Driver to drive?

Joerg · Feb 28, 2009

D from BC wrote:

On Fri, 27 Feb 2009 16:11:49 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Thu, 26 Feb 2009 19:40:45 -0800, D from BC
myrealaddress@comic.com> wrote:

I've seen a few schematics of opto's being used in linear mode for
smps designs..
But what about those digital isolators? Are they just for digital
circuits?

Right now I'm working on applying a digital isolator for a smps
design..
http://focus.ti.com/lit/ds/symlink/iso721.pdf
Note that the datasheet doesn't mention smps applications. hmmm

Anybody know some design examples of smps's using digital isolators
(opto digital, galvanic, GMR or RF)?

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design
I use both in switching power supplies. The analog opto for voltage
feedback, the digital isolator (Analog Devices ADuM1200 series) for
setting power supply voltage.

Three bucks for an isolator in a switcher? Yikes.

Relative to sluggish optos, the galvanic ISO721 is not cheap.
Probably the only reason I'm using it is to dodge modelling a fast
opto in ltspice.

Sluggish? How fast do you need it to be? I haven't seen loops much past
a couple hundred kHz in switcher.

Another reason I'm dodging a linear opto is that my smps design is
experimental and a poorly applied opto may cause loop stability
problems. If anything goes wrong, I can't blame an opto if it's not
there.

It's a tradeoff.. So the parts are expensive, but I get the design
done earlier.

<scratching head>

I had used optos up to 10Mb/sec, no problem. The only reason I kicked
some out and replaced them with signal transformers was because the
signal transformers were multi-sourceable and 5c cheaper back then. That
has changed though.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

D from BC · Feb 28, 2009

On Sat, 28 Feb 2009 08:14:08 GMT, Ross Herbert
<rherber1@bigpond.net.au> wrote:

On Fri, 27 Feb 2009 19:58:46 -0800, D from BC <myrealaddress@comic.com> wrote:

:On Sat, 28 Feb 2009 03:06:38 GMT, Ross Herbert
:<rherber1@bigpond.net.au> wrote:
:
:
:>I pulled a psu from a defunct Epson inkjet printer and it uses a similar setup
:>to your description. The mains input primary side switcher uses a mosfet
:>controlled by bjt's and the secondary side uses a L4962EA 1.5A smps controller
:>to produce a 42V output.
:
:>As for the OP's query, my initial reading is that the digital isolator cannot
:>be applied to smps feedback control. The output control of an smps relies on
:
:
:I don't think so.

:Once the analog error signal gets to a PWM (or other), the error
:signal crosses into digital land.
:This works when the PWM is on the secondary side.

Take a look at the data sheet for a typical controller IC commonly used in SMPS,
eg. UC3842.

"Pin 2 - Voltage feedback - This is the inverting input of the Error Amplifier.
It is normally connected to the switching power supply output through a resistor
divider."

That says the feedback signal is analog, not digital.

In SMPS which don't use a PWM controller IC, the feedback signal is always
analog.

I think the UC3842 is meant to be used on the primary side.
I don't think a digital isolator can be used with a current mode
controller (UC3842) because it uses 2 feedback loops. One loop is the
current ramp from the primary side and other loop is the voltage
monitoring (via linear opto) from the secondary side.
To use a digital isolator, there can only be linear feedback loops on
secondary side.
(The UC3842 uses a primary (I mode) and secondary (V mode) feedback
loops.)
A digital isolator can work with a voltage mode controller used on the
secondary side. (The UC3842 is a current mode controller.)
With a digital isolator, it's the mosfet gate signal that is
isocoupled not a sample of the output voltage.

:>sampling an analog voltage against a reference and producing an analog
:>feedback signal which is applied to the primary side switching control usually
:>via an opto-isolator. Using a digital isolator (which is quite complex in
:>itself) would
:
igital isolators are easy to apply and are easy to model.
:My digital isolator model uses a buffer with only 5 parameters Td Tr
:Tf Vh Vl..
:I tried modelling a 6N135 linear opto, what a pita.

