DC-DC converter, organic electroluminescent display device including the same, and method of driving the organic electroluminescent display device

1. An organic electroluminescent display device comprising:

a pixel unit comprising a plurality of scan lines arranged in a row direction, a plurality of data lines arranged in a column direction, and a plurality of pixels formed at intersections between the plurality of scan lines and the plurality of data lines;

a power supply unit to generate and to output a direct current (DC) power supply from an external power source; and

a DC-DC converter to receive the DC power supply from the power supply unit, to generate a first power supply voltage and a second power supply voltage, and to supply the first power supply voltage and the second power supply voltage to the pixel unit,

wherein the DC-DC converter comprises:

a boost converter to receive the DC power supply from the power supply unit and to generate the first power supply voltage comprising a first capacitor having a first terminal electrically connected to a first power supply voltage output terminal and a second terminal;

a buck-boost converter to receive the DC power supply from the power supply unit and to generate the second power supply voltage comprising a second capacitor having a first terminal electrically connected to a second power supply voltage output terminal and a second terminal electrically connected to the second terminal of the first capacitor such that the first power supply is coupled to the second power supply through the first and second capacitors; and

an output control unit to measure a temperature of the DC-DC converter, to compare the temperature of the DC-DC converter with a reference temperature, to stop output of the first power supply voltage of the boost converter and the second power supply voltage of the buck-boost converter if the temperature of the DC-DC converter is equal to or greater than the reference temperature, and to maintain a state where the output of the first and second power supply voltages are stopped.

2. The organic electroluminescent display device of claim 1 , wherein the boost converter comprises a first switching element forming an electrical path between a DC power supply source of the power supply unit and a ground voltage source, and a second switching element forming an electrical path between the DC power supply source of the power supply unit and the first power supply voltage output terminal, and

the buck-boost converter comprises a third switching element forming an electrical path between the DC power supply source of the power supply unit and the ground voltage source and a fourth switching element forming an electrical path between the DC power supply source of the power supply unit and the second power supply voltage output terminal.

3. The organic electroluminescent display device of claim 2 , wherein the output control unit comprises a switching controller to control the first switching element through the fourth switching element to be turned on or off.

4. The organic electroluminescent display device of claim 3 , wherein the output control unit comprises a temperature controller to measure the temperature of the DC-DC converter, to compare the temperature of the DC-DC converter with a reference temperature, and to output a signal to the switching controller if the temperature of the DC-DC converter is equal to or greater than the reference temperature.

5. The organic electroluminescent display device of claim 2 , wherein the boost converter or the buck-boost converter further comprises an inductor to transmit the DC power supply of the power supply unit to the first power supply voltage output terminal or the second power supply voltage output terminal.

6. The organic electroluminescent display device of claim 1 , wherein the output control unit maintains the state where the output of the first power supply voltage and the second power supply voltage is stopped until the DC-DC converter is reset.

7. The organic electroluminescent display device of claim 5 , further comprising a current comparing unit to compare an induced current output from the inductor with an allowable current, and to output a current detection signal to the output control unit if the induced current is equal to or greater than an allowable current,

wherein the output control unit stops the output of the first power supply voltage and the second power supply voltage according to the current detection signal.

8. The organic electroluminescent display device of claim 7 , wherein the output control unit maintains the state where the output of the first power supply voltage and the second power supply voltage is stopped until the DC-DC converter is reset.

9. A DC-DC converter comprising:

a boost converter to receive a DC power supply from a power supply unit and to generate a first power supply voltage comprising a first capacitor having a first terminal electrically connected to a first power supply voltage output terminal and a second terminal;

a buck-boost converter to receive the DC power supply from the power supply unit and to generate a second power supply voltage comprising a second capacitor having a first terminal electrically connected to a second power supply voltage output terminal and a second terminal electrically connected to the second terminal of the first capacitor such that the first power supply is coupled to the second power supply through the first and second capacitors; and

an output control unit to measure a temperature of the DC-DC converter, to compare the temperature with a reference temperature, to stop output of the first power supply voltage of the boost converter and the second power supply voltage of the buck-boost converter if the temperature is equal to or greater than the reference temperature, and to maintain a state where the output of the first and second power supply voltage is stopped.

10. The DC-DC converter of claim 9 , wherein the boost converter comprises a first switching element for forming an electrical path between a DC power supply source of the power supply unit and a ground voltage source and a second switching element for forming an electrical path between the DC power supply source of the power supply unit and the first power supply voltage output terminal, and

the buck-boost converter comprises a third switching element for forming an electrical path between the DC power supply source of the power supply unit and the ground voltage source and a fourth switching unit for forming an electrical path between the DC power supply source of the power supply unit and the second power supply voltage output terminal.

11. The DC-DC converter of claim 10 , wherein the output control unit comprises a switching controller to control the first switching element through the fourth switching unit to be turned on or off.

12. The DC-DC converter of claim 11 , wherein the output control unit comprises a temperature controller to measure a temperature of the DC-DC converter, to compare the temperature of the DC-DC converter with a reference temperature, and to output a signal to the switching controller if the temperature of the DC-DC converter is equal to or greater than the reference temperature.

13. The DC-DC converter of claim 10 , wherein the output control unit maintains the state where the output of the first power supply voltage and the second power supply voltage is stopped until the DC-DC converter is reset.

14. The DC-DC converter of claim 10 , wherein the boost converter or the buck-boost converter further comprises an inductor to transmit the DC power supply of the power supply unit to the first power supply voltage output terminal or the second power supply voltage output terminal.

15. The DC-DC converter of claim 14 , further comprising a current comparing unit to compare an induced current output from the inductor with an allowable current and to output a current detection signal to the output control unit if the induced current is equal to or greater than the allowable current,

wherein the output control unit stops the output of the first power supply voltage and the second power supply voltage according to the current detection signal.

16. The DC-DC converter of claim 15 , wherein the output control unit maintains the state where the output of the first power supply voltage and the second power supply voltage is stopped until the DC-DC converter is reset.

17. A method of driving an organic electroluminescent display device comprising a power supply unit for generating a DC power supply from an external power source and supplying the DC power supply to a DC-DC converter and the DC-DC converter for converting the DC power supply into a first power supply voltage and a second power supply voltage and supplying the first power supply voltage and the second power supply voltage to a plurality of pixels, the method comprising:

receiving the DC power supply from the power supply unit and generating the first power supply voltage utilizing a boost converter and the second power supply voltage utilizing a buck-boost converter;

detecting a temperature of the DC-DC converter;

comparing the temperature with a reference temperature;

stopping output of the first power supply voltage and the second power supply voltage if the temperature is equal to or greater than the reference temperature; and

maintaining a state where the output of the first power supply voltage and the second power supply voltage is stopped until the DC-DC converter is reset,

wherein: the boost converter comprises a first capacitor having a first terminal electrically connected to a first power supply voltage output terminal and a second terminal, and

the buck-boost converter comprises a second capacitor having a first terminal electrically connected to the second power supply voltage output terminal and a second terminal electrically connected to the second terminal of the first capacitor such that the first power supply is coupled to the second power supply through the first and second capacitors.

18. The method of claim 17 , further comprising:

detecting a current in a path through which the DC power supply of the DC-DC converter is transmitted;

comparing the current with an allowable current;

outputting a current detection signal if the current is equal to or greater than the allowable current; and

stopping the output of the first power supply voltage and the second power supply voltage according to the current detection signal.