Learning to specify and buy power supplies
Demystifying Switching Power Supplies, Raymond A. Mack, Jr., Newnes (books.elsevier.com), 2005. 323 pages. $49.95.
Rick Nelson, Chief Editor -- Test & Measurement World, 8/1/2006
Switching power supplies are ubiquitous in many types of test equipment, so it might behoove you to know something about them, even if you don't propose to design one yourself. In fact, from a test-and-measurement perspective, knowledge of power supplies can be invaluable, because they may be the source of problems in the equipment you are trying to test. Often selected as an afterthought, a power supply may not deliver the power or regulation a design requires, it may contribute unacceptable levels of jitter through crosstalk, or it may emit troublesome levels of EMI.
The author's stated goal with this book is to help you understand how a switching power supply works, how to intelligently specify a custom supply, and how to design one if need be. He succeeds at the first two goals, but with respect to helping the reader design a supply, he provides enough detail to suggest that design be left to power-supply professionals. You may feel you've come away with a sufficient understanding of the circuitry, but you're very unlikely to want to have to deal with the litany of EMC and safety standards you would need to comply with.
Mack takes you from the basics (v = Ldi/dt, plus buck, boost, inverting boost, buck-boost, and other supply circuit topologies) on through the details of passive component selection and semiconductor selection. Of particular note are his treatment of control circuits and their effect on ripple levels and electromagnetic compatibility. He provides a step-by-step test sequence for evaluating power-supply response using a variable load, an oscilloscope, and a function generator.
Mack concludes with two solid examples: a true sine-wave inverter uninterruptible power supply and a personal-computer power supply. (Disclosure: The book's publisher is owned by Test & Measurement World's parent company.)
