Organic light emitting display and method of compensating for image quality thereof

1. An organic light emitting diode (OLED) display device including a plurality of pixels to display images, each of the pixels including an OLED, a driving transistor connected to the OLED, and a switching transistor configured to supply data signals to the OLED, the device comprising:

a sensor configured to sense at least one voltage associated with a change amount of a mobility of the driving transistor, wherein the at least one voltage includes first and second output voltages sensed from the driving transistor in response to applying first and second data voltages to the driving transistor;

a compensation value calculator configured to obtain a change amount of a threshold voltage of the driving transistor based on a sensed change amount of the mobility,

wherein the compensation value calculator is further configured to:

obtain a functional relationship between the first and second output voltages and the first and second data voltages;

obtain a slope of a graph representing the functional relationship with respect to data voltages;

obtain a reference slope of a reference graph representing reference output voltages with respect to reference data voltages on the driving transistor; and

obtain the sensed change amount of the mobility of the driving transistor based on the slope and the reference slope; and

a data compensator configured to adjust the data signals based on the sensed change amount of mobility and the obtained change amount of the threshold voltage.

2. The OLED display device of claim 1 , wherein the sensor is further configured to detect a sensing voltage at a source of the driving transistor in response to the driving transistor being turned on by a voltage greater than the threshold voltage of the driving transistor.

3. The OLED display device of claim 1 , wherein the sensed change amount of the mobility is obtained during a non-display period before an image display begins or during a vertical blank period of an image display period.

4. The OLED display device of claim 1 , wherein the compensation value calculator is further configured to obtain the change amount of the threshold voltage without operating the driving transistor in a saturation state where a current between a source and a drain of the driving transistor becomes zero to detect a source voltage of the driving transistor.

5. The OLED display device of claim 1 , wherein the compensation value calculator is further configured to obtain the change amount of the threshold voltage based on the sensed change amount of the mobility and a function or a database relating to a correlation between the sensed change amount of the mobility and the change amount of the threshold voltage.

6. The OLED display device of claim 1 , further comprising:

a gain value calculator configured to obtain a gain value for data compensation based on the sensed change amount of the mobility; and

an offset value calculator configured to obtain an offset value for data compensation based on the obtained change amount of the threshold voltage,

wherein the data compensator is further configured to adjust the data signals based on the gain value and the offset value.

7. The OLED display device of claim 1 , wherein the compensation value calculator is further configured to:

obtain an intercept of the graph on an axis with respect to the data voltages;

obtain a reference intercept of the reference graph on the axis; and

obtain the change amount of the threshold voltage of the driving transistor based a difference between the intercept and the reference intercept.

8. A method for compensating for variations of an organic light emitting diode (OLED) display device, the OLED display device including a plurality of pixels to display images, and each of the pixels including an OLED, a driving transistor connected to the OLED, and a switching transistor configured to supply data signals to the OLED, the method comprising:

sensing a change amount of a mobility of the driving transistor;

obtaining a change amount of a threshold voltage of the driving transistor based on the sensed change amount of the mobility; and

adjusting the data signals based on the sensed change amount of the mobility and the obtained change amount of the threshold voltage,

wherein the step of sensing the change amount of the mobility comprises:

applying first and second data voltages to the driving transistor;

sensing first and second output voltages from the driving transistor;

obtaining a functional relationship between the first and second output voltages and the first and second data voltages;

obtaining a slope of a graph representing the functional relationship with respect to data voltages;

obtaining a reference slope of a reference graph representing reference output voltages with respect to reference data voltages on the driving transistor; and

obtaining the sensed change amount of the mobility of the driving transistor based on the slope and the reference slope.

9. The method of claim 8 , wherein the step of sensing the change amount of the mobility comprises detecting a sensing voltage at a source of the driving transistor in response to the driving transistor being turned on by a voltage greater than the threshold voltage of the driving transistor.

10. The method of claim 8 , wherein the step of sensing the change amount of the mobility is performed during a non-display period before an image display begins or during a vertical blank period of an image display period.

11. The method of claim 8 , wherein the change amount of the threshold voltage is obtained without operating the driving transistor in a saturation state where a current between a source and a drain of the driving transistor becomes zero to detect a source voltage of the driving transistor.

12. The method of claim 8 , wherein the change amount of the threshold voltage is obtained, based on the sensed change amount of the mobility, by using a function or a database relating to a correlation between the sensed change amount of the mobility and the change amount of the threshold voltage.

13. The method of claim 8 , further comprising:

obtaining a gain value for data compensation based on the sensed change amount of the mobility; and

obtaining an offset value for data compensation based on the obtained change amount of the threshold voltage,

wherein the data signals are adjusted based on the gain value and the offset value.

14. The method of claim 8 , wherein the step of obtaining the change amount of threshold voltage comprises:

obtaining an intercept of the graph on an axis with respect to the data voltages;

obtaining a reference intercept of the reference graph on the axis; and

obtaining the change amount of the threshold voltage of the driving transistor based a difference between the intercept and the reference intercept.

15. A method for compensating for variations of an organic light emitting diode (OLED) display device, the OLED display device including a plurality of pixels to display images, and each of the pixels including an OLED, a driving transistor connected to the OLED, and a switching transistor configured to supply data signals to the OLED, the method comprising:

applying first and second data voltages to the driving transistor;

sensing first and second output voltages from the driving transistor;

obtaining a functional relationship between the first and second output voltages and the first and second data voltages;

obtaining a slope of a graph representing the functional relationship with respect to data voltages;

obtaining a reference slope of a reference graph representing reference output voltages with respect to reference data voltages on the driving transistor;

obtaining a sensed change amount of a mobility of the driving transistor based on the slope and the reference slope;

obtaining a change amount of a threshold voltage based on the sensed change amount of the mobility; and

adjusting the data signals based on the sensed change amount of the mobility and the obtained change amount of the threshold voltage.

16. The method of claim 15 , wherein the obtaining the change amount of the threshold voltage comprises:

obtaining an intercept of the graph on an axis with respect to the data voltages;

obtaining a reference intercept of the reference graph on the axis; and

obtaining the change amount of a threshold voltage of the driving transistor based on a difference between the intercept and the reference intercept.