On Sun, 15 Jan 2012 10:11:07 -0800 (PST), Bill Sloman <bill.sloman@ieee.org> wrote:>On Jan 15, 6:06�pm, John Larkin ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >> On Sun, 15 Jan 2012 02:25:49 -0800 (PST), Bill Sloman >> >> >> >> >> >> >> >> >> >> <bill.slo...@ieee.org> wrote: >> >On Jan 15, 4:21�am, John Larkin >> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >> >> On Sat, 14 Jan 2012 18:03:56 -0800 (PST), Bill Sloman >> >> >> <bill.slo...@ieee.org> wrote: >> >> >On Jan 15, 12:05�am, John Larkin >> >> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >> >> >> On Sat, 14 Jan 2012 14:50:38 -0800 (PST),BillSloman >> >> >> >> <bill.slo...@ieee.org> wrote: >> >> >> >On Jan 14, 10:25�pm, John Larkin >> >> >> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >> >> >> >> On Sat, 14 Jan 2012 10:59:47 -0800 (PST),BillSloman >> >> >> >> >> <bill.slo...@ieee.org> wrote: >> >> >> >> >On Jan 14, 7:16�pm, John Larkin >> >> >> >> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >> >> >> >> >> On Sat, 14 Jan 2012 03:00:55 -0800 (PST),BillSloman >> >> >> >> >> >> <bill.slo...@ieee.org> wrote: >> >> >> >> >> >On Jan 14, 11:09�am, John Devereux <j...@devereux.me.uk> wrote: >> >> >> >> >> >> BillSloman<bill.slo...@ieee.org> writes: >> >> >> >> >> >> > On Jan 14, 5:36�am, John Larkin >> >> >> >> >> >> > <jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >> >> >> >> >> >> >> On Fri, 13 Jan 2012 17:44:04 -0800 (PST),BillSloman >> >> >> >> >> >> >> >> <bill.slo...@ieee.org> wrote: >> >> >> >> >> >> >> >The Baxandall parallel class-D oscillator "squegs" in real life if you >> >> >> >> >> >> >> >build it with a high value inductance in the current feed and bipolar >> >> >> >> >> >> >> >switches. An LTSpice circuit using the Gummel-Poon model for the >> >> >> >> >> >> >> >bipolar transistors doesn't show this - it settles down to a stable >> >> >> >> >> >> >> >sinusoidal oscillation within less than a hundred cycles. >> >> >> >> >> >> >> >> >The obvious effect of using a high value inductor is that the current >> >> >> >> >> >> >> >through the inductor over-shoots dramatically at start-up and actually >> >> >> >> >> >> >> >reverses polarity as it recovers, so the bipolar transistors briefly >> >> >> >> >> >> >> >run inverted (emitter and collector diffusions swap roles). In real >> >> >> >> >> >> >> >life this clearly makes the circuit �behave very oddly, but the Gummel- >> >> >> >> >> >> >> >Poon model equally clearly doesn't capture this particular oddness. >> >> >> >> >> >> >> >> >VBIC might do better, but it doesn't with the model parameters that >> >> >> >> >> >> >> >I �bodged out of Gummel-Poon parameters. Somebody who had a better - >> >> >> >> >> >> >> >some - understanding of the VBIC parameters might well be able to do >> >> >> >> >> >> >> >better. >> >> >> >> >> >> >> >> It seems to wobble a bit on startup, but doesn't actually squeg even >> >> >> >> >> >> >> with a full henry as the feed inductor. >> >> >> >> >> >> >> > That's what I'm complaining about. A real circuit would almost >> >> >> >> >> >> > certainly squeg. >> >> >> >> >> >> >> Well there's one way to find out isn't there? :) >> >> >> >> >> >> >The last one I built with an over-sized oscillator (which was the >> >> >> >> >> >first one I ever built, more than forty years ago) certainly squegged. >> >> >> >> >> >Building another just to prove the point would be something of a waste >> >> >> >> >> >of time. >> >> >> >> >> >> If the behavior of this oscillator is a waste of time, give it up. >> >> >> >> >> >> If it were interesting to me, I'd have one running in about 30 >> >> >> >> >> minutes, on a handsome, dremeled, labeled slice of copperclad. >> >> >> >> >> >A bit extravagant for a 16kHz oscillator. If I get enthusiastic enough >> >> >> >> >to build one I'll put it on a perforated prototyping board. I rather >> >> >> >> >like the one Farnell sells that comes with a "collander ground plane" >> >> >> >> >on the component side of the board. The copper rings around the holes >> >> >> >> >on the track side can be chopped up to support surface mount parts if >> >> >> >> >you want to mix and match. >> >> >> >> >> >It will take a bit longer than half an hour - winding transformers is >> >> >> >> >tedious, even when you've got access to a coil winding machine. >> >> >> >> >> You can wind a pot core in a few minutes, by hand. >> >> >> >> >I