KR101960762B1 - Organic light emitting display device and method for driving thereof - Google Patents

Abstract

The organic light emitting display according to the present invention is capable of preventing a change in luminance and image quality due to a temperature change by storing a difference voltage between a data voltage and a reference voltage in a capacitor and by a data current determined by a voltage stored in the capacitor A display panel including a plurality of sub-pixels each having an organic light emitting element for emitting light; A memory for storing an initial current value and an initial luminance value of the display panel according to the data voltage; A voltage supplier for supplying a pixel driving voltage and a cathode voltage to the display panel; And calculating a predicted current value according to input data of a current frame image by referring to an initial current value stored in the memory, And a panel driver for adjusting at least one of the reference voltage and the data voltage to be supplied to the sub-pixels during the current frame based on the current deviation between the current value and the predicted current value.

Description

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting display and a driving method thereof, and more particularly, to an organic light emitting display and a method of driving the same.

Recently, with the development of multimedia, the importance of flat panel display devices is increasing. In response to this, flat panel display devices such as liquid crystal display devices, plasma display devices, and organic light emitting display devices have been commercialized. Among such flat panel display devices, organic light emitting display devices have attracted attention as a next generation flat panel display device because they have a high response speed, low power consumption, and self light emission, so that there is no problem in viewing angle.

A general organic light emitting display includes a display panel including a plurality of pixels and a panel driver for emitting each pixel. Here, each pixel is formed in a pixel region defined by the intersection of a plurality of data lines and a plurality of gate lines.

Each pixel includes a switching transistor Tsw, a driving transistor Tdr, a capacitor Cst, and an organic light emitting diode OLED, as shown in Fig.

The switching transistor Tsw is switched in accordance with the gate signal GS supplied to the gate line GL to supply the data voltage Vdata supplied to the data line DL to the driving transistor Tdr.

The driving transistor Tdr is switched in accordance with the data voltage Vdata supplied from the switching transistor Tsw and controls the data current Ioled flowing to the organic light emitting element OLED by the driving voltage EVDD.

The capacitor Cst is connected between the gate terminal and the source terminal of the driving transistor Tdr to store a voltage corresponding to the data voltage Vdata supplied to the gate terminal of the driving transistor Tdr, Tdr).

The organic light emitting diode OLED is electrically connected between the source terminal of the driving transistor Tdr and the cathode electrode to which the cathode voltage VSS is applied and emits light by the data current Ioled supplied from the driving transistor Tdr.

Each pixel of such a general organic light emitting display device uses the switching of the driving transistor Tdr according to the data voltage Vdata to change the size of the data current Ioled flowing to the organic light emitting element OLED by the driving voltage EVDD to So that a predetermined image is displayed by causing the organic light emitting diode OLED to emit light.

In such a general OLED display device, the current flowing through the display panel varies depending on the input image. That is, in the case of a full black image, a current hardly flows through the display panel, but in the case of a full white image, a large amount of current flows through the display panel. Accordingly, in the case of a specific image having many white patterns, an excessive current flows to the display panel, which causes a problem that current consumption increases. In order to solve the current consumption problem, an automatic current limit algorithm for controlling the current flowing in the display panel according to an input image of one frame is applied to lower the luminance of the display panel.

The automatic current limit algorithm reduces the consumption current by limiting the peak luminance of the display panel according to the brightness of the input image. When it is predicted that more current will flow than the limit current according to the specific pattern, .

However, in recent years, an a-Si TFT and a poly-Si TFT, which have all the merits of a-Si and poly-Si thin film transistors, have been used as a transistor included in each pixel of an OLED. It is a trend to apply semiconductors.

However, in the case of an oxide thin film transistor using an oxide semiconductor, the characteristic of the threshold voltage shifts to a negative voltage as the external temperature increases. 2, when the external (or ambient) temperature of the organic light emitting display device is changed from a high temperature environment of 25 ° C to 50 ° C, the brightness of the input image is increased by the above- even if limited by a limit current (I _lIMIT) set the current (I _pANEL) flowing to the display panel, an actual display panel, the flow is set limit current (I _lIMIT) or more current (I _pANEL) depending on the threshold voltage variation of the oxide thin film transistor There is a problem that the luminance is changed and the image quality is distorted.

Further, when a black pattern is implemented on a display panel in a high temperature environment, a full black luminance can not be realized due to current flow as indicated by a dotted circle in FIG. 2 due to a change in threshold voltage of the oxide thin film transistor, There is a problem that image quality is distorted.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic light emitting diode (OLED) display device and a method of driving the same, which can prevent luminance variation and image quality distortion according to a temperature change.

Another object of the present invention is to provide an organic light emitting display device and a method of driving the same that can realize a full black luminance even in a temperature change.

According to an aspect of the present invention, there is provided an OLED display device including an organic light emitting diode that stores a difference voltage between a data voltage and a reference voltage in a capacitor and emits light by a data current determined by a voltage stored in the capacitor, A display panel including a plurality of sub-pixels; A memory for storing an initial current value and an initial luminance value of the display panel according to the data voltage; A voltage supplier for supplying a pixel driving voltage and a cathode voltage to the display panel; And calculating a predicted current value according to input data of a current frame image by referring to an initial current value stored in the memory, And a panel driver for adjusting at least one of the reference voltage and the data voltage to be supplied to the sub-pixels during the current frame based on the current deviation between the current value and the predicted current value.

Wherein the panel driver further calculates an average image level according to input data of a current frame image, and when a current deviation occurs between the measured current value and the predicted current value, And the data voltage are adjusted simultaneously or only the data voltage is adjusted.

Wherein the panel driver adjusts the maximum luminance value of the current frame image by adjusting the reference voltage and adjusting the data voltage corresponding to the current deviation when the average image level is equal to or lower than the reference image level, The maximum luminance value of the current frame image is adjusted by adjusting the data voltage corresponding to the current deviation.

Wherein the panel driver adjusts the maximum luminance value of the current frame image by modulating the data of the current frame image to correspond to the current deviation or adjusts the data voltage by adjusting a plurality of reference gamma voltages to correspond to the current deviation And adjusting a maximum luminance value of the current frame image by adjusting the maximum luminance value of the current frame image.

