Display device and brightness difference compensation method of display device

Abstract

According to one aspect of the present disclosure, a brightness difference compensation method of a display device includes: measuring a sensing voltage change at a node between a first driving transistor and a second driving transistor of a sub-pixel; calculating a first threshold voltage change of the first driving transistor according to the sensing voltage change; calculating a second threshold voltage change of the second driving transistor according to the first threshold voltage change and the prediction information; compensating the first data voltage based on the first threshold voltage change; and compensating the second data voltage based on the second threshold voltage change, and the prediction information is a difference between the first threshold voltage change and the second threshold voltage change according to the bias stress and time.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to Korean Patent Application No. 10 - 2023 - 0183130, filed with the Korean Intellectual Property Office on December 15, 2023, the disclosure of which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates to a display device and a method for compensating for a brightness difference of a display device, and more particularly, to a display device and a method for compensating for a brightness difference of a display device that simplify a method for sensing and compensating for a threshold voltage difference of sub - pixels. Background Art

[0004] The scope of application of display devices has been extended to personal digital assistants and monitors for computers and televisions, and display devices having a large display area and reduced volume and weight are being studied.

[0005] Meanwhile, various types of display elements are used in display devices, and in recent years, light - emitting diodes (LEDs) or micro - LEDs (micro light - emitting diodes) formed of inorganic materials to have high reliability and excellent luminous efficiency are being used. In addition, pixel circuits for driving LEDs are configured as follows: pulse - amplitude modulation (PAM) that represents a gray level using the amplitude of a driving current and / or pulse - width modulation (PWM) that represents a gray level using the pulse width of a driving current. Summary of the Invention

[0006] An object to be achieved by the present disclosure is to provide a display device and a method for compensating for a brightness difference of a display device that can reduce a brightness difference between a plurality of sub - pixels.

[0007] Another object to be achieved by the present disclosure is to provide a display device and a method for compensating for a brightness difference of a display device that use an external compensation method to compensate for the threshold voltages of driving transistors of a PAM circuit and a PWM circuit.

[0008] Another object to be achieved by the present disclosure is to provide a display device and a method for compensating for a brightness difference of a display device that simultaneously sense the threshold voltages of driving transistors of a PAM circuit and a PWM circuit to reduce the length of a sensing period.

[0009] Yet another object to be achieved by the present disclosure is to provide a display device and a method for compensating for a brightness difference of a display device that simultaneously sense the threshold voltages of driving transistors of a PAM circuit and a PWM circuit to use only one sensing transistor.

[0010] Another object to be achieved by the present disclosure is to provide a display device and a method for compensating for a brightness difference of a display device that simplifies a structure of a sensing unit for a threshold voltage of a driving transistor of a sensing PAM circuit and a threshold voltage of a driving transistor of a PWM circuit.

[0011] Another object to be achieved by the present disclosure is to provide a display device and a method for compensating for a brightness difference of a display device that additionally corrects prediction information on a change in a threshold voltage of a first driving transistor to more precisely calculate a change in a second threshold voltage of a second driving transistor.

[0012] Another object to be achieved by the present disclosure is to provide a display device and a method for compensating for a brightness difference of a display device that calculates a degradation level and a change in a second threshold voltage of a second driving transistor based on an image displayed on the display device and a change in a first threshold voltage of a first driving transistor.

[0013] Another object to be achieved by the present disclosure is to provide a display device and a method for compensating for a brightness difference of a display device that simplifies a threshold voltage difference sensing method and a configuration of a sensing unit to reduce the number of wirings and transistors.

[0014] The object of the present disclosure is not limited to the above-mentioned objects, and those skilled in the art can clearly understand other objects not mentioned above from the following description.

[0015] To achieve the object as described above, according to an aspect of the present disclosure, a display device includes: a display panel including a plurality of sub-pixels; a data driver connected to the display panel; a first circuit unit provided in each of the plurality of sub-pixels and including a first driving transistor; a second circuit unit provided in each of the plurality of sub-pixels and including a second driving transistor; and a sensing transistor connected to a drain electrode of the first driving transistor and a source electrode of the second driving transistor, the plurality of sub-pixels being configured to be driven in an emission period and a sensing period, and the sensing transistor being configured to detect a larger one of a first sensing voltage of the drain electrode of the first driving transistor and a second sensing voltage of the source electrode of the second driving transistor that overlap each other in time. Accordingly, one sensing transistor is connected to the first driving transistor and the second driving transistor, and simultaneously senses a threshold voltage of the first driving transistor and a threshold voltage of the second driving transistor, so as to shorten a length of the sensing period and simplify a structure of the sensing transistor.

[0016] According to one aspect of the present disclosure, a method for compensating a luminance difference of a display device includes: measuring a change in a sensed voltage at a node between a drain electrode of a first driving transistor and a source electrode of a second driving transistor of a sub-pixel; calculating a first threshold voltage change of the first driving transistor based on the change in the sensed voltage; calculating a second threshold voltage change of the second driving transistor based on the first threshold voltage change and prediction information; compensating a first data voltage based on the first threshold voltage change to apply the compensated first data voltage to the first driving transistor; and compensating a second data voltage based on the second threshold voltage change to apply the compensated second data voltage to the second driving transistor, and the prediction information is a difference between the first threshold voltage change and the second threshold voltage change according to a bias stress and time. Accordingly, prediction information of a difference between the first threshold voltage change and the second threshold voltage change can be used to more precisely compensate a threshold voltage difference of the second driving transistor.

[0017] According to another aspect of the present disclosure, a display device includes: a display panel in which a plurality of sub-pixels are defined, and each of the plurality of sub-pixels includes: a first circuit unit including a first driving transistor; a second circuit unit including a second driving transistor and connected to the first circuit unit; and a sensing transistor connected to the first circuit unit and the second circuit unit, the sensing transistor being connected to both the first driving transistor and the second driving transistor.

[0018] Other detailed matters of the exemplary embodiments are included in the detailed description and the drawings.

[0019] According to the present disclosure, a luminance difference between a plurality of sub-pixels is reduced.

[0020] According to the present disclosure, threshold voltages of driving transistors of a PAM circuit and a PWM circuit can be compensated by an external compensation method.

[0021] According to the present disclosure, a threshold voltage of a driving transistor of a PAM circuit and a threshold voltage of a driving transistor of a PWM circuit are simultaneously sensed to reduce a length of a sensing period.

[0022] According to the present disclosure, a threshold voltage of a driving transistor of a PAM circuit and a threshold voltage of a driving transistor of a PWM circuit are simultaneously sensed to use only one sensing transistor.

[0023] According to the present disclosure, a structure of a sensing unit for sensing a threshold voltage of a driving transistor of a PAM circuit and a threshold voltage of a driving transistor of a PWM circuit is simplified.

[0024] According to the present disclosure, prediction information is additionally corrected for a first threshold voltage change of a first driving transistor to more precisely calculate a second threshold voltage change of a second driving transistor.

[0025] According to the present disclosure, an image displayed on a display device is analyzed to predict a degradation level of a driving transistor and compensate for a threshold voltage difference of the driving transistor.

[0026] According to the present disclosure, a threshold voltage difference sensing method and a configuration of a sensing unit are simplified to reduce the number of wirings and transistors.

