circuit 14 on the basis of the electrode drive circuit group control signal S4 output from the control signal generation circuit 13. Further, the amplifier circuit 15 amplifies the sampled video signal with an output current capability defined by the value of the output current capability control signal S1, and outputs the amplified signal as a signal electrode signal S8.

The amplifier circuit 15 performs current amplification, and has a voltage gain of 1.0. The output current capability is a current value that the amplifier circuit 15 can supply to a load. In the case of liquid crystal, the load is a capacitor. Therefore, when the current value is large, the capacitor can be charged quickly. In addition, the magnitude of the output current of the amplifier circuit 15 changes by controlling the current of the current source that supplies the current to the amplifier circuit body by the output current capability control signal S1. If the output current capability of the amplifier circuit 15 is insufficient, the liquid crystal pixels are capacitors, so that the capacitors cannot be charged sufficiently. Therefore, the capacitor (load) cannot be charged to the potential (voltage value) held.

The output current capability control signal S1 at this time is a constant value of the direct current (DC) voltage, and is a value fixed by the size of the screen of the liquid crystal display device and the load.

The pixel 17 includes a pixel transistor 18 which is turned on / off by the scanning electrode signal S9 to pass or block the signal electrode signal S8, a pixel electrode, a counter electrode, and a liquid crystal layer formed between the electrodes. Liquid crystal pixel 1 composed of
9.

According to the scan electrode signal S9, the signal electrode signal S8 passes through the pixel transistor 18 and is applied to the pixel electrode while the pixel transistor 18 is on. The signal electrode signal S8 is an output current capability control signal S
It is output with an output current capability defined (fixed) by an arbitrary analog voltage as 1.

On the other hand, a counter signal S3 output from the counter electrode driving circuit 11 synchronized with the video signal S2 is applied to the counter electrode.

At this time, electric charges are accumulated in the liquid crystal pixel 19 from the signal electrode signal S8 side with the specified current capability, and the twist angle of the liquid crystal layer is controlled by the signal potential difference between the signal electrode and the counter electrode generated by this.

In the above, if the current capability of the amplifier circuit 15 is different, the signal potential difference generated between the signal electrode and the counter electrode changes as follows due to the electric charge accumulated by the addition of the signal electrode signal S8. I do. That is, the infinite time is not written in the liquid crystal pixel, and the written voltage cannot be held unless the writing is performed within a specified time (for example, one horizontal period). When charging the capacitor, the rising gradient of the voltage varies depending on the current capability of the amplifier circuit 15, and the time required to reach the voltage to be held varies. If the output current capability is sufficient, the gradient is large, and it is possible to reach the voltage to be held in a time sufficiently shorter than one horizontal period. Cannot reach the voltage desired to be maintained.

Next, the pixel transistor 18 is turned off by the scanning electrode signal S9, and the image information is held.
By performing such a process for all pixels, an image can be displayed on the liquid crystal display device.

Next, the above-described potential difference and image display will be described in more detail with reference to the signal waveform of FIG.

In FIG. 2, 21A, 21B, 21C,
Reference numeral 21D denotes a counter signal waveform of a counter signal S3 which is converted into an alternating voltage every horizontal period and applied to the counter electrode. 22A, 22
B, 22C and 22D are 1
This is a video signal waveform of a signal electrode signal S8 that is converted into an alternating voltage every horizontal period, passes through the pixel transistor 18, and is applied to the pixel electrode. Δ2A, Δ2B, Δ2C, and Δ2D are potential differences between the opposite signal waveform and the video signal waveform. VCOM is the peak-to-peak level of the opposite signal waveform due to the alternating current, and VRGB is the peak-to-peak level of the video signal waveform due to the alternating current.

(A) is a white display in which the potential is hardly applied to the liquid crystal layer, (B) is a black display in which the potential is sufficiently applied to the liquid crystal layer, and (C) is a certain potential in the liquid crystal layer [more than (A)]. (D) is the same video signal level as (RGB) of (C).
(C) applying a voltage higher than the VCOM voltage,
This is a neutral black display that realizes a darker display than the display of (C).

