Display device and method of driving the same

A display device includes a display panel including pixels, a data driver configured to apply a data voltage to each of the pixels, to apply a first reference voltage to the pixels in a first period of a first sensing period to generate first sensing data corresponding to a first driving current flowing through a driving transistor of each of the pixels, and to apply a second reference voltage to the pixels in a second period of the first sensing period to generate second sensing data corresponding to a second driving current flowing through the driving transistor of each of the pixels, and a driving controller configured to receive the first sensing data and the second sensing data from the data driver to compensate input image data based on the first sensing data and the second sensing data.

This application claims priority to Korean Patent Application No. 10-2021-0184441, filed on Dec. 22, 2021, and all the benefits accruing therefrom under 35 U.S.C. § 119, the content of which in its entirety is herein incorporated by reference.

BACKGROUND

Embodiments of the present invention relate to a display device and a method of driving a display device. More particularly, embodiments of the present invention relate to a display device and a method of driving a display device sensing a threshold voltage and a mobility of a driving transistor.

2. Description of the Related Art

Generally, a display device may include a display panel, a driving controller, gate driver, and a data driver. The display panel may include a plurality of gate lines, a plurality of data lines, and a plurality of pixels electrically connected to the gate lines and the data lines. The gate driver may provide gate signals to the gate lines. The data driver may provide data voltages to the data lines. The driving controller may control the gate driver and the data driver.

In the display device, differences in characteristics such as a threshold voltage and a mobility of a driving transistor may occur for each pixel due to process deviation, or the like. Accordingly, compensation of the data voltages applied to the pixels (i.e., compensation of input image data) may be performed to improve display quality.

Since a conventional display device requires a lot of time to sense the threshold voltage, the threshold voltage is sensed in a power-off state. However, in a case of the display device which power off for a short period of time, it is difficult to sense the threshold voltage in the power-off state.

SUMMARY

Embodiments of the present invention provide a display device for sensing a threshold voltage of a driving transistor of each of pixels by applying two voltages to the pixels.

Embodiments of the present invention also provide a method of driving the display device.

According to embodiments of the present invention, a display device includes a display panel including pixels, a data driver configured to apply a data voltage to each of the pixels, to apply a first reference voltage to the pixels in a first period of a first sensing period to generate first sensing data corresponding to a first driving current flowing through a driving transistor of each of the pixels, and to apply a second reference voltage to the pixels in a second period of the first sensing period to generate second sensing data corresponding to a second driving current flowing through the driving transistor of each of the pixels, and a driving controller configured to receive the first sensing data and the second sensing data from the data driver to compensate input image data based on the first sensing data and the second sensing data.

In an embodiment, the driving controller may be configured to calculate a threshold voltage value of the driving transistor of each of the pixels based on the first sensing data and the second sensing data, and to compensate the input image data based on the threshold voltage value.

In an embodiment, the threshold voltage value may be calculated by using an equation

VTH=VGS⁢2×ID⁢12-VGD⁢1×ID⁢22ID⁢12-ID⁢22,
where VTH may be the threshold voltage value, VGS1may be a gate-source voltage value of the driving transistor in the first period, VGS2may be a gate-source voltage value of the driving transistor in the second period, ID1may be a value of the first driving current, and ID2may be a value of the second driving current.

In an embodiment, the data driver may be configured to generate the first sensing data and the second sensing data in one frame.

In an embodiment, the data driver may be configured to generate the first sensing data in a first frame and to generate the second sensing data in a second frame different from the first frame.

In an embodiment, the data driver may be configured to apply a third reference voltage to the pixels in a second sensing period to generate third sensing data corresponding to a third driving current flowing through the driving transistor of each of the pixels, and the driving controller may be configured to receive the third sensing data from the data driver, to calculate a mobility value of the driving transistor of each of the pixels, and to compensate the input image data based on the mobility value and the threshold voltage value.

In an embodiment, generating of the first sensing data, the second sensing data, and the third sensing data may be performed in a power-on state.

In an embodiment, the driving controller may be configured to compensate the third reference voltage based on the first sensing data and the second sensing data.

In an embodiment, the data driver may include an output buffer circuit configured to apply the data voltage to each of the pixels, and a sensing circuit configured to generate the first sensing data, the second sensing data, and the third sensing data.

In an embodiment, the sensing circuit may include an integrator connected to the pixels through a sensing line and configured to receive a driving current flowing through the driving transistor of each of the pixels through the sensing line, where the driving current may include the first driving current, the second driving current, and the third driving current.

In an embodiment, the integrator may be configured to fix an anode voltage of a light emitting element of each of the pixels to an active voltage in the first sensing period.

In an embodiment, the integrator may operate in the first sensing period and does not operate in the second sensing period.

In an embodiment, the sensing circuit may further include an analog-to-digital converter configured to generate the first sensing data, the second sensing data, and the third sensing data, a first switch configured to selectively connect the sensing line and the integrator, a second switch configured to selectively connect the integrator and the analog-to-digital converter, and a third switch configured to selectively connect the sensing line and the analog-to-digital converter.

