KR100212289B1 - Liquid crystal display device and driving circuit to select one of line conversion driving or dot conversion driving - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data driving circuit of a thin film transistor liquid crystal display (TFT LCD), and includes an inversion selection circuit in a conventional single bank dot inversion driving circuit to drive line inversion. And a configuration of a drive circuit capable of selecting dot inversion driving.

In addition, when the above driving circuit is applied to the liquid crystal display device for a dual bank, the inverting selection signal is selected as the line inversion and the polarities of the output voltages of the upper driving circuit and the lower driving circuit are reversed. The dual bank liquid crystal display device of the dot inversion driving can be realized by applying to.

Since the driving circuit can apply a plurality of driving schemes, the use range is extended, and there is a cost reduction effect compared to the development of individual driving circuits separately.

Description

Liquid crystal display and drive circuit with selectable line inversion or dot inversion drive

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit of a thin film transistor liquid crystal display (TFT LCD), and more particularly to a data driving output stage configuration.

The data driving method of the liquid crystal display may be classified into a frame rate inversion, a line rate inversion, and a dot inversion according to a change in polarity relative to the opposite electrode voltage of the pixel voltage. The dot inversion driving method which is easy to suppress flicker phenomenon is mainly applied. In addition, the data driving circuit is arranged in a dual bank method in which most driving circuits are disposed above and below the panel to cross each other at the upper and lower sides of the signal line, and a single bank method in which the driving circuit is attached and driven to only one side of the panel. Separate. The dual bank driving method has a strong advantage against electromagnetic interference (EMI) and noise by lowering the operating frequency of the signal. The single bank method has a disadvantage of increasing the operating frequency, but it is easy to miniaturize by reducing the area occupied by the driving circuit. There is this.

1 illustrates a conventional 5-volt horizontal line inversion drive circuit. The digital image signal is input to a shift register 11 in synchronization with a shift clock (not shown), and then output to a level shifter 12 for high voltage driving. Analog voltages V (+) and V (−) are applied via bus lines L1 and L2. The analog voltage selection signal VSL turns on or off the switches S1 and S2 according to the output levels of the inverter G1 and the buffer G2, thereby providing an analog voltage V (+). Or V (−) is selected and applied to the conversion switch stage 13. The conversion switch stage 13 converts the digital image signal output from the level shifter 12 into a corresponding analog voltage and outputs it. The selected analog voltage is controlled by the output control signal OE in the output circuit 14 and is converted into respective output voltages O ₁ , O _2, O ₂ ... O _n to drive the panel. The output control signal OE is applied via line L3.

Here, the analog voltages V (+) and V (−) are applied to the bus lines L1 and L2 with the polarity reversed by one gate line period by the horizontal synchronization signal. Therefore, the polarities of the pixel applied voltages corresponding to the neighboring gate lines are applied differently. In addition, in order to eliminate the deterioration of the characteristics of the liquid crystal, the polarity of the pixel voltage is applied to the voltage of the counter electrode every frame.

The configuration of a single bank liquid crystal panel driven by applying this method is shown in FIG. The vertical lines are data lines I ₁ , I ₂ , ... I _n and the horizontal lines are gate lines J ₁ , J ₂ ... J _n , and each of the data lines I ₁ , I ₂ ,. .. Each pixel formed at the intersection of I _n ) and the gate lines J ₁ , J ₂ ... J _n includes a TFT, a pixel electrode Clc made of a liquid crystal capacitor, and a storage capacitor ( storage capacitor (Cst). As illustrated, the pixel electrode Clc is driven by a voltage whose polarity is inverted in a horizontal line period. Such a driving method has a problem in that distortion of a signal increases due to an increase in resistance and capacity when the panel is enlarged, thereby degrading image quality.

FIG. 3 illustrates a conventional single bank dot inversion driving circuit, in which components having the same contents as those in FIG. 1 are denoted by the same symbols and have the same function. As shown in Fig. 3, the analog voltage selection signal VSL is applied to the inputs of the inverter G1 and the buffer G2, and a plurality of analog switches (connected to the bus lines L1 and L2 according to the output level) 31 are turned on or off to select analog voltages V (+) and V (−) input through bus lines L1 and L2. The output levels of the inverter G1 and the buffer G2 are always opposite to each other and are applied to the plurality of analog switches 31 connected to the bus lines L1 and L2. Therefore, the digital image signals P ₁ , P ₂ ... P _n output from the level shifter are converted into analog voltages in which odd and even columns have opposite polarities and are output.

The configuration of the liquid crystal panel for a single bank driven by applying this method is shown in FIG. 4, and the components having the same contents as those in FIG. 2 are denoted by the same symbols. As shown in Fig. 4, the polarities of the voltages are reversed in one pixel period so that the polarities are driven differently in a mosaic shape.

