This application claims priority to Korean Patent Application No. 10-2021-0045696, filed on Apr. 8, 2021, and all the benefits accruing therefrom under 35 U.S.C. § 119, the content of which in its entirety is herein incorporated by reference.
Embodiments of the invention relate to a pixel and a display apparatus including the pixel. More particularly, embodiments of the invention relate to a display apparatus operating in a variable frame period and a pixel included the display apparatus.
Generally, a display apparatus displays (or refreshes) image at a constant frame frequency. However, a frame frequency of rendering performed by a host processor, e.g. a graphic processing unit (“GPU”), may not match a frame frequency of the display apparatus. In particular, when the host processor provides input image data for game image generated by a complex rendering to the display apparatus, such a mismatch of a frame frequency may be intensified. Also, a tearing phenomenon in which a boundary line is generated in image displayed on the display apparatus may be caused by the mismatch of the frame frequency.
To prevent such the tearing phenomenon, a technology in which a host processor provides input image data to a display apparatus at a variable frame frequency by changing a blank period per frame has been developed. The display apparatus may prevent the tearing phenomenon by displaying (or refreshing) image in synchronization with variable frame frequency.
In a case where an image is displayed on a display apparatus in synchronization with variable frame frequency, when a low grayscale image is displayed on a display panel, a luminance difference may be generated between a variable frame period and a basic frame period by a delay of an on-slew of a light emitting element, and thus a flicker may occur.
Embodiments of the invention provide a display apparatus which reduces or prevents a luminance difference between a basic frame period and a variable frame period.
Embodiments of the invention also provide a pixel which adjusts reduces or prevents a luminance difference between a basic frame period and a variable frame period.
In an embodiment of a pixel according to the invention, the pixel includes a capacitor, a first transistor, a second transistor, a third transistor, a forth transistor, and a light emitting element. In such an embodiment, the capacitor includes a first electrode and a second electrode. In such an embodiment, the first transistor generates a driving current, the second transistor applies a data voltage to the first electrode of the capacitor, the third transistor applies an initialization voltage to the second electrode of the capacitor, and the fourth transistor generates a leakage current in response to a dimming signal. In such an embodiment, the light emitting element emits light based on a residual driving current, and the residual driving current is obtained by subtracting the leakage current from the driving current.
In an embodiment, the pixel may further include a resistance element connected to the fourth transistor and having a fixed resistance.
In an embodiment, a sum of a turn-on resistance of the fourth transistor and the fixed resistance of the resistance element may be greater than a saturation resistance of the light emitting element.
In an embodiment, the dimming signal may be not activated in a basic frame period, and the dimming signal may be activated in a variable frame period.
In an embodiment, the dimming signal in the variable frame period may be activated at a same timing as an activation timing of a gate signal in the basic frame period.
In an embodiment, an activation of the dimming signal may be started in a blank period of the variable frame period.
In an embodiment, a length of an activation period of the dimming signal may be determined by a characteristic of the pixel.
In an embodiment, a voltage level of the dimming signal may be gradually changed during an activation period of the dimming signal.
In an embodiment, the voltage level of the dimming signal may be increased with time during the activation period of the dimming signal.
In an embodiment of a display apparatus according to the invention, the display apparatus includes a display panel, and a display panel driver. In such an embodiment, the display panel includes a plurality of pixels, and the display panel driver applies a gate signal and a dimming signal to the pixels. In such an embodiment, each of the pixels includes a capacitor, a first transistor, a second transistor, a third transistor, a forth transistor, and a light emitting element. In such an embodiment, the capacitor includes a first electrode and a second electrode. In such an embodiment, the first transistor generates a driving current, the second transistor applies a data voltage to the first electrode of the capacitor, the third transistor applies an initialization voltage to the second electrode of the capacitor, and the fourth transistor generates a leakage current in response to the dimming signal. In such an embodiment, the light emitting element emits light based on a residual driving current and the residual driving current is obtained by subtracting the leakage current from the driving current.
