bill.sloman@ieee.org wrote:> On Friday, August 5, 2016 at 1:07:26 PM UTC+10, Winfield Hill wrote: >> I've created all kinds of HV circuits in the last >> 5 years,** and each one needs an external HV supply. >> So I really need some simple HV-supply circuits to >> plop onto these PCB's to make them self-sufficient. >> >> Today's circuit is a basic flyback, to convert a >> 12V,1A wallwort source to 500V max, at 5-10W load. >> >> I used a UC3843B running at 100kHz driving a MOSFET >> switching a 47uH inductor (dI = dt V/L = 2A in 8us). >> This can provide up to 100uJ each cycle, to charge >> a say 2000uF storage cap to 400V in 16 seconds. >> >> I settled on an ES1J fast-recovery output diode >> (after rejecting an MRA4007), After rejecting >> an STP7NB60 as too lossy, I experimented and >> picked an Infineon IPP65R225C7 superjunction >> MOSFET: Rds(on) = 0.2 ohms (0.5 ohms max at Tj >> = 150C), and Coss = 14pF at 400V (20pF at 100V). >> Nice. >> >> But the flyback inductor was an issue. See photo >> https://www.dropbox.com/s/cwo10wm5upehvrw/PWR-741_flyback_350V-inductors_small.jpg?dl=0 >> >> I started with an older 1A part from the drawer: >> a Mouser 47uH, 0.1 ohms, rated 1.3A, see photo, >> lower right. With this part my circuit had 2.2W >> of wasted power at 5W out. Heating was bad, the >> inductor melted a soldered lead and disconnected >> itself from the circit! Whew, ugly! I needed a >> beefier part. Enter a Coilcraft PCV-0-473-05L, >> photo lower left. Those fat wires, this had to >> be the answer. Rated 0.035 ohms and 6A. But it >> increased my wasted power to 3.7W, double ouch! >> >> Giving up on my commercial inventory, I made >> an inductor using an RM8 bobbin and core. >> (See photo, upper part, mounted on the PCB.) >> >> I selected a large gap core, A_L = 100nH/t^2. >> N = sqrt(L / A_L) = 22 turns. With #20 wire, >> Rdc=0.036 ohms. I measured Q=39 at 100kHz, >> esr = 2pi f L/Q = 0.75 ohms. Q=80 at 1MHz. >> Looking pretty good, ignoring coreloss at >> full power (the ckt uses 40mW at no load). >> >> Yeah! With the RM8 inductor, total losses >> dropped to 1.1 watts. Note, the MOSFET, >> sense resistor, diode and capacitor share >> in the loss generation, so I don't know >> the inductor loss. Everything runs cool, >> which wasn't the case at the beginning. >> >> ** more on that later ... > > Why futz around with flyback supplies when you can use a Baxandall Class-D oscillator? > > Peter Baxandall invented it to deal with the problem of getting a kV or so for photomultiplier supplies, and Jim Williams used it to generate even higher voltages for the cold cathode back-lights that used to be popular in lap-top computers. > > http://sophia-elektronica.com/Baxandall_parallel-resonant_Class-D_oscillator1.htm* 404 - File or directory not found. The resource you are looking for might have been removed, had its name changed, or is temporarily unavailable.> > http://sophia-elektronica.com/0344_001_Baxandal.pdf > > It's two pot cores - transformer and inductor - rather than just one, but it's a lot tidier, and you should be able to get away with smaller pot cores. >
inductor for HV flyback supply
Started by ●August 5, 2016
Reply by ●August 7, 20162016-08-07
Reply by ●August 7, 20162016-08-07
Winfield Hill wrote:> bill.sloman@ieee.org wrote... >> >> On Friday, August 5, 2016 at 1:07:26 PM UTC+10, Winfield Hill wrote: >>> I've created all kinds of HV circuits in the last >>> 5 years,** and each one needs an external HV supply. >>> So I really need some simple HV-supply circuits to >>> plop onto these PCB's to make them self-sufficient. >>> >>> Today's circuit is a basic flyback, to convert a >>> 12V,1A wallwort source to 500V max, at 5-10W load. >>> >>> I used a UC3843B running at 100kHz ... > > https://www.dropbox.com/s/cwo10wm5upehvrw/PWR_s.jpg* Almost blank page is not exactly conducive to learning...