Toroid Core for LED V Boost

[Don Klipstein]

Hello John,


This depends on the material. The switchers I designed with non-gapped
toroids ran efficiently. The normal losses were all accounted for, such
as those in the transistor, the diode, the ESR etc. but pretty much none
in the inductor. No ringing, nice linear ramps and the cores didn't get
hot. Mostly Fair-Rite stuff.

The material could have been "Ferroxcube" 4C4 or some similar low
permeability ferrite.

- Don Klipstein ([email protected])

 

[Joerg]

Hello Don,

The material could have been "Ferroxcube" 4C4 or some similar low
permeability ferrite.

Low perm wouldn't make much sense in a switcher unless it runs at
several MHz. I usually take #77 material, Kaschke K2004/2006 or similar.

Regards, Joerg

 

[Jim Thompson]

Hello Don,


Low perm wouldn't make much sense in a switcher unless it runs at
several MHz. I usually take #77 material, Kaschke K2004/2006 or similar.

Regards, Joerg

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.

...Jim Thompson

 

[Joerg]

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

 

[Jim Thompson]

Hello Jim,


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

"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 ;-)

...Jim Thompson

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

"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.

 

[John Woodgate]

I read in alt.binaries.schematics.electronic that "Watson A.Name -

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.

 

[Michael A. Terrell]

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? ;-)

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

I read in alt.binaries.schematics.electronic that "Watson A.Name -


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.

 

[[email protected]]

"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

 

[[email protected]]

Hello Jim,



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

 

[Jim Thompson]

On Thu, 07 Apr 2005 14:31:26 GMT, [email protected] wrote:
[snip]

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

 

[Joerg]

Hello Jim,

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