Patent Grant
12073779
This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2019/006593, filed on May 31, 2019, the contents of which are all incorporated by reference herein in its entirety.
The present disclosure relates to a display device that displays an image and a method for controlling the same. More specifically, the present disclosure relates to a display device capable of improving an abnormality phenomenon of a screen due to a change in frequency, for example, when a viewer is continuously viewing images of different frequencies, and a method for controlling the same.
As the information society develops, various demands for a display device for displaying an image are increasing. Thus, a liquid crystal display device (LCD), a plasma display device (PDP), and an organic light emitting diode display device (OLED) are widely used as the display device. Further, recently, a micro light-emitting diode display device (Micro-LED) that renders a color using a micro light-emitting diode on a pixel basis is presented.
An organic light-emitting diode (OLED) includes an anode electrode and a cathode electrode, and an organic compound layer formed therebetween. The organic compound layer is composed of a hole transport layer (HTL), a light emission layer (EML), and an electron transport layer (ETL). When a driving voltage is applied to the anode electrode and the cathode electrode, holes passing through the hole transport layer (HTL) and electrons passing through the electron transport layer (ETL) move to the emission layer (EML) in which excitons are produced, and as a result, the emission layer (EML) generates visible light.
The micro light-emitting diode (Micro-LED) acts as a light-emitting element with a size of several tens of micrometers and has a heterojunction structure of a p-type semiconductor in which holes are majority carriers and an n-type semiconductor in which electrons are majority carriers. Majority carriers of the different types move in opposite directions due to applied voltage and thus meet and recombine with each other in an active layer and release excitation energy thereof in a form of photons. At this time, a wavelength of the photon may be based on a unique energy gap of the active layer. Unlike the organic light-emitting diode, the micro light-emitting diode (Micro-LED) is based on an inorganic material, and thus may minimize glare phenomenon of a display screen, and have excellent advantages in terms of power consumption and lifespan characteristics.
Further, in the display device using the organic light-emitting diode (OLED) or the display device using the micro light-emitting diode (Micro-LED), each of pixels and sub-pixels may be composed of an individual diode. Thus, the display device may be easily implemented as an active matrix type display device. Further, due to self-luminous characteristics thereof, the device has a fast response speed, high light-emitting efficiency, high luminance, and a large viewing angle.
However, in order to reproduce an image of high driving frequency naturally, a short motion picture response time (MPRT) is required.
The motion picture response time is evaluated based on a measuring result of movement of a moving image displayed on the screen of the display device. To this end, an international standard of evaluating the MPRT includes capturing the images as still images along a boundary of the motion picture based on human visual characteristics for an appropriate time using a CCD camera, and evaluating a sharpness of the captured still images.
That is, when an index of the motion picture response time is smaller, this may mean that a sharpness of the image is low, which means that the user's eye fatigue increases when the user views the motion picture displayed on the display device.
Recently, in order to improve the index of the motion picture response time, various schemes including BFI (Black Frame Insertion) in which a black frame is inserted between reproduced image frames are being introduced.
A purpose of an embodiment of the present disclosure is to reduce a screen abnormality phenomenon that occurs when images of different driving frequencies are continuously reproduced on a display device.
Further, a purpose of another embodiment of the present disclosure is to provide a display device to which a scheme of controlling a duty ratio of a light emission signal within one frame to achieve black data insertion effect is applied, in which a screen abnormality phenomenon that occurs when images of different driving frequencies are continuously reproduced is reduced.
A method for controlling a display device to achieve the purpose includes converting a first input frequency to a first driving frequency; when the device operates at the first driving frequency, controlling a signal based on a value of a first vertical blank interval set for the first driving frequency regardless of a time point; converting a second input frequency different from the first input frequency into a second driving frequency; when the device operates at the second driving frequency, controlling, at a first time point, the signal based on a value of a third vertical blank interval different from the value of the first vertical blank interval set for the first driving frequency and a value of a second vertical blank interval set for the second driving frequency; and at a second time point after the first time point, controlling the signal based on the value of the second vertical blank interval set for the second driving frequency.
