Abstract: In order to increase the weighted efficiency of the photovoltaic micro-inverter,a DC/DC converter for the microinverter with flexible topology is proposed.The flexible converter includes two operation modes—the improved dual-switches forward mode and the full-bridge mode.The operation principles of the two modes are described,and the design guideline of the key parameters,such as the turns-ratio of transformer and buffering inductor is provided.The power threshold value is determined according to the analysis of switching loss,conduction loss,driving loss and core loss of the converter in two operation modes.A duty ratio pre-calculation control strategy combined with closed-loop fine adjustment is proposed.The experimental results show that the proposed flexible converter has a good performance in addition to a high weighted efficiency.