In an embodiment, each of the pixels may further include a resistance element connected to the fourth transistor and having a fixed resistance.
In an embodiment, a sum of a turn-on resistance of the fourth transistor and the fixed resistance of the resistance element may be greater than a saturation resistance of the light emitting element.
In an embodiment, the dimming signal may be not activated in a basic frame period, and the dimming signal may be activated in a variable frame period.
In an embodiment, the dimming signal in the variable frame period may be activated at a same timing as an activation timing of the gate signal in the basic frame period.
In an embodiment, a length of an activation period of the dimming signal may be determined by a characteristic of the pixel.
In an embodiment, a voltage level of the dimming signal may be gradually changed during an activation period of the dimming signal.
In an embodiment, the voltage level of the dimming signal may be increased with time during the activation period of the dimming signal.
In an embodiment, an activation of the dimming signal may be started in a blank period of the variable frame period.
In an embodiment, the display panel driver may sequentially apply the dimming signal to the pixels on a row-by-row basis.
In an embodiment, the display panel driver may simultaneously apply the dimming signal to all of the pixels.
In embodiments of the invention, the pixel and the display apparatus including the pixel may prevent a luminance difference generated by a difference of a length of a blank period between a variable frame period and a basic frame period by controlling a leakage current of a driving current flowing into the light emitting element in the variable frame period, thereby improving image quality.
The above and other features of the invention will become more apparent by describing in detailed embodiments thereof with reference to the accompanying drawings, in which:
The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. This invention may, however, be embodied in many different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.
It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.
It will be understood that, although the terms “first,” “second,” “third” etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, “a first element,” “component,” “region,” “layer” or “section” discussed below could be termed a second element, component, region, layer or section without departing from the teachings herein.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, “a”, “an,” “the,” and “at least one” do not denote a limitation of quantity, and are intended to include both the singular and plural, unless the context clearly indicates otherwise. For example, “an element” has the same meaning as “at least one element,” unless the context clearly indicates otherwise. “At least one” is not to be construed as limiting “a” or “an.” “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.
Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element's relationship to another element as illustrated in the Figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on “upper” sides of the other elements. The term “lower,” can therefore, encompasses both an orientation of “lower” and “upper,” depending on the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The terms “below” or “beneath” can, therefore, encompass both an orientation of above and below.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings.
Referring to
In an embodiment, at least two selected from the driving controller 300, the gate driver 400, the data driver 500, and the power voltage generator 600 may be integrated into a single chip.
In an embodiment, the display panel 100 may be an organic light emitting diode display panel including an organic light emitting diode. In one embodiment, for example, the display panel 100 may be a quantum-dot organic light emitting diode display panel including an organic light emitting diode and a quantum-dot color filter. Alternatively, the display panel 100 may be a liquid crystal display panel including a liquid crystal layer.
The display panel 100 may include a plurality of gate lines GL, a plurality of data lines DL and a plurality of pixels P electrically connected to the gate lines GL and the data lines DL. The gate lines GL may extend in a first direction D1 and the data lines DL may extend in a second direction D2 crossing the first direction D1.
The driving controller 300 may receive input image data IMG and an input control signal CONT from a host processor, e.g. graphic processing unit (“GPU”). In one embodiment, for example, the input image data IMG may include red image data, green image data and blue image data. The input image data IMG may further include white image data. In an alternative embodiment, the input image data IMG may include magenta image data, yellow image data and cyan image data. In one embodiment, for example, the input control signal CONT may include a master clock signal and a data enable signal. The input control signal CONT may further include a vertical synchronizing signal and a horizontal synchronizing signal.
The driving controller 300 may generate a first control signal CONT1, a second control signal CONT2, a third control signal CONT3, and a data signal DATA based on the input image data IMG and the input control signal CONT.
The driving controller 300 may generate the first control signal CONT1 for controlling an operation of the gate driver 400 based on the input control signal CONT, and outputs the first control signal CONT1 to the gate driver 400. The first control signal CONT1 may include a vertical start signal, a gate clock signal, and a dimming signal DIM (or a driving current leakage control signal).
