KR20120133810A - Liquid crystal display device and driving method the same - Google Patents

Abstract

PURPOSE: A liquid crystal display device and a driving method thereof are provided to improve display quality of an image by minutely controlling the brightness of light supplied to a liquid crystal panel. CONSTITUTION: A plurality of LED units(610) supply light to a liquid crystal panel. A plurality of scan lines receives a scan signal. A plurality of light emitting data lines receives a light emitting data current. A light emitting signal controller generates a scan control signal and a light emitting data control signal. A scan signal driver supplies the scan signal to the plurality of scan lines. A light emitting data driver(530) supplies the light emitting data current to the plurality of data lines. [Reference numerals] (AA) Variable constant current

Description

Liquid crystal display and its driving method {LIQUID CRYSTAL DISPLAY DEVICE AND DRIVING METHOD THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and to a liquid crystal display device and a method of driving the same, which improve the display quality by improving the gray scale power by adjusting the driving current of the backlight light source and improving the flicker.

With the development of various portable electronic devices such as mobile communication terminals and notebook computers, there is an increasing demand for a flat panel display device applicable thereto.

The flat panel display includes a liquid crystal display device, a plasma display panel, a field emission display device, and an organic light emitting diode display device. Was developed.

Among such flat panel display devices, the liquid crystal display device has been expanded in application fields due to development of mass production technology, ease of driving means, low power consumption, light weight, thinness, high definition, and large screen.

The liquid crystal display device is composed of a liquid crystal panel for displaying an image, a backlight unit for supplying light to the liquid crystal panel, and a driving circuit portion for driving a light source of the liquid crystal panel and the backlight unit.

The backlight unit is composed of a plurality of light sources and a plurality of optical sheets. To date, Cold Cathode Fluorescent Lamps (CCFLs) or External Electrode Fluorescent Lamps (EEFLs) are widely used as light sources.

On the other hand, in recent years, LED (Light Emitting Diode) with low power consumption and long life advantages has been adopted as a light source.

The backlight unit is classified into an edge type in which the light source is disposed on the side of the liquid crystal panel and a direct type in which the light source is disposed on the rear surface of the liquid crystal panel according to the arrangement of the light sources.

1 is a view schematically showing a backlight unit according to the prior art employing a light emitting diode as a light source. 1 illustrates a direct-light emitting diode backlight unit.

Referring to FIG. 1, the backlight unit 40 includes a plurality of LED blocks 20 and a constant current circuit 30.

Here, the LED block 20 has a structure in which a plurality of LEDs 10 are connected in series and mounted on a PCB. Each LED block 20 is supplied with a driving voltage VDD, and a constant current circuit 30 is connected so that a plurality of LEDs 10 disposed in one LED block 20 emit light at the same time.

A plurality of constant current circuits 30 are configured in one multichannel drive IC. As a result, the multi-channel driving IC can drive the LED blocks 20 corresponding to the number of channels. Therefore, in order to drive the conventional LED backlight unit 40, a large number of driving ICs should be provided.

In order to increase the size of the liquid crystal display or to display an image with high luminance, the quantity of the LED 10, which is a light source, must be increased. Accordingly, the number of LED blocks 20 increases, and the number of driving ICs for driving the LEDs 10 also increases. As a result, the cost of circuit components for driving the plurality of LEDs 10 of the backlight unit 40 increases.

Meanwhile, in order to reduce circuit component costs, the number of LEDs 10 constituting each LED block 20 may be increased without increasing the number of LED blocks 20. However, the plurality of LEDs 10 constituting the LED block 20 are all supplied with the same constant current to emit light at once.

Therefore, when a plurality of LEDs 10 are included in one LED block 20 and the same constant current is supplied to emit the LEDs 10, there is a problem in that the luminance of light supplied to the liquid crystal panel cannot be finely adjusted.

The gray level of the image displayed on the liquid crystal display is determined by the luminance of the light supplied from the backlight unit 40 and the light transmittance of the liquid crystal panel.

Therefore, in order to finely adjust the gray level of the image to increase the display quality of the image, not only the fine control of the light transmittance of the liquid crystal panel but also the brightness of the light supplied from the backlight unit 40 to the liquid crystal panel must be finely adjusted.

The driving IC according to the related art supplies the constant current to the LED block 20 by controlling the constant current circuit 30 in a time division manner. Through this, the luminance of the plurality of LEDs 10 configured in one LED block 20 is controlled. At this time, the brightness of the LED 10 is controlled by adjusting the gray scale using an 8-bit scale.

