AA powered USB Charger

I am putting together a USB charger powered by 8 AA batteries. The schematic is on my page, labelled:switchingcharger.

Will this work? And also, what would I need to integrate to charge the AA's if they were rechargeable?

Thank you in advance, Robert

by rjojjr91
March 27, 2013

Please post circuits - or links to them - in help requests.

That's what the links are for and it is more helpful than making the viewer have to trawl through your workbench.

Your circuit as drawn will probably blow the schottky. It is too low a current part.

Apart from that you have not given enough information (a design spec) to make any practical comments.

Search CL for:

design spec

for more info.

CL will be of little help is designing this sort of SMPS based power supply.

It will be very hard to try to simulate the design.

You'd do much better to just go here:


Read this:


and this:


and learn to drive the design support tools TI provide.

by signality
March 27, 2013

Here is the link


It is actually a 1N5819, it was not listed with the program, and that is what TI's datasheet says to use.

by rjojjr91
March 27, 2013



shows 1N5819.

That's just about on the limit of OnSemi's own guidelines on p10 of their datasheet.


and others, show higher current parts.

Never under-rate SMPS components.

Unless you like the smell of burning epoxy.


by signality
March 27, 2013

Hi Robert,

Your topic is “AA …” but from you other posting I understand it’s your car … ?

So additionally,

Whenever you approach your car’s power supply:

  • Start by using a fuse !

The next element behind the fuse should be a (min 3A) diode, because your car’s voltage will go up to 15V (spikes) and down to 11.5C (spikes) or less, your input cap (rated 35V at least, 105°C) would only suffer from trying to stabilize that but it can’t.

Regards, Sancho

by Sancho_P
March 27, 2013

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