6N135 is not a good choice for SMPS feedback control imo. Why not use a device
which is designed and recognised for this application?
http://www.datasheetcatalog.org/datasheet/nec/PS2561-1-V.pdf

Another commonly used OC for f/b control in SMPS is the Sharp PC817 series.
There are others as well.
http://sharp-world.com/products/device/lineup/data/pdf/datasheet/pc817x_e.pdf

Maybe it's due to being a newbie at smps design, but it was taking too
much time for me to model an opto.
For example, I'd like to see a bode plot of those optos in spice.

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design

Jim Thompson · Feb 28, 2009

On Sat, 28 Feb 2009 09:52:12 -0800, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Jim Thompson wrote:
On Fri, 27 Feb 2009 16:11:49 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Thu, 26 Feb 2009 19:40:45 -0800, D from BC
myrealaddress@comic.com> wrote:

I've seen a few schematics of opto's being used in linear mode for
smps designs..
But what about those digital isolators? Are they just for digital
circuits?

Right now I'm working on applying a digital isolator for a smps
design..
http://focus.ti.com/lit/ds/symlink/iso721.pdf
Note that the datasheet doesn't mention smps applications. hmmm

Anybody know some design examples of smps's using digital isolators
(opto digital, galvanic, GMR or RF)?

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design
I use both in switching power supplies. The analog opto for voltage
feedback, the digital isolator (Analog Devices ADuM1200 series) for
setting power supply voltage.

Three bucks for an isolator in a switcher? Yikes.

Spricht so "El Cheapo" Joerg ;-)

Si, puedo construir una placa de circuito para todo con eso

Con "queso" ?

Martin Riddle · Feb 28, 2009

"Richard Henry" <pomerado@hotmail.com> wrote in message
news:15a19e14-5b29-4ccb-92cb-167d7af45bc6@x29g2000prf.googlegroups.com...

On Feb 27, 9:15 pm, Robert Baer <robertb...@localnet.com> wrote:
Martin Brown wrote:
Robert Baer wrote:

** Copied from an investment newsletter **

Chalk one up for dissent. Japanese scientists were smart enough to
find the fraud in the anthropogenic global warming hypothesis and
then
had the balls to publicly disagree with the UN's Intergovernmental
Panel on Climate Change about it.

The Japan Society of Energy and Resources issued a report that
says
global warming is related to solar activity, and the rise in
global
temperatures was primarily a recovery from the so-called Little
Ice
Age, which lasted from 1400 to 1800. Kanya Kusano, program
director
for the Earth simulator at the Japan Agency for Marine-Earth
Science &
Technology, says computer climate modeling used to support the
manmade
global warming theory is like "ancient astrology."

If you think fraudulent climate science doesn't affect you
financially, you may wish to know that, according to The Politico,
there are now four climate change lobbyists for every member of
Congress.

And we all know that the ethical standards of bankers and
investment
advisers are beyond reproach so it must be true...

Japanese science can be pretty flaky. They still have people
researching
Fleschmann and Pons style "cold fusion" and watching catfish to try
and
predict earthquakes. Some of it is good but by no means all.

The society for "Energy and Resources" sounds very much like a
fossil
fuel lobby group. AGW really only began to bite in the past 4
decades.
The bounce back from the Little Ice Age was over by then.

Regards,
Martin Brown

FYI, cold fusion has been verified and proven to be an alternate
approach to energy generation.
A lot cheaper and smaller than a Tokomak in the back yard...
**

????

Really? That is news. Tell us more.

It does seem to be alive an well.

http://home.netcom.com/~storms2/

I could not find the article but the US government research did prove
that there is a net engery gain in their experiements.