When a plurality of LEDs 10 are configured in one LED block 20 to emit light by the same constant current circuit 30, there is a problem in that the luminance of light supplied to the liquid crystal panel cannot be finely adjusted. Accordingly, there is a problem that the halo phenomenon becomes severe and the flicker of the image displayed on the liquid crystal panel increases.

In order to improve such a problem, the number of LEDs 10 constituting one LED block 20 should be reduced, or the driving of the constant current circuit 30 should be more finely adjusted to increase the gray bit of the LED 10. .

However, in the case of increasing the gray bit of the LED 10, in order to control the brightness of the LED 10 with a 12-bit grayscale, for example, a driver IC capable of controlling the grayscale to 12 bits should be applied. Accordingly, there is a problem in that the cost of circuit components increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and it is an object of the present invention to provide a liquid crystal display and a driving method thereof capable of finely adjusting the luminance of light supplied to a liquid crystal panel.

Disclosure of Invention The present invention has been made in view of the above-described problems, and a technical object of the present invention is to provide a liquid crystal display and a driving method thereof capable of improving the halo phenomenon of the liquid crystal display and the flicker of an image displayed on the liquid crystal panel.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and provides a liquid crystal display and a driving method thereof capable of increasing the gray bit of the LED while minimizing an increase in the cost of the LED driving IC driving the LED for supplying light to the liquid crystal panel. It is technical problem to do.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a liquid crystal display and a driving method thereof capable of minimizing the cost increase of circuit components while finely adjusting the gray level of LEDs.

Other features and advantages of the invention will be set forth in the description which follows, or may be obvious to those skilled in the art from the description and the claims.

In an embodiment, a liquid crystal display device includes a liquid crystal panel; A plurality of LED units for supplying light to the liquid crystal panel; A plurality of light emitting data lines connected to the plurality of LED units, each of the plurality of scan lines to which a scan signal is supplied and a plurality of light emitting data currents; A light emission signal controller configured to generate a scan control signal and a light emission data control signal using a backlight control signal and a light emission data signal supplied from a timing controller; A scan signal driver configured to supply a scan signal to the plurality of scan lines based on the scan control signal; And a light emitting data driver for supplying a light emitting data current to the plurality of light emitting data lines based on the light emitting data control signal, wherein the light emitting data driver generates a light emitting data current that is variable in an output range of 2 to 8 bits. It characterized in that the supply to the plurality of LED units.

The liquid crystal display according to an exemplary embodiment of the present invention controls the luminance of light supplied to the liquid crystal panel by controlling the magnitude of the light emitting data current supplied to the plurality of LED units and the time when the light emitting data current is supplied. It features.

The liquid crystal display according to the exemplary embodiment of the present invention adjusts the size of the light emitting data current to a variable range of 4 bits, and adjusts the supply time of the light emitting data current to a variable range of 8 bits, thereby adjusting the plurality of the light sources to a total of 12 bits. It characterized in that to adjust the light emission luminance of the LED unit.

The light emission data driver of the liquid crystal display according to an exemplary embodiment of the present invention generates a variable voltage in response to a light emission data signal input from the timing controller, and amplifies and rectifies the variable voltage so that the 2 to 8 bit A light emitting data current having a variable range is output.

A driving method of a liquid crystal display according to an exemplary embodiment of the present invention is a driving method of a liquid crystal display including a liquid crystal panel, a timing controller, a backlight driver, and a backlight unit. Generating a backlight control signal for controlling a plurality of LED units constituting the backlight unit and a light emitting data signal for emitting light of the plurality of LED units received by a furnace; Generating a scan control signal and a light emission data control signal based on the backlight control signal and the light emission data signal; Supplying a scan signal to the plurality of LED units based on the scan control signal; And supplying light emission data currents to the plurality of LED units based on the light emission data control signals, and generating and supplying light emission data currents varying in an output range of 2 to 8 bits. Characterized in that.

The liquid crystal display and the driving method thereof according to the embodiment of the present invention can improve the display quality of the image displayed on the liquid crystal panel by finely adjusting the brightness of the light supplied to the liquid crystal panel.

The liquid crystal display and the driving method thereof according to the embodiment of the present invention can improve the halo phenomenon of the liquid crystal display and the flicker of the image displayed on the liquid crystal panel.

