KR101818467B1 - Driving apparatus for liquid crystal display device and method for driving the same - Google Patents

Abstract

The present invention relates to a driving apparatus for a liquid crystal display device and a driving method thereof, which can prevent a sudden change in current amount of a swinging common current when applying a common voltage swing method, thereby further improving power consumption reduction effect. A liquid crystal panel for displaying an image; A data driver for driving data lines of the liquid crystal panel; A gate driver for driving gate lines of the liquid crystal panel; A timing controller for aligning image data input from the outside and supplying the data to the data driver and generating a gate data control signal to control the gate and the data driver; And a common voltage supply circuit for generating a common voltage swinging in at least one horizontal line or at least one frame unit by pre-charging for a predetermined period and supplying the generated common voltage to the common voltage supply line of the liquid crystal panel And a second electrode.

Description

Technical Field [0001] The present invention relates to a driving apparatus for a liquid crystal display,

The present invention relates to a liquid crystal display device, and more particularly, to a driving device and a driving method thereof for a liquid crystal display device which can prevent a sudden change in current amount of a swinging common voltage when a common voltage swing mode is applied, .

A liquid crystal display device displays an image using electrical and optical characteristics of a liquid crystal. Liquid crystals can have different anisotropic properties depending on the molecular axis and the direction of the short axis, such as refractive index and dielectric constant, and can easily control the molecular arrangement and optical properties. A liquid crystal display device using the same displays an image by changing the alignment direction of liquid crystal molecules according to the electric field size and adjusting the light transmittance transmitted through the polarizing plate.

The liquid crystal display device includes a liquid crystal panel in which a plurality of pixels are arranged in a matrix form, a gate driver for driving gate lines of the liquid crystal panel, and a data driver for driving the data lines of the liquid crystal panel.

In the liquid crystal display, an inversion driving method such as a frame inversion system, a line inversion system, and a dot inversion system is used to drive pixels of a liquid crystal panel . Among such inversion driving methods, the frame and line inversion methods can further reduce the power consumption as compared with the dot inversion method, and in the case of the dot inversion method, the image with higher image quality .

In recent years, the common voltage (Vcom) level supplied to each pixel of the liquid crystal panel is swinged in a line-inversion or a frame-inversion manner while a line inversion or a frame inversion method is applied to reduce power consumption, .

However, at the swing supply of the common voltage Vcom, since the swing width of the common voltage varies from full to minimum at the minimum level, the variation width of the current amount of the swinging common voltage has to be changed rapidly. The power consumption also increases if the common voltage level is dynamically variable even though the common voltage level is variable by at least one line unit or a short period unit of at least one frame. Therefore, although the common voltage swing method is applied to reduce the power consumption, there is a problem that the reduction effect is halved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems and it is an object of the present invention to provide a liquid crystal display device capable of preventing a sudden change in current amount of a swinging common voltage when applying a common voltage swing method, And an object of the present invention is to provide a device and a driving method thereof.

According to an aspect of the present invention, there is provided an apparatus for driving a liquid crystal display, including: a liquid crystal panel having a plurality of pixels to display an image; A data driver for driving data lines of the liquid crystal panel; A gate driver for driving gate lines of the liquid crystal panel; A timing controller for aligning image data input from the outside and supplying the data to the data driver and generating a gate data control signal to control the gate and the data driver; And a common voltage supply circuit for generating a common voltage swinging in at least one horizontal line or at least one frame unit by pre-charging for a predetermined period and supplying the generated common voltage to the common voltage supply line of the liquid crystal panel And a second electrode.

The common voltage supply unit is configured in a rail-to-rail manner between a high potential voltage source and a low potential voltage source, and outputs positive and negative selection signals to the positive and negative selection signal output terminals, respectively An operational amplifier circuit which is connected to positive and negative selection signal output terminals of the operational amplifier circuit and supplies positive and negative precharge voltages to the positive and negative selection signal output terminals during the predetermined period, 1 and the second switching element and the level of the common voltage according to the positive and negative selection signal levels formed between the high potential voltage source and the low potential voltage source and output from the positive and negative selection signal output terminals And a plurality of output switching elements for outputting the plurality of output switching elements.

