KR20080060890A - Driving method of amoled display and driving device of the same - Google Patents

Abstract

A method and a device for driving an AMOLED are provided to improve luminance reduction due to the degradation of thin film transistors by implementing a data controller of compensating for data signals. An AMOLED(Active Matrix Organic Light Emitting Display) device includes a display panel, scan and data drivers(120,130), a timing controller(140), and a data controller(150). The display panel includes plural pixels at sections where plural scan and data lines are crossed each other. The scan and data drivers, connected to the scan and data lines, supply scan driving signals and data signals to thin film transistors. The timing controller controls the scan and data drivers. The data controller receives the data signals in real time, identifies stress which is applied to the thin film transistors, determines a degradation degree, and compensates the data signals.

Description

Driving method and driving device thereof of active organic light emitting diode display

1 is an equivalent circuit diagram illustrating one pixel structure of a general AMOLED display device.

2 is a characteristic graph of a thin film transistor used to drive an AMOLED.

3 is a block diagram schematically illustrating an AMOLED display according to an embodiment of the present invention.

4 is a block diagram schematically illustrating a structure of an average calculating unit included in the data control unit of FIG. 3.

5 is a block diagram schematically illustrating a configuration of a data controller of an organic light emitting display according to an exemplary embodiment of the present invention.

FIG. 6 is a flowchart for describing a method of driving the data controller shown in FIG. 5.

<Brief description of the main parts of the drawing>

SL1 to SLn: scan line DL1 to DLm: data line

P: pixel portion 100: display panel

120: scan driver 130: data driver

140: timing controller 150: data control unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AMOLED display, and more particularly, to a driving method and a driving device of a display device for compensating for luminance deteriorated due to stress of a thin film transistor generated during long time driving of an AMOLED display.

Active Matrix Liquid Crystal Display (AMLCD), a display device that is widely used these days, has the characteristics of light weight, thin film, and low power consumption, but it does not have its own light emission characteristics, so it is necessary to use a backlight. There is this.

An active matrix organic light emitting display device (AMOLED) is a display device for solving the drawbacks of AMLCDs. AMOLED display devices are self-luminous display devices that electrically excite fluorescent organic compounds to emit light, and do not require a separate light source. It is possible to drive at a low voltage, and has advantages such as thinness.

FIG. 1 is an equivalent circuit diagram illustrating one pixel structure of a typical AMOLED display device, and illustrates a two-transistor 2T and a one-capacitor C1 structure.

One pixel P of a general organic light emitting display device includes a switching transistor SW-TFT, a storage capacitor Cst, a driving transistor D-TFT, and an organic light source between the scan line SL and the data line DL. An electroluminescent element (OLED) is provided.

The gate electrode of the switching transistor SW-TFT is connected to the scan line SL, and the drain electrode is connected to the data line DL. One electrode of the storage capacitor Cst is connected to the source electrode of the switching transistor SW-TFT, and the other electrode is connected to the first power supply voltage VDD terminal. In addition, the drain electrode of the PMOS driving transistor D-TFT is connected to the cathode of the organic light emitting diode OLED, the gate electrode is connected to the source electrode of the switching transistor SW-TFT, and the source electrode is formed of the first electrode. 1 It is connected to the power supply voltage (VDD) terminal. In addition, the anode of the organic light emitting diode is connected to the second power supply voltage (VSS) terminal.

Hereinafter, driving of one pixel P of the organic light emitting display device illustrated in FIG. 1 will be described as follows.

First, when the switching transistor S-TFT is turned on by a low voltage applied to the scan line SL, by the data voltage Vdata applied to the data line DL. Charge is accumulated in the storage capacitor Cst. Thereafter, the amount of current flowing through the driving transistor D-TFT through the driving line is determined according to the potential difference between the voltage charged in the storage capacitor Cst and the first power voltage VDD. The amount of light emitted is determined, and the organic light emitting diode OLED emits light.

By such driving, the organic light emitting diode OLED displays one color selected from three primary colors R, G, and B, and combines them to implement an image to be displayed.