As the high resolution and large area of the liquid crystal display device are gradually required, the single bank dot inversion driving method is difficult to apply due to the problem of electromagnetic interference or noise as the driving frequency increases. In order to solve this problem, it is possible to reduce the driving frequency by applying the dual bank dot inversion driving method. However, since the conventional technology requires a dedicated driving circuit only for the driving method, development and manufacturing costs are added and there is no general purpose.

Alternatively, the conventional single bank dot inversion driving circuit may be applied to the liquid crystal panel for the dual bank, the configuration of which is illustrated in FIG. 5 and the same components as those of FIG. As shown in FIG. 5, the pixel applied voltage has the same polarity every two lines along the vertical line. At this time, the pixel voltage is distorted by the parasitic capacitance Co between the data lines I ₁ , I ₂ , I ₃ , ... and the pixel electrode Clc. Since the sizes of the parasitic capacitance Co of the portions having different polarities from Co) are different from each other, the amount of distortion of the pixel voltage due to the capacitance also changes. As a result, uneven luminance occurs along the vertical line of the liquid crystal display.

This invention is derived from the above technical background, and is developed by designing a driving circuit capable of selecting one of line inversion and dot inversion driving, and applying a dot inversion method to both a single bank or dual bank liquid crystal panel. It is to reduce the burden of manufacturing cost and to expand the application range of the driving circuit.

1 is a configuration diagram of an output terminal of a conventional 5 volt line inversion driving circuit,

FIG. 2 is a configuration diagram of a liquid crystal panel for a single bank to which the driving method of FIG. 1 is applied.

3 is a configuration diagram of a conventional single bank dot inversion driving circuit,

4 is a configuration diagram of a liquid crystal panel for a single bank to which the driving method of FIG. 3 is applied.

5 is a configuration diagram of a liquid crystal panel for a dual bank to which a conventional single bank dot inversion driving circuit is applied.

6 is a configuration diagram of a data driving circuit capable of selecting one of line inversion and dot inversion according to the present invention;

7 is a configuration diagram of a liquid crystal panel for dual bank dot inversion by the driving circuit of FIG. 6.

As a means for achieving the above object, a data driving circuit for a liquid crystal display according to the present invention includes a shift register circuit for storing and outputting a digital image signal in synchronization with a shift clock, and a digital image signal output from the shift register at a high voltage. A level shifter circuit for converting a voltage level to drive a voltage; an inverted selection circuit for selecting one of a dot inversion and a line inversion for driving the liquid crystal panel; and a plurality of analogs turned on or off by the output of the inverting selection circuit. Switch, two bus lines connected to the plurality of analog switches for inputting an external analog voltage, and a voltage input through a bus line selected by the analog switches corresponds to a digital image signal output from a level shifter. Many to convert to value These current amplified voltage by the conversion of the switch and the mode switch to an output circuit which outputs the actual panel.

The data driving circuit for the liquid crystal display device adds an inversion selection circuit to the conventional single bank dot inversion driving circuit so that not only dot inversion but also line inversion driving is possible. The dual bank liquid crystal panel may be driven by dot inversion by inputting an inversion selection signal of the inversion selection circuit into a line inversion and applying a voltage to the pixel with a different output voltage polarity of the upper driving circuit and an output voltage polarity of the lower driving circuit. Can be. As a dual bank dot inversion driving circuit having a low driving frequency is realized, it can be applied to a liquid crystal display element of a high resolution large screen.

Referring to the accompanying drawings, preferred embodiments that can easily implement this invention by the above configuration are as follows.

First, an embodiment of the present invention will be described with reference to FIG. 6 and Table 1 below.

6 illustrates a configuration of a driving circuit of a liquid crystal panel in which one of line inversion and dot inversion according to the present invention can be selected. Components having the same contents as those in FIG. Table 1 shows the polarities of the output voltages O ₁ , O ₂ ... O _n according to the inversion selection signal ISL and the analog voltage selection signal VSL.

As shown in FIG. 6, the driving circuit according to the present invention takes an inverting selection signal ISL and an analog voltage selection signal VSL as inputs, an inverter G1, a buffer G2, and an exclusive OR. It is a drive circuit which can select either a dot inversion or a line inversion by including the inversion selection circuit 61 comprised from the gate G3.

First, in the case of applying the dot inversion driving voltage, the inversion selection signal ISL is given at a low level. The analog voltage selection signal VSL is changed in level by the inverter G1 and input to the exclusive OR gate G3, and its output OUT1 is output at the same level as the output level of the inverter G1. Accordingly, the levels of the output OUT1 and the output OUT2 are opposite to each other to selectively operate the plurality of analog switches 31 connected to the bus lines L1 and L2. Accordingly, the image signals P ₁ , P ₂ ... P _n output from the level shifter 12 are converted into analog voltages in which odd columns and even columns have opposite polarities. The converted image signal is applied to the liquid crystal panel by the output control signal OE, thereby driving the dot inversion method in which the polarity of the voltage is inverted in one pixel period as shown in FIG.