According to an aspect of the present invention, there is provided a method of driving an organic light emitting display, the method comprising: displaying an image by emitting an organic light emitting diode according to a data current determined by a difference voltage between a data voltage and a reference voltage; ; (B) measuring a panel current flowing through the display panel to generate a measured current value; (C) calculating a predicted current value according to input data of a current frame image by referring to an initial current value and an initial luminance value of the display panel according to the data voltage stored in the memory; And a step (D) of adjusting at least one of the reference voltage and the data voltage to be supplied to each of the sub-pixels during a current frame based on a current deviation between the measured current value and the predicted current value .

Wherein the step (C) further includes a step of calculating an average image level according to input data of a current frame image, and in the step (D), when a current deviation occurs between the measured current value and the predicted current value, (D1) simultaneously adjusting the reference voltage and the data voltage or adjusting only the data voltage based on the image level and the current deviation.

Wherein the controller adjusts the maximum luminance value of the current frame image through adjustment of the reference voltage and adjustment of the data voltage corresponding to the current deviation when the average image level is equal to or lower than the reference image level, And adjusts the maximum luminance value of the current frame image by adjusting the data voltage corresponding to the current deviation when the image level exceeds the reference image level.

Wherein the maximum luminance value of the current frame image is adjusted by data modulation of the current frame image based on the current deviation or by adjustment of a plurality of reference gamma voltages based on the current deviation.

The OLED display device and the driving method thereof according to the present invention have the following effects.

First, by adjusting at least one of the reference voltage and the data voltage to be supplied to each sub-pixel according to the current deviation of the predicted current value predicted through the measurement of the current flowing through the display panel and the image analysis, It is possible to prevent the change and the image quality distortion and to prevent the luminance change due to the threshold voltage change of the driving transistor by matching the measured current value with the predicted current value, thereby improving the image quality. Brightness can be realized.

Second, a burning phenomenon due to an overcurrent flowing in the display panel 100 in a high temperature environment can be prevented in advance through the measurement current value.

Third, the presence or absence of the burning phenomenon can be checked based on the current deviation between the measured current value and the predicted current value, thereby preventing the fire by shutting down the voltage supply unit before the combustion phenomenon occurs.

FIG. 1 is a view for explaining a pixel structure of a general organic light emitting display device.
2 is a waveform diagram for explaining a change in current flowing in a display panel in a high temperature environment in a general organic light emitting display device.
3 is a view schematically showing an organic light emitting display according to an embodiment of the present invention.
4 is a view showing one sub-pixel shown in FIG.
5 is a view for explaining a current measuring unit shown in FIG.
FIG. 6 is a diagram for explaining the timing control unit shown in FIG. 3. FIG.
7 is a block diagram for explaining the first embodiment of the luminance controller shown in FIG.
8 is a block diagram for explaining a second embodiment of the luminance controller shown in FIG.
9 is a flowchart for explaining a driving method of the organic light emitting diode display according to the present invention.
10 is a waveform diagram for explaining driving of one sub-pixel of the organic light emitting diode display according to the embodiment of the present invention.
FIG. 11 is a waveform diagram showing a change in panel current for each gradation of data in the organic light emitting display according to the embodiment of the present invention. FIG.

The meaning of the terms described herein should be understood as follows.

The word " first, "" second," and the like, used to distinguish one element from another, are to be understood to include plural representations unless the context clearly dictates otherwise. The scope of the right should not be limited by these terms.

It should be understood that the terms "comprises" or "having" does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

It should be understood that the term "at least one" includes all possible combinations from one or more related items. For example, the meaning of "at least one of the first item, the second item and the third item" means not only the first item, the second item or the third item, but also the second item and the second item among the first item, Means any combination of items that can be presented from more than one.

Hereinafter, preferred embodiments of the organic light emitting diode display and the driving method thereof according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a schematic view of an organic light emitting display according to an embodiment of the present invention, and FIG. 4 is a view illustrating one sub-pixel shown in FIG.

Referring to FIGS. 3 and 4, the OLED display includes a display panel 100, a voltage supply unit 200, a memory 300, and a panel driver 400.

The display panel 100 includes a plurality of sub-pixels SP. The plurality of sub-pixels (SPs) are formed in a pixel region defined by a plurality of gate control line groups GL and a plurality of data lines DL that intersect each other. Each of the plurality of sub-pixels SP is connected to a driving voltage line VL and a reference voltage line RL, which are arranged in parallel with the data line DL.

Each of the plurality of gate line groups GL is formed along a first direction of the display panel 100, for example, in the horizontal direction. At this time, each of the plurality of gate line groups GL includes first and second gate lines GLa and GLb adjacent to each other. The first and second gate signals GSa and GSb are separately supplied from the panel driver 400 to the first and second gate lines GLa and GLb of each gate line group GL.

Each of the plurality of data lines DL is formed to be parallel to the second direction of the display panel 100, for example, the longitudinal direction so as to intersect each of the plurality of gate line groups GL. The data voltage Vdata is separately supplied from the panel driver 400 to each data line DL.

Each of the plurality of driving voltage lines VL is formed in parallel with each of the data lines DL and supplies the driving voltage EVDD supplied from the voltage supplying unit 200 to the corresponding sub-pixel SP. At this time, each of the plurality of driving voltage lines (VL) may be formed between the plurality of data lines (DL) or may be formed so as to be shared by two right and left sub-pixels.

Each of the plurality of reference voltage lines RL is formed in parallel with each of the plurality of data lines DL. The reference voltage Vref is supplied from the panel driver 400 to each of the reference voltage lines RL.

Each of the plurality of sub-pixels SP may be any one of a red sub-pixel, a green sub-pixel, a blue sub-pixel, and a white sub-pixel. One unit pixel for displaying one image is composed of adjacent red sub-pixel, green sub-pixel, blue sub-pixel, and white sub-pixel. Hereinafter, it is assumed that one unit pixel is composed of a red sub-pixel, a green sub-pixel, a blue sub-pixel, and a white sub-pixel. Each of the plurality of sub-pixels SP includes a pixel circuit PC and an organic light emitting diode (OLED).

