Method of compensating for degradation of display device

Abstract

The present disclosure relates to a method of compensating for degradation of a display device including a pixel including a second transistor, a first transistor, a third transistor, a storage capacitor, and an organic light emitting diode, the method including: sensing a first sensing current flowing through a sensing line; switching the second transistor in response to logic of the first scan line, maintaining an on state of the third transistor in response to logic of the second scan line, and sensing a sensing voltage of the sensing line; estimating a second sense current using the sense voltage; and determining a deterioration compensation value by applying [Equation 1].

Description

[0001] This application is a divisional application of an invention patent application with an application date of July 23, 2020, an application number of 202010718013.8, and an invention name of “Method for compensating for degradation of a display device”. Technical Field

[0002] Exemplary embodiments of the present disclosure relate to a method of compensating for degradation of a display device. Background Art

[0003] An organic light emitting diode ("OLED") display uses an OLED whose brightness is controlled by current or voltage and a thin film transistor ("TFT") that drives the OLED. The OLED includes an anode layer and a cathode layer that form an electric field, and an organic light emitting material that emits light by the electric field. According to the type of active layer, TFTs are classified into amorphous silicon (amorphous-Si) TFTs, low temperature polycrystalline silicon ("LTPS") TFTs, and oxide TFTs.

[0004] The pixel degrades due to the degradation of the OLED and the TFT, and the degradation of the pixel causes the brightness of the pixel to decrease. Even when a constant voltage is applied to the pixel, the current flowing through the pixel decreases due to the degradation of the OLED and the TFT, and therefore, the brightness of the pixel decreases. Summary of the invention

[0005] Taking into account pixel degradation, the power supply voltage for providing the driving current of the pixel can be set when the product is shipped, but in this case, a voltage higher than the ideal voltage is supplied even before the organic light emitting diode ("OLED") and the thin film transistor ("TFT") degrade, which increases the power consumption of the display device.

[0006] The problem to be solved by the present disclosure is to provide a method for compensating for degradation of a display device, which method can compensate for the degradation of a pixel when the pixel driving current cannot be directly measured.

[0007] Problems of the present disclosure are not limited to the above-mentioned problems, and other technical problems not described may be clearly understood by those skilled in the art from the following description.

[0008] An exemplary embodiment of a method for compensating for degradation of a display device according to the present disclosure that solves the above-mentioned problem includes: sensing a first sensing current flowing through a sensing line connected to a pixel, which includes a programming period for writing a data voltage of a predetermined color into a storage capacitor of the pixel; sensing a sensing voltage of the sensing line, which includes a period for charging a linear capacitor connected to the sensing line; estimating a voltage of an anode electrode of an organic light emitting diode using a second sensing current estimated from the first sensing current and the sensing voltage; and determining a degradation compensation value using the voltage of the anode electrode.

[0009] In an exemplary embodiment, the pixel may include: a second transistor, the second transistor including a first terminal connected to a data line to which the data voltage is applied, a second terminal connected to a first node, and a first gate terminal connected to a first scan line to which a first scan signal is applied; a first transistor, the first transistor including a third terminal connected to a first power line to which a first power signal is applied, a fourth terminal connected to a second node, and a second gate terminal connected to the first node; a third transistor, the third transistor including a fifth terminal connected to the sensing line, a sixth terminal connected to the second node, and a third gate terminal connected to a second scan line to which a second scan signal is applied; the storage capacitor, the storage capacitor including a first electrode connected to the first node, and a second electrode connected to the second node; and the organic light emitting diode, the organic light emitting diode including the anode electrode connected to the second node, and a cathode electrode connected to a second power line to which a second power signal having a level lower than that of the first power signal is applied.

[0010] In an exemplary embodiment, the second transistor may be turned on in response to a logic of the first scan line to write the data voltage to the storage capacitor in the programming period.

[0011] In an exemplary embodiment, the data voltage may have a value obtained by adding a value of a threshold voltage compensation data of the pixel to a value of a reference voltage of the pixel.

[0012] In an exemplary embodiment, after the data voltage is written to the storage capacitor, the third transistor may be turned on in response to a logic of the second scan line to apply an initialization voltage from the sensing line to the second node.

[0013] In an exemplary embodiment, the first sensing current may be a current flowing through the sensing line when the second transistor is turned off in response to the logic of the first scan line after the programming period.

[0014] In an exemplary embodiment, the voltage of the anode electrode may be a voltage when a current flowing through the first transistor and a current flowing through the organic light emitting diode are balanced.

[0015] In an exemplary embodiment, in the sensing voltage of the sensing line, the second transistor may be turned on and off in response to a logic of the first scan line, and the third transistor may maintain a turned-on state in response to a logic of the second scan line.

[0016] In an exemplary embodiment, the voltage charged in the linear capacitor may be increased.

[0017] In an exemplary embodiment, the display device may further include an analog-to-digital converter which senses the voltage charged in the linear capacitor.

[0018] In exemplary embodiments, the sensing voltage of the sensing line may be used to sense electron mobility of the first transistor.

[0019] In an exemplary embodiment, the sensing the first sensing current, the sensing the sensing voltage of the sensing line, and the estimating the voltage of the anode electrode may be performed before and after degradation.

[0020] In an exemplary embodiment, in the determining of the degradation compensation value, the degradation compensation value may be determined as a ratio of the voltage of the anode electrode after the degradation to the voltage of the anode electrode before the degradation.

[0021] In an exemplary embodiment, in the determining of the degradation compensation value, the degradation compensation value may be determined by reflecting the panel characteristics of the display device as a function calculation of the ratio.

[0022] In an exemplary embodiment, the method may further include generating degradation compensation data after the determining the degradation compensation value.

