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Old 19th June 2012, 04:43 PM   #41
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Quote:
Originally Posted by darkfenriz View Post
Take it easy, 99% is a wet dream I suppose
Well... Depends how you measure? Right?
The 99 is achieved without the input and output inductors.
With them the efficiency is down to about 95%.
Could rethink the inductors a bit, but then again Im quite happy with the thing already as it is.

Transformers are 6 turns primary made from copper foil 0.125mm thick x 16mm wide...

Secondaries 2x 0.9mm 16 turns...

Flat out power is 560W but I would blow the diodes pretty soon (MUR1560) with that, so adjusted down to 440W only...
With 560W output power a 50A fuse holds - nice...

FETs are the suggested IRF3703. Their advantage is the fast switch off, which results in to close 50/50 duty cycle...
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Old 19th June 2012, 07:04 PM   #42
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37A at 12V makes 440W, right?
It takes as little as 3.2miliohms through Mosfets, transformer primary, PCB traces, inductors and cabling together to loose 1%, ie. 4.4W at 37A. It is very tough to achieve.
Rectifer diodes drop a volt or so, that's another percent at 100VDC secondary and two percent at 50VDC secondary.
Even a primary capacitor can be a bottleneck, a very good 10000uF cap will have like 20miliohms, draw several amperes through it and you loose another fraction of a watt, a watt or two.
Switching losses don't usually dominate at below 50kHz.
Ferrite cores are also pretty lossy unless you run them at <100mT.

Don't worry, 95% is already a very good result, I wasn't able to achieve that high with 12V/600W push-pull with buffered IRFB3004, tight tape (foil) wound primaries, HV secondaries, sendust chokes and so on.
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Old 20th June 2012, 01:01 AM   #43
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Hey! I was thinking about... If i want to put an over-current protection in a isolated SMPS, how can I do it?
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Old 20th June 2012, 01:32 AM   #44
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hi guys
sorrry for my bad english
i have ETD39 and IRFZ44N
can i use that?
i did not see any pcb in this topic.!!
please help me friends
thanks
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Old 20th June 2012, 03:27 AM   #45
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What is the advantage of full bridge switching with only an automotive B+? How is push-pull not inherently more efficient here?
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Old 20th June 2012, 02:09 PM   #46
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Quote:
Originally Posted by Andrew Eckhardt View Post
How is push-pull not inherently more efficient here?
Ofcourse it is. Just put in a bigger core and there you have it.

I myself prefer fullbridge because of the ridiculously simple transformer. No need to worry about perfectly symmetrical primaries with just a couple of turns around the core.
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Old 20th June 2012, 11:15 PM   #47
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Default 12V SMPS

Quote:
Originally Posted by Hadighorbani View Post
hi guys
sorrry for my bad english
i have ETD39 and IRFZ44N
can i use that?
i did not see any pcb in this topic.!!
please help me friends
thanks
Absolutely! An ETD39 core + IRFZ44N devices has the potential of a great supply. But, it takes a lot more than that. It depends a lot on the core material too. Do you know the core material?

There's no PCB because we've been discussing theory, simulations, and industry standards. We're not at the actual assembly of his 575W (now 400W) supply. I posted a pic of my 500W supply just as a reference of one way it can be built.

Keep watching for more details. Plus, read through this and other SMPS threads so you can begin designing your supply!
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Old 21st June 2012, 03:58 AM   #48
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Thanks for your reply and sorry for my bad english.
I am basic in electronic and i do not have a oscop to make a good smps.
I buy the 800 number of TL494 and 1000 number of IRFZ44N and 300 number of ETD39 in very low price in my city.
He quite him job and sele all of that things to me with half of price.
I want to creat smps with that beacuse i have that.
Sorry for my bad english egain.
Please give me a chance with that parts.
Thank you engineers.
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Old 21st June 2012, 04:01 AM   #49
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Is this good for me?
Download avt2732pdf pdf
Thanks to all
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Old 21st June 2012, 05:36 AM   #50
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Default You should attach the file to your post

Quote:
Originally Posted by Hadighorbani View Post
Is this good for me?
Download avt2732pdf pdf
Thanks to all
You can attach the pdf you linked in your post. It is nicer to do that instead of sending DIY-ers to a sharing site.

Thanks
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