At 11:35 AM 12/27/2011, Electron wrote: >At 18.51 2011.12.27, you wrote: > > > >Side question: are the diodes that make up the bridge rectifier fast > >or ultra-fast diodes? If not, you will be seeing significant losses > >from those diodes. > >No they ain't but now after Your post they will be. :D > >If it matters: max switching frequency is about only 1000Hz though. > >By the way, when are fast recovery diodes NOT necessary, talking=20 >about SMPS? Is there any situation ever when they can be safely avoided? I use fast diodes anytime I'm switching significantly faster than=20 line frequency (60Hz *2 in my case). I'm pretty sure that reverse=20 recovery currents will start to become a measurable problem at 1 kHz. The more important factor is the rise time of your spike, as opposed=20 to the actual switching frequency. The easy way to see if there is a difference is to actually try=20 it. Note - you may see your ringing problem actually get worse when=20 you change to fast diodes. However, I don't think that the ringing=20 is a problem unless it becomes an EMI issue. dwayne --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .