Display device

Abstract

The present disclosure relates to a display apparatus, and in particular, to a display apparatus and a driving method of the display apparatus, and a display apparatus according to an example embodiment includes a pixel unit including a plurality of pixels, and a light emitting driver outputting a light emitting control signal having a different light emitting period according to a driving frequency and a required brightness to the pixel unit.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2020-0101085, filed on August 12, 2020, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a display device and a driving method for the display device. More specifically, this disclosure relates to a display device capable of preventing step blur and increase in driving voltage, and a driving method for the display device. Background Technology

[0004] Organic light-emitting diode (OLED) displays consist of two electrodes and an organic emitting layer inserted between the two electrodes. Electrons injected from one electrode and holes injected from the other electrode recombine in the organic emitting layer to generate excitons. The generated excitons change from an excited state to a ground state, thereby releasing energy to emit light.

[0005] These organic light-emitting devices are attracting attention as the next generation of displays because they have fast response times and are driven by low power consumption.

[0006] In such organic light-emitting devices, it is not easy to precisely control the driving current during the driving period representing low brightness. Therefore, a method has been proposed to drive the device by adjusting the duty cycle of the emission control signal. In this case, as the width of the off-period increases, the black driving time increases, which allows the period of the emission control signal to be increased to solve the problem of flicker detection.

[0007] However, if the period of the signal is increased, step blur occurs in the moving image, and there is a problem of increased driving voltage.

[0008] The information disclosed above in this background section is only intended to enhance the understanding of the background art of the described art, and therefore may contain information that does not form prior art known to those skilled in the art in this country. Summary of the Invention

[0009] Example embodiments will provide a display device capable of preventing step blur and increase in driving voltage, as well as a driving method for the display device.

[0010] The display device according to the example embodiment includes: a pixel unit including a plurality of pixels; and a light-emitting driver that outputs a light-emitting control signal having a different number of light-emitting cycles according to the driving frequency and the desired brightness to the pixel unit.

[0011] The display device according to the example embodiment may further include a light emission cycle controller that receives a driving frequency and a desired brightness to determine the turn-on / turn-off duty cycle of the light emission control signal to be output to the light emission driver and the number of light emission cycles.

[0012] The light emission cycle controller may include: a drive frequency receiving unit for receiving drive frequency; a required brightness receiving unit for receiving required brightness; a duty cycle determining unit for determining the off duty cycle of the light emission control signal; and a light emission cycle determining unit for determining the number of light emission cycles.

[0013] The duty cycle determination unit can set the off duty cycle higher when the required brightness is lower.

[0014] The emission cycle determination unit can determine the number of emission cycles based on the driving frequency, the required brightness, and the off duty cycle.

[0015] The emission period determination unit can derive the number of emission periods by using a lookup table, and the lookup table can store information on the minimum number of emission periods, so that flickering is not visually detectable based on the driving frequency, the required brightness, and the off duty cycle.

[0016] When the driving frequency is above 100Hz, there can be a light emission cycle.

[0017] At a driving frequency of 90Hz, if the required brightness is less than 150 nits, there can be one emission cycle, and if the required brightness is more than 150 nits, there can be more than one emission cycle.

[0018] When the driving frequency is 90Hz and the required brightness is above 400 nits, one emission cycle can exist if the off duty cycle is below 50%, and six emission cycles can exist if the off duty cycle is above 50%.

[0019] A pixel unit may include multiple scan lines, multiple data lines, and multiple light emission control lines connected to each of the multiple pixels, and the light emission control lines may transmit light emission control signals from the light emission driver to the pixel unit.

[0020] A driving method for a display device according to an example embodiment includes: receiving a driving frequency of the display device; receiving a desired brightness representing the apparent brightness of the screen of the display device; and determining the number of light emission cycles of a light emission control signal output to a pixel unit based on the driving frequency and the desired brightness.

[0021] The driving method of the display device according to the example embodiment may further include determining the off duty cycle of the light emission control signal based on the desired brightness.

[0022] When determining the off duty cycle, the lower the required brightness, the higher the off duty cycle can be.

[0023] When determining the number of light emission cycles for the light emission control signal, the number of light emission cycles can be determined based on the driving frequency, the required brightness, and the off duty cycle.

[0024] Determining the number of light emission cycles for the light emission control signal may include: comparing the driving frequency with a reference frequency; comparing the desired brightness with a reference brightness; and determining the number of light emission cycles.

[0025] When the driving frequency is compared with the reference frequency and the driving frequency is above the reference frequency, a light emission cycle can exist.

[0026] The reference frequency can be 100Hz.

[0027] A light emission cycle can exist when the desired brightness is compared with a reference brightness and the desired brightness is less than the reference brightness.

[0028] The reference brightness can have different values ​​depending on the driving frequency.

[0029] When the desired brightness is compared with the reference brightness and the desired brightness is above the reference brightness, the number of light emission cycles can be determined by referring to a lookup table. The lookup table can store information on the minimum number of light emission cycles in which flickering is not visually perceptible based on the driving frequency, desired brightness, and off duty cycle.

[0030] According to the example embodiment, when the flicker is not visually recognizable, the number of signal cycles is not increased, thereby preventing step blurring and an increase in drive voltage. Attached Figure Description

[0031] Figure 1 This is a schematic block diagram illustrating a display device according to an example embodiment.

[0032] Figure 2 This is a circuit diagram of a pixel of a display device according to an example embodiment.

[0033] Figure 3 This is a block diagram of a light emission cycle controller for a display device according to an example embodiment.

[0034] Figure 4 This is a waveform diagram showing various light emission control signals of a display device according to an example embodiment.

[0035] Figure 5 It is a graph of the basic brightness of the display device according to the example embodiment and the off duty cycle of the light emission control signal.

[0036] Figure 6 This is a graph showing the composite flicker index based on driving frequency and brightness.

[0037] Figure 7 and Figure 8 It shows a graph of the composite flicker index based on the off duty cycle and brightness.

