KR102282171B1 - Orgainc emitting diode display device and sensing method thereof - Google Patents

Abstract

The present invention relates to an OLED display device capable of improving luminance uniformity by spatially dispersing a difference in resolution between a calculated voltage and an output voltage of a data driver in a sensing mode, and a sensing method thereof.
When the OLED display device of the present invention is in the sensing mode, voltage data is compensated by applying at least one of the first and second compensation values, and a preset dithering pattern set is applied to the compensated voltage data for dithering, followed by dithering. and a data processing unit configured to drive each subpixel using the voltage data and update a first compensation value or a second compensation value stored in a memory using a sensing voltage sensed from each driven subpixel.

Description

An organic light emitting diode display and a sensing method thereof {ORGAINC EMITTING DIODE DISPLAY DEVICE AND SENSING METHOD THEREOF}

The present invention relates to an organic light emitting diode (OLED) display device, and more particularly, to an OLED display device capable of improving luminance uniformity and a sensing method thereof.

Recently, as flat panel displays that display images using digital data, liquid crystal displays (LCDs) using liquid crystals, OLED displays using OLEDs, and electrophoretic displays (EPDs) using electrophoretic particles are used. ), etc., for example.

Among them, the OLED display device is a self-luminous device that emits light from an organic light emitting layer by recombination of electrons and holes, and is expected as a next-generation display device because of its high luminance, low driving voltage, and ultra-thin film.

Each of the plurality of pixels or sub-pixels constituting the OLED display includes an OLED device composed of an organic light emitting layer between an anode and a cathode, and at least a switching thin film transistor (TFT) and a storage capacitor to independently drive the OLED device. A pixel circuit including a driving TFT is provided.

OLED display devices have a problem in that luminance is not uniform due to differences in driving characteristics for each sub-pixel due to various causes. For example, there is a difference in driving characteristics for each sub-pixel such as the threshold voltage (hereinafter, Vth) and mobility of the driving TFT due to process deviation, etc. As the driving characteristics for each sub-pixel vary due to deterioration, etc., the current for each sub-pixel is not uniform compared to the same data, resulting in a luminance non-uniformity problem. To solve this problem, the OLED display uses an external compensation method of sensing the driving characteristics of each sub-pixel and compensating for data using the sensed characteristic information.

Specifically, the current Ids of the driving TFT is expressed by Equation 1 below.

<Equation 1>

Ids = α×(Vgs - Vth) ²

Here, α is a proportional coefficient including the mobility of the driving TFT and the channel width (W)/length (L) component, Vgs is the gate-source voltage of the driving TFT, and Vth is the threshold voltage of the driving TFT. Since Vth and α are different for each driving TFT, and Vth and α vary according to the lapse of driving time, the OLED display uses an external compensation method that senses and compensates Vth and α of each driving TFT.

For example, the conventional OLED display senses the Vth of each driving TFT using a specific data voltage in the initial sensing mode to store the Vth compensation value, and uses the voltage data to which the stored Vth compensation value is applied in the update sensing mode. The Vth change amount is sensed to update the Vth compensation value.

However, since the voltage range output from the data driver is larger than the voltage range of the compensation value, the voltage unit of the data driver is larger than the voltage unit of the compensation value. For this reason, the resolution of the voltage output from the data driver is not sufficient to represent the voltage data to which the compensation value is added.

Accordingly, an error component due to a difference in resolution is generated between a calculated voltage to which a compensation value is applied to a data voltage and an output voltage outputting the calculated voltage through a data driver. Accordingly, there is a problem in that the error component is included in the sensed value when the compensation value is updated and sensed, and luminance non-uniformity occurs because the error component affects the updated compensation value using the sensed value.

The present invention has been devised to solve the above problems, and the problem to be solved by the present invention is an OLED capable of improving luminance uniformity by spatially dispersing the difference in resolution between the calculated voltage and the output voltage of the data driver in the sensing mode. A display device and a sensing method thereof are provided.

In order to solve the above problems, an OLED display device according to an embodiment of the present invention includes a display panel including a plurality of subpixels having different colors, a first compensation value for compensating for mobility of each subpixel, and the and a memory in which a second compensation value for Vth compensation of each sub-pixel is stored. In addition, when the display device of the present invention is in a sensing mode in which the first compensation value or the second compensation value is updated, the voltage data is compensated by applying at least one of the first compensation value and the second compensation value, and the compensated voltage data is pre-applied After dithering is performed by applying the set dithering pattern set, each subpixel is driven using the dithered voltage data, and the first compensation value or the second compensation value is calculated using a sensing voltage sensed from each driven subpixel. A data processing unit for updating is provided.

