KR101423518B1 - Liquid crystal display device - Google Patents

Abstract

The present invention provides a liquid crystal display device comprising: a liquid crystal panel displaying an image; A plurality of light emitting diode units disposed under the liquid crystal panel and mounted on a printed circuit board; And a plurality of light emitting diode units connected to the plurality of light emitting diode units, each of the plurality of light emitting diode units including a scan line for transmitting a scan signal and a light emitting data line for transmitting a light emitting data current, Wow; A current mirror circuit connected to the switching circuit and outputting a light emission current in response to the light emission data current; And a light emitting diode that emits light by receiving the output light emission current.

Description

[0001] Liquid crystal display device [0002]

The present invention relates to a liquid crystal display device, and more particularly, to a light emitting diode backlight for a liquid crystal display device.

2. Description of the Related Art [0002] With the development of an information society, demands for a display device for displaying images have been increasing in various forms. Recently, a liquid crystal display (LCD), a plasma display panel (PDP) Various flat display devices such as an organic light emitting diode (OLED) have been utilized.

Of these flat panel display devices, liquid crystal display devices are widely used today because they have advantages of miniaturization, weight reduction, thinness, and low power driving. The liquid crystal display device has a backlight as a light source. The backlight supplies light to the liquid crystal panel, and the liquid crystal panel modulates the supplied light to display a desired image.

As backlights, cold cathode fluorescent lamps (CCFLs) and external electrode fluorescent lamps (EEFLs) have been widely used. Recently, light emitting diodes (LEDs) having low power consumption and high luminous efficiency have been adopted as backlights.

1 is a circuit diagram schematically showing a conventional light emitting diode backlight.

As shown in FIG. 1, light emitting diodes (LEDs) are arranged in units of blocks (BLK) in a light emitting diode backlight 40, and a large number of such blocks BLK are arranged. Such a backlight 40 is disposed under the liquid crystal panel, and such a structure is called a direct type structure.

In the block BLK, a plurality of light emitting diodes (LEDs) are connected to each other in series, and these are connected to a corresponding constant current source circuit (CRC). The constant current source circuit (CRC) applies a constant current to each block (BLK), so that the light emitting diode (LED) of the corresponding block (BLK) emits light.

On the other hand, a plurality of such constant current source circuits (CRC) are formed in one multi-channel driving IC. Thus, the multi-channel driving IC can drive blocks corresponding to the number of channels. Therefore, in order to drive the conventional LED backlight 40, a large number of driving ICs are provided.

However, when the size of the liquid crystal display device increases or a backlight 400 with a high luminance is required, the number of light emitting diodes (LEDs) increases. As a result, the number of blocks BLK increases, and the number of drive ICs required increases. This increases the cost of circuit components for driving the light emitting diodes (LEDs).

On the other hand, in order to reduce the circuit component cost, it may be considered to increase the number of light emitting diodes (LEDs) constituted in each block BLK. However, the light emitting diodes (LEDs) configured in the block BLK are all driven at the same time by receiving the same constant current. Therefore, as the number of the light emitting diodes (LEDs) configured in the block BLK is increased, the power consumption is increased.

Further, since the light emitting diodes (LEDs) constituted in the block BLK are driven all at once by receiving the same constant current, the halo phenomenon becomes severe and the contrast ratio is limited.

SUMMARY OF THE INVENTION The present invention has a problem in providing a liquid crystal display device capable of improving image quality in using a light emitting diode backlight.

The present invention has another problem in reducing the cost of circuit components for driving the light emitting diode backlight.

Further, the present invention has another problem in reducing the power consumption in using the light emitting diode backlight.

