Investigation of High Performance AC/DC Front-End Converter with Digital Control for Server Applications

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dc.contributor.authorluo, zhengen
dc.contributor.committeechairXu, Mingen
dc.contributor.committeememberWang, Fei Freden
dc.contributor.committeememberWang, Shuoen
dc.contributor.departmentElectrical and Computer Engineeringen
dc.date.accessioned2014-03-14T20:30:30Zen
dc.date.adate2009-03-03en
dc.date.available2014-03-14T20:30:30Zen
dc.date.issued2008-12-05en
dc.date.rdate2009-03-03en
dc.date.sdate2009-01-11en
dc.description.abstractWith the development of information technology, the market for power management of telecom and computing equipment keeps increasing. Distributed power systems are widely adopted in the telecom and computing applications for the reason of high performance and high reliability. Recently industry brought out aggressively high efficiency requirements for a wide load range for power management in telecom and computing equipment. High efficiency over a wide load range is now a requirement. On the other hand, power density is still a big challenge for front-end AC/DC converters. For DPS systems, front-end AC/DC converters are under the pressure of continuous increasing power density requirement. Although increasing switching frequency can dramatically reduce the passive component size, its effectiveness is limited by the converter efficiency and thermal management. Technologies to further increase the power density without compromising the efficiency need to be studied. The industry today is also at the beginning of transferring their design from analog control to full digital control strategy. Although issues are still exist, reducing components count, reducing the development cycle time, increasing the reliability, enhancing the circuit noise immunity and reducing the cost, all of these benefits indicate a great potential of the digital control. This thesis is focusing on how to improve the efficiency and power density by taking the advantages of the digital control. A novel Ï /2 phase shift two Channel interleaving PFC is developed to shrink the EMI filter size while maintain a good efficiency. A sophisticated power management strategy that associates with phase shedding and adaptive phase angle control is also discussed to increase the efficient for the entire load range without compromising the EMI filter size. The method of current sampling is proposed for Ï /2 phase shift two Channel interleaving PFC and multi-channel adaptive phase angle shift PFC is proposed to accurately extract the average total current information. A noise free current sampling strategy is also proposed that adjusting the sampling edge according to duty cycle information. An isolated ZVS dual boost converter is proposed to be the DC/DC stage of the front-end converter. This PWM converter has similar performance as the LLC resonant converter. It has hold up time extension capability without compromising the normal operation efficiency. It can achieve ZVS for all the switches. The current limit and SR implementation is much easier than LLC. State plane method, which potentially can be extent to other complex topologies, is used to fully study this circuit. All the operation modes are understood through the state plane method. The best operation mode is discovered for the front end applications. Light load efficiency is improved by the proposed pulse skipping method to guarantee the ZVS operation meanwhile reduce the switching frequency. Current limit operation is also proposed to restrict a best operation mode by fully taking the advantage of digital control that precisely control the circuit under the over current condition. High efficiency high power density is achieved by new topology, innovative interleaving, and the sophisticated digital control method.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-01112009-024104en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-01112009-024104/en
dc.identifier.urihttp://hdl.handle.net/10919/30905en
dc.publisherVirginia Techen
dc.relation.haspartthesis.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectDC/DCen
dc.subjectAC/DCen
dc.subjectHigh efficiencyen
dc.subjectHigh power densityen
dc.subjectDigital controlen
dc.subjectFront-end converteren
dc.subjectCurrent limiten
dc.subjectLight loaden
dc.subjectZVS isolated dual boosten
dc.subjectPFCen
dc.subject90 degree Interleavingen
dc.titleInvestigation of High Performance AC/DC Front-End Converter with Digital Control for Server Applicationsen
dc.typeThesisen
thesis.degree.disciplineElectrical and Computer Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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