KR102113737B1 - Liquid crystal display device And a method of driving the same - Google Patents

Abstract

The present invention provides a gate and data wiring crossing each other to define a pixel region, and a liquid crystal panel in which a switching thin film transistor formed in each pixel region is formed; A gate and a data driver connected to the gate and data wiring inside the liquid crystal panel; A timing controller for applying a control signal and a data signal to the gate and data driver; A power supply unit applying a first driving voltage to the data driver; It includes a transformer circuit formed inside the data driver and an abnormal power-off prevention circuit, the transformer circuit outputs a second driving voltage, and the power-off prevention circuit is applied through the first driving voltage and the first resistor. Provided is a liquid crystal display device configured to perform a power-off prevention driving using a second driving voltage.

Description

Liquid crystal display device and its driving method

The present invention relates to a liquid crystal display device and a driving method thereof.

The liquid crystal display device (LCD), which is actively used in TVs, monitors, etc. because it is advantageous for moving picture display and has a large contrast ratio, is an optical anisotropy and polarization of liquid crystal. It shows the principle of image implementation.

This liquid crystal display device is a liquid crystal panel (liquid crystal panel) bonded by interposing a liquid crystal layer between two parallel substrates (substrate), and the electric field in the liquid crystal panel to change the arrangement direction of the liquid crystal molecules to realize the difference in transmittance do.

In order to change the alignment direction of the liquid crystal molecules, the liquid crystal display device generally displays an image by applying a control signal and a data signal to the liquid crystal panel through a gate and a data driver in the system interface.

At this time, the control signal applied to the gate driver to implement the narrow bezel is supplied through the data driver in the system interface.

In addition, the control signal and the data signal are applied from the gate and data driver to the switching thin film transistor formed inside the liquid crystal panel through the gate and data wiring, and the liquid crystal inside the liquid crystal panel using the control signal and the data signal applied to the switching thin film transistor. Adjust the strength of the electric field applied to the layer.

As such, by adjusting the arrangement angle of the liquid crystal molecules through the control signal and the data signal, the intensity of light emitted from the backlight unit attached to the rear surface of the liquid crystal panel is controlled to display an image on the liquid crystal panel.

On the other hand, a plurality of switching thin film transistors are formed inside the liquid crystal panel, and control signals and data signals are sequentially applied to each of the gate and data lines connected to each of the plurality of switching thin film transistors, and the control signals and data signals are sequentially applied. To apply, the gate and data driver includes multiple gate and data stages therein.

Each of the gate and data stages is driven by receiving a power voltage from a power supply to sequentially operate.

At this time, a plurality of power supply voltages are applied to the power supply unit, and the voltage is boosted or stepped down using a plurality of power supply voltages in a transformer circuit formed inside the data driver to convert it to a driving voltage used in the gate and data driver.

On the other hand, when the power supply is momentarily turned off, a plurality of power voltages applied from the power supply are momentarily cut off, and the operation of the gate and data driver, which are sequentially driven, is momentarily stopped, resulting in the liquid crystal molecules of the liquid crystal panel. The arrangement is fixed.

More specifically, the switching thin film transistor is fixed in a turn-off state, so that the data signal applied to the liquid crystal layer is charged, so that the liquid crystal molecules having an array angle for displaying an image are fixed without returning to the original array state. .

That is, the liquid crystal molecules inside the panel maintain and fix an angle for displaying an image, and a problem occurs in that the screen of the previous frame remains as an afterimage.

In order to solve the problem that the screen of the previous frame remains as an afterimage when the abnormal power is turned off, an abnormal power off prevention circuit is mounted in the data driver.

Hereinafter, an abnormal power-off prevention circuit will be described with reference to the drawings.

1 is a timing diagram showing driving timing of an abnormal power-off prevention circuit of a general liquid crystal display device, and FIG. 2 is a circuit diagram showing power applied to a general abnormal power-off prevention circuit.

Referring to FIG. 1, the yellow line in the upper part shows the timing of occurrence of abnormal power off, the blue area in the center shows the operation timing according to the time of the data driver, and the pink area in the lower part prevents abnormal power off. It is a diagram showing the operation timing of the circuit.

