Display brightness control

Abstract

The present specification discloses a display brightness control device having an ACL circuit that is simplified compared to the prior art. If the display brightness control device in the present specification inputs video data, it calculates the average brightness Y_avg and determines the brightness change ΔY based on the average brightness. Moreover, in order to adjust the brightness, the display brightness control device in the present specification does not modify the video data, but can adjust the brightness of the display by adjusting the current (driving current) that drives the light-emitting diode included in the pixel. That is, the display brightness control device in the present specification is different from the prior art and does not modify the video data for brightness control.

Description

Technical Field

[0001] The present invention relates to a display brightness control device, and more particularly, to a device for controlling the brightness of a display to which automatic current limitation (ACL: Automatic Current Limitation) is applied. Background Art

[0002] This application claims priority based on patent application No. 10-2020-0062424 filed in South Korea on May 25, 2020, and all contents disclosed in the specification and drawings of the corresponding application are incorporated herein by reference.

[0003] With the development of electronic technology, a variety of electronic products including displays, such as smartphones, tablets, and wearable devices, are being developed and popularized. The power consumption of displays accounts for a large part of the total power consumption of electronic devices. As displays become larger, the larger the display size, the greater the power consumption of the display. The battery capacity of electronic devices is limited, so research and development aimed at saving the power consumption of displays is continuously being carried out.

[0004] In order to save power consumption on the display, automatic current limitation (ACL: automatic current limitation, hereinafter referred to as "ACL") technology for adjusting the brightness of the display is being used. The so-called ACL technology is a technology that aims to reduce unnecessary power consumption by adjusting the brightness (luminance) in a bright display screen to a degree that the human eye cannot distinguish. More specifically, in one frame of the screen displayed on the display, the average value of the RGB brightness is calculated based on the on pixel rate (OPR: on pixel rate, hereinafter referred to as "OPR"). Moreover, when the average brightness is above a certain brightness, ACL can be used to reduce the brightness within a range that is difficult for the eye to recognize in order to reduce unnecessary power consumption. At this time, the ratio of reducing the brightness can be determined based on ACL-related parameters (for example: 10%, 15%, 20%, etc.).

[0005] Figure 1 It is a reference image of brightness change based on ACL technology.

[0006] On the other hand, there are various driving methods depending on the type of display, and the methods of driving the display can be roughly divided into direct driving method (Direct), passive driving method (Passive Matrix), and active driving method (Active Matrix). The biggest difference between the passive driving method (Passive Matrix) and the active driving method (Active Matrix) is whether there is a storage capacitor (storage capacitor) or memory (memory) that stores information during 1 frame. Regarding the ACL technology of a display with an active driving method, there is Korean Publication Patent Gazette No. 10-2011-0099981 (2011.09.09).

[0007] Figure 2 This is a reference diagram of the previous ACL technology for displays with active drive.

[0008] according to Figure 2 As described in paragraphs

[0033] to

[0041] of the patent publication, if video data is input, the average brightness Y_avg is calculated. The brightness change ΔY is determined based on the average brightness. According to the determined brightness change, the input video data is adjusted and new video data is generated. Finally, the newly generated video data is output to the pixel circuit, and a picture with reduced brightness is output. That is, in order to adjust the brightness, the original video data needs to be processed.

[0009] This conventional ACL technology requires regeneration of video data, which makes the circuit structure more complex and causes a screen delay effect corresponding to the time it takes to regenerate video data. In addition, as the resolution of the screen increases, the input cycle of video data increases sharply, and the regenerated video data is directly applied to the pixel circuit, so gradual brightness adjustment cannot be performed, which makes the audience feel that the screen changes discontinuously. Summary of the invention

[0010] Technical issues

[0011] The purpose of this specification is to provide a display brightness control device having an ACL circuit that is simpler than the prior art.

[0012] In this specification, the present invention is not limited to the above-mentioned subjects, and other subjects not mentioned can be clearly understood by a person skilled in the art from the following description.

[0013] Technical Solution

[0014] In order to solve the above-mentioned problems, the display brightness control device in the present specification may include: an average brightness calculation unit, which receives video data constituting a frame and calculates the average brightness; a brightness change calculation unit, which calculates the brightness change amount to be reduced when the calculated average brightness is above a preset reference brightness; and a driving current control unit, which changes the driving current amount of the pixel driving circuit that applies the driving current to the light-emitting diode according to the brightness change amount.

[0015] According to an embodiment of the present specification, the average brightness calculation unit may calculate the average brightness based on an average value of an on-pixel rate (OPR: OnPixel Rate).

