KR20020065991A - A liquid crystal display device for thin film transistor - Google Patents

Abstract

PURPOSE: A liquid crystal display is provided to remove the flickering phenomenon and reduce the power consumption of a driving circuit in the improved dot inversion driving system for realizing a portable TFT-LCD. CONSTITUTION: A liquid crystal display includes a liquid crystal panel(100) including a plurality of gate lines for transmitting scanning signals, a plurality of data lines intersecting the gate lines and insulated from the gate lines for transmitting data voltages, and a plurality of pixels formed in the shape of matrix in areas surrounded by the gate and data lines and having switching elements connected to the gate and data lines, a scan driving part(200) for sequentially supplying gate driving signals to the gate lines for turning on or off the switching elements, a data driving part(300) for supplying gray level voltages to the data lines, and a driving control part(500) for applying a control signal to invert the liquid crystal charging polarity of the data voltages transmitted to the pixels via the data lines to pixel units in the longitudinal direction of 2N(N is an integer>=1).

Description

Liquid crystal display device {A LIQUID CRYSTAL DISPLAY DEVICE FOR THIN FILM TRANSISTOR}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor (hereinafter referred to as TFT) liquid crystal display (hereinafter referred to as LCD), and more particularly to a liquid crystal display device capable of improving flickering and power consumption. It is about.

TFT LCD displays image quality characteristics different from room temperature in high and low temperature environments due to the temperature characteristics of liquid crystal materials. This is because the transmittance of the liquid crystal material is changed due to the change in viscosity due to the change in temperature.

Currently, TFT LCDs which are generally used are driven by applying a range of voltages to a data line to which a liquid crystal can react based on a common voltage applied to a common electrode of a top plate. In order to prevent the liquid crystals from deteriorating as the liquid crystal continues to react in only one direction, an inversion driving method is applied to the data lines, in which data voltages that are positive and negative are repeated on the common voltage. As the inversion driving method, a line inversion driving method, a column inversion driving method, a dot inversion driving method, and the like are known.

Fig. 1 is a diagram showing the arrangement of the liquid crystal charge polarity by the normal dot inversion driving in the TFT LCD.

As shown in FIG. 1, the polarity of the liquid crystal charging by the general dot inversion driving is driven by inverting the polarity of the gray voltage to one pixel period so that the polarities are different from each other in a mosaic shape.

Currently, TFT LCDs are being developed at high definition and high resolution. Therefore, the time delay of 1H (one horizontal period) is reduced in line inversion driving and dot inversion driving, which causes a problem of RC delay in the data line. That is, in the line inversion driving and the dot inversion driving, a square wave signal having a large amplitude in a unit of 1H is applied to the data line, and the square wave signal is distorted due to the RC delay of the data line, resulting in a difference in charging rate between the top and bottom of the data line. By doing so, there is a problem in that a contrast ratio is lowered due to the difference in liquid crystal transmittance and flickering difference between the upper and lower sides is intensified.

In particular, when the TFT LCD adopting the dot inversion driving method is used in a window operating system (O / S), which is a general personal computer, the flickering phenomenon occurs severely on the window exit screen. This occurs when the inversion period in the dot inversion driving and the dot configuration in the end screen of the window coincide on the screen. Such flickering has a problem of making the user's eyes tired.

In order to solve such a problem, the technical problem to be achieved by the present invention is to provide a liquid crystal display device without a flickering phenomenon.

In addition, another object of the present invention is to reduce power consumption of a circuit driving a liquid crystal display due to the improved dot inversion driving scheme.

Fig. 1 is a diagram showing the arrangement of the liquid crystal charge polarity by the normal dot inversion driving in the TFT LCD.

2 is a block diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a diagram illustrating a polarity control signal generator according to an exemplary embodiment of the present invention.

4 is a timing diagram showing the output waveform of the liquid crystal charge electrode inversion portion.

5 is a view showing a portion of the liquid crystal charging electrode arrangement by the dot inversion driving according to an embodiment of the present invention.

According to one aspect of the present invention for achieving the above object,

A plurality of gate lines transferring scan signals, a plurality of data lines transferring data voltages and insulated from and intersecting the plurality of gate lines, and formed in an area surrounded by the gate lines and the data lines, respectively; A liquid crystal panel comprising a plurality of pixels arranged in a matrix form having a switching element connected to the liquid crystal panel;

A scan driver for sequentially supplying a gate driving signal for turning the switching element on or off to the gate line;

A data driver supplying a gray voltage to the data line; And

A driving controller for applying a control signal such that the polarity of the liquid crystal charging is inverted in units of vertical pixels having a data voltage of 2 ^N (N is an integer of 1 or more) through the data line;

It includes.

