KR102136263B1 - Organic light emitting display device - Google Patents

Abstract

The present invention provides an organic light emitting display device and a driving method thereof to prevent deterioration of image quality due to a sensing error due to temperature change. The organic light emitting display device according to the present invention provides an intersection area between a scan control line and a data line. A display panel including a pixel formed every time and a sensing line connected to the pixel; And a panel driver configured to sense the characteristic change of the pixel at least two times through the sensing line in a driving preparation period between a reception time of a power-on signal and a display time of the display panel, and generate sensing data for the pixel. Can be configured. In this case, the panel driver may sense a change in characteristics of the pixel at least once per second during the driving preparation period.

Description

Organic light emitting display device {ORGANIC LIGHT EMITTING DISPLAY DEVICE}

The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device capable of compensating for a change in characteristics of a pixel.

The organic light emitting display device is a self-emission device that emits an organic light emitting layer by recombination of electrons and holes. It has a high-speed response speed, low power consumption, and self-light emission, and thus has no problem in viewing angle, and thus is receiving attention as a next-generation flat panel display device.

The organic light emitting display device includes a plurality of pixels displaying an image, and each pixel includes an organic light emitting device including an organic light emitting layer between an anode electrode and a cathode electrode, and a pixel circuit emitting an organic light emitting device. The pixel circuit is composed of a switching transistor, a driving transistor, and a capacitor. The switching transistor is switched according to the gate signal to supply the data voltage to the driving transistor, and the driving transistor is switched according to the data voltage supplied from the switching transistor to control the current flowing through the organic light emitting device to emit light from the organic foot and the device. Control. The capacitor stores the voltage between the gate terminal and the source terminal of the driving transistor, and switches the driving transistor to the stored voltage. The organic light emitting device emits light by a current supplied from a driving transistor.

In such a conventional organic light emitting display device, due to process variation, a difference in characteristics of a driving transistor such as a threshold voltage (Vth) and mobility of a driving transistor is generated for each pixel, and thus the amount of current driving the organic light emitting device varies. As a result, there is a problem in that luminance deviation occurs between pixels. In order to solve this problem, in prior art documents such as Korean Patent Publication No. 10-2013-0066449, an external compensation that compensates for a characteristic change of a pixel by sensing the characteristic change of the pixel outside the pixel and reflecting it in the pixel data Technology is disclosed.

1 and 2, the data line connected to each pixel P is used as the sensing line 11, and the current flowing through the driving transistor of the pixel P is sensed by the prior art document. 11), the voltage Vout charged in the sensing line 11 is sensed through the analog-to-digital converter ADC, and the current flowing through the driving transistor of the pixel P is inferred according to the sensed voltage. . That is, the prior art document uses the voltage-sensing analog-to-digital converter (ADC) to sense the voltage without measuring the actual current to infer the current flowing through the driving transistor.

However, in the prior art literature, the charging time Tsen of the sensing line 11 is increased due to the large parasitic resistance (Rp) and the large parasitic capacitance (Cp) of the sensing line 11, In particular, it is difficult to sense the threshold voltage of the driving transistor in real time because there is a problem that the sensing time Tsen is too delayed when sensing a small current of low gradation.

In addition, since the threshold voltage of the driving transistor is changed by an external environment, that is, temperature change, as shown in FIG. 3, even if the gate-source voltage (Vgs) of the driving transistor is the same, depending on the temperature, The drain current (Ids) is changed. Accordingly, in the prior art document, since the threshold voltage of the driving transistor is sensed during driving of the organic light emitting diode display, a sensing error in which a sensing value for the threshold voltage of the driving transistor varies depending on temperature occurs. For example, when the threshold voltage of the driving transistor is sensed in real time by sensing the threshold voltage of the driving transistor when the display panel is in a high temperature state according to long-time driving of the organic light emitting display device, due to the temperature change of the driving transistor due to high temperature A sensing error occurs, and the threshold voltage of the driving transistor may be overcompensated due to the sensing error. When over-compensation occurs due to the sensing error, there is a problem in that the image quality is deteriorated due to a crack or color modulation phenomenon of an image and accelerates deterioration of the driving transistor.

The present invention has been devised to solve the above-mentioned problems, and an object of the present invention is to provide an organic light emitting display device and a driving method thereof to prevent deterioration of image quality due to sensing errors due to temperature changes.

In addition, another object of the present invention is to provide an organic light emitting display device capable of sensing changes in pixel characteristics at high speed.

In addition to the technical problems of the present invention mentioned above, other features and advantages of the present invention are described below, or it will be clearly understood by those skilled in the art from the description and description.

An organic light emitting display device according to an exemplary embodiment of the present invention for achieving the above-described technical problem includes a display panel including a pixel formed for each intersection region of a scan control line and a data line, and a sensing line connected to the pixel; And a panel driver configured to sense the characteristic change of the pixel at least two times through the sensing line in a driving preparation period between a reception time of a power-on signal and a display time of the display panel, and generate sensing data for the pixel. Can be configured. In this case, the panel driver may sense a change in characteristics of the pixel at least once per second during the driving preparation period.

