On Sat, 05 Nov 2011 01:53:47 -0500, legg <legg@nospam.magma.ca> wrote:>On Thu, 03 Nov 2011 11:42:10 -0500, John S <sophi.2@invalid.org> >wrote: > >>On 11/3/2011 11:51 AM, legg wrote: >>> On Wed, 02 Nov 2011 23:45:15 -0700, miso<miso@sushi.com> wrote: >>> >>>> Given base charge storage, if the driver rise/fall time is fast, the >>>> design could have shoot through. >>> >>> ...and given magnetizing energy, emitters will be pulled above and >>> below the rails. >> >>But only by one Vbe above or below. > >... just enough to cause the transistor to conduct the magnetising >current to the opposing rail - clamping the winding in the lossiest >way possible, Imag x VCC losses being absorbed by the bipolar >transistor that is supposed to be 'off'. > >RLThe magnetizing current tends to turn the "wrong" transistor on, but the load current mitigates that. A snubber helps, too. It's not hard to make all the currents play nice. I did find a weird asymmetry that turned out to be a feature of LT Spice. If you specify a pulse generator of Ton 5 us Tr 1 us Tf 1 us Tper 10 us you get an asymmetric waveform. You need Ton of 4u to get symmetry. John
isolated DC/DC converter
Started by ●November 3, 2011
Reply by ●November 5, 20112011-11-05
Reply by ●November 5, 20112011-11-05
On Sat, 05 Nov 2011 08:42:14 -0700, Joerg <invalid@invalid.invalid> wrote:>John Larkin wrote: >> On Fri, 04 Nov 2011 15:57:28 -0700, Joerg <invalid@invalid.invalid> >> wrote: >> >>> Vladimir Vassilevsky wrote: >>>> >>>> John Larkin wrote: >>>> >>>>> This >>>>> >>>>> http://www.panoramio.com/photo/61564837 >>>>> >>>>> might work for powering a thing I'm doing. I can use a standard cheap >>>>> Coiltronix dual-coil inductor as the transformer. The complementary >>>>> emitter followers will have no shoot-through and can have controllably >>>>> slow switching edges, since they will just follow the base drive. >>>>> >>>>> Anybody got ideas for the base driver device? Ideally it would be >>>>> self-oscillating, set with some R-C; have a moderate slew rate; swing >>>>> to the rails. I'm thinking roughly 150 KHz maybe, a few watts output. >>>>> >>>>> Maybe an LM8261 opamp? I'd have to see if it winds up when it rails. >>>>> It might not. >>>>> >>>>> Some sort of fet gate driver would be OK, but few go to 24 volts. >>>>> >>>>> Something discrete maybe, like a 2N7002 to 24-, and maybe a >>>>> bootstrapped pullup? >>>> You might want to check IR2085S >>>> >>> But I am sure John won't want to spend the two bux in the BOM :-) >> >> Actually, I ordered some IRS2153D's, a very simlar part. Maybe if I >> use biggish gate resistors and keep the frequency down I can get >> tolerable efficiency and low noise. It may need a snubber, not sure. >> I'll build one on Monday. >> >> My little emitter follower thing seems to work, but it's not very >> efficient. >> >> A couple of bux of parts cost is not a big deal here. Getting it to >> work the first time is. >> > >But yesterday you wrote that you wanted it cheap in case you build lots >of them :-)Within reason. I don't want to buy a 5-watt potted dc/dc converter for $30, or custom magnetics for $10. The IR thing is under $1 in quantity, and doesn't need a lot of external parts. This one even includes the bootstrap diode. I still want to use a stock dual-winding inductor as the transformer. Our per-part kitting/placement cost is high, so we take that into account too. Our customer, probably wildly optimistic, estimates maybe 800 boxes a year, so it's worth spending a day considering alternate ways to do this. Besides, playing with circuits is fun.> >Reminds me of a time when I was designing something for the guys where >things must have cast-iron robustness. I sat there in agony and a >manager asked me whether I had problems with my design. "Not technical >ones but these multipliers are over $6, a piece". A whole group of >people around me had listened in. They and the manager burst into >thundering laughter ...Our customer just decided to use a 600 watt single-mode fiber laser to *illuminate* part of this gadget. "Cost is no object" is the term I heard. That doesn't stop them from making occasional, and ineffective, stabs at us to cut our pricing. John
