DC-DC converter for a small boost

(snip)

I thought that was de rigeur for switcher cores. I know I've ALWAYS done it that way. I must have picked up the habit - and the rationale behind it - a very long time ago.

Hi Mr. J Nope, havent had a chance, MPEGs Ok if nothing moves while the camera is running, same for audio. The Camcorder audio domain is somewhat dire see what can be done with a semipro camcorder

I'm sort of retired from that biz for some years, and being over 50, fat chance of work, the rates are shit, thanks to Big Bruvver etc.

I'll stick to the C++ of audio, NE5534, (TM)

martin

There are some very nice self shielded surface mount inductors (a drum core with a ferrite surround with a thin gap between) being manufactured that give the toroids a run for their money and size.

I like the Sumida CDRH127/LD series and Coiltronics DR127 series.

Hello Budgie,

Depends on space. I did have to stand a few of them. Just make sure they can never get too toasty for whatever foam is being used.

Regards, Joerg

Hello John,

Yes, I have designed in quite a few Sumida shielded cores. For hi-rel stuff one has to test the heck out of such core types though. I have had shielded inductors shed part of their core on occasion. It was not a pretty sight.

Regards, Joerg

Hello Martin,

I don't know how it is over there in Espana but in the US I believe there is quite a market for A/V specialists. Lots of churches with elaborate gear but often there is nobody who maintains it well and they more or less wing it. We are lucky that we have a few electronics guys in ours but that isn't the case for otehrs.

Regards, Joerg

Under what conditions? I assume that the 3 parts of ferrite and the terminals are all held together with epoxy.

Hello John,

Rapid temperature changes and mechanical stress. Imagine a 50 year old truck thundering down a dirt road that looks like corrugated steel laid sideways. Rat-tat-tat. Anything that's not DOA after a few hundred miles is a good design. Before I bought a car I checked out the failure rates during the Paris-Dakar Rallye ;-)

Regards, Joerg

A push-pull half-bridge with AC coupling to the transformer neatly satisfies those requirements, because it results in a tidy 5v to 2.5+2.5v autotransformer, possibly on a toroid.

It doesn't solve the OP's underlying problem of proper filtering and screening though.

At 120 MHz perhaps he should be thinking of picking some of the bypass caps for series resonance...probably around 1.2nF, I'd guess, assuming SMD but depending somewhat on the size.

Steve

Actually that rang a bell, so I checked the BOM on a job two years back.

Sumida CDRH124-220

Yep, cute little beasties - but plagued by MOQ for small run jobs. We were having to order 150 pcs.

Hello Steve,

It's not that bad. I usually even forego the 3.3nF and live with 0.1uF throughout. Most brands are pretty good up to a few hundred MHz if you don't mess up the layout.

Regards, Joerg

Hello Budgie,

But it's only around a buck fifty a pop. That MOQ looks quite reasonable. I mean, you don't go to the butcher and order two and a half slices of peperoni.

Dikigey has the 127 series. But I found that when producing in China a custom made toroid solution can be more cost efficient, although maybe not quite as small as the Sumidas. Also, be careful with washing. Some of them don't like that.

Regards, Joerg

Hello Tony,

Yes, but a core without air gap often "talks less".

Regards, Joerg

That's correct, but we were trying for a pre-prod batch of about 20 boards. The local (.au) distributor actually sent us 25 samples to use in that first batch. A couple of prod batches later, the lot went offshore.

In article , Joerg wrote: [...]

I've never had a pot core come apart in a finshed product. This include stuff on trucks and aircraft and that includes aircraft that have crashed. How are you holding them together?

I have seen to toroid fail in a man carried situation, however. The product go run over by a truck. The person did not get run over BTW.

In article , John Popelish wrote: [...]

Those are really only sort of shielded. They leak magnetic fields out their ends. The same applies to them as I suggested about the DS5022 series. You want to put a largish conductive object above and below them to block the RF.

I agree that they are only mostly magnetically shielded. They still have a bit of magnetic dipole field. But they have weaker E-field patterns than a toroid does, because the winding is smaller and more buried, internally.

Hello Ken,

With the hardware specified and delivered by the core mfg. Usually springy clamps.

I also saw toroids that got chipped but that was in situations like yours, where the functionality of that toroid would not matter anymore.

Regards, Joerg