Research On Active Clamp Flyback Converter With Primary-second Resonance

With the rapid development of consumer electronics,the demands of portable power conversion with high power density and high efficiency are ever increasing.In the field of low-power adaptor,the traditional quasi-resonant flyback converter cannot fully recover the energy stored in the leakage inductance of the transformer.Active clamp flyback converter can solve this problem and becomes a research hotspot.Therefore,this dissertation carries out the research on the application of active clamp flyback converter in the field of adaptor,and analyzes the operation of this topology under different resonant conditions.In view of the complex working process of active clamp flyback converter and the large influence of parasitic components,this dissertation analyzes the working process of this circuit in different operating modes,and the circuit equivalent model is established to conduct mathematical demonstration.This dissertation also focuses on the achieving process of primary side soft-switching and gives the corresponding realizing conditions.In order to solve the problem that the secondary side synchronous rectifier may malfunction with the traditional active clamp flyback converter,this dissertation studies the circuit working process under different resonant conditions and proposes a solution of primary-secondary side resonance.The causes of the malfunction of the synchronous rectifier under the traditional primary resonance conditions is analyzed,and the equivalent circuit model for the primary current drop phenomenon in this process is established.Under this premise,this dissertation studies the resonant characteristics of the circuit under the condition of the traditional primary resonance and the novel secondary resonance.Based on this,this dissertation proposes the working mode of the primary-secondary resonance.After theoretical analysis and experimental demonstration,it is proved that this method can effectively reduce the RMS of the secondary current and preserves the advantage of the secondary resonance in the same time.According to the background of portable adaptor applications,this dissertation presents the design of an active clamp flyback power supply system,which is verified by the simulation in Simplis.At the same time,the primary-secondary side resonant working mode is implemented on the hardware platform which proves the consistency of theory and experiment.