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-   -   schottky vs. soft/fast recovery diodes (http://www.diyaudio.com/forums/parts/31675-schottky-vs-soft-fast-recovery-diodes.html)

metebalci 5th April 2004 08:50 PM

schottky vs. soft/fast recovery diodes
 
Hi,

Are schottky diodes always preferred to soft/fast recovery or stealth diodes in rectifiers as long as there are available schottky diodes with required maximum repetitive reverse voltage ?

Thanks...

MB

ClassD 6th April 2004 02:14 AM

Schottky diodes:

+ Low forward voltage
+ Fast recovery time
- Not available in ratings higher than about 60V
- high leakage current

Soft/Fast Recovery diodes:

+ Fast Recovery Time
+ High voltage rating
+ Low leakage current
- High foward voltage

Choose whichever is going to be more efficent in your circuit.

Magura 6th April 2004 02:19 AM

There is a noise aspect to this as well. Wich makes more noise?? It seems to differ from application to application.


Magura:)

joeling39 6th April 2004 05:38 AM

Seems that there are manufactureres who have managed to get round the low voltage limitation with Schottky diodes :

www.cree.com

I bought some 600V 1A ones from an online retailer a while back but have not tried them out yet.

Regards,
Joe Ling
Malaysia

Magura 6th April 2004 06:14 AM

Are they expensive??

Magura:)

ClassD 6th April 2004 08:03 AM

Quote:

Originally posted by Magura
There is a noise aspect to this as well. Wich makes more noise?? It seems to differ from application to application.


Magura:)


Well the 'Soft Recovery' diodes were specifically designed to reduce switching noise. They have a gradual turnoff which rounds off the switching current waveform. This results in a lot less RF noise, with a small sacrifice in efficency.

However if you are using the diodes in a standard 50Hz bridge rectifier then there will really be no diffrence because the frequency is so low.

till 6th April 2004 08:27 AM

Quote:

- Not available in ratings higher than about 60V
MBR10100

Quote:

Well the 'Soft Recovery' diodes were specifically designed to reduce switching noise. They have a gradual turnoff which rounds off the switching current waveform. This results in a lot less RF noise, with a small sacrifice in efficency.
And in my understanding the schottky does this even better

ClassD 6th April 2004 12:28 PM

Oops, meant to write "generally not available over 60V".

Circlotron 6th April 2004 01:11 PM

soft turnoff.
 
Quote:

Originally posted by ClassD
However if you are using the diodes in a standard 50Hz bridge rectifier then there will really be no diffrence because the frequency is so low.
I used to think so too. Get your scope out and have a look at the transformer secondary voltage under load. Zoom in to where the waveform is just starting to move away from the flattened peak and head toward zero again. As a slow diode recovers it will "snap" the reverse recovery current off suddenly, causing the transformer winding to ring somewhat. Fast, ultrafast and schottky diodes (and vacuum tube rectifiers for that matter) turn off more cleanly and don't "twang" the transformer winding and generate noise in the process.

joeling39 6th April 2004 01:46 PM

600V 1A ones cost USD1.60

Regards,
Joe Ling


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