The thin film transistors S-TFT and D-TFT for driving the organic light emitting diode OLED are deteriorated due to stress during long time driving, and the driving transistor D-TFT is organic. Since the function of determining the amount of current flowing through the electroluminescent device (OLED), in particular, the change in driving characteristics due to deterioration has a direct effect on the image quality.

FIG. 2 is a characteristic graph of a thin film transistor used to drive an AMOLED. As shown in FIG. 2, the drain-source current Ids of the gate-source voltage Vgs before the deterioration is generally shown in a graph (a). However, when the thin film transistor is deteriorated due to a long time stress, the drain-source current Ids due to the gate-source voltage Vgs becomes a b graph (b).

Accordingly, after the thin film transistor is deteriorated, when the data signal having the same level as the deterioration is applied to the gate electrode, the gate-source voltage Vgs is formed the same, but the corresponding drain-source current Ids amount is In particular, when the driving transistor D-TFT is deteriorated, the drain-source current Ids amount is the amount of current flowing through the organic light emitting diode OLED, and as a result, luminance reduction occurs.

This results in an afterimage of the image, which is directly related to the life of the display panel.

Accordingly, the present invention has been made to solve the above problems, in the AMOLED display, AMOLED that improves the luminance degradation caused by deterioration of the thin film transistor for driving the organic light emitting device due to the stress accumulated by long time driving. An object of the present invention is to propose a method of driving a display and a driving device thereof.

In order to achieve the above object, the present invention provides an organic electroluminescent device, a switching transistor for determining the timing of application of a data signal, and a driving transistor for controlling the amount of current flowing in the organic electroluminescent device in response to the data signal. A display method of driving an organic light emitting display device comprising: a data controller configured to display an image, determine a degree of degradation of the transistor based on the data signal, and compensate for the data signal accordingly. Turning on; Applying the data signal to the driving transistor; And determining the degree of deterioration of the driving transistor in response to the data signal through the data controller, and compensating the data signal accordingly.

In response to the data signal, determining a degree of deterioration of the driving transistor and compensating the data signal may include: receiving the data signal; Calculating an average value of the data signals; Determining a degree of stress applied to the driving transistor; Determining a degree of deterioration of the driving transistor; Outputting the data signal.

The calculating of the average value of the data signal may include storing the data signal input in real time on a pixel-by-frame basis; And receiving the data signal {data (n)} of the next frame and calculating an average value with the data signal of all the stored frames.

The average value is represented by the following formula, when the average value is {μ (n)} and the data signal is {data (n)}.

μ (n) =

)μ(n-1) +

= (1-

) μ (n-1) +

It is characterized by satisfying.

The determining of the degree of deterioration of the driving transistor may include determining the degree of deterioration of the driving transistor in consideration of a significant temporal duration in response to a stress applied to the driving transistor. .

The outputting of the data signal may include selecting a preset compensation signal corresponding to the average value when it is determined that the driving transistor is deteriorated; Selecting one of a plurality of preset data compensation degrees corresponding to the average value of the data signals, and outputting a compensation signal accordingly; And adding the compensation signal and the data signal.

The outputting of the data signal may include outputting an input data signal as it is determined that the driving transistor is not degraded.

In order to achieve the above object, the present invention provides a display panel including a plurality of pixel units at a point where a plurality of scan lines and data lines cross each other; A scan driver and a data driver connected to the scan line and the data line to supply a scan driving signal and a data signal to the thin film transistor; A timing controller controlling the scan driver and the data driver; And a data controller configured to receive the data signal in real time, determine a stress applied to the thin film transistor, determine a degree of degradation in response thereto, and compensate for the data signal.

The pixel unit may include: a switching transistor having a gate electrode connected to the scan line and a drain electrode connected to the data line; A driving transistor having a gate electrode connected to a source electrode of the switching transistor, and a source electrode connected to a power supply voltage terminal; A storage capacitor having a source electrode of the switching transistor, a gate electrode of the driving transistor and one electrode connected thereto, and a remaining electrode connected to a power supply voltage terminal; An anode is connected to the drain electrode of the driving transistor, characterized in that it comprises an organic light emitting device, the cathode is grounded.

