ripple capacitors - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 2nd March 2011, 03:39 PM   #1
diyAudio Member
 
Join Date: Jan 2011
Default ripple capacitors

hello all again

i have a quick question about capacitors. I'm STILL building the leach amp and have a bunch of different caps i want to use for the power supply

2 @15000uFD 100V
4 @33000uFD 50V
10 @680uFD 250V

now my question is these are to be used for + & - 90volt rails. id like to use all of these caps (just cause i have em). now when i wire them all up my plan is to use "1" "2" & "5" per rail, so im going to wire 2 of the 50v in series to make single 100v cap, from what i understand about caps, in parallel you get the same voltage and double the capacitance, in series you get double the voltage and HALF the capacitance, is this correct??? meaning to say once this is all said and done will my total capacitance per rail be 34900uFD and is there any benefit/fallback to this arrangement.

Thank you again
  Reply With Quote
Old 2nd March 2011, 05:15 PM   #2
Boofers is offline Boofers  Canada
diyAudio Member
 
Join Date: Oct 2008
Location: Ontario
Blog Entries: 1
Yes man.

Caps in parallel - Total capacitance is Cparallel = C1 + C2 + C3. The voltage rating is what you read on each cap.

Caps in series - The total capacitance is found by Cseries = 1 / [(1/C1) + (1/C2) + 1/C3)] Note that this formula is the same format as calculating resistance in parallel.

With series voltage it gets a bit more tricky. Yes you add the voltage ratings together to get a total voltage. The danger is if you use different values of capacitance in series you can potentially exceed the voltage ratings (because with different capacitance values you drop a different voltage across each cap) If you are using 2 x 33mF 50V caps, you should be ok, but as a general rule you use caps with voltage ratings 20% to 25% higher than your max voltage. With 90V rails, 100V caps are cutting it a bit close.

I generally don't put caps in series becasue the series resistance and inductance are added together, but hey sometimes you use the parts you have right?

Check out this cool power supply design program. You can maybe use it to explore different cap configurations.

PSUD2
  Reply With Quote
Old 2nd March 2011, 05:28 PM   #3
agdr is offline agdr  United States
diyAudio Member
 
agdr's Avatar
 
Join Date: Sep 2010
Here is exactly what Boofers said in an app note from Daewoo from a google search. Check out item #15, series caps, pg 3.

http://www.megastar.com/products/dae...guidelines.pdf
  Reply With Quote
Old 2nd March 2011, 07:23 PM   #4
Boofers is offline Boofers  Canada
diyAudio Member
 
Join Date: Oct 2008
Location: Ontario
Blog Entries: 1
That is a nice article agdr.

It is interesting that the formulas for voltage across series caps show that the series capacitor with the smallest capacitance will have the highest voltage drop.
  Reply With Quote
Old 3rd March 2011, 12:07 AM   #5
artu is offline artu  Chile
diyAudio Member
 
artu's Avatar
 
Join Date: Nov 2010
Location: Santiago, Chile
Parallel capacitors will also decrease ESR so the resultant cap. with be more fast, it should handle better fast demands of current transients.

Cheers
Arturo
  Reply With Quote
Old 3rd March 2011, 09:39 AM   #6
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Buy the correct capacitors for your project.
If your supply rails are a nominal +-90Vac then you need >=110V capacitors for the smoothing. 150V and 160V are available but they get much more expensive the further above 63V they are.

Select a transformer that allows 100Vdc caps to be used safely. probably <=62Vac
__________________
regards Andrew T.
  Reply With Quote
Old 5th March 2011, 04:57 PM   #7
diyAudio Member
 
Join Date: Sep 2006
Andrew T's advice is worth heeding.
But you could also add parallel resistors to your caps to force the voltages to be the same. They should be dimensioned so that the RC time constants are the same or you could still get a dynamic voltage division which causes one of them to get to be to high.
John
  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
78xx + FAT capacitors = ripple elimination?? smellygas Power Supplies 10 14th September 2009 10:05 PM
Help with ripple akis Solid State 18 4th September 2009 09:19 PM
too much ripple steevo Solid State 11 5th July 2007 07:27 PM
Ripple current in capacitors. beppe61 Power Supplies 5 3rd September 2006 11:37 AM
How much ripple?? JDeV Tubes / Valves 23 2nd April 2003 11:05 PM


New To Site? Need Help?

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