The data processing unit includes a data compensator for compensating and outputting voltage data by applying at least one of the first and second compensation values, a dithering unit for dithering and outputting the compensated voltage data supplied from the data compensator, and a dithering unit A data driver that converts the dithered voltage data supplied from the converter into an analog voltage and supplies it to each sub-pixel, senses a sensing voltage from the driven sub-pixel and outputs it, and Vth variation or movement using the sensing voltage supplied from the data driver and a compensation value detecting unit that detects a degree change and updates the first or second compensation value using the Vth change amount or the mobility change amount.

A sensing method of an OLED display device according to an embodiment of the present invention includes compensating for voltage data by applying a compensation value stored in a memory, dithering the compensated voltage data by applying a preset dithering pattern set, and dithering. Converting the processed voltage data into an analog voltage and supplying it to a corresponding subpixel to drive a driving TFT of the corresponding subpixel, sensing and outputting a sensing voltage from the driven driving TFT, and using the sensing voltage to memory and updating the reward value stored in the .

The dithering pattern set includes a plurality of dithering blocks different for each gradation and a plurality of different dithering patterns for each frame.

The dithering pattern set may be equally used in the sensing mode and the display mode.

A frame-by-frame change order of a plurality of dithering patterns in the dithering pattern set in the sensing mode may be different from a frame-by-frame change order of the plurality of dithering patterns in the dithering pattern set in the display mode.

The dithering pattern set used in the sensing mode may be set differently from the dithering pattern set used in the display mode.

The size of the first dithering block for each gradation included in each dithering pattern used in the sensing mode may be set to be smaller than the size of the second dithering block for each gradation included in each dithering pattern used in the display mode.

The OLED display device and the sensing method thereof according to the present invention spatially reduce an error component due to a voltage resolution difference between the calculated voltage and the output voltage of the data driver by dithering the calculated voltage applied with a compensation value to voltage data and supplying it to the data driver. It can be dispersed, and as a result, the error component is spatially dispersed and reduced, so that the luminance uniformity can be improved.

1 is a block diagram schematically illustrating an OLED display device according to an embodiment of the present invention.
FIG. 2 is an equivalent circuit diagram illustrating the R/W/B/G sub-pixel structure shown in FIG. 1 by way of example.
FIG. 3 is a block diagram showing the internal configuration of the image processing unit shown in FIG. 1 .
4 is an exemplary diagram illustrating a dithering pattern set applied to the LUT shown in FIG. 3 .
5 is a flowchart illustrating an update sensing method of an OLED display device according to an embodiment of the present invention in stages.
6 is an exemplary diagram illustrating a real-time sensing period of an OLED display device according to an embodiment of the present invention.
FIG. 7 is a block diagram showing another internal configuration of the image processing unit shown in FIG. 1 .
8A to 8D are exemplary diagrams illustrating comparison of output voltages of a data driver before and after dithering applied to voltage data to which Vth is applied in an OLED display device according to the present invention.
9A to 9C are exemplary diagrams comparing the amount of change in sensing Vth before and after applying dithering to voltage data to which Vth is applied in an OLED display device according to the present invention.

1 is a block diagram schematically illustrating an OLED display device according to an embodiment of the present invention.

The OLED display shown in FIG. 1 includes a timing controller 10 including a control signal generating unit 100 and an image processing unit 200 , a memory M, a data driver 20 , a gate driver 30 , and a display. A panel 40 and the like are provided. Here, the image processing unit 200 and the data driver 20 may be expressed as a data processing unit.

The image processing unit 200 may be built into the timing controller 10 as shown in FIG. 1 and configured as a single IC, or may be separated from the timing controller 10 and configured as a separate IC, although not shown, in this case, the timing controller 10 ) may be connected between the image processing unit 200 and the data driver 20 . Hereinafter, a case in which the timing controller 10 includes the image processing unit 200 will be described as an example.

The memory M stores compensation information set according to the characteristics of each sub-pixel for a uniform current of each sub-pixel. The compensation information includes a Vth compensation value for compensating the Vth of the driving TFT of each subpixel and a mobility compensation value for compensating for the mobility of the driving TFT.

