The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: Tony Williams
Subject: Re: zero-power toggle circuit; was, how to master electronics
Date: Fri, 15 Nov 2002 12:17:05 +0000 (GMT)
References: <3DC517EB.firstname.lastname@example.org> <3DC57B4E.email@example.com> <firstname.lastname@example.org> <email@example.com> <3DD39D90.firstname.lastname@example.org>
NNTP-Posting-Date: Fri, 15 Nov 2002 12:35:34 +0000 (UTC)
User-Agent: Pluto/1.14i (RISC-OS/3.60)
In article ,
Winfield Hill wrote:
> I'll withdraw my comment asserting a lo-side switching preference, but
> I'll stick by my assertion that an effective shutoff protection scheme
> is required for high-side switching. A fuse alone is likely inadequate,
> because in the event of a complete short many FETs may or will become
> damaged before the fuse blows. One can add a current-sensing resistor
> and some circuitry responding to the voltage across it, etc.,
There has been something similar in another
thread here in sed. See;
Subject: Re: Turning on a circuit till current increases...
Date: Mon, 11 Nov 2002 07:42:37 +0000 (GMT)
If the latching-feedback is taken directly off
the power device then the circuit will unlatch
at some (unspecified) overcurrent.
A more respectable unlatcher would be a current
sense resistor running with (say?) 150mV across
it at normal full load, with a transistor b-e
across it... the transistor unlatches the circuit
at about 3x full load. The b-e unlatcher gets
more sensitive with temperature and there may
even be circumstances where the transistor is
deliberately mounted close to the power switch.
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup