| Author |
Message |
Watson A.Name - \"Watt Su
Guest
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 Posted:
Thu Apr 07, 2005 3:10 am Post subject:
Re: Toroid Core for LED V Boost |
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"Jim Thompson" <thegreatone@example.com> wrote in message
news:nsm85154bj01k0tntqm0p2e7v8e7ljj89k@4ax.com...
| Quote: | On Wed, 06 Apr 2005 21:31:21 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:
Hello Jim,
Toroids are treacherous unless you can guarantee perfect balance...
any DC is death... that's why, back in the days when I was SMPSing,
I
preferred pot cores (or E-I, or E-E) WITH air-gaps.
Yes, and that is a fairly little understood subject among engineers.
A
saturated core behaves almost as if it wasn't there.
Most of the switchers I designed have a current mode loop which will
prevent such catastrophes. But I have seen designs without it that
were
uncomfortably close to CCM. From there to kablouie it can be as
little
as a few milliseconds. The resulting fireworks are usually quite
impressive.
Regards, Joerg
http://www.analogconsultants.com
"kablouie" reminds of another fun event in my life...
One of the first off-line switchers I was designing (for
OmniComp/GenRad, ~1978) was of great interest to marketing, because it
would significantly decrease the weight of their portable tester
concept, called the PSP (Portable Service Processor).
So all these marketing clowns come trooping into my laboratory when
they got wind that I was testing it.
So they crowd around my workbench.
I warn them that it's not been powered up before and they should stand
back.
They ignore me.
I plug it in.
KABLOUIE!
Flame blew out of the (ferrite) transformer, then it burned back along
the line cord, back toward the receptacle, in a way reminiscent of the
way you see bomb fuses burn, before the breaker finally let go.
After the marketing types regained their skin color, they accused me
of setting the whole thing up to scare them ;-)
|
Any of them wet their pants?? ;-)
You gave them a demonstration of why the dept's high R&D budget is
justified.
| Quote: | ...Jim Thompson
-- |
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Michael A. Terrell
Guest
|
| Posted:
Thu Apr 07, 2005 6:10 am Post subject:
Re: Toroid Core for LED V Boost |
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John Woodgate wrote:
| Quote: |
They would interpret the incident as showing that the department was
staffed by dangerous incompetents and should be closed down immediately.
|
Marketing, or R&D? ;-)
--
Former professional electron wrangler.
Michael A. Terrell
Central Florida |
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John Woodgate
Guest
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| Posted:
Thu Apr 07, 2005 6:10 am Post subject:
Re: Toroid Core for LED V Boost |
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I read in alt.binaries.schematics.electronic that "Watson A.Name -
\"Watt Sun, the Dark Remover\"" <NOSPAM@dslextreme.com> wrote (in
<115965dgmcden0f@corp.supernews.com>) about 'Toroid Core for LED V
Boost', on Wed, 6 Apr 2005:
| Quote: | You gave them a demonstration of why the dept's high R&D budget is
justified.
|
They would interpret the incident as showing that the department was
staffed by dangerous incompetents and should be closed down immediately.
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
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Watson A.Name - \"Watt Su
Guest
|
| Posted:
Thu Apr 07, 2005 9:10 am Post subject:
Re: Toroid Core for LED V Boost |
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"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> wrote in message
news:zw4YkWB6YMVCFweN@jmwa.demon.co.uk...
| Quote: | I read in alt.binaries.schematics.electronic that "Watson A.Name -
\"Watt Sun, the Dark Remover\"" <NOSPAM@dslextreme.com> wrote (in
115965dgmcden0f@corp.supernews.com>) about 'Toroid Core for LED V
Boost', on Wed, 6 Apr 2005:
You gave them a demonstration of why the dept's high R&D budget is
justified.
They would interpret the incident as showing that the department was
staffed by dangerous incompetents and should be closed down
immediately. |
Something in there about biting the hand that feeds it, I think.
