optocoupling power stage - hiss with 6N137 - diyAudio
Go Back   Home > Forums > Amplifiers > Class D

Class D Switching Power Amplifiers and Power D/A conversion

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 7th February 2008, 08:04 AM   #1
diyAudio Member
 
Join Date: Jul 2006
Default optocoupling power stage - hiss with 6N137

I'm wondering why 6n137 is rated at 100v/us in some datasheets, or 10000v/us in other places. Certainly, after i remove other variables (like pcb, power fet, inductor, etc), a small hiss is presented at output, even if i drive only power stage with clean square wave 250khz (offcourse, with deadtime).
It is a posible cause for hiss this 6n137 optocoupler?

Description on final stage: 6n137+tc429+power fet+floating 15v supply
  Reply With Quote
Old 7th February 2008, 08:56 AM   #2
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
The hiss may be just due to the sum of time errors of all components (jitter). Power supply noise is a direct contributor too. When doing open loop tests, note that output filter resonance may boost some frequencies unles it happens well above 20Khz.

6N137 performance depends on manufacturer. I think that Avago (formerly Agilent (formerly Hewlett packard)) supplies the one rated at 10KV/us. You may consider trying other fast shielded optocouplers.

Anyway, if erratic switching due to false optocoupler triggering is actually taking place, the oscilloscope should show it. False triggering only happens during transients and may create a self oscillating system (this has happened to me).
__________________
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote
Old 7th February 2008, 09:25 AM   #3
diyAudio Member
 
Join Date: Jul 2006
Thanks Eva for your quick answer. This is my sch:
Attached Files
File Type: pdf schematic1 _ page1.pdf (25.4 KB, 433 views)
  Reply With Quote
Old 7th February 2008, 09:29 AM   #4
diyAudio Member
 
Join Date: Jul 2006
And this is my layout. The yellow traces is from top ground plane (unfigured for clarity reason). May i ask to you to analyse this and give your valuable advice?
Attached Files
File Type: pdf classd-rc4-5.pdf (74.5 KB, 759 views)
  Reply With Quote
Old 7th February 2008, 02:52 PM   #5
fredos is offline fredos  Canada
diyAudio Member
 
Join Date: Mar 2005
Location: Quebec
Synchronize your floating power supply to amplifier clock....This should fix your probleme!
  Reply With Quote
Old 7th February 2008, 03:30 PM   #6
diyAudio Member
 
Join Date: Jul 2006
Thanks Fredos!
But i'm already checked that... even if i synch, even if i adjust the Fosc of smps, same white noise... (ok, small, but perceptible)
  Reply With Quote
Old 7th February 2008, 03:46 PM   #7
diyAudio Member
 
Join Date: Jul 2006
This is top layer:
Attached Files
File Type: pdf classd-rc4-5 top.pdf (28.3 KB, 106 views)
  Reply With Quote
Old 7th February 2008, 03:47 PM   #8
diyAudio Member
 
Join Date: Jul 2006
And bottom:
Attached Files
File Type: pdf classd-rc4-5 bot.pdf (46.4 KB, 91 views)
  Reply With Quote
Old 7th February 2008, 04:01 PM   #9
diyAudio Moderator Emeritus
 
lumanauw's Avatar
 
Join Date: Oct 2002
Location: Bandung
Send a message via Yahoo to lumanauw
Could you try change C20 to 4n7 and R11 to 1k8?
  Reply With Quote
Old 7th February 2008, 04:08 PM   #10
diyAudio Member
 
Join Date: Jul 2006
In fact, i tryiet with semireglable in place of R11, modifying Fosc, but give more noise (other type of noise, more like radio interference or something like this). Indeed, i tryiet before to sync SG with 62.5kHZ, but result if the same with RC with values showed in the sch.
  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
EL34 Power Stage AmpBuilder225 Tubes / Valves 6 16th February 2009 05:39 PM
phono stage hiss woodturner-fran Tubes / Valves 6 15th April 2008 09:59 PM
2 stage power amp Leolabs Solid State 3 29th March 2006 02:48 AM
Single Stage power amp. lumanauw Solid State 10 2nd April 2004 10:03 AM
power output stage Jennice Pass Labs 22 19th June 2003 12:59 PM


New To Site? Need Help?

All times are GMT. The time now is 03:24 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