The driving controller 300 may generate the second control signal CONT2 for controlling an operation of the data driver 500 based on the input control signal CONT, and output the second control signal CONT2 to the data driver 500. The second control signal CONT2 may include a horizontal start signal and a load signal.
The driving controller 300 may generate the data signal DATA based on the input image data IMG. The driving controller 300 may output the data signal DATA to the data driver 500.
The gate driver 400 generates gate signals SC and SS (see in
The data driver 500 may receive the second control signal CONT2 and the data signal DATA from the driving controller 300. The data driver 500 may convert the image data into a data voltage DV (see in
The power voltage generator 600 may generate power voltages ELVDD and ELVSS and provide the power voltages ELVDD and ELVSS to the display panel 100. In one embodiment, for example, the power voltage generator 600 may apply a first power voltage ELVDD and a second power voltage ELVSS to the pixel P including a light emitting element EL (see in
The power voltage generator 600 may receive a third control signal CONT3 for adjusting the level of the power voltages ELVDD and ELVSS from the driving controller 300. The power voltage generator 600 may generate the power voltages ELVDD and ELVSS based on the third control signal CONT3.
Referring to
One frame may be divided into an active period AP and a blank period BP (shown in
In the active period AP, a first gate signal SC and a second gate signal SS may be activated. When the first gate signal SC is activated, the second transistor T2 may be turned on. When the second transistor T2 is turned on, the data voltage DV may be applied to the first electrode N1. When the second gate signal SS is activated, the third transistor T3 may be turned on. When the third transistor T3 is turned on, the initialization voltage Vinit may be applied to the second electrode N2. The initialization voltage Vinit may be maintained in the second electrode N2 during an activation period of the second gate signal SS. When the initialization voltage Vinit is applied to the anode electrode of the light emitting element EL, the light emitting element EL may not emit light. When the first gate signal SC and the second gate signal SS are deactivated, the light emitting element EL may emit light based on the residual driving current LDC. In the blank period BP, the first gate signal SC and the second gate signal SS may be deactivated.
Referring to
The length of the blank period BP may be changed to match a frame frequency of a rendering performed by the host processor (e.g. graphic processing unit “GPU”) and a frame frequency of the display apparatus 1000 (see in
While the gate signals SC and SS are activated, the light emitting element EL (see in
Referring to
The dimming signal DIM may not include an activation period HP in the basic frame period BF. The dimming signal DIM may include the activation period HP and a deactivation period LP in the blank period BP of the variable frame period CF. The dimming signal DIM may start the activation period HP only in the blank period BP of the variable frame period CF. In the activation period HP of the dimming signal DIM, the driving current DC may be leaked.
In a case where there is no delay time until the light emitting element EL (see in
Referring to
In an embodiment of the pixel P (see in
When a low grayscale image is displayed on the display panel 100 (see in
In one embodiment, for example, when the sum of the turn-on resistance of the fourth transistor T4 (see in
Referring to
The turn-on resistance of the fourth transistor T4 (see in
Referring to
Referring to
According to an embodiment, since the data voltage DV (see in
Embodiments of the invention may be applied any electronic device including the display apparatus that changes the frame frequency by changing the blank period. In one embodiment, for example, the inventions may be applied to a television (“TV”), a digital TV, a three-dimensional (“3D”) TV, a mobile phone, a smart phone, a tablet computer, a virtual reality (“VR”) device, a wearable electronic device, a personal computer (“PC”), a home appliance, a laptop computer, a personal digital assistant (“PDA”), a portable multimedia player (“PMP”), a digital camera, a music player, a portable game console, a navigation device, etc.
The invention should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the invention to those skilled in the art.
While the invention has been particularly shown and described with reference to embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit or scope of the invention as defined by the following claims.
Number | Date | Country | Kind |
---|---|---|---|
10-2021-0045696 | Apr 2021 | KR | national |