The driving controller includes N + 1 first flip-flops connected in series to output an output signal of a previous stage as a clock signal of a next stage, and receives a horizontal line start signal STH as a clock signal. It is preferable to output an inverted signal of.

The driving controller may further include a second flip-flop configured to receive and output a vertical line start signal STV as a clock signal; And an exclusive OR gate for receiving the output signal of the first flip-flop and the output signal of the second flip-flop and outputting a polarity control signal.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 2, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel (LCD panel) 100, a gate driving driver 200, a source driving driver 300, and a gray voltage. And a polarity control signal generator 500.

The LCD panel 100 includes a plurality of gate lines (not shown) and a plurality of data lines (not shown) that are insulated from and intersect the gate lines, and are surrounded by the gate lines and the data lines ( A plurality of TFTs are formed in each pixel. The gate electrode, the source electrode and the drain electrode of the TFT are respectively connected to a gate line, a data line, and a pixel electrode (not shown). A liquid crystal material is injected between the pixel electrode and the counter substrate on which the common electrode is formed. The liquid crystal material injected between the substrates may equivalently be represented by a liquid crystal capacitor.

The source driving driver 300, also called a data driving driver, serves to lower the voltage value transmitted to each pixel in the LCD panel 100 by one line. In more detail, the source driving driver 300 stores the digital data from the timing controller 500 to be described later in a shift register in the source driving driver 300 and then instructs the LCD panel 100 to lower the data. When (LOAD signal) comes, it selects a voltage corresponding to each data and serves to transfer this voltage into the LCD panel 100.

The gate driving driver 200 opens a road so that data from the source driving driver 300 can be transferred to the pixel. Each pixel of the LCD panel 100 is turned on or off by a TFT serving as a switch, which is turned on and off by applying a constant voltage (Von, Voff) to a gate. In this way, the Von voltage for turning on the gate and the Voff voltage for turning off the gate signal are generated by the Von Voff Vcom generator (not shown). The Von Voff Vcom generating section generates not only the Von and Voff voltages, but also the Vcom voltage which is a reference for the data voltage difference in the TFT.

The gray voltage generator 400 creates a gray voltage entering the source driving driver 300. The gray voltage generator 400 generates a gray voltage to be applied to the data line of the LCD panel 100 and sends a gray signal to the source driving driver 300. In general, gradation means light and dark color, and gradation voltage means voltage applied to the source electrode of the TFT, that is, the data line, to generate the gradation. In a color TFT LCD, the gradation is determined by the number of bits of red (R), green (G), and blue (G) data coming from the graphic controller.

The polarity control signal generation unit 500 includes a control signal for inverting the liquid crystal charging polarity in units of horizontal pixel lines having a data voltage of 2 ^N (N is an integer of 1 or more) transmitted through the data line, and one frame unit. Each time, a control signal for inverting the liquid crystal charging electrode property is applied to the source driving driver 300.

3 is a diagram illustrating a polarity control signal generator according to an exemplary embodiment of the present invention.

As shown in FIG. 3, the polarity control signal generator 500 is an STH that is a reference signal for accurately latching the R, G, and B data from the gray voltage generator 400 to the source driving driver 300. A first D flip-flop 510 that receives a signal (STart Horizontal, STH) as a clock signal and outputs a signal divided by two; A second D flip-flop 520 which receives an output signal Q1 of the first D flip-flop 510 as a clock signal and outputs a signal Q2 divided by two of the clock signals; A third D flip-flop 530 that receives the output signal Q2 of the second flip-flop 520 as a clock signal and outputs a signal Q3 divided by two of the clock signals; A fourth D flip-flop 540 which receives the output signal Q3 of the third flip-flop 530 as a clock signal and outputs a signal Q4 divided by two of the clock signal; A fifth D flip-flop 550 for receiving a STV signal, which is a reference signal for outputting a Von voltage, as a clock signal and outputting a processing result; An exclusive OR gate 560 is configured to receive the output signal Q4 of the fourth D flip flop and the output signal Q5 of the fifth flip flop to implement an exclusive OR.

The polarity control signal generator 500 inputs an STH signal to a clock signal of the first D flip-flop 510, and an output terminal of the first D flip-flop 510 is a clock input of the second D flip-flop 520. Connected to a stage, an output terminal of the second D flip-flop 520 is connected to a clock input terminal of the third D flip-flop 530, and an output terminal of the third D flip-flop 530 is connected to a fourth D flip-flop The inverted output terminal of each flip-flop 510, 520, 530, 540 is connected to the D input terminal of each flip-flop 510, 520, 530, 540. In addition, the STV signal is input to the clock signal of the fifth D flip-flop 550, and the inverted output terminal of the fifth flip flop 550 is connected to the D input terminal. The exclusive OR gate 560 receives an output terminal of the fourth D flip-flop 540 and an output terminal of the fifth flip flop 550, respectively, and outputs the result of the exclusive OR to the source driving driver 300.

