Apparatus for improving yields and uniformity of active matrix oled panels

• US 20040227704A1
• Filed: 05/14/2003
• Published: 11/18/2004
• Est. Priority Date: 05/14/2003
• Status: Abandoned Application

• Current Assignee: Wintek Corporation
• Original Assignee: Wintek Corporation
• Inventors: Kuo, Chien-Chung, Han, Hsi-Rong, Wang, Wen-Chun, Liao, Wen-Tui
• Application Number:
  US10/437,291
• Publication Number:
  US 20040227704A1
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2330/08 Fault-tolerant or redundant circuits, or circuits in which repair of defects is prepared
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element

Abstract

An apparatus for improving yields and uniformity of active matrix organic light emitting diode (AMOLED) panels mainly adds a ballast resistor between a drive transistor and an organic light emitting diode (OLED) of each pixel. The ballast resistor can prevent short circuit of the drive transistor or excessive drive current in the pixel, and prevent the voltage source and the common electrode from directly occurring short circuit together when the OLED has occurred short circuit thereby improve yields and uniformity of the panel.

Claims

1. An apparatus for improving yields and uniformity of an active matrix organic light emitting diode (AMOLED) panel which consists of a plurality of pixel units, each of the pixel units comprising:

a switch transistor having a gate electrode, a drain electrode and a source electrode, the drain electrode and the gate electrode connecting respectively to a data line and a select line;

a drive transistor having a gate electrode, a drain electrode and a source electrode, the source electrode connecting to an input end of a voltage source, the gate electrode connecting to the source electrode of the switch transistor;

a storage element having one end connecting to the source electrode of the drive transistor or a common electrode and another end connecting to the source electrode of the switch transistor and the gate electrode of the drive transistor;

a ballast resistor having one end connecting to the drain electrode of the drive transistor; and

an organic light emitting diode (OLED) having an input end connecting to another end of the ballast resistor and an output end connecting to a common electrode;

wherein the ballast resistor prevents the voltage source and the common electrode from occurring short circuit together when short circuit has occurred to the drive transistor and the OLED of the pixel unit so that the entire panel is still functioning normally regardless existing of point defect.

2. The apparatus of claim 1, wherein the switch transistor and the drive transistor are selectively N-channel or P-channel metal oxide semiconductor field effect transistors (MOSFETs) or thin film transistors (TFTs).

3. The apparatus of claim 1, wherein the storage element is a capacitor.

4. The apparatus of claim 1, wherein the ballast resistor is a resistor.

5. The apparatus of claim 1, wherein the ballast resistor is a variable resistor.

6. The apparatus of claim 1, wherein the ballast resistor is an element which has resistance properties.

7. An apparatus for improving yields and uniformity of an active matrix organic light emitting diode (AMOLED) panel which consists of a plurality of pixel units, each of the pixel units comprising:

a switch transistor which has a gate electrode, a drain electrode and a source electrode, the drain electrode and the gate electrode connecting respectively to a data line and a select line;

a redundancy serial circuit connecting to the source electrode of the switch transistor; and

a storage element having one end connecting to a voltage source of the redundancy serial circuit and another end connecting to the source electrode of the switch transistor;

wherein the redundancy serial circuit prevents the panel from occurring point defect.

8. The apparatus of claim 7, wherein the redundancy serial circuit consists of a drive transistor, a ballast resistor and an OLED connecting in a serial fashion.

9. The apparatus of claim 8, wherein the drive transistor includes a gate electrode, a drain electrode and a source electrode, the source electrode connecting to the input end of the voltage source, the gate electrode connecting to the source electrode of the switch transistor and one end of the storage element, the drain electrode connecting to one end of the ballast resistor.

10. The apparatus of claim 8, wherein the ballast resistor has one end connecting to the drain electrode of the drive transistor and another end connecting to an input end of the OLED.

11. The apparatus of claim 8, wherein the OLED has an input end connecting to one end of the ballast transistor and an output end connecting to a common electrode.

12. The apparatus of claim 7, wherein each pixel unit connects to a plurality of the redundancy serial circuits.

13. An apparatus for improving yields and uniformity of an active matrix organic light emitting diode (AMOLED) panel which consists of a plurality of pixel units, each of the pixel elements comprising:

a switch transistor having a gate electrode, a drain electrode and a source electrode, the drain electrode and the gate electrode connecting respectively to a data line and a select line;

a drive transistor having a gate electrode, a drain electrode and a source electrode, the source electrode connecting to an input end of a voltage source, the gate electrode connecting to the source electrode of the switch transistor;

a storage element having one end connecting to the input end of the voltage source or a common electrode and another end connecting to the source electrode of the switch transistor and the gate electrode of the drive transistor; and

a redundancy serial circuit connecting to the drain electrode of the drive transistor for preventing point defect from occurring to the panel.

14. The apparatus of claim 13, wherein the redundancy serial circuit consists of a ballast resistor and an OLED.

15. The apparatus of claim 14, wherein the ballast resistor has one end connecting to the drain electrode of the drive transistor and another end connecting to the OLED.

16. The apparatus of claim 14, wherein the OLED has an input end connecting to one end of the resistor element and an output end connecting to a common electrode.

17. The apparatus of claim 13, wherein each pixel unit connects to a plurality of redundancy serial circuits.