JPH11231840A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which can finely display an image with a little consumed electric power. SOLUTION: A voltage VA inputted from a power source supply section 20 is divided into a plurality of gradation voltages VD1 -VDn through a DC-DC converter 22. An image data DV is supplied at dotclock frequency from a controller 10 to a signal line driving section 12, and the gradation voltage is selected in accordance with the image data supplied from a driving section 12 and supplied to the signal line of a liquid crystal panel 30. The frequency of a drive signal CD supplied from the controller 10 to the converter 22 is decided so as to be equal to the dot clock frequency or one integer-th of it for driving the converter 22. Even when an interference due to a switching motion of the converter 22 appares on the image of the liquid crystal panel 30, its influence is turned into a static state and does not obstruct one's view.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal display device. Specifically, when converting the voltage input by the power supply unit into a plurality of grayscale voltages, the operation is performed using a drive signal generated based on a predetermined reference signal. By selecting one of the plurality of obtained gradation voltages at a frequency based on a predetermined reference signal in accordance with the image data supplied from the controller and supplying the selected voltage to the signal lines of the liquid crystal panel, An image is displayed favorably with power consumption.

[0002]

2. Description of the Related Art Hitherto, a multi-gradation liquid crystal display device has been used as a thin image display device in a personal computer, a color television and the like. In the signal line driving unit used in such a liquid crystal display device, any one of a plurality of DC voltages having different voltage levels is selected based on the supplied input data or upper bits of the input data. The selected DC voltage is supplied from the signal driver to the liquid crystal panel, and the liquid crystal panel performs gradation display according to the input data.

In such a method, for example, in order to realize a gray scale of 5 bits or more, about 10 or more DC voltages having different voltage levels are required. In order to generate DC voltages having different voltage levels, a plurality of DC voltages required by using a series regulator are generated from a voltage higher than a DC voltage required for performing multi-gradation display. I have.

[0004]

In the case where a series regulator is used as described above, the power consumption is increased due to the low conversion efficiency of the series regulator, and when a liquid crystal image display device is driven using a battery or the like. The driving time is short.

[0005] Therefore, the present invention provides a liquid crystal display device capable of displaying an image satisfactorily with low power consumption.

[0006]

A liquid crystal display device according to the present invention comprises a power supply unit for converting an input voltage into a plurality of gray scale voltages, and a method for converting input image data at a frequency based on a predetermined reference signal. A controller that supplies a drive signal to the line drive unit and generates a drive signal for driving the power supply unit based on a predetermined reference signal.The power supply unit operates based on a drive signal from the controller and receives an input signal. The signal line driving means selects one of the plurality of gradation voltages obtained by the power supply unit according to the supplied image data, and selects a signal line of the liquid crystal panel. Is to be supplied to

In the present invention, when a voltage input by the power supply unit is converted into a plurality of gray scale voltages, the operation is performed using a drive signal generated based on a predetermined reference signal. The signal line driving means selects one of a plurality of gradation voltages from a plurality of gradation voltages obtained by the power supply unit in accordance with image data supplied from the controller at a frequency based on a predetermined reference signal, and controls the operation of the liquid crystal panel. It is supplied to the signal line.

Further, when the image data is supplied to the signal line driving section at a dot clock frequency based on a predetermined reference signal, the power supply section operates at a frequency equal to the dot clock frequency or a frequency which is an integer fraction of the dot clock frequency. Is performed.

Further, when a synchronizing signal is supplied as a predetermined reference signal together with the image data, the power supply unit operates at a frequency equal to the dot clock frequency or a frequency that is an integer fraction of the dot clock frequency, The operation is performed at a frequency equal to the frequency or an integer multiple of the horizontal frequency. Alternatively, the operation is performed at a frequency “M / 2 (M is a positive odd number)” times the horizontal frequency of the synchronization signal.

[0010]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a liquid crystal display device. The image data DV is supplied to the controller 10 together with a synchronization signal SY as a reference signal or a control signal SC for transmitting the image data DV. In the controller 10, the synchronization signal SY or the control signal SC
, A control signal TA for controlling the operation of the signal line driving unit 12 and a control signal TB for controlling the operation of the scanning line driving unit 14 described later are generated. In the controller 10, the supplied image data DV is latched, and the latched image data DV is transmitted to the signal line driver 12 at a timing corresponding to the control signal TA or the control signal TB.
Supplied to

The power supply unit 20 has a DC-
A DC converter 22 is connected, and the DC-DC converter 22 converts the DC voltage VA supplied from the power supply unit 20 into gradation voltages VD1 to VDn of a predetermined voltage level.
And supplied to the signal line drive unit 12.

The signal line drive section 12 is constituted by using a latch circuit, a voltage selection circuit and the like, and the latch circuit sequentially latches the image data DV supplied from the controller 10. The image data DV is supplied from the controller 10 to the signal line driver 12 at a predetermined dot clock frequency. The signal line driver 12 latches the image data DV at this dot clock frequency based on the control signal TA. Will be When the pixel data of one line of pixels is latched by the latch circuit, any one of the gray scale voltages VD1 to VDn supplied from the DC-DC converter 22 according to the data value of the latched pixel data. The voltage is selected by the voltage selection circuit and supplied to each signal line of the liquid crystal panel 30.