In order to achieve the above-mentioned object, the present invention provides a liquid crystal display device comprising: a liquid crystal panel displaying an image; A plurality of light emitting diode units disposed under the liquid crystal panel and mounted on a printed circuit board; And a plurality of light emitting diode units connected to the plurality of light emitting diode units, each of the plurality of light emitting diode units including a scan line for transmitting a scan signal and a light emitting data line for transmitting a light emitting data current, Wow; A current mirror circuit connected to the switching circuit and outputting a light emission current in response to the light emission data current; And a light emitting diode that emits light by receiving the output light emission current.

The current mirror circuit may include a first transistor receiving the light emission data current and a second transistor outputting the light emission current to the light emitting diode.

Wherein the switching circuit includes first and second switching elements that switch in the same manner in accordance with the scan signal, the first switching element is connected between the light emitting data line and the drain terminal of the first transistor, 2 switching element may be connected between the drain terminal and the gate terminal of the first transistor.

Wherein the switching circuit includes first and second switching elements that switch in the same manner in accordance with the scan signal, the first switching element is connected between the light emitting data line and the drain terminal of the first transistor, 2 switching element may be connected between the gate terminal of the first transistor and the gate terminal of the second transistor.

Wherein the switching circuit includes first and second switching elements that switch in the same manner in accordance with the scan signal, the first switching element is connected between the light emitting data line and the drain terminal of the first transistor, 2 switching element may be connected between the light emitting data line and the gate terminal of the first transistor.

And a storage capacitor connected between a gate terminal and a source terminal of the second transistor.

The first and second transistors may be P-type or N-type transistors.

A scan driver circuit comprising at least one drive IC having a plurality of channels; Wherein the channel of the scan driving circuit corresponds to the scan wiring and the channel of the light emitting data driving circuit corresponds to the light emitting data wiring .

The current mirror circuit, the switching circuit, and the light emitting diode may be packaged together and mounted on the printed circuit board.

At least one of the current mirror circuit and the switching circuit may be mounted on the back surface of the printed circuit board.

In the present invention, the light emitting diodes are stably driven through the current mirror circuit, and such light emitting diodes are arranged in a matrix form. Such light emitting diodes are driven in an active matrix manner and can be driven individually. Accordingly, it is possible to improve the halo phenomenon caused by driving the light emitting diodes all at once in block units. In addition, since the backlight luminance can be partially adjusted in units of light emitting diodes, the contrast ratio can be improved. Therefore, a considerable effect can be obtained in terms of image quality.

Further, since the light emitting diodes can be individually driven, even if some light emitting diodes are defective, the defective light emitting diodes do not affect other light emitting diodes. Accordingly, when a defect occurs in a light emitting diode in the past, it is possible to improve the problem that the operation of the entire light emitting diode of the block is stopped by affecting the entire light emitting diode of the block.

Further, the light emitting diodes can individually control the operation current. Thus, the power consumption can be reduced.

Further, when the scan driver circuit and the light emission data driver circuit for driving the light emitting diodes are each formed of a multi-channel driver IC, the cost of circuit components can be reduced to a considerable extent.

Further, the light emitting diode unit may be manufactured in a package form and mounted on a printed circuit board. As described above, in the case where the light emitting diode unit is packaged and mounted, the packaging efficiency and yield can be significantly improved as compared with the case where the components of the light emitting diode unit are separately mounted.

1 is a circuit diagram schematically showing a conventional light emitting diode backlight;
2 is a view schematically showing a liquid crystal display device according to a first embodiment of the present invention.
3 is a view schematically showing a backlight and a backlight driving circuit according to a first embodiment of the present invention;
4 is a circuit diagram showing a light emitting diode unit according to a first embodiment of the present invention.
5 is a circuit diagram illustrating a method of driving a light emitting diode according to a first embodiment of the present invention.
6 is a circuit diagram showing a light emitting diode unit of a liquid crystal display device according to a second embodiment of the present invention.
7 is a circuit diagram showing a light emitting diode unit of a liquid crystal display device according to a third embodiment of the present invention.
8 is a circuit diagram showing a light emitting diode unit of a liquid crystal display device according to a fourth embodiment of the present invention
9 is a circuit diagram showing a light emitting diode unit of a liquid crystal display device according to a fifth embodiment of the present invention.
10 is a circuit diagram showing a light emitting diode unit of a liquid crystal display device according to a sixth embodiment of the present invention.
11 is a cross-sectional view schematically showing a liquid crystal display device according to a seventh embodiment of the present invention.