The potential difference between the signal electrode and the counter electrode in the conventional liquid crystal display device and the image display will be described with the waveforms configured as described above.

Usually, when a state where no voltage is applied to the liquid crystal is white display (hereinafter, normally white), if a pixel of the liquid crystal display device is to display white, a signal waveform as shown in FIG. The opposing signal 21A is applied to the opposing electrode, and the signal electrode signal 22A is applied to the pixel electrode. At this time, the potential difference Δ2A between the opposing signal waveform and the video signal waveform (VCOM−V
A voltage such that the voltage difference between RGB is close to 0 (V) is applied so that a twist angle hardly occurs in the liquid crystal layer.

Conversely, if black is to be displayed,
A counter signal 21B having a signal waveform as shown in FIG. 4B is applied to the counter electrode, and a signal electrode signal 22B is applied to the pixel electrode. At this time, the potential difference Δ2B (V
A voltage is applied so that the voltage difference (COM-VRG voltage difference) becomes extremely large, so that the twist angle of the liquid crystal layer is increased.

Further, if an intermediate color is to be displayed, a counter signal 21C having a signal waveform as shown in (C) is applied to the counter electrode, and a signal electrode signal 22C is applied to the pixel electrode.
The potential difference Δ2C between the opposite signal waveform and the video signal waveform at this time
(Voltage difference between VCOM-VRGB) is Δ2A <Δ2C <
A voltage that gives Δ2B is applied to appropriately generate a twist angle in the liquid crystal layer.

[0034]

However, when an intermediate color display such as the waveform shown in FIG. 2C is being performed, and when it is desired to make the image of the liquid crystal display device darker, the signal signal S3 applied to the counter electrode. Can be realized without changing the video signal waveform 22D.

However, when the above configuration is adopted, the DC current of the output current capability control signal S1
It is necessary to predict the voltage level to increase the amplitude of the counter signal waveform 21D as described above and set the voltage level higher. That is, it is necessary to take into consideration the voltage difference between the counter electrode and the video signal, and to set in advance such that the output current capability of the amplifier circuit 15 of the signal electrode drive circuit group 16 will not be insufficient.

In the conventional example, the video signal S2 and the opposite signal S3
Since the current capability is constant irrespective of the potential difference from the above, power consumption increases if the above setting is made.

Further, when the size of the screen of the liquid crystal display device becomes large and the load on the signal electrode driving circuit group 16 becomes large, or when the variation in the output current capability of the signal electrode driving circuit group 16 becomes large, the worst value is reduced. Since the output current capability control signal S1 is determined in consideration of the above, the power consumption is further increased.

Accordingly, it is an object of the present invention to provide a liquid crystal display device capable of realizing low power consumption without insufficient output current capability of a signal electrode drive circuit group.

Another object of the present invention is to prevent the output current capability of the signal electrode drive circuit group from becoming insufficient by absorbing the variations even if the characteristics of the signal electrode drive circuit group are varied. In addition, an object of the present invention is to provide a liquid crystal display device that can achieve low power consumption.

[0040]

According to a first aspect of the present invention, there is provided a liquid crystal display device comprising: a liquid crystal panel, a scan electrode drive circuit group, a signal electrode drive circuit group, a counter electrode drive circuit, a control signal generation circuit, and a signal level comparison circuit. And a circuit.

In a liquid crystal panel, a scanning electrode and a signal electrode are formed in a matrix, and a pixel electrode is provided in each pixel where the scanning electrode and the signal electrode intersect, and a pixel electrode is provided between the pixel electrode and a counter electrode. A liquid crystal layer is provided on the substrate, and has a function of controlling a twist angle of the liquid crystal by a potential difference between the pixel electrode and the counter electrode to display an image.

The scan electrode drive circuit group has a function of driving the scan electrodes.

The signal electrode drive circuit group samples and holds the video signal in time series within the horizontal scanning period, and holds the sampled and held video signal within the next horizontal retrace period. And the output current capability can be changed in an analog manner by an externally supplied output current capability control signal.

The counter electrode driving circuit has a function of generating a signal for driving the counter electrode.

The control signal generation circuit has a function of sending a control signal for displaying a video signal as an image on the liquid crystal panel to the scan electrode drive circuit group, the signal electrode drive circuit group, and the counter electrode drive circuit.

