Re: Dropping a few volts ?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "John Haddy" <jhaddy@c...>
wrote:

> I misread the intent, sorry.
>
> I thought that the desire was to drop the supply permanently to keep
> it under the voltage limit.
>
> Mosfets are nice (with their near zero static gate current) but

there

> is a wide variation in Vgs_threshold which means that

the "regulated"

> output level will be device (as well as load) dependent (for

example,

> the MTP10N10E has 2.0V <= Vgs_threshold <= 4.5V). I've therefore

only

> used them in closed-loop regulator applications.
>
> I'd prefer a power darlington NPN for an open-loop application (or

I'd

> design a proper closed loop regulator).
>
> JohnH
>

Hi John,

I'll look into the appropriate ranges of power darlingtons to see how
they might compare.

Going off into uncharted waters and throwing caution to the wind (and
sage advice) I was looking for a high voltage limit sort of circuit
that would kick in around the 70 volt mark.

Since Mariss had cautioned that failures increase dramatically with
an increase in voltage, and reading between the lines that the
Gecko's are tested at a higher voltage, I go out on a limb thinking
that over volting by a few volts is not going to send smoke signals
to customer support.

Having some form of upper limit will hopefully prevent any drastic
ventures into the upper ranges where the Gecko's are uncomfortable.

My NOT RECOMENDED premise is that fudging the limit will not be
catastrophic, but going blindly into the voltage limit with no
protection is, well, no protection.

If the circuit were viable, then people could use the near max
voltage with some safety net for when the power utility decides to do
funny things.

Dave
ps: did I mention that this is NOT a well enginerred and thought out
plan ?

(Wanna try to make sure readers do not think this is a great and/or
tested proceedure.)