KR20130011906A - Apparatus and method for driving back light, liquid crystal display device and driving method the same - Google Patents

Abstract

PURPOSE: A back light operating device, an operating method thereof, a liquid crystal display device thereof, and an operating method thereof are provided to minimize a glimmer according to a frequency of a back light unit by making a frequency of a back light dimming signal same as or higher than a frame sync signal. CONSTITUTION: A back light unit includes plural light sources. Plural light sources emit light to a liquid crystal display panel. A back light operating unit sequentially lights the light sources by frame units. A back light control unit generates a back light dimming signal. A back light dimming signal has a frequency same as or higher than a frame sync signal. A control unit includes a comparing unit(210), a back light sync signal generating unit(220), and a dimming signal generating unit(230). The comparing unit compares reference duty-on information with current duty-on information. The back light sync signal generating unit supplies a first back light sync signal to the dimming signal generating unit. The dimming signal generating unit generates a back light dimming signal to supply the same to the back light operating unit.

Description

Backlight driving device and driving method, liquid crystal display using same and driving method thereof {APPARATUS AND METHOD FOR DRIVING BACK LIGHT, LIQUID CRYSTAL DISPLAY DEVICE AND DRIVING METHOD THE SAME}

The present invention relates to a backlight driving apparatus and a liquid crystal display, and more particularly, to a backlight driving apparatus and a driving method capable of reducing power consumption, a liquid crystal display using the same, and a driving method thereof.

In general, a motion blurring phenomenon in which a contour of an image is blurred due to a slow response speed of a liquid crystal appears in a moving image displayed by a liquid crystal display. In order to prevent such a motion blur phenomenon, the conventional liquid crystal display device uses a scanning backlight method of sequentially lighting a plurality of light sources disposed on the rear surface of the liquid crystal display panel according to the backlight dimming signal.

In a conventional liquid crystal display using a scanning backlight method, a plurality of light sources are sequentially turned on during a duty on period according to a frequency of a backlight dimming signal having a predetermined duty on period and a duty off period. By turning on, the period from when the outline of the image is blurred to clear again (that is, the motion picture response time) is improved.

In such a scanning backlight type liquid crystal display device, the frequency of the backlight dimming signal is set to be the same as the frequency of the frame synchronization signal. Meanwhile, in order to reduce power consumption, it is desirable to reduce the frequency of the frame synchronization signal, in which case the frequency of the backlight dimming signal is also reduced. However, when the frequency of the backlight dimming signal is reduced, there is a problem that the flicker is recognized by turning on and off the backlight.

Disclosure of Invention The present invention has been made to solve the above-described problem, and the present invention provides a backlight driving apparatus capable of minimizing flicker caused by a scanning backlight and improving moving image quality even if the frequency of the frame synchronization signal is reduced to reduce power consumption. It is a technical problem to provide a driving method, a liquid crystal display using the same, and a driving method thereof.

According to an aspect of the present invention, there is provided a backlight driving apparatus including: a backlight unit including a plurality of light sources that irradiate light onto a liquid crystal display panel displaying an image according to a liquid crystal response; A backlight driver configured to sequentially light the plurality of light sources in units of frames based on a backlight dimming signal having a predetermined duty on period and a duty off period; And a backlight controller configured to generate the backlight dimming signal having a frequency equal to or higher than a frame synchronization signal of the liquid crystal display panel based on duty-on information provided from the outside through analysis of the image. It is done.

According to an aspect of the present invention, a liquid crystal display device includes: a liquid crystal display panel configured to display an image on a frame basis; A timing controller which analyzes input data on a frame-by-frame basis to generate duty-on information of the image and generates a timing control signal according to a timing synchronization signal including a frame synchronization signal; A panel driver configured to generate a gate signal and a data signal according to the timing control signal and to supply the gate signal and the data signal to the liquid crystal display panel; And a backlight driving device for irradiating light to the liquid crystal display panel based on the duty-on information and the frame synchronizing signal supplied from the timing controller, wherein the backlight driving device is arranged in the liquid crystal display panel. A backlight unit including a plurality of light sources for irradiating light; A backlight driver configured to sequentially light the plurality of light sources in units of frames based on a backlight dimming signal having a predetermined duty on period and a duty off period; And a backlight controller configured to generate the backlight dimming signal having a frequency equal to or higher than a frame synchronization signal of the liquid crystal display panel based on duty-on information provided from the outside through analysis of the image. It is done.

In the backlight driving method according to the present invention for achieving the above-described technical problem is a driving method of a backlight driving device comprising a plurality of light sources for irradiating light to a liquid crystal display panel for displaying an image according to the liquid crystal response, Generating a backlight dimming signal having a frequency equal to or higher than a frame synchronization signal of the liquid crystal panel based on duty on information provided from the outside according to the image; And sequentially lighting the plurality of light sources on a frame-by-frame basis during the duty-on period based on the backlight dimming signal.

The driving method of the liquid crystal display according to the present invention for achieving the above technical problem is to generate the duty-on information of the image by analyzing the input data on a frame-by-frame basis and to generate a timing control signal according to a timing synchronization signal including a frame synchronization signal. Generating; Generating and supplying a gate signal and a data signal according to the timing control signal to a liquid crystal display panel; And irradiating light to the liquid crystal display panel based on the duty on information and the frame synchronization signal, and irradiating light to the liquid crystal display panel. The irradiating light may include a backlight driving step, and the backlight driving step may include a frequency equal to or higher than a frame synchronization signal of the liquid crystal display panel based on duty-on information provided from the outside according to the image. Generating a backlight dimming signal having a; And sequentially lighting the plurality of light sources on a frame-by-frame basis during the duty-on period based on the backlight dimming signal.

