KR100599652B1 - A liquid crystal display and a driving method thereof - Google Patents

Abstract

The present invention relates to a liquid crystal display device and a driving method thereof, and detects a temperature of the panel or an ambient temperature of the panel, generates a driving frequency at a frequency corresponding to the sensed temperature, and supplies the same to a liquid crystal display panel. At this time, when the sensed temperature is low temperature, the driving frequency is generated and supplied at a frequency lower than room temperature. In this way, the image quality can be improved by lowering the driving frequency so as to be suitable for liquid crystals having a slow response at low temperatures.

LCD, low temperature, temperature sensor, frequency

Description

Liquid crystal display and its driving method {A LIQUID CRYSTAL DISPLAY AND A DRIVING METHOD THEREOF}

1 is a view showing a liquid crystal display device according to an embodiment of the present invention.

2 illustrates driving waveforms at room temperature of the liquid crystal display according to the exemplary embodiment of the present invention.

3 illustrates driving waveforms at low temperatures of the liquid crystal display according to the exemplary embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a driving method thereof, and more particularly, to a liquid crystal display device and a driving method thereof which enable stable operation at low temperatures.

Recently, display devices are also required to be lighter and thinner in accordance with the light weight and thickness of personal computers and televisions, and according to such requirements, a liquid crystal display ("LCD") is used instead of a cathode ray tube (CRT). Flat panel displays are being developed.

The LCD applies an electric field to a liquid crystal material having an anisotropic dielectric constant injected between two substrates, and adjusts the intensity of the electric field to control the amount of light transmitted from the external light source (backlight) to the substrate. Get the desired image.

Such LCDs are typical of portable flat panel displays, and among them, TFT-LCDs using thin film transistors (hereinafter referred to as TFTs) as switching elements are mainly used.

In general, the LCD can be divided into two methods, a color filter method and a field sequential driving method, according to a method of displaying a color image.

The color filter LCD forms a color filter layer consisting of three primary colors of red (R), green (G) and blue (B) on the upper substrate of the panel, and adjusts the amount of light transmitted through the color filter layer. The desired image is displayed. However, the color filter LCD requires unit pixels corresponding to each of the red (R), green (G), and blue (B) regions, and thus requires three times as many pixels as those for displaying black and white. Therefore, in order to obtain high resolution images, sophisticated manufacturing technology of LCD panels is required. In addition, in the color filter type LCD, red (R), green (G) and blue (B) color filters must be formed on the upper substrate, which is cumbersome in manufacturing, and the light transmittance of the color filter itself must be improved. There is a problem.

Field-sequential driving LCDs periodically turn on independent light sources of red (R), green (G), and blue (B) colors, and supply a pixel voltage (Vp) to each pixel at each lighting cycle. Is displayed. That is, a field-sequential driving LCD does not divide one pixel into unit pixels of red (R), green (G), and blue (B), and red (R), green (G), and blue in one pixel. (B) Color images are displayed using the afterimage effect of the eyes by sequentially displaying the light of the three primary colors supplied from each backlight in time division.

On the other hand, since the field sequential driving LCD drives one frame by dividing the R field, the G field, and the B field, the liquid crystal should have a higher response speed than the color filter type LCD. However, the lower the temperature, the lower the response speed of the liquid crystal. Therefore, when the field sequential driving LCD is used in a portable device (eg, a mobile phone) that is frequently exposed to a low temperature environment, the response speed of the liquid crystal is lowered and the color reproduction rate is lowered. Problems arise.

SUMMARY OF THE INVENTION The present invention has been made in an effort to solve the above-described problems of the prior art, and to provide a liquid crystal display device and a driving method thereof capable of performing stable operation at low temperature.

