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Old 26th May 2011, 03:21 PM   #11
luka is offline luka  Slovenia
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then calculate for this data only, you don't need wider range then this
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Old 26th May 2011, 04:25 PM   #12
luka is offline luka  Slovenia
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I get 1mH and 29t...but don't quote me on this

Edit: also, get this Transformer And Inductor Design Handbook, Third Edition

if you can't, I will try to provide you with it
you have everything that you would need to calculate PFC inductor, and that includes gap too!

if you already have core, take some no too big wire, and get L you need with core on
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Last edited by luka; 26th May 2011 at 04:39 PM.
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Old 26th May 2011, 05:14 PM   #13
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Quote:
Originally Posted by sekhar View Post
in every design i am seeing the pfc inductor does not have more than 50-60 turns ...... then hw am i getting 238 turns what am i doing wrong........??????????



regards
sekhar
Simply recalculate 'every design' and note the differences, this will bring evidence why different designs end up in different inductors.
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Old 26th May 2011, 05:33 PM   #14
sekhar is offline sekhar  India
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@luka it will be very help full if u could provide me the book...........and tell me wat exactly to read...........


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Old 26th May 2011, 05:53 PM   #15
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During your project you will probably struggle much more with parasitic effects of the layout and the components, rather than with the basic calculation.
-An ETD34 with 1mH (edit:875uH) and 238 turns might suffer from parasitic winding capacitance. ==> Check for winding constructions with small capacitance like multi section bobbins or wild windings.
- Or consider a core with larger Ae. ==> less turns.
- Or consider a higher ripple current ==> lower L ==> Less turns, but more demanding regarding HF-effects inside the winding (i.e. eddy currents due to fringing field and may be also headache with the proximity effect, might require multi stranded wires or HF-litz).
- Reverse recovery charge of the boost diode?
- Gate charge of the Switch?
- Parasitic layout inductances?
- Undesired fast ringing during/after the switching events?
- Safety: Fusing, clearances, creepages, isolation materials, temperatures, flamability, fault conditions..... !! Check for the relevant standards in your country.

Last edited by ChocoHolic; 26th May 2011 at 06:04 PM. Reason: 875uH
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Old 26th May 2011, 06:35 PM   #16
sekhar is offline sekhar  India
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@chocoholic
thanks...............i will post each and every stage of my design .................one question is etd34 capable of delivering 400W continuous at 100Khz


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sekhar
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Old 26th May 2011, 06:37 PM   #17
luka is offline luka  Slovenia
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I would think that it can do over 500w @100k in half or full bridge, but this is not it
I would believe that is does not,will see
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Old 26th May 2011, 07:42 PM   #18
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I doubt that the etd34 will be sufficient for a PFC 90V/AC==>400V/DC delivering continuous 400W.
But before heading for a bold design, check if you need it really continuously.

***
Edit:
And of course check, if you need 90V-264V.
Luka's hint might push you forward a huge step.
If you calculate it for input voltages around 200V-240V only, then things should relax a lot.
***

Let's hope that more people will jump in this thread.
I cannot talk for Luka, but I will not be able to give you support all the time. Running out of time, so I can give you hints just once and while.
..and it would be a wonder if everything would immediately work alright.
You are entering a difficult and dangerous playground.
It can exciting, but it can also be very frustrating.
In the beginning it usually does not save money vs buying a commercial product.
If it becomes passion, never give up. And always consider safety first, before powering up.

Last edited by ChocoHolic; 26th May 2011 at 07:59 PM. Reason: input voltage topic
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Old 27th May 2011, 07:31 AM   #19
hesener is offline hesener  Germany
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Hi sekhar, check out AN6086 from Fairchild, it has a detailed explanation on how to calculate the boost inductor (in this case for a interleaved PFC, but that doesnt matter)
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Old 27th May 2011, 08:21 AM   #20
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I do massively disagree regarding the opinion that it would not matter, which topology you use.
But AN6086 is a good paper to be compared vs the UC3854-related papers and study the differences and understand why it does matter which topology and core types+shapes you are going use.

Don't think that you would get everything for free in the Fairchild solution.
(Even if I am loving it, and it has proved to be pretty good up to 1kW at 230V.)
But:
You need two inductors.
You have 100% ripple in the inductor current ==> HF-loss-effects in the winding are a key factor for the real choke design!
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