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Old 21st November 2004, 07:02 PM   #21
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my suggestion to you young man, is to read Sanjay Maniktala's excellent series of articles on magnetics on the National Semiconductor website -- you have specified I(max) for your design, but I(min) is also critical -- Sanjay also did a webcast for Tech OnLine which was like going back and taking that E&M cours you shouldn't have slept through in college.

you will probably find that an LC filter on the output will be helpful (in fact, it is necessary). Bigger capacitors aren't better in this type of design -- at your switching frequency the ESL kicks in.

btw, Sanjay has just written a book on Optimization of SMPS -- like all technical books this one is pretty expensive.

more coming...
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Old 22nd November 2004, 04:36 PM   #22
Lauris is offline Lauris  Lithuania
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Sorry but I don't understand in this page anything, or maybe I found some other page, search of ["National Semiconductor" website SMPS] find a lot off them. in one I can make calculations but I think that there was onle low PW power sulies (very low power, ant low voltages).

maybe I just find not a right one site, o I don't undertant something.

can u give a link to page u are talking about?
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Old 22nd November 2004, 04:46 PM   #23
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put "maniktala" in the search engine -- you may still be able to get the online seminar he did back in April.
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Old 23rd November 2004, 03:29 AM   #24
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Default Xformer Turns Question

After reviewing some literature at www.mag-inc.com and reading some other threads I am having difficulty calculating the number of primary turns the transformer should have...

toroid for car amp smps

Here are my parameters:
Vin(min) = 10 Volts
B = 1000 Gauss
Ae = 15.5 cm^2 [mag-inc PN 46113 Ferrite: 2.4inch-OD 1.4inch-ID 0.5inch-Height]
F = 40 Khz

Here is the formula I have used...
Np = (10^8*Vin(min))/(4*B*Ae*F)
where:
Vin(min) = [volts]
B = [gauss]
Ae = [cm^2]
F = [Hz]

so...
Np = (10^8 * 10 Volts) / (4*1,000 gauss * 15.5cm^2*40,000Hz)
= 0.4 turns (!??)

Even if I round up I am still only at 1-turn...

What's all this 4-turn stuff everyone keeps talking about? Did I miss a (*10) somewhere?

Thanks,
-=Randy
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Old 23rd November 2004, 04:10 PM   #25
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MKS CGS-- meters kilograms seconds vs centimeters, grams seconds -- check your units

edit: 1 Tesla = 10^ 4 Gauss
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Old 23rd November 2004, 11:43 PM   #26
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and just check you math -- some of the maginc data is in millimetres, some in centimeters -- the official effective area of the core is 1.56cm^2, but you can't get there unless you divide the square mm by 100 !
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Old 24th November 2004, 04:38 PM   #27
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Default thanks

Jackinnj,
Thanks, that was my problem... Ae=1.5cm^2 not 15.5cm^2... I should have caught something that obvious! 4.16 turns. I will order that torroid.

Thanks!
Randy
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Old 28th November 2004, 08:22 PM   #28
bayezid is offline bayezid  Bangladesh
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Default need help

I think many SMPS expart are visited here. I have a some prob about SMPS . U can red details : please visit this

http://www.diyaudio.com/forums/showt...611#post517611
Threat # 177

any one give me answer about my question. I am very new about circuite making.

sorry for posting this thread.
Regards
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Old 1st December 2004, 07:36 PM   #29
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Randy: well, how did it turn out ?
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Old 3rd December 2004, 05:18 PM   #30
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jackinnj,
Thanks for inquiring about my progress. As of now the SMPS is on hold because I do not have the capability to do double sided boards with plated through holes. I found a board house but for the size of the board they are going to charge $78.00 for 2 boards. Since xmas is coming up funds are a little short. It will be a week before I can send it off.

This idle time has not been wasted as I have been using the time to design the preamplifier and 500-W class-g amplifier stage.

I will post pictures of things as I get them done.

When its all said and done I plan on setting up a website like rod-elliot where he shows the schematic / tutorial.

Thanks again for your help!
Randy
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