[0027] The effects according to the present disclosure are not limited to the contents of the above examples, and more various effects are included in this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and other aspects, features, and advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0029] Figure 1 is a schematic diagram of a display device according to an exemplary embodiment of the present disclosure;

[0030] Figure 2A is a schematic diagram of a sub-pixel of a display device according to an exemplary embodiment of the present disclosure;

[0031] Figure 2B is an exemplary circuit diagram of a sub-pixel of a display device according to an exemplary embodiment of the present disclosure;

[0032] Figure 3 is a flowchart for explaining a brightness difference compensation method of a display device according to an exemplary embodiment of the present disclosure;

[0033] Figure 4 is a driving timing diagram of a sub-pixel of a display device for a sensing period according to an exemplary embodiment of the present disclosure;

[0034] Figure 5 is a graph showing a change in a sensing voltage of a driving transistor of a display device over time according to an exemplary embodiment of the present disclosure; and

[0035] Figure 6 is a graph showing a change in a threshold voltage of a driving transistor of a display device over bias stress and time according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0036] Advantages and features of the present disclosure, and methods for realizing these advantages and features, will be clear by referring to the exemplary embodiments described in detail below in conjunction with the accompanying drawings. However, the present disclosure is not limited to the exemplary embodiments disclosed herein, but will be implemented in various forms. The exemplary embodiments are provided merely as examples so that those skilled in the art can fully understand the disclosure of the present disclosure and the scope of the present disclosure.

[0037] The shapes, sizes, ratios, angles, numbers, etc. shown in the accompanying drawings for describing the exemplary embodiments of the present disclosure are merely examples, and the present disclosure is not limited thereto. Throughout the specification, like reference numerals generally denote like elements. In addition, in the following description of the present disclosure, detailed descriptions of known related technologies may be omitted to avoid unnecessarily obscuring the subject matter of the present disclosure. Terms such as "comprising", "having", and "consisting of" used herein are generally intended to allow the addition of other components, unless these terms are used together with the term "only". Any reference to the singular may include the plural unless otherwise explicitly stated.

[0038] Even if not explicitly stated, components are construed to include a normal error range.

[0039] When terms such as "on", "above", "below", and "next to" are used to describe the positional relationship between two parts, unless these terms are used together with the terms "immediately" or "directly", one or more parts may be located between these two parts.

[0040] When an element or layer is disposed "on" another element or layer, another layer or another element may be directly disposed on another element or disposed therebetween.

[0041] Although terms such as "first", "second", etc. are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from other components. Thus, the first component to be mentioned below may be the second component in the technical concept of the present disclosure.

[0042] Throughout the specification, like reference numerals generally denote like elements.

[0043] For ease of description, the dimensions and thicknesses of each component shown in the accompanying drawings are shown, and the present disclosure is not limited to the dimensions and thicknesses of the components shown.

[0044] The features of the various embodiments of the present disclosure can be partially or completely combined or combined with each other and can be interlocked and operated in technically different ways, and the embodiments can be executed independently of each other or in association with each other.

[0045] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0046] Figure 1 is a schematic diagram of a display device according to an exemplary embodiment of the present disclosure. In Figure 1 for ease of description, among the various components of the display device 100, only the display panel PN, the gate driver GD, the data driver DD, and the timing controller TC are shown.

[0047] Referring to Figure 1 , the display device 100 includes: a display panel PN including a plurality of sub-pixels SP; a gate driver GD and a data driver DD that supply various signals to the display panel PN; and a timing controller TC that controls the gate driver GD and the data driver DD.

[0048] The gate driver GD supplies a plurality of scan signals to a plurality of scan lines SL according to a plurality of gate control signals supplied from the timing controller TC. Although in Figure 1 one gate driver GD is shown as being disposed at a distance from one side of the display panel PN, the number and placement of the gate drivers GD are not limited thereto.

[0049] The data driver DD supplies data voltages to a plurality of data lines DL according to a plurality of data control signals and image data supplied from the timing controller TC. The data driver DD converts the image data into data voltages using a reference gamma voltage and may supply the converted data voltages to the plurality of data lines DL.

[0050] In addition, the data driver DD includes a partial configuration of a sensing unit PCS to be described below for outputting a first data voltage Vdata1 compensated based on a threshold voltage change ΔVth of each of the plurality of sub-pixels SP and a compensated second data voltage Vdata2 to the plurality of sub-pixels SP.

[0051] The timing controller TC aligns the image data input from the outside to supply the image data to the data driver DD. The timing controller TC may generate gate control signals and data control signals using synchronization signals input from the outside, such as a dot clock signal, a data enable signal, and a horizontal / vertical synchronization signal. In addition, the timing controller TC supplies the generated gate control signals and data control signals to the gate driver GD and the data driver DD, respectively, to control the gate driver GD and the data driver DD.

[0052] The display panel PN is a configuration that displays an image to a user and includes a plurality of sub-pixels SP. In the display panel PN, a plurality of scan lines SL and a plurality of data lines DL intersect each other, and a plurality of sub-pixels SP are formed at the intersections of the scan lines SL and the data lines DL.

[0053] In the display panel PN, an active area AA and a non-active area NA can be defined.

[0054] The active area AA is an area where an image is displayed in the display device 100. In the active area AA, a plurality of sub-pixels SP configuring a plurality of pixels and a pixel circuit for driving the plurality of sub-pixels SP can be provided. The plurality of sub-pixels SP are the minimum units configuring the active area AA, and n sub-pixels SP can form one pixel. In each of the plurality of sub-pixels SP, a thin film transistor for driving a plurality of light emitting elements LED can be provided. Depending on the type of the display panel PN, the plurality of light emitting elements LED can be defined in different ways. For example, when the display panel PN is an inorganic light emitting display panel PN, the light emitting element LED can be a light emitting diode (LED) or a micro light emitting diode (LED).

[0055] In the active area AA, a plurality of signal lines for sending various signals to the plurality of sub-pixels SP are provided. For example, the plurality of signal lines can include a plurality of data lines DL for supplying a data voltage to each of the plurality of sub-pixels SP and a plurality of scan lines for supplying a scan signal to each of the plurality of sub-pixels SP. The plurality of scan lines SL extend in one direction in the active area AA to connect to the plurality of sub-pixels SP, and the plurality of data lines DL extend in a direction different from one direction in the active area AA to connect to the plurality of sub-pixels SP. In addition, in the active area AA, power lines can also be provided, but the present disclosure is not limited thereto.

[0056] The non-active area NA is an area where no image is displayed, so that the non-active area NA can be defined as an area extending from the active area AA. In the non-active area NA, link lines, pad electrodes, or driving ICs such as a gate driver IC or a data driver IC for sending signals to the sub-pixels SP of the active area AA can be provided.

[0057] Meanwhile, the non-active area NA can be located on the rear surface of the display panel PN, that is, on the surface where no sub-pixels SP are provided or sub-pixels SP can be omitted, and is not limited as shown in the drawings.

[0058] Meanwhile, drivers such as a gate driver GD, a data driver DD, and a timing controller TC can be connected to the display panel PN in various ways. For example, the gate driver GD can be mounted in the non-active area NA in a gate-in-panel (GIP) manner or between a plurality of sub-pixels SP in the active area AA in a gate-in-active-area (GIA) manner.

[0059] For example, a data driver DD and a timing controller TC are formed in separate flexible films and printed circuit boards, and the display panel PN can be electrically connected to the data driver DD and the timing controller TC by bonding the flexible film and the printed circuit board 110 to pad electrodes formed in a non-active region NA of the display panel PN.

[0060] As another example, when the gate driver GD is mounted in the active region AA in the GIA manner and the side line that connects signal lines on the front surface of the display panel PN to pad electrodes on the rear surface of the display panel PN is formed to bond the flexible film and the printed circuit board to the rear surface of the display panel PN, the non-active region NA can be minimized on the front surface of the display panel PN. That is, when the gate driver GD, the data driver DD, and the timing controller TC are connected to the display panel PN as described above, a zero bezel with substantially no bezel can be achieved.

[0061] Hereinafter, a plurality of sub-pixels SP will be described in more detail with reference to Figure 2A and Figure 2B FIGs.

[0062] Figure 2A is a schematic diagram of a sub-pixel of a display device according to an exemplary embodiment of the present disclosure. Figure 2B is an exemplary circuit diagram of a sub-pixel of a display device according to an exemplary embodiment of the present disclosure.