In an embodiment, in the first sensing period, the first switch and the second switch may be turned on and the third switch may be turned off, and in the second sensing period, the first switch and the second switch may be turned off, and the third switch may be turned on.

In an embodiment, the sensing circuit may further include a fourth switch configured to selectively apply an initialization voltage to the sensing line.

In an embodiment, the sensing circuit may further include a fifth switch configured to selectively connect an input terminal of the integrator and an output terminal of the integrator.

In an embodiment, each of the pixels may include light emitting element, a first switching transistor configured to apply the data voltage to a control electrode of the driving transistor in response to a first gate signal, a storage capacitor configured to store the data voltage, a driving transistor configured to apply a driving current to the light emitting element based on the data voltage, a second switching transistor configured to provide the driving current to a sensing line in response to a second gate signal, and a third switching transistor configured to apply a first power voltage to the driving transistor in response to an emission signal, where the driving current may include the first driving current, the second driving current, and the third driving current.

In an embodiment, in the first period, the second period, and the second sensing period, the third switching transistor may be turned on after the first switching transistor may be turned on.

According to embodiments of the present invention, a method of driving a display device includes: generating first sensing data corresponding to a first driving current flowing through a driving transistor of each of pixels by applying a first reference voltage to the pixels in a first period of a first sensing period, generating second sensing data corresponding to a second driving current flowing through the driving transistor of each of the pixels by applying a second reference voltage to the pixels in a second period of the first sensing period, compensating a voltage value of a third reference voltage based on the first sensing data and the second sensing data, generating third sensing data corresponding to a third driving current flowing through the driving transistor of each of the pixels by applying the compensated third reference voltage to the pixels in a second sensing period, and compensating input image data based on the first sensing data, the second sensing data, and the third sensing data.

In an embodiment, the method may further include calculating a threshold voltage value of the driving transistor of each of the pixels based on the first sensing data and the second sensing data, and calculating a mobility value of the driving transistor of each of the pixels based on the third sensing data, and the compensating of the input image data may be performed based on the threshold voltage value and the mobility value.

Therefore, the display device and the method of driving the display device may effectively improve display quality by sensing a threshold voltage and a mobility.

In addition, the display device and the method of driving the display device may sense a threshold voltage in a power-on state by sensing the threshold voltage using an integrator.

Further, the display device and the method of driving the display device may reflect a gate-source voltage difference of a driving transistor in a sensing period and a display period by sensing a mobility using a passive manner.

However, the effects of the present invention are not limited to the above-described effects, and may be variously expanded without departing from the spirit and scope of the present invention.

DETAILED DESCRIPTION

FIG.1is a diagram illustrating a display device1000according to embodiments of the present invention.

Referring toFIG.1, the display device1000may include a display panel100, a driving controller200, a gate driver300, a data driver400, and a emission driver500. In an embodiment, the driving controller200and the data driver400may be integrated into one chip.

The display panel100has a display region AA on which an image is displayed and a peripheral region PA adjacent to the display region AA. In an embodiment, the gate driver300and the emission driver500may be mounted on the peripheral region PA of the display panel100.

The display panel100may include a plurality of gate lines GL, a plurality of data lines DL, a plurality of emission lines EL and a plurality of pixels P electrically connected to the data lines DL, the gate lines GL, and the emission lines EL. The gate lines GL and the emission lines EL may extend in a first direction D1and the data lines DL may extend in a second direction D2crossing the first direction Dl.

The driving controller200may receive input image data IMG and an input control signal CONT from a host processor (e.g., a graphic processing unit; GPU). For example, the input image data IMG may include red image data, green image data and blue image data. In an embodiment, the input image data IMG may further include white image data. For another example, the input image data IMG may include magenta image data, yellow image data, and cyan image data. The input control signal CONT may include a master clock signal and a data enable signal. The input control signal CONT may further include a vertical synchronizing signal and a horizontal synchronizing signal.

The driving controller200may generate a first control signal CONT1, a second control signal CONT2, and output image data OIMG based on the input image data IMG, sensing data SD, and the input control signal CONT.

The driving controller200may generate the second control signal CONT2for controlling operation of the data driver400based on the input control signal CONT and output the second control signal CONT2to the data driver400. The second control signal CONT2may include a horizontal start signal and a load signal.

The driving controller200may receive the input image data IMG, the sensing data SD, and the input control signal CONT, and generate the output image data OIMG. The driving controller200may receive the sensing data SD to compensate the input image data IMG. The driving controller200may output the output image data OIMG to the data driver400.

The driving controller200may generate the third control signal CONT3for controlling operation of the emission driver500based on the input control signal CONT and output the third control signal CONT3to the emission driver500.

The gate driver300may generate gate signals for driving the gate lines GL in response to the first control signal CONT1input from the driving controller200. The gate driver300may output the gate signals to the gate lines GL. For example, the gate driver300may sequentially output the gate signals to the gate lines GL.

