smps forward - need help with bias voltage - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Old 6th March 2013, 02:30 AM   #1
diyAudio Member
gearheadgene's Avatar
Join Date: Jul 2005
Location: CT
Default smps forward - need help with bias voltage

I am looking for some help. The attached schematic is a partial of the whole thing, but I hope this is enough to give you the idea (not that there's a whole lot more, though). What you are looking at is the transformer, the driver, and some magnetics. On the right hand side of the transformer is the isolated secondaries. They all share the same filter coil, L202. I am still working on it, but for now let's just say it is working about as expected. But, on the upper side of line-side of the transformer, L201 pins 1 and 2 (top center of the picture), is supposed to be bias voltage to run the PWM chip. This part isn't working so well. The winding polarity was dorked up, but I got that all patched up now. As you may notice, L204 is its own inductor.

Well, although I can get the V50AP winding to regulate correctly, the bias voltage does not cross regulate for beans. I think it is because it doesn't share L202.

So that's the problem - I need to get that to run at around 13 volts or so. Any ideas? I have seen some designs that take couple onto L201 as a flyback design. Maybe I can consider that. Can anyone think of a way to get the bias winding to regulate better? An alternatives? I am open to suggestions

Attached Images
File Type: png snapshot1.png (70.6 KB, 57 views)
  Reply With Quote
Old 6th March 2013, 02:56 AM   #2
DUG is offline DUG  Canada
diyAudio Member
Join Date: Jan 2003
Location: mississauga ontario canada
Add an extra turn or two and add a LDO linear regulator.
Doug We are all learning...we can all help
"You can't stop the signal, Mal. Everything goes somewhere..."
  Reply With Quote
Old 6th March 2013, 04:07 PM   #3
diyAudio Member
gearheadgene's Avatar
Join Date: Jul 2005
Location: CT
Hey that sounds pretty good, thanks!
  Reply With Quote
Old 6th March 2013, 04:12 PM   #4
diyAudio Member
Osvaldo de Banfield's Avatar
Join Date: Dec 2011
Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
Perhaps the inductor is lesser than needed, and it runs dry, and lost regulation.
Osvaldo F. Zappacosta. Electronic Engineer UTN FRA from 2001.
Argentine Ham Radio LW1DSE since 1987.
  Reply With Quote
Old 6th March 2013, 04:53 PM   #5
diyAudio Member
gearheadgene's Avatar
Join Date: Jul 2005
Location: CT
Actually, I am having a tough time with the output inductor. Although initially followed some of the Unitrode notes, I remain stuck knowing the proper value.

What's hanging me up is setting up for minimum load - which might be really low, while max load could be very high. Then the windings go out of regulation when the loads are fubar.
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

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 Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
SMPS Forward Active Reset gearheadgene Power Supplies 7 17th July 2013 12:25 AM
Ultra-low forward voltage Schottky-rectifier h_a Parts 19 26th July 2008 11:41 AM
LED forward voltage plot ashok Solid State 7 26th October 2007 01:49 AM
Digital zero-voltage SPS with PID contrlol and feed forward Michael_V Power Supplies 0 26th September 2007 10:36 AM
Forward SMPS - unexpected behaviour vectorplane Power Supplies 19 18th December 2005 02:28 PM

New To Site? Need Help?

All times are GMT. The time now is 05:26 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2