Three-Switch ZVS Fly-Forward Is Quiet, Efficient, And Scalable

Focus:

At Preston Consulting, we have often pondered whether the forward converter and the flyback could be properly combined to give a true “fly-forward” that captured the best bits from both converters, while fully utlizing the transformer core— “storage” for the flyback part and simple transformer action for the forward part—thus fully utilizing the transformer core on both half cycles to push energy to the output. This article describes the operation of such a converter—the three-switch ZVS fly-forward circuit, discusses its benefits, and shows waveforms from an example design. It also offers some tips for designing this converter, tradeoffs, and operating conditions for which it is best suited.

What you’ll learn:

• How to understand the operation and benefits of the three-switch ZVS fly-forward
• How to achieve a fully soft switched converter with low EMI for power levels up to a few kilowatts

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Author & Publication:

Colin Tuck, Preston Consulting, Christchurch, New Zealand, How2Power Today, Mar 15 2026

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