Zero-voltage-switching buck-flyback isolated DC-DC converter with synchronous rectification

This paper presents a zero-voltage-switching (ZVS) buck-flyback isolated DC-DC converter with two isolated outputs on the primary side and secondary side respectively, wherein primary-side feedback control is used. The primary output is tightly regulated while achieving rough regulation for the secondary output. Since no control isolation is needed, the cost and complexity are reduced as compared with conventional flyback converters with two outputs. Moreover, no tertiary transformer winding is needed for the primary output with primary-side control, so the transformer copper window utilization and conversion efficiency are improved compared to the multi-output flyback converters. The ZVS operation for two main switches is achieved and is verified by experimental results. Both theoretical analyses and experimental results verify the good regulation on two outputs.