Offline full-bridge SMPS....need help - Page 68 - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

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
Reply
 
Thread Tools Search this Thread
Old 22nd September 2007, 12:29 PM   #671
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
I have experienced, Half Bridge smps used to develop noise problems when subjected to varying frequency of generator say from 60hz to 30hz, meanwhile fullbridge has no probs of this sort at all....


Whats your views N-Channel.....
  Reply With Quote
Old 22nd September 2007, 06:19 PM   #672
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
Quote:
Originally posted by N-Channel
Dave,

Amplifying mzzj's comments a bit, a current-sense transformer (as opposed to a series-sense resistor in line with the lower switch) also enables true symmetric current-sensing. Popular winding ratios for a current-sense transformer are 50:1, 100:1, and 200:1, the one turn being the primary. Coilcraft and others make small molded toroids with two or three leads (for either full-bridge or center-tap rectification of the signal). Simply shoot the primary thru the center hole, and you're off to a good start.

Steve
A single current transformer in series with the primary may saturate during big load transients giving erratic measurements and sometimes inhibiting current limiting, this only works reasonably well with voltage mode and slowly varying loads (like in a PC power supply). A workaround for this is using two current transformers, one in each switching path. Peak current control may be implemented in half bridges that way.
__________________
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote
Old 24th September 2007, 02:15 PM   #673
diyAudio Member
 
N-Channel's Avatar
 
Join Date: Mar 2003
Location: Sol System
Send a message via AIM to N-Channel
Quote:
Originally posted by Workhorse
I have experienced, Half Bridge smps used to develop noise problems when subjected to varying frequency of generator say from 60hz to 30hz, meanwhile fullbridge has no probs of this sort at all....


Whats your views N-Channel.....
I'm not sure what you mean "60hz to 30hz". Are you talking about the output of a portable generator? If so, then I believe this would happen only when the gen-set sees a sudden load increase, and the gen-set momentarily dips in speed while trying to meet the sudden load increase. As for niose problems occuring in a HB when thisa occurs, I can't be cretian, but perhaps you could try bigger DC Bulk Caps to make up for the momentary lower frequency. Also, since, at 30Hz, even incandescent lights will start to flicker, this condition could be contributing to the noise problem as the frequency passes through a value that is a funcamental harmonic of your switcher's operating frequency.


Quote:
Originally posted by Eva


A single current transformer in series with the primary may saturate during big load transients giving erratic measurements and sometimes inhibiting current limiting, this only works reasonably well with voltage mode and slowly varying loads (like in a PC power supply). A workaround for this is using two current transformers, one in each switching path. Peak current control may be implemented in half bridges that way.
I have heard of this technique, but never why. This is interesting, EVA.

Workhorse, If there were ever a danger of a sudden load inrease across the primary to the point of current xfmr saturation, I would definitely recommend trying EVA's approach, of stick with the series-sense resistor you describe regarding full-bridge.
__________________
-. ---.. -..- ---
  Reply With Quote
Old 25th September 2007, 02:23 PM   #674
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
Quote:
Originally posted by N-Channel


I'm not sure what you mean "60hz to 30hz". Are you talking about the output of a portable generator? If so, then I believe this would happen only when the gen-set sees a sudden load increase, and the gen-set momentarily dips in speed while trying to meet the sudden load increase. As for niose problems occuring in a HB when thisa occurs, I can't be cretian, but perhaps you could try bigger DC Bulk Caps to make up for the momentary lower frequency. Also, since, at 30Hz, even incandescent lights will start to flicker, this condition could be contributing to the noise problem as the frequency passes through a value that is a funcamental harmonic of your switcher's operating frequency.

Workhorse, If there were ever a danger of a sudden load inrease across the primary to the point of current xfmr saturation, I would definitely recommend trying EVA's approach, of stick with the series-sense resistor you describe regarding full-bridge.
Yes the frequency output of generator sometimes drop or vary alot from 60 to 30 Hz. I have seen many HB SMPS amps which begin to noise when frequency drops but this isnot the case with FB smps........
I never used current xfmr approach, i relied on resistor approach in FB SMPS for symmetric current sensing. In my new project i am implementing Hall-effect current sensors from Allegro, they also provide isolation as well as the series element drop resistance is just 150micro Ohm.....so no losses.....
  Reply With Quote
Old 7th October 2007, 10:41 PM   #675
diyAudio Member
 