Reply by ●November 5, 20112011-11-05
On Sat, 05 Nov 2011 10:59:48 -0500, Vladimir Vassilevsky <nospam@nowhere.com> wrote:> > >John Larkin wrote: > >>>Vladimir Vassilevsky wrote: >>>>John Larkin wrote: >>>> >>>>>This >>>>> >>>>>http://www.panoramio.com/photo/61564837 >>>>> >>>>>might work for powering a thing I'm doing. >>>>>Anybody got ideas for the base driver device? > >>>>You might want to check IR2085S >> Actually, I ordered some IRS2153D's, a very simlar part. > >So, getting a self oscillating thing to work seems too complicated ? >(http://www.abvolt.com/misc/self_osc.jpg)Actually, that does look complicated.> >> A couple of bux of parts cost is not a big deal here. Getting it to >> work the first time is. > >Use a PIC.Where would the PIC get its power from?! Just getting a square wave clock isn't hard. The power drivers are what I'm playing with. I want a quiet, efficient, cheap, low-risk 5-watt dc/dc converter that uses stock parts, and I want it designed and proven by, say, Monday afternoon. That's not unreasonable, is it? John
Reply by ●November 5, 20112011-11-05
John Larkin wrote:> On Sat, 05 Nov 2011 08:42:14 -0700, Joerg <invalid@invalid.invalid> > wrote: > >> John Larkin wrote: >>> On Fri, 04 Nov 2011 15:57:28 -0700, Joerg <invalid@invalid.invalid> >>> wrote: >>> >>>> Vladimir Vassilevsky wrote: >>>>> John Larkin wrote: >>>>> >>>>>> This >>>>>> >>>>>> http://www.panoramio.com/photo/61564837 >>>>>> >>>>>> might work for powering a thing I'm doing. I can use a standard cheap >>>>>> Coiltronix dual-coil inductor as the transformer. The complementary >>>>>> emitter followers will have no shoot-through and can have controllably >>>>>> slow switching edges, since they will just follow the base drive. >>>>>> >>>>>> Anybody got ideas for the base driver device? Ideally it would be >>>>>> self-oscillating, set with some R-C; have a moderate slew rate; swing >>>>>> to the rails. I'm thinking roughly 150 KHz maybe, a few watts output. >>>>>> >>>>>> Maybe an LM8261 opamp? I'd have to see if it winds up when it rails. >>>>>> It might not. >>>>>> >>>>>> Some sort of fet gate driver would be OK, but few go to 24 volts. >>>>>> >>>>>> Something discrete maybe, like a 2N7002 to 24-, and maybe a >>>>>> bootstrapped pullup? >>>>> You might want to check IR2085S >>>>> >>>> But I am sure John won't want to spend the two bux in the BOM :-) >>> Actually, I ordered some IRS2153D's, a very simlar part. Maybe if I >>> use biggish gate resistors and keep the frequency down I can get >>> tolerable efficiency and low noise. It may need a snubber, not sure. >>> I'll build one on Monday. >>> >>> My little emitter follower thing seems to work, but it's not very >>> efficient. >>> >>> A couple of bux of parts cost is not a big deal here. Getting it to >>> work the first time is. >>> >> But yesterday you wrote that you wanted it cheap in case you build lots >> of them :-) > > Within reason. I don't want to buy a 5-watt potted dc/dc converter for > $30, or custom magnetics for $10. The IR thing is under $1 in > quantity, and doesn't need a lot of external parts. ...Unfortunately it guzzles 5mA Iq though. It's a self-zenered device so you'll probably be burning 200mW by it just sitting there.> ... This one even > includes the bootstrap diode. I still want to use a stock dual-winding > inductor as the transformer. Our per-part kitting/placement cost is > high, so we take that into account too. Our customer, probably wildly > optimistic, estimates maybe 800 boxes a year, so it's worth spending a > day considering alternate ways to do this. Besides, playing with > circuits is fun. >That's why I suggested the A&Q part. It even has the timing RC integrated (or probably some sort of ring oscillator). I try to get companies away from kitting, never believed in it and always saw it as a waste of time. At Endosonics which was a fairly big company with around 150 folks in production we succeeded in getting rid of it and went to Kanban-style. Huge savings. Made the stock price rise :-)>> Reminds me of a time when I was designing something for the guys where >> things must have cast-iron robustness. I sat there in agony and a >> manager asked me whether I had problems with my design. "Not