The data driver400may receive the second control signal CONT2and the output image data OIMG from the driving controller200. The data driver400may convert the output image data OIMG into data voltages having an analog type. The data driver400may output the data voltage to the data lines DL. In an embodiment, the data driver400may output the data voltage in a display period. In an embodiment, the data driver400may generate the sensing data SD corresponding to a driving current flowing through a driving transistor DT of each of the pixels P. A detailed description thereof will be given later.

The emission driver500may generate emission signals for driving the emission lines EL in response to the third control signal CONT3input from the driving controller200. The emission driver500may output the emission signals to the emission lines EL. For example, the emission driver500may sequentially output the emission signals to the emission lines EL.

FIG.2is a block diagram illustrating an example of the display panel100and the data driver400of the display device1000ofFIG.1, andFIG.3is a circuit diagram illustrating an example of a sensing circuit420included in the data driver400of the display device1000ofFIG.1.

Referring toFIGS.2and3, each of the pixels P may include a light emitting element EE, a first switching transistor ST1for applying the data voltage to a control electrode of the driving transistor DT in response to a first gate signal GS1, a storage capacitor CST for storing the data voltage, the driving transistor for applying a driving current to the light emitting element EE based on the data voltage, a second switching transistor ST2for flowing the driving current to the sensing line SL in response to a second gate signal GS2, and a third switching transistor ST3for applying a first power voltage ELVDD to the driving transistor DT in response to the emission signal EM. In an embodiment, the first switching transistor ST1and the second switching transistor ST2may be an n-type transistor, and the third switching transistor ST3may be a p-type transistor.

In an embodiment, for example, the first switching transistor ST1may include a control electrode for receiving the first gate signal GS1, an input electrode connected to the data line DL, and an output electrode connected to a first node N1. The storage capacitor CST may include a first electrode connected to the first node N1and a second electrode connected to a second node N2. The driving transistor DT may include the control electrode connected to the first node N1, an input electrode connected to the third node N3, and an output electrode connected to the second node N2. The second switching transistor ST2may include a control electrode for receiving the second gate signal GS2, an input electrode connected to the second node N2, and an output electrode connected to the sensing line SL. The third switching transistor ST3may include a control electrode for receiving the emission signal EM, an input electrode for receiving the first power voltage ELVDD, and an output electrode connected to the third node N3. The light emitting element EE may include an anode electrode connected to the second node N2and a cathode electrode for receiving a second power voltage ELVSS. Each of the pixels P may include a parasitic capacitor CP between the first node N1and the second node N3.

An output buffer circuit410may apply the data voltage to each of the pixels P. In an embodiment, the output buffer circuit410may sequentially apply the data voltage to the pixels P through the data lines DL in an active period, and apply a reference voltage for a sensing operation to the pixels through the data lines DL in the vertical blank period. In an embodiment, the output buffer circuit410may provide the reference voltage (e.g., a first reference voltage, a second reference voltage, and a third reference voltage) for the sensing operation per one pixel row selected through the data lines DL in the vertical blank period.

The sensing circuit420may generate the sensing data SD. The sensing circuit420may generate a first sensing data SD1, a second sensing data SD2, and a third sensing data SD3. The sensing circuit420may receive the driving current of the driving transistor DT of each of the pixels P from the pixels P through the sensing lines SL, and generate the sensing data SD corresponding to the driving current value (i.e., the sensing operation).

The sensing circuit420may be connected to the pixels P through the sensing line SL, and include an integrator421for receiving the driving current of the driving transistor DT of each of the pixels P through the sensing line SL. In an embodiment, a one input terminal of the integrator421(e.g., a positive terminal of the integrator421ofFIG.3) may be set to constantly receive an active voltage VA. In an embodiment, the integrator421may operate in a first sensing period and may not operate in a second sensing period. A detailed description thereof will be given later.

In an embodiment, the sensing circuit420may include an analog-to-digital converter ADC for generating the first sensing data SD1, the second sensing data SD2, and the third sensing data SD3, a first switch SW1for selectively connecting the sensing line SL and the integrator421, a second switch SW2for selectively connecting the integrator421and the analog-to-digital converter ADC, and a third switch SW3for selectively connecting the sensing line SL and the analog-to-digital converter ADC. In an embodiment, the sensing circuit420may further include a fourth switch SW4for selectively applying an initialization voltage VINT to the sensing line SL. In an embodiment, the sensing circuit420may further include a fifth switch SW5for selectively connecting the input terminal of the integrator421and an output terminal of the integrator421.

FIG.4is a timing diagram illustrating an example in which the display device1000ofFIG.1operates in the display period DP. InFIG.4, it is assumed that the first switching transistor ST1and the second switching transistor ST2are n-type transistors, and the third switching transistor ST3is a p-type transistor.

Referring toFIGS.1to4, the data driver400may apply the data voltage VDATA to the pixels P through the data line DL in the display period DP. The display period DP may correspond to the active period AP of each frame. The display device1000may display an image corresponding to the input image data IMG on the display panel100in the display period DP.