The pixel circuit PC is supplied to the data line DL in response to the first and second gate signals GSa and GSb of the gate-on voltage level supplied from the panel driver 400 to the gate line group GL And supplies a data current corresponding to the data voltage Vdata to the organic light emitting diode OLED. For example, the pixel circuit PC may include a first switching transistor Tsw1, a second switching transistor Tsw2, a driving transistor Tdr, and a capacitor Cst. Here, the transistors Tsw1, Tsw2, and Tdr may be an a-Si TFT, a poly-Si TFT, an oxide TFT, an organic TFT, or the like as an N-type thin film transistor (TFT).

The first switching transistor Tsw1 includes a gate electrode connected to the first gate line GLa of the gate line group GLi, a first electrode connected to the data line DL, and a gate electrode connected to the gate electrode GLd of the driving transistor Tdr. And a second electrode connected to the first node n1. The first switching transistor Tsw1 may receive the data voltage Vdata supplied to the data line DL according to the first gate signal GSa of the gate-on voltage level supplied to the first gate line GLa To the gate electrode of the first node n1, that is, the driving transistor Tdr.

The second switching transistor Tsw2 includes a gate electrode connected to the second gate line GLb of the gate line group GLi, a first electrode connected to the reference voltage line RL, And a second electrode connected to a second node (n2) which is a source electrode. The second switching transistor Tsw2 may supply the reference voltage Vref supplied to the reference voltage line RL according to the second gate signal GSb of the gate-on voltage level supplied to the second gate line GLb And supplies the voltage of the second node n2 to the reference voltage Vref by supplying it to the second node n2, that is, the source electrode of the driving transistor Tdr.

The capacitor Cst includes first and second electrodes connected between the gate electrode and the source electrode of the driving transistor Tdr, that is, the first and second nodes n1 and n2. The capacitor Cst charges the difference voltage between the voltages supplied to the first and second nodes n1 and n2, and then switches the driving transistor Tdr according to the charged voltage.

The driving transistor Tdr includes a gate electrode commonly connected to the second electrode of the first switching transistor Tsw1 and the first electrode of the capacitor Cst, a first electrode of the second switching transistor Tsw2, and a capacitor Cst A source electrode commonly connected to the organic light emitting device OLED, and a drain electrode connected to the driving voltage line VL. This driving transistor Tdr controls the amount of current flowing from the driving voltage line VL to the organic light emitting element OLED by being turned on by the voltage of the capacitor Cst.

Although the pixel circuit PC is described as being composed of three transistors and one capacitor in the above-described embodiment, the pixel circuit PC supplies the reference voltage Vref to the second electrode of the capacitor Cst Except for the second switching transistor Tsw2, the number of transistors and capacitors may vary.

The organic light emitting diode OLED is connected between the pixel circuit PC and the cathode voltage VSS line and emits a predetermined color light by emitting light in proportion to the amount of data current supplied from the pixel circuit PC . The organic light emitting diode OLED includes an anode electrode (or a pixel electrode) connected to a source electrode of the driving transistor Tdr, a cathode electrode (or a reflective electrode) connected to a cathode voltage VSS line, And a light emitting cell formed between the electrode and the cathode electrode and emitting light of any one of red, green, blue, and white. Here, the light emitting cell may have a structure of a hole transporting layer / an organic light emitting layer / an electron transporting layer or a structure of a hole injecting layer / a hole transporting layer / an organic light emitting layer / an electron transporting layer / an electron injecting layer. Further, the light emitting cell may further include a functional layer for improving the luminous efficiency and / or lifetime of the organic light emitting layer.

The voltage supply unit 200 applies a driving voltage EVDD and a cathode voltage VSS used as a power source for emitting the organic light emitting diode OLED of each subpixel SP, And supplies the driving voltage EVDD to the driving voltage line VL of the display panel 100 through the first voltage supply line PL1 and supplies the driving voltage EVDD to the display panel 100 through the first voltage supply line PL2. The cathode voltage VSS is supplied to the cathode voltage VSS line. The voltage supplier 200 generates and supplies constant voltages SVDD and SVSS required for driving the panel driver 400 to the panel driver 400.

In the memory 300, a data table-based voltage table, a luminance table and a current table corresponding to a voltage are stored, respectively. Each of the luminance and current tables according to the gradation voltage table and the voltage is set by the initial optical compensation process during the final inspection process of the organic light emitting display and is stored in the memory 300. The initial optical compensation process The process of measuring the luminance value of the display panel 100 and the current value flowing in the display panel 100 in accordance with the voltage is repeatedly performed while gradually adjusting the data voltage in units of the set gray level value, The table is set. In the following description, the voltage value of the voltage table is defined as an " initial voltage value ", and the luminance value and current value of the luminance and current table are defined as an "initial luminance value"

The panel driver 400 generates a measured current value MCV by measuring the panel current flowing through the display panel 100 using the image of the previous frame and refers to the initial current value ICV stored in the memory 300 Gi and Bi of the current frame to be displayed on the display panel 100 and calculates a predicted current value corresponding to the current data of the current frame in accordance with the current deviation of the measured current value MCV and the predicted current value, And adjusts at least one of the reference voltage Vref and the data voltage Vdata to be supplied to the pixel SP. Here, when the current deviation between the measured current value MCV and the predicted current value occurs, the panel driver 400 calculates an average image level of the current frame image, and based on the calculated average image level and the current deviation Thereby increasing or decreasing the reference voltage Vref or the reference voltage Vref and the data voltage Vdata. That is, when the current deviation is generated and the average image level is less than or equal to the reference image level, the panel driver 400 increases or decreases the reference voltage Vref according to the current deviation, Thereby decreasing or increasing the maximum luminance value of the voltage (Vdata). On the other hand, when the current deviation is generated and the average image level exceeds the reference image level, the panel driver 400 decreases or increases the maximum luminance value of the data voltage Vdata to correspond to the current deviation. At this time, the panel driver 400 may reduce or increase the maximum luminance value of the data voltage (Vdata) for a plurality of frames in order to minimize image quality degradation due to a sudden change in luminance.

The panel driving unit 400 includes a current measuring unit 410, a row driving unit 420, a reference gamma voltage supplying unit 430, a column driving unit 440, and a timing control unit 450 .

The current measuring unit 410 measures the panel current flowing in the display panel 100 according to the emission of the organic light emitting diode OLED of each subpixel SP for one frame, (MCV) to the timing controller 450. [ To this end, the current measuring unit 410 includes a current sensing resistor Rs, an operational amplifier 412, and an analog-to-digital converter 414, as shown in FIG.

