Local dimming control with dual-line addressing

Abstract

An image display device with local dimming control having dual-line addressing is disclosed. The device includes a display panel, a light-emitting diode (LED) backlight divided into a plurality of zones, and a control unit. The control unit is configured to couple dimming data to the LED backlight. The plurality of zones of the LED backlight are driven by a row enable signal and a column drive signal based on the dimming data. Each individual column drive signal transmits common brightness data, first residual brightness data, and second residual brightness data. The first row enable signal has a first enable pulse within a frame period, and the second row enable signal has a second enable pulse within the frame period. The first enable pulse and the second enable pulse at least partially overlap to reduce the pulsed current of the LED backlight, thereby increasing the lifespan of the LED backlight.

Description

Technical Field

[0001] The present invention generally relates to dimming control. In particular, the present invention relates to an image display device having a light emitting diode (LED) backlight divided into a plurality of light source regions arranged in a two-dimensional (2D) array for supporting local dimming or brightness control of a display panel. Background Art

[0002] Local dimming is commonly used in LED backlight systems configured to perform zonal control of backlighting and dimming for local display regions or blocks of a display panel. For example, local dimming can be implemented in a liquid crystal display (LCD) having an LED backlight system. The LED backlight system is configured into a plurality of local regions or blocks and is located behind the LCD to illuminate corresponding local display regions on the LCD. Local dimming allows independent control of the brightness of each local display region without applying the same brightness condition across the entire display. Thus, LCDs with local dimming backlight systems are recognized as displays with enhanced dynamic range and reduced overall power consumption.

[0003] Figure 1 A possible display device with local dimming control according to the prior art is shown. The system includes an LCD panel 10 and an LED backlight 20. The LCD panel 10 is driven by a display driver 11, while the LED backlight 20 is preferably a submillimeter LED (mLED) backlight divided into 36 zones 23 arranged in a 2D array, each zone including an LED array 22. The LED backlight 20 is driven by an LED driver 21. The LCD panel 10 and the LED backlight 20 are controlled by a local dimming bridge chip 30. First, video data from an application processor 40 is analyzed by the local dimming bridge chip 30, and then the local dimming bridge chip 30 couples dimming data to the LED driver 21 and couples compensated video data to the display driver 11. For darker regions, the corresponding zones 23 on the LED backlight 20 are set to be darker. For brighter regions, the corresponding zones 23 on the LED backlight 20 are set to be brighter. The video data is compensated or scaled to match the LED backlight 20 for driving the LCD panel 10.

[0004] The LED backlight 20 is typically implemented as a passive matrix, which is particularly preferred for a 2D array of LEDs having no more than 1000 zones 23. In the presence of more than 1000 zones 23, an active matrix implementation is preferred. Generally, the backlight system in a passive matrix has higher power efficiency and lower cost but is limited by the number of scan lines. When the number of scan lines is too large, such as 40 lines or more, the pulsed current increases. When the pulsed current is too high, the passive matrix becomes infeasible and the backlight system can only be implemented in an active matrix.

[0005] High pulse current is not conducive to the lifespan of LEDs. Under normal circumstances, preferably, the pulse current does not exceed 30 times the rated DC forward current of an LED with a low pulse duty cycle. For example, for a 2% pulse duty cycle, the pulse width is within one millisecond. For a 2D backlight system with 30 scanning lines, the time division multiplexing is 30, and the pulse current is at least 30 times higher than the target continuous current. Therefore, there is a limit to the maximum number of scanning lines in a passive matrix backlight system.

[0006] Therefore, there is a need in the art to seek a driving scheme to solve at least some of the above problems in a passive matrix LED backlight system. Additionally, through the subsequent detailed description and the appended claims, in combination with the background art and the drawings of the present disclosure, other desired features and characteristics will become apparent. Summary of the Invention

[0007] In view of the above background art, an object of the present disclosure is to provide a backlight system with dual-line addressing for supporting local dimming or brightness control of a display panel, the backlight system having a plurality of LEDs arranged in a 2D array. The above object is achieved by the feature combination of the independent claims; the dependent claims disclose further advantageous embodiments of the present invention.

