This application claims the priority of Korean Patent Application No. 10-2016-0082726, filed on Jun. 30, 2016, which is hereby incorporated herein by reference.
The present disclosure relates to an organic light-emitting display.
An active-matrix organic light-emitting display comprises self-luminous organic light-emitting diodes (hereinafter, “OLEDs”), and typically has advantages of a fast response time, high luminous efficiency, high luminance, and wide viewing angle.
An OLED, which is a self-luminous device, typically includes an anode, a cathode, and organic compound layers formed between the anode and cathode. The organic compound layers may include a hole injection layer HIL, a hole transport layer HTL, an emission layer EML, an electron transport layer ETL, and an electron injection layer EIL. When a power supply voltage is applied to the anode and the cathode, a hole passing through the hole transport layer HTL and an electron passing through the electron transport layer ETL move to the emission layer EML, forming an exciton. As a result, the emission layer EML generates visible light.
In an organic light-emitting display, pixels each including an OLED and a driving TFT (thin-film transistor) may be arranged in a matrix, and the brightness of an image created by the pixels may be adjusted based on the grayscale of image data. The driving TFT may control the drive current flowing through the OLED based on the voltage applied between its gate electrode and source electrode. The amount of light emitted by the OLED may be determined by drive current, and the brightness of an image may be determined by the amount of light emitted by the OLED.
The OLED may deteriorate as the light-emitting time increases. Deterioration of the OLED may increase a threshold voltage (which may be termed an “operating point voltage”) for turning on the OLED, and reduce luminous efficiency. The OLED's accumulated light-emitting time may vary from pixel to pixel, and therefore, OLED deterioration also may vary from pixel to pixel. The difference in OLED deterioration among pixels may cause brightness variation and lead to image sticking.
Due to this reason, organic light-emitting displays of the related art may employ deterioration compensation technology that detects deterioration by sensing an OLED operating point voltage and corrects image data by a correction gain to compensate for OLED deterioration. In a related art organic light-emitting display, a data driver IC (integrated circuit) may have a plurality of built-in sensing units for sensing an OLED operating point voltage, and the pixels and the sensing units may be connected together through reference lines.
A display panel may be additionally equipped with such reference lines to sense an OLED operating point voltage, which may be a primary factor for reduction of wiring design margin in the display panel. To reduce the number of reference lines, a structure has been proposed, in which a plurality of neighboring pixels may share a single reference line. With this structure, however, it may not be possible to sense each individual pixel that shares the reference line.
Accordingly, embodiments of the present disclosure are directed to a display that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An aspect of the present disclosure is to provide an organic light-emitting display which can easily achieve wiring design margin in a display panel by eliminating reference lines from the display panel and sensing an OLED operating point voltage through data lines.
Additional features and advantages of the disclosure will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the disclosure. The objectives and other advantages of the disclosure will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other aspects of the inventive concepts as embodied and broadly described, an example embodiment of the present disclosure may provide an organic light-emitting display, comprising a display panel having a plurality of pixels, a plurality of data lines that are connected to the pixels, and a plurality of gate lines that are connected to the pixels; and a data drive circuit having a plurality of digital-to-analog converters configured to generate an image data voltage and a sensing data voltage to be applied to the pixels, a plurality of sensing units configured to sense an organic light-emitting diode (OLED) operating point voltage of the pixels, and a plurality of connecting switches configured to selectively connect the digital-to-analog converters and the sensing units to the data lines.
It is to be understood that both the foregoing general description and the following detailed description are example and explanatory and are intended to provide further explanation of the disclosure as claimed.
The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate embodiments of the disclosure and together with the description serve to explain the various principles of the disclosure. In the drawings:
Hereinafter, some embodiments of the present disclosure will be described in detail with reference to the accompanying illustrative drawings. In designating elements of the drawings by reference numerals, the same elements will be designated by the same reference numerals although they are shown in different drawings. Further, in the following description of the present disclosure, a detailed explanation of certain functions and configurations incorporated herein may have been merely for the sake of brevity.
The shapes, sizes, proportions, angles, numbers, etc. shown in the figures to describe the example embodiments of the present disclosure are merely examples and not limited to those shown in the figures. Like reference numerals denote like elements throughout the specification. In describing the present disclosure, detailed descriptions of related well-known technologies will be omitted to avoid unnecessarily obscuring the present disclosure. When the terms ‘comprise’, ‘have’, ‘consist of’ and the like are used, other parts may be added as long as the term ‘only’ is not used. The singular forms may be interpreted as the plural forms unless explicitly stated.
The elements may be interpreted to include an error margin even if not explicitly stated.
When the position relation between two parts is described using the terms ‘on’, ‘over’, ‘under’, ‘next to’ and the like, one or more parts may be positioned between the two parts as long as the term ‘immediately’ or ‘directly’ is not used.
