LNK3206 Switching Inductor Selection


How can i determine that an inductor is suitable for the switching node of LNK3206 at 66kHz 400V pulses in terms of high voltage?


That’s a fair question, also a difficult one to answer concretely, since the nature of how inductors are typically constructed makes it difficult to predict the precise point of failure or guarantee performance; some compromise to the film insulation on a length of magnet wire has to be expected from the process of wrapping it around a core, but exactly how much and where and whether it’s of material relevance to the question involves a lot of variables that aren’t easy to account for. Characterizing breakdown properties between winding and core may offer some comfort as a proxy measurement, but it’s not a direct test of the actual question at hand.

The flipside of this is that it’s often an irrelevant issue, given that the V=L*di/dt equation implies that by the time one imposes enough V for enough time to evaluate insulation breakdown, the coils have already turned into a vapor due to I2R heating. An inductor manufacturer may be able to offer guidance or insights as to a given device’s internal construction and likely tolerances, but at day’s end the answer to the question often boils down to “try it and see what happens.”

This said, I might suggest avoiding devices with a molded construction for such applications, since the molding process seems likely to pose greater risk to winding insulation integrity than other techniques.

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