know. I've done it. It doesn't have to take long to be tedious. >> >> >> >> >>ftp://jjlarkin.lmi.net/Z206_pcb.JPG >> >> >> >> >> Or buy one of those dual-winding inductors for about a dollar. >> >> >> >> >Any particular "dual-winding" inductor? It's not a name I'm familiar >> >> >> >with. As far as I'm concerned, any inductor carrying two or more >> >> >> >separate but magnetically linked windings is either a transformer or a >> >> >> >common mode choke. >> >> >> >> Things like this: >> >> >> >>http://search.digikey.com/us/en/products/DRQ74-220-R/513-1148-6-ND/19... >> >> >> >> People call these dual-winding inductors, probably because they are >> >> >> characterized to carry a lot of DC current. Of course they work nicely >> >> >> as transformers. >> >> >> >It's the first time I've heard of it being called a dual-winding >> >> >inductor. There one in my Peltier thermostat paper >> >> >> >Sloman A.W., Buggs P., Molloy J., and Stewart D. �A microcontroller- >> >> >based driver to stabilise the temperature of an optical stage to 1mK >> >> >in the range 4C to 38C, using a Peltier heat pump and a thermistor >> >> >sensor� Measurement Science and Technology, 7 1653-64 (1996) >> >> >> >I called it a balun on page 1663 and in Figure 8. The - English - >> >> >supplier called it a common mode choke. >> >> >> >> I used their big brothers in a power supply that we discussed here a >> >> >> while back. >> >> >> >Lots of people do. >> >> >> >>ftp://jjlarkin.lmi.net/ESM_power.pdf >> >> >> >T1 and T2? >> >> >> I used them as transformers so I called them transformers. PADS lets >> >> you do that. >> >> >> The other reason they are called "inductors" is that they have a >> >> specified inductance and tolerance. Transformers are seldom specified >> >> for inductance, and seldom specified for their DC current capacity. >> >> >> It really doesn't matter what you call them. >> >> >Unless you want other people to know what you are talking about. >> >> We follow proper conventions for reference designators. A resistor is >> R1, not RN1 or RV1 or POT1. A transistor is Q, not T or TR or TRN or >> any of that nonsense. Since thess parts look like a transformer [1] on >> the schematic and act like a transformer, I called them T on the >> schematic. When we use these as inductors, we put the windings in >> series or in parallel and call them L. >> >> [1] except that they have two cores. That's because the part was >> created as two inductors, and we plopped them alongside one another to >> make it look like a transformer. >> >> >> >> >> What you call them >> >> shouldn't constrain what you are willing to use them for. >> >> >Obviously. >> >> >> You could >> >> use these as baluns, common-mode chokes, inductors, power >> >> transformers, signal transformers, flyback transformers, resistors, or >> >> RTDs. Nice little parts. >> >> >They are a bit bulky for use as resistors and RTDs. The bulk might be >> >useful if you wanted to dissipate a significant amount of power, but >> >it strikes me as an expensive way of getting it. >> >> If you allow yourself to think, more opportunities are available. Add >> "gain control device" to the list. Maybe even "delay line." > >With two coils you could use one as a "saturable reactor" > >http://en.wikipedia.org/wiki/Saturable_reactorProbably not practical with this series of parts. They typically hit a thermal/current limit before magnetic saturation.> >I've never seen it done. and would have thought - as the wikipedia >article does - that the approach is close to obsolete.It never hurts to understand what parts can do.> >You can build up delay lines out of all sorts of RLC components. I >hadn't realised that common mode chokes had anything special to offer >as the inductive components in such a synthesis. > >http://jcatsc.com/media/TechnicalReports/02-CoupledInductorDelayFilter.pdfSince it's probably bifalar wound, maybe its windings could be used as a twisted-pair transmission line, a delay line all on their own. John
Baxandall class-D oscillator squegging and the VBIC model
Started by ●January 13, 2012
Reply by ●January 15, 20122012-01-15
Reply by ●January 15, 20122012-01-15