The panel driver includes a column driver having a sensing data generator that senses a change in characteristics of the pixel through the sensing line to generate the sensing data, and the sensing data generator flows from the pixel to the sensing line. The current may be converted into a voltage, and the converted voltage may be converted into analog to digital to generate sensing data for the pixel. Also, the panel driver may further include a timing control unit that corrects data to be supplied to the pixel based on sensing data sensed by the sensing at least twice.

The timing control unit calculates an average value of sensing data sensed by the sensing at least twice, and corrects the previous compensation value according to the previous compensation value and the average value of the pixels stored in the memory unit to compensate for the current compensation value. And update the previous compensation value stored in the memory unit with the current compensation value, and correct data to be supplied to the pixel according to the current compensation value.

According to the solving means of the said subject, this invention has the following effects.

First, in response to a power-on signal according to a user manipulation, a characteristic change of a pixel may be sensed while minimizing a sensing error due to a temperature change by sensing a characteristic change of the pixel at least two times through a sensing line before an image display time point.

Second, by changing the current flowing from the pixel to the sensing line into a voltage, a change in the characteristics of the pixel can be sensed at a high speed, and the sensing time delay and sensing due to the parasitic capacitance and parasitic resistance of the sensing line through preliminary charging of the sensing line. It is possible to sense changes in pixel characteristics at a high speed while minimizing errors.

1 is a view for explaining a conventional voltage sensing circuit.
2 is a waveform diagram showing a conventional sensing time.
3 is a waveform diagram for explaining a change in drain current of a driving transistor according to a change in temperature.
4 is a diagram for describing an organic light emitting diode display according to an exemplary embodiment of the present invention.
5 is a view for explaining the structure of the pixel illustrated in FIG. 4.
6 is a waveform diagram illustrating a driving preparation section in an organic light emitting diode display according to an exemplary embodiment of the present invention.
FIG. 7 is a view for explaining a column driver shown in FIG. 4.
8 is a view for explaining a sensing unit of the sensing data generation unit illustrated in FIG. 7.
9 is a block diagram illustrating a timing control unit according to an example of the present invention.
10 is a waveform diagram showing a driving waveform of a pixel in a sensing mode in an organic light emitting diode display according to an exemplary embodiment of the present invention.
11A and 11B are views sequentially illustrating an operation of a pixel according to a driving waveform of the pixel illustrated in FIG. 10.
12 is a waveform diagram illustrating driving waveforms of pixels in a display mode in an organic light emitting diode display according to an exemplary embodiment of the present invention.
13 is a waveform diagram illustrating a sensing time in an organic light emitting diode display according to an exemplary embodiment of the present invention.

The meaning of the terms described in this specification should be understood as follows.

It should be understood that a singular expression includes a plurality of expressions unless the context clearly defines otherwise, and the terms "first", "second", etc. are intended to distinguish one component from another component, The scope of rights should not be limited by these terms.

It should be understood that terms such as "include" or "have" do not preclude the presence or addition possibility of one or more other features or numbers, steps, actions, components, parts 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 2 of the first item, the second item, or the third item, as well as the first item, the second item, and the third item, respectively. Any combination of items that can be presented from more than one dog.

Hereinafter, a preferred embodiment of the organic light emitting display device according to the present invention will be described in detail with reference to the accompanying drawings.

4 is a diagram for describing an organic light emitting diode display according to an exemplary embodiment of the present invention, and FIG. 5 is a diagram illustrating a structure of each pixel illustrated in FIG. 4.

4 and 5, an organic light emitting display device according to an exemplary embodiment of the present invention includes a display panel 100 and a panel driver 200.

The display panel 100 includes a plurality of pixels P having a pixel circuit PC including an organic light emitting diode OLED and a driving transistor Tdr for controlling a current flowing through the organic light emitting diode OLED; And signal lines for defining a pixel region in which each of the plurality of pixels P is formed and supplying a driving signal to the pixel circuit PC.

The signal lines include first to m (however, m is a natural number) scan control lines (SCL1 to SCLm), first to mth sensing control lines (SSCL1 to SSCLm), and first to nth (where n is m Larger natural number) Data lines DL1 to DLn, first to nth sensing lines SL1 to SLn, a plurality of first driving power lines PL1 to PLn, and at least one second driving power line (not shown) ).

Each of the first to mth scan control lines SCL1 to SCLm is formed side by side to have a constant interval along a first direction, that is, a horizontal direction, of the display panel 100.

Each of the first to mth sensing control lines SSCL1 to SSCLm may be formed at regular intervals to be parallel to each of the scan control lines SCL1 to SCLm.

The first to nth data lines DL1 to DLn cross the scan control lines SCL1 to SCLm and the sensing control lines SSCL1 to SSCLm, respectively, in the second direction of the display panel 100, that is, It may be formed side by side to have a constant spacing along the longitudinal direction.

Each of the first to nth sensing lines SL1 to SLn may be formed at regular intervals to be parallel to each of the data lines DL1 to DLn.

Each of the plurality of first driving power lines PL1 to PLn may be formed at regular intervals to be parallel to each of the data lines DL1 to DLn. Here, each of the plurality of first driving power lines PL1 to PLn may be formed at regular intervals to be parallel to each of the scan control lines SCL1 to SCLm. Each of the plurality of first driving power lines PL1 to PLn is connected to a driving power supply (not shown) and supplies the first driving power EVdd supplied from the driving power supply (not shown) to each pixel P to provide.

