JP2012168286A - Backlight control device and backlight control method for liquid crystal display panels, and liquid crystal display apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backlight control device for liquid crystal display panels that can reduce fluctuations of loads on a plurality of power sources.SOLUTION: Light emitting blocks BL arrayed in row and column directions over each light emitting substrate 11 are divided into three column-based groups, and the groups are respectively matched with power sources 7A, 7B and 7C. The way of power distribution is such that a backlight drive unit 8 supplies a power output PA of the power source 7A to light emitting blocks BL of the group matched with the power source 7A, a power output PB of the power source 7B to light emitting blocks BL of the group matched with the power source 7B, and a power output PC of the power source 7C to light emitting blocks BL of the group matched with the power source 7C. The maximum levels of output power to the power sources 7A, 7B and 7C are thereby restrained, resulting in milder variations of the power outputs PA, PB and PC from the power sources 7A, 7B and 7C.

Description

  The present invention relates to a backlight control device, a backlight control method, and a liquid crystal display device for a liquid crystal display panel that controls output power to a plurality of light emitting blocks arranged in a matrix direction used as a backlight of a liquid crystal display panel.

  As a backlight of a liquid crystal display panel, a cold cathode tube, a light emitting element (for example, LED) or the like is used. In a large liquid crystal display panel, a backlight is configured by arranging a plurality of cold cathode tubes or a plurality of LEDs in a matrix direction.

  Also, when using a plurality of cold-cathode tubes or a plurality of LEDs as a backlight, in order to increase the contrast of an image displayed on the liquid crystal display panel or to reduce the power consumption of the backlight, Local dimming (local brightness control) may be performed.

  For example, in the case of using a backlight BK in which a plurality of light emitting blocks BL are arranged in a matrix direction as shown in FIG. 6, each row R1 to R8 is arranged in a row in the frame period of the liquid crystal display panel. The backlight scan and local dimming are performed by setting and adjusting the lighting period and extinguishing period of the light emitting block BL. In addition, each light emission block BL shall each be comprised from 1 thru | or several LED, for example.

  Further, when the liquid crystal display panel is enlarged, the backlight is also enlarged, and the power consumption of the backlight is increased. For this reason, the power may be supplied from a plurality of power supplies to the backlight to turn on the backlight. For example, as shown in FIG. 6, each row R1 to R8 is divided into three groups G1 to G3, and three sets of power sources S1 to S3 and drive circuits D1 to D3 are assigned to each group G1 to G3. The power P1, P2, and P3 are supplied from S3 to the groups G1 to G3 via the drive circuits D1 to D3, and the backlight BK is turned on.

  FIG. 7A is a timing chart showing the lighting period and the extinguishing period of each light-emitting block BL arranged in a row for each row R1 to R8. FIG. 7B shows changes (constant values) of the output powers P1, P2, and P3 of the power supplies S1 to S3 when the lighting periods and the extinguishing periods of the rows R1 to R8 are set at the timing shown in FIG. It corresponds to the change of the output current with voltage).

  As apparent from FIG. 7 (a), the lighting period Ton and the extinguishing period Toff of each light-emitting block BL arranged in the row are alternately switched for each row R1 to R8, and the lighting period Ton is changed between the rows R1 to R8. The extinguishing periods Toff are sequentially shifted. For this reason, as shown in FIG.7 (b), the output electric power P1-P3 of each power supply S1-S3 changes in steps.

  Further, in Patent Document 1, a plurality of light-emitting blocks are divided into a plurality of groups, and each group of light-emitting blocks is distributed and arranged in a backlight, and the lighting control of each light-emitting block in the group is switched and controlled. Thus, the load of the drive circuit of each group is distributed.

JP 2010-55053 A

  However, in the conventional power supply configuration as shown in FIG. 6, the difference between the maximum value and the minimum value is large for each of the output powers P1 to P3 as shown in FIG. The maximum value of the output power P1 to P3 was also large. For this reason, the load fluctuation of each power supply S1-S3 was large, and a loud noise sound (swelling sound) was generated from the transformer of each power supply S1-S3. Moreover, it was difficult to say that the loads of the power sources S1 to S3 are effectively distributed.

  Further, in Patent Document 1, since each light emitting block of the group is dispersedly arranged in the backlight for each group, it is difficult to simplify the power supply wiring to each light emitting block, and the wiring is complicated. It is thought that.