Flickin' marketing types think they're god's greatest gift to mankind.
but they wouldn't be there if it wasn't for the engineering types.
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Guest
|
| Posted:
Thu Apr 07, 2005 3:10 pm Post subject:
Re: Toroid Core for LED V Boost |
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|
Jim Thompson wrote:
| Quote: | On Wed, 06 Apr 2005 21:31:21 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:
Hello Jim,
Toroids are treacherous unless you can guarantee perfect balance...
any DC is death... that's why, back in the days when I was SMPSing, I
preferred pot cores (or E-I, or E-E) WITH air-gaps.
Yes, and that is a fairly little understood subject among engineers. A
saturated core behaves almost as if it wasn't there.
Most of the switchers I designed have a current mode loop which will
prevent such catastrophes. But I have seen designs without it that were
uncomfortably close to CCM. From there to kablouie it can be as little
as a few milliseconds. The resulting fireworks are usually quite impressive.
Regards, Joerg
http://www.analogconsultants.com
"kablouie" reminds of another fun event in my life...
One of the first off-line switchers I was designing (for
OmniComp/GenRad, ~1978) was of great interest to marketing, because it
would significantly decrease the weight of their portable tester
concept, called the PSP (Portable Service Processor).
So all these marketing clowns come trooping into my laboratory when
they got wind that I was testing it.
So they crowd around my workbench.
I warn them that it's not been powered up before and they should stand
back.
They ignore me.
I plug it in.
KABLOUIE!
Flame blew out of the (ferrite) transformer, then it burned back along
the line cord, back toward the receptacle, in a way reminiscent of the
way you see bomb fuses burn, before the breaker finally let go.
After the marketing types regained their skin color, they accused me
of setting the whole thing up to scare them ;-)
You gotta love it! |
If you didn't set it up, you *should* have. :-)
Ed
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Guest
|
| Posted:
Thu Apr 07, 2005 3:10 pm Post subject:
Re: Toroid Core for LED V Boost |
|
|
Joerg wrote:
| Quote: | Hello Jim,
Toroids are treacherous unless you can guarantee perfect balance...
any DC is death... that's why, back in the days when I was SMPSing, I
preferred pot cores (or E-I, or E-E) WITH air-gaps.
Yes, and that is a fairly little understood subject among engineers. A
saturated core behaves almost as if it wasn't there.
Most of the switchers I designed have a current mode loop which will
prevent such catastrophes. But I have seen designs without it that
were uncomfortably close to CCM. From there to kablouie it can be as
little as a few milliseconds. The resulting fireworks are usually
quite impressive.
|
Worse might be when the insulation on the windinginside the
L melts slowly and you can't see the problem. I won't say
"give me catastrophic failure every time..." but sometimes it's
helpful to see at a glance what died.
Ed
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Jim Thompson
Guest
|
| Posted:
Thu Apr 07, 2005 3:10 pm Post subject:
Re: Toroid Core for LED V Boost |
|
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On Thu, 07 Apr 2005 14:31:26 GMT, ehsjr@bellatlantic.net wrote:
[snip]
| Quote: |
Worse might be when the insulation on the windinginside the
L melts slowly and you can't see the problem. I won't say
"give me catastrophic failure every time..." but sometimes it's
helpful to see at a glance what died.
Ed
|
I've melted a few bobbins in my day.
Finally sat down and ran the math... up to the 9th harmonic (of 20KHz)
produces a heating term due to skin effect.
Switched to Litz. With a few outputs as tape.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food. |
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Joerg
Guest
|
| Posted:
Thu Apr 07, 2005 9:10 pm Post subject:
Re: Toroid Core for LED V Boost |
|
|
Hello Jim,
| Quote: | I've melted a few bobbins in my day.
Finally sat down and ran the math... up to the 9th harmonic (of 20KHz)
produces a heating term due to skin effect.
Switched to Litz. With a few outputs as tape.
|
Quite a few are all wound as tape.
Regards, Joerg
http://www.analogconsultants.com |
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