Choke formula - Marty Brown - diyAudio
 Choke formula - Marty Brown
 User Name Stay logged in? Password
 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
diyAudio Member

Join Date: May 2005
Location: Johannesburg
Choke formula - Marty Brown

Hi All

I am presently building a 12V to 330V converter and I have been using a book titled Power Supply Cookbook by Marty Brown as a guide. There is a formula that appears within for calculating the output choke value that I am having a tough time grasping as it seems the result is rather big for such a small smps.

The smps operates in push-pull config at 50kHz and is rated for 120mA max. Vin(min) = 11V
Vin(max) = 15V

Can someone please have a look at my calc. and advise if I misunderstood what was required?

Thank you

Ashraf
Attached Images
 Choke formula.png (80.8 KB, 254 views) Choke calculation.png (11.9 KB, 251 views)

 17th April 2012, 01:55 PM #2 diyAudio Member     Join Date: May 2005 Location: Johannesburg Anybody??
 17th April 2012, 02:09 PM #3 diyAudio Member     Join Date: Dec 2011 Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina The inductor at the output only smoots the voltage, and operates as a low pass filter with the out cap. Assuming a delta I, the choke is easy to calculate. Normally it is assumed as a 10% of I load. I also have this book, but it is a bit confusious the math he use. Read any inductor calculation for buck converter type, in fact the inductor operates in the same way as it. __________________ Osvaldo F. Zappacosta. Electronic Engineer UTN FRA from 2001. Argentine Ham Radio LW1DSE since 1987.
 17th April 2012, 02:39 PM #4 diyAudio Member     Join Date: May 2005 Location: Johannesburg Osvaldo, are you saying that calculating chokes for buck converters are exactly the same as calculating an output choke for a forward converter?
diyAudio Member

Join Date: Dec 2011
Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
Quote:
 Originally Posted by Archimedes Osvaldo, are you saying that calculating chokes for buck converters are exactly the same as calculating an output choke for a forward converter?
Yes!!!

http://www.ti.com/lit/ml/slup127/slup127.pdf

I hope this be usefully.
__________________
Osvaldo F. Zappacosta. Electronic Engineer UTN FRA from 2001.
Argentine Ham Radio LW1DSE since 1987.

diyAudio Member

Join Date: Sep 2006
Quote:
 Originally Posted by Archimedes Anybody??
The formula is dimensionally correct.
The only point open to debate is the 1.4 factor, it represents the level of ripple you tolerate for the current in the choke, but even if you choose a different trade off, the value will remain in the same range.
It is a normal value for a high voltage converter: the inductance value increase as the voltage squared.
__________________
. .Circlophone your life !!!! . .
♫♪ My little cheap Circlophone© ♫♪

 18th April 2012, 12:31 AM #7 Banned   Join Date: Apr 2012 Location: China can you use the common magnetic chokes or distance magnetic chokes for short the wave? i think we can solve your question regards Jay
diyAudio Member

Join Date: May 2005
Location: Johannesburg
Thanks for your responses.

Osvaldo, I read the TI note and I can't seem to find where it explains how the inductance of the choke was calculated. The inductance value of the choke was provided all that the note said was what type of core, winding etc.

Elvee, I came across a somewhat differennt formula for calulating the choke from Col. T. McLyman and when I did the calculation I come up with a value of 74.5mH. Now I am more confused as to which value is the correct one.

Jay, I don't understand your question. Please will you rephrase.
Attached Images
 Calc 2.png (5.2 KB, 177 views)

 19th April 2012, 08:59 AM #9 diyAudio Member     Join Date: Sep 2006 Can you post your schematic, it will make the discussion easier. __________________ . .Circlophone your life !!!! . . ♫♪ My little cheap Circlophone© ♫♪
diyAudio Member

Join Date: May 2005
Location: Johannesburg
Here is the schematic.
Attached Images
 PSU Schematic.png (86.5 KB, 169 views)

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post speakerfritz Tubes / Valves 7 2nd December 2011 06:05 PM Hubba Tubes / Valves 2 10th September 2010 02:33 PM cbutterworth Tubes / Valves 14 9th November 2007 04:43 PM Curly Woods Tubes / Valves 2 5th March 2007 08:30 PM

 New To Site? Need Help?

All times are GMT. The time now is 01:27 AM.

 Home - Contact Us - Advertise - Rules - diyAudio Store - Sponsors - Archive - Privacy Statement - Terms of Service - Top - Opt-out policy

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.