JP2011138673A - Backlighting device and image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlighting light device that prevents load variation even when a backing light scan driving is executed, and to provide an image display apparatus. <P>SOLUTION: The backlighting device includes: a light-emitting part (200) including a light-emitting means (210) for each of a plurality of light-emitting regions that are divided at least in a vertical direction and changing the light-emitting means to be a non-light-emitting state in the vertical direction in response to scanning of an image; and a driving part (300) including at least one or more driving means (310-340), each of which drives the light-emitting means. The diving means has voltage applying means that apply common voltage to needed to drive the multiple light-emitting means driven by each of the driving means, and drives the light-emitting means in the light-emitting regions whose vertical directional positions are different. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a backlight device that controls lighting of a plurality of light emitting areas, and an image display device using the backlight device.

  A non-self-luminous image display device typified by a liquid crystal display device includes a backlight device (also simply referred to as a backlight) on the back surface. These image display devices display an image via a light modulation unit such as a liquid crystal panel that adjusts the amount of reflection and transmission of light emitted from a backlight according to an image signal. Here, in an image display device using a liquid crystal panel or the like, there are problems called “moving image blur” and “tailing” depending on hold-type driving (driving for holding image display for one frame period). In order to improve this, Patent Documents 1 and 2 disclose a driving method (hereinafter simply referred to as backlight scanning) in which the backlight is turned off according to the scanning of the liquid crystal and the backlight is turned on according to the response of the liquid crystal. ) Is disclosed.

  FIG. 14 shows a configuration example of a backlight according to the above-mentioned document, and has light emitting areas 2a to 2d divided into four in the vertical direction. The inverters 3a to 3d are inverters for driving a light source (not shown) in each light emitting region, and convert the power supply voltage to a voltage for driving the light source. The inverters 3a to 3d are provided with PWM (Pulse Width Modulation) input terminals for performing dimming individually, and PWM signals are input at the timing shown in FIG.

  As described above, by the backlight scan driving in which the backlight is turned off / on in accordance with the image scanning, an impulse driving type represented by CRT (Cathode Ray Tube) can be approached. In addition, the backlight scanning drive can hide the image of the response process such as liquid crystal, and the problem of “moving image blur” and “tailing” can be improved.

  On the other hand, in recent years, LEDs (Light Emitting Diodes) as light sources have become highly efficient and cost-effective, and LEDs have been adopted as illumination light sources instead of CCFLs (Cold Cathode Fluorescent Lamps). It has become. It has also begun to be used in backlights for image display devices. When a backlight is configured using LEDs, a configuration is used in which the backlight illumination unit is divided into a plurality of divided regions and the luminance is controlled for each region for the purpose of, for example, expanding the dynamic range (for example, patents). Reference 3).

Japanese Patent No. 3998311 Japanese Patent Laid-Open No. 1-82019 JP 2008-51905 A JP 2003-332624 A JP 2007-13183 A

  FIG. 16 is a configuration example in the case where backlight scanning driving is performed on the light emitting section 4 having a light emitting area of 4 rows and 4 columns based on the above-described conventional technology. In FIG. 16, the drive circuit 51 drives the light-emitting regions of the light-emitting portion 4 from column a row 1 to column d row 1. Similarly, the driving circuit 52 drives the light emitting regions of column a row 2 to column d row 2, the driving circuit 53 drives the light emitting region of column a row 3 to column d row 3, and the driving circuit 54 drives column a row. The light emitting area from 4 to column d row 4 is driven. Each of the drive circuits 51 to 54 has four PWM input terminals for controlling the light emission amount of each light emitting region. The drive circuits 51 to 54 sequentially repeat light emission and light extinction in the vertical direction in order to perform backlight scan drive, but in each drive circuit, the four light emission regions are simultaneously illuminated and extinguished.

  FIG. 17 shows the current waveform of the LED 41 in the light emitting region driven by the drive circuit 51. In FIG. 17, 100% luminance dimming (duty 50 is set as the maximum luminance) is performed in all the light emitting regions. In this way, all of the light emitting areas driven by the drive circuit are turned ON / OFF at the same timing. Even if dimming other than 100% is performed on each light emitting area, it remains the same that all light emitting areas are turned ON / OFF within the same period.

