Ed Bloom: Lifetime Achievement Award Winner

Sep 1, 2007 12:00 PM
By David Morrison, Editor

Busting a Magnetics Myth

Although Bloom did not initially lead the classes on magnetics design that his company offered, he became well known to many engineers as an expert on this topic, for both his teaching and his writing on the subject of integrated magnetics.

“I started teaching when I began to work on integrated magnetics,” Bloom says. “There, in addition to describing a magnetics design, I had to show people how you go about combining a number of magnetic elements together.”

“The basic idea of multifunction magnetics is really old,” says Rudy Severns, who credits professors Slobodan Ćuk and David Middlebrook with reawakening interest in integrated magnetics as it applies to power electronics in the 1970s, when they addressed the topic in their work at Caltech.

However, the work done by Ćuk and Middlebrook on integrated magnetics was narrowly focused on its application to Ćuk's now-famous converter topology. In the mid-1980s, Bloom, together with Severns, published papers explaining how integrated magnetics had a much broader application in power electronics.

“One of the first things Dr. Ćuk talked about in describing his converter was how you go about integrating the transformer and inductor on a single core structure. So, when he started publishing that information, engineers thought that the Ćuk converter was the only one for which the magnetics could be integrated,” says Bloom. “One of the motivations that I had to start writing about the topic was to show people that that's not really the case. You can apply integrated magnetics to almost any converter topology.”

Bloom's earliest writings on this subject include “The Generalized Use of Integrated Magnetics and Zero-Ripple Techniques in Switchmode Power Converters,” which was presented in 1984 at the IEEE PESC conference.[3] As the title suggests, the zero-ripple concept was one of the motivations for combining multiple magnetic elements on the same core. But as Bloom notes, the main benefit of integrated magnetics is to save space and weight, as it allows the number of magnetic components to be reduced from three or four elements to one.

Following the publication of the PESC paper, Bloom proceeded to publish numerous papers on this topic at industry conferences as well as articles in trade journals.* He also authored two patents to discuss his work in this area.[4-5]

Bloom's work on integrated magnetics required the application of theory and real-world design. Ultimately, he built integrated magnetic components in his lab to test and demonstrate the concepts he was presenting in his writings. Perhaps the most familiar of these writings for most readers is his chapter on integrated magnetics in Modern DC-to-DC Switchmode Power Converter Circuits. Commenting on this text, Bloom notes, “It was and still is the only book that has a chapter on the integration of magnetics.”

Want to use this article? Click here for options!
© 2007 Penton Media, Inc.