[0008] According to a first aspect of the present invention, there is provided an apparatus for displaying an image. The apparatus includes: a display panel including a plurality of pixels for displaying an image; an LED backlight source divided into a plurality of zones arranged in a 2D array of rows and columns; and a control unit configured to couple compensated video data to the display panel and couple dimming data to the LED backlight source. The plurality of zones of the LED backlight source are driven by a row enable signal and a column drive signal based on the dimming data. Each individual column drive signal transmits common luminance data, first residual luminance data, and second residual luminance data. The first row enable signal includes a first enable pulse within a frame period, and the second row enable signal includes a second enable pulse within the frame period, wherein the first enable pulse and the second enable pulse at least partially overlap to reduce the pulse current of the LED backlight source compared to an arrangement without overlap, thereby being able to improve the lifespan of the LED backlight source.

[0009] In an embodiment of the first aspect, the common luminance data is applied to two rows of zones. The first residual luminance data is applied to the first row of the two rows of zones. The second residual luminance data is applied to the second row of the two rows of zones.

[0010] In an embodiment of the first aspect, the first row emits light according to the first residual luminance data and the common luminance data; and the second row emits light according to the second residual luminance data and the common luminance data.

[0011] Preferably, the first row is adjacent to the second row.

[0012] In one embodiment of the first aspect, the first enable pulse has a first pulse width, the first pulse width including a first pulse width portion and an overlapping pulse width portion. The second enable pulse has a second pulse width, the second pulse width including a second pulse width portion and an overlapping pulse width portion.

[0013] In one embodiment of the first aspect, the first pulse width portion is immediately before the overlapping pulse width portion; and the second pulse width portion is immediately after the overlapping pulse width portion.

[0014] In one embodiment of the first aspect, during the overlapping pulse width portion, two row regions are enabled simultaneously according to shared luminance data.

[0015] In one embodiment of the first aspect, during the first pulse width portion of the first pulse width, a first row is enabled according to first residual luminance data; and during the second pulse width portion of the second pulse width, a second row is enabled according to second residual luminance data.

[0016] In one embodiment of the first aspect, the LED backlight is driven by an LED driver, the LED driver being configured to receive dimming data and couple a row enable signal and a column drive signal to the LED backlight.

[0017] In one embodiment of the first aspect, the shared luminance data is adaptively selected from a plurality of predetermined comparison values for determining an optimized value of the shared luminance data to achieve a maximum total luminance data on the overlapping pulse width portions of all regions on the first row and the second row.

[0018] In one embodiment of the first aspect, the LED driver includes a plurality of accumulator blocks, each accumulator block being configured to perform data accumulation on the comparison values to thereby determine the comparison value for achieving the maximum total luminance data.

[0019] In one embodiment of the first aspect, a separate accumulator block includes a comparator and an adder, wherein the comparator is configured to receive a shared luminance factor from a column and couple a value equal to the comparison value to the adder when the received shared luminance factor is greater than the comparison value.

[0020] In one embodiment of the first aspect, the control unit is integrated into the LED driver or is integrated into a display driver configured to drive a display panel.

[0021] In a specific embodiment, the display panel is an LCD panel.

[0022] In a specific embodiment, the control unit is a local dimming bridge chip configured to receive video data from an application processor.

[0023] According to a second aspect of the present invention, there is provided an LED backlight for a display panel. The LED backlight includes: a plurality of LEDs arranged in a plurality of zones, wherein the plurality of zones are arranged in a two-dimensional (2D) array of rows and columns; and an LED driver configured to receive dimming data from a control unit and couple an enable signal and column drive signals to drive the plurality of zones based on the dimming data. Each individual column drive signal transmits common luminance data, first residual luminance data, and second residual luminance data. The first enable signal includes a first enable pulse within a frame period, and the second enable signal includes a second enable pulse within the frame period, wherein the first enable pulse and the second enable pulse at least partially overlap to reduce the pulsed current of the LED backlight compared to an arrangement without overlap, thereby being able to improve the lifespan of the LED backlight.

[0024] In an embodiment of the second aspect, the common luminance data is applied to two rows of zones. The first residual luminance data is applied to the first row of the two rows of zones. The second residual luminance data is applied to the second row of the two rows of zones.

[0025] In an embodiment of the second aspect, the first enable pulse has a first pulse width, the first pulse width including a first pulse width portion and an overlapping pulse width portion. The second enable pulse has a second pulse width, the second pulse width including a second pulse width portion and an overlapping pulse width portion.

[0026] In an embodiment of the second aspect, the first pulse width portion is immediately before the overlapping pulse width portion; and the second pulse width portion is immediately after the overlapping pulse width portion.

[0027] In an embodiment of the second aspect, the common luminance data is adaptively selected from a plurality of predetermined comparison values for determining an optimized value of the common luminance data to achieve a maximum total luminance data on the overlapping pulse width portions of all zones on the first row and the second row.

