Boost converter inductor choice

[evandude]

I am going to build a boost converter soon, just using the standard topology.

however the last thing remaining to be determined is the inductor size.

i can run the thing at anywhere between audio frequency and 100+ kHz, whatever works out best... but I don't know what inductor value to use. As far as I know, bigger is generally better, so I should just get the largest one that I can that still meets my current-handling needs. And for the most part, the inductors are all the same price regardless of the value... but i'd like to minimize size and danger... (if this thing blows up during testing i'd prefer it not to level the entire building)

the converter will be designed for these specs:
12.5v output
nominal 11.5-14v input, but capable of handling short (a few seconds) input droops down to 8v or so
(note that the converter will only need to operate when the input doesn't already keep the output above 12.5v)
output load handling of 5A (or at least 3A)
1000uF output capacitor

two capacitor values I had tossed around just from seeing in other people's designs are 13uH and 47uH. do either one of these sound reasonable?

thanks in advance...

 

[GrimReaper]

Inductor value needs calculated. Needs to be at least .75A higher than the rated
value, and the switching frequency will also be important. Just can't randomly
pick the components. Capactors are selected based on ripple current capability
and low esr. I suggest you go to Linear Tech and download their free switchercad
program and look at all their example circuits. You can scope ripple currents,
inductor currents and get a good feel for how switchers work. Great learning tool.

 

[evandude]

I am using switchercad, but for some reason never thought to take a look at the examples. thanks!

**EDIT*** wow, those examples really took care of everything. there were 2 examples that both fit my requirements nicely. thanks again!