be generalized, to predict the dc cotnponents of all converter wavefortns via averaging. In Part I of this book, averaged equivalent circuit models of converters operating in steady state are derived. These models not only predict the basic ideal behavior of switched-mode converters, but also model efficiency and losses. Realization of the switching elements, using power semiconductor devices, is also discussed.

Design of the converter control system requires models of the converter dynamics, tn Part tl of this book, the averaging technique is extended, to describe low-frequency variations in the converter waveforms. Small-signal equivalent circuit models are developed, which predict the control-to-output and line-to-transfer functions, as well as other ac quantities of interest. These models are then employed to design converter control systems and to lend an understanding of the well-known current-programmed contrd technique.

The magnetic elements are key components of any switching converter. The design of high-power high-frequency magnetic devices having high efficiency and small size and weight is central to most converter technologies. High-frequency power magnetics design is discussed in Part П1.

Pollution of the ac power system by rectifier harmonics is a growing problem. As a result, many converter systems now incorporate low-harmonic rectifiers, which draw sinusoidal currents from the utility system. These modem rectifiers are considerably more sophisticated than the conventional diode bridge; they may contain high-frequency switched-mode converters, with control systems that regulate the ac line current waveform. Modern rectifier technology is treated in Part IV.

Resonant converters employ quasi-sinusoidal waveforms, as opposed to the rectangular waveforms of the buck converter illustrated in Fig. 1.9. These resonant converters find application where high-frequency inverters and converters are needed. Resonant converters are modeled in Part V. Their loss mechanisms, including the processes of zero-voltage switching and zero-current switching, are discussed.

References

(1) W. E. Newell, Power Electronics-Emerging from Limbo, IEEE Pnwer ElecUonicx Speciatixis Cati/er-eiwe, 1973 Record, pp. 6-12.

12) R. D. MtDDLEBROOK, Power Electronics: An Emerging Discipline, IEEE International Symposium on Circuit}: amiSysrents, 1981 Proceedings, April 1981.

[31 R. D. MlDDLEBKOOK, Power Electronics: Topologies. Modeling, and Measurement, IEEE Inlemational Symiiiisintit HI) Circuits unit Syslfim. 1981 Proceedings, April 1981.

141 S. CUK, Basics of Switched-Mode Power Conversion: Topologies, Magnetics, and Control, in Adiances in Switched-Mi/de Pt/wer Cmtversioit, vol. 2, pp. 279-310, Irvine: Teslaco. 1981.

[5] N. Mohan, Power Electrotiics Circuhs: Ati Overview, IEEE lECON. 1988 Proceedings, pp. 522-527.

[6] B. K. BOSE, Power Electronics-A Technology Review, Proceedings of the IEEE, vol. 80, no. 8, August mi. pp. 1303-1334.

[7] M. NiSHiHARA, Power Electronics Diversity, International Power Electronics Conference (Tokyo), 1990 Proceedings, pp. 21-28.

Parti

Converters in Equilibrium

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