  Accordingly, the present invention has been made in view of the above-described conventional problems, and can reduce load fluctuations of a plurality of power supplies, and can simplify wiring for supplying power to each light emitting block. An object of the present invention is to provide a backlight control device, a backlight control method, and a liquid crystal display device for a liquid crystal display panel.

  In order to solve the above problems, a backlight control apparatus for a liquid crystal display panel according to the present invention includes a plurality of light emitting blocks arranged in a matrix direction used as a backlight of a liquid crystal display panel, and the frame period of the liquid crystal display panel A backlight control device for a liquid crystal display panel that performs local dimming by setting a light emission block lighting period and a light emission block extinction period for each row of the respective light emission blocks, wherein power is supplied to each light emission block. A plurality of power supplies to be supplied, and a power distribution unit that divides each light-emitting block into a plurality of groups in units of columns and supplies power from each power supply to each group.

  In such a backlight control apparatus of the present invention, each light emitting block arranged in the matrix direction is locally dimmed in units of rows, and each light emitting block arranged in the matrix direction is divided into a plurality of groups in units of columns. Each group has its own power supply. Therefore, each row receives power supply from any power source corresponding to any power source. As a result, the change in the output power of each power source becomes gradual, the load fluctuation of each power source is reduced, the maximum value of the output power of each power source is suppressed, and the load of each power source is effectively distributed. In addition, since each light emitting block is divided into a plurality of groups in units of columns, wiring for supplying power from the power source to each light emitting block can be simplified, and the wiring is not complicated.

  Each light emitting block is composed of, for example, one or a plurality of light emitting elements. Further, the row direction and the column direction of each light emitting block may correspond to the horizontal direction and the vertical direction, respectively, or the row direction and the column direction of each light emitting block may correspond to the vertical direction and the horizontal direction, respectively.

  In the backlight control device of the present invention, the same number of the light emission blocks is assigned to the groups.

  In this case, the output power of each group becomes the same, and the load fluctuation of each power supply and the maximum value of the output power can be effectively suppressed.

  Next, a backlight control method for a liquid crystal display panel according to the present invention includes a plurality of light emitting blocks arranged in the vertical and horizontal directions used as a backlight of the liquid crystal display panel, and each of the light emitting elements in a frame period of the liquid crystal display panel. A backlight control method for a liquid crystal display panel that performs local dimming by setting a lighting block lighting period and a lighting block extinguishing period for each vertical or horizontal arrangement of blocks, wherein each of the light emitting blocks is divided into a plurality of groups. Power is supplied to each group from a plurality of power sources, and the vertical or horizontal alignment direction of the respective light-emitting blocks to be subjected to the local dimming and the direction in which the respective groups are aligned Orthogonal.

  In such a backlight control method of the present invention, in the frame period of the liquid crystal display panel, the lighting block lighting period and the lighting block extinguishing period are set for each vertical or horizontal arrangement of the respective light emitting blocks, and the local dimming is performed. It is carried out. Here, the horizontal direction and the vertical direction of each light emitting block may correspond to the row direction and the column direction, respectively, or the horizontal direction and the vertical direction of each light emitting block may correspond to the column direction and the row direction, respectively. Therefore, similarly to the backlight control device of the above invention, in the frame period of the liquid crystal display panel, the lighting block lighting period and the lighting block extinguishing period are set for each row of the light emitting blocks, and the local dimming is performed. It can be said that there is. In addition, since the vertical or horizontal arrangement direction of each light-emitting block to be subjected to local dimming and the direction in which each group to which power from each power supply is arranged are orthogonal, the backlight control according to the above invention is performed. As with the device, each light-emitting block arranged in the matrix direction is locally dimmed in row units, each light-emitting block arranged in the matrix direction is divided into a plurality of groups, and each group is assigned a power source. Will be. For this reason, there exists an effect similar to the backlight control apparatus of the said invention.

  In the backlight control method of the present invention, the same number of the light emission blocks is assigned to the groups.

  In this case, the output power of each group becomes the same, and the load fluctuation of each power supply and the maximum value of the output power can be effectively suppressed.

