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LTC Switcher CAD3 ?

Started by Robert Baer June 2, 2012
Jamie wrote:
> Robert Baer wrote: > >> Switcher cad?? >> NO transformers. >> NO saturable inductors. >> NO selection of ferrite core materials. >> NO selection of ferrite core sizes or shapes. >> WTF?? > Who needs that? ;) > > Jamie > > >
Lemme see..i want to make a DC-DC converter, using (guess what kiddies) a ferrite pot core, maybe some kind of controller to (at minimum) generate drive waveforms to power devices, some feedback from output to give line and load regulation. BUT..like i said, the NO mentioned does not allow me to select or try different transformers..
Bill Sloman wrote:
> On Jun 2, 6:07 am, Robert Baer<robertb...@localnet.com> wrote: >> Switcher cad?? >> NO transformers. > > Use coupled inductors - K1 L1 L2 L3 0.99 tells the program that L1, L2 > and L3 are windings on a single transforemr with a coupling > coefficient of 0.99 > >> NO saturable inductors. > > The John Chan model represents real, hysteretic inductors pretty > accurately, if my limited experience is anything to go by. > >> NO selection of ferrite core materials. > > The John Chan model allows you to do that > >> NO selection of ferrite core sizes or shapes. > > The John Chan model allows you to do that. > > Go to "Help" and section L.Inductor. > >> WTF?? > > There's not a lot wrong with the program, but you do have to work out > how to get the most out of it. > > -- > Bill Sloman, Nijmegen > >
So i can pick a 2N2222 or a 2N3904 or a LT1026 or LT1105 or a 2W 110 ohm resistor or a 1uF 10V TDK X5R capacitor as if off the shelf. BUT. Transformers? Ferroxcube pot cores? Then accidentally overdrive them? Nope. You say i need to $pend $2,000 to IEEE to look at some paper i never heard about and that few others heard about if i want to know more than what is disclosed in that help section. Nobody gives the K or M of their transformers; i have to guess - and the numbers will most likely be wrong no matter what i pick. And.. nobody mentions that those values are non-linear and what changes them.
On Jun 3, 1:50=A0pm, Robert Baer <robertb...@localnet.com> wrote:
> Bill Sloman wrote: > > On Jun 2, 6:07 am, Robert Baer<robertb...@localnet.com> =A0wrote: > >> =A0 =A0 Switcher cad?? > >> =A0 =A0 NO transformers. > > > Use coupled inductors - K1 L1 L2 L3 0.99 tells the program that L1, L2 > > and L3 are windings on a single transforemr with a coupling > > coefficient of 0.99 > > >> =A0 =A0 NO saturable inductors. > > > The John Chan model represents real, hysteretic inductors pretty > > accurately, if my limited experience is anything to go by. > > >> =A0 =A0 NO selection of ferrite core materials. > > > The John Chan model allows you to do that > > >> =A0 =A0 NO selection of ferrite core sizes or shapes. > > > The John Chan model allows you to do that. > > > Go to "Help" and section L.Inductor. > > >> =A0 =A0 WTF?? > > > There's not a lot wrong with the program, but you do have to work out > > how to get the most out of it. > > > -- > > Bill Sloman, Nijmegen > > =A0 =A0So i can pick a 2N2222 or a 2N3904 or a LT1026 or LT1105 or a 2W 1=
10
> ohm resistor or a 1uF 10V TDK X5R capacitor as if off the shelf. > =A0 =A0BUT. > =A0 =A0Transformers? Ferroxcube pot cores? Then accidentally overdrive th=
em?
> =A0 =A0Nope. > =A0 =A0You say i need to $pend $2,000 to IEEE to look at some paper i nev=
er
> heard about and that few others heard about if i want to know more than > what is disclosed in that help section. > =A0 =A0Nobody gives the K or M of their transformers; i have to guess - a=
nd
> the numbers will most likely be wrong no matter what i pick. > =A0 =A0And.. nobody mentions that those values are non-linear and what > changes them.
The K for most ungapped ferrtie cored transformers is in the 0.99 to 0.999 range - anything in that range is usually close enough to model what is going on. We've just measured a coupling of 0.98 in a gapped RM14 core - EPCOS gapped it down from 6000uH/root turn for an ungapped pair to 630nH per root turn by grinding back the centre pillar by 0.4mm, http://www.farnell.com/datasheets/486650.pdf M is K.square root L1.L2 IIRR The transformer equations are V1=3D L1.dI1/dt + M.dI2/dt V2=3D M.dI1/dt + L2.dI2/dt The John Chan model explicitly deals with the non-linear elements - though it leaves coupling severely alone. Coupling does decline dramatically if you saturate the ferrite, but real circuits blow up if you saturate the ferrite. Ferrite permeability does rise with field at low field values, but not all that much, and you can usually get away with ignoring the effect on coupling - which usually isn't a critical parameter. -- Bill Sloman, Nijmegen
"Robert Baer" <robertbaer@localnet.com> wrote in message 
news:xqydnWyQzY_6HlTSnZ2dnUVZ_g-dnZ2d@posted.localnet...
> Switcher cad?? > NO transformers. > NO saturable inductors. > NO selection of ferrite core materials. > NO selection of ferrite core sizes or shapes. > WTF??
Here's a pretty good modeling example for transformers. Transformers are sort of a black art, it's rare to design one perfectly the first time around. <http://fmtt.com/Transformer%20SPICE%20Model%202-14-08.pdf> Cheers
On Fri, 01 Jun 2012 20:07:17 -0800, Robert Baer wrote:

