Display device having gate driving circuit and driving method thereof
A display device includes: a display panel; a voltage generator to output a gate on voltage to a voltage output terminal; a clock generator to receive the gate on voltage to generate at least one clock signal; a gate driving circuit including a plurality of driving stages to output gate signals to gate lines in response to the at least one clock signal, each of the driving stages including at least one transistor to adjust a threshold voltage based on a back bias control voltage; and a signal controller to detect a current variation of the voltage output terminal and including a back bias controller to search for the back bias control voltage to minimize a consumption current level of the voltage output terminal while changing the back bias control voltage from a default voltage level when the detected current variation is greater than a reference level.
1. A display device comprising:
a display panel comprising a plurality of pixels respectively connected to a plurality of gate lines;
a voltage generator configured to output a gate on voltage to a voltage output terminal;
a clock generator configured to receive the gate on voltage to generate at least one clock signal;
a gate driving circuit comprising a plurality of driving stages configured to output gate signals to the plurality of gate lines in response to the at least one clock signal; and
a signal controller configured to detect a current variation of the voltage output terminal to output a back bias control voltage when the detected current variation is greater than a reference level,
wherein each of the plurality of driving stages comprises at least one transistor configured to adjust a threshold voltage based on the back bias control voltage, and
wherein the signal controller comprises a back bias controller configured to search for the back bias control voltage that is capable of minimizing a consumption current level of the voltage output terminal while changing the back bias control voltage by a set level from a default voltage level when the detected current variation is greater than the reference level.
2. The display device of claim 1 , wherein the back bias controller comprises:
a boundary searcher configured to search for first and second boundary voltages that are capable of minimizing the consumption current level of the voltage output terminal while changing the back bias control voltage by a first voltage level from the default voltage level when the detected current variation is greater than the reference level;
a minimum current level searcher configured to search for first and second minimum current levels that are capable of minimizing the consumption current level of the voltage output terminal while changing the back bias control voltage by a second voltage level between the first and second boundary voltages; and
a back bias control voltage setter configured to output a voltage corresponding to a relatively low current level of the first and second minimum current levels as the back bias control voltage.
3. The display device of claim 2 , wherein the first voltage level is greater than the second voltage level.
4. The display device of claim 1 , wherein the clock generator is configured to provide at least one low voltage to the gate driving circuit.
5. The display device of claim 4 , wherein the gate driving circuit comprises:
a back bias voltage signal line configured to transmit the back bias control voltage to each of the plurality of stages;
a clock signal line configured to transmit the at least one clock signal to each of the plurality of stages; and
a low voltage line configured to transmit the at least one low voltage to each of the plurality of stages.
6. The display device of claim 5 , wherein the plurality of stages are configured to output the gate signals in response to the back bias control voltage, the at least one clock signal, and the at least one low voltage.
7. The display device of claim 6 , wherein a k-th stage (where k is natural number greater than 2) of the plurality of stages comprises:
a first output transistor comprising a control electrode configured to receive an output control signal from a first node, an input electrode configured to receive the at least one clock signal, and an output electrode configured to output a k-th gate signal;
a second output transistor comprising a control electrode configured to receive the output control signal from the first node, an input electrode configured to receive the at least one clock signal, and an output electrode configured to output a k-th carry signal; and
a control portion configured to output the output control signal to the first node in response to the at least one clock signal, to output a (k−1)-th carry signal outputted from a (k−1)-th stage, and to output a (k+1)-th carry signal outputted from a (k−1)-th stage.
8. The display device of claim 7 , wherein at least one of the first and second output transistors comprises a four-terminal transistor comprising a first electrode, a second electrode, a gate electrode, and a back gate electrode connected to a source of the back bias control voltage.
9. The display device of claim 8 , wherein each of the plurality of driving stages further comprises a back bias selection portion configured to provide the at least one clock signal to the back gate electrode of the four-terminal transistor when a gate signal having an activated level is outputted to a corresponding gate line, and configured to provide the back bias control voltage to the back gate electrode of the four-terminal transistor when the gate signal having an non-activated level is outputted.
10. The display device of claim 9 , wherein the back bias selection portion comprises:
a first control transistor comprising a first electrode connected to a source of the at least one clock signal, a second electrode connected to the back gate electrode of the four-terminal transistor, and a gate electrode connected to the first node;
a second control transistor comprising a first electrode connected to the back gate electrode of the four-terminal transistor, a second electrode connected to the source of the back bias control voltage, and a gate electrode connected to a source of an inversion signal of the k-th carry signal; and
a capacitor connected between the back gate electrode of the four-terminal transistor and a source of the at least one low voltage.