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

FIG. 2 is a view schematically showing a liquid crystal display device according to a first embodiment of the present invention. FIG. 3 is a view schematically showing a backlight and a backlight driving circuit according to the first embodiment of the present invention, and FIG. 4 FIG. 5 is a circuit diagram illustrating a method of driving a light emitting diode according to a first embodiment of the present invention. FIG. 5 is a circuit diagram illustrating a method of driving a light emitting diode according to a first embodiment of the present invention.

As shown in the figure, a liquid crystal display 100 according to an embodiment of the present invention includes a liquid crystal panel 200, a driving circuit, and a backlight 400. The driving circuit includes a timing control circuit 300, a gate driving circuit 310, a data driving circuit 320, and a backlight driving circuit 500.

A plurality of gate lines GL extending in the row direction and a plurality of data lines DL extending in the column direction cross each other in the liquid crystal panel 200 to form a plurality of pixels P).

In each pixel P, a switching transistor T connected to the gate wiring and the data lines GL and DL is formed. The switching transistor T is connected to the pixel electrode. On the other hand, a common electrode is formed corresponding to the pixel electrode, and an electric field is formed between the pixel electrode and the common electrode to drive the liquid crystal. The pixel electrode, the common electrode, and the liquid crystal located between these electrodes constitute a liquid crystal capacitor Clc. Each pixel P further includes a storage capacitor Cst, which serves to store the image data voltage applied to the pixel electrode to the next image frame.

The pixel P constructed in the liquid crystal panel 200 may include R (red), G (green), and B (blue) pixels. The corresponding R, G, and B image data signals are input to the R, G, and B pixels P, respectively. Here, neighboring R, G, and B pixels (P) constitute one image unit.

The timing control circuit 300 receives a data signal RGB, a vertical synchronizing signal Vsync, a horizontal synchronizing signal Hsync and a clock signal DCLK from a system such as a TV system or a video card and a data enable signal DE And the like. On the other hand, although not shown, such signals may be input to the timing control circuit 300 via an interface.

The timing control circuit 300 generates a gate control signal GCS for controlling the gate driving circuit 310 and a data control signal DCS for controlling the data driving circuit 320 by using the input control signal do. The gate control signal GCS includes a gate start pulse GSP, a gate shift clock GSC and a gate output enable signal GOE. The data control signal DCS includes a source start pulse (SSP), a source shift clock (SSC), a source output enable (SOE), a polarity (POL) And the like.

On the other hand, the timing control circuit 300 can generate the backlight control signal BCS for controlling the backlight driving circuit 500. [ Furthermore, the timing control circuit 300 can generate the light emission data signal LDAT for controlling the light emission luminance of the light emitting diode (LED). Here, each of the light emission data signals LDAT corresponds to a light emitting diode (LED).

Although not shown, the gamma reference voltage generating circuit divides the high-potential voltage and the low-potential voltage to generate a plurality of gamma reference voltages and supplies them to the data driving circuit 320. The power supply generating circuit receives a power supply voltage from the outside and generates and supplies a driving voltage for driving the components of the liquid crystal display device 100. [

The gate driving circuit 310 sequentially scans a plurality of gate lines GL in units of image frames in response to a gate control signal GCS supplied from the timing control circuit 300. During each scan period, an on voltage is supplied to the gate line GL. On the other hand, the off voltage is continuously supplied to the gate line GL until the scan period of the next image frame. By applying a turn-on voltage during the scan period, the switching transistor T is turned on.

