On Wed, 17 Jul 2013 12:50:10 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Wed, 17 Jul 2013 10:51:08 -0700 (PDT), Lasse Langwadt Christensen ><langwadt@fonz.dk> wrote: > >>On Wednesday, July 17, 2013 6:36:32 PM UTC+2, Phil Hobbs wrote: >>> On 07/17/2013 12:16 PM, Lasse Langwadt Christensen wrote: >>> >>> > On Wednesday, July 17, 2013 5:18:25 PM UTC+2, Phil Hobbs wrote: >>> >>> >> On 07/17/2013 10:00 AM, Joerg wrote: >>> >>> >> >>> >>> >>> Phil Hobbs wrote: >>> >>> >> >>> >>> >>>> On 7/16/2013 8:54 PM, Joerg wrote: >>> >>> >> >>> >>> >>>>> Phil Hobbs wrote: >>> >>> >> >>> >>> >>>>>> On 7/16/2013 3:53 PM, Joerg wrote: >>> >>> >> >>> >>> >>>>>>> Phil Hobbs wrote: >>> >>> >> >>> >>> >>>>>>>> So, I'm goofing off playing with small switchers. (Well, not exactly >>> >>> >> >>> >>> >>>>>>>> goofing off, but there are somewhat more pressing tasks waiting....) >>> >>> >> >>> >>> >>>>>>>> >>> >>> >> >>> >>> >>>>>>>> As I said in George's thread, "Opamp w/ Vsupply > 36V", I built a >>> >>> >> >>> >>> >>>>>>>> small >>> >>> >> >>> >>> >>>>>>>> half-bridge supply with positive and negative voltage doublers. >>> >>> >> >>> >>> >>>>>>>> I'm not >>> >>> >> >>> >>> >>>>>>>> that keen on it, because (a) it uses a fair number of parts for >>> >>> >> >>> >>> >>>>>>>> what it >>> >>> >> >>> >>> >>>>>>>> does, and (b) it has a nasty instability. >>> >>> >> >>> >>> >>>>>>>> >>> >>> >> >>> >>> >>>>>>> >>> >>> >> >>> >>> >>>>>>> (a) ... yes. (b) ... why? What happens? Changing to another >>> >>> >> >>> >>> >>>>>>> architecture >>> >>> >> >>> >>> >>>>>>> while using the same kind of loop usually doesn't do much to improve >>> >>> >> >>> >>> >>>>>>> stability. >>> >>> >> >>> >>> >>>>>>> >>> >>> >> >>> >>> >>>>>>> >>> >>> >> >>> >>> >>>>>>>> With a capacitively-coupled half bridge, if you let the transformer >>> >>> >> >>> >>> >>>>>>>> saturate, it instantly discharges the coupling cap, which about >>> >>> >> >>> >>> >>>>>>>> doubles >>> >>> >> >>> >>> >>>>>>>> the volt-seconds on the next half-cycle and guarantee that it will >>> >>> >> >>> >>> >>>>>>>> keep >>> >>> >> >>> >>> >>>>>>>> saturating until the FETs cook themselves. >>> >>> >> >>> >>> >>>>>>>> >>> >>> >> >>> >>> >>>>>>> >>> >>> >> >>> >>> >>>>>>> Not sure what you mean here, but usually current mode control is the >>> >>> >> >>> >>> >>>>>>> way >>> >>> >> >>> >>> >>>>>>> to avoid asymmetrical runaway. >>> >>> >> >>> >>> >>>>>> >>> >>> >> >>> >>> >>>>>> The IRS2153D puts a square wave out of a half-bridge--no feedback, no >>> >>> >> >>> >>> >>>>>> current limit, nada. If you put that into a transformer via a cap, all >>> >>> >> >>> >>> >>>>>> is well until you saturate the transformer. >>> >>> >> >>> >>> >>>>>> >>> >>> >> >>> >>> >>>>> >>> >>> >> >>> >>> >>>>> Ok, the IRS2153D is just a glorified gate driver with an oscillator in >>> >>> >> >>> >>> >>>>> there. I'd use a real switcher controller chip, some are in the same >>> >>> >> >>> >>> >>>>> price category. >>> >>> >> >>> >>> >>>>> >>> >>> >> >>> >>> >>>>> >>> >>> >> >>> >>> >>>>>> Say that happens on the positive half-cycle. >>> >>> >> >>> >>> >>>>>> At that moment, the voltage on the cap rapidly goes from V_DD/2 to V_DD. >>> >>> >> >>> >>> >>>>>> At the next edge, the voltage across the transformer is suddenly not >>> >>> >> >>> >>> >>>>>> V_DD/2 as expected, but V_DD. The transformer saturates in half the >>> >>> >> >>> >>> >>>>>> time it took previously, and the voltage on the cap goes from V_DD to 0. >>> >>> >> >>> >>> >>>>>> Then the cycle repeats. It's really obvious on a scope when this >>> >>> >> >>> >>> >>>>>> happens, and it's far from pretty. >>> >>> >> >>> >>> >>>>>> >>> >>> >> >>> >>> >>>>> >>> >>> >> >>> >>> >>>>> Did you use a really big cap? I've never had that happen. Usually >>> >>> >> >>> >>> >>>>> ferrite saturates softly enough to just "nudge" the cap. >>> >>> >> >>> >>> >>>> >>> >>> >> >>> >>> >>>> 1 uF. I can probably post a scope photo tomorrow, if I have time--a >>> >>> >> >>> >>> >>>> bunch of lawyering has just descended on my head. (Not that I mind very >>> >>> >> >>> >>> >>>> much--expert witness work uses a different part of my brain and >>> >>> >> >>> >>> >>>> generally pays somewhat better than design work.) >>> >>> >> >>> >>> >>>> >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>> That's one of the more serious problems we as a country have. Legal >>> >>> >> >>> >>> >>> skirmishes usually have zero productivity from a national perspective >>> >>> >> >>> >>> >>> but result in the fattest "payouts". It is the core problem why our >>> >>> >> >>> >>> >>> health care system is a mess. Of course, that is never brought up by >>> >>> >> >>> >>> >>> body politicus, for obvious reasons :-( >>> >>> >> >>> >>> >> >>> >>> >> >>> >>> >> You could say much the same thing about the army, but once the shooting >>> >>> >> >>> >>> >> starts, you're glad they're there. The case I'm working on today >>> >>> >> >>> >>> >> concerns an alleged misappropriation of trade secrets by a big >>> >>> >> >>> >>> >> semiconductor company. There's a lot of money at stake, so I'm pretty >>> >>> >> >>> >>> >> much in the noise. Designing stuff for start-ups is a bit different. >>> >>> >> >>> >>> >> >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>>> <snip> >>> >>> >> >>> >>> >>>>>>> John Larkin has recently used these tiny flyback transformers. Nothing >>> >>> >> >>> >>> >>>>>>> wrong with hanging two in parallel on the primary and using the 2nd one >>> >>> >> >>> >>> >>>>>>> with the secondary flipped around, for the -45V. >>> >>> >> >>> >>> >>>>>>> >>> >>> >> >>> >>> >>>>>>> Do