[0038] Figure 9 This is a flowchart illustrating a driving method for a display device according to an example embodiment.

[0039] Figure 10 This is a flowchart illustrating some steps of a driving method for a display device according to an example embodiment. Detailed Implementation

[0040] This disclosure will be described more fully below with reference to the accompanying drawings, in which exemplary embodiments of the disclosure are illustrated. As will be appreciated by those skilled in the art, the described embodiments can be modified in various different ways without departing from the spirit or scope of this disclosure.

[0041] For the purpose of clearly explaining this disclosure, parts not directly related to this disclosure have been omitted, and throughout the specification, the same reference numerals belong to the same or similar constituent elements.

[0042] Furthermore, for better understanding and ease of description, the dimensions and thicknesses of each configuration shown in the accompanying drawings are arbitrarily illustrated, but this disclosure is not limited thereto. In the drawings, the thicknesses of layers, films, panels, regions, etc., are exaggerated for clarity. In the drawings, the thicknesses of some layers and regions are exaggerated for better understanding and ease of description.

[0043] It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on that other element, or there may be intermediate elements present. Conversely, when an element is referred to as being "directly" on another element, there are no intermediate elements present. Furthermore, in this specification, the terms "on" or "above" mean located on or below the target portion, and do not necessarily mean located on the upper side of the target portion based on the direction of gravity.

[0044] In addition, unless explicitly stated otherwise, the word “including” and its variations such as “comprising” or “containing” will be understood to imply inclusion of the elements stated, but not to exclude any other elements.

[0045] Furthermore, in this specification, the phrase "in a plane" means the target portion viewed from above, and the phrase "in a cross section" means the cross section in which the target portion is vertically cut when viewed from the side.

[0046] First, refer to Figure 1 A display device according to an example embodiment is described.

[0047] Figure 1 This is a schematic block diagram illustrating a display device according to an example embodiment.

[0048] like Figure 1 As shown, the display device according to the example embodiment may include a pixel unit 10, a timing controller 20, a data driver 30, a gate driver 40, a light-emitting driver 50, and a power supply unit 60.

[0049] The pixel unit 10 includes multiple scan lines 151 extending in a first direction to transmit scan signals SL1 to SLn, multiple light emission control lines 155 to transmit light emission control signals EM1 to EMn, multiple data lines 171 extending in a second direction intersecting the first direction and transmitting data voltages DL1 to DLm, and multiple pixels PX connected to the multiple signal lines and arranged in a matrix. Each pixel PX receives scan signals SL1 to SLn and data voltages DL1 to DLm from the scan lines 151 and data lines 171, respectively. Light emission control signals EM1 to EMn are supplied from the light emission control lines 155. Each pixel PX emits light in response to the scan signals SL1 to SLn, data voltages DL1 to DLm, light emission control signals EM1 to EMn, driving voltage ELVDD, and common voltage ELVSS, thereby displaying an image. For each pixel PX, the light emission time can be adjusted in response to the light emission control signals EM1 to EMn.

[0050] The timing controller 20 receives first image data DATA and input control signals for controlling the display of the first image data DATA from an external image source, such as a horizontal synchronization signal Hsync, a vertical synchronization signal Vsync, and a clock signal CLK. The timing controller 20 can perform image processing on the input first image data DATA to generate second image data DATA' corrected for image display in the pixel unit 10, and provides the generated second image data DATA' to the data driver 30. Additionally, the timing controller 20 generates and outputs drive control signals DCS, SCS, ECCS, and PCS based on the input control signals to control the driving of the data driver 30, the gate driver 40, the light-emitting driver 50, and the power supply unit 60.

[0051] On the other hand, the timing controller 20 may include a light emission period controller 25 for adjusting the turn-on / off duty cycle and light emission period of the light emission control signals EM1 to EMn. The light emission period controller 25 can determine the turn-on / off duty cycle of the light emission control signals EM1 to EMn according to the desired brightness, and adjust the light emission period based on the driving frequency, the desired brightness, and the turn-on / off duty cycle of the light emission control signals EM1 to EMn. For example, when the desired brightness is high, the off duty cycle can be set relatively low. Furthermore, the lower the driving frequency, the lower the desired brightness, and the higher the off duty cycle, the larger the adjustable light emission period. More details on this are available in [link to relevant documentation]. Figure 3 Further details are provided below.

[0052] Data driver 30 is connected to multiple data lines 171 and generates data voltages DL1 to DLm in response to the data control signal DCS of timing controller 20, and outputs the generated data voltages DL1 to DLm to the data lines 171. At this time, data driver 30 converts the second image data DATA' provided by timing controller 20 into analog data voltages DL1 to DLm and outputs the data voltages DL1 to DLm to the data lines 171. The data voltages DL1 to DLm are generated based on a gamma reference voltage, and data driver 30 can receive the gamma reference voltage from a gamma reference voltage generator (not shown). Data driver 30 sequentially transmits the data voltages DL1 to DLm to each of the multiple pixels PX in the pixel unit 10, which are included in a predefined row.

[0053] The gate driver 40 is connected to multiple scan lines 151 and generates scan signals SL1 to SLn in response to the scan control signal SCS from the timing controller 20, and outputs the generated scan signals SL1 to SLn to the scan lines 151. Data voltages DL1 to DLm can be provided by sequentially selecting pixels PX of each line according to the scan signals SL1 to SLn. The gate driver 40 can supply scan signals SL1 to SLn according to a predefined driving frequency, and the driving frequency can be controlled by the timing controller 20.

[0054] The light-emitting driver 50 is connected to multiple light-emitting control lines 155. It generates light-emitting control signals EM1 to EMn via the light-emitting period control signal ECCS from the timing controller 20 and transmits these signals to each of the light-emitting control lines 155. At this time, in response to the light-emitting period control signal ECCS, the turn-on / off duty cycle and light-emitting period of the light-emitting control signals EM1 to EMn are adjusted. That is, according to the light-emitting control signals EM1 to EMn, the light-emitting time of pixel PX and the number of light-emitting events per frame can be adjusted.

