Active matrix organic light emitting diode (amoled) display pixel structure and data load/illuminate circuit therefor

• US 5,952,789 A
• Filed: 04/14/1997
• Issued: 09/14/1999
• Est. Priority Date: 04/14/1997
• Status: Expired due to Term

• Current Assignee: Hanger Solutions, LLC (IP Investments Group LLC)
• Original Assignee: Sarnoff Corporation (SRI International, Inc.)
• Inventors: Stewart, Roger Green, Ipri, Alfred Charles
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): Lee, Wilson
• Application Number:
  US08/834,067
• Time in Patent Office: 883 Days
• Field of Search: 315/169.1, 315/169.3, 315/169.4, 345/76, 345/36, 345/49, 345/82, 345/55, 345/46, 345/48
• US Class Current: 315/169.4
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• CPC Class Codes: G09G 2310/0259 with use of an analog or digital ramp generator in the column driver or in the pixel circuit
• 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 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2310/066 Waveforms comprising a gently increasing or decreasing portion, e.g. ramp
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• 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

A pixel structure for use in a display using organic light emitting diodes (O-LEDs) is described. Each pixel structure of an overall array includes an organic light emitting diode (O-LED). Additionally, the structure includes circuitry for allowing the structure to operate in three basic modes: write select mode, write deselect mode and an illuminate mode. Hence, the structure includes circuitry for causing the pixel structure to be selected such that data can be written to the pixel structure, said data representative of a programmed current level to be applied to the O-LED; circuitry for causing the pixel structure to be deselected when a pixel structure in a different row is having data written thereto; and circuitry for applying the programmed current level to the OLED, causing the O-LED to illuminate.

Claims

1. A pixel structure for use in a display comprising:

a light emitting diode (LED);

means for causing the pixel structure to be selected such that a data voltage can be written to the pixel structure, said data representative of a desired programmed current level to be applied to the LED to produce a desired brightness level;

means for monitoring the current flowing in the LED during write programming;

feedback means for adjusting the data voltage during write programming to obtain the desired programmed current level;

means for causing the pixel structure to be deselected when a pixel structure in a different row is having data written thereto; and

means for applying the programmed current level to the LED, causing the LED to illuminate.

2. A pixel structure for use in a display comprising:

a light emitting diode (LED);

means for causing the pixel structure to be selected such that a data voltage can be written to the pixel structure, said data representative of a programmed current level to be applied to the LED to produce a desired brightness level;

means for causing the pixel structure to be deselected when a pixel structure in a different row is having data written thereto; and

means for applying the programmed current level to the LED, causing the LED to illuminate;

wherein the means for causing the pixel structure to be deselected selectively blocks current flowing through the LED while write programming other pixel structures.

3. The pixel structure of claim 2 wherein the means for causing the pixel structure to be selected includes two independently-controlled select lines and a transistor.

4. The pixel structure of claim 2 wherein the means for causing the pixel structure to be deselected includes two independently-controlled select lines and a transistor.

5. The pixel structure of claim 2 wherein the means for applying includes a capacitor and a transistor.

6. An array of pixel structures, coupled to a digital current source, each pixel structure comprising:

first and second data lines;

first and second select lines;

first and second transistors, each transistor having a source electrode, a gate electrode and a drain electrode;

a capacitor for storing a potential representative of a programmed current level; and

an organic light emitting diode (O-LED),

wherein the source electrode of the first transistor is coupled to the first data line, the source electrode of the second transistor is coupled to the second data line, the gate electrode of the first transistor is coupled to the first select line, the gate electrode of the second transistor is coupled to the drain electrode of the first transistor and to the second select line by way of the capacitor, the drain of the second transistor is coupled to the O-LED.

7. The array of pixel structures of claim 6, further comprising means, coupled to the first and second data lines, for driving each pixel structure in the array in three modes including a write select mode, a write deselect mode and an illuminate mode.

8. An array of pixel structures, coupled to a digital current source, each pixel structure comprising:

first and second data lines;

first and second select lines;

first and second transistors, each transistor having a source electrode, a gate electrode and a drain electrode;

a capacitor;

an organic light emitting diode (O-LED),

wherein the source electrode of the first transistor is coupled to the first data line, the source electrode of the second transistor is coupled to the second data line, the gate electrode of the first transistor is coupled to the first select line, the gate electrode of the second transistor is coupled to the drain electrode of the first transistor and to the second select line by way of the capacitor, the drain electrode of the second transistor coupled to the O-LED; and

means, coupled to the first and second data lines, for driving each pixel structure in the array in three modes including a write select mode, a write deselect mode and an illuminate mode, wherein the write select mode causes the pixel structure to be selected such that a programmed current level can be established in the pixel structure, said programmed current level representative of a desired brightness to be displayed on the O-LED, the write deselect mode causes the pixel structure to be deselected when a pixel structure in a different row is having data written thereto, and the illuminate mode causes the O-LED to be driven at the programmed current level causing the pixel to illuminate.

9. A method for driving a pixel structure, including an organic light emitting diode (O-LED), for use in a display comprising:

causing the pixel structure to be write selected such that data can be written to the pixel structure, said data representative of a programmed current level to be applied to the O-LED;

causing the pixel structure to be write deselected when a pixel structure in a different row is having data written thereto; and

applying the programmed current level to the O-LED, causing the O-LED to illuminate.

10. The method of claim 9, wherein the pixel structure includes two select lines and both select lines are made logic-high when the pixel structure is write selected.

11. The method of claim 9, wherein the pixel structure includes two select lines and both select lines are made logic-low when the pixel structure is write deselected.

12. The method of claim 9, wherein the pixel structure includes two select lines and one select line is made logic-high while the other select line is made logic-low when the pixel structure is illuminated.