Organic light emitting diode display device

1. An organic light emitting diode display device comprising:

a driving element including a control electrode connected to a first node, a first electrode connected to an input terminal of a high potential driving voltage, and a second electrode connected to a second node, and controlling a driving current;

a first TFT that switches a current path between the first node and the second node in response to a scan pulse from a first gate line;

a second TFT that switches a current path between a data line and a third node in response to the scan pulse;

a third TFT that switches a current path between the third node and a reference voltage input terminal in response to a light emitting control pulse from a second gate line;

a fourth TFT that switches a current path between the second node and a fourth node in response to the light emitting control pulse;

an organic light emitting diode connected between the fourth node and a ground voltage input terminal to emit a light by the driving current;

a storage capacitor connected between the first node and the third node; and

a variable capacitor connected between the first node and the first gate line and having a capacity changed when the first TFT is turned on and off.

2. The organic light emitting diode display device of claim 1 , wherein the scan pulse and the light emitting control pulse are maintained at a turn-on level for a first period, the scan pulse is maintained at the turn-on level and the light emitting control pulse is maintained at a turn-off level for a second period, the scan pulse and the light emitting control pulse are maintained at the turn-off level for a third period, and the scan pulse is maintained at the turn-off level and the light emitting control pulse is maintained at the turn-on level for a fourth period.

3. The organic light emitting diode display device of claim 2 , wherein a capacity of the variable capacitor has a first value in the first and second periods, and a second value smaller than the first value in the third and fourth periods.

4. The organic light emitting diode display device of claim 1 , further comprising:

a fifth TFT that switches a current path between the fourth node and the reference voltage input terminal in response to the scan pulse.

5. The organic light emitting diode display device of claim 4 , wherein the first node is initialized with a reference voltage, which is applied from the reference voltage input terminal, in the first period.

6. The organic light emitting diode display device of claim 1 , further comprising:

an auxiliary capacitor connected between the input terminal of the high potential driving voltage and the first node.

7. The organic light emitting diode display device of claim 6 , wherein the auxiliary capacitor reduces a level of a kick back voltage, which has an influence on a potential of the first node, in the third period.

8. The organic light emitting diode display device of claim 1 , wherein a difference between a reference voltage applied to the reference voltage input terminal and a ground voltage applied to a ground voltage input terminal is smaller than a threshold voltage of the organic light emitting diode.

9. The organic light emitting diode display device according to claim 1 ,

wherein the variable capacitor has a structure in which a semiconductor layer, a gate insulating layer, and a gate layer are sequentially formed from a bottom to a top, and has a capacity changed according to a voltage between the semiconductor layer and the gate layer.

10. The organic light emitting diode display device according to claim 2 , wherein the variable capacitor has a structure in which a semiconductor layer, a gate insulating layer, and a gate layer are sequentially formed from a bottom to a top, and has a capacity changed according to a voltage between the semiconductor layer and the gate layer.

11. The organic light emitting diode display device according to claim 3 , wherein the variable capacitor has a structure in which a semiconductor layer, a gate insulating layer, and a gate layer are sequentially formed from a bottom to a top, and has a capacity changed according to a voltage between the semiconductor layer and the gate layer.

12. The organic light emitting diode display device according to claim 4 , wherein the variable capacitor has a structure in which a semiconductor layer, a gate insulating layer, and a gate layer are sequentially formed from a bottom to a top, and has a capacity changed according to a voltage between the semiconductor layer and the gate layer.

13. The organic light emitting diode display device according to claim 5 , wherein the variable capacitor has a structure in which a semiconductor layer, a gate insulating layer, and a gate layer are sequentially formed from a bottom to a top, and has a capacity changed according to a voltage between the semiconductor layer and the gate layer.

14. The organic light emitting diode display device according to claim 6 , wherein the variable capacitor has a structure in which a semiconductor layer, a gate insulating layer, and a gate layer are sequentially formed from a bottom to a top, and has a capacity changed according to a voltage between the semiconductor layer and the gate layer.

15. The organic light emitting diode display device according to claim 7 , wherein the variable capacitor has a structure in which a semiconductor layer, a gate insulating layer, and a gate layer are sequentially formed from a bottom to a top, and has a capacity changed according to a voltage between the semiconductor layer and the gate layer.

16. The organic light emitting diode display device according to claim 8 , wherein the variable capacitor has a structure in which a semiconductor layer, a gate insulating layer, and a gate layer are sequentially formed from a bottom to a top, and has a capacity changed according to a voltage between the semiconductor layer and the gate layer.