  The liquid crystal display device of the present invention includes a liquid crystal display panel and a plurality of light-emitting blocks arranged in a matrix direction used as a backlight of the liquid crystal display panel, and each of the above-described liquid crystal display panels in a frame period of the liquid crystal display panel A liquid crystal display device that performs local dimming by setting a light emitting block lighting period and a light emitting block extinguishing period for each row of the light emitting blocks, and a plurality of power supplies that supply power to each of the light emitting blocks; A power distribution unit that divides the light-emitting blocks into a plurality of groups in units of columns and supplies the power of each power source to the respective groups;

  Such a liquid crystal display device of the present invention also has the same effects as the backlight control device and backlight control method of the present invention.

  According to the present invention, each light emitting block arranged in the matrix direction is locally dimmed in row units, and each light emitting block arranged in the matrix direction is divided into a plurality of groups in column units. Each power supply is allocated to. Therefore, each row receives power supply from any power source corresponding to any power source. As a result, the change in the output power of each power source becomes gradual, the load fluctuation of each power source is reduced, the maximum value of the output power of each power source is suppressed, and the load of each power source is effectively distributed. In addition, since each light emitting block is divided into a plurality of groups in units of columns, wiring for supplying power from the power source to each light emitting block can be simplified, and the wiring is not complicated.

It is a block diagram which shows the liquid crystal display device to which one Embodiment of the backlight control apparatus of this invention is applied. It is a figure which shows the relationship between each power supply, each drive circuit, and each light emission block of the backlight control apparatus of FIG. It is a circuit diagram which shows the light emission block of FIG. (A) is a timing chart which shows the lighting period and the light extinction period of each light emission block arranged in a row for every row of each light emission block arranged in the matrix direction of FIG. 2, and (b) is (a). 6 is a graph showing a change in output power of each power supply (corresponding to a change in output current at a constant voltage) when the lighting period and the extinguishing period of each row are set at the timing shown in FIG. (A) shows experimentally measured peak values of output currents of three power sources in the backlight control device of FIG. 1 and peak values of output currents of three power sources in the conventional backlight control device of FIG. (B) is an experimental measurement of the fluctuation range of the output currents of the three power supplies in the backlight control device of FIG. 1 and the fluctuation range of the output currents of the three power supplies in the conventional backlight control device. It is a chart shown. It is a figure which shows the relationship between each power supply, each drive circuit, and each light emission block of the conventional backlight control apparatus. (A) is a timing chart which shows the lighting period and light extinction period of each light emission block arranged in the row for every row of each light emission block arranged in the matrix direction of FIG. 6, and (b) is (a). 6 is a graph showing a change in output power of each power supply (corresponding to a change in output current at a constant voltage) when the lighting period and the extinguishing period of each row are set at the timing shown in FIG.

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

  FIG. 1 is a block diagram showing a liquid crystal display device to which an embodiment of a backlight control device of the present invention is applied. The liquid crystal display device 1 includes a liquid crystal display panel 2, a backlight unit 3 having a backlight function of the liquid crystal display panel 2, an image signal, and an image signal suitable for driving control of the liquid crystal display panel 2. An interface conversion scaler unit 4 for converting data, a local dimming unit 5 for inputting and storing image data from the interface conversion scaler unit 4 and outputting a drive control signal for the backlight unit 3 based on the image data; Is input through the local dimming unit 5, the liquid crystal display panel 2 is driven and controlled based on the image data, and an image corresponding to the image data is displayed on the screen of the liquid crystal display panel 2. Supply each output power PA, PB, PC The three power supplies 7A, 7B, 7C and the drive control signal from the local dimming unit 5 are input, and the output power PA, PB from the power supplies 7A, 7B, 7C to the backlight unit 3 based on the drive control signal And a backlight drive unit 8 for adjusting and controlling the PC.

  In the liquid crystal display device 1 having such a configuration, an image signal indicating one image is input to the interface conversion scaler unit 4 for each frame period, where the image signal is converted into image data, and the image data is locally dimmed. The image is input to the LCD driving unit 6 through the unit 5, and one image corresponding to the image data is displayed on the liquid crystal display panel 2 by the LCD driving unit 6.

  On the other hand, the backlight control device of this embodiment includes the backlight unit 3, the local dimming unit 5, the power supplies 7 </ b> A, 7 </ b> B, and 7 </ b> C, and the backlight driving unit 8 in the liquid crystal display device 1.

  The backlight unit 3 includes eight light-emitting substrates 11 each mounted with the light-emitting blocks BL arranged in the row direction (lateral direction), and the light-emitting substrates 11 are arranged in parallel in the column direction (vertical direction). Each light emitting block BL on each light emitting substrate 11 is arranged in a matrix direction. Accordingly, each light emitting substrate 11 corresponds to the first row R1 to the eighth row R8.

