Patent ID: 8477519
Filing Date: 2013-07-02
Classification: H02M,Y02B

Abstract:
1. A method for controlling a switching power unit that converts AC input voltages of an AC source into DC voltages while improving a power-factor of the AC input voltages, the switching power unit comprising an AC/DC converter circuit that is composed of a power-factor correction unit and a current resonance converter unit, wherein at least a part of switching elements of the current resonance converter unit is shared with switching elements of the power-factor correction unit, the switching power unit includes a full-bridge type AC/DC converter circuit including: a series circuit comprising a first switching element and a second switching element, and a series circuit comprising a third switching element and a fourth switching element, the method comprising: around a time when polarities of the AC source are switched between a positive half cycle and a negative half cycle, controlling ON-and-OFF of the switching elements as high frequency voltages applied to a primary winding of a high frequency transformer, which is a part of the current resonance converter unit, the positive half cycle and the negative half cycle being symmetrical in a positive and a negative relation, each time polarity of the AC source is switched, controlling each of a pair of first and third switching elements and a pair of second and fourth switching elements to turn ON and OFF alternately, while one pair of the switching elements has been being controlled to turn ON and OFF, controlling each of the other pair of the switching elements to complementarily turn ON and OFF relative to one pair of the switching elements that are connected in series to each other, throughout the whole cycle of the AC source, controlling pulse signals that drive the first to fourth switching elements so that resonance voltages and resonance currents, polarities of which are changed in a certain cycle, are input to the high frequency transformer, the switching power unit further comprising: a PFC voltage detector that detects PFC voltages at both ends of a first smoothing capacitor of the power-factor correction unit; an output voltage detector that detects output voltages at both ends of a second smoothing capacitor provided on a secondary side of the high frequency transformer of the current resonance converter unit; a polar detector that detects polarity of the AC source; and a switching controller by which ON and OFF operation of the first to fourth switching elements is controlled, wherein