Wherein the operational amplifier circuit includes a positive polarity operational amplifier circuit and a negative polarity operational amplifier circuit which are arranged in parallel between the high potential voltage source and the low potential voltage source and the positive polarity operational amplifier circuit is adapted to swing at a predetermined positive voltage level and a reference voltage level And the negative polarity operational amplifier circuit generates a negative selection signal to swing at a predetermined negative voltage level and the reference voltage level in the same phase as the positive polarity selection signal do.

Wherein the positive voltage level of the positive selection signal is equal to the positive voltage level of the swinging common voltage and the negative voltage level of the negative selection signal is generated equal to the negative voltage level of the swinging common voltage And the selection signal of the positive polarity and the negative polarity is used as the swing common voltage.

Wherein each of the first and second switching elements is turned on during any one of 0.5us to 2.0us during a period in which the voltage levels of the positive and negative selection signals are varied to the positive or negative voltage level or the reference voltage level And the positive and negative precharge voltages are supplied to the positive and negative selection signal output terminals, respectively.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display, including: driving a gate and a data line of a liquid crystal panel; Controlling a gate and a data driver to generate a gate data control signal to drive the gate and data lines; And generating a common voltage swinging in at least one horizontal line or at least one frame unit by pre-charging for a predetermined period, and supplying the generated common voltage to a common voltage supply line of the liquid crystal panel.

The common voltage supply step may include a positive-polarity and negative-polarity selection signal output terminal using an operational amplifier circuit configured in a rail-to-rail manner between a high potential voltage source and a low potential voltage source, And outputting the selection signals to the positive and negative selection signal output terminals during the predetermined period using the first and second switching elements respectively connected to the positive and negative selection signal output terminals of the operational amplifier circuit. And a plurality of output switching elements formed between the high potential voltage source and the low potential voltage source to supply the positive polarity and negative polarity output voltages to the positive polarity and negative polarity output terminals, And outputting the level of the common voltage to be swung according to the polarity selection signal level .

Wherein the step of outputting the positive polarity and negative polarity selection signals comprises using a positive polarity and a negative polarity amplification circuit configured in parallel between the high potential voltage source and the low potential voltage source, A positive polarity selection signal is generated so as to swing at a positive polarity voltage level and a reference voltage level and a positive polarity voltage level and a negative polarity voltage level which are preset to the same phase as the positive polarity selection signal And generates a selection signal having a negative polarity to swing.

Wherein the positive voltage level of the positive selection signal is equal to the positive voltage level of the swinging common voltage and the negative voltage level of the negative selection signal is generated equal to the negative voltage level of the swinging common voltage And the selection signal of the positive polarity and the negative polarity is used as the swing common voltage.

The step of supplying the positive and negative precharging voltages to the positive and negative selection signal output stages may include supplying the positive and negative selection signals with the positive or negative voltage level or the reference voltage The positive and negative precharge voltages are supplied to the positive and negative selection signal output terminals during a period of 0.5us to 2.0us,

The driving device and the driving method of the liquid crystal display device according to the embodiments of the present invention having various technical features as described above can prevent a sudden change in the amount of current of the swinging common voltage when the common voltage swing mode of the liquid crystal display panel is applied, The effect can be further improved.

1 is a block diagram schematically showing a driving apparatus for a liquid crystal display according to an embodiment of the present invention.
FIG. 2 is a circuit diagram specifically showing the common voltage supply unit of FIG. 1; FIG.
FIG. 3 is a waveform diagram showing positive and negative selection signals output to the positive and negative selection signal output terminals of FIG. 2; FIG.
Fig. 4 is a circuit diagram specifically showing the positive polarity operational amplifier circuit of Fig. 2; Fig.
Fig. 5 is a waveform diagram of another example output from the positive polarity operational amplifier circuit of Fig. 4; Fig.

