Optimal Switch Timing Circuits (Part 1): The Relationship Between Switch Timing And Available Energy

Focus:

One of the benefits of leakage inductance is its use in realizing simple, single-magnetic isolated soft-switching converters. Here, leakage inductance provides the energy needed for soft switching. But to achieve soft switching over a broad range of line and load conditions an adaptive switch timing circuit is necessary. Part 1 explains why that is the case by describing switch timing issues and the relationship of optimal switch turn-on timing to stored magnetic energy. This lays the groundwork for a discussion of adaptive switch timing circuits in part 2. In part 1, conditions needed to achieve ZVS are explained in terms of the stored magnetic energy (EM) versus the electric energy (EE) needed to drive the switch’s drain-source voltage to zero. From these discussions, it is observed that the optimal turn-on timing of the main switch will vary with both EM and EE and the circuit conditions that influence them.

What you’ll learn:

• How to understand the factors that determine optimal timing for switch turn-on in soft-switching converters

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Author & Publication:

Ernie Wittenbreder, Technical Witts, Flagstaff, Ariz., How2Power Today, Jan 15 2016

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