The current sensing resistor Rs is connected to the first voltage supply line PL1 and generates a bias voltage Vs according to the current flowing through the first voltage supply line PL1, to which the drive voltage EVDD is supplied from the voltage supply unit 200, . The current sensing resistor Rs may have a resistance value of 0.01 OMEGA to minimize the voltage drop of the driving voltage EVDD.

The operational amplifier 412 is connected to both ends of the current sensing resistor Rs to sense a bias voltage across the current sensing resistor Rs, amplifies the bias voltage, and supplies the amplified voltage to the analog-to-digital converter 414. For example, the operational amplifier 412 may amplify the bias voltage by 5 times or more.

The analog-to-digital converter 414 converts the current flowing in the display panel into a digital signal for one frame based on the bias voltage amplified by the operational amplifier 412 to generate a measured current value MCV, And provides the current value MCV to the timing controller 450. [

3, the row driving unit 420 includes first and second gate signals GSa and GSb having gate-on voltage levels for each horizontal period according to a gate control signal GCS supplied from the timing controller 450, , And GSb, and supplies them to the gate line group GL. At this time, the first gate signal GSa has a gate-off voltage level during the initialization period of each sub-pixel SP, has a gate-on voltage level during the data charging period of each sub-pixel SP, Off voltage level during the light emission period of the scan lines SP and SP. The second gate signal GSb has a gate-on voltage level during the initialization period and the data charging period of each sub-pixel SP and has a gate-off voltage level during the emission period of each sub-pixel SP. The row driving unit 420 sequentially outputs the first and second gate signals GSa and GSb to be sequentially supplied to the gate line groups GL according to the gate control signal GCS And a shift register. The shift register may be formed directly on the substrate of the display panel 100 together with the transistor forming process of each subpixel SP and may be connected to one or both sides of each of the plurality of gate line groups GL.

The reference gamma voltage generator 430 includes a programmable gamma integrated circuit (GAM) IC that generates a plurality of different reference gamma voltages RVgam based on the gamma voltage setting data P_GAM supplied from the timing controller 450, . ≪ / RTI > The reference gamma voltage generator 430 generates a voltage distribution between the high potential positive voltage SVDD and the low potential constant voltage SVSS for generating the reference gamma voltage from the power supply unit 200 according to the gamma voltage setting data P_GAM A plurality of reference gamma voltages RVgam having different voltage levels are generated and supplied to a column driver 440. The reference gamma voltage generator 430 may generate a plurality of reference gamma voltages RVgam commonly used for each subpixel of the unit pixel, A plurality of different reference gamma voltages RVgam can be generated for each color used as the reference gamma voltage RVgam.

The reference gamma voltage generator 430 further generates a reference voltage Vref corresponding to the reference voltage setting data P_REF supplied from the timing controller 450 and supplies the reference voltage Vref to the column driver 440.

The column driver 440 receives pixel data DATA and a data control signal DCS from the timing controller 450 and receives a plurality of reference gamma voltages RVgam from the reference gamma voltage supplier 430, And a reference voltage Vref. The column driver 440 converts the pixel data DATA into an analog data voltage Vdata using the plurality of reference gamma voltages RVgam according to a data control signal DCS, Supplies the converted data voltage Vdata to the data line DL of the corresponding subpixel SP and simultaneously supplies the reference voltage Vref to the reference voltage line RL of the corresponding subpixel SP. The column driver 440 may be formed in the form of a plurality of integrated circuits (IC) and may be connected to one side and / or both sides of the data line DL and the reference voltage line RL.

The timing controller 450 generates a gate control signal GCS and a data control signal DCS based on a timing synchronization signal TSS input from an external system body (not shown) or a graphic card (not shown) And controls the driving timings of the row driving unit 420 and the column driving unit 440, respectively. The timing control unit 450 refers to the initial current value ICV stored in the memory 300 and outputs the input data of the current frame input from an external system body (not shown) or a graphic card (not shown) Ri, Gi, Bi of the current frame, based on the current deviation between the measured current value (MCV) supplied from the current measuring unit 410 and the predicted current value, And adjusts at least one of the reference voltage Vref and the data voltage Vdata to be supplied to the pixel SP. To this end, the timing controller 450 includes a control signal generator 452 and a data processor 454, as shown in FIG.

The control signal generating unit 452 generates a control signal for driving the row driver 420 and the column based on a timing synchronization signal TSS such as a vertical synchronization signal, a horizontal synchronization signal, a data enable signal, A gate control signal GCS and a data control signal DCS for controlling the driving timing of each of the driving units 440 are generated.

The data processing unit 454 includes a four-color data conversion unit 4541, a current predicting unit 4542, and a luminance control unit 4543.

The four-color data conversion unit 4541 converts the input data Ri, Gi, and Bi of the red, green, and blue input data into one unit pixel of the display panel 100 based on the input timing synchronization signal TSS. Green, blue and white four-color data (R, G, B, W) to be supplied to each of the red sub-pixel, the green sub-pixel, the blue sub-pixel and the white sub-pixel constituting the red, For example, the four-color data conversion unit 4541 calculates the input data Ri, Gi, Bi as the input data Ri, Gi, Bi by using the white data W as the input data having the minimum gray- G, B, W) by generating red, green, and blue data (R, G, B) by subtracting the white data (W) ). ≪ / RTI > Accordingly, any one of the three-color data (R, G, and B) of red, green, and blue has a tone value of 0 or black. In the case where each unit pixel of the display panel 100 includes only the red sub-pixel, the green sub-pixel, and the blue sub-pixel without including the white sub-pixel, Therefore, it is omitted.

The current predicting unit 4542 analyzes the 4-color data R, G, B, and W by referring to the initial current value ICV stored in the memory 300, G, B, and W) of the current frame. That is, the current predicting unit 4542 calculates the average image level APL of the four-color data R, G, B and W of the current frame and outputs the average image level APL to the average image level APL in the memory 300 The corresponding initial current value ICV is calculated as the predicted current value ECV of one frame.

The luminance controller 4543 compares the predicted current value ECV supplied from the current predicting unit 4542 with the measured current value MCV supplied from the current measuring unit 410, And at least one of the reference voltage (Vref) and the data voltage (Vdata) to be supplied to each sub-pixel (SP). At this time, the data voltage Vdata may be adjusted by adjusting the plurality of reference gamma voltages RVgam or by modulating the four-color data R, G, B, and W.

