KR20140040454A - Organic light emitting diode display apparatus and operating method thereof - Google Patents

Abstract

An organic light emitting diode display apparatus finds a present line load of a present scan line among multiple scan lines belong to one screen of a video signal, and finds a compensation modulus of the present scan line based on the present line load. The organic light emitting diode display apparatus applies the compensation modulus of the present scan line to multiple gradient values belong to the present scan line to find multiple compensated gradient values, applies multiple voltage values, which correspond to the multiple compensated gradient values respectively, to multiple pixels of the present scan line respectively. [Reference numerals] (151) Video arrangement unit; (152) Current line load calculation unit; (153) Compensation rate look-up table storage unit; (154) Compensation rate calculation unit; (155) Gradation value compensation unit; (156) Data control unit; (157) Gate control unit

Description

Organic light emitting diode display and its driving method {ORGANIC LIGHT EMITTING DIODE DISPLAY APPARATUS AND OPERATING METHOD THEREOF}

The present invention relates to an organic light emitting diode (OLED) display device and a driving method thereof.

The OLED display is a self-luminous device that emits an organic light-emitting layer by recombination of electrons and holes, and is expected to be a next-generation display device because of its high brightness, low driving voltage and ultra thin film.

Each of the plurality of pixels constituting the OLED display device includes an OLED pixel composed of an organic light emitting layer between an anode and a cathode, and a pixel circuit driving each OLED pixel independently. The pixel circuit mainly includes a switching transistor and a capacitor and a driving transistor. The switching transistor charges the data signal in the capacitor in response to the scan pulse, and the driving transistor adjusts the gray level of the OLED pixel by adjusting the amount of current supplied to the OLED pixel according to the magnitude of the data voltage charged in the capacitor.

However, conventional OLED display devices may have a line load effect. Such a line load effect will be described with reference to FIGS. 1 and 2.

1 illustrates an example of a screen in which a line load effect is shown in a conventional OLED display device.

As shown in FIG. 1, the displayed frame has a first area A, a second area B, and a third area C. FIG.

The first area A and the second area B are pixels having a maximum gray value (eg, 255), and the third area C is formed of a pixel having a minimum gray value (eg, 0).

In this case, since the line load of the scan line belonging to both the second area B and the third area C is smaller than the line load of the scan line belonging to the first area A, The second region B has the same maximum gray value, but the luminance of the first region A is reduced compared to the luminance of the second region B, thereby generating a boundary. This phenomenon is called the line load effect. That is, when the OLED display device is driven, the discharge intensity is reduced due to the voltage drop due to the line resistance and the inductor component of each electrode, and thus a line load effect may occur due to the luminance difference of each electrode line.

2 shows another example of a line load effect in a conventional OLED display.

As shown in FIG. 2, the line load effect may occur similarly to FIG. 1 even when the background has a relatively high gray value in the text document and the text has a relatively low gray value.

Embodiments of the present invention provide an OLED display and a driving method thereof for preventing a line load effect.

A method of driving an organic light emitting diode display according to an exemplary embodiment of the present invention may include: obtaining a current line load of a current scan line among a plurality of scan lines belonging to one frame of an image signal; Obtaining a compensation rate of the current scan line based on the current line load; Obtaining a plurality of compensated grayscale values by applying a compensation rate of the current scan line to a plurality of grayscale values belonging to the current scan line; And applying a plurality of voltage values respectively corresponding to the plurality of compensated grayscale values to the plurality of pixels of the current scan line, respectively.

In accordance with still another aspect of the present invention, an organic light emitting diode display includes: a plurality of pixels arranged in a matrix; A timing controller configured to obtain a plurality of compensated grayscale values by applying a compensation rate calculated based on a current line load of a current scan line to a plurality of grayscale values belonging to the current scan line; And a data driver configured to apply a plurality of voltage values respectively corresponding to the plurality of compensated gray levels to the plurality of pixels of the current scan line.

According to one embodiment of the invention, line load effects can be prevented.

