Another oops ... the .96uh should've been 0.96 (ratio).
I used 23 turns on the primary, and 22 on the secondary
to get the .96 ratio.

Cheers,
-Neil.



> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Jan-erik Soderholm (QAC)
> Sent: Wednesday, March 05, 2003 1:56 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]: Transformer Q...
>
>
> First you say :
>
> Primary:  18.18uh...
> Secondary:  0.96uh...
>
> then you say :
>
> Primary:  18.5uh...
> Secondary: 0.96 ratio...
>
> Why *ratio* in the second case ?
>
> >From the first cse I get a ratio of about 0.05 (or 20
> depending on which way you look at it).
>
> Jan-Erik Soderholm
>
> -----Original Message-----
> From: PicDude [mailto:picdude@NARWANI.ORG]
> Sent: den 5 mars 2003 19:30
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [EE]: Transformer Q...
>
>
> In my ongoing saga to get this DC-DC converter working, I'm
> questioning my transformer design, and would appreciate any
> help on this from you gurus in this area, as I've not done
> many of these in the past.  The design spec (from National's
> SMS tool) calls for...
>
> Primary:  18.18uh, 33.45 mOhms.
> Secondary:  0.96uh, 58.46 mOhms.
>
> I've calculated this as followings (using a T-130-3 (gray)
> toroidal core)...
> Primary:  23 turns of 20-awg, yielding 18.5uh, ~33 mOhms.
> Secondary:  22 turns of 20-awg, yielding 0.96 ratio, ~32 mOhms.
>
> The secondary resistance is much lower than required, but is
> that a problem?  NS's websim tool seems in indicate that it
> is not.
>
> I've wound the coils non-overlapping this time, btw.  See..
> http://www.narwani.org/neil/stuff/transformer-03.jpg
>
> For coil phase/orientation, I'm winding with the same direction
> (start over the core, going down thru the middle, and moving
> counter-clockwise as I wind the turns), with the start of each
> winding marked as the "dot".  See the following pic, in which
> my "dots" are on A1 and B1.
> http://www.narwani.org/neil/stuff/transformer-phase.jpg
>
> Can anyone spot a problem here?
>
> Thanks,
> -Neil.
>
> --
> http://www.piclist.com hint: The PICList is archived three different
> ways.  See http://www.piclist.com/#archives for details.
>
> --
> http://www.piclist.com hint: The PICList is archived three different
> ways.  See http://www.piclist.com/#archives for details.
> ---
> [This E-mail scanned for viruses]
>
>

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.