Compensation unit and organic light emitting display including the same

Patent metadata

Field	Value
Publication number	US-9491830-B2
Application number	US-201314036401-A
Country	US
Kind code	B2
Filing date	Sep 25, 2013
Priority date	May 24, 2013
Publication date	Nov 8, 2016
Grant date	Nov 8, 2016

Abstract

A compensation unit includes a current source unit, a current sink unit, a sensing resistor, a comparator, and a memory. The current source unit is configured to supply a first reference current to a first node. The current sink unit is configured to sink a second reference current from the first node. The sensing resistor is coupled between the first node and a second node. The comparator is configured to: compare a voltage at the first node with a voltage at the second node, and output a comparison result signal based on the comparison. The memory unit is configured to: store compensation data related to operational disparity of at least one organic light emitting diode and/or of at least one driving transistor, output the compensation data, and modify the compensation data based on the comparison result signal.

First claim

What is claimed is:

1. A compensation unit, comprising:
a current source unit configured to supply a first reference current to a first node, the first node being configured to provide feedback to a data driver configured to drive at least one organic light emitting diode;
a current sink unit configured to sink a second reference current from the first node;
a sensing resistor coupled between the first node and a second node, the second node being configured to receive output from the data driver;
a comparator configured to:
compare a voltage at the first node with a voltage at the second node, and
output a comparison result signal based on the comparison; and

a memory unit configured to:
store compensation data related to operational disparity of the at least one organic light emitting diode and/or of at least one driving transistor,
output the compensation data to affect the output of the data driver, and
modify the compensation data based on the comparison result signal.

2. The compensation unit of claim 1 , wherein:
the current source unit is configured to supply the first reference current to the first node during a first sensing period to enable determination of the operational disparity with respect to the at least one organic light emitting diode; and
the current sink unit is configured to sink the second reference current from the first node during a second sensing period to enable determination of the operational disparity of the at least one driving transistor.

3. The compensation unit of claim 2 , wherein:
the first node is coupled to a first terminal of a buffer amplifier of the data driver; and
the second node is coupled to a second terminal of the buffer amplifier.

4. The compensation unit of claim 2 , wherein the current source unit comprises:
a first reference current source configured to supply the first reference current to the first node;
a first switch coupled between the first reference current source and the first node;
the first switch is configured to be turned on in association with the first sensing period.

5. The compensation unit of claim 2 , wherein the current sink unit comprises:
a second reference current source configured to sink the second reference current source from the first node;
a second switch coupled between the second reference current source and the first node; and
the second switch is configured to be turned on in association with the second sensing period.

6. The compensation unit of claim 2 , further comprising:
a third switch coupled between the first and second nodes,
wherein the third switch is configured to be turned off in association with at least one of the first and second sensing periods.

7. The compensation unit of claim 1 , wherein the operational disparity corresponds to:
degradation in light output of the at least one organic light emitting diode; and/or
a difference in threshold voltage or mobility of the at least one driving transistor.

8. An organic light emitting display, comprising:
a pixel unit comprising pixels arranged at intersection portions of data lines with scan lines and sensing control lines;
a data driver configured to supply data signals to the data lines via output lines;
a scan driver configured to supply a scan signal to the scan lines;
a control line driver configured to supply a sensing control signal to the sensing control lines; and
a compensation unit coupled between the output lines and the data lines,
wherein the compensation unit comprises a compensation circuit disposed between an i-th (where “i” is a natural number greater than zero) output line and an i-th data line, the compensation circuit comprising:
a current source unit configured to supply a first reference current to the i-th data line,
a current sink unit configured to sink a second reference current from the i-th data line,
a sensing resistor coupled between the i-th data line and the i-th output line,
a comparator configured to:
compare a voltage of the i-th data line with a voltage of the i-th output line, and
output a comparison result signal based on the comparison, and

a memory unit configured to:
store compensation data related to operational disparity of respective organic light emitting diodes of the pixels and/or of respective driving transistors configured to correspondingly drive the organic light emitting diodes,
output the compensation data to affect the data signals of the data driver, and
modify the compensation data based on the comparison result signal.

9. The organic light emitting display of claim 8 , further comprising:
a timing controller configured to receive the compensation data from the memory unit,
wherein the timing controller is further configured to:
convert an input data signal into a second data based on the compensation data, and
supply the second data signal to the data driver.

10. The organic light emitting display of claim 9 , wherein the data driver comprises:
a shift register unit configured to generate sampling signals;
a sampling latch unit configured to receive the second data from the timing controller and store respective portions of the second data in correspondence with the sampling signals;
a holding latch unit configured to receive and temporarily store the respective portions of the second data;
a signal generating unit configured to receive and convert the respective portions of the second data into the data signals; and
a buffer unit comprising buffer amplifiers configured to receive and supply the data signals to the output lines.

11. The organic light emitting display of claim 10 , wherein a buffer amplifier, among the buffer amplifiers, disposed between the i-th output line and the i-th data line comprises:
a first input terminal coupled to the i-th data line;
a second input terminal coupled to the signal generating unit; and
an output terminal coupled to the i-th output line.

12. The organic light emitting display of claim 8 , wherein a pixel, among the pixels, disposed at an intersection portion of the i-th data line, a j-th (where “j” is a natural number greater than zero) scan line, and a j-th sensing control line comprises:
an organic light emitting diode;
a first transistor coupled between the i-th data line and a node, the first transistor being configured to turn on in response to reception of the scan signal via the j-th scan line;
a storage capacitor coupled between a first power source and the node, the storage capacitor being configured to store a voltage associated with the first power source;
a second transistor configured to supply current corresponding to the voltage stored in the storage capacitor to a second power source through the organic light emitting diode; and
a third transistor coupled between the i-th data line and a first electrode of the organic light emitting diode, the third transistor being configured to turn on in response to reception of the sensing control signal via the j-th sensing control line.

13. The organic light emitting display of claim 12 , wherein the pixel further comprises:
a fourth transistor coupled between the second transistor and the organic light emitting diode,
wherein the fourth transistor is configured to be turned off in association with the first or second reference currents being supplied to the i-th data line.

14. The organic light emitting display of claim 13 , wherein the pixel further comprises:
a fifth transistor coupled between the fourth transistor and the organic light emitting diode,
wherein the fifth transistor is configured to be turned off in association with th

Assignees

• Samsung Display Co Ltd

Inventors

• Lee Wook

Classifications

• H05B45/60 Primary

  Circuit arrangements for operating LEDs comprising organic material, e.g. for operating organic light-emitting diodes [OLED] or polymer light-emitting diodes [PLED] · CPC title

• G09G3/3233 Primary

  with pixel circuitry controlling the current through the light-emitting element · CPC title

• G09G2320/0295

  by monitoring each display pixel · CPC title

• G09G2320/0233

  Improving the luminance or brightness uniformity across the screen · CPC title

• G09G2300/0842

  forming a memory circuit, e.g. a dynamic memory with one capacitor · CPC title