> Switcher cad?? > NO transformers. > NO saturable inductors. > NO selection of ferrite core materials. NO selection of ferrite core > sizes or shapes. WTF??
AFAIK, SwitcherCad disappeared from the LTSpice suite at version IV, and is unsupported. Several years ago, now. There's now LTPowerCad, a Microsoft Excel based thing. LTSpice can do transformers, saturable inductors, and hysteretic model inductors. RTFM. -- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)
On Sat, 02 Jun 2012 06:40:27 -0700, Bill Sloman wrote:

> On Jun 2, 6:52&#2013266080;am, Jamie > <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote: >> Robert Baer wrote: >> > &#2013266080; Switcher cad?? >> > &#2013266080; NO transformers. >> > &#2013266080; NO saturable inductors. >> > &#2013266080; NO selection of ferrite core materials. &#2013266080; NO selection of ferrite >> > core sizes or shapes. &#2013266080; WTF?? >> >> Who needs that? ;) > > Grown-ups.
Engineers. -- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)
"Robert Baer" <robertbaer@localnet.com> wrote in message 
news:mvGdnb3Qc4Lg3FbSnZ2dnUVZ_uOdnZ2d@posted.localnet...
> Transformers? Ferroxcube pot cores? Then accidentally overdrive them? > Nope. > You say i need to $pend $2,000 to IEEE to look at some paper i never > heard about and that few others heard about if i want to know more than > what is disclosed in that help section. > Nobody gives the K or M of their transformers; i have to guess - and the > numbers will most likely be wrong no matter what i pick. > And.. nobody mentions that those values are non-linear and what changes > them.
So make your own macro model and implement them, sheesh. I've seen several manufacturers (VAC is one) state inductance and leakage of their products (which correspond to k and M), though unfortunately the most common often don't (Pulse, Murata, etc.). For regular SPICE, I wrote my own based on the saturable core model (which might be Chan, I don't remember), which includes the calculations to go from engineering units (short-circuit leakage, winding inductances) to turns ratios and coupling. The circuit forms an inductive tee network, where the core is the middle element shunting to ground: when permeability is high, core inductance is very high, and little is dropped across the leakage elements. When the core saturates, its inductance drops by up to a factor of mu, causing k to fall. LL remains constant, which is realistic because absolute LL is determined by winding geometry, independent of core. Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
On Sun, 3 Jun 2012 11:50:10 -0500, "Tim Williams"
<tmoranwms@charter.net> wrote:

>"Robert Baer" <robertbaer@localnet.com> wrote in message >news:mvGdnb3Qc4Lg3FbSnZ2dnUVZ_uOdnZ2d@posted.localnet... >> Transformers? Ferroxcube pot cores? Then accidentally overdrive them? >> Nope. >> You say i need to $pend $2,000 to IEEE to look at some paper i never >> heard about and that few others heard about if i want to know more than >> what is disclosed in that help section. >> Nobody gives the K or M of their transformers; i have to guess - and the >> numbers will most likely be wrong no matter what i pick. >> And.. nobody mentions that those values are non-linear and what changes >> them. > >So make your own macro model and implement them, sheesh.
Or buy a bunch of parts and test+breadboard. Works for me. http://dl.dropbox.com/u/53724080/Circuits/ESM/DCBB_2.JPG -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message 
news:3r5ns7hvt6apkqu9l8023jh7gclchnq1mm@4ax.com...
>>So make your own macro model and implement them, sheesh. > > Or buy a bunch of parts and test+breadboard. Works for me. > > http://dl.dropbox.com/u/53724080/Circuits/ESM/DCBB_2.JPG
Last project I needed a model, I overestimated leakage and DCR intentionally, and made it work. Boards came in: much better performance, and no problems with ringing (note that lower leakage means higher ringing frequency and lower impedances, making them harder to dampen). That ISDN transformer looks a lot bulkier than Ethernet transformers. How much flux goes into one of those? Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
On Sun, 3 Jun 2012 12:20:06 -0500, "Tim Williams"
<tmoranwms@charter.net> wrote:

>"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message >news:3r5ns7hvt6apkqu9l8023jh7gclchnq1mm@4ax.com... >>>So make your own macro model and implement them, sheesh. >> >> Or buy a bunch of parts and test+breadboard. Works for me. >> >> http://dl.dropbox.com/u/53724080/Circuits/ESM/DCBB_2.JPG > >Last project I needed a model, I overestimated leakage and DCR >intentionally, and made it work. Boards came in: much better performance, >and no problems with ringing (note that lower leakage means higher ringing >frequency and lower impedances, making them harder to dampen). > >That ISDN transformer looks a lot bulkier than Ethernet transformers. How >much flux goes into one of those? > >Tim
That's a 4-winding unit, 1:1:2:2, wired as a 5:1 step-up. I'm applying 24 volts p-p, around 150 KHz, to a "1" winding and getting 120 p-p out, into a diode doubler, to get 120 DC to drive a photodiode. I don't know the flux density. It doesn't get hot. It's often easier to drop parts into a breadboard than to characterize parts, create a model, and simulate. Measure temperatures with an IR gadget instead of simulating core losses. Besides, a boy needs to solder once in a while. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators