Research On Interleaved Two-switch Forward Converter Using Passive Auxiliary Circuit

With the rapid and remarkable development and advancement of the socity and technology,Power Electronics technology has been widly used in many fields such as aerospace,medical devices,industry,agriculture,transportation and national defense technology.In the equipment of power conversion,DC-DC converter plays an indispensable role.Two-switch forward converter is a classical DC-DC converter,which is widely used in aerospace because of its simple structure,high reliability and simple control mode.Interleaved parallel structure is commom structure.The combination of this structure and two-switch forward converter can effectively improve the overall power density of the converter and widen the adjustment range of output voltage.Consequently,it is great significant to study the interleaved two-switch forward(ITSF)converter.In order to satisfy the requirement of miniaturization and lightweight,one of the most important technology is improving frequency.For the reason to offset the problem caused by high frequency,soft-switching technology is necessary.Based on the research about the interleaved two-switch forward converter and its soft-switching technology,this paper analyzed the methods in different topology to achieve soft-switching and its advantages and disadvantages.This paper proposed a novel ZVZCS PWM interleaved two-switch forward converter based on passive auxiliary circuit and its modulation strategy,aiming at the problem in existing soft-switching interleaved two-switch forward converter about complex auxiliary circuit,large circulating current loss,complex control method,and the voltage stress and parasitic ringing in rectifier diode.This paper proposed a novel zero-voltage and zero-current switching(ZVZCS)interleaved two-switch forward(ITSF)DC/DC converter based on passive auxiliary circuit and its modulation strategy.By using the snubber capacitor,the coupled filter inductor,the transformer leakage inductor and the parallel capacitor of switch,the proposed converter can realize ZVS turn-off and ZVZCS turn-on of the leading switches and the ZCS turn-on and turn-off of lagging switches.In addition,the proposed converter can effectively reduce the primary circulating current loss.More importantly,the proposed converter eliminate the voltage stress and parasitic ringing in the rectifier diode.The operation principle,steady-state characteristics and soft switching conditions of the converter are analyzed based on the equivalent circuit of different mode.The design guide of the snubber capacitor and the turn-ratio of the coupled inductor is given in this paper.In addition,this paper also analyzed the power loss about the transformer and main devices.Finally,a 260V/500W-100kHz experimental prototype and a simulation established by Cadence verified the correctness of the converter.