ORGANIC LIGHT EMITTING DISPLAY AND DRIVING METHOD THEREOF

• US 20090184901A1
• Filed: 08/05/2008
• Published: 07/23/2009
• Est. Priority Date: 01/18/2008
• Status: Abandoned Application

• Current Assignee: Industry-University Cooperation Foundation Hanyang University, Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung SDI Company Limited, University-Industry Foundation Yonsei University
• Inventors: Kwon, Oh-Kyong
• Application Number:
  US12/186,013
• Publication Number:
  US 20090184901A1
• Time in Patent Office: Days
• US Class Current: 345/77
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• 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 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0295 by monitoring each display pixel
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• 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

Abstract

An organic light emitting display includes a pixel unit including a plurality of pixels arranged at intersecting points of data lines, scan lines and light emitting control lines; a temperature sensor provided to measure a temperature of the pixel unit; a first analog/digital converter (first ADC) to convert information of the temperature measured in the temperature sensor into a first digital value; a controller to receive the first digital value outputted from the first ADC and outputting a control signal corresponding to the received first digital value; a sensing unit to extract a degradation level of an organic light emitting diode included in each of the pixels; a second analog/digital converter (second ADC) to receive information of the degradation of the organic light emitting diode extracted from the sensing unit and a control signal outputted from the controller and generating a second digital value corresponding to the information of the degradation of the organic light emitting diode that is varied according to the temperature; a conversion unit to convert an input data (Data) into a correction data (Data′) so as to display an image having uniform luminance regardless of the changes in the degradation level of the organic light emitting diode according to temperature, by using the second digital value outputted from the second ADC; a data driver to receive the correction data (Data′) outputted from the conversion unit and generating data signals to be supplied to the pixels.

Claims

1. An organic light emitting display comprising:

a pixel unit including a plurality of pixels disposed at intersecting points of data lines, scan lines and light emitting control lines;

a temperature sensor provided to measure a temperature of the pixel unit;

a first analog/digital converter (first ADC) to convert temperature information measured by the temperature sensor into a first digital value;

a controller to receive the first digital value outputted from the first ADC and to output a control signal corresponding to the received first digital value;

a sensing unit to extract information of a degradation level of an organic light emitting diode included in each of the pixels;

a second analog/digital converter (second ADC) to receive the information of the degradation level of the organic light emitting diode extracted from the sensing unit and the control signal outputted from the controller and to generate a second digital value corresponding to the information of the degradation level of the organic light emitting diode and the temperature of the pixel unit;

a conversion unit to convert an input data (Data) into a correction data (Data′

) so as to display an image having uniform luminance regardless of the degradation level of the organic light emitting diode according and the temperature of the pixel unit, by using the second digital value outputted from the second ADC; and

a data driver to receive the correction data (Data′

) outputted from the conversion unit and to generate data signals to be supplied to the pixels.

2. The organic light emitting display according to claim 1, wherein the sensing unit includes a sensing circuit arranged in each of channels, wherein the sensing circuit comprises:

a first current source unit to supply a predetermined electric current into the organic light emitting diode in the pixel; and

a switching element provided between the current source unit and the data lines corresponding respectively to the channels.

3. The organic light emitting display according to claim 2, wherein the predetermined electric current has a value (Imax) of an electric current that flows in the organic light emitting diode (OLED) when the pixel is allowed to emit the light with the maximum luminance.

4. The organic light emitting display according to claim 1, wherein the second ADC comprises:

a (j*k)bit resistor string;

a (j*k)bit switch array to select some region from the resistor string through the control signal supplied from the controller and to provide information on a predetermined reference voltage (Vref) corresponding to the temperature measured in the temperature sensor;

a comparator to receive information on the reference voltage outputted by the switch array and information on the degradation level of the organic light emitting diode outputted from the sensing circuit provided in each of the channels of the sensing unit, and to compare capacities of the received information to output a predetermined digital bit value; and

a j bit register to sequentially store a bit value outputted from the comparator.

5. The organic light emitting display according to claim 4, wherein parameter “

j”

represents a digital bit number into which the information on the degradation level of the organic light emitting diode is finally converted, and parameter “

k”

represents a different reference number selected by the measured temperature.