technical >> ones but these multipliers are over $6, a piece". A whole group of >> people around me had listened in. They and the manager burst into >> thundering laughter ... > > Our customer just decided to use a 600 watt single-mode fiber laser to > *illuminate* part of this gadget. "Cost is no object" is the term I > heard. That doesn't stop them from making occasional, and ineffective, > stabs at us to cut our pricing. >I sometimes have that as well. Major project, 6-7 figures, and then someone occasionally worries about an additional travel expenses to the tune of a few hundred bucks. -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●November 5, 20112011-11-05
On Sat, 05 Nov 2011 12:15:02 -0400, Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:>On Sat, 05 Nov 2011 10:59:48 -0500, the renowned Vladimir Vassilevsky ><nospam@nowhere.com> wrote: > >> >> >>John Larkin wrote: >> >>>>Vladimir Vassilevsky wrote: >>>>>John Larkin wrote: >>>>> >>>>>>This >>>>>> >>>>>>http://www.panoramio.com/photo/61564837 >>>>>> >>>>>>might work for powering a thing I'm doing. >>>>>>Anybody got ideas for the base driver device? >> >>>>>You might want to check IR2085S >>> Actually, I ordered some IRS2153D's, a very simlar part. >> >>So, getting a self oscillating thing to work seems too complicated ? >>(http://www.abvolt.com/misc/self_osc.jpg) >> >>> A couple of bux of parts cost is not a big deal here. Getting it to >>> work the first time is. >> >>Use a PIC. > >It should be pretty easy to throw some randomness into the frequency >with a PIC for a spread-spectrum converter. > > >Best regards, >Spehro PefhanyI did a box that used a bunch of the LTM8023 bricks. I built a TinyLogic schmitt oscillator and used the triangle to FM all the switchers a little. It spread the switcher noise spectrum beautifully. John
Reply by ●November 5, 20112011-11-05
On Sat, 05 Nov 2011 10:33:49 -0700, Joerg <invalid@invalid.invalid> wrote:>John Larkin wrote: >> On Sat, 05 Nov 2011 08:42:14 -0700, Joerg <invalid@invalid.invalid> >> wrote: >> >>> John Larkin wrote: >>>> On Fri, 04 Nov 2011 15:57:28 -0700, Joerg <invalid@invalid.invalid> >>>> wrote: >>>> >>>>> Vladimir Vassilevsky wrote: >>>>>> John Larkin wrote: >>>>>> >>>>>>> This >>>>>>> >>>>>>> http://www.panoramio.com/photo/61564837 >>>>>>> >>>>>>> might work for powering a thing I'm doing. I can use a standard cheap >>>>>>> Coiltronix dual-coil inductor as the transformer. The complementary >>>>>>> emitter followers will have no shoot-through and can have controllably >>>>>>> slow switching edges, since they will just follow the base drive. >>>>>>> >>>>>>> Anybody got ideas for the base driver device? Ideally it would be >>>>>>> self-oscillating, set with some R-C; have a moderate slew rate; swing >>>>>>> to the rails. I'm thinking roughly 150 KHz maybe, a few watts output. >>>>>>> >>>>>>> Maybe an LM8261 opamp? I'd have to see if it winds up when it rails. >>>>>>> It might not. >>>>>>> >>>>>>> Some sort of fet gate driver would be OK, but few go to 24 volts. >>>>>>> >>>>>>> Something discrete maybe, like a 2N7002 to 24-, and maybe a >>>>>>> bootstrapped pullup? >>>>>> You might want to check IR2085S >>>>>> >>>>> But I am sure John won't want to spend the two bux in the BOM :-) >>>> Actually, I ordered some IRS2153D's, a very simlar part. Maybe if I >>>> use biggish gate resistors and keep the frequency down I can get >>>> tolerable efficiency and low noise. It may need a snubber, not sure. >>>> I'll build one on Monday. >>>> >>>> My little emitter follower thing seems to work, but it's not very >>>> efficient. >>>> >>>> A couple of bux of parts cost is not a big deal here. Getting it to >>>> work the first time is. >>>> >>> But yesterday you wrote that you wanted it cheap in case you build lots >>> of them :-) >> >> Within reason. I don't want to buy a 5-watt potted dc/dc converter for >> $30, or custom magnetics for $10. The IR thing is under $1 in >> quantity, and doesn't need a lot of external parts. ... > > >Unfortunately it guzzles 5mA Iq though. It's a self-zenered device so >you'll probably be burning 200mW by it just sitting there. > > >> ... This one even >> includes the bootstrap diode. I still want to use a stock