Each of the plurality of first driving power lines PL1 to PLn may be commonly connected to a first driving power common line CPL formed on an upper side and/or a lower side of the display panel 100. One driving power common line CPL is connected to a driving power supply (not shown) and transmits first driving power EVdd supplied from the driving power supply to each of the plurality of first driving power lines PL1 to PLn. .

The at least one second driving power line may be formed in a passage on the entire surface of the display panel 100 or be parallel to each of the data lines DL1 to DLn or the scan control lines SCL1 to SCLm. It may be formed at regular intervals. The at least one second driving power line provides the second driving power EVss supplied from the driving power supply unit to each pixel P. Optionally, the at least one second driving power line may be electrically grounded to a metal case (or cover) constituting the organic light emitting display device, in which case the at least one second driving power line is provided for each pixel. Provide ground power to (P).

Each of the plurality of pixels P is formed for each pixel area defined by each of the first to mth scan control lines SCL1 to SCLm and each of the first to nth data lines DL1 to DLn intersecting each other. do. Here, each of the plurality of pixels P may be any one of a red pixel, a green pixel, a blue pixel, and a white pixel. One unit pixel displaying one image may include adjacent red pixels, green pixels, blue pixels, and white pixels, or may include red pixels, green pixels, and blue pixels.

Each of the plurality of pixels P may include a pixel circuit PC and an organic light emitting diode (OLED).

The pixel circuit PC includes 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 a-Si TFT, poly-Si TFT, oxide TFT, or organic TFT as a thin film transistor (TFT).

The first switching transistor Tsw1 is switched by the first scan pulse SP1 to output a data voltage Vdata supplied to the data line DL. To this end, the first switching transistor Tsw1 includes a gate electrode connected to an adjacent scan control line SCL, a source electrode connected to an adjacent data line DL, and a first node that is a gate electrode of the driving transistor Tdr ( n1).

The second switching transistor Tsw2 is switched by the second scan pulse SP2 and the voltage Vref or Vpre supplied to the sensing line SL is the second node n2 that is the source electrode of the driving transistor Tdr. To supply. To this end, the second switching transistor Tsw2 includes a gate electrode connected to the adjacent sensing control line SSCL, a source electrode connected to the adjacent sensing line SL, and a drain electrode connected to the second node n2.

The capacitor Cst includes a gate electrode and a source electrode of the driving transistor Tdr, that is, first and second electrodes connected between first and second nodes n1 and n2. The first electrode of the capacitor Cst is connected to the first node n1, and the second electrode of the capacitor Cst is connected to the second node n2. The capacitor Cst charges after charging the difference voltage of the voltage supplied to each of the first and second nodes n1 and n2 according to the switching of the first and second switching transistors Tsw1 and Tsw2, respectively. The driving transistor Tdr is switched according to the voltage applied.

The driving transistor Tdr is turned on by the voltage of the capacitor Cst to control the amount of current flowing from the first driving power line PL to the organic light emitting diode OLED. To this end, the driving transistor Tdr includes a gate electrode connected to the first node n1, a source electrode connected to the second node n2, and a drain electrode connected to the first driving power line PL. .

The organic light emitting diode OLED emits light by the data current Ioled supplied from the driving transistor Tdr to emit monochromatic light having luminance corresponding to the data current Ioled. To this end, the organic light emitting device (OLED) is the second node (n2), that is, the first electrode connected to the source electrode of the driving transistor (Tdr) (eg, anode electrode), an organic layer formed on the first electrode (Not shown), and a second electrode (eg, a cathode electrode) connected to the organic layer. At this time, the organic layer may be formed to have a structure of a hole transport layer/organic light emitting layer/electron transport layer or a structure of a hole injection layer/hole transport layer/organic light emitting layer/electron transport layer/electron injection layer. Furthermore, the organic layer may further include a functional layer for improving luminous efficiency and/or lifespan of the organic light emitting layer. In addition, the second electrode may be the second driving power line formed on the organic layer, or may be further formed on the organic layer to be connected to the second driving power line.

The panel driver 200, as shown in FIG. 6, receives the power-on signal (POS) at the time of reception (T _{power On} ), a sensing mode (SM) is set for a driving preparation section between the image display timing (T _display ) of the display panel 100, and a display mode is displayed after the image display timing (T _display ) of the display panel 100. Set to (DM). That is, in general, when a user operates a power button through a remote control module (not shown), the organic light emitting display device displays an image after a preparation period for driving for a certain period of time from the time of operation. Further, in the driving preparation section, as a preliminary process of loading driving setting information and user setting information of the display panel 100 in order to display an image on the display panel 100, a power-on signal (POS) is approximately When to receive (T _{power On} ) may be approximately 1 to 5 seconds, and an image is not displayed on the display panel 100 during the driving preparation period.

In the driving preparation period, the panel driver 200 changes characteristics of each pixel P through each of the first to mth sensing control lines SSCL1 to SSCLm, for example, a threshold voltage of the driving transistor Tdr. Sensing at least two times to generate sensing data Sdata for each pixel P. In this case, the panel driving unit 200 may sense a change in characteristics of the pixel at least once per second during the preparation period for driving, and more preferably, 5 times per second. For example, when the display panel 100 has a resolution of UHD (Ultra High Definition), the sensing time of one frame may be set to about 200 ms.

