KR20130030877A

KR20130030877A - Liquid crystal display and method of restricting power comsumption thereof

Info

Publication number: KR20130030877A
Application number: KR1020110094443A
Authority: KR
Inventors: 정문수; 서보건
Original assignee: 엘지디스플레이 주식회사
Priority date: 2011-09-20
Filing date: 2011-09-20
Publication date: 2013-03-28

Abstract

PURPOSE: A liquid crystal display device and a method for limiting power consumption are provided to limit power consumption below a preset level regardless of an image by reducing block dimming values or block representative values below the preset level. CONSTITUTION: An input image is analyzed. Each block representative value of local diming blocks is determined(S1). Block dimming values corresponding to the block representative values are selected. A driving voltage of an optical source is controlled. The sum of the block representative values or block dimming values is compared with a limit value(S3). The block representative values or the block dimming values are reduced below a preset level(S5). [Reference numerals] (S1) Determining a dimming value(DIM) by BLU block; (S2) Calculating the sum(DSUM) of the dimming values by block

Description

LIQUID CRYSTAL DISPLAY AND METHOD OF RESTRICTING POWER COMSUMPTION THEREOF}

The present invention relates to a liquid crystal display and a method for limiting power consumption thereof.

BACKGROUND ART Liquid crystal display devices have tended to be gradually widened due to their light weight, thinness, and low power consumption. The transmissive liquid crystal display displays an image by controlling an electric field applied to the liquid crystal layer to modulate the light incident from the backlight unit.

Most of the power consumption of the liquid crystal display is generated in the backlight unit. In order to reduce power consumption and improve contrast characteristics of a display image, a liquid crystal display backlight dimming control method is applied. The backlight dimming control method may reduce power consumption by adaptively adjusting the brightness of the backlight according to the input image. The backlight dimming method includes a global dimming method for adjusting the luminance of the entire display surface and a local dimming method for dividing the display screen into a plurality of blocks and locally adjusting the luminance of the display surface. have.

The global dimming method may improve dynamic contrast measured between the previous frame and the next frame. The local dimming method locally improves the brightness of the display surface within one frame period, thereby improving static contrast, which is difficult to improve with the global dimming method.

The backlight dimming control method can reduce the average power consumption of the liquid crystal display, but the power consumption may not be sufficiently reduced because the power consumption may not be reduced depending on the input image. The light emitting surface of the backlight unit BLU is divided into four blocks B1 to B4 as shown in FIGS. 1 and 2, and the brightness of the light sources LS1 to LS4 responsible for each of the blocks B1 to B4 is localized. It can be controlled by the dimming method. 1 and 2, the light sources LS1 to LS4 indicated by the white boxes are light sources lit according to the input driving voltage, while the light sources LS1 to LS4 indicated by the black boxes are light sources to which no driving voltage is supplied. It is a light source turned off as. If only the portion of the input image that faces the first and third blocks B1 and B3 and the remaining portion is dark as shown in FIG. 1, the local dimming method is responsible for the first and third blocks B1 and B3. The brightness of the light sources LS1 and LS3 may be increased, and the brightness of the light sources LS2 and LS4 that are in charge of the second and fourth blocks B2 and B4 may be lowered to reduce power consumption and increase contrast ratio. On the other hand, if there is no luminance difference for each local dimming block of the backlight unit as shown in FIG. 2, even if the local dimming method is applied, the luminance difference of the light sources LS1 to LS4 cannot be increased, and thus there is no improvement in power consumption.

Meanwhile, the LCD may receive data from an external device through an interface. Here, the interface may be an interface such as a universal serial bus (USB), a Thunderbolt, or the like. This interface requires constant power to transmit data. For example, the driving power of the USB 2.0 1 port is 2.5W, and the driving power of the USB 3.0 1 port is 4.5W. Thunderbolt's maximum drive power is around 10W. However, it is difficult to secure the power required for driving the interface if the power consumption of the liquid crystal display device is large. Therefore, it is necessary to limit the power consumption of the liquid crystal display device to a predetermined level or less.

The present invention provides a liquid crystal display device and its power consumption that can limit the power consumption to a certain level or less in any image.