[0055] The power supply unit 60 can apply a high-potential driving voltage ELVDD and a low-potential common voltage ELVSS to the pixel unit 10 according to the power control signal PCS. The power supply unit 60 may include a DC-DC converter (not shown) for generating the driving voltage ELVDD and the common voltage ELVSS. Each of the pixels PX supplied with the driving voltage ELVDD and the common voltage ELVSS from the power supply unit 60 can emit light corresponding to the data voltage by the current flowing from the driving voltage ELVDD through the organic light-emitting element to the common voltage ELVSS.

[0056] Next, refer to Figure 2 Describes a pixel of a display device according to an example embodiment.

[0057] Figure 2 This is a circuit diagram of a pixel of a display device according to an example embodiment.

[0058] like Figure 2 As shown, a pixel PX of the display device according to the example embodiment includes a plurality of transistors T1, T2, T3, T4, T5, T6 and T7 connected to different signal lines, a storage capacitor Cst and a light-emitting diode LED.

[0059] The display device according to the example embodiment includes a display area in which an image is displayed, and the pixels PX are arranged in various shapes in the display area.

[0060] Multiple transistors T1, T2, T3, T4, T5, T6, and T7 include a driving transistor T1 and switching transistors (i.e., second transistor T2 and third transistor T3) connected to scan line 151, and other transistors (hereinafter referred to as compensation transistors) for the operation required to operate the light-emitting diode (LED). These compensation transistors T4, T5, T6, and T7 may include a fourth transistor T4, a fifth transistor T5, a sixth transistor T6, and a seventh transistor T7.

[0061] Multiple signal lines may include scan line 151, previous scan line 151a, light emission control line 155, bypass control line 154, data line 171, drive voltage line 172, initialization voltage line 127, and common voltage line 741. The bypass control line 154 may be part of the previous scan line 151a or may be electrically connected to the previous scan line 151a. Furthermore, the bypass control line 154 may be part of the scan line 151 or may be electrically connected to the scan line 151.

[0062] Scan line 151 is connected to the gate driver to transmit the scan signal SLn to the second transistor T2 and the third transistor T3. Previous scan line 151a is connected to the gate driver to transmit the previous scan signal SL(n-1) applied to the pixel PX set at the previous stage to the fourth transistor T4. Light emission control line 155 is connected to the light emission driver and transmits the light emission control signal EMn, which controls the timing of LED illumination, to the fifth transistor T5 and the sixth transistor T6. Bypass control line 154 transmits the bypass signal GB to the seventh transistor T7.

[0063] Data line 171 transmits the data voltage DLm generated by the data driver, and the brightness of the light-emitting diode (LED) changes according to the data voltage DLm. Drive voltage line 172 applies the drive voltage ELVDD. Initialization voltage line 127 transmits the initialization voltage Vint used to initialize the drive transistor T1. Common voltage line 741 applies the common voltage ELVSS. The voltages applied to drive voltage line 172, initialization voltage line 127, and common voltage line 741 can all be constant voltages.

[0064] Several transistors are described below.

[0065] The driving transistor T1 is a transistor used to adjust the amplitude of the output current according to the applied data voltage DLm. The output driving current Id is applied to the light-emitting diode (LED), causing the brightness of the LED to be adjusted according to the data voltage DLm. For this purpose, the first electrode S1 of the driving transistor T1 is configured to receive the driving voltage ELVDD. The first electrode S1 is connected to the driving voltage line 172 via the fifth transistor T5. The first electrode S1 of the driving transistor T1 is also connected to the second electrode D2 of the second transistor T2 to also receive the data voltage DLm. The second electrode D1 (output electrode) of the driving transistor T1 outputs current to the LED. The second electrode D1 of the driving transistor T1 is connected to the anode of the LED via the sixth transistor T6. On the other hand, the gate electrode G1 of the driving transistor T1 is connected to one electrode (second storage electrode E2) of the storage capacitor Cst. Therefore, the voltage of the gate electrode G1 changes according to the voltage stored in the storage capacitor Cst, and the driving current Id output from the driving transistor T1 changes accordingly.

[0066] The second transistor T2 receives the data voltage DLm into pixel PX. The gate electrode G2 of the second transistor T2 is connected to scan line 151, and the first electrode S2 of the second transistor T2 is connected to data line 171. The second electrode D2 of the second transistor T2 is connected to the first electrode S1 of the driving transistor T1. When the second transistor T2 is turned on according to the scan signal SLn transmitted through scan line 151, the data voltage DLm transmitted through data line 171 is transmitted to the first electrode S1 of the driving transistor T1.

[0067] The third transistor T3 allows its data voltage DLm, which is altered by the driving transistor T1, to be transmitted to the second storage electrode E2 of the storage capacitor Cst by a compensation voltage. The gate electrode G3 of the third transistor T3 is connected to scan line 151, and the first electrode S3 of the third transistor T3 is connected to the second electrode D1 of the driving transistor T1. The second electrode D3 of the third transistor T3 is connected to the second storage electrode E2 of the storage capacitor Cst and the gate electrode G1 of the driving transistor T1. The third transistor T3 is turned on according to the scan signal SLn received through scan line 151, connecting the gate electrode G1 and the second electrode D1 of the driving transistor T1, and also connecting the second electrode D1 of the driving transistor T1 and the second storage electrode E2 of the storage capacitor Cst.