[0016] According to an embodiment of the present specification, the pixel driving circuit may include: a switching element connected to a pixel driving line connected between a positive power supply and a negative power supply; and a light emitting diode connected between the switching element and the positive power supply or between the switching element and the negative power supply. Moreover, the driving current control unit may output a voltage to the switching element so that the switching element included in the pixel driving circuit operates in a range in which the amount of current flowing on the pixel driving line changes linearly according to the input voltage.

[0017] At this time, the driving current control unit may include: a non-inverting amplifier; a voltage amplification adjustment unit, which adjusts the resistance value between the inverting terminal of the non-inverting amplifier and the ground according to the brightness change; and a voltage tracker, which receives the voltage output to the non-inverting amplifier and outputs it to the switching element included in the pixel driving circuit.

[0018] According to an embodiment of the present specification, the device may further include a brightness control unit, wherein the brightness control unit outputs the brightness change amount and a reference brightness value used for calculation to the driving current control unit.

[0019] According to an embodiment of the present specification, the brightness control unit may further output a change ratio used to calculate the brightness change amount to the brightness change amount calculation unit.

[0020] At this time, when the previous brightness change amount calculated based on the average brightness of the previous frame and the current brightness change amount calculated based on the average brightness of the current frame are greater than a preset difference value, the brightness control unit can calculate at least one intermediate brightness change amount having a value between the previous brightness change amount and the current brightness change amount, and output the intermediate brightness change amount to the brightness change amount calculation unit.

[0021] The display brightness control device in this specification may be a component of a display device, the display device comprising: a display panel composed of a plurality of pixels arranged in m×n order; a scanning driving circuit, the scanning driving circuit sequentially driving a pixel driving circuit along a scanning line, the pixel driving circuit being a pixel driving circuit included in a pixel connected to each scanning line among a plurality of scanning lines, the plurality of scanning lines being connected to pixels arranged along a row direction among the plurality of pixels; and a data driving circuit, the data driving circuit outputting video data to each pixel connected to each data line through a plurality of data lines connected to pixels arranged along a vertical direction among the plurality of pixels. At this time, the video data received by the display brightness control device and the video data output by the data driving circuit to each pixel are the same data.

[0022] Other details of the present invention are included in the detailed description and the accompanying drawings.

[0023] Effects of the Invention

[0024] According to one aspect of the present specification, the configuration of the ACL circuit is simpler than in the prior art, and productivity can be improved and power consumption can be reduced.

[0025] According to another aspect of the present specification, gradual brightness adjustment can be performed to achieve natural picture changes.

[0026] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by ordinary technicians from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a reference image of brightness change based on ACL technology.

[0028] Figure 2 This is a reference diagram of the conventional ACL technology for a display having an active drive method.

[0029] Figure 3 It is a working reference diagram of the display brightness control device in this manual.

[0030] Figure 4 This is a block diagram schematically showing the structure of a display brightness control device in this specification.

[0031] Figure 5 It is a block diagram schematically showing the configuration of a display device. DETAILED DESCRIPTION

[0032] If you refer to the following and attached Figure 1The advantages, features and methods of achieving the invention disclosed in this specification will be clear with the detailed description of the embodiments. However, this specification is not limited to the embodiments disclosed below, and can be embodied in a variety of different forms. This embodiment is only provided to make the disclosure of this specification more complete and to fully inform the technical personnel in the technical field to which this specification belongs (hereinafter referred to as "practitioners") of the scope of this specification. The scope of rights of this specification is only defined by the scope of the claims.

[0033] The terms used in this specification are used to describe the embodiments and are not intended to limit the scope of the rights of this specification. In this specification, as long as it is not specifically mentioned in the sentence, the singular also includes the plural. The "comprises" and / or "comprising" used in the specification do not exclude the existence or addition of one or more other constituent elements in addition to the mentioned constituent elements.

[0034] Throughout the specification, the same reference numerals refer to the same constituent elements, and "and / or" includes all combinations of the individual constituent elements and more than one. Although "first" and "second" are used to describe a variety of constituent elements, these constituent elements are certainly not limited by these terms. These terms are only used to distinguish one constituent element from other constituent elements. Therefore, the first constituent element mentioned below can also be the second constituent element within the technical concept of the present invention.

[0035] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used as meanings that can be commonly understood by those skilled in the art to which this specification belongs. In addition, terms defined in commonly used dictionaries shall not be interpreted excessively or excessively unless they are specifically defined. Embodiments of the present invention are described below with reference to the accompanying drawings.