As described above, the backlight driving apparatus and driving method according to the present invention, the liquid crystal display using the same, and the driving method thereof have the following effects.

First, flickering according to the frequency of the backlight unit may be minimized by setting the frequency of the backlight dimming signal to be equal to or higher than the frame synchronization signal based on the duty-on information.

Secondly, the backlight dimming signal is generated at the same first frequency as the frame synchronization signal based on the duty-on information, or is incrementally increased from the first frequency to the second frequency or gradually reduced from the second frequency to the first frequency. As a result, flickering according to the frequency of the backlight unit can be minimized, and flickering due to a sudden frequency change of the backlight dimming signal can be prevented.

Third, by delaying the duty-on period of the backlight dimming signal generated to increase or decrease step by step according to the duty-on information to synchronize the duty-on period of the backlight dimming signal having the first frequency or the second frequency to the liquid crystal response speed. The image quality of a moving image displayed on the liquid crystal display panel can be improved.

1 is a view for explaining a backlight driving apparatus according to an embodiment of the present invention.
FIG. 2A is a diagram for describing a first embodiment of the backlight controller illustrated in FIG. 1, and FIG. 2B is a diagram for describing the backlight synchronization signal generator illustrated in FIG. 2A.
3A and 3B illustrate a backlight dimming signal according to a first embodiment of the present invention.
4 is a flowchart illustrating the operation of the backlight controller according to FIGS. 2A and 2B.
FIG. 5A is a diagram for describing a second embodiment of the backlight controller illustrated in FIG. 1, and FIG. 5B is a diagram for describing the backlight synchronization signal generator illustrated in FIG. 5A.
6A and 6B illustrate a backlight dimming signal according to a second embodiment of the present invention.
7 is a flowchart illustrating the operation of the backlight controller according to FIGS. 5A and 5B.
FIG. 8 is a view for explaining a third embodiment of the backlight control unit shown in FIG. 1, and FIG. 9 is a waveform diagram for explaining the dimming signal delay unit shown in FIG. 8.
10 is a diagram for describing a liquid crystal display according to an exemplary embodiment of the present invention.

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

1 is a view for explaining a backlight driving apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the backlight driving apparatus 100 according to an exemplary embodiment may include a backlight unit 110 including a plurality of light sources (not shown) and a backlight generating a backlight dimming signal BDS. The controller 120 and the backlight driver 130 sequentially lighting the plurality of light sources on a frame basis based on the backlight dimming signal BDS provided from the backlight controller 120.

The backlight unit 110 divides the liquid crystal display panel into a plurality of regions and includes a plurality of light sources installed to correspond to the divided regions. The plurality of light sources may use a fluorescent lamp (CCFL) or a light emitting diode (LED).

Each of the plurality of light sources made of the light emitting diodes may be driven in a series manner or in a parallel manner.

The backlight unit 110 may include a light guide plate (not shown) for propagating light emitted from a plurality of light sources toward the liquid crystal display panel, and a reflection sheet (not shown) disposed at a lower portion of the light guide plate to reflect incident light toward the liquid crystal display panel. And a plurality of optical sheets (not shown) disposed on the light guide plate to improve brightness characteristics of light.

The backlight controller 120 has the same or higher frequency as the frame synchronization signal based on the duty on information DOI and the frame synchronization signal Vsync and the gate control signal GCS provided from the outside, and the duty on information ( A backlight dimming signal BDS having a predetermined duty on period corresponding to the DOI is generated. In this case, the duty on information DOI may be generated based on the luminance of an image analyzed in units of frames by a timing controller (not shown) or a data analyzer (not shown) of the liquid crystal display. For example, the duty on information DOI may be generated according to an optimal power control method that more clearly controls the outline (or boundary portion) of the image.

The optimal power control method reduces the brightness of the backlight unit 110 by setting the duty on information DOI lower than the duty on information DOI based on the brightness of the original image, instead of reducing the brightness of the backlight unit 110. The power consumption of the backlight unit 110 is reduced by increasing the luminance of the original image through data compensation by the luminance.

The backlight driver 130 generates a light source driving voltage LDV having a light source on voltage and a light source off voltage from the backlight controller 120 in response to the backlight dimming signal BDS to generate a plurality of light sources in a predetermined duty on period. Lights up sequentially.

As described above, the backlight driving apparatus 100 may set the frequency of the backlight dimming signal BDS to be equal to or higher than the frame synchronization signal Vsync based on the duty-on information DOI. Flicker due to the light dimming signal BDS may be minimized.

FIG. 2A is a diagram for describing a first embodiment of the backlight controller illustrated in FIG. 1, and FIG. 2B is a diagram for describing the backlight synchronization signal generator illustrated in FIG. 2A.

Referring to FIGS. 2A and 2B and FIG. 1, the backlight controller 120 according to the first embodiment may have the same first frequency or frame synchronization signal Vsync as the frame synchronization signal Vsync according to the duty-on information DOI. Generate a backlight dimming signal BDS having a second frequency higher than e.g., a second frequency divided at least twice from the frame synchronization signal. For example, the frame sync signal Vsync may be 60 Hz and the second frequency may be 120 Hz or 180 Hz. To this end, the backlight controller 120 according to the first embodiment includes a comparator 210, a backlight sync signal generator 220, and a dimming signal generator 230.

The comparator 210 compares the set reference duty on information RDOI and the size of the duty on information DOI of the current frame with each other, thereby comparing the comparison signal CS of the first logic state or the comparison signal CS of the second logic state. ) Is set whether or not the frequency of the backlight dimming signal BDS is converted.

The comparison unit 210 generates the comparison signal CS of the first logic state when the duty on information DOI of the current frame is smaller than the reference duty on information RDOI. On the other hand, the comparator 210 generates the comparison signal CS of the second logic state when the duty on information DOI of the current frame is equal to or larger than the reference duty on information RDOI.

