Power Supply Filter Capacitor Size

[Paul Perry]

At 09:27 AM 8/12/99 +0100, Martin Czech  wrote:
>It may appear that the filter cap should be as large as possible.  But in
>this case the trafo sees a very low load, ie. almost a short when the
>coil voltage rises.
>
Well, this is true for the first cycle after switching on.
But, once the capacitor is charged, the currenf flowing in and out of the
capicator
depends only on the current drawn by the load (in this case the regulator
input).
So it doesn't matter how ginormous the cap is, though of course above a certain 
size it isn't really going to help.

Now one thing a big capacitor will do, is encourage such an inrush of current
on first turning on as to ruin the diode. But, that is another story.

paul perry Melbourne Australia