MOSFET retrofit in switching power supply... - 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 19th March 2007, 09:04 PM   #1
GordonW is offline GordonW  United States
diyAudio Member
 
GordonW's Avatar
 
Join Date: Mar 2005
Location: Marietta/Moultrie GA
Default MOSFET retrofit in switching power supply...

OK. I'm venturing into realms I've not been into in an LONG time... MOSFET retrofitting.

Got a box of big, high-end car amps and such... most need repair. One of the first (Alphasonik PMA2100) uses MOSFETS in the power supply (switching step-up with transformer). Here's what I'm thinking of doing:


Replacing THIS (BUZ71A)
http://pdf1.alldatasheet.co.kr/datas...CS/BUZ71A.html

...with THIS (STP16NF06)
http://www.st.com/stonline/books/pdf/docs/7980.pdf

Anyone see any reason this shouldn't work?

AFAIK, the only real significant operational difference, is that the newer mosfet has lower capacitance... I'd think that SHOULD NOT really be a problem. HIGHER capacitance, sure, that can overload driving transistors... but LOWER capacitance? Looks like it might just slew a bit better (better efficiency?)?

The extra current and power dissipation capacity (20% greater current, 10% greater power dissipation) certainly can't hurt either!

So, any comments/warnings?

Thanks!

Regards,
Gordon.
__________________
Speaker Design, Restoration and Repair- since 1985.
  Reply With Quote
Old 20th March 2007, 08:19 AM   #2
diyAudio Member
 
ifrythings's Avatar
 
Join Date: Oct 2005
I would go with some 70N06's for mosfets, they have 70A handling 60V rating and are .014 Ohm on resistence and are 150W dissipation

Gate cap, isn't a big deal in the slow speed switching (35KHz) and of course the drive transistors can take a bit more current than there use to.
  Reply With Quote
Old 21st March 2007, 11:47 AM   #3
diyAudio Member
 
N-Channel's Avatar
 
Join Date: Mar 2003
Location: Sol System
Send a message via AIM to N-Channel
I concur with ifrythings. Or better yet, try the IRF3205. Vdss = 55V; Rds(on) = 8mW; Id =110A, & Pdiss = 200W. Thjough the 70N06s should be plenty good enough.......
__________________
-. ---.. -..- ---
  Reply With Quote
Old 21st March 2007, 03:59 PM   #4
GordonW is offline GordonW  United States
diyAudio Member
 
GordonW's Avatar
 
Join Date: Mar 2005
Location: Marietta/Moultrie GA
With the toroidal power transformer, and the age of the design, I'd be worried about lowering the damping (raising the Q) of the transformer/MOSFET system (ie, inductive reactance interacting with the FETs), using a FET with THAT low of an on resistance (.008 ohms vs. .120 ohms). I don't want to have to possibly deal with current spikes as a result...

That's why I had looked at the STP16NF06... same range of on-resistance...

Regards,
Gordon.
__________________
Speaker Design, Restoration and Repair- since 1985.
  Reply With Quote
Old 23rd March 2007, 09:34 AM   #5
diyAudio Member
 
ifrythings's Avatar
 
Join Date: Oct 2005
Quote:
Originally posted by N-Channel
I concur with ifrythings. Or better yet, try the IRF3205. Vdss = 55V; Rds(on) = 8mW; Id =110A, & Pdiss = 200W. Though the 70N06s should be plenty good enough.......
I will admit, the IRF3205 is an awesome MOSFET but it's expensive and is limited to 75A (maximum current of the TO-220 package as where the DČ Pak (SMD-220, TO-263) can do the full 110A), It cost me 35 bucks (cad) just for 10 of them! As where the RFP70N06 only cost me <10 bucks for 10.

GordonW

I've done many upgrades of MOSFET's in car amps psu and never found any difference with current spikes as a result. I think this would matter if that design doesn't have snubber's incorporated.
  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
Split Voltage Switching Power Supply for Power Amp vectorplane Swap Meet 2 24th April 2011 12:48 AM
K6 Switching Power Supply microsim444 Swap Meet 0 23rd November 2008 10:21 AM
Switching Power Supply? Apocarm Class D 9 2nd March 2006 06:02 PM
Switching 12V power supply PCB soundNERD Power Supplies 35 27th April 2005 02:35 AM


New To Site? Need Help?

All times are GMT. The time now is 06:00 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