The switching transistor and the driving transistor are characterized in that the PMOS.

The data control unit includes an average calculation unit for calculating an average value of the data signals; A LUT unit for outputting a compensation signal corresponding to the average value; And an adder for adding the data signal and the compensation signal.

The average calculating unit includes: an calculating unit calculating a mean value between before and after frames of the data signal; And a frame memory for storing the average value of the previous frames.

The data controller is mounted in the timing controller or the data driver.

Hereinafter, a driving method and a driving apparatus of an AMOLED display according to an embodiment of the present invention will be described with reference to the accompanying drawings.

3 is a block diagram schematically illustrating an AMOLED display according to an embodiment of the present invention.

As illustrated, a plurality of scan lines SL1 to SLn and data lines DL1 to DLm are arranged in a matrix form, and pixel portions P for implementing three primary colors R, G, and B are disposed therebetween. The display panel 100 is provided, through the scan lines SL1 through SLn, through the scan driver 120 supplying a scan driving signal to the display panel 100, and through the data lines DL1 through DLm. The timing for controlling the scan driver 120 and the data driver 130 by receiving a control signal and a data signal from a data driver 130 for supplying a data signal to the display panel 100 and an external system (not shown). The controller receives the data signal from the controller 140 and the timing controller 140, analyzes the data signal, determines a degree of stress applied to the thin film transistor provided in the pixel unit P, and compensates the data signal. It consists of a data control unit 150.

Here, in the drawing, the data controller 150 is an example of a form provided separately between the data driver 130 and the timing controller 140, but according to the designer's intention, the data driver 130 or the timing controller 140 It can be mounted within.

Hereinafter, the operation of the AMOLED display according to an embodiment of the present invention with reference to the drawings.

First, when a control signal and a data signal are supplied from the external system (not shown) to the timing controller 140, a scan driving signal for driving the scan driver 120 and a data driver 130 for driving the data driver 130 correspondingly. Generates a data control signal and supplies it to each driver. In addition, the timing controller 140 rearranges the supplied data signal in a form that the data driver 130 can process.

The scan driver 120 sequentially supplies the scan driving signal to the display panel 100 by 1H for one frame through the scan lines SL1 to SLn in response to the scan driving signal supplied from the timing controller 140. do.

The data driver 130 receives a digital data signal from the timing controller 140 and converts it into an analog form in response to a reference voltage, and simultaneously displays the data signal of one horizontal line through all the data lines DL. Supply to (100).

The display panel 100 turns on / off a plurality of switching transistors (S-TFTs in FIG. 1) arranged in a matrix to drive the data signals into driving transistors (D-TFTs in FIG. 1). And a driving transistor (D-TFT in FIG. 1) adjust an amount of current flowing through the organic light emitting element (OLED in FIG. 1) to display an image in response to the data signal.

The data controller 150 receives the data signal supplied to each pixel unit P of the display panel 100 in real time, and applies a stress applied to the driving transistor (D-TFT of FIG. 1) through an average value thereof. Stress) and determine the degree of degradation of the transistor.

The data signal is compensated for in correspondence with the degree of deterioration of the transistor. In this case, the degree of degradation is proportional to the temporal duration of stress applied to the driving transistor (D-TFT of FIG. 1) and the voltage level of the data signal, and the data controller 150 is configured by the designer. The data signal compensation value corresponding to the deterioration degree is determined, and the data signal is compensated.

Here, the average value {μ (n)} of the data signal {data (n)} is obtained by the following expression (1).

Equation 1

μ (n) =

)μ(n-1) +

= (1-

) μ (n-1) +

Here, in order to display the equation more intuitively, the inverse α of the average value μ (n) can be taken as Equation 2 below.

Equation 2

μ (n) = (1-α) μ (n-1) +

That is, the value of α has a value between 0 and 1, and when the data signal of a higher voltage level is applied to the thin film transistor, the value of α will be close to 1, otherwise it will have a value close to zero.

This α value is an estimate of the degree of deterioration of stress applied to the thin film transistor, and the persistence of time must be considered.