Liquid crystal display device according to a feature of the present invention for achieving the above object
A liquid crystal display panel including a plurality of scan lines for transmitting a scan signal, a plurality of data lines insulated from and intersecting the scan lines, and a plurality of pixels formed in a region surrounded by the scan lines and data lines and arranged in a matrix form;
A temperature sensor for sensing a temperature of the liquid crystal display panel or an ambient temperature of the liquid crystal display panel;
A timing controller generating and outputting a control signal corresponding to the sensed temperature;
A light source sequentially outputting red, green, and blue light in the red field, the green field, and the blue field, respectively;
The data waveform is generated at the first frequency when the detected temperature is less than the reference temperature according to the control signal of the timing controller. The data waveform is generated at the second frequency higher than the first frequency when the detected temperature is above the reference temperature. A data driver to feed the line; And
The common voltage waveform is generated at the first frequency when the detected temperature is less than the reference temperature according to the control signal of the timing controller. The common voltage waveform is generated at the second frequency higher than the first frequency when the detected temperature is greater than the reference temperature. And a common voltage generator supplying the common electrode.

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DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like parts are designated by like reference numerals throughout the specification.

1 illustrates a liquid crystal display (LCD) according to an embodiment of the present invention.

Referring to FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel 100, a scan driver 200, a data driver 300, a gray voltage generator 400, and a timing controller 500. ), A common voltage generator 600, light emitting diodes 700a, 700b, and 700c respectively outputting R, G, and B light sources, a temperature sensor 900, and a light source controller 800.

A plurality of scan lines (not shown) are formed in the liquid crystal display panel 100 to transmit a gate-on signal, and are insulated from and intersect with the plurality of scan lines to transmit gray data voltages and reset voltages corresponding to gray data. A data line (not shown) is formed for this purpose. A plurality of pixels arranged in a matrix form is surrounded by a scan line and a data line, and each pixel includes a thin film transistor (not shown) and a drain electrode of the thin film transistor, in which a gate electrode and a source electrode are connected to the scan line and the data line, respectively. One side is connected to the other side, and the other side includes a pixel capacitor (not shown) and a storage capacitor (not shown) connected to the common electrode line.

The temperature sensor 900 detects a temperature of the liquid crystal display panel 100 or an ambient temperature of the liquid crystal display panel.

The timing controller 500 receives the gray level data signals R, G, and B data, the horizontal synchronization signal Hsync, and the vertical synchronization signal Vsync from an external or graphic controller (not shown), and controls necessary signals Sg, Sd and Sb are supplied to the scan driver 200, the data driver 300, and the light source controller 800, respectively, and the gray scale data R, G, and B DATA are supplied to the gray voltage generator 400. The timing controller 500 is a predetermined temperature at which the temperature or the ambient temperature of the liquid crystal display panel 100 is determined to be low temperature (in the embodiment of the present invention, the predetermined temperature is set to a temperature between −5 ° C. and 5 ° C., for convenience. And a control signal is generated to generate a driving frequency at the first frequency when it is sensed below the set value. The timing controller 500 generates a control signal to generate a driving frequency at a second frequency higher than the first frequency when the temperature or the ambient temperature of the liquid crystal display panel 100 is detected to be higher than a predetermined temperature determined to be low. To print. Here, the timing generator 500 changes and outputs a line clock signal for each output bit in order to change driving frequencies of the data driver 300, the common voltage generator 600, and the gate driver 200. This is possible. In addition, the timing controller 500 may output a clock signal corresponding to a temperature to change the driving frequency in various ways, and drive the liquid crystal display. In addition, the driving frequency may be changed for each group by dividing the temperature into groups.

The gray voltage generator 400 generates a gray voltage having a magnitude corresponding to gray data and supplies it to the data driver 300.

The data driver 300 generates a data waveform at a first frequency when the detected temperature is less than the reference temperature according to the control signal of the timing controller 500, and generates a data waveform higher than the first frequency when the detected temperature is greater than or equal to the reference temperature. A data waveform is generated at two frequencies and applied to the TFT of the liquid crystal display panel 100.

The common voltage generator 600 applies a common voltage to the TFTs of the liquid crystal display panel 100. The common voltage generator 600 generates a common voltage waveform at a first frequency when the detected temperature is less than the reference temperature according to the control signal of the timing controller 500, and generates the common voltage waveform at the first frequency when the detected temperature is greater than or equal to the reference temperature. The common voltage waveform is generated at a second frequency higher than one frequency and applied to the TFT of the liquid crystal display panel 100.