[0068] A fourth transistor T4 is used to initialize the gate electrode G1 of the driving transistor T1 and the second storage electrode E2 of the storage capacitor Cst. The gate electrode G4 of the fourth transistor T4 is connected to the previous scan line 151a, and the first electrode S4 of the fourth transistor T4 is connected to the initialization voltage line 127. The second electrode D4 of the fourth transistor T4 is connected to the second storage electrode E2 of the storage capacitor Cst and the gate electrode G1 of the driving transistor T1 via the second electrode D3 of the third transistor T3. The fourth transistor T4 transmits the initialization voltage Vint to the gate electrode G1 of the driving transistor T1 and the second storage electrode E2 of the storage capacitor Cst according to the previous scan signal SL(n-1) received via the previous scan line 151a. Therefore, the gate voltage of the gate electrode G1 of the driving transistor T1 and the storage capacitor Cst are initialized. The initialization voltage Vint can have a low voltage value and can be a voltage capable of turning on the driving transistor T1.

[0069] The fifth transistor T5 is used to transmit the drive voltage ELVDD to the drive transistor T1. The gate electrode G5 of the fifth transistor T5 is connected to the light-emitting control line 155, and the first electrode S5 of the fifth transistor T5 is connected to the drive voltage line 172. The second electrode D5 of the fifth transistor T5 is connected to the first electrode S1 of the drive transistor T1.

[0070] The sixth transistor T6 is used to transfer the drive current Id output from the driving transistor T1 to the light-emitting diode (LED). The gate electrode G6 of the sixth transistor T6 is connected to the light-emitting control line 155, and the first electrode S6 of the sixth transistor T6 is connected to the second electrode D1 of the driving transistor T1. The second electrode D6 of the sixth transistor T6 is connected to the anode of the LED.

[0071] The fifth transistor T5 and the sixth transistor T6 are simultaneously turned on according to the light-emitting control signal EMn transmitted through the light-emitting control line 155. If the driving voltage ELVDD is applied to the first electrode S1 of the driving transistor T1 through the fifth transistor T5, the driving transistor T1 outputs a driving current Id according to the voltage of its gate electrode G1 (i.e., the voltage of the second storage electrode E2 of the storage capacitor Cst). The output driving current Id is transmitted to the light-emitting diode LED through the sixth transistor T6. When the current I... led When the current flows to the LED, the LED lights up.

[0072] The seventh transistor T7 is used to initialize the anode of the light-emitting diode (LED). The gate electrode G7 of the seventh transistor T7 is connected to the bypass control line 154, the first electrode S7 of the seventh transistor T7 is connected to the anode of the LED, and the second electrode D7 of the seventh transistor T7 is connected to the initialization voltage line 127. In one embodiment, the bypass control line 154 may be connected to the previous scan line 151a, and the bypass signal GB may be applied with the same timing as the previous scan signal SL(n-1). However, in another embodiment, the bypass control line 154 is not connected to the previous scan line 151a and may transmit a signal separate from the previous scan signal SL(n-1). When the seventh transistor T7 is turned on according to the bypass signal GB, the initialization voltage Vint is applied to the anode of the LED to be initialized.

[0073] The first storage electrode E1 of the storage capacitor Cst is connected to the drive voltage line 172, and the second storage electrode E2 is connected to the gate electrode G1 of the drive transistor T1, the second electrode D3 of the third transistor T3, and the second electrode D4 of the fourth transistor T4. Therefore, the second storage electrode E2 determines the voltage of the gate electrode G1 of the drive transistor T1, and the data voltage DLm is applied through the second electrode D3 of the third transistor T3, or the initialization voltage Vint is applied through the second electrode D4 of the fourth transistor T4.

[0074] On the other hand, the anode of the light-emitting diode (LED) is connected to the second electrode D6 of the sixth transistor T6 and the first electrode S7 of the seventh transistor T7, and the cathode of the LED is connected to the common voltage line 741 that transmits the common voltage ELVSS.

[0075] Previously, it was described that a pixel PX includes seven transistors T1, T2, T3, T4, T5, T6 and T7 and a storage capacitor Cst, but it is not limited thereto, and the number of transistors, the number of capacitors and their connection relationships can be changed differently.

[0076] Next, refer to the following: Figure 3 The light emission cycle controller 25 of the display device according to the example embodiment is further described.

[0077] Figure 3 This is a block diagram illustrating a light emission cycle controller for a display device according to an example embodiment.

[0078] like Figure 3 As shown, the light emission cycle controller 25 of the display device according to the example embodiment may include a drive frequency receiving unit 251 for receiving a drive frequency, a desired brightness receiving unit 253 for receiving desired brightness, a duty cycle determining unit 255 for determining the turn-on / turn-off duty cycle of the light emission control signal, and a light emission cycle determining unit 257 for determining the light emission cycle.

[0079] The drive frequency receiving unit 251 can receive the drive frequency determined in the timing controller 20. The drive frequency is the number of images that can be displayed per second. In this case, an image refers to a frame of images, and the drive frequency is also called the frame rate. For example, the display device according to the example embodiment can be driven at a drive frequency of 60Hz. That is, a moving image can be represented by sequentially outputting 60 images per second. As another example, the display device according to the example embodiment can be driven at a drive frequency of 120Hz. That is, 120 images can be sequentially output per second to play a moving image. When the drive frequency is increased in this way, each movement of the moving image appears smoother and more natural to the user, and the drive voltage can be increased for faster driving. The drive frequency can be driven in various ways, such as 60Hz, 90Hz, 120Hz, and 240Hz, as needed. The drive frequency receiving unit 251 can receive information about this drive frequency.

[0080] The desired brightness receiving unit 253 receives information about the desired brightness of the screen from an external source (not shown herein). The desired brightness, representing the apparent brightness of the screen of the display device, can refer to, for example, the maximum brightness value required to display one frame of the screen. In dark places, setting the desired brightness of the screen to low is advantageous in terms of power consumption, while in bright places, setting the desired brightness of the screen to high is advantageous in terms of visibility. Therefore, the user can set the desired brightness as needed, and the desired brightness receiving unit 253 can receive information about this. For example, the maximum brightness can be set to a level of 400 nits, and the maximum brightness can be set to a level of 50 nits. In this case, even if the user does not set the desired brightness, it can be set to change automatically. For example, by detecting external light via a separate light sensor, when the amount of light to be detected is large, the desired brightness can be automatically increased by identifying it as a bright area. Conversely, when the amount of light to be detected is small, the desired brightness can be automatically decreased by identifying it as a dark area.

