Patent Application
20090051708
This application claims priority to Korean Application No. 10-2007-083328, filed on Aug. 20, 2007, and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which in its entirety are herein incorporated by reference.
1. Field of the Invention
The present invention relates to an active display device and a driving method for a pixel of an active display device. More particularly, the present invention relates to an active display device and a driving method for a pixel of an active display device having a decreased layout area and consumption current.
2. Description of the Related Art
Recently, active display devices such as active matrix organic lighting emitting diodes (“AMOLEDs”) are widely used for various electronic equipments. In the active display device, a pixel selected is driven to be illuminated for displaying an image data on a display panel. At this time, the illuminance is determined according to corresponding digital data.
Meanwhile, one of the conventional methods for driving the pixel is an ‘analog type driving method’. According to the analog type driving method, the selected pixel is illuminated with a constant illumination intensity during one unit frame period, as shown in
In the analog type driving method, the bit number to be converted is the same as the bit number of the digital data. For example, if the bit number of the digital data is 4, then 4 bits are required to be converted. Thus, 4 bit digital to analog conversion (“DAC”) is required for the analog type driving method.
In the analog type driving method, the bit number to be converted is increased as the bit number of the digital data is increased. Also, the layout area for DAC is increased as the number of the converted bits is increased. Furthermore, the consumption current for DAC is increased as the number of the converted bits is increased.
Accordingly, the present invention provides an active display device and a driving method for a pixel of an active display device which decreases the layout area and consumption current.
In accordance with exemplary embodiments of the present invention, a method of driving an active display device includes generating a digital data for a selected pixel, first driving the selected pixel to be illuminated with a first illumination intensity in a first illumination interval, and second driving the selected pixel to be illuminated with a second illumination intensity in a second illumination interval. The first and the second illumination intensity levels, and the first and the second illumination intervals are determined in a mapping table according to the digital data. The first illumination interval and the second illumination interval are included in one unit frame period. The length of the first illumination interval and the length of the second illumination interval are independent from the digital data. The relative ratio of the second illumination intensity to the first illumination intensity is changed according to a value of the digital data.
In accordance with exemplary embodiments of the present invention, the method of driving an active display device may include generating a digital data for a selected pixel, first driving the selected pixel to be illuminated with a first illumination intensity in a first illumination interval, and second driving the selected pixel to be illuminated with a second illumination intensity in a second illumination interval, wherein, the first illumination interval and the second illumination interval are included in one unit frame period, and for each of a plurality of different illuminating amounts of the selected pixel, a mapping table stores a first illumination intensity, a first illumination interval, a second illumination intensity, and a second illumination interval according to the digital data.
In accordance with other exemplary embodiments of the present invention an active display device includes a display panel and a driving circuit. The display panel includes a plurality of pixels. The driving circuit generates a digital data for a selected pixel, and drives the selected pixel to be illuminated with a first illumination intensity in a first illumination interval, and drives the selected pixel to be illuminated with a second illumination intensity in a second illumination interval. The first illumination intensity and the second illumination intensity are determined according to the digital data. The first illumination interval and the second illumination interval are included in one unit frame period. The length of the first illumination interval and the length of the second illumination interval are independent from the digital data. The relative ratio of the second illumination intensity to the first illumination intensity is changed according to a value of the digital data.
The above and other features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
‘Bloch's law’, also known as Bunsen-Roscoe law, tells about short time stimulation. According to ‘Bloch's law’, for short time-stimulation, if the product of stimulation intensity and stimulation time is the same, then there is little difference to the recognition human for stimulation. It may be expressed as 1×t=k, where 1 is the intensity of a flash or stimulation, t is its duration or stimulation time, and k is a constant.
Referring to
Thus, because the product, or constant k, is the same for both CASE 1 and CASE 2, a human cannot recognize the difference in stimulation between CASE 1 and CASE 2.
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. 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. In the drawings, the thickness of layers, films, and regions may be exaggerated for clarity.
It will be understood that when an element or layer is referred to as being “on”, “connected to” or “coupled to” another element or layer, it can be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It will be understood that, although the terms first, second, 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 of the present invention.
Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms, “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
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 invention 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 will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed descriptions may be omitted if it is determined that the detailed descriptions of related well-known functions and construction may make the gist of the present invention unclear.
Referring to
At step S120, the selected pixel is driven to be illuminated. At this time, the illumination intensity can be variable as more than two intensity levels among more than three selectable intensity levels in one unit frame period.
Step S120 includes a step S121 and a step S123. At step S121, the selected pixel is driven to be illuminated with a first illumination intensity in a first illumination interval. Herein, the first illumination intensity and the first illumination interval are determined according to the digital data with reference to a mapping table. But the length of the first illumination interval is independent from the digital data.
At step S123, the selected pixel is driven to be illuminated with a second illumination intensity in a second illumination interval. Herein, the second illumination intensity and the second illumination interval are determined according to the digital data with reference to the mapping table. But the length of the second illumination interval is independent from the digital data.