When a current deviation between two current values (ECV, MCV) occurs as a result of a comparison between the predicted current value (ECV) and the measured current value (MCV), the luminance controller 4543 according to the embodiment determines the current prediction 4524 The gamma voltage setting data P_GAM for increasing or decreasing the reference voltage Vref or the reference voltage Vref and the data voltage Vdata based on the current deviation and the average image level APL supplied from the reference G, B, and W supplied from the four-color data conversion unit 4541 to the reference gamma voltage supply unit 430. The four-color data R, G, B, (The display panel 100) and the pixel driving method, and supplies the data to the data driving circuit portion 440 described above. For example, when the average image level APL is equal to or lower than the reference image level, the luminance controller 4543 generates reference voltage setting data P_REF corresponding to the current deviation, and outputs the reference voltage Vref ), And simultaneously generates gamma voltage setting data (P_GAM) corresponding to the current deviation to reduce or increase the plurality of reference gamma voltages (RVgam) to obtain a maximum luminance value (Vdata) according to the data voltage ≪ / RTI > On the other hand, when the average image level APL exceeds the reference image level, the luminance controller 4543 generates the reference voltage setting data P_REF to set the reference voltage Vref to an initial value And the gamma voltage setting data P_GAM corresponding to the current deviation is generated to decrease or increase the maximum luminance value according to the data voltage Vdata.

If a current deviation between the two current values (ECV, MCV) occurs as a result of the comparison of the predicted current value (ECV) and the measured current value (MCV), the luminance controller 4543 according to another embodiment sets the initial set gamma voltage setting Generates reference voltage setting data (P_GAM) for supplying the reference gamma voltage to the reference gamma voltage supplier 430 and increasing or decreasing the reference voltage Vref based on the average image level APL and the current deviation (R, G, B, W) according to the current deviation, and supplies the modulated four-color data to the display panel 100) and pixel data (DATA) so as to be suitable for the pixel driving scheme and supplies the data to the data driving circuit unit 440 described above. For example, when the average image level APL is equal to or lower than the reference image level, the luminance controller 4543 generates reference voltage setting data P_REF corresponding to the current deviation, and outputs the reference voltage Vref ) And simultaneously generates the initial set gamma voltage setting data P_GAM to adjust the plurality of reference gamma voltages RVgam to the initial voltage level and at the same time to generate the four color data R , G, B, W) to reduce or increase the maximum luminance value according to the data voltage (Vdata). On the other hand, when the average image level APL exceeds the reference image level, the luminance controller 4543 generates the reference voltage setting data P_REF to set the reference voltage Vref to an initial value (R, G, B, W) so as to correspond to the current deviation, thereby reducing or increasing the maximum luminance value according to the data voltage (Vdata).

Meanwhile, the timing controller 450 may further include an overcurrent detector (not shown). The overcurrent detecting unit checks the occurrence of burning due to the overcurrent based on the measured current value (MCV) or the current deviation between the measured current value (MCV) and the predicted current value (ECV) The voltage supply unit 200 is shut down to prevent or prevent a fire in advance.

7 is a block diagram for explaining the first embodiment of the luminance controller shown in FIG.

Referring to FIGS. 6 and 7, the luminance controller 4543 according to the first embodiment includes a data converter 4543a, a current deviation calculator 4543b, and a voltage setting data generator 4543c.

The data conversion unit 4543a converts the four color data R, G, B, and W supplied from the four-color data conversion unit 4541 into the pixel arrangement structure and the pixel drive scheme of the display panel 100 And supplies the data to the data driving circuit unit 440 described above.

The current deviation calculator 4543b compares the predicted current value ECV supplied from the current predicting unit 4542 with the measured current value MCV supplied from the current measuring unit 410 and outputs two current values ECV, and MCV). At this time, the current deviation CDV is a parameter for predicting the threshold voltage change of the driving transistor Tdr included in each sub-pixel SP. That is, when the threshold voltage of the driving transistor Tdr is shifted to a negative voltage according to the driving time and the temperature, the current deviation CDV has a positive value, and conversely, And may have a negative value when the threshold voltage of the driving transistor Tdr is shifted to a positive voltage depending on the driving time and the temperature. For example, when the driving transistor Tdr includes an oxide semiconductor, the threshold voltage of the driving transistor Tdr is shifted to a negative voltage according to the driving time and temperature, CDV) has a positive value.

The voltage setting data generating section 4543c generates the voltage setting data generating section 4543c based on the current deviation CDV supplied from the current deviation calculating section 4543b and the average image level APL supplied from the current predicting section 4542, ) Or the gamma voltage setting data P_GAM and the reference voltage setting data P_REF for increasing or decreasing the reference voltage Vref and the data voltage Vdata and supplying the gamma voltage setting data P_REF to the reference gamma voltage supplying unit 430 do.

The voltage setting data generator 4543c generates the voltage setting data P_REF and the gamma voltage setting data P_REF when the current deviation CDV is within a reference current deviation of 0 or zero, And supplies the reference gamma voltage to the reference gamma voltage supplier 430. [

On the other hand, when the current deviation CDV exceeds the reference current deviation, the voltage setting data generation unit 4543c generates the voltage setting data signal Vref based on the current deviation CDV and the average image level APL, Or the gamma voltage setting data P_GAM and the reference voltage setting data P_REF for increasing or decreasing the reference voltage Vref and the data voltage Vdata, respectively. This will be described in more detail as follows.