In one embodiment of the method, the method comprises, when the device operates at the first driving frequency and the second driving frequency, controlling a light emission signal based on a preset duty ratio within one frame interval.
In one embodiment of the method, controlling the signal based on the value of the third vertical blank interval includes gradually changing the value of the third vertical blank interval.
In one embodiment of the method, gradually changing the value of the third vertical blank interval includes sequentially changing the value of the third vertical blank interval by a constant amount and between the value of the first vertical blank interval set for the first driving frequency and the value of the second vertical blank interval set for the second driving frequency.
In one embodiment of the method, the method comprises, when converting the second input frequency to the second driving frequency, determining the constant amount based on a difference between the second input frequency and the second driving frequency.
In one embodiment of the method, one of the first driving frequency and the second driving frequency is 100 Hz and the other thereof is 120 Hz.
A display device to achieve the purpose includes a processor; a display including a plurality of pixels; and a timing controller configured to temporally control a driving frequency to operate the display, wherein the timing controller is configured to: control a light emission signal based on a preset duty ratio within one frame interval; and when the display displays an image of a first input frequency and then an image of a second input frequency, gradually change a value of a vertical blank interval for each frame interval.
According to one embodiment of the various embodiments of the present disclosure, the display device has an effect of reducing the screen abnormality that occurs when images of different driving frequencies are continuously reproduced.
According to another embodiment of the various embodiments of the present disclosure, in a display device to which a scheme of controlling a duty ratio of a light emission signal within one frame to achieve black data insertion effect is applied, a screen abnormality phenomenon that occurs when images of different driving frequencies are continuously reproduced is reduced.
According to another embodiment of the various embodiments of the present disclosure, when the image of the input frequency is converted to the image of the driving frequency, the display device changes the value of the vertical blank interval based on the difference between the input frequency and the driving frequency, thereby minimizing the screen abnormality that occurs when images of different driving frequencies are continuously reproduced.
Hereinafter, an embodiment disclosed in the present specification will be described in detail with reference to the accompanying drawings. Regardless of the drawings, the same or similar components are assigned the same reference numerals, and duplicated descriptions thereof will be omitted. The suffixes “module” and “unit” for the components used in the following description are given or mixed in consideration of only the ease of writing of the specification, and do not have distinct meanings or roles by themselves. In addition, in describing the embodiment disclosed herein, when it is determined that a detailed description of a related known technology may obscure the gist of the embodiment disclosed herein, the detailed description thereof will be omitted. In addition, the accompanying drawings are only for easy understanding of the embodiment disclosed herein, and it should be understood that the technical idea disclosed herein is not limited by the accompanying drawings, and includes all changes, equivalents or substitutes included in the spirit and scope of the present disclosure.
It should be appreciated that following embodiments of the present disclosure are only intended to embody the present disclosure and do not restrict or limit the scope of the right of the present disclosure. What an expert in the technical field to which the present disclosure belongs may easily derive from the detailed description and the embodiments of the present disclosure is interpreted as belonging to the scope of the right of the present disclosure.
The detailed descriptions should not be construed as restrictive in all respects, but rather should be construed as illustrative. The scope of the present disclosure should be determined by a reasonable interpretation of the appended claims, and any changes within the equivalent scope of the present disclosure are included in the scope of the present disclosure.
A display device described in the present disclosure may include a mobile phone, a smart phone, a laptop computer, a digital broadcasting terminal, PDA (personal digital assistant), PMP (portable multimedia player), navigation, Slate PC, Tablet PC, Ultra Book, digital TV, desktop computer and the like. However, it will be readily apparent to those skilled in the art that a configuration according to the embodiment described herein may be applied to a device capable of displaying an image which will be a new product to be developed later.
Further, in the present specification, a frequency and a signal are expressed so as to be distinguished from each other. For example, only an input image signal or a driving image signal as periodically repeated may be expressed as an input frequency or a driving frequency. However, even when signals other than the input image signal or the driving image signal are periodically repeated over time, the signals are simply expressed as signals.
