Introduction

When confronted with the need to design a power converter, aspects of designing a transformer can be daunting as the engineer seeks to understand all the limiting aspects of winding a reliable transformer. By adopting the pre-designed, but configurable off-the-shelf transformers such as Würth’s WE-Flex range the use of a custom transformer may be avoided in many low power DC/DC power supply applications. The WEFlex transformers come in two configurations: with gapped cores or ungapped cores.

This application note will guide the designer through the use of an off-the-shelf, configurable transformer for flyback converters using gapped cores. By careful adherence to the guidance provided here, it will be possible for design engineers to quickly and confidently design a fully functioning power converter without resorting to custom magnetic design. By following this process, you will be able select the smallest part that meets your application requirements without overheating.

Detailed Step-by-Step design guidelines, rules and equations are given as well as a complete worked example based on a Flyback converter.

Whilst all relevant transformer equations are included in this application note, to make calculations easy a free spreadsheet (Würth WE-Flex Transformer selection spreadsheet) can be downloaded from here

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