Compensation information is preset based on the sensed value of each sub-pixel's characteristics (Vth, α) before shipment and is stored in the memory M. After the product is shipped, the compensation information stored in the memory M is updated by sensing the characteristics of each sub-pixel again through the real-time sensing mode for each desired driving time. The sensing mode may be executed for at least one desired driving time including a boot time at power-on, an end time at power-off, and a blanking period of each frame to update compensation information stored in the memory M.

For example, since mobility is greatly affected by external environmental conditions such as temperature and light, the mobility compensation value sensed and stored in the memory M is sensed every at least one of the booting time and the blanking period of each frame during power-on. may be updated. Vth may be sensed for at least one of a blanking period of each frame and an end time during power-off, and the Vth compensation value stored in the memory M may be updated.

In addition, the memory M detects and stores the initial Vth of each sub-pixel as a comparison reference when the Vth compensation value is updated.

Also, in the memory M, a mobility compensation coefficient (DTE) used together with the mobility compensation value when the voltage data is corrected is preset and stored for each color and each gradation, and the mobility compensation value is updated. An average value of mobility sensing used as a reference value is preset for each color and stored. The mobility compensation coefficient DTE is set in advance by being optimized according to the voltage data Vdata of each gray level for each color using the characteristic that the mobility varies according to the gray level, and serves to prevent overcompensation of the mobility.

In the timing controller 10 , the control signal generator 100 controls the driving timings of the data driver 20 and the gate driver 30 using a plurality of timing signals input to an external system (not shown), respectively. A control signal and a gate control signal are generated and output to the data driver 20 and the gate driver 30 . For example, the control signal generator 100 controls the driving timing of the data driver 20 using a plurality of timing signals such as a clock signal, a data enable signal, a horizontal synchronization signal, and a vertical synchronization signal inputted from the outside. a plurality of data control signals including a source start pulse, a source shift clock, a source output enable signal, and the like, and a plurality of gates including a gate start pulse and a gate shift clock for controlling the driving timing of the gate driver 30 . It generates and outputs a control signal.

In the timing controller 10 , the image processing unit 200 converts image data input from an external system into voltage data in the display mode, compensates the image data using the compensation information of the memory M, and dithers the compensated data to obtain data output to the driver 20 .

The image processing unit 200 compensates preset voltage data in the sensing mode using compensation information of the memory M, dithers the compensated voltage data, and outputs the compensated voltage data to the data driver 20 . Accordingly, in the sensing mode, an error value due to a voltage resolution difference between the calculated voltage to which the compensation information is applied to the voltage data and the output voltage of the data driver 20 may be dispersed and reduced.

Then, the image processing unit 200 processes the sensing information of each subpixel sensed through the data driver 20 according to a predetermined operation to detect a change amount of the compensation information, and compensates the memory M by applying the detected change amount. Update the information.

In addition, in order to reduce power consumption, the image processing unit 200 determines the peak luminance according to the image of each frame using the input image data, calculates the total current, and determines the high potential voltage according to the peak luminance and the total current. It is also supplied to the data driver 20 .

In addition, when R/G/B data is input as image data to an external system, the image processing unit 200 converts the R/G/B data into R/G/B/W data through a predetermined operation to convert the above-described image. available for processing.

The data driver 20 converts the voltage data supplied from the timing controller 10 into analog data voltages by using the data control signal supplied from the timing controller 10 in the display mode and the sensing mode to output the analog data voltage to the display panel 40 . supply The data driver 20 converts digital voltage data into analog data voltages using a gamma voltage set from a built-in gamma voltage generator (not shown). The gamma voltage generator generates a gamma voltage set including a plurality of gamma voltages by dividing the high potential voltage through the resistor string.

Also, in the sensing mode, the data driver 20 converts a sensing voltage (or sensing current) sensed from each subpixel of the display panel 50 through a sensing line into a digital sensing value and supplies it to the timing controller 10 . Any one of a data line, a reference line, and a power line connected to each subpixel may be used as the sensing line for sensing the characteristic of each subpixel.

The data driver 20 is composed of at least one data drive IC and is mounted on a circuit film such as a tape carrier package (TCP), a chip on film (COF), a flexible print circuit (FPC), and the like, and a TAB on the display panel 40 . It may be attached using a tape automatic bonding method or may be mounted on a non-display area of the display panel 40 using a chip on glass (COG) method.

