System and method for exposure timing compensation for row resistance

• US 20030169219A1
• Filed: 10/17/2002
• Published: 09/11/2003
• Est. Priority Date: 10/19/2001
• Status: Abandoned Application

• Current Assignee: Clare Micronix Integrated Systems, Inc.
• Original Assignee: Clare Micronix Integrated Systems, Inc.
• Inventors: LeChevalier, Robert
• Application Number:
  US10/274,491
• Publication Number:
  US 20030169219A1
• Time in Patent Office: Days
• US Class Current: 345/84
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• 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 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 3/3216 using a passive matrix
• 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

Abstract

A current driving circuit for use with a display of light emitting elements arranged in rows and columns. The current driving circuit is configured to control the exposure time of column current sources based on the row voltage seen by the pixel in that column. The current driving circuit allows for more closely matching the currents across the array of light emitting elements in the display by compensating for variations in voltage caused by resistance in the row lines. The invention also provides a method of balancing currents in a display device comprising controlling the exposure time of column current sources based on the row voltage seen by the light emitting elements in the column.

Claims

1. A circuit configured to drive current through at least one light emitting element in a display, the circuit comprising:

at least one driver, wherein the driver is configured to drive current through the light emitting element; and

a processor configured to determine a period of time during which the driver is to drive current through the at least one light emitting element, wherein the processor is further configured to adjust the duration of the period of time based at least in part on compensating for luminosity variations in the display.

2. The circuit of claim 1, wherein the light emitting diode is organic.

3. The circuit of claim 1, wherein processor is configured to determine the period of time based upon a line resistance of at least a part of the circuit.

4. The circuit of claim 1, additionally comprising a table for storing the determined period of time.

5. A method of driving a current, comprising:

determining a voltage drop across at least a portion of a line in a circuit;

identifying an exposure period, wherein the exposure period compensates for the determined voltage drop; and

driving a current through a light emitting diode during the exposure period.

6. The method of claim 5, wherein the portion of a line in the circuit is located in a path between the light emitting diode and ground.

7. The method of claim 5, additionally comprising storing a value identifying the exposure period in a table.

8. The method of claim 5, wherein the light emitting diode is organic.

9. The method of claim 5, wherein identifying an exposure period comprises determining an effective average line drop voltage.

10. The method of claim 5, wherein driving a current though the light emitting diode comprises:

comparing a compensating time value with a counter value; and

generating a signal to turn off a current source when the compensating exposure time value matches the counter value.

11. The method of claim 5 wherein determining a voltage drop across at least a portion of a line in a circuit comprises measuring a resistance between two light emitting diodes in the circuit.

12. A system configured to drive a current, the system comprising:

means for determining a voltage drop across at least a portion of a line in a circuit;

means for identifying an exposure period, wherein the exposure period compensates for the determined voltage drop; and

means for driving a current through a light emitting diode for the exposure period.

13. The system of claim 12, wherein the portion of a line in the circuit is located in a path between the light emitting diode and ground.

14. The system of claim 12, additionally comprising means for storing a value identifying the exposure period in a table.

15. The system of claim 12, wherein the light emitting diode is organic.

16. The system of claim 12, wherein the means for identifying an exposure period comprises means for determining an effective average line drop voltage.

17. The system of claim 12, wherein the means for driving a current though the light emitting diode comprises:

means for comparing a compensating time value with a counter value; and

means for generating a signal to turn off a current source when the compensating exposure time value matches the counter value.

18. The system of claim 12, wherein the means for determining a voltage drop across at least a portion of a line in a circuit comprises means for measuring a resistance between two light emitting diodes in the circuit.