  That is, if the backlight scan drive is realized with the configuration as shown in FIG. 16, a sudden load fluctuation occurs due to the ON / OFF control of the backlight in the power supply circuit included in the drive circuit. In order to withstand this, large-capacity L (inductor) and C (capacitor) components must be used, and the power supply cost increases. In addition, the size of the parts is increased, which is detrimental to thinner devices. In particular, when a large number of light emitting regions are driven by a single power supply circuit, the load fluctuation increases accordingly.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a backlight device and an image display device that suppress load fluctuations when performing backlight scan driving.

  The backlight device of the present invention has a light emitting unit for each of a plurality of light emitting regions divided at least in the vertical direction, and the light emitting unit that changes the light emitting unit in a non-light emitting state in the vertical direction according to image scanning. And a drive unit having at least one drive unit that drives each of the plurality of light-emitting units, and the drive unit is common to the plurality of light-emitting units that are each driven. Voltage applying means for applying a voltage is provided, and the light emitting means in the light emitting areas having different vertical positions are driven.

  The image display device of the present invention has the above-described backlight device and a plurality of image display regions corresponding to the plurality of light emitting regions, and the light emitted from the back surface is provided for each image display region according to the image signal. And a light modulation unit that displays an image by modulation.

  According to the present invention, it is possible to provide a backlight device and an image display device that suppress load fluctuations when performing backlight scan driving.

FIG. 3 is a diagram illustrating an overall configuration of a liquid crystal display device according to Embodiment 1; The figure which shows the structure of the LED driver of Embodiment 1, and a light emission part. Diagram showing the configuration of the drive circuit The figure which shows the LED electric current waveform in the light emission area which a drive circuit drives The figure which shows the LED current waveform in the case of setting luminance as 100% when the duty is 75% The figure which shows LED current waveform when the brightness | luminance dimming of a light emission area | region is not the same The figure which shows the structure when performing brightness control in line unit The figure which shows the structure of the LED driver of Embodiment 2, and a light emission part. The figure which shows the LED current waveform of the light emission area which the drive circuit of Embodiment 2 drives The figure which shows the structure of LED driver of Embodiment 3, and a light emission part. The figure which shows the LED electric current waveform of the light emission area which the drive circuit of Embodiment 3 drives The figure which shows the 1st other structural example. The figure which shows the 2nd other structural example. The figure which shows the backlight structure of a prior art example The figure which shows the PWM signal at the time of carrying out backlight scanning drive in FIG. The figure which shows the structural example which performs a backlight scan drive in the light emission area | region of 4 rows 4 columns. The figure which shows the current waveform of LED in the light emission area | region which the drive circuit 51 of FIG. 16 drives.

(Embodiment 1)
A first embodiment in which the present invention is applied to a liquid crystal display device which is an example of an image display device will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram showing the overall configuration of the liquid crystal display device 10. The liquid crystal display device 10 includes a liquid crystal panel 100, a light emitting unit 200, an LED driver 300, a luminance determining unit 400, and an image signal correcting unit 500. Hereinafter, the light emitting unit 200, the LED driver 300, and the luminance determining unit 400 are collectively referred to as a backlight device. The configuration of each part will be described in detail below.

  The liquid crystal panel 100 modulates illumination light irradiated from the back according to an image signal and displays an image. The liquid crystal panel 100 has a total of 16 image display areas each consisting of 4 rows and 4 columns as indicated by broken lines in the figure. Each image display area has a plurality of pixels.

  The liquid crystal panel 100 has a configuration in which a liquid crystal layer divided for each pixel is sandwiched between glass substrates. In the liquid crystal panel 100, a signal voltage is applied to a liquid crystal layer corresponding to each pixel by a gate driver (not shown), a source driver (not shown), or the like, and the aperture ratio is controlled for each pixel. The liquid crystal panel 100 uses an IPS (In Plane Switching) method. The IPS system is a system that performs a simple movement in which liquid crystal molecules rotate in parallel with a glass substrate. As a result, the liquid crystal panel adopting the IPS system has a wide viewing angle, and has a feature that there is little change in color tone depending on the viewing direction and color tone in all gradations.

  The liquid crystal panel 100 is an example of a light modulation unit. As a method of the liquid crystal panel, another method such as a VA (Vertical Alignment) method may be used.

