PIXEL CIRCUIT AND DRIVING METHOD THEREOF, AND THIN FILM TRANSISTOR BACKBOARD

• US 20150287360A1
• Filed: 08/29/2014
• Published: 10/08/2015
• Est. Priority Date: 10/09/2013
• Status: Active Grant

• Current Assignee: BOE Technology Group Co., Ltd.
• Original Assignee: BOE Technology Group Co., Ltd.
• Inventors: Yin, Jingwen, Wu, Zhongyuan, Wang, Lirong
• Granted Patent: US 9,489,894 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2320/0219 Reducing feedthrough effects in active matrix panels, i.e. voltage changes on the scan electrode influencing the pixel voltage due to capacitive coupling
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• 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: H10K 59/1213 the pixel elements being TFTs
• CPC Class Codes: H10K 59/1216 the pixel elements being capacitors
• CPC Class Codes: H10K 59/123 Connection of the pixel electrodes to the thin film transistors [TFT]
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals

Abstract

There is provided a pixel circuit comprising a driving transistor (DTFT), a signal loading module, a light emitting control module and a storage capacitor (Cs). The pixel circuit can effectively eliminate the non-uniformity due to the threshold voltage of the driving transistor (DTFT) itself and the afterimage phenomenon due to the threshold voltage drift when driving the OLED, avoid the display brightness non-uniformity due to different threshold voltages of the driving transistors (DTFT) between the OLEDs of different pixel units. There is further provided a driving method for the above pixel circuit and a TFT backboard comprising the above pixel circuit.

Claims

1. A pixel circuit comprising a driving transistor, a signal loading module, a light emitting control module and a storage capacitor, wherein

a gate of the driving transistor is connected to a third terminal of the signal loading module and a second terminal of the storage capacitor;

a first electrode of the driving transistor is connected to a second terminal of the signal loading module and a second terminal of the light emitting control module;

a second electrode of the driving transistor is connected to a fourth terminal of the signal loading module and a third terminal of the light emitting control module;

a first terminal of the storage capacitor is connected to a first terminal of the signal loading module and a first terminal of the light emitting control module;

a fifth terminal of the signal loading module is configured to receive a data signal;

both the first terminal of the light emitting control module and the first terminal of the signal loading module are configured to receive a first voltage signal; and

a fourth terminal of the light emitting control module is configured to output a driving voltage signal.

2. The pixel circuit according to claim 1, wherein the signal loading module comprises a first transistor, a second transistor and a third transistor;

a gate of the first transistor is configured to receive a gate control signal for a present stage;

a first electrode of the first transistor, as the third terminal of the signal loading module, is connected to the second terminal of the storage capacitor, the gate of the driving transistor and a second electrode of the second transistor;

a second electrode of the first transistor, as the fourth terminal of the signal loading module, is connected to the second electrode of the driving transistor and the third terminal of the light emitting control module;

a gate of the second transistor is configured to receive a gate control signal for a previous stage or a start signal;

a first electrode of the second transistor is configured to receive the first voltage signal, and as the first terminal of the signal loading module, is connected to the first terminal of the storage capacitor and the first terminal of the light emitting control module;

the second electrode of the second transistor, as the third terminal of the signal loading module, is connected to the first electrode of the first transistor, the second terminal of the storage capacitor and the gate of the driving transistor;

a gate of the third transistor is configured to receive the gate control signal for the present stage;

a first electrode of the third transistor is configured to receive a data signal;

a second electrode of the third transistor, as the second terminal of the signal loading module, is connected to the first electrode of the driving transistor and the second terminal of the light emitting control module.

3. The pixel circuit according to claim 1 or 2, wherein the light emitting control module comprises a fourth transistor and a fifth transistor;

a gate of the fourth transistor is configured to receive a light emitting control signal;

a first electrode of the fourth transistor is configured to receive a first voltage signal, and as the first terminal of the light emitting control module, is connected to the first terminal of the storage capacitor and the first terminal of the signal loading module;

a second electrode of the fourth transistor, as the second terminal of the light emitting control module, is connected to the first electrode of the driving transistor and the second terminal of the signal loading module;

a gate of the fifth transistor is configured to receive the light emitting control signal;

a first electrode of the fifth transistor, as the third terminal of the light emitting control module, is connected to the second electrode of the driving transistor and the fourth terminal of the signal loading module;

a second electrode of the fifth transistor, as the fourth terminal of the light emitting control module, is configured to output the driving voltage signal.