you need this isolated? Else you could consider just inverting and >>> >>> >> >>> >>> >>>>>>> boost. >>> >>> >> >>> >>> >>>>>>> >>> >>> >> >>> >>> >>>>>> >>> >>> >> >>> >>> >>>>>> Doesn't have to be isolated, but it does need to be quiet, hence the >>> >>> >> >>> >>> >>>>>> toroids. >>> >>> >> >>> >>> >>>>>> >>> >>> >> >>> >>> >>>>> >>> >>> >> >>> >>> >>>>> That usually rules out flybacks. They spew a lot of noise. Then I'd use >>> >>> >> >>> >>> >>>>> a half-bridge with CM control and series inductors on the output. >>> >>> >> >>> >>> >>>> >>> >>> >> >>> >>> >>>> Fortunately the half-bridge's worst-case condition is zero load, so it >>> >>> >> >>> >>> >>>> isn't too hard to control. ... >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>> They work ok with zero load if you can tolerate the voltage increase. >>> >>> >> >>> >>> >>> That would be determined by the turns ratio. If it has to be 45.000V >>> >>> >> >>> >>> >>> that's a different story. Then you'll have to let it go into a skipping >>> >>> >> >>> >>> >>> mode. >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>>> ... Of course the ungapped ferrite has a pretty >>> >>> >> >>> >>> >>>> frightening tempco of mu (it goes down by half when you hit it with cold >>> >>> >> >>> >>> >>>> spray), so some sort of current control is going to be required, for sure. >>> >>> >> >>> >>> >>>> >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>> Yes, needs current control but that's standard even in sub-Dollar chips. >>> >>> >> >>> >>> >> >>> >>> >> >>> >>> >> I may just make a boost with a two-winding toroid, and return the other >>> >>> >> >>> >>> >> end of the second winding to the raw -15V supply. (A lot of the Murata >>> >>> >> >>> >>> >> toroids are actually dual-winding, but they expect you to wire them in >>> >>> >> >>> >>> >> parallel to get the current handling capacity.) >>> >>> >> >>> >>> > >>> >>> > they generally spec them both for series and parallel ;) >>> >>> >>> >>> You'd think so, but no. The ones I'm using (Murata 32331C) aren't >>> >>> called out in the datasheet as anything except a single winding between >>> >>> pins 1 and 3, whereas in reality there's another independent one between >>> >>> pins 2 and 4 (the datasheet is at http://tinyurl.com/oyxguho ). >>> >>> >>> >>> > >>> >>> > how about a capacitive coupled boost? >>> >>> > >>> >>> > something like this: >>> >>> > http://obsoletetechnology.wordpress.com/projects/studio-electronics/dc-dc-bipolar-power-supply-for-effect-pedals/ >>> >>> > >>> >>> > -Lasse >>> >>> > >>> >>> >>> >>> It's a possibility, for sure. I normally don't think of capacitive >>> >>> boosters and hundreds of milliwatts at the same time, but it could work >>> >>> OK. It's slightly inconvenient due to having to run off +-15 to get the >>> >>> required output, but not awful. >>> >> >>I wouldn't call a capacitive booster, it a normal boost just capacitive coupled >> >>you can get +/-45V just pick a controller that can handle 45V >> >>hacked together from the lt1071 test fixture: >> >>Version 4 >>SHEET 1 2808 1492 >>WIRE 1600 880 1488 880 >>WIRE 1824 880 1600 880 >>WIRE 1872 880 1824 880 >>WIRE 1984 880 1952 880 >>WIRE 2144 880 1984 880 >>WIRE 2160 880 2144 880 >>WIRE 2272 880 2224 880 >>WIRE 2320 880 2272 880 >>WIRE 2416 880 2384 880 >>WIRE 2528 880 2416 880 >>WIRE 2640 880 2528 880 >>WIRE 1488 896 1488 880 >>WIRE 2528 896 2528 880 >>WIRE 2640 896 2640 880 >>WIRE 1600 912 1600 880 >>WIRE 1824 944 1824 880 >>WIRE 2416 960 2416 880 >>WIRE 2272 976 2272 944 >>WIRE 2528 992 2528 960 >>WIRE 2640 992 2640 976 >>WIRE 1488 1008 1488 976 >>WIRE 1600 1008 1600 976 >>WIRE 1984 1024 1984 880 >>WIRE 1984 1024 1952 1024 >>WIRE 2416 1088 2416 1040 >>WIRE 2416 1088 1952 1088 >>WIRE 2416 1104 2416 1088 >>WIRE 1968 1152 1952 1152 >>WIRE 2064 1152 2048 1152 >>WIRE 2064 1168 2064 1152 >>WIRE 2416 1200 2416 1184 >>WIRE 1824 1248 1824 1232 >>WIRE 2064 1248 2064 1232 >>WIRE 2144 1408 2144 880 >>WIRE 2304 1408 2208 1408 >>WIRE 2368 1408 2304 1408 >>WIRE 2544 1408 2432 1408 >>WIRE 2656 1408 2544 1408 >>FLAG 2640 880 OUT >>FLAG 2416 1200 0 >>FLAG 2528 992 0 >>FLAG 2640 992 0 >>FLAG 2064 1248 0 >>FLAG 1824 1248 0 >>FLAG 1600 1008 0 >>FLAG 1488 1008 0 >>FLAG 1488 880 IN >>FLAG 2272 976 0 >>FLAG 2304 1344 0 >>FLAG 2656 1328 0 >>FLAG 2544 1344 0 >>SYMBOL ind 1856 896 R270 >>WINDOW 0 32 56 VTop 2 >>WINDOW 3 5 56 VBottom 2 >>SYMATTR InstName L1 >>SYMATTR Value 150� >>SYMATTR SpiceLine Rser=0.02 Rpar=5000 >>SYMBOL schottky 2320 896 R270 >>WINDOW 0 32 32 VTop 2 >>WINDOW 3 0 32 VBottom 2 >>SYMATTR InstName D1 >>SYMATTR Value MBRS360 >>SYMBOL RES 2400 944 R0 >>SYMATTR InstName R1 >>SYMATTR Value 44K >>SYMBOL RES 2400 1088 R0 >>SYMATTR InstName R2 >>SYMATTR Value 1.24K >>SYMBOL RES 1952 1168 R270 >>WINDOW 0 32 56 VTop 2 >>WINDOW 3 0 56 VBottom 2 >>SYMATTR InstName R3 >>SYMATTR Value 1K >>SYMBOL polcap 2512 896 R0 >>SYMATTR InstName C1 >>SYMATTR Value 100� >>SYMATTR SpiceLine Rser=15m >>SYMBOL CAP 2048 1168 R0 >>SYMATTR InstName C2 >>SYMATTR Value 1� >>SYMBOL VOLTAGE 1488 880 R0 >>WINDOW 123 0 0 Left 2 >>SYMATTR InstName V1 >>SYMATTR Value 19 >>SYMATTR SpiceLine Rser=0.1 >>SYMBOL polcap 1584 912 R0 >>SYMATTR InstName C3 >>SYMATTR Value 100� >>SYMBOL PowerProducts\\LT1071HV 1824 1088 R0 >>SYMATTR InstName U1 >>SYMBOL res 2624 880 R0 >>SYMATTR InstName Rload >>SYMATTR Value 2000 >>SYMBOL schottky 2288 944 R180 >>WINDOW 0 24 64 Left 2 >>WINDOW 3 -27 0 Left 2 >>SYMATTR InstName D2 >>SYMATTR Value MBRS360 >>SYMBOL cap 2224 864 R90 >>WINDOW 0 0 32 VBottom 2 >>WINDOW 3 32 32 VTop 2 >>SYMATTR InstName C4 >>SYMATTR Value 1� >>SYMATTR SpiceLine V=50 Irms=0 Rser=0.008 Lser=0 mfg="TDK" pn="C3225X7RlHlO5M" type="X7R" >>SYMBOL schottky 2432 1392 R90 >>WINDOW 0 0 32 VBottom 2 >>WINDOW 3 32 32 VTop 2 >>SYMATTR InstName D3 >>SYMATTR Value MBRS360 >>SYMBOL schottky 2320 1408 R180 >>WINDOW 0 24 64 Left 2 >>WINDOW 3 24 0 Left 2 >>SYMATTR InstName D4 >>SYMATTR Value MBRS360 >>SYMBOL polcap 2528 1344 R0 >>SYMATTR InstName C6 >>SYMATTR Value 100� >>SYMATTR SpiceLine Rser=15m >>SYMBOL res 2640 1312 R0 >>SYMATTR InstName Rload1 >>SYMATTR Value 2000 >>SYMBOL cap 2208 1392 R90 >>WINDOW 0 0 32 VBottom 2 >>WINDOW 3 32 32 VTop 2 >>SYMATTR InstName C5 >>SYMATTR Value 1� >>SYMATTR SpiceLine V=50 Irms=0 Rser=0.008 Lser=0 mfg="TDK" pn="C3225X7RlHlO5M" type="X7R" >>TEXT 1424 1136 Left 2 !.tran 200m startup >> >> >> >>-Lasse > >Cute! That would nicely fit Larkin's needs... with no significant >surge. Somewhat similar to my self-charging CD ignition from the late >'60's at Philco-Ford and in the early '70's at Dickson electronics... > > http://www.analog-innovations.com/SED/CD-Ignition-Basic.pdf > > ...Jim ThompsonYup. I posted the Spice model three days ago. "Bubble Converter." I'm using a dual comparator, one Schmitt buffer, and a SOT23 mosfet, instead of a store-bought chip. Seems to work. https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/BB_Boost1.JPG The 2N7000 is just a hack, because I don't have the right open-drain comparator yet. -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Flyback vs half-bridge
Started by ●July 16, 2013
Reply by ●July 17, 20132013-07-17
Reply by ●July 17, 20132013-07-17
John Larkin wrote: [...]> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/BB_Boost1.JPG > > > The 2N7000 is just a hack, because I don't have the right open-drain > comparator yet. > >Is that blood on the lower left solder pad? -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●July 17, 20132013-07-17
John Devereux wrote:> Joerg <invalid@invalid.invalid> writes: > >> Jim Thompson wrote: >> >> [...] >> >> >>> Have you ever posted the input voltage? I haven't found it in the >>> thread. >>> >> Probably follows the Hobbs house standard, 19V (laptop supply). > > Hmm, most of those use a 3 pin mains connector, does that mean they are > free from the high voltage high frequency leakage currents that plague > modern wall-warts? Do they earth the DC 0V? >Some are remarkably quiet, for example on my Gammatech Durabook. But that's more like mil-spec laptop and has a proper gruond structure. On the Samsung NC-10 netbook, different story. Only two mains pins and lot of noise. -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●July 17, 20132013-07-17
On Wed, 17 Jul 2013 13:29:51 -0700, Joerg <invalid@invalid.invalid> wrote:>John Larkin wrote: > >[...] > > >> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/BB_Boost1.JPG >> >> >> The 2N7000 is just a hack, because I don't have the right open-drain >> comparator yet. >> >> > >Is that blood on the lower left solder pad?No, Sharpie. Red is +5. I cleaned up all the blood. The burns heal by themselves. -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Reply by ●July 17, 20132013-07-17
On Wed, 17 Jul 2013 09:35:32 -0700, George Herold wrote:> Do they make gapped toroids?Metglas do. For boost PFC correction circuits. -- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)
Reply by ●July 17, 20132013-07-17
On 7/17/2013 1:51 PM, Lasse Langwadt Christensen wrote:> On Wednesday, July 17, 2013 6:36:32 PM UTC+2, Phil Hobbs wrote: >> On 07/17/2013 12:16 PM, Lasse Langwadt Christensen wrote: >> >>> On Wednesday, July 17, 2013 5:18:25 PM UTC+2, Phil Hobbs wrote: >> >>>> On 07/17/2013 10:00 AM, Joerg wrote: >> >>>> >> >>>>> Phil Hobbs wrote: >> >>>> >> >>>>>> On 7/16/2013 8:54 PM, Joerg wrote: >> >>>> >> >>>>>>> Phil Hobbs wrote: >> >>>> >> >>>>>>>> On 7/16/2013 3:53 PM, Joerg wrote: >> >>>> >> >>>>>>>>> Phil Hobbs wrote: >> >>>> >> >>>>>>>>>> So, I'm goofing off playing with small switchers. (Well, not exactly >> >>>> >> >>>>>>>>>> goofing off, but there are somewhat more pressing tasks waiting.....) >> >>>> >> >>>>>>>>>> >> >>>> >> >>>>>>>>>> As I said in George's thread, "Opamp w/ Vsupply > 36V", I built a >> >>>> >> >>>>>>>>>> small >> >>>> >> >>>>>>>>>> half-bridge supply with positive and negative voltage doublers. >> >>>> >> >>>>>>>>>> I'm not >> >>>> >> >>>>>>>>>> that keen on it, because (a) it uses a fair number of parts for >> >>>> >> >>>>>>>>>> what it >> >>>> >> >>>>>>>>>> does, and (b) it has a nasty instability. >> >>>> >> >>>>>>>>>> >> >>>> >> >>>>>>>>> >> >>>> >> >>>>>>>>> (a) ... yes. (b) ... why? What happens? Changing to another >> >>>> >> >>>>>>>>> architecture >> >>>> >> >>>>>>>>> while using the same kind of loop usually doesn't do much to improve >> >>>> >> >>>>>>>>> stability. >> >>>> >> >>>>>>>>> >> >>>> >> >>>>>>>>> >> >>>> >> >>>>>>>>>> With a capacitively-coupled half bridge, if you let the transformer >> >>>> >> >>>>>>>>>> saturate, it instantly discharges the coupling cap, which about >> >>>> >> >>>>>>>>>> doubles >> >>>> >> >>>>>>>>>> the volt-seconds on the next half-cycle and guarantee that it will >> >>>> >> >>>>>>>>>> keep >> >>>> >> >>>>>>>>>> saturating until the FETs cook themselves. >> >>>> >> >>>>>>>>>> >> >>>> >> >>>>>>>>> >> >>>> >> >>>>>>>>> Not sure what you mean here, but usually current mode control is the >> >>>> >> >>>>>>>>> way >> >>>> >> >>>>>>>>> to avoid asymmetrical runaway. >> >>>> >> >>>>>>>> >> >>>> >> >>>>>>>> The IRS2153D puts a square wave out of a half-bridge--no feedback, no >> >>>> >> >>>>>>>> current limit, nada. If you put that into a transformer via a cap, all >> >>>> >> >>>>>>>> is well until you saturate the transformer. >> >>>> >> >>>>>>>> >> >>>> >> >>>>>>> >> >>>> >> >>>>>>> Ok, the IRS2153D is just a glorified gate driver with an oscillator in >> >>>> >> >>>>>>> there. I'd use a real switcher controller chip, some are in the same >> >>>> >> >>>>>>> price category. >> >>>> >> >>>>>>> >> >>>> >> >>>>>>> >> >>>> >> >>>>>>>> Say that happens on the positive half-cycle. >> >>>> >> >>>>>>>> At that moment, the voltage on the cap rapidly goes from V_DD/2 to V_DD. >> >>>> >> >>>>>>>> At the next edge, the voltage across the transformer is suddenly not >> >>>> >> >>>>>>>> V_DD/2 as expected, but V_DD. The transformer saturates in half the >> >>>> >> >>>>>>>> time it took previously, and the voltage on the cap goes from V_DD to 0. >> >>>> >> >>>>>>>> Then the cycle repeats. It's really obvious on a scope when this >> >>>> >> >>>>>>>> happens, and it's far from pretty. >> >>>> >> >>>>>>>> >> >>>> >> >>>>>>> >> >>>> >> >>>>>>> Did you use a really big cap? I've never had that happen. Usually >> >>>> >> >>>>>>> ferrite saturates softly enough to just "nudge" the cap. >> >>>> >> >>>>>> >> >>>> >> >>>>>> 1 uF. I can probably post a scope photo tomorrow, if I have time--a >> >>>> >> >>>>>> bunch of lawyering has just descended on my head. (Not that I mind very >> >>>> >> >>>>>> much--expert witness work uses a different part of my brain and >> >>>> >> >>>>>> generally pays somewhat better than design work.) >> >>>> >> >>>>>> >> >>>> >> >>>>> >> >>>> >> >>>>> That's one of the more serious problems we as a country have. Legal >> >>>> >> >>>>> skirmishes usually have zero productivity from a national perspective >> >>>> >> >>>>> but result in the fattest "payouts". It is the core problem why our >> >>>> >> >>>>> health care system is a mess. Of course, that is never brought up by >> >>>> >> >>>>> body politicus, for obvious reasons :-( >> >>>> >> >>>> >> >>>> >> >>>> You could say much the same thing about the army, but once the shooting >> >>>> >> >>>> starts, you're glad they're there. The case I'm working on today >> >>>> >> >>>> concerns an alleged misappropriation of trade secrets by a big >> >>>> >> >>>> semiconductor company. There's a lot of money at stake, so I'm pretty >> >>>> >> >>>> much in the noise. Designing stuff for start-ups is a bit different. >> >>>> >> >>>> >> >>>> >> >>>>> >> >>>> >> >>>>> >> >>>> >> >>>>>> <snip> >> >>>> >> >>>>>>>>> John Larkin has recently used these tiny flyback transformers. Nothing >> >>>> >> >>>>>>>>> wrong with hanging two in parallel on the primary and using the 2nd one >> >>>> >> >>>>>>>>> with the secondary flipped around, for the -45V. >> >>>> >> >>>>>>>>> >> >>>> >> >>>>>>>>> Do you need this isolated? Else you could consider just inverting and >> >>>> >> >>>>>>>>> boost. >> >>>> >> >>>>>>>>> >> >>>> >> >>>>>>>> >> >>>> >> >>>>>>>> Doesn't have to be isolated, but it does need to be quiet, hence the >> >>>> >> >>>>>>>> toroids. >> >>>> >> >>>>>>>> >> >>>> >> >>>>>>> >> >>>> >> >>>>>>> That usually rules out flybacks. They spew a lot of noise. Then I'd use >> >>>> >> >>>>>>> a half-bridge with CM control and series inductors on the output. >> >>>> >> >>>>>> >> >>>> >> >>>>>> Fortunately the half-bridge's worst-case condition is zero load, so it >> >>>> >> >>>>>> isn't too hard to control. ... >> >>>> >> >>>>> >> >>>> >> >>>>> >> >>>> >> >>>>> They work ok with zero load if you can tolerate the voltage increase. >> >>>> >> >>>>> That would be determined by the turns ratio. If it has to be 45.000V >> >>>> >> >>>>> that's a different story. Then you'll have to let it go into a skipping >> >>>> >> >>>>> mode. >> >>>> >> >>>>> >> >>>> >> >>>>> >> >>>> >> >>>>>> ... Of course the ungapped ferrite has a pretty >> >>>> >> >>>>>> frightening tempco of mu (it goes down by half when you hit it with cold >> >>>> >> >>>>>> spray), so some sort of current control is going to be required, for sure. >> >>>> >> >>>>>> >> >>>> >> >>>>> >> >>>> >> >>>>> Yes, needs current control but that's standard even in sub-Dollar chips. >> >>>> >> >>>> >> >>>> >> >>>> I may just make a boost with a two-winding toroid, and return the other >> >>>> >> >>>> end of the second winding to the raw -15V supply. (A lot of the Murata >> >>>> >> >>>> toroids are actually dual-winding, but they expect you to wire them in >> >>>> >> >>>> parallel to get the current handling capacity.) >> >>>> >> >>> >> >>> they generally spec them both for series and parallel ;) >> >> >> >> You'd think so, but no. The ones I'm using (Murata 32331C) aren't >> >> called out in the datasheet as anything except a single winding between >> >> pins 1 and 3, whereas in reality there's another independent one between >> >> pins 2 and 4 (the datasheet is at http://tinyurl.com/oyxguho ). >> >> >> >>> >> >>> how about a capacitive coupled boost? >> >>> >> >>> something like this: >> >>> http://obsoletetechnology.wordpress.com/projects/studio-electronics/dc-dc-bipolar-power-supply-for-effect-pedals/ >> >>> >> >>> -Lasse >> >>> >> >> >> >> It's a possibility, for sure. I normally don't think of capacitive >> >> boosters and hundreds of milliwatts at the same time, but it could work >> >> OK. It's slightly inconvenient due to having to run off +-15 to get the >> >> required output, but not awful. >> > > I wouldn't call a capacitive booster, it a normal boost just capacitive coupled > > you can get +/-45V just pick a controller that can handle 45V > > hacked together from the lt1071 test fixture: ><snipped circuit> Thanks, Lasse, that's an interesting approach. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 USA +1 845 480 2058 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●July 17, 20132013-07-17