The signal level comparison circuit calculates the potential difference between the level of the video signal output from the video signal processing circuit and the level of the counter signal output from the counter electrode driving circuit during the period of sending the sampled and held video signal to the signal electrode. It has a function of detecting and generating an analog output voltage substantially proportional to this potential difference.

In this liquid crystal display device, the analog output voltage output from the signal level comparison circuit is given to the signal electrode drive circuit group as an output current capability control signal, whereby the signal is output in accordance with the value of the analog output voltage. The output current capability of the electrode drive circuit group is increased or decreased.

According to this configuration, the signal level comparison circuit is provided, and during the period in which the sampled and held video signal is sent to the signal electrode, the level of the video signal output from the video signal processing circuit and the output from the counter electrode drive circuit are provided. The potential difference of the level of the opposite signal is detected, an analog output voltage substantially proportional to the potential difference is generated, and this analog output voltage is given to the signal electrode drive circuit group as an output current capability control signal, thereby obtaining the analog output voltage value. Since the output current capability of the signal electrode drive circuit group is increased or decreased according to the magnitude, the output current capability of the signal electrode drive circuit group does not become insufficient, and power consumption can be reduced.

The liquid crystal display device according to the second aspect of the present invention comprises:
2. The liquid crystal display device according to claim 1, wherein a proportionality coefficient between a potential difference between a level of the video signal output from the video signal processing circuit, a level of the counter signal output from the counter electrode driving circuit, and an analog output voltage to be output is determined. The signal level comparison circuit is configured to be variable.

According to this configuration, since the proportional coefficient between the potential difference between the level of the video signal and the level of the counter signal and the analog output voltage to be output is variable, there is a variation in the characteristics of the signal electrode drive circuit group. In addition, by adjusting the proportional coefficient, it is possible to prevent the output current capability of the signal electrode drive circuit group from becoming insufficient by absorbing the variation and to achieve low power consumption.

[0051]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a liquid crystal display device according to a first embodiment of the present invention. In this liquid crystal display device, as shown in FIG. 1, a signal level comparison circuit 10 is added to the configuration of the conventional example shown in FIGS. The signal level comparison circuit 10 outputs the video signal S2 output from the video signal processing circuit 12 during the period of sending the sampled and held video signal to the signal electrode.
Has a function of detecting a potential difference between the level of the counter signal and the level of the counter signal S3 output from the counter electrode driving circuit 11, and generating an analog output voltage proportional to this potential difference.
Note that the input and output of the signal level comparison circuit 10 need not be exactly proportional, but may be approximately proportional. That is, the relationship between the input and output does not need to be a perfect straight line, but may be, for example, a step-like shape.

The liquid crystal display device supplies the analog output voltage output from the signal level comparison circuit 10 to the amplifier circuit 15 of the signal electrode drive circuit group 16 as the output current capability control signal S1 to thereby control the analog output voltage. The output current capability of the signal electrode drive circuit group 16 is increased or decreased according to the magnitude of the value. In particular,
When the potential difference between the level of the video signal S2 and the level of the counter signal S3 is large, the analog output voltage is increased, and the output current capability of the signal electrode drive circuit group 16 is increased. When the potential difference is small, the analog output voltage is reduced, The output current capability of the signal electrode drive circuit group 16 is reduced.

Structures other than those described above are the same as those of the conventional example shown in FIGS.

The operation of the liquid crystal display device configured as described above will be described below.

The signal electrode drive circuit group 16 is composed of a sampling circuit 14 and an amplifier circuit 15, and receives a video signal S2, an electrode drive circuit group control signal S4, and an output current capability control signal S1 as input signals. Control signal S
4, the pixel 17 to be displayed by the sampling circuit 14
, And the amplifier circuit 15 amplifies the sampled video signal with the output current capability defined by the value of the output current capability control signal S1 and outputs the amplified signal as the signal electrode signal S8.