Cheers

qrk · Feb 28, 2009

On Fri, 27 Feb 2009 18:22:52 -0800, D from BC
<myrealaddress@comic.com> wrote:

On Fri, 27 Feb 2009 16:11:49 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Thu, 26 Feb 2009 19:40:45 -0800, D from BC
myrealaddress@comic.com> wrote:

I've seen a few schematics of opto's being used in linear mode for
smps designs..
But what about those digital isolators? Are they just for digital
circuits?

Right now I'm working on applying a digital isolator for a smps
design..
http://focus.ti.com/lit/ds/symlink/iso721.pdf
Note that the datasheet doesn't mention smps applications. hmmm

Anybody know some design examples of smps's using digital isolators
(opto digital, galvanic, GMR or RF)?

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design

I use both in switching power supplies. The analog opto for voltage
feedback, the digital isolator (Analog Devices ADuM1200 series) for
setting power supply voltage.

Three bucks for an isolator in a switcher? Yikes.

Relative to sluggish optos, the galvanic ISO721 is not cheap.
Probably the only reason I'm using it is to dodge modelling a fast
opto in ltspice.
Another reason I'm dodging a linear opto is that my smps design is
experimental and a poorly applied opto may cause loop stability
problems. If anything goes wrong, I can't blame an opto if it's not
there.

It's a tradeoff.. So the parts are expensive, but I get the design
done earlier.

A linear opto in the feedback loop is plenty fast enough. I'm using a
PS2801-1, about $0.40 in quantity, in a 50W, 600 kHz switcher. It's
almost trival to use an opto. Programmable shunt regulators like the
LMV431 are about $0.20.

--
Mark

qrk · Feb 28, 2009

On Fri, 27 Feb 2009 16:11:49 -0800, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Thu, 26 Feb 2009 19:40:45 -0800, D from BC
myrealaddress@comic.com> wrote:

I've seen a few schematics of opto's being used in linear mode for
smps designs..
But what about those digital isolators? Are they just for digital
circuits?

Right now I'm working on applying a digital isolator for a smps
design..
http://focus.ti.com/lit/ds/symlink/iso721.pdf
Note that the datasheet doesn't mention smps applications. hmmm

Anybody know some design examples of smps's using digital isolators
(opto digital, galvanic, GMR or RF)?

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design

I use both in switching power supplies. The analog opto for voltage
feedback, the digital isolator (Analog Devices ADuM1200 series) for
setting power supply voltage.

Three bucks for an isolator in a switcher? Yikes.

Price isn't an issue since this is a low volume item and the sensor it
goes into sells for >$100k. Plus, the size of the solution is small so
it fits nicely on our board. BTW, the ADuM1200 is under $2.

Jon Kirwan · Feb 28, 2009

On Sat, 28 Feb 2009 12:12:12 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote:

On Sat, 28 Feb 2009 09:52:12 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Jim Thompson wrote:
On Fri, 27 Feb 2009 16:11:49 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Thu, 26 Feb 2009 19:40:45 -0800, D from BC
myrealaddress@comic.com> wrote:

I've seen a few schematics of opto's being used in linear mode for
smps designs..
But what about those digital isolators? Are they just for digital
circuits?

Right now I'm working on applying a digital isolator for a smps
design..
http://focus.ti.com/lit/ds/symlink/iso721.pdf
Note that the datasheet doesn't mention smps applications. hmmm

Anybody know some design examples of smps's using digital isolators
(opto digital, galvanic, GMR or RF)?

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design
I use both in switching power supplies. The analog opto for voltage
feedback, the digital isolator (Analog Devices ADuM1200 series) for
setting power supply voltage.

Three bucks for an isolator in a switcher? Yikes.

Spricht so "El Cheapo" Joerg ;-)

Si, puedo construir una placa de circuito para todo con eso

Con "queso" ?

Now that's slightly under the belt.

