Coupled Inductor Design For A Flyback With Very Wide Input Voltage Range

Focus:

There is an automotive and railroad class of flyback converters that demands operability over a very wide input voltage range—from 30 V to 800 V. These are backup power supplies that should operate when the traction battery decays. With such a wide input range, duty cycle will vary widely. Yet rather than assuming a duty cycle range, most flyback designs assume some average value for duty cycle. This can have serious implications for the performance of the coupled inductor, particularly in a flyback design with a very wide input voltage range. This article offers a procedure for designing the coupled inductor that takes into account the full duty-cycle range of the flyback. The procedure is demonstrated in a design example using the 30-V to 800-V input range.

What you’ll learn:

• How to design a coupled inductor for a flyback converter with wide input voltage range
• How to design a coupled inductor for a flyback while accounting for duty cycle range

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Author & Publication:

Gregory Mirsky, Design Engineer, Deer Park, Ill., How2Power Today, Mar 14 2025

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