On 05/04/2016 11:52 AM, Tim Williams wrote:> "Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message > news:Nv2dnSAO7JJ4k7fKnZ2dnUU7-bHNnZ2d@supernews.com... >> Anybody got a favourite sync buck that'll handle at least 36V input and >> 400 mA, and keeps on PWMing at light loads? > > Was about to say TPS54233 or something like that, but I immediately > realized those miss exactly those specs (30V and pulse skipping)... > > LTC3810 is the only controller I know offhand, but that's rather a lot > of brain (and additional circuit) for present levels. I don't know if > there's a smaller, cheaper, integrated version out there, but hopefully > it's a hint at least. > > Suppose I might suggest dropping the sync requirement, since the max > voltage is high enough not to matter much. But you'd know better than I.. > > Tim >It's a flybuck converter, so I need to use the bottom FET to dump the voltseconds into the secondaries. Normal bucks can generate isolated power too, but only if the main output carries most of the load. In this design, the 'main' output (the usual buck converter output point) isn't loaded at all--the voltseconds all go to the secondary winding of the coupled inductors. The Microchip MCP16312 looks like a good possibility, though the 32V abs max rating is a bit skimpy--it's running off a 24V supply, so that doesn't leave too much room for the transzorb to operate. I'll give it a whack though. Other possibilities solicited! 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
Flybuck converter funnies
Started by ●April 26, 2016
Reply by ●May 4, 20162016-05-04
Reply by ●May 4, 20162016-05-04
On Wed, 4 May 2016 12:30:59 -0500, "Tim Williams" <tiwill@seventransistorlabs.com> wrote:>"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message >news:1u6kib9i52tcvl3skum47ocdnct9tnkqbm@4ax.com... >> The flybuck architecture (which I understand to be a buck with a >> second winding, to make a negative voltage) needs a pushpull drive to >> work over the full load range. > >Not strictly, but you do need more load on the normal output. Otherwise, >the "flyback" doesn't fly all the way back because it's being clamped by the >negative output's load. > >TimOr think off-the-wall... "OldStyleBuckSwitcherWithAddedNegativeOutput.pdf" on the S.E.D/Schematics Page of my website. ...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 | The touchstone of liberalism is intolerance
Reply by ●May 4, 20162016-05-04
On Wed, 4 May 2016 13:57:22 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 05/04/2016 11:52 AM, Tim Williams wrote: >> "Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message >> news:Nv2dnSAO7JJ4k7fKnZ2dnUU7-bHNnZ2d@supernews.com... >>> Anybody got a favourite sync buck that'll handle at least 36V input and >>> 400 mA, and keeps on PWMing at light loads? >> >> Was about to say TPS54233 or something like that, but I immediately >> realized those miss exactly those specs (30V and pulse skipping)... >> >> LTC3810 is the only controller I know offhand, but that's rather a lot >> of brain (and additional circuit) for present levels. I don't know if >> there's a smaller, cheaper, integrated version out there, but hopefully >> it's a hint at least. >> >> Suppose I might suggest dropping the sync requirement, since the max >> voltage is high enough not to matter much. But you'd know better than I.. >> >> Tim >> > >It's a flybuck converter, so I need to use the bottom FET to dump the >voltseconds into the secondaries. Normal bucks can generate isolated >power too, but only if the main output carries most of the load. > >In this design, the 'main' output (the usual buck converter output >point) isn't loaded at all--the voltseconds all go to the secondary >winding of the coupled inductors. > >The Microchip MCP16312 looks like a good possibility, though the 32V abs >max rating is a bit skimpy--it's running off a 24V supply, so that >doesn't leave too much room for the transzorb to operate. I'll give it >a whack though. > >Other possibilities solicited! > >Cheers > >Phil HobbsBuy a cheap potted dc/dc converter? -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●May 4, 20162016-05-04