[0063] Referring to Figure 2A , the sub-pixel SP includes a light-emitting diode LED, a first circuit unit PC1 and a second circuit unit PC2 for driving the light-emitting diode LED, and a sense transistor SST. The sense transistor SST senses the threshold voltage difference between a first driving transistor DT1 of the first circuit unit PC1 and a second driving transistor DT2 of the second circuit unit PC2.

[0064] Specifically, the first circuit unit PC1 may be a pulse width modulation (PWM) circuit. The first circuit unit PC1 as a PWM circuit is a circuit that displays images with various gray levels by adjusting the pulse width of a driving current. The first circuit unit PC1 including the first driving transistor DT1 may adjust the pulse width of the driving current to be supplied to the light emitting diode LED based on the scan signal Vsweep, the first data voltage Vdata1, and the first scan signal SPWM. The first circuit unit PC1 may adjust the pulse width of the driving current differently according to the gray level of the image to adjust the emission period and gray level of the light emitting diode LED. At this time, the pulse width may be represented by the duty ratio of the driving current or the duration of the driving current. For example, when displaying an image with a low gray level, the first circuit unit PC1 shortens the pulse width of the driving current, such as shortening the duty ratio of the driving current or the output duration of the driving current, to reduce the emission period of the light emitting diode LED, thereby displaying an image with a low gray level. For example, when displaying an image with a high gray level, the first circuit unit PC1 increases the pulse width of the driving current, such as increasing the duty ratio of the driving current or the output duration of the driving current, to increase the emission period of the light emitting diode LED, thereby displaying an image with a high gray level.

[0065] The second circuit unit PC2 may be a pulse amplitude modulation (PAM) circuit. The second circuit unit PC2 as a PAM circuit is a circuit that displays images with various gray levels by adjusting the amplitude of a driving current. The second circuit unit PC2 including the second driving transistor DT2 may adjust the amplitude of the driving current to be supplied to the light emitting diode LED based on the second data voltage Vdata2 and the second scan signal SPAM. The second circuit unit PC2 adjusts the amplitude of the driving current, that is, the intensity of the driving current, differently according to the gray level of the image to adjust the emission period and gray level of the light emitting diode LED. For example, when displaying an image with a low gray level, the second circuit unit PC2 reduces the intensity of the driving current to reduce the brightness of the light emitted from the light emitting diode LED, and displays an image with a low gray level. On the contrary, when displaying an image with a high gray level, the second circuit unit PC2 increases the intensity of the driving current to increase the brightness of the light emitted from the light emitting diode LED, and displays an image with a high gray level.

[0066] The light emitting diode LED is connected to any one of the first circuit unit PC1 and the second circuit unit PC2 to be supplied with a driving current. The first circuit unit PC1 and the second circuit unit PC2 adjust the amplitude and pulse width of the driving current according to the image to be displayed, and the light emitting diode LED is supplied with the driving current from the first circuit unit PC1 and the second circuit unit PC2 to emit light. Even when Figure 2AIn [the figure], a light-emitting diode LED is shown connected between a second circuit unit PC2 and a first power line PL1. The light-emitting diode LED may also be connected to a first circuit unit PC1 or connected between the second circuit unit PC2 and a second power line PL2. However, the present disclosure is not limited thereto.

[0067] In addition, a sensing transistor SST of each of the plurality of sub-pixels SP may be connected to a first switch SPRE, a second switch SAM, a sampling capacitor Csam, and an analog-to-digital converter ADC. At least some of the first switch SPRE, the second switch SAM, the sampling capacitor Csam, and the analog-to-digital converter ADC may be configurations provided in a data driver DD. For example, the first switch SPRE, the second switch SAM, the sampling capacitor Csam, and the analog-to-digital converter ADC are provided in the data driver DD and may be connected to each of the plurality of sub-pixels SP. As another example, at least one of the first switch SPRE, the second switch SAM, and the sampling capacitor Csam is provided together with the sub-pixel SP in the display panel PN, and the remaining configurations may be provided in the data driver DD together with the analog-to-digital converter ADC.

[0068] The sensing transistor SST of the sub-pixel SP and the first switch SPRE, the second switch SAM, the sampling capacitor Csam, and the analog-to-digital converter ADC are configurations for sensing a change ΔVth in the threshold voltages of the first driving transistor DT1 and the second driving transistor DT2 to compensate for the threshold voltage difference of the plurality of sub-pixels SP. Therefore, the sensing transistor SST, the first switch SPRE, the second switch SAM, the sampling capacitor Csam, and the analog-to-digital converter ADC may be defined as a sensing unit PCS. Hereinafter, the description will be made by defining the sensing transistor SST, the first switch SPRE, the second switch SAM, the sampling capacitor Csam, and the analog-to-digital converter ADC as the sensing unit PCS, but it is not limited thereto.

[0069] Meanwhile, the first circuit unit PC1 including the first driving transistor DT1 includes at least one or more transistors and capacitors in addition to the first driving transistor DT1 to control the pulse width of the driving current. In addition, the second circuit unit PC2 including the second driving transistor DT2 includes at least one or more transistors and capacitors in addition to the second driving transistor DT2 to control the amplitude of the driving current.

[0070] Hereinafter, with reference to Figure 2B will refer to Figure 2B Describe exemplary circuit configurations of the first circuit unit PC1 and the second circuit unit PC2 of the sub-pixel SP.

[0071] With reference to Figure 2B, the first circuit unit PC1 may include a first driving transistor DT1, a first switching transistor ST1, and a first capacitor C1.

[0072] The first switching transistor ST1 of the first circuit unit PC1 is a transistor that is turned on by the first scan signal SPWM to send the first data voltage Vdata1 to the first driving transistor DT1. The gate electrode of the first switching transistor ST1 is connected to the first scan line, the source electrode of the first switching transistor ST1 is connected to the first data line, and the drain electrode of the first switching transistor ST1 is connected to the gate electrode of the first driving transistor DT1, which is the first node N1. The first switching transistor ST1 is turned on by the first scan signal SPWM to send the first data voltage Vdata1 to the gate electrode of the first driving transistor DT1.

[0073] The first driving transistor DT1 of the first circuit unit PC1 is a transistor that controls the duty cycle or output time of the driving current based on the first data voltage Vdata1 transmitted from the first switching transistor ST1. The gate electrode of the first driving transistor DT1 is connected to the first node N1, the source electrode of the first driving transistor DT1 is connected to the first power line PL1, and the drain electrode of the first driving transistor DT1 is connected to the second node N2. The driving current from the first driving transistor DT1 can be sent to the second circuit unit PC2.

[0074] The first capacitor C1 of the first circuit unit PC1 is a capacitor that sends the scan signal Vsweep of the scan line to the first node N1. The first capacitor C1 includes a plurality of capacitor electrodes, and some of the capacitor electrodes are connected to the scan line, while the remaining capacitor electrodes are connected to the gate electrode of the first driving transistor DT1, which is the first node N1. The scan signal Vsweep of the scan line is a linearly varying voltage. When the scan signal Vsweep is applied to one end of the first capacitor C1, a coupled voltage can be generated in the gate electrode of the first driving transistor DT1. Therefore, the voltage of the gate electrode of the first driving transistor DT1 is coupled to the scan signal Vsweep to decrease or increase, and the first driving transistor DT1 can be turned on or off.

[0075] The second circuit unit PC2 may include a second driving transistor DT2, a second switching transistor ST2, and a second capacitor C2.