  The light emitting unit 200 irradiates illumination light for displaying an image on the liquid crystal panel 100 from the back side. The light emitting unit 200 has a total of 16 light emitting regions each having 4 rows and 4 columns. Each light emitting area is provided opposite to the image display area of the liquid crystal panel 100, and irradiates the opposite image display area. Each light emitting area has four LEDs 210 as light sources. The LED 210 is an example of a light emitting unit.

  The light emitting unit 200 is driven by backlight scanning. That is, the light emitting unit 200 emits or turns off the LED 210 so as to change the light emitting region in the non-light emitting state in the vertical direction in accordance with the scanning of the image displayed on the liquid crystal panel 100.

  An LED driver 300 that is an example of a drive unit drives the LED 210 of the light emitting unit 200. As described in Patent Document 4, the LED driver 300 is configured by a constant current circuit, has a DC / DC converter for each of a plurality of light emitting regions, and has the lowest voltage among the LED strings in the connected light emitting regions. There is a method of detecting and controlling the voltage supplied to the LED. Alternatively, as disclosed in Patent Document 5, there is a method of controlling the voltage supplied to the LED by having a DC / DC converter for each light emitting region, detecting the current flowing in the LED array. In the former method, since one DC / DC converter can be shared by a plurality of light emitting region units, the cost is lower than that in the latter method. However, the former method is disadvantageous in terms of efficiency compared to the latter method because it cannot absorb a loss due to variations in forward voltage of each LED array. On the other hand, the latter method is expensive because it requires a DC / DC converter in each light emitting region. However, the latter method is advantageous in terms of power efficiency because it can absorb variations in the forward voltage of each LED array. Usually, as the number of light emitting regions increases, the former has a greater cost advantage. Further, the former method is advantageous in terms of variation in current for driving LEDs by incorporating a plurality of drive circuits in the same IC with a slight increase in circuit configuration. Therefore, in the former method, a plurality of drive circuits are generally integrated on the same chip.

  The luminance determining unit 400 determines the light emission luminance value for each of the plurality of light emitting areas of the light emitting unit 200 based on the input image signal for each of the plurality of image display areas of the liquid crystal panel 100. That is, the luminance determination unit 400 inputs an input image signal for each image display area of the liquid crystal panel 100 and outputs a light emission luminance value for each light emission area to the LED driver 300.

  The image signal correction unit 500 corrects the image signal input to the liquid crystal panel 100 based on the light emission luminance value determined by the luminance determination unit 400. When brightness control is performed for each light emitting area, even if the image display area has the same original image signal, the light emission brightness value of the corresponding light emitting area is determined to be low and high. The brightness of the displayed image will be different. Therefore, the displayed image may appear unnatural. In order to reduce this, the image signal correction unit 500 corrects the image signal of the displayed image in conjunction with the light emission luminance value for each light emitting region. Specifically, the image signal correction unit 500 changes the contrast gain of the image displayed on the liquid crystal panel 100 in accordance with how the light emission luminance value is changed. As a result, the image signal correction unit 500 corrects the adverse effects associated with the above-described luminance control for each light emitting area.

  FIG. 2 is a diagram showing the configuration of the LED driver 300 and the light emitting unit 200 in more detail. Here, when explaining each light emission area | region using a code | symbol, it is shown as a1, a2, a3, ..., d3, d4 using row numbers 1-4 and column numbers ad.

  The LED driver 300 includes four drive circuits 310 to 340 that drive LEDs each belonging to a plurality of light emitting regions. FIG. 3 is a diagram illustrating a configuration of the drive circuit 310. The drive circuit 310 includes a DC / DC converter 311 that converts an input DC power source into a voltage that drives the LED 210 in each light emitting region, and a constant current source unit 312 that supplies a drive current. The constant current source unit 312 includes constant current sources 312-a 1 to 312-a 4 corresponding to the light emitting regions a 1 to a 4. The DC / DC converter is an example of a voltage applying unit that applies a common voltage necessary for driving to LEDs belonging to a plurality of light emitting regions driven by each of the driving circuits. Although not shown, similarly, the drive circuit 320 includes a DC / DC converter unit 321 and a constant current source unit 322, and the drive circuit 330 includes a DC / DC converter unit 331 and a constant current source unit 332. The drive circuit 340 includes a DC / DC converter unit 341 and a constant current source unit 342.