On 05/04/2016 02:17 PM, Jim Thompson wrote:> On Wed, 4 May 2016 12:30:59 -0500, "Tim Williams" > <tiwill@seventransistorlabs.com> wrote: > >> "John Larkin" <jjlarkin@highlandtechnology.com> wrote in message >> news:1u6kib9i52tcvl3skum47ocdnct9tnkqbm@4ax.com... >>> The flybuck architecture (which I understand to be a buck with a >>> second winding, to make a negative voltage) needs a pushpull drive to >>> work over the full load range. >> >> Not strictly, but you do need more load on the normal output. Otherwise, >> the "flyback" doesn't fly all the way back because it's being clamped by the >> negative output's load. >> >> Tim > > Or think off-the-wall... > > "OldStyleBuckSwitcherWithAddedNegativeOutput.pdf" on the > S.E.D/Schematics Page of my website. > > ...Jim Thompson >I'm making two isolated +5V from +24. 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 ●May 4, 20162016-05-04
On Wednesday, May 4, 2016 at 1:57:27 PM UTC-4, Phil Hobbs wrote:> On 05/04/2016 11:52 AM, Tim Williams wrote: > > "Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message > > news:Nv2dnSAO7JJ4k7fKnZ2dnUU7-bHNnZ2d@supernews.com... > >> Anybody got a favourite sync buck that'll handle at least 36V input and > >> 400 mA, and keeps on PWMing at light loads? > > > > Was about to say TPS54233 or something like that, but I immediately > > realized those miss exactly those specs (30V and pulse skipping)... > > > > LTC3810 is the only controller I know offhand, but that's rather a lot > > of brain (and additional circuit) for present levels. I don't know if > > there's a smaller, cheaper, integrated version out there, but hopefully > > it's a hint at least. > > > > Suppose I might suggest dropping the sync requirement, since the max > > voltage is high enough not to matter much. But you'd know better than I.. > > > > Tim > > > > It's a flybuck converter, so I need to use the bottom FET to dump the > voltseconds into the secondaries. Normal bucks can generate isolated > power too, but only if the main output carries most of the load. > > In this design, the 'main' output (the usual buck converter output > point) isn't loaded at all--the voltseconds all go to the secondary > winding of the coupled inductors. > > The Microchip MCP16312 looks like a good possibility, though the 32V abs > max rating is a bit skimpy--it's running off a 24V supply, so that > doesn't leave too much room for the transzorb to operate. I'll give it > a whack though. > > Other possibilities solicited!Sorry Phil, can you give the specs again. 36V in, you want two 5V outputs at 400 mA each? Or is one of those negative? And I believe you've got a price point too, how much money? For $4-5 you can get made pre-packaged DC-DC converters on DK. (ROF-78E5.0-0.5) George H.> > 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 ●May 4, 20162016-05-04
On 05/04/2016 03:06 PM, John Larkin wrote:> On Wed, 4 May 2016 13:57:22 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 05/04/2016 11:52 AM, Tim Williams wrote: >>> "Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message >>> news:Nv2dnSAO7JJ4k7fKnZ2dnUU7-bHNnZ2d@supernews.com... >>>> Anybody got a favourite sync buck that'll handle at least 36V input and >>>> 400 mA, and keeps on PWMing at light loads? >>> >>> Was about to say TPS54233 or something like that, but I immediately >>> realized those miss exactly those specs (30V and pulse skipping)... >>> >>> LTC3810 is the only controller I know offhand, but that's rather a lot >>> of brain (and additional circuit) for present levels. I don't know if >>> there's a smaller, cheaper, integrated version out there, but hopefully >>> it's a hint at least. >>> >>> Suppose I might suggest dropping the sync requirement, since the max >>> voltage is high enough not to matter much. But you'd know better than I.. >>> >>> Tim >>> >> >> It's a flybuck converter, so I need to use the bottom FET to dump the >> voltseconds into the secondaries. Normal bucks can generate isolated >> power too, but only if the main output carries most of the load. >> >> In this design, the 'main' output (the usual buck converter output >> point) isn't loaded at all--the voltseconds all go to the secondary >> winding of the coupled inductors. >> >> The Microchip MCP16312 looks like a good possibility, though the 32V abs >> max rating is a bit skimpy--it's running off a 24V supply, so that >> doesn't leave too much room for the transzorb to operate. I'll give it >> a whack though. >> >> Other possibilities solicited! >> >> Cheers >> >> Phil Hobbs > > Buy a cheap potted dc/dc converter? > >They're ratiometric, though, and may or may not have the required product life. (Plus the application is cost-sensitive and high enough in volume to justify a certain amount of assing around getting there.) 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 ●May 4, 20162016-05-04