The data driving circuit 320 supplies the video data voltages to the plurality of data lines DL in response to the data control signal DCS supplied from the timing control circuit 300. [ That is, a gamma reference voltage is used to generate a video data voltage corresponding to the video data signal RGB, and the generated video data voltage is output to the corresponding data line DL.

The backlight 400 serves to supply light to the liquid crystal panel 200. As the backlight 400, a direct-type backlight that is positioned below the liquid crystal panel 200 and supplies light may be used.

A plurality of light emitting diodes (LEDs) are arranged in a matrix form in the backlight 400, and such light emitting diodes (LEDs) can be driven in an active matrix manner. In this regard, it will be described in more detail with further reference to Figs.

The backlight driving circuit 500 may include a backlight control circuit 510, a scan driving circuit 520, and a light emission data driving circuit 530.

The scan driving circuit 520 is connected to a plurality of scan lines SL1 to SLn and the emission data driving circuit 530 is connected to a plurality of emission data lines LDL1 to LDLm.

The scan line SL and the light emission data line LDL are connected to the corresponding light emitting diode unit LEDU to drive the same.

The light emitting diode unit (LEDU) may include a light emitting diode (LED), a current mirror circuit (CMC), and a switching circuit (SWC).

The switching circuit SWC is connected to the corresponding scan line SL and the emission data line LDL. The current mirror circuit CMC is connected to the switching circuit SWC. The light emitting diode (LED) is connected to the current mirror circuit CMC.

Each of the light emitting diodes (LEDs) disposed under the liquid crystal panel 200 may correspond to a plurality of pixels P of the liquid crystal panel 200. For example, the liquid crystal panel 200 may be divided into pixel blocks corresponding to each of the light emitting diode units (LEDU), and each pixel block may include a plurality of pixels P. The light emitting diodes (LEDs) Each may correspond to a pixel block.

The current mirror circuit CMC may include first and second transistors T1 and T2 symmetrical to each other and having the same characteristics as each other. As the first and second transistors T1 and T2, an N-type (negative type) transistor may be used. For example, an NMOS transistor may be used.

The current mirror circuit CMC is connected to the corresponding light emission data line LDL through the switching circuit SWC to be able to receive the signal. Such a switching circuit (SWC) may include at least one switching element. For example, the switching circuit SWC may include two first and second switching elements SW1 and SW2.

A first switching device SW1 may be connected between the drain terminal of the first transistor T1 and the light emitting data line LDL. A second switching device SW2 may be connected between the gate terminal and the drain terminal of the first transistor T1. Here, the first and second switching elements SW1 and SW2 are commonly connected to the scan wiring SL to perform the same switching operation.

The gate terminal of the second transistor T2 is connected to the gate terminal of the first transistor T1. The drain terminal of the second transistor T2 is connected to the light emitting diode (LED). The source terminal of the second transistor T2 is connected to the source terminal of the first transistor T1. Here, the source terminals of the first and second transistors T1 and T2 may be grounded.

The light emitting diode (LED) is connected to the power supply voltage VDD. A storage capacitor C may be provided between the gate terminal and the source terminal of each of the first and second transistors T1 and T2.

The operation of the light emitting diode unit (LEDU) having the above configuration will be described with reference to FIG.

For example, when an on-level scan signal is input through the scan line SL, the first and second switching elements SW1 and SW2 are turned on.

When the first and second switching elements SW1 and SW2 are turned on in this way, the emission data current I_LDAT applied to the corresponding emission data line LDL passes through the first and second switching elements SW1 and SW2 And is input to the first transistor T1 of the current mirror circuit CMC. In response to this, the current mirror circuit CMC outputs the light emission current I_LED through the second transistor T2. The light emission current I_LED outputted as described above is applied to the light emitting diode (LED), so that the light emitting diode (LED) emits light.

Here, the current mirror circuit CMC outputs a substantially same output current as the input current due to its characteristics. Thus, the light emission current I_LED as the output current is substantially equal to the light emission data current I_LDAT as the input current (I_LED? I_LDAT).