At this time, the abnormal power-off prevention circuit detects the voltage level of the power supply, and if the voltage level of the power supply decreases below a preset power level, it is determined that an abnormal power-off has occurred, and a power-off signal is applied to the gate driver. A high signal is applied to the entire gate stage inside the gate driver.

The high signal is applied to each of the plurality of switching thin film transistors through the gate wiring to turn on the switching thin film transistor.

Therefore, the voltage charged in the liquid crystal layer is discharged to return the liquid crystal molecules to the original arrangement.

That is, even if an abnormal power-off occurs, an afterimage of the liquid crystal panel may be prevented by controlling the gate driver with the power-off signal of the abnormal power-off prevention circuit.

However, the abnormal power-off prevention circuit is driven using the first driving voltage V1 applied from the power supply to the data driver.

Therefore, when an abnormal power-off occurs in the power supply unit, the abnormal power-off prevention circuit does not sufficiently apply a power-off signal to the gate driver because the first driving voltage V1 for driving is cut off.

Referring to FIG. 2, when an abnormal power-off occurs in the power supply unit, the abnormal power-off prevention circuit (APO) is driven. At this time, the abnormal power-off prevention circuit APO is driven using the first driving voltage V1 supplied from the power supply unit to the data driver. When the abnormal power-off occurs, the data driver is stopped.

At this time, there is a first driving time t1 until the driving of the data driver is completely stopped, and in the first driving time t1, the power voltage applied from the power supply unit is boosted or stepped down in the transformer circuit inside the data driver, and the liquid crystal panel is turned on. It is time to be applied.

On the other hand, the abnormal power-off prevention circuit (APO) may use the voltage charged in the first capacitor (C1), but the power-off signal cannot be sufficiently applied to the switching thin film transistor, so that the charged data signal of the liquid crystal layer is not completely discharged. can not do it.

That is, the abnormal power-off prevention circuit APO is driven during the first driving time t1 like a data driver and applies a power-off signal to the gate driver during the first driving time t1.

The first driving time t1 is driven at 3 μm in a typical liquid crystal display device, and the power-off signal is not sufficiently applied to the gate driver during the first driving time t1.

That is, the power-off signal is applied to the switching thin film transistor inside the liquid crystal panel for the first driving time t1, which is too short to discharge the voltage charged in the liquid crystal layer, and the abnormal power-off prevention circuit (APO) Even if it works, there is a problem that the image of the previous frame is displayed as an afterimage on the LCD panel.

The present invention has been proposed in order to solve the above-mentioned problems, and is intended to solve the problem that an afterimage is displayed on the liquid crystal display panel when the power of the liquid crystal display is abnormally turned off.

In order to achieve the above object, the present invention includes a liquid crystal panel in which a gate and data wiring crossing each other to define a pixel region, and a switching thin film transistor formed in each pixel region are formed; A gate and a data driver connected to the gate and data wiring inside the liquid crystal panel; A timing controller for applying a control signal and a data signal to the gate and data driver; A power supply unit applying a first driving voltage to the data driver; It includes a transformer circuit formed inside the data driver and an abnormal power-off prevention circuit, the transformer circuit outputs a second driving voltage, and the power-off prevention circuit is applied through the first driving voltage and the first resistor. Provided is a liquid crystal display device configured to perform a power-off prevention driving using a second driving voltage.

Here, the first to third power voltages output from the power supply unit to the data driver may be output, and the transformer circuit may be configured to boost or step down the first to third power voltages to generate a second driving voltage. have.

The first driving voltage may be 1.8V, the second driving voltage may be 2.8V, and the first resistance may be 500mA.

In another aspect, the present invention provides a liquid crystal panel, a gate driver and a data driver for applying a control signal and a data signal to the liquid crystal panel, a timing control unit for driving the gate and data driver, and a transformer circuit formed inside the data driver. And a power supply unit for applying a first driving voltage to the abnormal power-off prevention circuit and applying a power voltage to the transformer circuit and the liquid crystal panel, wherein the power from the abnormal power-off prevention circuit is provided. Sensing a power supply voltage of the supply unit; Comparing the sensed power voltage with a preset reference power voltage; Outputting a second driving voltage from the first driving voltage and the transformer circuit to the abnormal power-off prevention circuit when the sensed power voltage is less than the reference power voltage; Outputting a power-off signal from the abnormal power-off prevention circuit to the gate driver; It provides a driving method of a liquid crystal display device comprising the step of driving the gate driver to discharge the data signal charged therein.

