Soft Switching Techniques For Hybrid Full-Bridge Three-Level Converter

The zero-voltage-switching (ZVS) PWM hybrid full-bridge three-level (H-FB TL) converter can operate in both three-level mode and two-level mode, the output rectified voltage is close to the output voltage over the entire input voltage range, thus the output filter can be reduced significantly, leading to high power density and fast dynamic response. So the ZVS PWM H-FB TL converter is very attractive for the applications such as fuel cells, photovoltaic cells, and telecom power supplies, where the voltage varies in a wide range. The objective of this paper is to do further research on the soft-switching techniques for the ZVS PWM H-FB TL converter.In order to eliminate the voltage oscillation and voltage spike across the rectifier diodes resulted by the reverse recovery, this paper introduces two clamping diodes into the basic ZVS PWM H-FB TL converter. The converter not only keeps all the characteristics of the basic ZVS PWM H-FB TL converter, but also eliminates the voltage oscillation and voltage spike across the rectifier diodes in both three-level mode and two-level mode, leading to a reduced voltage stress of the rectifier diodes.The operation principle and characteristics of the proposed converter are analyzed in detail, and the effectiveness is verified by a 1.2kW prototype converter.A current-doubler-rectifier (CDR) ZVS PWM H-FB TL converter is proposed in this paper, the proposed converter can achieve ZVS for all the switches in a wide load range with the use of the energy stored in the output filter inductance, in the meanwhile, the voltage oscillation and voltage spike across the rectifier diodes resulted by the reverse recovery are eliminated. This paper analyzes the operation principle, discusses the design of the block capacitor and the output inductance. A prototype converter rated 1.2kW is built in the lab to verify the effectiveness of the CDR ZVS PWM H-FB TL converter.By removing the two freewheeling diodes of the basic ZVS PWM H-FB TL converter, a capacitor-clamped ZVS PWM H-FB TL converter is obtained in this paper, and a new control strategy is proposed for the novel converter. The novel...