fast bridge rectifiers

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#21
Eva said:
As an example, see datasheets for RHRP860 and RHRP1560 from Fairchild[Harris]

15A diode shows higher Trr than 8A diode for currents beteen 0,5A and 8A and same dI/dt and temperature

So Trr depends on diode current rating, at least for these particular series or hyperfast diodes

I suppose different processes are used for different current ratings and bigger diodes use a process that causes slower recovery
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For some diode lines, the trr is designed as part of carrier recombination.

For some, it is by using an epitaxial process.

Some diodes are sandblasted out of a wafer, some are photolithographically designed...

They may have changed the trr to drop the VF at the rated current..

In other words, there is a huge amount of things that were done to achieve the higher current rating..

But, none of that means that higher current ratings are inverse to trr.. unless you are intimately involved with the product line, (or me, for that matter), claiming the relation of current vs trr is unsupported..

I've dealt with bigger diodes that were quite fast..you should see some of the 100 mm product out of brown boveri or powerex..

Cheers, John
 
#23
But you can't just blindly use fast-recovery diodes. Many of the have horrible artifacts when they turn off (dumping sometimes giant stored charges onto the line). What you want is a controlled recovery, where the turn off condition is fully characterized.

I had some MUR series diodes once they caused the most heinous problems with power line oscillations. In that application I switched to controlled (ultra-fast/ultra-soft) recovery diodes from IRF. Which model I cannot presently remember.

Since then I've used Schottky and been pretty happy. I'm even using Schottky rectifiers in the low-current supply of my Krell clone. They make quite high votage and high current rated Schottky rectifiers these days. Just be careful about the thermals.
 
#25
Good designed amp, which have good PSR, have typical SNR over than 120 dB with standard " slow " rectifier. Don't talk about recovery times ( by normal line frequency 50-60 Hz ), talk about which paramerer of amp will be better in case, when will be used fast diodes. I take only logical arguments, not something like " It use XY too ". Personaly I mean, that all is only humbuk for " milking " of customers 😉 .
 
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