[0023] In addition, an exemplary embodiment of a method for compensating for degradation of a display device that solves the above-mentioned problem is provided. The display device includes a pixel. The pixel includes: a second transistor, the second transistor including a first terminal connected to a data line to which a data voltage is applied, a second terminal connected to a first node, and a first gate terminal connected to a first scan line to which a first scan signal is applied; a first transistor, the first transistor including a third terminal connected to a first power line to which a first power signal is applied, a fourth terminal connected to a second node, and a second gate terminal connected to the first node; a third transistor, the third transistor including a fifth terminal connected to a sensing line to which an initialization voltage is applied, a sixth terminal connected to the second node, and a third gate terminal connected to a second scan line to which a second scan signal is applied; a storage capacitor, the storage capacitor including a first electrode connected to the first node, and a second electrode connected to the second node; and an organic light emitting diode, the organic light emitting diode including an anode electrode connected to the second node, and a cathode electrode connected to a second power line, the second power line being applied with a second power signal having a level lower than that of the first power signal. The method includes: sensing a first sensing current flowing through the sensing line, which sequentially includes: a reset period, in which the second transistor is turned on in response to the logic of the first scan line, and the data voltage is written to the storage capacitor; a light-emitting period, in which the third transistor is turned off in response to the logic of the second scan line; and an initialization period, in which the second transistor is turned off in response to the logic of the first scan line; switching the second transistor in response to the logic of the first scan line, maintaining the on state of the third transistor in response to the logic of the second scan line, and sensing a sensing voltage of the sensing line; estimating a second sensing current using the sensing voltage; and determining a degradation compensation value by applying the following [Equation 1].

[0024] [Equation 1]

[0025]

[0026] Here, V anode represents the voltage of the anode electrode, V ref_el represents the reference voltage applied from the data line in the process of sensing the first sensing current, I el represents the first sensing current, I u represents the second sensing current, V ref_u represents the reference voltage applied from the data line in the sensing of the sensing voltage, and V init represents the initialization voltage applied from the sensing line in the sensing of the sensing voltage.

[0027] In an exemplary embodiment, the display device may further include a linear capacitor connected to the sensing line. The sensing the sensing voltage may include charging a linear capacitor to sense the sensing voltage of the sensing line, and the estimating the second sensing current may be performed by applying the following [Equation 2].

[0028] [Equation 2]

[0029] I u ×t=C line ×V line

[0030] Here, t represents the time when the second sensing current is applied to the sensing line, C line represents the capacitance of the linear capacitor, and V line represents the sensed voltage.

[0031] According to an exemplary embodiment of the present disclosure, degradation of the pixel may be compensated by estimating the voltage of the anode electrode of the organic light emitting diode, and image quality of the display device may be improved.

[0032] The effects according to the exemplary embodiments are not limited to the above-mentioned contents, and more various effects are included in the specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and other features of the present disclosure will become more apparent by describing exemplary embodiments of the present disclosure in more detail with reference to the accompanying drawings, in which:

[0034] Figure 1 is a block diagram showing an exemplary embodiment of a display device according to the present disclosure;

[0035] Figure 2 It is shown Figure 1 A circuit diagram of a relationship between a pixel and external components of the pixel;

[0036] Figure 3 It is shown Figure 1 an equivalent circuit diagram of the one pixel after the one pixel is degraded;

[0037] Figure 4 is a flow chart illustrating an exemplary embodiment of a method of compensating for degradation of a display device;

[0038] Figure 5 is a timing diagram showing a process of sensing a first sensing current;

[0039] Figures 6 to 9 It is shown Figure 5A circuit diagram showing the flow of current in a pixel during each time period;

[0040] Fig.10 is a timing diagram showing a process of determining a sense voltage;

[0041] Fig.11 It shows that according to Fig.10 A timing diagram of the current flow in the circuit diagram;

[0042] Fig.12 is a graph showing a driving current flowing through an organic light emitting diode relative to a gate-source voltage of a driving transistor;

[0043] Fig.13 is a schematic block diagram for schematically describing a method of generating degradation compensation data; and

[0044] Fig.14 and Fig.15 is a graph showing the ratio of the voltage of the anode electrode after degradation to the voltage of the anode electrode before degradation as a function in some exemplary embodiments. DETAILED DESCRIPTION

[0045] By referring to the following exemplary embodiments and the attached Figure 1 The advantages and features of the present disclosure and the methods for achieving the advantages and features of the present disclosure will become more easily understood with the detailed description given above. However, the present disclosure may not be limited to the exemplary embodiments disclosed below and may be implemented in many different forms. The illustrated exemplary embodiments are provided so that the present disclosure will be detailed and complete, and those skilled in the art to which the present disclosure belongs can fully understand the scope of the present disclosure. The present disclosure is limited only by the scope of the claims.

[0046] It will be understood that when an element is referred to as being “on” another element, the element can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.

[0047] Although the terms "first, second, etc." are used to describe various components, it is undoubted that these components should not be limited by these terms. These terms are only used to distinguish one component from another component. Therefore, it is undoubted that the first component mentioned below can be the second component within the technical spirit of the present disclosure. Unless the context clearly indicates otherwise, singular expressions include plural expressions.

[0048] The terms used herein are only for the purpose of describing specific embodiments and are not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms "one", "a kind of" and "the" are intended to include plural forms, which include "at least one (kind)". "Or" means "and / or". As used herein, the term "and / or" includes any combination and all combinations of one or more related listed items. It will be further understood that when the terms "include" and / or "comprise" or "contain" and / or "have" are used in this specification, it is indicated that the stated features, regions, wholes, steps, operations, elements and / or components exist, but the presence or addition of one or more other features, regions, wholes, steps, operations, elements, components and / or their groups is not excluded.