Accordingly, as the light emission data current I_LDAT is adjusted, the light emission luminance of the light emitting diode (LED) is adjusted.

On the other hand, when the scan signal becomes off-level, the first and second switching elements 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 even if the first and second switching elements SW1 and SW2 are turned off. Thus, until the next scan is performed, the light emitting diode (LED) can continuously emit light of the luminance corresponding to the inputted light emission data current I_LDAT.

The backlight control circuit 510 receives the backlight control signal BCS from the timing control circuit 300 and supplies the scan control signal SCS for controlling the scan drive circuit 520 and the light emission data driving circuit 530 And generates a light emission data control signal LDCS to be controlled. On the other hand, the backlight control circuit 510 may be configured inside the timing control circuit 300. [

The scan driver circuit 510 sequentially scans a plurality of scan lines SL1 to SLn for each emission frame in response to a scan control signal SCS. Here, the light emitting frame corresponds to a period for scanning a plurality of scan lines SL1 to SLn. Such a light emitting frame can be synchronized with the image display on the liquid crystal panel 200. [ For example, the light emitting frame can be synchronized to be the same as the image frame.

The light emission data driving circuit 530 supplies the light emission data current I_LDAT to the corresponding light emission data line LDL in response to the light emission data control signal LDCS. That is, a light emission data current I_LDAT corresponding to the light emission data signal LDAT for the row lines is generated, and the generated light emission data current I_LDAT is output to the corresponding data line DL.

The output of the light emission data current I_LDAT can be performed at every scan. For example, at each scan, corresponding 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 outputted is inputted to a light emitting diode unit (LEDU) connected to the selected scan line. Accordingly, the light emitting diode (LED) of the light emitting diode unit LEDU emits light of the luminance corresponding to the light emitting data current I_LDAT.

As described above, the backlight 400 using the light emitting diode (LED) is controlled by the scan driving circuit 520 and the light emission data driving circuit 530, and can be driven in an active matrix manner. Accordingly, the corresponding light emitting data current I_LDAT is input to each of the plurality of light emitting diode units LEDU, and light corresponding to the light emitting data current I_LDAT is emitted in units of the light emitting frames.

As described above, the light emitting diode units (LEDU) receive the corresponding emission data current I_LDAT and can be independently driven independently.

Since the light emitting diode units (LEDU) can be individually driven, the brightness of the displayed image can be partially controlled. In this regard, let us suppose that there is a bright part and a dark part in one image. In such a case, the light emission luminance of the light emitting diode (LED) of the light emitting diode unit (LEDU) corresponding to the pixels P that display the bright portion is relatively increased, The light emission luminance of the light emitting diode (LED) of the light emitting diode unit (LED) becomes relatively low. In this way, in the finally displayed image, the bright part becomes relatively brighter and the dark part becomes relatively darker. As a result, the contrast ratio can be increased. For this operation, the emission data signal LDAT can be generated reflecting the video data signal RGB. For example, the light emission data signal LDAT corresponding to the light emitting diode unit (LEDU) may be generated to have a value corresponding to a representative value, for example, an average value of the image data signals of the corresponding pixel block.

Meanwhile, the scan driving circuit 520 according to the first embodiment of the present invention may be constituted by at least one multi-channel driving IC having a plurality of output terminals. For example, an n-channel driver IC having n output terminals corresponding to the plurality of scan wirings SL1 to SLn, respectively, can be used as the scan driver circuit 510. [

In addition, the light-emitting data driving circuit 530 according to the first embodiment of the present invention may be composed of at least one multi-channel IC having a plurality of output terminals. For example, an m-channel driver IC having m output terminals corresponding to the plurality of light emission data lines LDL1 to LDLm, respectively, can be used as the light emission data drive circuit 530. [

6 is a circuit diagram showing a light emitting diode unit of a liquid crystal display device according to a second embodiment of the present invention. The liquid crystal display of the second embodiment is similar to the liquid crystal display of the first embodiment except for the structure of the light emitting diode unit. As such, the description of the portions similar to those of the first embodiment can be omitted.