The gate driver 30 drives a plurality of gate lines of the display panel 40 using a gate control signal supplied from the timing controller 10 . The gate driver 30 supplies a scan pulse of a gate-on voltage in a corresponding scan period to each gate line using a gate control signal, and supplies a gate-off voltage in the remaining period. The gate driver 30 may receive a gate control signal directly from the timing controller 10 or may receive a gate control signal from the timing controller 10 via the data driver 20 .

The gate driver 30 is composed of at least one gate drive IC, is mounted on a circuit film such as TCP, COF, FPC, etc. and is attached to the display panel 40 in a TAB method or is not displayed on the display panel 40 in a COG method. It can be mounted on the area. In contrast, the gate driver 30 is formed in the non-display area of the TFT substrate together with the TFT array formed in the pixel array of the display panel 40 to form a gate in panel (GIP) type embedded in the display panel 40 . can be

The display panel 40 includes a matrix-type pixel array. Each pixel of the pixel array is comprised of R/W/B/G subpixels. Alternatively, each pixel may comprise R/G/B subpixels.

FIG. 2 is an equivalent circuit diagram illustrating the R/W/B/G sub-pixel structure shown in FIG. 1 by way of example.

The R/W/B/G sub-pixels are respectively connected to the data lines DL1 to DL4 , share a pair of gate lines GL1 and GL2 , and share a reference line RL. Alternatively, although not shown, the R/W/B/G sub-pixels may share one gate line or may be respectively connected to different reference lines. A pair of data lines DL1 and DL2 are arranged in parallel between the R/W subpixels, and the other pair of data lines DL3 and DL4 are arranged in parallel between the B/G subpixels.

One power supply line PL disposed on the left side of the R subpixel is commonly connected with the R/W subpixels, and another power supply line PL disposed on the right side of the G subpixel is commonly connected with the B/G subpixels. A high potential voltage (EVDD) is supplied.

Each of the R/W/B/G sub-pixels includes an OLED device, first and second switching TFTs ST1 and ST2, a driving TFT DT, and a storage capacitor Cst to independently drive the OLED device A pixel circuit is provided.

The first and second switching TFTs ST1 and ST2 and the driving TFT DT are an amorphous silicon (a-Si) TFT, a poly-Si TFT, an oxide TFT, or an organic TFT. etc. may be used.

The OLED element has an anode connected to the driving TFT DT, a cathode connected to the low potential voltage EVSS, and a light emitting layer between the anode and the cathode. The anode is formed independently for each sub-pixel, but the cathode is formed so that all sub-pixels share it. The light emitting layer may include a hole injection layer, a hole transport layer, an organic light emitting layer, an electron transport layer, an electron injection layer, etc. sequentially stacked between the anode and the cathode, and a functional layer for improving the luminous efficiency and / or lifespan of the organic light emitting layer. may include more. In the OLED device, when a positive bias is applied between the anode and the cathode, electrons from the cathode are supplied to the organic light emitting layer via the electron injection layer and the electron transport layer, and holes from the anode are transferred to the organic light emitting layer via the hole injection layer and the hole transport layer. is supplied Accordingly, the organic light emitting layer emits light proportional to the amount of current supplied from the driving TFT DT by emitting a fluorescent or phosphorescent material by recombination of supplied electrons and holes.

The first switching TFT ST1 is driven by the scan signal of one gate line GL1 to supply the data voltage Vdata from the corresponding data line DL to the gate node of the driving TFT DT. The second switching TFT ST2 is driven by the scan signal of the other gate line GL2 to supply the reference voltage Vref from the corresponding reference line RL as an initialization voltage to the source node of the driving TFT DT. The second switching TFT ST2 is further used as a path for outputting the current from the driving TFT DT to the reference line RL in the sensing mode.

The storage capacitor Cst is connected between the gate node and the source node of the driving TFT DT. The storage capacitor Cst is a voltage difference between the data voltage Vdata supplied to the gate node through the first switching TFT ST1 and the reference voltage Vref supplied to the source node through the second switching TFT ST2. Vdata-Vref) is charged and supplied to the driving voltage Vgs of the driving TFT DT.

The driving TFT DT controls the current supplied from the high potential voltage EVDD supply line PL according to the driving voltage Vgs supplied from the storage capacitor Cst, thereby controlling the current Ids proportional to the driving voltage Vgs. ) to the OLED device to make the OLED device emit light.