The scanning line driving section 14 generates a scanning signal RS based on a control signal TB, and generates a scanning signal RS.
Are sequentially selected, and a scanning signal RS is supplied to the selected scanning line.

The liquid crystal panel 30 performs a gray scale display corresponding to the image data DV based on the gray scale voltage supplied from the signal line driver 12 and the scanning signal RS.

Here, the DC-DC converter 22 includes:
A converter drive signal CD is supplied from the controller 10, and a switching operation is performed based on the converter drive signal CD to generate a plurality of gradation voltages VD1 to VDn. As described above, since the DC-DC converter 22 is used instead of the series regulator, power consumption can be reduced.

The frequency of the converter drive signal CD is set to the dot clock frequency or an integer fraction of the dot clock frequency. For this reason, even if interference due to the switching operation of the DC-DC converter 22 appears on the screen of the liquid crystal panel 30, the interference caused by the interference, for example, the stripe pattern is stopped without moving on the screen, which is annoying. Can be eliminated. Further, the influence of the interference can be made stationary by making the frequency of the converter drive signal CD equal to the horizontal frequency or an integer multiple of the horizontal frequency.

If the frequency of the converter drive signal CD is set to an integral multiple of the dot clock frequency which is an integral multiple of the horizontal frequency, a stripe pattern can be eliminated even if the influence of interference occurs. Further, by setting the frequency of the converter drive signal CD to a frequency of "M / 2 (M is a positive odd number) times the horizontal frequency, the phase of the interference is reversed every line on the interlaced display screen. Since the averaging is performed, the stripe pattern can be made inconspicuous.

If the operation of the DC-DC converter 22 can be performed at the above-described frequency, the frequency of the converter drive signal CD is varied to change the DC-DC
It is not limited to the one supplied to the DC converter 22.

[0019]

According to the present invention, the power supply section operates by the drive signal generated based on the reference signal, and the signal line drive means controls the image data supplied from the controller at the frequency based on the reference signal. , One of the plurality of gradation voltages obtained by the power supply unit is selected and supplied to the signal lines of the liquid crystal panel. Here, the operation of the power supply unit is performed at a frequency equal to the dot clock frequency, a frequency that is an integer fraction of the dot clock frequency, a frequency equal to the horizontal frequency of the synchronization signal, or an integer multiple of the horizontal frequency. For this reason,
Even if the interference due to the switching operation appears on the screen, the influence of the interference is kept stationary or inconspicuous, so that an image can be displayed satisfactorily with low power consumption.

Further, since the operation of the power supply section is performed at a frequency of "M / 2 (M is a positive odd number)" times the horizontal frequency of the synchronization signal, the interference due to the switching operation is averaged on the interlaced display screen. Since the image is inconspicuous, an image can be similarly displayed with low power consumption.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a liquid crystal display device according to the present invention.

[Description of Signs] 10 ... Controller, 12 ... Signal line drive unit, 1
4 scanning line driving unit, 20 power supply unit, 22
..DC-DC converters, 30 liquid crystal panels

Claims (4)

[Claims] 1. A liquid crystal display device which performs display by supplying a gray scale voltage from a signal line driver to a signal line of a liquid crystal panel and a scanning signal from a scanning line driver to a scanning line of the liquid crystal panel. A power supply unit for converting the input voltage into a plurality of gradation voltages; and supplying the input image data to the signal line driving unit at a frequency based on a predetermined reference signal, and A controller for generating a drive signal for driving the power supply unit, wherein the power supply unit operates based on a drive signal from the controller, and converts the input voltage to the plurality of gradation voltages. Wherein the signal line driving means selects one of the plurality of gradation voltages obtained by the power supply unit according to the supplied image data and supplies the selected voltage to a signal line of a liquid crystal panel. Liquid crystal display device. 2. The controller supplies the image data to the signal line driving section at a dot clock frequency based on the predetermined reference signal. The power supply section controls the dot clock based on a driving signal from the controller. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device operates at a frequency equal to the frequency or a frequency that is an integer fraction of the dot clock frequency. 3. The power supply section according to claim 1, wherein the predetermined reference signal is a synchronization signal, and the power supply section has a frequency equal to the dot clock frequency or a frequency that is an integer fraction of the dot clock frequency based on a drive signal from the controller. 3. The liquid crystal display device according to claim 2, wherein the liquid crystal display device operates at a frequency equal to the horizontal frequency of the synchronization signal or at an integer multiple of the horizontal frequency. 4. The predetermined reference signal is a synchronizing signal, and the power supply unit multiplies a horizontal frequency of the synchronizing signal by “M / 2 (M is a positive odd number)” based on a driving signal from the controller. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device operates at a frequency.