In the display mode, the panel driver 200 corrects data to be supplied to the pixel P based on sensing data Sdata sensed by sensing at least twice in the driving preparation period, thereby correcting each pixel P ).

The panel driving unit 200 may include a timing control unit 210, a row driving unit 220, and a column driving unit 230.

The timing control unit 210 controls the driving of the row driver 220 based on a timing synchronization signal TSS inputted from the outside and a power-on signal POS input from the power-on detection unit 10. The row driver 220 and the column (B) by generating a row control signal RCS for controlling the data and a data control signal DCS for controlling the driving of the column driver 230 respectively column) The driving unit 230 is controlled by the sensing mode SM or the display mode DM. For example, the timing control unit 210 drives the display panel 100 in the sensing mode SM during the driving preparation period in response to the power-on signal POS input from the power-on sensing unit 10. For generating the sensing data (DATA) and the row (row) control signal (RCS) and data control signal (DCS) and switch control signal (SCS), and after the driving preparation section, the display panel 100, the display mode While generating control signals (SCS, DCS) for driving with (DM), the input data (Idata) of each pixel (P) is corrected based on the sensing data (Sdata) of each pixel (P), and pixel data is corrected. Create (DATA).

The timing controller 210 generates the sensing data DATA for setting the current flowing in the driving transistor Tdr of each pixel P to a low current, for example, 150 nA or less in the sensing mode SM. Can. That is, according to the present invention, since the organic light emitting display device is switched from the power-off state to the power-on state, the characteristic change of each pixel P is sensed before the image is displayed on the display panel 100. The current flowing in the driving transistor Tdr is set to the low current so that the organic light emitting diode OLED of the pixel P does not emit light, and is sensed several times at a low current to sense the threshold voltage of the driving transistor Tdr.

The row driver 220 sequentially generates the first scan pulse SP1 in response to the row control signal RCS supplied from the timing controller 210 to scan the first to mth scans. In addition to sequentially supplying to the control lines SCL1 to SCLm, a second scan pulse SP2 is sequentially generated in response to the row control signal RCS, so that the first to mth sensing control lines SSCL1 to SSCLm). Here, the row control signal RCS may include a start signal and a plurality of clock signals.

The row driver 220 according to an example may include a scan line driver 222 and a sensing line driver 224.

The scan line driver 222 is connected to one side and/or the other side of each of the first to mth scan control lines SCL1 to SCLm. The scan line driver 222 generates a first scan pulse SP1 shifted sequentially based on the row control signal RCS, and the first to mth scan control lines SCL1 to SCLm are generated. In order to feed.

The sensing line driver 224 is connected to one side and/or the other side of each of the first to mth sensing control lines SSCL1 to SSCLm. The sensing line driver 224 generates second scan pulses SP2 sequentially shifted based on the row control signal RCS, and the first to mth sensing control lines SSCL1 to SSCLm are generated. In order to feed. The sensing line driver 224 may generate the second scan pulse SP2 according to a scan control signal different from the row control signal RCS supplied to the scan line driver 222. In addition, the scan control line SCL and the sensing control line SSCL are disposed one by one in the pixel P. The scan control line SCL and the sensing control line SSCL disposed in one pixel P are It may be formed to be connected to each other, in this case, the sensing line driver 224 is omitted.

The row driving unit 220 may be directly formed on the display panel 100 or formed in the form of an integrated circuit (IC) along with a process of forming a thin film transistor of each pixel P, so that the scan control line ( SCL) and one side and/or the other side of the sensing control line SSCL.

The column driver 230 is connected to each of the first to nth data lines DL1 to DLn and the first to nth sensing lines SL1 to SLn, according to mode control of the timing controller 210. It operates in sensing mode (SM) or display mode (DM).

In the sensing mode SM, the column driving unit 230 responds to the control of the timing controller 210 according to the sensing mode SM through each of the first to nth sensing lines SL1 to SLn. The current flowing through each pixel P is sensed by a current sensing method to generate sensing data Sdata corresponding to the threshold voltage of the driving transistor Tdr included in each pixel P, and the generated sensing data Sdata Is provided to the timing control unit 210.

In the display mode, the column driver 230 converts the input pixel data DATA into an analog data voltage in response to the control of the timing control unit 210 according to the display mode DM and converts the corresponding data. While supplying to the lines DL1 to DLn, the display reference voltage Vref1 is supplied to the corresponding sensing lines SL1 to SLn.

The column driver 230, as illustrated in FIG. 7, is a data driver that supplies a data voltage or a sensing data voltage to each of the first to nth data lines DL1 to DLn according to a driving mode. (232), in the sensing mode SM, the threshold voltage of the driving transistor Tdr included in each pixel P is sensed through each of the first to nth sensing lines SL1 to SLn, thereby sensing data Sdata ), and a reference voltage supply unit 236 which supplies a reference voltage Vref1 for display to each of the plurality of sensing lines SL1 to SLn in the display mode DM. It is configured by.

