Can anyone point me in the right direction to either a web site or text
for transformer design?
I have some experiance, but there are a few things that still stump me.
(low freq, and high freq, pulse would be good too)
TIA,
Martin
Texas Instruments' "Magnetics Design Handbook" is pretty comprehensive.
They have both a PDF version of all the info as well as narrated slides
available using TI's online training service (both are free).
Go here to get the goods:
http://focus.ti.com/docs/training/catalog/events/event.jhtml?sku=SEM401014
The single most important formula to know (IMO) is the following:
(Winding Turns)=(Volts Applied)/[2*(Frequency)*(Core cross sectional
area)*(delta B max)]
All units in SI quantities, and this formula applies to transformers that
will be seeing squarewaves (it is ever so slightly different for sinusoids,
the factor "2" appearing in the denominator is slightly larger). This
formula tells you basically how many turns a given winding will need on your
core to prevent core saturation. Delta B max is the maximum flux density
swing your convertor will be operated with. For half bridges and full
bridges this can be as much as 2X the saturation flux density of your core
(although in real applications it is often beneficial to use a much smaller
limit). For forward converters this is at most only 1X the saturation flux
density of the core. This formula does not apply for flyback transformers.