One more thing, that I'm always repeating.... If you find yourself needing an obscure item from an obscure manufacturer that is not sold by digikey or mouser, don't be afraid to call up the manufacturer and ask for a sample. They won't sell it to you directly (probably.. unless you want 50,000 of them anyways) but will almost always send you a couple of them if you tell them that you're prototyping a new design.
-Adam On Sat, Aug 4, 2012 at 9:09 AM, John Rehwinkel <jreh...@mac.com> wrote: > > A flyback transformer seems to give higher conversion ratios, but I am > puzzled about it being an isolated topology by nature. > > Yeah, a transformer can give you an isolated output, but then voltage > feedback is more complicated. Also, transformers are > harder to find than plain inductors, and have more parameters to play with > (for example, most flyback converters use transformers > with a gapped core). > > > A "tapped inductor boost converter" might be just what I need. It is > very elegant really, split the inductor in two and connect the switch to > the center tap. Sometimes such inductor is called 'autotransformer' since > only one winding acting on itself. When the energy of the magnetic field is > dumped during the discharge period there will be a substantial voltage gain > since the number of turns in the second part of the inductor is greater. > > Right. > > > 2, There does not seem to be that many inductors available seems limited > at best. > > Quite true. You have four basic choices here. One is to try to find a > stock transformer that does what you want - as you've > seen, this can be tricky. Another is to take a basic inductor, and add > some turns on top of the winding, and use those turns > as the primary - there's a lot of trial and error involved, and some > learning on magnetics*. The third step is to wind your own > transformer from the ground up - having a coil winding machine is a help > (our own David Forbes has taken this approach). > The fourth one, which I am in the process of investigating, is to use a > "universal" transformer - these have six identical > windings, which can be connected in series and parallel in various > combinations in order to implement a variety of > transformer functions. One example is Digikey 732-2449-1-ND. > > > Maybe I am just using the wrong phrases when I search. Any ideas on > suitable inductors are appreciated. > > One approach I use is to look up the example circuits put up by the chip > manufacturers and examine the part numbers > and manufacturers of the transformers used there. While a "Pulse > Engineering gobblydegook" may not be a line item > at Digikey, it's worth asking Pulse Engineering about them. > > * Wurth Electronics used to offer a dandy set of books, among them "ABCs > of Transformers" (Digikey 732-1415-ND) > for $18 and that explained a lot of useful concepts. They seem to have > discontinued that one, and have combined them, > along with some new material, into a single book called "Trilogy of > Inductors" (Digikey 732-1414-ND), which is also > discontinued, and replaced it with "Trilogy of Magnetics" (Digikey > 732-2511-ND), that covers a lot more ground, but is $72. > > - John > > -- > You received this message because you are subscribed to the Google Groups > "neonixie-l" group. > To post to this group, send an email to neonixie-l@googlegroups.com. > To unsubscribe from this group, send email to > neonixie-l+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