Referring to
The timing controller 120 starts scanning according to a timing implemented in each frame, and converts the image of the driving frequency received from the processor 110 according to a data signal format used by the data driver 130, and outputs the converted image data and controls data operation at an appropriate time according to the scan.
The timing controller 120 and the processor 110 may be embodied as one integrated circuit or may be implemented as separate components.
The data driver 130 drives a plurality of data lines by supplying a data voltage to the plurality of data lines. In this connection, the data driver 130 is also referred to as a source driver.
The data driver 130 may include at least one data driver IC to drive the plurality of data lines.
Each data driver IC may include a shift register, a latch circuit, a digital-to-analog converter (DAC), an output buffer, and, etc.
In some cases, each data driver IC may further include an analog-to-digital converter (ADC).
The gate driver 140 sequentially drives the plurality of gate lines by sequentially supplying a scan signal to the plurality of gate lines. In this connection, the gate driver is referred to as a scan driver.
The gate driver 140 may include at least one gate driver IC.
Each gate driver IC may include a shift register, a level shifter, and the like.
The gate driver 140 sequentially supplies a scan signal of an on voltage or an off voltage to the plurality of gate lines under the control of the timing controller 120.
When a specific gate line is opened by the gate driver 140, the data driver 130 converts the image data received from the timing controller 120 into an analog data voltage and supplies the analog data voltage to the plurality of data lines.
The data driver 130 may be located only at one side of the display device 100, for example, an upper side or a lower side thereof, as shown in
The gate driver 140 may be located only at one side of the display device 100, for example, a left or right side thereof, as shown in
The above-described timing controller 120 receives, from the processor 110, input image data, and various timing signals including a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, an input data enable (DE) signal and a clock signal CLK.
For example, the timing controller 120 outputs various data control signals DCS including a data start pulse DSP, a data shift clock DSC, and a data output enable (DOE) signal to control the data driver 130.
In this connection, the data start pulse DSP controls an operation start timing of one or more data drivers IC constituting the data driver 130. The data shift clock DSC refers to a clock signal commonly input to one or more data drivers IC, and controls a shift timing of a scan signal (data pulse). The data output enable signal DOE specifies timing information of one or more data drivers 130.
Further, the timing controller 120 outputs various gate control signals GCS including a gate start pulse GSP, a gate shift clock GSC, a gate output enable signal GOE, etc. to control the gate driver 140.
In this connection, the gate start pulse GSP controls an operation start timing of one or more gate drivers IC constituting the gate driver 140. The gate shift clock GSC refers to a clock signal commonly input to one or more gate drivers IC and controls a shift timing of a scan signal (gate pulse). The gate output enable signal GOE specifies timing information of one or more gate drivers 140.
In this connection, the display 150 may include a display used in the display devices such as a liquid crystal display device (LCD), a plasma display device (PDP), an organic light emitting diode display device (OLED), and a micro light emitting diode display device (Micro-LED). Hereinafter, an example in which the display 150 is embodied as the organic light-emitting diode display will be described.
Each of sub-pixels of each of pixels (not shown) arranged on the display 150 is composed of an organic light-emitting diode as a self light-emitting element, and a circuit element such as a driving transistor to drive the organic light-emitting diode.
More specifically, the circuit element basically includes a data transistor connected to the data driver, a gate transistor connected to the gate driver, and a storage capacitor that maintains a data voltage corresponding to an image signal voltage or a voltage corresponding thereto for a predetermined time.
Further, a transistor receiving a separate control signal may be further included in the circuit element so that black data may be implemented according to a set time within one frame.
The waveform diagram of the light emission signal in which the duty ratio varies within one frame as shown in
In the BFI for inserting the black frame, basically, original frames and black frames may be displayed alternately as odd number-th and even number-th frames. An entirety of a screen of the display 150 is maintained to be black at a timing when the black frame is inserted. Thus, average luminance decreases while the plurality of frames are reproduced.
In order to solve the above problem, a scheme of setting the duty ratio of the light emission signal within one frame interval and controlling the light emission signal based on the set duty ratio has been newly introduced.
