WO2010122724A1

WO2010122724A1 - Display device and method for driving same

Info

Publication number: WO2010122724A1
Application number: PCT/JP2010/002617
Authority: WO
Inventors: 中西敦士
Original assignee: パナソニック株式会社
Priority date: 2009-04-20
Filing date: 2010-04-09
Publication date: 2010-10-28
Also published as: JP2012137508A

Abstract

A display device includes a display panel (100) that displays images; a backlight unit (104) disposed at the rear side of the display panel and including a plurality of light emitting diodes in each of a plurality of areas defined by partitioning the display panel; a motion detecting unit (108) that detects a feature amount of an image in each area; a PWM frequency determining unit (110) that determines a pulse width modulation frequency in each area in accordance with the feature amount of the image detected by the motion detecting unit; and a driving unit (106) that drives the backlight unit at the pulse width modulation frequencies determined by the PWM frequency determining unit during lighting periods, the light emitting diodes in each area not emitting light during non lighting periods and emitting light during the lighting periods in one vertical interval.

Description

Display device and driving method of display device

The present invention relates to a display device including a backlight unit composed of a plurality of LEDs (light emitting diodes) installed on the back surface of a display panel and a driving method of the display device for improving moving image display performance.

In a conventional display device, in one vertical period, a period in which the fluorescent lamp is turned off and a period in which the fluorescent lamp is turned on are provided, and the fluorescent lamp is driven (applied with PWM (Pulse Width Modulation)) so as to be repeatedly turned on and off in the lighting period. There has been known a display device that performs a driving method in which light emission luminance is controlled by controlling voltage application time (see, for example, Patent Document 1). In such a display device, it is known that the moving image display performance can be improved as the lighting duty (duty) of the backlight unit (ratio between the lighting period and the extinguishing period) is reduced.

However, the display device described above employs a configuration using a fluorescent tube for the backlight unit. Due to the response speed and afterglow characteristics of the fluorescent tube, there arises a problem that it is difficult to light with correct luminance when the lighting duty is small. In addition, when a fluorescent tube is used and, for example, the duty ratio is 30% or less, there is a problem that flicker occurs on the screen.

JP 2002-91400 A

The object of the present invention is to use a light emitting diode with a high response speed in the backlight unit, further divide the screen into many regions and variably control the PWM frequency for each region, even in the case of low duty. Another object of the present invention is to provide a display device and a driving method of the display device that can be lit at an appropriate luminance and can improve the moving image display performance by suppressing the occurrence of flicker.

A display device according to an aspect of the present invention includes a display panel that displays an image, a back panel of the display panel, the display panel is divided into a plurality of regions, and a plurality of light emitting diodes arranged in each region are provided. Including a backlight unit, a detection unit that detects a feature amount of an image for each region, and a frequency determination unit that determines a pulse width modulation frequency of each region according to the feature amount of the image detected by the detection unit For each of the regions, a light-off period in which the light-emitting diode is turned off and a light-on period in which the light-emitting diode is turned off are provided in one vertical period. And a drive unit for driving the light unit.

A display device driving method according to another aspect of the present invention includes a display panel that displays an image, and a plurality of display panels that are installed on the back surface of the display panel, divided into a plurality of regions, and arranged for each region. A display device comprising a backlight unit including a light emitting diode, wherein a detection step of detecting a feature amount of an image for each region and a feature amount of the image detected in the detection step A determination step for determining a pulse width modulation frequency of each region; and for each region, a light-off period in which the light-emitting diode is turned off and a light-on period in which the light-emitting diode is turned on are provided within one vertical period. Driving the backlight unit at the pulse width modulation frequency determined in the step.

As described above, a light emitting diode with a high response speed is used for the backlight unit, and further, the screen is divided into many regions, and the pulse width modulation frequency is variably controlled for each region. However, it is possible to light with appropriate luminance, and further, by suppressing the occurrence of flicker, the moving image display performance can be improved.