It will be understood that, although the terms first, second, etc., may be used to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, a first element discussed below could be termed a second element without departing from the technical spirit of the present disclosure.
Like reference numerals denote like elements throughout the specification.
The sizes and thicknesses of the components shown in the drawings are illustrated for explanatory convenience, but the present disclosure is not necessarily limited thereto.
The features of various example embodiments of the present disclosure may be combined with one another either partly or wholly, and may technically interact or work together in various ways. The example embodiments may be carried out independently or in combination with one another.
Hereinafter, various example embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.
With reference to
A plurality of data lines 14 and a plurality of gate lines 15 and 16 intersect each other on the display panel 10, and pixels P are arranged in a matrix at every intersection. The display panel 10 is additionally equipped with high-voltage power lines 21, which are parallel to the data lines 14 and apply a high-level driving voltage to the pixels P, and low-voltage power lines 22, which are parallel to the data lines 14 and apply a low-level driving voltage to the pixels P.
Each high-voltage power line 21 is connected to a first power input terminal EVDD in the data drive circuit 12, and may be shared by at least two pixels P neighboring in a direction (e.g., horizontal direction) in which the gate lines 15 and 16 extend. For example, each high-voltage power line 21 may be shared by four pixels neighboring in a horizontal direction, as shown in
Each low-voltage power line 22 is connected to a second power input terminal EVSS in the data drive circuit 12, and may be shared by at least two pixels P neighboring in a direction (e.g., horizontal direction) in which the gate lines 15 and 16 extend. For example, each low-voltage power line 22 may be shared by four pixels neighboring in a horizontal direction, as shown in
By reducing the number of power lines 21 and 22 through such a sharing structure, the display panel 10 may have a better wiring design margin than the related art. In addition, in the case of bottom-emission organic light-emitting displays, the aperture ratio may be improved.
To further improve the wiring design margin and/or aperture ratio in the display panel 10, no reference lines may be formed on the display panel 10 of an example embodiment of the present disclosure. For example,
The gate lines 15 and 16 may comprise a plurality of first gate lines 15 to which a first gate control signal is applied and a plurality of second gate lines 16 to which a second gate control signal is applied.
In an example deterioration sensing method (e.g., direct sensing method) according to the present disclosure, as shown in
In another example sensing method (e.g., indirect sensing method) according to the present disclosure, as shown in
Each pixel P may operate differently in normal operation (e.g., an image display operation) for writing input image data RGB to the display panel 10 and in sensing operation for measuring the OLED's operating point voltage. The sensing operation may be performed in a period in which the writing of image data RGB is stopped. For example, the sensing operation may be performed in a power-on sequence interval immediately after system power is applied, or in a power-off sequence interval immediately after system power is cut off.
The sensing operation is an operation for sensing OLED deterioration, which may be performed directly or indirectly. The sensing operation may inlcude an operation of the data drive circuit 12 and gate drive circuit 13 under control of the timing controller 11.
With reference to
In a sensing operation, the DACs generate a data voltage for sensing under control of the timing controller 11, and in a normal operation, generate a data voltage for image display corresponding to input image data RGB under control of the timing controller 11.
The sensing units SU may operate only in a sensing operation and sense an OLED operating point voltage for the pixels P. The sensing units SU may be implemented as voltage sensing type or current sensing type. A voltage sensing type sensing unit SU may sense the voltage stored in the OLED's anode by using a sample & hold part. The current sensing type sensing unit SU further comprises a current integrator connected to the front end of the sample & hold part, and may sense a current flowing through the OLED and convert it to a voltage and produce the integrator's output voltage through the sample & hold part.
The connecting switches SA selectively connect the DACs and the sensing units SU to the data lines 14. In a normal operation, the connecting switches SA connect the DACs to the data lines 14 in a consecutive manner so that a data voltage for image display generated from the DACs is supplied to the data lines 14.
In a sensing operation, the connecting switches SA connect the DACs and the sensing units to the data lines in an alternating manner so that a data voltage for sensing generated from the DACs is supplied to the data lines 14, and an OLED operating point voltage sensed through the data lines 14 is supplied to the sensing units SU.
In the sensing operation, the shift register 124 generates a selection control signal (not shown) and sequentially turns on switches SS1 to SSk of the MUX 123. In the sensing operation, the MUX 123 selectively connects the sensing units SU to the ADC in response to a selection control signal. In the sensing operation, the ADC converts a sensing voltage fed from the sensing units SU to digital sensing data SD, and sends the sensing data SD to the timing controller 11.
The gate drive circuit 13 generates first and second gate control signals, corresponding to sensing and normal operations, respectively, under control of the timing controller 11, and may supply the first gate control signal to the first gate lines 15(i) to 15(i+3), and the second gate control signal to the second gate lines 16(i) to 16(i+3).