[0036] Figure 3 It is a working reference diagram of the display brightness control device in this manual.

[0037] Will Figure 3 and Figure 2 By contrast, if video data is input, the process of calculating the average brightness Y_avg and determining the brightness change ΔY based on the average brightness is the same. However, unlike the prior art, the display brightness control device in this specification does not modify the video data to adjust the brightness, but can adjust the brightness of the display by adjusting the current (driving current) driving the light-emitting diode included in the pixel. That is, the display brightness control device in this specification is different from the prior art and does not modify the video data for brightness control.

[0038] Figure 4This is a block diagram schematically showing the structure of a display brightness control device in this specification.

[0039] Reference Figure 4 The display brightness control device 100 in this specification may include an average brightness calculation unit 110 , a brightness change calculation unit 120 , and a driving current control unit 130 .

[0040] The average brightness calculation unit 110 may receive video data constituting a frame and calculate the average brightness. According to an embodiment of the present specification, the average brightness calculation unit 110 may calculate the average brightness Y_avg based on the average value of the on pixel rate (OPR: On Pixel Rate). Figure 4 In the illustrated example, an example in which RGB data is 8 bits each is illustrated, but the present specification is not limited to the example illustrated in the drawings.

[0041] The brightness change calculation unit 120 can calculate the brightness change amount ΔY to be reduced when the calculated average brightness is above the preset reference brightness. The process of calculating the brightness change amount ΔY for ACL is a well-known technology for technicians in the industry, so it will not be repeated. In addition, the reference brightness amount can be set in a variety of ways, which is self-evident.

[0042] The driving current control unit 130 can change the driving current amount of the pixel driving circuit that applies the driving current to the light-emitting diode according to the brightness change amount. Usually, the pixel driving circuit is connected to a switching element (e.g., a transistor) on the pixel driving line connected between the positive power supply (+) and the negative power supply (-, GND). Moreover, a light-emitting diode LED is connected between the switching element and the positive power supply or between the switching element and the negative power supply. Therefore, when the switching element is turned on, the driving current is applied to the light-emitting diode, and the light-emitting diode is turned on. On the other hand, when the switching element included in the pixel driving circuit is, for example, a field-effect transistor (FET), there is a section in which the current amount flowing between the drain terminal and the source terminal changes linearly according to the voltage applied to the gate terminal, and a saturation section in which a predetermined current amount flows regardless of the voltage. The driving current control unit 130 can output a voltage to the switching element so that the switching element operates in a linear section.

[0043] According to an embodiment of the present specification, the driving current control unit 130 may include: a non-converting amplifier 131; a voltage amplification adjustment unit 132, the voltage amplification adjustment unit 132 adjusting the resistance value R1 between the inverting terminal (-) of the non-converting amplifier 131 and the ground according to the brightness change; and a voltage follower 133, the voltage follower 133 receiving the voltage output to the non-converting amplifier 131, and outputting it to the switching element included in the pixel driving circuit. For reference, Figure 4 The “BGR” shown in the figure serves as a “BandGap Reference” and plays a role of inputting a predetermined voltage to the non-inverting terminal (+) of the non-inverting amplifier 131 .

[0044] On the other hand, the display brightness control device 100 in this specification may further include a brightness control unit 140 .

[0045] The brightness control unit 140 may output the brightness variation and a reference brightness value for calculation to the driving current control unit 130, more specifically, to the voltage amplification adjustment unit 132. The reference brightness value refers to the brightness output in the screen when the ACL is not applied.

[0046] The brightness control unit 140 may output a change ratio for calculating the brightness change amount to the brightness change amount calculation unit 120. The change ratio refers to the degree of reduction from the reference brightness, and may be set in various ways, such as 1%, 3%, 5%, 10%, 15%, etc., and may also be changed during the operation of the display. The brightness control unit 140 outputs a value related to the change ratio to the brightness change amount calculation unit 120, and the brightness change amount calculation unit 120 calculates the brightness change amount according to the changed change ratio.

[0047] On the other hand, the display brightness control device 100 in this specification reduces the brightness by considering the average brightness of the frame. When the brightness difference between the previous frame and the current frame is large, a sharp brightness change will occur. At this time, for the audience, the picture continuity is reduced due to the brightness change, so it needs to be compensated.

[0048] To this end, when a previous brightness change amount calculated based on the average brightness of a previous frame and a current brightness change amount calculated based on the average brightness of a current frame are greater than a preset difference value, the brightness control unit 140 can calculate at least one intermediate brightness change amount having a value between the previous brightness change amount and the current brightness change amount, and output the intermediate brightness change amount to the brightness change amount calculation unit 120.

