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Research On Soft Switched PWM DC-DC Converter

Posted on:2007-08-06Degree:MasterType:Thesis
Country:ChinaCandidate:P L ZhangFull Text:PDF
GTID:2132360182460831Subject:Pattern Recognition and Intelligent Systems
Abstract/Summary:PDF Full Text Request
Switching losses is prime factor limiting utilization of much higher switching frequency in PWM DC-DC converter. Only by reducing the switching losses can we get DC-DC converter that has smaller volume and higher efficiency. Based on the analysis of switching losses causes, principle of Soft Switching is introduced, basic implementation of soft switching is proposed, features and limit of present soft switching technology are analyzed. Aiming at the requirement in big power converter application, this dissertation is focused on the realization of soft switching in full bridge converter. Based on analyzing the steady state of phase-shifted full bridge converter with full bridge rectifier, some intrinsic limits and shortages of PS FB Converter with FB Rectifier are introduced, which are as follows: lose ZVS with light load; Duty cycle losses in secondary side; Hard switch of secondary rectifier diode and intrinsic parasitic ringing in secondary side. In order to resolve these problems a PS FB Converter with Current Doubler is proposed.The steady state of CDR(Current Doubler Rectifier) converter is analyzed. The equivalent circuits and corresponding formulas are proposed in each mode of overall 12 modes. It is concluded by those analysis that the proposed converter can realize ZVS from none load to full load, eliminate the duty cycle losses and parasitic ringing in secondary side diode, which hereby make higher efficiency and reduce the converter volume.To reduce the converter volume , theory and technology of Integrated Magnetic component (IM) are introduced. IM methods are discussed in two aspects -the way that magnets introduced by each winding interact with each other and type of combination of Integrated components. According to basic laws in magnetism and law of electromagnetic reaction(Farady's law), three methods to establish the equivalent circuit model of magnetic component are discussed , which are as follows: magnetic path-electric circuit paring transformation, Source shifting, Gyrator-Capacitor equivalent model. Application of IM technology in CDR converter is discussed, which include inductor-inductor IM and inductor-transformer IM.Simulations of CDR converter are performed with Orcad Pspice. Two 3 kw modular DC-DC power supply for power station dc system are made in lab , which utilize the proposed converter. Detailed design formulas and parameters are introduced. The applicationof new Phase-shifted controller IC UCC3895 is introduced .Discussions on control mode of DC-DC converter are also addressed. Experiment result show that theory analysis is correct.
Keywords/Search Tags:Soft Switching, Phase-shifted Full Bridge, DC-DC Converter, Current Doubler, Pspice Simulation, Integrated Magnetics
PDF Full Text Request
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