> >> Why futz around with flyback supplies when you can >> use a Baxandall Class-D oscillator? >> >> Peter Baxandall invented it to deal with the problem >> of getting a kV or so for photomultiplier supplies, >> and Jim Williams used it to generate even higher >> voltages for the cold cathode back-lights that used >> to be popular in lap-top computers. >> >> http://sophia-elektronica.com/Baxandall_parallel-resonant_Class-D_oscillator1.htm >> >> http://sophia-elektronica.com/0344_001_Baxandal.pdf >> >> It's two pot cores - transformer and inductor - >> rather than just one, but it's a lot tidier, you >> should be able to get away with smaller pot cores. > > Thanks for the suggestion Bill, I know you love > that circuit, and resonance is good. Indeed for > higher power and voltages it'd be the right idea. > > But the uc3843 and other parts are small, SO-8, > etc., mounted on the underside of the PCB, and > in the beginning I had hoped to use a single > simple commercial off-the-shelf inductor, and > avoid any custom magnetics. May still do so. > > Anyway, even with having to wind 22 turns on an > RM8, the result is still simple, small and cheap. > > BTW, some of your web article links are broken. > > >
Reply by ●August 7, 20162016-08-07
On Sunday, August 7, 2016 at 8:47:08 PM UTC+10, Robert Baer wrote:> bill.sloman@ieee.org wrote: > > On Friday, August 5, 2016 at 1:07:26 PM UTC+10, Winfield Hill wrote: > >> I've created all kinds of HV circuits in the last > >> 5 years,** and each one needs an external HV supply. > >> So I really need some simple HV-supply circuits to > >> plop onto these PCB's to make them self-sufficient. > >> > >> Today's circuit is a basic flyback, to convert a > >> 12V,1A wallwort source to 500V max, at 5-10W load. > >> > >> I used a UC3843B running at 100kHz driving a MOSFET > >> switching a 47uH inductor (dI = dt V/L = 2A in 8us). > >> This can provide up to 100uJ each cycle, to charge > >> a say 2000uF storage cap to 400V in 16 seconds. > >> > >> I settled on an ES1J fast-recovery output diode > >> (after rejecting an MRA4007), After rejecting > >> an STP7NB60 as too lossy, I experimented and > >> picked an Infineon IPP65R225C7 superjunction > >> MOSFET: Rds(on) = 0.2 ohms (0.5 ohms max at Tj > >> = 150C), and Coss = 14pF at 400V (20pF at 100V). > >> Nice. > >> > >> But the flyback inductor was an issue. See photo > >> https://www.dropbox.com/s/cwo10wm5upehvrw/PWR-741_flyback_350V-inductors_small.jpg?dl=0 > >> > >> I started with an older 1A part from the drawer: > >> a Mouser 47uH, 0.1 ohms, rated 1.3A, see photo, > >> lower right. With this part my circuit had 2.2W > >> of wasted power at 5W out. Heating was bad, the > >> inductor melted a soldered lead and disconnected > >> itself from the circit! Whew, ugly! I needed a > >> beefier part. Enter a Coilcraft PCV-0-473-05L, > >> photo lower left. Those fat wires, this had to > >> be the answer. Rated 0.035 ohms and 6A. But it > >> increased my wasted power to 3.7W, double ouch! > >> > >> Giving up on my commercial inventory, I made > >> an inductor using an RM8 bobbin and core. > >> (See photo, upper part, mounted on the PCB.) > >> > >> I selected a large gap core, A_L = 100nH/t^2. > >> N = sqrt(L / A_L) = 22 turns. With #20 wire, > >> Rdc=0.036 ohms. I measured Q=39 at 100kHz, > >> esr = 2pi f L/Q = 0.75 ohms. Q=80 at 1MHz. > >> Looking pretty good, ignoring coreloss at > >> full power (the ckt uses 40mW at no load). > >> > >> Yeah! With the RM8 inductor, total losses > >> dropped to 1.1 watts. Note, the MOSFET, > >> sense resistor, diode and capacitor share > >> in the loss generation, so I don't know > >> the inductor loss. Everything runs cool, > >> which wasn't the case at the beginning. > >> > >> ** more on that later ... > > > > Why futz around with flyback supplies when you can use a Baxandall Class-D oscillator? > > > > Peter Baxandall invented it to deal with the problem of getting a kV or so for photomultiplier supplies, and Jim Williams used it to generate even higher voltages for the cold cathode back-lights that used to be popular in lap-top computers. > > > > http://sophia-elektronica.com/Baxandall_parallel-resonant_Class-D_oscillator1.htm > * 404 - File or directory not found. > The resource you are looking for might have been removed, had its name > changed, or is temporarily unavailable.Sure. They linked back to my old Dutch web-site that no longer exists. I think I've fixed the duff links, but until my Australian IP up-loads the corrected files, probably in the next few hours, I won't know. -- Bill Sloman, Sydney
Reply by ●August 7, 20162016-08-07