In an emission initialization period EIP of the display period DP, the emission signal EM may have an inactive level, the first gate signal GS1and the second gate signal GS2may have an activation level, and the first switch SW1, the second switch SW2, and the third switch SW3may be turned off, the fourth switch SW4may be turned on, the fifth switch SW5may be turned off, and the data voltage VDATA may be applied to the data line DL. For example, in the light emission initialization period EIP of the display period DP, the data voltage VDATA may be applied to the control electrode (i.e., the first node N1) of the driving transistor DT, and the initialization voltage VINT may be applied to the anode electrode (i.e., the second node N2) of the light emitting element EE. Accordingly, a gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT may have a value corresponding to a difference between the data voltage VDATA and the initialization voltage VINT, and the storage capacitor CST may store the gate-source voltage corresponding to the difference between the data voltage VDATA and the initialization voltage VINT.

In the emission period EP of the display period DP, the emission signal EM may have an activation level, the first gate signal GS1and the second gate signal GS2may have an inactivation level, and the first switch SW1, the second switch SW2, the third switch SW3, the fourth switch SW4, and the fifth switch SW5may be turned off. For example, in the emission period EP of the display period DP, the first power voltage ELVDD may be applied to the input electrode of the driving transistor DT, and the driving current corresponding to the gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT may be generated. Also, since the first switching transistor ST1is turned off, the first node N1may be in a floating state. However, due to an influence of the parasitic capacitor CP, a voltage of the first node N1may not increase by an increase width of the anode voltage of the anode electrode (i.e., the second node N2) of the light emitting element EE. For example, when the anode voltage increases by ΔV with a flow of the driving current in the emission period EP, the gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT in the emission period EP may be decreased by

where CP may be a capacitance of the parasitic capacitor and CST may be a capacitance of the storage capacitor, than the gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT in the emission initialization period EIP.

FIG.5is a timing diagram illustrating an example in which the display device1000ofFIG.1operates in a first sensing period ASP, andFIG.6is a circuit diagram illustrating an example of a flow of the driving current of the display device1000ofFIG.1in the first sensing period ASP. InFIG.5, it is assumed that the first switching transistor ST1and the second switching transistor ST2are n-type transistors, and the third switching transistor ST3is a p-type transistor.

FIGS.1to3,5and6, the data driver400may apply a first reference voltage VREF1to the pixels P in the first period P1of the first sensing period ASP, and generate the first sensing data SD1corresponding to a first driving current value ID1(See the equation 1 below) of the driving transistor DT of each of the pixels P. The data driver400may apply a second reference voltage VREF2to the pixels P in the second period P2of the first sensing period ASP, and generate the second sensing data SD2corresponding to a second driving current value ID2(See the equation 1 below) of the driving transistor DT of each of the pixels P. The driving controller200may receive the first sensing data SD1and the second sensing data SD2from the data driver400to compensate the input image data IMG. In an embodiment, the driving controller200may calculate a threshold voltage value of the driving transistor DT of each of the pixels P based on the first sensing data SD1and the second sensing data SD2, and compensate the input image data IMG based on the threshold voltage value. That is, the display device1000may sense the threshold voltage of the driving transistor DT of each of the pixels P based on the first sensing data SD1and the second sensing data SD2. Generating of the first sensing data SD1and the second sensing data SD2may be performed in a power-on state. The power-on state may mean a state in which a power of the display device1000is turned on.

The data driver400may apply the first reference voltage VREF1and the second reference voltage VREF2to the pixels P through the data line DL in the first sensing period ASP. In an embodiment, the data driver400may generate the first sensing data SD1and the second sensing data SD2in one frame. That is, the first period P1and the second section P2of the first sensing period ASP may be included in one vertical blank period VBP. The vertical blank period VBP may include the first sensing period ASP and a second sensing period PSP to be described later. In an embodiment, in the vertical blank period VBP, the first sensing period ASP and the second sensing period PSP may be alternately repeated. For example, when the vertical blank period VBP of a current frame is the first sensing period ASP, the vertical blank period VBP of a next frame may be the second sensing period PSP.

The integrator421may operate in the first sensing period ASP. For example, in the first sensing period ASP, the first switch SW1and the second switch SW2may be turned on and the third switch SW3may be turned off.

The first sensing period ASP may include the first period P1generating the first sensing data SD1and the second period P2generating the second sensing data SD2, the first period P1may include a first threshold voltage initialization period VIP1, a first integral initialization period IIP1, and a first threshold voltage sensing period VSP1, and the second period P2may include a second threshold voltage initialization period VSP2, a second integral initialization period IIP2, and a second threshold voltage sensing period VSP2. After the first switching transistor ST1is turned on in the first period P1and the second period P2, the third switching transistor ST3may be turned on. In addition, as the first switching transistor ST1is turned off in the first period P1and the second period P2, the third switching transistor ST3may be turned on. Accordingly, in the first sensing period ASP, the control electrode (i.e., the first node N1) of the driving transistor DT may be in a floating state.