On 05/04/2016 03:46 PM, George Herold wrote:> On Wednesday, May 4, 2016 at 1:57:27 PM UTC-4, Phil Hobbs wrote: >> On 05/04/2016 11:52 AM, Tim Williams wrote: >>> "Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message >>> news:Nv2dnSAO7JJ4k7fKnZ2dnUU7-bHNnZ2d@supernews.com... >>>> Anybody got a favourite sync buck that'll handle at least 36V input and >>>> 400 mA, and keeps on PWMing at light loads? >>> >>> Was about to say TPS54233 or something like that, but I immediately >>> realized those miss exactly those specs (30V and pulse skipping)... >>> >>> LTC3810 is the only controller I know offhand, but that's rather a lot >>> of brain (and additional circuit) for present levels. I don't know if >>> there's a smaller, cheaper, integrated version out there, but hopefully >>> it's a hint at least. >>> >>> Suppose I might suggest dropping the sync requirement, since the max >>> voltage is high enough not to matter much. But you'd know better than I.. >>> >>> Tim >>> >> >> It's a flybuck converter, so I need to use the bottom FET to dump the >> voltseconds into the secondaries. Normal bucks can generate isolated >> power too, but only if the main output carries most of the load. >> >> In this design, the 'main' output (the usual buck converter output >> point) isn't loaded at all--the voltseconds all go to the secondary >> winding of the coupled inductors. >> >> The Microchip MCP16312 looks like a good possibility, though the 32V abs >> max rating is a bit skimpy--it's running off a 24V supply, so that >> doesn't leave too much room for the transzorb to operate. I'll give it >> a whack though. >> >> Other possibilities solicited! > > Sorry Phil, can you give the specs again. > 36V in, you want two 5V outputs at 400 mA each? Or is one of those negative? > And I believe you've got a price point too, how much money? > > For $4-5 you can get made pre-packaged DC-DC converters on DK. > (ROF-78E5.0-0.5)Thanks. The cheap ones aren't isolated (yours), or aren't regulated (John's CUI ones). Once I get this working, it'll be about $2 per side all told. 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 ●May 4, 20162016-05-04
On Wed, 4 May 2016 15:46:18 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 05/04/2016 03:06 PM, John Larkin wrote: >> On Wed, 4 May 2016 13:57:22 -0400, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 05/04/2016 11:52 AM, Tim Williams wrote: >>>> "Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message >>>> news:Nv2dnSAO7JJ4k7fKnZ2dnUU7-bHNnZ2d@supernews.com... >>>>> Anybody got a favourite sync buck that'll handle at least 36V input and >>>>> 400 mA, and keeps on PWMing at light loads? >>>> >>>> Was about to say TPS54233 or something like that, but I immediately >>>> realized those miss exactly those specs (30V and pulse skipping)... >>>> >>>> LTC3810 is the only controller I know offhand, but that's rather a lot >>>> of brain (and additional circuit) for present levels. I don't know if >>>> there's a smaller, cheaper, integrated version out there, but hopefully >>>> it's a hint at least. >>>> >>>> Suppose I might suggest dropping the sync requirement, since the max >>>> voltage is high enough not to matter much. But you'd know better than I.. >>>> >>>> Tim >>>> >>> >>> It's a flybuck converter, so I need to use the bottom FET to dump the >>> voltseconds into the secondaries. Normal bucks can generate isolated >>> power too, but only if the main output carries most of the load. >>> >>> In this design, the 'main' output (the usual buck converter output >>> point) isn't loaded at all--the voltseconds all go to the secondary >>> winding of the coupled inductors. >>> >>> The Microchip MCP16312 looks like a good possibility, though the 32V abs >>> max rating is a bit skimpy--it's running off a 24V supply, so that >>> doesn't leave too much room for the transzorb to operate. I'll give it >>> a whack though. >>> >>> Other possibilities solicited! >>> >>> Cheers >>> >>> Phil Hobbs >> >> Buy a cheap potted dc/dc converter? >> >> > > >They're ratiometric, though, and may or may not have the required >product life. (Plus the application is cost-sensitive and high enough >in volume to justify a certain amount of assing around getting there.) > >Cheers > >Phil HobbsSome are regulated, but they cost a little more. But there are lots of multi-sourced parts, especially the SIPs. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●May 4, 20162016-05-04