Since the second switching TFT ST2 of each of the R/W/B/G sub-pixels shares one reference line RL, the characteristics of each of the R/W/B/G sub-pixels are different at different times. It may be sensed through the shared reference line RL. For example, when the characteristic of any one of the R/W/B/G sub-pixels is sensed, the data voltage for sensing is supplied to the sub-pixel to be driven, while the other sub-pixels have an off voltage ( black data voltage) may be supplied to be turned off.

FIG. 3 is a block diagram specifically illustrating the internal configuration of the image processing unit 200 shown in FIG. 1 .

The image processing unit 200 illustrated in FIG. 4 includes a data conversion unit 210 , a data compensation unit 220 , a compensation value detection unit 230 , a dithering unit 240 , and the like. In addition, the image processing unit 200 determines the peak luminance and total current of each frame using image data input from an external system, determines a high potential voltage according to the peak luminance and the total current, and outputs it to the data driver 20 . RGB-to-RGBW for converting R/G/B data into R/G/B/W data by additionally including a current control unit (not shown) at the input terminal of the data conversion unit 210 or converting R/G/B data into R/G/B/W data A converter (not shown) may be additionally included at the input terminal of the current controller.

The data converter 210 converts input image data, ie, grayscale data, into voltage data and outputs the converted image data to the data compensator 220 . Specifically, the data conversion unit 210 converts the R/G/B/W grayscale data using a LUT in which voltage data for each R/G/B/W grayscale data is previously stored in an internal memory (not shown). It is converted into R/G/B/W voltage data and output to the data compensator 220 . Since all of the compensation information stored in the memory M, ie, the Vth compensation value and the mobility compensation value, are voltage values, image data, which is grayscale data, is converted into voltage data for compensation using them.

The data compensator 220 compensates the voltage data input from the data converter 210 using compensation information stored in the memory M in each of the display mode and the sensing mode, and applies the compensated voltage data to the data driver 20 . ) is output.

Specifically, in each of the display mode and the sensing mode, the data compensator 220 reads the mobility compensation value α_cmp and the mobility compensation coefficient DTE stored in the memory M, and as shown in Equation 2 below, The gain value g is calculated by performing a predetermined operation. Next, the data compensator 220 multiplies the input voltage data Vdata by the gain value g as shown in Equation 2 below, and adds the Vth compensation value of the corresponding sub-pixel read from the memory M to the voltage data. (Vdata) is compensated, and the compensated voltage data (MVdata) is output to the dithering unit 240 .

<Equation 2>

g = DTE × (α_cmp - 1) + 1

MVdata = g×Vdata + Vth

Meanwhile, when the data compensator 220 is in the sensing mode for updating the Vth compensation value, it is possible to compensate the voltage data Vdata by applying only the Vth compensation value, and is a sensing mode for updating the mobility compensation value α_cmp. When the Vth compensation value and the mobility compensation value α_cmp are applied, the voltage data Vdata may be compensated.

The dithering unit 240 performs a dithering process for applying a dithering pattern stored in a look-up table (LUT) to the compensated voltage data from the data compensator 220 in the display mode and the sensing mode. output to the data driver 20 . In other words, the dithering unit 240 performs a dithering process for spatially and temporally dispersing the lower bits of the compensated voltage data using dithering patterns that are different for each frame and each gray level, thereby finely adjusting the gray level to express the gray level, that is, Increase the Color Depth.

For example, as shown in FIG. 4 , a dithering pattern set including a plurality of different dithering patterns P1 to P1 for each frame is stored in the LUT, and the dithering pattern set may be stored for each color. Each of the plurality of dithering patterns P1 to P4 has a size of 4*4 pixels, and the number of pixels having a dither bit of [1] gradually increases according to grayscale values of 0, 1/4, 2/4, and 3/4. a plurality of dithering blocks arranged to Each dithering block having a size of 4*4 pixels has a dither bit of [1] or [0] for each pixel, and a grayscale value is determined in proportion to the number of dither bits [1]. Also, in the plurality of dithering patterns P1 to P4, positions of pixels having a dither bit of [1] are set differently for each frame with respect to the same grayscale value. In the plurality of dithering patterns P1 to P4, the 4*4 pixel size of each dithering block and the position of the dither bit [1] may be variously changed according to the needs of a designer.