Referring to Fig. 6, the second switching device SW2 in the second embodiment is connected between the gate terminal of the first transistor T1 and the gate terminal of the second transistor T2. On the other hand, the gate terminal and the drain terminal of the first transistor T1 are directly connected.

7 is a circuit diagram showing a light emitting diode unit of a liquid crystal display device according to a third embodiment of the present invention. The liquid crystal display of the third embodiment is similar to the liquid crystal display of the first embodiment except for the configuration of the light emitting diode unit. As such, the description of the portions similar to those of the first embodiment can be omitted.

Referring to Fig. 7, the second switching device SW2 in the third embodiment is connected between the gate terminal of the first transistor T1 and the corresponding light emitting data lines LDL1 and LDL2.

8 is a circuit diagram showing a light emitting diode unit of a liquid crystal display according to a fourth embodiment of the present invention. The liquid crystal display of the fourth embodiment is similar to the liquid crystal display of the first embodiment except for the structure of the light emitting diode unit. As such, the description of the portions similar to those of the first embodiment can be omitted.

Referring to FIG. 8, as the first and second transistors T1 and T2 in the fourth embodiment, a P-type transistor can be used. For example, a PMOS transistor may be used as the first and second transistors T1 and T2.

9 is a circuit diagram showing a light emitting diode unit of a liquid crystal display device according to a fifth embodiment of the present invention. The liquid crystal display device of the fifth embodiment is similar to the liquid crystal display device of the fourth embodiment except for the structure of the light emitting diode unit. As such, the description of the portions similar to those of the fourth embodiment can be omitted.

Referring to Fig. 9, the second switching device SW2 in the fifth embodiment is connected between the gate terminal of the first transistor T1 and the gate terminal of the second transistor T2. On the other hand, the gate terminal and the drain terminal of the first transistor T1 are directly connected.

10 is a circuit diagram showing a light emitting diode unit of a liquid crystal display device according to a sixth embodiment of the present invention. The liquid crystal display device of the sixth embodiment is similar to the liquid crystal display device of the fourth embodiment except for the structure of the light emitting diode unit. As such, the description of the portions similar to those of the fourth embodiment can be omitted.

Referring to FIG. 10, the second switching device SW2 in the sixth embodiment is connected between the gate terminal of the first transistor T1 and the corresponding light emitting data lines LDL1 and LDL2.

In the above-described first to sixth embodiments, various types of current mirror circuits and switching circuits can be used. On the other hand, it is apparent to those skilled in the art that a current mirror circuit and / or a switching circuit other than these can be used.

11 is a cross-sectional view schematically showing a liquid crystal display device according to a seventh embodiment of the present invention. In the seventh embodiment, the light emitting diode units in the first to sixth embodiments described above can be used.

11, a printed circuit board (PCB), for example, a first printed circuit board PCB1, on which a light emitting diode (LED) arranged in a matrix form is mounted, is disposed under the liquid crystal panel 200 do. Although not shown, a plurality of optical sheets, such as a diffusion sheet and a prism sheet, may be positioned between the liquid crystal panel 200 and the first printed circuit board PCB1.

On the other hand, a printed circuit board (for example, a second printed circuit board PCB2) having a backlight driving circuit (500 of FIG. 3) mounted thereon may be disposed on at least one side of the first printed circuit board PCB1.

The second printed circuit board PCB2 may be connected to the first printed circuit board PCB1 through at least one flexible circuit member FCM. Here, the flexible circuit member (FCM) is an electrically connecting member having a flexible characteristic and having a plurality of wiring patterns, for example, a flexible circuit film, a flexible cable, or the like can be used.

