witches' brew
in [Design]
|
From: whit3rd on 19 Jul 2010 10:35 On Jul 18, 2:29 pm, "Tim Williams" <tmoran...(a)charter.net> wrote: > Yuck, hard switching into a capacitor, too? Maybe not; series inductance might be designed into the transformer-looking gizmo. I once had an ... amusing... half hour trying to explain to a colleague about a constant-voltage transformer. He kept thinking it was a transformer. Not true, the magnetic circuit is much different, but the lack of a distinctive name got in the way of any understanding.
From: John Larkin on 19 Jul 2010 11:08 On Mon, 19 Jul 2010 07:35:56 -0700 (PDT), whit3rd <whit3rd(a)gmail.com> wrote: >On Jul 18, 2:29�pm, "Tim Williams" <tmoran...(a)charter.net> wrote: >> Yuck, hard switching into a capacitor, too? > >Maybe not; series inductance might be designed into the >transformer-looking gizmo. It's a tiny toroid in the CUI thing, so I'd suspect insignificant leakage inductance. John
From: Spehro Pefhany on 19 Jul 2010 11:17 On Mon, 19 Jul 2010 08:08:22 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Mon, 19 Jul 2010 07:35:56 -0700 (PDT), whit3rd <whit3rd(a)gmail.com> >wrote: > >>On Jul 18, 2:29�pm, "Tim Williams" <tmoran...(a)charter.net> wrote: >>> Yuck, hard switching into a capacitor, too? >> >>Maybe not; series inductance might be designed into the >>transformer-looking gizmo. > >It's a tiny toroid in the CUI thing, so I'd suspect insignificant >leakage inductance. > >John Does it conduct much switching noise back into the supply?
From: Tim Williams on 19 Jul 2010 11:19 "Spehro Pefhany" <speffSNIP(a)interlogDOTyou.knowwhat> wrote in message news:n2r84658pa40h7cvejjbvceenamlu6fndv(a)4ax.com... >>It's a tiny toroid in the CUI thing, so I'd suspect insignificant >>leakage inductance. >> >>John > > Does it conduct much switching noise back into the supply? Funny, I made a chopper recently, having need of isolating a few hundred milivolts. Quite noisy, but it's low bandwidth so it all filters away. http://myweb.msoe.edu/williamstm/Images/Shunt_Isolator_Schem.pdf http://myweb.msoe.edu/williamstm/Images/Shunt_Isolator.jpg Off topic: doesn't use toroids. The interesting thing is, since the chopper is shorting-mode commutated, it *doesn't* work with a bypassed supply. It astonishes me how many of these circuits are out there, with 2N3055s and iron core transformers, and they'd work *so much better* with just a little series inductance in the supply! Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: John Larkin on 19 Jul 2010 11:54
On Mon, 19 Jul 2010 10:19:54 -0500, "Tim Williams" <tmoranwms(a)charter.net> wrote: >"Spehro Pefhany" <speffSNIP(a)interlogDOTyou.knowwhat> wrote in message news:n2r84658pa40h7cvejjbvceenamlu6fndv(a)4ax.com... >>>It's a tiny toroid in the CUI thing, so I'd suspect insignificant >>>leakage inductance. >>> >>>John >> >> Does it conduct much switching noise back into the supply? > >Funny, I made a chopper recently, having need of isolating a few hundred milivolts. Quite noisy, but it's low bandwidth so it all filters away. > >http://myweb.msoe.edu/williamstm/Images/Shunt_Isolator_Schem.pdf >http://myweb.msoe.edu/williamstm/Images/Shunt_Isolator.jpg > >Off topic: doesn't use toroids. They are small, efficient, and apparently cheap. But harder to wind at home. I once worked for a company that had a small toroid winding machine, and we could make our own. That was sort of cool. I can't imagine how they wind those tiny bifalar ones in the dc/dc bricks, or Ethernet magnetics. Maybe by hand with starvation-pay suicide-prone labor? >The interesting thing is, since the chopper is shorting-mode commutated, it *doesn't* work with a bypassed supply. It astonishes me how many of these circuits are out there, with 2N3055s and iron core transformers, and they'd work *so much better* with just a little series inductance in the supply! Yikes! John |