available toroids

Hul Tytus · 2020-01-17T15:10:44+00:00

I've been looking for a toroid with a cross section area (one side) of probably 2 or 3 square centimeters and an id of about 10 or 12 mm. The intended inductor is about 14 micro henries and will handle between 40 to 80 amps in a flyback power supply at, again probably, 100 kc. Fair-Rite, Micrometals, and Magnetics show, at the desired id, cross sections typically less than 1 sqcent. Greater cross sections show greater id's and consequently greater lengths. These toroids would result in windings using only a portion of available space with the rest of the toroid doing nothing but dissipating power. Anyone know of some suppliers that have the bulky type of toroids that are required in this case? Or, perhaps, another approach to limit the dissipation? Hul

Jan 17, 2020 26 Replies

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Bill Sloman 6 years ago

TDK took over the Siemens EPCOS ferrite range, which always struck me as of fering better value the Mullard/Philips/Ferrocube range. Siemens certainly had better application notes - Miullard's E.C.Snelling might have known a lot but he wans't good at making his knowledge accessible.

2Fsearch

Mouser does a 50x25mm half core

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You might have to dig harder and find a specialist ferrite supplier to get something bigger.

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is a supplier I've used for prototype quantities, but they do seem to be a Ferrocube shop.

Bill Sloman, Sydney

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Piotr Wyderski 6 years ago

OTOH, the charger should be phase factor corrected, which implies a similarly sized inductor for a boost converter. If the output current doesn't need to be constant, but abs(sin(t)) is sufficient, the PFC could be integrated with the flyback stage.

Bumping up the switching frequency from 100kHz to 1MHz, replacing the switch with a SiC device and selecting a multiphase flyback topology might in fact work with a low-loss ferrite "transformer" on, say, 3C95.

Best regards, Piotr

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Bill Sloman 6 years ago

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lists a bunch of higher frequency ferrites. 3C95 is listed as good to about 0.5MHz. 3F4 gets up to about 2MHz.

Bill Sloman, Suydney

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Piotr Wyderski 6 years ago

3C95/N95 is a super low loss ferrite, which is good for a wide B swing topology like the flyback. I would design this power stage around the FoM of the ferrite, whatever the switching frequency might turn out to be.

Best regards, Piotr

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Hul Tytus 6 years ago

You may be right. I'll keep you informed.

Hul

Sergey Kubushyn wrote:

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Hul Tytus 6 years ago

Thanks for the links, Bill. Mouser would be a handy avenue of supply.

Hul

Bill Sloman wrote:

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Hul Tytus 6 years ago

Piotr - "super low loss" does catch the eye at present. I'll take a look in hopes a toroid of that mix would fit, numbers wise.

Hul

Piotr Wyderski wrote:

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