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Old 8th February 2010, 04:01 PM   #1
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Default Best rectifier diodes?

Which diodes are better for a rectifier, Schottky or soft recovery ones?
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Old 9th February 2010, 06:41 PM   #2
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THIS DEPENDS ON THE OPERATING FREQUENCY.
BUT overall heat is the concern and main criteria.
For power frequency, duty cycle in reverse half cycle is negligible for power PN diodes (ton/(ton+toff)) and can be negligible and so can be used. but where frequency is quite high like in SMPS, the turn off time is the factor and the duty cycle of negative half cycle increases.

For any device, Power consumption = voltage across device x current through device.

Now for the same avarage current, calculate the power loss, and also the heat generated during transition (Recovery time). Which produce the more heat, should be avoided.

But this is purely Datasheet dependent or practical oriented. Better to leave for others.

One question,
We know, as thumb-rule, 6-8A/mm2 average current density be allowed for Cu. But in 2 x 30A datasheet, PIN no 2 may carry Max 60A. with that tiny crossection, Unbelievable. (0.9 x 0.6 mm2) = 0.54 sqmm.

Current dencity = 60/0.54 = 111A/mm2

Can anybody explain this ?
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Old 9th February 2010, 09:24 PM   #3
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I referred to switching noise, neither heat nor power consumption.
Also, I referred to conventional (bridge) rectifiers operating at 50/60 Hz, not to SMPS ones.
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Old 9th February 2010, 10:15 PM   #4
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The IR Hexfred series soft recovery ones work well, with very little switching noise and are available from 1.2a up and piv to 1200v. They also come in a twin-pak configuration with a common cathode, which makes for simple grounded CT rectifiers. I bypass the output to ground physically as close as practical with a .01uf and they produce almost undetectable levels of switching noise or ringing.
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