An isolated full bridge boost converter with active soft switching

Isolated full bridge boost converter is attractive in applications such as single-stage Power Factor Correction (PFC) with isolation requirement or bi-direction DC-DC converter. It features several merits such as multiple-output capability with one shared choke, single-stage energy processing and good input current shaping ability. But the major disadvantages is that the transformer leakage inductance causes high transient voltage across the bridge switches, which increases the switching rating and decreases the reliability. In this paper, an active soft switching circuit is proposed for the isolated full bridge boost converter. The proposed soft switching circuit clamps the voltage across the full bridge, transfers the energy in the leakage inductance to the load, and provides zero voltage turn-off for all the main switches. Furthermore, the auxiliary switch features zero current turn-on and zero voltage turn-off. Therefore, the efficiency is improved. The analysis is verified by experimental results.