[0028] The present invention content is provided to introduce, in a simplified form, a selection of concepts that are further described in the detailed description below. The present invention content is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to assist in determining the scope of the claimed subject matter. Other aspects and advantages of the present invention are disclosed as set forth in the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings include figures for further illustrating and explaining the above and other aspects, advantages, and features of the present disclosure. It should be understood that these drawings depict only specific embodiments of the present disclosure and are not intended to limit its scope. It should also be understood that these drawings are shown for simplicity and clarity and are not necessarily drawn to scale. The present disclosure will now be described and explained with additional specificity and detail by using the accompanying drawings, wherein:

[0030] Figure 1 depicts a possible display device with local dimming control according to the prior art;

[0031] Figure 2A depicts a typical timing diagram of source currents for implementing conventional local dimming in a display system according to the prior art;

[0032] Figure 2B depicts a typical timing diagram of enable signals for implementing conventional local dimming in a display system according to the prior art;

[0033] Figure 3 depicts an exemplary timing diagram of column drive signals for each zone for implementing two - line addressing local dimming in a display system according to a specific embodiment of the present disclosure;

[0034] Figure 4 depicts an exemplary timing diagram of enable signals for implementing two - line addressing local dimming in a display system according to a specific embodiment of the present disclosure;

[0035] Figure 5 depicts a breakdown of shared luminance data and residual luminance data according to a specific embodiment of the present disclosure;

[0036] Figure 6A depicts exemplary luminance data for each zone of an LED backlight;

[0037] Figure 6B depicts based on Figure 6A the perceived luminance of each zone of an LED backlight for the exemplary luminance data;

[0038] Figure 7 depicts based on Figure 6A the residual luminance data and shared luminance data for each row of each zone using two - line addressing local dimming for the exemplary luminance data;

[0039] Figure 8A depicts a second exemplary luminance data for each zone of an LED backlight;

[0040] Figure 8B depicts based on Figure 8A the perceived luminance of each zone of an LED backlight for the exemplary luminance data;

[0041] Figure 9 depicts the residual luminance data and common luminance data for each row of each zone of dual-line addressed local dimming based on Figure 8A exemplary luminance data;

[0042] Figure 10 depicts a schematic diagram of a logic circuit for calculating common luminance data for dual-line addressing according to an embodiment of the present disclosure;

[0043] Figure 11 depicts an exemplary determination of a common luminance factor;

[0044] Figure 12 depicts the logic circuit in an accumulator block for using Figure 10 and an exemplary calculation of a comparison value for reaching a maximum total luminance data based on the common luminance factor on Figure 11 ; and

[0045] Figure 13 depicts the calculation results of the common luminance data and the residual data. DETAILED DESCRIPTION

[0046] The present disclosure generally relates to a backlight system with dual-line addressing, the backlight system having a plurality of LEDs arranged in a 2D array for supporting local dimming or brightness control of a display panel. More particularly but not limited to, the dual-line addressing drive scheme of the present disclosure can be deployed to a passive matrix backlight system to at least partially relax the limitations on high pulse currents.

[0047] The following detailed description is merely exemplary in nature and is not intended to limit the present disclosure or its application and / or uses. It should be understood that there are numerous variations. The detailed description will enable a person of ordinary skill in the art to implement exemplary embodiments of the present disclosure without undue experimentation, and it should be understood that various changes or modifications can be made to the functions and structures described in the exemplary embodiments without departing from the scope of the present disclosure as set forth in the appended claims.

[0048] Some portions of the following description are presented explicitly or implicitly in terms of algorithms and functional or symbolic representations of operations on data within a computer memory. These algorithmic descriptions and functional or symbolic representations are the means by which those skilled in the data processing arts most effectively convey the substance of their work to others skilled in the art. An algorithm is here generally regarded as a self-consistent sequence of steps leading to a desired result. These steps are those requiring physical manipulation of physical quantities such as electrical, magnetic, or optical signals capable of being stored, transferred, combined, compared, and otherwise manipulated.

[0049] Benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more apparent should not be construed as critical, essential, or necessary features or elements of any or all of the claims. The present invention is defined only by the appended claims, including any amendments made during the pendency of this application and all equivalent arrangements of those claims as issued.

