Morgan Olsson wrote:
>
> Regarding efficiency and other spec i use to be very careful.

> while also have margins for component variations such as min/max hFE
> of transistors, ESR of caps, etc. Maybe some combinations cause stability
>problems.
> Also remember zeners have typically 5% tolerance, add voltage change due to
> current change due to input voltage change, regulation of input volt, and load,
> and i guess simple regulators like theese have problems qualifying in a lot of areas.

Good points. Do you think I was hasty making that
"replaces a 7805" claim? Basically the web page is
written from my perspective, with the enthusiasm
thrown in. :o) It is what it is, I spent some hours
fiddling with the circuits and then put up the results
obtained. The efficiency tests were done just to see
that it IS possible, and improvements or de-provements
are up to the user.

Any serious manufacturer using the circuit would be
sure to spice it and/or lab test it with their chosen
parts. And for hobby/PIC use etc the circuits I gave
should work pretty good off the shelf.

> Using some combinations of worst case values is sometimes very tough
> for a cirquit,

Any suggestions to improving this? :o)

> It takes much calculations and verifying labs to make a design that
> performes good in all conditions High/low temp, High/low input volt etc,
> while also have margins for component variations such as min/max hFE of
> transistors, ESR of caps, etc.

How much work did you expect me to do? <grin>

>  Also note that the relatively bigger inductors in the Black is
> making slower load pulse reponse and also cost more in component cost
> and board estate if talking production.

Not totally true, in the smaller size "RF choke" type
parts they are usually the same price so comparing a
50uH or 100uH choke to the larger 470uH show the same
price. The cost is in increased losses in the choke,
not $$. As long as overall efficiency is still ok for
the task at hand. There should be substantial $$ saved
from not having to buy a dedicated switcher chip.


> Btw, new cadidates for the switch: BD438 (high gain high current
> pretty low cost TO126) and also check out Zetex "Matrix" range ZTXnnn
> IIRC for low voltage drop and very high gain.

Thanks, I will check them out. :o)
-Roman

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