On Sunday, 7 August 2016 04:39:41 UTC+2, bill....@ieee.org wrote:> On Saturday, August 6, 2016 at 2:24:37 AM UTC+10, John Larkin wrote: > > On 5 Aug 2016 05:53:42 -0700, Winfield Hill <hill@rowland.harvard.edu> > > wrote: > > > > >bill.sloman@ieee.org wrote... > > >> > > >> Too many people make a habit of avoiding custom magnetics. > > <snip> > > > I hate custom magnetics. Expensive, boring hassle. The technical > > challenge of designing transformers is to NOT design transformers. > > Sadly, the habit of not designing transformers leaves you stuck with messy, expensive, sub-optimal solutions. > > The design process is complicated, with lots of choices, but no more boring than > any other design process. I suspect that what you are saying is that you've never bothered to get your head around all the issues involved, and find yourself embarrassed when you have to discuss a transformer design in front of your subordinates. > > There are lots of variables in a transformer design - starting with core size and core material, gapped or ungapped, and proceeding through turns ratio and wire size, and choosing between plain wire and Litz, and on to winding configuration - bifilar or separate coils - plain windings or winding in banks (for lower parallel capacitance). > > This means that buying an off-the-transformer is unlikely to give you anything all that close to optimal. The process of getting small runs of custom transformers made by sub-contractors isn't all that demanding - no worse than printed circuit boards. It's nice if you can avoid it, but little more sensible than it would be to insist of building everything on off-the-shelf printed circuit boards. >True, you cannot beat the performance of a custom design. But, for a given converter, you may be able to get so close performance wise to the custom design using an COTS part, which will be a lot easier and may be cheaper For low volume, the hassle and NRE cost of getting a custom part UL approved part, often results in the selection of the COTS part Cheers Klaus
Reply by ●August 7, 20162016-08-07
On Sun, 7 Aug 2016 09:08:31 -0700 (PDT), klaus.kragelund@gmail.com wrote:>On Sunday, 7 August 2016 04:39:41 UTC+2, bill....@ieee.org wrote: >> On Saturday, August 6, 2016 at 2:24:37 AM UTC+10, John Larkin wrote: >> > On 5 Aug 2016 05:53:42 -0700, Winfield Hill <hill@rowland.harvard.edu> >> > wrote: >> > >> > >bill.sloman@ieee.org wrote... >> > >> >> > >> Too many people make a habit of avoiding custom magnetics. >> >> <snip> >> >> > I hate custom magnetics. Expensive, boring hassle. The technical >> > challenge of designing transformers is to NOT design transformers. >> >> Sadly, the habit of not designing transformers leaves you stuck with messy, expensive, sub-optimal solutions. >> >> The design process is complicated, with lots of choices, but no more boring than >> any other design process. I suspect that what you are saying is that you've never bothered to get your head around all the issues involved, and find yourself embarrassed when you have to discuss a transformer design in front of your subordinates. >> >> There are lots of variables in a transformer design - starting with core size and core material, gapped or ungapped, and proceeding through turns ratio and wire size, and choosing between plain wire and Litz, and on to winding configuration - bifilar or separate coils - plain windings or winding in banks (for lower parallel capacitance). >> >> This means that buying an off-the-transformer is unlikely to give you anything all that close to optimal. The process of getting small runs of custom transformers made by sub-contractors isn't all that demanding - no worse than printed circuit boards. It's nice if you can avoid it, but little more sensible than it would be to insist of building everything on off-the-shelf printed circuit boards. >> > >True, you cannot beat the performance of a custom design.Usually, you can. You can generally get a product finished with standard parts for a fraction of the cost, in a fraction of the time. Needing custom magnetics may be a character defect, a lack of imagination. Or an irrational desire to design magnetics. If you plan to build 30,000 power supplies, custom magnetics may make sense. If you are designing a complex instrument and need some transformers or inductors, try Coilcraft first.