  Further, the drive circuit 310 inputs the light emission luminance values of the light emission regions a1 to a4 determined by the luminance determination unit 400 according to the image signal as PWM signals a1 to a4. The drive circuit 310 drives the light emitting areas a1 to a4 based on the input PWM signals a1 to a4. Similarly, the drive circuit 320 inputs the light emission luminance values of the light emission regions b1 to b4 determined by the luminance determination unit 400 according to the image signal as PWM signals b1 to b4, and emits light based on the input PWM signals b1 to b4. The regions b1 to b4 are driven. In addition, the drive circuit 330 inputs the light emission luminance values of the light emission regions c1 to c4 determined by the luminance determination unit 400 according to the image signal as PWM signals c1 to c4, and the light emission regions based on the input PWM signals c1 to c4. Drives c1 to c4. Further, the drive circuit 340 inputs the light emission luminance values of the light emission regions d1 to d4 determined by the luminance determination unit 400 according to the image signal as PWM signals d1 to d4, and the light emission region based on the input PWM signals d1 to d4. d1 to d4 are driven. That is, each drive circuit drives LEDs in the light emitting areas having different vertical positions in the light emitting section. In particular, in the present embodiment, each drive circuit drives LEDs in the light emitting region belonging to the same column in the light emitting unit.

  FIG. 4 shows LED current waveform diagrams of the light emitting areas a1 to a4 at the time of 100% dimming when backlight scanning driving is performed in the backlight device configured as described above. That is, FIG. 4 shows the LED current waveform in the light emitting region driven by the drive circuit 310. Although not shown in FIG. 4, the PWM signals a <b> 1 to a <b> 4 have the same waveforms as the LED current waveforms of the light emitting areas a <b> 1 to a <b> 4. In the example of FIG. 4, the backlight is adjusted to have the maximum brightness when the drive duty is 50%, and brightness dimming is performed in the range of the duty of 0 to 50%. 4 (1) shows the LED current waveform in the light emitting area a1, FIG. 4 (2) shows the LED current waveform in the light emitting area a2, and FIG. 4 (3) shows the LED current waveform in the light emitting area a3. (4) shows the LED current waveform in the light emitting region a4. FIG. 4 (5) shows the load current of the DC / DC converter 311 when the dimming is 100% (drive duty 50%).

  As shown in FIG. 4, even when the LED current is turned on / off by the backlight scan driving, each driving circuit drives the light emitting regions having different vertical positions in the light emitting unit 200. Therefore, the load current of the DC / DC converter 311 is It becomes constant. That is, the DC / DC converter can supply a stable voltage without sudden load fluctuations, and is advantageous in terms of radiation noise.

  FIG. 5 shows an example in which the backlight luminance is set to 100% when the drive duty is 75%. Even in this case, the load current is constant as in the case of FIG.

  As in FIG. 4, FIG. 6 shows a case where the backlight is adjusted to have the maximum brightness when the driving duty is 50%, and the brightness dimming of the light emitting areas a1, a2, a3, and a4 is adjusted. The case where it is not the same is shown. Specifically, the light emitting area a1 is 100% dimming (drive duty is 1.0 × 50% = 50%), and the light emitting area a2 is 75% dimming (drive duty is 0.75 × 50% = 37). 0.5%), the light emitting area a3 is 50% dimming (drive duty is 0.5 × 50% = 25%), and the light emitting area a4 is 25% dimming (drive duty is 0.25 × 50% = 12). 5%) is a waveform diagram when light is emitted. In this case, the load current of the DC / DC converter 311 is not constant as shown in FIG. However, since the currents of all the light emitting regions a1 to a4 are not simultaneously turned on or off, the amplitude of the current fluctuation can be suppressed to a small value. Further, since the frequency of current fluctuation is high, smoothing is possible even without large L and C parts.

  As described above, in the present embodiment, as shown in FIG. 1, each column of the light emitting region is driven with one DC / DC converter instead of each row. Thus, the load of each DC / DC converter does not fluctuate greatly. As a result, large-capacity L and C are not required, component costs can be reduced, and the component size can be reduced, which greatly contributes to a reduction in thickness. Further, it is possible to reduce radiation noise accompanying current fluctuation.

