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UBM Tech

Review: Trilogy of Magnetics by Würth Electronics

-September 06, 2012

Many may not be aware, but Würth Electronics Midcom (WE Midcom) sells a monster 4-pound, 700-page book, the Trilogy of Magnetics, now in its 4th edition. The cost is 49 Euros or $49.99 USD, orderable through the WE Midcom web site or your local sales rep. This comprehensive design guide includes theory and applications for EMI filter, switch-mode power supply and RF circuit design. Now, many vendors supply application notes and white papers on their web sites or included with their catalogs, but usually, you need to wade through countless lists of products to find the meager theory and application information. While WE Midcom includes a few lists of ferrites in the book, the bulk of the content (99%) is packed with theory and applications. If you want the part information, that's included on a CDROM in the back of the book. The CD also includes a copy of LTspice (from Linear Technology), plus a couple of WE selection/design programs.

Figure 1 - The book, Trilogy of Magnetics, by Würth Electronics.

The hardbound book has been greatly expanded and reorganized into three main sections: basic principles, components and applications.

The section on basic principles (150 pages) covers the foundations of inductive and ferrite components and includes equivalent circuit diagrams and simulation models. The section on components (140 pages) introduces inductive and ferrite components, their properties and best applications. Included are EMC components and inductors, transformers, RF components, circuit protection components, shielding materials and capacitors. The applications section (320 pages) offers a comprehensive overview of filter circuits and numerous industrial and consumer applications pulled from real-world designs. If you'd like to sample extracts from each section, there are links here.

Some of the questions the book answers include:

How are we supposed to understand the information about inductors and ferrets that is given in data sheets?
What effect does the core material have?
What do core losses and saturation mean in my application?
How do you calculate SMPS transformers?
How can I take EMC into account right when I begin my design?
How should I design my circuit board layout?

The book focuses on selecting components, circuitry and layout recommendations, and takes EMC perspectives into account. There is also a dictionary of terms in the appendices.

LED lighting is becoming a very big deal lately. An example from the applications section is this 4.2W LED driver schematic with measured conducted emissions plot.

Figure 2 - One of many examples from the applications section - here, an LED driver. Image courtesy of Würth Electronics.

Figure 3 - The corresponding conducted emission plot as measured. Image courtesy of Würth Electronics.

Other applications include everything from small-signal and mains filters to audio and video circuits to interfaces, RF and power supply circuits.

The CD attached to the back cover includes three freeware design programs: LTspice/SwitcherCAD III, WE Inductor Selector and WE-FLEX Designer. The LTspice included is an older version of Linear Technology's program (now in version IV), so I'd suggest downloading it from Linear's web site. WE Inductor Selector helps you design the right inductor for your SMPS application. WE-FLEX Designer is a program that can help you design the right SMPS transformer for your specific application. You can request free samples directly from the program.

I own a number of good reference books on EMC and this one deserves a space on your bookshelf. Recommended.

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