Push-Pull question - 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 December 2008, 11:03 AM   #1
diyAudio Member
 
roomi's Avatar
 
Join Date: Jul 2008
Default Push-Pull question

I want to make a sine wave inverter of capacity 500W.
I have decided to use push pull topology for the 12V-320V boost converter and wanted to use sg3525 for this purpose. the feedback will be from the 320V output to keep the voltage constant.

Is push-pull appropriate for this purpose ?

I looked at the app note of microchip for sine wave inverter. they used a second stage chopper after dc-dc push-pull stage. why they did that ?
  Reply With Quote
Old 22nd December 2008, 03:34 PM   #2
dtproff is offline dtproff  United States
diyAudio Member
 
Join Date: Oct 2008
Location: Plano, TX, USA
You'll need to list the operating frequency.

If you are wanting something in the 50-100KHz range I would probably use a series/parallel (or even a LLC) resonant full bridge. And before you ask, I will admit to being biased against push pull topologies and I really like resonant converters. At least this is what I would use if I wanted a SIN wave at 70KHz and no intermediate stage boost votlage.

Please list the Microchip spec to which you refer and we'll take a look at answering the question as to why there are two stages. But to hazard a guess it is because of the large discrepancy between the 12V and the 320Vac voltage you want. Usually you would boost to 320V*sqrt(2) and then use a HB LLC to convertert to a sin wave from there.

I hope that helps.

Tony
  Reply With Quote
Old 22nd December 2008, 04:32 PM   #3
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
At these current levels (over 40A) and frequencies (below 100Khz), sine like current waveforms due to fully resonant operation are not a good idea. Switching losses are already much smaller than conduction losses.

The traditional push-pull becomes ZVS by adding enough dead time.

The second switching stage makes it easier to produce the sine or quasi-sine wave. It's required anyway in order to produce both halves of the waveform, since the rectified output from the transformer can only be either positive or negative.
__________________
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote
Old 22nd December 2008, 06:27 PM   #4
diyAudio Member
 
roomi's Avatar
 
Join Date: Jul 2008
I was mentioning abt the microchip app note "PICREF-1"(Uninterruptible Power Supply Reference Design). in this they used 2 stage dc-dc.

Infact I have already made a sg3525 based push-pull 12-330V dc-dc converter. But waveshape across the two end of the tranfrmr is not like as it should be. and sometimes the fet blew up during load test (i am using irf3205). and even at 15A drain current the temp. of the FETs are really high as it shoud't be.
  Reply With Quote
Old 23rd December 2008, 02:40 AM   #5
diyAudio Member
 
roomi's Avatar
 
Join Date: Jul 2008
The switching freq I am using is 40Khz
  Reply With Quote
Old 26th December 2008, 10:53 PM   #6
dtproff is offline dtproff  United States
diyAudio Member
 
Join Date: Oct 2008
Location: Plano, TX, USA
Roomi;

Can you pst what you have (schematic and transformer construction)? Maybe we can help with what you already have.

Tony
  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
Push - Pull improvement question ? goldyrathore Multi-Way 20 1st January 2011 03:34 PM
push pull power amp design question (a lot of actually :) ) krusty75 Tubes / Valves 6 25th September 2008 05:07 PM
modify parallel push-pull EL84 to single push-pull chungtat Tubes / Valves 12 3rd November 2005 11:25 PM
Double push-pull versus single push-pull jraraujo Tubes / Valves 19 19th October 2002 12:23 AM
Push Pull driver newbie question Diogo Solid State 9 10th August 2002 06:13 PM


New To Site? Need Help?

All times are GMT. The time now is 04:13 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