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This paper extends the original complementary pulsewidth modulation concept and proposes an improved dual-output dc-dc converter, in which one output branch gets the pulsewidths and is regulated by the duty cycle, while the other output branch gets the complementary pulsewidths and is regulated by the pulse-frequency modulation. The improved converter preserves all the advantages of its original version: both outputs can be fully regulated without additional switches, and all the primary-side switches can achieve the full-range zero-voltage switching. Besides, the improved converter overcomes the disadvantages of the original one: the resonant tank is moved to the primary side; the leakage and magnetizing inductances of the transformers are utilized as parts of the circuit parameters; the bulky output inductor and dissipative snubber are eliminated; both rectifiers can be clamped at the low output voltage; and they can work in the full-range zero-current switching. With these improvements, the cost and size of the proposed converter are significantly reduced, and the overall efficiency is increased. The derivation, operational principle, and circuit analysis of the proposed converter are presented in this paper, and they are verified by a prototype with 300-330 V input, and 24-V/10-A and 48-V/5-A outputs.
Date of Publication: Nov. 2011