The voltage setting data generating unit 4543c generates the voltage setting data generating unit 4543c such that the current deviation CDV corresponds to the current deviation CDV when the current deviation CDV exceeds the reference current deviation and the average image level APL is less than the reference image level And generates the reference voltage setting data P_REF and the gamma voltage setting data P_GAM, which are increased or decreased, respectively. For example, when the average image level APL is less than or equal to the reference image level and the current deviation CDV has a positive value, the voltage setting data generation unit 4543c generates a positive voltage Generates reference voltage setting data P_REF for increasing the reference voltage Vref by a current deviation CDV and outputs a plurality of reference gamma voltages RVgam by a current deviation CDV having a positive value Gamma voltage setting data (P_GAM) for reducing the gamma voltage. As a result, the voltage setting data generation unit 4543c determines that the frame image to be displayed on the display panel 100 is a relatively dark black pattern when the average image level APL is equal to or lower than the reference image level, The reference voltage Vref is increased in order to prevent luminance variation and image quality distortion due to the luminance increase of the black pattern due to the current deviation CDV of the positive By reducing the data voltage (Vdata) by a positive current deviation (CDV) in order to compensate for the rise, thereby compensating for and preventing image quality distortion due to the overall luminance rise generated in the high temperature environment. As another example, when the average image level APL is less than or equal to the reference image level and the current deviation CDV has a negative value, the voltage setting data generator 4543c generates a voltage Generates reference voltage setting data P_REF for reducing the reference voltage Vref by a current deviation CDV and generates a plurality of reference gamma voltages RVgam by a current deviation CDV having a negative value Gamma voltage setting data P_GAM for increasing the gamma voltage.

Next, when the current deviation CDV exceeds the reference current deviation and the average image level APL exceeds the reference image level, the voltage setting data generation unit 4543c generates initial voltage reference data And generates gamma voltage setting data P_GAM which is increased or decreased to correspond to the current deviation. For example, when the average image level APL exceeds the reference image level and the current deviation CDV has a positive value, the voltage setting data generator 4543c generates an initial set reference voltage Generates the setting data P_REF and generates gamma voltage setting data P_GAM for reducing the plurality of reference gamma voltages RVgam by a current deviation CDV having a positive value. As a result, the voltage setting data generation unit 4543c determines that a frame image to be displayed on the display panel 100 is a relatively bright image when the average image level APL exceeds the reference image level, By reducing the data voltage Vdata by the positive current deviation CDV in order to compensate for the rise in the maximum luminance according to the current deviation CDV of the positive polarity signal + Compensation and Prevention. As another example, when the average image level APL exceeds the reference image level and the current deviation CDV has a negative value, the voltage setting data generation unit 4543c generates an initial set reference voltage Generates the setting data P_REF and generates the gamma voltage setting data P_GAM for increasing the plurality of reference gamma voltages RVgam by a current deviation CDV having a negative value.

8 is a block diagram for explaining a second embodiment of the luminance controller shown in FIG.

Referring to FIGS. 6 and 8, the luminance controller 4543 according to the second embodiment includes a data converter 4543a, a current deviation calculator 4543b, and a voltage setting data generator 4543c.

First, the current deviation calculation section 4543b is the same as the brightness control section of the first embodiment shown in FIG. 7, and thus a duplicate description thereof will be omitted.

The data converter 4543a converts the four color data R, G, B and W supplied from the four-color data converter 4541 into the current deviation CDV supplied from the current deviation calculator 4543b, And supplies the modulated four-color data to the data driving circuit unit 440 by arranging the modulated four-color data in accordance with the pixel arrangement structure and the pixel driving method of the display panel 100 and pixel data (DATA). For example, the data converter 4543a may calculate the luminance compensation gain value based on the current deviation (CDV) and reflect the calculated luminance compensation gain value to the four-color data (R, G, B, W) So that four-color modulation data can be generated. At this time, the data conversion unit 4543a may generate the 4-color modulation data by multiplying the luminance compensation gain value with the 4-color data R, G, B, and W to generate 4-color modulation data. However, The four-color modulation data can be generated through another calculation method in accordance with the gain calculation algorithm. As a result, when the current deviation (CDV) has a positive value, the data converter 4543a outputs the 4-color data (440) according to the luminance compensation gain value according to the positive current deviation (CDV) R, G, B, and W) to compensate for the increase in the maximum luminance according to the positive current deviation (CDV). Conversely, when the current deviation CDV has a negative value, the data converter 4543a increases the gray level of the four-color data R, G, B, and W so that the negative Compensates for the reduction of the maximum luminance according to the current deviation (CDV).

The voltage setting data generating section 4543c generates the voltage setting data generating section 4543c based on the current deviation CDV supplied from the current deviation calculating section 4543b and the average image level APL supplied from the current predicting section 4542, And supplies the generated reference voltage setting data P_REF to the reference gamma voltage supply unit 430. [ The voltage setting data generating unit 4543c generates the initial gamma voltage setting data P_GAM and supplies the gamma voltage setting data P_GAM to the reference gamma voltage supplying unit 430. [ The voltage setting data generator 4543c generates the voltage setting data P_REF and the gamma voltage setting data P_REF when the current deviation CDV is within a reference current deviation of 0 or zero, And supplies the reference gamma voltage to the reference gamma voltage supplier 430. [

If the current deviation (CDV) exceeds the reference current deviation, the voltage setting data generation unit 4543c generates the initial set gamma voltage setting data P_GAM, And generates reference voltage setting data P_REF for increasing or decreasing the reference voltage Vref based on the average image level APL. This will be described in more detail as follows.

The voltage setting data generating unit 4543c generates the voltage setting data generating unit 4543c such that the current deviation CDV corresponds to the current deviation CDV when the current deviation CDV exceeds the reference current deviation and the average image level APL is less than the reference image level And generates reference voltage setting data P_REF that is increased or decreased. For example, when the average image level APL is equal to or lower than the reference image level and the current deviation CDV has a positive value, the voltage setting data generator 4543c generates the voltage setting data Vref The reference voltage setting data P_REF for increasing the reference voltage setting data P_REF. As a result, the voltage setting data generation unit 4543c determines that the frame image to be displayed on the display panel 100 is a relatively dark black pattern when the average image level APL is equal to or lower than the reference image level, ) By increasing the reference voltage (Vref) in order to prevent luminance variation and image quality distortion due to the luminance increase of the black pattern by the current deviation (CDV) of the black pattern Compensate and prevent distortion. Conversely, when the average image level APL is equal to or lower than the reference image level and the current deviation CDV has a negative value, the voltage setting data generator 4543c generates the voltage reference data Vref The reference voltage setting data P_REF for reducing the reference voltage is generated. Therefore, the voltage setting data generation unit 4543c performs the process of increasing or decreasing the reference voltage Vref according to the current deviation CDV during a plurality of frames, ECV) to each other.

