Re: Medium voltage switching-mode power supply.

From: John Popelish (jpopelish_at_rica.net)
Date: 06/23/04 

Date: Wed, 23 Jun 2004 09:17:09 -0400

Richard wrote:
>
> John
>
> Thanks for the ideas.
>
> The original receiver has one regular PSU outputing the voltages mentioned.
> I'm going to reconstruct the rx by having three modules, rf, if and af. I'm
> trying to get the whole rx into a 6U 19" rack cabinet, but it's tight for
> space, and that's why I think of getting rid of the original PSU that has
> quite a large transformer. I'm faced with a choice of either using one PSU
> to power everything, or to put a PSU on each module. I kinda like that idea
> for various reasons but it's not essential by any means, and might still go
> for the one PSU solution.
>
> I think what you are saying is wind 4 seperate secondaries and treat each
> one as a seperate PSU in it's own right. But don't regulate each secondary
> seperately.

Yes. There would be quite good regulation of all the outputs if you
regulate their sum. The big problem in a receiver would be to contain
all the high frequency noise of the supply. You would probable have
to enclose it is a separate metal box and filter all input and output
lines, besides the normal DC filter capacitors.
 
> Anyway, I think a key point here is the notion of winding ones own
> transformer. This is a must.

To use my method, certainly. for any other method, almost certainly.

> So, I've got to find a transformer supplier and
> a circuit. Maybe if I look around I might come across some low-voltage
> circuits and it's simply a matter of just upgrading the component voltages.

Finding a core and bobbin is your challenge (besides designing the
rest of the circuit.

> I think then task is to find a low-voltage circuit, then more-or-less copy
> that design, but replicate the secondary circuit for as many secondary
> windings that I have.
>
> For instance:
>
> http://www.coilws.com/Switch%20Mode%20Power/5W_SMPS.htm

THis design is sort of regulated, by using the second secondary to
approximate what the main secondary is doing.
 
> This particular circuit is not regulated, but I think were saying that if I
> were as an example to use this circuit I could stick to the circuit
> arrangement except for component voltages in the secondary circuit, and I'd
> have 4 rectified secondary circuits instead of one. Which I would join in
> series.

That is what I was describing.

> Of course I must calculate the needed power output of the desired PSU. And
> I'd have to figure out how to regulate.

Some other examples:
http://henry.fbe.fh-darmstadt.de/smps_e/smps_e.asp
http://www.maxim-ic.com/appnotes.cfm/appnote_number/2039
http://www.powerint.com/PDFFiles/an31.pdf
http://www.smps.us/Unitrode.html
http://www.fairchildsemi.com/an/AN/AN-4134.pdf
http://www.fairchildsemi.com/an/AN/AN-9015.pdf
http://www.onsemi.com/pub/Collateral/AND8039-D.PDF 

-- 
John Popelish

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