dual-winding >> inductor as the transformer. Our per-part kitting/placement cost is >> high, so we take that into account too. Our customer, probably wildly >> optimistic, estimates maybe 800 boxes a year, so it's worth spending a >> day considering alternate ways to do this. Besides, playing with >> circuits is fun. >> > >That's why I suggested the A&Q part. It even has the timing RC >integrated (or probably some sort of ring oscillator). I try to get >companies away from kitting, never believed in it and always saw it as a >waste of time. At Endosonics which was a fairly big company with around >150 folks in production we succeeded in getting rid of it and went to >Kanban-style. Huge savings. Made the stock price rise :-) > > >>> Reminds me of a time when I was designing something for the guys where >>> things must have cast-iron robustness. I sat there in agony and a >>> manager asked me whether I had problems with my design. "Not technical >>> ones but these multipliers are over $6, a piece". A whole group of >>> people around me had listened in. They and the manager burst into >>> thundering laughter ... >> >> Our customer just decided to use a 600 watt single-mode fiber laser to >> *illuminate* part of this gadget. "Cost is no object" is the term I >> heard. That doesn't stop them from making occasional, and ineffective, >> stabs at us to cut our pricing. >> > >I sometimes have that as well. Major project, 6-7 figures, and then >someone occasionally worries about an additional travel expenses to the >tune of a few hundred bucks.Uh, we're talking 10 figures here. John
Reply by ●November 5, 20112011-11-05
John Larkin wrote:> On Sat, 05 Nov 2011 10:33:49 -0700, Joerg <invalid@invalid.invalid> > wrote: > >> John Larkin wrote: >>> On Sat, 05 Nov 2011 08:42:14 -0700, Joerg <invalid@invalid.invalid> >>> wrote: >>>[...]>> >>>> Reminds me of a time when I was designing something for the guys where >>>> things must have cast-iron robustness. I sat there in agony and a >>>> manager asked me whether I had problems with my design. "Not technical >>>> ones but these multipliers are over $6, a piece". A whole group of >>>> people around me had listened in. They and the manager burst into >>>> thundering laughter ... >>> Our customer just decided to use a 600 watt single-mode fiber laser to >>> *illuminate* part of this gadget. "Cost is no object" is the term I >>> heard. That doesn't stop them from making occasional, and ineffective, >>> stabs at us to cut our pricing. >>> >> I sometimes have that as well. Major project, 6-7 figures, and then >> someone occasionally worries about an additional travel expenses to the >> tune of a few hundred bucks. > > Uh, we're talking 10 figures here. >Oh, sounds like courtesy of the taxpayer. As in "free" :-) -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●November 5, 20112011-11-05
John Larkin a �crit :> On Sat, 05 Nov 2011 12:15:02 -0400, Spehro Pefhany > <speffSNIP@interlogDOTyou.knowwhat> wrote: > >> On Sat, 05 Nov 2011 10:59:48 -0500, the renowned Vladimir Vassilevsky >> <nospam@nowhere.com> wrote: >> >>> >>> John Larkin wrote: >>> >>>>> Vladimir Vassilevsky wrote: >>>>>> John Larkin wrote: >>>>>> >>>>>>> This >>>>>>> >>>>>>> http://www.panoramio.com/photo/61564837 >>>>>>> >>>>>>> might work for powering a thing I'm doing. >>>>>>> Anybody got ideas for the base driver device? >>>>>> You might want to check IR2085S >>>> Actually, I ordered some IRS2153D's, a very simlar part. >>> So, getting a self oscillating thing to work seems too complicated ? >>> (http://www.abvolt.com/misc/self_osc.jpg) >>> >>>> A couple of bux of parts cost is not a big deal here. Getting it to >>>> work the first time is. >>> Use a PIC. >> It should be pretty easy to throw some randomness into the frequency >> with a PIC for a spread-spectrum converter. >> >> >> Best regards, >> Spehro Pefhany > > I did a box that used a bunch of the LTM8023 bricks. I built a > TinyLogic schmitt oscillator and used the triangle to FM all the > switchers a little. It spread the switcher noise spectrum beautifully. > > John >Arghhhh, why did I forgot that for my last project? (PCB has just been sent to fab...) Thanks for the reminder. -- Thanks, Fred.