4. The pixel circuit according to claim 1, further comprising an OLED, wherein the OLED is connected to the fourth terminal of the light emitting control module and is configured to receive the driving voltage signal to emit light.

5. The pixel circuit according to claim 4, further comprising a first voltage signal source, wherein an output terminal of the first voltage signal source is connected to the first terminal of the signal loading module and the first terminal of the light emitting control module, and the first voltage signal source is configured to output the first voltage signal to the signal loading module and the light emitting control module.

6. The pixel circuit according to claim 5, further comprising a second voltage signal source, wherein the driving transistor is an N type transistor;

a first terminal of the OLED is connected to the fourth terminal of the light emitting control module, and a second terminal of the OLED is connected to the second voltage signal source;

the first voltage signal source is a high voltage signal source, and the second voltage signal source is a low voltage signal source.

7. The pixel circuit according to claim 5, further comprising a second voltage signal source, wherein the driving transistor is a P type transistor;

a second terminal of the OLED is connected to the fourth terminal of the light emitting control module, and a first terminal of the OLED is connected to the second voltage signal source;

the first voltage signal source is a low voltage signal source, and the second voltage signal source is a high voltage signal source.

8. The pixel circuit according to claim 2, further comprising gate control signal sources and a start signal source, wherein the gate of the first transistor and the gate of the third transistor in the signal loading module are connected to the gate control signal source for the present stage;

the gate of the second transistor in the signal loading module is connected to the gate control signal source for the previous stage or the start signal source;

the gate control signal source for the present stage is configured to output the gate control signal for the present stage, and the gate control signal source for the previous stage is configured to output the gate control signal for the previous stage; and

the start signal source is configured to output the start signal.

9. The pixel circuit according to claim 3, further comprising a light emitting control signal source, wherein the light emitting control signal source is connected to the gate of the fourth transistor and the gate of the fifth transistor in the light emitting control module, and the light emitting control signal source is configured to output the light emitting control signal.

10. A driving method for the pixel circuit according to claim 1, comprising:

in a reset phase, controlling the first terminal of the signal loading module to receive the first voltage signal and controlling the third terminal of the signal loading module to apply the first voltage signal to the second terminal of the storage capacitor, so as to reset the storage capacitor;

in a storage phase, turning on the driving transistor via the second terminal of the storage capacitor;

discharging the second terminal of the storage capacitor to the second terminal of the signal loading module through the third terminal of the signal loading module, the fourth terminal of the signal loading module and the driving transistor;

receiving the data signal via the second terminal of the signal loading module and applying the data signal to the second terminal of the storage capacitor via the driving transistor, and the fourth terminal of the signal loading module and the third terminal of the signal loading module; and

in a light emitting phase, turning on the driving transistor continuously via the second terminal of the storage capacitor and applying the data signal to the driving transistor;

receiving the first voltage signal via the first terminal of the light emitting control module and applying the same to the third terminal of the light emitting control module via the second terminal of the light emitting control module and the driving transistor;

applying the data signal to the third terminal of the light emitting control module via the driving transistor; and

outputting the driving voltage signal via the fourth terminal of the light emitting control module.

11. A TFT backboard comprising a pixel circuit according to claim 1.

12. The TFT backboard according to claim 11, wherein, in the pixel circuit, the signal loading module comprises a first transistor, a second transistor and a third transistor;

a gate of the first transistor is configured to receive a gate control signal for a present stage;

a first electrode of the first transistor, as the third terminal of the signal loading module, is connected to the second terminal of the storage capacitor, the gate of the driving transistor and a second electrode of the second transistor;

a second electrode of the first transistor, as the fourth terminal of the signal loading module, is connected to the second electrode of the driving transistor and the third terminal of the light emitting control module;

a gate of the second transistor is configured to receive a gate control signal for a previous stage or a start signal;

a first electrode of the second transistor is configured to receive the first voltage signal, and as the first terminal of the signal loading module, is connected to the first terminal of the storage capacitor and the first terminal of the light emitting control module;

the second electrode of the second transistor, as the third terminal of the signal loading module, is connected to the first electrode of the first transistor, the second terminal of the storage capacitor and the gate of the driving transistor;

a gate of the third transistor is configured to receive the gate control signal for the present stage;

a first electrode of the third transistor is configured to receive a data signal;

a second electrode of the third transistor, as the second terminal of the signal loading module, is connected to the first electrode of the driving transistor and the second terminal of the light emitting control module.