[0049] In addition, relative terms such as "lower" or "bottom" and "upper" or "top" may be used herein to describe the relationship of one element to another element as shown in the accompanying drawings. It will be understood that relative terms are intended to cover different orientations of the device in addition to the orientation depicted in the accompanying drawings. For example, if the device is turned over in one drawing, the element described as being on the "lower" side of the other elements will subsequently be positioned on the "upper" side of the other elements. Therefore, depending on the specific orientation of the drawings, the exemplary term "lower" can cover both "lower" and "upper" orientations. Similarly, if the device is turned over in one drawing, the element described as being "below" or "below" the other elements will subsequently be positioned "above" the other elements. Therefore, the exemplary terms "below..." or "below..." can cover both upper and lower orientations.

[0050] For ease of description, spatially relative terms such as "below," "beneath," "below," "above," and "on" may be used herein to describe the relationship of one element or feature to another element (or elements) or feature (or features) as shown in the accompanying drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the accompanying drawings. For example, if the device in the accompanying drawings is flipped, an element described as "below" or "below" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below" may encompass both above and below orientations. The device may be oriented in other ways (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein interpreted accordingly.

[0051] As used herein, "about" or "approximately" includes the stated value and means within an acceptable range of deviation of the specified value as determined by one of ordinary skill in the art, taking into account the determination in question and the errors associated with the determination of the specified amount (i.e., the limitations of the determination system). For example, "about" can mean within one or more standard deviations, or within ±30%, ±20%, ±10%, or ±5% of the stated value.

[0052] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present disclosure belongs. It will be further understood that, unless explicitly defined as such herein, terms such as those defined in general dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formalized sense.

[0053] Exemplary embodiments are described herein with reference to cross-sectional views as schematic diagrams of idealized embodiments. Thus, variations in the shapes of the diagrams due to, for example, manufacturing techniques and / or tolerances are anticipated. Therefore, the embodiments described herein should not be construed as being limited to the specific shapes of the regions as shown herein, but rather include deviations in shapes due to, for example, manufacturing. For example, a region shown or described as flat may typically have rough and / or nonlinear features. In addition, the sharp corners shown may be rounded. Therefore, the regions shown in the accompanying drawings are schematic in nature, and their shapes are not intended to illustrate the precise shapes of the regions, nor are they intended to limit the scope of the claims.

[0054] According to the present disclosure, the display device may be implemented in the form of various smart devices including a smart phone, a notebook computer, a monitor, a television, a mobile phone, an MP3 player, a medical measurement device, a wearable device, and an HMD.

[0055] Exemplary embodiments of the present disclosure will be described hereinafter with reference to the accompanying drawings. The same or similar reference numerals are used for the same components in the drawings.

[0056] Figure 1 is a block diagram illustrating an exemplary embodiment of a display device according to the present disclosure. Figure 2 It is shown Figure 1 A circuit diagram of the relationship between a pixel and the external components of the pixel. Figure 3 It is shown Figure 1 An equivalent circuit diagram of a pixel after the pixel is degraded.

[0057] Reference Figure 1 and Figure 2The display device may include a display unit 100, a scan driver 120, a data driver 130, a sensing unit 140, and a timing controller 110, wherein the display unit 100 includes a plurality of pixels PX.

[0058] The display device may include a display surface on which a light-emitting element emits light, and an image may be displayed through the display surface. In an exemplary embodiment, the display device may be an organic light-emitting display device. However, the present disclosure is not limited thereto, and unless the spirit of the present disclosure is changed, the present disclosure may be applied to a display device using an organic light-emitting diode ("OLED") as a light-emitting device, such as a quantum dot OLED device, or to a display device including an OLED on a backplane, such as a liquid crystal display device.

[0059] The timing controller 110 may control the operation of the display device by providing a predetermined control signal to the data driver 130, the scan driver 120, and the sensing unit 140. The timing controller 110 may generate a scan drive control signal and a data drive control signal DCS based on a signal input from the outside. The scan drive control signal generated by the timing controller 110 may be supplied to the scan driver 120, and the data drive control signal DCS may be supplied to the data driver 130.

[0060] The scan driving control signal may include a plurality of clock signals CLK and a scan start signal SSP. The scan start signal SSP may control an output time of the first scan signal.

[0061] The data driving control signal DCS may include a source start pulse and a clock signal. The source start pulse may control the sampling start time of the data, and the clock signal may be used to control the sampling operation.

[0062] The scan driver 120 may output a scan signal to the scan lines SC1 to SCn and SS1 to SSn in response to a scan drive control signal, where n is a natural number greater than 1. The scan driver 120 may sequentially supply the scan signal to the scan lines SC1 to SCn and SS1 to SSn. Here, the scan signal may be set to a scan-on voltage (e.g., a voltage of a high level) so that a transistor included in the pixel PX may be turned on.

[0063] The scan driver 120 includes a shift register that drives the scan lines SC1 to SCn and SS1 to SSn connected to the display unit 100 in a sequential method or an interlaced method, respectively, in response to a scan drive control signal from the timing controller 110. The scan driver 120 supplies a scan pulse of a scan-on voltage in a driving period of the scan lines SC1 to SCn and SS1 to SSn to enable the corresponding scan lines, and supplies a scan-off voltage in the remaining period to disable the corresponding scan lines. In an exemplary embodiment, the scan driver 120 is disposed in one outer region, but the present disclosure is not limited thereto, and the scan driver 120 may be disposed in at least two outer regions of the display unit 100.

