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In Reply to: RE: Full wave bridge into Choke PS posted by vetmedrobert@gmail.com on March 26, 2017 at 10:28:28
If you use SS diodes anywhere in the bridge, be sure to use either a snubber cap. or MOV, as protection against inductive kick back spikes. Think cLC filter, where c is 0.01 μF. and its WVDC is very large.
Eli D.
Follow Ups:
I parallel every diode with a 0.01u disc cap and 470K resistor (values not critical). This has been a standard commercial treatment for more than 50 years.
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Buy Chinese. Bury freedom.
"I parallel every diode with a 0.01u disc cap and 470K resistor (values not critical)."A very reasonable action, when most PN junction diodes are employed. FREDs can exhibit "funny" behavior, when snubbed. Snubbing diodes is unnecessary, when they are Schottkys.
The single snubber I mentioned is specifically for choke I/P filters associated with SS diodes. Without the cap. or MOV, inductive kick back spikes can destroy SS diodes. The situation is 1 where the electrical fragility of SS is illustrated.
Tubes are mechanically fragile and electrically robust. SS parts are mechanically robust and electrically fragile.
Eli D.
Edits: 03/28/17
OK what's a MOV? and if I follow the LC section with another LC section is it really needed?
MOV = metal oxide varistor. They are what make surge suppressor power strips work.
Regardless of what you follow an I/P LC section with, inductive kick back spikes are a potential source of SS diode destruction. "An ounce of prevention is worth a pound of cure."
A link to a modestly price part that will get the job done is provided below.
Eli D.
I presume that each diode in the bridge is paralleled with one of these snubbing caps? Thanks for the link, much appreciated.
Only 1 snubber, connected between the bridge's O/P and ground, is needed. Remember, think cLC filter, where the 1st cap. is tiny .
Eli D.
Thanks, very cool and very easy to implement.
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