  In FIG. 1, the luminance control can be performed independently for all the light emitting regions. However, the luminance control may be performed in units of rows. When the luminance control is performed in units of rows, the light emitting areas a1, b1, c1, and d1 may have the same luminance, and the light emitting areas a2, b2, c2, and d2 may have the same luminance. Similarly, the light emitting areas a3, b3, c3, d3 may have the same luminance, and similarly, the light emitting areas a4, b4, c4, and d4 may have the same luminance. In this case, as shown in FIG. 7, PWM signals having four scan phases corresponding to four rows may be branched and given to the respective input terminals of the drive circuits 310 to 340. Even in this case, the effect of suppressing the load fluctuation and the effect of reducing the component size remain the same.

  In the present embodiment, the number of light emitting areas is 16 in 4 rows and 4 columns, but the present invention is not limited to this. Further, the number of light emitting regions may be increased or decreased. In general, assuming that the number of light emitting regions in the horizontal direction is N and the number in the vertical direction is M, the LED driver has N drive circuits, and each of the drive circuits has M different vertical positions. If the LED in the light emitting region is driven, the same effect as in the present embodiment can be obtained. Here, M is an integer of 2 or more, and N is an integer of 1 or more. This embodiment is an example of M = 4 and N = 4.

(Embodiment 2)
Next, a second embodiment of the present invention will be described with reference to the drawings. The second embodiment is different from the first embodiment in that one light emitting region row is driven by a plurality of drive circuits. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  FIG. 8 is a diagram showing in detail the configuration of the LED driver 700 and the light emitting unit 600 according to the second embodiment. The light emitting unit 600 has a total of 32 light emitting regions each having 8 rows and 4 columns. Each light emitting area is provided opposite to the image display area of the liquid crystal panel, and irradiates the opposite image display area. The LED driver 700 has eight drive circuits 710 to 780.

  The drive circuit 710 in FIG. 8 inputs the light emission luminance values of the light emission regions a2, a4, a6, and a8 determined by the luminance determination unit according to the image signal as PWM signals a2, a4, a6, and a8. The drive circuit 710 drives the light emitting areas a2, a4, a6, a8 based on the input PWM signals a2, a4, a6, a8. In addition, the drive circuit 750 inputs the light emission luminance values of the light emission regions a1, a3, a5, and a7 determined by the luminance determination unit according to the image signal as PWM signals a1, a3, a5, and a7. The drive circuit 750 drives the light emitting areas a1, a3, a5, a7 based on the input PWM signals a1, a3, a5, a7. In this way, the light emitting regions belonging to the column a are driven by the two drive circuits 710 and 750. Similarly, the driving circuits 720 and 760 drive the light emitting region belonging to the column b, the two driving circuits 730 and 770 drive the light emitting region belonging to the column c, and the two driving circuits 740 and 780 drive the light emitting region. The light emitting area belonging to the column d is driven.

  FIG. 9 is a diagram showing LED current waveform diagrams of the light emitting regions a1, a3, a5, and a7 at the time of 100% dimming when the backlight scan driving is performed in the configuration as shown in FIG. . That is, FIG. 9 shows the LED current waveform in the light emitting region driven by the drive circuit 750. 9 (1) shows the LED current waveform in the light emitting area a1, FIG. 9 (2) shows the LED current waveform in the light emitting area a3, and FIG. 9 (3) shows the LED current waveform in the light emitting area a5. (4) shows the LED current waveform in the light emitting region a7. FIG. 9 (5) shows the load current of the DC / DC converter 751 when the dimming is 100% (drive duty 50%). The DC / DC converter 751 is a DC / DC converter included in the drive circuit 750. In the example of FIG. 9, the backlight is adjusted to have the maximum luminance when the driving duty is 50%, and luminance dimming is performed in the range of the duty of 0 to 50%.

  From FIG. 9, even when the LED current is turned on / off by the backlight scan drive, the drive circuit drives the light emitting areas alternately positioned in the vertical direction, so that the load current of the DC / DC converter 751 is constant. Become. That is, the DC / DC converter can supply a stable voltage without sudden load fluctuations, and is advantageous in terms of radiation noise. Here, even if the respective drive circuits that drive the light emitting regions belonging to the same column drive the light emitting regions that are not alternately positioned in the vertical direction, the load reduction effect can be obtained. However, as in the present embodiment, it is preferable that each driving circuit drives light emitting regions that are alternately positioned in the vertical direction. In other words, it is preferable that each drive circuit drives the light emitting region at a position where the vertical intervals are even. This is because the load fluctuation can be further reduced.