Next, when the current deviation CDV exceeds the reference current deviation and the average image level APL exceeds the reference image level, the voltage setting data generation unit 4543c generates initial voltage reference data P_REF). For example, when the average image level APL exceeds the reference image level, the voltage setting data generation unit 4543c generates initial set voltage reference data P_REF irrespective of the current deviation CDV do. As a result, when the average image level APL exceeds the reference image level, the voltage setting data generation unit 4543c determines that one frame image to be displayed on the display panel 100 is a relatively bright image, (Vref) to an initial set voltage level. At this time, the reference voltage Vref may have a voltage level of zero or a voltage level lower than the conduction voltage of the organic light emitting diode OLED.

9 is a flowchart for explaining a driving method of the organic light emitting diode display according to the present invention.

A driving method of the OLED display according to the present invention will now be described with reference to FIGS. 3 and 9. FIG.

First, input data of an input image is converted into a data voltage Vdata based on an initial reference voltage Vref and a plurality of reference gamma voltages RVgam, and an image of one frame is displayed on the display panel 100 (S100 ).

Then, the current measuring unit 410 senses the current flowing from the power supply unit 200 to the first voltage supply line PL1 to measure the measured current value MCV corresponding to the current flowing through the display panel 100 (S110).

Then, the average image level APL and the predicted current value ECV corresponding to the input data of the current frame image to be displayed on the display panel 100 are calculated by referring to the initial current value ICV stored in the memory 300 (S120).

Then, the current deviation (CDV) between the two current values (ECV and MCV) is calculated by comparing the measured current value (MCV) with the predicted current value (ECV) (S130).

Then, it is determined whether the current deviation (CDV) is 0 (Zero) or the reference current deviation Rcdv having the set value to generate a current deviation (S140).

If it is determined in step S140 that the current deviation does not occur ("No" in S140), the input data of the current frame image is calculated based on the initially set reference voltage Vref and the plurality of reference gamma voltages RVgam Data voltage Vdata, and displays the image of one frame on the display panel 100 (S100).

On the other hand, if it is determined in step S140 that a current deviation has occurred (Yes in S140), the average image level APL is compared with the reference image level R_APL, It is determined whether it is equal to or lower than the image level R_APL (S150).

If it is determined in step S150 that the average image level APL is less than the reference image level R_APL ("Yes" in S150), the reference voltage setting data P_REF is set to correspond to the current deviation CDV And adjusts the reference voltage Vref supplied to each sub-pixel SP of the display panel 100 (S160). Here, since the adjustment of the reference voltage Vref is the same as that described above, a duplicate description thereof will be omitted.

Thereafter, the gamma voltage setting data P_GAM, which is increased or decreased to correspond to the current deviation CDV, is generated to adjust the gamma voltage RVgam, or the input data of the current frame is modulated to generate the data voltage Vdata, Thereby adjusting and preventing the image quality distortion due to the luminance change due to the temperature change of the surrounding environment (S170). Here, since the adjustment of the data voltage Vdata is the same as the above description, a duplicate description thereof will be omitted.

On the other hand, if it is determined in step S150 that the average image level APL exceeds the reference image level Lref ("No" in S150), the voltage level of the reference voltage Vref having the initially set voltage level The process proceeds to step S170.

Then, the image is displayed on the display panel 100 by repeating steps S100 to S170 described above.

10 is a waveform diagram for explaining driving of one sub-pixel of the organic light emitting diode display according to the embodiment of the present invention.

The driving method of the sub-pixel shown in FIG. 4 will now be described with reference to FIGS. 3, 4 and 10. FIG.

First, one subpixel operates in the initializing period t1, the data charging period t2, and the light emitting period t3.

In the initialization period t1, the first gate signal GSa of the gate-off voltage level is supplied to the first gate line GLa by driving the row driver 420, The second gate signal GSb is supplied to the second gate line GLb and the reference voltage Vref is supplied to the reference voltage line RL by driving the column driver 440. [ At this time, the reference voltage Vref has a voltage level initially set or adjusted by the current deviation between the measured current value MCV and the predicted current value ECV, as described above. Accordingly, in the initialization period t1, the first switching transistor Tsw1 is turned off by the first gate signal GSa and the second switching transistor Tsw2 is turned off by the second gate signal GSb The reference voltage Vref supplied to the reference voltage line RL is supplied to the second node n2 by turning on the voltage of the second node n2 and the voltage of the capacitor Cst, (Vref).

In the data charge period t2, the first gate signal GSa of the gate-on voltage level is supplied to the first gate line GLa by driving the row driver 420, The second gate signal GSb supplied to the line GLb is maintained at the gate-on voltage level and the reference voltage line RL is maintained at the reference voltage line RL by driving the column driver 440 And the data voltage Vdata is supplied to the data line DL. At this time, the data voltage Vdata has a voltage level corresponding to the input data or a voltage level regulated by the current deviation between the measured current value MCV and the predicted current value ECV, as described above . Accordingly, in the data charging period t2, the first switching transistor Tsw1 is turned on by the first gate signal GSa, the second switching transistor Tsw2 is turned on by the second gate signal GSb, The data voltage Vdata is supplied to the first node n1 and the reference voltage Vref is supplied to the second node n2.

Therefore, in the data charging period t2, the capacitor Cst is charged with the difference voltage Vdata-Vref between the data voltage Vdata and the reference voltage Vref.

In the light emission period t3, the first and second gate signals GSa and GSb of the gate-off voltage level are applied to the first and second gate lines GLa , And GLb. Accordingly, in the light emission period t3, each of the first and second switching transistors Tsw1 and Tsw2 is turned off by the first and second gate signals GSa and GSb so that the driving transistor Tdr is turned on And is turned on by the voltage stored in the capacitor Cst.

Therefore, in the light emission period t3, the turn-on driving transistor Tdr is turned on by applying the difference voltage Vdata-Vref between the data voltage Vdata and the reference voltage Vref, The data current Ioled is supplied to the light emitting element OLED so that the light emitting element OLED emits light. That is, when the first and second switching transistors Tsw1 and Tsw2 are turned off in the light emission period t3, the driving transistor Tdr is driven by the driving voltage EVDD supplied to the driving voltage line VL The voltage of the second node n2 is increased while the light emitting device OLED starts to emit light in proportion to the current and the voltage of the first node n2 is increased by the voltage of the second node n2 by the capacitor Cst, The gate-source voltage Vgs of the driving transistor Tdr is continuously maintained by the voltage of the capacitor Cst as the voltage of the node n1 rises and the light emitting device OLED emits light until the next initialization period t1 It continues.