[0050] In the context of describing the present invention (especially in the context of the following claims), the use of the terms "a", "an", "the", "at least one", and similar reference terms shall be construed to cover both the singular and the plural, unless otherwise specified herein or clearly contradicted by the context. The terms "comprising", "having", "including", and "containing" shall be construed as open-ended terms (i.e., meaning "including but not limited to"), unless otherwise stated. The use of any and all examples or exemplary language (e.g., "such as") provided herein is merely intended to better illustrate the present invention and not to limit the scope of the present invention, unless otherwise required. No language in the specification shall be construed to indicate that any non-claimed element is essential for the practice of the present invention.

[0051] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the described technology. As used herein, the term "display panel" may be an LCD, a flexible display, or other display devices composed of multiple pixels capable of displaying images and / or videos. The term "frame" as used herein refers to the period of a complete screen refresh cycle of the display panel, including the time for updating the pixels on the display panel and the time for activating the backlight source. Terms such as "LED" and "mLED" are used interchangeably as the backlight source of the display panel.

[0052] Local Dimming with Dual-Line Addressing

[0053] According to Figure 1 the embodiments described in. There is provided an apparatus for displaying an image, the apparatus comprising an LCD panel 10, an LED backlight source 20 for generating backlight, and a local dimming bridge chip 30. The LCD panel 10 is driven by a display driver 11, while the LED backlight source 20 is divided into a plurality of zones 23, which are arranged in a 2D array of rows and columns, wherein each zone 23 includes a plurality of LEDs 22. The LED backlight source 20 is driven by an LED driver 21. The LCD panel 10 and the LED backlight source 20 are controlled by the local dimming bridge chip 30. The plurality of zones 23 are not enabled simultaneously. In a preferred embodiment, the plurality of zones 23 are enabled row by row. Each row of zones 24 is activated to emit light during a specific period, and another row of zones 24 is activated to emit light in sequence until all the zones 23 of the LED backlight source 20 are enabled once.

[0054] Figure 2Ashows a typical timing diagram of source currents that display conventional local dimming implemented using single-line addressing in a display system, while Figure 2B correspondingly shows a typical timing diagram of an enable signal. In the illustrated embodiment, for clarity and simplicity, a 6-row region 24 is shown. Obviously, the number of rows in region 24 can be other numbers without departing from the scope and spirit of the present disclosure. For each frame 50, the period is divided into two parts. The first part 51 of frame 50 is allocated for updating liquid crystal (LC) by sending signals to LCD panel 10. LC is a relatively slow switching material and takes some time to twist to a new angle after a new voltage level is applied. During the time when LC is updated in the first part 51, the corresponding regions 23 of LED backlight 20 should not be enabled, and there should be enough time for the data to stabilize. Otherwise, motion blur will be observed, especially for fast-moving images. The second part 52 of frame 50 is allocated for enabling LED backlight 20 based on dimming data. In this example, there are six row regions 24, so there are six pulses in one frame. Figure 2B The corresponding enable signal is shown in. The enable pulses 55 for row region 24 are provided non-overlapping. Generally, the pulse width of enable pulses 55 is consistent. On the same row, different regions 23 can have different brightness levels. The pulse width for activating each region 23 can be further adjusted based on the desired brightness of the region 23. Preferably, the brightness of region 23 is controlled by pulse width modulation (PWM). This timing is controlled by dimming data and should not overlap with the corresponding timing of the first part 51 for updating LC. The row regions 24 are not enabled simultaneously to avoid current surges. In a specific embodiment, regions 23 are sequentially controlled along the scan direction and repeated again in the next frame 50. Through the single-line control of regions 23, the LED drive current is always constant. The variable factor is the duration of enabling region 23.

[0055] Figure 3 illustrates an exemplary timing diagram of column drive signals for each row showing local dimming implemented with dual-line addressing in a display device according to a specific embodiment of the present disclosure. Similar to Figure 1In the conventional architecture described, the display device includes: a display panel, such as the LCD panel 10, having a plurality of pixels for displaying an image; an LED backlight 20; and a control unit configured to dynamically control the display panel and the LED backlight 20, and couple compensated video data to the display panel and dimming data to the LED backlight 20. The LED backlight 20 is divided into a plurality of zones 23 of light sources arranged in a 2D array of rows and columns, where each zone 23 includes a plurality of LEDs 22. The LED backlight 20 is driven by an LED driver 21 configured to receive dimming data. For each frame 50, the time period is divided into two parts. The first part 51 of the frame 50 is allocated for updating the LC by sending a signal to the LCD panel 10, while the second part 52 is allocated for enabling the LED backlight 20 based on the dimming data. For each row of pixels on the LCD panel 10, the LC is updated row by row along the scan direction. Thus, the LED backlight 20 is also driven row by row sequentially outside the time interval for updating the LC (i.e., the first part 51). The plurality of zones 23 of the LED backlight 20 are driven by a row enable signal and a column drive signal based on the dimming data, which are coupled from the LED driver 21 after receiving the dimming data from the control unit. Preferably, the control unit is a local dimming bridge chip configured to receive video data from the application processor 40. Alternatively, the control unit is integrated as a single integrated circuit chip into the LED driver 21 or the display driver 11 and is configured to receive video data from the application processor 40.