> >But, for a given converter, you may be able to get so close performance wise to the custom design using an COTS part, which will be a lot easier and may be cheaper > >For low volume, the hassle and NRE cost of getting a custom part UL approved part, often results in the selection of the COTS part > >Cheers > >KlausSloman loves custom magnetics, which explains why he has been working on his beloved oscillator for over a decade, and it still doesn't oscillate. Tne reason I dislike custom magnetics is because I've done so many custom magnetic designs, probably 20x more than he has. The best inductor is cheap, multi-sourced, surface mount. This one doesn't qualify: https://dl.dropboxusercontent.com/u/53724080/PP5.JPG -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●August 7, 20162016-08-07
On 08/07/2016 12:32 PM, John Larkin wrote:> On Sun, 7 Aug 2016 09:08:31 -0700 (PDT), klaus.kragelund@gmail.com > wrote: > >> On Sunday, 7 August 2016 04:39:41 UTC+2, bill....@ieee.org wrote: >>> On Saturday, August 6, 2016 at 2:24:37 AM UTC+10, John Larkin wrote: >>>> On 5 Aug 2016 05:53:42 -0700, Winfield Hill <hill@rowland.harvard.edu> >>>> wrote: >>>> >>>>> bill.sloman@ieee.org wrote... >>>>>> >>>>>> Too many people make a habit of avoiding custom magnetics. >>> >>> <snip> >>> >>>> I hate custom magnetics. Expensive, boring hassle. The technical >>>> challenge of designing transformers is to NOT design transformers. >>> >>> Sadly, the habit of not designing transformers leaves you stuck with messy, expensive, sub-optimal solutions. >>> >>> The design process is complicated, with lots of choices, but no more boring than >>> any other design process. I suspect that what you are saying is that you've never bothered to get your head around all the issues involved, and find yourself embarrassed when you have to discuss a transformer design in front of your subordinates. >>> >>> There are lots of variables in a transformer design - starting with core size and core material, gapped or ungapped, and proceeding through turns ratio and wire size, and choosing between plain wire and Litz, and on to winding configuration - bifilar or separate coils - plain windings or winding in banks (for lower parallel capacitance). >>> >>> This means that buying an off-the-transformer is unlikely to give you anything all that close to optimal. The process of getting small runs of custom transformers made by sub-contractors isn't all that demanding - no worse than printed circuit boards. It's nice if you can avoid it, but little more sensible than it would be to insist of building everything on off-the-shelf printed circuit boards. >>> >> >> True, you cannot beat the performance of a custom design. > > Usually, you can. You can generally get a product finished with > standard parts for a fraction of the cost, in a fraction of the time. > Needing custom magnetics may be a character defect, a lack of > imagination. Or an irrational desire to design magnetics. > > If you plan to build 30,000 power supplies, custom magnetics may make > sense. If you are designing a complex instrument and need some > transformers or inductors, try Coilcraft first. > > >> >> But, for a given converter, you may be able to get so close performance wise to the custom design using an COTS part, which will be a lot easier and may be cheaper >> >> For low volume, the hassle and NRE cost of getting a custom part UL approved part, often results in the selection of the COTS part >> >> Cheers >> >> Klaus > > Sloman loves custom magnetics, which explains why he has been working > on his beloved oscillator for over a decade, and it still doesn't > oscillate. > > Tne reason I dislike custom magnetics is because I've done so many > custom magnetic designs, probably 20x more than he has. The best > inductor is cheap, multi-sourced, surface mount. > > This one doesn't qualify: > > https://dl.dropboxusercontent.com/u/53724080/PP5.JPG >Wow, Cthulhu the transformer. Now, too late, you know what strange and forbidden rituals those web monkeys were up to in the back of your shop. ;) 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 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●August 7, 20162016-08-07
On 07/08/2016 17:32, John Larkin wrote:> This one doesn't qualify: > > https://dl.dropboxusercontent.com/u/53724080/PP5.JPG > > >That looks complicated. I'd worry that it gains consciousness and runs away.
