I need some transformers for a low noise SMPS

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Martin Griffith

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Joined
Apr 6, 2016
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151
Location
Medina Sidonia,Spain
I want to prototype a couple of low noise switched supplies. Any suggestions of EU suppliers/coil winders. Similar to this http://uk.rs-online.com/web/p/switch-mode-power-supply-smps-transformers/5226190/ but with different turns ratios. I'm aiming to get +- 12V @50mA and maybe P48, from a Li-ion 3.4V cell, 18650 sort of thing.
 
  Note that in your case you don't really need the insulation, so for the 12V rails you might get away with an inductor. For the 48V you still probably need a transformer as is beyond practical limits a boost converter do 14 times boost.

JS
 
It seems to me that custom HF transformers might be expensive, surely far more expensive than off the shelf magnetics.

I inherited one design that used a transformer in a switching supply to put out two different regulated voltages. It worked well enough but I could never get the transformer quiet, it appeared to be sized properly to prevent saturation and regulated adequately just was unacceptable for a studio product PS always singing along.  ???

Since the transformer was single sourced and kind of an odd ball, I just backed up to make it a simpler single voltage regulator using a more common standard inductor and added a pass regulator for the lower regulated voltage.  Less clever, but dead silent.  ;D

I ASSume the regulators are adjustable over a range so common off the shelf inductors should cover most applications, but in my (limited) experience, transformers in switchers are less common, resulting in less favorable price and availability.

JR 
 
Martin Griffith said:
I want to prototype a couple of low noise switched supplies. Any suggestions of EU suppliers/coil winders. Similar to this http://uk.rs-online.com/web/p/switch-mode-power-supply-smps-transformers/5226190/ but with different turns ratios. I'm aiming to get +- 12V @50mA and maybe P48, from a Li-ion 3.4V cell, 18650 sort of thing.

We use these guys in many SMPS applications.
 
You can do that without transformers (which are expensive and difficult to find) if you do not need insulation.
Flyback are also more difficult to design, with some stability issues, low frequency oscillations, etc ...
A simple boost/inverter converter design will do it for the +-12V (with some post regulation and/or filtering)
For the 48V, do a search with "SEPIC Multiplied Boost Converter". There is a Analog Device AN on Multiplied Boost converter, and the charge pump multiplied boost design is adapted to the 48V.
 

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