You can get some good power supply application information at Vicor (www.vicr.com).
>> Be sure and address both differential and common mode signals. X >> and Y caps in line filtering terms. In other words, put some C >> between the lines and also to ground. > The switcher only provides +5 and ground. What's the third line? The X cap would go across the +5V and ground. You would use two Y caps -- one from +5V to earth ground and the other from ground (or return) to earth ground. >> For an AC signal, you can put a common mode choke on the incoming >> line. By this I mean, take the pair of wires that bring 24 VAC in >> and wrap them around a magnetic core. > This can be done just off the board, yes? Just a ferrite on those > lines? This depends on the frequency you are trying to filter. I would think you would be better off with a larger inductance. Something like a few mH toroid. (* jcl *) -- http://www.luciani.org