From
Also, the relative ratio of the second illumination intensity to the first illumination intensity is changed according to the value of the digital data. But the length of the first illumination interval EXP1 and the length of the second illumination interval EXP2 are independent from the digital data. So, according to the present invention, the number of the access time can be decreased.
In the example shown for the K-frame, the value of the digital data stands for (11/16), which means that the ratio of the corresponding illuminating amount to maximum illuminating amount is (11/16). And, in the example shown for the (K+1)-frame, the value of the digital data stands for (5/16), which means that the ratio of the corresponding illuminating amount to the maximum illuminating amount is (5/16).
In both cases of the K-frame and the (K+1)-frame, the selected pixel is illuminated with a first illumination intensity during the first illumination interval EXP1. And then, the selected pixel is illuminated with a second illumination intensity during the second illumination interval EXP2.
In the K-frame, the level of the first illumination intensity is (2/4) of the maximum intensity level, and the level of the second illumination intensity is (3/4) of the maximum intensity level. In the (K+1)-frame, the level of the first illumination intensity is (2/4) of the maximum intensity level, and the level of the second illumination intensity is (1/4) of the maximum intensity level.
In both cases of the K-frame and the (K+1)-frame, the first illumination interval EXP1 includes one unit time UT, and the second illumination interval EXP2 includes 3 unit times UT. That is, the length of the first illumination interval EXP1 and the length of the second illumination interval EXP2 are independent from the digital data.
Therefore, in the exemplary K-frame, the ratio of the corresponding illuminating amount to the maximum illuminating amount is (11/16), and 11 sectors are covered with the deviant lined area. That is to say, the ratio of the deviant lined area to the maximum area is (11/16), in the exemplary K-frame.
And, in the exemplary (K+1)-frame, the ratio of the corresponding illuminating amount to the maximum illuminating amount is (5/16), and 5 sectors are covered with the deviant lined area. That is to say, the ratio of the deviant lined area to the maximum area is (5/16), in the exemplary (K+1)-frame.
Meanwhile, the selected pixel is driven to be illuminated with the corresponding illumination intensity by only two times accesses. In other words, there are only two different illumination intensities, each occurring within an illumination interval, within the unit frame interval.
For the first illumination during the first illumination interval EXP1, the selected pixel is accessed at time t11 for the K-frame, and time t21 for the (K+1)-frame. And, for the second illumination during the second illumination interval EXP2, the selected pixel is accessed at time t12 for the K-frame, and time t22 for the (K+1)-frame.
The length of the second illumination interval EXP2 is different from that of the first illumination interval EXP1.
As shown in
Extending the present invention to a general case, when the digital data is n-bit data, unit times of 2i are arranged in the X-axis of the mapping table. And, in the Y-axis of the mapping table, intensity levels of 2i are arranged. Therefore, in the maximum area of one-frame, 16(=22×22) sectors are included. Herein, n is a natural number more than 2. Also, i and j are natural numbers. Preferably, the sum of i and j is n. More preferably, i and j are the same number. But, it should be understood to those skilled in the art that the spirit of the present invention is still embodied, even if i is different from j.
Referring to
The driving circuit 230 generates a digital data for a selected pixel. The driving circuit 230 drives the selected pixel to be illuminated with a first illumination intensity during a first illumination interval. The driving circuit 230 drives the selected pixel to be illuminated with a second illumination intensity during a second illumination interval. Herein, the second illumination intensity is different from the first illumination intensity.
The first and the second illumination intensity levels, and the first and the second illumination intervals are determined in a mapping table according to the digital data. The mapping table may be stored in the active display device. The first illumination interval and the second illumination interval are included in one unit frame period.
Also, a relative ratio of the second illumination intensity to the first illumination intensity is changed according to the value of the digital data.
The driving circuit 230 includes a gate driver portion 231, a source driver portion 233 and a controller 235. The gate driver portion 231 drives a gate line GL of the selected pixel. The source driver portion 233 supplies the corresponding digital data through the data line DL for illuminating the selected pixel. The controller 235 controls the gate driver portion 231 and the source driver portion 233, so that the selected pixel of the display panel 210 illuminates during the illumination interval with the illumination intensity. At this time, the illumination interval and the illumination intensity depend on the corresponding digital data.
In the pixel driving method according to the comparison example, the illumination intensity is constant, and the length of the illumination interval is changed according to the value of the digital data.
In the active display device for the pixel driving method of
However, in the pixel driving method of
Therefore, in the active display device for the pixel driving method of
According to the mixing type pixel driving method of the present invention, the number of the converted bits by DAC is reduced. Therefore, the reduced bit DAC is adaptable for the mixing type pixel driving method of the present invention. Therefore, the layout area and the consumption current can be decreased according to the present invention.
Although exemplary embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Therefore, the technical scope of the present invention should be defined by the technical spirit of the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2007-0083328 | Aug 2007 | KR | national |