Hereinafter, a driving apparatus and a driving method of a liquid crystal display according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram schematically showing a driving apparatus for a liquid crystal display according to an embodiment of the present invention.

The driving apparatus of the liquid crystal display shown in FIG. 1 includes a liquid crystal panel 2 having a plurality of pixels and displaying an image; A data driver 4 for driving the data lines DL1 to DLm of the liquid crystal panel 3; A gate driver 6 for driving the gate lines GL1 to GLn of the liquid crystal panel; A timing controller 8 for aligning image data RGB inputted from outside and supplying the data to the data driver 4 and generating a gate data control signal to control the data driver 4 and the gate driver 6; And a common voltage SVcom swinging in at least one horizontal line or at least one frame unit by pre-charging for a preset period of time and supplies the generated common voltage Vcom to the common terminal of the liquid crystal panel 2 And a common voltage supply unit 10 for supplying the voltage to the voltage supply line.

The liquid crystal panel 2 includes a thin film transistor (TFT) formed in each pixel region defined by a plurality of gate lines GL1 to GLn and a plurality of data lines DL1 to DLm, and a liquid crystal capacitor (Clc). The liquid crystal capacitor Clc is composed of a pixel electrode connected to the TFT, and a common electrode facing the pixel electrode and the liquid crystal. Here, the common electrode is integrally formed with a common voltage supply line formed in at least one horizontal line or frame unit. The TFT supplies data signals from the data lines DL1 to DLm to the pixel electrodes in response to a scan pulse from the gate lines GL1 to GLn, that is, a gate-on signal. The liquid crystal capacitor Clc charges the difference voltage between the data signal supplied to the pixel electrode and the common voltage supplied to the common electrode, and adjusts the light transmittance by varying the arrangement of the liquid crystal molecules according to the difference voltage. The storage capacitor Cst is connected in parallel to the liquid crystal capacitor Clc so that the voltage charged in the liquid crystal capacitor Clc is maintained until the next data signal is supplied. The storage capacitor Cst is formed by overlapping the pixel electrode with the previous gate line and the insulating film interposed therebetween. Alternatively, the storage capacitor Cst may be formed by overlapping the pixel electrode with the storage line and the insulating film interposed therebetween.

The data driver 4 is composed of at least one data integrated circuit (IC) and receives a data control signal DCS from the timing controller 8, for example, a source start signal SSP (Source Start Pulse) An analog data signal is supplied to each data line DL1 to DLm by using a shift clock (SSC), a source output enable (SOE) signal or the like. In other words, each of the at least one data IC latches the digital image data input according to the SSC, and then converts the digital image data Data into an analog data signal. Then, each of the gate lines GL1 through GLn, A data signal for one horizontal line is supplied to each data line DL1 to DLm for every one horizontal period in which a scan pulse is supplied. At this time, the data driver 4 selects a gamma voltage having a predetermined level according to the gray level value of the digital image data Data, and supplies the selected gamma voltage to each of the data lines DL1 to DLm as a data signal.

The gate driver 6 is constituted by at least one data integrated circuit (IC) and includes a gate control signal GCS from the timing controller 8, for example, a gate start signal (GSP) A scan pulse or a gate low voltage is supplied to each of the gate lines GL1 to GLn by using a shift clock (GSC) and a gate output enable (GOE) signal or the like. Each of the at least one gate IC sequentially supplies a scan pulse (or a gate-on voltage) to each of the gate lines GL1 to GLn of the liquid crystal panel 2 while a gate low voltage , Gate-off voltage).

