Organic electroluminescent display

• US 20060244695A1
• Filed: 04/27/2006
• Published: 11/02/2006
• Est. Priority Date: 04/29/2005
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Mobile Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: Komiya, Naoaki
• Granted Patent: US 7,564,452 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• 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 2310/0256 with the purpose of reversing the voltage across a light emitting or modulating element within a pixel
• CPC Class Codes: G09G 2330/02 Details of power systems and of start or stop of display operation
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• 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
• CPC Class Codes: G09G 3/325 the data current flowing through the driving transistor during a setting phase, e.g. by using a switch for connecting the driving transistor to the data driver
• CPC Class Codes: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements

Abstract

An organic electroluminescent display supplies a reverse bias voltage to an Organic Light-Emitting Diode (OLED) for emitting light. The organic electroluminescent display additionally includes a reverse bias transistor to supply the reverse bias voltage. The reverse bias transistor is connected between an anode of the OLED and a reverse bias power supply, between the anode of the OLED and a first power line supplying a positive source voltage, or between the anode of the OLED and a data line. Furthermore, the reverse bias transistor can be connected between an initialization line and the anode of the OLED. The reverse bias voltage is supplied to the OLED before displaying an image or within a non-display period of a vertical synchronous signal, thereby enabling detection of whether or not the OLED has a defect.

Claims

1. An organic electroluminescent display arranged in a region in which a scan line and a data line intersect each other, the display comprising:

a pixel driving part connected to a first power line and adapted to receive a scan signal from the scan line and to generate a driving current corresponding to a data signal received from the data line;

an Organic Light-Emitting Diode (OLED) connected between the pixel driving part and a second power line and adapted to emit light in response to the driving current; and

a reverse bias transistor connected between an anode of the OLED and a reverse bias power supply.

2. The organic electroluminescent display according to claim 1, wherein the reverse bias transistor is adapted to be turned on/off in response to a reverse bias control signal, and wherein the pixel driving part is prevented from generating the driving current upon the reverse bias transistor being turned on.

3. The organic electroluminescent display according to claim 2, wherein the OLED is supplied with a reverse bias voltage upon the reverse bias transistor being turned on.

4. The organic electroluminescent display according to claim 3, wherein a reverse bias voltage difference between the anode and a cathode of the OLED is in a range of from −

14V to −

10V.

5. The organic electroluminescent display according to claim 4, wherein the pixel driving part comprises:

a switching transistor connected to the data line and adapted to be turned on/off in response to the scan signal;

a capacitor connected to the switching transistor and adapted to store the data signal received via the switching transistor; and

a driving transistor connected to both the switching transistor and the first power line and adapted to generate the driving current corresponding to the data signal stored in the capacitor.

6. The organic electroluminescent display according to claim 5, wherein the data signal comprises a voltage.

7. The organic electroluminescent display according to claim 6, wherein the pixel driving part further comprises an emission control transistor connected between the driving transistor and the OLED and adapted to be turned on/off in response to an emission control signal.

8. The organic electroluminescent display according to claim 4, wherein the pixel driving part comprises:

a first switching transistor connected to the data line and adapted to be turned on/off in response to the scan signal;

a capacitor connected between the first switching transistor and the first power line and adapted to store a voltage corresponding to a data current;

a driving transistor connected to both the first switching transistor and the first power line and adapted to generate a driving current corresponding to the voltage stored in the capacitor;

a second switching transistor connected between the driving transistor and the data line and adapted to supply the data current to the data line in response to the scan signal; and

an emission control transistor connected between the driving transistor and the OLED and adapted to supply the driving current to the OLED in response to an emission control signal.

12. The organic electroluminescent display according to claim 1, wherein a reverse bias voltage difference between the anode and a cathode of the OLED is in a range of from −

14V to −

10V.

9. An organic electroluminescent display, comprising:

a pixel driving part connected to a first power line and adapted to receive a scan signal from a scan line and to generate a driving current corresponding to a data signal received from a data line;

an Organic Light-emitting Diode (OLED) connected between the pixel driving part and a second power line and adapted to emit light in response to the driving current; and

a reverse bias transistor connected between an anode of the OLED and the first power line and adapted to supply a reverse bias voltage to the OLED.

10. The organic electroluminescent display according to claim 9, wherein the reverse bias transistor is adapted to be turned on/off in response to a reverse bias control signal, and wherein the pixel driving part is prevented from generating the driving current upon the reverse bias transistor being turned on.

11. The organic electroluminescent display according to claim 10, wherein the OLED is supplied with a reverse bias voltage upon the reverse bias transistor being turned on.

13. An organic electroluminescent display, comprising:

a pixel driving part connected to a first power line and adapted to receive a scan signal from a scan line and to generate a driving current corresponding to a data signal received from a data line;

an Organic Light-Emitting Diode (OLED) connected between the pixel driving part and a second power line and adapted to emit light in response to the driving current;

a first reverse bias transistor connected between an anode of the OLED and the data line and adapted to supply a reverse bias voltage to the OLED; and

a second reverse bias transistor connected between the data line and a reverse bias power supply and adapted to supply the reverse bias voltage to the first reverse bias transistor.