  Each power supply 7A, 7B, 7C includes three power supply circuits 7a, 7b, 7c, respectively. The output power PA of the power supply 7A (the sum of the output power of each power supply circuit 7a) is output to the backlight drive unit 8 through the three power supply lines 14R, 14G, and 14B. Further, the output power PB of the power supply 7B (the sum of the output power of each power supply circuit 7b) is output to the backlight driving unit 8 through the three power supply lines 15R, 15G, and 15B. Further, the output power PC of the power supply 7C (the sum of the output power of each power supply circuit 7c) is output to the backlight drive unit 8 through the three power supply lines 16R, 16G, and 16B.

  Further, the local dimming unit 5 obtains the lighting period and the extinguishing period of each row R1 to R8 based on the image data for each frame period, and backlight-drives a drive control signal indicating the lighting period and the extinguishing period of each row R1 to R8. Add to part 8.

  When the backlight drive unit 8 inputs a drive control signal indicating the lighting period and the extinguishing period of each row R1 to R8 for each frame period, the light emitting substrate 11 corresponding to the row during the lighting period of the row for each row R1 to R8. The output power PA, PB, PC of each power supply 7A, 7B, 7C is supplied to the light source, each light emitting block BL of the row is turned on, and each output to the light emitting substrate 11 corresponding to the row is performed during the light extinction period of the row. The supply of power PA, PB, and PC is stopped, and each light emitting block BL in the row is turned off. Therefore, for each row R1 to R8, the backlight drive unit 8 controls (PWM control) the output width (lighting period) of each output power PA, PB, and PC. In each of the rows R1 to R8, the frame For each period, each light emitting block BL is turned on during the lighting period, and each light emitting block BL is turned off during the extinguishing period (backlight scan and local dimming).

  As described above, by determining and setting the lighting period and the extinguishing period of each row R1 to R8 based on the image data, it is possible to reduce the afterimage feeling of the image displayed on the liquid crystal display panel 2 or increase the contrast of the image. it can. For example, by shortening the extinction period of each light-emitting block BL in the row corresponding to the bright area of the image or increasing the extinction period of each light-emitting block BL in the line corresponding to the dark area of the image, the contrast of the image is increased. Make it high.

  When the liquid crystal display device 1 is large, the liquid crystal display panel 2 and the backlight unit 3 are also large, and the power consumption of the backlight unit 3 is increased. Further, when the liquid crystal display device 1 is used as an IDP (Information Display Panel), it is necessary to increase the luminance of the backlight unit 3, which also increases the power consumption of the backlight unit 3. Therefore, three power supplies 7A, 7B, and 7C are provided as power supplies for the backlight unit 3.

  In addition, the light emitting blocks BL arranged in the matrix direction on each light emitting substrate 11 are divided into three groups on a column basis, and each group is associated with each power source 7A, 7B, 7C on a one-to-one basis. The backlight driving unit 8 supplies the output power PA of the power source 7A to each light emitting block BL of the group corresponding to the power source 7A through the wiring line of each light emitting substrate 11, and the output power PB of the power source 7B to the power source 7B. Power distribution is performed such that the power is supplied to each light emitting block BL of the corresponding group, and the output power PC of the power source 7C is supplied to each light emitting block BL of the group corresponding to the power source 7C. Such power distribution effectively distributes the load of each power source 7A, 7B, 7C.

  Next, the correspondence between each group and each power source 7A, 7B, 7C and the power distribution from each power source 7A, 7B, 7C to each group will be described in detail.

  FIG. 2 is a diagram conceptually showing a power supply path from each power source 7A, 7B, 7C to each light emission block BL of the backlight unit 3 through the backlight driving unit 8. As shown in FIG.

  As shown in FIG. 2, the backlight unit 3 is configured by arranging a plurality of light emission blocks BL in a matrix direction (horizontal direction and vertical direction), and each light emission block BL is divided into three groups GA, GB. , Divided into GC. Each light emitting block BL in the first column to the sixth column belongs to the group GA, each light emitting block BL in the seventh column to the tenth column belongs to the group GB, and each light emitting block BL in the eleventh column to the sixteenth column is a group. Each group GA, GB, GC and each power source 7A, 7B, 7C are associated with each other on a one-to-one basis.