Through such a flexible circuit member (FCM), it is possible to transmit signals for driving the LED unit (LEDU of FIG. 3) located on the first printed circuit board PCB1.

The above-described second printed circuit board PCB2 can be used as the first printed circuit board PCB1 due to the deflection of the flexible circuit member FCM in the process of assembling a plurality of electrical mechanical components constituting the liquid crystal display device. Can be located on the back side.

On the other hand, the second printed circuit board PCB2 may be located on each side of the first printed circuit board PCB1. In this case, some of the light emitting diode units LEDU located on the first printed circuit board PCB1 are connected to and driven by one of the two second printed circuit boards PCB2 located on both sides, The remaining part of the units LEDU may be connected to and driven by the other of the two second printed circuit boards PCB2 located on both sides.

The light emitting diode (LED) may be fabricated in a package form, which may be referred to as a light emitting diode package (LEDP). For example, a light emitting diode package (LEDP) can refer to a light emitting diode (LED) and a configuration for protecting it and associated with components for mounting on a first printed circuit board (PCB1). The packaged light emitting diode (LED) can be mounted on the first printed circuit board PCB1.

On the other hand, in such a light emitting diode package (LEDP), at least one of the switching circuit and the current mirror circuit (see the first to sixth embodiments) constituting the light emitting diode unit (LEDU) as well as the light emitting diode have.

Alternatively, at least one of the switching circuit and the current mirror circuit may be mounted on a portion of the first printed circuit board (PCB1) outside the light emitting diode package (LEDP). Here, at least one of the switching circuit and the current mirror circuit may be located on one of the upper surface and the back surface of the first printed circuit board PCB1. On the other hand, it is more preferable that the switching circuit and the current mirror circuit are located on the back surface of the first printed circuit board PCB1. In this way, when the switching circuit and the current mirror circuit are located outside the light emitting diode package (LEDP), they may be separately manufactured in an IC form and mounted on the first printed circuit board PCB1.

As described above, in the liquid crystal display device according to the embodiment of the present invention, the light emitting diodes are stably driven through the current mirror circuit, and such light emitting diodes can be arranged in a matrix form. Such light emitting diodes can be driven in an active matrix manner, and can be driven individually. Accordingly, it is possible to improve the halo phenomenon caused by driving the light emitting diodes all at once in block units. In addition, since the backlight luminance can be partially adjusted in units of light emitting diodes, the contrast ratio can be improved. Therefore, a considerable effect can be obtained in terms of image quality.

Further, since the light emitting diodes can be individually driven, even if some light emitting diodes are defective, the defective light emitting diodes do not affect other light emitting diodes. Accordingly, when a defect occurs in a light emitting diode in the past, it is possible to improve the problem that the operation of the entire light emitting diode of the block is stopped by affecting the entire light emitting diode of the block.

Further, the light emitting diodes can individually control the operation current. Thus, the power consumption can be reduced.

Further, when the scan driver circuit and the light emission data driver circuit for driving the light emitting diodes are each formed of a multi-channel driver IC, the cost of circuit components can be reduced to a considerable extent.

In this regard, suppose that 720 light emitting diodes are arranged in a 36 * 20 matrix. Conventionally, if four light emitting diodes are constituted by one block, the total light emitting diodes are divided into 180 (= 720/4) blocks. In this case, if a 16-channel driver IC is used, approximately 12 16-channel driver ICs are required (one block is connected to one channel). That is, since 180/16 = 11.25, 12 16-channel driving ICs are required.

In contrast, according to the embodiment of the present invention, a 36-channel driving IC can constitute an emission data driving circuit, and a 20-channel driving IC can constitute a scan driving circuit (36 * 20 = 720).

In such a case, in the embodiment of the present invention, it is possible to drive 720 light emitting diodes using only two driving ICs, whereas 12 driving ICs are conventionally required. Therefore, the cost of circuit components is reduced as much as the difference between the driving ICs, and the cost reduction effect is significant.