Jon

Joerg · Feb 28, 2009

Jim Thompson wrote:

On Sat, 28 Feb 2009 09:45:55 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Jim Thompson wrote:
On Fri, 27 Feb 2009 11:24:16 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Jim Thompson wrote:
[snip]
I'm really happy with my filters. I'll share my info with anyone
running Agent v5 (required for Message-ID filtering).

To be honest I don't want to spend time massaging exceptions all the
time. There's always PM (where I haven't set a block).
Exceptions are trivial... there aren't very many ;-)

How I work it is I notice a thread of interest, discover that the OP
was reputable, drop his name, Message-ID, or whatever, into the
exception filter... very easy.

You sure complain a lot, then whine about difficulty.

Huh? No complaints here. Filtered google-domains to bucket, spam gone.

Can you white-list good guys who use googlegroups?

Looks like you could:

http://www.neilturner.me.uk/2006/08/06/stopping_image_spam_in_th.html

But then you'd have to first collect all the garbage in a trash file,
then once in a while don the waders and sift through that. Right now I
just have it go "poof". If someone really wants my opinion on something
I guess it's not too much to ask that this poster either obtain a
reputable NG address or send me a PM (which people have done since the
time I banned the google domain).

[...]

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Joerg · Feb 28, 2009

qrk wrote:

On Fri, 27 Feb 2009 16:11:49 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Thu, 26 Feb 2009 19:40:45 -0800, D from BC
myrealaddress@comic.com> wrote:

I've seen a few schematics of opto's being used in linear mode for
smps designs..
But what about those digital isolators? Are they just for digital
circuits?

Right now I'm working on applying a digital isolator for a smps
design..
http://focus.ti.com/lit/ds/symlink/iso721.pdf
Note that the datasheet doesn't mention smps applications. hmmm

Anybody know some design examples of smps's using digital isolators
(opto digital, galvanic, GMR or RF)?

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design
I use both in switching power supplies. The analog opto for voltage
feedback, the digital isolator (Analog Devices ADuM1200 series) for
setting power supply voltage.

Three bucks for an isolator in a switcher? Yikes.

Price isn't an issue since this is a low volume item and the sensor it
goes into sells for >$100k. Plus, the size of the solution is small so
it fits nicely on our board. BTW, the ADuM1200 is under $2.

Ok, low volume apps are a different game. On many of my designs even $2
would be a small fortune.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Jon Kirwan · Feb 28, 2009

On Sat, 28 Feb 2009 19:14:08 GMT, "Martin Riddle"
<martin_rid@verizon.net> wrote:

snip
I could not find the article but the US government research did prove
that there is a net engery gain in their experiements.

At the time, I surveyed much of the following few years of attempts at
replication. There were related experiments also performed at a
nearby university, which is part of why F&P were "forced" into an
early release at the start. While no one actually was able to state
that the original experiments produced energy (who can, after all?),
and while there were energy gains from some of the replications --
most importantly from Texas A&M's pre-eminent calorimetrist, John
Bockris. However, none of them were able to demonstrate fusion above
the level of detectability. So far as I'm still aware, and I'm not
privy to secret military research obviously, there are no replicable
demonstrations of _cold fusion_ at room temperatures beyond what was
already known by physicists earlier (muon catalyzed and ion fusion,
for example.) At all. And not by "US government research" that has
been later confirmed through the weight of independent experiments.

(Bockris had had earlier 'disasters' such as a secret catalyst that
split water into hydrogen and oxygen even without energy announced
about 6 years before he "confirmed" cold fusion and a claimed material
that yielded a complete conversion of sunlight to electricity about 4
years earlier. Both were from basic errors in his research --
although Bockris, as in the case of his cold fusion experiments too,
never has acknowledged these mistakes. He was absolved a few years
later, after some further transmutation idiocy, by a four-professor
panel for violating Texas A&M standards in proposing, conducting or
reporting controversial research.)

