Typically the buck fed push pull (or full bridge) topology is combined by a pre-regulated buck followed by a unregulated push pull power stage. This is a two-stage conguration. The first stage functions as voltage regulation and the second stage functions as isolation and voltage step-up /step down.The second stage can also be a full bridge. The ZVS operation can be implemented in the second stage.
The benefites of this topology are:
1. support ultra input voltage range
2. very low voltage stress on the synchronous rectifier during the tests of dip and surge.
ADP1051 can be used to control this power stage well. See the attached reference schematic for the details.
See the link forthe reference design. It is in Chinese.
参考设计 | 基于ADP1051的高效低成本400W电源设计 | ADI参考设计 | 亚德诺半导体