In order to control the duty ratio of the light emission signal within one frame, for example, it is necessary to control the light emission signal per each individual pixel. To this end, generally, a separate transistor to control the light emission signal other than the existing data transistor or gate transistor is introduced. An additional control signal is transmitted from the timing controller 120 to the separate transistor.
The duty ratio indicates a percentage of an interval having a signal-on within a certain period. In the present disclosure, for example, the duty ratio means a ratio of a time duration for which the display 150 emits light relative to a time duration of one frame.
Further, the duty ratio may be set per each individual pixel. An entire area of the display 150 may be divided into sub-areas. The duty ratio of the light emission signal may be set per each sub-area.
Further, the ratio of the light emission signal may be set per each of all pixels included in the display 150 within one frame.
Assuming that all pixels included in the display 150 within one frame are defined as one area, (a) to (d) in
For example, in (c)
The above approach may be achieved by the processor 110 only controlling the light emission signal of the timing controller without creating a separate black frame. Thus, an effect corresponding to increase in the driving frequency may be achieved without changing the driving frequency, thereby improving the motion picture response time and improving the quality of the reproduced image.
Further, specific areas of the display 150 may be specified and thus the light emission signal may be controlled per each area within one frame, such that a black frame may be inserted or a black image may be displayed within one frame, thereby minimizing average degradation of luminance characteristics.
The display device to which the scheme for controlling the duty ratio of the light emission signal within one frame as described in
In this connection, a general display device converts an input frequency of a newly input image into a driving frequency and only needs to control the driving frequency. However, the display device to which the scheme for setting the duty ratio is applied should control a separate light emission signal within one frame, which makes it difficult to temporarily control the changing frequency for the period for which the change occurs.
Further, an unexpected frequency change in the change period may lead to screen abnormality. Symptoms of the screen abnormality include tearing due to mismatch between an input vertical synchronization signal and an output vertical synchronization signal, stuttering due to a difference between frequencies of reproduced frames, or flicker phenomenon in which the screen brightness is not constant and the image is shaken.
(a) in
(b) in
The experiment of (b) in
Therefore, when a first image with a driving frequency of 120 Hz is reproduced as shown in (b) in
(a) in
The vertical blank interval refers to an interval between a timing at which a vertical scan signal to implement an image of one frame on the display is outputted and a timing at which a vertical scan signal to implement an image of a next frame on the display is outputted. In this connection, a synchronization signal is usually inserted thereto to achieve synchronization of the vertical scan signal and the horizontal scan signal.
In general, the vertical blank interval value is set based on the driving frequency. When the driving frequency is 100 Hz, the value is 540H. When the driving frequency is 120 Hz, the value is 90H.
H which denotes the value of the vertical blank interval has a temporal meaning and refers to a unit related to a signal scanned in horizontal and vertical directions to implement an image of one frame.
As shown in (a) in
(b) in
The sudden change in the driving frequency causes the screen abnormality. For this reason, in accordance with the present disclosure, when changing from the first image to the second image, for example, the display device may gradually change the value of the vertical blank interval per each frame and thus create a buffer period in the process of changing from the first image to the second image, such that the screen abnormality due to the frequency change may be minimized.
For the vertical blank interval, no image is output. The approach of creating the buffer period by gradually changing the value of the vertical blank interval is much simpler and achieves the effect more immediately than an approach of devising a separate complex signal processing technique using the processor is and does.
(a) in
(b) in
The value of the vertical blank interval set at the driving frequency of 100 Hz is 540H, and the value of the vertical blank interval set at the driving frequency of 120 Hz is 90H. A difference between the values of the vertical blank intervals is calculated. The value of the vertical blank interval per each frame gradually varies by a constant amount for the change period.
For example, as shown in (b) in
Therefore, as the frame changes, the vertical blank interval value changes from 540H, to 535H, to 530H, to 525H, . . . , to 90H. This change continues over a total of 90 frames. At the driving frequency of 120 Hz, a time duration of each frame is 10 ms. Thus, as shown in (b) in
As shown in
For example, when the driving frequency is changed from 100 Hz to 120 Hz, a lager number of frames must be reproduced within the same time duration, and thus a reproduction time of one frame must be shortened. In this connection, when the value of the value of the vertical blank interval decreases, the reproduction time may be reduced.
