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Researchers Submit Patent Application, "Pixel, Display Device Comprising the Pixel and Driving Method of the Display Device", for Approval

June 18, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Choi, Yang-Hwa (Yongin-City, KR); Kim, Cheol-Min (Yongin-City, KR), filed on May 23, 2013, was made available online on June 5, 2014.

No assignee for this patent application has been made.

News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates to a display device and a driving method thereof. More particularly, the present invention relates to a display device including an organic light emitting diode (OLED) and a pixel that is digitally driven, and a driving method thereof.

"Recently, a display panel has increased in size and reduced in weight, and a stable driving method of a frame has been developed in order to display an accurate and clear image with high-integration and high-precision of a display device which is required to implement a 3D stereoscopic image.

"An analog-type driving method of a conventional display device increases the number of circuit elements in a pixel so that it cannot be applied to a large-sized panel, and causes problems in high-resolution display panel, particularly, FULL HD panel. A conventional pixel circuit is formed of 7 to 8 transistors and 2 to 3 capacitors, and this becomes a difficulty in layout design and manufacturing of the display panel.

"In order to solve such a problem, a digital driving method replaces the analog driving method and high integration and high resolution can be realized by reducing the number of circuits in a pixel. In particular, in the pixel employing the digital driving method can be formed of 2 to 3 transistors and 1 capacitor so that the difficulty in layout design and manufacturing of the display panel can be solved.

"However, a driving transistor transmitting a driving current according to a data signal is operated in a linear area in the digitally driven pixel, and thus luminance is not uniform in the entire panel depending on a material of an organic light emitting diode and a distribution characteristic such as processing. Thus, a failure such as long range uniformity (LRU) or a short range uniformity (SRU) occurs in the display panel, thereby causing deterioration of the display device.

"Accordingly, development and research for a pixel structure having high integration and high resolution adaptability in the digital driving method while having a screen display characteristic of the conventional analog driving method, and a display device including the same and a driving method thereof are required.

"The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "The present invention has been made in an effort to provide a pixel circuit corresponding to a digital driving method to provide a display device appropriate to high integration and high resolution while controlling a driving transistor of a pixel of the display device to be operated in a saturation area, thereby increasing display quality that equals to display quality of an analog driving method.

"In addition, the present invention simplifies the complex pixel circuit by reducing the number of elements so that a layout of the pixel can be simply designed, and provides a pixel structure that does not sensitively respond characteristic deterioration of an organic light emitting element so that durability and productivity of the display device can be improved.

"A display device according to an exemplary embodiment of the present invention includes: a data driver transmitting a plurality of data signals; a scan driver generating and transmitting a plurality of scan signals; a display panel including a plurality of pixels, each emitting light with a driving current according to the plurality of data signals; a compensation signal unit generating and transmitting a compensation control signal for controlling simultaneous transmission of a predetermined bias voltage to each of the plurality of pixels before a data voltage according to the plurality of data signals is applied to each of the plurality of pixels; a power controller controlling voltage levels of the first power source voltage and the second power source voltage and supplying the level-controlled first and second power source voltages; and a timing controller generating the plurality of data signals by processing an external image signal and generating a plurality of driving control signals that respective control driving of the data driver, the scan driver, the compensation signal unit, and the power controller.

"The predetermined bias voltage is set as a white voltage that displays the maximum luminance along the plurality of data signals.

"The display panel may be formed of a first pixel area including a plurality of first pixels among the plurality of pixels and a second pixel area including a plurality of second pixels that are the rest of pixels, excluding the first pixels from the plurality of pixels. In this case, the compensation signal unit may be connected to a first compensation control line connected to the plurality of first pixels include in the first pixel area and a second compensation control line connected to the plurality of second pixels included in the second pixel area, and the compensation signal unit may generate and transmit a first compensation control signal and a second compensation control signal controlling application of the bias voltage respectively through the first compensation control line and the second compensation control line.

"The plurality of first pixels included in the first pixel area and the plurality of second pixels included in the second pixel area respectively have an iterative alignment of a unit of a first color pixel, a second color pixel, a third color pixel, and the second color pixel.

"The compensation signal unit transmits the first compensation control signal and the second compensation control signal before a plurality of data signals are transmitted to the plurality of pixels included in the display panel.

"The bias voltage may be applied to each of the plurality of pixels through the plurality of data lines connected to the data driver and each of the plurality of pixel, but the present invention is not limited thereto.

