UF4004 vs. N4004

DECKY999 · 7th April 2008, 05:17 AM

Is there any advantage using ultra fast 4004 over normal 4004 diodes in linear power supplies? What is the man advantage of MUR860 type diodes over UF4004 variety?

Ouroboros · 7th April 2008, 06:56 AM

The UH400x range have a soft turn-off as well as being fast so they produce a lot less switching noise as a result of the 'snap' turn-off of the reverse currnet that flows for a short time when the diode gets reverse biased. On normal 50/60Hz ac supplies that effect is not normally a problem. (When you get up to SMPSU switching frequencies it is a very different matter!)

Ouroboros · 7th April 2008, 06:57 AM

I meant UF400x range, not UH of course!

DECKY999 · 7th April 2008, 11:06 PM

Does that mean that ultra fast and soft switching diodes are simply an overkill for a linear PSU?

Ouroboros · 8th April 2008, 06:50 AM

I have seen simple linear PSUs where there was an issue with EMC (mains conducted noise) which replacement of the 1N540x range devices with UF equivalents solved. It does no harm to use fast, soft-switching diodes at mains frequencies, and might help to keep EMC problems to a minimum.

DECKY999 · 9th April 2008, 02:18 AM

That's what I thought as well - thanks. But what about UF4004 against MUR860 or other more expensive fast diodes. Is the higher current rating only advantage?

7th April 2008, 05:17 AM	#1
DECKY999 diyAudio Member Join Date: Jul 2007	UF4004 vs. N4004 Is there any advantage using ultra fast 4004 over normal 4004 diodes in linear power supplies? What is the man advantage of MUR860 type diodes over UF4004 variety? __________________ The only true way is no way.

7th April 2008, 11:06 PM	#4
DECKY999 diyAudio Member Join Date: Jul 2007	Does that mean that ultra fast and soft switching diodes are simply an overkill for a linear PSU? __________________ The only true way is no way.

9th April 2008, 02:18 AM	#6
DECKY999 diyAudio Member Join Date: Jul 2007	That's what I thought as well - thanks. But what about UF4004 against MUR860 or other more expensive fast diodes. Is the higher current rating only advantage? __________________ The only true way is no way.

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7th April 2008, 06:56 AM	#2
Ouroboros diyAudio Member Join Date: Dec 2003 Location: Nottingham UK	The UH400x range have a soft turn-off as well as being fast so they produce a lot less switching noise as a result of the 'snap' turn-off of the reverse currnet that flows for a short time when the diode gets reverse biased. On normal 50/60Hz ac supplies that effect is not normally a problem. (When you get up to SMPSU switching frequencies it is a very different matter!)

7th April 2008, 06:57 AM	#3
Ouroboros diyAudio Member Join Date: Dec 2003 Location: Nottingham UK	I meant UF400x range, not UH of course!

8th April 2008, 06:50 AM	#5
Ouroboros diyAudio Member Join Date: Dec 2003 Location: Nottingham UK	I have seen simple linear PSUs where there was an issue with EMC (mains conducted noise) which replacement of the 1N540x range devices with UF equivalents solved. It does no harm to use fast, soft-switching diodes at mains frequencies, and might help to keep EMC problems to a minimum.