Looking for DC/DC converter

In article <405B1310.3AE229AD@yahoo.com>
           spamgoeshere4@yahoo.com "rickman" writes:

> I would suggest taking a look at building your own.  I worked on a board
> where one of the engineers spec'd a hand made choke/transformer.  He
> wrote out assembly instructions and they had an assembler make them. 
> Winding a transformer is not really that hard unless you are trying to
> make it very small.  I know that several of the coil companies sell
> cores.  

I am more fortunate than most at present I suppose. I have reasonable 
access to a coil winding machine. RS Components do a range of small
transformer cores and assemblies that make the task quite easy. With 
1W power requirement you could probably get away with a small ferrite 
ring and wind it by hand (takes an investment of time but for one-off 
or just a few may well be worth such hassle).

Calculating a transformer for a psu is not really that hard. Rough 
and ready calculations can be done on just the turns ration required 
to get the sought voltage step. A PWM driven pair of transistors on 
either leg of a centre tapped primary would act as a suitable input 
chopper and by varying the ON time of each device you can adjust the 
output voltage.

The result may, however, be slightly more expensive in board real-
estate than two of the TRAMCO or BB devices. When it comes to wanting 
five isolated outputs then there is no contest. The self-wound 
transformer wins out in small numbers and I can get production 
quantities wound from the details i have already documented.

-- 
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