[0064] The data driver 130 may output data signals to the data lines D1 to Dm in response to a data driving control signal DCS, where m is a natural number greater than 1. The data driver 130 may output the data signals by converting digital data of an input image received in each frame period into compensation data using a digital-to-analog converter ("DAC").

[0065] The data signals supplied to the data lines D1 to Dm may be supplied to the pixels PX supplied with the scan signals. To this end, the data driver 130 may supply the data signals to the data lines D1 to Dm in synchronization with the scan signals.

[0066] The sensing unit 140 may supply an initialization voltage Vref to the pixel PX through the sensing lines R1 to Rm, and may determine degradation information of the pixel PX by outputting a sensing current to the sensing lines R1 to Rm in response to the initialization voltage Vref. Figure 1 , the sensing unit 140 is illustrated as a separate configuration, but in another exemplary embodiment, the sensing unit 140 may be included in the data driver 130.

[0067] In an exemplary embodiment, a plurality of pixels PX may be arranged in a matrix shape in a row direction and a column direction. In the specification, the row direction refers to a horizontal direction on the drawing, and the column direction refers to a vertical direction on the drawing as a direction crossing the row direction, but is not limited thereto. In an exemplary embodiment, the row direction and the column direction may be understood as relative directions crossing each other.

[0068] A row of pixels PX among the plurality of pixels PX arranged in the row direction may be connected to the same first scan lines SC1 to SCn and second scan lines SS1 to SSn. In addition, a column of pixels PX among the plurality of pixels PX arranged in the column direction may be connected to the same data lines D1 to Dm. That is, one pixel PX may be connected to one data line Dj among the data lines D1 to Dm, one first scan line SCi among the first scan lines SC1 to SCn, one second scan line SSi among the second scan lines SS1 to SSn, and one sensing line Rj among the sensing lines R1 to Rm, where i and j are natural numbers.

[0069] Each pixel PX is independently driven by a plurality of transistors T1, T2, and T3. Amorphous silicon (α-Si) transistors, polycrystalline silicon (poly-Si) transistors, oxide transistors, organic transistors, etc. may be used as transistors T1, T2, and T3. In an exemplary embodiment, the pixel PX may include a first transistor T1, a second transistor T2, a third transistor T3, a storage capacitor C ST In an exemplary embodiment, the first transistor T1, the second transistor T2, and the third transistor T3 may be a driving transistor, a switching transistor, and a sensing transistor, respectively.

[0070] The pixel PX may receive a high potential first power signal ELVDD from the outside through the first power line, and may receive a low potential second power signal ELVSS from the outside through the second power line.

[0071] The second transistor T2 may include a first terminal connected to the data line Dj, a second terminal connected to the first node N1, and a gate terminal connected to the first scan line SCi. Here, the first node N1 may be a gate terminal connected to the first scan line SCi by the second terminal of the second transistor T2, the gate terminal of the first transistor T1, and the storage capacitor C ST The first electrode provides a node.

[0072] The second transistor T2 may transmit the data signal provided from the data driver 130 to the storage capacitor C in response to the scan signal applied from the scan driver 120. ST and a gate terminal of the first transistor T1.

[0073] Storage capacitor C ST The first electrode connected to the first node N1 and the second electrode connected to the second node N2 may be included. Here, the second node N2 may be connected to the storage capacitor C ST A node where the second electrode of the first transistor T1, the second terminal of the third transistor T3, and the anode electrode of the OLED are electrically connected.

[0074] Storage capacitor C STThe data signal transmitted through the second transistor T2 can be stored. The storage capacitor C ST A voltage equal to or greater than a threshold voltage of the first transistor T1 may be stored between the first electrode and the second electrode for a predetermined time.

[0075] The first transistor T1 may include a first terminal connected to the first power line to which the first power signal ELVDD is transmitted, a second terminal connected to the second node N2, and a gate terminal connected to the first node N1. ST In an exemplary embodiment, when a data signal having a level greater than a threshold voltage of the first transistor T1 is applied to the gate terminal, for example, the first transistor T1 may be turned on and a driving current may flow from the first terminal to the second terminal of the first transistor T1.

[0076] The OLED may include an anode electrode connected to the second node N2 and a cathode electrode connected to the second power line. While the first transistor T1 is turned on, the OLED may emit light based on a driving current flowing from the first power line to the second power line. The OLED may include a light emitting element layer between the anode electrode and the cathode electrode, and may emit light in proportion to the current amount of the driving current.

[0077] The third transistor T3 may include a first terminal connected to the sensing line Rj, a second terminal connected to the second node N2, and a gate terminal connected to the second scan line SSi. The third transistor T3 operates to supply the initialization voltage Vref transmitted to the first terminal through the sensing line Rj to the second node N2 connected to the second terminal of the first transistor T1, or sense the voltage or current of the second node N2 connected to the second terminal of the first transistor T1.

[0078] The third transistor T3 may be turned on according to a logic state of the second scan line SSi to supply the initialization voltage Vref to the second node N2. When the initialization voltage Vref is supplied to the second node N2, a data voltage written to the anode electrode of the OLED may be initialized.

[0079] According to an external compensation algorithm (not shown), the operation time of the third transistor T3 may be similar / same or different from the operation time of the second transistor T2. In an exemplary embodiment, the gate terminal of the second transistor T2 may be connected to the first scan line SCi, and the gate terminal of the third transistor T3 may be connected to the second scan line SSi. In this case, the scan signal is transmitted to the first scan line SCi, and the sensing signal is transmitted to the second scan line SSi. In another exemplary embodiment, the first scan line SCi connected to the gate terminal of the second transistor T2 and the second scan line SSi connected to the gate terminal of the third transistor T3 may be commonly connected so as to be shared.

[0080] The initialization voltage Vref may be provided from the sensing unit 140 through the sensing line Rj. In this case, during a non-display period of an image or at least one frame period, the sensing unit 140 may sense the second node N2 of the pixel PX in real time and may generate a sensing result. In an exemplary embodiment, the initialization voltage Vref may be, for example, about 2 volts (V).

[0081] The threshold voltage and electron mobility of the first transistor T1 may be sensed through the third transistor T3 and the sensing line Rj, and the threshold voltage compensation data V may be generated. th , the threshold voltage compensation data V th Used to compensate the data voltage of the anode electrode in proportion to the difference between a sensing value and a reference voltage, wherein the sensing value is, for example, a value corresponding to the threshold voltage and electron mobility of the first transistor T1, and the reference voltage is applied to the gate electrode of the first transistor T1 for sensing through the data line Dj.

[0082] In an exemplary embodiment, the data driver 130, the sensing unit 140, the scan driver 120, and the timing controller 110 may be implemented as one integrated circuit ("IC"). In another exemplary embodiment, the data driver 130, the scan driver 120, and the timing controller 110 may be implemented as two or more ICs.

[0083] The exemplary embodiment shown includes three transistors T1, T2 and T3 and a capacitor C ST The structure of the pixel PX may be more suitable for the enlargement of the display device, but is not limited thereto. The present exemplary embodiment is not limited to the number of transistors and the number of capacitors forming the pixel PX. In another exemplary embodiment, the pixel PX may include seven transistors and one capacitor, and in this case, the pixel PX may be more suitable for the miniaturization of the display device.

[0084] The display device may include an analog-to-digital converter ("ADC") connected to one end of the sensing line Rj and a sensing switch circuit, etc. The sensing switch circuit may include a first switching element T4 and a second switching element T5. In the exemplary embodiment shown, the first switching element T4 and the second switching element T5 are shown to be provided in the form of thin film transistors ("TFTs"), respectively. The display device may also include a linear capacitor C LINE , linear capacitor C LINE is connected to the sensing line Rj and performs a charging operation to sense the current of the first transistor T1.

[0085] In an exemplary embodiment, the sensing line Rj may sense a voltage of a second terminal (eg, a source electrode) of the first transistor T1 (a voltage of the second node N2 ) to sense electrical characteristics of the first transistor T1 .

[0086] The first switching element T4 may supply a predetermined initialization voltage Vref to the sensing line Rj to initialize the voltage of the second terminal of the first transistor T1 (the voltage of the second node N2 ) to the initialization voltage Vref.

[0087] The second switching element T5 can be turned on after the first switching element T4 is turned off to supply the voltage of the second terminal of the first transistor T1 (the voltage of the second node N2) to the ADC. The ADC converts the analog sensing voltage into digital sensing data and transmits the digital sensing data to the compensator 210. According to the sensing method, the voltage of the second terminal of the first transistor T1 (the voltage of the second node N2) can represent the threshold voltage or electron mobility of the first transistor T1. The method of sensing the threshold voltage of the first transistor T1 through the sensing line Rj or the method of sensing the electron mobility of the first transistor T1 through the sensing line Rj can use a known sensing method. The ADC, the compensator 210 and the DAC can be included in the application processor ("AP") 200 or the driver chip (driver IC) 200, and can be set as a separate component or integrated with the data driver 130. In an exemplary embodiment, an initialization capacitor C may also be included in the AP200 or the driver chip (driver IC) 200. INT , the initialization capacitor C INT It includes a first electrode connected to the second switching element T5 and the sensing line Rj and a second electrode connected to the ground.

[0088] In the normal pixel PX, the threshold voltage and electron mobility characteristics of the first transistor T1 are reflected in the driving current. Figure 3 , in the case where the degraded pixel PX_aging occurs, since the characteristics of the OLED change, the current value of the first transistor T1 changes, and thus degradation compensation data may be expected. Figure 3An equivalent circuit is shown, in which a pixel PX_aging that is degraded due to the change in the characteristics of the OLED has a degradation capacitance C EL .

[0089] In an exemplary embodiment, the degradation compensation data may be determined according to the ratio of the voltage of the anode electrode after degradation of the OLED connected to the first transistor T1 to the voltage of the anode electrode before degradation. However, in some cases, it may not be possible to directly measure the voltage of the anode electrode for each pixel PX. In this case, the voltage of the anode electrode may be estimated by the following method, and the degradation compensation data may be generated by the estimated voltage.

[0090] Figure 4 is a flow chart illustrating an exemplary embodiment of a method of compensating for degradation of a display device.

[0091] Reference Figure 4 , a method for compensating for degradation of a display device may include: writing a data voltage of a predetermined color into a storage capacitor of a pixel, and sensing a first sensing current flowing through a sensing line (S100), charging a linear capacitor connected to the sensing line and sensing a sensing voltage of the sensing line (S200), estimating a second sensing current through the sensing voltage (S300), estimating a voltage of an anode electrode through the first sensing current and the second sensing current (S400), determining a degradation compensation value (S500), and generating degradation compensation data (S600).

[0092] In the specification, each operation is described as being performed sequentially according to the flowchart, but unless the spirit of the present disclosure is changed, some operations shown as being performed sequentially may be performed simultaneously, the order of each operation may be changed, some operations may be omitted, or another operation may be further included between each operation.

[0093] First, common reference Figures 5 to 9 , sensing the first sensing current ( S100 ) is described.

[0094] Figure 5 is a timing diagram showing a process of sensing a first sensing current. Figures 6 to 9 It is shown Figure 5 Circuit diagram showing the current flow in a pixel during each time period. Figures 5 to 9 Indicating the degraded capacitance with a dotted line shows that this operation can be equally applied before and after pixel degradation.

