[time-nuts] Need help with transformer core

EWKehren at aol.com EWKehren at aol.com
Sun Aug 31 07:15:02 EDT 2014


Attila
Any opinion or observation on Mean Well's SD series, they are a key  
component on most of our projects.
Bert Kehren
 
 
In a message dated 8/31/2014 6:51:13 A.M. Eastern Daylight Time,  
attila at kinali.ch writes:

On Sat,  30 Aug 2014 01:58:40 +0000
Mark Sims <holrum at hotmail.com>  wrote:

> Frankly,  anybody that builds up a Simple Switcher  type converter
> from scratch is more than a little nuts and/or awfully  lonely.
>  You can buy small,  adjustable pre-built boards  (buck or boost configs)
> off of Ebay for as little as a dollar each...  including shipping from
> Old Cathay.  I usually buy them 10 or 20  at a time.

I slightly disagree here. There are half a dozen parameters  that one
has to design for when building a DC/DC converter. Simply using  one
badly specified converter bought of ebay is not going to work  unless
your requirements are very docile. There is a reason why most  electronics
devices have a custom build DC/DC converter onboard instead of  using
one of the available modules (and it's not only money), or that  there
are companies who have specilized in designing custom DC/DC  converters for
other electronic design houses to use.

As for  time-nuts, probably the most important factor in a DC/DC converter
is the  output voltage/current ripple and its spectrum. Closely followed
by  magnetic and electrical fields around the converter. Unfortunately,
these  depend quite a bit on things that are neither specified nor can
be easily  measured: cleannes of layout and quality of components.
Ie whether you use  a $0.01 or a $0.05 ceramic capacitor can make the
difference whether you  have high frequency components (a couple MHz)
in the output ripple.  

Also, i would not dare to change the DC/DC converter of a device  unless
i know exactly what happens downstream and how the whole system was  
designed.
Especially in bigger, complex devices, there is a strange  interdependence
between power supply behaviour and consumer  behaviour.

Attila Kinali

-- 
I pity people who can't find laughter or at least  some bit of amusement in
the little doings of the day. I believe I could  find something ridiculous
even in the saddest moment, if necessary. It has  nothing to do with being
superficial. It's a matter of joy in  life.
-- Sophie  Scholl
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