KR20150077171A - Organic light emitting diode display and method for driving the same - Google Patents

Organic light emitting diode display and method for driving the same Download PDF

Info

Publication number
KR20150077171A
KR20150077171A KR1020130166089A KR20130166089A KR20150077171A KR 20150077171 A KR20150077171 A KR 20150077171A KR 1020130166089 A KR1020130166089 A KR 1020130166089A KR 20130166089 A KR20130166089 A KR 20130166089A KR 20150077171 A KR20150077171 A KR 20150077171A
Authority
KR
South Korea
Prior art keywords
threshold voltage
sensing
plurality
pixels
driving tft
Prior art date
Application number
KR1020130166089A
Other languages
Korean (ko)
Inventor
문경수
Original Assignee
엘지디스플레이 주식회사
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 엘지디스플레이 주식회사 filed Critical 엘지디스플레이 주식회사
Priority to KR1020130166089A priority Critical patent/KR20150077171A/en
Publication of KR20150077171A publication Critical patent/KR20150077171A/en

Links

Images

Abstract

An OLED display according to an exemplary embodiment of the present invention includes a plurality of scan lines, a plurality of data lines intersecting with the scan lines, and a plurality of data lines arranged in a matrix form at intersections of the plurality of scan lines and the plurality of data lines. A display panel including pixels of the display panel; An external compensation unit for compensating digital image data according to a sensing value of a threshold voltage value of the driving TFT of the plurality of pixels; A data driving circuit for converting the compensated digital image data into an analog data voltage and supplying the analog data voltage to the plurality of data lines; And a scan driving circuit for supplying a scan signal to the plurality of scan lines, wherein the external compensation unit divides the display panel into a plurality of blocks, senses a threshold voltage value of a driving TFT of some pixels for each block, Sets the sensed threshold voltage value as a threshold voltage representative value of the block, and compensates digital image data supplied to the plurality of pixels of the block according to the set threshold voltage representative value.

Description

Technical Field [0001] The present invention relates to an organic light emitting diode (OLED) display device,

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

As the information society develops, the demand for display devices for displaying images is increasing in various forms. Accordingly, in recent years, various kinds of flat panel display devices such as a liquid crystal display (LCD), a plasma display panel (PDP), and an organic light emitting diode (OLED) . Among these flat panel display devices, the organic light emitting diode display device is capable of low power driving, is thin, has excellent viewing angle, and has a high response speed. An active matrix type organic light emitting diode display device in which a plurality of pixels are arranged in a matrix form and displays an image is widely studied and used.

A display panel of an active matrix type organic light emitting diode display device includes a plurality of pixels arranged in a matrix form. Each of the pixels includes a switching TFT (Switching Thin Film Transistor) for supplying a data voltage of a data line in response to a scan signal of a scan line, and a current And a driving TFT (Driving Thin Film Transistor) for adjusting the amount of the driving TFT. At this time, the drain-source current Ids of the driving TFT supplied to the organic light emitting diode can be expressed by Equation (1).

[Equation 1]

I ds = K '(V gs - V th ) 2

In Equation 1, K 'is a proportional coefficient determined by the structure and physical characteristics of the driving TFT, Vgs is the gate-source voltage of the driving TFT, and Vth is the threshold voltage of the driving TFT.

On the other hand, each driving TFT exhibits different threshold voltage (Vth) characteristics in the manufacturing process of the organic light emitting diode display device. Particularly, in the driving process of the display device, the threshold voltage (Vth) can be shifted by the deterioration of the driving TFT according to the driving time, and the driving TFTs of the pixels can have different threshold voltage (Vth) values . In this case, since the drain-source current Ids of the driving TFT depends on the threshold voltage Vth of the driving TFT, even if the same data voltage is supplied to each of the pixels, the current Ids supplied to the organic light- It is different. Therefore, the brightness of light emitted by each organic light emitting diode is changed, resulting in distortion of the image. In order to solve this problem, a compensation method for sensing and compensating the threshold voltage (Vth) of the driving TFT has been proposed.

The method of compensating the threshold voltage (Vth) of the driving TFT is largely divided into internal compensation and external compensation. Internal compensation means that the threshold voltage of the driving TFT is sensed and compensated in real time within each of the pixels. To this end, a plurality of compensating TFTs are included in addition to the switching TFT and the driving TFT, so that the circuit becomes complicated.

The external compensation means sensing the threshold voltage of the driving TFT through the sensing line, compensating the digital image data to be supplied to the pixels using the sensed voltage, and supplying the compensated digital image data to the pixels. To this end, the threshold voltage of the sensed driving TFT is directly stored in a separate memory or the compensation value corresponding to the threshold voltage is stored in a separate memory to compensate the digital image data.

1 and 2 are circuit diagrams of pixels for external compensation and examples of timing of driving them. 1 and 2, a pixel includes a switching TFT ST1 for supplying a data voltage of a data line DL to a gate electrode of a driving TFT DT in response to a first scan signal of a first scan line SL1 A driving TFT DT for adjusting the amount of current supplied to the organic light emitting diode according to a voltage applied to the gate electrode, a sensing line SENL responsive to a second scan signal of the second scan line SL2, A sensing TFT ST2 for sensing a threshold voltage of the driving TFT DT through a sampling capacitor Csam and a sampling capacitor Csam for storing a gate-source voltage difference of the driving TFT DT.