However, in the display device 100, for example, when a signal playing a separate role such as the vertical synchronization signal uses the vertical blank interval, a sudden change in the driving frequency and the corresponding change in the vertical blank interval value may cause the processor not to control the signal stably. This may lead to the screen abnormalities such as flicker.
In (a) in
As the frame changes, the difference between the ratios for adjacent frames is 0.22%.
In (b) in
In (c) in
It was identified based on the result of the experiment of the device display to which the scheme of controlling the duty ratio of the light emission signal within one frame was applied under the conditions (a), (b), and (c) of the
That is, the larger the amount by which the vertical blank interval value per each frame changes, the higher the probability of occurrence of the screen abnormalities such as flicker for the period for which the image of the driving frequency changes.
Therefore, the smaller the amount by which the vertical blank interval value per each frame changes, the lower the probability of occurrence of the screen abnormalities such as flicker for the period for which the image of the driving frequency changes. However, in this case, a larger number of frames are required before the value of the vertical blank interval reaches a last value, and accordingly, a time required to change the vertical blank interval becomes larger. For this reason, the amount by which the vertical blank interval value per each frame changes should be adjusted to an appropriate value.
As shown in
Unlike the first driving frequency, the second driving frequency is designed so that the value of the vertical blank interval per each frame gradually changes by the same amount.
In (a) in
In the conversion process, the same frame may be repeated four times in succession. Even when the difference between the values of the vertical blank intervals for the temporally adjacent frames is set to be relatively larger, the probability of the occurrence of screen abnormality is reduced for a period in which the same frame is continuously reproduced.
In (b) in
However, in (c) in
Further, in (d) in
Relatively setting the difference between the values of the vertical blank intervals for the temporally adjacent frames may mean, for example, setting a difference between specific input and driving frequencies as a reference value, and when the difference between the frequencies is larger than the reference value, setting the difference between the values of the vertical blank intervals to be larger and, when the difference between the frequencies is smaller than the reference value, setting the difference between the values of the vertical blank intervals to be smaller.
Further, relatively setting the difference between the vertical blank interval values for the temporally adjacent frames may be performed based on the number of repetitions of the same frame. When converting from the input frequency to the driving frequency, the number of repetitions of the same frame will vary based on the difference between the driving frequency and the input frequency. As the number of repetitions of the same frame increases, the difference between the vertical blank interval values for the temporally adjacent frames may be set to be relatively larger.
In the frequency conversion as shown in
For example, when an input frequency of 40 Hz is converted to a driving frequency of 100 Hz, two different frames may be repeated at a ratio of 2:3. The frame reproduced at 40 Hz is divided into odd and even frames. In the conversion thereof into 100 Hz, the same odd-numbered frame is repeated twice, and the even-numbered frame is repeated three times.
In this way, when the image of the input frequency is converted to the image of the driving frequency, the amount by which the vertical blank interval changes on the frame basis may be adjusted based on the frequency difference or the number of times by which the same frame is repeated, thereby minimizing the screen abnormality that occurs when images of different driving frequencies are continuously reproduced.
First, the processor 910 detects the first input frequency in S911 and converts the same to the first driving frequency in S913. In this connection, as described above, the frequency conversion does not simply mean an increase or decrease in Hz, but may mean a concept including a frame replication ratio based on the frequency difference and, further, signal processing for image quality improvement.
The converted first driving frequency is transmitted to the timing controller 920 in S915. The timing controller 920 outputs the control signals for adjusting a timing of the video signal corresponding to the first driving frequency and a timing based on the duty ratio of the light emission signal set for each frame in S917.
The display 930 will display the first image based on the control signals received (S919) from the timing controller 92 in S921.
When the processor 910 detects the second input frequency used for reproducing the second image while the first image is being displayed in S923, the processor 910 converts the second input frequency to the second driving frequency in S925.