[0076] The second switching transistor ST2 of the second circuit unit PC2 is a transistor that is turned on by the second scan signal SPAM to transmit the second data voltage Vdata2 to the second driving transistor DT2. The gate electrode of the second switching transistor ST2 is connected to the second scan line, the source electrode of the second switching transistor ST2 is connected to the second data line, and the drain electrode of the second switching transistor ST2 is connected to the gate electrode of the second driving transistor DT2 and the third node N3. The second switching transistor ST2 is turned on by the second scan signal SPAM to transmit the second data voltage Vdata2 to the gate electrode of the second driving transistor DT2.

[0077] The second driving transistor DT2 of the second circuit unit PC2 is a transistor that controls the intensity of the driving current based on the second data voltage Vdata2 transmitted from the second switching transistor ST2. The gate electrode of the second driving transistor DT2 is connected to the third node N3, the source electrode of the second driving transistor DT2 is connected to the light-emitting diode LED and the second node N2, and the drain electrode of the second driving transistor DT2 is connected to the second power line PL2. The second driving transistor DT2 is turned on to supply a driving current to the light-emitting diode LED.

[0078] The second capacitor C2 of the second circuit unit PC2 maintains the potential difference between the gate electrode and the source electrode of the second driving transistor DT2 when the light-emitting diode LED emits light, so as to supply a constant driving current to the light-emitting diode LED. The second capacitor C2 includes a plurality of capacitor electrodes, and some of the capacitor electrodes are connected to the source electrode of the second driving transistor DT2, the second node N2, and the light-emitting diode LED. The remaining capacitor electrodes are connected to the gate electrode of the second driving transistor DT2 and the third node N3.

[0079] The sensing unit PCS is a compensation unit that senses the threshold voltages of the first driving transistor DT1 of the first circuit unit PC1 and the second driving transistor DT2 of the second circuit unit PC2 to compensate for the brightness difference between the plurality of sub-pixels SP. The sensing unit PCS can sense the threshold voltage changes ΔVth of the first driving transistor DT1 and the second driving transistor DT2. The data driver DD can compensate the first data voltage Vdata1 and the second data voltage Vdata2 applied to the first circuit unit PC1 and the second circuit unit PC2 respectively based on the sensing result.

[0080] The sense transistor SST senses the threshold voltages of the first driving transistor DT1 and the second driving transistor DT2 to compensate for the threshold voltage difference between the first driving transistor DT1 and the second driving transistor DT2 in each of the plurality of sub-pixels SP. The gate electrode of the sense transistor SST is connected to the sense line, the source electrode of the sense transistor SST is connected to the second node N2, and the drain electrode of the sense transistor SST is connected to the fourth node N4. The sense transistor SST is turned on by a sense signal SENSE from the sense line to electrically connect the reference line or the analog-to-digital converter ADC to the second node N2.

[0081] The first switch SPRE is a switch that connects the sense transistor SST and the reference line. The first switch SPRE can be provided between the fourth node N4 and the reference line. In the beginning part of the sensing period, the sense transistor SST and the reference line can be connected through the first switch SPRE, and the second node N2 can be initialized to the reference voltage Vref.

[0082] The second switch SAM is a switch that connects the sense transistor SST and the analog-to-digital converter ADC. The second switch SAM can be provided between the fourth node N4 and the analog-to-digital converter. In the latter half of the sensing period, the second switch SAM can connect the sense transistor SST and the analog-to-digital converter ADC, and can send the sense voltage Vsen to the analog-to-digital converter ADC.

[0083] The analog-to-digital converter ADC is configured to sense the sense voltage Vsen to calculate the threshold voltage change ΔVth. The analog-to-digital converter ADC can convert the analog sense voltage Vsen into digital data. Therefore, the data driver DD calculates the threshold voltage change ΔVth based on the digital data, and can generate compensation data to compensate for the threshold voltage difference.

[0084] The sampling capacitor Csam can charge the voltage of the fourth node N4, that is, the voltage of the second node N2 sent to the fourth node N4 through the sense transistor SST. When the second switch SAM is turned on to connect the analog-to-digital converter ADC and the fourth node N4, the analog-to-digital converter ADC can convert the voltage stored in the sampling capacitor Csam into a digital signal.

[0085] Next, the light-emitting diode LED is connected between the first power line PL1 and the second circuit unit PC2. The light-emitting diode LED can use various components according to the type of the display device 100 and can be, for example, a micro light-emitting diode (LED). The light-emitting diode LED includes an anode and a cathode. The anode of the light-emitting diode LED is connected to the first power line PL1, and the cathode is connected to the source electrode of the second driving transistor DT2 of the second circuit unit PC2. The light-emitting diode LED can emit light based on the driving current flowing from the first power line PL1 to the second driving transistor DT2 and the second power line PL2.

[0086] The first power line PL1 is a wiring for supplying the high-potential power voltage VDD and the low-potential power voltage VSS to the sub-pixel SP, and the second power line PL2 is a wiring for supplying the low-potential power voltage VSS to the sub-pixel SP. The first power line PL1 supplies the low-potential power voltage VSS to the sub-pixel SP during the sensing period and can supply the high-potential power voltage VDD to the sub-pixel during the remaining period other than the sensing period. Regardless of the sensing period, the second power line PL2 can always supply the low-potential power voltage VSS to the sub-pixel SP.

[0087] Meanwhile, according to the related art, the threshold voltage differences of the first driving transistor and the second driving transistor are sequentially sensed. A sensing transistor for detecting the first threshold voltage change of the first driving transistor and a sensing transistor for detecting the second threshold voltage change of the second driving transistor are respectively provided. In addition, the period for detecting the first threshold voltage change and the period for detecting the second threshold voltage change are set to different timings to detect the threshold voltage change. Therefore, the threshold voltage change of the first driving transistor and the threshold voltage change of the second driving transistor are sensed in different periods, such that the sensing period increases, and two or more sensing transistors are required. However, there is a problem in that it is difficult to ensure a sufficient sensing period for one frame and the structure of the display device for placing multiple sensing transistors is complex.

[0088] Accordingly, in the display device 100 according to an exemplary embodiment of the present disclosure, the sensing unit PCS includes only one sensing transistor SST. One sensing transistor can sense the threshold voltage change ΔVth of the first driving transistor DT1 and the threshold voltage change ΔVth of the second driving transistor DT2 simultaneously. In addition, the data driver DD can compensate for the threshold voltage difference between the first driving transistor DT1 and the second driving transistor DT2 based on the sensing result and the predicted information of the threshold voltage change ΔVth stored in the memory. Accordingly, the length of the sensing period in one frame is shortened, and the sensing process can be simplified. Accordingly, in the display device 100 according to an exemplary embodiment of the present disclosure, the threshold voltage difference of each of the plurality of sub-pixels is compensated based on the threshold voltage change ΔVth of the driving transistor and the predicted information. In addition, the brightness difference between the plurality of sub-pixels SP of the display device 100 can be reduced.

[0089] Hereinafter, Figures 3 to 6 a method for compensating the brightness difference of the display device 100 according to an exemplary embodiment of the present disclosure will be described with reference to

[0090] Figure 3 is a flowchart for explaining a method for compensating the brightness difference of a display device according to an exemplary embodiment of the present disclosure. Figure 4 is a driving timing diagram of sub-pixels of a display device for a sensing period according to an exemplary embodiment of the present disclosure. Figure 5 is a graph showing the change in the sensing voltage of a driving transistor of a display device over time according to an exemplary embodiment of the present disclosure. Figure 6 is a graph showing the change in the threshold voltage of a driving transistor of a display device over bias stress and time according to an exemplary embodiment of the present disclosure.

[0091] With reference to Figure 3 and Figure 5 , the sensing unit PCS is used to measure the sensing voltage change ΔVsen. The sensing unit PCS can be used to detect the voltage of the second node N2 during the sensing period, i.e., the sensing voltage Vsen. The sensing voltage Vsen is a voltage that reflects the threshold voltage of the first driving transistor DT1 and the threshold voltage of the second driving transistor DT2, and the threshold voltage can be detected based on the difference between the sensing voltage Vsen and the reference voltage Vref.