An operation of sensing the threshold voltage of the driving TFT DT in the pixel having the above structure will be described.

An initialization step and an sensing step are performed in order to sense a threshold voltage. In the initialization step, the threshold voltage of the driving TFT DT is reflected to the sensing line SENL And the sensing step is a step of reading the threshold voltage.

First, a voltage for turning off the organic light emitting element OLED is applied to the high-potential voltage VDD or the low-potential voltage VSS in order to sense the threshold voltage of the driving TFT DT.

This utilizes the source follower operation in such a manner that the voltage across the gate and source of the driver TFT DT is measured while no current flows through the organic light emitting device OLED.

According to FIG. 2, the organic light emitting diode OLED is turned off by raising the low voltage VSS to the high voltage VDD level, but conversely, the high voltage VDD may be lowered.

Thereafter, or simultaneously with this, the data line is supplied with the sensing data voltage SED which serves as a reference for the sensing voltage measurement. The sensing data voltage SED is supplied to the gate terminal of the driving TFT DT through the switching TFT ST1 turned on in response to the turn-on voltage of the first scan line SL1.

Thereafter or simultaneously, the sensing reference voltage SER is supplied to the source terminal of the driving TFT DT through the sensing TFT ST2. The sensing reference voltage SER is applied to only a part of the initialization time through the sensing line SENL and serves to initialize the voltage at the source terminal of the driving TFT DT.

After the sensing reference voltage SER is applied, the sensing line SENL is floated from the outside. Therefore, the source terminal of the driving TFT DT connected through the sensing line SENL and the sensing TFT ST2 is floated, and then the voltage is affected by the sampling capacitor Csam.

Since the sensing data voltage SED is applied to the gate electrode of the driving TFT DT during the floating operation, the sensing data voltage SED under the influence of the sensing data voltage SED is applied to the source electrode of the driving TFT DT. And finally changes to a voltage value added / subtracted by the threshold voltage of the driving TFT DT on the basis of the sensing data voltage SED.

After a sufficient time for voltage variation is maintained, the sensing TFT (ST2) is turned off and the sensing step (Sensing Time) proceeds.

The voltage of the source electrode of the driving TFT DT is applied to the sensing line SENL and the sensing line SENL is in the floating state even when the sensing switching ST2 is turned off so that its value is maintained by its own capacitance.

The threshold voltage value of the driving TFT DT is sensed by reading the voltage value applied to the source electrode of the driving TFT DT through the sensing line SENL.

In order to sense the threshold voltage, a considerable time is required until the gate-source voltage difference of the driving TFT DT reaches the threshold voltage.

It is assumed that the display panel includes 1920 x 1080 pixels, and one pixel includes four sub-pixels. If the four sub-pixels share one sensing line, it is assumed that the time to reach the threshold voltage is 10 ms. In order to sense the threshold voltage of each driving TFT DT of all the sub-pixels of the display panel, 1080 × 4 × 10 msec ≈43 sec (sec). That is, there is a problem that the period for sensing the threshold voltage of the driving TFT DT of each of the sub-pixels of the display panel for external compensation is too long.

In order to solve this problem, there is a method in which the user senses when the user turns off the power supply of the organic light emitting diode display in order to compensate the threshold voltage of the driving TFT DT of each of the sub pixels of the display panel. In this method, even if the user turns off the organic light emitting diode display device, the organic light emitting diode display device does not display an image, and has a function of sensing the threshold voltage of the driving TFT DT of each of the sub pixels of the display panel The power supply is continuously supplied so that it can be performed. However, since the threshold voltage sensing period of the driving TFT DT of each of the sub-pixels of the display panel corresponds to approximately 43 sec (sec), the user can not perform the action of extracting the outlet and knowing that the power supply of the organic light emitting diode display device is turned off , It is impossible to perform external compensation because the sensing is not performed properly, or incorrect external compensation may be performed due to an error in the process of storing in a separate memory.

In addition, unexpected power consumption is caused by long-time sensing, which is disadvantageous in terms of power consumption.

The present invention provides an organic light emitting diode display device and a driving method thereof that can minimize a threshold voltage sensing time of a driving TFT of each of sub pixels of a display panel.

An OLED display according to an exemplary embodiment of the present invention includes a plurality of scan lines, a plurality of data lines intersecting with the scan lines, and a plurality of data lines arranged in a matrix form at intersections of the plurality of scan lines and the plurality of data lines. A display panel including pixels of the display panel; An external compensation unit for compensating digital image data according to a sensing value of a threshold voltage value of the driving TFT of the plurality of pixels; A data driving circuit for converting the compensated digital image data into an analog data voltage and supplying the analog data voltage to the plurality of data lines; And a scan driving circuit for supplying a scan signal to the plurality of scan lines, wherein the external compensation unit divides the display panel into a plurality of blocks, senses a threshold voltage value of a driving TFT of some pixels for each block, Sets the sensed threshold voltage value as a threshold voltage representative value of the block, and compensates digital image data supplied to the plurality of pixels of the block according to the set threshold voltage representative value.