  Further, the backlight drive unit 8 includes a drive circuit 8A that controls connection between the light emitting blocks BL of the group GA (first column to sixth column) and the power source 7A, and a group GB (seventh column to tenth column). ) Driving circuit 8B for controlling connection between each light emitting block BL and power source 7B, and driving for controlling connection between each light emitting block BL and power source 7C in group GC (11th to 16th columns). A circuit 8C is provided.

  FIG. 3 illustrates the configuration of the light emission block BL. As shown in FIG. 3, the light emitting block BL includes eight red LEDs 12R, eight green LEDs 12G, and four blue LEDs 12B, and two blue LEDs 12B are arranged around the blue LED 12B. If the configuration in which the red LED 12R and the two green LEDs 12G are arranged is one set, four sets of the arrangement configuration are provided. Also, each red LED 12R is connected in series, each green LED 12G is connected in series, each blue LED 12B is connected in series, a wiring line 13R for each red LED 12R, a wiring line 13G for each green LED 12G, and a wiring line 13B for each blue LED 12B. Are provided separately.

  The light emitting block BL can be composed of one to a plurality of light emitting elements, and other types of elements (cold cathode tubes, incandescent lamps, etc.) different from the LED may be applied as the light emitting elements.

  As shown in FIG. 1, three power supply lines 14 </ b> R, 14 </ b> G, and 14 </ b> B are led out from the power source 7 </ b> A and connected to the backlight driving unit 8. In addition, the wiring lines 13R, 13G, and 13B of the light emitting blocks BL in the first to sixth columns (group GA) receiving the output power PA of the power source 7A are connected to the backlight driving unit 8 for each light emitting substrate 11. Has been. As shown in FIG. 2, the drive circuit 8A of the backlight drive unit 8 is supplied with the output power PA of the power source 7A through the power supply lines 14R, 14G, and 14B for each light emitting substrate 11 (each row R1 to R8). Connected to the wiring lines 13R, 13G, 13B of the light emitting blocks BL in the first to sixth columns (group GA), the light emitting blocks BL (each red LED 12R, each green LED 12G, each of the first column to the sixth column) In addition, each blue LED 12B) is turned on or this connection is cut off, and each light emitting block BL in the first to sixth columns is turned off.

  Further, as shown in FIG. 1, three power supply lines 15R, 15G, and 15B are led out from the power source 7B and connected to the backlight driving unit 8. In addition, the wiring lines 13R, 13G, and 13B of the light emitting blocks BL in the seventh column to the tenth column (group GB) that receive the supply of the output power PB of the power supply 7B are connected to the backlight driving unit 8 for each light emitting substrate 11. Has been. As shown in FIG. 2, the drive circuit 8B of the backlight drive unit 8 receives the supply of the output power PB of the power supply 7B through the power supply lines 15R, 15G, and 15B for each light-emitting substrate 11 (rows R1 to R8). Connected to the wiring lines 13R, 13G, 13B of the respective light emitting blocks BL in the seventh column to the tenth column (group GB), the light emitting blocks BL (the respective red LEDs 12R, the respective green LEDs 12G, In addition, each blue LED 12B) is turned on or this connection is cut off, and each light emitting block BL in the seventh column to the tenth column is turned off.

  Further, as shown in FIG. 1, three power supply lines 16R, 16G, and 16B are led out from the power source 7C and connected to the backlight driving unit 8. In addition, the wiring lines 13R, 13G, and 13B (each row R1 to R8) of each light emission block BL in the 11th column to the 16th column to which the output power PC of the power source 7C is supplied for each light emitting substrate 11 are the backlight driving unit 8. It is connected to the. As shown in FIG. 2, the drive circuit 8C of the backlight drive unit 8 is supplied with the output power PC of the power supply 7C through the power supply lines 16R, 16G, and 16B for each light emitting substrate 11 (each row R1 to R8). Connected to the wiring lines 13R, 13G, 13B of the respective light emitting blocks BL in the eleventh column to the sixteenth column (group GC), the respective light emitting blocks BL (each red LED 12R, each green LED 12G, In addition, each blue LED 12B) is turned on or this connection is cut off, and each light emitting block BL in the 11th to 16th columns is turned off.