Hereinafter, the operation of the liquid crystal display according to the exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

4 is a timing diagram illustrating an output waveform of the polarity control signal generation unit, and FIG. 5 is a view illustrating a part of the arrangement of the liquid crystal charging electrodes by dot inversion driving according to an exemplary embodiment of the present invention.

As shown in FIG. 4, when the STH signal is input as the clock signal of the first D flip-flop 510, the first D flip-flop 510 inverts the input signal every one period of STH, thereby inverting the signal every 1H (Q1). ) That is, the first D flip-flop 520 divides the input signal by two.

When the signal Q1 is input as a clock signal of the second D flip-flop 520, the second D flip-flop 520 receives the signal Q1 and outputs a signal Q2 that is inverted every 2H.

When the signal Q2 is input as the clock signal of the third D flip-flop 530, the third D flip-flop 530 obtains an output signal Q3 which is inverted every 4H, and the output signal Q3 is the fourth D. When the clock signal of the flip-flop 540 is input, an output signal Q4 that is inverted every 8H may be obtained. That is, in the inverted signal of the liquid crystal charging polarity, as shown in Fig. 5, one period of the horizontal pixel line is 2 ^{(N + 1)} (N is an integer of 1 or more).

Since the TFT LCD must invert the liquid crystal charging polarity every frame unit (1V time), a frame inversion signal is required. In this case, when the STV signal is input as the clock signal of the fifth D flip-flop 550, an output signal Q5 inverted every frame unit (1V time) may be obtained.

That is, when the output signal Q4 inverted every 8H and the output signal Q5 of the fifth D flip-flop 550 are used as the inputs of the exclusive OR gate 560, the fifth D flip-flop by the STV signal ( The output of the exclusive OR gate 560 is determined by the output signal Q5 of 550. In this case, when the output of the exclusive OR gate 560 is used as the frame unit inversion signal, the liquid crystal charging polarity is inverted every 8H, and the liquid crystal charging electrode characteristics are also inverted in every frame unit.

The inversion of the liquid crystal charging electrode may be performed to be inverted every 8H only with the output signal Q4 of the fourth flip-flop 540, but the present invention is not limited to the embodiment.

Such an inversion driving method can be used in the window operating system, which is the main use environment of the TFT LCD. That is, since the structure of the 'pattern editor' basically adopted in the window O / S is an 8 X 8 pixel matrix, the pattern editing following the liquid crystal charging polarity of the 16-line period cannot be performed. In addition, since the same pattern editing as the liquid crystal polarity arrangement of the 8H-VIM (Vertical Inversion Method) has no opportunity to be encountered in actual use, there is almost no chance of flickering compared to the conventional inversion driving method.

In addition, the output power consumption of the TFT LCD driving circuits 200 and 300 is proportional to f XCXV ² (f: square wave frequency, C: capacitance, V: applied voltage), but the frequency is lowered from 1 / 1H to 1 / 8H. Therefore, the output power consumption of the TFT LCD driving circuits 200 and 300 by the inversion driving method is lowered to 1/8.

Embodiment of the present invention is only one embodiment, and many variations and modifications to the components of the circuit for the liquid crystal charge electrode reversal within the scope not departing from the gist of the present invention, of course, the present invention embodiment It is not limited only to.

As described above, the liquid crystal display of the present invention can provide a liquid crystal display without flickering.

In addition, due to the improved dot inversion driving method, a portable TFT LCD having low power consumption can be realized by reducing power consumption of a circuit driving the liquid crystal display.

Claims (3)

A plurality of gate lines transferring scan signals, a plurality of data lines transferring data voltages and insulated from and intersecting the plurality of gate lines, and formed in an area surrounded by the gate lines and the data lines, respectively; A liquid crystal panel comprising a plurality of pixels arranged in a matrix form having a switching element connected to the liquid crystal panel; A scan driver for sequentially supplying a gate driving signal for turning the switching element on or off to the gate line; A data driver supplying a gray voltage to the data line; And A driving controller for applying a control signal such that the polarity of the liquid crystal charging is inverted in units of vertical pixels having a data voltage of 2 ^N (N is an integer of 1 or more) through the data line; Liquid crystal display comprising a. The method of claim 1, The drive control unit An output signal of the previous stage includes N + 1 first flip-flops connected in series to be input as a clock signal of the next stage, And a horizontal line start signal (STH) as a clock signal to output an inverted signal of the liquid crystal charging electrode. The method of claim 2, The drive control unit A second flip-flop that receives the vertical line start signal STV as a clock signal and outputs the clock signal; An exclusive OR gate for receiving the output signal of the first flip-flop and the output signal of the second flip-flop and outputting a polarity control signal. Liquid crystal display comprising a.