A method of driving an organic light emitting diode display according to an exemplary embodiment of the present invention includes a plurality of scan lines, a plurality of data lines intersecting with the scan lines, and a plurality of scan lines and a plurality of data lines, A method of driving an organic light emitting diode display device including a display panel including a plurality of pixels arranged in a matrix, the method comprising: compensating digital image data according to a sensing value of a threshold voltage value of a driving TFT of the plurality of pixels; Converting the compensated digital image data to an analog data voltage and supplying the analog data voltage to the plurality of data lines; And supplying a scan signal to the plurality of scan lines. The step of compensating for digital image data according to a sensing value of a threshold voltage value of the driving TFT of the plurality of pixels includes: Dividing the pixel into blocks and sensing a threshold voltage value of a driving TFT of some pixels for each block; And setting the sensed threshold voltage value as a threshold voltage representative value of the block to compensate digital image data supplied to the plurality of pixels of the block according to the threshold voltage representative value.

The present invention can reduce the time required for external compensation of the organic light emitting diode display device to within a few seconds, thereby enhancing the stability of the external compensation. That is, even if the user thinks that the power of the display device is turned off and the electric outlet is disconnected, the external compensation can be sufficiently performed. Further, the present invention can reduce the power consumption required for sensing the pixel characteristics for a long time.

1 is a diagram illustrating a pixel structure of a general organic light emitting diode display device.
2 is a timing chart for sensing the threshold voltage of the driving TFT in the pixel structure of FIG.
3 is a block diagram of an organic light emitting diode display according to the present invention.
4 is a diagram illustrating a pixel structure of an organic light emitting diode display device according to the present invention.
5 is a diagram illustrating a sensing operation according to an embodiment of the present invention.
6 is a circuit block diagram of the external compensation unit of the present invention.
7 is a diagram illustrating a sensing operation according to another embodiment of the present invention.
8 is a timing chart for sensing a threshold voltage of a driving TFT in the pixel structure of FIG. 4 according to the present invention.
9 is a diagram illustrating a driving sequence of an organic light emitting diode display according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The names of components used in the following description are selected in consideration of ease of specification, and may be different from actual product names.

The present invention relates to an organic light emitting diode display device which externally compensates a threshold voltage of a driving TFT of each of pixels. The compensation method for compensating the threshold voltage of the driving TFT is roughly divided into internal compensation and external compensation. Internal compensation means to sense and compensate the threshold voltage of the driving TFT in real time in each of the pixels. The external compensation senses the threshold voltage of the driving TFT of each pixel through the sensing lines, compensates the digital image data to be supplied to the pixels by using the sensed threshold voltages, and supplies the compensated digital image data to the pixels .

3 is a block diagram schematically showing an organic light emitting diode display device according to an embodiment of the present invention. 3, an OLED display according to an exemplary embodiment of the present invention includes a display panel 10, a scan driver 110, a data driver 120, a timing controller 130, and an external compensator 140, Respectively.

The display panel 10 is formed to intersect the data lines DL and the scan lines SL1 and SL2. The display panel 10 is formed with a pixel array in which pixels P are arranged in the form of a matrix at intersections of the data lines DL and the scan lines SL1 and SL2. The display panel 10 can display an image in various forms such as bottom emission and top emission.

Each of the pixels P of the display panel 10 is turned on in response to the first scan signal of the first scan line SL1 to apply the data voltage of the data line DL to the gate electrode of the drive TFT DT A driving TFT DT for adjusting the amount of current supplied to the organic light emitting diode according to a voltage applied to the gate electrode, and a driving TFT DT for controlling the amount of current supplied to the organic light emitting diode in response to a second scan signal of the second scan line SL2 A sensing TFT ST2 for sensing the threshold voltage of the driving TFT DT through the sensing line SENL and a sampling capacitor Csam for storing the gate-source voltage difference of the driving TFT DT have.

The switching TFT ST1 supplies the data voltage of the data line DL to the gate electrode of the driving TFT DT in response to the first scan signal of the first scan line SL1. The gate electrode of the switching TFT ST1 may be connected to the first scan line SL1 and the source electrode thereof may be connected to the data line DL and the drain electrode thereof may be connected to the gate electrode of the driver TFT DT.

The sensing TFT ST2 senses the threshold voltage of the driving TFT DT through the sensing line SENL in response to the second scan signal of the second scan line SL2. The gate electrode of the second switching TFT ST2 may be connected to the second scan line SL2 and the source electrode thereof may be connected to the first node N1 and the drain electrode thereof may be connected to the sensing line SENL.

The driving TFT DT adjusts the amount of current supplied to the organic light emitting diode OLED according to the voltage of the gate electrode. The gate electrode of the driving TFT DT is connected to the drain electrode of the first switching TFT ST1, the source electrode thereof is connected to the high potential voltage VDD, and the drain electrode thereof is connected to the first node N1 . The anode electrode of the organic light emitting diode element OLED may be connected to the first node N1, and the cathode electrode thereof may be connected to the low potential voltage VSS.

The sampling capacitor Csam stores the gate-source voltage difference of the driving TFT DT. When the display panel 10 is in a driving mode for displaying an image, the sampling capacitor Csam stores a voltage difference between the gate and the source capable of passing an appropriate current for expressing an image, The sampling capacitor Csam stores a voltage including the threshold voltage value of the driving TFT DT.

