Re: Diode Strings

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 

 >  >
 >  > It actually depends on whether the bridge is feeding a capacitor or
 >  > not which, if it is, the above arguments rigidly apply since the
 >  > reversed diodes have to hold off the voltage across the capacitor
 >  > plus the peak voltage of the transformer.
 >  >
 >  > Malcolm
 >  >
 >  >
 >
 > I setup a low voltage bridge using a filter cap  and using an O-scope
looked
 > at the voltage across each diode. There was only 1/2 of the peak-to-peak
 > voltage across any one diode. In other words the diode in any leg needs to
 > be 1.414 x RMS even with a filter cap.
 >
 > Of course add some voltage rating for safety.
 >
 > Rick W.


It also pays to consider what happens if the output gets shorted
momentarily.  I've killed a number of bridge rectifiers in pulse discharge
applications because I didn't realize that if the output voltage reverses
(as in the ringing from a sudden discharge of the filter), the diodes die a
quick death.

There are other scenarios that one should consider, too.  What if one or
both the input to the rectifier goes open or shorted?  This might never
occur in your design, then you wouldn't need to consider it, but you should
look at all the "credible faults", at least casually.