AC, DC, and Peak Currents

The dc level of the inductor current (largely) determines the I2R losses in the copper windings ( copper loss ). However, the final temperature of the inductor is also affected by another term — the core loss — that occurs inside the magnetic material (core) of the inductor. Core loss is, to a first approximation, determined only by the ac (swinging) 

We must pay the closest attention to the peak current. Note that in any converter, the terms peak inductor current , peak switch current and peak diode current are all synonymous. Therefore, in general, we just refer to all of them as simply the peak current Ipk where 

Note A slight amount of core saturation may turn out to be acceptable on occasion, especially if it occurs 

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