The liquid crystal display device of the present invention comprises a liquid crystal display panel; A backlight unit radiating light to the liquid crystal display panel through a light emitting surface divided into a plurality of local dimming blocks; A local dimming controller configured to analyze input images, determine representative values for each block of each of the local dimming blocks, and select dimming values for each block corresponding to the representative values for each block; A light source driver configured to adjust driving voltages of light sources for irradiating light to the local dimming blocks based on the dimming values of the blocks; And comparing the sum of the representative values of each block or the sum of the dimming values of each block with a preset limit value, and if the sum of the representative values of each block or the sum of the dimming values of each block is greater than the limit value, the representative of each block. And a power consumption limiter for lowering each of the values below a predetermined level or lowering each of the block-specific dimming values below a certain level.

If the total sum of the dimming values for each block is greater than a preset dimming limit value, the power consumption limiter dims the dividing block as much as the value obtained by subtracting the dimming limit value from the total sum of the dimming values for each block divided by the number of local dimming blocks. Subtract each of the values.

If the sum of the dimming values for each block is less than or equal to the dimming limit value, the power consumption limiter supplies the dimming values for each block to the light source driver as it is.

If the total sum of the representative values for each block is greater than a predetermined representative gray level threshold value, the power consumption limiting unit divides the result of subtracting the representative gray level limit value from the total sum of representative values for each block by the number of the local dimming blocks. Subtract each of the star representative values.

The power consumption limiter supplies the representative values of each block to the local dimming control unit if the sum of the representative values of each block is less than or equal to the representative gray scale limit value.

The method for limiting power consumption of the liquid crystal display may include analyzing representative images to determine representative values for each block of the local dimming block; Selecting block-specific dimming values corresponding to the block-specific representative values; Adjusting a driving voltage of light sources for irradiating light to the local dimming blocks based on the dimming values for each block; Comparing the sum of the representative values of the blocks or the sum of the dimming values of the blocks with a preset limit value; If the sum of the representative values of each block or the sum of the dimming values of each block is greater than the threshold, lowering each of the representative values of each block to a predetermined level or less or lowering each of the dimming values of each block to a predetermined level or less. Include.

According to the present invention, when the sum of the dimming values of each block or the sum of the representative values of each block is greater than a preset limit value, the power consumption is constant in any image by lowering each of the dimming values of each block or the representative values of each block to a predetermined level or less. You can limit it below the level.

1 is a diagram illustrating an example of an image in which a power consumption reduction effect may be obtained by a local dimming method.
2 is a diagram illustrating an example of an image in which a power consumption reduction effect may not be obtained by a local dimming method.
3 is a block diagram illustrating a liquid crystal display according to a first embodiment of the present invention.
4 is a flowchart illustrating a method of limiting power consumption of a liquid crystal display according to a first embodiment of the present invention.
5A through 5C illustrate various local dimming block division types.
6 is a block diagram illustrating a liquid crystal display according to a second exemplary embodiment of the present invention.
7 is a flowchart illustrating a method of limiting power consumption of a liquid crystal display according to a second embodiment of the present invention.
8 to 10 are diagrams illustrating an example of a method of limiting power consumption of a liquid crystal display according to a second exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, when it is determined that a detailed description of known functions or configurations related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

3 and 4 illustrate a liquid crystal display according to a first exemplary embodiment of the present invention and a method of limiting power consumption thereof.

Referring to FIG. 3, the liquid crystal display of the present invention includes a liquid crystal display panel PNL, a backlight unit BLU for irradiating light to the liquid crystal display panel PNL, and a light source driver for driving light sources of the backlight unit BLU. 34, a source driver 12 for driving the data lines DL of the liquid crystal display panel PNL, a gate driver 14 for driving the gate lines GL of the liquid crystal display panel PNL, A timing controller 10 for controlling the operation timing of the source driver 12 and the gate driver 14, a local dimming controller 30 for controlling local dimming, and a power consumption limiter 32 for limiting dimming values for each block. And the like.