It is a block diagram which shows the structure of the display apparatus in Embodiment 1 of this invention. It is a schematic diagram for demonstrating the backlight scan in Embodiment 1 of this invention. It is a wave form diagram for demonstrating the backlight scan in Embodiment 1 of this invention. It is the figure which compared the characteristic of a fluorescent tube and LED. It is the figure which compared the characteristic of the fluorescent tube and LED in the case of a low duty. It is a block diagram which shows an example of a structure of the motion detection part in Embodiment 1 of this invention. It is a wave form diagram for demonstrating operation | movement of the display apparatus in Embodiment 1 of this invention. It is a block diagram which shows the structure of the display apparatus in Embodiment 2 of this invention. It is a block diagram which shows an example of a structure of the frequency detection part in Embodiment 2 of this invention. It is a wave form diagram for demonstrating operation | movement of the display apparatus in Embodiment 2 of this invention.

(Embodiment 1)
Embodiment 1 of the present invention will be described with reference to FIGS. Note that the display device and the driving method of the display device described in this embodiment mode are just examples, and the present invention is not limited thereto.

<1-1. Overall Configuration of Display Device>
First, each configuration of the display device according to the first embodiment will be described in detail with reference to the block diagram showing the entire configuration of the display device according to the first embodiment of the present invention shown in FIG. The display device according to the present embodiment is installed on the display panel 100 that displays an input image, a panel drive unit 102 that controls driving of the display panel 100, and the display panel 100, and conceptually shows the display panel 100. The display unit 100 is conceptually divided into a plurality of regions by dividing the display unit 100 into a plurality of regions, and a backlight unit 104 composed of a plurality of LEDs (light emitting diodes) arranged in each region. For each region, there are provided an extinguishing period during which the LED is extinguished and a lighting period during which the LED is lit in one vertical period, and the driving unit 106 that drives the LED with a predetermined PWM (pulse width modulation) frequency in the lighting period, As an example of a detection unit that detects a feature amount of an image, a motion detection unit 108 that detects a motion amount for each region of the input video, and a motion detection unit 1 8 determines the PWM frequency of each region in accordance with the amount of motion detected in step 8, and detects the luminance of each region of the input video, and determines the luminance of the backlight unit 104 based on the detected luminance. The area luminance determining unit 112 is determined for each area.

Also, the motion detection unit 108 detects whether each region is a still image or a moving image as the feature amount of the image, and notifies the PWM frequency determination unit 110 of the detection result. When it is detected that the region is a moving image, the PWM frequency determination unit 110 sets the PWM frequency to the same frequency as the vertical synchronization frequency of the video for each of the regions, and may be a still image. If detected, the PWM frequency is set higher than the vertical synchronization frequency of the video for the drive unit 106 for each region. The drive unit 106 drives the LEDs of the backlight unit 104 for each region using the PWM frequency determined by the PWM frequency determination unit 110 and the lighting duty corresponding to the luminance determined by the region luminance determination unit 112. .

In addition, as a method of conceptually dividing the display panel 100 described above into a plurality of regions, not only division in the horizontal direction or division in the vertical direction, but also division in the vertical and horizontal directions to form a matrix. Is also possible. In addition, the present invention can be applied to the display panel 100 as long as it is not only a liquid crystal panel but also a panel that requires a backlight unit.

<1-2. Operation of display device>
Next, a specific operation of the display device having the above configuration will be described with reference to FIGS. Here, FIG. 2 is a diagram illustrating an outline of a backlight scan in which an LED is turned off and a lighting period in which the LED is turned on within one vertical period. FIG. 3 illustrates the backlight scan. FIG. 4 and FIG. 5 explain the superiority of the present invention by comparing the light emission in the conventional fluorescent tube and the light emission by the LED of the present invention. FIG. 6 is a diagram illustrating an example of a detailed configuration of the motion detection unit 108 that constitutes a part of the display device illustrated in FIG. 1, and FIG. It is the figure explaining the lighting state of the backlight unit 104 of embodiment.

<1-2-1, Backlight scan>
First, in the display device of the present embodiment, as shown in FIG. 2, the backlight unit 104 is provided for each region (for example, four regions divided into four along the horizontal direction in FIG. 2). Thus, the backlight scan is realized by providing the extinguishing period for turning off and the lighting period for turning on within one vertical period. Specifically, in (1) of FIG. 2, the LED of the backlight unit 104 is turned on only for the uppermost area of the screen, and the LED of the backlight unit 104 is turned off for the other three areas. . Similarly, in (2) of FIG. 2, the LED of the backlight unit 104 is turned on only for the second area from the top of the screen, and the LED of the backlight unit 104 is turned off for the other three areas. ing.