In addition, it is possible to minimize the luminance degradation while preventing the line load effect.

1 illustrates an example of a screen in which a line load effect is shown in a conventional OLED display device.
2 shows another example of a line load effect in a conventional OLED display.
3 is a circuit diagram illustrating an OLED display device 100 according to an exemplary embodiment of the present invention.
4 is an equivalent circuit diagram illustrating a pixel P according to an exemplary embodiment of the present invention.
5 shows a timing controller according to an embodiment of the present invention.
6 illustrates a method of driving an OLED display device according to an exemplary embodiment of the present invention.
7 shows an example of a screen displayed according to an embodiment of the present invention.
8 shows a timing controller according to another embodiment of the present invention.
9 illustrates a method of driving an OLED display device according to still another embodiment of the present invention.

Hereinafter, a mobile terminal related to the present invention will be described in detail with reference to the drawings. The suffix "module" and " part "for the components used in the following description are given or mixed in consideration of ease of specification, and do not have their own meaning or role.

Hereinafter, an OLED display device 100 according to an exemplary embodiment of the present invention will be described with reference to FIGS. 3 to 4.

3 is a circuit diagram illustrating an OLED display device 100 according to an exemplary embodiment of the present invention.

As shown in FIG. 3, the OLED display device 100 according to an exemplary embodiment of the present invention includes a display panel 110, a gate driver 120, a data driver 130, a power supply 140, and a timing controller 150. ).

The display panel 110 includes a plurality of pixels P arranged in a matrix.

Next, a pixel P according to an exemplary embodiment of the present invention will be described with reference to FIG. 4.

4 is an equivalent circuit diagram illustrating a pixel P according to an exemplary embodiment of the present invention.

Each pixel P of the display panel 110 includes a light emitting diode OEL and a cell driver DRV for independently driving the light emitting diode OEL. The cell driver DRV includes a switching transistor T1, a driving transistor T2, and a capacitor C.

The gate electrode of the switching transistor T1 is connected to the gate line GL, the source electrode is connected to the data line DL, and the drain electrode is connected to the gate electrode of the driving transistor T2. One end of the capacitor C is connected to the power supply line PL, and the other end is connected to the drain electrode of the switching transistor T1. The source electrode of the driving transistor T2 is connected to the power supply line PL, and the drain electrode is connected to the anode of the light emitting diode OEL. The cathode of the light emitting diode OEL is connected to ground.

When the gate-on signal is supplied to the gate line GL, the switching transistor T1 is turned on to supply an analog image signal supplied to the data line DL to the gate electrode of the capacitor C and the driving transistor T2. do.

The driving transistor T2 controls the amount of current I supplied from the power supply line PL to the light emitting diode OEL according to the analog image signal from the switching transistor T1 to adjust the amount of light emitted from the light emitting diode OEL. .

Thereafter, even when the switching transistor T1 is turned off, the driving transistor T2 is kept on by the voltage charged in the capacitor C. FIG. As a result, the driving transistor T2 maintains emission of the light emitting diode OEL until the analog image signal of the next frame is supplied. Here, the switching and driving transistors T1 and T2 may be PMOS or NMOS transistors, but only the case of the NMOS transistors is described herein.

The gate driver 120 sequentially generates scan pulses and sequentially supplies the scan pulses to the gate lines GL1 to GLn in response to the gate control signal GVS from the timing controller 150.

The data driver 130 converts the image data Data input from the timing controller 150 into an analog voltage, that is, an analog image signal according to the data control signal DVS from the timing controller 150. The data driver 130 outputs analog image signals corresponding to one horizontal line of pixels every one horizontal period in which an analog image signal is supplied to the gate lines GL1 through GLn, and the data lines DL1 through DLm. To feed. In other words, the data driver 130 selects a gamma voltage having a predetermined level according to the gray value of the analog image signal and supplies the selected gamma voltage to the data lines DL1 to DLm.

