Pixel driven by pulse width modulation and display device including the same

1 . A display device, comprising:

a display panel including a plurality of pixels;

a scan driver which sequentially provides scan signals to the plurality of pixels; and

a data driver which supplies a data voltage and a constant current generation voltage to each of the plurality of pixels, wherein

each of the plurality of pixels includes:

a light-emitting element including a first electrode and a second electrode connected to a low power line which transmits a low power voltage;

a pulse width modulator which controls an emission time duration of the light-emitting element based on the data voltage and a sweep signal; and

a constant current generator which supplies a driving current having a constant level to the light-emitting element based on the constant current generation voltage, and

the sweep signal has a first high voltage level in a non-emission period, and is boosted to a second high voltage level, which is higher than the first high voltage level, before decreasing to a low voltage level lower than the first high voltage level in an emission period, and

wherein the pulse width modulator includes:

a first driving transistor including a gate electrode connected to a first node, a first electrode connected to a second node, and a second electrode connected to a third node;

a first write transistor including a gate electrode which receives a scan signal, a first electrode connected to a data line which transmits the data voltage, and a second electrode connected to the second node;

a first compensation transistor including a gate electrode which receives the scan signal, a first electrode connected to the third node, and a second electrode connected to the first node;

a first emission control transistor including a gate electrode which receives an emission control signal, a first electrode which receives a first high power voltage, and a second electrode connected to the second node;

a second emission control transistor including a gate electrode which receives the emission control signal, a first electrode connected to the third node, and a second electrode connected to a fourth node;

a first initialization transistor including a gate electrode which receives a first initialization gate signal, a first electrode which receives a first initialization voltage, and a second electrode connected to the first node; and

a first capacitor including a first electrode which receives the sweep signal and a second electrode connected to the first node.

2 . A pixel, comprising:

a light-emitting element including a first electrode and a second electrode connected to a low power line which transmits a low power voltage;

a pulse width modulator which controls an emission time duration of the light-emitting element based on a data voltage and a sweep signal; and

a constant current generator which supplies a driving current having a constant level to the light-emitting element based on a constant current generation voltage,

wherein the sweep signal has a first high voltage level in a non-emission period and is boosted to a second high voltage level, which is higher than the first high voltage level, before decreasing to a low voltage level lower than the first high voltage level in an emission period, and

wherein the pulse width modulator includes:

a first driving transistor including a gate electrode connected to a first node, a first electrode connected to a second node, and a second electrode connected to a third node;

a first write transistor including a gate electrode which receives a scan signal, a first electrode connected to a data line which transmits the data voltage, and a second electrode connected to the second node;

a first compensation transistor including a gate electrode which receives the scan signal, a first electrode connected to the third node, and a second electrode connected to the first node;

a first emission control transistor including a gate electrode which receives an emission control signal, a first electrode which receives a first high power voltage, and a second electrode connected to the second node;

a second emission control transistor including a gate electrode which receives the emission control signal, a first electrode connected to the third node, and a second electrode connected to a fourth node;

a first initialization transistor including a gate electrode which receives a first initialization gate signal, a first electrode which receives a first initialization voltage, and a second electrode connected to the first node; and

a first capacitor including a first electrode which receives the sweep signal and a second electrode connected to the first node.

3 . The pixel of claim 2 , wherein the sweep signal maintains the second high voltage level for a selected time period before decreasing to the low voltage level in the emission period.

4 . The pixel of claim 2 , wherein the sweep signal linearly decreases from the second high voltage level to the low voltage level in the emission period.

5 . The pixel of claim 2 , wherein

the first driving transistor is a P-type transistor, and

each of the first write transistor and the first compensation transistor is an N-type transistor.

6 . The pixel of claim 1 , wherein the constant current generator includes:

a second driving transistor including a gate electrode connected to the fourth node, a first electrode connected to a fifth node, and a second electrode connected to a sixth node;

a second write transistor including a gate electrode which receives a constant current generation scan signal, a first electrode connected to the data line which transmits the constant current generation voltage, and a second electrode connected to the fifth node;

a second compensation transistor including a gate electrode which receives the constant current generation scan signal, a first electrode connected to the sixth node, and a second electrode connected to the fourth node;

a third emission control transistor including a gate electrode which receives the emission control signal, a first electrode which receives a second high power voltage, and a second electrode connected to the fifth node;

a fourth emission control transistor including a gate electrode which receives the emission control signal, a first electrode connected to the sixth node, and a second electrode connected to the first electrode of the light-emitting element;

a second initialization transistor including a gate electrode which receives a second initialization gate signal, a first electrode which receives the first initialization voltage, and a second electrode connected to the fourth node;

a bypass transistor including a gate electrode which receives a bypass gate signal, a first electrode connected to a second initialization voltage line which transmits a second initialization voltage, and a second electrode connected to the first electrode of the light-emitting element; and

a second capacitor including a first electrode which receives the second high power voltage and a second electrode connected to the fourth node.