The liquid crystal display panel PNL includes a liquid crystal layer formed between two glass substrates. The liquid crystal cells of the liquid crystal display panel PNL are arranged in a matrix defined by the cross structure of the data lines DL and the gate lines GL. Pixels of a liquid crystal cell connected to data lines DL, gate lines GL, TFTs, and TFTs may be formed on a thin film transistor (TFT) array substrate of the liquid crystal display panel PNL. An electrode, a storage capacitor (Cst), and the like are formed. A black matrix, a color filter, a common electrode, and the like are formed on the color filter array substrate of the liquid crystal display panel PNL. On each of the TFT array substrate and the color filter array substrate, an alignment film for setting pre-tilt of liquid crystal molecules is formed on the liquid crystal facing surface. A polarizing film is attached to the outer surface of each of the TFT array substrate and the color filter array substrate. The liquid crystal display panel (PNL) is realized by a vertical electric field driving method such as twisted nematic (TN) mode and a vertical alignment (VA) mode, or by a horizontal electric field driving method such as IPS (In Plane Switching) mode and FFS (Fringe Field Switching) mode. It may be implemented in any known liquid crystal mode.

The backlight unit BLU is disposed under the liquid crystal display panel PNL to irradiate light to the liquid crystal display panel PNL. The light emitting surface of the backlight unit BLU is divided into N or more blocks (N is a positive integer of 2 or more) to enable local dimming. In the following, it should be noted that the number N of local dimming blocks is illustrated as 4 but is not limited thereto. The local dimming blocks B1 to B4 may be divided in the longitudinal direction or in the transverse direction of the liquid crystal display panel PNL as shown in FIGS. 5A to 5B, and may also be divided in the longitudinal and transverse directions.

The backlight unit BLU includes a plurality of light sources LS1 to LS4 individually controlled for each of the local dimming blocks B1 to B4. The backlight unit (BLU) may be implemented as a direct type backlight unit or an edge type backlight unit. The light source of the backlight unit may be implemented as a point light source such as a light emitting diode (LED). The light sources LS1 to LS4 independently adjust the luminance of the local dimming blocks B1 to B4 according to the driving voltage supplied from the light source driver 34. The first light source LS1 radiates light to the first local dimming block B1, and the second light source LS2 radiates light to the second local dimming block B2. The third light source LS3 irradiates light to the third local dimming block B3, and the fourth light source LS4 irradiates light to the fourth local dimming block B4.

The light source driver 34 modulates the first to fourth pulse widths in response to the dimming values DIM '(B1) to DIM' (B4) for each of the first to fourth blocks input from the power consumption limiter 32. Pulse Width Modulation (PWM) Adjusts the duty ratio of the signal. The dimming value DIM '(B1) for each first block determines the duty ratio of the first PWM signal for controlling the brightness of the first light source LS1. The dimming value DIM '(B2) for each second block determines the duty ratio of the second PWM signal for controlling the brightness of the second light source LS2. The dimming value DIM '(B3) for each third block determines the duty ratio of the third PWM signal for controlling the brightness of the third light source LS3. The fourth block-specific dimming value DIM '(B4) determines the duty ratio of the fourth PWM signal for controlling the brightness of the fourth light source LS4. Therefore, the light source driver 34 independently adjusts the luminance of each of the local dimming blocks B1 to B4 in response to the block-specific dimming values DIM '(B1) to DIM' (B4), thereby controlling the contrast of the display image. In addition, the power consumption of the light sources LS1 to LS4 may be adjusted to a predetermined level or less in response to dimming values DIM '(B1) to DIM' (B4) for each block.

