KR101268950B1 - Back light unit for liquid crystal display - Google Patents

Abstract

The present invention relates to a backlight unit for a liquid crystal display device, and more particularly, to a backlight unit for a liquid crystal display device for improving image display quality.

The backlight unit for a liquid crystal display according to the present invention controls supply of driving voltages to at least two external electrode fluorescent lamp groups and a plurality of external electrode fluorescent lamp groups in which a plurality of external electrode fluorescent lamps are grouped into a predetermined number. The number of inverter units equal to the number of external electrode fluorescent lamp groups.

According to the present invention, it is possible to implement a natural video by reducing the blurring of the screen, it is possible to minimize the reduction of the brightness to improve the display quality of the image.

External electrode fluorescent lamp group, inverter section

Description

Back light unit for liquid crystal display

1 is a view illustrating a conventional backlight unit employing an external electrode fluorescent lamp (EEFL).

2 is a view showing a conventional blinking backlight driving method.

3 is a view illustrating an operation of a backlight unit according to a conventional blinking driving method.

4 is a diagram illustrating a backlight unit for a liquid crystal display according to an exemplary embodiment of the present invention.

5 is a view for explaining the operation of the backlight unit according to the driving method of the present invention.

The present invention relates to a backlight unit for a liquid crystal display device, and more particularly, to a backlight unit for a liquid crystal display device for improving image display quality.

Recently, a liquid crystal display (LCD) has been widely used as a device for displaying various images including still and moving images. Such a liquid crystal display device is characterized by light weight, thinness, low power consumption, and the like, and the image quality is accelerated by the improvement of the liquid crystal material and the development of the fine pixel processing technology, and its application range is gradually increasing.

In general, the driving principle of the liquid crystal display device uses the optical anisotropy and polarization property of the liquid crystal. Since the liquid crystal is thin and long in structure, the liquid crystal has directivity in the arrangement of molecules, and the direction of the molecular arrangement can be controlled by artificially applying an electric field to the liquid crystal.

Accordingly, if the molecular arrangement direction of the liquid crystal is arbitrarily adjusted, the molecular arrangement of the liquid crystal is changed, and light polarized by optical anisotropy can be arbitrarily modulated to express image information.

These liquid crystals have positive dielectric anisotropy according to the electrical property classification.

Positive liquid crystal and negative (-) negative liquid crystal can be divided into, liquid crystal molecules having a positive dielectric anisotropy double the long axis of the liquid crystal molecules in the direction in which the electric field is applied

The liquid crystal molecules having heat and negative dielectric anisotropy are arranged such that the direction in which the electric field is applied and the long axis of the liquid crystal molecules are perpendicular to each other.

Since the liquid crystal display is a light-receiving display device that does not emit light by itself, it uses a backlight unit (BLU) that is installed on the back of the liquid crystal panel for displaying an image and maintains the brightness of the entire screen uniformly. have.

As a conventional backlight unit, a light guide plate method of converting a light source installed at a side surface into a planar light source by a light guide plate and a direct type method of installing a light source at a rear surface thereof are used. Fluorescent lamps used as a light source in the direct type backlight unit are classified into a cold cathode fluorescent lamp (CCFL) and an external electrode fluorescent lamp (EEFL). In general, a plurality of fluorescent lamps are provided.

In the case of a liquid crystal display device employing a direct type backlight unit, the image quality of the video is lower than that of the conventional CRT.

In particular, since the CRT performs an impulse driving while the liquid crystal display performs a hold-type driving, motion blurring occurs, and in the case of the CRT, a particular screen is displayed. The instantaneous luminance can be greatly increased by increasing the intensity of the electron beam on the screen, so that a dynamic screen can be realized. However, in the case of a liquid crystal display, the brightness is determined by the amount of light of the backlight unit. There is this.

Blinking backlight driving method is proposed as a method to slightly compensate for the disadvantages of the conventional liquid crystal display.

Hereinafter, the principle and problems of the conventional blinking backlight driving method will be described with reference to FIGS. 1 to 3.

1 is a view illustrating a conventional backlight unit employing an external electrode fluorescent lamp (EEFL), FIG. 2 is a view illustrating a conventional blinking backlight driving method, and FIG. 3 is a view of a backlight unit according to a conventional blinking driving method. It is a figure which shows operation | movement.

As shown in FIG. 1, the conventional backlight unit 100 employing an external electrode fluorescent lamp (EEFL) includes a plurality of external electrode fluorescent lamps 10 as one control unit 12 and one transformer 13. It drives using the configured inverter 11.