Phil Hobbs wrote:> On 7/17/2013 1:51 PM, Lasse Langwadt Christensen wrote:[...]>> I wouldn't call a capacitive booster, it a normal boost just >> capacitive coupled >> >> you can get +/-45V just pick a controller that can handle 45V >> >> hacked together from the lt1071 test fixture: >> > <snipped circuit> > > Thanks, Lasse, that's an interesting approach. >But use a better chip that doesn't do subharmonic stuff and shield at least the inductor. -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●July 17, 20132013-07-17
On Thursday, 18 July 2013 01:32:53 UTC+10, George Herold wrote:> On Wednesday, July 17, 2013 10:14:40 AM UTC-4, Joerg wrote:=20 > > George Herold wrote: > > > On Tuesday, July 16, 2013 6:12:17 PM UTC-4, Phil Hobbs wrote:=20 > > >> On 7/16/2013 3:53 PM, Joerg wrote: > > >>> Phil Hobbs wrote: > > >=20 > > > <snip original question> > > >=20 > > >>>> Any words of wisdom?=20 > > >>> > > >>> ISDN transformers don't have much air gap, and you need air gap =20 > > >>> for a flyback. Plus ISDN is on the way out in many areas so if=20 > > >>> this has to remain in production until the cows come home I =20 > > >>> wouldn't.=20 > > >>=20 > > >> So I'm discovering. The actual amount of energy I can store in > > >> that toroid isn't very large, so to get any power out of it I have > > >> to run it pretty fast. With 2.2 mH of primary inductance, that=20 > > >> takes quite a bit of voltage, which makes the whole flyback thing ==20> > >> sort of moot. > > > > > > Sorry for the diverting question, but help me out here. (I find > > > magnet material a bit magical.) So I thought the energy in an > > > inductor was 1/2*L*i^2.=20 > > > =20 > > > But your and Joerg's comments seem to imply the energy is mostly in > > > the gap. =20 > >=20 > > Yes, it is. But the gap is just called air gap, usually it's some sort > > of filler material. High-end plastics, phenolic or FR4, and in very > > cheap "solutions" ... post-consumer cardboard.=20 > > =20 > > One of the issues with flybacks and gapped cores is that the gap doesn'=t=20> > know where it is supposed to end at its sides. It extends into the > > surroundings and that can result in egg in the face at the EMC lab.In RM and pot cores manufactured with a build-in air gap, only the central = face is relieved - the outside layer of ferrite is continuous, which does h= elp the shielding.> > > Now my very limited understanding of making a gap in an inductor was > > > that the gap sorta sets the inductance... the actual value isn't so ==20> > > dependent on the magnetic material. And doesn't the gap reduce the==20> > > inductance? > > =20 > > It does, unfortunately. As in "no free lunch" :-) > > =20 > > > I seem to be missing something fundamental. > >=20 > > Maybe something like this helps: > > =20 > > http://www.monolithicpower.com/DesignNoteDoc/AN017_r1.0.pdf=20 > > =20 > > http://www.ti.com/lit/ml/slup127/slup127.pdf >=20 > Wow, great! (lunch time reading material.) Thanks Joerg. =20 >=20 > I think I see my problem. Without the gap the B field in the material is=much higher (for a given current) and it's that much closer to saturation.= (Maybe a lot closer!) So I guess I can believe that for a gapped inductor= you can get more energy storage... you just have to run it at a higher cur= rent. (I'll have to try putting in some numbers.) =20>=20 > Say are there any good books about transformers/ inductors/ magnetic=20 > materials? >=20 > The subject seems to go from the trivial freshman physics transformer. T=o=20> the "full hair ball" real world situation, with nothing in between.There are books, and E.C. Snelling of Mullard, which got taken over by Phil= ips, wrote several of them. They were horrible - Snelling produced the most= confusing and misleading technical expositions that I ever came across. When I ran into the Siemens Magnetic Materials data book in the late 1970's= , it was a revelation - the application notes were clear, concise, well org= anised and informative. The late great Tony Williams shared my enthusiasm a= nd was known to forward several mega-bytes of .pdf files to interested part= ies. When Siemens became EPCOS, and the magnetic business was eventually sold of= f to TDK the situation got a bit confused, and I've lost touch with the rel= evant web-sites. If Winfield Hill ever does get around to releasing the third edition of "Th= e Art of Electronics" it may include a decent section on magnetics - I cert= ainly put in a personal plea for one a few years ago. At the time I laid a fair bit of emphasis on the transformer equation V1 =3D L1. dI1/dt + M. dI2/dt V2 =3D M. dI1/dt + L2. dI2/dt where M =3D k.(L1.L2)^0.5=20 and k is around 0.99 for a well-coupled transformer. L1 and L2 are the indu= ctances of the coupled windings and M is the mutual inductance of the two w= indings (in Henries). Snelling never seems to have used it, and it came as a revelation to me whe= n I found it in the Siemens application notes. For advanced stuff, look for the John Chan model of hysteritic inductors in= the LTSpice help files where they do include the reference "John Chan et l= a. in IEEE Transactions On Computer-Aided Design, Vol. 10. No. 4, April 199= 1". --=20 Bill Sloman, Sydney
Reply by ●July 17, 20132013-07-17