[0056] As shown, two row regions are driven together to adjust the brightness of the LEDs according to the local brightness data of each region 23. For simplicity and clarity, the first row 24A is adjacent to the second row 24B. Obviously, without departing from the scope and spirit of the present disclosure, the first row 24A and the second row 24B can also be any row regions 24 of the LED backlight 20. The first row 24A and the second row 24B of the two row regions have similar column drive signals. The two row regions are driven substantially simultaneously, but not exactly in the same way. The time periods for enabling the first row 24A and the second row 24B of the two regions partially overlap, and the first row 24A can be enabled earlier than the second row 24B, and the second row 24B can continue to be enabled after the overlapping time period. This demonstrates the distinguishing feature of dual-line addressing in which the first row 24A and the second row 24B have an overlapping time period to emit light of the same intensity simultaneously. The brightness difference between the first row 24A and the second row 24B is handled by controlling the time period for enabling the first row 24A before the overlapping time period and the time period for enabling the second row 24B after the overlapping time period. Each row region 24 is still driven once per frame 50 so that errors caused by charging and discharging the source lines can be minimized. In a passive matrix organic light emitting diode (PMOLED) display, such errors related to charging and discharging of the source lines are more serious and detrimental to the overall performance.

[0057] In particular, PMOLED displays typically have more than 100 rows, while LED backlights typically have only 10 to 30 rows. In addition, the source lines of PMOLEDs are transparent conductive thin films, such as indium tin oxide (ITO), which have a much higher resistance than the source lines of LED backlights, which are copper traces on a printed circuit board (PCB).

[0058] In a particular embodiment, each individual column drive signal transmits the common luminance data 52B, the first residual luminance data 52A, and the second residual luminance data 52C to the LED backlight 20 to drive two rows along the column. During the overlapping period, the common luminance data 52B is applied to the two-row area. Before the overlapping period, the first residual luminance data 52A is applied to the first row 24A. Thus, the first row 24A emits light according to the first residual luminance data 52A and the common luminance data 52B. After the overlapping period, the second residual luminance data 52C is applied to the second row 24B. Thus, the second row 24B emits light according to the second residual luminance data 52C and the common luminance data 52B. It should also be noted that if the target luminance of the area is exactly the same as the common luminance data 52B, the first residual luminance data 52A and the second residual luminance data 52C can be zero. This situation is illustrated in the second row area. It should also be noted that the common luminance data 52B can be set to zero (labeled 52D). This typically occurs when at least one of the two rows in the two-row area has a smaller luminance data. When that row is driven by the first residual data 52A or the second residual data 52C, the LED drive current is not shared by two lines, so the current is significantly higher than the overlapping period when the two-row area is driven by the common luminance data 52B.

[0059] Figure 4 An exemplary timing diagram is provided showing the enable signals for implementing two-line addressing local dimming in a display system. The enable signals are provided to each row area 24 to enable that area to receive the column drive signals. In some embodiments, the enable signals are independent of the luminance data. However, the enable signals can also be adjusted according to the desired luminance. A first enable signal 53 is provided for the first row 24A, and a second enable signal 54 is provided for the second row 24B. The first enable signal 53 includes a first enable pulse 53A in a frame period 50, and the second enable signal 54 includes a second enable pulse 54A in the same frame period 50. The first enable pulse 53A and the second enable pulse 54A are repeated in the next frame 50 and in the previous frame again. The first enable pulse 53A and the second enable pulse 54A at least partially overlap. Since the LED drive current on the pixel is typically lower during the overlapping period, compared to a backlight arrangement using conventional local dimming without overlap, the configuration with the first enable pulse 53A and the second enable pulse 54A can effectively reduce the pulsed current of the LED backlight 20. Thus, the high pulsed current is less severe, which can improve the lifespan of the LED backlight 20. This improvement is particularly evident for PMOLED applications.