[0049] Figure 5It is a block diagram schematically showing the configuration of a display device.

[0050] Reference Figure 5 The display device 10 may include a display panel 11 , a scan driving circuit 12 , a data driving circuit 13 and a processor 14 .

[0051] The display panel 11 may include a plurality of pixels PX. The plurality of pixels PX may be arranged in a matrix form of m×n (m, n are natural numbers). However, the plurality of pixels may be arranged in a variety of patterns according to the embodiment, such as a zigzag pattern.

[0052] The display panel 110 may be implemented as one of LCD (liquid crystal display), LED (light emitting diode) display, OLED (organic LED) display, AMOLED (active-matrix OLED) display, ECD (Electrochromic Display), DMD (Digital Mirror Device), AMD (Actuated Mirror Device), GLV (Grating Light Valve), PDP (Plasma Display Panel), ELD (ElectroLuminescent Display), VFD (Vacuum Fluorescent Display), and may be implemented as other types of flat panel displays or flexible displays. In this specification, as an example, an LED display panel will be described.

[0053] Each pixel PX may include multiple light-emitting elements. The light-emitting element may be a light-emitting diode LED. The light-emitting diode may be a micro LED (Micro LED) having a size of less than 80 um. A pixel PX may output multiple colors through multiple light-emitting elements having different colors. As an example, a pixel PX may include light-emitting elements composed of red, green, and blue. As another example, a white light-emitting element may also be included, and the white light-emitting element may also replace any one of the red, green, and blue light-emitting elements. Each light-emitting element included in a pixel PX is referred to as a "sub-pixel".

[0054] Each pixel PX may include a pixel driving circuit for driving a plurality of sub-pixels. The pixel driving circuit may drive the start or shut down action of the sub-pixel according to the control signal output by the scanning driving circuit 12 and / or the data driving circuit 13. The pixel driving circuit may include at least one thin film transistor and at least one capacitor, etc. The pixel driving circuit may be implemented by a stacked structure on a semiconductor wafer.

[0055] The display panel 110 may include scan lines SL1-SLm arranged in a row (raw) direction and data lines DL1-DLn arranged in a column (column) direction. The pixel PX may be located at the intersection of the scan lines SL1-SLm and the data lines DL1-DLn. Each pixel PX may be connected to any scan line SLk and any data line DLk. The scan lines SL1-SLm may be connected to the scan driving circuit 120, and the data lines DL1-DLn may be connected to the data driving circuit 130.

[0056] The scanning driving circuit 12 may be configured to drive the pixels connected to any one of the scanning lines SL1 to SLm. Preferably, the scanning driving circuit 12 may select the scanning lines SL1 to SLm in sequence. For example, during a first scanning driving period, the pixels connected to the first scanning line SL1 may be driven, and during a second scanning driving period, the pixels connected to the second scanning line SL2 may be driven.

[0057] The data driving circuit 13 can output a grayscale voltage to each pixel through the data lines DL1 to DLn. One data line can be connected to a plurality of pixels in the longitudinal direction, but during the one scanning drive period, only the pixels connected to the scanning line selected by the scanning driving circuit 12 can be driven. Therefore, during the scanning drive period, the data driving circuit 13 can output a grayscale voltage to the pixels corresponding to one scanning line through the data lines DL1 to DLn. On the other hand, in the case of a display having a memory unit built into the pixel to replace the capacitor (MIP: Memory In Pixel), data related to the grayscale can be output instead of the grayscale voltage.

[0058] The processor 14 may output control signals to operate the scan driving circuit 12 and the data driving circuit 13. The control unit 14 may output control signals corresponding to image data corresponding to one image frame to the scan driving circuit 12 and the data driving circuit 13, respectively.

[0059] The display brightness control device 100 in this specification can be a component of the processor 14. At this time, the video data received by the display brightness control device is the same as the video data output to each pixel by the data driving circuit 13. In other words, the display brightness control device 100 in this specification does not modify the original video data, so compared with the prior art, the circuit structure will be simpler, and the processing speed can be improved due to the simple circuit structure.

[0060] Including the processor 14, the display brightness control device 100 in this specification may include a microprocessor, an ASIC (application-specific integrated circuit), other chipsets, logic circuits, registers, communication modems, data processing devices, etc., known in the technical field of the present invention, in order to calculate and run various control logics. In addition, when the above control logic is implemented in software, the processor 14, etc. can be implemented as a set of program modules. In this case, the program modules can be stored in a storage device and run by the processor.