The data driving unit 232 operates under the control of the timing control unit 210 to supply the data voltage Vdata to the data lines DL1 to DLn, and not shown in the shift register unit, the latch unit, and digital- It includes an analog converter. The shift register unit sequentially outputs a sampling signal by shifting the source start signal according to the source shift clock using a source start signal and a source shift clock of the data control signal DCS. The latch unit sequentially samples and latches the pixel data DATA input according to the sampling signal, and simultaneously outputs one horizontal line of latch data according to the source output enable signal of the data control signal DCS. The digital-analog converter selects a gradation voltage corresponding to a gradation value of latch data from among a plurality of gradation voltages supplied from a gradation voltage generation unit (not shown) and outputs the gradation voltage to the data lines DL1 to DLn. The data driver 232 supplies a data voltage corresponding to the pixel data DATA in the display mode to the data lines DL1 to DLn, and sets the sensing data voltage set in the sensing mode to the data lines DL1 to DLn. To supply.

The sensing data generation unit 234 converts the current flowing from each pixel P to the corresponding sensing lines SL1 to SLn into a sensing voltage in the sensing mode SM, and converts the converted sensing voltage into analog-digital conversion. The sensing data Sdata of each pixel P is generated. To this end, the sensing data generation unit 234 includes a plurality of sensing units 234-1 to 234-n connected to each of the plurality of sensing lines SL1 to SLn.

Each of the plurality of sensing units 234-1 to 234-n includes a current-voltage converter 234a and an analog-digital converter 234b, as shown in FIG.

The current-voltage converter 234a converts the current flowing from each pixel P to the corresponding sensing lines SL1 to SLn into the voltage Vout in the sensing mode SM. To this end, the current-voltage converter 234a may include an operational amplifier OA, a first switch SW1, a second switch SW2, and a feedback capacitor Cf.

The operational amplifier OA includes an inverting terminal (-), a non-inverting terminal (+), and an output terminal (No). The inverting terminal (-) is selectively connected to the sensing line SL, and the output terminal No is connected to the analog-to-digital converter 234b. In addition, a reference voltage (Vref2) for sensing is supplied to the non-inverting terminal (+). Here, the sensing reference voltage Vref2 may have the same DC voltage level as the display reference voltage Vref1, but is limited thereto and may have a different DC voltage level.

The first switch SW1 is switched according to the first switch signal SCS1 of the switch control signal SCS supplied from the timing controller 210 to reverse the sensing line SL of the operational amplifier OA. Connect to the terminal (-). The first switch SW1 is turned on during the initialization (or reset) period and the sensing period of the sensing line SL in the sensing mode SM.

The second switch SW2 is switched according to the second switch signal SCS2 of the switch control signal SCS supplied from the timing control unit 210, so that the inverting terminal (-) and the output terminal of the operational amplifier OA are output. Connect (No). The second switch SW2 is turned on only in the initialization period in the sensing mode.

The feedback capacitor Cf is connected between the inverting terminal (-) of the operational amplifier OA and the output terminal No. The feedback capacitor Cf is connected to a short of the inverting terminal (-) and the output terminal (No) of the operational amplifier (OA) according to the turn-on of the second switch (SW2) during the initialization period. Is initialized to zero voltage (OV). In addition, the feedback capacitor Cf is the sensing line SL from the pixel P according to the turn-off state of the second switch SW2 and the turn-on state of the first switch SW1 during the sensing period. The output voltage Vout output to the output terminal No of the operational amplifier OA is changed by charging the current flowing through the.

The analog-to-digital converter 234b generates analog-digital conversion of the output voltage Vout output from the current-voltage converter 234a to generate sensing data Sdata.

The reference voltage supply unit 236 supplies the reference voltage Vef1 for display to each of the plurality of sensing lines SL1 to SLn only in the display mode. To this end, the reference voltage supply unit 236 is switched according to the third switch signal SCS3 of the switch control signal SCS supplied from the timing control unit 210 only in the display mode DM to display the reference voltage Vef1 for display. ) May be formed of a plurality of switching elements SW3 supplied to each of the plurality of sensing lines SL1 to SLn. Additionally, the reference voltage supply unit 236 may be omitted according to a driving method of the pixel P.

9 is a block diagram illustrating a timing controller according to an example of the present invention.

9 and 4, the timing controller 210 according to an example of the present invention includes a control signal generator 211, a sensing data processor 213, a data processor 215, and a memory 217. Including.

The control signal generation unit 211 is based on the timing synchronization signal (TSS) such as a vertical synchronization signal, a horizontal synchronization signal, a data enable signal, a main clock, and the power-on signal (POS), and the row driver ( Generate a row control signal (RCS) for controlling the driving of the 220, and a data control signal (DCS) and a switch control signal (SCS) for controlling the driving of the column driver 230, respectively. do.

The sensing data processor 213 receives sensing data Sdata of each pixel P provided from the column driver 230 by driving each pixel P according to the sensing mode SM. Then, based on the received sensing data Sdata of each pixel P, a current compensation value CCV for compensating for a characteristic change of each pixel P, that is, a threshold voltage change of the driving transistor Tdr, is generated. do. To this end, the sensing data processing unit 213 may include an average value calculation unit 213a, a deviation calculation unit 213b, and a compensation value calculation unit 213c.

