piclist 2002\09\24\090550a >
Thread: 2-tran SMPS 5v reg now 90% efficicient!
face BY : Alexandre Guimar„esemail (remove spam text)

Hi, Russel

> >  My only concerns about using it in a product is the lack of overvoltage
> > and overcurrent protection. It would not be nice to have 100 bucks going
> > away because the switching transistor got short circuited :-(
> Because I didn't want a failed pass transistor etc to take out the low
> voltage electronics I specd a fused output with a 12v zener behind the
> (1w glass bead body DOxx Philips can't remember the number and too lazy to
> go and look it up). Zeners almost always (essentially always) fail short
> the leads on these are like mini crowbars compared to PCB tracks etc. All
> the (few) failures I am aware of have shorted the zener and blown the fuse
> without hurting the low voltage electronics. Arguably a reasonably cheap
> of protecting against failure but may cost almost as much as Roman's whole
> converter :-)

   I was thinking about the zener and a polyfuse before it. Should give
good protection but would really cost almost the same as the full power
supply :-( I just asked about it because, as we all know, Roman can bring
some very innovative solutions to some classic problems. We never know.. I
will test it in the next few weeks with the zener and fuse and make sure
that I hit the switching transistor hard enough to make it fail and see how
the zener and fuse acts. Should be quite reliable. I will let the list know
how the testing goes.

Best regards,
Alexandre Guimaraes

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Subject (change) 2-tran SMPS 5v reg now 90% efficicient!

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