In Fig. 3, the switching TFT ST1, the sensing TFT ST2, or the driving TFT DT are described as N type TFTs, but the present invention is not limited to this. P type TFT and the organic light emitting diode OLED is connected to the low potential voltage VSS. However, the present invention is not limited to this, and it may be connected to the high potential voltage VDD.

A sensing line SENL for sensing the threshold voltage of the driving TFT DT of each of the pixels P may be formed in the display panel 10. [ To this end, the sensing lines SENL may be connected to the respective pixels P and connected to the data driver 120.

The threshold voltage of the driving TFT DT sensed through the sensing line SENL can be converted to digital for subsequent computation operations. When the data driver 120 performs the threshold voltage, the sensing line SENL outputs data May be connected to the driving unit 120, and if it is implemented in a separate configuration, it may be directly connected to another configuration without passing through the data driving unit 120.

The sensing line SENL may be formed by matching with each pixel P as shown in the drawing, but may be formed by being commonly connected to a plurality of pixels.

The data driver 120 includes a plurality of source drive ICs. The source drive ICs receive the digital video data RGB 'in which the threshold voltage of the driving TFT DT of each of the pixels P is compensated from the timing control unit 130. The source drive ICs convert the compensated digital video data RGB 'into analog data voltages in response to the source timing control signal DCS from the timing controller 130 and synchronize the analog data voltages with the scan pulses To the data lines (DL) of the display panel (10).

The data driver 120 may be mounted on a tape carrier package (TCP) or a chip on film (COF), bonded to a lower substrate of the display panel 10 by a tape automated bonding (TAB) And may be connected to a printed circuit board (PCB). The data driver 120 may be bonded on the lower substrate of the display panel 10 by a COG (chip on glass) process.

The scan driver 110 supplies scan pulses to the scan lines SL1 and SL2 in order to control the switching TFTs ST1 and the sensing TFTs ST2 of the pixels P, respectively. The scan driver 110 may be mounted on the TCP and bonded to the lower substrate of the display panel 10 by a TAB process. In addition, the scan driver 110 may be formed directly on the lower substrate simultaneously with the pixel array by a GIP (Gate In Panel) process.

The timing controller 130 receives the compensated digital video data RGB 'from the external compensator 140. The timing controller 130 receives a timing signal such as a vertical synchronization signal, a horizontal synchronization signal, a data enable signal, and a dot clock from the outside Receive. The timing controller 130 arranges the compensated digital video data RGB 'supplied from the external compensator 140 so as to output the compensated digital video data RGB' to the data driver 120 based on the timing signal, And generates timing control signals for controlling the operation timing of the data driver 120. [

The timing control signals include a scan timing control signal GCS for controlling the operation timing of the scan driver 110 and a data timing control signal DCS for controlling the operation timing of the data driver 120. The timing controller 130 outputs a scan timing control signal GCS to the scan driver 110 and a data timing control signal DCS to the data driver 120.

The external compensation unit 140 receives digital image data RGB from an external host system through an interface such as a Low Voltage Differential Signaling (LVDS) interface or a Transition Minimized Differential Signaling (TMDS) interface. The external compensation unit 140 may receive a vertical synchronization signal, a horizontal synchronization signal, a data enable signal, and a dot clock signal from the host system in order to perform an external compensation operation. clock, etc., can be input.

The external compensation unit 140 reads the compensation weight corresponding to the threshold voltage value or the threshold voltage value of each area of the display panel 10 stored in the internal or separately configured memory during the video display period of the display panel 10, Compensates the digital image data RGB to be displayed and outputs the compensated digital image data RGB '.

At the power-off time of the display panel 10, a characteristic value change of a region in which each pixel is located, that is, a threshold voltage value, is sensed and the characteristic is stored in the memory.

The external compensation unit 140 divides and defines the display panel 10 into a plurality of blocks in order to reduce the threshold voltage sensing time and senses the threshold voltage value of the driving TFT DT of each pixel for each block, The representative threshold voltage value (SVTH) is stored in the memory. The sensed threshold voltage value is commonly used when compensating data to be displayed in a corresponding region in a video display period as a threshold voltage representative value of the corresponding block.

Some of the pixels may be one pixel or two or more horizontally adjacent pixels. In the case of two or more pixels, the threshold voltage representative value is obtained by averaging the threshold voltage values (SVTH) of two or more sensed pixels or by a separate calculation operation.

Since the characteristics of the normal driving TFT DT are similar in a narrow peripheral region, even if the threshold voltage of one driving TFT DT per region is sensed and set to a representative value as in the present invention, . Therefore, the sensing time can be reduced by sensing only the necessary pixels and skipping the sensing operation of the remaining pixels.

FIG. 5 is a view for explaining a method of sensing a block according to an embodiment of the present invention.

The scan driver 110 and the data driver 120 apply a scan signal to the pixels requiring threshold voltage sensing on the first and second scan lines SL1 and SL2 at the time when the display panel 10 is powered off Supply. At this time, the sensing reference voltage and the sensing data voltage are supplied as shown in FIG. 8 to sense the threshold voltage of the corresponding pixel. 5, when it is desired to measure the threshold voltages of the pixels B11, B21, B31, B12, B22, B32, B13, B23 and B33, the scan signals are supplied to the pixels through the first and second scan lines SL1 and SL2 And the sensing time can be reduced to half because only the odd columns are sequentially applied in the drawing.