[0095] Reference Figure 5 , sensing the first sensing current (S100) may include a reset period T RESET , light-emitting period T EL_PFOG , initialization period T TFT_INIT and sensing period TSENSE .

[0096] When the OLED emits a predetermined color, the current flowing through the OLED may be used to estimate the voltage of the anode electrode (the potential of the second node N2 ).

[0097] In an exemplary embodiment, the storage capacitor C ST The storage capacitor C is programmed to sense the current flowing through the OLED for a predetermined color. Typically, the initialization voltage Vref supplied to the second node N2 through the sensing line Rj is commonly applied to pixels emitting red, green, and blue light. Therefore, in order to sense the current flowing through the OLED for a predetermined color, the storage capacitor C may be programmed to sense the current flowing through the OLED for a predetermined color. ST Programming is performed. In an exemplary embodiment, the predetermined color may be, for example, gray. Hereinafter, as an example, operations and parts are performed by sensing gray, but the type of the predetermined color is not limited thereto.

[0098] First, the following [Equation 3] may be applied to the relationship between a current flowing through an OLED and a voltage of an anode electrode.

[0099] [Equation 3]

[0100] I el =u×(V ref_el -V anode ) 2

[0101] Here, I el corresponds to the current flowing through the OLED (first sensing current), u corresponds to the electron mobility factor, V ref_el corresponds to the reference voltage, and V anode Corresponds to the voltage at the anode electrode.

[0102] In an exemplary embodiment, the reset period T RESET It can be used to write the data voltage of the predetermined color into the storage capacitor C ST programming period.

[0103] Reference Figure 5 and Figure 6 , during the reset period T RESET In the embodiment, the second transistor T2 may be turned on in response to a high logic state of the first scan line SCi (i.e., a state in which the first scan signal Si having a high level is applied to the first scan line SCi) to apply the data signal to the first node N1. In an exemplary embodiment, for example, for each pixel, the voltage level of the data signal may be equal to the reference voltage V ref_el and the threshold voltage compensation data V of the first transistor T1 th The reference voltage V can be predetermined by the driver of the display device.ref_el and threshold voltage compensation data V th , so the voltage level of the data signal can be determined.

[0104] The third transistor T3 may be turned on in response to a high logic state of the second scan line SSi (i.e., a state in which the second scan signal Si+1 having a high level is applied to the second scan line SSi) to apply the initialization voltage Vref to the second node N2. The sensing line and the anode electrode may have the same potential as the second node N2. The second node N2 may be initialized to have the same voltage level as the initialization voltage Vref. In an exemplary embodiment, the initialization voltage Vref may be, for example, about 2V.

[0105] A voltage corresponding to the potential difference between the first node N1 and the second node N2 may be written into the storage capacitor C ST That is, for each pixel, by setting the reference voltage V ref_el The value of the threshold voltage compensation data V of the first transistor T1 th The value of the initialization voltage Vref is subtracted from the value obtained by adding to obtain an absolute value, and a voltage equal to the absolute value can be written into the storage capacitor C ST .

[0106] Here, the potential difference between the first node N1 and the second node N2 may be a gate-source voltage of the first transistor T1.

[0107] In an exemplary embodiment, the light emitting period T EL_PFOG It may be the period during which the OLED emits light.

[0108] Reference Figure 5 and Figure 7 , during the luminous period T EL_PFOG In the embodiment, the second transistor T2 may maintain a turned-on state in response to a high logic state of the first scan line SCi, and the third transistor T3 may be turned off in response to a low logic state of the second scan line SSi. The first power signal ELVDD may be applied to the second node N2 through the first transistor T1. The first power signal ELVDD may gradually increase, and when the first power signal ELVDD reaches a predetermined voltage, the OLED may emit light.

[0109] The current flowing through the OLED may gradually increase and may form a balanced state with the current flowing through the first transistor T1. The potential of the anode electrode in the balanced state may be V anode , which is the voltage of the anode electrode mentioned above. However, the V anode The value of may vary depending on the degradation state.

[0110] Reference Figure 5 and Figure 8 , in the initialization period T TFT_INIT In the embodiment, the second transistor T2 may be turned off in response to a low logic state of the first scan line SCi, and the third transistor T3 may be turned on in response to a high logic state of the second scan line SSi.

[0111] The initialization voltage Vref may be applied to the second node N2 connected to the anode electrode through the sensing line Rj. The potential of the second node N2 may again have a potential of the same voltage level as that of the initialization voltage Vref.

[0112] During the reset period T RESET In the case of reflecting the threshold voltage compensation data V th The data voltage is written into the storage capacitor C ST , so in the initialization period T TFT_INIT In the threshold voltage compensation data V th The storage capacitor C ST The voltage is shifted and the storage capacitor C ST The voltage can have a value equal to the reference voltage V ref_el The voltage that is different from the voltage at the anode electrode.

[0113] That is, the following [Equation 4] may be applied to the gate-source voltage of the first transistor T1.

[0114] [Equation 4]

[0115] V gs =V ref_el -V anode

[0116] Here, V gs Corresponding to the gate-source voltage of the first transistor T1.

[0117] Reference Figure 5 and Fig. 9 , in the sensing period T SENSE In the sensing period T, the second transistor T2 can maintain the off state in response to the low logic state of the first scan line SCi, and the third transistor T3 can maintain the on state in response to the high logic state of the second scan line SSi. SENSE In the embodiment, the above [Equation 2] can also be applied to the gate-source voltage of the first transistor T1.

