[AMPS] SMPS design. My 2c.

[alex]

This was then Phil :)

Today you can integrate a lot more in silicon so the part count is not a big
problem.
The real challenge becomes the design of the magnetics which has to switch
currents
in voltages that are extremely high. Isolation and feed back linearity
preservation is a daunting issue at these levels. Peak overshoot voltages
can reach many times the output which for a 5V SMPS is not a problem but for
one delivering 5000VDC it could became a spark gap transmitter.

Also the switching devices must have a extremely high reverse break down
voltage but nowadays this is not a real stopper. Protection against reverse
magnetic field dumping
must bee extremely fast as the energy in the falling edge of the squarewave
is very high.

Also, if you want good efficiency you need a Power Factor Correction stage.
The PFC must deploy a different philosophy than the SMPS-eses at lower
voltages as you run fast in trouble designing a 20KW/4A PFC for 10KVA SMPS.

You do need the PFC as every percent of inefficiency at these levels
translate into many hundred of watts of heat. Without PFC thermal management
becomes the prohibitive factor
for a commercial unit. But for a HAM it might be used as coffee heater so
...

For one of our projects, I have contacted the Dean of EE dep at a university
in Florida
that was bragging on the internet about his expertise in SMPS design. We
offered to pay him for a prototype. After 4 weeks he had to decline as he
did not have the necessary "talent"
in his group of students :)

I,personally, I did a SMPS design. It is only 50V/22A. We needed it for our
MRF157
amplifiers. You can see it on http://www.sandlabs.com/power.htm But the
10KVA
must wait a it more :)



Alex.



===================================
If we can accept the notion that GUNS are
the killers and not the people, why is it that
we can not accept the idea that CARS are
the speeders and not the drivers?

Alex, trying to understand the world around.

==================================.

----- Original Message -----
From: "Phil (VA3UX)" <phil@vaxxine.com>
To: <amps@contesting.com>
Sent: Saturday, December 15, 2001 3:44 PM
Subject: Re: [AMPS] Transformer Current ratings


>
> I remember this - it was done by a guy with a dutch last name. It was a 2
> KVA supply, around 2 KV. It was the size of a shoe box and weighed 10 or
15
> lbs. I believe it was included just one year in the ARRL Handbook -
> possibly mid- to- late 80's.
>
> The only problem I see with these SMPS is that the parts count is high,
and
> they're far more complex than the simple brute-force linear supplies we
use
> for amps. I think the trade-off of high weight/volume and low parts count
> against low weigh/volume but high complexity is what has kept SMPS out of
> the amateur linear amp scene.
>
> Phil
>
> At 07:33 PM 12/15/2001 +0000, you wrote:
>
>
> >There was a design for a high voltage (~ 2 kV) SMPS in an old issue of
QEX
> >- the
> >ARRL's technical journal. I don't know if it is possible to search (or
perhaps
> >even find the article online at the ARRL web site). I can't recall the
exact
> >power level, but it was only a couple of kW or so. This was about 5 or
> >possibly
> >10 years ago.
> >
> >I did contemplate trying to design a larger (10 kW) SMPS, but came to the
> >conclusion it would be a nice thing to do if my employer was paying for
the
> >inevitable blown up components. One can't go too far wrong with a simple
> >transformer/rectifier, but I think building a switch mode supply is a
> >different
> >matter altogether.
> >--
> >Dr. David Kirkby Ph.D,
> >email: drkirkby@ntlworld.com
> >former email address: davek@medphys.ucl.ac.uk
> >web page: http://www.david-kirkby.co.uk/
> >Amateur radio callsign: G8WRB
> >
> >--
> >FAQ on WWW:               http://www.contesting.com/FAQ/amps
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> >Problems:                 owner-amps@contesting.com
>
>
>
> --
> FAQ on WWW:               http://www.contesting.com/FAQ/amps
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