When a threshold voltage of two or more pixels is measured in one block, the threshold voltage of a horizontally adjacent pixel is sensed. In this case, the threshold voltage representative value of the block is averaged Or obtained by a separate calculation operation.

In the case of measuring the threshold voltage of two or more pixels in one block, if the vertically arranged pixels are sensed, the scan signals are applied to all vertically arranged pixels, It may be disadvantageous that the sensing of horizontally adjacent pixels is advantageous.

Accordingly, each of the divided blocks includes at least two or more pixel columns including a row for sensing and a column for skipping.

The external compensation unit 140 receives the threshold voltage value of each block sensed through the sensing line SENL, sets the threshold voltage representative value SVTH of the corresponding block, and stores it in the memory.

Referring to FIG. 6, the external compensator 140 includes a memory 220 for storing threshold voltage representative values (SVTH) of the driving of each block, a threshold voltage representative value (SVTH) supplied to a pixel of the block using the threshold voltage representative value And a data compensator 210 for compensating the digital image data RGB.

The threshold voltage representative value SVTH may be stored in the memory as it is received from the external compensation unit 140 or may be compensated for using the compensated digital image data RGB And may be stored in the memory 220 in a modified form.

Since the memory 220 stores only the threshold voltage representative value (SVTH) for each block, the storage capacity can be significantly reduced compared with a conventional method in which a threshold voltage value is stored for each pixel.

The data compensator 210 receives the digital image data RGB in the video display period of the display panel 10 and receives the representative threshold voltage value SVTH or the threshold voltage value SVC of each block of the display panel 10 stored in the memory 220 Reads the correction weight according to the threshold voltage value, and compensates the digital image data (RGB) to be displayed in the corresponding area to output the compensated digital image data (RGB ').

The external compensation unit 140 may be formed as a single circuit with the timing controller 130, and the memory 220 may be separately configured as an external flash memory or the like.

FIG. 7 is a view for explaining a sensing method for each block according to another embodiment of the present invention.

The scan driver 110 and the data driver 120 apply a scan signal to the pixels requiring threshold voltage sensing on the first and second scan lines SL1 and SL2 at the time when the display panel 10 is powered off Supply. At this time, the sensing reference voltage and the sensing data voltage are supplied as shown in FIG. 8 to sense the threshold voltage of the corresponding pixel. When a threshold voltage for B11, B21, B12, B22, B13, and B23 is measured as shown in FIG. 7, the scan signal is simultaneously applied to the pixel column where each pixel is located.

Since the sensing of all blocks is implemented by applying one scan signal, the sensing time is drastically reduced.

However, since the pixels to be sensed supply the sensed threshold voltage values using different sensing lines (SENL) among the blocks arranged in the vertical direction, pixels located in different columns in the vertical direction are selected and sensed.

The external compensation unit 140 sets a pixel at a position different from a pixel that has been previously measured at each time when the user turns off the power, and performs the sensing operation. If only the same pixel is measured for each block, it is possible to continuously perform erroneous compensation when the pixel exhibits an abnormal characteristic. Therefore, a sensing operation is performed by setting pixels at different positions for each block at every off- .

8 is a timing chart related to the operation of sensing the threshold voltage of the driving TFT DT.

An initialization step and an sensing step are performed in order to sense a threshold voltage. In the initialization step, the threshold voltage of the driving TFT DT is reflected to the sensing line SENL And the sensing step is a step of reading the threshold voltage.

First, a voltage for turning off the organic light emitting element OLED is applied to the high-potential voltage VDD or the low-potential voltage VSS in order to sense the threshold voltage of the driving TFT DT.

This utilizes the source follower operation in such a manner that the voltage across the gate and source of the driver TFT DT is measured while no current flows through the organic light emitting device OLED.

According to FIG. 8, the organic light emitting diode OLED is turned off by raising the low potential VSS to the high potential level VDD, but conversely, the high potential voltage VDD may be lowered.

Thereafter, or simultaneously with this, the data line is supplied with the sensing data voltage SED which serves as a reference for the sensing voltage measurement. The sensing data voltage SED is supplied to the gate terminal of the driving TFT DT through the switching TFT ST1 turned on in response to the turn-on voltage of the first scan line SL1.

Thereafter or simultaneously, the sensing reference voltage SER is supplied to the source terminal of the driving TFT DT through the sensing TFT ST2. The sensing reference voltage SER is applied to only a part of the initialization time through the sensing line SENL and serves to initialize the voltage at the source terminal of the driving TFT DT.

After the sensing reference voltage SER is applied, the sensing line SENL is floated from the outside. Therefore, the source terminal of the driving TFT DT connected through the sensing line SENL and the sensing TFT ST2 is floated, and then the voltage is affected by the sampling capacitor Csam.

Since the sensing data voltage SED is applied to the gate electrode of the driving TFT DT during the floating operation, the sensing data voltage SED under the influence of the sensing data voltage SED is applied to the source electrode of the driving TFT DT. And finally changes to a voltage value added / subtracted by the threshold voltage of the driving TFT DT on the basis of the sensing data voltage SED.