  According to the present embodiment, even if the number of light emitting regions is increased and not all the light emitting regions belonging to the same column can be driven by one drive circuit, an effect of reducing the load can be obtained.

  In the present embodiment, the number of drive circuits that drive the light emitting regions belonging to the same column is two, but the present invention is not limited to this. As long as each driving circuit is configured to drive a plurality of light emitting regions, two or more driving circuits may be used for the light emitting regions in the same column.

  FIG. 9 shows the case where the backlight is adjusted to have the maximum brightness when the driving duty is 50%, but the backlight brightness is set to 100% when the driving duty is 75%. But the same is true.

  In the present embodiment, the number of light emitting regions is 32 in 8 rows and 4 columns, but is not limited thereto. Further, the number of light emitting regions may be increased or decreased. In general, if the number of light emitting areas in the horizontal direction is N and the number in the vertical direction is M, the LED driver has n × N drive circuits, and each of the drive circuits has different vertical positions. The same effect as this embodiment can be obtained by driving the LEDs in the / n light emitting areas. Here, M and n are integers of 2 or more, and N is an integer of 1 or more. This embodiment is an example of M = 8, N = 4, and n = 2.

(Embodiment 3)
Next, Embodiment 3 of the present invention will be described with reference to the drawings. The third embodiment is different from the first embodiment in that the drive circuit drives light emitting regions other than the same column. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  FIG. 10 is a diagram showing in detail the configuration of the LED driver 800 and the light emitting unit 200 according to the third embodiment. The LED driver 800 has four drive circuits 810 to 840.

  The drive circuit 810 in FIG. 10 inputs the light emission luminance values of the light emission regions a1, b2, c3, and d4 determined by the luminance determination unit 400 according to the image signal as PWM signals a1, b2, c3, and d4. The drive circuit 810 drives the light emitting areas a1, b2, c3, d4 based on the input PWM signals a1, b2, c3, d4. Similarly, the drive circuit 820 inputs the light emission luminance values of the light emission regions a2, b3, c4, and d1 determined by the luminance determination unit 400 according to the image signal as PWM signals a2, b3, c4, and d1, and inputs the input PWM. The light emitting areas a2, b3, c4, d1 are driven based on the signals a2, b3, c4, d1. Further, the drive circuit 830 inputs the light emission luminance values of the light emission regions a3, b4, c1, and d2 determined by the luminance determination unit 400 according to the image signal as PWM signals a3, b4, c1, and d2, and receives the input PWM signal. The light emitting regions a3, b4, c1, d2 are driven based on a3, b4, c1, d2. Further, the drive circuit 840 inputs the emission luminance values of the emission regions a4, b1, c2, and d3 determined by the luminance determination unit 400 according to the image signal as PWM signals a4, b1, c2, and d3, and the input PWM signal The light emitting areas a4, b1, c2, and d3 are driven based on a4, b1, c2, and d3. That is, the four light emitting regions driven by one driving circuit are light emitting regions located in different rows and different columns.

  FIG. 11 is a diagram showing LED current waveform diagrams of the light emitting regions a1, b2, c3, and d4 at the time of 100% dimming when the backlight scan driving is performed in the configuration as shown in FIG. . That is, FIG. 11 shows the LED current waveform in the light emitting region driven by the drive circuit 810. 11 (1) shows the LED current waveform in the light emitting area a1, FIG. 11 (2) shows the LED current waveform in the light emitting area b2, and FIG. 11 (3) shows the LED current waveform in the light emitting area c3. (4) shows the LED current waveform in the light emitting region d4. FIG. 11 (5) shows the load current of the DC / DC converter 811 when the light control is 100% (drive duty 50%). The DC / DC converter 811 is a DC / DC converter included in the drive circuit 810. In the example of FIG. 11, the backlight is adjusted to have the maximum luminance when the driving duty is 50%, and the luminance is adjusted in the range of the duty of 0 to 50%.

  From FIG. 11, even when the LED current is turned on / off by the backlight scan driving, each drive circuit drives the light emitting region located at a different position in the vertical direction, so that the load current of the DC / DC converter 811 is constant. It becomes. That is, the DC / DC converter can supply a stable voltage without sudden load fluctuations, and is advantageous in terms of radiation noise.