The average value calculating unit 213a calculates an average sensing value ASV of sensing data Sdata sensed by sensing at least twice provided from the column driver 230 during the driving preparation period. . For example, the average value calculating unit 213a may temporarily store sensing data Sdata using an internal register and calculate an average sensing value ASV of the temporarily stored sensing data Sdata.

The deviation calculating unit 213b calculates the average sensing value (ASV) of each pixel P and the previous compensation value (PCV) of the corresponding pixel P stored in the memory unit 217 as a deviation value (ΔASV) ).

The compensation value calculator 213c reflects the deviation value ΔASV of each pixel P to the previous compensation value PCV of the corresponding pixel P to calculate the current compensation value CCV of each pixel P Then, the stored current compensation value (CCV) is stored in the memory unit 217 to update the previous compensation value (PCV) stored in the memory unit 217 to the current compensation value (CCV). Here, the compensation value calculator 213c may calculate the current compensation value CCV by adding (+) or subtracting (-) the deviation value ΔASV to the previous compensation value PCV.

As described above, the sensing data processing unit 213 averages at least two sensing data Sdata for sensing at least two times for each pixel P during the driving preparation period, and based on this, the current compensation value CCV ), the sensing error due to the change in the threshold voltage of the driving transistor Tdr according to the temperature change is minimized to prevent deterioration of image quality due to the sensing error.

The data processing unit 215 corrects the input data Idata of each pixel P based on the current compensation value CCV of each pixel P stored in the memory unit 217 to correct the pixel data DATA ). To this end, the data processing unit 215 according to an example may include a data alignment unit 215a and a data correction unit 215b.

The data alignment unit 215a arranges input data Idata input from an external driving system (or graphic card) to correspond to the pixel arrangement structure of the display panel 100, and displays the aligned data of each pixel P. Sort data (RGB) is generated.

The data correction unit 215b reads the current compensation value CCV of each pixel P from the memory unit 217, and reads the current compensation value CCV of each pixel P from the data alignment unit 215a. The alignment data RGB of each pixel P is corrected by adding the alignment data RGB and the read current compensation value CCV to generate pixel data DATA of each pixel P. Then, the data correction unit 215b provides the pixel data DATA of each pixel P to the column driver 230 according to a set data interface method.

The memory unit 217 stores the current compensation value (CCV) of each pixel P, and is mounted in an internal memory built in the timing control unit 210 or a printed circuit board on which the timing control unit 210 is mounted. External memory.

10 is a waveform diagram illustrating a driving waveform of a pixel in a sensing mode in an organic light emitting diode display according to an exemplary embodiment of the present invention, and FIGS. 11A and 11B are operation of a pixel according to a driving waveform of the pixel illustrated in FIG. 10 It is a drawing showing sequentially.

First, the sensing mode is repeatedly performed over a plurality of sensing frames SF during the driving preparation period, and in each sensing frame SF, the pixel P is initialized for each horizontal period (t1_SM), and sensing By operating in the period t2_SM, the characteristic change of the pixel P is sensed.

Hereinafter, the pixel operation in the initialization period t1_SM of the sensing mode in connection with FIGS. 10 and 11A with FIGS. 4 and 7 will be described as follows.

First, in the initialization period t1_SM, first and second scan pulses SP1 and SP2 of a gate-on voltage level are supplied to each of the scan control line SCL and the sensing control line SSCL, respectively, and the column ( column) Sensing pixel data DATA for sensing a characteristic change of the pixel P using a low current is supplied to the data driving unit 232 of the driving unit 230, and sensing of the column driving unit 230 The data generating unit 234 is supplied with first and second switch signals SCS1 and SCS2 having a switch-on voltage level. Accordingly, in the initialization period t1_SM, each of the first switching transistor Tsw1 and the second switching transistor Tsw2 is turned on by the first and second scan pulses SP1 and SP2, respectively. The sensing voltage (Vdata_sen) is supplied from the data driver 232 of the column driver 230 to the first node n1, and the column driver 230 to the second node n2. ), the sensing reference voltage Vref2 is supplied from the sensing data generator 234. Therefore, during the initialization period t1_SM, the difference voltage Vdata_sen-Vref2 between the sensing data voltage Vdata_sen and the sensing reference voltage Vref2 is charged in the capacitor Cst.

In the initialization period t1_SM, the sensing line SL is a reference voltage for sensing Vref2 by the current-voltage converter 234a included in the sensing unit 234-i of the sensing data generator 234. Is initialized as follows.

In the initialization period t1_SM, the first and second switches SW1 and SW2 included in the current-voltage converter 234a are the first and second switch signals SCS1 and SCS2 of the switch-on voltage level. Turned on by each. Accordingly, the inverting terminal (-) and the output terminal (No) of the operational amplifier (OA) included in the current-voltage converter 234a are short-circuited to each other through the turned-on second switch (SW2). The feedback capacitor Cf included in the voltage converter 234a is initialized to 0V. In addition, since the reference voltage for sensing (Vref2) is supplied to the non-inverting terminal (+) of the operational amplifier OA, the reference for sensing is also applied to the inverting terminal (-) connected to the non-inverting terminal (+) and virtual ground. The voltage Vref2 is supplied, thereby supplying the sensing reference voltage Vref2 supplied to the inverting terminal (-) to the output terminal No of the operational amplifier OA through the second switch SW2 that is turned on. do. At the same time, the reference voltage for sensing (Vref2) is charged to the sensing line (SL) at a high speed through the first switch (SW1) is turned on, thereby, the reference voltage for sensing charged in the sensing line (SL) (Vref2) is supplied to the second node n2 through the turned-on second switching transistor Tsw2.