After a sufficient time for voltage variation is maintained, the sensing TFT (ST2) is turned off and the sensing step (Sensing Time) proceeds.

The voltage of the source electrode of the driving TFT DT is applied to the sensing line SENL and the sensing line SENL is in the floating state even when the sensing switching ST2 is turned off so that its value is maintained by its own capacitance.

The threshold voltage value of the driving TFT DT is sensed by reading the voltage value applied to the source electrode of the driving TFT DT through the sensing line SENL.

FIG. 9 is a flowchart illustrating a method of driving an organic light emitting diode display according to an embodiment of the present invention shown in FIG. Referring to FIG. 9, a method of driving an organic light emitting diode display according to an exemplary embodiment of the present invention includes a case where power is supplied to the display device 10 to display an image, and a case where power is turned off, Sensing.

Referring to FIG. 9, when the organic light emitting diode display device is powered on (S101), the external compensation unit 140 reads the threshold voltage representative value (SVTH) of each block from the memory 220 as described in FIG. 6, And uses the representative value SVTH to compensate the digital image data RGB supplied to the pixels of the block.

Accordingly, the compensated digital image data RGB 'is output to the display device 10, thereby outputting a uniform image irrespective of deterioration of the drive TFT DT or characteristic change.

To this end, the compensated digital image data RGB 'is converted into an analog data voltage, which is supplied to a plurality of data lines, and a scan signal is supplied to a plurality of scan lines to display an image on the display panel 10 do.

When the off signal of the display device is received from the user (103), the external compensation unit 140 operates in the sensing mode. The organic light emitting diode OLED is turned off by controlling the high or low potential voltage VDD or VSS applied to each pixel as described in FIG. 8, and the threshold voltage of the pixels is sensed (S104) .

For this purpose, the display panel 10 is divided into a plurality of blocks and defined, and the threshold voltage value of the driving TFT of some pixels is sensed for each block.

The threshold voltage representative value SVTH of the block corresponding to the sensed threshold voltage is stored and stored in the memory 220 in step S 105. The threshold voltage of each pixel in each block is sensed and stored in the memory 220 The power is finally turned off (S106).

Then, when the power is turned on, the compensated digital image data RGB 'is compensated by using the stored threshold value SVTH of each block to compensate the digital image data RGB supplied to the pixels of the corresponding block, .

In the sensing mode driving, the sensing operation may be performed by setting a pixel at a position different from the pixel that has been measured at the time when the user turns off the power. If only the same pixel is measured for each block, it is possible to continuously perform erroneous compensation when the pixel exhibits an abnormal characteristic. Therefore, a sensing operation is performed by setting pixels at different positions for each block at every off- .

In the sensing mode, the step of sensing the threshold voltage of the driving TFT DT of each pixel in each of the blocks is performed such that the organic light emitting device OLED is first turned off to sense the threshold voltage of the normal driving TFT DT To the high-potential voltage (VDD) or the low-potential voltage (VSS). The low potential voltage VSS can be raised, and conversely, the high potential voltage VDD can be lowered.

At the same time, a sensing data voltage SED is supplied to the data line as a reference for sensing voltage measurement. The sensing data voltage SED is supplied to the gate terminal of the driving TFT DT through the switching TFT ST1 turned on in response to the turn-on voltage of the first scan line SL1.

At this time, a sensing reference voltage (SER) is supplied to the source terminal of the driving TFT (DT) through the sensing TFT (ST2). The sensing reference voltage SER is applied to only a part of the initialization time through the sensing line SENL and serves to initialize the voltage at the source terminal of the driving TFT DT.

After the sensing reference voltage SER is applied in the initialization step (Initial Time), the sensing line SENL is floated so that the source electrode voltage of the driving TFT DT is boosted from the sensing reference voltage SER, The voltage value is increased or decreased by the amount of the threshold voltage of the driving TFT DT based on the voltage SED.

The threshold voltage of the driving TFT DT is sensed by reading the voltage value of the source electrode of the driving TFT DT applied to the sensing line SENL in the sensing period.

In this case, the first scan signal supplied to the first scan line SL1 and the second scan signal supplied to the second scan line SL2 may correspond to a pixel to be sensed as shown in FIG. 5 according to an embodiment of the present invention. And can be sequentially supplied for each of the upper and lower blocks.

According to another embodiment of the present invention, the first scan signal supplied to the first scan line SL1 and the second scan signal supplied to the second scan line SL2 are simultaneously supplied to the pixels to be sensed by the upper and lower blocks, The pixels sensed by the upper and lower blocks can supply the threshold voltage value through the different sensing lines.

As described above, the present invention divides and defines the display panel 10 into a plurality of blocks and senses the threshold voltage of the driving TFT DT of some pixels for each block at the power-off time of the display panel 10 , Sets the sensed threshold voltage value as a threshold voltage representative value of the block, and stores it in the memory.

Then, by compensating the digital image data by using the threshold voltage representative value of each block stored in the memory at the time of image output of the display panel, uneven output according to the characteristic of the driving TFT (DT) can be reduced.