The light source driver 34 may include a first constant voltage generator that generates a drive voltage of the first light source LS1, a second constant voltage generator that generates a drive voltage of the second light source LS2, and a third light source LS3. A third constant voltage generator for generating a voltage, a fourth constant voltage generator for generating a driving voltage of the fourth light source LS4, a PWM controller for controlling the constant voltage generators as a PWM signal, and the like. The constant voltage generators are implemented as known boost converters or buck converters to adjust the driving voltage of the light source in response to the PWM signal from the PWM controller. The PWM controller generates PWM signals in response to block-specific dimming values DIM '(B1) to DIM' (B4) input from the power consumption limiter 32 to switch ON / OFF of the constant voltage generators. Off) Control timing. The first constant voltage generator may adjust the driving voltage of the first light source LS1 by adjusting the on / off timing of the switch element for adjusting the driving voltage of the first light source LS1 by the duty ratio of the first PWM signal. The second constant voltage generator may adjust the driving voltage of the second light source LS2 by adjusting the on / off timing of the switch element for adjusting the driving voltage of the second light source LS2 by the duty ratio of the second PWM signal. The third constant voltage generator may adjust the driving voltage of the third light source LS3 by adjusting the on / off timing of the switch element for adjusting the driving voltage of the third light source LS3 by the duty ratio of the third PWM signal. The fourth constant voltage generator may adjust the driving voltage of the fourth light source LS4 by adjusting the on / off timing of the switch element for adjusting the driving voltage of the fourth light source LS4 by the duty ratio of the fourth PWM signal. The current flowing through the light sources LS1 to LS4 and the brightness of the light sources LS1 to LS4 are increased or decreased in proportion to the driving voltages applied to the light sources LS1 to LS4.

The source driver 12 latches the digital video data R'G'B 'under the control of the timing controller 10. The source driver 12 converts the digital video data R'G'B 'into positive / negative analog data voltages using the positive / negative gamma compensation voltages and supplies them to the data lines DL. . The gate driver 14 sequentially supplies gate pulses (or scan pulses) to the gate lines GL, which are synchronized with the data voltages supplied to the data lines DL.

The timing controller 10 receives timing signals Vsync, Hsync, DE, and DCLK from an external host system and supplies digital video data RGB to the source driver 12. The timing signals Vsync, Hsync, DE, and DCLK include a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable signal DE, a main clock signal DCLK, and the like. The timing controller 10 may include timing control signals DDC, for controlling an operation timing of the source driver 12 and the gate driver 14 based on timing signals Vsync, Hsync, DE, and DCLK from the host system. GDC). The timing controller 10 supplies the digital video data RGB of the input image input from the host system to the local dimming controller 30 and modulates the digital video data R'G 'modulated by the local dimming controller 30. B ') can be supplied to the source driver 12.

The local dimming control unit 30 executes a preset local dimming algorithm and analyzes the input image in units of local dimming blocks to represent representative values for each block (or representative gray values for each block) of the local dimming blocks B1 to B4. Determine. The local dimming algorithm can be any known. Representative values for each block may be determined by any one of a mode value, a maximum value, and an average value of the histogram obtained as a result of histogram analysis on the input image divided by the local dimming block. The block-specific representative values include the first to fourth block representative values indicating the representative gray level of each of the local dimming blocks B1 to B4. Representative values for each block are representative gray values of respective local dimming blocks, and have a value of 0 or more and 255 or less when the input image is input as 8-bit data. The local dimming controller 30 selects dimming values for each block according to the representative values for each of the first to fourth blocks. Representative values of the first to fourth blocks are input to a lookup table in which a dimming value is preset. The lookup table receives the representative values of each block and outputs a dimming value stored at an address indicated by the representative values of each block to output the dimming values DIM (B1) ˜1 corresponding to the representative values of each block. DIM (B4)). The local dimming control unit 30 limits the power consumption of the dimming values DIM (B1) to DIM (B4) for each of the first to fourth blocks through a spatial filter and a temporal filter (not shown). It supplies to the part 32. The local dimming controller 30 and the power consumption limiter 32 may be integrated in a single chip together with the timing controller 10.

The power consumption limiting unit 32 is implemented by a program or logic circuit that processes the power consumption limiting algorithm of FIG. 4. The power consumption limiting unit 32 may adjust the dimming values DIM (B1) to DIM (B4) for each of the first to fourth blocks input from the local dimming control unit 30 based on the power limitation algorithm as shown in FIG. 4. Limit below a certain level.

