Organic electro-luminescence device and method for driving the same

1. An organic electro-luminescence device, comprising:

a light-emitting device in a pixel for emitting light;

a data line for providing a data voltage;

a driving transistor connected to the light emitting device, wherein when the driving transistor is turned on to drive the light-emitting device, a driving voltage applied to the light emitting device reaches a value of a difference between a supply voltage and the data voltage;

a power line to supply the supply voltage;

a capacitor between the data line and a gate of the driving transistor for storing a voltage of a difference between the data voltage and a threshold voltage of the driving transistor;

a first switching device between the data line and the capacitor;

a second switching device between the gate of the driving transistor and a drain of the driving transistor; and

a third switching device between one of an anode and a cathode of the light-emitting device and a node between the first switching device and the capacitor,

wherein the supply voltage is supplied via the power line to an anode of the light-emitting device,

wherein the driving transistor includes a negative gain circuit in which the drain of the driving transistor is connected to the gate of the driving transistor by the second switching device,

wherein the third switching device is operated by a logic level opposite to the logic level supplied to the first and second switching devices,

wherein the driving transistor and the capacitor constitutes a buffer circuit configured to buffer a driving voltage applied to the inside of the pixel,

wherein each of the first switching device, the second switching device and the third switching device is a thin film transistor of the type which is identical,

wherein the gate and the drain of the driving transistor is equal when the first and second switching devices are turned on, and the third switching device is turned off, the capacitor is charged with the difference between the data voltage and a voltage of the gate,

wherein the voltage of the drain of the driving transistor adds the charged voltage of the capacitor to the threshold voltage when the first and second switching devices are turned off, and the third switching device is turned on,

wherein the first and second switching devices are operated in response to a first scan signal applied from a first gate line among a plurality of gate lines, the third switching device is operated by a second scan signal applied from a next gate line of the first gate line, and

wherein the second scan signal has a period of a low level when the first scan signal has a period of a high level, the second scan signal has a period of a high level when the first scan signal has a period of a low level.

2. The organic electro-luminescence device of claim 1 , wherein the first switching device and the second switching device are on and the third switching device is off in a first period to charge the capacitor to the voltage of the difference between the data voltage and a threshold voltage of the driving transistor, and the first switching device and the second switching device are off and the third switching device is on in a second period so that a voltage of the drain of the driving transistor reaches the data voltage.

3. The organic electro-luminescence device of claim 1 , wherein each of the first switching device, the second switching device and the third switching device is one of a p-type transistor and an n-type transistor.

4. The organic electro-luminescence device of claim 1 , wherein the driving transistor is a CMOS (complementary metal oxide semiconductor) transistor.

5. The organic electro-luminescence device of claim 1 , wherein the light-emitting device is an organic light-emitting diode.

6. A method for driving an organic electro-luminescent display device, comprising:

supplying a data voltage via a data line in a first period to charge a capacitor between the data line and a driving transistor to a value of a difference between the data voltage and a threshold voltage of the driving transistor;

applying a driving voltage via the driving transistor and the capacitor to a light emitting device with a value of a difference between a supply voltage and the data voltage in a second period;

supplying the supply voltage to an anode of the light-emitting device; and

supplying the supply voltage to a source of the driving transistor,

wherein the driving transistor includes a negative gain circuit in which a drain of the driving transistor is connected to a gate of the driving transistor by a switching elements,

wherein the switching elements include a first switching device between the data line and the capacitor, a second switching device between the gate of the driving transistor and the drain of the driving transistor and a third switching device between one of an anode and a cathode of the light-emitting device and a node between the first switching device and the capacitor,

wherein the third switching device is operated by a logic level opposite to the logic level supplied to the first and second switching devices,

wherein the driving transistor and the capacitor constitutes a buffer circuit configured to buffer a driving voltage applied to the inside of the pixel,

wherein each of the first switching device, the second switching device and the third switching device is a thin film transistor,

wherein the gate and the drain of the driving transistor is equal when the first and second switching devices are turned on, and the third switching device is turned off, the capacitor is charged with the difference between the data voltage and a voltage of the gate,

wherein the voltage of the drain of the driving transistor adds the charged voltage of the capacitor to the threshold voltage when the first and second switching devices are turned off, and the third switching device is turned on,

wherein the first and second switching devices are operated in response to a first scan signal applied from a first scan line among a plurality of scan lines, the third switching device is operated by a second scan signal applied from a next scan second gate line of the first scan line,

wherein each of the first switching device, the second switching device and the third switching device is a thin film transistor of the type which is identical, and

wherein the second scan signal has a period of a low level when the first scan signal has a period of a high level, the second scan signal has a period of a high level when the first scan signal has a period of a low level.

7. The method of claim 6 , wherein the step of supplying the data voltage to charge the capacitor includes:

substantially short-circuiting the gate and the drain of the driving transistor in the first period; and

supplying the data voltage to the capacitor to charge the capacitor to the value of the difference between the data voltage and the threshold voltage of the driving transistor.

8. The method of claim 7 , wherein the step of applying the driving voltage to the light emitting device includes:

stopping supplying of the data voltage to the capacitor in the second period;

stopping short-circuiting of the gate and the drain of the driving transistor in the second period; and

substantially short-circuiting the drain of the driving transistor and one electrode of the capacitor opposite to another electrode connected to the gate of the driving transistor, so as to apply the driving voltage to the light emitting device with a value of a difference between a supply voltage and the data voltage in a second period.

9. The method of claim 8 , wherein the steps of substantially short-circuiting the gate and the drain of the driving transistor, stopping supplying of the data voltage, stopping short-circuiting of the gate and the drain of the driving transistor in the second period, and substantially short-circuiting the drain of the driving transistor and the one electrode of the capacitor are performed by using a scan signal.

10. The method of claim 6 , wherein the step of applying the driving voltage to the light emitting device includes:

substantially short-circuiting a drain of the driving transistor and one electrode of the capacitor opposite to another electrode connected to a gate of the driving transistor, so as to apply the driving voltage to the light emitting device with a value of a difference between a supply voltage and the data voltage in a second period.