The liquid crystal display and the driving method thereof according to an embodiment of the present invention can increase the gray level bits of the LED while minimizing the cost increase of the LED driving IC for driving the LED for supplying light to the liquid crystal panel.

The liquid crystal display and the driving method thereof according to the embodiment may minimize the increase in the cost of circuit components while finely adjusting the gray level of the LED.

Other features and effects of the present invention may be newly understood through the embodiments of the present invention in addition to the features and effects of the present invention mentioned above.

1 is a schematic view of a backlight unit according to the prior art employing a light emitting diode as a light source;
2 is a diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.
3 is a diagram illustrating a backlight driver of a liquid crystal display according to an exemplary embodiment of the present invention.
4 is a diagram illustrating a light emitting data driver of a liquid crystal display according to an exemplary embodiment of the present invention.
FIG. 5 is a diagram illustrating a variable constant current output from the light emitting data driver shown in FIG. 4. FIG.
6 is a view showing a light emitting diode unit of a liquid crystal display according to an exemplary embodiment of the present invention.
7 and 8 illustrate a method of driving a liquid crystal display according to an exemplary embodiment of the present invention.
9 and 10 are views illustrating a light emitting diode unit of a liquid crystal display according to another exemplary embodiment of the present invention.

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

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

2, a liquid crystal display according to an exemplary embodiment of the present invention may include a liquid crystal panel 100 displaying an image (image) according to input image data; A backlight unit 600 for supplying light to the liquid crystal panel 100; And a driving circuit unit driving the light source of the liquid crystal panel 100 and the backlight unit.

The driving circuit unit includes a gate driver 200, a data driver 300, a timing controller 400, and a backlight driver 500.

The liquid crystal panel 100 includes a lower substrate and an upper substrate bonded to face each other, and a liquid crystal layer formed between the lower substrate and the upper substrate. The lower polarizing film is disposed on the rear surface of the lower substrate, and the upper polarizing film is disposed on the upper surface of the upper substrate.

The upper substrate includes a color filter for converting the light incident through the pixels of the lower substrate into color light to display a color image.

The lower substrate includes n gate lines G1 to Gn and m data lines D1 to Dm. Pixels are defined by crossing gate lines and data lines, and each pixel includes a thin film transistor (TFT) and a storage capacitor Cst.

The TFT is switched by the scan signal supplied through the gate line, and supplies the image data (data voltage) supplied through the data line to the pixel when the TFT is turned on.

In addition, the liquid crystal panel 100 may include a pixel electrode applying a data voltage to a pixel and a common electrode applying a common voltage Vcom. The pixel electrode may be formed on the lower substrate, and the common electrode may be formed on the lower substrate or the upper substrate.

The liquid crystal panel 100 changes an arrangement state of liquid crystals by an electric field difference between a data voltage and a common voltage, and displays an image by adjusting the transmittance of light incident from the backlight unit 600 by adjusting the arrangement of liquid crystals.

The timing controller 400 generates a gate control signal GCS for controlling the gate driver 200 and a data control signal DCS for controlling the data driver 300 using the input timing signal TS. .

In addition, the timing controller 400 converts the input image data into digital image data in units of frames and supplies it to the data driver 300.

Here, the timing signal TS includes a data enable signal DE, a horizontal synchronization signal Hsync, a vertical synchronization signal Vsync, and a clock signal CLK.

The generated gate control signal GCS is supplied to the gate driver 200, and the data control signal DCS is supplied to the data driver 300.

The gate control signal GCS may include a gate start pulse (GSP), a gate shift clock (GSC), a gate output enable (GOE), and the like.

The data control signal DCS includes a source start pulse (SSP), a source sampling clock (SSC), a source output enable (SOE), and a polarity control signal (POL: polarity). And the like.

In addition, the timing controller 400 generates a backlight control signal (BCS) and a light emission data signal LDATA for emitting light of a plurality of LEDs constituting the backlight unit 600.

The generated backlight control signal BCS and the emission data signal LDATA are supplied to the backlight driver 500. In this case, the light emission data signal LDATA may be generated to correspond to the LED unit or the individual LEDs.

The gate driver 200 generates a scan signal for driving (On-Off) the TFTs formed in each pixel of the liquid crystal panel 100 based on the gate control signal GCS supplied from the timing controller 400. The generated scan signal is sequentially supplied to the plurality of gate lines.

