On Tue, 21 Jul 2015 09:48:57 -0700 (PDT), Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:>Den tirsdag den 21. juli 2015 kl. 18.21.55 UTC+2 skrev John Larkin: >> On Tue, 21 Jul 2015 11:52:23 -0400, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >> >On 07/21/2015 11:46 AM, Bill Sloman wrote: >> >> On Tuesday, July 21, 2015 at 12:38:07 AM UTC+2, Lasse Langwadt >> >> Christensen wrote: >> >>> Den mandag den 20. juli 2015 kl. 17.24.11 UTC+2 skrev Bill Sloman: >> >>>> On Sunday, July 19, 2015 at 7:40:19 PM UTC+2, John Larkin wrote: >> >>>>> On Sat, 18 Jul 2015 19:53:31 -0400, M Philbrook >> >>>>> <jamie_ka1lpa@charter.net> wrote: >> >>>>> >> >>>>>> In article >> >>>>>> <c228b7df-ec64-469a-ae5f-f4ae29cfe028@googlegroups.com>, >> >>>>>> bill.sloman@gmail.com says... >> >>>>>>> >> >>>>>>> On Saturday, July 18, 2015 at 5:50:11 PM UTC+2, John Larkin >> >>>>>>> wrote: >> >>>>>>>> On Sat, 18 Jul 2015 09:39:34 -0400, bitrex >> >>>>>>>> <bitrex@de.lete.earthlink.net> wrote: >> >>>>>>>> >> >>>>>>>>> >> >>>>>>>>> For a hobby project, I'd like to be able to generate >> >>>>>>>>> +48 volts or so from +5 volt USB. Current requirements >> >>>>>>>>> are small, maybe 15 mA or so? I'd like uh, low noise (I >> >>>>>>>>> don't have an exact spec so this is just kind of >> >>>>>>>>> existential at this point), so maybe a charge pump >> >>>>>>>>> would be in order rather than a boost switcher? >> >>>>>>>>> >> >>>>>>>>> Does anyone make a charge pump IC that I could feed an >> >>>>>>>>> external clock to, with outputs suitable for running >> >>>>>>>>> something like a Dickson pump? Maybe that would be too >> >>>>>>>>> many stages to go from +5 to +48... >> >>>>>>>> >> >>>>>>>> Two of these >> >>>>>>>> >> >>>>>>>> http://www.digikey.com/product-detail/en/PDS1-S5-S24-M-TR/102-2973-2-ND/4006941 >> >>>>>>>> >> >>>>>>>> >> >>>>>>>> >> >with the outputs in series would work. They are fairly quiet, and you >> >>>>>>>> could add a little filtering to help. At light loads, >> >>>>>>>> their output tends to be a few per cent high. But then, 5 >> >>>>>>>> volts from USB may not really be 5 volts. >> >>>>>>>> >> >>>>>>>> For really quiet, consider some sort of sinewave drive >> >>>>>>>> step-up transformer. >> >>>>>>> >> >>>>>>> A Baxandall Class-D oscillator - one step-up transformer >> >>>>>>> and one inductor - would work well. MOS-FET transistors do >> >>>>>>> a bit better than bipolar transistors, but Baxandall's >> >>>>>>> paper rather pre-dates them. >> >>>>>>> >> >>>>>>> http://sophia-elektronica.com/0344_001_Baxandal.pdf >> >>>>>>> >> >>>>>>> http://sophia-elektronica.com/Baxandall_parallel-resonant_Class-D_oscillator1.htm >> >>>>>> >> >>>>>> >> >>>>>>> >> >Oh God, You just couldn't keep that failed OSC out of th subject! >> >>>>> >> >>>>> It's an interesting circuit from a time scaling standpoint. It >> >>>>> will oscillate at tens of KHz, but it takes decades to build. >> >>>> >> >>>> John Larkin is too dim to notice the difference between a low >> >>>> distortion oscillator and the Baxandall/Jim Williams oscillator. >> >>> >> >>> Though it can hardly come as a surprise that you get teased about >> >>> it since you have been talking about for years and still haven't >> >>> gotten around to building it, as if a bit of table space for a >> >>> soldering iron and time, for someone who doesn't have to go to work >> >>> everyday, is impossible to find. >> >> >> >> I'd gotten most of the way to building an example - bought all the >> >> parts, including getting the specially wound transformers - a few >> >> years ago, just before I moved back to Australia, which gave me >> >> enough time to think up a better variation, which I may get built >> >> real soon now, if I'm lucky. >> >> >> >> It's not got much to do with Baxandall's class-D oscillator (though >> >> my variant of that is what got me started) but Jamie and John are too >> >> dim to make that kind of fine distinction. >> >> >> >>>> "The circuit is probably best known from Jim Williams' series