Backlight unit and local dimming control method using same

Abstract

A display device according to one embodiment of the present invention comprises: a main board for acquiring brightness information from image information; a driver board, which sets an output current value for a local dimming operation on the basis of the brightness information, sets an available current region on the basis of a preset unused current region, and sets an output current value on the basis of the set available current region; and a driver IC for outputting a local dimming current on the basis of the output current value.

Description

Backlight unit and local dimming control method using the same

[0001] The present invention relates to a display device, and more specifically to a method for controlling local dimming of a backlight unit.

[0002] Representative display devices that display images using digital data include Liquid Crystal Displays (LCDs) using liquid crystals, OLED displays using Organic Light Emitting Diodes (OLEDs), and Electrophoretic Displays (EPDs) using electrophoretic particles.

[0003] Among these, in an OLED display device, each subpixel is equipped with an OLED element and a pixel circuit that independently drives the OLED element. The pixel circuit controls the brightness of the OLED element by adjusting the current through which a thin film transistor (hereinafter TFT) drives the OLED element according to a driving voltage corresponding to a data signal.

[0004] However, an image is displayed by modulating the light incident from the backlight unit used in the OLED display device.

[0005] Meanwhile, backlight dimming methods have been proposed to reduce the power consumption of the backlight unit. Local dimming, one of the backlight dimming methods, can improve contrast by locally controlling the brightness of the display surface within a frame period.

[0006] The local dimming method may be a method of separating input image data into virtual blocks divided in a matrix form on the display screen of a liquid crystal display panel, deriving a representative value of the input image data for each block, and controlling the brightness of the light sources of the backlight unit for each block by adjusting the dimming value for each block according to the representative value for each block.

[0007] However, conventional local dimming methods have a problem in that brightness resolution decreases when an unused current range occurs during local dimming operation.

[0008] Accordingly, one embodiment of the present invention aims to provide a local dimming control method for setting a current range in which a driver IC of a backlight unit operates.

[0009] The problems of the present invention are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0010] To achieve the above objective, a display device according to one embodiment of the present invention comprises: a main board that acquires brightness information from image information; a driver board that sets an output current value for local dimming operation based on the brightness information, sets a usable current area based on a preset unused current area, and sets an output current value based on the set usable current area; and a driver IC that outputs a local dimming current based on the output current value.

[0011] According to an embodiment, the driver board sets the available current range to a value between the maximum current value of the unused current range and the maximum output current of the driver IC.

[0012] According to an embodiment, the driver board sets the maximum current value of the unused current region as the initial output current value for the local dimming operation.

[0013] According to an embodiment, the driver board sets the output current value by dividing the set available current range by grayscale level.

[0014] According to an embodiment, the driver board is configured so that the output current value increasing per grayscale level is the same.

[0015] Specific details of other embodiments are included in the detailed description and drawings.

[0016] According to an embodiment of the present invention, there is one or more of the following effects.

[0017] According to any one embodiment of the present invention, the backlight unit of the display device can have the advantage of increasing brightness detail without increasing cost by controlling local dimming.

[0018] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims.

[0019] FIG. 1 is a block diagram for explaining each configuration of a display device according to one embodiment of the present invention.

[0020] FIG. 2 is a block diagram showing a backlight unit according to one embodiment of the present invention.

[0021] Figures 3 and 4 are drawings for explaining a conventional local dimming current setting method.

[0022] FIGS. 5 and 6 are drawings for explaining a local dimming current setting method according to an embodiment of the present invention.

[0023] FIG. 7 is a diagram illustrating the output current of a driver IC according to a current limiting region according to an embodiment of the present invention.

[0024] FIG. 8 is a diagram illustrating a local dimming control method of a backlight unit according to an embodiment of the present invention.

[0025] It can be said to be the rear. Meanwhile, the display unit (151) is configured as a touch screen and can be used as an input device in addition to an output device.

[0026] The audio output unit (152) receives a voice-processed signal from the control unit (180) and outputs it as voice.

[0027] The control unit (180) may include at least one processor and can control the overall operation of the display device (100) using the included processor. Here, the processor may be a general processor such as a CPU (central processing unit). Of course, the processor may be a dedicated device such as an ASIC (de-driver ICated device) or another hardware-based processor.