The gate driver 200 sequentially applies a scan signal to the scan line to turn on the TFT to which the scan signal is applied, and scans at the first frequency when the detected temperature is less than the reference temperature according to the control signal of the timing controller 500. When the signal is generated and the sensed temperature is higher than or equal to the reference temperature, a scan signal is generated at a second frequency higher than the first frequency and applied to the TFT of the liquid crystal display panel 100.

The light emitting diodes 700a, 700b, and 700c respectively output light corresponding to R, G, and B to the LCD panel, and the light source controller 800 controls the lighting timing of the light emitting diodes 700a, 700b, and 700c. In this case, according to an exemplary embodiment of the present invention, the timing controller 500 may be configured to supply the grayscale data from the data driver 300 to the data line and to turn on the R, G, and B light emitting diodes by the light source controller 800. It can be synchronized by the control signal provided by.

As described above, when the temperature of the liquid crystal display panel is lowered below the predetermined temperature, the timing controller 500 outputs a control signal to change the driving frequency, thereby lowering the driving frequency. Therefore, the data waveform is applied to the liquid crystal display panel 100 at a low driving frequency, thereby creating driving conditions corresponding to the liquid crystal having a low response speed, thereby improving image quality.

2 is a view showing a driving waveform at room temperature of the liquid crystal display according to the exemplary embodiment of the present invention.

Referring to FIG. 2, at a normal temperature, the driving frequency is normally maintained as before, and the data driver 300 and the common voltage generator 600 respectively set the data waveform and the common voltage waveform at a normal frequency (about 90 Hz). It is applied to the TFT of the panel 100.

3 illustrates driving waveforms at low temperatures of the liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 3, at a low temperature, the driving frequency is lower than the normal frequency of FIG. 2, for example, at a frequency of 60 to 75 Hz, so that the data driver 300 and the common voltage generator 600 respectively generate the data waveform and the common voltage waveform. Is generated and applied to the TFT of the liquid crystal display panel 100. As such, when the data waveform and the common voltage waveform are applied to the liquid crystal display panel 100 at a low driving frequency, the liquid crystal having a low response speed may sufficiently operate corresponding thereto, thereby improving image quality.

In the above process, the timing controller 500 controls the clock signal to change the frequency, but if necessary, the data driver 300, the common voltage generator 600, and the scan driver 200 directly control the output of the temperature sensor. Accordingly, the driving frequency may be changed.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

For example, in the above-described embodiment of the present invention, the liquid crystal display of the field sequential driving method has been described as an example, but may be applied to various liquid crystal display devices other than the field sequential driving liquid crystal display.

As described above, according to the present invention, when the panel temperature or the ambient temperature of the panel is detected at a low temperature, the driving frequency is lowered to drive the liquid crystal display under driving conditions that match the response speed of the liquid crystal, thereby improving image quality. have.

Claims (8)

delete delete delete delete A liquid crystal display panel including a plurality of scan lines for transmitting a scan signal, a plurality of data lines insulated from and intersecting the scan lines, and a plurality of pixels formed in a region surrounded by the scan lines and data lines and arranged in a matrix form; A temperature sensor for sensing a temperature of the liquid crystal display panel or an ambient temperature of the liquid crystal display panel; A timing controller generating and outputting a control signal corresponding to the sensed temperature; A light source sequentially outputting light of red, green, and blue in the red field, the green field, and the blue field, respectively; The data waveform is generated at the first frequency when the detected temperature is less than the reference temperature according to the control signal of the timing controller. The data waveform is generated at the second frequency higher than the first frequency when the detected temperature is above the reference temperature. A data driver to feed the line; And The common voltage waveform is generated at the first frequency when the detected temperature is less than the reference temperature according to the control signal of the timing controller. The common voltage waveform is generated at the second frequency higher than the first frequency when the detected temperature is greater than the reference temperature. And a common voltage generator supplying the common electrode. The method of claim 5, The reference temperature is a liquid crystal display, characterized in that the temperature between -5 ℃ to 5 ℃. The method of claim 5, The second frequency is 60 ~ 75Hz characterized in that the liquid crystal display device. delete

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