The present invention can reduce the time required for threshold voltage sensing of each pixel at the time of power-off to within a few seconds. Therefore, even when a user thinks that the power of the organic light emitting diode display device is turned off, And the power consumption can be reduced by reducing the operation time by that much. In addition, there is an advantage that the memory capacity used for existing external compensation can be reduced by the number of blocks.

ST1: switching TFT DT: driving TFT
SL1: first scan line SL2: second scan line
SENL: sensing line DL: data line
ST2: sensing TFT 10: display panel
110: scan driver 120: data driver
130: timing control unit 140: external compensation unit
SVTH: threshold voltage representative value P: pixel
210: Data Compensation Unit 220: Memory

Claims (16)

  1. A display panel including a plurality of scan lines, a plurality of data lines intersecting with the scan lines, and a plurality of pixels arranged in a matrix form at intersections of the plurality of scan lines and the plurality of data lines;
    An external compensation unit for compensating digital image data according to a sensing value of a threshold voltage value of the driving TFT of the plurality of pixels;
    A data driving circuit for converting the compensated digital image data into an analog data voltage and supplying the analog data voltage to the plurality of data lines;
    And a scan driving circuit for supplying a scan signal to the plurality of scan lines,
    Wherein the external compensation unit comprises:
    The display panel is divided into a plurality of blocks, and a threshold voltage value of a driving TFT of some pixels is sensed for each block, and the sensed threshold voltage value is set as a threshold voltage representative value of the block, And compensates the digital image data supplied to the plurality of pixels of the block.
  2. The method according to claim 1,
    Wherein the external compensation unit comprises:
    And the threshold voltage value of the driving TFT is sensed for each of the divided blocks at the time of power-off.
  3. 3. The method of claim 2,
    Wherein the external compensation unit comprises:
    Wherein the pixels to be sensed for each of the blocks are set differently at each power-off time.
  4. The method according to claim 1,
    Wherein the external compensation unit comprises:
    A memory for storing threshold voltage representative values of the driving TFTs for each block;
    And a data compensator compensating the digital image data supplied to the pixels of the block using the threshold voltage representative value.
  5. The method according to claim 1,
    In sensing the threshold voltage value of the driving TFT,
    A first scan signal for controlling a switching TFT to supply a sensing data voltage supplied from the data line to the driving TFT, and a sensing TFT for sensing a threshold voltage value of the driving TFT located between the driving TFT and the sensing line The second scan signal is supplied,
    Wherein the first scan signal and the second scan signal are supplied to the pixels to be sensed in each of the blocks and sequentially supplied to the upper and lower blocks.
  6. The method according to claim 1,
    In sensing the threshold voltage value of the driving TFT,
    A first scan signal for controlling a switching TFT to supply a sensing data voltage supplied from the data line to the driving TFT, and a sensing TFT for sensing a threshold voltage value of the driving TFT located between the driving TFT and the sensing line The second scan signal is supplied,
    Wherein the first scan signal and the second scan signal are simultaneously supplied to the pixels to be sensed for the respective blocks and to the pixels to be sensed for the upper and lower blocks.
  7. The method according to claim 6,
    Wherein the pixels to be sensed by the upper and lower blocks supply the threshold voltage value through different sensing lines.
  8. The method according to claim 1,
    Each of the divided blocks is divided into a plurality of blocks,
    Wherein the organic light emitting diode display device comprises at least two columns arranged vertically.
  9. And a display panel including a plurality of scan lines, a plurality of data lines intersecting the scan lines, and a plurality of pixels arranged in a matrix form at intersections of the plurality of scan lines and the plurality of data lines, A method of driving a display device,
    Compensating digital image data according to a sensing value of a threshold voltage value of a driving TFT of the plurality of pixels;
    Converting the compensated digital image data to an analog data voltage and supplying the analog data voltage to the plurality of data lines; And
    And supplying a scan signal to the plurality of scan lines,
    Wherein the step of compensating for the digital image data comprises:
    Dividing the display panel into a plurality of blocks and sensing a threshold voltage value of a driving TFT of some pixels for each block; And
    And setting the sensed threshold voltage value as a threshold voltage representative value of the block to compensate digital image data supplied to the plurality of pixels of the block according to the threshold voltage representative value. A method of driving a light emitting diode display device.
  10. 10. The method of claim 9,
    The step of sensing the threshold voltage value of the driving TFT includes:
    Wherein the driving of the organic light emitting diode display device is performed when the power supply is turned off.
  11. 11. The method of claim 10,
    The step of sensing the threshold voltage value of the driving TFT includes:
    Wherein the pixels to be sensed for each of the blocks are set differently for each off-time of the power source.
  12. 10. The method of claim 9,
    Storing a threshold voltage representative value for each block; And
    And compensating the digital image data supplied to the pixels of the block using the threshold voltage representative value.
  13. 10. The method of claim 9,
    The step of sensing the threshold voltage value of the driving TFT includes:
    Supplying a first scan signal for controlling a switching TFT to supply a sensing data voltage supplied from the data line to the driving TFT; And
    And supplying a second scan signal, which is located between the drive TFT and the sensing line, for controlling the sensing TFT to sense a threshold voltage value of the driving TFT,
    Wherein the first scan signal and the second scan signal are supplied to the pixels to be sensed in each of the blocks and sequentially supplied to the upper and lower blocks.
  14. 10. The method of claim 9,
    The step of sensing the threshold voltage value of the driving TFT includes:
    Supplying a first scan signal for controlling the switching TFT to supply the sensing data voltage supplied from the data line to the driving TFT; And
    And supplying a second scan signal, which is located between the drive TFT and the sensing line, for controlling the sensing TFT to sense a threshold voltage value of the driving TFT,
    Wherein the first scan signal and the second scan signal are simultaneously supplied to the pixels to be sensed in the respective blocks and to the pixels to be sensed in the upper and lower blocks.
  15. 15. The method of claim 14,
    Wherein the pixels to be sensed by the upper and lower blocks supply the threshold voltage value through the different sensing lines.
  16. 10. The method of claim 9,
    Each of the divided blocks is divided into a plurality of blocks,
    Wherein the organic light emitting diode display comprises at least two columns arranged vertically.
KR1020130166089A 2013-12-27 2013-12-27 Organic light emitting diode display and method for driving the same KR20150077171A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
KR1020130166089A KR20150077171A (en) 2013-12-27 2013-12-27 Organic light emitting diode display and method for driving the same