The reference duty on information RDOI is set to a value corresponding to a duty on interval of 25% to 35% in one frame. The reference duty on information RDOI is a value set through a flicker recognition experiment according to the duty on period. For example, an 8-bit full white image is displayed on a liquid crystal display panel and blinking while increasing the duty-on interval ratio of a backlight dimming signal (BDS) having a frequency of 60 Hz from 1% to 99%. As a result of the experiment, it was confirmed that the flicker is not recognized at the luminance of approximately 17 nits or less, but the flicker is recognized at the luminance of approximately 17 nits or more. According to this experiment, it can be seen that the flicker according to the luminance of the duty-on period is not recognized at the low luminance but is recognized at the high luminance. The luminance of about 17 nits corresponds to a duty-on period of 25% to 35% in one frame.

When the comparison signal CS of the first logic state is supplied from the comparator 210, the backlight synchronization signal generator 220 outputs the frame synchronization signal Vsync as it is and is identical to the frame synchronization signal Vsync. The first backlight synchronization signal Bsync1 having one frequency is supplied to the dimming signal generator 230. When the comparison signal CS of the second logic state is supplied from the comparator 210, the backlight synchronization signal generator 220 has a second backlight having a second frequency higher than that of the frame synchronization signal Vsync. The synchronization signal Bsync2 is supplied to the dimming signal generator 330. To this end, the backlight synchronization signal generator 220 includes a selection output unit 222 and a frequency generator 224.

The selection output unit 222 may use the frame synchronization signal Vsync as the first backlight synchronization signal Bsync1 having the first frequency according to the comparison signal CS of the first logic state to the dimming signal generator 230. Supply. On the other hand, the selection output unit 222 supplies the frame synchronization signal Vsync to the frequency generator 224 according to the comparison signal CS of the second logic state. The selection output unit 222 may be a demultiplexer.

The frequency generator 224 divides the frame synchronization signal Vsync supplied from the selection output unit 222 and has a second frequency higher than the frame synchronization signal Vsync, for example, a frequency having a frequency of 90 Hz, 120 Hz, or 180 Hz. The second backlight synchronization signal Bsync2 is generated, and the generated second backlight synchronization signal Bsync2 is supplied to the dimming signal generator 230.

The dimming signal generator 230 may include a duty-on period corresponding to the duty-on information DOI based on the first or second backlight synchronization signals Bsync1 and Bsync2 supplied from the backlight synchronization signal generator 220. The backlight dimming signal BDS is generated in synchronization with the gate control signal GCS and has a duty off section OFF except for the ON) and the duty on section ON, and is supplied to the backlight driver 130. . For example, when the first backlight synchronization signal Bsync1 supplied from the backlight synchronization signal generator 220 is supplied to the dimming signal generator 230, as shown in FIG. A backlight dimming signal BDS having a first frequency F1 synchronized to each frame of Vsync is generated and supplied to the backlight driver 130. On the other hand, when the second backlight synchronization signal Bsync2 supplied from the backlight synchronization signal generator 220 is supplied to the dimming signal generator 230, the frame synchronization signal Vsync is illustrated in FIG. 3B. The backlight dimming signal BDS having the second frequency F2 synchronized with each frame of the frame 1 is generated and supplied to the backlight driver 130.

The dimming signal generator 230 may include a delay unit (not shown) for delaying the backlight dimming signal BDS by a delay time. The delay unit may include a duty-on period of the backlight dimming signal BDS having the first or second frequencies F1 and F2 based on a delay time set to be synchronized with the response speed of the liquid crystal according to the frequency of the frame synchronization signal Vsync. ON) delay.

As described above, the backlight controller 120 according to the first exemplary embodiment may set the frequency of the backlight dimming signal BDS to be equal to the frame synchronization signal Vsync or the frame synchronization signal Vsync based on the duty-on information DOI. By setting a higher value, flicker due to the backlight dimming signal BDS may be minimized.

4 is a flowchart illustrating the operation of the backlight controller according to FIGS. 2A and 2B.

As shown in FIG. 4, when the duty-on information DOI and the frame synchronization signal Vsync are provided from the outside (1S), it is determined whether the flicker is recognized based on the duty-on information D0I (2S). Whether such flicker is recognized is determined by the comparison unit 210 described above.

If the blink is not recognized (No), the frame sync signal Vsync is output as it is to generate the first backlight sync signal Bsync1 having the same first frequency as the frame sync signal Vsync (3S). .

If the flicker is recognized (Yes), the second flash sync signal Bsync2 having a second frequency higher than the frame sync signal Vsync is generated (4S), thereby causing flicker according to the backlight dimming signal BDS. To prevent.

FIG. 5A is a diagram for describing a second embodiment of the backlight controller illustrated in FIG. 1, and FIG. 5B is a diagram for describing the backlight synchronization signal generator illustrated in FIG. 5A.

5A and 5B and FIG. 1, the backlight controller 120 according to the second embodiment has a backlight dimming signal having the same first frequency as the frame synchronization signal Vsync according to the duty-on information DOI. (BDS) or generate a backlight dimming signal (BDS) having a second frequency that is higher than the frame sync signal (Vsync), for example, divided from the frame sync signal, or step by step from the first frequency to the second frequency. Generate an increasing backlight dimming signal BDS or a backlight dimming signal BDS that is stepped down from the second frequency to the first frequency. For example, the frame sync signal Vsync may be 60 Hz and the second frequency may be 90 Hz, 120 Hz, or 180 Hz. To this end, the backlight controller 120 according to the second embodiment includes a comparator 310, a frequency conversion determiner 315, a backlight sync signal generator 320, and a dimming signal generator 330. It is configured by.

