Prev: creating delay with passive rc-network
Next: Phase Lock Indicator
From: oparr on 21 Mar 2010 08:38
>A fuse is a over current detector that latches open.

Too slow.


On Mar 19, 10:41 pm, MooseFET <kensm...(a)rahul.net> wrote:
>
From: oparr on 21 Mar 2010 08:40
>PTC fuse?

Too slow.


On Mar 20, 11:16 am, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...(a)charter.net> wrote:
>

From: Joerg on 21 Mar 2010 11:12
oparr(a)hotmail.com wrote:
>> Best to post your schematic so people can see what's driving it.
>
> Driver is a simple two resistor voltage divider...One resistor from
> high side to gate and the other from gate to low side. Vgs is normally
> half Vs. Overvoltage protection (a design requirement) prevents Vgs
> from exceeding Vgs max. That works fine.
>

Is there a uC driving this (via a transistor)? Does it have a free port
pin to reset a latch that comes up in a random state when powering up?

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
From: MooseFET on 21 Mar 2010 11:39
On Mar 21, 5:38 am, "op...(a)hotmail.com" <op...(a)hotmail.com> wrote:
> >A fuse is a over current detector that latches open.
>
> Too slow.

How about:

----------------
! !
V N-JFET !
-------- !
! ! !
--------+--- ---- ---+------
! ! !
! ------- P-JFET
! V
! !
---------------

When the drop on one becomes enough to start to bias the other off,
the whole thing latches into the off state. It resets if power is
cycled.
From: oparr on 21 Mar 2010 17:07
>Is there a uC driving this (via a transistor)? Does it have a free port
>pin to reset a latch that comes up in a random state when powering up?

Nothing like that. It's a power management circuit in a "black
box" (BB) containing voltage sensitive modules. The BB has no power
supply, this is responsibility of the end-user. Hence the need for the
circuit to provide overvoltage and reverse polarity protection. That
is already implemented and works fine. BB connections to the outside
world are DC power in and module power out.

As already indicated, the switch in the PM circuit is a P-MOSFET, it's
turned off when an overvoltage condition is detected. I then decide to
expand this to overcurrent and short circuit protection as well.
Getting that to work for all voltages in the range 12V to 40V, using
discretes, is a challenge so a high side current monitor and
comparator approach is being investigated.

To be honest, overcurrent and short circuit protection for the MOSFET
is not an absolute necessity since each BB internal module already has
that on the ouput. So if the end-user shorts the ouput of any of the
modules, it will not impact the MOSFET.

On Mar 21, 11:12 am, Joerg <inva...(a)invalid.invalid> wrote:
>
First  |  Prev  |  Next  |  Last
Pages: 1 2 3
Prev: creating delay with passive rc-network
Next: Phase Lock Indicator