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Old 10th December 2007, 11:29 PM   #1
Tolik is offline Tolik  Israel
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Question Anybody used these ferrite cores ?

Hello,

I found some ferrite toroids at ebay. Anybody used them for SMPS ?
Are they preforming well ?
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Old 28th December 2007, 07:42 AM   #2
Serge66 is offline Serge66  Switzerland
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Hi,
We normally use E-shaped cores.
Toroids are difficult to wind. And would only be useful for small power smps. The bars are mostly used for antenna.
Have a look on EPCOS website. There is another manufacturer, but I am having a brain freeze.
Cheers.
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Old 28th December 2007, 10:25 AM   #3
Eva is offline Eva  Spain
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Ferrite toroid transformers are useful sometimes, for example in 12V (or 24V) powered high-current applications where no mains isolation is required.

Concerning this ebay offer, I would ask the seller about the manufacturer and the material of the cores (and also wether they are coated or not) before buying. Knowing only that permeability is 2000 is very little data.
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Old 28th December 2007, 08:41 PM   #4
Tolik is offline Tolik  Israel
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Hi Eva,

I contacted the seller... He told that it`s russian made ferrite toroids.
Due to m=2000, it`s should to be 2000HM or 2000HH ferrite - very poor quality , & unstable materials. (I was living in ex USSR for 19 years, so I have some expirience with russian made parts)
I found better supplier at Amidon website. In addition to their own cores they are selling a lot of other brands like EPCOS, Magnetics, TDK, Fair-Rite etc. Their 77 and F materians are seems to be intresting. Their prices & shipping rates are very resonable. I ordered some toroids to try them out ...


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Old 28th December 2007, 10:38 PM   #5
Eva is offline Eva  Spain
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Hey! Amidon has estabilished an online store!! These are very good news
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Old 28th December 2007, 10:43 PM   #6
Tolik is offline Tolik  Israel
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Farnell added a lot of cores from Epcos N87 & N97,FERROXCUBE 3C90 high power materials.

Also look here http://www.cwsbytemark.com/prices/toroidal.php
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Old 30th December 2007, 04:15 PM   #7
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Quote:
Originally posted by Tolik
........I found better supplier at Amidon website....... Their 77 and F materians are seems to be intresting. Their prices & shipping rates are very resonable. I ordered some toroids to try them out ...

HAVE GREAT HOLIDAYS GUYS !!!
Tolik-

I have used the Amidon #77 Ferrite toroids with excellent results in both 12V input DC-DC and off-line AC-DC supplies. Regarding off-line, toroids should NOT be used if there is a high primary-to-secondary turns ratio (like 38 : 2 for 5V outputs). I use these numbers based on my calculations for my particular application. Of course, they are material- and frequency-dependent. Toroids are much better suited for lower ratios, like 38 : (8+8), or similar, where the secondary windings can easily cover the entire core. Also, it is a good idea to wind half the primary, tape, secondaries, tape, and then second half of primary. This will ensure good pri-sec magnetic coupling.

For powdered-iron toroids, the big yellow one in almost every AT/ATX psu is the #26 material. I have ordered these from Amidon in a variety of sizes: 50, 68, 80, 94, 106, and 130 sizes.

Steve
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Old 30th December 2007, 04:42 PM   #8
Tolik is offline Tolik  Israel
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Hi Steve,

Thank you for sharing your experience.
I know about magnetic leakage losses problem. I wont to try to design
one small SMPS for my digital soldering station project, and one powerfull DC DC for car amp. For offline SMPS I ordered EA 77 500 E-type core, & for DC-DC 2 toroids made from 77 & F materials. Will see them soon.
By the way , I have some MOSFETS : IRFP460 for offline, - should be good for 100W SMPS, and IRF3205 or STP80NF06 for DC- DC.
What is your suggestion for Car amp SMPS - IRF or STP ?

sorry for my English
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Old 31st December 2007, 01:15 AM   #9
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Definitely IRF. International Rectifier has extremely high quality, and I trust it implicitly. '460s, huh? These are hefty MOSFETs. I still have a rail of old MTW20N50Es, (500V 20A), the Motorola equivalent to the IRFP460. Sadly, ONSemi (Motorola's spin-off) no longer makes any MOSFETS above 200Vdss.

The IRF3205 is a very good choice for your car amp. Parallel a few of these for the DC-DC section, and you're ready to rock-n-roll. For rectifiers, I have used 4 of either the MBR20200CT (200PIV, 20A Common-Anode Schottky), or the MUR1520, or the MUR1620CT (+), and MUR1620CTR (-). Using the complimentary '1620 pair yielded a (+) rail about 600mV higher in magnitude than the (-) rail. I recommend using the MUR1620CT & -CTR only if space is at a premium, otherwise, go with four individual diodes. As for the Schottkys, I use these because of their lower forward drop. A few percentage points better in efficiency, I think.
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Old 31st December 2007, 03:28 PM   #10
Tolik is offline Tolik  Israel
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I agree, IR is my favorite power MOSFET`s manufacturer.
But I still intresting about STP80NF06. If somebody tried, share your experience please.

Quote:
For rectifiers, I have used 4 of either the MBR20200CT (200PIV, 20A Common-Anode Schottky), or the MUR1520, or the MUR1620CT (+), and MUR1620CTR (-). Using the complimentary '1620 pair yielded a (+) rail about 600mV higher in magnitude than the (-) rail. I recommend using the MUR1620CT & -CTR only if space is at a premium, otherwise, go with four individual diodes. As for the Schottkys, I use these because of their lower forward drop. A few percentage points better in efficiency, I think.
What about IR diodes, I mean HFA25PB60 HEXFRED or same diodes with soft recovery? HEXFRED`s from IXYS are also seems to be intresting...
Today I recived my order from Amidon - 3 cores. Packed very well to prevent damage during shipping.
I found some datasheet about amidon`s stuff. It`s 19mB .pdf file, so if anybody intresting I can to shot it by email...

HAPPY NEW YEAR !!!
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