As described above, the screen is divided into four in the vertical direction, and the process of shifting the light emission timing of the LEDs constituting the backlight unit 104 is sequentially performed for each region. With such a configuration, for example, in (1) of FIG. 2, when the video is displayed in the uppermost area of the screen, while the black image is displayed in the other areas, the backlight unit 104 is displayed. In addition, it is possible to improve the visibility of moving images by turning off the lights.

FIG. 3 shows such a backlight scan process in terms of time and luminance. FIG. 3 is a diagram showing time on the horizontal axis and the luminance of the LEDs of the backlight unit 104 on the vertical axis for the backlight scan described with reference to FIG. 2 described above. As shown in FIG. 3, in FIG. 3A, the luminance of the first area for displaying the video is high at the first time, and the luminance is 0 for the other areas. It has become. Similarly, in FIG. 3B, in the second time, the brightness of the second area displaying the video is high, and the brightness of the other areas including the first area is 0. It has become. In this way, the screen is divided into a plurality of areas, and the process of shifting the light emission timing of the LEDs constituting the backlight unit 104 is sequentially performed for each area in conjunction with the display of the video.

<1-2-2, Comparison between fluorescent tube and LED>
Next, referring to FIG. 4, when performing the above-described backlight scan, the backlight unit 104 is a conventional fluorescent tube (FIG. 4A) and the backlight unit 104 is an LED ( FIG. 4B is compared. As shown in FIG. 4A, in the lighting period, in the case of a fluorescent tube as compared with the LED, the lighting period is switched from the unlit state to the lit state, and the lit state is turned off in the unlit period. Response time for switching to is longer. As a result, the time to reach a predetermined luminance is delayed, and there is a problem that afterglow remains even after the lights are turned off. On the other hand, as shown in FIG. 4B, when the LED is adopted for the backlight unit 104, the response time is fast, so the arrival time to the predetermined brightness is fast, and after the light is turned off. There is no afterglow.

Furthermore, with reference to FIG. 5, a description will be given of processing in the case of a low duty (duty) in which a problem when a fluorescent tube is adopted in the backlight unit 104 becomes more prominent. FIG. 5 shows a case where the backlight unit 104 is a conventional fluorescent tube (FIG. 5A) when performing the above-described backlight scan at a low duty, and a case where the backlight unit 104 is an LED (FIG. 5). It is the figure which compared (B)).

As described above, when a fluorescent tube is employed in the backlight unit 104 as in the prior art, the response speed of the fluorescent tube is slow, and as shown in FIG. 5A, the fluorescent tube has a short lighting period. In this case, that is, in the case of a low duty, the luminance does not sufficiently rise to a target value (for example, a rectangular wave indicated by a broken line), and it becomes difficult to emit light with a necessary luminance. Therefore, it is difficult to set the lighting time short, and the light control range is narrowed. As a result, the luminance that can be expressed in the display device is limited.

On the other hand, when the LED is used for the backlight unit 104, the response speed of the LED is fast, so that impulse driving can be performed as shown in FIG. Even in a short case, it is possible to emit light with the required luminance. Therefore, since the lighting time can be set short, the dimming range is widened, and as a result, the luminance that can be expressed in the display device is not limited.

<1-2-3, Operations of Motion Detection Unit 108 and PWM Frequency Determination Unit 110>
Next, operations of the motion detection unit 108 and the PWM frequency determination unit 110 in FIG. 1 will be described with reference to FIGS. 6 and 7. First, an example of the configuration of the motion detection unit 108 will be described with reference to FIG.

As illustrated in FIG. 6, the motion detection unit 108 records a frame memory 700 that records one frame of input input video, a video output from the frame memory 700, and a motion vector of a currently input video. A difference calculation unit 702 that calculates a difference for each region, a summation unit 704 that sums the motion vector differences calculated by the difference calculation unit 702 for one frame, a motion vector value summed by the summation unit 704, and The comparison unit 706 compares the set threshold value.

With such a configuration, as a result of the comparison by the comparison unit 706, for example, when the total motion vector value is larger than a preset threshold value, the comparison unit 706 indicates that the input video input is a moving image. On the other hand, if the motion vector is equal to or less than a preset threshold value, it is determined that the input image is a still image, and the determination result is output to the PWM frequency determination unit 110 for each region. Note that the motion detection process is not particularly limited to the above example. For example, when the difference value of the motion vector for each region is larger than a preset threshold, the region is determined to be a moving image, and is set in advance. Various changes such as determining that the image is a still image when it is equal to or less than the set threshold value are possible.

