capacitors voltage rating - 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 10th July 2006, 08:44 PM   #1
diyAudio Member
 
Join Date: Oct 2004
Default capacitors voltage rating

maybe a stupid question but...using a power supply scheme for a dual voltage(+/-35V) and 1 rectifier bridge the filter capacitors form a capacitor voltage divider; so the max voltage of the capacitors is 70V or 35V?because i remember that in a capacitive voltage divider it's mandatory to use the max imput voltage as max voltage for the capacitors...am I wrong?
  Reply With Quote
Old 10th July 2006, 08:47 PM   #2
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
In your example, you would need caps able to handle 35V or more.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  Reply With Quote
Old 10th July 2006, 09:05 PM   #3
Shredly is offline Shredly  United States
diyAudio Member
 
Join Date: May 2006
As long as the caps aren't connected rail-to-rail but rail-to-ground, and this is the standard method, 35V rated caps should be fine. DON'T connect one 35V cap directly from +35V to -35V.

Remember to check ripple current and the ripple rating of the caps, too.
  Reply With Quote
Old 10th July 2006, 09:16 PM   #4
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
what is the open circuit output voltage of the transformer when connected to a nominal mains supply voltage?

How high can the output voltage go when the mains supply voltage is at maximum?

In the UK this is +6%. i.e 254Vac for a nominal 240Vac supply

Now calculate the maximum peak voltage on each of the smoothing caps.

Select a voltage rating to suit the rail to ground voltage.

Some manufacturers trim this substantially to allow cheaper/smaller components to be used.

I have an amplfier that has 51Vdc on the PSU at 240Vac input and it uses 50Vdc caps. I think they should be shot for selling this potential death trap.
__________________
regards Andrew T.
  Reply With Quote
Old 11th July 2006, 12:16 AM   #5
Shredly is offline Shredly  United States
diyAudio Member
 
Join Date: May 2006
I keep telling you about commercial design practices, Andrew.

Good job telling the really correct way to judge what voltage capacitors to use; listen to him, raikkonen, he speaks the truth.
  Reply With Quote
Old 11th July 2006, 06:46 AM   #6
diyAudio Member
 
Join Date: Oct 2004
ok, guys, so if the secondary has 50vac,and I split it in 2 separate after the bridge, I think will be a good idea to use 50V capacitors instead of 35, right?the schematic is something like this...
Attached Images
File Type: jpg psu2.jpg (7.5 KB, 247 views)
  Reply With Quote
Old 11th July 2006, 08:15 AM   #7
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
your 2*25Vac will produce a nominal +-34Vdc.
The upper and lower voltage limits, assuming 6% regulation, will be 31Vdc to 38Vdc.
Your choice of 50V caps is just fine.
__________________
regards Andrew T.
  Reply With Quote
Old 11th July 2006, 08:43 AM   #8
diyAudio Member
 
Join Date: Oct 2004
yes, considering also that italian mains will vary more than 6% i think it's a good choice, thanx a lot!!
  Reply With Quote
Old 12th July 2006, 03:30 AM   #9
diyAudio Member
 
Join Date: Mar 2004
Location: Arkansas
Gonna need a 80v+ cap for C5.
It's gonna see the Peak to Peak voltage of both secondaries because the cap sees them wired in series.
__________________
Writing is good exercize for the texticles!
  Reply With Quote
Old 12th July 2006, 06:58 AM   #10
diyAudio Member
 
Join Date: Oct 2004
wait wait...are you sure?that was my problem...i thought this too, cos it's a voltage divider...probably during a transient it will go upper 50 volts...damn...does anybody has a sure experience with this schematic??please!!!
  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
Edcor OPT Voltage Rating? sorenj07 Tubes / Valves 10 26th January 2009 07:40 PM
voltage rating for Ci? rfenergy Chip Amps 10 21st June 2008 09:24 AM
Using a cap above its voltage rating? h_a Parts 10 6th October 2007 03:46 PM
NOS pF capacitors voltage rating? bembel Tubes / Valves 10 16th September 2006 08:56 PM
Rating Capacitors for Power Amp PSUs colin betts Solid State 7 22nd November 2001 11:07 PM


New To Site? Need Help?

All times are GMT. The time now is 04:28 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