Hereinafter, the operation of the pixel in the sensing period t2_SM in the sensing mode will be described with reference to FIGS. 10 and 11B with respect to FIGS. 4 and 7.

In the sensing period t2_SM, each of the first and second scan pulses SP1 and SP2 supplied to each of the scan control line SCL and the sensing control line SSCL is maintained at a gate-on voltage level, and the column ( column) The first switch signal SCS1 of the switch-on voltage and the second switch signal SCS2 of the switch-off voltage are supplied to the sensing data generating unit 234 of the driver 230, and supplied to the data line DL The sensing data voltage Vdata_sen is stopped. Accordingly, each of the first switching transistor Tsw1, the second switching transistor Tsw2, and the first switch SW1 maintains a turn-on state, so that the inverting terminal (-) of the operational amplifier OA is the first switch It is connected to the source electrode of the second node n2, that is, the driving transistor Tdr connected to the organic light emitting diode OLED through the SW1 and the sensing line SL and the second switching transistor Tsw2. In addition, the inverting terminal (-) of the operational amplifier (OA) and the output terminal (No) are separated from each other due to the turn-off of the second switch (SW2), so that the operational amplifier (OA) operates as an integrator, thereby sensing line SL ) Converts the current (Isen) flowing into voltage. Therefore, the driving transistor Tdr is turned on by the voltage charged in the capacitor Cst, and the current Isen flowing in the turned-on driving transistor Tdr is previously charged with the sensing reference voltage Vref2. Since the feedback capacitor Cf connected to the operational amplifier OA is rapidly charged by the sensing line SL without variation, the output voltage Vout of the operational amplifier OA is linear at the sensing reference voltage Vref2. Will decrease.

In addition, the analog-to-digital converter 234b of the sensing data generator 234 converts the output voltage Vout of the operational amplifier OA to analog-digital converter just before the end of the sensing period t2_SM to drive transistors. The sensing data Sdata corresponding to the current Isen flowing in the Tdr is generated, and the generated sensing data Sdata is provided to the timing controller 210.

12 is a waveform diagram illustrating a driving waveform of a pixel in a display mode in an organic light emitting diode display according to an exemplary embodiment of the present invention.

First, the display mode is performed after the driving preparation period, and in each frame, an image is displayed on the pixel P by operating the pixel P for each horizontal period in the data addressing period t1_DM and the light emission period t2_DM. Is displayed.

Hereinafter, the operation of the pixel in the display mode in connection with FIG. 12 and FIGS. 4 and 7 will be described.

First, the timing control unit 210 corrects the input data Idata of each pixel P based on the current compensation value CCV of each pixel P stored in the memory unit 217 to perform pixel data. (DATA) is generated and supplied to the data driver 232 of the column driver 230, and the row driver 220 to correspond to the data addressing period t1_DM and the light emission period t2_DM, respectively. And each of the column drivers 230.

In the data addressing period t1_DM, the first and second scan pulses SP1 and SP2 of the gate-on voltage level are supplied to each of the scan control line SCL and the sensing control line SSCL, respectively, and the data line DL ), a data voltage Vdata corresponding to the pixel data DATA reflecting the compensation value CCV of the driving transistor Tdr included in the corresponding pixel P is supplied, and the reference voltage for display is displayed on the sensing line SL (Vref1) is supplied. Accordingly, in the data addressing period t1_DM, each of the first switching transistor Tsw1 and the second switching transistor Tsw2 is turned on by the first and second scan pulses SP1 and SP2, respectively. The data voltage Vdata is supplied from the data driver 232 of the column driver 230 to the first node n1, and the column driver 230 to the second node n2. The reference voltage Vref1 for display is supplied from the sensing data generator 234. Therefore, during the data addressing period t1_DM, the capacitor Cst is charged with the difference voltage Vdata-Vref1 between the data voltage Vdata and the display reference voltage Vref1.

Subsequently, in the light emission period t2_DM, the first and second scan pulses SP1 and SP2 of the gate-off voltage level are supplied to each of the scan control line SCL and the sensing control line SSCL, respectively, so that the first switching is performed. Each of the transistor Tsw1 and the second switching transistor Tsw2 is turned off, and the driving transistor Tdr is turned on by the voltage stored in the capacitor Cst. Accordingly, the turned-on driving transistor Tdr supplies the data current determined by the difference voltage Vdata-Vref1 between the data voltage Vdata and the display reference voltage Vref1 to the organic light emitting diode OLED. The organic light emitting device (OLED) emits light. That is, in the light emission period t2_DM, when each of the first switching transistor Tsw1 and the second switching transistor Tsw2 is turned off, a current flows in the driving transistor Tdr by the driving voltage EVdd, In proportion to this current, the voltage of the second node n2 increases as the OLED starts to emit light, and the first node n1 is equal to the voltage rise 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, so that the organic light emitting diode OLED continues to emit light until the next data addressing period t1_DM. Is done.