The data driver 300 converts the digital image data R, G, and B supplied from the timing controller 400 into analog image data (data voltage) and supplies them to each pixel of the liquid crystal panel 100. In this case, the data voltage is supplied to the liquid crystal panel 100 based on the data control signal DCS supplied from the timing controller 400.

Referring to FIG. 3, the backlight unit 600 is for irradiating light to the liquid crystal panel 100, and the plurality of LED units 610 are arranged in a matrix form in the horizontal and vertical directions.

In FIG. 3, the LED, which is a light source, is positioned on the rear surface of the liquid crystal panel 100 and shows a direct type backlight unit 600 that supplies light to the liquid crystal panel 100.

Here, one LED unit 610 is configured to include a plurality of LEDs for generating light. The plurality of LED units 610 may be connected to the plurality of scan lines SL1 to LSn and the plurality of light emitting data lines LDL1 to LDLm to be driven in an active matrix manner.

The backlight driver 500 controls driving (on-off) of a plurality of LEDs, and the backlight driver 500 controls the plurality of LEDs according to a backlight control signal (BCS) and a light emitting data signal (LDATA) supplied from the timing controller 400. The magnitude of the driving current supplied to the LED unit 610 and the supply time of the driving current are adjusted. Through this, it is possible to control the on-off time, duty and brightness of the plurality of LEDs.

To this end, the backlight driver 500 includes a light emission signal controller 510, a scan signal driver 520, and a light emission data driver 530.

The light emission signal controller 510 generates a scan control signal SCS for controlling the scan signal driver 520 based on the backlight control signal BCS input from the timing controller 400. The generated scan control signal SCS is supplied to the scan signal driver 520.

In addition, the emission signal controller 510 generates the emission data control signal LDCS for controlling the emission data driver 530 based on the backlight control signal BCS input from the timing controller 400. The generated light emission data control signal LDCS is supplied to the light emission data driver 530.

In addition, the emission signal controller 510 supplies the emission data signal LDATA input from the timing controller 400 to the emission data driver 530.

In FIG. 3, the light emission signal controller 510 is illustrated as being configured in the backlight driver 500. However, the light emission signal controller 510 is illustrated in FIG. 3.

In another embodiment of the present invention, the emission signal controller 510 may be implemented in the timing controller 400 or may be implemented in an independent configuration in the liquid crystal display.

The scan signal driver 520 is connected to the plurality of scan lines SL1 to SLn to supply a scan signal to the plurality of LED units 610. In this way, driving of the LED unit 610 corresponding to the scan line SL is switched.

The light emission data driver 530 is connected to the plurality of light emission data lines LDL1 to LDLm to supply light emission data, that is, a driving current to the plurality of LED units 610. As a result, the LED unit 610 corresponding to the light emitting data line LDL is driven.

Here, the liquid crystal display according to an exemplary embodiment of the present invention increases the number of gray level bits of light supplied to the liquid crystal panel so that the gray level of the plurality of LEDs can be finely adjusted. To this end, the light emission data driver 530 generates a variable constant current and supplies it to the LEDs configured in the plurality of LED units 610.

4 is a view showing a light emitting data driver of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 5 is a view showing a variable constant current output from the light emitting data driver shown in FIG. 4.

Hereinafter, a configuration and a driving method of the light emitting data driver 530 according to an exemplary embodiment of the present invention will be described with reference to FIGS. 4 and 5.

The light emission data driver 530 includes a variable voltage generator 531, an OP amplifier 532, and a transistor 533.

The variable voltage generator 531 generates a variable voltage in response to the light emission data control signal LDCS input from the timing controller 400. The generated variable voltage becomes the OP amplifier 532.

Here, the variable voltage is supplied to the positive input terminal of the OP amplifier 532 as a reference voltage, and the VCC voltage passing through the resistor is transmitted to the negative input terminal of the OP amplifier 532. The output of the OP amplifier 532 is input to the gate of the transistor 533 due to the difference between the variable voltage (reference voltage) and the VCC voltage. The voltage input to the transistor 533 is rectified to output the light emission data current I_LDAT. In this case, the light emission data current I_LDAT is output to the LED unit 610.

That is, the light emission data driver 530 generates the light emission data current I_LDAT corresponding to the light emission data signal LDAT on a horizontal line basis, and outputs the generated light emission data current I_LDAT to the corresponding light emission data line LDL. To each LED unit 610.

Here, the variable voltage generator 531 generates a variable voltage in response to the light emission data signal LDAT input from the timing controller.