[0061] In order to enable the computer to read the program and run the method implemented by the program, the computer program may include a code (Code) encoded in a computer language such as C / C++, C#, JAVA, Python, or a mechanical language that can be read by the processor (CPU) of the computer through the computer device interface. This code may include relevant functional codes (Functional Code) such as functions for defining the functions required to run the method, and may include relevant control codes for the operation steps required for the computer processor to run the function according to the established steps. In addition, this code may also include memory reference-related codes for which position (address) of the internal or external memory of the computer is referenced by the additional information or medium required for the computer processor to run the function. In addition, when the processor of the computer needs to communicate with a remote other computer or server in order to run the function, the code may also include communication-related codes such as how to use the communication module of the computer to communicate with a remote other computer or server, and what information or media needs to be sent and received during communication.

[0062] The storage medium is not a medium that can store data temporarily and instantaneously like a register, a cache, a memory, etc., but refers to a medium that stores data semi-permanently and can be read by a device. Specifically, the storage medium is, for example but not limited to, a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, etc. That is, the program can be stored in a variety of recording media on a variety of servers accessible to the computer or in a variety of recording media on the user's computer. In addition, the medium can be distributed in a computer system connected by a network to store computer-readable codes in a distributed manner.

[0063] The embodiments of the present specification are described above with reference to the accompanying drawings. Those skilled in the art of the present specification can understand that the present invention can be implemented in other specific forms without changing its technical ideas or essential features. Therefore, the embodiments described above should be understood in all aspects as being illustrative only and not restrictive.

[0064] Reference numerals

[0065] 100: Display brightness control device

[0066] 110: Average brightness calculation unit

[0067] 120: Brightness change calculation unit

[0068] 130: Driving current control unit

[0069] 140: Brightness control unit

Claims

1. A display brightness control device, comprising: an average brightness calculation unit that receives video data constituting one frame and calculates average brightness; a brightness variation calculation unit configured to calculate a brightness variation to be reduced when the calculated average brightness is equal to or greater than a preset reference brightness; and a driving current control unit configured to change a driving current amount of a pixel driving circuit that applies a driving current to the light emitting diode according to the brightness change amount; The pixel driving circuit includes: a switching element connected to a pixel driving line connected between a positive power supply and a negative power supply; and a light emitting diode connected between the switching element and the positive power supply or between the switching element and the negative power supply; The driving current control unit outputs a voltage to the switching element, so that the switching element included in the pixel driving circuit operates in a range in which the amount of current flowing through the pixel driving line changes linearly according to the input voltage; The driving current control unit includes: non-inverting amplifier; a voltage amplification amount adjustment unit configured to adjust a resistance value between an inverting terminal of the non-inverting amplifier and a ground according to the brightness variation; and A voltage tracker receives the voltage output to the non-inverting amplifier and outputs the voltage to a switching element included in the pixel driving circuit.

2. The display brightness control device according to claim 1, wherein: The average brightness calculation unit calculates average brightness based on an average value of ON pixel rates.

3. The display brightness control device according to claim 1, wherein: The device further includes a brightness control unit configured to output the brightness change amount and a reference brightness value for calculation to the driving current control unit.

4. The display brightness control device according to claim 3, wherein: The brightness control section further outputs a change ratio for calculating the brightness change amount to the brightness change amount calculation section.

5. The display brightness control device according to claim 4, characterized in that: When the previous brightness change amount calculated based on the average brightness of the previous frame and the current brightness change amount calculated based on the average brightness of the current frame are greater than a preset difference value, the brightness control unit calculates at least one intermediate brightness change amount having a value between the previous brightness change amount and the current brightness change amount, and outputs the intermediate brightness change amount to the brightness change amount calculation unit.

6. A display device comprising: The display brightness control device according to any one of claims 1 to 5; A display panel having a plurality of pixels arranged in m×n order; a scan driving circuit that sequentially drives a pixel driving circuit along a scan line, wherein the pixel driving circuit is a pixel driving circuit included in a pixel connected to each of a plurality of scan lines, wherein the plurality of scan lines are connected to pixels arranged in a row direction among the plurality of pixels; and a data driving circuit configured to output video data to each pixel connected to each data line through a plurality of data lines connected to pixels arranged in a longitudinal direction among the plurality of pixels; The display device is characterized in that the video data received by the display brightness control device and the video data output to each pixel by the data driving circuit are the same data.

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