The dithering unit 240 includes frame information in which the number of frames is counted using a plurality of synchronization signals, for example, a vertical synchronization signal, pixel position information in which pixel positions are counted using a horizontal synchronization signal and a dot clock, and input data. supply the lower bits of The LUT selects one of a plurality of dithering patterns P1 to P4 according to frame information, and selects lower bits of input data and a dither bit corresponding to pixel position information from the selected dithering pattern to the dithering unit 240 . print out The dithering unit 240 outputs data having a reduced number of bits compared to the input data to the data driver 20 by adding the dither bit supplied to the LUT to the remaining upper bits of the input data. Of course, the data processed by the dithering unit 240 means voltage data supplied from the data compensating unit 220 .

In each of the display mode and the sensing mode, the data driver 20 drives the corresponding subpixel using the voltage data compensated by the data compensator 220 and dithered through the dithering unit 240 , and is driven in the sensing mode. The voltage output from the sub-pixel is sensed and output to the compensation value detection unit 230 .

The compensation value detector 230 updates compensation information of the memory M by using a sensing value sensed from each subpixel of the display panel 40 through the data driver 20 in the sensing mode.

Specifically, the compensation value detection unit 230 detects a mobility sensed value from a sensed value sensed through the data driver 20 in the sensing mode, and a mobility change amount that is a difference between the mobility sensed value and a previously stored mobility reference value. , and updates the mobility compensation value of the memory M by reflecting the detected mobility change amount.

In addition, the compensation value detector 230 detects the Vth sensed value of the driving TFT of each subpixel from the sensed value (sensed voltage value) sensed through the data driver 20 in the sensing mode, and the Vth sensed value and the stored initial Vth The Vth change amount ΔVth, which is the difference between , is detected, and the Vth compensation value of the memory M is updated by reflecting the detected Vth change amount ΔVth.

As described above, the OLED display device according to the present invention dithers the calculated voltage obtained by applying the compensation information to the voltage data in the sensing mode as well as the display mode and outputs the dithered output to the data driver 20 . Accordingly, in the update sensing mode, the calculated voltage to which the compensation information is applied to the voltage data is spatially and temporally dispersed and finely adjusted, thereby distributing the error value due to the voltage resolution difference between the calculated voltage and the output voltage of the data driver 20 through dispersion. can be reduced

5 is a flowchart illustrating a method for sensing an update of an OLED display according to an embodiment of the present invention step by step, which will be described in conjunction with FIG. 3 .

In the update sensing mode, in step 2 ( S2 ), the data compensator 220 receives the preset voltage data Vdata from the compensation value (Vth compensation value and the mobility compensation value) of the corresponding sub-pixel read from the memory M. at least one) is applied to compensate the voltage data and output the compensated voltage data.

In step 4 ( S4 ), the dithering unit 240 performs a dithering process for applying a dithering pattern to the voltage data supplied from the data compensating unit 220 and supplies it to the data driver 20 , and the data driver 20 performs the dithering process. The voltage data supplied from the unit 240 is converted into an output voltage and supplied to the gate node of the driving TFT of the corresponding subpixel.

In step 6 ( S6 ), when the driving TFT driven in the sub-pixel is in the saturated state, the data driver 20 senses the voltage of the source node and supplies the sensed voltage to the compensation value detector 230 .

In step 8 ( S8 ), the compensation value detection unit 230 detects Vth variation or mobility variation from the sensed value supplied from the data driver 20 , and in step 10 ( 10 ), Vth using the Vth variation or mobility variation Update the compensation value or the mobility compensation value.

Meanwhile, the OLED display device according to the present invention may use voltage data in which dithering does not occur as voltage data supplied to the data compensator 220 in the initial sensing mode. For example, if the voltage data calculated by the data compensator 220 is 16 bits and the output of the data driver 20 is 10 bits, dithering is performed in the initial sensing mode if a multiple of ^{2 6 = 64 is used as the voltage data.} doesn't happen

6 is a diagram illustrating an example of a real-time update sensing period of an OLED display device according to the present invention.

Referring to FIG. 6 , each frame includes a writing period and a blanking period. In each writing period, image data is written to each subpixel line sequentially. In each blanking period, the compensation information of the memory M is updated by sensing the characteristics of the sub-pixels for one horizontal line.

For example, in the blanking period of the n frame, the compensation value of the subpixels is updated in the memory M by sensing the characteristics of the subpixels of the n line, and the subpixels of the n+1 line in the blanking period of the n+1 frame The compensation values of the corresponding sub-pixels are updated in the memory by sensing the characteristics of the sub-pixels, and the compensation values of the corresponding sub-pixels are updated in the memory M by sensing the characteristics of the sub-pixels of the n+2 line in the blanking period of the n+2 frame. do.