In the case of the line inversion driving, the inversion selection signal ISL is given at a high level. The analog voltage selection signal VSL is changed in level by the inverter G1 and input to the exclusive OR gate G3, and its output OUT1 is output at a level opposite to the output level of the inverter G1. Accordingly, the levels of the output OUT1 and the output OUT2 have the same level and selectively operate the plurality of analog switches 31 connected to the bus lines L1 and L2. Accordingly, the image signals P ₁ , P ₂ ... P _n output from the level shifter 12 are converted into analog voltages in which odd columns and even columns have the same polarity.

The image signal thus converted is applied to the liquid crystal panel by the output control signal OE, thereby realizing the driving of the line inversion method in which the polarity of the voltage is inverted in the horizontal line period as shown in FIG.

6 output voltage polarity control signal and output voltage polarity Invert selection input (ISL) Analog voltage selection signal (VSL) Output voltage polarity Even lines (O ₂ , O _4, O ₆ ... O _n ) Odd lines (O ₁ , O _3, O ₅ ... O _n-1 ) H H V (+) V (-) L V (-) V (+) L H V (+) V (+) L V (-) V (-)

The above driving circuit can be driven by dot inversion even in a liquid crystal panel for dual banks. FIG. 7 is a configuration diagram of a liquid crystal panel for a dual bank when the line inversion driving method is selected in FIG. 6 and the output voltage polarities of the upper data driving circuit and the lower data driving circuit are reversed and applied. FIG. It is marked with the same symbol.

In order to perform the dual bank dot inversion driving with the above-described driving circuit, the inversion selection signal ISL is applied at a high level so that the line inversion is selected, and thus the image signals P ₁ and P ₂ output from the level shifter 12 are selected. .. P _n ) is outputted by converting odd and even columns into analog voltages with the same polarity. In FIG. 7, when the first gate line J ₁ is selected, the applied voltages of the upper data lines I ₁ , I ₃ ... Are applied to the pixel with positive polarity and the lower data lines I ₂ , I ₄ . Is applied to the pixel with negative polarity. When the next gate line J ₂ is selected, the polarities of the output voltages O ₁ , O ₂ ... O _n are reversed and applied, so that voltages having different polarities are applied to each adjacent pixel as shown in FIG. 7. do. The polarity of the pixel voltage is applied inverted every frame. Therefore, the dual bank dot inversion driving can be realized by the above driving circuit.

The data driving circuit configured as described above can apply both the line inversion method and the dot inversion method to both the single bank and the dual bank driving methods, thereby increasing the scope of application and reducing the cost compared to developing the individual driving circuits separately. Has the effect of.

Claims (4)

A shift register circuit for storing and outputting a digital image signal in synchronization with a shift clock, a level shifter circuit for converting a voltage level to drive the digital image signal output from the shift register at a high voltage, and a driving method of a liquid crystal panel using dot inversion or An inversion selection circuit for selecting one of line inversions, a plurality of analog switches turned on or off by an output of the inverting selection circuit, a bus line connected to the plurality of analog switches for inputting an external analog voltage, and A plurality of conversion switches for converting a voltage input through a bus line selected by a plurality of analog switches into a value corresponding to a digital image signal output from a level shifter and a voltage selected by the plurality of conversion switches as described above Amplify to real panel An output circuit to output, the liquid crystal display driving circuit. The inverter of claim 1, wherein the inverting selection circuit converts the level of the analog voltage selection signal, performs an exclusive OR operation using the inverting selection signal and the output signal of the inverter as inputs, and outputs the plurality of analogs. A drive circuit for a liquid crystal display device, comprising a buffer for applying an exclusive OR gate applied to a switch and a level of an analog voltage selection signal to the plurality of analog switches without conversion. A shift register circuit for storing and outputting a digital image signal in synchronization with a shift clock, a level shifter circuit for converting a voltage level to drive the digital image signal output from the shift register at a high voltage, and a driving method of a liquid crystal panel using dot inversion or An inversion selection circuit for selecting one of line inversions, a plurality of analog switches turned on or off by an output of the inverting selection circuit, a bus line connected to the plurality of analog switches for inputting an external analog voltage, and A plurality of conversion switches for converting the voltage input through the bus line selected by the plurality of analog switches into a value corresponding to the digital image signal output from the level shifter, the current selected by the plurality of conversion switches Amplify and output to the real panel And a plurality of data driving circuits including an output circuit, and a liquid crystal panel for dual banks, wherein the plurality of data driving circuits are disposed above and below the liquid crystal panel, and output voltages of the upper driving circuit and the lower driving circuit. The polarity of the polarity is applied to the pixel in reverse, the liquid crystal display device of the dot inversion driving method. 4. The liquid crystal display device according to claim 3, wherein the inversion selection signal input to the inversion selection circuit is selected by line driving.

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