Half bridge smps voltage drop problem - Page 4 - 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 26th March 2006, 11:16 PM   #31
subwo1 is offline subwo1  United States
diyAudio Member
 
subwo1's Avatar
 
Join Date: Jan 2002
Location: North American Continent
One thing I don't like about transformers is that they seem to need low impedance drive themselves if they are not to load down the control circuit output. I don't like winding them either. I guess they would be OK with most of the standard controller chips which can drive MOSFET gates directly, anyway.

I like the IR2113's CMOS inputs, too. It also has enough instantaneous current ability to drive the hefty IRF7343 buffers without increasing rise and fall time. Small transformers are a problem with regard to creepages and circuit placement, IMO, too.
__________________
USMPS
http://groups.yahoo.com/group/switchmode/
  Reply With Quote
Old 26th March 2006, 11:21 PM   #32
subwo1 is offline subwo1  United States
diyAudio Member
 
subwo1's Avatar
 
Join Date: Jan 2002
Location: North American Continent
Quote:
Originally posted by Eva
...power it...
I do like this advantage, though.
__________________
USMPS
http://groups.yahoo.com/group/switchmode/
  Reply With Quote
Old 27th March 2006, 03:49 AM   #33
diyAudio Member
 
N-Channel's Avatar
 
Join Date: Mar 2003
Location: Sol System
Send a message via AIM to N-Channel
Default IRF740 casserole

Alex,

All this talk about your supply has re-ignited my interest in re-assembling my old SMPS. Thing is, in trying to remove the '740s today, I broke the gate terminal off one of them. My last Motorola IRF740 has gone the that big MOSFET in the sky! I do have a couple rails of MTW20N50E lying about. At 20A and 500Vdss, with 240mW Rds(on), I guess I will use two of them.

Joe, the gate capacitance of the MTWs varies from 3900pF to 7000pF. Do you think I should look into the source-follower buffer you mentioned?

Steve
  Reply With Quote
Old 27th March 2006, 04:55 AM   #34
MOER is offline MOER  United States
diyAudio Member
 
Join Date: Aug 2003
Location: SIMI VALLEY CA
Default SMPS

We do our off line supplies a little differently. We use TL494 driving a set of PNPs which drive a small gate drive xfr. Regulat half bridge configuration for the main switchers. We do not use TO220 fets bur rather IRFP360N. These are more robust than the smaller guys.

Advantage of the use of the drive transformer is that my TL494 can be at audio ground potential (It is always driven by a small houskeeping transformer) We apply full balanced feedback from our secondaries which allow us to keep the output voltage constant whether loaded or not. The seondary used a common mode choke and the transformer is wound to give about a 25% overwind ratio. Feedabck resistors at the TL494 set the final value of the output

We have used the IR2113 chips, nice but no isolation. Opto coupled feedback is required but this does not allow us to have the perfect regulation we have with balanced feedback.

At 62KHz the transformer you want to use with the amount of power you want is way to small. Check the charts on the Magentics web site

Steve
  Reply With Quote
Old 27th March 2006, 09:08 AM   #35
subwo1 is offline subwo1  United States
diyAudio Member
 
subwo1's Avatar
 
Join Date: Jan 2002
Location: North American Continent
Default Re: IRF740 casserole

Quote:
Originally posted by N-Channel


Joe, the gate capacitance of the MTWs varies from 3900pF to 7000pF. Do you think I should look into the source-follower buffer you mentioned?

Steve
Steve,
I think probably yes. In a standard type design (not ZVS) for efficiency, it can be good to have extra drive, especially to turn off the MOSFETs quickly because that is when they dissipate maximum power. Also, you can be more confident that you won't blow your IR211x MOSFET driver if you should decide to experiment with the circuit. If you would like me to clarify anything about adding the IRF7343 buffers, feel free to ask since I am not sure if any information is available from other Internet sources.

MOER,
thanks for relaying that information. It is good to see what has worked well for others, especially with regard to future work in which we might like to try new things, or if we encounter a problem which something we read about on the forum might solve.
__________________
USMPS
http://groups.yahoo.com/group/switchmode/
  Reply With Quote
Old 27th March 2006, 10:12 AM   #36
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
Hi Folks,

Try this link offline smps of pulse series amps from Crown:

http://www.crownaudio.com/pdf/legacy/s-c650as-03.pdf

K a n w a r
  Reply With Quote
Old 27th March 2006, 04:09 PM   #37
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
That's straightforward non-regulated half-bridge stuff. However, I like how they are reading the analog temperature sense signals with a PIC that does not have any ADC input (I use the same trick)
  Reply With Quote
Old 27th March 2006, 04:26 PM   #38
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
So Eva tell us that secret trick please...something from your magicbox.....
  Reply With Quote
Old 27th March 2006, 05:07 PM   #39
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
It's very straightforward, try to figure out first...
  Reply With Quote
Old 27th March 2006, 05:20 PM   #40
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
OK got it they have used LM35 precision temp sensor along with TL072 as comparator to get high/low output for the PIC to read...correct me if iam wrong....

K a n w a r
  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


Similar Threads
Thread Thread Starter Forum Replies Last Post
half bridge SMPS secondary voltage drop problem ? alexclaire Power Supplies 6 10th November 2006 03:19 PM


New To Site? Need Help?

All times are GMT. The time now is 04:46 PM.


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