  Thus, the backlight drive unit 8 connects the power source 7A to each light emitting block BL of the group GA on the light emitting substrate 11 for each light emitting substrate 11 (each row R1 to R8), cuts off this connection, 7B is connected to each light emitting block BL of the group GB on the light emitting substrate 11, or this connection is cut off. Further, the power source 7C is connected to each light emitting block BL of the group GC on the light emitting substrate 11, or this connection is cut off. As a result, the lighting periods and extinguishing periods of the respective rows R1 to R8 are set, and the output powers PA, PB, PC of the power supplies 7A, 7B, 7C are distributed to the groups GA, GB, GC. As described above, the lighting period and the extinguishing period of each of the rows R1 to R8 are obtained and set based on the image data by the local dimming unit 5.

  In each of the light emitting substrates 11 (each row R1 to R8), each group GA, GB, GC (first column to sixth column, seventh column to tenth column, eleventh column to sixteenth column) is classified. The wiring lines 13R, 13G, and 13B can be shared by a single line, the wiring can be simplified, and the wiring is not complicated.

  FIG. 4A is a timing chart showing the lighting period and the extinguishing period of each row for each group GA, GB, GC. In FIG. 4A, symbols RA1 to RA8 are attached to the first row to the eighth row of the group GA, symbols RB1 to RB8 are attached to the first row to the eighth row of the group GB, and the first row of the group GC. Reference numerals RC1 to RC8 are attached to the first to eighth lines. In FIG. 4A, the lighting period and the extinguishing period are each set to a fixed length for the sake of simplicity of explanation.

  FIG. 4B shows changes in the output power PA, PB, PC of the power supplies 7A, 7B, 7C (constant voltage) when the lighting period and the extinguishing period of each row are set at the timing shown in FIG. (Corresponding to the change in the output current at 1).

  As is clear from FIG. 4A, in the group GA that receives power supply from the power source 7A, the lighting period Ton and the light-off period Toff of each light-emitting block BL arranged in a row are alternately switched for each row RA1 to RA8. Also, in the group GB that receives power supply from the power source 7B, the lighting period Ton and the light-off period Toff of each light-emitting block BL are alternately switched for each row RB1 to RB8, and also in the group GC that receives power supply from the power source 7C. For each row RC1 to RC8, the lighting period Ton and the extinguishing period Toff of each light emitting block BL are alternately switched.

  In addition, between the groups GA to GC, the timing of the lighting period Ton of the first row RA1, RB1, RC1 and the timing of the extinguishing period Toff match, and the timing of the lighting period Ton of the second row RA2, RB2, RC2 And the timing of the turn-off period Toff coincide with each other. Similarly, the timing of the turn-on period Ton and the timing of the turn-off period Toff coincide in any of the third to eighth rows. Therefore, in any row, the timing of the lighting period Ton of each light emitting block BL and the timing of the extinguishing period Toff coincide.

  Further, in each of the groups GA to GC, the lighting period Ton and the extinguishing period Toff are sequentially shifted between the first to eighth rows.

  In this way, when the output power PA, PB, PC of each power source 7A, 7B, 7C is distributed to each group GA, GB, GC, and the lighting period and extinguishing period of each row are set to a certain length, The output power PA is the sum of the power consumed in the lighting period Ton of each of the rows RA1 to RA8 of the group GA, and changes as shown in FIG. Similarly, the output power PB of the power supply 7B is the sum of the power consumed in the lighting periods Ton of the rows RB1 to RB8 of the group GB, and changes as shown in FIG. 4B, and further the output of the power supply 7C. The electric power PC is the sum of electric power consumed in the lighting period Ton of each row RC1 to RC8 of the group GC, and changes as shown in FIG.

  As is apparent from FIG. 4B, the output power PA of the power source 7A, the output power PB of the power source 7B, and the output power PC of the power source 7C change gradually, and the load fluctuations thereof. And the maximum value thereof is suppressed, and the loads of the power supplies 7A, 7B, and 7C are effectively distributed.

  FIG. 5A shows the peak values of the output currents of the three power supplies 7A, 7B, and 7C in the backlight control apparatus of the present embodiment of FIG. 1, and FIGS. 6, 7A, and 7B. It is a table | surface which measures and shows the peak value of the output current of three power supplies S1, S2, and S3 in the conventional backlight control apparatus by experiment. It is assumed that the output voltage is constant.

  As apparent from FIG. 5 (a), the peak value of the output current of each power source 7A, 7B, 7C of this embodiment is 4.2A or 2.8A, and the output current of each conventional power source S1, S2, S3. The peak value of is 6.72A or 4.48A. Therefore, the peak value of the output current of each power source 7A, 7B, 7C of this embodiment is 37.5% lower than the peak value of the output current of each conventional power source S1, S2, S3.

