schottky vs. soft/fast recovery diodes

metebalci · 5th April 2004, 07:50 PM

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, 01:14 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, 01:19 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, 04:38 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, 05:14 AM

Are they expensive??

Magura

ClassD · 6th April 2004, 07:03 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, 07:27 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, 11:28 AM

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

Circlotron · 6th April 2004, 12:11 PM

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, 12:46 PM

600V 1A ones cost USD1.60

Regards,
Joe Ling

5th April 2004, 07:50 PM	#1
metebalci diyAudio Member Join Date: Feb 2004 Location: Istanbul/TURKEY	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

6th April 2004, 01:19 AM	#3
Magura diyAudio Member Join Date: Oct 2003 Location: Denmark, Viborg	There is a noise aspect to this as well. Wich makes more noise?? It seems to differ from application to application. Magura __________________ Everything is possible....to do the impossible just takes a little while longer. www.class-a-labs.com

6th April 2004, 05:14 AM	#5
Magura diyAudio Member Join Date: Oct 2003 Location: Denmark, Viborg	Are they expensive?? Magura __________________ Everything is possible....to do the impossible just takes a little while longer. www.class-a-labs.com

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6th April 2004, 01:14 AM	#2
ClassD diyAudio Member Join Date: Apr 2004 Location: Brisbane	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.

6th April 2004, 04:38 AM	#4
joeling39 diyAudio Member Join Date: Jun 2002 Location: Malaysia	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

6th April 2004, 11:28 AM	#8
ClassD diyAudio Member Join Date: Apr 2004 Location: Brisbane	Oops, meant to write "generally not available over 60V".

6th April 2004, 12:46 PM	#10
joeling39 diyAudio Member Join Date: Jun 2002 Location: Malaysia	600V 1A ones cost USD1.60 Regards, Joe Ling

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