Here, the second driving voltage may be generated by boosting or stepping down the power supply voltage.

In the present invention, when an abnormal power-off occurs in the liquid crystal display device, power is drawn from the transformer circuit inside the data driver and applied to the abnormal power-off prevention circuit, thereby preventing an afterimage generated in the liquid crystal display panel.

1 is a timing diagram showing a driving timing of an abnormal power-off prevention circuit of a typical liquid crystal display device.
2 is a circuit diagram showing power applied to a normal abnormal power-off prevention circuit.
3 is a block diagram showing a liquid crystal display device according to an exemplary embodiment of the present invention.
4 is a timing diagram showing a driving timing of an abnormal power-off prevention circuit of a liquid crystal display device according to an embodiment of the present invention.
5 is a circuit diagram showing power applied to the abnormal power-off prevention circuit according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

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

As illustrated, the liquid crystal display device according to an exemplary embodiment of the present invention includes a liquid crystal panel including a gate and data wiring crossing each other to define a pixel region, and a switching thin film transistor Tr formed in each pixel region. 100), a gate driver 127 and a data driver 130 for applying a signal to the liquid crystal panel 100, a timing controller 120 for driving the signal, and a power supply unit 110 for supplying power to them. It is composed of a system interface unit 105 for transmitting a driving signal and a video signal to the timing control unit 120.

On the other hand, the liquid crystal panel 100 is a device that expresses color with a constant luminance. When the liquid crystal display device is not a self-emission type structure, a light source device is provided on the rear surface of the liquid crystal panel 100 to express a color having a constant luminance. have.

In addition, the luminance of light emitted to the outside may be controlled by adjusting the arrangement direction of the liquid crystal molecules of the liquid crystal layer (not shown) formed in the liquid crystal panel 110 of the light emitted from the light source device.

At this time, the control signal and data signal from the system interface unit 105 to the timing control unit 120 are input to the display panel through the gate and data drivers 127 and 130 using a low voltage differential signal (LVDS) interface or a TTL interface. By doing so, an image is displayed.

At this time, the control signal includes an input clock (CLK), a horizontal synchronization signal (Hsync), a vertical synchronization signal (Vsync), a data enable signal (Data enable, DE), and a start signal (Vst), which are on the liquid crystal panel. It is required to sequentially apply voltage to each formed gate wiring.

In addition, between the timing controller 120 and the liquid crystal panel 100, a gate driver 127 and a data driver (for driving the switching thin film transistor Tr formed on the panel according to a control signal transmitted from the timing controller 120) 130) is connected.

The gate driver 127 may be formed on the liquid crystal panel 100 by using an amorphous silicon thin film transistor. The gate driver 127 formed in the liquid crystal panel 100 is gate-in-panel. In-Panel: GIP).

The gate-in-panel (GIP) type gate driver 127 includes a plurality of gate stages (not shown) therein, and each gate stage is sequentially connected, It is controlled through a control signal.

In addition, the data driver 130 includes a plurality of data stages (not shown) and a transformer circuit (not shown) therein, and each data stage and transformer circuit includes elements such as transistors and capacitors therein. do.

Each of the gate and data drivers 127 and 130 is driven by receiving a power voltage from the power supply 110 to sequentially operate.

At this time, the power supply unit 110 supplies power to each part of the liquid crystal display device, and when a light source device is formed on the rear surface of the liquid crystal panel 100, serves to supply power to the light source device.

Although not shown, a plurality of power voltages of the power supply unit 110 may be applied, for example, 1.0V, 1.8V, and 0.5V may be applied to the data driver 130, and 5V may be a light source device and a liquid crystal panel. It may be applied to (100).

At this time, the data driver 130 is boosted or stepped down using a plurality of power voltages in an internal transformer circuit (not shown) to transform it into a driving voltage used in the gate and data drivers 127 and 130.

