[time-nuts] Need help with transformer core

Attila Kinali attila at kinali.ch
Sun Aug 31 06:50:42 EDT 2014


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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