Designing Low-Power Flyback Inductors Using Tiny Toroids (Part 1): A Boost Converter Application
by Dennis Feucht, Innovatia Laboratories, Cayo, Belize, How2Power Today, Jun 17 2019
Focus:
For power supply applications requiring 0.2 W to 2 W, a linear power supply design may be the
simplest, but if input and output voltages are significantly different the losses may be
unacceptable. The three configurations of PWM-switch converters can deliver the power at high
efficiency using a tiny toroidal inductor. The smallest Micrometals Fe-pwd toroid core in the
low-cost 26 material is the T20-26, which is 0.2 inches in diameter. This particular core will
be used in an example design procedure for a 5-V to 12-V isolated flyback converter, which is
developed here as a design template. The example inductor uses three stacked T20-26 cores with
unibundle construction of the winding. Along with its analytical details, this procedure
includes numerous tips to simplify wire and core selection and to ease building of prototypes.
But before explaining the design procedure, the article explains how core geometry relates to
circuit voltages and currents.
What you’ll learn:
- How to build low-power (0.2 to 2 W) isolated flyback power supplies with bead-size toroidal inductors
- How to design and wind tiny toroidal inductors for 0.2- to 2-W power supplies
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