DISPLAY DEVICE AND A METHOD OF DRIVING THE SAME

• US 20200020278A1
• Filed: 07/15/2019
• Published: 01/16/2020
• Est. Priority Date: 07/16/2018
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Group)
• Original Assignee: Samsung Display Company Limited (Samsung Group)
• Inventors: Lee, Wook
• Granted Patent: US 10,755,644 B2
• Time in Patent Office: Days
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/043 Compensation electrodes or other additional electrodes in matrix displays related to distortions or compensation signals, e.g. for modifying TFT threshold voltage in column driver
• CPC Class Codes: G09G 2300/0439 Pixel structures
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• CPC Class Codes: G09G 2310/0291 Details of output amplifiers or buffers arranged for use in a driving circuit
• CPC Class Codes: G09G 2320/0295 by monitoring each display pixel
• CPC Class Codes: G09G 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3275 Details of drivers for data electrodes

Abstract

A display device includes: a pixel circuit including a switching transistor connected to a data line, a storage capacitor connected to the switching transistor, a driving transistor connected to the storage capacitor, an organic light-emitting diode connected to the driving transistor and a sensing transistor connected between a sensing line and the driving transistor; and a data-sensing circuit including a first selector connected to the data line and the sensing line, a second selector connected to an output terminal of an amplifier, he first selector and a feedback capacitor, where the second selector selectively connects the output terminal of the amplifier to the first selector and the feedback capacitor, a third selector connected to the sensing line, and a fourth selector connected to the output terminal of the amplifier and the third selector.

Claims

1. A display device comprising:

a pixel circuit comprising;

a switching transistor connected to a data line;

a storage capacitor connected to the switching transistor;

a driving transistor connected to the storage capacitor;

an organic light-emitting diode connected to the driving transistor; and

a sensing transistor connected between a sensing line and the driving transistor; and

a data-sensing circuit comprising;

a first selector connected to the data line and the sensing line;

a second selector connected to an output terminal of an amplifier, the first selector and a feedback capacitor, wherein the second selector selectively connects the output terminal of the amplifier to the first selector and the feedback capacitor;

a third selector connected to the sensing line; and

a fourth selector connected to the output terminal of the amplifier and the third selector.

2. The display device of claim 1, wherein the second selector comprises:

a third switch connected between the output terminal of the amplifier and the feedback capacitor; and

a fourth switch connected between the output terminal and a first input terminal of the amplifier.

3. The display device of claim 2, wherein

the first selector comprises:

a first switch connected between the data line and the fourth switch; and

a second switch connected between the sensing line and the fourth switch, and

the third selector comprises;

a fifth switch connected between a voltage terminal and the sensing line; and

a sixth switch connected between the sensing line and the fourth selector.

4. The display device of claim 3, wherein the fourth selector comprises:

a seventh switch connected between the second selector and the sixth switch; and

an eighth switch connected between the seventh switch and a capacitor of the data-sensing circuit.

5. The display device of claim 4, wherein

a sensing period comprises an initializing period, in which the pixel circuit is initialized, and a signal sensing period, in which a sensing signal formed in the pixel circuit is sensed,

wherein,

the switching transistor and the sensing transistor are turned on in the initializing period,

the first, third, fourth and fifth switches are turned on in the initializing period,

the second, sixth, seventh and eighth switches are turned off in the initializing period,

the voltage terminal receives a first reference voltage in the initializing period,

a second input terminal of the amplifier receives a second reference voltage in the initializing period,

the first reference voltage is applied to an electrode of the driving transistor, in the initializing period and

the second reference voltage is applied to a control electrode of the driving transistor in the initializing period.

6. The display device of claim 5, wherein

the signal sensing period, in which a sensing voltage is sensed from the pixel circuit, is defined in a power-off period,

the switching transistor and the sensing transistor are turned on in the signal sensing period,

the first, third, fourth, sixth and eighth switches are turned on in the signal sensing period,

the second, fifth and seventh switches are turned off in the signal sensing period, and

a sensing signal corresponding a threshold voltage of the driving transistor received from the sensing line is stored in the capacitor of the data-sensing circuit in the signal sensing period.

7. The display device of claim 5, wherein

the signal sensing period, in which a sensing current is sensed from the pixel circuit, is defined in a power-off period,

the switching transistor is turned off in the signal sensing period,

the sensing transistor is turned on in the signal sensing period,

the sixth and eighth switches are turned on in the signal sensing period,

the first, second, third, fourth, fifth and seventh switches are turned off in the signal sensing period, and

a sensing signal corresponding a current flowing through the driving transistor received from the sensing line is stored in the capacitor of the data-sensing circuit in the signal sensing period.