Afterwards, the converted second driving frequency is transmitted to the timing controller 920 in S927. When the first driving frequency and the second driving frequency are different from each other, the timing controller controls the vertical blank interval value so as to be gradually changed on a frame basis by the constant amount in S929.
The timing controller 920 may determine the constant amount corresponding to the change in the frequency when converting from the second input frequency to the second driving frequency. The process of determining the constant amount may be pre-performed by the processor 910.
Further, the timing controller 920 outputs control signals for adjusting the timing of the video signal corresponding to the second driving frequency and the timing based on the duty ratio of the light emission signal set for each frame in S931.
Finally, the display 930 will display the second image based on the control signals received (S933) from the timing controller 92 in S935.
The scheme of changing the value of the vertical blank interval according to the present disclosure is more effective in a display device that may control the light emission ratio within one frame. Thus, first, the processor determines whether a display device of interest is a display device whose light-emitting ratio within one frame is adjusted in S1010.
When the display device of interest is not the display device whose light-emitting ratio within one frame is controlled, a separate vertical blank time change is not applied to the device but the device is set to operate in a normal mode in S1030.
When the display device of interest is the display device whose light-emitting ratio within one frame is controlled, the processor registers a callback function S1020. When the image having the changed driving frequency is reproduced, the callback function is executed.
Subsequently, the process checks whether the driving frequency has been changed in S1040. When the driving frequency has not been changed, the device is set to operate in the normal mode in S1030.
When the driving frequency has been changed, it is checked whether a function of adjusting the light-emitting ratio within one frame in the display device is currently being executed in S1050.
When the above function is disabled, the device may be set to operate in the normal mode in S1030. When the function is enabled, the value of the vertical blank interval is gradually changed while the image of the changed driving frequency is reproduced in S1060.
In
Although the present disclosure has been described with reference to the accompanying drawings, the drawings are only the embodiments and the disclosure is not limited to the embodiments, and the disclosure may be modified by a person skilled in the art in the field to which the present disclosure belongs. The modifications belong to the scope of rights based on Claims. Further, such variant implementations should not be understood separately from the technical spirit of the present disclosure.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2019/006593 | 5/31/2019 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2020/241946 | 12/3/2020 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 8299985 | Shin | Oct 2012 | B2 |
| 20030020699 | Nakatani et al. | Jan 2003 | A1 |
| 20150310814 | Umekida et al. | Oct 2015 | A1 |
| 20150379665 | Kwa et al. | Dec 2015 | A1 |
| 20160035297 | Oh | Feb 2016 | A1 |
| 20180068610 | Cho | Mar 2018 | A1 |
| 20180268761 | Kuo | Sep 2018 | A1 |
| 20190057633 | Li | Feb 2019 | A1 |
| 20200211471 | Park | Jul 2020 | A1 |
| 20200302893 | Lin | Sep 2020 | A1 |
| 20200349893 | Lee | Nov 2020 | A1 |
| 20220019332 | Ko | Jan 2022 | A1 |
| 20220208066 | Kikuchi | Jun 2022 | A1 |
| Number | Date | Country |
|---|---|---|
| 1020060018393 | Mar 2006 | KR |
| 1020080040281 | May 2008 | KR |
| 1020130018493 | Feb 2013 | KR |
| 10-2018-0018939 | Feb 2018 | KR |
| 10-2018-0058279 | Jun 2018 | KR |
| 10-2018-0059017 | Jun 2018 | KR |
| 10-2019-0140760 | Dec 2019 | KR |
| Entry |
|---|
| PCT International Application No. PCT/KR2019/006593, International Search Report dated Feb. 27, 2020, 10 pages. |
| European Patent Office Application Serial No. 19930370.2, Search Report dated Oct. 25, 2022, 12 pages. |
| Korean Intellectual Property Office Application No. 10-2021-7030903, Office Action dated Aug. 22, 2023, 6 pages. |
| Korea Patent Office Application No. 10-2021-7030903, Office Action dated Dec. 19, 2023, 7 pages. |
| Number | Date | Country | |
|---|---|---|---|
| 20220199006 A1 | Jun 2022 | US |
