Power supply system, display device including the same, and method of driving the same
A display device according to embodiments of the present inventive concept includes pixels connected to scan lines, data lines, sensing lines, a first power line, and a second power line; and a power supply unit supplying at least one of a first driving power source, a second driving power source, and a third driving power source to the second power line as a second power source, and the power supply unit supplies voltages of the first driving power source and the third driving power source to the second power line during a normal driving period in which the pixels emit light.
1 . A display device comprising:
pixels connected to scan lines, data lines, sensing lines, a first power line connected to an anode of a light emitting element, and a second power line connected to a cathode of the light emitting element; and
a power supply unit supplying at least one of a first driving power source, a second driving power source, and a third driving power source to the second power line as a second power source,
wherein the power supply unit supplies voltages of the first driving power source to the second power line through a first transistor and an output of a third driving power generator connected to the first transistor for output of the third driving power source during a normal driving period in which the pixels emit light.
2 . The display device of claim 1 , wherein the first driving power source is set to a ground potential (GND).
3 . The display device of claim 1 , wherein the first power line receives a voltage of a first power source from an external system.
4 . The display device of claim 3 , wherein the voltage of the first power source is set to a higher voltage than those of the first driving power source and the third driving power source.
5 . The display device of claim 1 , wherein the power supply unit supplies a voltage of the second driving power source to the second power line during a sensing driving period in which characteristics of the pixels are sensed, and
wherein the power supply unit supplies a voltage of the third driving power source to the second power line during a protective driving period for preventing overcurrent flowing through the first power line.
6 . The display device of claim 5 , wherein the voltage of the third driving power source is set higher than that of the first driving power source and lower than that of the second driving power source.
7 . The display device of claim 6 , wherein the voltage of the second driving power source is set such that the pixels do not emit light.
8 . The display device of claim 6 , wherein the voltage of the third driving power source is set so that the pixels maintain a light emitting state.
9 . The display device of claim 5 , wherein the power supply unit includes:
the first transistor connected between the second power line and the first driving power source;
the second driving power generator connected to the second power line and supplying the second driving power source; and
the third driving power generator connected to the second power line and supplying the third driving power source.
10 . The display device of claim 9 , further comprising:
a current sensing unit sensing the amount of current of the first power line and outputting an alert signal in response to a sensed result;
a load determination unit determining a load of frame data input from an external system and outputting a load signal corresponding to a determined result; and
a timing controller controlling the power supply unit in response to the alert signal and the load signal.
11 . The display device of claim 10 , wherein, when a load included in the load signal exceeds a predetermined threshold value, the timing controller sets the first transistor and the third driving power generator to be in an on state so that the display device is driven in the normal driving period regardless of the alert signal.
12 . The display device of claim 10 , wherein the current sensing unit receives a reference current and outputs an alert signal having an enable level when the amount of current of the first power line is equal to or greater than the reference current.
13 . The display device of claim 12 , wherein the timing controller sets the third driving power generator to be in an on state so that the display device is driven in the protective driving period for preventing overcurrent flowing through the first power line when the alert signal having the enable level is input and the voltage of the third driving power source is supplied to the second power line.
14 . The display device of claim 12 , wherein the timing controller sets the second driving power generator to be in an on state so that the voltage of the second driving power source is supplied to the second power line during a sensing driving period in which characteristics of a driving transistor included in the pixels are sensed.
15 . A power supply system comprising:
a first transistor disposed between a first driving power source and a power line connected to a cathode of a light emitting element to supply a first driving power source to a panel;
a second driving power generator supplying a second driving power source to the power line; and
a third driving power generator supplying a third driving power source to the power line,
wherein the third driving power source has a voltage higher than that of the first driving power source and lower than that of the second driving power source.
16 . A method of driving a display device including pixels that emit light when current flows from a first power line to a second power line, comprising:
supplying voltages of a first driving power source to the second power line and a third driving power generator outputting a third driving power source during a normal driving period in which the pixels emit light;
supplying a voltage of a second driving power source to the second power line during a sensing driving period in which information of a driving transistor included in the pixels is sensed; and
supplying a voltage of the third driving power source to the second power line during a protective driving period for preventing overcurrent flowing through the first power line.
17 . The method of claim 16 , wherein the voltage of the third driving power source is higher than that of the first driving power source and lower than that of the second driving power source.
18 . The method of claim 17 , wherein the voltages of the first driving power source and the third driving power source are set such that the pixels emit light, and the voltage of the second driving power source is set such that the pixels do not emit light.
19 . The method of claim 17 , wherein the first driving power source is set to a ground potential (GND).
20 . The method of claim 16 , further comprising:
comparing the amount of current flowing through the first power line with a reference current; and
driving in the protective driving period when the amount of current of the first power line is equal to or greater than the reference current.