Meanwhile, in each blanking period, sub-pixels of a corresponding horizontal line may be separated by color and sensed. For example, when the display panel has N horizontal lines, R subpixels are sensed in units of horizontal lines every blanking period of N frames, and then W subpixels are configured in units of horizontal lines every blanking period of N frames. Then, after sensing the B subpixels in the same way, the G subpixels may be sensed.

As described above, in the real-time update sensing period implemented in the blanking period of each frame, only subpixels of one horizontal line are sensed, so the order of changing the dithering pattern applied to the image data in the writing period (display mode) of each frame and the real-time The order of changing the dithering pattern applied to the voltage data for sensing in the sensing period (sensing mode) may be set differently.

For example, as shown in FIG. 6, in the writing period of n frames to n+2 frames, the dithering pattern is selected and applied in the order of P1, P2, and P3 for each frame, but in the real-time sensing period of n frames to n+2 frames, P1 This may continue to be selected and applied.

Fig. 7 is a block diagram showing another configuration example of the image processing unit shown in Fig. 1;

7 is different from FIG. 3 only in that the dithering unit 250 selectively uses LUT1 and LUT2 according to the display mode and the sensing mode, and since the remaining components are the same, a description of the same components is omitted. decide to do

In FIG. 7 , LUT1 stores a set of dithering patterns for display used in the display mode, and LUT2 stores a set of dithering patterns for sensing used in the sensing mode. For example, LUT1 stores a plurality of dithering patterns for display in which 4*4 pixel-sized dithering blocks are different for each gradation and frame-by-frame as shown in FIG. 4, and LUT2 is a 4*4 pixel-sized dithering block of the display dithering pattern. Dithering blocks having a smaller size of 2*2 pixels are different for each gray level, and thus a plurality of different dithering patterns for senses can be stored for each frame.

In the display mode, the dithering unit 250 selects LUT1 to use dithering patterns for display, and in the sensing mode, selects LUT2 to use the dithering patterns for sensing.

8A to 8D are exemplary diagrams illustrating comparison of output voltages of a data driver before and after dithering applied to voltage data to which Vth is applied in an OLED display device according to the present invention.

8A shows the levels of the Vth compensation values of each sub-pixel in color, and it can be seen that the Vth compensation values of the sub-pixels are not uniform.

FIG. 8B shows the voltage data compensated by adding a Vth compensation value to the voltage data 50 by converting the compensated voltage data into an output voltage of the data driver. It can be seen that the contour line due to the Vth compensation is visible because the voltage resolution of the data driver is insufficient.

8C is a diagram illustrating dithering by applying a different dithering pattern for each frame to compensated voltage data according to an embodiment of the present invention, and then converting the dithered voltage data into an output voltage of the data driver. It can be seen that the contour lines are blurred for each frame due to the lack of voltage resolution.

FIG. 8C shows the output voltage of the dithered voltage data averaged over 4 frames, and it can be seen that the contour line is blurred for each frame due to the lack of voltage resolution of the data driver through spatial and temporal dispersion through the dithering process.

9A to 9C are exemplary diagrams comparing the amount of change in sensing Vth before and after applying dithering to voltage data to which Vth is applied of an OLED display device according to the present invention.

FIG. 9A shows the levels of the Vth compensation values of each subpixel in color, similar to FIG. 8A, and it can be seen that the Vth compensation values of the subpixels are not uniform.

9B shows a Vth change amount detected from a sensed value sensed from each subpixel after converting the compensated voltage data into an output voltage of the data driver by adding a Vth compensation value to the voltage data 50 and supplying it to each subpixel. ΔVth), it can be seen that the contour line is visible in the sensed Vth variation (ΔVth) due to insufficient voltage resolution of the data driver.

9C is a diagram illustrating dithering by applying a different dithering pattern for each frame to the compensated voltage data according to an embodiment of the present invention, then converting the dithered voltage data into an output voltage of the data driver and supplying it to each sub-pixel; It shows the amount of Vth change (ΔVth) detected from the sensed value sensed from each sub-pixel. It shows that the contour line of the Vth change amount (ΔVth) is blurred due to the lack of voltage resolution of the data driver through spatial and temporal dispersion through dithering processing. Able to know.