In an embodiment, for example, in the first threshold voltage initialization period VIP1, the emission signal EM may have an inactivation level, the first gate signal GS1and the second gate signal GS2may have an activation level, and the first switch SW1, the second switch SW2, and the third switch SW3may be turned off, the fourth switch SW4may be turned on, the fifth switch SW5may be turned off, and the first reference voltage VREF1may be applied to the data line DL. For example, in the first threshold voltage initialization period VIP1, the first reference voltage VREF1may be applied to the control electrode (i.e., the first node N1) of the driving transistor DT, and the initialization voltage VINT may be applied to the anode electrode (i.e., the second node N2) of the light emitting element EE.

In an embodiment, for example, in the first integral initialization period IIP1, the emission signal EM may have a inactivation level, the first gate signal GS1may have an activation level, and the second gate signal GS2may have an activation level, the first switch SW1and the second switch SW2may be turned on, the third switch SW3may be turned off, the fourth switch SW4may be turned off, the fifth switch SW5may be turned on, and the first reference voltage VREF1may be applied to the data line DL. As the fifth switch SW5is turned on in the first integral initialization period IIP1, the integrator421may be initialized. For example, as the fifth switch SW5is turned on, a voltage stored in an integration capacitor CF of the integrator421may be initialized. Also, the integrator421may fix the anode voltage of the light emitting element EE (i.e., the voltage of the second node N2) to the active voltage VA. For example, the active voltage VA may be applied to a positive terminal of the integrator421, and the anode voltage (i.e., the voltage of the second node N2) of the light emitting element EE may be fixed as the active voltage VA when the negative terminal of the integrator421is connected to the anode electrode (i.e., the second node N2) of the light emitting element EE through the sensing line SL.

In an embodiment, for example, in the first threshold voltage sensing period VSP1, the emission signal EM may have an activation level, the first gate signal GS1may have an inactivation level, the second gate signal GS2may have an activation level, the first switch SW1and the second switch SW2may be turned on, the third switch SW3may be turned off, the fourth switch SW4may be turned off, and the fifth switch SW5may be turned off. For example, in the first threshold voltage sensing period VSP1, the first power voltage ELVDD may be applied to the input electrode of the driving transistor DT, and the driving current I corresponding to the gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT may be generated.

The driving current I may be applied to the analog-to-digital converter ADC through the sensing line SL and the integrator421. The analog-to-digital converter ADC may generate the first sensing data SD1corresponding to the first driving current value ID1(i.e., a current value of the driving current I in the first threshold voltage sensing period VSP1). Also, since the first switching transistor ST1is turned off, the first node N1may be in the floating state. However, since the anode voltage of the light emitting element EE is fixed to the active voltage VA, an increment of the anode voltage generated by the driving current I may not occur. That is, a decrement of the gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT generated by the increment of the anode voltage in the display period DP ofFIG.4may not occur.

In an embodiment, for example, in the second threshold voltage initialization period VIP2, the emission signal EM may have an inactive level, the first gate signal GS1and the second gate signal GS2may have an active level, and the first switch SW1, the second switch SW2, and the third switch SW3may be turned off, the fourth switch SW4may be turned on, the fifth switch SW5may be turned off, and the second reference voltage VREF2may be applied to the data line DL. For example, in the second threshold voltage initialization period VIP2, the second reference voltage VREF2may be applied to the control electrode (i.e., the first node N1) of the driving transistor DT, and the initialization voltage VINT may be applied to the anode electrode (i.e., the second node N2) of the light emitting element EE.

In an embodiment, for example, in the second integral initialization period IIP2, the emission signal EM may have a inactivation level, the first gate signal GS1may have an activation level, and the second gate signal GS2may have an activation level, the first switch SW1and the second switch SW2may be turned on, the third switch SW3may be turned off, the fourth switch SW4may be turned off, and the fifth switch SW5may be turned on, and the second reference voltage VREF2may be applied to the data line DL. As the fifth switch SW5is turned on in the first integral initialization period IIP1, the integrator421may be initialized. For example, as the fifth switch SW5is turned on, a voltage stored in an integration capacitor CF of the integrator421may be initialized. Also, the integrator421may fix the anode voltage of the light emitting element EE (i.e., the voltage of the second node N2) to the active voltage VA. For example, the active voltage VA may be applied to a positive terminal of the integrator421, and the anode voltage (i.e., the voltage of the second node N2) of the light emitting element EE may be fixed as the active voltage VA when the negative terminal of the integrator421is connected to the anode electrode (i.e., the second node N2) of the light emitting element EE through the sensing line SL.