11. The display device of claim 8 , wherein the signal controller is further configured to output a switching signal, and
each of the plurality of driving stages further comprises a back bias selection portion configured to provide the back bias control voltage to the back gate electrode of the four-terminal transistor when the switching signal is activated.
12. The display device of claim 11 , wherein the back bias selection portion comprises:
a control transistor comprising a first electrode connected to the source of the back bias control voltage, a second electrode connected to the back gate electrode of the four-terminal transistor, and a control electrode connected to a source of the switching signal; and
a capacitor connected between the back gate electrode of the four-terminal transistor and the second electrode of the four-terminal transistor.
13. A display device comprising:
a display panel comprising a plurality of pixels respectively connected to a plurality of gate lines;
a voltage generator configured to output a gate on voltage to a voltage output terminal;
a clock generator configured to receive the gate on voltage to generate at least one clock signal;
a gate driving circuit comprising a plurality of driving stages configured to output gate signals to the plurality of gate lines in response to the at least one clock signal; and
a signal controller configured to detect a current variation of the voltage output terminal to output a back bias control voltage when the detected current variation is greater than a reference level,
wherein each of the plurality of driving stages comprises:
at least one transistor comprising a back gate electrode configured to adjust a threshold voltage according to the back bias control voltage provided to the back gate electrode; and
a back bias selection portion configured to provide a first signal to the back gate electrode when a gate signal having an activated level is outputted to a corresponding gate line, and configured to provide the back bias control voltage to the back gate electrode when the gate signal having an non-activated level is outputted.
14. The display device of claim 13 , wherein the at least one transistor comprises a four-terminal transistor comprising a first electrode, a second electrode, a gate electrode, and the back gate electrode.
15. The display device of claim 13 , wherein the back bias selection portion comprises:
a first control transistor comprising a first electrode connected to a source of the at least one clock signal, a second electrode connected to the back gate electrode of the at least one transistor, and a gate electrode connected to a first node;
a second control transistor comprising a first electrode connected to the back gate electrode of the at least one transistor, a second electrode connected to a source of the back bias control voltage, and a gate electrode connected to a source of an inversion signal of a k-th carry signal; and
a capacitor connected between the back gate electrode of the at least one transistor and a source of at least one low voltage.
16. The display device of claim 13 , wherein the signal controller is further configured to output a switching signal,
the back bias selection portion is configured to provide the back bias control voltage to the back gate electrode of the at least one transistor when the switching signal is activated, and
the back bias selection portion comprises:
a control transistor comprising a first electrode connected to a source of the back bias control voltage, a second electrode connected to the back gate electrode of the at least one transistor, and a control electrode connected to a source of the switching signal; and
a capacitor connected between the back gate electrode of the at least one transistor and the second electrode of the at least one transistor.
17. A method for driving a display device comprising a display panel comprising a plurality of pixels respectively connected to a plurality of gate lines, and a gate driving circuit comprising a plurality of driving stages configured to output gate signals to the plurality of gate lines, the method comprising:
generating a gate on voltage to output the gate on voltage to a voltage output terminal;
generating at least one clock signal according to the gate on voltage;
driving the plurality of gate lines by utilizing the plurality of driving stages in response to the at least one clock signal;
detecting a current variation of the voltage output terminal; and
searching for a back bias control voltage that is capable of minimizing a consumption current level of the voltage output terminal while changing the back bias control voltage by a set level from a default voltage level when the detected current variation is greater than a reference level; and
outputting the back bias control voltage,
wherein each of the plurality of driving stages comprises at least one transistor configured to adjust a threshold voltage according to the back bias control voltage.
18. The method of claim 17 , wherein the outputting of the back bias control voltage comprises:
searching for first and second boundary voltages that are capable of minimizing consumption current level of the voltage output terminal while changing the back bias control voltage by a first voltage level from the default voltage level when the detected current variation is greater than the reference level;
searching for first and second minimum current levels that are capable of minimizing the consumption current level of the voltage output terminal while changing the back bias control voltage by a second voltage level between the first and second boundary voltages; and
outputting a voltage corresponding to a relatively low current level of the first and second minimum current levels as the back bias control voltage.
19. The method of claim 18 , wherein the first voltage level is greater than the second voltage level.
20. The method of claim 17 , wherein the at least one transistor comprises a four-terminal transistor comprising a first electrode, a second electrode, a gate electrode, and a back gate electrode connected to a source of the back bias control voltage.