On Wed, 4 May 2016 11:01:57 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
>On 04/26/2016 03:54 PM, Phil Hobbs wrote:
>> On 04/26/2016 03:37 PM, John Larkin wrote:
>>> On Tue, 26 Apr 2016 15:11:01 -0400, Phil Hobbs
>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>
>>>> So I built this board for my fire prevention equipment customer. (An
>>>> excellent outfit BTW: Argus Fire Control.) It needed two isolated 5-V
>>>> supplies, one for the analogue stuff and one for RS-485.
>>>>
>>>> A few months ago we were discussing those supplies in this very
>>>> boutique, in the "Coupled Inductors--how coupled is coupled?" thread. I
>>>> wound up with a flybuck design using an LM3103 sync buck chip.
>>>>
>>>> Using a simple fixed duty-cycle model with realistic resistances for the
>>>> switches and inductors, it simulated very nicely. However this switcher
>>>> chip doesn't work very well at all in the application, apparently on
>>>> account of its DCM mode, which makes it stutter unless there's a serious
>>>> load on the non-isolated side (as in a normal buck).
>>>>
>>>> When it stutters, the feedback voltage stays stable, but the isolated
>>>> outputs collapse, of course--I need the output FETS to keep on
>>>> switching, and they don't. There's no apparent way to turn this feature
>>>> off.
>>>>
>>>> Looks like I'll have to use something simpler.
>>>>
>>>> Cheers
>>>>
>>>> Phil Hobbs
>>>
>>> Yeah, the block diagrams of modern switcher controller chips look like
>>> the aerial view of Baltimore (with the burning bits too!)
>>
>> The leading contenders so far are the Richtek RT7272 and RT2862A.
>
>Well, I tried, and both stutter at light loads too. The RT2862
>datasheet makes no such claim, but does it anyway. The plus side is
>that when I load down the primary, they produce heaps of isolated power,
>so the magnetics and so forth are working fine.
>
>Anybody got a favourite sync buck that'll handle at least 36V input and
>400 mA, and keeps on PWMing at light loads?
It's close but LM536x5?
If you can use an async buck, the LMR140x0 works.
>'Cuz otherwise I'm going to have to do it the fully-manual way, with a
>bridge driver and so on (yuck).
Reply by Phil Hobbs●May 4, 20162016-05-04
On 05/04/2016 06:43 PM, dagmargoodboat@yahoo.com wrote:
> On Tuesday, April 26, 2016 at 12:11:07 PM UTC-7, Phil Hobbs wrote:
>> So I built this board for my fire prevention equipment customer. (An
>> excellent outfit BTW: Argus Fire Control.) It needed two isolated 5-V
>> supplies, one for the analogue stuff and one for RS-485.
>>
>> A few months ago we were discussing those supplies in this very
>> boutique, in the "Coupled Inductors--how coupled is coupled?" thread. I
>> wound up with a flybuck design using an LM3103 sync buck chip.
>>
>> Using a simple fixed duty-cycle model with realistic resistances for the
>> switches and inductors, it simulated very nicely. However this switcher
>> chip doesn't work very well at all in the application, apparently on
>> account of its DCM mode, which makes it stutter unless there's a serious
>> load on the non-isolated side (as in a normal buck).
>>
>> When it stutters, the feedback voltage stays stable, but the isolated
>> outputs collapse, of course--I need the output FETS to keep on
>> switching, and they don't. There's no apparent way to turn this feature
>> off.
>>
>> Looks like I'll have to use something simpler.
>
> Nearly every wallwart uses an optoisolator + TL431 for isolated feedback.
>
> Might help your situation?
Thanks. If I have to use two separate controllers, I'll probably do that.
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 Phil Hobbs●May 4, 20162016-05-04
On 05/04/2016 04:46 PM, John Larkin wrote:
> 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 Hobbs
>
> How will you get regulation and isolation from a flybuck converter? I
> guess I don't understand the topology.
The Microchip MCP16312 seems to work okay, hurrah. Amazingly small--an
MSOP-8 with no power pad. (It has thermal shutdown, which helps.) It
has some loop stability problems, but then I'm testing it in a proto
with longish connections to some nodes. Changing the bypassing improves
things, so on a proper board layout it ought to work fine.
The idea is for one of the +5's to power a RPi, the analogue stuff, and
the logic side of an isolated RS485 transceiver. The other one powers
the line side of the RS485 (160 mA if double-terminated).
I'm using some of those Bourns coupled inductors we were talking about a
couple of months ago, two 100 uH with their primaries in parallel,
connected with 20 uF to ground from the cold end (i.e. the normal buck
output).
Each secondary gets its own Schottky rectifier and filter, making two
isolated supplies--isolated from each other as well as from the input.
If the coupling coefficient were above 0.99, the cross-regulation would
be good enough by itself, but with those parts it's more like 0.95.
Thus the isolated voltage varies a fair amount--from about 5.5 to 8V or
so at the lightest loads. The measured output impedance is about 5
ohms, which isn't terrible.
However, that's not a bad match for an LDO apiece--a 20-cent AOmega
part. (This is not an ultrasensitive application, so SMPS-quiet is okay.)
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 Tuesday, April 26, 2016 at 12:11:07 PM UTC-7, Phil Hobbs wrote:
> So I built this board for my fire prevention equipment customer. (An
> excellent outfit BTW: Argus Fire Control.) It needed two isolated 5-V
> supplies, one for the analogue stuff and one for RS-485.
>
> A few months ago we were discussing those supplies in this very
> boutique, in the "Coupled Inductors--how coupled is coupled?" thread. I
> wound up with a flybuck design using an LM3103 sync buck chip.
>
> Using a simple fixed duty-cycle model with realistic resistances for the
> switches and inductors, it simulated very nicely. However this switcher
> chip doesn't work very well at all in the application, apparently on
> account of its DCM mode, which makes it stutter unless there's a serious
> load on the non-isolated side (as in a normal buck).
>
> When it stutters, the feedback voltage stays stable, but the isolated
> outputs collapse, of course--I need the output FETS to keep on
> switching, and they don't. There's no apparent way to turn this feature
> off.
>
> Looks like I'll have to use something simpler.
Nearly every wallwart uses an optoisolator + TL431 for isolated feedback.
Might help your situation?
Cheers,
James Arthur
Reply by Lasse Langwadt Christensen●May 4, 20162016-05-04
Den onsdag den 4. maj 2016 kl. 22.46.30 UTC+2 skrev John Larkin:
> 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 Hobbs
>
> How will you get regulation and isolation from a flybuck converter? I
> guess I don't understand the topology.
>
> Are the +-5 mutually isolated?
>
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 Hobbs
How 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
Reply by George Herold●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 John Larkin●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 Hobbs
Some 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 Phil Hobbs●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 Phil Hobbs●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