[0028] The control unit (180) can demultiplex a stream input through a tuner unit, a demodulator unit, an external device interface unit (112), or a network interface unit (113), or process the demultiplexed signals to generate and output a signal for video or audio output.

[0029] The image signal processed by the control unit (180) is input to the display unit (151) and can be displayed as an image corresponding to the image signal. Additionally, the image signal processed by the control unit (180) may be input to an external output device through the external device interface unit (112).

[0030] The voice signal processed by the control unit (180) can be sound-outputted to the audio output unit (152). Additionally, the voice signal processed by the control unit (180) can be input to an external output device through the external device interface unit (112).

[0031] In addition, the control unit (180) can control the overall operation within the display device (100). For example, the control unit (180) can control the tuner unit (111) to control the selection (tuning) of a broadcast corresponding to a channel selected by the user or a previously stored channel.

[0032] Additionally, the control unit (180) can control the display device (100) by means of a user command or an internal program input through the user input interface unit (173). Meanwhile, the control unit (180) can control the display unit (151) to display an image. At this time, the image displayed on the display unit (151) may be a still image or a video, and may be a 2D image or a 3D image.

[0033] Meanwhile, the control unit (180) can make a predetermined 2D object appear within the image displayed on the display unit (151). For example, the object may be at least one of a connected web screen (newspaper, magazine, etc.), an EPG (Electronic Program Guide), various menus, widgets, icons, still images, videos, and text.

[0034] Meanwhile, the control unit (180) can modulate and / or demodulate the signal using an Amplitude Shift Keying (ASK) method. Here, the Amplitude Shift Keying (ASK) method may refer to a method of modulating the signal by varying the amplitude of the carrier wave according to the data value, or restoring the analog signal to a digital data value according to the amplitude of the carrier wave.

[0035] For example, the control unit (180) can modulate the video signal using an amplitude shift keying (ASK) method and transmit it through a wireless communication module.

[0036] For example, the control unit (180) can demodulate and process the video signal received through the wireless communication module using an amplitude shift keying (ASK) method.

[0037] Through this, the display device (100) can easily transmit and receive signals with other adjacent video display devices without using a unique identifier such as a MAC address (Media Access Control Address) or a complex communication protocol such as TCP / IP.

[0038] Meanwhile, the display device (100) may further include a shooting unit. The shooting unit can photograph the user. The shooting unit may be implemented with one camera, but is not limited thereto, and may also be implemented with multiple cameras. Meanwhile, the shooting unit may be embedded in the display device (100) on the upper part of the display unit (151) or may be placed separately. Image information captured by the shooting unit may be input to the control unit (180).

[0039] The control unit (180) can recognize the user's location based on the image captured by the shooting unit. For example, the control unit (180) can determine the distance (z-axis coordinate) between the user and the display device (100). Additionally, the control unit (180) can determine the x-axis coordinate and y-axis coordinate within the display unit (151) corresponding to the user's location.

[0040] The control unit (180) can detect a user's gesture based on each of the images captured by the shooting unit or the signals detected by the sensor unit, or a combination thereof.

[0041] The storage unit (185) may store programs for each signal processing and control within the control unit (180), and may also store signal-processed video, audio, or data signals. For example, the storage unit (185) may store applications designed for the purpose of performing various tasks that can be processed by the control unit (180), and may selectively provide some of the stored applications upon request from the control unit (180).

[0042] The program, etc. stored in the storage unit (185) is not specifically limited as long as it can be executed by the control unit (180). The storage unit (140) may also perform the function of temporarily storing video, audio, or data signals received from an external device through the external device interface unit (112). The storage unit (185) may store information regarding a predetermined broadcast channel through a channel memory function such as a channel map.

[0043] Although the storage unit (185) of FIG. 1 is shown as being provided separately from the control unit (180), the scope of the present invention is not limited thereto, and the storage unit (185) may be included within the control unit (180).

[0044] The storage unit (185) may include at least one of volatile memory (e.g., DRAM, SRAM, SDRAM, etc.) or non-volatile memory (e.g., flash memory, hard disk drive (HDD), solid-state drive (SSD), etc.).

[0045] The power supply unit (190) can supply power throughout the display device (100). In particular, it can supply power to a control unit (180) which can be implemented in the form of a System On Chip (SOC), a display unit (151) for displaying images, and an audio output unit (152) for audio output.