8. The display device of claim 5, wherein

the signal sensing period, in which a sensing current is sensed from the pixel circuit, is defined in a display period,

the switching transistor is turned off in the signal sensing period,

the sensing transistor is turned on in the signal sensing period,

the second, third, fourth, seventh and eighth switches are turned on in the signal sensing period,

the first, fifth and sixth switches are turned off in the signal sensing period,

the second input terminal of the amplifier receives a third reference voltage in the signal sensing period,

a current flows between the driving transistor, which receives a power source voltage, the sensing line connected to the driving transistor, the amplifier connected to the sensing line and a ground connected to the output terminal of the amplifier in the signal sensing period, and

the amplifier and the feedback capacitor are reset in the signal sensing period.

9. The display device of claim 8, wherein

the switching transistor is turned off after the amplifier is reset,

the sensing transistor is turned on after the amplifier is reset,

the second, third, seventh and eighth switches are turned on after the amplifier is reset,

the first, fourth, fifth and sixth switches are turned off after the amplifier is reset,

a sensing signal corresponding to a current flowing through the driving transistor is applied to the amplifier and the feedback capacitor after the amplifier is reset, and

a voltage outputted from the output terminal of the amplifier is stored in the capacitor of the data-sensing circuit after the amplifier is reset.

10. The display device of claim 5, wherein

the signal sensing period, in which a sensing voltage is sensed from the pixel circuit, is defined in a display period,

the switching transistor is turned on in the signal sensing period,

the sensing transistor is turned off in the signal sensing period,

the first, third and fourth switches are turned on in the signal sensing period,

the second, fifth, sixth, seventh and eighth switches are turned off in the sensing period,

the second input terminal of the amplifier receives a third reference voltage in the signal sensing period,

the third reference voltage is applied to the control electrode of the driving transistor through the data line in the signal sensing period, and

the sensing voltage corresponding to a threshold voltage of the driving transistor is stored in the storage capacitor in the signal sensing period.

11. The display device of claim 10, wherein

the switching transistor is turned off after the sensing voltage is stored in the storage capacitor,

the sensing transistor is turned on after the sensing voltage is stored in the storage capacitor,

the second, third, fourth, seventh and eighth switches are turned on after the sensing voltage is stored in the storage capacitor,

the first, fifth and sixth switches are turned off after the sensing voltage is stored in the storage capacitor,

the second input terminal of the amplifier receives a fourth reference voltage after the sensing voltage is stored in the storage capacitor,

the sensing line is connected to the first input terminal of the amplifier after the sensing voltage is stored in the storage capacitor,

the output terminal of the amplifier is connected to the capacitor of the data-sensing circuit after the sensing voltage is stored in the storage capacitor, and

the sensing line and the feedback capacitor are initialized through the amplifier after the sensing voltage is stored in the storage capacitor.

12. The display device of claim 11, wherein

the switching transistor and the sensing transistor are turned on after the sensing line is initialized,

the second, third, seventh and eighth switches are turned on after the sensing line is initialized, and

the first, fourth, fifth and sixth switches are turned off after the sensing line is initialized,

wherein when the sensing transistor is turned on, the storage capacitor and the feedback capacitor connected to each other through the sensing line are charge-shared with each other and an output voltage of the amplifier is stored in the capacitor of the data-sensing circuit.

13. A display device comprising:

a pixel circuit comprising;

a switching transistor connected to a data line;

a storage capacitor connected to the switching transistor;

a driving transistor connected to the storage capacitor;

an organic light-emitting diode connected to the driving transistor; and

a sensing transistor connected between the data line and the driving transistor; and

a data-sensing circuit comprising;

a first selector connected to the data line;

a second selector connected to an output terminal of an amplifier, the first selector and a feedback capacitor, wherein the second selector selectively connects the output terminal of the amplifier to the first selector and the feedback capacitor;

a third selector connected to the first selector; and

a fourth selector connected to the output terminal of the amplifier and the third selector.

14. The display device of claim 13, wherein the second selector comprises:

a third switch connected between the output terminal of the amplifier and the feedback capacitor; and

a fourth switch connected between the output terminal and a first input terminal of the amplifier.

15. The display device of claim 14, wherein

the first selector comprises:

a first switch connected between the data line and the fourth switch; and

a second switch connected between the data line and the third selector, and the third selector comprises;

a fifth switch connected between a voltage terminal and the second switch; and

a sixth switch connected between the second switch and the fourth selector.

