Calculating smoth capacitor ripple current

[zainka]

Hi
This might be a stupid question, but if so, think of me as a cow on a large field chewing on grass looking at you throug my brown innocent cow eyes.

I have som trouble finding a way to calculate how much ripple current my smooth capacitor should be rated for while using an 15V/35VA transfomer phused to its edges. The transformer output is bridge rectified. I have tought of using som "United chemi-con" caps in the MVY series (smt) with 2200uF /35V but this is rated for app. 1,750mA ripple current, and i think that is a bit to little. However, I dont seem to remember how to calculate my needs. Any tip will do, if so only pointing to some online tutorials.

Thanks
Z

 

[12ax7]

Hello chewing cow..

To a first approx capacitor ripple current is independent of value of C it only depends on load dc current.

Assuming a full wave bridge rect:

Ic ripple~= 1.1xIdc

In practice its a bit higher than this by some % because of ripple harmonics and the above assumes sine wave ripple. ( assume 20% higher)