J
John Larkin
Guest
On Fri, 16 Jun 2023 15:17:31 -0700, boB <boB@K7IQ.com> wrote:
I\'ll need to insulate my fets from the copper cooler, with AlN
insulators, so a TO-220 and a screw is a good way to clamp each one
down.
I could fit six TO-247s or eight TO-220s, but the 220\'s would be
better thermally. The more power dissipation I can spec, the more
people might buy one.
On Fri, 16 Jun 2023 14:56:14 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:
On Fri, 16 Jun 2023 14:25:06 -0700, boB <boB@K7IQ.com> wrote:
On Fri, 16 Jun 2023 21:16:29 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Fri, 16 Jun 2023 18:43:59 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Fri, 16 Jun 2023 17:58:05 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Fri, 16 Jun 2023 04:16:02 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Fri, 16 Jun 2023 02:19:21 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:
John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
On Thu, 15 Jun 2023 17:19:23 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2023-06-15 01:23, Jan Panteltje wrote:
On a sunny day (Wed, 14 Jun 2023 17:59:32 +0100) it happened \"Commander
Kinsey\" <CK1@nospam.com> wrote in <op.16jf5imhmvhs6z@ryzen.home>:
Is it easy to make a simple circuit to limit a 12V DC current to 50A using a mosfet?
Can I just give it a variable voltage to turn it on a certain amount?
Or is it not that easy?
Dissipation is your issue, using a MOSFET in series
50 A with a voltage drop over it will bake it
volts multiplied by voltage dropped makes watts.
You could use a switcher with filter.
So define what you find \'simple\'
?
Not to mention that a good many modern FETs have safe operating areas
that are hard to distinguish from the Y axis.
Cheers
Phil Hobbs
On. Off. What else is there?
Gas. Some of those jokey IR datasheets give new meaning to vaporware.
As in, exploded all over the inside of a box.
I blew a fet across a room once. I didn\'t know the soldering iron was grounded.
You mean the dpaks that run at 200 amps?
Uh oh....
I got these: https://www.vishay.com/docs/77646/sum40014m.pdf
375 watts is absurd for that toy fet. Even 125 is crazy.
I don\'t like the package. I like them screwed firmly to the heatsink like TO-247. Those are the size I see inside 1-3kW supplies.
Phil is referring to IR posting absurd specs for their fets, like
ignoring the leads, or submerging them in boiling coolants to get the
ratings. So, everybody else had to do it to be competitive.
It does say \"at 25C\".
That FET is perfect for this application. BUT it will still have to
just turn OFF when you exceed your 50 amp threshold.
You can not use it in a linear voltage regulating mode at these high
values of current. And you won\'t be able to keep the tab at 25
degrees C either.
He precisely wants to use it as a 50 amp linear regulator.
You COULD turn it into a switcher though and buck converter to reduce
the voltage. Just add some switching circuitry, FET drive and an
inductor and capacitor basically.
Forget trying to dissipate hundreds of watts in that one FET.
He would dissipate 50 watts or less. One big fet on a giant heat sink
could do that, but not a surface-mount dpak sort of thing.
That particular FET is about the best junction to case resistance you
are going to get for the price. Even a TO-247 is not going to be much
better, if at all. These D-Squared-pak FETs are FULL of silicon.
But they can\'t \"easily\" dissipate 50 watts I would say. Maybe with a
lot of air blowing. How much does he want to spend on this ? I guess
that is really the question.
However, he could parallel FETs and make it a bit easier but then you
know how that goes for a linear stage of FETs.
I was recently playing with the idea of mounting power fets on a cpu
cooler-fan assembly, as a programmable dummy load, for maybe 200
watts. Turns out that lots of fets are available in TO-247 and the
same chip in TO-220, and the thermal resistance is the same. So I may
as well use TO-220s, cause I can fit more on a cooler.
The Dynatron R25 is a beast. Lots of copper surface for mounting fets
on, like eight TO-220s maybe.
We use TO-220s on big heat sinks too. We also make D2PAK FETs work
well through PCB heat transfer. Much easier to work with than TO-220s
but a bit less good of sinking of course.
boB
I\'ll need to insulate my fets from the copper cooler, with AlN
insulators, so a TO-220 and a screw is a good way to clamp each one
down.
I could fit six TO-247s or eight TO-220s, but the 220\'s would be
better thermally. The more power dissipation I can spec, the more
people might buy one.