[0118] Even when the second transistor T2 is STWhen the first transistor T1 is turned off due to the charged voltage, the first transistor T1 may also be turned on, and current may flow through the first transistor T1. Since the resistance of the OLED is relatively greater than the resistance of the sensing line Rj, most of the current does not flow to the OLED, but may flow through the sensing line Rj as the first sensing current. That is, the first sensing current may have a value substantially similar to the driving current when the OLED emits light, and the first sensing current may be in the sensing period T SENSE It is sensed by the sensing line Rj.

[0119] Next, we will refer to Fig.10 and Fig.11 Charging a linear capacitor connected to a sensing line and sensing a sensing voltage of the sensing line ( S200 ) and estimating a second sensing current through the sensing voltage ( S300 ) are described.

[0120] Fig.10 is a timing chart showing the process of measuring the sense voltage. Fig.11 It shows that according to Fig.10 The timing diagram of the current flow in the circuit diagram. Fig.11 The reference voltage and initialization voltage V init The reference numerals and symbols applied to equations of the operations are different from those of the above-mentioned operations in order to be distinguished from the above-mentioned operations.

[0121] In an exemplary embodiment, a linear capacitor C connected to a sensing line Rj is LINE Charging and sensing the sensing voltage of the sensing line Rj ( S200 ) and estimating the second sensing current based on the sensing voltage ( S300 ) may be sensing electron mobility of the current flowing through the first transistor T1 and the OLED.

[0122] In an exemplary embodiment, a linear capacitor C connected to a sensing line Rj is LINE Charging and sensing the sensing voltage of the sensing line Rj (S200) may include charging the linear capacitor C LINE Charging time T INT .

[0123] The second transistor T2 may be turned on in response to the pulse of the first scan line SCi. ST After being charged, the second transistor T2 may be turned off, and the third transistor T3 may be turned on in response to a high logic state of the second scan line SSi and may maintain a turned-on state.

[0124] When the second transistor T2 is turned on and the third transistor T3 is turned on, the gate-source voltage of the first transistor T1 may be the reference voltage and the initialization voltage V init In addition, the storage capacitor CST The reference voltage and initialization voltage V init The difference between the two corresponds to the charge being charged.

[0125] When the third transistor T3 remains in the on state and the second transistor T2 is turned off, the first transistor T1 can ST The voltage charged in the sensing line maintains the on state, and the driving current can flow along the sensing line Rj and increase. Therefore, while the applied voltage increases, the linear capacitor C connected to the sensing line Rj can be LINE The linear capacitor C LINE The voltage can be measured.

[0126] Based on the linear capacitor C LINE The second sensing current may be estimated by applying the following [Equation 5] based on the amount of charge charged in the OLED. As described above, the second sensing current may be substantially similar to the current flowing when the OLED emits light.

[0127] [Equation 5]

[0128] I u ×t=C line ×V line

[0129] Here, t corresponds to the time when the second sensing current flows, C line Corresponding linear capacitor C LINE The capacitance, and V line Corresponding linear capacitor C LINE The voltage (sense voltage)

[0130] [Equation 6] corresponding to [Equation 3] may be applied to the second sensing current.

[0131] [Equation 6]

[0132] I u =u×(V ref_u -V init ) 2

[0133] Here, I u corresponds to the current flowing through the OLED (the second sensing current), u corresponds to the electron mobility factor, V ref_u Corresponding to the reference voltage applied by the data line Dj during operation, V init Corresponding to the initialization voltage applied through the sensing line Rj.

[0134] Next, the estimating of the voltage of the anode electrode (S400) will be described.

[0135] Before degradation, [Equation 7] corresponding to [Equation 3] and [Equation 8] corresponding to [Equation 6] may be applied to the first sensing current and the second sensing current, respectively.

[0136] [Equation 7]

[0137] I el1 =u 1 ×(V ref_el -V anode1 ) 2

[0138] [Equation 8]

[0139] I u1 =u 1 ×(V ref_u -V init ) 2

[0140] The ratio of the first sensing current to the second sensing current may be expressed as [Equation 9] through [Equation 7] and [Equation 8], and the voltage of the anode electrode before degradation may be estimated as [Equation 10] through [Equation 9].

[0141] [Equation 9]

[0142]

[0143] [Equation 10]

[0144]

[0145] The voltage of the anode electrode before degradation can be estimated through the above process.

[0146] After degradation, [Equation 11] corresponding to [Equation 3] and [Equation 12] corresponding to [Equation 6] may be applied to the first sensing current and the second sensing current, respectively.

[0147] [Equation 11]

[0148] I el2 =u 2 ×(V ref_el -V anode2 ) 2

[0149] [Equation 12]

[0150] I u2 =u 2 ×(V ref_u -V init ) 2

[0151] Similar to the case before degradation, the voltage of the anode electrode may be estimated after degradation, and [Equation 13] may be applied to the voltage of the anode electrode after degradation.

[0152] [Equation 13]

[0153]

[0154] The voltage of the anode electrode after deterioration can be estimated through the above process.

[0155] Next, the determination of the degradation compensation value (S500) and the generation of the degradation compensation data (S600) will be described.

[0156] Fig.12 is a graph showing the drive current flowing through an OLED relative to the gate-source voltage of the drive transistor. Fig.13 is a schematic block diagram for schematically describing a method of generating degradation compensation data. Fig.14 and Fig.15 is a graph showing the ratio of the voltage of the anode electrode after degradation to the voltage of the anode electrode before degradation as a function in some exemplary embodiments. Fig.12 The figure shows the first sensing current I before degradation (before aging). el1 and the second sensing current I u1 And the first sensing current I after degradation (after aging) el2 and the second sensing current I u2 .