16. The display device of claim 15, wherein the fourth selector comprises:

a seventh switch connected between the second selector and the sixth switch; and

an eighth switch connected between the seventh switch and a capacitor of the data-sensing circuit.

17. The display device of claim 16, wherein

a sensing period comprises an initializing period, in which the pixel circuit is initialized, and a signal sensing period, in which a sensing signal formed in the pixel circuit is sensed,

wherein

in a first period of the initializing period, a second reference voltage is received from a second input terminal of the amplifier, the switching transistor is turned on, the sensing transistor is turned off, the first, third and fourth switches are turned on, the second, fifth, sixth, seventh and eighth switches are turned off, and the second reference voltage is applied to a control electrode of the driving transistor, and

in a second period of the initializing period, a voltage terminal receives a first reference voltage, the switching transistor is turned off, the sensing transistor is turned on, the fifth switch is turned on, the first, second, third, fourth, sixth, seventh and eighth switches are turned off, and an electrode of the driving transistor receives the first reference voltage.

18. The display device of claim 16, wherein

the signal sensing period, in which a sensing voltage is sensed from the pixel circuit, is defined in a power-off period,

in a first period of the signal sensing period, a second input terminal of the amplifier receives a reference voltage, the switching transistor is turned on, the sensing transistor is turned off, the first, third and fourth switches are turned on, the second, fifth, sixth, seventh and eighth switches are turned off, and the driving transistor forms a threshold voltage, and

in a second period of the signal sensing period, the switching transistor is turned off, the sensing transistor is turned on, the sixth and eighth switches are turned on, the first, second, third, fourth, fifth and seventh switches are turned off, and a sensing signal corresponding to the threshold voltage of the driving transistor is stored in the capacitor of the data-sensing circuit through the data line.

19. The display device of claim 16, wherein

the signal sensing period, in which a sensing current is sensed from the pixel circuit, is defined in a power-off period,

the switching transistor is turned off in the signal sensing period,

the sensing transistor is turned on in the signal sensing period,

the sixth and eighth switches are turned on in the signal sensing period,

the first, second, third, fourth, fifth and seventh switches are turned off in the signal sensing period, and

a sensing signal corresponding a current flowing through the driving transistor received from the data line is stored in the capacitor of the data-sensing circuit in the signal sensing period.

20. The display device of claim 16, wherein

the signal sensing period, in which a sensing current is sensed from the pixel circuit, is defined in a display period,

the switching transistor is turned off in the signal sensing period,

the sensing transistor is turned on, the first, third, fourth, seventh and eighth switches are turned on in the signal sensing period,

the second, fifth and sixth switches are turned off in the signal sensing period,

the second input terminal of the amplifier receives a reference voltage in the signal sensing period,

a current flows between the driving transistor, which receives a power source voltage, the data line connected to the driving transistor, the amplifier connected to the data line and a ground connected to the output terminal of the amplifier in the signal sensing period, and

the amplifier and the feedback capacitor are reset in the signal sensing period.

21. The display device of claim 20, wherein after the amplifier is reset,

the switching transistor is turned off, the sensing transistor is turned on, the first, third, seventh and eighth switches are turned on, the second, fourth, fifth and sixth switches are turned off,

a sensing signal corresponding to a current flowing through the driving transistor is applied to the amplifier and the feedback capacitor, and

a voltage outputted from the output terminal of the amplifier is stored in the capacitor of the data-sensing circuit.

22. The display device of claim 16, wherein

the signal sensing period, in which a sensing voltage is sensed from the pixel circuit, is defined in a display period,

the switching transistor is turned on in the signal sensing period,

the sensing transistor is turned off in the signal sensing period,

the first, third and fourth switches are turned on in the signal sensing period,

the second, fifth, sixth, seventh and eighth switches are turned off in the signal sensing period,

a second input terminal of the amplifier receives a second reference voltage in the signal sensing period,

the second reference voltage is applied to the control electrode of the driving transistor through the data line in the signal sensing period, and

the sensing voltage corresponding to a threshold voltage of the driving transistor is stored in the storage capacitor in the signal sensing period.