Jon

Jim Thompson · Feb 28, 2009

On Sat, 28 Feb 2009 20:30:37 GMT, Jon Kirwan
<jonk@infinitefactors.org> wrote:

On Sat, 28 Feb 2009 12:12:12 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote:

On Sat, 28 Feb 2009 09:52:12 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Jim Thompson wrote:
On Fri, 27 Feb 2009 16:11:49 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Thu, 26 Feb 2009 19:40:45 -0800, D from BC
myrealaddress@comic.com> wrote:

I've seen a few schematics of opto's being used in linear mode for
smps designs..
But what about those digital isolators? Are they just for digital
circuits?

Right now I'm working on applying a digital isolator for a smps
design..
http://focus.ti.com/lit/ds/symlink/iso721.pdf
Note that the datasheet doesn't mention smps applications. hmmm

Anybody know some design examples of smps's using digital isolators
(opto digital, galvanic, GMR or RF)?

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design
I use both in switching power supplies. The analog opto for voltage
feedback, the digital isolator (Analog Devices ADuM1200 series) for
setting power supply voltage.

Three bucks for an isolator in a switcher? Yikes.

Spricht so "El Cheapo" Joerg ;-)

Si, puedo construir una placa de circuito para todo con eso

Con "queso" ?

Now that's slightly under the belt.

Jon

480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

With all this hope and change, all you need is a dab of mayonaisse
and you'll have a tasty lunch on which you will choke to death.

Jon Kirwan · Feb 28, 2009

On Sat, 28 Feb 2009 13:53:40 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote:

On Sat, 28 Feb 2009 20:30:37 GMT, Jon Kirwan
jonk@infinitefactors.org> wrote:

On Sat, 28 Feb 2009 12:12:12 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote:

On Sat, 28 Feb 2009 09:52:12 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Jim Thompson wrote:
On Fri, 27 Feb 2009 16:11:49 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Thu, 26 Feb 2009 19:40:45 -0800, D from BC
myrealaddress@comic.com> wrote:

I've seen a few schematics of opto's being used in linear mode for
smps designs..
But what about those digital isolators? Are they just for digital
circuits?

Right now I'm working on applying a digital isolator for a smps
design..
http://focus.ti.com/lit/ds/symlink/iso721.pdf
Note that the datasheet doesn't mention smps applications. hmmm

Anybody know some design examples of smps's using digital isolators
(opto digital, galvanic, GMR or RF)?

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design
I use both in switching power supplies. The analog opto for voltage
feedback, the digital isolator (Analog Devices ADuM1200 series) for
setting power supply voltage.

Three bucks for an isolator in a switcher? Yikes.

Spricht so "El Cheapo" Joerg ;-)

Si, puedo construir una placa de circuito para todo con eso

Con "queso" ?

Now that's slightly under the belt.

Jon

My wife makes a marvelous chili con queso dip, definitely under the
belt ;-)

Well, that's an entirely different, and sometimes tasty, thing.

(Although I'm not sure how I'd feel having my work compared to it.)

Red or green chiles, more yellow or more white cheeses?

Jon

Feb 28, 2009

Bit Farmer wrote:

krw wrote:
In article <go9hfm$k3u$1@localhost.localdomain>,
ruffrecords@yahoo.com says...
Bit Farmer wrote:
I just canceled my SuperNews subscription. Seems there are not many
free readers around. Times are tough and it makes little sense to pay
for access to what is written here. I rarely post anyway. That leaves
Google for reading. So be it.

Most ISPs these days provide newsnet access for free. Mine has done for
the last 10 years.

Several are shutting them down.

We just switched corporate T1 providers. Our new provider does not support newsgroups.
For that matter, our old ISP did not support them either, which is why I used SuperNews.
The point was that I can still read the group for free via Google Groups. Since I rarely
post, it was just not worth $ 3.95 a month for to post through SuperNews. Minor news.