of >> >>>> application notes for Linear Technology, on high frequency >> >>>> inverters for driving cold cathode back-lights used in laptop >> >>>> computers (application notes AN45, AN49, AN51, AN55, AN61, >> >>>> AN65)." These apparently were Linear Technology's most popular >> >>>> application notes for quite a while. >> >>>> >> >>>> Nobody has had any trouble building them in jig time. Except >> >>>> perhaps John Larkin, who can't cope with transformers that he >> >>>> can't buy off the shelf.. >> >>>> >> >>> >> >>> Aiming to build stuff from things you can get cheap and fast off >> >>> the shelf is just common sense >> >> >> >> Restricting yourself to components which you can buy cheaply off the >> >> shelf rather narrows your range, particularly when it comes to >> >> transformers. >> >> >> > >> >Oh, I don't know about that. A big PSU or one with special requirements >> >might well need custom magnetics, and it probably pays to micro-optimize >> >high volume designs. For annual quantities of tens to hundreds, though, >> >(where John lives and I aspire to) ;) the performance advantage probably >> >doesn't pay for the increased pain in procurement. >> >> Custom magnetics is a real pain. Winding them yourself is crazy; they >> will wind up costing ten or more times what a commercial surface-mount >> part would cost. Just a bobbin will cost more than an entire finished >> inductor. Ordering them from a magnetics house takes weeks of waiting >> and a lot of engineering work documenting the part. >> >> It can take a little ingenuity to make a circuit from standard parts, >> but there are tons of standard inductors available too. >> >> There's seldom a justification for building an off-line switcher. >> Things like wall-warts and MeanWell bricks are absurdly cheap and have >> all the UL/CE/FCC stickers you would ever want. >> >> > >> >SMPSes can be fun once in awhile, but doing vanilla ones as a steady >> >diet must be booooorrrinnnggg. >> >> There are lots of interesting packaged switchers around these days, >> like 7805 drop-in replacements, hybrid bucks with magnetics and caps, >> tiny dc/dc converters; they tend to cluster in the $4 range. It's >> seldom worth even the parts cost of making your own standard switcher; >> well, some small synchronous bucks aren't too bad, like to go from +5 >> to +1.2 or something. >> >> Time to move up the abstraction stack. >> > >I bough stack of these for prototypes: http://www.ebay.com/itm/171381728637 >almost cheaper than buying a 7805 > >-LasseThis series is really cool: http://www.digikey.com/product-detail/en/P7805-Q24-S5-S/102-2705-ND/4009632 Depending on which of the pins you ground, it will convert a positive input to a positive or negative output. -- John Larkin Highland Technology, Inc lunatic fringe electronics jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
charge pump/boost converter
Started by ●July 18, 2015
Reply by ●July 21, 20152015-07-21
Reply by ●July 22, 20152015-07-22
On 2015-07-21, John Larkin <jlarkin@highlandtechnology.com> wrote:> On Tue, 21 Jul 2015 09:48:57 -0700 (PDT), Lasse Langwadt Christensen ><langwadt@fonz.dk> wrote: > > > This series is really cool: > > http://www.digikey.com/product-detail/en/P7805-Q24-S5-S/102-2705-ND/4009632 > > Depending on which of the pins you ground, it will convert a positive > input to a positive or negative output.well, a buck and a buck-boost are kind of similar ==== (1)----. .--+---mmmm-+--(3) ---- | | ---. | | | | | `----------magic | | `--|<----+--(2) "magic" senses the voltage between 2 and 3 and drives the switch apropriately, possibly with a vcc input from 1 also, I expect it's an off-the shelf switcher chip. -- umop apisdn
Reply by ●July 22, 20152015-07-22
>Depending on which of the pins you ground, it will convert a positive >input to a positive or negative outputOf course, the same is true of the $1.50 eBay buck converters. To make a negative supply, you ground the output apply power between there and the +in wire, and let it pump its 'ground' pin negative. (You knew that already.) Cheers Phil Hobbs