[0060] The details of the first enable pulse 53A and the second enable pulse 54A are further explained below. The first enable pulse 53A has a first pulse width including a first pulse width portion 53B and an overlapping pulse width portion 55B. The first pulse width portion 53B is immediately before the overlapping pulse width portion 55B. Similarly, the second enable pulse 54A has a second pulse width including a second pulse width portion 54B and an overlapping pulse width portion 55B. The second pulse width portion 54B is immediately after the overlapping pulse width portion 55B. As Figure 3 shown, during the overlapping pulse width portion 55B, two row regions are enabled simultaneously according to the common luminance data 52B. During the first pulse width portion 53B of the first pulse width, the first row 24A is enabled according to the first residual luminance data 52A. During the second pulse width portion 54B of the second pulse width, the second row 24B is enabled according to the second residual luminance data 52C. In the example of the present disclosure, the first enable pulse 53A and the second enable pulse 54A are active high. However, in some cases, the first enable pulse 53A and the second enable pulse 54A may be active low.

[0061] Referring to Figure 5 the example shown, the LED backlight 20 is divided into 12 regions arranged in a 2×6 row and column array. The 6 columns can be referred to as "source columns", successively as "S1", "S2",..., and "S6", respectively, and are controlled by 6 column drive signals. Two row enable signals 53, 54 and six column drive signals are used to drive the 12 regions, and each region has local luminance data. The local luminance data for each region is exemplarily shown in the figure. By applying dual-line addressing, each luminance data can be divided into residual data and common luminance data. The common luminance data 52B used in this example is "6", which is uniformly applied to two row regions. Referring to Example 1 shown in the figure, the local luminance data is "11" (Row 1, S1), which can be divided into the common luminance data 52B of "6" and the first residual data 52A of "5". Similarly, Example 2 has a luminance data of "9" (Row 2, S5), which can be divided into the common luminance data 52B of "6" and the second residual data 52C of "3". The drive current for the LED backlight 20 is constant, so the adjustment of the luminance defined by the common luminance data 52B, the first residual data 52A, and the second residual data 52C is controlled by pulse width modulation.

[0062] The first pulse width portion 53A and the second pulse width portion 54A partially overlap to provide an overlapping pulse width portion 55B for enabling LEDs in two row regions according to the common luminance data 52B (i.e., "6"). The first pulse width portion 53A is also enabled immediately before the overlapping pulse width portion 55B for enabling LEDs in the first row region according to the first residual data 52A (i.e., "5", e.g., 1). On the other hand, the second pulse width portion 54A is enabled immediately after the overlapping pulse width portion 55B for enabling LEDs in the second row region according to the second residual data 52C (i.e., "3", e.g., 2).

[0063] Figure 6A Exemplary luminance data for respective regions of an LED backlight 20 having a 6x6 array region are shown. Figure 6B Corresponding perceived luminance for respective regions of the LED backlight is shown. To implement dual-line addressing in dimming control, adjacent two row regions are paired. As Figure 7 shown, row 1 and row 2 are paired with a first common luminance data 162. Similarly, row 3 and row 4 are paired with a second common luminance data 99. Row 5 and row 6 are paired with a third common luminance data 102. Each of the three common luminance data is adaptively selected according to the luminance data of respective regions on the corresponding two rows. In many cases, adjacent regions have similar local luminance data. The arrangement of the present disclosure jointly examines the local luminance data of all regions on two rows and determines an optimized value of the common luminance data 52B.

[0064] In some cases, adjacent regions may have a large interval deviation in local luminance data. As Figure 8A and Figure 8B exemplarily shown, the luminance data of respective regions of the LED backlight 20 vary more along the same row. This is also shown in the corresponding perceived luminance. The common luminance data is an optimized value adaptively selected based on the luminance data of respective regions on the corresponding two rows, as Figure 9 shown. If the local luminance data of a region is less than the optimized value, the common luminance data of that specific source column is set to 0. This is demonstrated in Example 3. If any one of the local luminance data on two rows along the same source column is less than the optimized value, the luminance data is equal to the residual data, while the common luminance data is 0.

