APPARATUS AND METHOD FOR SUPPLYING DC POWER SOURCE

Abstract

An apparatus and method for supplying a direct current power source which is capable of compensating a power factor of an input power source by detecting an input current amount according to load changes, the apparatus comprising an input current detecting unit for detecting an input current amount to determine a load size, a power factor control unit for outputting a power factor control signal and an input current amount control signal according to the determined load size, an input current refluxing unit for refluxing the input current by cutting off an input power source based upon the input current amount control signal, an active filter for reducing a harmonic of the input current, rectifying an input alternating current (AC) voltage and boosting a smoothing voltage, a power factor compensating unit for supplying charged energy to the load based upon the power factor control signal, a smoothing unit for smoothing the rectified input AC voltage into a direct current (DC) voltage, and an inverter for converting the smoothed DC voltage into an AC voltage, whereby a power factor compensation (PFC) spec can be satisfied although the load is increased and fabricating cost can be decreased by allowing the use of 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 view showing an apparatus for supplying a DC power source according to the related art;

FIGS. 2( a) and 2(b) are waveform views of an input current of an apparatus for supplying a 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 waveform view of an input current when controlling a power factor in accordance with an embodiment of the present invention; and

FIG. 5 is a flowchart showing an embodiment of a method for supplying a DC power source according to 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 power factor control unit for outputting a power factor control signal and an input current amount control signal according to the determined load size;an input current refluxing unit for refluxing the input current by cutting off an input power source based upon the input current amount control signal;an active filter for reducing a harmonic of the input current, rectifying an input alternating current (AC) voltage and boosting a smoothing voltage;a power factor compensating unit for supplying charged energy to the load based upon the power factor control signal;a smoothing unit for smoothing the rectified AC voltage into a direct current (DC) voltage; andan inverter for converting the smoothed DC voltage into an AC voltage.

2. The apparatus of claim 1, wherein the input current detecting unit further includes a memory for storing a data table indicating a relation between the input current amount and the 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 power factor 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 an input current amount control signal to control a first switch and a power factor control signal to control a second switch.

5. The apparatus of claim 4, wherein the input current amount control signal and the power factor control signal are generated by being synchronized with the synchronous signal.

6. The apparatus of claim 4, wherein the on/off controller turns off the second switch and outputs the input current amount control signal to control the first switch when the determined load size is smaller than a reference load size, and outputs both the input current amount control signal to control the first switch and the power factor control signal to control the second switch when the determined load size is equal to or greater than the reference load size.

7. The apparatus of claim 4, wherein the on/off controller determines a pulse width modulation (PWM) ratio of each of the input current amount control signal and the power factor control signal in proportion to the load size.

8. The apparatus of claim 1, wherein the input current refluxing unit comprises: a diode bridge circuit for forming a reflux path of the input current toward the input power source; anda first switch for turning on/off the reflux path of the input current based upon the input current amount control signal.

9. The apparatus of claim 1, wherein the active filter comprises: a small reactor for reducing a harmonic and boosting a smoothing voltage; anda diode bridge circuit for rectifying an input alternating current (AC) voltage.

10. The apparatus of claim 1, wherein the power factor compensating unit charges energy from the input power source and discharges energy to the load.

11. The apparatus of claim 1, wherein the power factor compensating unit comprises: a second switch for turning on/off a path for charging or discharging energy based upon the power factor control signal; anda capacitor for charging energy from the input power source and discharging energy to the smoothing unit.

12. A method for supplying a direct current power source comprising: detecting an input current amount to determine a load size;outputting a power factor control signal and an input current amount control signal according to the determined load size;refluxing the input current by cutting off an input power source based upon the input current amount control signal;reducing a harmonic of the input current, rectifying the input AC voltage and boosting a smoothing voltage;supplying charged energy to the load based upon the power factor control signal;smoothing the rectified input AC voltage into a DC voltage; andconverting the smoothed DC voltage into an AC voltage.

13. The method of claim 12, wherein determining the load size comprises: using a data table stored in a memory, the 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 power factor control signal and the input current amount control signal comprises: detecting a zero-crossing time point of the input power source and generating a synchronous signal based upon the detected zero-crossing time point; andoutputting the input current amount control signal to control the first switch and the power factor control signal to control the second switch based upon the determined load size.

16. The method of claim 15, wherein outputting the input current amount control signal and the power factor control signal comprises: generating the input current amount control signal and the power factor control signal which are synchronized with the synchronous signal.

17. The method of claim 15, wherein outputting the input current amount control signal and the power factor control signal comprises: varying a switching time of each of the first switch and the second switch based upon the load size.

18. The method of claim 15, wherein outputting the input current amount control signal and the power factor control signal comprises: turning off the second switch and outputting the input current amount control signal to control the first switch, when the determined load size is smaller than a reference load size; andoutputting both the input current amount control signal to control the first switch and the power factor control signal to control the second switch, when the determined load size is equal to or greater than the reference load size.

19. The method of claim 15, wherein outputting the input current amount control signal and the power factor control signal comprises: determining a pulse width modulation (PWM) ratio of each of the input current amount control signal and the power factor control signal in proportion to the determined load size.

20. The method of claim 12, wherein refluxing the input current comprises: forming a reflux path of the input current toward the input power source; andcutting off the reflux path of the input current based upon the input current amount control signal.

21. The method of claim 12, wherein supplying energy to the load comprises: cutting off the second switch based upon the power factor control signal to accordingly charge energy in the capacitor from the input power source and discharge energy to the load.