Reply by ●July 22, 20152015-07-22
On Tuesday, July 21, 2015 at 6:21:55 PM UTC+2, John Larkin wrote:> On Tue, 21 Jul 2015 11:52:23 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >On 07/21/2015 11:46 AM, Bill Sloman wrote: > >> On Tuesday, July 21, 2015 at 12:38:07 AM UTC+2, Lasse Langwadt > >> Christensen wrote: > >>> Den mandag den 20. juli 2015 kl. 17.24.11 UTC+2 skrev Bill Sloman: > >>>> On Sunday, July 19, 2015 at 7:40:19 PM UTC+2, John Larkin wrote: > >>>>> On Sat, 18 Jul 2015 19:53:31 -0400, M Philbrook > >>>>> <jamie_ka1lpa@charter.net> wrote: > >>>>> > >>>>>> In article > >>>>>> <c228b7df-ec64-469a-ae5f-f4ae29cfe028@googlegroups.com>, > >>>>>> bill.sloman@gmail.com says... > >>>>>>> > >>>>>>> On Saturday, July 18, 2015 at 5:50:11 PM UTC+2, John Larkin > >>>>>>> wrote: > >>>>>>>> On Sat, 18 Jul 2015 09:39:34 -0400, bitrex > >>>>>>>> <bitrex@de.lete.earthlink.net> wrote: > >>>>>>>> > >>>>>>>>> > >>>>>>>>> For a hobby project, I'd like to be able to generate > >>>>>>>>> +48 volts or so from +5 volt USB. Current requirements > >>>>>>>>> are small, maybe 15 mA or so? I'd like uh, low noise (I > >>>>>>>>> don't have an exact spec so this is just kind of > >>>>>>>>> existential at this point), so maybe a charge pump > >>>>>>>>> would be in order rather than a boost switcher? > >>>>>>>>> > >>>>>>>>> Does anyone make a charge pump IC that I could feed an > >>>>>>>>> external clock to, with outputs suitable for running > >>>>>>>>> something like a Dickson pump? Maybe that would be too > >>>>>>>>> many stages to go from +5 to +48... > >>>>>>>> > >>>>>>>> Two of these > >>>>>>>> > >>>>>>>> http://www.digikey.com/product-detail/en/PDS1-S5-S24-M-TR/102-2973-2-ND/4006941 > >>>>>>>> > >with the outputs in series would work. They are fairly quiet, and you > >>>>>>>> could add a little filtering to help. At light loads, > >>>>>>>> their output tends to be a few per cent high. But then, 5 > >>>>>>>> volts from USB may not really be 5 volts. > >>>>>>>> > >>>>>>>> For really quiet, consider some sort of sinewave drive > >>>>>>>> step-up transformer. > >>>>>>> > >>>>>>> A Baxandall Class-D oscillator - one step-up transformer > >>>>>>> and one inductor - would work well. MOS-FET transistors do > >>>>>>> a bit better than bipolar transistors, but Baxandall's > >>>>>>> paper rather pre-dates them. > >>>>>>> > >>>>>>> http://sophia-elektronica.com/0344_001_Baxandal.pdf > >>>>>>> > >>>>>>> http://sophia-elektronica.com/Baxandall_parallel-resonant_Class-D_oscillator1.htm > >>>>>> > >Oh God, You just couldn't keep that failed OSC out of th subject! > >>>>> > >>>>> It's an interesting circuit from a time scaling standpoint. It > >>>>> will oscillate at tens of KHz, but it takes decades to build. > >>>> > >>>> John Larkin is too dim to notice the difference between a low > >>>> distortion oscillator and the Baxandall/Jim Williams oscillator. > >>> > >>> Though it can hardly come as a surprise that you get teased about > >>> it since you have been talking about for years and still haven't > >>> gotten around to building it, as if a bit of table space for a > >>> soldering iron and time, for someone who doesn't have to go to work > >>> everyday, is impossible to find. > >> > >> I'd gotten most of the way to building an example - bought all the > >> parts, including getting the specially wound transformers - a few > >> years ago, just before I moved back to Australia, which gave me > >> enough time to think up a better variation, which I may get built > >> real soon now, if I'm lucky. > >> > >> It's not got much to do with Baxandall's class-D oscillator (though > >> my variant of that is what got me started) but Jamie and John are too > >> dim to make that kind of fine distinction. > >> > >>>> "The circuit is probably best known from Jim Williams' series of > >>>> application notes for Linear Technology, on high frequency > >>>> inverters for driving cold