The timing controller 8 arranges image data (RGB) from the outside so as to be suitable for driving the liquid crystal panel 2 and supplies it to the data driver 4. [ A gate control signal GCS and a data control signal DCS are generated using external synchronous signals DCLK, DE, Hsync and Vsync to control the data driver 4 and the gate driver 6 respectively do.

The common voltage supply unit 10 generates the common voltage SVcom so as to swing at least one horizontal line or at least one frame unit in accordance with the inversion method of the liquid crystal panel 2. [ And is precharged to a pre-charging voltage for a predetermined period preset during a period in which the common voltage SVom is supplied to the common voltage supply line in at least one horizontal line or at least one frame unit.

2 is a circuit diagram specifically showing the common voltage supply unit of FIG.

The common voltage supply unit 10 shown in FIG. 2 is constructed in a rail-to-rail manner between a high potential voltage source VDD and a low potential voltage source GND, An operational amplifier circuit 20 for outputting selection signals of positive and negative polarity respectively to the positive and negative selection signal output terminals of the operational amplifier circuit 20, First and second switching elements SW1 and SW2 for supplying positive and negative precharging voltages P-PCV and N-PCV to the selection signal output terminals, respectively, and high and low potential power sources VDD and VDD, And a plurality of output switching elements PTr and NTr formed between the first and second output terminals GND and GND to swing the level of the common voltage SVcom according to the positive and negative selection signal levels output from the positive and negative selection signal output terminals, Respectively.

The operational amplifier circuit 20 includes positive and negative polarity operational amplifying circuits 22 and 24 formed in parallel between a high potential voltage source VDD and a low potential voltage source GND and includes positive and negative polarity operational amplifying circuits 22 and 24 respectively generate positive and negative selection signals according to the input voltage VIn and the high and low potential voltage sources VDD and GND, respectively. Then, the generated positive and negative selection signals are output to the positive and negative selection signal output terminals, respectively. Specifically, the positive polarity operational amplifier circuit 22 generates a negative polarity selection signal to swing at a predetermined positive voltage level and a reference voltage level, and the negative polarity operational amplifier circuit 24 has the same phase as the positive polarity selection signal And generates a negative selection signal to swing to a predetermined negative voltage level and a reference voltage level.

The positive and negative selection signals are generated so as to swing with the common voltage level of the positive and negative polarities and the reference voltage level, respectively, and can be used as the common voltage of the positive polarity and the negative polarity. In particular, the positive voltage level of the positive selection signal is equal to the positive voltage level of the swinging common voltage, and the negative voltage level of the negative selection signal is generated equal to the negative voltage level of the swinging common voltage, The positive and negative selection signals can be used as a common voltage swinging.

Each of the first and second switching elements SW1 and SW2 is connected to the selection signal output terminal of each of the positive and negative operational amplification circuits 22 and 24. [ Then, the positive and negative precharge voltages (P-PCV, N-PCV) are respectively supplied to the positive and negative selection signal output terminals during a predetermined period of time, for example, 0.5us to 2.0us Supply. At this time, each of the first and second switching elements SW1 and SW2 is turned on in response to a turn-on signal supplied for a predetermined period of time during at least one horizontal line or at least one frame period, (P-PCV, N-PCV) are supplied to the positive and negative selection signal output terminals, respectively.

The positive precharging voltage (P-PCV) may be preset to any voltage level between the positive common voltage level and the intermediate voltage level, and the negative precharging voltage (N-PCV) may be set to the negative common voltage level And the intermediate voltage level. For example, the common voltage of positive polarity may be 12V, the intermediate voltage may be 6V, and the common voltage of negative polarity may be 0V.

Each of the output switching elements PTr and NTr is constituted by a positive output switching element PTr and a negative output switching element NTr respectively and the positive output switching element PTr and the negative output switching element NTr are constituted by a classical And is connected in parallel between the upper voltage source (VDD) and the lower voltage source (GND). The positive output switching element PTr and the negative output switching element NTr respond to the positive and negative selection signal levels respectively supplied from the positive and negative selection signal output terminals, And outputs the common voltage SVcom.