The comparator 310 compares the set reference duty-on information RDOI and the size of the duty-on information DOI of the current frame with each other, thereby comparing the comparison signal CS of the first logic state or the comparison signal CS of the second logic state. )

The comparison unit 310 generates a comparison signal CS of a first logic state when the duty-on information DOI of the current frame is smaller than the reference duty-on information RDOI. On the other hand, the comparator 310 generates the comparison signal CS of the second logic state when the duty-on information DOI of the current frame is larger than the reference duty-on information RDOI.

As described above, the reference duty on information RDOI is set to a value in the range of 25% to 35% of the duty on period in one frame.

The frequency conversion determiner 315 generates the frequency determination signal DS of the first to fourth logic states based on the comparison signal CS and the frequency information of the previous frame. Here, the frequency information of the previous frame may be frequency information of the backlight synchronization signal of the previous frame or frequency information of the backlight dimming signal.

The frequency conversion determining unit 315 may be configured such that the comparison signal CS is the comparison signal of the first logic state and the frequency of the previous frame (more specifically, the final frequency of the previous frame) is equal to the frame synchronization signal Vsync. In the case of one frequency, the frequency determination signal DS of the first logic state is generated. On the other hand, the frequency conversion determining unit 315, the comparison signal CS is a comparison signal of the first logic state and the frequency of the previous frame (more specifically, the final frequency of the previous frame) is the frame synchronization signal (Vsync) When the second frequency is higher, the frequency determination signal DS of the second logic state is generated.

The frequency conversion determiner 315 may include a first signal in which a comparison signal CS is a comparison signal of a second logic state and a frequency of a previous frame (more specifically, a final frequency of a previous frame) is equal to the frame synchronization signal Vsync. In the case of frequency, the frequency determination signal DS of the third logic state is generated. On the other hand, in the frequency conversion determiner 315, the comparison signal CS is the comparison signal of the second logic state and the frequency of the previous frame (more specifically, the final frequency of the previous frame) is higher than the frame synchronization signal Vsync. When the second frequency is high, the frequency determination signal DS of the fourth logic state is generated.

When the frequency determining signal DS of the first logic state is supplied from the frequency conversion determining unit 315, the backlight synchronization signal generator 320 may convert the frame synchronization signal Vsync into the first backlight synchronization signal Bsync1. The dimming signal generator 330 is supplied to the dimming signal generator 330.

When the frequency determining signal DS of the second logic state is supplied from the frequency conversion determining unit 315, the backlight synchronization signal generating unit 320 receives the first frequency from the second frequency based on the frame synchronization signal Vsync. The second backlight sync signal Bsync2 is gradually reduced until it is supplied to the dimming signal generator 330.

The backlight synchronization signal generator 320 may supply a second frequency from the first frequency based on the frame synchronization signal Vsync when the frequency determination signal DS of the third logic state is supplied from the frequency conversion determiner 315. The third backlight synchronization signal Bsync3 which is gradually increased until is generated and supplied to the dimming signal generator 330.

The backlight synchronization signal generator 320 may include a fourth back having a second frequency higher than that of the frame synchronization signal Vsync when the frequency determination signal DS of the fourth logic state is supplied from the frequency conversion determiner 315. The write sync signal Bsync4 is generated and supplied to the dimming signal generator 330.

To this end, the backlight synchronization signal generator 320 may include a selection output unit 322, a step down frequency generator 324, a step up frequency generator 326, and a fixed signal. It is configured to include a frequency generator 328.

The selection output unit 322 dims the frame synchronization signal Vsync as the first backlight synchronization signal Bsync1 when the frequency conversion signal DS of the first logic state is supplied from the frequency conversion determination unit 315. The signal generator 330 is supplied. On the other hand, when the frequency determining signal DS of the second logic state is supplied from the frequency conversion determining unit 315, the selection output unit 322 steps down the frame synchronizing signal Vsync. To 324. In addition, when the frequency determining signal DS of the third logic state is supplied from the frequency conversion determining unit 315, the selection output unit 322 steps up the frame synchronizing signal Vsync. 326). In addition, the selection output unit 322 supplies the frame synchronization signal Vsync to the fixed frequency generation unit 328 when the frequency conversion signal DS of the fourth logic state is supplied from the frequency conversion determination unit 315. . The selection output unit 321 may be a demultiplexer.

The step down frequency generator 324 reduces the step down frequency from the second frequency to the first frequency based on the frame synchronization signal Vsync supplied from the selection output unit 322. Is generated and supplied to the dimming signal generator 330 using the generated step down frequency as the second backlight synchronization signal Bsync2. In detail, the step down frequency generator 324 generates a second backlight synchronization signal Bsync2 having a step down frequency corresponding to each step of the set number of frequency steps. As an example, when the first frequency is 60 Hz, the second frequency is 120 Hz, and the number of frequency steps is 3, the step down frequency generator 324 may step by step from 120 Hz to 100 Hz to 80 Hz to 60 Hz. It is possible to generate a decreasing step down frequency.

The frequency step number may be set to N (where N is a natural number of 2 or more) by experiment. The frequency step number may be set to vary in real time according to the duty on information DOI. In this case, the step down frequency generator 324 may include a memory device (not shown) and a detector (not shown).

The memory device stores the duty on information DOI in units of frames and provides the detector with the duty on information DOI of the stored previous frame.

The detector detects a change amount of the duty-on information according to a difference value between the duty-on information DOI of the current frame and the duty-on information DOI of the previous frame provided from the memory device, and corresponds to the detected amount of change in the duty-on information. Set the frequency step number. In this case, when the change amount of the duty-on information is lower than the set reference change amount, the detector sets the frequency step number to the set N (where N is a natural number of two or more), and the change amount of the duty-on information is equal to or higher than the reference change amount. In this case, the frequency step number is set to M (where M is a natural number different from N).