13. The TFT backboard according to claim 11, wherein, in the pixel circuit, the light emitting control module comprises a fourth transistor and a fifth transistor;

a gate of the fourth transistor is configured to receive a light emitting control signal;

a first electrode of the fourth transistor is configured to receive a first voltage signal, and as the first terminal of the light emitting control module, is connected to the first terminal of the storage capacitor and the first terminal of the signal loading module;

a second electrode of the fourth transistor, as the second terminal of the light emitting control module, is connected to the first electrode of the driving transistor and the second terminal of the signal loading module;

a gate of the fifth transistor is configured to receive the light emitting control signal;

a first electrode of the fifth transistor, as the third terminal of the light emitting control module, is connected to the second electrode of the driving transistor and the fourth terminal of the signal loading module;

a second electrode of the fifth transistor, as the fourth terminal of the light emitting control module, is configured to output the driving voltage signal.

14. The TFT backboard according to claim 11, wherein the pixel circuit further comprises an OLED, wherein the OLED is connected to the fourth terminal of the light emitting control module and is configured to receive the driving voltage signal to emit light.

15. The TFT backboard according to claim 14, wherein the pixel circuit further comprises a first voltage signal source, wherein an output terminal of the first voltage signal source is connected to the first terminal of the signal loading module and the first terminal of the light emitting control module, and the first voltage signal source is configured to output the first voltage signal to the signal loading module and the light emitting control module.

16. The TFT backboard according to claim 15, wherein the pixel circuit further comprises a second voltage signal source, wherein the driving transistor is an N type transistor;

a first terminal of the OLED is connected to the fourth terminal of the light emitting control module, and a second terminal of the OLED is connected to the second voltage signal source;

the first voltage signal source is a high voltage signal source, and the second voltage signal source is a low voltage signal source.

17. The TFT backboard according to claim 15, wherein the pixel circuit further comprises a second voltage signal source, wherein the driving transistor is a P type transistor;

a second terminal of the OLED is connected to the fourth terminal of the light emitting control module, and a first terminal of the OLED is connected to the second voltage signal source;

the first voltage signal source is a low voltage signal source, and the second voltage signal source is a high voltage signal source.

18. The TFT backboard according to claim 12, wherein the pixel circuit further comprises gate control signal sources and a start signal source, wherein the gate of the first transistor and the gate of the third transistor in the signal loading module are connected to the gate control signal source for the present stage;

the gate of the second transistor in the signal loading module is connected to the gate control signal source for the previous stage or the start signal source;

the gate control signal source for the present stage is configured to output the gate control signal for the present stage, and the gate control signal source for the previous stage is configured to output the gate control signal for the previous stage; and

the start signal source is configured to output the start signal.

19. The TFT backboard according to claim 13, wherein the pixel circuit further comprises a light emitting control signal source, wherein the light emitting control signal source is connected to the gate of the fourth transistor and the gate of the fifth transistor in the light emitting control module, and the light emitting control signal source is configured to output the light emitting control signal.

20. The pixel circuit according to claim 2, wherein the light emitting control module comprises a fourth transistor and a fifth transistor;

a gate of the fourth transistor is configured to receive a light emitting control signal;

a first electrode of the fourth transistor is configured to receive a first voltage signal, and as the first terminal of the light emitting control module, is connected to the first terminal of the storage capacitor and the first terminal of the signal loading module;

a second electrode of the fourth transistor, as the second terminal of the light emitting control module, is connected to the first electrode of the driving transistor and the second terminal of the signal loading module;

a gate of the fifth transistor is configured to receive the light emitting control signal;

a first electrode of the fifth transistor, as the third terminal of the light emitting control module, is connected to the second electrode of the driving transistor and the fourth terminal of the signal loading module;

a second electrode of the fifth transistor, as the fourth terminal of the light emitting control module, is configured to output the driving voltage signal.