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
KR1020130166089A KR20150077171A (en) 2013-12-27 2013-12-27 Organic light emitting diode display and method for driving the same

Publications (1)

Publication Number Publication Date
KR20150077171A true KR20150077171A (en) 2015-07-07

Family

ID=53789990

Family Applications (1)

Application Number Title Priority Date Filing Date
KR1020130166089A KR20150077171A (en) 2013-12-27 2013-12-27 Organic light emitting diode display and method for driving the same

Country Status (1)

Country Link
KR (1) KR20150077171A (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105575350A (en) * 2016-02-26 2016-05-11 京东方科技集团股份有限公司 Mura compensation circuit, Mura compensation method, driving circuit and display device
CN107633810A (en) * 2017-10-27 2018-01-26 京东方科技集团股份有限公司 Image element circuit compensation method and device, display panel and display device
CN107749280A (en) * 2017-12-06 2018-03-02 京东方科技集团股份有限公司 The driving method and display device of display device
CN108630147A (en) * 2017-03-17 2018-10-09 昆山工研院新型平板显示技术中心有限公司 Active matrix/organic light emitting display and its driving method
CN109166524A (en) * 2018-07-13 2019-01-08 友达光电股份有限公司 Display panel

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105575350A (en) * 2016-02-26 2016-05-11 京东方科技集团股份有限公司 Mura compensation circuit, Mura compensation method, driving circuit and display device
WO2017143669A1 (en) * 2016-02-26 2017-08-31 京东方科技集团股份有限公司 Mura compensation circuit and method, drive circuit, and display device
US10403218B2 (en) 2016-02-26 2019-09-03 Boe Technology Group Co., Ltd. Mura compensation circuit and method, driving circuit and display device
CN108630147A (en) * 2017-03-17 2018-10-09 昆山工研院新型平板显示技术中心有限公司 Active matrix/organic light emitting display and its driving method
CN107633810A (en) * 2017-10-27 2018-01-26 京东方科技集团股份有限公司 Image element circuit compensation method and device, display panel and display device
CN107749280A (en) * 2017-12-06 2018-03-02 京东方科技集团股份有限公司 The driving method and display device of display device
CN109166524A (en) * 2018-07-13 2019-01-08 友达光电股份有限公司 Display panel

Similar Documents

Publication Publication Date Title
US8289247B2 (en) Display device and method of driving the same
US8199074B2 (en) System and method for reducing mura defects
EP1158483A2 (en) Solid-state display with reference pixel
US8937581B2 (en) Display device having shared column lines
CN103165078B (en) Organic light-emitting display device and method of operating thereof
DE102013114348B4 (en) Organic light emitting diode display device and method of operating the same
KR101396004B1 (en) Organic light emitting diode display device
TWI424412B (en) Pixel driving circuit of an organic light emitting diode
US9218768B2 (en) Organic light-emitting diode display device
TWI476748B (en) Organic light emitting diode display device
CN103050083B (en) Oganic light-emitting display device
CN103077662B (en) Organic light-emitting display device
KR101699089B1 (en) Display method of organic el display device and organic el display device
US9041705B2 (en) Organic light emitting display device
KR101938880B1 (en) Organic light emitting diode display device
KR101498094B1 (en) Display device and driving method thereof
US8830148B2 (en) Organic electroluminescence display device and organic electroluminescence display device manufacturing method
US8305374B2 (en) Display device having precharge operations and method of driving the same
KR101411619B1 (en) Pixel circuit and method for driving thereof, and organic light emitting display device using the same
KR20150076028A (en) Organic light emitting diode display device and method of sensing driving characteristics thereof
US9019187B2 (en) Liquid crystal display device including TFT compensation circuit
US20120293482A1 (en) Pixel unit circuit and oled display apparatus
JP5342111B2 (en) organic EL display device
KR20150068154A (en) Pixel circuit of display device, organic light emitting display device and method for driving thereof
JP5282146B2 (en) Display device and control method thereof

Legal Events

Date Code Title Description
A201 Request for examination
E902 Notification of reason for refusal
E701 Decision to grant or registration of patent right