The step up frequency generator 326 increases step by step frequency from the first frequency to the second frequency based on the frame synchronization signal Vsync supplied from the selection output unit 322. And generate the generated step up frequency as the third backlight synchronization signal Bsync3 to supply the dimming signal generator 330. In detail, the step up frequency generator 326 generates a third backlight synchronization signal Bsync3 having a step up frequency corresponding to each step of the set number of frequency steps. As an example, when the first frequency is 60 Hz, the second frequency is 120 Hz, and the number of step-up frequencies is 3, the step up frequency generator 326 may vary from 60 Hz to 80 Hz to 100 Hz to 120 Hz. It is possible to generate step up frequencies that increase in stages. As described above, the frequency step number may be set to N (where N is a natural number of 2 or more), or may be set to vary in real time according to the duty-on information DOI.

The fixed frequency generator 328 divides the frame synchronization signal Vsync supplied from the selection output unit 322 to generate a second frequency higher than the frame synchronization signal Vsync, for example, 90 Hz, 120 Hz, or 180 Hz. A fourth backlight synchronization signal Bsync4 having a frequency is generated and supplied to the dimming signal generator 330.

The dimming signal generator 330 is configured to perform a duty based on one of the first to fourth backlight synchronization signals Bsync1, Bsync2, Bsync3, and Bsync4 supplied from the backlight synchronization signal generator 320. A backlight dimming signal BDS having a duty on period ON corresponding to the on information DOI and a duty off period other than the duty on period ON, and synchronized with the gate control signal GCS. Produces and supplies to the backlight driver 130.

For example, when the first backlight synchronization signal Bsync1 supplied from the backlight synchronization signal generator 320 is supplied to the dimming signal generator 330, as illustrated in FIG. 3A, the first backlight may be used. The backlight dimming signal BDS having the same first frequency F1 as the frame synchronization signal Vsync is generated and supplied to the backlight driver 130 according to the synchronization signal Bsync1.

As another example, the dimming signal generator 330 may output the fourth dimming signal Bsync4 from the backlight synchronizing signal generator 320 while outputting the backlight dimming signal BDS having the first frequency F1. 3b), as shown in FIG. 3B, the backlight dimming signal BDS having the second frequency F2 is generated according to the fourth backlight synchronization signal Bsync4 to the backlight driver 130. Supply.

As another example, while the dimming signal generator 330 is outputting the backlight dimming signal BDS having the first frequency F1, the dimming signal generator 330 may output the third backlight synchronizing signal from the backlight synchronizing signal generator 320. When Bsync3 is supplied, as shown in FIG. 6A, step-up increases from the first frequency F1 to the second frequency F2 according to the third backlight synchronization signal Bsync3. The backlight dimming signal BDS including the frequencies SUF1 and SUF2 is generated and supplied to the backlight driver 130.

As another example, the dimming signal generator 330 may output the second backlight sync signal from the backlight sync signal generator 320 while outputting the backlight dimming signal BDS having the second frequency F2. When Bsync2 is supplied, as shown in FIG. 6B, a step down decreases from the second frequency F2 to the first frequency F1 according to the second backlight synchronization signal Bsync2. The backlight dimming signal BDS including the frequencies SDF1 and SDF2 is generated and supplied to the backlight driver 130.

As described above, the backlight controller 120 according to the second exemplary embodiment increases the frame synchronization signal Vsync step by step when frequency conversion of the backlight dimming signal BDS is necessary based on the duty-on information DOI. By decreasing in steps, it is possible to prevent flicker caused by sudden frequency change of the backlight dimming signal BDS.

7 is a flowchart illustrating the operation of the backlight controller according to FIGS. 5A and 5B.

As shown in FIG. 7, when the duty on information DOI and the frame synchronization signal Vsync are provided from the outside (10S), it is determined whether the blink is recognized based on the duty on information D0I (20S). Whether such blink is recognized is determined by the comparison unit 310 described above.

In the process of determining whether the blink is recognized, if the blink is not recognized (No), it is determined whether to convert the frequency of the backlight synchronization signal (30S). Whether to convert the frequency of the backlight synchronization signal is determined by the frequency conversion determiner 315 described above.

If the frequency conversion of the backlight synchronization signal is not necessary (No), the first backlight synchronization signal Bsync1 having the same first frequency as the frame synchronization signal Vsync by outputting the frame synchronization signal Vsync as it is. ) Is generated (40S).

On the other hand, when frequency conversion of the backlight synchronization signal is required (Yes), the second backlight includes a step down frequency that decreases in steps from the second frequency F2 to the first frequency F1. By generating the synchronization signal Bsync2 (50S), flickering due to a sudden frequency change of the backlight synchronization signal is prevented.

On the other hand, in the process of determining whether the blink is recognized, if the blink is recognized (Yes), it is determined whether the frequency of the backlight synchronization signal is converted (60S). Whether to convert the frequency of the backlight synchronization signal is determined by the frequency conversion determiner 315 described above.

If the frequency conversion of the backlight synchronization signal is not necessary (No), the backlight is generated by generating a fourth backlight synchronization signal Bsync4 having a second frequency higher than the frame synchronization signal Vsync (70S). Prevents flicker due to the dimming signal (BDS).

On the other hand, if frequency conversion of the backlight synchronization signal is required (Yes), the third backlight includes a step up frequency that increases step by step from the first frequency F1 to the second frequency F2. By generating the synchronization signal Bsync3 (80S), flickering due to a sudden frequency change of the backlight synchronization signal is prevented.

FIG. 8 is a view for explaining a third embodiment of the backlight control unit shown in FIG. 1, and FIG. 9 is a waveform diagram for explaining the dimming signal delay unit shown in FIG. 8.