[0046] Specifically, the power supply unit (190) may be equipped with a converter (not shown) that converts AC power into DC power and a DC / DC converter (not shown) that converts the level of DC power.

[0047] Meanwhile, the power supply unit (190) receives power from an external source and distributes power to each component. The power supply unit (190) may use a method of supplying AC power by directly connecting to an external power source, and may include a power supply unit (190) that can be recharged and used by including a battery.

[0048] In the former case, it is used by connecting a wired cable, making movement difficult or limiting the range of motion. In the latter case, movement is free, but the weight increases by the amount of the battery, the volume becomes larger, and for charging, it must be directly connected to a power cable for a certain period of time or combined with a charging dock (not shown) that supplies power.

[0049] The charging dock can be connected to a display device through an externally exposed terminal, or the built-in battery can be charged by bringing it close using a wireless method.

[0050] Meanwhile, the block diagram of the display device (100) illustrated in FIG. 1 is merely a block diagram for one embodiment of the present invention, and each component of the block diagram may be integrated, added, or omitted according to the specifications of the actual implemented display device (100).

[0051] That is, as needed, two or more components may be combined into a single component, or a single component may be subdivided into two or more components. In addition, the functions performed in each block are intended to explain embodiments of the present invention, and the specific operations or devices thereof do not limit the scope of the present invention.

[0052] FIG. 2 is a block diagram showing a backlight unit according to one embodiment of the present invention.

[0053] Referring to FIG. 2, the backlight unit (1000) may include a main board (1100), a driver board (1200), and a driver IC (1300).

[0054] The main board (1100) can obtain brightness information by analyzing the received video information.

[0055] The driver board (1200) can set an output current value for performing local dimming operation based on brightness information received from the main board (1100). The driver board (1200) can set the set output current value.

[0056] The driver board (1200) can set an available current area based on a preset unused current area.

[0057] The driver board (1200) can set the available current range to a value between the maximum current value of the unused current range and the maximum output current of the driver IC.

[0058] The driver board (1200) can set the maximum current value of the unused current area as the initial output current value for the local dimming operation.

[0059] The driver board (1200) can set the output current value by dividing the set available current range by gradation level.

[0060] The driver board (1200) can be set so that the output current value increasing per gradation level is the same.

[0061] The driver board (1200) can set an output current value based on a set available current range. Through this, the driver board (1200) can control the amount of current output from the driver IC (1300) through local dimming information.

[0062] Specifically, the driver board (1200) can set a current value to be output for local dimming operation based on brightness information and transmit it to the driver IC (1300) as local dimming information.

[0063] Here, the current value is the amount of local dimming current applied to the driver IC (1300) for the backlight unit (BLU, 1000) to output one grayscale.

[0064] The driver IC (1300) can output a local dimming current based on the output current value of the driver board (1200). The local dimming current value output by the driver IC (1300) will be explained in detail later with reference to FIGS. 3 to 7.

[0065] The driver IC (1300) can output a local dimming current to emit light from the backlight. The backlight includes a plurality of light-emitting elements, and the light-emitting elements can be implemented as LEDs (Light Emitting Diodes), etc. Depending on the current value applied from the driver IC (1300), a backlight of different brightness can be provided.

[0066] Figures 3 and 4 are drawings for explaining a conventional local dimming current setting method.

[0067] Referring to Figure 3, a graph showing the relationship between the gray level and the current according to brightness is illustrated.

[0068] The driver IC (1300) may be a driver IC (1300) having 8-bit resolution. The current value according to the maximum brightness in the backlight unit can be assumed to be 60mA.

[0069] Referring to FIG. 3, when the maximum current that the driver IC (1300) can use is 60mA, it may be a graph showing the relationship between the current and the grayscale level.

[0070] When the current range available in the driver IC (1300) is 0mA to 60mA, the gradation level can be expressed in 255 steps.

[0071] Here, one step can correspond to a current of 0.235mA (60mA / 255). That is, to increase one grayscale level, an additional current of 0.235mA must be applied to the light source.

[0072] Therefore, the conventional driver IC (1300) can increase the steps linearly from 0mA, which is the brightness off state, to a maximum of 60mA, which is the brightness state, so that the user can select and use the desired current, and the local dimming function can operate.