For example, the variable voltage generator 531 may generate a variable voltage having a 2-bit to 8-bit output range corresponding to the light emitting data signal LDAT.

Preferably, the variable voltage generator 531 may generate a variable voltage in a 4-bit output range. When the variable voltage generator 531 generates a variable voltage in a 4-bit output range, the variable voltage generator 531 may generate a variable voltage in units of 1V within a range of 0V to 15V and supply the variable voltage to the OP amplifier 532.

As shown in FIG. 5, the light emission data current I_LDAT output from the light emission data driver 530 to the LED unit 610 is changed in time according to the light emission data signal LDAT. Becomes

6 is a view illustrating a light emitting diode unit of a liquid crystal display according to an exemplary embodiment of the present invention, and FIGS. 7 and 8 are views illustrating a method of driving a liquid crystal display according to an exemplary embodiment of the present invention.

6 to 8, the plurality of LED units 610 constituting the backlight unit 600 are switched according to a scan signal supplied from the scan signal driver 520 and supplied from the light emitting data driver 530. The light is emitted using the light emission data current I_LDAT. In this case, the light emission data current I_LDAT is a variable constant current that varies variably with time based on the light emission data signal LDAT.

Each of the plurality of LED units 610 includes a switching circuit 612, a current mirror circuit 614, and an LED 616. The LED 616 is connected with the VDD terminal and the current mirror circuit 614.

Each of the plurality of LEDs 616 disposed under the liquid crystal panel 100 may correspond to a predetermined number of pixels P formed in the liquid crystal panel 100.

For example, the liquid crystal panel 100 may be divided into pixel blocks corresponding to the LED units 610, and a plurality of pixels P may be configured in each pixel block. Thus, each of the LED units 610 may correspond to one or more pixel blocks.

The current mirror circuit 614 includes a first transistor Tr1 and a second transistor Tr2 and a storage capacitor C that are symmetrical to each other and have the same characteristics. The first transistor Tr1 is connected to the switching circuit 612, and the second transistor Tr2 is connected to the LED 616.

As the first transistor and the second transistors Tr1 and Tr2, an N type transistor may be used. For example, an NMOS transistor can be used.

The storage capacitor C may be provided between the gate terminal and the source terminal of the first transistor Tr1 and the second transistor Tr2.

The current mirror circuit 614 may be connected to the corresponding light emitting data line LDL through the switching circuit 612 to receive the light emitting data current I_LDAT which is a variable constant current.

The switching circuit 612 may include at least one switching device.

As an example, the switching circuit 612 includes a first switching element SW1 and a second switching element SW2, and the first switch SW1 and the second switch SW2 correspond to the corresponding scan line SL. And a light emitting data line LDL.

The first switching device SW1 may be connected between the drain terminal of the first transistor Tr1 and the light emitting data line LDL.

The second switching element SW2 may be connected between the gate terminal and the drain terminal of the first transistor Tr1.

Here, the first switching element and the second switching elements SW1 and SW2 are commonly connected to the scan line SL to perform the same switching operation.

The gate terminal of the second transistor Tr2 and the gate terminal of the first transistor Tr1 are connected to each other.

The drain terminal of the second transistor Tr2 is connected to the LED 616.

The source terminal of the first transistor Tr1 and the source terminal of the second transistor Tr2 may be grounded.

The first terminal of the LED 616 may be connected to the power supply voltage VDD, and the second terminal may be connected to the drain terminal of the second transistor Tr2.

Operations of the light emitting data driver 530 and the LED unit 610 having the above-described configuration will be described with reference to FIGS. 4 to 7.

Here, since the driving of the entire LED unit 610 is made by the same method, an operation method of one LED unit 610 among all the LED units 610 will be described.

The scan signal driver 520 generates a scan signal and sequentially supplies the scan signal to the plurality of scan lines SL1 to SLn.

When an on level scan signal is input through one of the scan lines SL, the first switching element and the second switching elements SW1 and SW2 are turned on.

When the first switching element and the second switching element SW1 and SW2 are turned on, the light emission data current I_LDAT applied to the corresponding light emitting data line LDL turns on the first switching element and the second switching element SW1 and SW2. It passes through and is input to the first transistor T1 of the current mirror circuit 614.

The light emission data current I_LDAT is generated in the light emission data driver 530 based on the light emission data signal LDAT. For example, the light emission data current I_LDAT is a variable constant current having a 4-bit variable range.