6. The organic light emitting display according to claim 1, wherein the conversion unit comprises:

a look-up table (LUT) addressed by a signal outputted from the second ADC to generate a certain corrected value; and

a frame memory to store the corrected value generated in the look-up table.

7. The organic light emitting display according to claim 1, wherein the data driver includes a shift register unit, a sampling latch unit, a holding latch unit, a digital/analog converting (DAC) unit and a buffer unit.

9. The organic light emitting display according to claim 7, wherein the shift register unit includes m-numbered shift registers for sequentially generating the m-numbered sampling signal.

8. The organic light emitting display according to claim 8, wherein the shift register unit receives a source start pulse (SSP) and a source shift clock (SSC) from a timing controller and sequentially generates an m-numbered sampling signal while shifting a source start pulse (SSP) in each one cycle of the source shift clock (SSC).

10. The organic light emitting display according to claim 8, wherein the sampling latch unit sequentially stores the correction data (Data′

) in response to the m-numbered sampling signal sequentially supplied from the shift register unit.

12. The organic light emitting display according to claim 10, wherein the holding latch unit receives a source output enable (SOE) signal from the timing controller and receives the correction data (Data′

) from the sampling latch unit, and supplies the Data′

to the DAC unit.

13. The organic light emitting display according to claim 12, wherein the holding latch unit includes m-numbered holding latches for storing the Data′

.

14. The organic light emitting display according to claim 12, wherein the DAC unit receives the Data′

from the holding latch unit, and generates m-numbered data signals to correspond to the received Data′

.

15. The organic light emitting display device according to claim 14, wherein the DAC unit includes m-numbered digital/analog converters arranged in each channel, which generate m-numbered data signals and supply the generated m-numbered data signals to the buffer unit.

16. The organic light emitting display device according to claim 15, wherein the buffer unit supplies the m-numbered data signals to the data lines.

11. The organic light emitting display according to claim 11, wherein the sampling latch unit includes m-numbered sampling latches so as to store m-numbered correction data (Data′

).

17. A method of driving an organic light emitting display, the method comprising:

measuring a temperature of a pixel unit including a plurality of pixels;

converting information of the measured temperature into a first digital value;

outputting a control signal corresponding to the converted first digital value;

extracting information of the degradation of the organic light emitting diode included in each of the pixels;

receiving the control signal and the extracted information of the degradation of the organic light emitting diode to generate a second digital value corresponding to the information of the degradation of the organic light emitting diode that is varied according to temperature;

converting an input data (Data) into a correction data (Data′

) so as to display an image having uniform luminance regardless of changes in the degradation level of the organic light emitting diode according to temperature, by using the generated second digital value; and

receiving the correction data (Data′

) to generate data signals to be supplied to the pixels.

18. The method of driving the organic light emitting display according to claim 17, wherein the extracting information of the degradation of the organic light emitting diode included in each of the pixels comprises:

supplying a first electric current to the organic light emitting diode included in the each of the pixels; and

measuring a first voltage generated in the organic light emitting diode through the application of the first electric current.

19. The method of driving the organic light emitting display according to claim 17, wherein the receiving of the control signal and the extracted information of the degradation of the organic light emitting diode to generate a second digital value corresponding to the information on the degradation of the organic light emitting diode that is varied according to temperature comprises:

selecting some region from a (j*k)bit resistor string through the control signal to provide information on a predetermined reference voltage (Vref) corresponding to the measured temperature;

receiving the information on the reference voltage and the information on the degradation of the organic light emitting diode and comparing capacities of the received information to output a predetermined digital bit value; and

generating a digital value of j bits corresponding to the information of the degradation of the organic light emitting diode that is varied according to temperature by sequentially storing the outputted bit value.

20. The method of driving the organic light emitting display according to claim 19, wherein parameter “

j”

represents a digital bit number into which the information of the degradation of the organic light emitting diode is finally converted, and parameter “

k”

represents a different reference number selected by the measured temperature.

21. A method of driving an organic light emitting display, the method comprising:

obtaining temperature information of a pixel unit including a plurality of pixels;

converting the temperature information into a first digital value;

outputting a control signal corresponding to the first digital value;

obtaining degradation information of an organic light emitting diode included in each of the pixels;

converting input data (Data) into a correction data (Data′

) using the control signal and the second digital data value; and

generating data signals to be supplied to the pixels using the correction data (Data′

).