3 is a waveform diagram showing positive and negative selection signals output to the positive and negative selection signal output terminals of FIG.

3, a positive selection signal is output to the positive selection signal output terminal so as to swing to a predetermined positive voltage level and a reference voltage level, and a negative selection signal is output to the positive selection signal output terminal in the same phase as the positive selection signal output A negative selection signal is outputted so as to swing to the set negative voltage level and the reference voltage level. At this time, each of the first and second switching devices SW1 and SW2 supplies the positive and negative precharge voltages P-PCV, N (N-1) and N-2, respectively, during a predetermined period of time during which the voltage levels of the positive- -PCV) are supplied to the positive and negative selection signal output terminals, respectively. In this case, as shown in the following Table 1, it is possible to prevent a sudden change in the amount of current of the positive and negative selection signals during a period in which the voltage level is variable.

In addition, it is possible to prevent a sudden change in current amount of the common voltage SVcom swinging at the positive and negative polarity levels generated by the rapid change of the amount of current of the positive and negative selection signals.

4 is a circuit diagram specifically showing the positive polarity operational amplifier circuit of FIG.

The positive polarity operational amplifier circuit 22 shown in FIG. 4 includes an operational amplifier which receives an input voltage VIn and a high potential voltage source VDD as inverted and non-inverted input terminals, a stabilizer for feeding back the output signal, An output section for outputting the positive selection signal through the switching element of the positive selection signal, and a waveform generating section for setting the output waveform of the positive selection signal to be output.

The operational amplifier outputs a positive control signal in accordance with the input voltage VIn and the high potential source VDD input through the inverting and noninverting terminals, and the switching elements of the output section output the control voltage And outputs a positive polarity selection signal to the output terminal so that the level swings. At this time, the output waveform of the positive selection signal outputted to the output terminal may be gradually changed by at least one capacitor connected to the output terminal.

The negative polarity operational amplifier circuit 24 may also be constructed in the same manner as the positive polarity operational amplifier circuit 22 except that the low potential and high potential voltage sources are connected in reverse to the positive polarity operational amplifier circuit 22.

On the other hand, the positive and negative selection signals output from the positive and negative operational amplification circuits 22 and 24 may be directly used as a common voltage as described above. In this case, as shown in FIG. 5, the common voltages of the positive polarity and the negative polarity may be generated so as to be inverted in units of at least one frame and selectively used in at least one frame unit. As described above, by using the positive polarity and negative polarity operational amplifier circuits 22 and 24, a common voltage whose voltage level is gradually changed can be generated in units of odd and even frames.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Will be clear to those who have knowledge of.

Claims (10)