FIG. 4 is a block diagram schematically showing the structure of an average calculating unit included in the data control unit 150 of FIG. 3 to calculate the above-described average value {μ (n)} of the data signal. As shown in FIG. (10) and frame memory (20).

More specifically, the calculating unit 10 of the average calculating unit 152 is a real time input data signal {data (n)} and the average value {μ (n−) of the previous data signal {data (n-1)} 1)}, and outputs the average value {μ (n)} of the last data signal {data (n)}, and calculates the average value {μ (n)} of the data signal {data (n)}. It is stored in the frame memory 20 in units of one frame.

Thereafter, the above operation is repeated to store the average value μ (n) of the data signals {data (n)} input for each pixel.

Hereinafter, a data controller (150 of FIG. 3) according to an exemplary embodiment of the present invention including the average calculator 152 described above with reference to FIG. 5 will be described in detail.

5 is a block diagram schematically illustrating a configuration of a data controller of an organic light emitting display according to an exemplary embodiment of the present invention.

As illustrated, the data controller 150 of the organic light emitting display according to the embodiment of the present invention includes an average calculating unit 152, a LUT unit 154, and an adder 158.

More specifically, as described above, the average calculating unit 152 receives the data signal {data (n)} in real time, reads an average value for each pixel, and supplies the average value to the LUT unit 154.

 The LUT unit 154 is a kind of look up table, and the luminance compensation voltage level is stored for each pixel compared to the average value predefined by the setter, and according to the average value input from the average calculating unit 152, The compensation signal is supplied to the adder 158. The LUT unit 154 is not limited to a specific kind.

The adder 158 adds the data signal {data (n)} input to the data controller 150 and the compensation signal.

Accordingly, the data signal is compensated according to the degree of deterioration of the thin film transistor, thereby improving the low luminance and the afterimage of the image.

FIG. 6 is a flowchart for describing a method of driving the data controller shown in FIG. 5.

As shown, first, the data input step ST1 is a step in which the data signal {data (n)} input in real time from the outside is input to the average calculation unit, which is a type provided with a data controller, that is, a timing controller or It may be different depending on whether it is mounted in the data driver or provided as a separate circuit.

The average value calculation step ST2 of the data is a step of calculating the average value {μ (n)} of the front / rear frame data signals {data (n, n-1)} for each pixel, and the first data signal { data (n-1)} is stored for each pixel in one frame of data signal {data (n-1)}, and then the data signal {data (n)} of the next frame is received and the stored data signal {data It is a step of calculating | requiring the average value (micro (n)) with (n-1)}.

In the step ST3 of determining the stress level of the device, the driving transistor (Fig. 1) is applied to the thin film transistor of the pixel unit according to the average value {μ (n)} of the data signal {data (n)}. The stress applied to the gate electrode of the D-TFT is determined.

Here, the average value μ (n)} may be regarded as a higher degree of stress applied to the device as the numerical value is higher.

Determining whether the device is deteriorated (ST4), according to the average value (μ (n)) of the data signal (data (n)), in response to the stress applied to the thin film transistor of the pixel portion of the thin film transistor It is a step to determine the degree of deterioration.

Here, the degree of deterioration of the thin film transistor is not simply determined by maintaining a high voltage level of the average value {μ (n)}, but is determined by considering a considerable temporal sustainability.

Accordingly, when it is determined that the thin film transistor is deteriorated, the data signal {data (n)} is compensated (ST6). If not, the input data signal {data (n)} is output as it is. (ST7).

Here, the step ST6 of compensating the data signal {data (n)} is one of a plurality of preset data compensation degrees corresponding to the average value {μ (n)} of the data signal {data (n)}. Next, a step of outputting the compensation signal (ST6-1) and adding the compensation signal and the data signal (data (n)) are performed (ST6-2).

In the exemplary embodiment of the present invention, the data signal is compensated according to the degree of deterioration of the thin film transistor and the luminance degradation is improved.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art various modifications and variations of the present invention without departing from the spirit and scope of the present invention described in the claims below I can understand that you can.