Next, the operation of the PWM frequency determination unit 110 using the determination result (moving image, still image) of the motion detection unit 108 (comparison unit 706) will be described with reference to FIG. FIG. 7A shows processing when the motion detection unit 108 determines that the video is a moving image, while FIG. 7B shows processing performed by the motion detection unit 108 described above. It shows the processing when it is determined.

As shown in FIG. 7A, when it is determined that the image is a moving image, the PWM frequency determination unit 110 sets the PWM frequency to the same frequency as the vertical synchronization frequency of the video for the drive unit 106 for each region. Set. As a result, as shown in FIG. 7A, PWM is performed once within one vertical period. On the other hand, as shown in FIG. 7B, when it is determined that the image is a still image, the PWM frequency determination unit 110 sets the PWM frequency to the drive unit 106 for each region more than the vertical synchronization frequency of the video. Set high. In FIG. 7B, for example, since the PWM frequency is set to three times the vertical synchronization frequency, PWM is performed three times within one vertical period. This is to prevent flicker by setting the PWM frequency higher than the vertical synchronization frequency of the video in the case of still images because flicker is more noticeable in the case of still images than in the case of moving images. .

Here, as apparent from FIGS. 7A and 7B, although the PWM frequency is set differently for still images and moving images, the lighting duty (ratio between the lighting period and the extinguishing period) is Since the same value (for example, lighting period 30%: extinguishing period 70%), the total lighting time within one vertical period does not change. By such processing, it is possible to change the PWM frequency between a still image and a moving image without changing the brightness of the screen itself.

As described above, in this embodiment, an LED having a high response speed is used as the light source of the backlight unit 104, and the screen is divided into many regions, and the PWM frequency is variably controlled for each region. Even in the case of duty, it is possible to provide a display device and a display device driving method that can be lit at an appropriate luminance and improved in moving image display performance by suppressing the occurrence of flicker. It will be possible. Furthermore, since the lighting duty (ratio between the lighting period and the extinguishing period) is the same value for both still images and moving images, the brightness of the screen itself changes. It is possible to prevent the user from feeling uncomfortable due to a change in luminance.

(Embodiment 2)
Next, a display device according to Embodiment 2 of the present invention will be described with reference to FIGS. Note that the present embodiment is different only in that the configuration of the frequency detection unit 808 is employed instead of the motion detection unit 108 employed in the first embodiment. Therefore, the description overlapping with the content described in the first embodiment is omitted.

<2-1. Overall configuration of display device>
First, each configuration of the display device according to the second embodiment will be described in detail with reference to the block diagram showing the overall configuration of the display device according to the second embodiment of the present invention shown in FIG. The display device according to the present embodiment is installed on the display panel 100 that displays an input image, a panel drive unit 102 that controls driving of the display panel 100, and the display panel 100, and conceptually shows the display panel 100. A backlight unit 104 composed of a plurality of LEDs divided into a plurality of regions and arranged for each region, and the backlight unit 104 is conceptually divided into a plurality of regions, and the display panel 100 is divided into a plurality of regions. In one vertical period, an extinguishing period in which the LED is extinguished and a lighting period in which the LED is lit are provided, and the drive unit 106 that drives the LED with a predetermined PWM frequency in the lighting period and the feature amount of the image are detected for each region As an example of the detection unit, a frequency detection unit 808 that detects an image frequency for each area of the input video, and an image detected by the frequency detection unit 808 A PWM frequency determination unit 810 that determines the PWM frequency of the region according to the wave number, and a region luminance that detects the luminance of each region of the input video and determines the luminance of the backlight unit 104 for each region based on the detected luminance It is comprised by the determination part 112. FIG.

Further, the frequency detection unit 808 detects whether each region is a high-frequency image or a low-frequency image as a feature amount of the image by detecting whether or not the high-frequency component of the video signal of each region is larger than a predetermined threshold. Is detected. When it is detected that the region is a high-frequency image, the PWM frequency determination unit 810 sets the PWM frequency to the same frequency as the vertical synchronization frequency of the video for the drive unit 106 for each region, and is a low-frequency image. When this is detected, the PWM frequency is set higher than the vertical synchronization frequency of the video for the drive unit 106 for each region. The driving unit 106 drives the LEDs of the backlight unit 104 for each region using the PWM frequency determined by the PWM frequency determining unit 810 and the lighting duty corresponding to the luminance determined by the region luminance determining unit 112. .