[0092] Hereinafter, the threshold voltage of the first driving transistor DT1 will be referred to as the first threshold voltage, and the threshold voltage of the second driving transistor DT2 will be referred to as the second threshold voltage.

[0093] With reference to Figure 2B and Figure 4, a low-potential power voltage VSS is output from the first power line PL1 during the sensing period. Thus, the light-emitting diode LED having an anode connected to the first power line PL1 does not emit light during the sensing period. In addition, the threshold voltage change of the first driving transistor DT1 can be sensed by causing current to flow from the second node N2 through the first driving transistor DT1 to the first power line PL1.

[0094] First, at a first time t1 of the sensing period, the conductive levels of the first scan signal SPMW and the second scan signal SPAM are applied to the sub-pixel SP. The first switching transistor ST1 can be turned on by the first scan signal SPMW, and the first data voltage Vdata1 for sensing can be applied to the gate electrode of the first driving transistor DT1 by means of the first switching transistor ST1. In addition, the second switching transistor ST2 can be turned on by the second scan signal SPAM. The second data voltage Vdata2 for sensing can be applied to the gate electrode of the second driving transistor DT2 by means of the second switching transistor ST2. Thus, at the first time t1, the data voltages Vdata1 and Vdata2 for sensing are applied to the gate electrode of the first driving transistor DT1 and the gate electrode of the second driving transistor DT2 to turn on the first driving transistor DT1 and the second driving transistor DT2.

[0095] At the first time t1, the conductive level of the sensing voltage Vsen is applied to the sub-pixel SP through the sensing line. Thus, the sensing transistor SST can be kept in an on state during the sensing period by the sensing voltage Vsen applied to the gate electrode.

[0096] In addition, at the first time t1, the first switch SPRE is turned on to supply the reference voltage Vref to the fourth node N4. Thus, the reference voltage Vref can be charged from the reference line into the second node N2 by means of the turned-on first switch SPRE and the sensing transistor SST. Thus, the voltages of the drain electrode of the first driving transistor DT1 and the source electrode of the second driving transistor DT2 can be set to the reference voltage Vref.

[0097] Thus, at the first time t1, current flows from the first driving transistor DT1 to the first power line PL1 through the first data voltage Vdata1 for sensing applied to the gate electrode of the first driving transistor DT1 and the reference voltage Vref applied at the drain electrode. Similarly, at the first time t1, current can flow from the second driving transistor DT2 to the second power line PL2 through the second data voltage Vdata2 for sensing applied to the gate electrode of the second driving transistor DT2 and the reference voltage Vref applied at the source electrode.

[0098] Next, the first switch SPRE is turned off at the second time t2 to float the second node N2. In addition, current flows from the second node N2 to the first driving transistor DT1 and the first power line PL1, and current flows to the second driving transistor DT2 and the second power line PL2, so that the voltage of the second node N2 can be reduced.

[0099] The current flowing through the first driving transistor DT1 can flow until the voltage difference between the gate electrode and the drain electrode of the first driving transistor DT1 becomes the first threshold voltage. The current flows through the first driving transistor DT1 so that the voltage of the drain electrode can be reduced. When the difference between the voltage of the drain electrode and the first data voltage Vdata1 for sensing of the gate electrode is the first threshold voltage, the first driving transistor DT1 is turned off so that the current does not flow, and the voltage of the drain electrode can converge to the first sensing voltage Vsen1.

[0100] The current flowing through the second driving transistor DT2 can flow until the voltage difference between the gate electrode and the drain electrode of the second driving transistor DT2 becomes the second threshold voltage. The current flows through the second driving transistor DT2 so that the voltage of the source electrode can be reduced. When the difference between the voltage of the source electrode and the second data voltage Vdata2 for sensing of the gate electrode becomes the second threshold voltage, the second driving transistor DT2 is turned off so that the current does not flow, and the voltage of the source electrode can converge to the second sensing voltage Vsen2.

[0101] At this time, the voltage of the second node N2 connected to both the drain electrode of the first driving transistor DT1 and the source electrode of the second driving transistor DT2 can be the relatively higher one of the first sensing voltage Vsen1 and the second sensing voltage Vsen2. In addition, the first sensing voltage Vsen1 from the first driving transistor DT1 having a relatively low threshold voltage change ΔVth can have a higher value than the second sensing voltage Vsen2.

[0102] Specifically, the second driving transistor DT2 among the first driving transistor DT1 and the second driving transistor DT2 can supply more driving current to the light-emitting diode LED. More current can flow through the second driving transistor DT2 than through the first driving transistor DT1. Therefore, when driving the display device 100, the change in the second threshold voltage of the second driving transistor DT2 through which more current flows should be higher than the change in the first threshold voltage of the first driving transistor DT1. Therefore, as more current flows from the source electrode of the second driving transistor DT2 to the second power line PL2, the voltage of the source electrode of the second driving transistor DT2 may be reduced more than the voltage of the drain electrode of the first driving transistor DT1. In addition, the second sensing voltage Vsen2 can be lower than the first sensing voltage Vsen1. Therefore, the voltage of the second node N2 can be the first sensing voltage Vsen1 having a relatively high value.

[0103] Next, the second switch SAM is turned on at the third time t3. When the second switch SAM is turned on, the analog-to-digital converter ADC can be connected to the drain electrode of the sensing transistor SST of the sub-pixel SP serving as the fourth node N4. At this time, the sensing transistor SST can send the first sensing voltage Vsen1 of the second node N2 to the fourth node N4 in the on state. Accordingly, the analog-to-digital converter ADC detects the first sensing voltage Vsen1 sent to the fourth node N4 through the sensing transistor SST to finally measure the change in the sensing voltage ΔVsen. The change in the sensing voltage ΔVsen can be confirmed based on the difference between the reference voltage Vref initially applied to the second node N2 and the first sensing voltage Vsen1. That is, the initial sensing voltage Vsen is the reference voltage Vref, and the finally measured sensing voltage Vsen is the first sensing voltage Vsen1, such that the difference between the reference voltage Vref and the first sensing voltage Vsen1 can become the change in the sensing voltage ΔVsen.

[0104] For example, referring to Figure 5 , the first sensing voltage Vsen1 from the first driving transistor DT1 is higher than the second sensing voltage Vsen2 from the second driving transistor DT2. Accordingly, the change in the sensing voltage ΔVsen of the first driving transistor DT1 can be smaller than the change in the sensing voltage ΔVsen of the second driving transistor DT2. In addition, at the third time t3 when the second switch SAM is turned on, the analog-to-digital converter ADC can sense the value A of the change in the sensing voltage ΔVsen of the first driving transistor DT1.

[0105] Next, referring to Figure 3 , the data driver DD calculates the change in the first threshold voltage ΔVth1 of the first driving transistor DT1 based on the value A of the change in the sensing voltage ΔVsen. The change in the sensing voltage ΔVsen is the differential voltage between the reference voltage Vref and the first sensing voltage Vsen1, and the first sensing voltage Vsen1 is a voltage reflecting the first threshold voltage of the first driving transistor DT1 and the reference voltage Vref. Accordingly, the change in the first threshold voltage ΔVth1 can be calculated based on the value A of the change in the sensing voltage ΔVsen and the reference voltage Vref.

[0106] However, it may be difficult to calculate the change in the second threshold voltage ΔVth2 of the second driving transistor DT2 based on the change in the sensing voltage ΔVsen. In other words, based on the change in the sensing voltage ΔVsen, only the change in the first threshold voltage ΔVth1 of the first driving transistor DT1 can be calculated. Accordingly, in the display device 100 according to an exemplary embodiment of the present disclosure, the change in the second threshold voltage ΔVth2 can be calculated based on the change in the first threshold voltage ΔVth1 and the prediction information stored in the memory.

