> Hi Alexandre! :o)

    Hi...

> I'm very busy at the moment with a new PIC
> project, but I can give some quick help with your
> circuit. :o)

    Nice to see that your sore back is cured..

> * flyback diode should be a faster one.
> maybe try a 600v 1A TV fast recovery diode
> like the 1N4936 or 1N4937?? It's important.
> I know you have trouble sometimes getting parts
> in Brazil, these diodes are the normal diodes
> they use on TV flyback secondary windings,
> just about any modern TV will have a few
> attached to the flyback transformer. :o)

    Great option... Already found a distributor for it.

> * R2 is not needed

    R2 helps on the turning off time of Q1 !! And it helps a lot actually. I
will have to check the value on the working circuit to make sure it is
right. It makes Q1 BE capacitance have a better path to discharge when Q2
cuts.

> * R1 is a good value, about 6v (6%) drop
> nice to see R1 there.

    I use the resistor and diode on the input of most of my power supplies.
It helps a lot with transients. When space and cost permits I also like a
small inductor in series.

> * put a 47uF 25v cap across D3, will help
> save D3 if you get spikes on 100v supply

    Done already :-) Makes sense. Thanks for the tip. What about a  100 nf
there also ?

> * reduce R3 to about 2.7k for better turn off

    I will try that one once I build it on the protoboard. I guess I will
have to fiddle with all the values to see how far I can get on the input
range and how efficient it can get on the usual range.

> * D2 and C4 are not needed.

    It will make the ripple lower and let the digital circuits do a more
"normal" turning off when the supply input is disconnected. When you
disconnect the supply no current will flow from the digital power to the
power supply. The voltage drop gets to be more stable and predictable. At
least that is what I have seen on some measurements I have done on some
power supplies. They can do pretty nasty things when getting disconected.

> Good luck! :o)

    I hope ;-) This project might be a nice one and I do not want to make
any silly mistakes. It has to be very reliable.

> PS thanks for the circuits you sent, i'll add
> them to the web page.

    No problems. If you need something else I have the list archived for
quite a while. It saves a lot of time and makes us ask less silly questions
:-)

Best regards,
Alexandre Guimaraes

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