The patent's assignee is
News editors obtained the following quote from the background information supplied by the inventors: "An Organic Light-Emitting Diode (OLED) display consists of a matrix of Organic Light-Emitting Diode (OLED) pixels that generate light upon electrical activation. Conventionally, luminance of each OLED increases with more current flowing to it. Typically, this continuous current flow is controlled by at least two transistors at each pixel, one to start or stop the charging of a storage capacitor and the second to provide a voltage source at the level needed to create a constant current to the pixel. In a commonly adopted RGB color model, each light emitting element, i.e., pixel, comprises a red ® OLED element, a green (G) OLED element, and a blue (B) OLED element for emitting red color, green color and blue color light, respectively. A pixel can express a desired color in a certain frame by mixing light of the three colors from respective light emitting elements. Typically, a system encodes pixel color values by devoting 8 bits to each of the R, G, and B components for control.
"One approach to achieve control of an OLED display is to use an active matrix thin-film-transistor (TFT) backplane in an Active matrix Organic Light-Emitting Diode (AMOLED) display. The active matrix functions as switches to control the current flowing to each individual color element in each frame. Conventionally, the current flowing to each OLED is continuous and controlled by at least two TFTs, the first one for activating and deactivating the charging of a storage capacitor, and the second one for providing a voltage required to drive a constant current of intended level to control the luminance of the color element. Since the second transistor operates in its linear region, a considerable fraction of the power can be consumed by the internal resistance of the second transistor which wastes a significant amount of valuable power, especially when used in a mobile computing device fitted with a limited size battery. For example, the TFT transistors in an AMOLED display device may consume 40-60% of the power supplied to drive the AMOLED display device.
"Further, in a conventional design, since luminance of each OLED is driven by a continuous current through an associated transistor, the binary color values, e.g. in the format of a 8:8:8 byte, usually have to be converted to analog data through a Digital-Analog-Converter (DAC) in a timing controller, which complicates the circuit design in the timing control logic.
"Moreover, a display device for a portable device is often used in a wide range of ambient light levels. Conventionally, as the ambient light level increases, the luminance contrast decreases due to a fixed brightness emitted from the display panel. Although setting the display panel luminance constantly at its maximum level would ensure the images are visible in the widest range of ambient light levels, the unnecessarily brightness increases power consumption, and shortens operating lifetime of the display panel. Also, excessive contrast between the displayed images and dark ambient environments may cause eye discomforts."
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventor's summary information for this patent application: "Therefore, it would be advantageous to reduce the power consumed by the transistors in an AMOLED display device and thereby increase power consumption efficiency of the display device. It would also be advantageous if the timing control logic for such a device can be simplified. Moreover, it would be also advantageous to be capable of adjusting the global luminance of a display panel in response to ambient light level.
"Accordingly, embodiments of the present disclosure provide a mechanism to reduce power consumption by using transistors operating in a binary on/off mode to drive an array of OLEDs. The mechanism also allows for simplified designs of timing control logic and global luminance control of the display device. Embodiments of the present disclosure advantageously include an AMOLED layer with each color element comprising a discrete array of OLED junctions coupled to a plurality of transistors. Thus, luminance of the color element can be digitally controlled by turning on a selected combination of the transistors and thereby activating luminance of the associated OLED junctions. The plurality of OLED junctions of a respective color element vary in size in accordance with the value of the binary digit to which they are controlled. In one embodiment, the plurality of junctions that make up a color element may vary in size according to 2.sup.n, where n is the junction number and may correspond to a bit position of a control color bit that that controls the junction. The color bit is located within a color byte for controlling the entire color element.