The above-mentioned video signal S2 is processed by the video signal processing circuit 12 into a signal to be given to the signal electrode by the video signal processing circuit 12, based on the video signal processing circuit control signal S5 output from the control signal generation circuit 13. Things. For example, assuming that the display image signal S7 is a video signal, the video signal processing circuit 12 performs RGB separation, RGB voltage amplification, RGB 1H / 1V cycle AC conversion, and the like as a liquid crystal pixel potential. To the appropriate voltage value.

The electrode drive circuit group control signal S4 is output from the control signal generation circuit 13 to control the signal electrode drive circuit group 16. Output current capability control signal S
1 is a signal for controlling the current capability of the video signal S2 to be written to the signal electrode, and this signal is generated by the signal level comparison circuit 10.

The signal level comparison circuit 10 compares the potential of the video signal S2, which is the basis of the signal electrode signal S8, with the potential of the counter signal S3, and outputs an analog voltage proportional to the potential difference as the output current capability control signal S1. .

The counter electrode drive circuit 11 receives a control signal S6 for the counter electrode drive circuit for controlling the counter electrode drive circuit 11 from the control signal generation circuit 13 which operates in synchronization with the video signal S2. An opposite signal S3 synchronized with the video signal S2 is generated. The control signal generation circuit 13
Specifically, the device operates in synchronization with a clock for moving the shift register of the driver IC, a start pulse, a write signal to a pixel, a synchronization signal of a scanning system, and the like.

On the other hand, the pixel 17 includes a pixel transistor 18
And a liquid crystal pixel 19 comprising a pixel electrode, a counter electrode, and a liquid crystal layer formed between the electrodes. The pixel transistor 18 is turned on / off in response to a scan electrode signal S9 generated by inputting the electrode drive circuit group control signal S4 from the control signal generation circuit 13 to the scan electrode drive circuit group,
The signal electrode signal S8 is turned on or off.

Here, the signal electrode signal S8 conducts the pixel transistor 18 and is applied to the pixel electrode by the scanning electrode signal S9. The signal electrode signal S8 is output with the output current capability specified by the output current capability control signal S1. As described above, the output current capability control signal S1 is obtained by comparing the potential difference between the video signal S2 and the counter signal S3 with the signal level comparison circuit 10 during the period in which the pixel transistor 18 is on, and using the analog voltage proportional to the potential difference. It is.

On the other hand, the counter signal S3 output from the counter electrode drive circuit 11 synchronized with the video signal S2 is applied to the counter electrode.

At this time, charges are accumulated in the liquid crystal pixel 19 from the signal electrode signal S8 side with the specified current capability, and the twist angle of the liquid crystal layer is controlled by the potential difference of the signal between the signal electrode and the counter electrode.

Next, the pixel transistor 18 is turned off by the scanning electrode signal S9, and the image information is held.
By performing such a process for all the pixels, an image is displayed on the liquid crystal display device.

In such driving, the potential difference between the video signal S2 and the counter signal S3 is compared, and the output current capability control signal S1, which is an analog voltage proportional to the potential difference, is output from the signal electrode and the counter electrode. If the potential difference of the signal is large, the output current capability of the signal electrode drive circuit group 16 is set to a value to increase the twist angle of the liquid crystal layer of the liquid crystal pixel 19. That is, when the potential difference between the signal of the signal electrode and the signal of the counter electrode is large, in order to increase the twist angle of the liquid crystal layer of the liquid crystal pixel 19, the charge is increased, that is, the output current capability of the signal electrode drive circuit group 16 is increased. This is because it is necessary.

Conversely, if the potential difference between the signal of the signal electrode and the signal of the counter electrode is small, the torsion angle of the liquid crystal layer of the liquid crystal pixel 19 is reduced so that the output current capability of the signal electrode driving circuit group is reduced. . That is, when the potential difference between the signal of the signal electrode and the signal of the counter electrode is small, the twist angle of the liquid crystal layer of the liquid crystal pixel 19 may be small, so that the charge is small, that is, the output current capability of the signal electrode drive circuit group 16 is small. This is because things are fine.

As a result, the output current capability control signal S1 can always be specified to an optimized value, the output current capability of the signal electrode drive circuit group is optimized, and the output current of the signal electrode drive circuit group is wasted. Can be none.

