As shown in FIG. 12, the full bridge switching unit 532 may include first and second switching elements Q1 and Q2 connected in parallel, and third and fourth switching elements Q3 and Q4 respectively connected in series to the first and second switching elements Q1 and Q2.

In addition, an input side na and nb of the transformer 536 may be connected between a first mode n1, which is between the first switching element Q1 and the second switching element Q2, and a second node n2, which is between the third switching element Q3 and the fourth switching element Q4.

Meanwhile, the inverter 570 may include a first leg including a fifth switching element Q5 and a sixth switching element Q6 connected in series to each other, and a second leg including a seventh switching element Q7 and an eighth switching element Q8 connected in series to each other.

Meanwhile, the first leg and the second leg in the unfolding inverter 540 may have different switching frequencies.

Ac power may be output through the fifth node n5 between the fifth switching element Q5 and the sixth switching element Q6 and the sixth node n6 between the seventh switching node Q7 and the eighth switching element Q8.

Meanwhile, as shown in FIG. 12, the synchronization rectification unit 538 may include ninth and tenth switching elements S1 and S2 connected in series, and first and second capacitor C1 and C2 connected in series.