# Filter Capacitors in Parallel for power supply

Discussion in 'The Projects Forum' started by Blatboy, Mar 10, 2013.

1. ### Blatboy Thread Starter Member

Jun 11, 2012
46
0
Hey there. This is my first post, and I'm pretty new to electronics in general, so please be gentle.

I have been slowly working on building a power supply as explained in G. Randy Slone's book Electricity and Electronics from Tab Electronics. (This project was also referenced here in this forum.)

the project calls for two 4400uF 50 W capacitors as the main filter capacitors after the rectifier. I've attached the page that describes this portion of the power supply.

For the life of me I can't find 4400uF 50W caps. (Ok, I found some on Mouser, and they were really expensive!) I have, however, found four 2200uF 50W caps. Would it be safe to instead use two pairs of the 2200uF caps in parallel? I feel like I remember reading somewhere that using caps in parallel wasn't a good idea in certain types of switching power supplies, but my built in RAM has always been faulty. (The RAM in my brain that is...)

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2. ### MrChips Moderator

Oct 2, 2009
17,559
5,450
They don't make 50W capacitors. You mean 50V.
It really depends on the specific power supply, the output voltage and the current rating.
What do you plan to do with the power supply?
4700μF 50V or 63V capacitors are very common.
If your voltage is below 15V then a capacitor rated for 25V would do.

3. ### gerty AAC Fanatic!

Aug 30, 2007
1,238
343
Another possibility is 50 wvdc,(working volts direct current)

4. ### patricktoday Member

Feb 12, 2013
157
42
Yeah, use this size. I have a +/- 15V adjustable power supply I use a lot that uses 2 4700uF, 63V caps and it works very well. The larger the caps, the less the ripple. You could use two 2200uF's in parallel (provided the same minimum voltage rating is met) but it's more parts and probably costs more.

5. ### Blatboy Thread Starter Member

Jun 11, 2012
46
0
Aha. Yes, I meant V or wvdc. sorry about that.

And I'm even more embarrassed to say that yes, I now see the 4700uF caps on Jameco.

I have no idea where my head was (er, though I have a suspicion) when I was searching for those caps before. For some reason I didn't see them. I think I tried using the fancy "parametric search" and they didn't come up on either jameco or mouser.

6. ### Blatboy Thread Starter Member

Jun 11, 2012
46
0
I may still end up using the two pairs of 2200uF 50V caps, being that I already have them. Why get more parts? I've certainly got enough room in my enclosure. (the enclosure is from an old DVD player I gutted.)

Last edited: Mar 10, 2013