<2-2. Operation of display device>
<1-2-1, Backlight scan> and <1-2-2, Comparison between fluorescent tube and LED> are the same as those described above, and thus description thereof is omitted. .

<2-2-1. Operations of Frequency Detection Unit 808 and PWM Frequency Determination Unit 810>
Next, operations of the frequency detection unit 808 and the PWM frequency determination unit 810 in FIG. 8 will be described with reference to FIGS. 9 and 10. First, an example of the configuration of the frequency detection unit 808 will be described with reference to FIG.

As shown in FIG. 9, the frequency detection unit 808 includes, for each region described above, a contour detection unit 900 that detects a contour portion of an input video that is input, and the number of contour portions detected by the contour detection unit 900 as regions. And a comparison unit 904 that compares the number of contour portions totaled by the summation unit 902 with a preset threshold value. With this configuration, the frequency detection unit 808 detects whether or not the high-frequency component of the video signal in each region is greater than a predetermined threshold value.

With such a configuration, as a result of the comparison by the comparison unit 904, when the total number of contour portions is larger than a preset threshold value, the high-frequency component of the video signal is larger than a predetermined threshold value. The input video is determined to be a high-frequency image. On the other hand, if the number of contour portions is less than or equal to a preset threshold, the high-frequency component of the video signal is less than or equal to a predetermined threshold, so the input video input Is determined to be a low-frequency image, and the determination result is output to the PWM frequency determination unit 810 for each region.

In the above-described embodiment, the configuration for determining the frequency of the image based on the number of contour portions has been described. However, the present invention is not limited to this, and a configuration such as a density histogram or a frequency histogram is adopted. It is also possible.

Next, the operation of the PWM frequency determination unit 810 using the discrimination result (high frequency image, low frequency image) of the frequency detection unit 808 (comparison unit 904) will be described with reference to FIG. FIG. 10A shows processing when the above-described frequency detection unit 808 determines that the image is a high-frequency image, while FIG. 10B shows low-frequency processing at the above-described frequency detection unit 808. The process when it is determined to be an image is shown.

As shown in FIG. 10A, when it is determined that the image is a high-frequency image, the PWM frequency determining unit 810 sets the PWM frequency to the drive unit 106 for each region at the same frequency as the vertical synchronization frequency of the video. Set to. As a result, as shown in FIG. 10A, PWM is performed once within one vertical period. On the other hand, as shown in FIG. 10B, when it is determined that the image is a low frequency image, the PWM frequency determination unit 810 sets the PWM frequency to the drive unit 106 from the vertical synchronization frequency of the video for each region. Set too high. In FIG. 10B, since the PWM frequency is set to three times the vertical synchronization frequency, PWM is performed three times within one vertical period. This is because flicker is more noticeable in a low-frequency image than in a high-frequency image, and in the case of a low-frequency image, flicker is prevented by setting the PWM frequency higher than the vertical synchronization frequency of the video. Is.

Here, as apparent from FIGS. 10A and 10B, the PWM frequency is set to a different frequency depending on the high-frequency image and the low-frequency image, but the lighting duty (ratio between the lighting period and the extinguishing period). ) Have the same value (for example, lighting period 30%: extinguishing period 70%), the total lighting time within one vertical period does not change. By such processing, it is possible to change the PWM frequency between the high-frequency image and the low-frequency image without changing the brightness of the screen itself.

As described above, in this embodiment, an LED having a high response speed is used as the light source of the backlight unit 104, and the screen is divided into many regions, and the PWM frequency is variably controlled for each region. Even in the case of duty, it is possible to provide a display device and a display device driving method that can be lit at an appropriate luminance and further improve moving image display performance by suppressing the occurrence of flicker. It will be possible. Further, since the lighting duty (ratio between the lighting period and the extinguishing period) is the same value for both high-frequency images and low-frequency images, the brightness of the screen itself is It is possible to prevent a user from feeling uncomfortable due to a change in luminance without changing.