Meanwhile, in the embodiment of the present invention, the light emitting diode unit may be manufactured in a package form and mounted on a printed circuit board. As described above, in the case where the light emitting diode unit is packaged and mounted, the packaging efficiency and yield can be significantly improved as compared with the case where the components of the light emitting diode unit are separately mounted.

The embodiment of the present invention described above is an example of the present invention, and variations are possible within the spirit of the present invention. Accordingly, the invention includes modifications of the invention within the scope of the appended claims and equivalents thereof.

400: backlight 400: light emission data driving circuit
SL: scan wiring
LDL: Emission data wiring
LEDU: Light Emitting Diode Unit
LED: Light emitting diode
T1, T2: first and second transistors
SW1 and SW2: first and second switching elements
C: Storage capacitor

Claims (11)

A liquid crystal panel for displaying an image;
A plurality of light emitting diode units disposed under the liquid crystal panel and mounted on the first printed circuit board;
And a plurality of light emitting diodes connected to each of the plurality of light emitting diode units for transmitting a scan signal and a light emitting data line for transmitting a light emitting data current,
The light emitting diode unit includes: a switching circuit connected to the scan wiring and the light emission data line; A current mirror circuit connected to the switching circuit and outputting a light emission current in response to the light emission data current; And a light emitting diode which emits light by receiving the output light emission current,
The current mirror circuit includes a first transistor connected to the light emitting data line via a drain terminal and receiving the light emitting data current, and a second transistor connected to the light emitting diode through a drain terminal, for outputting the light emitting current to the light emitting diode. 2 transistors,
A gate terminal of the first transistor is connected to a gate terminal of the second transistor, a source terminal of the first transistor is connected to a source terminal of the second transistor,
Further comprising a second printed circuit board on which at least one of the current mirror circuit and the switching circuit is mounted and which is connected to the first printed circuit board via a flexible circuit member (FCM)
Wherein the second printed circuit board is located on the back side of the first printed circuit board through a flexible circuit member (FCM)
Wherein the liquid crystal panel includes a pixel block corresponding to each of the light emitting diode units and including a plurality of pixels,
Wherein a light emission data current input to the light emitting diode unit has a value corresponding to an average value of image data signals of a plurality of pixels included in the pixel block corresponding to the light emitting diode unit.
delete The method according to claim 1,
Wherein the switching circuit includes first and second switching elements for switching in accordance with the scan signal,
The first switching element is connected between the light emitting data line and the drain terminal of the first transistor,
The second switching element is connected between the drain terminal and the gate terminal of the first transistor
Liquid crystal display device.
The method according to claim 1,
Wherein the switching circuit includes first and second switching elements for switching in accordance with the scan signal,
The first switching element is connected between the light emitting data line and the drain terminal of the first transistor,
The second switching element is connected between a gate terminal of the first transistor and a gate terminal of the second transistor
Liquid crystal display device.
The method according to claim 1,
Wherein the switching circuit includes first and second switching elements for switching in accordance with the scan signal,
The first switching element is connected between the light emitting data line and the drain terminal of the first transistor,
And the second switching element is connected between the light emitting data line and the gate terminal of the first transistor
Liquid crystal display device.
The method according to claim 1,
And a storage capacitor coupled between a gate terminal and a source terminal of the second transistor
Liquid crystal display device.
delete The method according to claim 1,
A scan driver circuit comprising at least one drive IC having a plurality of channels;
Further comprising an emission data driving circuit comprising at least one driving IC having a plurality of channels,
The channel of the scan driving circuit corresponds to the scan wiring, and the channel of the light emitting data driving circuit corresponds to the light emitting data wiring
Liquid crystal display device.
delete delete The method according to claim 1,
Wherein the flexible circuit member is an electrically connecting member having a flexible characteristic and having a plurality of wiring patterns,
And the second printed circuit board is positioned on both sides of the first printed circuit board through the flexible circuit member.

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