Referring to FIG. 4, the power consumption limiting unit 32 receives dimming values DIM (B1) to DIM (B4) for each block input from the local dimming control unit 30 and sums the total dimming values for the blocks ( DSUM) (S1 and S2) Each of the block-specific dimming values DIM (B1) to DIM (B4) output from the local dimming control unit 30 is 0 as digital data including duty ratio information of the PWM signal. It has a value of 100 or more. Subsequently, the power consumption limiter 32 compares the sum of the dimming values per block DSUM with a preset limit value DLIM. (S3) The limit value DLIM may be set by a module / set maker or a user. This is a limit value of the PWM duty ratio that is set according to the target power reduction target. The user can set the limit value DLIM through a user input device connected to the host system. The user input device may include a keypad, a keyboard, a mouse, an on screen display (OSD), a remote controller, a touch screen, and the like.

When limiting the PWM duty ratio to 85% to reduce the power consumption of the backlight unit (BLU) by more than 15%, the limit value DLIM is set to "Local dimming block number N × 85 = 4 × 85 = 340". Can be. Here, "85" means the maximum PWM duty ratio that can reduce the power consumption of the local dimming block by 15%. The limit value DLIM is not limited to "340" but may be set to a value desired by the module / set maker or the user.

If the sum of the dimming values per block DSUM is less than or equal to the limit value DLIM, when the light sources LS1 to LS4 are driven with the dimming values DIM (B1) to DIM (B4) per block, the local dimming method is used. The target value of power consumption reduction of the backlight unit BLU is met. Accordingly, the power consumption limiter 32 may include block dimming values DIM (B1) to DIM (B4) received from the local dimming control unit 30 when the sum of the dimming values for each block is less than or equal to the limit value DLIM. )) Is supplied to the light source driver 34 as the final dimming values DIM '(B1) to DIM' (B4) for each block. (S3 and S4) For example, the sum of the dimming values for each block (DSUM). When the value is equal to or less than "DLIM = 340", the light source driver 34 may generate light sources LS1 at PWM duty ratios of the block-specific dimming values DIM '(B1) to DIM' (B4) determined by the local dimming controller 30. ~ LS4).

If the sum of the dimming values per block DSUM is greater than the limit value DLIM, the backlight unit BLU when driving the light sources LS1 to LS4 with the dimming values DIM (B1) to DIM (B4) per block. ) Does not reduce power consumption or does not meet the power reduction target. Therefore, the power consumption limiter 32 may include block dimming values DIM (B1) to DIM (B4) received from the local dimming control unit 30 when the sum of the dimming values per block is greater than the limit value DLIM. )) By dividing each block by a predetermined level to determine the final dimming values DIM '(B1) to DIM' (B4) for each block, and dimming values DIM '(B1) to DIM' (B4) for each block. The light source driving unit 34 is supplied to the light source driving unit 34 (S3 and S5). When the sum of the dimming values DSD of each block is greater than the limit value DLIM, the power consumption limiting unit 32 subtracts the DLIM from the DSUM to the local dimming block. The dimming value of each block can be subtracted by the number of times. For example, if DSUM = 380, DLIM = 340, DIM (B1) = 100, DIM (B2) = 100, DIM (B3) = 100, and DIM (B4) = 80, the power consumption limiter dimms by the final block. (DIM '(B1)-DIM' (B4)), "DIM '(B1) = DIM (B1)-((DSUM-DLIM) / 4) = 100-((380-340) / 4) = 90 "," DIM '(B2) = DIM (B2)-((DSUM-DLIM) / 4) = 100-((380-340) / 4) = 90 "," DIM' (B3) = DIM (B3) -((DSUM-DLIM) / 4) = 100-((380-340) / 4) = 90 "," DIM '(B4) = DIM (B4)-((DSUM-DLIM) / 4) = 80- ((380-340) / 4) = 70 ". In this case, the light source driver 34 has a duty of DIM '(B1) = 90%, DIM' (B2) = 90%, DIM '(B3) = 90% adjusted downward by the power consumption limiter 32. The driving voltage of each of the first to third light sources LS1 to LS3 is adjusted by the ratio, and the driving voltage of the fourth light source LS4 is adjusted to a duty ratio of DIM '(B4) = 70%.

In general, the lower the representative value for each block, the lower the dimming value. Therefore, the second embodiment of the present invention limits the representative value for each block to a value less than or equal to the target value of power consumption reduction.