[0081] The duty cycle determination unit 255 can determine the turn-on / turn-off duty cycle of the light emission control signal by receiving information about the desired brightness from the desired brightness receiving unit 253. Based on the light emission control signal, the current I... led Light is emitted by a light-emitting diode (LED). The section in which light is emitted is called the light-emitting section, and the length of the light-emitting section is determined according to the light-emitting control signal. In this case, the grayscale of the display can be controlled by adjusting the gating / off duty cycle of the light-emitting control signal. The grayscale of the display can be determined by the total amount of brightness emitted during the light-emitting section. When the same data voltage is applied, a higher gating duty cycle of the light-emitting control signal results in a longer light-emitting section and an increased amount of light emitted during a light-emitting section, thus increasing the grayscale of the display. Conversely, when the same data voltage is applied, a higher off duty cycle of the light-emitting control signal results in a shorter light-emitting section and a decreased amount of light emitted during a light-emitting section, thus decreasing the grayscale of the display. Therefore, when the desired brightness received from the desired brightness receiving unit 253 is high, the off duty cycle of the light-emitting control signal can be set relatively low. In this case, the gating duty cycle of the light-emitting control signal can be set relatively high. Conversely, when the desired brightness received from the desired brightness receiving unit 253 is low, the off duty cycle of the light-emitting control signal can be set relatively high. In this case, the gating duty cycle of the light emission control signal can be set to a relatively low value.

[0082] The emission period determination unit 257 can receive information about the driving frequency from the driving frequency receiving unit 251, and determine the emission period by receiving information about the required brightness and the off duty cycle of the emission control signal from the duty cycle determination unit 255. The emission period refers to the number of times the emission control signal is turned on / off within one frame.

[0083] When the off duty cycle of the light emission control signal is set high, the display time in black becomes longer, and the user's eye perceives the cyclical repetition of the light-emitting / non-light-emitting segments, which can manifest as flickering. In the display device according to the example embodiment, to prevent such flickering from being visually detected, it can be driven such that the gating / off state of the light emission control signal is repeated several times within a frame when flickering is expected. For example, it can be driven such that the gating / off state of the light emission control signal is repeated twice within a frame. Alternatively, it can be driven such that the gating / off state of the light emission control signal is repeated four or six times within a frame. In this way, when the gating / off state of the light emission control signal is repeated several times, step blurring may occur and the driving voltage may increase. Therefore, in the display device according to the example embodiment, if flicker is not expected to be detected, the light emission control signal is driven such that the gating / off state of the light emission control signal is not repeated within a frame, and if flicker is expected to be visually detected, the light emission control signal can be driven such that the gating / off state of the light emission control signal is repeated at least two or more times within a frame. That is, the light emission period determination unit 257 can determine whether to repeatedly drive the gating / off state of the light emission control signal by predicting whether flicker occurs based on information about the driving frequency, desired brightness, and the off duty cycle of the light emission control signal. In this case, the light emission period determination unit 257 may include a lookup table (LUT). The lookup table may store information about a minimum light emission period in which flicker is not visually detected based on the driving frequency, desired brightness, and the off duty cycle of the light emission control signal. The light emission period determination unit 257 can use the lookup table from the information about the input driving frequency, desired brightness, and the off duty cycle of the light emission control signal to determine the minimum light emission period in which flicker may not occur. Therefore, by selectively controlling the emission period of the emission control signal instead of fixing it to one or several times, flickering can be prevented and the occurrence of step blurring or the increase of driving voltage can be minimized.

[0084] In the following text, see references Figure 4 Various light emission control signals of a display device according to an example embodiment are described based on variations in the turn-on / turn-off duty cycle and the light emission period.

[0085] Figure 4This is a waveform diagram illustrating various light emission control signals of a display device according to an example embodiment. The waveform at the top is the vertical synchronization signal Vsync, and five light emission control signals are shown sequentially below the vertical synchronization signal Vsync.

[0086] like Figure 4 As shown, the display device according to the example embodiment can be driven at 60Hz. A vertical synchronization signal Vsync is applied and a light emission control signal is applied. At this time, the off voltage of the light emission control signal can be applied first, and then the gating voltage can be applied.

[0087] In the case of the first emission control signal (1 cycle, 0.2%), a turn-off voltage and a gating voltage are applied within one frame. In this case, the turn-off duty cycle can be approximately 0.2%, and the gating duty cycle can be approximately 99.8%.

[0088] In the case of the second emission control signal (2 cycles, 25%), two turn-off voltages and two gating voltages are applied within one frame. They can be applied in the order of turn-off voltage-gating voltage-turn-off voltage-gating voltage. In this case, considering the entire time when the turn-off voltage is applied, the turn-off duty cycle is approximately 25%. Conversely, considering the entire time when the gating voltage is applied, the gating duty cycle is approximately 75%. In the case of the second emission control signal (2 cycles, 25%), compared to the first emission control signal (1 cycle, 0.2%), the turn-off duty cycle is increased and the emission cycle is increased. In the second emission control signal (2 cycles, 25%), lower brightness can be achieved by increasing the turn-off duty cycle. Furthermore, by increasing the emission cycle, it can be seen that the effect of driving at 120Hz occurs by essentially causing emission to occur twice within one frame.

[0089] In the case of the third emission control signal (2 cycles, 50%), two turn-off voltages and two gating voltages are applied within one frame. They can be applied in the order of turn-off voltage-gating voltage-turn-off voltage-gating voltage. In this case, considering the entire time the turn-off voltage is applied, the turn-off duty cycle is approximately 50%. Similarly, considering the entire time the gating voltage is applied, the gating duty cycle is approximately 50%. In the case of the third emission control signal (2 cycles, 50%), compared to the second emission control signal (2 cycles, 25%), the turn-off duty cycle is increased while the emission cycle remains the same. In the third emission control signal (2 cycles, 50%), lower brightness can be achieved by increasing the turn-off duty cycle. Furthermore, it can be seen that the effect of driving at 120Hz is achieved by essentially emitting light twice within one frame.