Subsequently, the current mirror circuit 614 outputs the light emission current I_LED through the second transistor T2.

The luminous current I_LED output from the current mirror circuit 614 is applied to the LED 616, whereby the LED 616 emits light.

Here, the current mirror circuit 614 outputs an output current that is substantially the same as the input current due to its characteristics. Accordingly, the light emission current I_LED as the output current is substantially the same as the light emission data current I_LDAT as the input current (I_LED ≒ I_LDAT).

Therefore, as the amplitude (magnitude) of the light emission data current I_LDAT is adjusted, the light emission luminance of the LED 616 is adjusted.

On the other hand, when the scan signal is turned off, the first switching element and the second switching elements SW1 and SW2 are turned off.

At this time, even when the first and second switching devices SW1 and SW2 are turned off, the voltage applied to the gate terminal of the second transistor T2 during the scan period is stored in the storage capacitor C. FIG.

Accordingly, until the next scan is performed, the LED 616 may continue to emit light having a luminance corresponding to the input emission data current I_LDAT. At this time, the time for the LED 616 to emit light is determined according to the amount of current stored in the storage capacitor (C).

As shown in FIG. 8, the light emission luminance of the LED 616 is a variable constant current, and the light emission current I_LED is determined by the size of the light emission data current I_LDAT and the switching circuit 612 and the current mirror circuit 614. This is determined by the time supplied to 616.

For example, when the light emission data current I_LDAT is changed to a range of 4 bits, and the supply of the light emission current I_LED is adjusted to a range of 8 bits, the luminance of the LED 616 may be adjusted to a gradation range of 12 bits in total. have.

The emission signal controller 510 receives the backlight control signal BCS from the timing controller 400, and scans the scan control signal SCS for controlling the scan signal driver 520, and emits light for controlling the emission data driver 530. The data control signal LDCS is generated.

The scan signal driver 520 sequentially scans the plurality of scan lines SL1 to SLn per emission frame in response to the scan control signal SCS. In this case, the emission frame corresponds to a period of scanning the plurality of scan lines SL1 to SLn.

Such a light emitting frame may be synchronized with an image display in the liquid crystal panel 100. For example, the light emission frame can be synchronized with the same as the video frame.

The emission data driver 530 generates the emission data current I_LDAT in response to the emission data control signal LDCS, and supplies the generated data current I_LDAT to the corresponding emission data line LDL.

In this case, the output of the emission data current I_LDAT may be performed at every scan. For example, in every scan, the emission data current I_LDAT is simultaneously output to each of the plurality of emission data lines LDL1 to LDLm. The light emission data current I_LDAT thus output is input to the LED unit 610 connected to the selected scan line.

The plurality of LEDs 616 of the LED unit 610 emit light having a luminance corresponding to the input light emission data current I_LDAT.

The backlight unit 600 using the plurality of LEDs 616 as a light source is controlled by the backlight driver 500 including the emission signal controller 510, the scan signal driver 520, and the emission data driver 530. It is driven in a matrix manner.

Accordingly, the light emission data current I_LDAT corresponding to each of the plurality of LED units 610 is input in units of light emission frames, and light corresponding to the light emission data current I_LDAT may be emitted.

As such, the plurality of LED units 610 may be independently driven by receiving corresponding emission data currents I_LDAT. As the plurality of LED units 610 are individually driven, the brightness of an image displayed on the liquid crystal panel 100 may be partially controlled.

That is, the light emission luminance of the LEDs 616 corresponding to the pixels P displaying a bright image is relatively increased, and the light emission luminance of the LEDs 616 corresponding to the pixels P displaying a dark portion is relatively increased. The contrast ratio of the image finally displayed can be increased.

For this driving, the light emitting data signal LDAT may be generated by reflecting the image data signal RGB.

For example, the emission data signal LDAT corresponding to the LED unit 610 may be generated to have a representative value, for example, a mean value of the image data signals of the corresponding pixel block.

Meanwhile, the scan signal driver 520 according to the exemplary embodiment of the present invention may be configured with at least one multichannel driver IC having a plurality of output terminals.

For example, an n-channel driver IC having n output terminals respectively corresponding to the plurality of scan lines SL1 to SLn may be applied to the scan signal driver 520.

In addition, the light emitting data driver 530 according to an exemplary embodiment of the present invention may be configured with at least one multichannel IC having a plurality of output terminals.