A liquid crystal panel having a plurality of pixels to display an image;
A data driver for driving data lines of the liquid crystal panel;
A gate driver for driving gate lines of the liquid crystal panel;
A timing controller for aligning image data input from the outside and supplying the data to the data driver and generating a gate data control signal to control the gate and the data driver; And
Charging a common voltage swinging in at least one horizontal line or at least one frame unit by supplying a precharging voltage having a positive polarity or a negative polarity for a predetermined period of time and outputting the generated common voltage to the liquid crystal display And a common voltage supply unit for supplying the common voltage supply line of the panel,
Wherein the positive precharge voltage is preset to a voltage level between a positive common voltage level and an intermediate voltage level and the negative precharge voltage is either a negative common voltage level or an intermediate voltage level And the voltage level is set in advance. The method according to claim 1,
The common voltage supply unit
An operational amplifier circuit which is configured in a rail-to-rail manner between a high potential voltage source and a low potential voltage source and which outputs positive and negative selection signals at positive and negative selection signal output terminals,
A first and a second output terminal connected respectively to the positive and negative selection signal output terminals of the operational amplifier circuit for supplying the positive and negative precharge voltages to the positive and negative selection signal output terminals during the predetermined period, A switching element, and
And a plurality of output switching elements which are formed between the high potential voltage source and the low potential voltage source and output the level of the common voltage according to the positive and negative selection signal levels output from the positive and negative selection signal output terminals, And a driving circuit for driving the liquid crystal display device. 3. The method of claim 2,
The operational amplifier circuit
And a positive polarity and a negative polarity operational amplifier circuit configured in parallel between the high potential voltage source and the low potential voltage source,
The positive polarity operational amplifier circuit generates a positive selection signal to swing at a predetermined positive voltage level and a reference voltage level,
Wherein the negative polarity operational amplifier circuit generates a negative selection signal to swing at a predetermined negative voltage level and the reference voltage level in the same phase as the positive selection signal. The method of claim 3,
The positive voltage level of the positive selection signal
And the negative polarity voltage level of the negative selection signal is generated to be equal to the negative polarity voltage level of the swinging common voltage so that the positive polarity and negative polarity selection signals are generated Wherein the common voltage is used as the common voltage swinging. The method of claim 3,
Each of the first and second switching elements
Wherein the positive and negative polarity precharge voltages are set to a positive polarity and a negative polarity for a period of 0.5us to 2.0us during a period in which the voltage levels of the positive and negative selection signals are varied to the positive or negative voltage level or the reference voltage level, To the positive polarity and negative polarity signal output terminals, respectively. Driving the gate and data lines of the liquid crystal panel, respectively;
Controlling a gate and a data driver to generate a gate data control signal to drive the gate and data lines; And
Charging a common voltage swinging in at least one horizontal line or at least one frame unit by supplying a precharging voltage having a positive polarity or a negative polarity for a predetermined period of time and outputting the generated common voltage to the liquid crystal display To a common voltage supply line of the panel,
Wherein the positive precharge voltage is preset to a voltage level between a positive common voltage level and an intermediate voltage level and the negative precharge voltage is either a negative common voltage level or an intermediate voltage level Wherein the voltage level is set in advance. The method according to claim 6,
The common voltage supply step
A positive and negative selection signal is output to the positive and negative selection signal output terminals using an operational amplifier circuit configured in a rail-to-rail manner between the high potential voltage source and the low potential voltage source step,
The first and second switching elements respectively connected to the positive and negative selection signal output terminals of the operational amplifier circuit are used to output positive and negative precharge voltages Respectively, and
The level of the common voltage is swung according to the positive and negative selection signal levels output from the positive and negative selection signal output terminals using a plurality of output switching elements formed between the high potential voltage source and the low potential voltage source And outputting the driving signal to the liquid crystal display device. 8. The method of claim 7,
The step of outputting the positive polarity and negative polarity selection signals, respectively,
A positive polarity and a negative polarity operational amplifier circuit configured in parallel between the high potential voltage source and the low potential voltage source are used,
A positive selection signal is generated so as to swing at a predetermined positive voltage level and a reference voltage level using the positive polarity operational amplifier circuit,
Wherein the negative polarity operational amplifier circuit generates a positive polarity voltage signal having the same phase as that of the positive polarity selection signal and a negative polarity selection signal for swinging at the reference voltage level, Way. 9. The method of claim 8,
The positive voltage level of the positive selection signal
And the negative polarity voltage level of the negative selection signal is generated to be equal to the negative polarity voltage level of the swinging common voltage so that the positive polarity and negative polarity selection signals are generated Wherein the common voltage is used as the common voltage swinging. 9. The method of claim 8,
Supplying the positive and negative precharging voltages to the positive and negative selection signal output terminals, respectively,
Wherein the positive and negative polarity precharge voltages are set to a positive polarity and a negative polarity for a period of 0.5us to 2.0us during a period in which the voltage levels of the positive and negative selection signals are varied to the positive or negative voltage level or the reference voltage level, Are supplied to the positive and negative selection signal output terminals, respectively.

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