Recently we all heard about a new HV supply for KW amps, being sold by Watts
Unlimited. As promised, I contacted them for some inside info, and they were
very open and co-operative. (More and more I am beginning to realize that the
only people who are hyper-secretive with basic product info are those who
don't really know what they are doing, or are overtly scamming.)
This product is called PSA2500 and is the brainchild of Tim, W9QQ, and in my
opinion he is a very capable power supply designer. I have discussed the
thing with him offline and his logic for design and marketing of this product
are FB.
As some of us suspected, it is an open-loop inverter, running at 64KHZ, which
explains the stated voltage regulation. In reality, it acts pretty much like
a conventional transformer/rectifier/capacitor supply with regard to
transient response, and has a healthy amount of C.
The fact that it runs open-loop is very significant from a design standpoint,
particularly with regard to EMI generation. His basic design topology must,
unfortunately, run open loop. But that topology has an overwhelming benefit:
very low HF ripple current on the input. Large supplies like this are
nightmares to EMI proof. So in order to be able to produce a product that is
practical, this compromise was accepted. The result is a usable product, and
more importantly, it can be produced affordably.
In the power supply business, retail prices generally run in the .$.5-1.0 per
watt range for a 'full-featured' supply. If we had to pay this price, I don't
think there would be any takers - hence, no suppliers. I say congrats to Tim
(no, he is not a relative or creditor of mine) for bringing to the ham market
a product which has practical value and suitable performance.
As a previous participant myself in the power electronics market, I am
extremely sensitive to reliability of these designs. A serious circuit
failure frequently leads, in milliseconds, to a handful of expensive MOSFETS
being reduced to rubble. The mfr. must be prepared to replace these on
warranteed products, so he better do his homework in the design/testing -
otherwise any profit is quickly converted into income for the transistor
mfrs. Let's hope Tim has done his homework. Time will tell.
73
Eric von Valtier
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