KR20150100997A - Organic light emitting display device - Google Patents

Abstract

According to the present invention, an organic light emitting display device comprises: a pixel unit connected to data lines, scanning lines, and sensing lines, and having a plurality of pixels; a data drive unit supplying a data signal to the data lines; a scanning drive unit operated by dividing one frame period into a subfield drive period having a plurality of subfields and a sensing period, and supplying scanning signals corresponding to the subfields to the scanning lines; and a sensing drive unit supplying a sensing signal to draw out degradation information of an organic light emitting diode contained in the pixel to at least one of the sensing lines during the sensing period.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light-

An embodiment of the present invention relates to an organic light emitting display.

2. Description of the Related Art Various flat panel display devices capable of reducing weight and volume, which are disadvantages of cathode ray tubes (CRTs), have recently been developed. Examples of the flat panel display include a liquid crystal display, a field emission display, a plasma display panel, and an organic light emitting display.

Of the flat panel display devices, the organic light emitting display device displays an image using an organic light emitting diode (OLED) that generates light by recombination of electrons and holes. The organic electroluminescent display device has advantages of fast response speed and low power consumption.

The pixel of the organic light emitting display may be driven by an analog driving method or a digital driving method. The analog driving method is a method of controlling the amount of light emitted from the organic light emitting diode by controlling the current between the drain and the source of the driving transistor according to a data signal (or a data voltage). The digital driving method is a method of controlling the turn-on of the driving transistor according to a data signal to control the light emitting period of the organic light emitting diode. The digital driving method is advantageous in that it includes a pixel circuit and a driving IC (Integrated Circuit) having a simpler structure as compared with an analog driving method. In addition, as the display panel of the organic light emitting display device is enlarged and the resolution is increased, the necessity of using the digital driving method is increasing.

In a digital driving type organic electroluminescent display device, a data signal having a high voltage value, in which the driving transistor is turned on in the saturation region, is supplied during the light emitting period of the organic light emitting diode. A high driving current corresponding to the data signal is applied to the organic light emitting diode for all gradations having a predetermined light emitting period, so that the organic light emitting diode deteriorates rapidly. In order to solve the problem of luminance non-uniformity due to deterioration, a method has been proposed in which deterioration information of the organic light emitting diode is fetched in a specific sensing period, and the image data of the next frame is converted based on the deterioration information.

However, in the conventional deterioration compensation method, there is a separate sensing period for performing deterioration information sensing in one frame period, and the voltage of the power source is changed during the sensing period. Frequent fluctuations of the power source, which is required to maintain the constant voltage, increase the power consumption, make the power supply unstable, complicate the power supply circuit, and change the gradation expression during the sensing period, resulting in distortion of image quality.

It is therefore an object of the present invention to provide an organic electroluminescent display device capable of improving image quality without increasing power consumption during deterioration compensation.

An organic light emitting display according to an embodiment of the present invention includes a pixel portion connected to data lines, scan lines and sensing lines and including a plurality of pixels; A data driver for supplying a data signal to the data lines; A scan driver for driving one frame period in a subfield driving period and a sensing period including a plurality of subfields and supplying scan signals corresponding to the subfields to the scan lines; And a sensing driver for supplying a sensing signal for sensing deterioration information of the organic light emitting diode included in the pixel to at least one of the sensing lines during the sensing period.

In one embodiment, the sensing period may be included in the blank period. In one embodiment, the sensing driver may supply the sensing signal to one sensing line per frame. In one embodiment, the scan driver may be connected to a plurality of emission control lines, and may supply emission control signals corresponding to the subfield driving period to the emission control lines. In one embodiment, the periods of each of the subfields can be set differently.

In one embodiment, a sensing unit fetches deterioration information of the organic light emitting diode; A switching unit selectively connecting any one of the data driver and the sensing unit to the data lines; And a deterioration compensation unit for performing deterioration compensation of image data based on the deterioration information.

In one embodiment, the data driver and the data lines may be connected during the subfield driving period, and the timing controller may control the switching unit to connect the sensing unit and the data lines during the sensing period.

In one embodiment, each of the pixels includes: a driving transistor connected between the first power source and the organic light emitting diode; A first transistor connected between the driving transistor and the data line; A storage capacitor connected between the first electrode of the driving transistor and the first power supply; And a second transistor connected between the organic light emitting diode and the data line.