    In addition, as shown in FIG. 2, in the conventional blinking backlight driving method, black data is inserted between each frame as image data input to the liquid crystal display is displayed on a screen by progressing from frame to frame, When the black data is displayed on the screen, the lamp of the backlight unit is turned off.

That is, the image data and the black data are sequentially displayed in successive frames, and when the image data is displayed, the lamps of the backlight unit are turned on to irradiate light, and the black data is displayed. In this case, the lamp 10 of the backlight unit is turned off to block light, thereby implementing impulse driving of the CRT, thereby minimizing a motion blurring phenomenon in which the screen is blurred.

Various driving schemes for optimizing the efficiency of the backlight unit, such as the blinking driving scheme, have been introduced. Recently, the entire area of the liquid crystal panel displaying an image is divided into several unit blocks in the horizontal or vertical direction. Accordingly, a split driving method of a backlight unit that individually controls whether light is generated for each unit block is actively introduced.

However, since the cold cathode fluorescent lamp is generally used in the divided driving of the backlight unit, there are many problems in manufacturing, use, and luminous efficiency characteristics due to the limitation of the cold cathode fluorescent lamp in which the electrode must be installed inside the lamp. .

In addition, when the external electrode fluorescent lamp is applied to the backlight unit, by connecting the lamps to the common electrode in a bundle of 1 to 2, and driving them simultaneously using one or two inverters, it is difficult to individually drive the lamps, which is an area due to the characteristics of the image. There is a problem in that it is difficult to apply when divided driving is required such as a lack of synchronization.

Accordingly, a technical problem to be achieved by the present invention is to optimize a split driving structure using an external electrode fluorescent lamp to improve image quality degradation such as motion blurring and to improve brightness of a backlight unit for a liquid crystal display device. To provide.

The technical objects to be achieved by the present invention are not limited to the technical matters mentioned above, and other technical subjects which are not mentioned can be clearly understood by those skilled in the art from the following description. There will be.

In order to accomplish the above technical problem, a backlight unit for a liquid crystal display according to an exemplary embodiment includes two or more external electrode fluorescent lamp groups in which a plurality of external electrode fluorescent lamps are grouped into a predetermined number, and the external device. The number of inverter units equal to the number of external electrode fluorescent lamp groups controlling the supply of a driving voltage for each electrode fluorescent lamp group is included.

Each inverter unit includes a transformer for supplying a driving voltage to the external electrode fluorescent lamps belonging to each group in a one-to-one correspondence with each of the external electrode fluorescent lamp groups, and a control unit for controlling an input voltage supplied to the transformer. It is done.

The inverter unit and the external electrode fluorescent lamp group is characterized by three each.

The inverter unit may differently control the time point of applying the driving voltage supplied to the external electrode fluorescent lamp group in one frame.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a diagram illustrating a backlight unit for a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 4, a backlight unit for a liquid crystal display according to an exemplary embodiment may include two or more external electrode fluorescent lamp groups 40 in which a plurality of external electrode fluorescent lamps are grouped into a predetermined number. -1, 40-2, 40-3) and the same number of inverters as the number of external electrode fluorescent lamp groups for controlling the supply of the driving voltage for each of the external electrode fluorescent lamp groups 40-1, 40-2, and 40-3 The parts 41-1, 41-2, and 41-3 are included.

For example, when the total number of external electrode fluorescent lamps is 21, the external electrode is divided into three external electrode fluorescent lamp groups 40-1, 40-2, and 40-3 including seven external electrode fluorescent lamps. The fluorescent lamps are grouped, and each of the external electrode fluorescent lamp groups 40-1, 40-2, and 40-3 is separately driven using the independent inverter units 41-1, 41-2, and 41-3. will be.

Unlike ordinary fluorescent lamps or similar luminaires, the external electrode fluorescent lamps are connected to each other by using external electrodes composed of electrode plates on the outer wall of the tube, and are grouped into external electrode fluorescent lamp groups 40-1, 40-2, and 40-3. Electrode fluorescent lamps are arranged in parallel to the output terminal of the inverter unit (41-1, 41-2, 41-3) for converting the DC voltage to the AC voltage and outputted in a group unit structure.

Unlike the cold cathode fluorescent lamp in which the electrode is inside the tube, the external electrode fluorescent lamp is advantageous to operate in parallel because the electrode is outside, and the external electrode fluorescent lamp group 40-1, 40-2, and 40-3 Each can be driven according to the characteristics of the displayed image.