The timing controller 11 generates data control signals DDC for controlling the operation timing of the data drive circuit 12 and gate control signals GDC for controlling the operation timing of the gate drive circuit 13, based on timing signals, such as a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a dot clock signal DCLK, and a data enable signal DE. The timing controller 11 may distinguish normal operation and sensing operation based on a driving power enable signal, a vertical synchronization signal, a data enable signal, etc., and may generate a data timing control signal DDC and a gate timing control signal GDC differently for each type of operation.
The timing controller 11 may preset a relation equation between the current flowing through the driving TFT and the OLED operating point voltage and store it in a first region of the memory 17. In a sensing operation, the timing controller 11 may update and keep first and second sensing data SD1 and SD2 sent from the data drive circuit 12 in a second region of the memory 17 and correct the second sensing data SD2 by the preset relation equation, thereby improving the accuracy of the second sensing data SD2 according to the indirect sensing method.
In the sensing operation, the timing controller 11 updates the sensing data SD sent from the data drive circuit 12 and stores it in the memory 17, and compares the updated sensing data SD with a preset initial sensing value. The initial sensing value is set at the time of product shipment, and corresponds to the OLED's operating point voltage before deterioration. The timing controller 11 reads out a deterioration compensation value from a preset compensation value table (e.g., look-up table) by using the difference between the updated sensing data SD and the initial sensing value as a read address. Based on the read-out deterioration compensation value, the timing controller 11 may modulate input image data RGB for image display and then send the modulated data to the data drive circuit 12 for normal operation.
With reference to
The OLED has an anode connected to a source node Ns, a cathode connected to a second power input terminal EVSS, and organic compound layers located between the anode and the cathode.
The driving TFT DT controls the amount of drive current fed to the OLED based on a gate-source voltage. The driving TFT DT has a gate electrode connected to a gate node Ng, a drain electrode connected to a first power input terminal EVDD, and a source electrode connected to the source node Ns.
The storage capacitor Cst is connected between the gate node Ng and the source node Ns and maintains the gate-source voltage of the driving TFT DT for a desired amount of time.
The first switching TFT ST1 turns on/off in response to a first gate control signal SP1, and has a drain electrode connected to a data line 14 and a source electrode connected to the source node Ns. A gate electrode of the first switching TFT ST1 is connected to a first gate line 15 to which the first gate control signal SP1 is applied.
The second switching TFT ST2 turns on/off in response to a second gate control signal SP2, and has a drain electrode connected to the second power input terminal EVSS and a source electrode connected to the gate node Ng. A gate electrode of the second switching TFT ST2 is connected to a second gate line 16 to which the second gate control signal SP2 is applied.
In the direct sensing method of
One sensing period for the direct sensing method may comprise a programming period Tpgm, a sensing period Tsen, and a sampling period Tsam, which occur consecutively. In the programming period Tpgm, sensing period Tsen, and sampling period Tsam, the first and second gate control signals SP1 and SP2 are maintained at ON level Lon, and therefore the first and second switching TFTs ST1 and ST2 are kept turned on.
With reference to
With reference to
With reference to
In the example indirect sensing method of
One sensing period for the indirect sensing method may comprise a programming period Tpgm, a sensing period Tsen, and a sampling period Tsam, which occur consecutively. In the programming period Tpgm, the first and second switching TFTs ST1 and ST2 turn on because the first and second gate control signals SP1 and SP2 are all maintained at ON level Lon. In the sensing period Tsen, the first and second switching TFTs ST1 and ST2 turn off because the first and second gate control signals SP1 and SP2 are all maintained at OFF level Loff. In the sampling period Tsam, the first switching TFT ST1 is turned on and then turned off because the first gate control signal SP1 changes from ON level Lon to OFF level Loff, and the second switching TFT ST2 is kept turned off because the second gate control signal SP2 is maintained at OFF level Loff.
With reference to
With reference to
With reference to
As stated above, example embodiments of the present disclosure may easily achieve wiring design margin in a display panel by eliminating reference lines from the display panel and sensing an OLED operating point voltage through data lines.
Moreover, example embodiments of the present disclosure may further achieve wiring design margin by designing power lines in such a way as to be shared by a plurality of pixels.
Furthermore, example embodiments of the present disclosure may further achieve wiring design margin by connecting only a single gate line to each pixel, because an OLED operating point voltage is sensed through data lines.
It will be apparent to those skilled in the art that various modifications and variations may be made in the present disclosure without departing from the technical idea or scope of the disclosure. Thus, it is intended that embodiments of the present disclosure cover the modifications and variations of the disclosure provided they come within the scope of the appended claims and their equivalents.
Number | Date | Country | Kind |
---|---|---|---|
10-2016-0082726 | Jun 2016 | KR | national |