In an embodiment, for example, in the second threshold voltage sensing period VSP2, the emission signal EM may have an activation level, the first gate signal GS1may have an inactivation level, the second gate signal GS2may have an activation level, the first switch SW1and the second switch SW2may be turned on, the third switch SW3may be turned off, the fourth switch SW4may be turned off, and the fifth switch SW5may be turned off. For example, in the second threshold voltage sensing period VSP2, the first power voltage ELVDD may be applied to the input electrode of the driving transistor DT, and the driving current I corresponding to the gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT may be generated. The driving current I may be applied to the analog-to-digital converter ADC through the sensing line SL and the integrator421. The analog-to-digital converter ADC may generate the second sensing data SD2corresponding to the second driving current value ID2(i.e., a current value of the driving current I in the second threshold voltage sensing period VSP2). Also, since the first switching transistor ST1is turned off, the first node N1may be in the floating state. However, since the anode voltage of the light emitting element EE is fixed to the active voltage VA, an increment of the anode voltage generated by the driving current I may not occur. That is, a decrement of the gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT generated by the increment of the anode voltage in the display period DP ofFIG.4may not occur.

Generating of the first sensing data SD1and the second sensing data SD2may be performed in the power-on state. For example, when the driving current I is sensed using the integrator421, it may take a shorter time than when a voltage of the second node N2is sensed (i.e., a time to charge an internal capacitor may not be required). Accordingly, the display device1000may sense the threshold voltage in the power-on state using the integrator421.

The driving controller200may calculate the threshold voltage value of the driving transistor DT of each of the pixels P based on the first sensing data SD1and the second sensing data SD2. For example, the threshold voltage value may be calculated by using the following equation 1:

VTH=VGS⁢2×ID⁢12-VGD⁢1×ID⁢22ID⁢12-ID⁢22,
where VTH may be the threshold voltage value, VGS1may be a gate-source voltage value of the driving transistor in the first period, VGS2may be a gate-source voltage value of the driving transistor in the second period, ID1may be the first driving current value, and ID2may be the second driving current value. The gate-source voltage value VGS1of the driving transistor DT in the first period P1and the gate-source voltage value VGS2of the driving transistor DT in the second period P2may be obtained from the first reference voltage VREF1, the second reference voltage VREF2, and the active voltage VA directly applied, the first driving current value ID1and the second driving current value ID2may be obtained from the first sensing data SD1and the second sensing data SD2. However, as described above, the decrement of the gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT generated by the increment of the anode voltage may be not reflected to the first sensing data SD1and the second sensing data SD2. Accordingly, when the input image data IMG is compensated based on only the threshold voltage value, an error may occur due to the decrement of the gate-source voltage in the display period DP.

FIG.7is a timing diagram illustrating an example in which the display device1000ofFIG.1operates in the second sensing period PSP.FIG.8is a circuit diagram illustrating an example of a flow of the driving current I of the display device1000ofFIG.1in the second sensing period PSP. In an embodiment, the first switching transistor ST1and the second switching transistor ST2may be an n-type transistor, and the third switching transistor ST3may be a p-type transistor.

Referring toFIGS.1to3,7, and8, The data driver400may apply a third reference voltage VREF3to the pixels P in the second sensing period PSP to generate a third sensing data SD3corresponding to a third driving current value ID3of the driving transistor DT of each of the pixels. In an embodiment, the driving controller200may compensate the third reference voltage VREF3based on the first sensing data SD1and the second sensing data SD2. For example, the driving controller200may calculate the threshold voltage value based on the first sensing data SD1and the second sensing data SD2, and compensate the third reference voltage VREF3based on the threshold voltage value. For example, similar to the compensation of the input image data IMG, the driving controller200may compensate the third reference voltage VREF3applied to each of the pixels P based on the threshold voltage value of the driving transistor DT of each of the pixels P. For example, the third reference voltage VREF3may be calculated by using the following equation 2:
VREF3=IVREF3−VTHT+VTHP.
where VREF3may be the compensated third reference voltage, IVREF3may be the third reference voltage before compensation, VTHT may be a targeted threshold voltage value, and VTHP may be a sensed threshold voltage value.

The driving controller200may receive the third sensing data SD3from the data driver400, and calculate a mobility value of the driving transistor DT of each of the pixels P, and compensate the input image data IMG based on the mobility value and the threshold voltage value. For example, the driving controller200may calculate an amount of change in the anode voltage of the light emitting element EE based on the third sensing data SD3, and calculate the mobility value of the driving transistor DT based on the amount of the change. That is, the display device1000may sense the mobility of the driving transistor DT of each of the pixels P based on the third sensing data SD3. Generating of the third sensing data SD3may be performed in the power-on state.

The data driver400may apply the third reference voltage VREF3to the pixels P through the data line DL in the second sensing period PSP. As described above, the vertical blank period VBP may include the second sensing period PSP.

The integrator421may not operate in the second sensing period PSP. For example, in the second sensing period PSP, the first switch SW1and the second switch SW2may be turned off and the third switch SW3may be turned on. Therefore, in the second sensing period PSP, the driving current I may be provided to the third switch SW3and may not be provided to the integrator421.