Next, an OLED display and a driving method thereof according to an exemplary embodiment will be described with reference to FIGS. 5 and 6.

5 shows a timing controller according to an embodiment of the present invention.

As shown in FIG. 5, the timing controller 150 may include an image aligner 151, a current line load calculator 152, a compensation rate lookup table storage 153, a compensation factor calculator 154, and a gray level compensation unit 155. ), A data controller 156, and a gate controller 157. A detailed operation of the components of the timing controller 150 will be described with reference to FIG. 6.

6 illustrates a method of driving an OLED display device according to an exemplary embodiment of the present invention.

First, the image aligning unit 151 receives image data RGB from at least one frame unit from the outside, and arranges the received image data according to the resolution of the display panel 110 (S101).

The current line load calculator 152 obtains the line load of the scan line at the current timing from the aligned image data in the frame unit (S103). In this case, the current line load calculator 152 may calculate the current line load based on a plurality of grayscale values belonging to the current scan line.

In particular, the current line load calculator 152 may obtain the current line load CLL according to Equation 1 below.

In Equation 1, V1 to Vm represent a plurality of grayscale values belonging to the current scan line, and m represents a number of grayscale values belonging to the current scan line. On the other hand, in Equation 1, the coefficient 4 is used to extend the range that the value of the line load may have, and may be changed for another embodiment. For example, if the range of gray values can be 0 to 255, the range of the line load value obtained from Equation 1 can range from 0 to 1023.

As shown in Equation 1, the current line load calculator 152 may calculate the current line load based on the sum of a plurality of grayscale values belonging to the current scan line.

In addition, the current line load calculator 152 may obtain the current line load according to Equation 2 below.

In Equation 2, RV1 to RVk represent a plurality of red grayscale values belonging to the current scan line, GV1 to GVk represent a plurality of green grayscale values belonging to the current scan line, and BV1 to BVk represent a plurality of green grayscale values belonging to the current scan line. The blue tone value is shown. W _R denotes the weight of the red pixel on the line load, W _G denotes the weight of the green pixel on the line load, and W _B denotes the weight of the blue pixel on the line load. The sum of W _R , W _G and W _B may be one.

In Equation 2, the coefficient 4 is used to extend the range that the value of the line load may have, and may be changed for another embodiment. For example, the range of gray values can range from 0 to 255. If the sum of W _R , W _G , and W _B is 1, the range that the value of the line load obtained from Equation 2 can have is from 0 to 1023.

As shown in Equation 2, the current line load calculator 152 may obtain a current line load CLL by applying a plurality of weights corresponding to a plurality of colors to a plurality of grayscale values belonging to the current scan line. .

The compensation rate calculator 154 calculates a compensation rate G of the current scan line based on the current line load (S105). The compensation rate calculator 154 may retrieve the compensation rate corresponding to the current line load from the compensation rate lookup table stored in the compensation rate lookup table storage 153.

The compensation rate lookup table storage unit 153 stores a compensation rate lookup table as shown in Table 1 below. As shown in Table 1, the compensation rate lookup table may include a matching relationship between a plurality of scan line loads and a plurality of compensation rates.

Load (CLL) Reward Rate (G) 0 0.90 One 0.90 2 0.90 3 0.90 ... ... 510 0.98 511 0.98 512 0.98 513 0.98 ... ... 1020 1.00 1021 1.00 1022 1.00 1023 1.00

The gray value compensator 155 applies the compensation rate G of the current scan line to the plurality of gray values Vi, i = 1 to m belonging to the current scan line, thereby providing a plurality of compensated gray values CVi, i = 1. m), and the plurality of compensated grayscale values are provided to the data driver 130 (S107). As shown in Equation 3, the gray value compensation unit 155 multiplies the compensation rate G of the current scan line by a plurality of gray values belonging to the current scan line, respectively, to compensate for the plurality of compensated gray values CVi, i = 1. ~ m) can be obtained.

The data controller 156 supplies the data control signal DVS to the data driver 130 according to the synchronization signals HSync, VSync, DCLK, and DE input from the outside (S109).

