Hybrid dual full-bridge DC-DC converter with reduced circulating current, output filter and conduction loss of rectifier stage for RF power generator application

In this paper, a hybrid dual full-bridge DC-DC converter for radio-frequency (RF) power generator application is proposed to overcome the drawbacks of conventional phase-shift full-bridge (PSFB) converter such as large circulating current of primary side and large output filter size. The proposed converter adopts dual full-bridge hybrid structure with a small series capacitor in the primary side and full-bridge rectifier with two additional low-voltage-rated diodes in the secondary side. With this structure, the proposed converter has advantages of reduction of circulating current, zero-voltage switching (ZVS) operation of all primary switches, size reduction of output inductor, and low conduction loss of rectifier stage. Furthermore, the proposed converter can regulate the output voltage very wide by changing the operational mode according to the output voltage. These advantages result in the improvement of whole load efficiency. The operational principle and analysis of proposed converter are presented and analyzed. A 3kW 40-200V output laboratory prototype is designed and built to verify the feasibility and the effectiveness of the proposed converter.