The second sensing period PSP may include a mobility initialization period MIP, and a mobility sensing period MSP. After the first switching transistor ST1is turned on in the second sensing period PSP, the third switching transistor ST3may be turned on. In addition, as the first switching transistor ST1is turned off in the second sensing period PSP, the third switching transistor ST3may be turned on. Accordingly, in the second sensing period PSP, the control electrode (i.e., the first node N1) of the driving transistor DT may be in the floating state.

In an embodiment, for example, in the mobility initialization period MIP, the emission signal EM may have an inactivation level, the first gate signal GS1and the second gate signal GS2may have an activation level, and the first switch SW1, the second switch SW2, and the third switch SW3may be turned off, the fourth switch SW4may be turned on, the fifth switch SW5may be turned off, and the third reference voltage VREF3may be applied to the data line DL. For example, in the mobility initialization period MIP, the third reference voltage VREF3may be applied to the control electrode (i.e., the first node N1) of the driving transistor DT, and the initialization voltage VINT may be applied to the anode electrode (i.e., the second node N2) of the light emitting element EE.

In an embodiment, for example, in the mobility sensing period MSP, the emission signal EM may have an activation level, the first gate signal GS1may have an inactivation level, the second gate signal GS2may have an activation level, the first switch SW1and the second switch SW2may be turned off, the third switch SW3may be turned on, the fourth switch SW4may be turned off, and the fifth switch SW5may be turned off. For example, in the mobility sensing period MSP, the first power voltage ELVDD may be applied to the input electrode of the driving transistor DT, and the driving current I corresponding to the gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT may be generated. The driving current I may be applied to the analog-to-digital converter ADC through the sensing line SL and not the integrator421. The analog-to-digital converter ADC may generate the third sensing data SD3corresponding to the third driving current value ID3(i.e., a current value of the driving current I in the mobility sensing period MSP). Also, since the first switching transistor ST1is turned off, the first node N1may be in the floating state. However, due to an influence of the parasitic capacitor CP, a voltage of the first node N1may not increase by an increase width of the anode voltage of the anode electrode (i.e., the second node N2) of the light emitting element EE. For example, when the anode voltage increases by ΔV with a flow of the driving current in the mobility sensing period MSP, the gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT in the mobility sensing period MSP may be decreased by

CPCST+CP×Δ⁢V,
where CP may be a capacitance of the parasitic capacitor and CST may be a capacitance of the storage capacitor, than the gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT in the mobility initialization period MIP. That is, like in the display period DP ofFIG.4, the gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT may decrease due to the increment of the anode voltage.

The driving controller200may calculate the mobility value of the driving transistor DT of each of the pixels P based on the third sensing data SD3. In addition, in the third sensing data SD3, a decrement of the gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT generated by the increment of the anode voltage may be reflected. Accordingly, when compensating the input image data IMG based on the mobility value and the threshold voltage value, the compensation may reflect a decrement of the gate-source voltage (i.e., a voltage between the control electrode and the output electrode of the driving transistor DT) of the driving transistor DT generated by the increment of the anode voltage.

The driving controller200may compensate the input image data IMG based on the mobility value and the threshold voltage value. For example, the driving controller200may compensate the input image data IMG by using the following equation 3:

VDATA=(MOBTMOBP)2×(IVDATA-VINT-VTHT)+VINT+VTHT+(VTHP-VTHT),
where VDATA is the compensated data voltage, IVDATA is the data voltage before compensation, VTHT is a targeted threshold voltage value, VTHP is a sensed threshold voltage value of the driving transistor, VINT is the initialization voltage, and MOBT is a targeted mobility value, MOBP is a sensed mobility value of the driving transistor.

Accordingly, the driving controller200may compensate differences in the characteristics of the threshold voltage and the mobility of the driving transistor DT of each of the pixels P, which are generated due to process deviation or the like.

FIG.9is a timing diagram illustrating an example in which a display device according to embodiments operates in the first sensing period ASP. InFIG.9, it is assumed that the first switching transistor ST1and the second switching transistor ST2are n-type transistors, and the third switching transistor ST3is a p-type transistor.

The display device according to the present embodiment is substantially the same as the display device1000ofFIG.1except that operation of the first period P1and operation of the second period P2of the first sensing period ASP are performed in different frames. Thus, the same reference numerals are used to refer to the same or similar element, and any repetitive explanation will be omitted.

Referring toFIG.9, the data driver400may apply the first reference voltage VREF1and the second reference voltage VREF2to the pixels P through the data line DL in the first sensing period ASP. In an embodiment, the data driver400may generate the first sensing data SD1in a first frame1Frame, and generate the second sensing data SD2in a second frame2Frame different from the first frame1Frame. That is, the operation of the first period P1and the operation of the second period P2of the first sensing period ASP may be performed in different frames. The vertical blank section VBP may include the first sensing period ASP and the second sensing period PSP. In an embodiment, in the vertical blank period VBP, the first sensing period ASP and the second sensing period PSP may be alternately repeated. For example, when the vertical blank period VBP of a current frame is the first period P1of the first sensing period ASP, the vertical blank period VBP of a next frame may be the second period P2of the first sensing period ASP. And, when the vertical blank period VBP of a current frame is the second period P2of the first sensing period ASP, the vertical blank period VBP of a next frame may be the second sensing period PSP. Also, when the vertical blank period VBP of a current frame is the second sensing period PSP, the vertical blank period VBP of a next frame may be the first period P1of the first sensing period ASP.

