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Old 03-27-2012, 08:02 PM   #49 (permalink)
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Originally Posted by mort View Post
The diodes you link to are Schottke, which are low forward voltage and fast, both things you don't need and cost extra.
You definitely need faster-than-fast diodes. Regular "fast" diodes are quite slow, and usually 'snappy'. These work fine rectifying a slow sine wave, where the zero crossing is a gentle slope. Horrible things happen when they are faced with the sharp cut-off of a semiconductor switch. They briefly continue to pass current after the voltage reverses and then "snap", which results in localized melting and cascading failure.

You want "ultra-fast" diodes with soft recovery. Schottky diodes do nicely, if you are working with low enough voltages. They cost more to fabricate, but this is usually offset by their lower forward voltage drop and thus higher current capacity in the same package type.

If you are designing a new circuit, using a MOSFET switched to emulate an ideal diode ("active rectification" / synchronous rectification) is an even more efficient solution.

Last edited by DJBecker; 03-27-2012 at 08:09 PM..
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