On 7/17/2013 5:46 PM, Joerg wrote:> Phil Hobbs wrote: >> On 7/17/2013 1:51 PM, Lasse Langwadt Christensen wrote: > > [...] > > >>> I wouldn't call a capacitive booster, it a normal boost just >>> capacitive coupled >>> >>> you can get +/-45V just pick a controller that can handle 45V >>> >>> hacked together from the lt1071 test fixture: >>> >> <snipped circuit> >> >> Thanks, Lasse, that's an interesting approach. >> > > But use a better chip that doesn't do subharmonic stuff and shield at > least the inductor. >Okay, thanks all--I think I've got it figured out. I'm already using a Simple Switcher buck to make -15 from +16-20, and I'll piggyback off the free AC and then use regulated cap multipliers to make a nice quiet +-40ish volts. Cartoon attached. Cheers Phil Hobbs Version 4 SHEET 1 880 900 WIRE -528 48 -656 48 WIRE -336 48 -528 48 WIRE -256 48 -336 48 WIRE -112 48 -160 48 WIRE -64 48 -112 48 WIRE 80 48 -64 48 WIRE 96 48 80 48 WIRE 256 48 240 48 WIRE 304 48 256 48 WIRE 464 48 368 48 WIRE 576 48 464 48 WIRE 592 48 576 48 WIRE 256 80 256 48 WIRE -656 96 -656 48 WIRE 464 112 464 48 WIRE 592 112 592 48 WIRE -336 128 -336 48 WIRE -240 128 -240 96 WIRE -64 144 -64 112 WIRE 256 144 -64 144 WIRE 80 192 80 48 WIRE 208 192 144 192 WIRE -240 208 -336 208 WIRE 208 224 208 192 WIRE 464 224 464 176 WIRE 592 224 592 192 WIRE -656 240 -656 176 WIRE 80 240 80 192 WIRE -64 272 -64 144 WIRE -64 336 -64 272 WIRE 0 336 -64 336 WIRE 80 336 80 320 WIRE 80 336 64 336 WIRE -64 352 -64 336 WIRE -64 352 -128 352 WIRE 208 352 208 304 WIRE 272 352 208 352 WIRE 288 352 272 352 WIRE 480 352 352 352 WIRE 592 352 480 352 WIRE 640 352 592 352 WIRE 80 368 80 336 WIRE -128 400 -128 352 WIRE -64 400 -64 352 WIRE 640 400 640 352 WIRE 272 416 272 352 WIRE 480 416 480 352 WIRE -128 512 -128 464 WIRE -64 512 -64 480 WIRE -64 512 -128 512 WIRE -64 528 -64 512 WIRE 480 528 480 480 WIRE 640 528 640 480 WIRE -528 560 -528 48 WIRE 272 560 272 480 WIRE 272 560 -528 560 FLAG 464 224 0 FLAG -656 240 0 FLAG 576 48 Out- FLAG 480 528 0 FLAG 592 352 Out+ FLAG 80 368 0 FLAG -64 528 0 FLAG -112 48 Switch FLAG -64 272 -15 FLAG 640 528 0 FLAG 592 224 0 SYMBOL ind2 64 224 R0 WINDOW 0 50 51 Left 2 WINDOW 3 60 86 Left 2 SYMATTR InstName L1 SYMATTR Value 150u SYMATTR Type ind SYMBOL cap 448 112 R0 SYMATTR InstName C1 SYMATTR Value 10u SYMBOL schottky 368 64 M270 WINDOW 0 32 32 VTop 2 WINDOW 3 -3 -7 VBottom 2 SYMATTR InstName D1 SYMATTR Value MBRS1100 SYMATTR Description Diode SYMATTR Type diode SYMBOL voltage -656 80 R0 SYMATTR InstName V1 SYMATTR Value 16 SYMBOL cap 464 416 R0 SYMATTR InstName C2 SYMATTR Value 10u SYMBOL schottky 288 368 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D2 SYMATTR Value MBRS1100 SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 256 480 M180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D3 SYMATTR Value MBRS1100 SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 240 80 R0 SYMATTR InstName D4 SYMATTR Value MBRS1100 SYMATTR Description Diode SYMATTR Type diode SYMBOL cap 240 32 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C5 SYMATTR Value 1u SYMBOL cap 144 176 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C6 SYMATTR Value 1u SYMBOL cap 0 320 M90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C4 SYMATTR Value 10u SYMBOL schottky -80 112 M180 WINDOW 0 47 33 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D5 SYMATTR Value MBRS1100 SYMATTR Description Diode SYMATTR Type diode SYMBOL res -80 384 R0 WINDOW 3 25 4 Left 2 SYMATTR InstName R2 SYMATTR Value 100 SYMBOL pmos -160 96 M270 SYMATTR InstName M1 SYMATTR Value Si9407AEY SYMBOL voltage -336 224 R180 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 WINDOW 3 -236 -15 Left 2 SYMATTR InstName V2 SYMATTR Value PULSE(0 -10 100n 10n 10n 2.75u 6.6u) SYMBOL res -256 112 R0 SYMATTR InstName R4 SYMATTR Value 100 SYMBOL schottky -144 400 R0 WINDOW 0 -58 28 Left 2 WINDOW 3 -104 94 Left 2 SYMATTR InstName D6 SYMATTR Value MBRS1100 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 624 384 R0 SYMATTR InstName R1 SYMATTR Value 2k SYMBOL res 576 96 R0 SYMATTR InstName R5 SYMATTR Value 4k SYMBOL res 80 64 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R3 SYMATTR Value 5 SYMBOL res 192 208 R0 SYMATTR InstName R6 SYMATTR Value 5 TEXT 360 624 Left 2 !.tran 12m -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 USA +1 845 480 2058 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●July 17, 20132013-07-17
On Wed, 17 Jul 2013 12:50:10 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Wed, 17 Jul 2013 10:51:08 -0700 (PDT), Lasse Langwadt Christensen ><langwadt@fonz.dk> wrote: > >>On Wednesday, July 17, 2013 6:36:32 PM UTC+2, Phil Hobbs wrote: >>> On 07/17/2013 12:16 PM, Lasse Langwadt Christensen wrote: >>> >>> > On Wednesday, July 17, 2013 5:18:25 PM UTC+2, Phil Hobbs wrote: >>> >>> >> On 07/17/2013 10:00 AM, Joerg wrote: >>> >>> >> >>> >>> >>> Phil Hobbs wrote: >>> >>> >> >>> >>> >>>> On 7/16/2013 8:54 PM, Joerg wrote: >>> >>> >> >>> >>> >>>>> Phil Hobbs wrote: >>> >>> >> >>> >>> >>>>>> On 7/16/2013 3:53 PM, Joerg wrote: >>> >>> >> >>> >>> >>>>>>> Phil Hobbs wrote: >>> >>> >> >>> >>> >>>>>>>> So, I'm goofing off playing with small switchers. (Well, not exactly >>> >>> >> >>> >>> >>>>>>>> goofing off, but there are somewhat more pressing tasks waiting....) >>> >>> >> >>> >>> >>>>>>>> >>> >>> >> >>> >>> >>>>>>>> As I said in George's thread, "Opamp w/ Vsupply > 36V", I built a >>> >>> >> >>> >>> >>>>>>>> small >>> >>> >> >>> >>> >>>>>>>> half-bridge supply with positive and negative voltage doublers. >>> >>> >> >>> >>> >>>>>>>> I'm not >>> >>> >> >>> >>> >>>>>>>> that keen on it, because (a) it