Accordingly, the AMOLED display driving method and the driving apparatus thereof according to the embodiment of the present invention includes a data control unit for determining the degree of degradation of the thin film transistor caused by the continuously applied stress, and correspondingly compensates for the data signal. In addition, the luminance decrease due to the deterioration of the thin film transistor is improved.

Therefore, there is an effect of improving the afterimage phenomenon caused by the deterioration of the thin film transistor and extending the life of the display.

Claims (13)

An organic light emitting display device includes: a switching transistor configured to determine an application timing of a data signal; and a driving transistor configured to adjust an amount of current flowing through the organic light emitting display device in response to the data signal to display an image, and display the data signal. In the method of driving an organic light emitting display device comprising a data control unit for determining the degree of degradation of the transistor and correspondingly compensates for the data signal, Turning on the switching transistor; Applying the data signal to the driving transistor; Determining a degree of deterioration of the driving transistor in response to the data signal through the data controller and compensating the data signal accordingly; The method of driving an organic light emitting display device comprising a. The method of claim 1, In response to the data signal, determining the degree of deterioration of the driving transistor and accordingly compensating the data signal, Receiving the data signal; Calculating an average value of the data signals; Determining a degree of stress applied to the driving transistor; Determining a degree of deterioration of the driving transistor; Outputting the data signal; A method for driving an AMOLED display comprising a. The method of claim 2, Calculating the average value of the data signal, Storing the data signal input in real time in units of one frame for each pixel; Receiving a data signal {data (n)} of a next frame and obtaining an average value with the data signal of all the stored frames; The method of driving an organic light emitting display device comprising a. The method of claim 2, The average value is represented by the following formula, when the average value is {μ (n)} and the data signal is {data (n)}. μ (n) =

= (1-

) μ (n-1) +

Method of driving an AMOLED display, characterized in that satisfying the. The method of claim 2, Determining the degree of deterioration of the driving transistor, In response to a stress applied to the driving transistor, determining a degree of deterioration of the driving transistor in consideration of a considerable time duration; The method of driving an organic light emitting display device comprising a. The method of claim 2, The outputting of the data signal may include: If it is determined that the driving transistor is deteriorated, selecting a preset compensation signal corresponding to the average value; Selecting one of a plurality of preset data compensation degrees corresponding to the average value of the data signals, and outputting a compensation signal accordingly; Adding the compensation signal and the data signal; The method of driving an organic light emitting display device comprising a. The method of claim 2, The outputting of the data signal may include: If it is determined that the driving transistor is not deteriorated, outputting the input data signal as it is; The method of driving an organic light emitting display device comprising a. A display panel including a plurality of pixel units at points where a plurality of scan lines and data lines cross each other; A scan driver and a data driver connected to the scan line and the data line to supply a scan driving signal and a data signal to the thin film transistor; A timing controller controlling the scan driver and the data driver; A data controller configured to receive the data signal in real time, determine a stress applied to the thin film transistor, determine a degree of degradation in response thereto, and compensate for the data signal; Driving device for an organic light emitting display device comprising a The method of claim 8, The pixel portion, A switching transistor having a gate electrode connected to the scan line and a drain electrode connected to the data line; A driving transistor having a gate electrode connected to a source electrode of the switching transistor, and a source electrode connected to a power supply voltage terminal; A storage capacitor having a source electrode of the switching transistor, a gate electrode of the driving transistor and one electrode connected thereto, and a remaining electrode connected to a power supply voltage terminal; An organic light emitting diode having an anode connected to the drain electrode of the driving transistor and having a cathode grounded; AMOLED display drive device comprising a. The method of claim 8, The switching transistor and the driving transistor is a driving device of the AMOLED display, characterized in that the PMOS. The method of claim 8, The data control unit includes an average calculation unit for calculating an average value of the data signals; A LUT unit for outputting a compensation signal corresponding to the average value; An adder for adding the data signal and the compensation signal; AMOLED display drive device comprising a. The method of claim 11, The average calculating unit includes: an calculating unit calculating a mean value between before and after frames of the data signal; A frame memory for storing an average value of all the frames; AMOLED display drive device comprising a. The method of claim 8, And the data controller is mounted in the timing controller or the data driver.

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