When the level of the signal electrode signal S8 is constant and the counter signal S3 changes, the output current capability of the signal electrode drive circuit group may be insufficient depending on the set value of the output current capability control signal S1. However, in the present invention,
Since the potential difference between the video signal S2 and the opposing signal S3 is constantly compared, the output current capability is optimized, and a necessary current is always supplied.

According to the liquid crystal display of this embodiment,
A signal level comparison circuit 10 is provided to transmit the sampled and held video signal to the signal electrode during the period of sending the video signal S2 output from the video signal processing circuit 12 and the counter signal S3 output from the counter electrode drive circuit 11. A level potential difference is detected, an analog output voltage is generated in proportion to the potential difference, and the analog output voltage is given to the signal electrode drive circuit group 16 as an output current capability control signal S1, so that the value of the analog output voltage can be changed. Thus, the output current capability of the signal electrode drive circuit group 16 is increased or decreased, so that the output current capability of the signal electrode drive circuit group 16 does not run short and power consumption can be reduced.

The signal level comparison circuit 10 may use, as an input, the signal electrode signal S8 instead of the video signal S2. However, since the signal electrode signal S8 is sampled and held, when it is actually output, 1
The signal is delayed in the horizontal period, and the handling as a signal becomes more complicated.

Next, the structure of a liquid crystal display device according to a second embodiment of the present invention will be described.

In the first embodiment, the proportional coefficient between the potential difference between the video signal S2 and the counter signal S3 and the output analog voltage in the signal level comparison circuit 10 is fixed. In the embodiment, a variable configuration is adopted. Other configurations are the same as those of the first embodiment.

In the first embodiment, even if the characteristics of the liquid crystal display device vary, the video signal S2 and the counter signal S3
If the potential difference is the same, the analog voltage output from the signal level comparison circuit 10, that is, the output current capability control signal S1 applied to the signal electrode drive circuit group is at the same level.

Therefore, when the output current capability of the signal electrode drive circuit group with respect to the output current capability control signal S1 varies in the characteristics of the signal electrode drive circuit group for each liquid crystal display device, the output current capability control signal S1 becomes It is necessary to take this variation into consideration, and under the worst conditions it is necessary to specify an optimized value, so that the output current capability of the signal electrode drive circuit group cannot be optimized in the true sense, and the signal The output current of the electrode drive circuit group is wasted.

However, in the second embodiment, the proportionality between the potential difference between the video signal S2 and the opposing signal S3 and the analog voltage to be output, that is, the output current capability control signal S1 in the signal level comparison circuit 10. The coefficient is variable, the proportionality constant is changed for each liquid crystal display device, and the output current capability control signal S1 of the signal electrode drive circuit group is optimized for each liquid crystal display device in consideration of the variation in the characteristics of the signal electrode drive circuit group. It is possible to provide a high output current capability. As a result, it is possible to realize a liquid crystal display device with the least waste and low power consumption.

The above proportional coefficient is adjusted, for example, as follows. That is, one point, one point for each liquid crystal display device.
Adjust in the point and process. The proportional coefficient is converted into a resistance value or the like, and the resistance value is adjusted by using a configuration that can be varied with a volume (variable resistor) or the like.

According to the liquid crystal display of this embodiment,
Since the proportional coefficient between the potential difference between the level of the video signal and the level of the counter signal and the analog output voltage to be output is variable, even if there is a variation in the characteristics of the signal electrode drive circuit group,
By adjusting the proportional coefficient, it is possible to prevent the output current capability of the signal electrode drive circuit group from becoming insufficient by absorbing the variation, and to achieve low power consumption.

[0079]

According to the liquid crystal display device according to the first aspect of the present invention, the signal output from the video signal processing circuit is provided during the period of sending the sampled and held video signal to the signal electrode by providing the signal level comparison circuit. Detects the potential difference between the signal level and the level of the counter signal output from the counter electrode drive circuit, generates an analog output voltage proportional to this potential difference, and uses the analog output voltage as an output current capability control signal for the signal electrode drive circuit group. The output current capability of the signal electrode drive circuit group is increased or decreased according to the value of the analog output voltage by providing the signal electrode drive circuit group. Electricity can be realized.