In one embodiment, the second transistor may be turned on in response to the sensing signal during the sensing period. In one embodiment, a sensing current is applied to the organic light emitting diode during the sensing period, and a sensing voltage corresponding to the sensing current may be fed back to the data line. In one embodiment, the driving transistor may be turned on in response to scan signals corresponding to each of the subfields to supply the data signal to the organic light emitting diode.

According to the present invention, the sensing period is set within the blank period of one frame, so that power consumption is not increased due to no power swing during the sensing period, and sensing is performed on a part of the pixels, , The phenomenon that the number of pixels for fetching deterioration information at the time of sensing is reduced and image quality is distorted can be improved.

FIG. 1 is a schematic diagram showing an organic light emitting display according to an embodiment of the present invention. Referring to FIG.
2 is an exemplary diagram for explaining the configuration of one frame in the digital driving method.
3 is a circuit diagram of the pixel shown in Fig.
FIG. 4 is a configuration diagram showing the sensing unit and the switching unit shown in FIG. 1 in detail.
5 is a waveform diagram for explaining a sensing method of an organic light emitting display according to an embodiment.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an organic light emitting display according to an embodiment of the present invention, and FIG. 2 is an exemplary diagram illustrating a configuration of one frame in a digital driving method. Referring to FIG.

1, an organic light emitting display according to an exemplary embodiment of the present invention includes a pixel portion 10, a scan driver 20, a data driver 30, a sensing driver 40, a sensing portion 50, A switching unit 60 and a timing control unit 70. [

The pixel unit 10 includes n scan lines S1 through Sn which are formed in a row direction to transmit a scan signal, n emission control lines E1 through En that transmit an emission control signal, N data lines D1 to Dm which are formed in the column direction and transmit data signals, the scan lines S1 to Sn and the emission control lines E1 to En A plurality of pixels PX connected to the sensing lines C1 to Cn and the data lines D1 to Dm and arranged in a matrix form. The pixels PX are supplied with a first power ELVDD having a high potential from the outside and a second power source ELVSS having a low potential.

The scan driver 20 is connected to the plurality of scan lines S1 to Sn and supplies scan signals to the scan lines S1 to Sn during one frame period (one horizontal period). The scan driver 20 generates a scan signal in response to the scan control signal SCS of the timing controller 70 and supplies the generated scan signal to the scan lines S1 to Sn.

The scan driver 20 is connected to the plurality of emission control lines E1 to En and supplies emission control signals corresponding to the subfield driving period to the emission control lines E1 to En. The light emission time of the pixels PX is adjusted in accordance with the light emission control signal.

Referring to FIG. 2, one frame period is divided into a subfield driving period SFD and a vertical blank time period B, and a subfield driving period SFD is divided into a plurality of subfields SF1 through SF4 . Each of the subfields SF1 to SF4 corresponds to a bit value of a data signal represented by a binary code and the gray level of one frame is represented by the sum of the emission times of the subfields SF1 to SF4 .

In the digital driving method of the present embodiment, the binary weight of the subfields SF1 to SF4 can be set in advance. That is, the periods of the first to fourth subfields SF1 to SF4 may be set differently from each other. For example, the period of the subfield may become longer from the first subfield SF1 to the fourth subfield SF4. The second subfield SF2 is twice the first subfield SF1 and the third subfield SF3 is twice the second subfield SF2 on the basis of the first subfield SF1, The fourth subfield SF4 may be twice the third subfield SF3. In this case, the fourth subfield SF4 having the longest period (i.e., the maximum emission time) may correspond to most significant bits (MSB) of the data signal, and the shortest period (i.e., the minimum emission time) The first sub-field SF1 having the first data line SF1 may correspond to least significant bits (LSB) of the data signal.

The blank period B may include or overlap a sensing period S for fetching deterioration information of the organic light emitting diode. The sensing period S is a period in which the degree of deterioration of the organic light emitting diodes of each of the plurality of pixels PX is sensed.

In this embodiment, the subfield driving period SFD is divided into four subfields. However, the present invention is not limited thereto. Further, as another embodiment of the digital driving, each of the subfields may be evenly divided, and may further include an initialization period, an erase period, and the like.