  In the present embodiment, the number of light emitting areas is 16 in 4 rows and 4 columns, but the present invention is not limited to this. Further, the number of light emitting regions may be increased or decreased. In general, assuming that the number of light emitting regions in the horizontal direction is N and the number in the vertical direction is M, the LED driver has N drive circuits, and each of the drive circuits has M different vertical positions. If the LED in the light emitting region is driven, the same effect as in the present embodiment can be obtained. Here, M is an integer of 2 or more, and N is an integer of 1 or more. This embodiment is an example of M = 4 and N = 4.

(Other forms)
The present invention is not limited to the embodiment described above. For example, the first embodiment and the third embodiment may be combined as shown in FIG. In this configuration, one drive circuit drives four light emitting areas, two of which are light emitting areas belonging to the same column. Even if it is such a structure, the effect similar to Embodiment 1, 3 can be acquired.

  Further, the number of light emitting regions driven by each driving circuit may be other than four. FIG. 13 shows a configuration example in which one drive circuit drives eight light emitting regions. Even if it is such a structure, the effect similar to Embodiment 1, 3 can be acquired.

  In general, if the number of light emitting areas in the horizontal direction is N and the number in the vertical direction is M, the LED driver has N / n drive circuits, and each of the drive circuits has a horizontal position. The same effect as that of the configuration of FIG. 13 can be obtained by driving the LEDs of M light emitting regions included in the same column that are the same for n columns.

  As described above, the backlight device and the image display device according to the present invention have been described based on the embodiment, but the present invention is not limited to this embodiment. Unless it deviates from the meaning of this invention, the form which carried out the various deformation | transformation which those skilled in the art can think to the said embodiment, and the form constructed | assembled combining the component in a different embodiment is also contained in the scope of the present invention. .

  That is, the embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The backlight device and the image display device of the present invention are suitable for display devices such as a liquid crystal television and a liquid crystal monitor, and their backlight devices.

2a, 2b, 2c, 2d Light emitting area 3a, 3b, 3c, 3d Inverter 10 Liquid crystal display device 100 Liquid crystal panel 4, 200, 600 Light emitting part 41, 210 LED
300, 700, 800, 900, 1000 LED driver 51, 52, 53, 54 Driving circuit 310, 320, 330, 340 Driving circuit 710, 720, 730, 740, 750, 760, 770, 780 Driving circuit 810, 820, 830, 840 Drive circuit 910, 920, 930, 940 Drive circuit 1010, 1020, 1030, 1040 Drive circuit 311 DC / DC converter 312 Constant current source unit 312-a1, 312-a2, 312-a3, 312-a4 Constant current Source 400 Luminance determination unit 500 Image signal correction unit

Claims (6)

A light-emitting unit that has light-emitting means for each of a plurality of light-emitting regions divided at least in the vertical direction, and changes the light-emitting means that is in a non-light-emitting state in accordance with scanning of the image in the vertical direction;
Each having at least one driving means for driving a plurality of the light emitting means,
The driving means includes
Voltage applying means for applying a common voltage necessary for driving to the plurality of light emitting means that each drive, and driving the light emitting means in the light emitting regions having different vertical positions;
Backlight device. When the number of the light emitting regions in the horizontal direction is N and the number in the vertical direction is M,
The driving unit has N driving means,
Each of the driving means drives M light emitting means having different vertical positions.
The backlight device according to claim 1.
However, M is an integer greater than or equal to 2, and N is an integer greater than or equal to 1. When the number of the light emitting regions in the horizontal direction is N and the number in the vertical direction is M,
The driving unit includes n × N driving units,
Each of the driving means drives M / n light emitting means having different vertical positions.
The backlight device according to claim 1.
However, M and n are integers of 2 or more, and N is an integer of 1 or more.   4. The backlight device according to claim 3, wherein each of the driving units drives the light emitting units at positions at which vertical intervals are equal. When the number of the light emitting regions in the horizontal direction is N and the number in the vertical direction is M,
The driving unit has N / n driving means.
Each of the driving means drives the M light emitting means included in the same column having the same horizontal position by n columns.
The backlight device according to claim 1.
However, M and n are integers of 2 or more, and N is an integer of 1 or more. The backlight device according to claim 1;
A light modulation section that has a plurality of image display areas corresponding to the plurality of light emission areas, and displays an image by modulating light emitted from the back surface for each of the image display areas in accordance with an image signal. The
Image display device.

Images