Schottky or ultrafast soft recovery diodes? - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 20th September 2006, 10:42 PM   #1
novec is offline novec  Norway
diyAudio Member
novec's Avatar
Join Date: Aug 2005
Send a message via MSN to novec
Default Schottky or ultrafast soft recovery diodes?

I'm putting together a 60V PSU for a classD amp, using 1kVA toroid and dual bridges. But what's best - Schottkys or ultrafast soft recovery diodes? (FRED?) The ones I'm looking at are the 43CTQ100 Schottky and the 60EPU02 FRED.

From the datasheets, all I can find is that the Schottkys have much higher junction capacitance and reverse leakage current, but I have to admit that doesn't tell me much. All I've picked up is that while FREDs have a fast recovery time (35 us for the 60EPU02), Schottkys have none at all, which makes them more suitable for very high frequencies. Is that right?

When that's sorted, there's the issue with bypass caps, snubbers and all that, which can get pretty complicated... But as far as I've understood, there's a substantial difference between the two types of diodes, in the way of filtering them.

EDIT: I'm planning on running BHC or Jensen 4-pole caps.
  Reply With Quote
Old 20th September 2006, 10:46 PM   #2
BWRX is offline BWRX  United States
diyAudio Moderator Emeritus
Join Date: Jan 2005
Location: Pennsylvania
Try both and see which you like better.
  Reply With Quote
Old 20th September 2006, 10:50 PM   #3
novec is offline novec  Norway
diyAudio Member
novec's Avatar
Join Date: Aug 2005
Send a message via MSN to novec
That's probably the best solution, but that means twice the designing work and twice the component cost... Which, considering I don't have any low cost electronics supplier nearby, will be atleast a couple of Benjamins. I know there are no absolutes in audio design, but I figured some of you have some experiences to share.
  Reply With Quote
Old 21st September 2006, 12:22 AM   #4
cerrem is offline cerrem  United States
diyAudio Member
cerrem's Avatar
Join Date: Jun 2005
Location: San Diego, CA
Some key questions ...
What is the current demand on this power supply?????
What value Caps/filtering is involved???

  Reply With Quote
Old 21st September 2006, 01:55 AM   #5
diyAudio Member
ifrythings's Avatar
Join Date: Oct 2005
Isn't there a problem with parelleling diodes, I thought that if you parellel two or more diode the one with the lowest on voltage will be the one doing all the work (basicly not sharing current with the other diodes)?
  Reply With Quote
Old 21st September 2006, 02:02 AM   #6
diyAudio Member
metalman's Avatar
Join Date: Jun 2003
Location: Victoria, BC, Canada
I've had very good results from the ultrafast soft recovery diodes. I have used the HFA08TB60 diodes from International Rectifier, and the MBR860 from On Semiconductor. Both are very good, but I prefer the HFA diodes myself. Either work quite well and don't ring significantly even without bypassing or snubbing.

Cheers, Terry
  Reply With Quote
Old 21st September 2006, 02:18 AM   #7
Bare is offline Bare  Canada
diyAudio Member
Join Date: Dec 2001
Location: vancouver
I'm under the understanding that one can simply use the "Diode 'of the week" downstream from yer Bridge
Thereby gaining ALL of that particular diodes benefits and only having to pay for ONE 'special' diode.

It's about using yer brain .. not just paying for unecessary parts :-)
  Reply With Quote
Old 21st September 2006, 02:36 AM   #8
diyAudio Member
Workhorse's Avatar
Join Date: Dec 2004
Hi Novec,

The HFA series diodes from IRF have soft recovery and fast recovery characteristics...
Meanwhile I do prefer EP series schottkys because I have seen the results better than HFA series in some high current applications, where switching noise was a significant contributor..and schottky's produce less switching noise than any of the high current UFR diodes during high current operation. The reverse leakage current of schottky's doesnot degrade any performance form in the application.

K a n w a r
  Reply With Quote
Old 21st September 2006, 05:54 AM   #9
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
Any power diode will do for 50/60Hz rectification. Schottky and ultrafast diodes are strictly required for SMPS applications only, where they are driven from very low source inductances and are forced to commutate within 100ns or faster at very high dI/dt rates.

In 50/60Hz applications, the huge leakage inductance of the transformer and the mains line results in a very slow commutation process lasting 100us or so, thus the 1us reverse recovery period of a slow conventional diode is not enough to produce any reverse current peak (as opposed to what happens when commutation is forced in SMPS circuits, where you usually get a 50% 'If' reverse peak even with the best diodes). Read also about snubbers, there is a thread where I posted very interesting oscilloscope captures somewhere.
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote
Old 21st September 2006, 11:01 AM   #10
diyAudio Member
Join Date: May 2006
... posted very interesting oscilloscope captures somewhere ...
For the searchwise challenged: Fast Recovery rectifier diodes
  Reply With Quote


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
schottky vs. soft/fast recovery diodes metebalci Parts 35 25th March 2017 01:47 AM
BYM26C soft recovery high speed diodes hihopes Parts 20 20th July 2016 06:24 AM
Fairchild Stealth soft recovery fast switching diodes KevinLee Swap Meet 3 10th January 2006 09:53 PM
IR HFA08TB60 Ultrafast Soft-recovery DIODE canvas Swap Meet 1 21st August 2004 04:47 PM
High speed soft recovery diodes Piersma Digital Source 6 9th April 2003 08:32 PM

New To Site? Need Help?

All times are GMT. The time now is 04:19 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2