FIGS.10and11are flowcharts illustrating a method of driving a display device according to embodiments.

Referring toFIGS.10and11, the method may generate first sensing data corresponding to a first driving current flowing through a driving transistor of each of pixels by applying a first reference voltage to the pixels in a first period of a first sensing period (S610), generate second sensing data corresponding to a second driving current flowing through the driving transistor of each of the pixels by applying a second reference voltage to the pixels in a second period of the first sensing period (S620), compensate a third reference voltage based on the first sensing data and the second sensing data (S630), generate third sensing data corresponding to a third driving current flowing through the driving transistor of each of the pixels by applying the compensated third reference voltage to the pixels in a second sensing period (S640), and compensate input image data based on the first sensing data, the second sensing data, and the third sensing data (S650).

Specifically, the method may generate first sensing data corresponding to a first driving current flowing through a driving transistor of each of pixels by applying a first reference voltage to the pixels in the first period of a first sensing period (S610), and generate second sensing data corresponding to a second driving current flowing through the driving transistor of each of the pixels by applying a second reference voltage to the pixels in a second period of the first sensing period (S620). In an embodiment, the first driving current value may be a current flowing through a driving current generated by applying a first reference voltage to the pixels in the first period, and the driving current may be received through an integrator. In an embodiment, a value of the second driving current may be a current value of a driving current generated by applying a second reference voltage to the pixels in the second period, and the driving current may be received through the integrator.

Specifically, the method may compensate a third reference voltage based on the first sensing data and the second sensing data (S630). Similar to the compensation of the input image data, the third reference voltage applied to each of the pixels may be compensated based on the threshold voltage value of the driving transistor of each of the pixels.

In an embodiment, for example, the threshold voltage value may be calculated by using the following equation 4:

VTH=VGS⁢2×ID⁢12-VGD⁢1×ID⁢22ID⁢12-ID⁢22,
where VTH may be the threshold voltage value, VGS1may be a gate-source voltage value of the driving transistor in the first period, VGS2may be a gate-source voltage value of the driving transistor in the second period, ID1may be the first driving current value, and ID2may be the second driving current value. The gate-source voltage value of the driving transistor in the first period and the gate-source voltage value of the driving transistor in the second period may be obtained from the first reference voltage, the second reference voltage, and the active voltage directly applied, the first driving current value and the second driving current value may be obtained from the first sensing data and the second sensing data.

In an embodiment, for example, the method may calculate the threshold voltage value based on the first sensing data and the second sensing data, and compensate the third reference voltage based on the threshold voltage value. For example, the third reference voltage VREF3may be compensated by using the following equation 5:
VREF3=IVREF3−VTHT+VTHP,
where VREF3may be the compensated third reference voltage, IVREF3may be the third reference voltage before compensation, VTHT may be a targeted threshold voltage value, and VTHP may be a sensed threshold voltage value.

Specifically, the method may generate third sensing data corresponding to a third driving current flowing through the driving transistor of each of the pixels by applying the compensated third reference voltage to the pixels in the second sensing period (S640). In an embodiment, the third driving current value may be a current value of a driving current generated by applying the third reference voltage to the pixels in the second sensing period, and the driving current may be received without going through the integrator.

Specifically, the method may compensate input image data based on the first sensing data, the second sensing data, and the third sensing data (S650). In an embodiment, the method may calculate the threshold voltage value of the driving transistor of each of the pixels based on the first sensing data and the second sensing data (S641), generate third sensing data corresponding to a third driving current flowing through the driving transistor of each of the pixels by applying the compensated third reference voltage to the pixels in the second sensing period (S640), calculate the mobility value of the driving transistor of each of the pixels based on the third sensing data (S642), and compensate the input image data based on the threshold voltage value and the mobility value (S643). For example, the driving controller200may compensate the input image data by using the following equation 6:

VDATA=(MOBTMOBP)2×(IVDATA-VINT-VTHT)+VINT+VTHT+(VTHP-VTHT),
where VDATA is the compensated data voltage, IVDATA is the data voltage before compensation, VTHT is a targeted threshold voltage value, VTHP is a sensed threshold voltage value of the driving transistor, VINT is the initialization voltage, and MOBT is a targeted mobility value, MOBP is a sensed mobility value of the driving transistor.

The inventions may be applied to any electronic device including the display device. For example, the inventions may be applied to a television (“TV”), a digital TV, a 3D TV, a mobile phone, a smart phone, a tablet computer, a virtual reality (“VR”) device, a wearable electronic device, a personal computer (“PC”), a home appliance, a laptop computer, a personal digital assistant (“PDA”), a portable multimedia player (“PMP”), a digital camera, a music player, a portable game console, a navigation device, etc.