In Equation (1), "k" is a value determined by the structure and physical characteristics of the driving transistor DT as a proportional constant. The mobility of the driving transistor DT and the channel width Quot; W / L "which is the ratio of the channel length W to the channel length L, and the like.

The data current Ioled flowing through the light emitting device OLED during the light emission period t3 is controlled by the reference voltage Vref adjusted according to the current deviation described above, Is determined by the difference between the data voltage (Vdata) and the reference voltage (Vref), which is adjusted only in accordance with the above-described current deviation, without being influenced by the variation of the threshold voltage (Vth) / mobility.

On the other hand, in the above description, the initialization period t1 may be omitted. That is, since the reference voltage Vref is supplied to the second node n2 during the data charging period t2, the data voltage Vdata and the reference voltage Vdata are applied to the capacitor Cst without the initialization period t1, (Vdata-Vref) of the reference voltage Vref.

FIG. 11 is a waveform diagram showing a change in panel current of data according to a gradation of data according to a temperature change in an ambient environment in an organic light emitting display according to an embodiment of the present invention. This is because the threshold voltage of the driving transistor is a negative voltage The change of the panel current of the data in the case of the change in the direction of the panel.

11, when the present invention is changed to a high temperature environment of 25 ° C to 50 ° C, the reference voltage is increased based on the above measured current value and the predicted current value, so that the threshold voltage of the driving transistor The current I _PANEL flowing in the display panel due to the decrease of the data voltage by the current deviation between the measured current value and the predicted current value can be prevented from increasing in the black pattern due to the change to the negative voltage, It can be seen that the overall increase in luminance generated in a high-temperature environment is suppressed.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. Will be clear to those who have knowledge of.

100: display panel 200:
300: memory 400: panel driver
410: current measuring unit 420: row driving unit
430: reference gamma voltage supplier 440: column driver
450: timing control unit 452: control signal generation unit
454: Data processing section 4541: Four-color data conversion section
4542: current predicting unit 4543: luminance control unit
4543a: Data conversion section 4543b: Current deviation calculation section
4543c: Voltage setting data generating section

Claims (10)

A display panel including a plurality of subpixels having an organic light emitting element that stores a difference voltage between a data voltage and a reference voltage in a capacitor and emits light by a data current determined by a voltage stored in the capacitor;
A memory for storing an initial current value of the display panel according to the data voltage;
A voltage supplier for supplying a pixel driving voltage and a cathode voltage to the display panel; And
Calculating a measured current value by measuring a panel current flowing through the display panel according to a previous frame image, calculating a predicted current value according to input data of a current frame image with reference to an initial current value stored in the memory, And a panel driver for calculating an average image level according to input data of the image,
Wherein the panel driving unit simultaneously applies the reference voltage and the data voltage to be supplied to the respective sub-pixels during the current frame based on the average image level and the current deviation when the current deviation between the measured current value and the predicted current value occurs And adjusts only the data voltage. The method according to claim 1,
Wherein the panel driving unit further includes an overcurrent detecting unit for detecting the presence or absence of an overcurrent based on the measured current value or the current deviation and shutting down the power supply unit according to a detection result. The method according to claim 1,
Wherein the panel-
Adjusting a maximum luminance value of the current frame image through adjustment of the reference voltage and adjustment of the data voltage corresponding to the current deviation when the average image level is equal to or lower than a reference image level,
And adjusts the maximum luminance value of the current frame image by adjusting the data voltage corresponding to the current deviation when the average image level exceeds the reference image level. The method of claim 3,
Wherein the panel driver adjusts the maximum luminance value of the current frame image by modulating the input data of the current frame image to correspond to the current deviation or adjusts the maximum luminance value of the current frame image by adjusting the plurality of reference gamma voltages to correspond to the current deviation, To adjust the maximum luminance value of the current frame image. 5. The method according to any one of claims 1 to 4,
Wherein each of the plurality of sub-
A driving transistor for supplying a data current, which is determined by a voltage stored in the capacitor, connected between the gate electrode and the source electrode to the organic light emitting element;
The data voltage is applied to the gate electrode of the driving transistor by a first switching transistor; And
And a second switching transistor for supplying the reference voltage to a node to which the organic light emitting element and the driving transistor are connected. (A) displaying an image on a display panel by emitting an organic light emitting element of each of a plurality of sub-pixels according to a data current determined by a difference voltage between a data voltage and a reference voltage;
(B) measuring a panel current flowing through the display panel to generate a measured current value;
Calculating a predicted current value according to input data of a current frame image by referring to an initial current value of the display panel according to the data voltage stored in the memory and calculating an average image level according to input data of the current frame image C); And
The reference voltage and the data voltage to be supplied to the respective subpixels during the current frame are simultaneously adjusted based on the average image level and the current deviation, And a step (D) of adjusting only the voltage. The method according to claim 6,
Wherein the step (C) further comprises detecting the presence or absence of an overcurrent based on the measured current value or the current deviation,
Wherein the step (D) further comprises the step of shutting down the power supply unit supplying the pixel drive voltage and the cathode voltage to the display panel in accordance with the detection result of the presence / absence of the overcurrent. The method according to claim 6,
The step (D)
Adjusting a maximum luminance value of the current frame image through adjustment of the reference voltage and adjustment of the data voltage corresponding to the current deviation when the average image level is equal to or lower than a reference image level,
And adjusting a maximum luminance value of the current frame image by adjusting the data voltage corresponding to the current deviation when the average image level exceeds the reference image level. 9. The method of claim 8,
Wherein the maximum luminance value of the current frame image is adjusted by modulation of input data of the current frame image based on the current deviation or by adjustment of a plurality of reference gamma voltages based on the current deviation, Driving method. 10. The method according to any one of claims 6 to 9,
The step (A)
Storing a difference voltage between the data voltage and the reference voltage in a capacitor; And
And turning on the driving transistor according to a voltage stored in the capacitor to cause the organic light emitting element to emit light with a data current determined by a difference voltage between the data voltage and the reference voltage. .

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