[0065] Determining Shared Luminance Data

[0066] Another aspect of the present disclosure provides a method and logic circuit for determining common luminance data 52B, which is applied to a two-line region. The common luminance data 52B is adaptively selected from a plurality of predetermined comparison values to determine an optimized value of the common luminance data 52B to achieve a maximum total luminance data on the overlapping pulse-width portions 55B of all regions on the first line 24A and the second line 24B. Figure 10 A logic circuit diagram for determining the common luminance data 52B is provided. The logic circuit is configured to check the local luminance data of all regions on the two lines 24A, 24B and determine an optimized value of the common luminance data 52B. In a particular embodiment, the common luminance data 52B is adaptively selected from 16 predetermined comparison values. The logic circuit has 16 accumulator blocks 110, each accumulator block being configured to perform data accumulation on the comparison values. The number of predetermined comparison values is not restrictive and may be other numbers without departing from the scope and spirit of the present disclosure. If the number of predetermined comparison values is larger, the chip size of the LED driver 21 may be larger, but the performance of improving the lifespan of the LED backlight 20 is desired.

[0067] The purpose of having a plurality of accumulator blocks 110 is to determine which comparison value can achieve the maximum total luminance data on the overlapping pulse-width portions 55B of all regions on the two lines. In the foregoing discussion, if the local luminance data of a region is less than the optimized value, the common luminance data of the specific source column is set to 0. The accumulator block 110 is configured to calculate the sum of the luminance data on the overlapping pulse-width portion 55B that is higher than the comparison value of the accumulator block 110.

[0068] Referring to the logic circuit, each individual accumulator block 110 includes a comparator 111 and an adder 112. The comparator 111 is configured to receive the common luminance factor of each source column from the two-line region 24. The comparator determines whether the received common luminance factor is greater than the comparison value. If it is greater than the comparison value, the comparator 111 couples a value equal to the comparison value to the adder 112. If it is less than the comparison value, the comparator 111 couples a zero value to the adder 112. After a delay 113, the evaluation is repeated for another data source column on the two-line region 24 by receiving another common luminance factor. After evaluating all source columns, the maximum accumulator 120 is determined by determining the comparison value of the accumulator block 110 with the highest value summed by the adder 112, and this highest value represents the maximum total luminance data of the two-line region 24.

[0069] Figure 11An example of luminance data for two rows and the corresponding common luminance factor for each source column is provided. Referring to the first source column, as highlighted in Example 4, the n-th row has luminance data of "173", and the (n + 1)-th row has luminance data of "176". Thus, the common luminance factor for coupling to the accumulator block 110 is "173", which is the smaller value of the two luminance data.

[0070] Figure 12 The operation of the accumulator block 110 for determining the comparison value for the maximum total luminance data that can reach the two-row region 24 is shown. For the source columns, the accumulation is processed one by one. The accumulator block 110 is first initially set to zero. When the common luminance factor of the first source column is coupled to the accumulator block 110, the comparator 111 compares the common luminance factor with the comparison value. Referring to the case of 173 highlighted in Example 4, the common luminance factor is greater than the following comparison values: 16, 32, 48, 64, 80, 96, 112, 128, 144, and 160. Thus, the corresponding accumulator block 110 sums the comparison values through the adder 112. At the same time, when the comparison value is greater than or equal to the common luminance factor of this source column (i.e., 173), the comparator 111 in the accumulator block 110 for the comparison values 176, 192, 208, 224, 240, and 255 couples zero values to the next stage. The comparison and accumulation processes are repeated until all source columns are evaluated. The maximum value of the accumulation is determined. In the illustrated embodiment, the accumulator block 110 with the maximum total luminance data is ACC96, which is the accumulator block 110 with a comparison value of 96.

[0071] Figure 13 The calculation results of the common luminance data and the residual data are shown. When the determined comparison value is 96, the two-row region 24 has common luminance data of 96, i.e., 52B. The first residual data 52A and the second residual data 52B are also calculated. The calculation results also show the case where when one of the two luminance data in the same source column is less than the comparison value, the corresponding common luminance data 52B of this source column is set to zero. Thus, the two lines are driven separately without any overlapping areas.

[0072] This illustrates a basic embodiment of the present disclosure for a display panel, with an emphasis on controlling an LED backlight with local dimming. It is obvious that the above-described variations and other features and functions or their alternative layouts can be combined into many other different systems or devices. Therefore, this embodiment should be considered illustrative in all aspects rather than restrictive. The scope of the present disclosure is indicated by the appended claims rather than the preceding description, and thus all variations falling within the equivalent meaning and scope of the claims are intended to be included therein.

