Research On Soft Switch Push-pull Converter

Reducing switching losses and electromagnetic interference,thus improving the power density and working efficiency of power electronic devices,are the advantages of soft switching technology and the direction of DC power technology advancement.Therefore,the development of soft switching technology with the continuous deepening and promotion,it has become an integral part of today's DC power technology.In this field,previous researches have mostly focused on soft-switching phase-shifted full-bridge circuits,while soft-switching technology research on push-pull circuits has been relatively rare.The advantages of push-pull circuits are that they have a simple structure and are suitable for high-current input.The types of soft-switching push-pull circuits include push-pull forward converters,resonant push-pull converters,and active clamped push-pull converters.This paper presents a soft-switching current-fed three-switches push-pull DC converter and analyzes it in detail.Its topology is to add a power switch between the midpoint of the primary side of the main transformer of the traditional current-fed push-pull circuit and the flyback transformer.The circuit has the characteristics of simple structure and can be applied to high current input and output applications.It is derived from the boost circuit and has advantages over the push-pull circuit in situations where higher voltage gain is required.At the same time,this topology does not require output filter inductors,and is suitable for multi-output applications with high voltage output.In the larger power range,the additional switch can achieve ZCS,and the main switch can achieve ZVS,thereby achieving higher efficiency and power density.Then the article introduces the principle of different working stages and its equivalent circuit,gives the design method of the parameters of switches,transformers and other devices,analyzes the similarities and differences of the soft switching conditions of each switch and the realization conditions,and proposes the results through the experimental results.The topology performance was verified.Aiming at the problem that the topology needs to work in the current discontinuous mode,which results in limited input power,voltage spikes,and high startup current,an active-clamped ZVS current-fed three-switches push-pull converter is proposed,which can make three power The switches can achieve ZVS in a larger load range,thereby widening its power range.The addition of active clamp effectively limits its voltage spikes.The circuit adopts a special starting method to solve the high starting current caused by the output voltage lower than the input voltage in the initial stage of startup.Then,the working modes of the proposed topology at different stages are analyzed,the working principle,voltage gain,parameter design are introduced,and the realization of the switches ZVS is analyzed,which is demonstrated through experiments.Finally,the theoretical analysis and combination of the two current-fed three-switches push-pull converters proposed in this paper with traditional push-pull converters and voltage-type ZVS three-switches push-pull converters are combined in terms of voltage gain,device stress,soft switching conditions and efficiency.The experiments were compared,and the respective losses were calculated.The sources of various losses were analyzed.Finally,the advantages and disadvantages of each other were summarized and summarized,which provided a reference value for their practical applications.