On Jan 15, 7:42=A0pm, John Larkin <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:> On Sun, 15 Jan 2012 10:11:07 -0800 (PST), Bill Sloman > > > > > > > > > > <bill.slo...@ieee.org> wrote: > >On Jan 15, 6:06=A0pm, John Larkin > ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > >> On Sun, 15 Jan 2012 02:25:49 -0800 (PST), Bill Sloman > > >> <bill.slo...@ieee.org> wrote: > >> >On Jan 15, 4:21=A0am, John Larkin > >> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > >> >> On Sat, 14 Jan 2012 18:03:56 -0800 (PST), Bill Sloman > > >> >> <bill.slo...@ieee.org> wrote: > >> >> >On Jan 15, 12:05=A0am, John Larkin > >> >> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > >> >> >> On Sat, 14 Jan 2012 14:50:38 -0800 (PST),BillSloman > > >> >> >> <bill.slo...@ieee.org> wrote: > >> >> >> >On Jan 14, 10:25=A0pm, John Larkin > >> >> >> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > >> >> >> >> On Sat, 14 Jan 2012 10:59:47 -0800 (PST),BillSloman > > >> >> >> >> <bill.slo...@ieee.org> wrote: > >> >> >> >> >On Jan 14, 7:16=A0pm, John Larkin > >> >> >> >> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > >> >> >> >> >> On Sat, 14 Jan 2012 03:00:55 -0800 (PST),BillSloman > > >> >> >> >> >> <bill.slo...@ieee.org> wrote: > >> >> >> >> >> >On Jan 14, 11:09=A0am, John Devereux <j...@devereux.me.uk= > wrote: > >> >> >> >> >> >> BillSloman<bill.slo...@ieee.org> writes: > >> >> >> >> >> >> > On Jan 14, 5:36=A0am, John Larkin > >> >> >> >> >> >> > <jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > >> >> >> >> >> >> >> On Fri, 13 Jan 2012 17:44:04 -0800 (PST),BillSloman > > >> >> >> >> >> >> >> <bill.slo...@ieee.org> wrote: > >> >> >> >> >> >> >> >The Baxandall parallel class-D oscillator "squegs" =in real life if you> >> >> >> >> >> >> >> >build it with a high value inductance in the curren=t feed and bipolar> >> >> >> >> >> >> >> >switches. An LTSpice circuit using the Gummel-Poon =model for the> >> >> >> >> >> >> >> >bipolar transistors doesn't show this - it settles =down to a stable> >> >> >> >> >> >> >> >sinusoidal oscillation within less than a hundred c=ycles.> > >> >> >> >> >> >> >> >The obvious effect of using a high value inductor i=s that the current> >> >> >> >> >> >> >> >through the inductor over-shoots dramatically at st=art-up and actually> >> >> >> >> >> >> >> >reverses polarity as it recovers, so the bipolar tr=ansistors briefly> >> >> >> >> >> >> >> >run inverted (emitter and collector diffusions swap=roles). In real> >> >> >> >> >> >> >> >life this clearly makes the circuit =A0behave very =oddly, but the Gummel-> >> >> >> >> >> >> >> >Poon model equally clearly doesn't capture this par=ticular oddness.> > >> >> >> >> >> >> >> >VBIC might do better, but it doesn't with the model=parameters that> >> >> >> >> >> >> >> >I =A0bodged out of Gummel-Poon parameters. Somebody=who had a better -> >> >> >> >> >> >> >> >some - understanding of the VBIC parameters might w=ell be able to do> >> >> >> >> >> >> >> >better. > > >> >> >> >> >> >> >> It seems to wobble a bit on startup, but doesn't act=ually squeg even> >> >> >> >> >> >> >> with a full henry as the feed inductor. > > >> >> >> >> >> >> > That's what I'm complaining about. A real circuit wou=ld almost> >> >> >> >> >> >> > certainly squeg. > > >> >> >> >> >> >> Well there's one way to find out isn't there? :) > > >> >> >> >> >> >The last one I built with an over-sized oscillator (which=was the> >> >> >> >> >> >first one I ever built, more than forty years ago) certai=nly squegged.> >> >> >> >> >> >Building another just to prove the point would be somethi=ng of a waste> >> >> >> >> >> >of time. > > >> >> >> >> >> If the behavior of this oscillator is a waste of time, giv=e it up.> > >> >> >> >> >> If it were interesting to me, I'd have one running in abou=t 30> >> >> >> >> >> minutes, on a handsome, dremeled, labeled slice of copperc=lad.> > >> >> >> >> >A bit extravagant for a 16kHz oscillator. If I get enthusias=tic enough> >> >> >> >> >to build one I'll put it on a perforated prototyping board. =I rather> >> >> >> >> >like the one Farnell sells that comes with a "collander grou=nd plane"> >> >> >> >> >on the component side of the board. The copper rings around =the holes> >> >> >> >> >on the track side can be chopped up to support surface mount=parts if> >> >> >> >> >you want to mix and match. > > >> >> >> >> >It will take a bit longer than half an hour - winding transf=ormers is> >> >> >> >> >tedious, even when you've got access to a coil winding machi=ne.> > >> >> >> >> You can wind a pot core in a few minutes, by hand. > > >> >> >> >I know. I've done it. It doesn't have to take long to be tediou=s.