8 and 9 with FIG. 1, the backlight control unit 120 according to the third embodiment includes a comparison unit 310, a frequency conversion determination unit 315, a backlight synchronization signal generation unit 320, a dimming A signal generator 330, and a dimming signal delay unit 340. The other components except for the dimming signal delay unit 340 in the backlight control unit 120 according to the third exemplary embodiment having the above configuration are configured in the same way as the backlight control unit 120 according to the second exemplary embodiment. Detailed description will be replaced with the above description, and the same reference numerals will be given below.

The dimming signal delay unit 340 delays the duty-on period ON of the backlight dimming signal BDS supplied from the dimming signal generator 330 to be synchronized with the liquid crystal response speed, and delays the backlight dimming signal BDS '. ) Is supplied to the backlight driver 130. That is, the dimming signal delay unit 340 detects the rising edge of the duty-on period ON and delays the detected rising edge by a predetermined time DT1, DT2, or DT3 for a liquid crystal response. By synchronizing to the interval, the motion picture response time is improved.

Meanwhile, the backlight driver 130 illustrated in FIG. 1 may have a light source driving voltage having a light source on voltage and a light source off voltage according to the delayed backlight dimming signal BDS ′ provided from the dimming signal delay unit 340. LDV) is generated to sequentially light the plurality of light sources during a predetermined duty on period.

As described above, the backlight control unit 120 according to the third embodiment not only provides the same effect as the backlight control unit 120 according to the second embodiment, but also increases or decreases the backlight dimming signal ( The image quality of the moving image displayed on the liquid crystal display panel can be improved by delaying the duty on period ON of the BDS and synchronizing the duty on period ON of the backlight dimming signal BDS to the liquid crystal response speed.

10 is a diagram for describing a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 10, a liquid crystal display according to an exemplary embodiment of the present invention analyzes the duty-on information DOI of an image by analyzing the liquid crystal display panel 500 displaying an image in a frame unit and input data RGB in a frame unit. According to the timing control unit 600 and the data and gate control signals DCS and GCS which generate and generate data and gate control signals DCS and GCS according to the timing synchronization signal TSS including the frame synchronization signal Vsync. A panel driver 600 generating and supplying a gate signal and a data signal to the liquid crystal display panel 500, a duty-on information DOI supplied from the timing controller 600, a frame synchronization signal Vsync, and a gate control signal ( And a backlight driving device 800 for irradiating light to the liquid crystal display panel 500 according to a scanning backlight method based on GCS.

The liquid crystal display panel 500 displays an image through a pixel matrix in which a plurality of pixels P are arranged. Each pixel P implements a desired color by using a combination of red, green, and blue sub-pixels that adjust light transmittance by varying a liquid crystal array according to a data signal. Each sub-pixel includes a thin film transistor T connected to the gate line GL and the data line DL, a liquid crystal capacitor Clc connected to the thin film transistor T, and a storage capacitor Cst.

The liquid crystal capacitor Clc charges a difference voltage between the data signal supplied to the pixel electrode (not shown) and the common voltage supplied to the common electrode (not shown) through the thin film transistor T, and according to the charged voltage. The light transmittance is adjusted by driving the liquid crystal.

The storage capacitor Cst keeps the voltage charged in the liquid crystal capacitor Clc stable until the data signal of the next frame is supplied.

The panel driver 600 may include a gate driver circuit part 610 for driving the gate line GL of the liquid crystal display panel 500, and a data driver circuit part 620 for driving the data line DL of the liquid crystal display panel 500. It includes.

The gate driving circuit unit 610 generates a gate signal according to the gate control signal GCS supplied from the timing controller 700 and sequentially supplies the gate signal to the gate lines GL. Here, the gate driving circuit unit 610 may be formed on the substrate at the same time as the thin film transistor is formed and may be embedded in the liquid crystal display panel 500.

The data driving circuit unit 620 latches the digital data R, G, and B supplied from the timing control unit 700 according to the data control signal DCS supplied from the timing control unit 700, and performs analog positive / negative polarity. After converting the latched digital data into a positive / negative analog data voltage using a gamma voltage, a data voltage having a polarity corresponding to the polarity control signal POL is generated and synchronized with the gate signal. Supplies).

The timing controller 700 arranges the input data RGB input from the outside so as to be suitable for driving the liquid crystal display panel 500, and generates the aligned digital data R, G, and B to generate the data driving circuit unit 620. To feed. The timing controller 700 controls a gate timing of the gate driver circuit 610 by using a timing synchronization signal TSS including a frame synchronization signal, a horizontal synchronization signal, a data enable signal, and a dot clock. The data control signal DCS for controlling the driving timing of the signal GCS and the data driving circuit unit 620 is generated.

The timing controller 700 analyzes the input data RGB on a frame basis and generates duty on information DOI corresponding to one frame image on a frame basis and provides the same to the backlight driving apparatus 800. In this case, the timing controller 700 generates duty-on information DOI according to an Optimal Power Control method for more clearly controlling the outline (or boundary portion) of the image, and also arranges the digital data R. FIG. The gray scale values of, G, and B) can be corrected.

Meanwhile, the timing controller 700 may adjust an overshoot value or an undershoot value according to a difference between the current frame and the previous frame of the alignment digital data R, G, and B in order to improve the response speed of the liquid crystal. It may further comprise an over-driving circuit (not shown) for modulating the alignment digital data (R, G, B) of the current frame.

