Pixel circuit and organic electro-luminescent display apparatus

1. A pixel circuit for driving a light emitting device comprising a first electrode and a second electrode, the pixel circuit comprising:

a driving transistor comprising a gate electrode, a first electrode, and a second electrode, the gate electrode of the driving transistor being coupled to a second node, the driving transistor being configured to output a driving current corresponding to a data signal;

a second transistor configured to electrically couple the gate electrode and the second electrode of the driving transistor to each other in response to a current scan signal applied to a gate electrode of the second transistor;

a third transistor comprising a first electrode configured to receive the data signal, the third transistor being configured to transfer the data signal to a first node in response to the current scan signal;

a fourth transistor comprising a first electrode coupled to a first power source, the fourth transistor being configured to transfer a voltage from the first power source to the first node in response to a next emission control signal;

a fifth transistor coupled in series between the second electrode of the driving transistor and the first electrode of the light emitting device, and configured to transfer the driving current from the driving transistor to the first electrode of the light emitting device in response to a current emission control signal;

a sixth transistor configured to transfer an initialization voltage to the second node in response to a previous scan signal; and

a first capacitor comprising a first electrode coupled to the first node and a second electrode coupled to the second node,

wherein, during an initialization period, the third transistor and the second transistor are configured to be off and the fourth transistor and the sixth transistor are configured to be on to initialize the first node and the second node, respectively, and

wherein, during an emission period, the fifth transistor is configured to be on to transfer the driving current to the light emitting device and the fourth transistor is configured to be on to transfer the voltage from the first power source to the first node.

2. The pixel circuit of claim 1 , wherein the light emitting device comprises an organic light emitting diode (OLED).

3. The pixel circuit of claim 1 , wherein the second transistor comprises a first electrode coupled to the gate electrode of the driving transistor, and a second electrode coupled to the second electrode of the driving transistor.

4. The pixel circuit of claim 1 , wherein the second electrode of the light emitting device is coupled to a third power source.

5. The pixel circuit of claim 4 , wherein the initialization voltage has substantially the same voltage level as a voltage of the third power source.

6. The pixel circuit of claim 1 , further comprising a second capacitor comprising a first electrode coupled to the second electrode of the first capacitor, and a second electrode coupled to a second power source.

7. The pixel circuit of claim 1 , further comprising a second capacitor comprising a first electrode coupled to the first electrode of the first capacitor, and a second electrode coupled to a second power source.

8. The pixel circuit of claim 1 , wherein:

the first electrode of the driving transistor comprises a source electrode, and

the second electrode of the driving transistor comprises a drain electrode.

9. The pixel circuit of claim 1 , wherein the previous and current scan signals, and the current and next emission control signals are configured to be driven during a first time period, a second time period, a third time period, and a fourth time period, wherein:

during the first time period, the previous scan signal and the next emission control signal have a first level, and the current scan signal and the current emission control signal have a second level;

during the second time period, the data signal is effective for the pixel circuit, the current scan signal has the first level, and the previous scan signal and the current and next emission control signals have the second level;

during the third time period, the previous and current scan signals and the next emission control signal have the second level, and the current emission control signal has the first level;

during the fourth time period, the previous and current scan signals have the second level, and the current and next emission control signals have the first level; and

the first level is a level at which the driving transistor and the second to sixth transistors are turned on, and the second level is a level at which the driving transistor and the second to sixth transistors are turned off.

10. An organic electro-luminescent display apparatus comprising:

a plurality of pixels;

a scan driver configured to output previous and current scan signals, and current and next emission control signals to each of the pixels; and

a data driver configured to generate and output data signals to the pixels,

wherein each of the pixels comprises:

an organic light emitting diode (OLED) comprising first and second electrodes;

a driving transistor comprising a gate electrode, a first electrode, and a second electrode, and configured to output a driving current corresponding to one of the data signals;

a second transistor configured to electrically couple the gate electrode and the second electrode of the driving transistor to each other in response to a respective one of the current scan signals applied to a gate electrode of the second transistor;

a third transistor comprising a first electrode configured to receive a respective one of the data signals, the third transistor being configured to transfer the respective one of the data signals to a second electrode of the third transistor in response to the respective one of the current scan signals;

a fourth transistor comprising a first electrode coupled to a first power source, the fourth transistor being configured to transfer a voltage from the first power source to the second electrode of the third transistor in response to a respective one of the next emission control signals;

a fifth transistor coupled in series between the second electrode of the driving transistor and the first electrode of the OLED, and configured to transfer the driving current from the driving transistor to the first electrode of the OLED in response to a respective one of the current emission control signals;

a sixth transistor configured to transfer an initialization voltage to the gate electrode of the driving transistor in response to a respective one of the previous scan signals; and

a first capacitor comprising a first electrode coupled to the second electrode of the third transistor and a second electrode of the fourth transistor, and a second electrode coupled to the gate electrode of the driving transistor,

wherein, during an initialization period, the third transistor and the second transistor are configured to be off and the fourth transistor and the sixth transistor are configured to be on to initialize the first electrode and the second electrode of the first capacitor, respectively, and

wherein, during an emission period, the fifth transistor is configured to be on to transfer the driving current to the light emitting device and the fourth transistor is configured to be on to transfer the voltage from the first power source to the first electrode of the first capacitor.

11. The apparatus of claim 10 , wherein the second transistor comprises a first electrode coupled to the gate electrode of the driving transistor, and a second electrode coupled to the second electrode of the driving transistor.

12. The apparatus of claim 10 , wherein the second electrode of the OLED is coupled to a third power source.

13. The apparatus of claim 12 , wherein the initialization voltage has substantially the same voltage level as a voltage of the third power source.

14. The apparatus of claim 10 , further comprising a second capacitor comprising a first electrode coupled to the second electrode of the first capacitor, and a second electrode coupled to a second power source.

15. The apparatus of claim 10 , further comprising a second capacitor comprising a first electrode coupled to the first electrode of the first capacitor, and a second electrode coupled to a second power source.

16. The apparatus of claim 10 , wherein:

the first electrode of the driving transistor comprises a source electrode, and

the second electrode of the driving transistor comprises a drain electrode.

17. The apparatus of claim 10 , wherein the scan driver is configured to be driven during a first time period, a second time period, a third time period, and a fourth time period, wherein:

during the first time period, the respective ones of the previous scan signals and the next emission control signals have a first level, and the respective ones of the current scan signals and the current emission control signals have a second level,

during the second time period, the respective one of the data signals is effective for the respective one of the pixels, the respective one of the current scan signals has a first level, and the respective ones of the previous scan signals and the current and next emission control signals have the second level,

during the third time period, the respective ones of the previous and current scan signals and the next emission control signals have the second level, and the respective one of the current emission control signals has the first level,

during the fourth time period, the respective ones of the previous and current scan signals have the second level, and the respective ones of the current and next emission control signals have the first level, and

the first level is a level at which the driving transistor and the second to sixth transistors are turned on, and the second level is a level at which the driving transistor and the second to sixth transistors are turned off.