SG3524 SMPS help needed. - 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 24th October 2013, 10:06 AM   #1
diyAudio Member
 
lazzer408's Avatar
 
Join Date: Sep 2010
Location: Chicago
Default SG3524 SMPS help needed.

I'm building a high voltage push-pull SMPS (300-400v) and need help understanding the current limiting of the SG3524

I was going to shunt the mosfets source's to ground and measure the drop across that "resistor" (12~10ga solid wire).

Please take a look at this datasheet as it's the one I'm using. http://www.ti.com/lit/ds/symlink/sg3524.pdf

In the datasheet on page 9 figure 7 it shows pin 4 to ground and pin 5 as input. On page 13 figure 15 it shows pin 5 to ground and pin 4 as input.

I'm guessing the page 11 drawing of "foldback limiting" is measuring a flyback current? which is reversed? This is where I'm confused.
  Reply With Quote
Old 24th October 2013, 10:38 AM   #2
diyAudio Member
 
lazzer408's Avatar
 
Join Date: Sep 2010
Location: Chicago
Here's what I have so far.

Click the image to open in full size.
Attached Images
File Type: jpg SG3524_SMPS_v1.JPG (102.5 KB, 337 views)
  Reply With Quote
Old 25th October 2013, 06:59 PM   #3
diyAudio Member
 
payloadde's Avatar
 
Join Date: Mar 2008
fig.7 seems to be a buck regulator case, current is measured when transistors are off, current continues to flow thru inductor, load, Rs, diode back into inductor ... thus "ground" side of Rs is actually more positive than other side, hence Lim+ at "ground".

in fig 12 emitter current of switcher transistors is measured when transistors are on, current flows thru RS to ground, so ground side is more negative than other side, hence Lim- at ground.

think you got it right ...
__________________
Judge: This court appreciates that you invented physics, Mr.Newton, but unfortunately you can't have a patent on it.
  Reply With Quote
Old 31st October 2013, 10:17 AM   #4
diyAudio Member
 
lazzer408's Avatar
 
Join Date: Sep 2010
Location: Chicago
So many questions...

I need a ~150w power supply to output a regulated ~350vdc with a current limit of around ~430ma. Above 430ma the voltage could/should sag as a means of protection. I'm still deciding on what IC to use.

1: Current mode? Voltage mode? Can someone explain the difference? 3524, 3535, 3825, 494, ect?
2: Will a pair of IRFz44 handle 150w?
3: Is the totem pole needed with a single pair of mosfets?
4: Am I on the right path with the above schematic?
5: Should I be measuring the secondary current instead?
6: Would you like to learn to fly?
7: Would you like to see me try?

I'm sure it's been said a million times but once the design is final, I'd like to order some extra boards or even make kits to sell.
  Reply With Quote
Old 4th November 2013, 08:23 AM   #5
diyAudio Member
 
lazzer408's Avatar
 
Join Date: Sep 2010
Location: Chicago
I'm still looking for help.

I drew this up for the 3525 but without current limiting and remote turn-on was added. I eliminated the gate drivers because I think the 3525 can handle 2 mosfets. I still have to work out some of the values.

I started a pcb layout and had a friend cut one in vinyl for etching mask. It worked very well.
Attached Images
File Type: jpg 3525smps_tube_v1.JPG (90.3 KB, 240 views)
  Reply With Quote
Old 4th November 2013, 09:20 AM   #6
diyAudio Member
 
lazzer408's Avatar
 
Join Date: Sep 2010
Location: Chicago
Here's my pcb layout so far. I've been trying to get it as small as I can. I forgot to add input filters though. I may have to just use an inline filter choke. Regulation goal is around ~350vdc.

Layout doesn't match the schematic 100%. I left a few pads for snubbers.
Attached Images
File Type: jpg layout.JPG (115.3 KB, 232 views)
  Reply With Quote
Old 8th November 2013, 03:57 AM   #7
diyAudio Member
 
lazzer408's Avatar
 
Join Date: Sep 2010
Location: Chicago
I built the circuit above and it works... without a load. 12vdc in gets me adjustable 200-380vdc out but as soon as I put a load on it (two 40w laps in series) the output drops off, input current climbs to 8A, and the mosfets get hot. The switching frequency may not be high enough?

Transformer is a 10t CT primary and a 160t CT secondary with four 1n4006 diodes for the rectifiers (all I had on hand). I'm pretty sure this core is an ETD34 but the bobbin didn't line up with my PCB which was drawn using a ETD34 pinout. I saved this core from an old PC power supply. I'll measure it in a moment to see if the core is the same as the ETD34.

Is there any tricks to getting transformers apart without breaking them? I broke 6 trying to get a good one.
  Reply With Quote
Old 8th November 2013, 04:26 AM   #8
diyAudio Member
 
andrewlebon's Avatar
 
Join Date: Feb 2008
Is there any tricks to getting transformers apart without breaking them? I broke 6 trying to get a good one.

Put the core in boiling hot water for 30 mins
__________________
[image][/image]"It's Better to try and fail than to never know and always wonder"
  Reply With Quote
Old 8th November 2013, 04:36 AM   #9
diyAudio Member
 
lazzer408's Avatar
 
Join Date: Sep 2010
Location: Chicago
Really? Does that soften of the glue? I'll be back in about 30min.
  Reply With Quote
Old 8th November 2013, 04:50 AM   #10
diyAudio Member
 
andrewlebon's Avatar
 
Join Date: Feb 2008
Really? Does that soften of the glue?
Yes it works
__________________
[image][/image]"It's Better to try and fail than to never know and always wonder"
  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
Car amp smps needed kissendi Car Audio 5 28th January 2008 04:08 AM
Synchronizing SG3524. Help! darw82 Power Supplies 0 27th May 2006 06:06 PM
Synchronizing SG3524 darw82 Power Supplies 8 30th December 2005 10:58 PM
1KW SMPS help needed gearheadgene Power Supplies 93 27th September 2005 12:12 PM


New To Site? Need Help?

All times are GMT. The time now is 09:22 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