"John Popelish" wrote in message
...
Steve Nosko wrote:
(snip)
FYI:
On one I built, I wound a few extra turns on the transformer and added
some
diodes to provide the driver collector voltage. ...

That is a very good idea. You can do something like that very cheaply
by just providing a small extra filter cap that is fed by two extra
diodes, to make a positive supply that doesn't have the full ripple
sag of the big caps.

FYI: It was a 28 V supply when I started. I re-wound the secondary, I think
it was #10 wire, so a few extra turns of smaller wire (added to each end of
the secondary, as I recall) was a treat at the end.

...lower the peak currents and cool
the transformer, capacitors and output transistors off by putting a
big resistor in series with the transformer primary, such that at full
load you just barely have enough DC to keep the regulator
functioning. You still get the heat, but it is dumped into a
resistor, instead of those other components.

This is interesting. I have to think about it. It'll slow the filter
cap charge time and lower and spread out the peak current.
T=RC and all that....

It also reduces the
current thump

I like that.

I think you can also improve the load transient response by putting a
10 ohm resistor across the output transistors, base to emitter, and a
100 ohm resistor base to emitter on the driver transistor. I haven't
calculated the closed loop frequency response of this design.
John Popelish

Yikes! Shades of my final year in control theory. I don't think I
even bothered to look at this for the supply above.

--
Steve N, K,9;d, c. i My email has no u's.