"In one embodiment of the present disclosure, a flat panel display apparatus comprises a cathode layer, an anode layer, an OLED layer and a plurality of sets of transistors coupled to the OLED layer. The OLED layer comprises a plurality of pixels arranged in a matrix. Each pixel comprises a plurality of color elements, and each of the plurality of color elements comprises a plurality of diode junctions arranged in a pattern. Each transistor controls a corresponding diode junction in a binary mode by a respective bit of a respective binary color value. A nominal luminance of each diode junction of a color element may correspond to a binary value represented by a respective bit position of a respective bit in a corresponding binary color value. Each transistor may be further coupled to a storage device operable to store the binary color value. The global luminance of the pixels may be adjustable by adjusting a voltage across the cathode and anode of the display panel. The transistors may be integrated on a thin film transistor TFT layer.
"In another embodiment of the present disclosure, a system comprises a memory, a display panel and a display control logic, where the display panel comprises a cathode layer, an anode layer an AMOLED layer and a plurality of switches coupled to the AMOLED layer. The AMOLED layer comprises a plurality of pixels. Each of the plurality of pixels comprises a plurality of color element and each color element comprises a plurality of diode junctions coupled to a set of switches. The display control logic is operable to control luminance of each diode junction of respective color element by controlling a respective switch. The switches may be configured by transistors operating in on/off mode. Each of the transistors may have the gate coupled to a bit of corresponding binary color value provided by the display control logic, the drain coupled to the anode layer, and a source coupled to an associated diode junction. The total number of the plurality of diode junctions in a respective color element may be equal to a total number of bits in a corresponding binary color value, and each diode in a respective color element may have nominal luminance proportional to 2.sup.n, where n is the bit position of the bit controlling the diode. The system may further comprise a plurality of flip-flops coupled to the plurality of switches.
"In another embodiment of the present disclosure, a method for displaying images on a display device comprises receiving image data that comprises a binary number representing luminance of a color element of a corresponding pixel of the display device and the color element comprises a plurality of discrete illuminating units. The method further comprises controlling each discrete illuminating unit individually between a first state and a second state with a respective bit of the binary number. The discrete illuminating units may comprise OLEDs coupled to transistors. The transistors may be configured to receive a respective bit of a binary number and provide binary control to the associated OLED. Each discrete illuminating unit in a color element may have nominal luminance proportional to 2.sup.n, where n indicates a bit position of a respective bit of the binary number used to control the illuminating unit.
"The foregoing is a summary and thus contains, by necessity, simplifications, generalizations and omissions of detail; consequently, those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the present invention, as defined solely by the claims, will become apparent in the non-limiting detailed description set forth below.
BRIEF DESCRIPTION OF THE DRAWINGS
"Embodiments of the present invention will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying drawing figures in which like reference characters designate like elements and in which:
"FIG. 1 depicts an exemplary layout of the pixels and color elements in an organic light emitting diode (OLED) display panel in accordance with an embodiment of the present disclosure.
"FIG. 2A depicts an exemplary layout of diode junctions fabricated in rectangular shapes of varying sizes in an individual color element in accordance with one embodiment of the present disclosure.
"FIG. 2B depicts an exemplary layout of the diode junctions fabricated in circular shapes of varying sizes in an individual color element in accordance with another embodiment of the present disclosure.
"FIG. 3 is a block diagram illustrating a display control system configuration associated with an organic light emitting diode (OLED) display panel in accordance with an embodiment of the present disclosure.
"FIG. 4 depicts an exemplary circuit configuration used to control the diode junctions in an individual color element in accordance with one embodiment of the present disclosure.
"FIG. 5A is a flow diagram illustrating a method for digitally driving the diode junctions directly using a RGB pixel data in accordance with an embodiment of the present disclosure.
"FIG. 5B is a flow diagram illustrating a method for driving the pixels with a decoded RGB pixel data in accordance with an embodiment of the present disclosure.
"FIG. 6 is a block diagram illustrating a configuration of a mobile computing system comprising an AMOLED display panel in accordance with an embodiment of the current application."
For additional information on this patent application, see: Xu, Shuang. Display Device with Binary Mode Amoled Pixel Pattern. Filed
Keywords for this news article include: Electronics,
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