[0107] Specifically, referring to Figure 3 and Figure 6 , the second threshold voltage change ΔVth2 of the second driving transistor DT2 can be calculated based on the first threshold voltage change ΔVth1 of the first driving transistor DT1 calculated according to the value A of the sensed voltage change ΔVsen and the prediction information stored in the memory. The prediction information is information about the difference between the first threshold voltage change ΔVth1 and the second threshold voltage change ΔVth2 according to the bias stress and time. The first threshold voltage change ΔVth1 of the first driving transistor DT1 and the second threshold voltage change ΔVth2 of the second driving transistor DT2 according to the bias stress and time can be calculated based on a plurality of samples. In addition, the difference information between the first threshold voltage change ΔVth1 and the second threshold voltage change ΔVth2 is stored in the memory based on its average value. For example, in the memory, the difference between the first threshold voltage change ΔVth1 and the second threshold voltage change ΔVth2 according to the bias stress and time can be stored in the memory as a look-up table. Therefore, the second threshold voltage change ΔVth2 can be calculated based on the prediction information of the second threshold voltage change ΔVth2 obtained according to the bias stress and time of the image displayed in the display device 100.

[0108] The bias stress is the stress generated when a voltage is applied to the gate electrode of the transistor. When a voltage is applied to the gate electrodes of the first driving transistor DT1 and the second driving transistor DT2, the first driving transistor DT1 and the second driving transistor DT2 may deteriorate. In addition, the voltages applied to the gate electrodes of the first driving transistor DT1 and the second driving transistor DT2 can change according to the displayed image, which can change the bias stress. For example, as the bias stress applied to the gate electrodes of the first driving transistor DT1 and the second driving transistor DT2 increases, the deterioration of the first driving transistor DT1 and the second driving transistor DT2 accelerates to increase the threshold voltage change ΔVth. The greater the voltage applied to the gate electrode of the first driving transistor DT1, the greater the first threshold voltage change ΔVth1 of the first driving transistor DT1. Similarly, the greater the voltage applied to the gate electrode of the second driving transistor DT2, the greater the second threshold voltage change ΔVth2 of the second driving transistor DT2.

[0109] In addition, as the time of applying the bias stress increases, the deterioration of the first driving transistor DT1 and the second driving transistor DT2 may accelerate. For example, compared with the case where the voltage is applied to the gate electrode of the first driving transistor DT1 for one hour, when the voltage is applied to the gate electrode of the first driving transistor DT1 for ten hours, the first threshold voltage change ΔVth1 may increase.

[0110] Therefore, when a bias stress with a specific voltage is applied, the difference between the first threshold voltage change ΔVth1 of the first driving transistor DT1 and the second threshold voltage change ΔVth2 of the second driving transistor DT2 can be stored as prediction information according to the application time of the bias stress. For example, when the display device 100 displays an image with gray levels from 0 to 255, the voltages applied to the gate electrodes at each of the gray levels from 0 to 255 and the threshold voltage change ΔVth according to the voltage application time are extracted from a plurality of samples. The results are organized into a look-up table and stored in a memory.

[0111] Next, referring to Figure 3 , the difference B between the first threshold voltage change ΔVth1 and the second threshold voltage change ΔVth2 extracted from the memory by means of data counting is determined. The image displayed on the display device 100 is analyzed by means of the data voltage and data counting for displaying the image, and the data voltage application time can be stored in the memory. In order to display a specific image by means of data counting, after detecting the data voltages applied to the gate electrodes of the first driving transistor DT1 and the second driving transistor DT2 and the application time of the data voltages, information can be pre-stored in the memory. The image displayed on the display device 100 is analyzed to calculate the degradation level of the second driving transistor DT2, that is, the predicted value of the second threshold voltage transformation ΔVth2.

[0112] Next, among the differences between the first threshold voltage change ΔVth1 and the second threshold voltage change ΔVth2 stored in the memory look-up table, the difference B corresponding to the data voltage pre-stored in the memory by means of data counting and the application time of the data voltage can be extracted. For example, when the first data voltage Vdata1 and the second data voltage Vdata2 of mV are applied to the memory for n seconds by means of data counting, if a bias stress of mV is applied for n seconds in the look-up table, the difference B between the first threshold voltage change ΔVth1 and the second threshold voltage change ΔVth2 can be extracted. In addition, the second threshold voltage change ΔVth2 of the second driving transistor DT2 can be calculated by adding the difference value B to the first threshold voltage change ΔVth1 of the first driving transistor DT1 calculated according to the value A of the sensed voltage change ΔVsen.

[0113] For example, when a first data voltage Vdata1 and a second data voltage Vdata2 of mV are applied for n seconds to display an image in the display device 100, prediction information on a first threshold voltage change ΔVth1 and prediction information on a second threshold voltage change ΔVth2 for the data voltage of mV and the application time of n seconds can be confirmed from a look-up table. Further, when the data voltage of mV stored in the prediction information in the look-up table is applied for n seconds, if the first threshold voltage change ΔVth1 is 1V and the second threshold voltage change ΔVth2 is 2V, the difference B can be 1V. That is, it can be confirmed from the prediction information that when the data voltage of mV is applied for one minute, the second threshold voltage change ΔVth2 is 1V greater than the first threshold voltage change ΔVth1. In fact, when the data voltage of mV is applied for n minutes to display an image on the display device 100, it can be predicted from the prediction information that the second threshold voltage change ΔVth2 is 1V greater than the first threshold voltage change ΔVth1. Therefore, when the difference B is added to the first threshold voltage change ΔVth1 calculated based on the value A of the sensed voltage change ΔVsen, the second threshold voltage change ΔVth2 can be predicted.

[0114] Finally, in the next frame, the first data voltage Vdata1 is compensated based on the first threshold voltage change ΔVth1, and the compensated first data voltage Vdata1 can be applied to the first circuit unit PC1 of the sub-pixel SP. In addition, in the next frame, the second data voltage Vdata2 is compensated based on the second threshold voltage change ΔVth2, and the compensated second data voltage Vdata2 can be applied to the second circuit unit PC2 of the sub-pixel SP. The compensated first data voltage Vdata1 is a voltage for compensating the difference in the first threshold voltage change ΔVth1 for each of the plurality of sub-pixels SP, and can vary according to the first threshold voltage change ΔVth1. For example, the compensated first data voltage Vdata1 applied to each of the sub-pixels SP having a relatively high first threshold voltage change ΔVth1 and the sub-pixels SP having a relatively low first threshold voltage change ΔVth1 can be different. In addition, the compensated second data voltage Vdata2 is a voltage for compensating the difference in the second threshold voltage change ΔVth2 for each of the plurality of sub-pixels SP, and can vary according to the second threshold voltage change ΔVth2. For example, the compensated second data voltage Vdata2 applied to each of the sub-pixels SP having a relatively high second threshold voltage change ΔVth2 and the sub-pixels SP having a relatively low second threshold voltage change ΔVth2 can be different. Therefore, the luminance difference according to the difference in the first threshold voltage change ΔVth1 and the difference in the second threshold voltage change ΔVth2 can be reduced by applying the compensated first data voltage Vdata1 and the compensated second data voltage Vdata2 to each of the plurality of sub-pixels SP.

