Page 235 - Rashid, Power Electronics Handbook

224 D. Czarkowski

delivery gave rise to various types of uninterruptible power solution in applications where there is a need for one closely
supplies (UPSs). Thus dc-dc converters are used in UPSs to regulated output voltage and for one or more other noncritical
adjust the level of a recti®ed grid voltage to that of the backup output voltage levels.
source. Because during normal operation the energy ¯ows
from the grid to the backup source and during emergency
conditions the backup source must supply the load, bidirec-
tional dc-dc converters are often used. Moreover dc-dc conver- References
ters are also used in dedicated battery chargers. 1. R. P. Severns and G. Bloom, Modern DC-to-DC Switchmode Power
Power electronic loads, especially those with front-end Converter Circuits, Van Nostrand Reinhold Company, New York, 1985.
recti®ers, pollute the ac grid with odd harmonics. Thus dc- 2. M. H. Rashid, Power Electronics, 2nd ed., Prentice-Hall, Englewood
dc converters are used as intermediate stages, just after a Cliffs, NJ, 1993.
recti®er and before the load-supplying dc-dc converter, for 3. N. Mohan, T. M. Undeland, and W. P. Robbins, Power Electronics:
shaping the input ac current to improve power factor and Converters, Applications and Design, 2nd ed., John Wiley & Sons, New
decrease the harmonic content. The boost converter is espe- York, 1995.
cially popular in such power factor correction (PFC) applica- 4. R. Erickson, Fundamentals of Power Electronics, Chapman and Hall,
tions. Another utility grid-related application of dc-dc New York, 1997.
5. D. W. Hart, Introduction to Power Electronics, Prentice-Hall, Engle-
converters is in interfaces between ac networks and dc renew-
wood Cliffs, NJ, 1997.
able energy sources such as fuel cells and photovoltaic arrays.
6. P. T. Krein, Elements of Power Electronics, Oxford University Press,
In isolated dc-dc converters, multiple outputs are possible
??????, 1998.
with additional secondary windings of transformers. Only one 7. A. I. Pressman, Switching Power Supply Design, 2nd ed., McGraw-Hill,
output is regulated with a feedback loop, but other outputs New York, 1998.
depend on the duty ratio of the regulated one and on their 8. A. M. Trzynadlowski, Introduction to Modern Power Electronics, Wiley
loads. A multiple-output dc-dc converter is a convenient Interscience, New York, 1998.