Reply by ●August 7, 20162016-08-07
On Sun, 07 Aug 2016 18:19:00 +0100, JM <dontreplytothis173@gmail.com> wrote:>On 07/08/2016 17:32, John Larkin wrote: >> This one doesn't qualify: >> >> https://dl.dropboxusercontent.com/u/53724080/PP5.JPG >> >> >> > >That looks complicated. > >I'd worry that it gains consciousness and runs away.Looks like a giant steel and copper octopus that lurks under your bed. I do like the colorful trimmed wire bits, great to have around the house. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●August 7, 20162016-08-07
On Sun, 7 Aug 2016 12:43:50 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 08/07/2016 12:32 PM, John Larkin wrote: >> On Sun, 7 Aug 2016 09:08:31 -0700 (PDT), klaus.kragelund@gmail.com >> wrote: >> >>> On Sunday, 7 August 2016 04:39:41 UTC+2, bill....@ieee.org wrote: >>>> On Saturday, August 6, 2016 at 2:24:37 AM UTC+10, John Larkin wrote: >>>>> On 5 Aug 2016 05:53:42 -0700, Winfield Hill <hill@rowland.harvard.edu> >>>>> wrote: >>>>> >>>>>> bill.sloman@ieee.org wrote... >>>>>>> >>>>>>> Too many people make a habit of avoiding custom magnetics. >>>> >>>> <snip> >>>> >>>>> I hate custom magnetics. Expensive, boring hassle. The technical >>>>> challenge of designing transformers is to NOT design transformers. >>>> >>>> Sadly, the habit of not designing transformers leaves you stuck with messy, expensive, sub-optimal solutions. >>>> >>>> The design process is complicated, with lots of choices, but no more boring than >>>> any other design process. I suspect that what you are saying is that you've never bothered to get your head around all the issues involved, and find yourself embarrassed when you have to discuss a transformer design in front of your subordinates. >>>> >>>> There are lots of variables in a transformer design - starting with core size and core material, gapped or ungapped, and proceeding through turns ratio and wire size, and choosing between plain wire and Litz, and on to winding configuration - bifilar or separate coils - plain windings or winding in banks (for lower parallel capacitance). >>>> >>>> This means that buying an off-the-transformer is unlikely to give you anything all that close to optimal. The process of getting small runs of custom transformers made by sub-contractors isn't all that demanding - no worse than printed circuit boards. It's nice if you can avoid it, but little more sensible than it would be to insist of building everything on off-the-shelf printed circuit boards. >>>> >>> >>> True, you cannot beat the performance of a custom design. >> >> Usually, you can. You can generally get a product finished with >> standard parts for a fraction of the cost, in a fraction of the time. >> Needing custom magnetics may be a character defect, a lack of >> imagination. Or an irrational desire to design magnetics. >> >> If you plan to build 30,000 power supplies, custom magnetics may make >> sense. If you are designing a complex instrument and need some >> transformers or inductors, try Coilcraft first. >> >> >>> >>> But, for a given converter, you may be able to get so close performance wise to the custom design using an COTS part, which will be a lot easier and may be cheaper >>> >>> For low volume, the hassle and NRE cost of getting a custom part UL approved part, often results in the selection of the COTS part >>> >>> Cheers >>> >>> Klaus >> >> Sloman loves custom magnetics, which explains why he has been working >> on his beloved oscillator for over a decade, and it still doesn't >> oscillate. >> >> Tne reason I dislike custom magnetics is because I've done so many >> custom magnetic designs, probably 20x more than he has. The best >> inductor is cheap, multi-sourced, surface mount. >> >> This one doesn't qualify: >> >> https://dl.dropboxusercontent.com/u/53724080/PP5.JPG >> > >Wow, Cthulhu the transformer.Yes! http://img01.deviantart.net/5fe3/i/2016/014/e/0/cthulhu_and_the_ninth_wave_by_fantasio-d9nw88r.jpg Now, too late, you know what strange and>forbidden rituals those web monkeys were up to in the back of your shop. ;) > >Cheers > >Phil HobbsThey finally gave up on the yet-another-social-thing-web-app, returned the remaining money to the investors, and got jobs. M is now the engineering manager of a cubesat company a few blocks away (there are two cubesat companies a few blocks away!), trying to inflict some order on them. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●August 7, 20162016-08-07
