DC-DC converter and display apparatus having the same

1. A DC-DC converter, comprising:

a power switch to be repetitively turned on and off to generate an output DC voltage based on an input DC voltage; and

a switching controller to control operation of the power switch over a plurality of repeating time periods within a slew rate changing cycle, wherein the switching controller includes a slew rate controller to adjust a slew rate of a switch voltage of an electrode of the power switch to vary with different slew rates over the plurality of repeating time periods.

2. The converter as claimed in claim 1 , wherein the switching controller includes a switch gate driver to adjust a level of a first voltage having a first cycle to generate a second voltage having the first cycle.

3. The converter as claimed in claim 2 , wherein the slew rate of the switch voltage decreases with an increase in a resistance of a resistor of the slew rate controller which connects the switch gate driver to the power switch.

4. The converter as claimed in claim 2 , wherein:

the slew rate controller includes N resistors connected one another in parallel, and

the N resistors sequentially connect the switch gate driver to the power switch by N switches respectively connected to the N resistors, where N being a positive integer.

5. The converter as claimed in claim 4 , the N resistors have different resistances.

6. The converter as claimed in claim 4 , wherein:

first to N-th switches of the slew rate controller are sequentially turned on, and

after the N-th switch is turned on, the first switch of the slew rate controller is turned on, wherein:

the slew rate changing cycle corresponds to time from a moment when the first switch is turned on to a moment when the first switch is turned on again, and

the slew rate changing cycle is greater than the first cycle by N times.

7. The converter as claimed in claim 4 , wherein:

first to N-th switches of the slew rate controller are sequentially turned on, and

after the N-th switch is turned on, (N−1)-th to the first switches of the slew rate controller are sequentially turned on, wherein:

the slew rate changing cycle corresponds to a time from a moment when the first switch is turned on to a moment when the first switch is turned on again, and

the slew rate changing cycle is greater than the first cycle by 2N−2 times.

8. The converter as claimed in claim 4 , wherein:

a first switch of the slew rate controller is turned on based on a rising edge of a first pulse of the first voltage, and

a second switch of the slew rate controller is turned on based on a rising edge of a second pulse of the first voltage.

9. The converter as claimed in claim 4 , wherein:

a first switch of the slew rate controller is turned on based on a rising edge of a first pulse of the first voltage, and

a second switch of the slew rate controller is turned on based on a falling edge of the first pulse of the first voltage.

10. The converter as claimed in claim 9 , wherein:

a first switch group including switches to be turned on based on rising edges of pulses of the first voltage has a first turn-on repeating cycle,

a second switch group including switches to be turned on based on falling edges of pulses of the first voltage has a second turn-on repeating cycle, and

the first turn-on repeating cycle is different from the second turn-on repeating cycle.

11. The converter as claimed in claim 4 , wherein:

the switch gate driver includes a first switch, a second switch, and a third switch,

the first switch includes a control electrode to which the first voltage is applied, an input electrode connected to a control electrode of the second switch, and an output electrode to which a second DC voltage of a first level is applied,

the second switch includes the control electrode connected to the input electrode of the first switch, an input electrode to which a first DC voltage of a second level is applied, and an output electrode connected to an input electrode of the third switch, the second level greater than the first level, and

the third switch includes a control electrode connected to the input electrode of the first switch, the input electrode connected to the output electrode of the second switch, and an output electrode to which the second DC voltage is applied.

12. The converter as claimed in claim 2 , wherein the slew rate controller is to generate a variable power voltage having various levels according to an input signal.

13. The converter as claimed in claim 12 , wherein the slew rate controller includes:

an digital-to-analog converter to receive the input signal and to generate an input analog signal;

an amplifier connected to the digital to analog converter; and

a fourth switch connected to the amplifier.

14. The converter as claimed in claim 12 , wherein the slew rate of the switch voltage increases as the variable power voltage increases.

15. The converter as claimed in claim 12 , wherein:

the variable power voltage sequentially decreases from a first level to an N-th level, and

after the level of the variable power voltage reaches the N-th level, the level of the variable power voltage increases to the first level, wherein:

the slew rate changing cycle corresponds to a time from a moment when the variable power voltage is on the first level to a moment when the variable power voltage is on the first level again after decreasing to the N-th level, and

the slew rate changing cycle is greater than the first cycle by N times.

16. The converter as claimed in claim 12 , wherein:

the variable power voltage sequentially decreases from a first level to an N-th level, and

after the level of the variable power voltage reaches the N-th level, the level of the variable power voltage sequentially increases from an (N−1)-th level to the first level, wherein:

the slew rate changing cycle corresponds to a time from a moment when the variable power voltage is on the first level to a moment when the variable power voltage is on the first level again after decreasing to the N-th level, and

the slew rate changing cycle is greater than the first cycle by 2N−2 times.

17. The converter as claimed in claim 12 , wherein:

the switch gate driver includes a first switch, a second switch, and a third switch,

the first switch includes a control electrode to which the first voltage is applied, an input electrode to which the variable power voltage is applied, and an output electrode to which a second DC voltage of a first level is applied,

the second switch includes a control electrode connected to the input electrode of the first switch, an input electrode to which a first DC voltage of a second level is applied, and an output electrode connected to an input electrode of the third switch, the second level higher than the first level, and

the third switch includes a control electrode connected to the input electrode of the first switch, the input electrode connected to the output electrode of the second switch, and an output electrode to which the second DC voltage is applied.

18. A display apparatus, comprising:

a display panel to display an image;

a DC-DC converter including a power switch and a switching controller, the power switch to be repetitively turned on and off to generate an output DC voltage based on an input DC voltage, and the switching controller to control operation of the power switch over a plurality of repeating time periods within a slew rate changing cycle; and

a display panel driver to drive the display panel based on the output DC voltage, wherein the switching controller includes a slew rate controller to adjust a slew rate of a switch voltage of an electrode of the power switch to vary with different slew rates over the plurality of repeating time periods.

19. The display apparatus as claimed in claim 18 , wherein the display panel driver includes a gate driver to output a gate signal to a gate line of the display panel, the output DC voltage of the DC-DC converter corresponding to a gate-on voltage.

20. The display apparatus as claimed in claim 18 , wherein:

the display panel driver includes a data driver to output a data voltage to a data line of the display panel, and

the output DC voltage of the DC-DC converter corresponds to an analog power voltage to generate the data voltage.