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A parallel soft-switching DC-DC converter with fewer switch count is presented to achieve zero-voltage switching (ZVS), load current sharing and partially output ripple current cancellation. Two buck-type converters are connected in parallel to achieve load current sharing. Only two MOSFETs are used in the proposed converter instead of four switches in a conventional parallel ZVS forward converter. Therefore the proposed converter has fewer active switches. Current-doubler rectifiers are used in the output side in order to achieve partially ripple current cancellation. Therefore the current ripple on output capacitor is decreased and the size of the output choke and output capacitor are reduced. An active snubber is connected between two power transformers to absorb the energy stored in the leakage and magnetising inductances of transformers, to limit voltage stresses across switches, and to achieve ZVS turn-on for all switches. The ZVS turn-on is implemented in the transition interval of two complementary switches such that the switching losses and thermal stresses on semiconductors are reduced. Operation principle, circuit analysis and design example are discussed in detail. Finally, experimental results for a 360-W (12-V/30-A) prototype were presented to verify the effectiveness of the proposed converter.
Date of Publication: November 2012