The backlight driving apparatus 800 includes a plurality of light sources in units of frames according to a scanning backlight method based on the duty on information DOI, the frame synchronization signal Vsync, and the gate control signal GCS provided from the timing controller 700. By sequentially turning on (not shown), light is sequentially irradiated onto the liquid crystal display panel 500. To this end, the backlight driving apparatus 800 may include a backlight unit 810 including a plurality of light sources, a duty on information DOI provided from the timing controller 700, a frame synchronization signal Vsync, and a gate control signal ( A backlight control unit 820 for generating a backlight dimming signal BDS having a frequency equal to or higher than that of the frame synchronization signal Vsync based on the GCS, and a backlight dimming signal provided from the backlight control unit 820. And a backlight driver 830 for sequentially lighting a plurality of light sources on a frame basis based on BDS).

The backlight unit 810 divides the liquid crystal display panel 500 into a plurality of regions, and includes a plurality of light sources installed to correspond to the divided regions. The plurality of light sources may use a fluorescent lamp (CCFL) or a light emitting diode (LED).

Each of the plurality of light sources made of the light emitting diodes may be driven in a series manner or in a parallel manner.

The backlight unit 810 reflects the light guide plate (not shown) for advancing the light emitted from the plurality of light sources toward the liquid crystal display panel 500 and the light that is disposed under the light guide plate toward the liquid crystal display panel 500. And a plurality of optical sheets (not shown) disposed on the light guide plate to improve brightness characteristics of light.

The backlight controller 820 may have a frequency equal to or higher than that of the frame synchronization signal Vsync based on the duty-on information DOI provided from the timing controller 700, the frame synchronization signal Vsync, and the gate control signal GCS. And a backlight dimming signal BDS having a predetermined duty-on period corresponding to the duty-on information DOI. The backlight controller 820 may include the backlight controller 120 according to any one of the first to third embodiments of the present invention illustrated in FIGS. 2A and 2B, 5A and 5B, or 8. Since it has the same configuration as the detailed description thereof will be replaced by the above description.

The backlight driver 830 generates a light source driving voltage LDV having a light source on voltage and a light source off voltage from the backlight controller 820 according to the backlight dimming signal BDS to generate a plurality of light sources in a predetermined duty on period. Lights up sequentially.

As described above, the liquid crystal display according to the exemplary embodiment of the present invention sets the frequency of the backlight dimming signal BDS to be equal to or higher than the frame synchronization signal Vsync based on the duty-on information DOI. ) Can minimize flickering according to the frequency, reduce power consumption, and improve the quality of moving images.

It will be understood by those skilled in the art that the present invention may 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, 800: backlight drive unit 110, 810: backlight unit
120, 820: backlight control unit 130, 830: backlight control unit
210, 310: comparison unit 220, 320: backlight synchronization signal generation unit
230, 330: dimming signal generator 340: delay time setting unit
350: dimming signal delay unit 500: liquid crystal display panel
600: panel driver 610: gate driver circuit
620: data driving circuit unit 700: timing control unit

Claims (18)

