Pixel structure for an active matrix OLED

• US 6,753,655 B2
• Filed: 12/30/2002
• Issued: 06/22/2004
• Est. Priority Date: 09/19/2002
• Status: Expired due to Fees

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Chen, Shang-Li, Chen, Chien-Ru, Shih, Jun-Ren
• Primary Examiner(s): Lee, Wilson
• Assistant Examiner(s): TRAN, THUY V
• Application Number:
  US10/330,247
• Publication Number:
  US 20040056604A1
• Time in Patent Office: 540 Days
• Field of Search: 315/169.2, 315/169.3, 345/211, 345/55, 345/76, 345/80, 345/82, 345/92
• US Class Current: 315/169.3
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• 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 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 3/3241 the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror

Abstract

A pixel structure for an active matrix OLED. A first switching transistor has a control terminal coupled to a first scan line, and a first terminal coupled to a data line. A first P-type transistor has a drain and a gate coupled to each other, and a source coupled to a voltage source. The drain is also coupled to a second terminal of the first switching transistor. A second P-type transistor has a source coupled to the voltage source, and a second switching transistor has two terminals coupled between gates of the first and second P-type transistors, and a control terminal coupled to a second scan line. A storage capacitor is coupled between the voltage source and the gate of the second P-type transistor. An OLED has an anode coupled to the drain of the second P-type transistor and a cathode coupled to ground.

Claims

1. A pixel structure for an active matrix OLED, comprising:

a first switching device having a control terminal coupled to a first scan line and a first terminal coupled to a data line;

a first P-type transistor having a drain terminal and a gate terminal coupled to each other and a source terminal coupled to a voltage source, wherein the drain terminal of the first P-type transistor is coupled to a second terminal of the first switch transistor;

a second switching device having a first terminal coupled to the gate terminal of the first P-type transistor and a control terminal coupled to a second scan line;

a second P-type transistor having a source terminal coupled to the voltage source and a gate terminal coupled to a second terminal of the second switch transistor;

a storage capacitor coupled between the voltage source and the gate terminal of the second P-type transistor; and

an OLED having an anode coupled to a drain terminal of the second P-type transistor, and a cathode coupled to ground.

2. The pixel structure of claim 1, further comprising:

a capacitive device having two terminals coupled between the second terminal of the second switching transistor and the gate terminal of the second P-type transistor, and a third terminal coupled to a compensation scan line, wherein the compensation scan line is activated when the second scan line is deactivated, and the compensation scan line is deactivated when the second scan line is activated.

3. The pixel structure of claim 2, wherein the capacitive device is a dummy transistor having a source terminal and a drain terminal coupled to a second terminal of the second switching transistor and the gate terminal of the second P-type transistor respectively, and a gate terminal coupled to the compensation scan line, wherein the source terminal and the drain terminal of the dummy transistor are coupled to each other.

4. The pixel structure of claim 3, wherein the dummy transistor is half the size of the second switching device.

5. The pixel structure of claim 1, further comprising:

a third switching transistor having two terminals coupled to the first terminal and the second terminal of the second switching transistor respectively, and a control terminal coupled to a compensation scan line, wherein the second and third switching transistors construct a CMOS switching device, and the compensation scan line is activated when the second scan line is deactivated and the compensation scan line is deactivated when the second scan line is activated.

6. The pixel structure of claim 5, wherein the third switching transistor is an N-type thin film transistor when the second transistor is a P-type thin film transistor.

7. The pixel structure of claim 5, wherein the third switching transistor is a P-type thin film transistor when the second transistor is an N-type thin film transistor.

8. The pixel structure of claim 1, wherein the first switching transistor is an N-type thin film transistor.

9. The pixel structure of claim 1, wherein the first switching transistor is an P-type thin film transistor.

10. The pixel structure of claim 1, wherein the second switching transistor is an N-type thin film transistor.

11. The pixel structure of claim 1, wherein the second switching transistor is a P-type thin film transistor.

12. The pixel structure of claim 1, wherein the first switching transistor is an N-type thin film transistor and the second switching transistor is a P-type thin film transistor.

13. The pixel structure of claim 1, wherein the first switch transistor is a P-type thin film transistor, and the second switching transistor is an N-type thin film transistor.

14. A pixel structure for an active matrix OLED, comprising:

a first switching device having a control terminal coupled to a first scan line and a first terminal coupled to a data line;

a first P-type transistor having a drain terminal and a gate terminal coupled to each other and a source terminal coupled to a voltage source, wherein the drain terminal of the first P-type transistor is coupled to a second terminal of the first switch transistor;

a second switching device having a first terminal coupled to a gate terminal of the first P-type transistor, and a control terminal coupled to a second scan line;

a second P-type transistor having a source terminal coupled to the voltage source;

a dummy transistor having a source terminal and a drain terminal coupled to a second terminal of the second switching transistor and the gate terminal of the second P-type transistor respectively, and a gate terminal coupled to a compensation scan line, wherein the source terminal and the drain terminal of the dummy transistor are coupled to each other, the dummy transistor is half the size of the second switching transistor, the compensation scan line is activated when the second scan line is deactivated and the compensation scan line is deactivated when the second scan line is activated;

a storage capacitor coupled between the voltage source and a gate terminal of the second P-type transistor; and

an OLED having an anode coupled to a drain terminal of the second P-type transistor, and a cathode coupled to ground.

15. A pixel structure for an active matrix OLED, comprising:

a first switching device having a control terminal coupled to a first scan line and a first terminal coupled to a data line;

a first P-type transistor having a drain terminal and a gate terminal coupled to each other and a source terminal coupled to a voltage source, wherein the drain terminal of the first P-type transistor is coupled to a second terminal of the first switch transistor;

a second switching device having a first terminal coupled to a gate terminal of the first P-type transistor and a control terminal coupled to a second scan line;

a third switching transistor having two terminals coupled to the first terminal and the second terminal of the second switching transistor respectively, and a control terminal coupled to a compensation scan line, wherein the second and third switching transistors construct a CMOS switching device and the compensation scan line is activated when the second scan line is deactivated and the compensation scan line is deactivated when the second scan line is activated;

a second P-type transistor having a source terminal coupled to the voltage source and a gate terminal coupled to a second terminal of the second switch transistor;

a storage capacitor coupled between the voltage source and the gate terminal of the second P-type transistor; and

an OLED having an anode coupled to a drain terminal of the second P-type transistor, and a cathode coupled to ground.

16. The pixel structure of claim 15, wherein the first switching transistor is an N-type thin film transistor.

17. The pixel structure of claim 15, wherein the first switching transistor is a P-type thin film transistor.

18. The pixel structure of claim 15, wherein the second switching transistor is an N-type thin film transistor and the third switching transistor is a P-type thin film transistor.

19. The pixel structure of claim 15, wherein the second switching transistor is a P-type thin film transistor and the third switching transistor is an N-type thin film transistor.