In the display mode, the threshold voltage of the driving transistor Tdr of each pixel P is compensated by the data voltage Vdata corresponding to the pixel data DATA in which the corresponding compensation value CCV is reflected.

On the other hand, in the display mode, in the data addressing period t1_DM, the second switching transistor Tsw2 is turned on to turn on the reference voltage for display on the source electrode of the second node n2, that is, the driving transistor Tdr. Although it has been described as applying (Vref1), the present invention is not limited thereto, and the second switching transistor Tsw2 may not be operated during the display mode according to a driving method of the pixel P.

13 is a waveform diagram illustrating a sensing time in an organic light emitting diode display according to an exemplary embodiment of the present invention.

As can be seen in FIG. 13, according to the present invention, in the sensing mode, the voltage of the sensing line is pre-charged with a constant reference voltage Vref2 for sensing, and senses the current flowing through the driving transistor Tdr of the actual pixel P. During this, the sensing time (Tsen) can be reduced because it is maintained without voltage fluctuation. That is, when comparing the sensing time of the present invention with the conventional sensing time shown in FIG. 2, it can be seen that the conventional sensing time (Tsen) is 100us, while the sensing time (Tsen) of the present invention is reduced to 20us level. have. As a result, the present invention can sense the current flowing from the driving transistor of the pixel to the sensing line at a high speed by using the current-voltage converter for converting the current into voltage, without any user inconvenience due to the sensing time during the driving preparation period. The characteristic change of each pixel P can be sensed at least twice.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is common in the technical field to which the present invention pertains that various substitutions, modifications and changes are possible without departing from the technical details of the present invention. It will be clear to those who have the knowledge of Therefore, the scope of the present invention is indicated by the following claims, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts should be interpreted to be included in the scope of the present invention.

10: power-on detection unit 100: display panel
200: panel driving unit 210: timing control unit
220: east of row 230: column drive
232: data driving unit 234: sensing data generating unit
236: reference voltage supply unit 234-1 to 234-n: sensing unit
234a: current to voltage converter 234b: analog to digital converter

Claims (10)

A display panel including a pixel formed for each intersection region of the scan control line and the data line, and a sensing line connected to the pixel; And
And a panel driver configured to sense the characteristic change of the pixel at least twice through the sensing line in a driving preparation period between a power-on signal reception time and a video display time of the display panel, and generate sensing data for the pixel. ,
The panel driver converts current flowing from the pixel to the sensing line into a voltage using a current-voltage converter, and analog-digital converts the converted voltage using an analog-to-digital converter to receive sensing data for the pixel. Create,
The current-voltage converter,
An operational amplifier having an inverting terminal connected to the sensing line, a non-inverting terminal supplied with a reference voltage for sensing, and an output terminal connected to the analog-to-digital converter;
A feedback capacitor connected between the inverting terminal of the operational amplifier and the output terminal;
A first switch switched according to a first switch signal to connect the sensing line to an inverting terminal of the operational amplifier; And
And a second switch that is switched according to a second switch signal to connect the inverting terminal and the output terminal of the operational amplifier. According to claim 1,
The panel driving unit senses a change in characteristics of the pixel at least once per second during the driving preparation period. According to claim 1,
The panel driver includes a column driver having a sensing data generating unit that senses a characteristic change of the pixel through the sensing line to generate the sensing data,
The sensing data generating unit converts the current flowing from the pixel to the voltage into a voltage, and converts the converted voltage into analog-digital to generate sensing data for the pixel. The method of claim 3,
The sensing data generation unit includes a sensing unit connected to the sensing line,
The sensing unit,
A current-voltage converter that is connected to the sensing line and converts and outputs a current flowing from the pixel to the sensing line into a voltage; And
And an analog-to-digital converter for analog-to-digital conversion of the output voltage of the current-voltage converter to generate sensing data for the pixel. delete The method of claim 4,
In the sensing mode, the pixel operates in an initialization period and a sensing period,
During the initialization period, each of the first and second switches is turned on,
During the sensing period, the first switch maintains a turn-on state, and the second switch is turned off. The method of claim 6,
During the initialization period, the feedback capacitor is initialized to 0V by a short circuit between the inverting terminal and the output terminal of the operational amplifier according to the turn-on of the second switch,
During the initialization period, an organic light-emitting display characterized in that the reference voltage for sensing is supplied to the sensing line through the inverting terminal connected to a virtual ground to the non-inverting terminal of the operational amplifier and the turned-on first switch. Device. The method according to any one of claims 1 to 4, 6, and 7,
The panel driving unit further comprises a timing control unit for correcting data to be supplied to the pixel based on sensing data sensed by the sensing at least twice. The method of claim 8,
The timing control unit,
Calculate the average value of the sensing data sensed by the sensing at least twice,
A current compensation value is generated by correcting the previous compensation value according to the previous compensation value of the pixel and the average value stored in the memory unit,
The previous compensation value stored in the memory unit is updated with the current compensation value,
And correcting data to be supplied to the pixel according to the current compensation value. The method of claim 8,
The pixel includes an organic light emitting device; And a driving transistor that controls a current flowing through the organic light emitting device according to a voltage between a gate and a source including a data voltage corresponding to the corrected data,
The characteristic change of the pixel is the threshold voltage of the driving transistor, characterized in that the organic light emitting display device.

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