6 and 7 illustrate a liquid crystal display according to a second exemplary embodiment of the present invention and a method of limiting power consumption thereof. 8 to 10 are diagrams illustrating an example of a method of limiting power consumption of a liquid crystal display according to a second exemplary embodiment of the present invention.

Referring to FIG. 6, the liquid crystal display of the present invention includes a liquid crystal display panel PNL, a backlight unit BLU for irradiating light to the liquid crystal display panel PNL, and a light source driver for driving light sources of the backlight unit BLU. 36, the source driver 12 for driving the data lines DL of the liquid crystal display panel PNL, the gate driver 14 for driving the gate lines GL of the liquid crystal display panel PNL, The timing controller 20 controls the operation timing of the source driver 12 and the gate driver 14, the power consumption limiter 40 selectively lowers the representative values of each block, and local dimming based on the representative values of the blocks. It includes a local dimming controller 50 for controlling.

The liquid crystal display panel PNL, the backlight unit BLU, the source driver 12 and the gate driver 14 are substantially the same as those of the first embodiment described above.

The light source driver 36 adjusts the duty ratio of the first to fourth PWM signals in response to the first to fourth block dimming values DIM (B1) to DIM (B4) input from the local dimming controller 50. Adjust. Accordingly, the light source driver 36 independently adjusts the luminance of each of the local dimming blocks B1 to B4 divided by the backlight unit BLU in response to the dimming values DIM B1 to DIM B4 for each block. By adjusting the contrast ratio of the display image, the power consumption of the backlight unit BLU may be adjusted to a predetermined level or less. The light source driver 36 independently adjusts driving voltages of the light sources in units of local dimming blocks according to PWM duty information of the dimming values DIM (B1) to DIM (B4) for each of the first to fourth blocks. And a PWM control unit.

The timing controller 20 receives timing signals Vsync, Hsync, DE, and DCLK from an external host system, and supplies digital video data RGB to the source driver 12. The timing controller 20 may include timing control signals DDC, for controlling an operation timing of the source driver 12 and the gate driver 14 based on timing signals Vsync, Hsync, DE, and DCLK from the host system. GDC). The timing controller 20 supplies the digital video data RGB of the input image input from the host system to the local dimming controller 50 and modulates the digital video data R'G 'modulated by the local dimming controller 50. B ') can be supplied to the source driver 12.

The power consumption limiter 40 is implemented by a program or logic circuit that processes the power consumption limitation algorithm of FIG. 7. The power consumption limiter 40 analyzes the input image in units of local dimming blocks to determine representative values G (B1) to G (B4) of each of the local dimming blocks B1 to B4. The representative value for each block may be determined by any one of a mode value, a maximum value, and an average value obtained as a result of histogram analysis of the input image divided by the local dimming block unit, and indicate a representative gray level of each of the local dimming blocks B1 to B4. Representative values for each of the first to fourth blocks are included.

When the sum of the representative values G (B1) to G (B4) for each block is a high value that does not meet a predetermined power consumption reduction target value, the power consumption limiter 40 includes the representative values for each block G ( B1) to G (B4)) are lowered to output representative values G '(B1) to G' (B4) for each final block. The power consumption limiter 40 and the local dimming controller 50 may be integrated in a single chip together with the timing controller 20.

The local dimming control unit 50 executes a preset local dimming algorithm to perform block-based dimming corresponding to representative values G '(B1) to G' (B4) for each final block received from the power consumption limiter 40. Values DIM (B1) to DIM (B4) are output. Block-specific dimming values DIM (B1) to DIM (B4) may be supplied to the light source driver 36 through a spatial filter and a temporal filter.

Referring to FIG. 7, the power consumption limiter 40 determines representative values G (B1) to G (B4) for each block through input image analysis, and representative values G (B1) for each block. Calculate the sum GSUM of the plurality of G (B4). (S21 to S23) Representative values G (B1) to G (B4) for each block are representative gray values of respective local dimming blocks. When input as 8-bit data, it has a value between 0 and 255. Subsequently, the power consumption limiter 40 compares the sum GSUM of the representative values G (B1) to G (B4) for each block with a preset limit value GLIM. (S24) The limit value DLIM ) Is a limit value of a block-specific representative value set according to a power consumption reduction target value that can be set by a module / set maker or a user. The user can set the limit value GLIM through a user input device connected to the host system.