[0157] Reference Fig.12 As the voltage of the anode electrode increases, the resistance component of the OLED may increase. The size of the resistance component may generally be proportional to the amount of degradation. Therefore, the degradation compensation value may be determined in proportion to the voltage of the anode electrode.

[0158] Reference Fig.13 , the compensator 210 may receive a data signal Gray_in(i,j) of a predetermined color of a pixel at a predetermined position, a voltage Vanode_init(i,j) of an anode electrode before degradation, a voltage Vanode(i,j) of an anode electrode after degradation, and an average voltage Vanode_init_avg of an anode electrode before pixel degradation. Here, the compensator 210 may receive a data signal Gray_in(i,j) of a predetermined color of a pixel at a predetermined position, a voltage Vanode_init(i,j) of an anode electrode before degradation, a voltage Vanode(i,j) of an anode electrode after degradation, and an average voltage Vanode_init_avg of an anode electrode before pixel degradation. Figures 5 to 11 The process estimates the voltage Vanode_init(i, j) of the anode electrode before degradation for each pixel and calculates the average value of the voltage Vanode_init(i, j) of the anode electrodes of all pixels before degradation to estimate the average voltage Vanode_init_avg of the anode electrodes of all pixels before degradation.

[0159] The compensator 210 can determine the degradation compensation value using the data signal Gray_in(i,j) of the predetermined color of the pixel at the predetermined position and the ratio Vanode(i,j) / Vanode_init(i,j) of the voltage Vanode(i,j) of the anode electrode of the pixel at the predetermined position after degradation to the voltage Vanode_init(i,j) of the anode electrode of the pixel at the predetermined position before degradation, can use the ratio to generate compensation data, and can output the data signal Gray_out(i,j) to which the compensation data is applied.

[0160] In an optional exemplary embodiment, the compensator 210 may determine the degradation compensation value using the data signal Gray_in(i,j) of the predetermined color of the pixel at the predetermined position and the ratio Vanode(i,j) / Vanode_init_avg of the voltage Vanode(i,j) of the anode electrode of the pixel at the predetermined position after degradation to the average voltage Vanode_init_avg of the anode electrode of all pixels before degradation, may use the ratio to generate compensation data, and may output the data signal Gray_out(i,j) to which the compensation data is applied. The compensation data may be generated by reflecting at least one panel characteristic among material characteristics, degradation characteristics, and brightness characteristics as the value of the ratio Vanode(i,j) / Vanode_init_avg of the voltage Vanode(i,j) of the anode electrode of the pixel at the predetermined position after degradation to the average voltage Vanode_init_avg of the anode electrode of all pixels before degradation, and performing a function operation. In addition to gray, compensation data for red, green, and blue may also be generated.

[0161] The function for generating compensation data for red, green, and blue can be expressed as Fig.14 The linear function shown in Fig.15 The nonlinear function shown in .

[0162] Degradation of the display device can be compensated through the above process.

[0163] The order of sensing the flowing first sensing current ( S100 ), charging the linear capacitor connected to the sensing line and sensing the sensing voltage of the sensing line ( S200 ), and estimating the second sensing current through the sensing voltage ( S300 ) may be variously modified.

[0164] Although the exemplary embodiments of the present disclosure have been described with reference to the accompanying drawings, it will be understood by those skilled in the art that the exemplary embodiments may be implemented in other specific forms without changing the technical spirit and basic features of the present disclosure. Therefore, it should be understood that the above exemplary embodiments are illustrative and not limiting to all exemplary embodiments.

Claims

1. A method for compensating for degradation of a display device, the display device comprising pixels, wherein: The pixels include: a second transistor including a first terminal connected to a data line to which a data voltage is applied, a second terminal connected to a first node, and a first gate terminal connected to a first scan line to which a first scan signal is applied; a first transistor including a third terminal connected to a first power line to which a first power signal is applied, a fourth terminal connected to a second node, and a second gate terminal connected to the first node; a third transistor including a fifth terminal connected to a sensing line to which an initialization voltage is applied, a sixth terminal connected to the second node, and a third gate terminal connected to a second scan line to which a second scan signal is applied; a storage capacitor including a first electrode connected to the first node and a second electrode connected to the second node; and an organic light emitting diode including an anode electrode connected to the second node and a cathode electrode connected to a second power line to which a second power signal having a level lower than that of the first power signal is applied, The method comprises: sensing a first sensing current flowing through the sensing line, which sequentially includes: a reset period, in which the second transistor is turned on in response to the logic of the first scan line, and the data voltage is written to the storage capacitor; a light emitting period, in which the third transistor is turned off in response to the logic of the second scan line; and an initialization period, in which the second transistor is turned off in response to the logic of the first scan line; switching the second transistor in response to the logic of the first scan line, maintaining a turned-on state of the third transistor in response to the logic of the second scan line, and sensing a sensing voltage of the sensing line; estimating a second sense current using the sense voltage; and The degradation compensation value is determined by applying the following [Equation 1], [Equation 1] Here, V anode represents the voltage of the anode electrode, V ref_el represents the reference voltage applied from the data line in the process of sensing the first sensing current, I el represents the first sensing current, I u represents the second sensing current, V ref_u represents the reference voltage applied from the data line in the sensing of the sensing voltage, and V init represents the initialization voltage applied from the sensing line in the sensing of the sensing voltage.

2. The method according to claim 1, wherein: The display device further includes a linear capacitor connected to the sensing line, The sensing the sensing voltage includes charging a linear capacitor to sense the sensing voltage of the sensing line, and The estimating the second sensing current is performed by applying the following [Equation 2], [Equation 2] I u ×t=C line ×V line Here, t represents the time when the second sensing current is applied to the sensing line, C line represents the capacitance of the linear capacitor, and V line represents the sensed voltage.

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