APPARATUS AND METHOD FOR SUPPLYING DC POWER SOURCE

Abstract

An apparatus and method for supplying a direct current power source capable of compensating a power factor of an input power source by increasing and decreasing energy required by load changes, the apparatus comprising: an input current detecting unit for detecting an input current amount to determine a load size, a switching control unit for outputting a switching control signal to compensate a power factor of an input power source based upon the determined load size, a filtering/rectifying unit for reducing a harmonic of the input current and rectifying an input AC voltage, a power factor compensating unit for supplying charged energy to the load based upon the switching control signal, a smoothing unit for smoothing the rectified input AC voltage into a DC voltage, and an inverter for converting the smoothed DC voltage into an AC voltage and outputting the converted AC voltage to drive the load, whereby the power factor compensation (PFC) standard can be satisfied although the load is increased, and a fabricating cost can be reduced by using a reactor with a low capacity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

In the drawings:

FIG. 1 is a circuit view showing an apparatus for supplying a DC power source according to the related art;

FIGS. 2( a) and 2(b) are views showing a current waveform of the apparatus for supplying the DC power source according to the related art;

FIG. 3 is a circuit view showing an embodiment of an apparatus for supplying a DC power source according to the present invention;

FIG. 4 is a view showing a current waveform when controlling a power factor in accordance with an embodiment of the present invention;

FIG. 5 is a flowchart showing an embodiment of a method for supplying a DC power source according to the present invention;

FIGS. 6( a) and 6(b) are views respectively showing a voltage of a smooth capacitor and a current waveform of a reactor for a low load in accordance with an embodiment of the present invention; and

FIGS. 7( a) and 7(b) are views respectively showing a voltage of a smooth capacitor and a current waveform of a reactor for a high load in accordance with an embodiment of the present invention.

Claims

1. An apparatus for supplying a direct current power source comprising: an input current detecting unit for detecting an input current amount to determine a load size;a switching control unit for outputting a switching control signal to compensate a power factor of an input power source based upon the determined load size;a filtering/rectifying unit for reducing a harmonic of the input current and rectifying an input alternating current (AC) voltage;a power factor compensating unit for supplying charged energy to the load based upon the switching control signal;a smoothing unit for smoothing the rectified input AC voltage into a DC voltage; andan inverter for converting the smoothed DC voltage into an AC voltage and outputting the converted AC voltage to drive the load.

2. The apparatus of claim 1, wherein the input current detecting unit includes a memory for storing a data table indicating a relation between the input current amount and a load size corresponding thereto.

3. The apparatus of claim 1, wherein the input current detecting unit determines the load size by detecting a DC-link current.

4. The apparatus of claim 1, wherein the switching control unit comprises: a synchronous signal generator for detecting a zero-crossing time point of the input power source and generating a synchronous signal based upon the detected zero-crossing time point; andan on/off controller for outputting a switching control signal to compensate a power factor according to the determined load size.

5. The apparatus of claim 4, wherein the switching control signal is generated by being synchronized with the synchronous signal.

6. The apparatus of claim 4, wherein the on/off controller varies a turn-on time of a switch and a turn-on delay time thereof based upon the load size.

7. The apparatus of claim 4, wherein the on/off controller increases the turn-on time of the switch accordingly as the load size is increased.

8. The apparatus of claim 4, wherein the on/off controller determines a Pulse Width Modulation (PWM) ratio of the switching control signal in proportion to the determined load size.

9. The apparatus of claim 1, wherein the filtering/rectifying unit comprises: a small reactor for reducing the harmonic of the input current and preventing an influx of an inrush current; anda diode bridge circuit for rectifying the input AC voltage.

10. The apparatus of claim 1, wherein the power factor compensating unit comprises: first and second capacitors for charging and discharging energy; andfirst through fourth diodes for forming a charging/discharging path of the first and second capacitors.

11. The apparatus of claim 1, wherein the power factor compensating unit compensates a power factor of the input power source by alternately charging and discharging energy according to the switching control signal.

12. A method for supplying a direct current (DC) power source comprising: detecting an input current amount to determine a load size;outputting a switching control signal to compensate a power factor of an input power source based upon the detected load size;reducing a harmonic of the input current and rectifying an input AC voltage;supplying charged energy to the load based upon the switching control signal;smoothing the rectified input AC voltage into a DC voltage; andconverting the smoothed DC voltage into an AC voltage to drive the load.

13. The method of claim 12, wherein determining the load size comprise: using a data table indicating a relation between the input current amount and the load size corresponding thereto.

14. The method of claim 12, wherein determining the load size comprises determining the load size by detecting a DC-link current.

15. The method of claim 12, wherein outputting the switching control signal comprises: detecting a zero-crossing time point of the input power source and generating a synchronous signal according to the detected zero-crossing time point; andoutputting the switching control signal for compensating the power source according to the determined load size.

16. The method of claim 15, wherein outputting the switching control signal comprise: generating the switching control signal synchronized with the synchronous signal.

17. The method of claim 15, wherein outputting the switching control signal comprises varying a turn-on time of a switch and a turn-on delay time thereof based upon the load size.

18. The method of claim 15, wherein outputting the switching control signal comprises increasing a switching time of the switch accordingly as the load size is increased.

19. The method of claim 15, wherein outputting the switching control signal comprises determining a Pulse Width Modulation (PWM) ratio of the switching control signal in proportion to the determined load size.

20. The method of claim 12, wherein reducing the harmonic of the input current and rectifying the input AC voltage comprises: reducing the harmonic of the input current and preventing an influx of an inrush current; andrectifying the input AC voltage.

21. The method of claim 12, wherein supplying the energy to the load comprises compensating a power factor of the input power source by alternately charging and discharging energy based upon the switching control signal.

22. The method of claim 21, wherein supplying the energy to the load comprises: a first capacitor charging energy and a second capacitor discharging energy accordingly as first and second diodes are turned on and third and fourth diodes are turned off at a starting time point of a plus half period of the input power source when turning on the switch; andthe first capacitor discharging energy and the second capacitor charging energy accordingly as the first and second diodes are turned off and the third and fourth diodes are turned on at a starting time point of a minus half period of the input power source when turning on the switch.