Pixel and organic light emitting display device using the same

• US 9,007,283 B2
• Filed: 01/21/2011
• Issued: 04/14/2015
• Est. Priority Date: 07/20/2010
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: Choi, Deok-Young
• Primary Examiner(s): EURICE, MICHAEL
• Application Number:
  US13/011,743
• Publication Number:
  US 20120019501A1
• Time in Patent Office: 1,544 Days
• Field of Search: 257/57, 257/59, 257/E51.018, 315/169.3, 365/177, 345/76, 345/77, 345/81, 345/82, 345/92, 345/204, 327/91
• US Class Current: 345/82
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than 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 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 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: H10K 59/1216 the pixel elements being capacitors

Abstract

A pixel and display having the pixel are disclosed. The pixel includes transistors along a leakage path from a storage capacitor. The pixel also includes transistors to apply a reference voltage to the leakage path to minimize leakage.

Claims

1. A pixel comprising:

an organic light emitting diode of which a cathode electrode is connected to a second power supply;

a first transistor for controlling the amount of current that flows to the second power supply through the organic light emitting diode from a first power supply;

a second transistor connected between a data line and a second node, and turned on by a scanning signal supplied to an i-th scanning line, wherein i is a natural number;

a first capacitor connected between a first node and the second node, wherein the first node is connected to a gate electrode of the first transistor;

a second capacitor connected between the first power supply and the first node;

a plurality of third transistors connected between the first node and a second electrode of the first transistor, wherein the third transistors are turned on by the scanning signal supplied to the i-th scanning line;

a plurality of fourth transistors connected between an initial power supply and the first node, and turned on by a scanning signal supplied to the i-1-th scanning line to supply initial power to the gate electrode of the first transistor; and

a leakage current prevention unit for supplying a fixed voltage to a fourth node between the fourth transistors and to a third node between the third transistors,

wherein the leakage current prevention unit includes;

a sixth transistor connected between a reference voltage supply supplying the fixed voltage and the fourth node, and

a seventh transistor connected between the reference voltage supply and the third node, and

wherein the voltage of the reference voltage supply is higher than the voltage of the initial power supply.

2. The pixel as claimed in claim 1, wherein the reference voltage supply has a voltage higher than the voltage of the second power supply and higher than the data signal supplied to the data line.

3. The pixel as claimed in claim 1, wherein the sixth transistor and the seventh transistor are off while the third transistors and the fourth transistors are on.

4. The pixel as claimed in claim 1, wherein the fourth node and the second node are electrically connected.

5. The pixel as claimed in claim 1, further comprising a fifth transistor connected between the organic light emitting diode and the second electrode of the first transistor, and is on while the third transistors and the fourth transistors are off.

6. An organic light emitting display device, comprising:

a scanning driver for supplying a scanning signal to scanning lines and for supplying an emission control signal to emission control lines;

a data driver for supplying a data signal to data lines;

a plurality of pixels located near intersections of the scanning lines and the data lines;

wherein i is a natural number and a pixel that is located on the i-th horizontal line, includes;

an organic light emitting diode of which a cathode electrode is connected to a second power supply;

a first transistor for controlling the amount of current that flows to the second power supply through the organic light emitting diode from a first power supply;

a second transistor connected between a data line and a second node, and turned on by a scanning signal supplied to an i-th scanning line;

a first capacitor connected between a first node and the second node, wherein the first node is connected to a gate electrode of the first transistor;

a second capacitor connected between the first power supply and the first node;

a plurality of third transistors connected between the first node and a second electrode of the first transistor, wherein the third transistors are turned on by the scanning signal supplied to the i-th scanning line;

a plurality of fourth transistors connected between an initial power supply and the first node, and turned on by a scanning signal supplied to the i-1-th scanning line to supply initial power to the gate electrode of the first transistor; and

a leakage current prevention unit for supplying a reference voltage to a fourth node between the fourth transistors and to a third node between the third transistors,

wherein the leakage current prevention unit includes;

a sixth transistor between a reference voltage supply supplying the reference voltage and the fourth node, and is turned off by supplying the emission control signal to the i-th emission control line, and

a seventh transistor between the reference voltage supply and the third node, and

wherein the voltage of the reference voltage supply is higher than the voltage of the initial power supply.

7. The organic light emitting display device as claimed in claim 6, wherein the scanning driver supplies the emission control signal to an i-th emission control line while the scanning signal is supplied to the i-1-th scanning line and while the scanning signal is supplied to the i-th scanning line.

8. The organic light emitting display device as claimed in claim 6, wherein the reference voltage supply is a higher voltage than the data signal supplied to the data line.

9. The organic light emitting display device as claimed in claim 6, wherein the second node and the fourth node are electrically connected.

10. The organic light emitting display device as claimed in claim 6, further comprising:

a fifth transistor connected between the organic light emitting diode and the second electrode of the first transistor, and turned off by supplying the emission control signal to the i-th emission control line.