5 is a view for explaining the operation of the backlight unit according to the driving method of the present invention. The common electrode coupled to both electrodes of the external electrode fluorescent lamps is divided into three, and the inverter units 41-1, 41-2, 41 The case of supplying the output of -3) divided into three divisions is shown.

The driving method of the present invention is to turn on / off the lamp of the backlight unit in synchronization with the scan pulse applied to the gate lines on the liquid crystal panel. The liquid crystal panel includes a plurality of pixels separated by horizontal gate lines and vertical data lines that cross each other.

 In this case, as shown in FIG. 5, the backlight unit is driven by synchronizing the on / off synchronization of the backlight unit in the center of the engineering and the upper and lower parts of the additional content such as text.

For example, when the On Time Duty is 60% in the backlight unit including the liquid crystal panel consisting of 768 gate lines and the 21 external electrode fluorescent lamps, the driving is performed as follows.

After the scan pulse is applied to the 128th gate line and the signal is applied to the 435th gate line after the 307th gate line, the seven external electrode fluorescent lamps on the top of the N frame are turned on and the next frame (N +1 frame) to the 128th gate line.

The next frame (N + 1 Frame) turns on the seven external electrode fluorescent lamps in the center when a signal is applied to the 691th gate line after the 307th gate line after the scan pulse is applied to the 384th gate line, and the next frame is next. Turn off at the 384th gate line of the frame (N + 2 Frame).

Finally, the next frame (N + 2 Frame) is the lower seven external electrode fluorescence at the 187th gate line of the next frame (N + 3 Frame) after the 307th gate line after the scan pulse is applied to the 640th gate line Turn on the lamp and turn it off at the 640th gate line.

On the other hand, in consideration of the manufacturing cost and efficiency of the liquid crystal display device, it is preferable that the inverter units 41-1, 41-2, 41-3 and the external electrode fluorescent lamp group be three each.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that.

Therefore, it should be understood that the above-described embodiments are provided so that those skilled in the art can fully understand the scope of the present invention. Therefore, it should be understood that the embodiments are to be considered in all respects as illustrative and not restrictive, The invention is only defined by the scope of the claims.

As described above, the backlight unit for the liquid crystal display according to the exemplary embodiment of the present invention has an optimized split driving structure using an external electrode fluorescent lamp, so that a natural video can be realized and the brightness is improved to improve the display quality of the image. Can be improved.

Claims (5)

Two or more external electrode fluorescent lamp groups in which a plurality of external electrode fluorescent lamps are grouped into a predetermined number; And A plurality of inverter units equal to the number of external electrode fluorescent lamp groups for controlling supply of a driving voltage to each external electrode fluorescent lamp group; The fluorescent lamp groups correspond to display blocks of the liquid crystal panel, respectively; The inverter unit turns on and off a fluorescent lamp group corresponding to each display block based on a time point at which a scan pulse is supplied to a central gate line of each of the display blocks; The external electrode fluorescent lamp groups may include a first fluorescent lamp group corresponding to a first display block of the liquid crystal panel, a second fluorescent lamp group corresponding to a second display block of the liquid crystal panel, and a third display of the liquid crystal panel. A third fluorescent lamp group corresponding to the block; The first fluorescent lamp group is turned on a predetermined time after the scan pulse is supplied to the center gate line of the first display block in the Nth frame (N is a natural number), and then, in the N + 1th frame, the first fluorescent lamp group is turned on. The light is turned off when a scan pulse is supplied to the central gate line of the display block; The second fluorescent lamp group is turned on after the predetermined time elapses from the time when the scan pulse is supplied to the center gate line of the second display block in the Nth frame, and then the second display block in the N + 1th frame. Extinguished at the time when a scan pulse is supplied to the central gate line of? The third fluorescent lamp group is turned on after the predetermined time has elapsed since the scan pulse is supplied to the center gate line of the third display block in the Nth frame, and then the third display block in the N + 1th frame. The backlight unit for the liquid crystal display device, characterized in that the light is turned off when the scan pulse is supplied to the central gate line. The method of claim 1, Each inverter unit A transformer that supplies one-to-one correspondence to each of the external electrode fluorescent lamp groups and supplies a driving voltage to the external electrode fluorescent lamps belonging to the respective groups; And Control unit for controlling the input voltage supplied to the transformer Backlight unit for a liquid crystal display device comprising a. The method of claim 2, And three inverter groups and three external electrode fluorescent lamp groups. The method of claim 3, wherein And the inverter unit differently adjusts an application time point of a driving voltage supplied to the external electrode fluorescent lamp group in one frame. delete

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