[0090] In the case of the fourth emission control signal (4 cycles, 25%), four turn-off voltages and four gating voltages are applied within one frame. They can be applied in the order of turn-off voltage-gating voltage-turn-off voltage-gating voltage-turn-off voltage-gating voltage-turn-off voltage-gating voltage. In this case, considering the entire time the turn-off voltage is applied, the turn-off duty cycle is approximately 25%. Additionally, considering the entire time the gating voltage is applied, the gating duty cycle is approximately 75%. In the case of the fourth emission control signal (4 cycles, 25%), compared to the first emission control signal (1 cycle, 0.2%), the turn-off duty cycle and emission cycle are increased. In the fourth emission control signal (4 cycles, 25%), lower brightness can be achieved by increasing the turn-off duty cycle. Furthermore, by increasing the emission cycle, it can be seen that the effect of driving at 240Hz is achieved by emitting light approximately four times within one frame.

[0091] In the case of the fifth emission control signal (4 cycles, 50%), four turn-off voltages and four gating voltages are applied within one frame. These can be applied in the following order: turn-off voltage, gating voltage, turn-off voltage, gating voltage, turn-off voltage, gating voltage, turn-off voltage, and gating voltage. In this case, considering the entire time the turn-off voltage is applied, the turn-off duty cycle is approximately 50%. Similarly, considering the entire time the gating voltage is applied, the gating duty cycle is approximately 50%. In the case of the fifth emission control signal (4 cycles, 50%), compared to the fourth emission control signal (4 cycles, 25%), the turn-off duty cycle is increased while the emission cycle remains the same. In the fifth emission control signal (4 cycles, 50%), lower brightness can be achieved by increasing the turn-off duty cycle. Furthermore, it can be seen that the effect of driving at 240Hz is achieved by emitting light approximately four times per frame.

[0092] In a display device according to an example embodiment, a light emission cycle controller determines the turn-on / turn-off duty cycle and light emission cycle of the light emission control signal and transmits them to the light emission driver so that various light emission control signals can be output.

[0093] Hereinafter, an example is described of determining the off duty cycle of the light emission control signal based on the desired brightness of the display device according to an example embodiment.

[0094] Figure 5 It is a graph showing the basic brightness of the display device according to the example embodiment and the off duty cycle of the light emission control signal for the desired brightness.

[0095] like Figure 5As shown, in the case of No. 1 on the far left, the desired brightness of the display device according to the example embodiment can be set to approximately 350 nits. In this case, the desired brightness of approximately 350 nits can be achieved by setting the basic brightness to approximately 350 nits and setting the off duty cycle of the light emission control signal to approximately 0%. Desired brightness refers to the actual brightness output on the screen, and basic brightness refers to the maximum brightness that can be represented by the voltage supplied to the pixels. Even if the same basic brightness voltage is supplied, the actual brightness output to the screen can be adjusted by adjusting the off duty cycle.

[0096] For sections No.1 to No.7, the required brightness can be reduced from approximately 350 nits to approximately 250 nits. At this point, while keeping the off duty cycle at approximately 0%, the required brightness can be achieved from approximately 350 nits to approximately 250 nits by reducing the base brightness from approximately 350 nits to approximately 250 nits.

[0097] In the section from No.7 to No.13, the required brightness can be reduced from approximately 250 nits to approximately 150 nits. At this point, while keeping the basic brightness at approximately 250 nits, the required brightness of approximately 250 nits to approximately 150 nits can be achieved by increasing the off duty cycle from approximately 0% to approximately 40%.

[0098] For the sections from No.13 to No.30, the required brightness can be reduced from approximately 150 nits to approximately 70 nits. At this point, while keeping the off duty cycle at approximately 40%, the required brightness of approximately 150 nits to approximately 70 nits can be achieved by reducing the base brightness from approximately 250 nits to approximately 120 nits.

[0099] For the section from No.30 to No.61, the required brightness can be reduced from approximately 70 nits to approximately 0 nits. At this point, the required brightness of approximately 70 nits to approximately 0 nits can be achieved by increasing the off duty cycle from approximately 40% to approximately 100% while maintaining the basic brightness at approximately 120 nits.

[0100] The preceding text has described examples of methods for adjusting the base brightness and the off duty cycle to achieve the desired brightness, but is not limited to these examples. As described above, the desired brightness can be achieved by maintaining the base brightness while changing the off duty cycle in some sections, and by maintaining the off duty cycle while changing the base brightness in some sections. In this case, the section settings can be changed differently. Furthermore, the values ​​of the base brightness and the off duty cycle used to achieve the desired brightness can be changed differently.

[0101] In the following text, see references Figure 6 , Figure 7and Figure 8 The description is based on a composite flicker index that takes into account driving frequency, brightness, off duty cycle, and emission period.

[0102] Figure 6 This is a graph showing the composite flicker index based on driving frequency and brightness. Figure 6 In this system, the off duty cycle is fixed at 40%, and there is a single emission cycle. Figure 7 and Figure 8 This is a graph showing the composite flicker index based on the off duty cycle and brightness. Figure 7 In this system, the driving frequency is fixed at 90Hz, and there exists one emission cycle. Figure 8 In this system, the driving frequency is fixed at 120Hz, and there is one emission cycle.

[0103] The composite flicker index is a numerical value indicating the degree of flickering. It reflects the sensitivity to frequency components after the optical waveform has been extracted and converted into frequency components. A higher composite flicker index indicates a greater likelihood of flickering. If the composite flicker index is less than 1, flickering is not detected and can be ignored.