The gate and data drivers 127 and 130 are driven by applying the driving voltage to the gate and data drivers, and each of the gate and data drivers 127 and 130 switches a control signal and a data signal through a gate and data wiring. The image is displayed by applying to (Tr).

In more detail, a plurality of switching thin film transistors Tr are sequentially turned on by applying a control signal, and a data signal is applied to the liquid crystal layer through the switching thin film transistor Tr to form a liquid crystal layer. Adjust the orientation of liquid crystal molecules.

Then, the plurality of switching thin film transistors Tr are sequentially turned off to discharge the data signal from the liquid crystal layer to control the liquid crystal molecule arrangement of the liquid crystal layer to return to the original arrangement state.

At this time, when an abnormal power-off of the power supply unit 110 occurs, the liquid crystal display according to an embodiment of the present invention receives the power-off signal from the abnormal power-off prevention circuit (APO in FIG. 5) formed inside the data driver 130. Output it and apply it to the gate driver.

At this time, the abnormal power-off prevention circuit senses whether an abnormal power-off occurs by sensing the power voltage output from the power supply unit 110.

The abnormal power-off prevention circuit compares a preset reference power voltage and a power voltage, and determines that an abnormal power-off occurs when the power voltage is smaller than the reference power voltage.

Hereinafter, an abnormal power-off prevention circuit will be described with reference to the drawings.

4 is a timing diagram showing a driving timing of an abnormal power-off prevention circuit of a general liquid crystal display device, and FIG. 5 is a circuit diagram showing a power applied to the abnormal power-off prevention circuit.

Referring to FIG. 4, the yellow line at the top is a waveform showing the timing of abnormal power-off, and the blue area at the center is a waveform showing the operation timing over time of the data driver (130 in FIG. 3), and the pink at the bottom. The area is a waveform showing the operation timing of the abnormal power-off prevention circuit.

At this time, the abnormal power-off prevention circuit senses the power voltage of the power supply (110 of FIG. 3), and when the power voltage of the power supply (110 of FIG. 3) decreases below a preset reference power voltage, the abnormal power-off It is judged that it has occurred, and a power-off signal is applied to the gate driver (127 in FIG. 3) to apply a high signal to the entire gate stage inside the gate driver (127 in FIG. 3).

At this time, the power voltage sensed by the abnormal power-off prevention circuit may be, for example, a 5V voltage applied by the power supply unit (110 of FIG. 3) to the liquid crystal panel or the dimming device.

Meanwhile, the high signal is applied to each of the plurality of switching thin film transistors (Tr in FIG. 3) through the gate wiring to turn on the switching thin film transistor.

Therefore, the data signal charged in the liquid crystal layer is discharged to return the liquid crystal molecules to the original arrangement state.

That is, even if an abnormal power-off occurs, the residual image of the liquid crystal panel (100 in FIG. 3) may be prevented by controlling the gate driver (127 in FIG. 3) with the power-off signal of the abnormal power-off prevention circuit.

The abnormal power-off prevention circuit includes a plurality of first driving voltages V1 applied from a power supply (110 in FIG. 3) to a data driver (130 in FIG. 3) and a plurality of applied from a power supply (110 in FIG. 3). The power supply voltage of is driven using the second driving voltage V2 transformed in the transformer circuit (not shown).

Referring to FIG. 5, the first driving voltage V1 is applied to the abnormal power-off prevention circuit APO to drive the abnormal power-off prevention circuit APO, and the second driving voltage V2 is a data driver It is applied to the inside of (130 in FIG. 3) is a voltage for driving the internal element of the data driver (130 in FIG. 3).

As such, the first driving voltage V1 and the second driving voltage V2 may be connected to the first resistor R, but the first driving voltage V1 and the second driving connected through the first resistor R may be connected. Even if the abnormal power-off of the power supply unit (110 of FIG. 3) occurs due to the voltage V2, the abnormal power-off prevention circuit may operate normally.