uses a fair number of parts for >>> >>> >> >>> >>> >>>>>>>> what it >>> >>> >> >>> >>> >>>>>>>> does, and (b) it has a nasty instability. >>> >>> >> >>> >>> >>>>>>>> >>> >>> >> >>> >>> >>>>>>> >>> >>> >> >>> >>> >>>>>>> (a) ... yes. (b) ... why? What happens? Changing to another >>> >>> >> >>> >>> >>>>>>> architecture >>> >>> >> >>> >>> >>>>>>> while using the same kind of loop usually doesn't do much to improve >>> >>> >> >>> >>> >>>>>>> stability. >>> >>> >> >>> >>> >>>>>>> >>> >>> >> >>> >>> >>>>>>> >>> >>> >> >>> >>> >>>>>>>> With a capacitively-coupled half bridge, if you let the transformer >>> >>> >> >>> >>> >>>>>>>> saturate, it instantly discharges the coupling cap, which about >>> >>> >> >>> >>> >>>>>>>> doubles >>> >>> >> >>> >>> >>>>>>>> the volt-seconds on the next half-cycle and guarantee that it will >>> >>> >> >>> >>> >>>>>>>> keep >>> >>> >> >>> >>> >>>>>>>> saturating until the FETs cook themselves. >>> >>> >> >>> >>> >>>>>>>> >>> >>> >> >>> >>> >>>>>>> >>> >>> >> >>> >>> >>>>>>> Not sure what you mean here, but usually current mode control is the >>> >>> >> >>> >>> >>>>>>> way >>> >>> >> >>> >>> >>>>>>> to avoid asymmetrical runaway. >>> >>> >> >>> >>> >>>>>> >>> >>> >> >>> >>> >>>>>> The IRS2153D puts a square wave out of a half-bridge--no feedback, no >>> >>> >> >>> >>> >>>>>> current limit, nada. If you put that into a transformer via a cap, all >>> >>> >> >>> >>> >>>>>> is well until you saturate the transformer. >>> >>> >> >>> >>> >>>>>> >>> >>> >> >>> >>> >>>>> >>> >>> >> >>> >>> >>>>> Ok, the IRS2153D is just a glorified gate driver with an oscillator in >>> >>> >> >>> >>> >>>>> there. I'd use a real switcher controller chip, some are in the same >>> >>> >> >>> >>> >>>>> price category. >>> >>> >> >>> >>> >>>>> >>> >>> >> >>> >>> >>>>> >>> >>> >> >>> >>> >>>>>> Say that happens on the positive half-cycle. >>> >>> >> >>> >>> >>>>>> At that moment, the voltage on the cap rapidly goes from V_DD/2 to V_DD. >>> >>> >> >>> >>> >>>>>> At the next edge, the voltage across the transformer is suddenly not >>> >>> >> >>> >>> >>>>>> V_DD/2 as expected, but V_DD. The transformer saturates in half the >>> >>> >> >>> >>> >>>>>> time it took previously, and the voltage on the cap goes from V_DD to 0. >>> >>> >> >>> >>> >>>>>> Then the cycle repeats. It's really obvious on a scope when this >>> >>> >> >>> >>> >>>>>> happens, and it's far from pretty. >>> >>> >> >>> >>> >>>>>> >>> >>> >> >>> >>> >>>>> >>> >>> >> >>> >>> >>>>> Did you use a really big cap? I've never had that happen. Usually >>> >>> >> >>> >>> >>>>> ferrite saturates softly enough to just "nudge" the cap. >>> >>> >> >>> >>> >>>> >>> >>> >> >>> >>> >>>> 1 uF. I can probably post a scope photo tomorrow, if I have time--a >>> >>> >> >>> >>> >>>> bunch of lawyering has just descended on my head. (Not that I mind very >>> >>> >> >>> >>> >>>> much--expert witness work uses a different part of my brain and >>> >>> >> >>> >>> >>>> generally pays somewhat better than design work.) >>> >>> >> >>> >>> >>>> >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>> That's one of the more serious problems we as a country have. Legal >>> >>> >> >>> >>> >>> skirmishes usually have zero productivity from a national perspective >>> >>> >> >>> >>> >>> but result in the fattest "payouts". It is the core problem why our >>> >>> >> >>> >>> >>> health care system is a mess. Of course, that is never brought up by >>> >>> >> >>> >>> >>> body politicus, for obvious reasons :-( >>> >>> >> >>> >>> >> >>> >>> >> >>> >>> >> You could say much the same thing about the army, but once the shooting >>> >>> >> >>> >>> >> starts, you're glad they're there. The case I'm working on today >>> >>> >> >>> >>> >> concerns an alleged misappropriation of trade secrets by a big >>> >>> >> >>> >>> >> semiconductor company. There's a lot of money at stake, so I'm pretty >>> >>> >> >>> >>> >> much in the noise. Designing stuff for start-ups is a bit different. >>> >>> >> >>> >>> >> >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>>> <snip> >>> >>> >> >>> >>> >>>>>>> John Larkin has recently used these tiny flyback transformers. Nothing >>> >>> >> >>> >>> >>>>>>> wrong with hanging two in parallel on the primary and using the 2nd one >>> >>> >> >>> >>> >>>>>>> with the secondary flipped around, for the -45V. >>> >>> >> >>> >>> >>>>>>> >>> >>> >> >>> >>> >>>>>>> Do you need this isolated? Else you could consider just inverting and >>> >>> >> >>> >>> >>>>>>> boost. >>> >>> >> >>> >>> >>>>>>> >>> >>> >> >>> >>> >>>>>> >>> >>> >> >>> >>> >>>>>> Doesn't have to be isolated, but it does need to be quiet, hence the >>> >>> >> >>> >>> >>>>>> toroids. >>> >>> >> >>> >>> >>>>>> >>> >>> >> >>> >>> >>>>> >>> >>> >> >>> >>> >>>>> That usually rules out flybacks. They spew a lot of noise. Then I'd use >>> >>> >> >>> >>> >>>>> a half-bridge with CM control and series inductors on the output. >>> >>> >> >>> >>> >>>> >>> >>> >> >>> >>> >>>> Fortunately the half-bridge's worst-case condition is zero load, so it >>> >>> >> >>> >>> >>>> isn't too hard to control. ... >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>> They work ok with zero load if you can tolerate the voltage increase. >>> >>> >> >>> >>> >>> That would be determined by the turns ratio. If it has to be 45.000V >>> >>> >> >>> >>> >>> that's a different story. Then you'll have to let it go into a skipping >>> >>> >> >>> >>> >>> mode. >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>>> ... Of course the ungapped ferrite has a pretty >>> >>> >> >>> >>> >>>> frightening tempco of mu (it