The gate controller 157 supplies the gate control signal GVS to the gate driver 120 according to the synchronization signals HSync, VSync, DCLK, and DE input from the outside (S111).

The gate driver 120 provides a scan pulse to the gate line corresponding to the current scan line according to the gate control signal GVS (S113).

At a timing at which a scan pulse is provided to a gate line corresponding to the current scan line, the data driver 130 provides a plurality of voltage values to each of the plurality of pixels belonging to the current scan line according to the gate control signal GVS ( S115). In this case, the plurality of voltage values correspond to the plurality of compensated grayscale values belonging to the current scan line, respectively.

Meanwhile, according to the exemplary embodiment shown in FIGS. 5 and 6, since the negative compensation is performed, the luminance may be reduced. This phenomenon will be described with reference to FIG. 7.

7 shows an example of a screen displayed according to an embodiment of the present invention.

In FIG. 7, it is assumed that a dark area includes pixels having a minimum gray value and a bright area includes pixels having a maximum gray value.

In this case, the line load of the scan line covering only the dark region is 0, and the line load of the scan line covering the bright region is 512, which is 50%.

As shown in Table 1 and Equation 3, since a compensation factor belonging to a scan line having a line load of 512 is 0.98, a gray scale value corresponding to 255 * 0.98 = 249.9 is output in an actual bright area. As described above, according to the exemplary embodiment shown in FIGS. 5 and 6, when the screen of FIG. 7 is output, the brightness of the bright area may be reduced by 2%.

Hereinafter, an exemplary embodiment of the present invention will be described with reference to FIGS. 7 and 8 to minimize such luminance reduction.

8 shows a timing controller according to another embodiment of the present invention.

As illustrated in FIG. 8, the timing controller 150 may include an image aligner 151, a current line load calculator 152, a compensation factor lookup table storage 153, a compensation factor calculator 154, and a gray value compensator 155. ), A data controller 156, a gate controller 157, and a maximum line load calculator 158. Detailed operations of the components of the timing controller 150 will be described with reference to FIG. 8.

9 illustrates a method of driving an OLED display device according to still another embodiment of the present invention.

First, the image aligning unit 151 receives image data RGB in at least one frame unit from the outside and aligns the received image data according to the resolution of the display panel 110 (S201).

The current line load calculator 152 obtains the line load of the scan line at the current timing from the aligned image data in the frame unit (S203). In this case, the current line load calculator 152 may calculate the current line load based on a plurality of grayscale values belonging to the current scan line. The current line load calculator 152 may obtain the current line load CLL according to Equation 1 or Equation 2.

The maximum line load calculator 158 obtains the maximum line load among the line loads of the plurality of scan lines belonging to the current frame (S204). The maximum line load calculator 158 may obtain each of the line loads of the plurality of scan lines belonging to the current frame, and obtain the maximum line load by taking a maximum value among the obtained line loads. When the maximum line load calculator 158 obtains each of the line loads of the plurality of scan lines, Equation 1 or Equation 2 may be used.

The compensation rate calculator 154 calculates a compensation rate G of the current scan line based on the current line load and the maximum line load (S205).

In particular, the compensation rate calculator 154 converts the current line load (CLL) based on the maximum line load (MLL) using the following Equation 4 to transform the current line load. Line Load, TCLL) can be obtained.

In Equation 4, Limit_Line_Load represents a limit value of the line load. In particular, in the embodiment of the present invention, 1024 is assumed, but is not limited thereto.

Thereafter, the compensation rate calculator 154 may retrieve the compensation rate corresponding to the converted current line load by searching the compensation rate lookup table as shown in Table 1 below. As such, the compensation rate calculator 154 may calculate the compensation rate of the current scan line based on the ratio CLL / MLL of the current line load to the maximum line load.

The gray value compensator 155 applies the compensation rate G of the current scan line to the plurality of gray values Vi, i = 1 to m belonging to the current scan line, thereby providing a plurality of compensated gray values CVi, i = 1. m), and the plurality of compensated grayscale values are provided to the data driver 130 (S207). In this case, the gray value compensation unit 155 may use Equation 5.

The data controller 156 supplies the data control signal DVS to the data driver 130 according to the synchronization signals HSync, VSync, DCLK, and DE input from the outside (S209).

The gate controller 157 supplies the gate control signal GVS to the gate driver 120 according to the synchronization signals HSync, VSync, DCLK, and DE input from the outside (S211).

The gate driver 120 provides a scan pulse to the gate line corresponding to the current scan line according to the gate control signal GVS (S213).

At a timing at which a scan pulse is provided to a gate line corresponding to the current scan line, the data driver 130 provides a plurality of voltage values to each of the plurality of pixels belonging to the current scan line according to the gate control signal GVS ( S215). In this case, the plurality of voltage values correspond to the plurality of compensated grayscale values belonging to the current scan line, respectively.

8 and 9 will be described with reference to FIG.

In this case, the line load of the scan line covering only the dark region is 0, and the line load of the scan line covering the bright region is 512, which is 50%. Therefore, the maximum line load is 512, so the converted line load of the scan line covering the bright area is 1024.

As shown in Table 1 and Equation 3, since a compensation factor belonging to a scan line having a line load of 1024 is 1, a gray scale value corresponding to 255 * 1 = 255 is output in an actual bright area. As described above, according to the exemplary embodiment shown in FIGS. 8 and 9, when the screen of FIG. 7 is output, there is no decrease in luminance.

According to an embodiment of the present invention, the above-described method can be implemented as a code readable by a processor on a medium on which a program is recorded. Examples of the medium that can be read by the processor include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, etc., and may be implemented in the form of a carrier wave (e.g., transmission over the Internet) .

The mobile terminal described above can be applied to not only the configuration and method of the embodiments described above but also all or some of the embodiments may be selectively combined so that various modifications may be made to the embodiments It is possible.

Claims (7)

In the driving method of the organic light emitting diode display device,
Obtaining a current line load of a current scan line among a plurality of scan lines belonging to one frame of an image signal;
Obtaining a compensation rate of the current scan line based on the current line load;
Obtaining a plurality of compensated grayscale values by applying a compensation rate of the current scan line to a plurality of grayscale values belonging to the current scan line; And
And applying a plurality of voltage values respectively corresponding to the plurality of compensated grayscale values to a plurality of pixels of the current scan line. The method of claim 1,
Obtaining a maximum line load among the line loads of the plurality of scan lines,
Obtaining a compensation rate of the current scan line,
Obtaining a compensation rate of the current scan line based on the current line load and the maximum line load.
Driving method. 3. The method of claim 2,
Obtaining a compensation rate of the current scan line based on the current line load and the maximum line load,
Obtaining a compensation rate of the current scan line based on the ratio of the current line load to the maximum line load.
Driving method. The method of claim 3,
Obtaining a compensation rate of the current scan line based on the ratio of the current line load
Obtaining a compensation rate corresponding to the ratio from a lookup table;
Driving method. 5. The method according to any one of claims 1 to 4,
Obtaining the current line load
Obtaining a current line load by applying a plurality of weights corresponding to a plurality of colors to a plurality of gray values belonging to the current scan line, respectively.
Driving method. In an organic light emitting diode display,
A plurality of pixels arranged in a matrix;
A timing controller configured to obtain a plurality of compensated grayscale values by applying a compensation rate calculated based on a current line load of a current scan line to a plurality of grayscale values belonging to the current scan line; And
And a data driver configured to apply a plurality of voltage values respectively corresponding to the plurality of compensated gray levels to the plurality of pixels of the current scan line.
Organic LED display. The method according to claim 6,
The timing controller obtains a maximum line load among line loads of a plurality of scan lines belonging to one frame of an image signal, and calculates the compensation rate based on the current line load and the maximum line load.
Organic LED display.

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