Most SMPS use coupled magnetics of various kinds. While designing buck/boost and their isolated versions, construction of the coupled magnetic element is straight forward. In many of these converters the issue of discontinuous current (both on the input and output exist) . I came across literature which claim zero ripple using coupled inductors. The results are fascinating to say the least

However it requires the need of coupled inductors with coupling factors <1. Designs specifically mention critical values to be around 0.6. I don't seem to find any links for construction of such inductors.

How are such coupled inductors constructed? (what type of cores, winding detail etc.,)

  • \$\begingroup\$ Take an E core and wind coils on the outer limbs. \$\endgroup\$
    – Andy aka
    Mar 23, 2022 at 9:10
  • \$\begingroup\$ I don't understand the physics of this. Intuitively, it seems that this method of construction would provide a fixed coupling factor \$\endgroup\$ Mar 23, 2022 at 9:35
  • \$\begingroup\$ Yes, a fixed coupling factor of less than 1. You didn't say you needed a variable coupling factor did you? Anyway, your on your own on this because you don't appear to recognize the importance of formally accepting answers to some of your previous questions raised nor upvoting good answers to some of your questions. \$\endgroup\$
    – Andy aka
    Mar 23, 2022 at 9:47
  • \$\begingroup\$ My apologies Andy, I seem to have misunderstood the platform. I was under the impression that up-votes are to be done by the community. Will get to rectify these \$\endgroup\$ Mar 23, 2022 at 9:55
  • \$\begingroup\$ You have the reputation to make upvotes to any answer and you always have had the ability to formally accept any particular answer to any question you have raised. \$\endgroup\$
    – Andy aka
    Mar 23, 2022 at 9:58

1 Answer 1


A unity coupling factor k is a perfect nonexistent transformer. Real transformers have magnetizing inductance in parallel and leakage inductance in series. So if k is too high you can place some fixed inductances around your coupled coil to make k arbitrarily low. When designing a transformer there are known tricks like air core, magnetic shunts, bucking windings, etc. Remember that low k transformers tend to be more lossy.


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