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Maximum Inductor size limit for Buck converter

I found min inductor required for Buck converter using this formula, enter image description here

We usually take 40% buffer on the calculated minimum inductance value(so, that inductance at rated current will not vary much and ripple will be under control) and choose the inductor.

I think lower inductor values will have more ripple, good transient response, as inductor value increases less ripple--> less pressure on Output capacitors.

Is there any higher limit on the inductor value for a buck converter.

I have requirement like this,

Vin =10.8 -13.2V,typ =12V, vout = 0.9V, Iout =15A, ripple =30%, Vout ripple =2.5% and possible transients can occur up to 10A/2us.

I have seen in webench tool from TI where maximum value of inductor specified, but not sure how they have calculated..

calculated.

  • The equation you show is the usual method.  So for low output currents the inductor value can get very high.  If I am using a converter at much less than its rated capability, i nmay use a smaller inductor than what that equation would specify.  I am not sure how webench calculates anything.  While smaller inductors do have better transient reponse, output capacitance is more important.  I usually try to design with the smallest inductor value that is practical and never worry about the upper limit.  I'll see if i can find out the answer to your webench question.