[0104] like Figure 6 As shown, with the off duty cycle and emission period fixed, the composite flicker index tends to decrease as the driving frequency increases when the same brightness is achieved. For example, at a brightness of approximately 50 nits, if the driving frequency is 75 Hz or higher, the composite flicker index is 1 or lower. Furthermore, at a brightness of approximately 100 nits, if the driving frequency is 80 Hz or higher, the composite flicker index is 1 or lower. Additionally, at a brightness of approximately 250 nits, if the driving frequency is 85 Hz or higher, the composite flicker index is 1 or lower. Moreover, at a brightness of approximately 400 nits, if the driving frequency is 90 Hz or higher, the composite flicker index is 1 or lower.

[0105] Furthermore, with the off-duty cycle and emission period fixed, the composite flicker index tends to decrease as the brightness decreases at the same driving frequency. For example, at a driving frequency of 75 Hz, if the brightness is approximately 50 nits or less, the composite flicker index is 1 or less. Similarly, at a driving frequency of 80 Hz, if the brightness is approximately 100 nits or less, the composite flicker index is 1 or less. Furthermore, at a driving frequency of 85 Hz, if the brightness is 250 nits or less, the composite flicker index is 1 or less. Moreover, at a driving frequency of 90 Hz, if the brightness is approximately 400 nits or less, the composite flicker index is 1 or less. At driving frequencies above 90 Hz, the composite flicker index can be 1 or less regardless of the brightness.

[0106] like Figure 7 As shown, with the driving frequency and emission period fixed, the composite flicker index tends to decrease as the off-duty cycle decreases when the same brightness is achieved. For example, at a brightness of approximately 400 nits, and if the off-duty cycle is approximately 50% or less, the composite flicker index is 1 or less. Furthermore, at a brightness of approximately 250 nits, and if the off-duty cycle is approximately 65% ​​or less, the composite flicker index is 1 or less. Moreover, at a brightness of approximately 100 nits or less, the composite flicker index can be 1 or less regardless of the off-duty cycle.

[0107] Furthermore, with the driving frequency and emission period fixed, the composite flicker index tends to decrease as brightness decreases when the same off-duty cycle is achieved. For example, at an off-duty cycle of approximately 80%, and if the brightness is approximately 100 nits or less, the composite flicker index is 1 or less. Additionally, at an off-duty cycle of approximately 60%, and if the brightness is approximately 250 nits or less, the composite flicker index is 1 or less. Moreover, when the off-duty cycle is less than approximately 40%, the composite flicker index can be 1 or less regardless of the brightness.

[0108] like Figure 8 As shown, with the driving frequency and emission period fixed, the composite flicker index tends to decrease as the off-duty cycle decreases when the same brightness is achieved. Furthermore, with the driving frequency and emission period fixed, the composite flicker index tends to decrease as the brightness decreases when the same off-duty cycle is obtained. Figure 8 With a driving frequency of 120Hz, the composite flicker index varies depending on the off duty cycle and brightness, but all composite flicker indices are found to be below 1. Therefore, at a driving frequency of 120Hz, flicker is not visually perceptible.

[0109] according to Figure 6 , Figure 7 and Figure 8The graph analysis shows that when the composite flicker index is below 1, flicker is not visually perceptible, thus allowing for one emission cycle. Conversely, when the composite flicker index is above 1, flicker is visually perceptible, allowing for two or more emission cycles. For example, at a drive frequency of 120Hz, the composite flicker index is below 1 regardless of brightness and duty cycle, so one emission cycle can be performed. Even at a drive frequency of 100Hz, the composite flicker index is below 1 regardless of brightness and duty cycle, so one emission cycle can be performed. At a drive frequency of 90Hz, the composite flicker index is below 1 regardless of the duty cycle at low brightness levels (below 100 nits), so one emission cycle can be performed. At a driving frequency of 90 Hz, with a brightness of 250 nits or more, and a low duty cycle, one emission cycle can exist because the composite flicker index is less than 1. At a high duty cycle, with a composite flicker index greater than 1, two or more emission cycles can exist. At a driving frequency of 90 Hz and a brightness of 400 nits, one emission cycle can exist if the duty cycle is less than 50%, and six emission cycles can exist if the duty cycle exceeds 50%.

[0110] Considering the number of such cases, the number of emission cycles in which the composite flicker index can be less than 1 depending on the driving frequency, desired brightness, and off-duty cycle can be configured as a lookup table. That is, if the information of the driving frequency, desired brightness, and off-duty cycle is input, the number of emission cycles can be determined. Therefore, the determined information of the emission cycles, together with the information of the off-duty cycle, is transmitted to the light-emitting driver, thereby outputting a light-emitting control signal.

[0111] In the following text, see references Figure 9 A driving method for a display device according to an example embodiment is described.

[0112] Figure 9 This is a flowchart illustrating a driving method for a display device according to an example embodiment.

[0113] like Figure 9 As shown, firstly, in step S1100, the display device according to the example embodiment receives a driving frequency. The driving frequency receiving unit of the light emission cycle controller of the display device according to the example embodiment can receive the driving frequency of the display device. For example, the driving frequency can be 60Hz, 90Hz, or 120Hz.

[0114] Next, in step S1200, the desired brightness receiving unit of the light emission cycle controller can receive the desired brightness. For example, the desired brightness can be approximately 400 nits, 250 nits, 100 nits, or 50 nits, etc.

[0115] At step S1300, the duty cycle determination unit of the light emission cycle controller can receive information about the desired brightness to determine the off duty cycle of the light emission control signal. For example, the off duty cycle can be approximately 0%, 20%, 40%, 60%, or 80%, etc. When the desired brightness is 400 nits, the off duty cycle can be approximately 0%, and when the desired brightness is 150 nits, the off duty cycle can be approximately 40%. The lower the desired brightness, the higher the off duty cycle can be set. However, this is just an example, and the value of the off duty cycle can be changed differently depending on the desired brightness. The desired brightness can be achieved by adjusting the basic brightness and the off duty cycle. Specifically, it is advantageous to achieve the desired brightness by increasing the off duty cycle in the low brightness range.

