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I was curious and looking at the datasheet of the buck converter IC LM2576, looking at the inductor selection guide it feels counter intuitive to me.

Why is the inductor value needed reducing as we increase the peak current? Also what are the consequences of choosing a different inductor?

thanks for your help. datasheet

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Inductor ripple current (in an absolute sense) increases with decreasing inductor values.

It is usual to choose an inductor (in a buck supply) for about 30% to 40% ripple current at maximum output current, so as the maximum output current increases so does the absolute amount of inductor ripple current, so the inductance decreases with increasing output currents.

Depending on the architecture, there are other considerations, but setting the peak ripple current is a fundamental step when designing a buck supply.

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Why is the inductor value needed reducing as we increase the peak current?

Firstly, if you want to regulate voltage on a more powerful load, the peak current will clearly be higher. A higher peak load current necessitates a lower value of inductance because if the inductance is too high, its natural series resistance will be too high and losses will be greater (resistive and core losses) or the inductor will be bigger and more costlier.

On the other hand, you could decide to design your buck circuit to be able to deal with heavy loads but only run it on a light load so why bother with using a higher value inductor? If you are designing a buck circuit to run with a light load then it makes sense to choose a higher value of inductance because then, the losses (at low loads), will not be as much i.e. you design it to be as efficient as you can for the load range you want.

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