Further, according to the liquid crystal display device of the second aspect of the present invention, since the proportional coefficient between the potential difference between the level of the video signal and the level of the opposite signal and the analog output voltage to be output is variable, the signal Even if the characteristics of the electrode drive circuit group vary, by adjusting the proportionality coefficient, it is possible to absorb the variation and prevent the output current capability of the signal electrode drive circuit group from becoming insufficient, and to reduce power consumption. Can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a liquid crystal display device according to first and second embodiments of the present invention.

FIG. 2 is a waveform diagram showing signal waveforms of a signal electrode and a counter electrode in the liquid crystal display device.

FIG. 3 is a block diagram illustrating a detailed configuration of a conventional liquid crystal display device.

FIG. 4 is a block diagram showing an overall configuration of a conventional liquid crystal display device.

[Explanation of symbols]

 Reference Signs List 10 signal level comparison circuit 11 counter electrode drive circuit 12 video signal processing circuit 13 control signal generation circuit 14 sampling circuit 15 amplifier circuit 16 signal electrode drive circuit group 17 pixel 18 pixel transistor 19 liquid crystal pixel S1 output current capability control signal S2 video signal S3 Counter signal S4 Electrode drive circuit group control signal S5 Video signal processing circuit control signal S6 Counter electrode drive circuit control signal S7 Display image signal S8 Signal electrode signal S9 Scanning electrode signal 21A Counter signal waveform 21B Counter signal waveform 21C Counter signal waveform 21D Counter signal waveform 22A Video signal waveform 22B Video signal waveform 22C Video signal waveform 22D Video signal waveform Δ2A Potential difference between counter signal waveform and video signal waveform Δ2B Potential difference between counter signal waveform and video signal waveform Δ2C Voltage between counter signal waveform and video signal waveform Difference Δ2D counter signal waveform and the potential difference 41 scan electrode driving circuit group 42 liquid crystal panel of the video signal waveform

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H093 NA16 NA43 NC16 NC23 NC34 ND09 ND37 ND39 ND60 5C006 AA16 AF54 AF69 BB16 BC13 BF11 BF14 FA20 FA22 FA47 5C080 AA10 BB05 DD01 DD05 DD26 EE19 FF11 JJ02 JJ04 KK02 KK02 KK02

Claims (2)

[Claims] 1. A scanning electrode and a signal electrode are formed in a matrix, and a pixel electrode is provided at each pixel where the scanning electrode and the signal electrode intersect, and a pixel electrode is provided between the pixel electrode and a counter electrode. A liquid crystal panel that displays a video image by controlling a twist angle of the liquid crystal by a potential difference between the pixel electrode and the counter electrode, a scan electrode driving circuit group that drives the scan electrode, and a video signal. Sampling and holding are performed in time series during the horizontal scanning period, the sampled and held video signal is sent to the signal electrode within the next horizontal retrace period, and the output current capability is externally given. A signal electrode drive circuit group that can be changed in an analog manner by an output current capability control signal; a counter electrode drive circuit that generates a signal for driving the counter electrode; A control signal generation circuit for sending a control signal for displaying the video signal as an image on the liquid crystal panel to the electrode drive circuit group, the signal electrode drive circuit group, and the counter electrode drive circuit; and a sampled and held video. During the period of sending the signal to the signal electrode, a potential difference between the level of the video signal output from the video signal processing circuit and the level of the counter signal output from the counter electrode driving circuit is detected, and an analog output voltage substantially proportional to this potential difference is detected. And a signal level comparing circuit for generating the analog output voltage. The analog output voltage output from the signal level comparing circuit is supplied to the signal electrode driving circuit group as an output current capability control signal, so that the analog output voltage can be changed according to the magnitude of the analog output voltage. Wherein the output current capability of the signal electrode drive circuit group is increased or decreased by Display devices. 2. A signal level comparison circuit, comprising: a proportional circuit configured to calculate a proportionality between a potential difference between a level of a video signal output from a video signal processing circuit, a level of a counter signal output from the counter electrode driving circuit, and an analog output voltage to be output. 2. The liquid crystal display device according to claim 1, wherein the coefficient is variable.