[0073] Referring to FIG. 4, when there is an unused current region in a conventional driver IC (1300), it may be a graph showing the relationship between the gray level and the current according to brightness.

[0074] This is the case where the usable current range of the driver IC (1300) is 0mA to 60mA, and the unused current range is 0 to 20mA.

[0075] At this time, the driver IC (1300) has a total of 255 grayscale levels when operating at a current of 0mA to 60mA for local dimming, but only some of the 255 grayscale levels (20mA to 60mA) can be used for local dimming.

[0076] Specifically, the grayscale levels corresponding to the unused current range of 0mA to 20mA are 85 steps, and the grayscale levels corresponding to the 20mA to 60mA range used for local dimming operate with 170 steps. Therefore, due to the unused current range during local dimming, only 170 grayscale levels can be local dimmed, resulting in a problem where the brightness resolution is reduced during local dimming.

[0077] Therefore, during local dimming, the brightness resolution is affected by the unused current area, and as the unused current area increases, the brightness resolution may decrease.

[0078] FIGS. 5 and 6 are drawings for explaining a local dimming current setting method according to an embodiment of the present invention.

[0079] Referring to FIGS. 5 and 6, when there is an unused current region during local dimming operation, the graph may show the relationship between the current and the grayscale level.

[0080] According to the first embodiment, when the current usage range of the driver IC (1300) is 20mA to 60mA and the non-current usage range is 0 to 20mA, the graph may show the relationship between the current and the grayscale level.

[0081] The driver IC (1300) according to the present invention can have 255 steps for the grayscale level in the usage current range of 20mA to 60mA.

[0082] Here, one step can correspond to a current of 0.157 mA (40 mA / 255). That is, to increase one grayscale level, an additional current of 0.157 mA must be applied to the light source.

[0083] Accordingly, the driver IC (1300) of the present invention designates the range from 0mA to 20mA as an unused area, so that it can operate only at 20mA to 60mA.

[0084] The driver IC (1300) can operate the local dimming function by increasing the step non-linearly and selecting and using current only in the actual current range used.

[0085] The unused current region of the driver IC (1300) can be changed by controlling the resistor to maximize efficiency in the usage region.

[0086] Referring to Fig. 6, when there is an unused current region during local dimming operation, it may be a graph showing the relationship between the current and the grayscale level.

[0087] According to the second embodiment, when the current usage range of the driver IC (1300) is 30mA to 60mA and the non-current usage range is 0 to 30mA, the graph may show the relationship between the current and the grayscale level.

[0088] The driver IC (1300) according to the present invention can have 255 steps for the grayscale level in the usage current range of 30mA to 60mA.

[0089] Here, one step can correspond to a current of 0.118 mA (30 mA / 255). That is, to increase one grayscale level, an additional current of 0.118 mA can be applied to the light source.

[0090] Accordingly, the driver IC (1300) of the present invention designates the range from 0mA to 30mA as an unused area, so that it can operate only at 30mA to 60mA.

[0091] The driver IC (1300) can operate the local dimming function by increasing the step non-linearly and selecting and using current only in the actual current range used.

[0092] FIG. 7 is a diagram illustrating the output current of a driver IC according to a current limiting region according to an embodiment of the present invention.

[0093] Referring to FIG. 7, the driver IC (1300) can output a local dimming current corresponding to a grayscale level from 0 bit to 255 bit.

[0094] The driver IC (1300) can output a local dimming current value, which is set based on a set limiting current value, as shown in Table 1 below.

[0095] Bit Limit Current Not Applied Limit Current 30mA Applied Limit Current 40mA Applied 00.000.000.0010.2430.0040.0020.4730.1240.0830.7130.2440.1640.9430.3540.24....25058.8259.4159.6125159.0659.5359.6925259.2959.6559.7625359.5359.7659.8425459.7659.8859.9225560.0060.0060.00

[0096] When the driver IC (1300) has no limiting current applied, it outputs a current of 0.24mA based on a 1-bit grayscale level, and when the grayscale level increases by 1, the current increases by 0.235mA (60mA / 255), so that it can output a current of 60mA at a 255-bit grayscale level. When the driver IC (1300) has 30mA applied as the limiting current, it outputs a current of 30mA at a 1-bit grayscale level, and when the grayscale level increases by 1, the current increases by 0.118mA (30mA / 255), so that it can output a current of 60mA at a 255-bit grayscale level.