Since this account is paid for one more day, let me ask the obvious: Why is posting from
Google Groups so bad? What do they do (aside from a worthless user interface) that lowers
my status to scum of the earth? Seriously, I do not know and would like an honest straight
forward answer.

b. farmer.

You're lucky to have a choice. I dream of having a working newsfeed!.
No choice other than this Googlegroup thing.

Jim Thompson · Feb 28, 2009

On Sat, 28 Feb 2009 21:03:55 GMT, Jon Kirwan
<jonk@infinitefactors.org> wrote:

On Sat, 28 Feb 2009 13:53:40 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote:

On Sat, 28 Feb 2009 20:30:37 GMT, Jon Kirwan
jonk@infinitefactors.org> wrote:

On Sat, 28 Feb 2009 12:12:12 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote:

On Sat, 28 Feb 2009 09:52:12 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Jim Thompson wrote:
On Fri, 27 Feb 2009 16:11:49 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Thu, 26 Feb 2009 19:40:45 -0800, D from BC
myrealaddress@comic.com> wrote:

I've seen a few schematics of opto's being used in linear mode for
smps designs..
But what about those digital isolators? Are they just for digital
circuits?

Right now I'm working on applying a digital isolator for a smps
design..
http://focus.ti.com/lit/ds/symlink/iso721.pdf
Note that the datasheet doesn't mention smps applications. hmmm

Anybody know some design examples of smps's using digital isolators
(opto digital, galvanic, GMR or RF)?

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design
I use both in switching power supplies. The analog opto for voltage
feedback, the digital isolator (Analog Devices ADuM1200 series) for
setting power supply voltage.

Three bucks for an isolator in a switcher? Yikes.

Spricht so "El Cheapo" Joerg ;-)

Si, puedo construir una placa de circuito para todo con eso

Con "queso" ?

Now that's slightly under the belt.

Jon

My wife makes a marvelous chili con queso dip, definitely under the
belt ;-)

Well, that's an entirely different, and sometimes tasty, thing.
(Although I'm not sure how I'd feel having my work compared to it.)

Red or green chiles, more yellow or more white cheeses?

Jon

480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

The first sign of senility is persistently trying to be an asshole

The second sign of senility is touting your company's wonderful
circuit designs as your own, while posting amateur crap on S.E.D

D from BC · Feb 28, 2009

On Sat, 28 Feb 2009 19:39:53 GMT, qrk <SpamTrap@spam.net> wrote:

On Fri, 27 Feb 2009 18:22:52 -0800, D from BC
myrealaddress@comic.com> wrote:

On Fri, 27 Feb 2009 16:11:49 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Thu, 26 Feb 2009 19:40:45 -0800, D from BC
myrealaddress@comic.com> wrote:

I've seen a few schematics of opto's being used in linear mode for
smps designs..
But what about those digital isolators? Are they just for digital
circuits?

Right now I'm working on applying a digital isolator for a smps
design..
http://focus.ti.com/lit/ds/symlink/iso721.pdf
Note that the datasheet doesn't mention smps applications. hmmm

Anybody know some design examples of smps's using digital isolators
(opto digital, galvanic, GMR or RF)?

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design

I use both in switching power supplies. The analog opto for voltage
feedback, the digital isolator (Analog Devices ADuM1200 series) for
setting power supply voltage.

Three bucks for an isolator in a switcher? Yikes.

Relative to sluggish optos, the galvanic ISO721 is not cheap.
Probably the only reason I'm using it is to dodge modelling a fast
opto in ltspice.
Another reason I'm dodging a linear opto is that my smps design is
experimental and a poorly applied opto may cause loop stability
problems. If anything goes wrong, I can't blame an opto if it's not
there.

It's a tradeoff.. So the parts are expensive, but I get the design
done earlier.

A linear opto in the feedback loop is plenty fast enough. I'm using a
PS2801-1, about $0.40 in quantity, in a 50W, 600 kHz switcher. It's
almost trival to use an opto. Programmable shunt regulators like the
LMV431 are about $0.20.