23. The display device of claim 22, wherein

the switching transistor is turned off, the sensing transistor is turned on after the sensing voltage is stored in the storage capacitor,

the first, third, fourth, seventh and eighth switches are turned on after the sensing voltage is stored in the storage capacitor,

the second, fifth and sixth switches are turned off after the sensing voltage is stored in the storage capacitor,

a second input terminal of the amplifier receives a third reference voltage after the sensing voltage is stored in the storage capacitor,

the data line is connected to a first input terminal of the amplifier after the sensing voltage is stored in the storage capacitor,

the output terminal of the amplifier is connected to the capacitor of the data-sensing circuit after the sensing voltage is stored in the storage capacitor, and

the data line and the feedback capacitor are initialized through the amplifier after the sensing voltage is stored in the storage capacitor.

24. The display device of claim 23, wherein

the switching transistor is turned off after the data line is initialized,

the sensing transistor is turned on after the sensing line is initialized,

the first, third, seventh and eighth switches are turned on and the second, fourth, fifth and sixth switches turned off after the sensing line is initialized,

wherein when the sensing transistor is turned on, the storage capacitor and the feedback capacitor connected to each other through the data line are charge-shared with each other and an output voltage of the amplifier is stored in a capacitor of the data-sensing circuit.

25. A method of driving a display device comprising:

a pixel circuit comprising an organic light-emitting diode; and

a data-sensing circuit comprising a first selector connected a data line of the pixel circuit and a sensing line, a second selector which selectively connects an output terminal of an amplifier to the first selector and a feedback capacitor, a third selector connected to the sensing line, and a fourth selector connected to the output terminal of the amplifier and the third selector, the method comprising;

initializing the pixel circuit,

wherein the initializing the pixel circuit comprises;

transferring a first reference voltage to the sensing line through the third selector,

turning on a sensing transistor of the pixel circuit, which is connected to the sensing line in the pixel circuit, such that the first reference voltage is applied to the pixel circuit,

transferring a second reference voltage received from an amplifier of the data-sensing circuit to the data line through the first selector, and

turning on a switching transistor of the pixel circuit, which is connected to the data line in the pixel circuit, such that the second reference voltage is applied to the pixel circuit.

26. The method of claim 25, further comprising:

sensing a sensing voltage formed in the pixel circuit in a power-off period,

wherein the sensing the sensing voltage in the power-off period comprises;

transferring a reference voltage received from the amplifier to the data line through the first selector and the second selector;

turning on the switching transistor connected to the data line in the pixel circuit such that reference voltage is applied to the pixel circuit; and

storing the sensing voltage of the pixel circuit transferred from the sensing line by the third selector and the fourth selector in a capacitor.

27. The method of claim 25, further comprising:

sensing a sensing current formed in the pixel circuit in a power-off period,

wherein the sensing the sensing current in the power-off period comprises;

turning off the switching transistor;

turning on the sensing transistor; and

storing the sensing current of the pixel circuit transferred from the sensing line by the third selector and the fourth selector in a capacitor of the data-sensing circuit.

28. The method of claim 25, further comprising:

initializing an amplifier in a display period,

wherein the initializing the amplifier in the display period comprises;

turning on the sensing transistor,

connecting the sensing line to an amplifier by the first selector, wherein an input terminal and an output terminal of the amplifier are connected to each other by the second selector,

connecting the output terminal of the amplifier to a capacitor of the data-sensing circuit by the fourth selector, wherein the capacitor is connected to a ground, and

flowing a current between the driving transistor, which receives a power source voltage, the sensing line connected to the driving transistor, the amplifier connected to the sensing line and a ground connected to the output terminal of the amplifier such that the amplifier and the feedback capacitor are reset.

29. The method of claim 28, further comprising:

sensing a sensing current formed in the pixel circuit in the display period,

wherein the sensing the sensing current in the display period comprises;

turning on the sensing transistor,

connecting the sensing line to an amplifier by the first selector, wherein an input terminal and an output terminal of the amplifier are connected to each other through the feedback capacitor by the second selector,

connecting the output terminal of the amplifier to a capacitor of the data-sensing circuit by the fourth selector, and

storing the sensing current flowing through the driving transistor to the capacitor by the amplifier and the feedback capacitor.

30. The method of claim 28, further comprising:

sensing a sensing voltage of the pixel circuit in the display period,

wherein the sensing the sensing voltage in the display period comprises;

turning on the sensing transistor,

connecting the sensing line to an amplifier by the first selector, wherein an input terminal and an output terminal of the amplifier are connected to each other through the feedback capacitor by the second selector, and

connecting the output terminal of the amplifier to a capacitor of the data-sensing circuit by the fourth selector,

wherein when the sensing transistor is turned on, the storage capacitor and the feedback capacitor connected to each other through the sensing line are charge-shared with each other, and an output voltage of the amplifier is stored in the capacitor of the data-sensing circuit.