In the above-described embodiment, the configuration for determining the PWM frequency based on either the motion detection unit 108 or the frequency detection unit 808 has been described. However, the present invention is not limited to this, and the motion is not limited to this. A configuration in which the PWM frequency is determined based on the detection results of both the detection unit 108 and the frequency detection unit 808 may be employed.

In the above-described embodiments, the configuration in which the screen is divided into a plurality of regions has been described. However, the present invention is not limited to this, and for example, the same control is performed for each LED. Is also possible. As a result, it is possible to perform more detailed processing.

From the above embodiments, the present invention is summarized as follows. That is, a display device according to the present invention is provided with a display panel for displaying an image, a back panel of the display panel, the display panel is divided into a plurality of regions, and a plurality of light emitting diodes arranged for each region are provided. Including a backlight unit, a detection unit that detects a feature amount of an image for each region, and a frequency determination unit that determines a pulse width modulation frequency of each region according to the feature amount of the image detected by the detection unit For each of the regions, a light-off period in which the light-emitting diode is turned off and a light-on period in which the light-emitting diode is turned off are provided in one vertical period, and the back-up is performed at the pulse width modulation frequency determined by the frequency determination unit in the lighting period. And a drive unit for driving the light unit.

In this display device, a light emitting diode with a high response speed is used for the backlight unit, the screen is further divided into many regions, and the pulse width modulation frequency in each region can be varied according to the feature amount of the detected image. Since the control is performed, it is possible to light at an appropriate luminance even in the case of a low duty, and it is possible to improve the moving image display performance by suppressing the occurrence of flicker.

It is preferable that the detection unit includes a motion detection unit that detects whether each region is a still image or a moving image as the feature amount of the image.

In this case, it is possible to suppress the occurrence of flicker with respect to a still image and improve the visibility of the moving image with respect to the moving image.

The frequency determination unit sets the pulse width modulation frequency to be higher than the vertical synchronization frequency of the video when the motion detection unit detects that the region is configured by a still image, while the motion detection unit When the unit detects that the region is composed of moving images, it is preferable to set the pulse width modulation frequency to the same frequency as the vertical synchronization frequency of the video.

In this case, since the pulse width modulation frequency is set higher than the vertical synchronization frequency of the video for the still image, the occurrence of flicker can be suppressed, and the pulse width modulation frequency is set for the video. Since it is set to the same frequency as the vertical synchronization frequency, the video visibility can be improved.

The driving unit drives the backlight unit using the same lighting duty as a lighting duty that is a ratio of the lighting period and the extinguishing period regardless of whether each region is a still image or a moving image. Is preferred.

In this case, since the total lighting time within one vertical period does not change, it is possible to change the pulse width modulation frequency between the still image and the moving image without changing the brightness of the screen itself.

The detection unit detects whether the high-frequency component of the video signal of each region is larger than a predetermined threshold as the feature amount of the image, so that each region is a high-frequency image or a low-frequency image. It is preferable to include a frequency detection unit for detecting the above.

In this case, the occurrence of flicker can be suppressed with respect to the low-frequency image, and the moving image visibility can be improved with respect to the high-frequency image.

The frequency detection unit includes a contour detection unit that detects a contour part of a video signal, and the frequency detection unit has a number of contour parts detected by the contour detection unit as a feature amount of the image based on a predetermined threshold value. If there are many, it is detected that the region is a high-frequency image, while if the number of contour portions detected by the contour detection unit is equal to or less than a predetermined threshold, the region is detected as a low-frequency image. Is preferred.

In this case, whether each region is a high-frequency image or a low-frequency image can be detected with high accuracy by simple processing.

The frequency determination unit, when the frequency detection unit detects that the region is configured by a low frequency image, sets the pulse width modulation frequency higher than the vertical synchronization frequency of the video, while the frequency When the detection unit detects that the region is constituted by a high-frequency image, it is preferable to set the pulse width modulation frequency to the same frequency as the vertical synchronization frequency of the video.

In this case, since the pulse width modulation frequency is set to be higher than the vertical synchronization frequency of the video for the low-frequency image, the occurrence of flicker can be suppressed, and the pulse width modulation frequency for the high-frequency image. Is set to the same frequency as the vertical synchronization frequency of the video, so that the video visibility can be improved.

The driving unit drives the backlight unit using the same lighting duty as a lighting duty that is a ratio between a lighting period and a non-lighting period regardless of whether each region is a low-frequency image or a high-frequency image. It is preferable.