For example, an m-channel driving IC having m output terminals respectively corresponding to the plurality of light emitting data lines LDL1 to LDLm may be used as the light emitting data driver 530.

9 and 10 are views illustrating a light emitting diode unit of a liquid crystal display according to another exemplary embodiment of the present invention.

In the liquid crystal display according to other exemplary embodiments of the present disclosure, other configurations except for the configuration of the LED unit are the same as those described above with reference to FIG. 3 and FIG. 8. Therefore, detailed description of the same configuration as in the above-described embodiment will be omitted.

Referring to FIG. 9, in the liquid crystal display according to another exemplary embodiment, the LED unit 610 may be configured as shown in FIG. 9.

The first switching device SW1 may be connected between the drain terminal of the first transistor Tr1 and the light emitting data line LDL.

The second switching element SW2 may be connected between the gate terminal of the first transistor Tr1 and the gate terminal of the second transistor Tr2.

The first terminal of the storage capacitor C may be grounded, and the second terminal may be connected between the second switching element SW2 and the gate terminal of the second transistor Tr2.

 Meanwhile, the gate terminal and the drain terminal of the first transistor Tr1 may be directly connected.

Referring to FIG. 10, in the liquid crystal display according to another exemplary embodiment, the LED unit 610 may be configured as shown in FIG. 10.

The first switching device SW1 may be connected between the drain terminal of the first transistor Tr1 and the light emitting data line LDL.

The second switching element SW2 is connected between the gate terminal of the first transistor Tr1 and the light emitting data lines LDL1 and LDL2.

The first terminal of the storage capacitor C may be grounded, and the second terminal may be connected between the gate terminal of the first transistor Tr1 and the gate terminal of the second transistor Tr2.

In the above description, the first transistor Tr1 and the second transistor Tr2 of the LED unit 610 are illustrated and described as being an N-type transistor, but this represents one embodiment of the present invention.

In another embodiment of the present invention, the first transistor Tr1 and the second transistor Tr2 may be P-type transistors, for example, PMOS transistors.

The switching circuit 612 and the current mirror circuit 614 are only a part of the various embodiments of the present invention.

It is apparent to those skilled in the art that other types of switching circuits and current mirror circuits can be used in the liquid crystal display of the present invention in addition to those shown in the drawings.

The liquid crystal display according to the exemplary embodiment of the present invention can stably drive LEDs through a current mirror circuit and can individually drive a plurality of LEDs in an active matrix manner.

Accordingly, it is possible to improve the halo phenomenon caused by driving LEDs at once in units of blocks in the related art. In addition, since the brightness of the backlight may be partially adjusted by the LED unit, the contrast ratio may be improved.

In addition, since the LEDs can be driven individually, even if some LEDs fail, the driving of other LEDs is not affected.

According to an exemplary embodiment of the present invention, a liquid crystal display and a driving method thereof generate a variable constant current emission data current I_LDAT through a light emission data driver, and supply the generated emission data current I_LDAT to an LED unit to provide a liquid crystal panel. It is possible to finely adjust the brightness of the light supplied. Through this, the display quality of the image displayed on the liquid crystal panel can be improved.

The liquid crystal display and the driving method thereof according to the embodiment of the present invention can improve the flicker of the image displayed on the liquid crystal panel by driving the plurality of LEDs individually and finely adjusting the light emission luminance of the LEDs.

The liquid crystal display and the driving method thereof according to an embodiment of the present invention can increase the gray level bits of the LED while minimizing the cost increase of the LED driving IC for driving the LED for supplying light to the liquid crystal panel.

In addition, the circuit component cost can be reduced by configuring the scan signal driver and the light emitting data driver to drive the LED as multi-channel driver ICs, respectively.

It will be understood by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

100: liquid crystal panel 200: gate driver
300: data driver 400: timing controller
500: backlight driver 510: light emission signal controller
520: scan signal driver 530: light emission data driver
531: variable voltage generator 532: OP amplifier
533: transistor 600: backlight unit
610: LED unit 612: switching circuit
614: current mirror circuit 616: LED
SL: Scan Line LDL: Luminescent Data Line
Tr1: first transistor Tr2: second transistor
SW1: first switching element SW2: second switching element
C: storage capacitor

Claims (14)