14. The organic electroluminescent display according to claim 13, wherein the first and second reverse bias transistors are adapted to be turned on/off in response to a reverse bias control signal, and wherein the pixel driving part is prevented from generating the driving current upon the first and second reverse bias transistors being turned on.

15. The organic electroluminescent display according to claim 14, wherein the OLED is supplied with a reverse bias voltage from the reverse bias power supply upon the first and second reverse bias transistors being turned on.

16. The organic electroluminescent display according to claim 15, wherein a reverse bias voltage difference between the anode and a cathode of the OLED is in a range of from −

14V to −

10V.

17. The organic electroluminescent display according to claim 16, wherein the pixel driving part comprises:

a switching transistor connected to the data line and adapted to be turned on/off in response to the scan signal;

a capacitor connected to the switching transistor and adapted to store the data signal received via the switching transistor; and

a driving transistor connected to both the switching transistor and the first power line and adapted to generate the driving current corresponding to the data signal stored in the capacitor.

18. The organic electroluminescent display according to claim 17, wherein the data signal comprises a voltage.

19. The organic electroluminescent display according to claim 18, wherein the pixel driving part further comprises an emission control transistor connected between the driving transistor and the OLED and adapted to be turned on/off in response to an emission control signal.

20. The organic electroluminescent display according to claim 16, wherein the pixel driving part comprises:

a first switching transistor connected to the data line and adapted to be turned on/off in response to the scan signal;

a capacitor connected between the first switching transistor and the first power line and adapted to store a voltage corresponding to a data current;

a driving transistor connected to both the first switching transistor and the first power line and adapted to generate a driving current corresponding to a voltage stored in the capacitor;

a second switching transistor connected between the driving transistor and the data line and adapted to supply the data current to the data line in response to the scan signal; and

an emission control transistor connected between the driving transistor and the OLED and adapted to supply the driving current to the OLED in response to an emission control signal.

21. An organic electroluminescent display, comprising:

a pixel driving part connected to a first power line and adapted to receive an initialization signal via an initialization line in response to a previous scan signal, to receive a data signal from a data line in response to a current scan signal, and to generate a driving current corresponding to the received data signal;

an Organic Light-Emitting Diode (OLED) connected between the pixel driving part and a second power line and adapted to emit light in response to the driving current; and

a reverse bias transistor connected between the initialization line and an anode of the OLED and adapted to supply a reverse bias voltage to the OLED.

22. The organic electroluminescent display according to claim 21, wherein the reverse bias transistor is adapted to be turned on/off in response to a reverse bias control signal, and wherein the pixel driving part is prevented from generating the driving current upon the reverse bias transistor being turned on.

23. The organic electroluminescent display according to claim 22, wherein the OLED is supplied with a reverse bias voltage via the initialization line upon the reverse bias transistor being turned on.

24. The organic electroluminescent display according to claim 23, wherein a reverse bias voltage difference between the anode and a cathode of the OLED is in a range of from −

14V to −

10V.

25. The organic electroluminescent display according to claim 24, wherein the pixel driving part comprises:

an initialization transistor connected to the initialization line and adapted to receive an initialization signal in response to the previous scan signal;

a first switching transistor connected to the data line and adapted to receive a data signal from the data line in response to the current scan signal;

a diode connected compensation transistor connected between the first switching transistor and the initialization transistor and adapted to compensate for a threshold voltage;

a capacitor connected between the compensation transistor and the first power line and adapted to be initialized by the initialization signal and to store a data signal received via the first switching transistor and the compensation transistor;

a driving transistor connected to the first power line and adapted to generate the driving current corresponding to the data signal stored in the capacitor; and

an emission control transistor connected between the driving transistor and the OLED and adapted to supply the driving current to the OLED in response to an emission control signal.

26. The organic electroluminescent display according to claim 24, wherein the pixel driving part comprises:

an initialization transistor connected to the initialization line and adapted to receive an initialization signal in response to the previous scan signal;

a first switching transistor connected to the data line and adapted to receive a data signal from the data line in response to the current scan signal;

a driving transistor connected to the first switching transistor and adapted to generate a driving current corresponding to the data signal;

a second switching transistor connected between a gate electrode and a drain electrode of the driving transistor and adapted to be turned on/off in response to the current scan signal;

a third switching transistor connected between the driving transistor and the first power line and adapted to be turned on/off in response to an emission control signal;

a capacitor connected between the first power line and the initialization transistor and adapted to be initialized by the initialization signal and to store the data signal needed for generating a driving current of the driving transistor; and

an emission control transistor connected between the driving transistor and the OLED and adapted to supply the driving current to the OLED in response to the emission control signal.