In more detail, the second driving voltage V2 receives the first to third power voltages applied from the power supply unit (110 of FIG. 3) from the data driver (130 of FIG. 3) and the data driver (FIG. 3). 130 is a voltage transformed by using the first to third power voltages in an internal transformer circuit (not shown).

In this case, the first to third power voltages may be, for example, 1.8V, 1.0V, 0.5V, and the first power voltage may be the same voltage as the first driving voltage V1.

In addition, the transformer circuit includes elements such as a capacitor and a resistor therein for step-up or step-down, and undergoes various steps of step-transformation to output the second driving voltage V2 to a desired output.

The second driving voltage V2 that has undergone various stages of voltage transformation may be, for example, 2.8V, and undergoes various stages of voltage transformation even if an instantaneous abnormal power-off occurs in the power supply unit (110 of FIG. 3). It is output during the driving time T1.

At this time, since the second driving voltage V2 is output through various stages of the transformation process, it is output for a longer time than the first driving voltage V1.

Therefore, when an instantaneous abnormal power-off occurs in the power supply unit (110 of FIG. 3), the second driving voltage V2 is applied to the abnormal power-off prevention circuit through the first resistor R for the first driving time T1. Is authorized.

At this time, the first resistor (R) may have a size of 500 Ω or less, for example.

In addition, the first driving time T1 may be, for example, 13us, and the abnormal power-off prevention circuit may operate during the first driving time T1.

In addition, the second driving voltage V2 may be uniformly applied during the first driving time T1 by using the voltages charged in the first and second capacitors C1 and C2 simultaneously with the second driving voltage V2. have.

This can secure about 10us longer driving time than the normal abnormal power-off prevention circuit operates for 3us of time, so that the arrangement of the liquid crystal molecules in the liquid crystal layer can be returned to the original arrangement.

That is, when an abnormal power-off occurs, the liquid crystal display device according to an embodiment of the present invention draws power from the transformer circuit inside the data driver and applies it to the abnormal power-off prevention circuit, thereby preventing an afterimage generated on the liquid crystal display panel. It has the effect.

Although described above with reference to preferred embodiments of the present invention, those skilled in the art variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You can understand that you can.

V1: First driving voltage V2: Second driving voltage
C1: first capacitor C2: second capacitor
130: data driver

Claims (5)

A liquid crystal panel in which a gate and data wiring crossing each other to define a pixel region, and a switching thin film transistor formed in each pixel region are formed;
A gate and a data driver connected to the gate and data wiring inside the liquid crystal panel;
A timing controller for applying a control signal and a data signal to the gate and data driver;
A power supply unit applying a first driving voltage to the data driver;
It includes a transformer circuit formed inside the data driver and an abnormal power-off prevention circuit,
The transformer circuit outputs a second driving voltage,
The abnormal power-off prevention circuit is configured to perform power-off prevention driving using the first driving voltage and the second driving voltage applied through the first resistor.
Liquid crystal display device.
According to claim 1,
The first to third power voltages output from the power supply to the data driver are output,
The transformer circuit is a liquid crystal display device configured to generate a second driving voltage by boosting or stepping down the first to third power voltages.
According to claim 1,
The first driving voltage is 1.8V, the second driving voltage is 2.8V, and the first resistance is 500mA.
A liquid crystal panel, a gate driver and a data driver for applying control signals and data signals to the liquid crystal panel, a timing control unit for driving the gate and data drivers, a transformer circuit formed inside the data driver, and an abnormal power-off prevention circuit In the driving method of a liquid crystal display device comprising a power supply for applying a first driving voltage to the power supply voltage to the transformer circuit and the liquid crystal panel,
Sensing a power supply voltage of the power supply in the abnormal power-off prevention circuit;
Comparing the sensed power voltage with a preset reference power voltage;
Outputting a second driving voltage from the first driving voltage and the transformer circuit to the abnormal power-off prevention circuit when the sensed power voltage is less than the reference power voltage;
Outputting a power-off signal from the abnormal power-off prevention circuit to the gate driver;
Discharging the data signal charged therein by driving the gate driver
Method of driving a liquid crystal display device comprising a.
According to claim 4,
The second driving voltage is a method of driving a liquid crystal display device generated by boosting or stepping down the power supply voltage.

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