| 摘要 |
A synchronous rectification circuit for a DC-DC power converter can operate efficiently with a primary drive voltage that remains at a zero voltage level during a portion of the power conduction cycle. The DC-DC power converter includes a primary side power circuit providing a symmetrically varying power signal that remains at a zero voltage level for a portion of a conduction cycle. A first secondary side power circuit is inductively coupled to the primary side power circuit, and has an output terminal that provides an output voltage. The first secondary side power circuit further comprises first and second synchronous rectifiers having respective activation terminals. The synchronous rectifiers are adapted to alternately activate in synchronism with non-zero voltage level portions of the conduction cycle. A second secondary side power circuit is inductively coupled to the first secondary side power circuit and has polarity reversed with respect to the first secondary side power circuit. The second secondary side power circuit comprises first and second switching devices having respective activation terminals respectively coupled to the activation terminals of the first and second synchronous rectifiers. The first and second switching devices are adapted to alternately activate in inverse synchronism with the non-zero voltage level portions of the conduction cycle. The first and second synchronous rectifiers are selected to have lower activation voltage thresholds than the first and second switching devices such that both the first and second synchronous rectifiers remains activated during a successive zero voltage level portion of the conduction cycle.
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