[0115] Therefore, in the display device 100 according to an exemplary embodiment of the present disclosure, first, a sensing unit PCS including one sensing transistor SST is used to calculate a first threshold voltage change ΔVth1. A predicted value of a second threshold voltage change ΔVth2 is calculated based on the first threshold voltage change ΔVth1 and prediction information to reduce the luminance difference between a plurality of sub-pixels SP. Specifically, one sensing transistor SST is connected to a first driving transistor DT1 and a second driving transistor DT2. A sensing voltage change ΔVsen reflecting the threshold voltage changes ΔVth of the first driving transistor DT1 and the second driving transistor DT2 can be detected by means of the sensing transistor SST. At this time, the second driving transistor DT2 transmits relatively more current, such that a second sensing voltage Vsen2 of the second driving transistor DT2 is lower than a first sensing voltage Vsen1 of the first driving transistor DT1. In addition, the sensing voltage Vsen sensed by the sensing transistor SST can become a first sensing voltage Vsen1 having a relatively high value. Therefore, a value A of the sensing voltage change ΔVsen is calculated according to a difference between the first sensing voltage Vsen1 and a reference voltage Vref, and the first threshold voltage change ΔVth1 can be calculated according to the value A. In addition, the second threshold voltage change ΔVth2 can be derived by adding the first threshold voltage change ΔVth1 and a difference B between the first threshold voltage change ΔVth1 and the second threshold voltage change ΔVth2 according to the bias stress and time for the displayed image to calculate a predicted value. Therefore, only one sensing transistor SST is provided in the sub-pixel SP, and prediction information of a relative difference between the first threshold voltage change ΔVth1 and the second threshold voltage change ΔVth2 according to the bias stress and time is pre-stored in a memory. In this way, both the first threshold voltage change ΔVth1 and the second threshold voltage change ΔVth2 can be calculated. In addition, the second threshold voltage change ΔVth2 is calculated according to the first threshold voltage change ΔVth1, such that a sensing period for the first driving transistor DT1 and a sensing period for the second driving transistor DT2 can be combined into one without being separately provided. Therefore, the structure of the sensing unit PCS is simplified, and the sensing period is shortened to increase the compensation power. In addition, at least one sensing transistor SST is provided in the sub-pixel SP, such that the number of sensing transistors SST and wirings for driving the sensing transistors is reduced as a whole. In addition, since some wirings and transistors are deleted, a plurality of driving transistors can be more easily formed in the sub-pixel SP, and a high-resolution display device 100 can be realized.

[0116] The exemplary embodiments of the present disclosure can also be described as follows:

[0117] According to one aspect of the present disclosure, a display device may include a display panel including a plurality of sub-pixels; a data driver connected to the display panel; a first circuit unit disposed in each of the plurality of sub-pixels and including a first driving transistor; a second circuit unit disposed in each of the plurality of sub-pixels and including a second driving transistor; and a sensing transistor connected to a drain electrode of the first driving transistor and a source electrode of the second driving transistor. The plurality of sub-pixels are configured to be driven in an emission period and a sensing period, and the sensing transistor is configured to detect a larger one of a first sensing voltage of the drain electrode of the first driving transistor and a second sensing voltage of the source electrode of the second driving transistor that overlap each other in time.

[0118] The display device may further include: a first power line connected to a source electrode of the first driving transistor; and a second power line connected to a drain electrode of the second driving transistor. The first power line may supply a low-potential power voltage during the sensing period and a high-potential power voltage during the emission period, and the second power line may supply a low-potential power voltage during the sensing period and the emission period.

[0119] During the sensing period, current may flow from the first driving transistor to the first power line, and current may flow from the second driving transistor to the second power line.

[0120] The sensing transistor may be connected to the data driver, the data driver may detect a change in the sensing voltage from the sensing transistor during the sensing period, and the change in the sensing voltage may be a difference between the first sensing voltage and a reference voltage.

[0121] A change in a first threshold voltage of the first driving transistor may be less than a change in a second threshold voltage of the second driving transistor.

[0122] The display device may further include a light-emitting diode electrically connected to the source electrode of the second driving transistor.

[0123] The change in the second threshold voltage may be a value obtained by adding prediction information to the change in the first threshold voltage, and the prediction information may be a difference between the change in the first threshold voltage and the change in the second threshold voltage according to bias stress and time.

[0124] According to one aspect of the present disclosure, a method for compensating a brightness difference of a display device includes: measuring a change in a sensed voltage at a node between a drain electrode of a first driving transistor and a source electrode of a second driving transistor of a sub-pixel, calculating a first threshold voltage change of the first driving transistor according to the change in the sensed voltage, calculating a second threshold voltage change of the second driving transistor according to the first threshold voltage change and prediction information; compensating a first data voltage based on the first threshold voltage change to apply the compensated first data voltage to the first driving transistor; and compensating a second data voltage based on the second threshold voltage change to apply the compensated second data voltage to the second driving transistor, where the prediction information is a difference between the first threshold voltage change and the second threshold voltage change according to a bias stress and time.

[0125] Measuring the change in the sensed voltage may include: initializing the node with a reference voltage; allowing current to flow from the node to the first driving transistor by turning on the first driving transistor; allowing current to flow from the node to the second driving transistor by turning on the second driving transistor, and measuring the voltage of the node as the sensed voltage after turning off the first driving transistor and the second driving transistor, and the change in the sensed voltage may be a difference between the reference voltage and the sensed voltage.

[0126] The first threshold voltage change of the first driving transistor may be less than the second threshold voltage change, and the second threshold voltage change of the second driving transistor and the sensed voltage may be a first sensed voltage between a first sensed voltage of the first driving transistor and a second sensed voltage of the second driving transistor.

[0127] The method for compensating the brightness difference of the display device may further include: extracting prediction information from a memory by means of data counting, where the data counting may include analyzing an image displayed on the display device to detect data voltages applied to the first driving transistor and the second driving transistor and application times of the data voltages, and the prediction information may be a difference between the first threshold voltage change and the second threshold voltage change corresponding to the data voltages and application times detected by means of data counting.

[0128] Calculating the second threshold voltage change may include calculating the second threshold voltage change by adding the first threshold voltage change and the prediction information.

[0129] According to another aspect of the present disclosure, a display device includes: a display panel in which a plurality of sub-pixels are defined, each of the plurality of sub-pixels including: a first circuit unit including a first driving transistor; a second circuit unit including a second driving transistor, the second circuit unit being connected to the first circuit unit; and a sensing transistor connected to the first driving transistor and the second driving transistor.

[0130] Each of the plurality of sub-pixels may further include a light-emitting diode having a cathode connected to a second driving transistor of the second circuit unit, and the light-emitting diode may be configured to be supplied with driving current from the first circuit unit and the second circuit unit.

[0131] The first circuit unit may be a pulse width modulation (PWM) circuit configured to control the pulse width of the driving current, and the second circuit unit may be a pulse amplitude modulation (PAM) circuit configured to control the amplitude of the driving current.

[0132] The display device may further include: a data driver connected to the display panel, and the sensing transistor may be configured to simultaneously send a first sensing voltage from the first driving transistor and a second sensing voltage from the second driving transistor to the data driver.

[0133] The display panel may further include: a first power line connected to the anode of the first driving transistor and the light-emitting diode; and a second power line connected to the drain electrode of the second driving transistor, and the same power voltage may be applied to the first power line and the second power line during a period when the sensing transistor sends the first sensing voltage and the second sensing voltage to the data driver, and different power voltages may be applied to the first power line and the second power line during a period when the light-emitting diode emits light.

[0134] According to still another aspect of the present disclosure, a display device includes: a display panel including a plurality of sub-pixels; a data driver connected to the display panel; a first circuit unit provided in each of the plurality of sub-pixels and including a first driving transistor; a second circuit unit provided in each of the plurality of sub-pixels and including a second driving transistor; and a sensing unit configured to sense threshold voltages of the first driving transistor of the first circuit unit and the second driving transistor of the second circuit unit to compensate for a brightness difference between the plurality of sub-pixels, wherein the sensing unit includes only one sensing transistor.