7 . The pixel of claim 6 , wherein

the second driving transistor is a P-type transistor, and

each of the second write transistor and the second compensation transistor is an N-type transistor.

8 . The pixel of claim 6 , wherein the second initialization voltage line is electrically disconnected from the low power line.

9 . The pixel of claim 6 , wherein

a frame includes a display scan period in which the data voltage is written and a self-scan period in which the data voltage is not written, and

the second initialization gate signal has a turn-on voltage level in a first initialization period of the display scan period and a second initialization period of the self-scan period.

10 . The pixel of claim 9 , wherein the first initialization gate signal has a turn-on voltage level in the first initialization period, and has a turn-off voltage level in the second initialization period.

11 . A pixel of a display device driven in a normal mode and a high brightness mode, the pixel comprising:

a light-emitting element including a first electrode and a second electrode connected to a low power line which transmits a low power voltage;

a pulse width modulator which controls an emission time duration of the light-emitting element based on a data voltage and a sweep signal; and

a constant current generator which provides a driving current having a constant level to the light-emitting element based on a constant current generation voltage, wherein

the sweep signal decrease from a first high voltage level to a first low voltage level lower than the first high voltage level in an emission period of the normal mode, and

the sweep signal is boosted to a second high voltage level higher than the first high voltage level before decreasing to a second low voltage level in an emission period of the high brightness mode, and

wherein the second low voltage level is higher than the first low voltage level.

12 . The pixel of claim 11 , wherein the sweep signal maintains the second high voltage level for a selected time period before decreasing to the second low voltage level in the emission period of the high brightness mode.

13 . The pixel of claim 11 , wherein a maximum voltage level of the data voltage in the high brightness mode is equal to a maximum voltage level of the data voltage in the normal mode.

14 . The pixel of claim 11 , wherein the pulse width modulator includes:

a first driving transistor including a gate electrode connected to a first node, a first electrode connected to a second node, and a second electrode connected to a third node;

a first write transistor including a gate electrode which receives a scan signal, a first electrode connected to a data line which transmits the data voltage, and a second electrode connected to the second node;

a first compensation transistor including a gate electrode which receives the scan signal, a first electrode connected to the third node, and a second electrode connected to the first node;

a first emission control transistor including a gate electrode which receives an emission control signal, a first electrode which receives a first high power voltage, and a second electrode connected to the second node;

a second emission control transistor including a gate electrode which receives the emission control signal, a first electrode connected to the third node, and a second electrode connected to a fourth node;

a first initialization transistor including a gate electrode which receives a first initialization gate signal, a first electrode which receives a first initialization voltage, and a second electrode connected to the first node; and

a first capacitor including a first electrode which receives the sweep signal and a second electrode connected to the first node.

15 . The pixel of claim 14 , wherein the constant current generator includes:

a second driving transistor including a gate electrode connected to the fourth node, a first electrode connected to a fifth node, and a second electrode connected to a sixth node;

a second write transistor including a gate electrode which receives a constant current generation scan signal, a first electrode connected to the data line which transmits the constant current generation voltage, and a second electrode connected to the fifth node;

a second compensation transistor including a gate electrode which receives the constant current generation scan signal, a first electrode connected to the sixth node, and a second electrode connected to the fourth node;

a third emission control transistor including a gate electrode which receives the emission control signal, a first electrode which receives a second high power voltage, and a second electrode connected to the fifth node;

a fourth emission control transistor including a gate electrode which receives the emission control signal, a first electrode connected to the sixth node, and a second electrode connected to the first electrode of the light-emitting element;

a second initialization transistor including a gate electrode which receives a second initialization gate signal, a first electrode which receives the first initialization voltage, and a second electrode connected to the fourth node;

a bypass transistor including a gate electrode which receives a bypass gate signal, a first electrode connected to a second initialization voltage line which transmits a second initialization voltage, and a second electrode connected to the first electrode of the light-emitting element; and

a second capacitor including a first electrode which receives the second high power voltage and a second electrode connected to the fourth node.

16 . The pixel of claim 15 , wherein the second initialization voltage line is electrically disconnected from the low power line.

17 . The pixel of claim 15 , wherein

a frame includes a display scan period in which the data voltage is written and a self-scan period in which the data voltage is not written, and

the second initialization gate signal has a turn-on voltage level in a first initialization period of the display scan period and a second initialization period of the self-scan period.

18 . The pixel of claim 17 , wherein the first initialization gate signal has a turn-on voltage level in the first initialization period, and has a turn-off voltage level in the second initialization period.