On Wednesday, May 4, 2016 at 3:48:42 PM UTC-4, Phil Hobbs wrote:> On 05/04/2016 03:46 PM, George Herold wrote: > > On Wednesday, May 4, 2016 at 1:57:27 PM UTC-4, Phil Hobbs wrote: > >> On 05/04/2016 11:52 AM, Tim Williams wrote: > >>> "Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message > >>> news:Nv2dnSAO7JJ4k7fKnZ2dnUU7-bHNnZ2d@supernews.com... > >>>> Anybody got a favourite sync buck that'll handle at least 36V input and > >>>> 400 mA, and keeps on PWMing at light loads? > >>> > >>> Was about to say TPS54233 or something like that, but I immediately > >>> realized those miss exactly those specs (30V and pulse skipping)... > >>> > >>> LTC3810 is the only controller I know offhand, but that's rather a lot > >>> of brain (and additional circuit) for present levels. I don't know if > >>> there's a smaller, cheaper, integrated version out there, but hopefully > >>> it's a hint at least. > >>> > >>> Suppose I might suggest dropping the sync requirement, since the max > >>> voltage is high enough not to matter much. But you'd know better than I.. > >>> > >>> Tim > >>> > >> > >> It's a flybuck converter, so I need to use the bottom FET to dump the > >> voltseconds into the secondaries. Normal bucks can generate isolated > >> power too, but only if the main output carries most of the load. > >> > >> In this design, the 'main' output (the usual buck converter output > >> point) isn't loaded at all--the voltseconds all go to the secondary > >> winding of the coupled inductors. > >> > >> The Microchip MCP16312 looks like a good possibility, though the 32V abs > >> max rating is a bit skimpy--it's running off a 24V supply, so that > >> doesn't leave too much room for the transzorb to operate. I'll give it > >> a whack though. > >> > >> Other possibilities solicited! > > > > Sorry Phil, can you give the specs again. > > 36V in, you want two 5V outputs at 400 mA each? Or is one of those negative? > > And I believe you've got a price point too, how much money? > > > > For $4-5 you can get made pre-packaged DC-DC converters on DK. > > (ROF-78E5.0-0.5) > > Thanks. The cheap ones aren't isolated (yours), or aren't regulated > (John's CUI ones). Once I get this working, it'll be about $2 per side > all told.I bought some cui's that were regulated and isolated (more $).. I think the max V spec was32 and not 36V... As long as you've looked those over. George H.> > 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 ●May 4, 20162016-05-04
On Wed, 4 May 2016 15:48:36 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 05/04/2016 03:46 PM, George Herold wrote: >> On Wednesday, May 4, 2016 at 1:57:27 PM UTC-4, Phil Hobbs wrote: >>> On 05/04/2016 11:52 AM, Tim Williams wrote: >>>> "Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message >>>> news:Nv2dnSAO7JJ4k7fKnZ2dnUU7-bHNnZ2d@supernews.com... >>>>> Anybody got a favourite sync buck that'll handle at least 36V input and >>>>> 400 mA, and keeps on PWMing at light loads? >>>> >>>> Was about to say TPS54233 or something like that, but I immediately >>>> realized those miss exactly those specs (30V and pulse skipping)... >>>> >>>> LTC3810 is the only controller I know offhand, but that's rather a lot >>>> of brain (and additional circuit) for present levels. I don't know if >>>> there's a smaller, cheaper, integrated version out there, but hopefully >>>> it's a hint at least. >>>> >>>> Suppose I might suggest dropping the sync requirement, since the max >>>> voltage is high enough not to matter much. But you'd know better than I.. >>>> >>>> Tim >>>> >>> >>> It's a flybuck converter, so I need to use the bottom FET to dump the >>> voltseconds into the secondaries. Normal bucks can generate isolated >>> power too, but only if the main output carries most of the load. >>> >>> In this design, the 'main' output (the usual buck converter output >>> point) isn't loaded at all--the voltseconds all go to the secondary >>> winding of the coupled inductors. >>> >>> The Microchip MCP16312 looks like a good possibility, though the 32V abs >>> max rating is a bit skimpy--it's running off a 24V supply, so that >>> doesn't leave too much room for the transzorb to operate. I'll give it >>> a whack though. >>> >>> Other possibilities solicited! >> >> Sorry Phil, can you give the specs again. >> 36V in, you want two 5V outputs at 400 mA each? Or is one of those negative? >> And I believe you've got a price point too, how much money? >> >> For $4-5 you can get made pre-packaged DC-DC converters on DK. >> (ROF-78E5.0-0.5) > >Thanks. The cheap ones aren't isolated (yours), or aren't regulated >(John's CUI ones). Once I get this working, it'll be about $2 per side >all told. > >Cheers > >Phil HobbsHow will you get regulation and isolation from a flybuck converter? I guess I don't understand the topology. Are the +-5 mutually isolated? -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