[0135] According to still another aspect of the present disclosure, a display device includes: a display panel including a plurality of sub-pixels; a data driver connected to the plurality of sub-pixels; a sensing unit connected to the data driver, wherein each of the plurality of sub-pixels includes: a light-emitting device; a first driving transistor having a drain terminal connected to a first electrode of the light-emitting device; a second driving transistor having a source terminal connected to the first electrode of the light-emitting device; and wherein the sensing unit is connected to detect a voltage at the first electrode of the light-emitting device.

[0136] The sensing unit may include: a sensing transistor connected between the node and the first electrode of the light-emitting device; and a first transistor connected between the node and the reference voltage terminal.

[0137] The sensing unit may include a capacitor connected to the node.

[0138] Although the exemplary embodiments of the present disclosure have been described in detail with reference to the accompanying drawings, the present disclosure is not limited thereto and may be embodied in many different forms without departing from the technical concept of the present disclosure. Therefore, the exemplary embodiments of the present disclosure are provided for illustrative purposes only and are not intended to limit the technical concept of the present disclosure. The scope of the technical concept of the present disclosure is not limited thereto. Therefore, it should be understood that the above exemplary embodiments are illustrative in all respects and do not limit the present disclosure. All technical concepts within the equivalent scope of the present disclosure should be construed as falling within the scope of the present disclosure.

Claims

1. A display device, comprising: A display panel, the display panel comprising a plurality of sub-pixels; a data driver connected to the display panel; a first circuit unit disposed in each of the plurality of sub-pixels and including a first driving transistor; a second circuit unit disposed in each of the plurality of sub-pixels and including a second driving transistor; as well as a sensing transistor connected to a drain electrode of the first driving transistor and a source electrode of the second driving transistor, wherein the plurality of sub-pixels are configured to be driven during an emission period and a sensing period, and the sensing transistor is configured to detect the larger of a first sensing voltage of the drain electrode of the first driving transistor and a second sensing voltage of the source electrode of the second driving transistor that overlap with each other in time.

2. The display device according to claim 1, further comprising: a first power line connected to a source electrode of the first drive transistor; as well as a second power line connected to a drain electrode of the second driving transistor; The first power line supplies a low potential power voltage during the sensing period and a high potential power voltage during the transmitting period, and the second power line supplies the low potential power voltage during the sensing period and the transmitting period.

3. The display device according to claim 2, wherein: During the sensing period, current flows from the first drive transistor to the first power line, and current flows from the second drive transistor to the second power line.

4. The display device according to claim 2, wherein: The sensing transistor is connected to the data driver, the data driver detects a sensing voltage variation from the sensing transistor during the sensing period, and the sensing voltage variation is a difference between the first sensing voltage and a reference voltage.

5. The display device according to claim 4, wherein: A first threshold voltage variation of the first driving transistor is smaller than a second threshold voltage variation of the second driving transistor.

6. The display device according to claim 5, further comprising: A light emitting diode is electrically connected to the source electrode of the second driving transistor.

7. The display device according to claim 5, wherein: The second threshold voltage variation is a value obtained by adding prediction information to the first threshold voltage variation, and the prediction information is a difference between the first threshold voltage variation and the second threshold voltage variation according to bias stress and time.

8. A method for compensating brightness difference of a display device, comprising: measuring a sense voltage change at a node between a drain electrode of a first drive transistor and a source electrode of a second drive transistor of a subpixel; calculating a first threshold voltage change of the first driving transistor according to the sensing voltage change; Calculating a second threshold voltage change of the second driving transistor according to the first threshold voltage change and prediction information; compensating a first data voltage based on the first threshold voltage change to apply the compensated first data voltage to the first driving transistor; as well as compensating a second data voltage based on the second threshold voltage change to apply the compensated second data voltage to the second driving transistor, The prediction information is a difference between the first threshold voltage change and the second threshold voltage change according to bias stress and time.

9. The brightness difference compensation method of a display device according to claim 8, wherein: The measuring of the sensing voltage change comprises: Initializing the node using a reference voltage; allowing current to flow from the node to the first drive transistor by turning on the first drive transistor; allowing current to flow from the node to the second drive transistor by turning on the second drive transistor; and measuring a voltage of the node as a sensing voltage after turning off the first driving transistor and the second driving transistor, The sensing voltage variation is a difference between the reference voltage and the sensing voltage.

10. The brightness difference compensation method of a display device according to claim 9, wherein: The first threshold voltage variation of the first driving transistor is smaller than the second threshold voltage variation of the second driving transistor, and the sensing voltage is the first sensing voltage between a first sensing voltage of the first driving transistor and a second sensing voltage of the second driving transistor.

11. The brightness difference compensation method of a display device according to claim 10, further comprising: extracting the prediction information from the memory by means of the data count, wherein the data counting includes analyzing an image displayed on the display device to detect a data voltage applied to the first driving transistor and the second driving transistor and an application time of the data voltage, and The prediction information is a difference between the first threshold voltage variation and the second threshold voltage variation corresponding to the data voltage detected by means of the data count and the application time.

12. The brightness difference compensation method of a display device according to claim 11, wherein: The calculating of the second threshold voltage variation includes calculating the second threshold voltage variation by adding the first threshold voltage variation and the prediction information.

13. A display device, comprising: a display panel, in which a plurality of sub-pixels are defined, Wherein, each of the plurality of sub-pixels comprises: A first circuit unit including a first driving transistor; a second circuit unit including a second driving transistor, the second circuit unit being connected to the first circuit unit; and A sense transistor connected to the first drive transistor and the second drive transistor.

14. The display device according to claim 13, wherein: Each of the plurality of sub-pixels further includes a light emitting diode having a cathode connected to the second driving transistor of the second circuit unit, and The light emitting diode is configured to be supplied with a driving current from the first circuit unit and the second circuit unit.

15. The display device according to claim 14, wherein: The first circuit unit is a pulse width modulation (PWM) circuit configured to control a pulse width of the driving current, and the second circuit unit is a pulse amplitude modulation (PAM) circuit configured to control an amplitude of the driving current.

16. The display device according to claim 14, further comprising: a data driver connected to the display panel, The sensing transistor is configured to simultaneously send a first sensing voltage from the first driving transistor and a second sensing voltage from the second driving transistor to the data driver.

17. The display device according to claim 16, wherein: The display panel further includes: a first power line connected to a source electrode of the first driving transistor and an anode of the light emitting diode; and a second power line connected to a drain electrode of the second driving transistor, and The same power voltage is applied to the first power line and the second power line during a period in which the sensing transistor sends the first sensing voltage and the second sensing voltage to the data driver, and different power voltages are applied to the first power line and the second power line during a period in which the light emitting diode emits light.

18. A display device comprising: A display panel, the display panel comprising a plurality of sub-pixels; a data driver connected to the display panel; a first circuit unit disposed in each of the plurality of sub-pixels and including a first driving transistor; a second circuit unit disposed in each of the plurality of sub-pixels and including a second driving transistor; as well as a sensing unit configured to sense threshold voltages of the first driving transistor of the first circuit unit and the second driving transistor of the second circuit unit to compensate for brightness differences between the plurality of sub-pixels, Wherein, the sensing unit includes only one sensing transistor.

19. A display device comprising: A display panel, the display panel comprising a plurality of sub-pixels; a data driver connected to the plurality of sub-pixels; a sensing unit connected to the data driver, Wherein, each of the plurality of sub-pixels comprises: Light emitting device; a first driving transistor, wherein a drain terminal of the first driving transistor is connected to a first electrode of the light emitting device; a second driving transistor having a source terminal connected to the first electrode of the light emitting device; and Wherein, the sensing unit is connected to detect the voltage at the first electrode of the light emitting device.

20. The display device according to claim 19, wherein: The sensing unit comprises: a sensing transistor connected between a node and the first electrode of the light emitting device; and A first transistor is connected between the node and a reference voltage terminal.

21. The display device according to claim 20, wherein: The sensing unit includes a capacitor connected to the node.

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