Join Date: Sep 2007
I so sorry. I design SMPS but I'm not yet in business, and given the SMPS migration that the PA market is experimenting, I can't provide such a ready-made schematic to you for free because I still expect to make some profit from my work before other people could start cloning and selling my prototypes like crazy
  Reply With Quote
Old 8th October 2007, 12:07 PM   #676
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
Quote:
Originally posted by linbhunt
I so sorry. I design SMPS but I'm not yet in business, and given the SMPS migration that the PA market is experimenting, I can't provide such a ready-made schematic to you for free because I still expect to make some profit from my work before other people could start cloning and selling my prototypes like crazy
Who are you and who told you to give smps schematic??
  Reply With Quote
Old 26th October 2007, 08:21 PM   #677
luka is offline luka  Slovenia
diyAudio Member
 
luka's Avatar
 
Join Date: Sep 2005
Location: in Slovenia :)
Send a message via Skype™ to luka
Default All finished

Hi

It is time to say that all is done, nothing more to be upgraded. I am posting my PCB and SCHEMATIC of offline/mains powered Half-Bridge supply.It is regulated, with main output voltages + 2 for +/-12V or whatever. Pcb was made for ETD44, but I didn't used it.

Here are the photos

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Enjoy and have fun with is, like I did

Here is first file...
Attached Files
File Type: pdf smps (mos-fet) vr.5.pdf (76.9 KB, 1430 views)
__________________
home page @ http://www.classdaudio.tk/ @ 24/7 all year long
I FEEL SLOVENIA
  Reply With Quote
Old 26th October 2007, 08:24 PM   #678
luka is offline luka  Slovenia
diyAudio Member
 
luka's Avatar
 
Join Date: Sep 2005
Location: in Slovenia :)
Send a message via Skype™ to luka
And 2nd...
Attached Files
File Type: zip smps (mos-fet) vr.5 pcb.pdf.zip (69.8 KB, 962 views)
__________________
home page @ http://www.classdaudio.tk/ @ 24/7 all year long
I FEEL SLOVENIA
  Reply With Quote
Old 27th October 2007, 04:10 AM   #679
diyAudio Member
 
N-Channel's Avatar
 
Join Date: Mar 2003
Location: Sol System
Send a message via AIM to N-Channel
Someone's been busy. Luka, That is some very nice work. Couple o' questions: What happened to the E-E core Xfmr? Does the Toroid give better performance?

Also, I noticed that the two series resistors R15 & R16 are only 680W. When I briefly had my HB SG3525-controlled SMPS working, I used 2- 8.2kW 5-watters in series, this limiting the max current thru the TIP50 to ~25mA. During Start-up, do you notice these two resistors getting hot?

Other than those points, it looks really kick-a$$!
__________________
-. ---.. -..- ---
  Reply With Quote
Old 27th October 2007, 08:00 AM   #680
luka is offline luka  Slovenia
diyAudio Member
 
luka's Avatar
 
Join Date: Sep 2005
Location: in Slovenia :)
Send a message via Skype™ to luka
Hi

First of all I would like to thank you for all help that you gave me, also Chas1 and Eva + others too ofcourse... Big thanks to all

I didn't use it because it had big ratio(or in this case small(20:11,11)I would be better looking and better performing if ETD would be used, but I have rewinded that sucker so many times, that I couldn't do it once more and I wanted to see if toroids are any good (giving power, not with EMI) coz I have a lot of smaller ones, that I have no use for them yet...

R15 & R16: I know that is quiet low value, I would use 2.2k now, but they don't heat up, not one bit. Only Tip50 if there is no aux voltage from Xfmr.I had SMPS like that at first, to see how this works, Tip got hot (no heatsink), but after 10s of running that I think is more then normal. And such low value of resistors mean that SG and IR could be powered all the time from bulk caps, but with high losses.

To tell the truth, it is not as good as I want it to be, there could be current limiting, proper regulation (This one works, just I don't know how stable).... Basically new diffrent board that I don't have will to do one from start again for some time. Maybe I will do that for Battery charger....

Whole point of this design was to make it low, to fit it in 1HE or 4cm.
__________________
home page @ http://www.classdaudio.tk/ @ 24/7 all year long
I FEEL SLOVENIA
  Reply With Quote

Reply


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



New To Site? Need Help?

All times are GMT. The time now is 02:00 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2