Roman Black wrote...

>I apologise Dave! You are completely correct
>and I got my efficiencies reversed...

Absolutely no need to apologize, Roman; none whatsoever.

>Ok so first attempt at the one-transistor SMPS
>5v regulator is a complete failure... Back to the
>drawing board. I've got some designs that oscillate
>well and are efficient, that's fairly easy with one
>transistor and 2 or 3 windings, but no output voltage
>regulation...

Yes, it's tricky.  My opinion is that you either "pay over here" or
"pay over there"- that is, either a single inductor and several
transistors, or else a single transistor and a multi-winding inductor.
The former arrangement tends to be somewhat less expensive.

There is a school of thought that says, "the best design is the one
with the fewest parts" and I've gathered that philosophy is common
here on the PICLIST.  I've been in the "will do circuits for food"
racket, in one capacity or another, since 1966 and I abandoned that
philosopy long ago: in my experience, the best design is one which
includes EVERY component that is necessary and has NO components which
are not; every one has an important function, and that function can be
clearly described AND quantified.  If a part performs an important
function, removing it is folly; and if it doesn't perform an important
function, it didn't belong there in the first place.

A good design will be nearly incapable of doing anything other than
what its creator intended, and it is constrained to doing what it's
supposed to do by design- not by luck, or magic, or accident.

Ahem.  I'll stop ranting, now...

Cheers,

Dave

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