The data driver 30 is connected to the plurality of data lines D1 to Dm and supplies data signals to the data lines D1 to Dm. The data driver 30 converts the digital image data DATA 'into analog data signals (or data voltages) in response to the data control signal DCS of the timing controller 70. The data driver 30 supplies the data signals to the data lines D1 to Dm in synchronization with the scan signals.

The sensing driver 40 is connected to the plurality of sensing lines C1 to Cn and supplies sensing signals for sensing deterioration information of the organic light emitting diodes included in the pixels PX to sensing lines C1 to Cn during a sensing period S, Cn). For example, the sensing driver 40 selects one of the sensing lines for each frame in response to the sensing control signal SSCS of the timing controller 70, and supplies the sensing signals to the pixels PX connected to the selected sensing line. The detection signal is supplied collectively. That is, one row of pixels per frame is sensed. In the present embodiment, the sensing driver 40 is illustrated as being separate from other drivers, but it may be integrated with other drivers.

The sensing unit 50 fetches the deterioration information of the organic light emitting diode included in each of the pixels PX and provides the deteriorated information to the deterioration compensating unit 75. The sensing unit 50 can fetch deterioration information of the organic light emitting diode during the sensing period S. [

The switching unit 60 selectively connects any one of the data driver 30 and the sensing unit 50 to the data lines D1 to Dm. The switching unit 60 electrically connects any one of the data driver 30 and the sensing unit 50 to the data lines D1 to Dm in response to the switching control signal SWCS of the timing controller 70 . For example, the switching unit 60 connects the data driver 30 to the data lines D1 to Dm during the sub-field driving period SFD and applies the data signals to the data lines D1 to Dm during the sensing period S 50 can be connected.

The timing controller 70 receives input control signals such as a horizontal synchronization signal Hsync, a vertical synchronization signal Vsync, and a clock signal CLK). The timing controller 70 generates various control signals DCS and SCS for controlling the driving of the scan driver 20, the data driver 30, the sensing driver 40 and the switching unit 50 based on the input control signals. , SSCS, and SWCS) can be generated and output.

The timing controller 70 may further include a deterioration compensator 75 for compensating deterioration of the first image data DATA based on the deterioration information provided from the sensing unit 50. [ The deterioration compensating unit 75 stores and analyzes deterioration information to determine the degree of deterioration of the organic light emitting diodes included in the pixels PX and compensates the luminance of the first image data DATA according to the degree of deterioration (DATA ') so as to display an image of a uniform brightness and provides the second image data (DATA') to the data driver (30). To this end, the deterioration compensating unit 75 may include a memory (not shown) and a video data conversion circuit (not shown).

As described above, in the organic light emitting display of the present embodiment, the sensing signal can be selectively applied to the plurality of pixels PX in units of at least one row in the sensing period S, and degradation of the organic light emitting diodes And reflects the degree of the deterioration of the organic light emitting diode to the data signal of the next frame, thereby compensating for deterioration of the organic light emitting diode, thereby increasing the lifetime of the pixel.

3 is a circuit diagram of the pixel shown in Fig.

Referring to FIG. 3, a pixel PX according to an embodiment of the present invention includes an organic light emitting diode OLED and a pixel circuit 14 for supplying current to the organic light emitting diode OLED.

The anode electrode of the organic light emitting diode (OLED) is connected to the pixel circuit 14, and the cathode electrode is connected to the second power source ELVSS. The organic light emitting diode (OLED) generates light having a predetermined luminance corresponding to the current supplied from the pixel circuit 14.

The pixel circuit 14 receives a data signal from the data line Dm during a subfield drive period SFD in which a scan signal is supplied to the scan line Sn. The pixel circuit 14 provides deterioration information of the organic light emitting diode OLED to the sensing unit 50 during a sensing period S during which a sensing signal is supplied to the sensing line Cn. To this end, the pixel circuit 14 may include a plurality of transistors DT, T1, T2, and T3 and a storage capacitor Cst. The pixel circuit 14 may be selected from the various types of circuits currently known.