cathode back-lights used in laptop > >>>> computers (application notes AN45, AN49, AN51, AN55, AN61, > >>>> AN65)." These apparently were Linear Technology's most popular > >>>> application notes for quite a while. > >>>> > >>>> Nobody has had any trouble building them in jig time. Except > >>>> perhaps John Larkin, who can't cope with transformers that he > >>>> can't buy off the shelf.. > >>> > >>> Aiming to build stuff from things you can get cheap and fast off > >>> the shelf is just common sense > >> > >> Restricting yourself to components which you can buy cheaply off the > >> shelf rather narrows your range, particularly when it comes to > >> transformers. > >> > >Oh, I don't know about that. A big PSU or one with special requirements > >might well need custom magnetics, and it probably pays to micro-optimize > >high volume designs. For annual quantities of tens to hundreds, though, > >(where John lives and I aspire to) ;) the performance advantage probably > >doesn't pay for the increased pain in procurement. > > Custom magnetics is a real pain. Winding them yourself is crazy; they > will wind up costing ten or more times what a commercial surface-mount > part would cost.If it existed.> Just a bobbin will cost more than an entire finished > inductor.We were talking about transformers rather than inductors. Even with inductors one has to be aware that a small 100uH inductor will saturate or burn out rather earlier than a larger (and more expensive) part. If you know enough to be aware of self-resonant frequencies, the situation gets even more complicated.> Ordering them from a magnetics house takes weeks of waiting > and a lot of engineering work documenting the part.If you put in a little more effort you might be able to find a coil winder who didn't take weeks.> It can take a little ingenuity to make a circuit from standard parts, > but there are tons of standard inductors available too.We were talking about transformers, rather than inductors. Even so "tons" isn't a useful measure.> There's seldom a justification for building an off-line switcher. > Things like wall-warts and MeanWell bricks are absurdly cheap and have > all the UL/CE/FCC stickers you would ever want.If they provide the performance you need, fine. +48V from +5V USB doesn't seem to be a mass market application.> >SMPSes can be fun once in awhile, but doing vanilla ones as a steady > >diet must be booooorrrinnnggg. > > There are lots of interesting packaged switchers around these days, > like 7805 drop-in replacements, hybrid bucks with magnetics and caps, > tiny dc/dc converters; they tend to cluster in the $4 range. It's > seldom worth even the parts cost of making your own standard switcher; > well, some small synchronous bucks aren't too bad, like to go from +5 > to +1.2 or something.This thread doesn't seem to have thrown up a specific "standard switcher" for bitrex's application.> Time to move up the abstraction stack.Vapour-ware is so much easier to generate. -- Bill Sloman, Sydney
Reply by ●July 22, 20152015-07-22
On Wed, 22 Jul 2015 01:27:44 -0700 (PDT), Phil Hobbs <pcdhobbs@gmail.com> wrote:>>Depending on which of the pins you ground, it will convert a positive >>input to a positive or negative output > >Of course, the same is true of the $1.50 eBay buck converters. To make a negative supply, you ground the output apply power between there and the +in wire, and let it pump its 'ground' pin negative. (You knew that already.) >Does that always work? I hadn't thought it through. Given this horrible flu thing that I have, there are lots of things I'm not thinking through. I think I'll draw a schematic; that's easy. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●July 22, 20152015-07-22