goes down by half when you hit it with cold >>> >>> >> >>> >>> >>>> spray), so some sort of current control is going to be required, for sure. >>> >>> >> >>> >>> >>>> >>> >>> >> >>> >>> >>> >>> >>> >> >>> >>> >>> Yes, needs current control but that's standard even in sub-Dollar chips. >>> >>> >> >>> >>> >> >>> >>> >> >>> >>> >> I may just make a boost with a two-winding toroid, and return the other >>> >>> >> >>> >>> >> end of the second winding to the raw -15V supply. (A lot of the Murata >>> >>> >> >>> >>> >> toroids are actually dual-winding, but they expect you to wire them in >>> >>> >> >>> >>> >> parallel to get the current handling capacity.) >>> >>> >> >>> >>> > >>> >>> > they generally spec them both for series and parallel ;) >>> >>> >>> >>> You'd think so, but no. The ones I'm using (Murata 32331C) aren't >>> >>> called out in the datasheet as anything except a single winding between >>> >>> pins 1 and 3, whereas in reality there's another independent one between >>> >>> pins 2 and 4 (the datasheet is at http://tinyurl.com/oyxguho ). >>> >>> >>> >>> > >>> >>> > how about a capacitive coupled boost? >>> >>> > >>> >>> > something like this: >>> >>> > http://obsoletetechnology.wordpress.com/projects/studio-electronics/dc-dc-bipolar-power-supply-for-effect-pedals/ >>> >>> > >>> >>> > -Lasse >>> >>> > >>> >>> >>> >>> It's a possibility, for sure. I normally don't think of capacitive >>> >>> boosters and hundreds of milliwatts at the same time, but it could work >>> >>> OK. It's slightly inconvenient due to having to run off +-15 to get the >>> >>> required output, but not awful. >>> >> >>I wouldn't call a capacitive booster, it a normal boost just capacitive coupled >> >>you can get +/-45V just pick a controller that can handle 45V >> >>hacked together from the lt1071 test fixture: >> >>Version 4 >>SHEET 1 2808 1492 >>WIRE 1600 880 1488 880 >>WIRE 1824 880 1600 880 >>WIRE 1872 880 1824 880 >>WIRE 1984 880 1952 880 >>WIRE 2144 880 1984 880 >>WIRE 2160 880 2144 880 >>WIRE 2272 880 2224 880 >>WIRE 2320 880 2272 880 >>WIRE 2416 880 2384 880 >>WIRE 2528 880 2416 880 >>WIRE 2640 880 2528 880 >>WIRE 1488 896 1488 880 >>WIRE 2528 896 2528 880 >>WIRE 2640 896 2640 880 >>WIRE 1600 912 1600 880 >>WIRE 1824 944 1824 880 >>WIRE 2416 960 2416 880 >>WIRE 2272 976 2272 944 >>WIRE 2528 992 2528 960 >>WIRE 2640 992 2640 976 >>WIRE 1488 1008 1488 976 >>WIRE 1600 1008 1600 976 >>WIRE 1984 1024 1984 880 >>WIRE 1984 1024 1952 1024 >>WIRE 2416 1088 2416 1040 >>WIRE 2416 1088 1952 1088 >>WIRE 2416 1104 2416 1088 >>WIRE 1968 1152 1952 1152 >>WIRE 2064 1152 2048 1152 >>WIRE 2064 1168 2064 1152 >>WIRE 2416 1200 2416 1184 >>WIRE 1824 1248 1824 1232 >>WIRE 2064 1248 2064 1232 >>WIRE 2144 1408 2144 880 >>WIRE 2304 1408 2208 1408 >>WIRE 2368 1408 2304 1408 >>WIRE 2544 1408 2432 1408 >>WIRE 2656 1408 2544 1408 >>FLAG 2640 880 OUT >>FLAG 2416 1200 0 >>FLAG 2528 992 0 >>FLAG 2640 992 0 >>FLAG 2064 1248 0 >>FLAG 1824 1248 0 >>FLAG 1600 1008 0 >>FLAG 1488 1008 0 >>FLAG 1488 880 IN >>FLAG 2272 976 0 >>FLAG 2304 1344 0 >>FLAG 2656 1328 0 >>FLAG 2544 1344 0 >>SYMBOL ind 1856 896 R270 >>WINDOW 0 32 56 VTop 2 >>WINDOW 3 5 56 VBottom 2 >>SYMATTR InstName L1 >>SYMATTR Value 150� >>SYMATTR SpiceLine Rser=0.02 Rpar=5000 >>SYMBOL schottky 2320 896 R270 >>WINDOW 0 32 32 VTop 2 >>WINDOW 3 0 32 VBottom 2 >>SYMATTR InstName D1 >>SYMATTR Value MBRS360 >>SYMBOL RES 2400 944 R0 >>SYMATTR InstName R1 >>SYMATTR Value 44K >>SYMBOL RES 2400 1088 R0 >>SYMATTR InstName R2 >>SYMATTR Value 1.24K >>SYMBOL RES 1952 1168 R270 >>WINDOW 0 32 56 VTop 2 >>WINDOW 3 0 56 VBottom 2 >>SYMATTR InstName R3 >>SYMATTR Value 1K >>SYMBOL polcap 2512 896 R0 >>SYMATTR InstName C1 >>SYMATTR Value 100� >>SYMATTR SpiceLine Rser=15m >>SYMBOL CAP 2048 1168 R0 >>SYMATTR InstName C2 >>SYMATTR Value 1� >>SYMBOL VOLTAGE 1488 880 R0 >>WINDOW 123 0 0 Left 2 >>SYMATTR InstName V1 >>SYMATTR Value 19 >>SYMATTR SpiceLine Rser=0.1 >>SYMBOL polcap 1584 912 R0 >>SYMATTR InstName C3 >>SYMATTR Value 100� >>SYMBOL PowerProducts\\LT1071HV 1824 1088 R0 >>SYMATTR InstName U1 >>SYMBOL res 2624 880 R0 >>SYMATTR InstName Rload >>SYMATTR Value 2000 >>SYMBOL schottky 2288 944 R180 >>WINDOW 0 24 64 Left 2 >>WINDOW 3 -27 0 Left 2 >>SYMATTR InstName D2 >>SYMATTR Value MBRS360 >>SYMBOL cap 2224 864 R90 >>WINDOW 0 0 32 VBottom 2 >>WINDOW 3 32 32 VTop 2 >>SYMATTR InstName C4 >>SYMATTR Value 1� >>SYMATTR SpiceLine V=50 Irms=0 Rser=0.008 Lser=0 mfg="TDK" pn="C3225X7RlHlO5M" type="X7R" >>SYMBOL schottky 2432 1392 R90 >>WINDOW 0 0 32 VBottom 2 >>WINDOW 3 32 32 VTop 2 >>SYMATTR InstName D3 >>SYMATTR Value MBRS360 >>SYMBOL schottky 2320 1408 R180 >>WINDOW 0 24 64 Left 2 >>WINDOW 3 24 0 Left 2 >>SYMATTR InstName D4 >>SYMATTR Value MBRS360 >>SYMBOL polcap 2528 1344 R0 >>SYMATTR InstName C6 >>SYMATTR Value 100� >>SYMATTR SpiceLine Rser=15m >>SYMBOL res 2640 1312 R0 >>SYMATTR InstName Rload1 >>SYMATTR Value 2000 >>SYMBOL cap 2208 1392 R90 >>WINDOW 0 0 32 VBottom 2 >>WINDOW 3 32 32 VTop 2 >>SYMATTR InstName C5 >>SYMATTR Value 1� >>SYMATTR SpiceLine V=50 Irms=0 Rser=0.008 Lser=0 mfg="TDK" pn="C3225X7RlHlO5M" type="X7R" >>TEXT 1424 1136 Left 2 !.tran 200m startup >> >> >> >>-Lasse > >Cute! That would nicely fit Larkin's needs... with no significant >surge. Somewhat similar to my self-charging CD ignition from the late >'60's at Philco-Ford and in the early '70's at Dickson electronics... > > http://www.analog-innovations.com/SED/CD-Ignition-Basic.pdf > > ...Jim ThompsonOn further examination it has 100A peaks. Can the LT1071HV handle that? ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