In the case of limiting the representative value of each block to 85% in order to reduce the power consumption of the backlight unit BLU by 15% or more, the limit value GLIM is set to "Local dimming block number N × 238 = 4 × 238 = 952". Can be set. Here, "238" means a maximum gray value that can reduce the power consumption of the local dimming block by 15%. The limit value DLIM is not limited to "952" but may be set to a value desired by the module / set maker or the user.

If the sum GSUM of the block-specific representative values G (B1) to G (B4) is less than or equal to the threshold value GLIM, the PWM duty ratio of the block-specific dimming values DIM (B1) to DIM (B4) is Since the value satisfies the power consumption reduction target, the power consumption reduction target of each of the local dimming blocks B1 to B4 may be met. Therefore, when the sum GSUM of the block-specific representative values G (B1) to G (B4) is less than or equal to the threshold value GLIM, the power consumption limiter 40 represents the block-specific representative values G (B1). ~ G (B4)) is supplied to the local dimming control unit 50 as the final block representative values G '(B1) to G' (B4). (S24 and S25) For example, the block representative values If the sum GSUM of the fields G (B1) to G (B4) is equal to or less than " 952 ", the light source driving unit 34 is based on the representative values G (B1) to G (B4) per circle block. The light sources LS1 to LS4 are driven by the PWM duty ratios of the block-specific dimming values DIM (B1) to DIM (B4) determined by the local dimming controller 30.

If the sum GSUM of the block-specific representative values G (B1) to G (B4) is greater than the threshold value GLIM, the PWM duty ratio of the block-specific dimming values DIM (B1) to DIM (B4) is It does not meet the target for reducing power consumption because it becomes a high value that does not meet the target for reducing power consumption. Therefore, when the sum GSUM of the block-specific representative values G (B1) to G (B4) is larger than the threshold value GLIM, the power consumption limiter 40 may include the block-specific representative values G (B1) to G (B4)) is lowered by a predetermined level to determine representative values G '(B1) to G' (B4) for each final block, and are supplied to the local dimming controller 50. (S24 and S26) Power consumption limitation If the sum 40 is greater than the sum GSUM of the representative values G (B1) to G (B4), the value obtained by subtracting the GLIM from the GSUM is divided by the number of local dimming blocks. Values G (B1) to G (B4) can be lowered.

As shown in FIG. 8, representative values G (B1) to G (B4) for each block are “G (B1) = 255, G (B2) = 255, G (B3) = 255, G (B4) = 255 If GSUM = 1020, then GSUM-GLIM = 1020-952 = 68. In this case, the power consumption limiter 40 is ((GSUM)-(GLIM) because the sum GSUM of the representative values G (B1) to G (B4) for each block is larger than the threshold value GLIM. Lower the representative values G (B1) to G (B4) by one block by / 4 = 17, so the final representative values G '(B1) = 238, G' (B2) = 238, G ' (B3) = 238, G '(B4) = 238) is calculated.

As shown in FIG. 9, representative values G (B1) to G (B4) for each block are “G (B1) = 251, G (B2) = 255, G (B3) = 255, G (B4) = 255 If GSUM = 1016, then GSUM-GLIM = 1016-952 = 64. In this case, the power consumption limiter 40 is ((GSUM)-(GLIM) because the sum GSUM of the representative values G (B1) to G (B4) for each block is larger than the threshold value GLIM. ) / 4 = 16 to decrease the representative values (G (B1) to G (B4)) for each block, thereby reducing the representative values for the final block (G '(B1) = 235, G' (B2) = 239, G ' (B3) = 239 and G '(B4) = 239).