In this case, since the total lighting time within one vertical period does not change, the pulse width modulation frequency can be changed between the low-frequency image and the high-frequency image without changing the brightness of the screen itself.

A display device driving method according to the present invention includes a display panel for displaying an image, and a plurality of light emitting diodes installed on the back of the display panel, the display panel being divided into a plurality of regions, and arranged for each of the regions. And a backlight unit including a backlight unit including a detection step of detecting a feature amount of an image for each region, and each region according to the feature amount of the image detected in the detection step. A determination step for determining the pulse width modulation frequency of each of the regions, and a turn-off period in which the light-emitting diode is turned off and a turn-on period in which the light-emitting diode is turned on are provided for each region in one vertical period. Driving the backlight unit at a modulated pulse width modulation frequency.

In the present invention, an LED having a high response speed is used for the backlight unit, and the screen is divided into many regions, and the PWM frequency is variably controlled for each region, so that even when the duty is low, it is appropriate. It is possible to light up with luminance, and further, it is useful for a display device and a display device driving method in which moving image display performance is improved by suppressing occurrence of flicker.

Claims

A display panel for displaying images,
A backlight unit that is installed on the back surface of the display panel, divides the display panel into a plurality of regions, and includes a plurality of light emitting diodes arranged for each region;
A detection unit that detects a feature amount of an image for each region;
A frequency determining unit that determines a pulse width modulation frequency of each region according to the feature amount of the image detected by the detecting unit;
For each of the regions, a light-off period in which the light-emitting diode is turned off and a light-on period in which the light-emitting diode is turned off are provided in one vertical period, and the backlight unit has a pulse width modulation frequency determined by the frequency determination unit in the lighting period. And a drive unit for driving the display.
The display device according to claim 1, wherein the detection unit includes a motion detection unit that detects whether each region is a still image or a moving image as a feature amount of the image.
The frequency determination unit sets the pulse width modulation frequency to be higher than the vertical synchronization frequency of the video when the motion detection unit detects that the region is configured by a still image, while the motion detection unit 3. The display device according to claim 2, wherein the unit sets the pulse width modulation frequency to the same frequency as the vertical synchronization frequency of the video when the unit detects that the region is configured by a moving image.
The driving unit drives the backlight unit using the same lighting duty as a lighting duty that is a ratio of the lighting period and the extinguishing period regardless of whether each region is a still image or a moving image. The display device according to claim 2, wherein:
The detection unit detects whether the high-frequency component of the video signal of each region is larger than a predetermined threshold as the feature amount of the image, so that each region is a high-frequency image or a low-frequency image. The display device according to claim 1, further comprising: a frequency detection unit that detects the above.
The frequency detection unit includes a contour detection unit that detects a contour part of a video signal,
When the number of contour portions detected by the contour detection unit is greater than a predetermined threshold as the feature amount of the image, the frequency detection unit detects that the region is a high-frequency image, while the contour detection The display device according to claim 5, wherein the area is detected as a low-frequency image when the number of contour portions detected by the unit is equal to or less than a predetermined threshold value.
The frequency determination unit, when the frequency detection unit detects that the region is configured by a low frequency image, sets the pulse width modulation frequency higher than the vertical synchronization frequency of the video, while the frequency The detection unit according to claim 5 or 6, wherein when the detection unit detects that the region is configured by a high-frequency image, the pulse width modulation frequency is set to the same frequency as a vertical synchronization frequency of an image. Display device.
The driving unit drives the backlight unit using the same lighting duty as a lighting duty that is a ratio between a lighting period and a non-lighting period regardless of whether each region is a low-frequency image or a high-frequency image. The display device according to claim 5, wherein the display device is a display device.
A display device comprising: a display panel that displays an image; and a backlight unit that is installed on a back surface of the display panel, divides the display panel into a plurality of regions, and includes a plurality of light-emitting diodes arranged in the regions. A driving method comprising:
A detection step of detecting a feature amount of an image for each region;
A determination step of determining a pulse width modulation frequency of each region according to the feature amount of the image detected in the detection step;
For each of the regions, a light-off period in which the light-emitting diode is turned off and a light-on period in which the light-emitting diode is turned off are provided within one vertical period. In the lighting period, the backlight unit is turned on at the pulse width modulation frequency determined in the determination step. And a step of driving the display device.