
Home  Forums  Rules  Articles  diyAudio Store  Gallery  Wiki  Blogs  Register  Donations  FAQ  Calendar  Search  Today's Posts  Mark Forums Read  Search 

Please consider donating to help us continue to serve you.
Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving 

Thread Tools  Search this Thread 
27th August 2012, 12:43 PM  #1 
diyAudio Member
Join Date: Aug 2012

Help with SMPS Transformer
Hello guys, I am new around here and I need some help to build my SMPS transformer.
I was thinking designing a transformer to use on a forward converter. My goal is to, first, learn how to do a transformer and second, how the forward converter works. I was wondering if there is someone who can help me out here with the design of that trafo. I will wait for some answers and see if someone can help me. After that, I'll post the specifications and the calculations that I have done so far. Kind Regards. 
27th August 2012, 07:07 PM  #2 
diyAudio Member
Join Date: Aug 2012

Hi again.
Maybe would be better to post directly the specifications. Specifications Input Vin = 230VAC Vin(nominal) = sqrt(2) * 230VAC = 325V Vin(minimum) = 300V Vin(maximum) = 350V Output Vout = 30V ; Iout = 5A ; Pout = 150W Expected efficiency = 80% Pin = 150W / 0,8 = 190W Iin(maximum) = 190W / 300V = 0,65A Transformer specifications: I got this transformer from an old power supply. It is an EI type core. I don't know what kind of core material and because of that I do not intend to strive the transformer that much. The specifications are: Bmax = 1600Gauss Ae (center leg crosssection) = 1,21cm2 f = 100kHz TRANFORMER CALCULATIONS Just before start, I have a couple of questions here. From what I have read, in forums, books, applications notes, there are two methods to calculate the primary transformers turns. The first one is: Np = ( Vin(min) * Delta(max) ) / (Ae * Bmax * f ) Ns = Np * ( (Vout + Vf * Delta(max) ) / ( Vin(min) * Delta(max) ) ) The second one is: Np = ( Vin(max) * 10^8 ) / ( k * f * Ae * Bmax ) Ns = Np * ( ( Vout + Vf ) / Vin(min) ) The Ns, from the first method I saw it on a paper, but I have seen too the Ns from the second method, applied on the first. I have calculated the turns with both methods and both turns gave me completely different values. Here they are: Using the first method I got: Np = 70T ; Ns = 17T; Using the second method I got: Np = 45T ; Ns = 5T; Now my question is, which method should be used? Why they give so different values? The method that doesn't use the Delta, is less accurate than the other? I would appreciate if someone could help me out. Kind regards. 
29th August 2012, 03:37 AM  #3  
diyAudio Member
Join Date: Oct 2008
Location: Plano, TX, USA

Quote:
It will go a long ways in explaining things. After you have read through it we can chat some about the important design considerations around a forward converter. Tony 

29th August 2012, 09:18 AM  #4 
diyAudio Member
Join Date: Aug 2012

Thank you Tony. I'll read that.
Regards. 
29th August 2012, 03:29 PM  #5 
diyAudio Member
Join Date: Oct 2008
Location: Plano, TX, USA

Here is a fairly thorough treatment of a forward converter that I wrote about 10 years ago but it still applies today.
Tony 
9th April 2016, 11:27 PM  #6 
diyAudio Member
Join Date: Apr 2016

Hi Tony
Would you share the schematic of this Forward converter? Thanks Jack 
10th April 2016, 05:50 PM  #7 
diyAudio Member
Join Date: Aug 2010

dtproff, in the past you had posted a design procedure for flybacks but i was unable to find it. Could you please post it again.

Thread Tools  Search this Thread 


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Winding SMPS transformer  Sara001  Power Supplies  8  4th June 2012 10:35 AM 
Using a large 60hz toroid transformer as an SMPS transformer  EWorkshop1708  Power Supplies  20  22nd June 2011 08:05 PM 
SMPS transformer  jegandren  Parts  4  24th April 2008 01:30 AM 
transformer for SMPS  jarthel  Power Supplies  2  22nd June 2007 02:17 PM 
SMPS Transformer Equations  jackinnj  Solid State  7  21st March 2003 12:28 PM 
New To Site?  Need Help? 