-=> Roy J. Tellason said to Greg Mayman
 -=> about "VEHICLE LED'S" on 09-16-03  04:06.....

 RJT> Ok,  how would you do that?

First you sniff a bit of the AC input, amplify it and clip it and
feed it back to the transistor bases so they turn on/off at zero
crossing.
 
 RJT> It would seem to me that at the high current levels (tens of amps)
 RJT> they're wasting a bunch of power as heat,  and the voltage being
 RJT> dropped a bit is also going to cause the charging rate to be just a
 RJT> little slower. 

I have seen these things in the past, but I can't remember what
the heatsinks were like, probably they were pretty big. Yes, I
guess the charging rate would be slower.

And I've also wondered what the drop across the diode would do to
the regulator. Should it be set a bit higher than normal? No-one
I've spoken to about this seems to think it is necessary.

OTOH someone once said the regulator should be connected to one
of the batteries AFTER the isolator diode.

 RJT> I used to be able to acquire the occasional data book here and there, 
 RJT> but haven't in years now.  It's probably a good thing,  as the ones I
 RJT> do have take up a bunch of space now!  :-)  This stuff is also coming
 RJT> out on cdrom,  and may be downloadable as pdf files,  I haven't looked
 RJT> yet.

Theree is a lot of stuff on the 'net, but only very rarely do you
find data for outdated devices. I suspect the same would apply to
CD-ROMs :-(

 RJT> I'm thinking those part numbers are actually "2SK707"
and "2SK799", 
 RJT> that sound any better?

Could be. It sounds logical.

But I still don't have any data for those either.

 RJT> There were some of those parts that also seemed to have diodes across
 RJT> the gate-source connection,  though not all of them.  I've seen some of
 RJT> those parts that seem to have something of the sort built in,  too, 
 RJT> though I can't recall just why.  Maybe to prevent breakdown at the
 RJT> gate? 

Could be. Offhand I can't think of another reason. Were they
zeners or just ordinary diodes?

From Greg Mayman, in beautiful Adelaide, South Australia
   "Queen City of The South"    34:55 S  138:36 E

... Humankind cannot bear very much reality. - T.S. Eliot
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