"Each of the plurality of pixels may include a switching element of which switching operation is controlled by the compensation control signal, and the bias voltage may be applied to the turn-on switching element corresponding to the compensation control signal.

"Each of the plurality of pixels receives the bias voltage through a source electrode of a driving transistor thereof corresponding to the compensation control signal.

"The power controller supplies the first power source voltage as a predetermined high-level voltage during one frame, and supplies the second power source voltage as a predetermined high-level voltage for a compensation period during which the compensation control signal is transmitted in one frame.

"A pixel according to another exemplar embodiment of the present invention includes: an organic light emitting diode; a driving transistor electrically connected to a first power source voltage supply line and supplying a driving current to the organic light emitting diode; a switching transistor connected to the corresponding scan line among a plurality of scan lines transmitting a plurality of scan signals to transmit a data voltage according to the corresponding data signal among a plurality of data signal to a gate electrode of the driving transistor according to the corresponding scan signal; a compensation transistor connected between the first power source voltage supply line and the driving transistor to receive a predetermined bias voltage during a compensation period in one frame; a control transistor connected to a data line transmitting the data voltage to transmit the bias voltage to a gate electrode of the compensation transistor through the data line in response to a compensation control signal during the compensation period; a compensation capacitor connected to the gate electrode of the compensation transistor; and a storage capacitor connected to the gate electrode of the driving transistor.

"The control transistor includes a gate electrode receiving the compensation control signal, a source electrode connected to the data line to receive the bias voltage during the compensation period, and a drain electrode connected to the gate electrode of the compensation transistor.

"The control transistors included in the respective pixel areas receive compensation control signals respectively transmitted during different periods in the compensation period through compensation control lines connected with gate electrodes thereof.

"According to another exemplary embodiment of the present invention provides a method for driving a display device including a plurality of pixels, each including an organic light emitting diode, a driving transistor connected to a first power source voltage supply line to supply a driving current to the organic light emitting diode, a compensation transistor provided between the first power source voltage supply line and the driving transistor to receive a predetermined bias voltage for the driving transistor to be operated in a saturation area, a compensation capacitor connected to a gate electrode of the compensation transistor, and a storage capacitor connected to a gate electrode of the driving transistor. In further detail, The method includes: a compensation step for simultaneously storing the bias voltage in the compensation capacitor of the respective pixels; a scanning and data writing step for the plurality of pixels sequentially store data voltages according to the corresponding data signals among a plurality of data signals of one frame for each pixel line to the storage capacitors thereof in response to the corresponding scan signals among a plurality of scan signals of the frame; and a light emission step for the organic light emitting diode emits light according to the driving current corresponding to the data voltage applied to the gate electrode of the driving transistor.

"Accordingly to the present invention, a simple pixel circuit structure corresponding to a digital driving method is suggested to provide a display device that is appropriate to high integration and high resolution. Furthermore, the present invention enables a driving transistor of the pixel circuit to be operated in a saturation to thereby display quality with improved reliability and uniformity by preventing luminance from being changed in a display panel due to characteristic deterioration of the organic light emitting element.

"In addition, the number of elements is reduced in a complicated pixel circuit so that layout design of the circuit can be simplified and accordingly productivity of the display device can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

"A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:

"FIG. 1 is a block diagram of a display device according to an exemplary embodiment of the present invention;

"FIG. 2 is a circuit diagram of a pixel according to the exemplary embodiment of the present invention;

"FIG. 3 is a timing diagram of a driving waveform of the pixel of FIG. 2;

"FIG. 4 shows a display panel having a pixel alignment structure according to another exemplary embodiment of the present invention and a compensation signal unit of the display device of FIG. 1;

"FIG. 5 is a circuit diagram of a partial pixel in the display panel according to the exemplary embodiment of FIG. 4; and

"FIG. 6 is a timing diagram of a driving waveform of the pixel of FIG. 5."

For additional information on this patent application, see: Choi, Yang-Hwa; Kim, Cheol-Min. Pixel, Display Device Comprising the Pixel and Driving Method of the Display Device. Filed May 23, 2013 and posted June 5, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4125&p=83&f=G&l=50&d=PG01&S1=20140529.PD.&OS=PD/20140529&RS=PD/20140529

Keywords for this news article include: Patents, Electronics, Light-emitting Diode.

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Source: Electronics Newsweekly


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