davidc@vlsisj.uucp (David Chapman) (04/26/91)
I need to power various battery-powered electronic gizmos from a 12V source
(automobile battery and solar panels, to be precise). So I need to step
up and step down to 18V (I think - I need to wait for delivery of the laptop),
14-15V, 9-10V, and 6V.
I also have a "6 volt" solar panel that I'd like to step up (double, to be
precise).
The inputs won't be very regulated (solar panels are notorious for this), but
the output should be. Efficiency is paramount. Fortunately power
requirements are low, 5-10 watts max. If I use the output of the regulator
only to charge batteries, the requirement could be only 2-3 watts.
So - does anyone know of any chips that I could use? I remember hearing
about a voltage doubler IC I could use for the 6V-12V conversion, but I
don't have any references to look it up in.
I've built switching regulators using a TL497 (because someone gave me a spec
sheet for it), but I'm a bit concerned about the widely varying input voltage
because it's a fixed on-time regulator. (Would this cause problems?) Also,
it's bipolar and I'd rather not lose the 10 mA of current that it takes to
run it (the solar panels are 300 mA) unless I have no choice.
I'm a competent enough EE (mostly digital, but I can remember the analog
stuff if I need to :-) that I could build something from discrete devices
if it's better than any merchant IC. I have a book on switching supplies that
I haven't read yet. It looks real good (explains theory, such as stability
of the feedback systems) but it uses mostly custom-made ring core transformers
(I know there's a proper term for that but it's late and my mind is fogged)
and I was hoping for something simpler. I don't know where I can buy cores
to a particular specification (haven't looked either). Also, I need these
converters before I leave on a year-long trip in early June and I don't think
I will be able to finish the book (maybe not even start it) before then.
One last thing - what can I do to protect my valuable electronic equipment
against transients from the engine alternator? Would a choke on the input
do the job? How big should it be?
Apologies if this has been recently discussed; my news connection just came
back after a 2+ month absence.
E-mail or postings are fine. I can summarize E-mail responses if requested.
Thanks!
David Chapman
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