  FIG. 5B shows the fluctuation range of the output currents of the three power supplies 7A, 7B, and 7C in the backlight control device of this embodiment shown in FIG. 1, and FIGS. 6, 7A, and 7B. 6 is a chart showing experimentally measured fluctuation ranges of output currents of three power sources S1, S2, and S3 in the conventional backlight control device shown in FIG. It is assumed that the output voltage is constant and the change in output current corresponds to the change in output voltage.

  As apparent from FIG. 5B, the fluctuation range of the output current of each power source 7A, 7B, 7C of this embodiment is 0.84A or 0.56A, and the output current of each conventional power source S1, S2, S3. The fluctuation range is 6.72A or 4.48A. Therefore, the fluctuation range of the output current of each power source 7A, 7B, 7C of this embodiment is reduced by 80.0% compared with the fluctuation range of the output current of each conventional power source S1, S2, S3.

  Also from the measured values of such experiments, in this embodiment, the maximum values of the output power PA of the power source 7A, the output power PB of the power source 7B, and the output power PC of the power source 7C are suppressed, and their changes are gradual. I understand that.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. It is understood.

  For example, the same number of power supplies may be provided by setting the number of divisions of each light emitting block of the backlight, that is, the number of groups to 2 or 4 or more. In addition, the same number of light emission blocks may be assigned to each group. In this case, the output power of each group becomes the same, and the load fluctuation of each power supply and the maximum value of the output power can be effectively suppressed. Further, the row direction and the column direction of each light emitting block BL are respectively associated with the vertical direction and the horizontal direction, each light emitting block BL is locally dimmed in units of rows, and each light emitting block BL is divided into a plurality of groups in units of columns. Each power source may be allocated to each group.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Liquid crystal display panel 3 Backlight unit (backlight)
4 Interface conversion scaler unit 5 Local dimming unit 6 LCD drive unit 7A, 7B, 7C Power supply 8 Backlight drive unit (power distribution unit)
11 Light Emitting Board 12R Red LED
12G green LED
12B Blue LED
13R to 13B Wiring lines 14R to 14B, 15R to 15B, 16R to 16B Power supply line BL Light emitting block GA, GB, GC group

Claims (5)

A plurality of light emitting blocks arranged in a matrix direction used as a backlight of a liquid crystal display panel, and in a frame period of the liquid crystal display panel, for each row of the light emitting blocks, the light emitting block is turned on and the light emitting block is turned off. A backlight control device for a liquid crystal display panel that sets a period and performs local dimming,
A plurality of power supplies for supplying power to each light emitting block;
A backlight control device for a liquid crystal display panel, comprising: a power distribution unit that divides each light emitting block into a plurality of groups in units of columns and supplies power of each power source to each group. The backlight control device for a liquid crystal display panel according to claim 1,
The backlight control device for a liquid crystal display panel, wherein the same number of the respective light emission blocks is assigned to each group. A plurality of light emitting blocks arranged in the vertical and horizontal directions used as a backlight of the liquid crystal display panel, and in the frame period of the liquid crystal display panel, for each vertical or horizontal arrangement of the light emitting blocks, A backlight control method for a liquid crystal display panel that performs local dimming by setting a light-out block off period,
Each light emitting block is divided into a plurality of groups, and power is supplied to each group from a plurality of power sources.
A method for controlling a backlight of a liquid crystal display panel, characterized in that a vertical or horizontal arrangement direction of the respective light emitting blocks to be subjected to the local dimming is orthogonal to a direction in which the respective groups are arranged. A backlight control method for a liquid crystal display panel according to claim 3,
A method for controlling a backlight of a liquid crystal display panel, wherein the same number of the respective light emitting blocks is assigned to each group. A liquid crystal display panel, and a plurality of light emitting blocks arranged in a matrix direction used as a backlight of the liquid crystal display panel, and for each row of the light emitting blocks in the frame period of the liquid crystal display panel, A liquid crystal display device that performs local dimming by setting a lighting period and a lighting block extinguishing period,
A plurality of power supplies for supplying power to each light emitting block;
A liquid crystal display device comprising: a power distribution unit that divides each light emitting block into a plurality of groups in a column unit and supplies power of each power source to each group.

Images