Reply by ●November 5, 20112011-11-05
On a sunny day (Sat, 05 Nov 2011 10:11:37 -0700) it happened John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in <18rab7t8aheb55q4s8m7b26nhmscdlk3bm@4ax.com>:>On Sat, 05 Nov 2011 10:59:48 -0500, Vladimir Vassilevsky ><nospam@nowhere.com> wrote: > >> >> >>John Larkin wrote: >> >>>>Vladimir Vassilevsky wrote: >>>>>John Larkin wrote: >>>>> >>>>>>This >>>>>> >>>>>>http://www.panoramio.com/photo/61564837 >>>>>> >>>>>>might work for powering a thing I'm doing. >>>>>>Anybody got ideas for the base driver device? >> >>>>>You might want to check IR2085S >>> Actually, I ordered some IRS2153D's, a very simlar part. >> >>So, getting a self oscillating thing to work seems too complicated ? >>(http://www.abvolt.com/misc/self_osc.jpg) > >Actually, that does look complicated. > >> >>> A couple of bux of parts cost is not a big deal here. Getting it to >>> work the first time is. >> >>Use a PIC. > >Where would the PIC get its power from?! > >Just getting a square wave clock isn't hard. The power drivers are >what I'm playing with. I want a quiet, efficient, cheap, low-risk >5-watt dc/dc converter that uses stock parts, and I want it designed >and proven by, say, Monday afternoon. That's not unreasonable, is it? > >JohnI do not get it, you can use that same circuit you recommended and I used for the PMT HV supply. Just one transistor, 1 resistor, 1 transformer, 3 caps, and some diodes. I have used it in the past with the feedback in the base to power many things, for example my old EPROM programmer, from 5 V.
Reply by ●November 5, 20112011-11-05
On Sat, 05 Nov 2011 10:36:42 -0700, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:>On Sat, 05 Nov 2011 12:15:02 -0400, Spehro Pefhany ><speffSNIP@interlogDOTyou.knowwhat> wrote: > >>On Sat, 05 Nov 2011 10:59:48 -0500, the renowned Vladimir Vassilevsky >><nospam@nowhere.com> wrote: >> >>> >>> >>>John Larkin wrote: >>> >>>>>Vladimir Vassilevsky wrote: >>>>>>John Larkin wrote: >>>>>> >>>>>>>This >>>>>>> >>>>>>>http://www.panoramio.com/photo/61564837 >>>>>>> >>>>>>>might work for powering a thing I'm doing. >>>>>>>Anybody got ideas for the base driver device? >>> >>>>>>You might want to check IR2085S >>>> Actually, I ordered some IRS2153D's, a very simlar part. >>> >>>So, getting a self oscillating thing to work seems too complicated ? >>>(http://www.abvolt.com/misc/self_osc.jpg) >>> >>>> A couple of bux of parts cost is not a big deal here. Getting it to >>>> work the first time is. >>> >>>Use a PIC. >> >>It should be pretty easy to throw some randomness into the frequency >>with a PIC for a spread-spectrum converter. >> >> >>Best regards, >>Spehro Pefhany > >I did a box that used a bunch of the LTM8023 bricks. I built a >TinyLogic schmitt oscillator and used the triangle to FM all the >switchers a little. It spread the switcher noise spectrum beautifully.What exactly did you do? Dither the voltage? If you were using a bunch, wouldn't multi-phase synchronous operation be better?