> > >> >> >> >>ftp://jjlarkin.lmi.net/Z206_pcb.JPG > > >> >> >> >> Or buy one of those dual-winding inductors for about a dollar=.> > >> >> >> >Any particular "dual-winding" inductor? It's not a name I'm fam=iliar> >> >> >> >with. As far as I'm concerned, any inductor carrying two or mor=e> >> >> >> >separate but magnetically linked windings is either a transform=er or a> >> >> >> >common mode choke. > > >> >> >> Things like this: > > >> >> >>http://search.digikey.com/us/en/products/DRQ74-220-R/513-1148-6-N=D/19...> > >> >> >> People call these dual-winding inductors, probably because they =are> >> >> >> characterized to carry a lot of DC current. Of course they work =nicely> >> >> >> as transformers. > > >> >> >It's the first time I've heard of it being called a dual-winding > >> >> >inductor. There one in my Peltier thermostat paper > > >> >> >Sloman A.W., Buggs P., Molloy J., and Stewart D. =93A microcontrol=ler-> >> >> >based driver to stabilise the temperature of an optical stage to 1=mK> >> >> >in the range 4C to 38C, using a Peltier heat pump and a thermistor > >> >> >sensor=94 Measurement Science and Technology, 7 1653-64 (1996) > > >> >> >I called it a balun on page 1663 and in Figure 8. The - English - > >> >> >supplier called it a common mode choke. > > >> >> >> I used their big brothers in a power supply that we discussed he=re a> >> >> >> while back. > > >> >> >Lots of people do. > > >> >> >>ftp://jjlarkin.lmi.net/ESM_power.pdf > > >> >> >T1 and T2? > > >> >> I used them as transformers so I called them transformers. PADS let=s> >> >> you do that. > > >> >> The other reason they are called "inductors" is that they have a > >> >> specified inductance and tolerance. Transformers are seldom specifi=ed> >> >> for inductance, and seldom specified for their DC current capacity. > > >> >> It really doesn't matter what you call them. > > >> >Unless you want other people to know what you are talking about. > > >> We follow proper conventions for reference designators. A resistor is > >> R1, not RN1 or RV1 or POT1. A transistor is Q, not T or TR or TRN or > >> any of that nonsense. Since thess parts look like a transformer [1] on > >> the schematic and act like a transformer, I called them T on the > >> schematic. When we use these as inductors, we put the windings in > >> series or in parallel and call them L. > > >> [1] except that they have two cores. That's because the part was > >> created as two inductors, and we plopped them alongside one another to > >> make it look like a transformer. > > >> >> What you call them > >> >> shouldn't constrain what you are willing to use them for. > > >> >Obviously. > > >> >> You could > >> >> use these as baluns, common-mode chokes, inductors, power > >> >> transformers, signal transformers, flyback transformers, resistors,=or> >> >> RTDs. Nice little parts. > > >> >They are a bit bulky for use as resistors and RTDs. The bulk might be > >> >useful if you wanted to dissipate a significant amount of power, but > >> >it strikes me as an expensive way of getting it. > > >> If you allow yourself to think, more opportunities are available. Add > >> "gain control device" to the list. Maybe even "delay line." > > >With two coils you could use one as a "saturable reactor" > > >http://en.wikipedia.org/wiki/Saturable_reactor > > Probably not practical with this series of parts. They typically hit a > thermal/current limit before magnetic saturation. > > > > >I've never seen it done. and would have thought - as the wikipedia > >article does - that the approach is close to obsolete. > > It never hurts to understand what parts can do. > > > > >You can build up delay lines out of all sorts of RLC components. I > >hadn't realised that common mode chokes had anything special to offer > >as the inductive components in such a synthesis. > > >http://jcatsc.com/media/TechnicalReports/02-CoupledInductorDelayFilte... > > Since it's probably bifalar wound, maybe its windings could be used as > a twisted-pair transmission line, a delay line all on their own.Some are bifilar wound, some not. The length of the winding - and thus the delay - isn't something the manufacturer specifies all that tightly on the data sheet, and might change without notice if they changed core materials. Probably not the ideal building block. -- Bill Sloman, Nijmegen