The gate electrode of the first transistor T1 is connected to the scan line Sn, and the first electrode thereof is connected to the data line Dm. The second electrode of the first transistor T1 is connected to the first terminal of the storage capacitor Cst. Here, the first electrode may be a source electrode and the second electrode may be a drain electrode. The first transistor T1 is turned on when a scan signal is supplied to the scan line Sn and transmits a data signal supplied from the data line Dm to the storage capacitor Cst.

The gate electrode of the driving transistor DT is connected to the first terminal of the storage capacitor Cst and the first electrode of the driving transistor DT is connected to the second terminal of the storage capacitor Cst and the first power source ELVDD. The driving transistor DT controls the amount of current flowing from the first power source ELVDD to the second power source ELVSS via the organic light emitting diode OLED in response to a voltage value stored in the storage capacitor Cst. At this time, the organic light emitting diode OLED generates light corresponding to the amount of current supplied from the driving transistor DT.

The gate electrode of the second transistor T2 is connected to the sensing line Cn and the first electrode of the second transistor T2 is connected to the anode electrode of the organic light emitting diode OLED. The second electrode of the second transistor T2 is connected to the data line Dm. The second transistor T2 is turned on during the sensing period S and turned off during the subfield driving period SFD in response to the sensing signal supplied to the sensing line Cn.

The gate electrode of the third transistor T3 is connected to the emission control line En and the first electrode thereof is connected to the second electrode of the driving transistor DT. Also, the second electrode of the third transistor T3 is connected to the organic light emitting diode OLED. The third transistor T3 is turned on during the subfield driving period SFD and turned off during the sensing period S in response to the emission control signal supplied to the emission control line En.

FIG. 4 is a configuration diagram illustrating the sensing unit and the switching unit shown in FIG. 1 in detail, and FIG. 5 is a waveform diagram illustrating a sensing method of the organic light emitting display according to one embodiment.

4, the sensing unit 50 of the OLED display according to the present embodiment includes a sensing circuit 51 and an analog-to-digital converter (ADC) 55 can do. The sensing circuit 51 may have a current source unit (not shown) for supplying a predetermined current to the pixel PX during the sensing period S. [ The sensing circuit 51 supplies a sensing current to the pixel PX during the sensing period S and feeds the sensing voltage to the data line Dm when the sensing current is supplied to the ADC 55. [ Since the sensing current flows through the organic light emitting diode OLED included in the pixel PX, the sensing voltage applied to the data line Dm has deterioration information of the organic light emitting diode OLED. The magnitude of the sensing current may be determined experimentally. The ADC 55 converts the sensing voltage into a digital value and provides the digital value to the deterioration compensating unit 75.

The switching unit 60 may include a pair of switching elements SW1 to SW2 connected to the data lines Dm. The first and second switching elements SW1 and SW2 are selectively turned on in response to the switching control signal SWCS. The first switching element SW1 is connected between the data line Dm and the data driver 30 and is turned on during the subfield driving period SFD. The second switching element SW2 is connected between the data line Dm and the sensing unit 50 and is turned on during the sensing period S. [

The timing controller 70 is connected to the data driver 30 and the data lines Dm during the subfield driving period SFD and switches the sensing unit 50 and the data lines Dm during the sensing period S, (60). To this end, the timing controller 70 may output a switching control signal SWCS.

The deterioration compensating unit 75 generates the second image data DATA 'by changing the bit value of the first image data DATA so that the deterioration of the organic light emitting diode OLED can be compensated, DATA ') to the data driver 30. For example, the deterioration compensating unit 75 increases the bit value of the first image data (DATA) as the degree of deterioration of the organic light emitting diode OLED increases with reference to the digital value provided from the ADC 55, (DATA ').

The sensing unit 50 and the switching unit 60 are not limited to the above structure and may be modified into various structures capable of fetching deterioration information of the organic light emitting diode OLED during the sensing period S. [

Referring to FIG. 5, one frame may be defined by a scan start signal (STV), and a subfield driving period (SFD) in which the organic light emitting diode (OLED) And a sensing period (S) for fetching deterioration information. As described above, the sensing period S can be included or overlapped in the blank period B and can be set in succession to the most significant bit of the data signal applied during the sub-field driving period SFD, have. In the present embodiment, it is assumed that the sensing period S and the blank period B overlap each other for convenience.