On Monday, August 8, 2016 at 2:32:46 AM UTC+10, John Larkin wrote:> On Sun, 7 Aug 2016 09:08:31 -0700 (PDT), klaus.kragelund@gmail.com > wrote: > > >On Sunday, 7 August 2016 04:39:41 UTC+2, bill....@ieee.org wrote: > >> On Saturday, August 6, 2016 at 2:24:37 AM UTC+10, John Larkin wrote: > >> > On 5 Aug 2016 05:53:42 -0700, Winfield Hill <hill@rowland.harvard.edu> > >> > wrote: > >> > > >> > >bill.sloman@ieee.org wrote... > >> > >> > >> > >> Too many people make a habit of avoiding custom magnetics. > >> > >> <snip> > >> > >> > I hate custom magnetics. Expensive, boring hassle. The technical > >> > challenge of designing transformers is to NOT design transformers. > >> > >> Sadly, the habit of not designing transformers leaves you stuck with messy, expensive, sub-optimal solutions. > >> > >> The design process is complicated, with lots of choices, but no more boring than > >> any other design process. I suspect that what you are saying is that you've never bothered to get your head around all the issues involved, and find yourself embarrassed when you have to discuss a transformer design in front of your subordinates. > >> > >> There are lots of variables in a transformer design - starting with core size and core material, gapped or ungapped, and proceeding through turns ratio and wire size, and choosing between plain wire and Litz, and on to winding configuration - bifilar or separate coils - plain windings or winding in banks (for lower parallel capacitance). > >> > >> This means that buying an off-the-transformer is unlikely to give you anything all that close to optimal. The process of getting small runs of custom transformers made by sub-contractors isn't all that demanding - no worse than printed circuit boards. It's nice if you can avoid it, but little more sensible than it would be to insist of building everything on off-the-shelf printed circuit boards. > > > >True, you cannot beat the performance of a custom design. > > Usually, you can. You can generally get a product finished with > standard parts for a fraction of the cost, in a fraction of the time.That's beating the cost of a custom design, not it's performance.> Needing custom magnetics may be a character defect, a lack of > imagination. Or an irrational desire to design magnetics.More likely the the lack of an irrational desire not to design magnetics, coupled with with the intellectual capacity to do it.> If you plan to build 30,000 power supplies, custom magnetics may make > sense. If you are designing a complex instrument and need some > transformers or inductors, try Coilcraft first.Always worth doing, but expect to come up empty most of the time.> >But, for a given converter, you may be able to get so close performance wise to the custom design using an COTS part, which will be a lot easier and may be cheaper. > > > >For low volume, the hassle and NRE cost of getting a custom part UL approved part, often results in the selection of the COTS part. > > Sloman loves custom magnetics, which explains why he has been working > on his beloved oscillator for over a decade, and it still doesn't > oscillate.The oscillator project started - in a sense - back in 1986, and that oscillator has been part of a single-crystal GaAs pulling machine ever since. The wound parts got dumped last year when it became clear that even a well-gapped ferrite core was going to introduced harmonics 105dB below the fundemental.> Tne reason I dislike custom magnetics is because I've done so many > custom magnetic designs, probably 20x more than he has. The best > inductor is cheap, multi-sourced, surface mount.If it will do the job you want. Most won't.> This one doesn't qualify: > > https://dl.dropboxusercontent.com/u/53724080/PP5.JPGLooks like a power transformer. I've designed similar-sized power transformers into arc-lamp power supplies, but we used used graduate students to man-handle them onto the chassis. -- Bill Sloman, Sydney