Maybe I'll go back and try again to model an opto.

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design

D from BC · Feb 28, 2009

On Sat, 28 Feb 2009 12:48:28 -0800, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Fri, 27 Feb 2009 16:11:49 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Thu, 26 Feb 2009 19:40:45 -0800, D from BC
myrealaddress@comic.com> wrote:

I've seen a few schematics of opto's being used in linear mode for
smps designs..
But what about those digital isolators? Are they just for digital
circuits?

Right now I'm working on applying a digital isolator for a smps
design..
http://focus.ti.com/lit/ds/symlink/iso721.pdf
Note that the datasheet doesn't mention smps applications. hmmm

Anybody know some design examples of smps's using digital isolators
(opto digital, galvanic, GMR or RF)?

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design
I use both in switching power supplies. The analog opto for voltage
feedback, the digital isolator (Analog Devices ADuM1200 series) for
setting power supply voltage.

Three bucks for an isolator in a switcher? Yikes.

Price isn't an issue since this is a low volume item and the sensor it
goes into sells for >$100k. Plus, the size of the solution is small so
it fits nicely on our board. BTW, the ADuM1200 is under $2.

Ok, low volume apps are a different game. On many of my designs even $2
would be a small fortune.

In my case, fast design time trumps expensive parts. My product idea
may flop. All the time put into making the design cheap could be
wasted.
If the product doesn't flop, then the pcb can be cost optimized.
Also, the product volume is low and each unit sells for about $700.00
.... A couple of extra bucks on expensive parts is ok at this time..

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design

D from BC · Feb 28, 2009

On Sat, 28 Feb 2009 09:55:41 -0800, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

D from BC wrote:
On Fri, 27 Feb 2009 16:11:49 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Thu, 26 Feb 2009 19:40:45 -0800, D from BC
myrealaddress@comic.com> wrote:

I've seen a few schematics of opto's being used in linear mode for
smps designs..
But what about those digital isolators? Are they just for digital
circuits?

Right now I'm working on applying a digital isolator for a smps
design..
http://focus.ti.com/lit/ds/symlink/iso721.pdf
Note that the datasheet doesn't mention smps applications. hmmm

Anybody know some design examples of smps's using digital isolators
(opto digital, galvanic, GMR or RF)?

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design
I use both in switching power supplies. The analog opto for voltage
feedback, the digital isolator (Analog Devices ADuM1200 series) for
setting power supply voltage.

Three bucks for an isolator in a switcher? Yikes.

Relative to sluggish optos, the galvanic ISO721 is not cheap.
Probably the only reason I'm using it is to dodge modelling a fast
opto in ltspice.

Sluggish? How fast do you need it to be? I haven't seen loops much past
a couple hundred kHz in switcher.

True.
For my design, it only needs loop gain less than 10khz. Alls fine in
that case if I use an optoisolator to feedback the output voltage.
But if I change the design to use a digital isolator, I have to use
something really fast since my PWM is at 1Mhz.
Optos are sluggish in a digital role compared to the other isolation
methods (GMR, galvanic etc..)
I've never seen a digital isolator used in an smps design. Only
linear.

Another reason I'm dodging a linear opto is that my smps design is
experimental and a poorly applied opto may cause loop stability
problems. If anything goes wrong, I can't blame an opto if it's not
there.

It's a tradeoff.. So the parts are expensive, but I get the design
done earlier.

scratching head

I had used optos up to 10Mb/sec, no problem. The only reason I kicked
some out and replaced them with signal transformers was because the
signal transformers were multi-sourceable and 5c cheaper back then. That
has changed though.

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design

Charles · Feb 28, 2009

"Robert Baer" <robertbaer@localnet.com> wrote in message
news:_5adnaBD9I6METrUnZ2dnUVZ_rvinZ2d@posted.localnet...

** Copied from an investment newsletter **

Chalk one up for dissent.