As described above, in the OLED display device and the sensing method thereof according to the present invention, the calculated voltage obtained by applying a compensation value to voltage data is dithered and supplied to the data driver, resulting in a voltage resolution difference between the calculated voltage and the output voltage of the data driver. The error component can be spatially dispersed, and as a result, the error component is reduced while being spatially dispersed, thereby improving luminance uniformity.

In the above, it has been illustrated and described as a specific embodiment to illustrate the technical idea of the present invention, but the present invention is not limited to the same configuration and operation as the specific embodiment as described above, and various modifications do not depart from the technical spirit of the present invention. It can be implemented within the scope. Accordingly, such modifications should be considered to fall within the scope of the present invention, and the scope of the present invention should be determined by the following claims.

10: timing controller 20: data driver
30: gate driver 40: display panel
100: control signal generating unit 200: image processing unit
210: data conversion unit 220: data compensation unit
230: compensation value detection unit 240, 250: dithering unit
M: memory LUT, LUT1, LUT2: look-up table

Claims (5)

A display panel including a plurality of subpixels having different colors;
a memory storing a first compensation value for compensating for mobility of each sub-pixel and a second compensation value for compensating a threshold voltage (hereinafter referred to as Vth) of each sub-pixel;
In the sensing mode for updating the first compensation value or the second compensation value, voltage data is compensated by applying at least one of the first and second compensation values, and a preset dithering pattern set is applied to the compensated voltage data. a data processing unit configured to perform dither processing, drive each sub-pixel using the dithered voltage data, and update the first compensation value or the second compensation value using a sensing voltage sensed from each driven sub-pixel An organic light emitting diode (hereinafter referred to as OLED) display device. The method according to claim 1,
The data processing unit
a data compensator for compensating and outputting voltage data by applying at least one of the first and second compensation values;
a dithering unit for dithering and outputting the compensated voltage data supplied from the data compensator;
a data driver converting the dithered voltage data supplied from the dithering unit into an analog voltage, supplying it to each of the sub-pixels, sensing the sensing voltage from the driven sub-pixels, and outputting;
OLED display having a compensation value detection unit that detects Vth variation or mobility variation using the sensing voltage supplied from the data driver, and updates the first or second compensation value using the Vth variation or mobility variation Device. 3. The method according to claim 2,
The data compensator compensates voltage data set to sense the characteristic of the sub-pixel in the sensing mode and compensates voltage data of image data input from the outside in the display mode,
The dithering unit outputs the compensated voltage data by dithering,
The dithering pattern set includes a plurality of dithering patterns different for each frame while including a plurality of dithering blocks different for each gradation,
The dithering pattern set is used the same in the sensing mode and the display mode, or
A frame-by-frame change order of the plurality of dithering patterns in the dithering pattern set in the sensing mode is different from a frame-by-frame change order of the plurality of dithering patterns in the dithering pattern set in the display mode,
The dithering pattern set used in the sensing mode is set differently from the dithering pattern set used in the display mode, and the size of the first dithering block for each gradation included in each dithering pattern used in the sensing mode is, An OLED display set smaller than a size of a second dithering block for each gray level included in each dithering pattern used in the display mode. Compensating the voltage data by applying the compensation value stored in the memory;
dithering the compensated voltage data by applying a preset dithering pattern set;
converting the dithered voltage data into an analog voltage and supplying it to a corresponding sub-pixel to drive a driving TFT of the corresponding sub-pixel;
sensing and outputting a sensing voltage from the driven driving TFT;
and updating the compensation value stored in the memory by using the sensing voltage. 5. The method according to claim 4,
Compensating the voltage data includes compensating for voltage data set to sense the characteristic of the sub-pixel in a sensing mode and compensating for voltage data of image data input from the outside in a display mode,
The dithering process includes dithering the voltage data compensated in the sensing mode and the display mode by applying the dithering pattern set,
The dithering pattern set includes a plurality of dithering patterns different for each frame while including a plurality of dithering blocks different for each gradation,
The dithering pattern set is used the same in the sensing mode and the display mode, or
A frame-by-frame change order of the plurality of dithering patterns in the dithering pattern set in the sensing mode is different from a frame-by-frame change order of the plurality of dithering patterns in the dithering pattern set in the display mode,
The dithering pattern set used in the sensing mode is set differently from the dithering pattern set used in the display mode, and the size of the first dithering block for each gradation included in each dithering pattern used in the sensing mode is, A sensing method of an OLED display set to be smaller than a size of a second dithering block for each gray level included in each dithering pattern used in the display mode.

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