Den onsdag den 22. juli 2015 kl. 19.37.31 UTC+2 skrev John Larkin:> On Wed, 22 Jul 2015 01:27:44 -0700 (PDT), Phil Hobbs > <pcdhobbs@gmail.com> wrote: > > >>Depending on which of the pins you ground, it will convert a positive > >>input to a positive or negative output > > > >Of course, the same is true of the $1.50 eBay buck converters. To make a negative supply, you ground the output apply power between there and the +in wire, and let it pump its 'ground' pin negative. (You knew that already.) > > > > Does that always work? I hadn't thought it through. > > Given this horrible flu thing that I have, there are lots of things > I'm not thinking through. I think I'll draw a schematic; that's easy. >it is shown in some datasheets/appnotes http://www.digikey.com/en/articles/techzone/2012/oct/generating-negative-output-from-positive-input-voltage -Lasse
Reply by ●July 23, 20152015-07-23
On 07/22/2015 01:37 PM, John Larkin wrote:> On Wed, 22 Jul 2015 01:27:44 -0700 (PDT), Phil Hobbs > <pcdhobbs@gmail.com> wrote: > >>> Depending on which of the pins you ground, it will convert a >>> positive input to a positive or negative output >> >> Of course, the same is true of the $1.50 eBay buck converters. To >> make a negative supply, you ground the output, apply power between >> there and the +in wire, and let it pump its 'ground' pin negative. >> (You knew that already.) >> > > Does that always work? I hadn't thought it through. > > Given this horrible flu thing that I have, there are lots of things > I'm not thinking through. I think I'll draw a schematic; that's > easy.I do it a fair amount with 150 kHz Simple Switchers (my fave) and have never had a problem. You design a buck that goes from Vin-Vout to -Vout. The two issues are: 1. The voltage stress on the IC is Vin-Vout rather than Vin 2. The feedback pin isn't ground referenced, so you can't put a cap multiplier inside the DC loop, which I like to do when I can. (You use split feedback, as with driving a capacitive load with an op amp and series resistor.) There are bandaids for this, of course, e.g. hanging a TLV431 on the cap multiplier. Get well soon! 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 ●July 23, 20152015-07-23
It's well past midnight for me, sorry excuse, but a cap multiplier inside a DC loop in a buck or boost , what the heck is that? Cheers Klaus
Reply by ●July 23, 20152015-07-23
On 7/23/2015 7:22 PM, Klaus Kragelund wrote:> > It's well past midnight for me, sorry excuse, but a cap multiplier > inside a DC loop in a buck or boost , what the heck is that? > > Cheers > > Klaus >Capacitance multipliers are amazingly good at cleaning up SMPSes, but they're a bit squishy on the DC regulation. If you close the DC loop of an LM2594 (or something like that) around the emitter of the cap multiplier, and the AC loop around from the switcher's output, you get the best of all worlds: decent efficiency and very very low noise. It's pretty simple: normal buck + cap multiplier, FB pin driven by a resistor from the cap multiplier output (to keep the regulation reasonable) and a capacitor from the FB pin to the SMPS output (to keep the loop stable). 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 ●July 24, 20152015-07-24
On Friday, July 24, 2015 at 2:04:50 AM UTC+2, Phil Hobbs wrote:> On 7/23/2015 7:22 PM, Klaus Kragelund wrote: > > > > It's well past midnight for me, sorry excuse, but a cap multiplier > > inside a DC loop in a buck or boost , what the heck is that? > > > > Cheers > > > > Klaus > > > > Capacitance multipliers are amazingly good at cleaning up SMPSes, but > they're a bit squishy on the DC regulation. > > If you close the DC loop of an LM2594 (or something like that) around > the emitter of the cap multiplier, and the AC loop around from the > switcher's output, you get the best of all worlds: decent efficiency and > very very low noise. > > It's pretty simple: normal buck + cap multiplier, FB pin driven by a > resistor from the cap multiplier output (to keep the regulation > reasonable) and a capacitor from the FB pin to the SMPS output (to keep > the loop stable). > >Ok, but for the efficiency, you loose some power in the capacitance multiplier. Like those made for class A amplifiers, right? Cheers Klaus