A backlight unit including a plurality of light sources for irradiating light to a liquid crystal display panel which displays an image according to a liquid crystal response;
A backlight driver configured to sequentially light the plurality of light sources in units of frames based on a backlight dimming signal having a predetermined duty on period and a duty off period; And
And a backlight controller configured to generate the backlight dimming signal having a frequency equal to or higher than a frame synchronization signal of the liquid crystal display panel based on duty on information provided from the outside through analysis of the image. Backlight driving device. The method of claim 1,
The backlight control unit,
A comparator configured to generate a comparison signal by comparing the duty-on information with a set reference duty-on information;
A backlight synchronization signal generation unit receiving a comparison signal from the comparison unit to generate a backlight synchronization signal;
And a dimming signal generator configured to generate the backlight dimming signal and supply the backlight dimming signal to the backlight driver based on a backlight synchronization signal supplied from the backlight synchronization signal generator. The method of claim 2,
The comparison unit generates a comparison signal of a first logic state when the duty on information is less than the reference duty on information, and generates a comparison signal of a second logic state when the duty on information is equal to or greater than the reference duty on information. Back light driving device, characterized in that for generating. The method of claim 3, wherein
The backlight synchronization signal generator generates a first backlight synchronization signal having a first frequency equal to the frame synchronization signal when a comparison signal having a first logic state is supplied from the comparison unit, and generates a second synchronization signal from the comparison unit. And a second backlight synchronization signal having a second frequency higher than the frame synchronization signal when a comparison signal of a logic state is supplied. The method of claim 4, wherein
The backlight synchronization signal generator,
A selection output unit which supplies the frame synchronization signal to the dimming signal generation unit as the first backlight synchronization signal; And
And a frequency generator configured to divide the frame synchronization signal supplied from the selection output unit, generate the second backlight synchronization signal, and supply the second backlight synchronization signal to the dimming signal generator. The method of claim 2,
The backlight control unit further includes a frequency conversion determiner, wherein the frequency conversion determiner generates a frequency determination signal based on the comparison signal and frequency information of a previous frame, and generates the generated frequency determination signal. And a backlight driving device which is supplied to the backlight synchronization signal generator. The method according to claim 6,
The comparison unit generates a comparison signal of a first logic state when the duty on information is less than the reference duty on information, and generates a comparison signal of a second logic state when the duty on information is equal to or greater than the reference duty on information. Generate; And,
The frequency conversion determiner is configured to generate a frequency determination signal in a first logic state when the comparison signal is a comparison signal in a first logic state and the frequency of a previous frame is the same frequency as the frame synchronization signal, and the comparison signal When the comparison signal of one logic state and the frequency of the previous frame is a second frequency higher than the frame synchronization signal, generates a frequency determination signal of the second logic state, the comparison signal is the comparison signal of the second logic state and the frequency of the previous frame Is a first frequency equal to the frame synchronization signal, and generates a frequency determination signal in a third logic state, wherein the comparison signal is a comparison signal in a second logic state and the frequency of the previous frame is a second frequency higher than the frame synchronization signal. And generating a frequency determination signal in four logic states. The method of claim 7, wherein
The backlight synchronization signal generator generates a first backlight synchronization signal having the same first frequency as the frame synchronization signal when the frequency conversion signal of the first logic state is supplied from the frequency conversion determiner, and converts the frequency. When the frequency determining signal of the second logic state is supplied from the determination unit, the second backlight synchronization signal is generated to be gradually reduced from the second frequency to the first frequency, and the frequency of the third logic state is determined from the frequency conversion determination unit. Generates a third backlight synchronization signal that is incrementally increased from the first frequency to the second frequency when the determination signal is supplied, and when the frequency determination signal of the fourth logic state is supplied from the frequency conversion determination unit. And generating a fourth backlight synchronization signal having a second backlight synchronization signal. The method of claim 8,
The backlight synchronization signal generator,
A selection output unit configured to supply a frame synchronization signal as a first backlight synchronization signal to the dimming signal generator according to the frequency determination signal of the first logic state;
A step dyne frequency generator configured to receive a frame synchronization signal from the selection output unit and generate the second backlight synchronization signal;
A step-up frequency generation unit receiving the frame synchronization signal from the selection output unit and generating the third backlight synchronization signal; And
And a fixed frequency generator configured to receive a frame sync signal from the selection output unit and to generate the fourth backlight sync signal. The method of claim 2,
And the backlight controller delays the duty-on period of each of the backlight dimming signals such that the duty-on period is synchronized with the liquid crystal response. A liquid crystal display panel displaying images on a frame basis;
A timing controller which analyzes input data on a frame-by-frame basis to generate duty-on information of the image and generates a timing control signal according to a timing synchronization signal including a frame synchronization signal;
A panel driver configured to generate a gate signal and a data signal according to the timing control signal and to supply the gate signal and the data signal to the liquid crystal display panel; And
And a backlight driving device for irradiating light to the liquid crystal display panel based on the duty on information and the frame synchronizing signal supplied from the timing controller.
In this case, the backlight driving device
A backlight unit including a plurality of light sources for irradiating light to a liquid crystal display panel which displays an image according to a liquid crystal response;
A backlight driver configured to sequentially light the plurality of light sources in units of frames based on a backlight dimming signal having a predetermined duty on period and a duty off period; And
And a backlight controller configured to generate the backlight dimming signal having a frequency equal to or higher than a frame synchronization signal of the liquid crystal display panel based on duty on information provided from the outside through analysis of the image. Liquid crystal display. In the driving method of a backlight driving device comprising a plurality of light sources for irradiating light to a liquid crystal display panel for displaying an image in accordance with the liquid crystal response,
Generating a backlight dimming signal having a frequency equal to or higher than a frame synchronizing signal of the liquid crystal display panel based on duty-on information provided from outside according to the image; And
And sequentially lighting the plurality of light sources on a frame-by-frame basis during the duty-on period based on the backlight dimming signal. 13. The method of claim 12,
Generating the backlight dimming signal,
Generating a comparison signal of a first logic state when the duty on information is less than the reference duty on information, and generating a comparison signal of a second logic state when the duty on information is equal to or greater than the reference duty on information Back light driving method comprising a. The method of claim 13,
Generating the backlight dimming signal,
Generating a first backlight synchronization signal having the same first frequency as the frame synchronization signal when the comparison signal of the first logic state is generated,
Generating a second backlight synchronization signal having a second frequency higher than the frame synchronization signal when the comparison signal of the second logic state is generated. The method of claim 13,
Generating the backlight dimming signal,
Generate a frequency determination signal of a first logic state when the comparison signal of the first logic state is generated and the frequency of a previous frame is a first frequency equal to the frame sync signal;
Generate a frequency determination signal of a second logic state when the comparison signal of the first logic state is generated and the frequency of a previous frame is a second frequency higher than the frame synchronization signal;
Generate a frequency determination signal of a third logic state when the comparison signal of the second logic state is generated and the frequency of a previous frame is the same first frequency as the frame synchronization signal; And,
And generating a frequency determining signal of a fourth logic state when the comparison signal of the second logic state is generated and the frequency of the previous frame is a second frequency that is higher than the frame synchronization signal. Way. 16. The method of claim 15,
Generating the backlight dimming signal,
Generating a first backlight synchronization signal having a first frequency equal to the frame synchronization signal when the frequency determination signal in the first logic state is generated;
Generating a second backlight synchronization signal that is stepped down from the second frequency to a first frequency when the frequency determination signal of the second logic state is generated;
Generating a third backlight synchronization signal that is incremented step by step from the first frequency to a second frequency when the frequency determination signal of the third logic state is generated; And,
And generating a fourth backlight synchronization signal having the second frequency when the frequency determination signal of the fourth logic state is generated. 13. The method of claim 12,
And delaying the duty-on period of each of the backlight dimming signals such that the duty-on period is synchronized with the liquid crystal response. In the driving method of a liquid crystal display device comprising a liquid crystal display panel for displaying an image on a frame basis,
Analyzing the input data on a frame-by-frame basis to generate duty on information of the image and generating a timing control signal according to a timing synchronization signal including a frame synchronization signal;
Generating a gate signal and a data signal according to the timing control signal and supplying the gate signal and the data signal to the liquid crystal display panel; And
Irradiating light to the liquid crystal display panel based on the duty on information and the frame synchronization signal;
Irradiating light to the liquid crystal display panel includes a backlight driving step,
The backlight driving step,
Generating a backlight dimming signal having a frequency equal to or higher than a frame synchronizing signal of the liquid crystal display panel based on duty-on information provided from outside according to the image; And
And sequentially lighting the plurality of light sources on a frame-by-frame basis during the duty-on period based on the backlight dimming signal.

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