As shown in FIG. 10, representative values G (B1) to G (B4) for each block are “G (B1) = 223, G (B2) = 223, G (B3) = 223, and G (B4) = 255 If GSUM = 924, GSUM is smaller than GLIM. In this case, the power consumption limiting unit 40 represents the one-block representative values G (B1) because the one-to-one representative values G (B1) to G (B4) satisfy the power consumption reduction target value. G (B4)) is determined as representative values G '(B1) to G' (B4) for each final block.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

PNL: LCD panel BLU: Backlight unit
30, 50: local dimming control unit 32, 40: power consumption limiting unit
34, 36: light source driver

Claims

A liquid crystal display panel;
A backlight unit radiating light to the liquid crystal display panel through a light emitting surface divided into a plurality of local dimming blocks;
A local dimming controller configured to analyze input images, determine representative values for each block of each of the local dimming blocks, and select dimming values for each block corresponding to the representative values for each block;
A light source driver configured to adjust driving voltages of light sources for irradiating light to the local dimming blocks based on the dimming values of the blocks; And
The total sum of the representative values for each block or the sum of the dimming values for each block is compared with a preset limit value, and if the total sum of the representative values for each block or the total sum of the dimming values for each block is greater than the threshold, the representative value for each block. And a power consumption limiting unit for lowering each of them to below a predetermined level or lowering each of the dimming values for each block to below a predetermined level.

The method of claim 1,
The power consumption limit unit,
If the total sum of the dimming values for each block is greater than a preset dimming limit value, each dimming value for each block is subtracted by the result of subtracting the dimming limit value from the total dimming value for each block divided by the number of local dimming blocks. Liquid crystal display characterized in that.

The method of claim 2,
The power consumption limit unit,
And if the total sum of the dimming values for each block is less than or equal to the dimming limit value, the dimming values for each block are supplied to the light source driver as it is.

The method of claim 1,
The power consumption limit unit,
If the total sum of the representative values for each block is greater than a preset representative gray level threshold, each of the representative values for each block is obtained by dividing the result of subtracting the representative gray level from the total sum of the representative gray level values by the number of the local dimming blocks. Liquid crystal display, characterized in that for subtracting.

The method of claim 4, wherein
The power consumption limit unit,
And if the sum of the representative values for each block is less than or equal to the representative gradation threshold, supplying the representative values for each block to the local dimming control unit as it is.

In the method of limiting power consumption of a liquid crystal display device comprising a liquid crystal display panel and a backlight unit for irradiating light to the liquid crystal display panel through a light emitting surface divided into a plurality of local dimming block,
Analyzing the input image to determine representative values for each block of the local dimming block;
Selecting block-specific dimming values corresponding to the block-specific representative values;
Adjusting a driving voltage of light sources for irradiating light to the local dimming blocks based on the dimming values for each block; And
Comparing the sum of the representative values for each block or the sum of the dimming values for each block with a preset limit value;
If the sum of the representative values of each block or the sum of the dimming values of each block is greater than the threshold, lowering each of the representative values of each block to a predetermined level or less, or lowering each of the dimming values of each block to a predetermined level or less. Method for limiting the power consumption of the liquid crystal display device comprising a.

The method according to claim 6,
Lowering each of the representative values for each block below a predetermined level or lowering each of the dimming values for each block below a predetermined level may include:
If the total sum of the dimming values for each block is greater than a preset dimming limit value, each dimming value for each block is subtracted by the result of subtracting the dimming limit value from the total dimming value for each block divided by the number of local dimming blocks. Method for limiting the power consumption of the liquid crystal display, characterized in that.

The method of claim 7, wherein
Lowering each of the representative values for each block below a predetermined level or lowering each of the dimming values for each block below a predetermined level may include:
And dimming value of each block is supplied to the light source driver as it is if the sum of the dimming values of each block is less than or equal to the dimming limit value.

The method according to claim 6,
Lowering each of the representative values for each block below a predetermined level or lowering each of the dimming values for each block below a predetermined level may include:
If the total sum of the representative values for each block is greater than a preset representative gray level threshold, each of the representative values for each block is obtained by dividing the result of subtracting the representative gray level from the total sum of the representative gray level values by the number of the local dimming blocks. A method of limiting power consumption of a liquid crystal display device, comprising: subtracting the difference.

The method of claim 9,
Lowering each of the representative values for each block below a predetermined level or lowering each of the dimming values for each block below a predetermined level may include:
And if the sum of the representative values for each block is less than or equal to the representative gradation threshold, supplying the representative values for each block to the local dimming control unit as it is.