[0116] In step S1400, the light emission cycle determination unit of the light emission cycle controller can receive information on the driving frequency, the required brightness, and the off-duty cycle of the light emission control signal to determine the light emission cycle. For example, at a driving frequency of 120Hz, one light emission cycle can exist regardless of the required brightness and the off-duty cycle. At a driving frequency of 90Hz, a required brightness of 400 nits, and an off-duty cycle of 0%, one light emission cycle can exist. At a driving frequency of 90Hz, a required brightness of 400 nits, and an off-duty cycle of 60%, six light emission cycles can exist.

[0117] In step S1500, the light emission period controller can output information about the determined light emission period. The light emission period controller can transmit the determined light emission period and off duty cycle information to the light emission driver. The light emission driver can output a light emission control signal to the pixel unit according to the transmitted information.

[0118] The following references are provided below. Figure 10 The steps for determining the emission period are further described (S1400).

[0119] Figure 10 This is a flowchart illustrating the steps of a driving method for a display device according to an example embodiment. Figure 10 The steps for determining the emission period are shown.

[0120] like Figure 10As shown, in step S1410, the light emission cycle determination unit of the light emission cycle controller compares the driving frequency with the reference frequency. In step S1420, when the driving frequency is greater than or equal to the reference frequency, the number of light emission cycles can be determined to be one. For example, when the driving frequency is above 100Hz, since flickering is not visually perceptible regardless of the required brightness and the off-duty cycle, one light emission cycle can exist. That is, when the reference frequency is determined to be 100Hz and the driving frequency is above 100Hz, one light emission cycle can exist regardless of the required brightness and the off-duty cycle information. If the driving frequency is less than 100Hz, the next step can be performed. In this case, the reference frequency has been described as 100Hz; however, this is only an example, and the reference frequency can be changed differently.

[0121] Then, at step S1430, the desired brightness is compared with the reference brightness. When the desired brightness is less than the reference brightness, the number of light emission cycles can be determined as shown in step S1420. At this time, the reference brightness can be changed according to the driving frequency. For example, at a driving frequency of 90 Hz, the reference brightness can be 150 nits. When the driving frequency is 90 Hz and the desired brightness is less than 150 nits, the number of light emission cycles can be determined as one. When the driving frequency is 90 Hz and the desired brightness is 150 nits or more, the next step can be performed. At this time, at a driving frequency of 90 Hz, the reference brightness is described as 150 nits, but this is only an example, and the reference brightness can be changed differently. Furthermore, the reference brightness can be set differently for each driving frequency.

[0122] Next, in step S1440, when the driving frequency is less than the reference frequency and the required brightness is greater than the reference brightness, the number of emission cycles can be determined by referring to a lookup table. The lookup table may include information on the minimum emission cycle in which the composite flicker index is less than 1 based on the driving frequency, the required brightness, and the off duty cycle. That is, information on the minimum emission cycle that can prevent flicker from being visually detected can be derived from the lookup table.

[0123] The information about the emission period can be output through this process.

[0124] According to the driving method of the display device according to the example embodiment, the number of light emission cycles of the light emission control signal can be selectively adjusted instead of being fixed. In the driving method of the display device according to the example embodiment, when flicker is not expected to be visually recognized, the number of light emission cycles is determined and driven to one, and when flicker is expected to be visually recognized, the number of light emission cycles can be determined and driven to two or more. As described above, by selectively controlling and driving the light emission cycle of the light emission control signal, flicker can be prevented compared to the case where the number of light emission cycles is fixed to be driven once. In addition, by selectively controlling and driving the light emission cycle of the light emission control signal, the occurrence of step blur can be minimized and the driving voltage can be reduced compared to the case where the number of light emission cycles is fixed to be driven several times (e.g., six times).

[0125] While this disclosure has been described in conjunction with exemplary embodiments now considered practical, it will be understood that this disclosure is not limited to the disclosed embodiments. Rather, this disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A display device, comprising: A pixel unit, comprising multiple pixels; The light-emitting driver outputs a light-emitting control signal with a different number of light-emitting cycles according to the driving frequency and the required brightness to the pixel unit; and A light emission cycle controller is configured to receive the driving frequency and the desired brightness to determine the off duty cycle of the light emission control signal to be output to the light emission driver and the number of light emission cycles. in, The emission cycle controller derives the number of emission cycles using a lookup table, and The lookup table stores information about the minimum number of light emission cycles, so that flickering is not visually detectable based on the driving frequency, the desired brightness, and the off duty cycle.

2. The display device according to claim 1, wherein, The light emission cycle controller includes: A drive frequency receiving unit receives the drive frequency; The required brightness receiving unit receives the required brightness; The duty cycle determination unit determines the off duty cycle of the light emission control signal; and The emission period determination unit determines the number of emission periods.

3. The display device according to claim 2, wherein, The duty cycle determination unit sets the off duty cycle higher when the required brightness is lower.

4. The display device according to claim 2 or 3, wherein, The light emission cycle determination unit determines the number of light emission cycles based on the driving frequency, the required brightness, and the off duty cycle.

5. The display device according to claim 4, wherein, When the driving frequency is above 100Hz, there is a light emission cycle.

6. The display device according to claim 4, wherein, When the driving frequency is 90Hz, If the required brightness is less than 150 nits, then there is one emission cycle, and If the required brightness is above 150 nits, then there is more than one emission cycle.

7. The display device according to claim 6, wherein, When the driving frequency is 90Hz and the required brightness is above 400 nits. If the off duty cycle is below 50%, then there is a light emission cycle, and If the shutdown duty cycle is greater than 50%, there are six emission cycles.

8. The display device according to claim 4, wherein, The pixel unit includes: Multiple scan lines, multiple data lines, and multiple light emission control lines are connected to each of the plurality of pixels, and The light emission control line transmits the light emission control signal from the light emission driver to the pixel unit.

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