Liquid crystal panels;
A plurality of LED units for supplying light to the liquid crystal panel;
A plurality of light emitting data lines connected to the plurality of LED units, each of the plurality of scan lines to which a scan signal is supplied and a plurality of light emitting data currents;
A light emission signal controller configured to generate a scan control signal and a light emission data control signal using a backlight control signal and a light emission data signal supplied from a timing controller;
A scan signal driver configured to supply a scan signal to the plurality of scan lines based on the scan control signal; And
And a light emission data driver configured to supply light emission data currents to the plurality of light emission data lines based on the light emission data control signals.
The light emitting data driver generates a light emitting data current that varies in an output range of 2 bits to 8 bits and supplies the light emitting data current to the plurality of LED units. The method of claim 1,
The luminance of the light supplied to the liquid crystal panel is controlled by controlling the magnitude of the light emitting data current supplied to the plurality of LED units and the time for which the light emitting data current is supplied. The method of claim 1,
Adjusting the size of the light emitting data current in a variable range of 4 bits, and adjusts the emission time of the plurality of LED units in a total of 12 bits by adjusting the supply time of the light emitting data current in a variable range of 8 bits. Liquid crystal display device. The light emitting device of claim 1, wherein the light emission data driver comprises:
Generate a variable voltage in response to a light emission data signal input from the timing controller,
And amplifying and rectifying the variable voltage to output a light emitting data current having a variable range of 2 to 8 bits. The method of claim 1, wherein the LED unit,
A switching circuit connected to the scan line and the light emitting data line;
A current mirror circuit connected to the switching circuit and configured to charge the input light emitting data current and output the light emitting current; And
And a light emitting diode (LED) which emits light using the light emitting current output from the current mirror circuit. The method of claim 1, wherein the current mirror circuit,
A first transistor configured to receive and output the light emitting data current;
A storage capacitor charging the light emitting data current to the light emitting current;
And a second transistor configured to supply the light emitting current stored in the storage capacitor to the LED. The method of claim 6, wherein the switching circuit,
A first switching element and a second switching element that switch in the same manner according to the scan signal,
The first switching device is connected between the light emitting data line and a drain terminal of the first transistor,
And the second switching element is connected between a drain terminal and a gate terminal of the first transistor. The method of claim 6, wherein the switching circuit
A first switching element and a second switching element that switch in the same manner according to the scan signal,
The first switching device is connected between the light emitting data line and a drain terminal of the first transistor,
The second switching element is connected to a gate terminal of the first transistor.
And a gate terminal of the second transistor. The method of claim 1,
The scan signal driver and the light emitting data driver include at least one driving IC having a plurality of channels.
Channels of the scan signal driver correspond to the plurality of scan lines,
And a channel of the light emitting data driver corresponds to the plurality of light emitting data lines. In the driving method of a liquid crystal display device comprising a liquid crystal panel, a timing controller, a backlight driver and a backlight unit,
Generating a backlight control signal for controlling a plurality of LED units constituting the backlight unit and a light emission data signal for emitting a plurality of LED units by receiving the image signal and a timing signal input from an external device; ;
Generating a scan control signal and a light emission data control signal based on the backlight control signal and the light emission data signal;
Supplying a scan signal to the plurality of LED units based on the scan control signal;
Supplying light emission data currents to the plurality of LED units based on the light emission data control signals;
A method of driving a liquid crystal display device, characterized in that for generating a light emitting data current that is variable in the output range of 2 to 8 bits to supply to the plurality of LED units. 11. The method of claim 10,
And controlling the magnitude of the light emitting data current supplied to the plurality of LED units and the time for which the light emitting data current is supplied to control the brightness of light supplied to the liquid crystal panel. 11. The method of claim 10,
Adjusting the size of the light emitting data current in a variable range of 4 bits, and adjusts the emission time of the plurality of LED units in a total of 12 bits by adjusting the supply time of the light emitting data current in a variable range of 8 bits. A method of driving a liquid crystal display device. 11. The method of claim 10,
In the step of supplying a light emission data current to the plurality of LED units,
Generate a variable voltage in response to a light emission data signal input from the timing controller,
And amplifying and rectifying the variable voltage to output a light emitting data current having a variable range of 2 to 8 bits to the plurality of LED units. The method of claim 10, wherein the LED unit,
A switching circuit connected to the scan line and the light emitting data line;
A current mirror circuit connected to the switching circuit and configured to charge the input light emitting data current and output the light emitting current; And
And a light emitting diode (LED) which emits light using the light emitting current output from the current mirror circuit.

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