Chalk one up for mining for specious data.

Here is what is actually happening:

http://www.sciam.com/article.cfm?id=risks-of-global-warming-rising

Cold fusion is over; forget about it.

Joerg · Mar 1, 2009

D from BC wrote:

On Sat, 28 Feb 2009 09:55:41 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

D from BC wrote:
On Fri, 27 Feb 2009 16:11:49 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Thu, 26 Feb 2009 19:40:45 -0800, D from BC
myrealaddress@comic.com> wrote:

I've seen a few schematics of opto's being used in linear mode for
smps designs..
But what about those digital isolators? Are they just for digital
circuits?

Right now I'm working on applying a digital isolator for a smps
design..
http://focus.ti.com/lit/ds/symlink/iso721.pdf
Note that the datasheet doesn't mention smps applications. hmmm

Anybody know some design examples of smps's using digital isolators
(opto digital, galvanic, GMR or RF)?

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design
I use both in switching power supplies. The analog opto for voltage
feedback, the digital isolator (Analog Devices ADuM1200 series) for
setting power supply voltage.

Three bucks for an isolator in a switcher? Yikes.
Relative to sluggish optos, the galvanic ISO721 is not cheap.
Probably the only reason I'm using it is to dodge modelling a fast
opto in ltspice.

Sluggish? How fast do you need it to be? I haven't seen loops much past
a couple hundred kHz in switcher.

True.
For my design, it only needs loop gain less than 10khz. Alls fine in
that case if I use an optoisolator to feedback the output voltage.
But if I change the design to use a digital isolator, I have to use
something really fast since my PWM is at 1Mhz.
Optos are sluggish in a digital role compared to the other isolation
methods (GMR, galvanic etc..)
I've never seen a digital isolator used in an smps design. Only
linear.

I just never saw a compelling reason to use any fancy isolators. One of
my staples for very high isolation and where cost is warranted is the
CNW137 widebody:

http://www.avagotech.com/docs/AV02-0940EN

Rise/fall times in the 25nsec range, how much more would you want?

[...]

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Joerg · Mar 1, 2009

qrk wrote:

On Fri, 27 Feb 2009 18:22:52 -0800, D from BC
myrealaddress@comic.com> wrote:

On Fri, 27 Feb 2009 16:11:49 -0800, Joerg
notthisjoergsch@removethispacbell.net> wrote:

qrk wrote:
On Thu, 26 Feb 2009 19:40:45 -0800, D from BC
myrealaddress@comic.com> wrote:

I've seen a few schematics of opto's being used in linear mode for
smps designs..
But what about those digital isolators? Are they just for digital
circuits?

Right now I'm working on applying a digital isolator for a smps
design..
http://focus.ti.com/lit/ds/symlink/iso721.pdf
Note that the datasheet doesn't mention smps applications. hmmm

Anybody know some design examples of smps's using digital isolators
(opto digital, galvanic, GMR or RF)?

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design
I use both in switching power supplies. The analog opto for voltage
feedback, the digital isolator (Analog Devices ADuM1200 series) for
setting power supply voltage.

Three bucks for an isolator in a switcher? Yikes.
Relative to sluggish optos, the galvanic ISO721 is not cheap.
Probably the only reason I'm using it is to dodge modelling a fast
opto in ltspice.
Another reason I'm dodging a linear opto is that my smps design is
experimental and a poorly applied opto may cause loop stability
problems. If anything goes wrong, I can't blame an opto if it's not
there.

It's a tradeoff.. So the parts are expensive, but I get the design
done earlier.

A linear opto in the feedback loop is plenty fast enough. I'm using a
PS2801-1, about $0.40 in quantity, in a 50W, 600 kHz switcher. It's
almost trival to use an opto. Programmable shunt regulators like the
LMV431 are about $0.20.

If you use a TL431 you can shave off another $0.15

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Driver to drive?

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