Claims

1. A device for displaying an image, comprising: a display panel including a plurality of pixels for displaying the image; a light-emitting diode (LED) backlight source divided into a plurality of zones arranged in a two-dimensional (2D) array of rows and columns; and a control unit configured to couple compensated video data to the display panel and couple dimming data to the LED backlight source; wherein: the plurality of zones of the LED backlight source are driven by a row enable signal and a column drive signal based on the dimming data; each individual column drive signal transmits common luminance data, first residual luminance data, and second residual luminance data; a first row enable signal includes a first enable pulse within a frame period, and a second row enable signal includes a second enable pulse within the frame period, wherein the first enable pulse and the second enable pulse at least partially overlap to reduce the pulsed current of the LED backlight source compared to an arrangement without overlap, thereby being able to increase the lifespan of the LED backlight source; the common luminance data is applied to two rows of zones, the first residual luminance data is applied to the first row of the two rows of zones, and the second residual luminance data is applied to the second row of the two rows of zones; the first enable pulse has a first pulse width including a first pulse width portion and an overlapping pulse width portion, the second enable pulse has a second pulse width including a second pulse width portion and the overlapping pulse width portion; the LED backlight source is driven by an LED driver configured to receive the dimming data and couple the row enable signal and the column drive signal to the LED backlight source; and the common luminance data is adaptively selected from a plurality of predetermined comparison values for determining an optimized value of the common luminance data to achieve a maximum total luminance data on the overlapping pulse width portions of all zones on the first row and the second row.

2. The device according to claim 1, wherein, the first row emits light according to the first residual luminance data and the common luminance data; and the second row emits light according to the second residual luminance data and the common luminance data.

3. The device according to claim 1, wherein, the first row is adjacent to the second row.

4. The device according to claim 1, wherein, the first pulse width portion is immediately before the overlapping pulse width portion; and the second pulse width portion is immediately after the overlapping pulse width portion.

5. The device according to claim 1, wherein, during the overlapping pulse width portion, the two rows of zones are simultaneously enabled according to the common luminance data.

6. The device according to claim 5, wherein, during the first pulse width portion of the first pulse width, the first row is enabled according to the first residual luminance data; and during the second pulse width portion of the second pulse width, the second row is enabled according to the second residual luminance data.

7. The device according to claim 1, wherein, the LED driver includes a plurality of accumulator blocks, each accumulator block being configured to perform data accumulation on a comparison value so as to determine the comparison value reaching the maximum total brightness data.

8. The device according to claim 7, wherein, a separate accumulator block includes a comparator and an adder, wherein the comparator is configured to receive a common brightness factor from the column and couple a value equal to the comparison value to the adder when the received common brightness factor is greater than the comparison value.

9. The device according to claim 1, wherein, the control unit is integrated into the LED driver or integrated into a display driver configured to drive the display panel.

10. The device according to any one of claims 1 to 9, wherein, the display panel is a liquid crystal display (LCD) panel.

11. The device according to any one of claims 1 to 9, wherein, the control unit is a local dimming bridge chip configured to receive video data from an application processor.

12. A light emitting diode (LED) backlight for a display panel, comprising: a plurality of LEDs, the plurality of LEDs being arranged in a plurality of zones, wherein the plurality of zones are arranged in a two-dimensional (2D) array of rows and columns; and an LED driver for driving the LED backlight, the LED driver being configured to receive dimming data from a control unit and couple an enable signal and a column drive signal to drive the plurality of zones based on the dimming data; wherein: each individual column drive signal transmits common brightness data, first residual brightness data, and second residual brightness data; a first enable signal includes a first enable pulse within a frame period, and a second enable signal includes a second enable pulse within the frame period, wherein the first enable pulse and the second enable pulse at least partially overlap to reduce the pulsed current of the LED backlight compared to an arrangement without overlap, thereby being able to improve the lifespan of the LED backlight; the common brightness data is applied to two rows of zones, the first residual brightness data is applied to the first row of the two rows of zones, and the second residual brightness data is applied to the second row of the two rows of zones; the first enable pulse has a first pulse width, the first pulse width including a first pulse width portion and an overlapping pulse width portion, the second enable pulse has a second pulse width, the second pulse width including a second pulse width portion and the overlapping pulse width portion; and the common brightness data is adaptively selected from a plurality of predetermined comparison values for determining an optimized value of the common brightness data to reach a maximum total brightness data on the overlapping pulse width portions of all zones on the first row and the second row.

13. The LED backlight according to claim 12, wherein, the first pulse width portion is immediately before the overlapping pulse width portion; and the second pulse width portion is immediately after the overlapping pulse width portion.

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