During the subfield driving period SFD, the scanning signal Scan is sequentially output corresponding to each of the first to fourth subfields SF1 to SF4. During the subfield driving period SFD, the first switching device SW1 is turned on so that the data line Dm and the data driver 30 are connected. Then, the organic light emitting diode OLED of the pixels PX emits light at a predetermined luminance by the data signal supplied through the data line Dm.

A sensing signal Sense for fetching deterioration information of the organic light emitting diode OLED is supplied to at least one of the sensing lines C1 to Cn during the sensing period S. [ The sensing signal Sense is supplied to one sensing line per frame and the sensing signal Sense is supplied to the first sensing line C1 during the sensing period S. In this case, In the next frame, the sense signal Sense may be sequentially supplied to the second sensing line C2.

First, during the sensing period S, the second switching device SW2 is turned on, and the data line Dm and the sensing unit 50 are connected. The pixels of the first column connected to the selected first sensing line C1 are turned on by the sense signal Sense supplied to the first sensing line C1. The third transistor T3 is turned off by the emission control signal ECS supplied to the first emission control line E1.

During the sensing period S, the switching unit 60 turns on the second switching device SW2 by the switching control signal SWCS so that the data line Dm and the sensing unit 50 are connected. Then, a sensing current from the sensing circuit 51 is supplied to the second power source ELVSS via the data line Dm, the second transistor T2, and the organic light emitting diode OLED. At this time, deterioration information (that is, a predetermined sensing voltage) is applied to the anode electrode of the organic light emitting diode (OLED), and such deterioration information DI can be sensed by the sensing circuit 51.

According to the present invention, a sensing period is set within a blank period of one frame, and deterioration correction is performed on a part of pixels per one frame, so that power consumption is not increased due to no power swing in the sensing period, It is possible to improve the phenomenon that the image quality at the time of sensing is distorted.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be apparent to those skilled in the art that various modifications may be made without departing from the scope of the present invention.

10: pixel portion 20: scan driver
30: Data driver 40: Sensing driver
50: sensing part 51: sensing circuit
55: ADC 60:
70: timing control section 75: deterioration compensating section
SFD: subfield driving period B: blank period
S: sensing period

Claims (11)

A pixel portion connected to the data lines, the scan lines and the sense lines and including a plurality of pixels;
A data driver for supplying a data signal to the data lines;
A scan driver for driving one frame period in a subfield driving period and a sensing period including a plurality of subfields and supplying scan signals corresponding to the subfields to the scan lines; And
And a sensing driver for supplying a sensing signal for sensing deterioration information of the organic light emitting diode included in the pixel to at least one of the sensing lines during the sensing period. The method according to claim 1,
Wherein the sensing period is included in the blank period. The display device according to claim 1, wherein the sensing driver comprises:
And the sensing signal is supplied to one sensing line per one frame. The liquid crystal display according to claim 1,
Wherein the plurality of light emitting control lines are connected to a plurality of light emitting control lines, and the light emitting control lines corresponding to the subfield driving period are supplied to the light emitting control lines. The method according to claim 1,
Wherein a period of each of the subfields is differently set. The method according to claim 1,
A sensing unit for extracting deterioration information of the organic light emitting diode;
A switching unit selectively connecting any one of the data driver and the sensing unit to the data lines; And
Further comprising a deterioration compensator configured to compensate deterioration of image data based on the deterioration information. The method according to claim 6,
And a timing controller for controlling the switching unit such that the data driver and the data lines are connected during the subfield driving period and the sensing unit and the data lines are connected during the sensing period. Device. 2. The display device according to claim 1,
A driving transistor connected between the first power source and the organic light emitting diode;
A first transistor connected between the driving transistor and the data line;
A storage capacitor connected between the first electrode of the driving transistor and the first power supply; And
And a second transistor connected between the organic light emitting diode and the data line. 9. The method of claim 8,
And the second transistor is turned on in response to the sensing signal during the sensing period. 10. The method of claim 9,
Wherein a sensing current is applied to the organic light emitting diode during the sensing period, and a sensing voltage corresponding to the sensing current is fed back to the data line and sensed. 9. The method of claim 8,
Wherein the driving transistor is turned on in response to scan signals corresponding to each of the subfields and supplies the data signal to the organic light emitting diode.

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