[0097] When a limiting current of 40 mA is applied to the driver IC (1300), it outputs a current of 40 mA at a 1-bit grayscale level, and for every increase in one grayscale level, the current increases by 0.078 mA (20 mA / 255), so that it can output a current of 60 mA at a 255-bit grayscale level.

[0098] For example, if the backlight unit (1000) requests a current of 59.41 mA based on brightness information of the input image, and the driver IC (1300) has no limiting current applied, it may output 59.29 mA, which is close to 59.41 mA.

[0099] However, if a limiting current of 30mA is applied to the driver IC (1300), it can output a requested current of 59.41mA based on the erection information.

[0100] Therefore, the driver IC (1300) can have the effect of increasing the precision of the current that can be used for local dimming by adjusting the limiting current value.

[0101] FIG. 8 is a diagram illustrating a local dimming control method of a backlight unit according to an embodiment of the present invention.

[0102] Referring to FIG. 8, the backlight unit (1000) can set the output limit range of the driver IC (1300) (S10). The backlight unit (1000) can set the unused current area as the output limit range.

[0103] After the above step S10, the backlight unit (1000) can select a current within the current usage range according to the output limit range (S20). Specifically, the driver IC (1300) determines the minimum output current value according to the maximum output current value limit range as the usage range, and can select a current value to be output based on the grayscale level that can be output by the driver IC (1300).

[0104] After the above step S20, the backlight unit (1000) can perform a local dimming operation based on the selected output current value (S30).

[0105] The detailed description of the preferred embodiments of the present invention disclosed above is provided to enable those skilled in the art to implement and practice the present invention. Although the present invention has been described with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the scope of the invention. For example, those skilled in the art may utilize each configuration described in the above embodiments in a manner that combines with one another.

[0106] Accordingly, the present invention is not intended to be limited to the embodiments shown herein, but rather to provide an optimal scope consistent with the principles and novel features disclosed herein.

[0107] Various embodiments for implementing the present invention have been described in detail in the previous table of contents.

[0108] Since the present invention is applicable to technology related to display devices, its industrial applicability is recognized.

Claims

1. In a backlight unit of a display device, Main board that acquires brightness information from image information; Based on the brightness information above, set the output current value for local dimming operation, and Based on the preset unused current area, set the available current area, and A driver board that sets an output current value based on a set available current range; and It includes a driver IC that outputs a local dimming current based on the above output current value, and Backlight unit.

2. In Paragraph 1, The above driver board is Characterized by setting the value between the maximum current value of the above unused current region and the maximum output current of the above driver IC as the above available current region. Backlight unit.

3. In Paragraph 2, The above driver board is Characterized by setting the maximum current value of the above unused current region as the initial output current value for the above local dimming operation. Backlight unit.

4. In Paragraph 3, The above driver board is Characterized by dividing the set available current range by grayscale level to set the output current value. Backlight unit.

5. In Paragraph 4, The above driver board is Characterized by setting the output current value increasing per grayscale level to be the same. Backlight unit.

6. A method for controlling local dimming of a backlight unit of a display device, A step of setting an output current value for local dimming operation based on brightness information obtained from image information; A step of setting an available current area based on a preset unused current area; and A step of setting an output current value based on a set available current range; and A step comprising outputting a local dimming current based on the above output current value Local dimming control method.

7. In Paragraph 6, The step of setting an available current area based on the aforementioned preset unused current area is A step comprising setting a value between the maximum current value of the above unused current region and the maximum output current of the driver IC as the above available current region. Local dimming control method.

8. In Paragraph 7, The step of setting the output current value based on the above-set available current range is to set the output current value. A step including setting the maximum current value of the above unused current region as the initial output current value for the local dimming operation Local dimming control method.

9. In Paragraph 8, The method further includes the step of setting the output current value by dividing the set available current range by grayscale level. Local dimming control method.

10. In Paragraph 9, The step of setting the output current value by dividing the above-set available current range by grayscale level Includes a step of setting the output current value increasing per grayscale level to be the same. Local dimming control method.

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