Research On Phase-shift Full-bridge ZVS Converter With Auxiliary Circuit For Lagging-leg

Phase-Shift PWM ZVS full bridge converter is preferred in medium to high power conversionapplication. ZVS of primary switches can be achieved via the resonance between leakage inductanceand parasitic capacitance of switches, which improves the conversion efficiency. However, thedrawbacks of the conventional full bridge converter, like narrow ZVS range, large duty cycle loss,serious parasitic oscillation on rectifier, large circulating loss, limit its further application. Auxiliarynetwork technique of full bridge converter is widely studied aimed at solving the inherent drawbacks.In this paper, contrary to medium to high power application, full bridge converter is selected to be theresearch focus.Firstly, this paper classifies the soft-switching full bridge converter and discusses the advantagesand disadvantages and background of traditional ZVS full bridge converter in detail. Phase-shift fullbridge converter with parallel auxiliary network for lagging-leg is the research focus in this paper.Secondly, a full bridge converter with parallel passive adaptive auxiliary network for lagging-legis proposed. The lagging-switches achieve ZVS in whole conversion range utilizing the energy storedin the leakage inductance and auxiliary inductance. There is no dissipative element in auxiliary circuitand auxiliary energy can change adaptively as the load current varies. Duty ratio loss and parasiticoscillation are also reduced. The efficiency of the proposed converter is high in whole conversionrange. The operation principle of this converter is discussed in detail and design method of keyparameter is carefully depicted. Experimental results are given.The active auxiliary network technique is also an important research direction. So an activeauxiliary circuit in parallel with lagging leg switches is proposed in this paper. The energy stored inauxiliary circuit helps lagging switches achieving ZVS in whole load range and auxiliary energy canbe adaptively regulated by the load current. The control of auxiliary switches is quite simple and canbe implemented easily. The operation principle of the proposed converter is discussed in detail andfurther simplification of the proposed topology is suggested. The design method of key parameters iscarefully depicted. Experimental results are given.Finally, the major results of the work are summarized and future work is suggested.