SMPS Topologies

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Gentlemen,

What's the exact technical term for the switcher topology where you only  
have one large toroidal (typically) transformer right at the mains entry  
point which takes line AC and outputs it at a lower voltage level  
whereupon it's fed into the bridge rectifier and thence into a large  
storage cap whereupon it can be chopped up, regulated and finally  
filtered, there being no other transformers involved?

thanks.

Re: SMPS Topologies
Cursitor Doom wrote:

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Hmm, not sure there is an exact name for this.  Sounds like an offline 60Hz  
transformer/rectifier/capacitor-input filter, and then a buck regulator.
The regulator would have an inductor in it.

Jon

Re: SMPS Topologies
On Monday, July 3, 2017 at 1:26:34 PM UTC-4, Cursitor Doom wrote:
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The new way to do this is with a small transformer running in the multi-hundreds of kHz and even into the Mhz region.  The toroidal 60Hz transformers are Big, Heavy, and expensive.

Re: SMPS Topologies
On Mon, 03 Jul 2017 11:56:12 -0700, Yzordderrex wrote:

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True, but they're also the quietest option when you can't afford the  
least itty bit of noise riding on the output - and this is in a high-end  
signal generator where purity is a major criterion.

Re: SMPS Topologies
On Mon, 3 Jul 2017 19:56:42 -0000 (UTC), Cursitor Doom

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I'm 'old school', most of my G-job SMPS's run at just over 20kHz ;-)
        
                                        ...Jim Thompson
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| Analog Innovations                               |     et      |
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Re: SMPS Topologies
On 2017-07-03 13:37, Jim Thompson wrote:
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That's nasty for animals. Mine mostly run north of 300kHz.

Once when our Shepherd mix was still with us I had a SMPS prototype go  
into choking. I couldn't hear it but the scope showed it. She gave me  
"the look" and left the office with a sigh that I am sure she did on  
purpose.

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: SMPS Topologies
On Monday, July 3, 2017 at 1:00:37 PM UTC-7, Cursitor Doom wrote:
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[about transformer/rectifier/filter/DC converter power supplies]
  
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There are some VERY quiet power supplies in the switchmode
camp.   'least itty bit' isn't how the manufacturer describes 'em, though.

Size and efficiency matter; a low-power supply can easily get LOTS of
RF filtering from the big 60 Hz magnetics, and those are lossy at lower
frequency, too.   It's a 'free' broadband filter.   A switchmode topology
can be just as quiet, with similar bulk and expense, if filtering is designed
into it.   That filtering is the place to study, not the block-diagram.

Re: SMPS Topologies
On 2017-07-03 14:16, whit3rd wrote:
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Yup.



The filtering is fairly easy. What is much tougher is the layout where  
you need clever tricks to avoid radiating noise. Many design engineers  
think that the shield will take care of all that but don't realize that  
radiated noise gets couple back into conducted more right before cables  
or traces leave the box. For example, into the last CM choke.

Another tricky area are the winding techniques in the ferrite  
transformer. It pays off to partner with an experienced magnetics company.

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: SMPS Topologies
Cursitor Doom wrote:

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In that case, if the power is low enough, skip all the switching crap, and  
use a linear regulator.  If not, then serious shielding and filtering is  
required.  This is some of the stuff that can keep you awake at night.

Jon

Re: SMPS Topologies
On Mon, 3 Jul 2017 19:56:42 -0000 (UTC), Cursitor Doom

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High frequency actually makes a clean output easier.  All of the
components get small and cheap.  I rarely do SMPS supplies under 2MHz
anymore.

Re: SMPS Topologies
On 07/03/2017 01:22 PM, Cursitor Doom wrote:
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an antique switcher topology

Re: SMPS Topologies
On Mon, 03 Jul 2017 16:09:16 -0400, bitrex wrote:

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I really don't think so, Snowflake 1. If you know better, by all means  
post a link and disprove it.

Re: SMPS Topologies
On 07/03/2017 06:25 PM, Cursitor Doom wrote:
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One of the few logical reasons I can think of for doing it the way you  
describe is if semiconductor switches with a high enough  
collector-emitter or drain-source breakdown voltage that could handle  
the peak rectified 220VRMS line voltage weren't available or too  
expensive, or the few devices that could withstand the voltage stresses  
and were affordable weren't fast enough to build an efficient flyback.

These were probably significant engineering challenges at one time but I  
ain't that old. I don't see why a PS topology using an iron step-down  
input transformer plus a chopper afterwards would be intrinsically lower  
noise than any other as far as the output signal is concerned, but it  
would be interesting to know why if it is the case.

That'd be a good vanity license plate though: SNWFLK1



Re: SMPS Topologies
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Snowflake?

The last time I handled a supply of that description, its semis had late 80s  
date codes.  (It didn't even use the SG3524 or TL494, but a functionally  
similar predecessor to them.)

That's antique as SMPS go.

So antique, you can't find web links of them to post.  Isn't that  
interesting?  :-)

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
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Re: SMPS Topologies
On Mon, 03 Jul 2017 22:04:13 -0500, Tim Williams wrote:

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Nope. 2007.


Here you go: enjoy...

http://www.avionteq.com/Document/IFR-2030-opt-006-specification-sheet.pdf

If anyone can find a schematic for it, that'd be "double-plus good" (as  
Winston Smith would have put it).

Re: SMPS Topologies
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That's a signal generator, not a power supply.

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
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Re: SMPS Topologies
On Tue, 04 Jul 2017 22:45:45 -0500, Tim Williams wrote:

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sheet.pdf

The PSU in this particular generator is the one under discussion here.

Re: SMPS Topologies
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Oh.  Well, there's hundreds of pages, could you add which pages are  
relevant?

(I guess the relevancy isn't very high anyway, if as you say, it has no  
schematic? :-/ )

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
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Re: SMPS Topologies
On Wed, 05 Jul 2017 16:14:38 -0500, Tim Williams wrote:

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Exactly. There's some half-arsed block diagram buried in there somewhere  
but IIRC it doesn't reference the PSU section anyway.

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Re: SMPS Topologies
On 07/05/2017 05:14 PM, Tim Williams wrote:
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I like how the first 20 pages are just various warnings and advisories  
in six different languages.

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