Stacking SiC Schottky diodes

[Navyblue]

So I have been reading this thread:

https://www.diyaudio.com/forums/tubes-valves/54603-sic-schottky-rectifiers.html

Is stacking SiC Schottky diodes allowed?

I bought some STPSC2H12D from ST. The datasheet doesn't seem to mention this.

https://www.farnell.com/datasheets/2290164.pdf

On one of my amp, the maximum secondary is 520-0-520V. I planned to stack 3 of them.

If it is not allowed, stacking with other types of rectifiers, silicon or tube, is acceptable?

 

[Tom Bavis]

I've seen recommendations against series connecting Schottkys; but equalizing resistors would take care of differences in reverse characteristics. But you need high voltage resistors - common 1/2W are 350V or so. You need 1500PIV (absolute minimum); stacking 3 diodes is best. If it's a choke input filter, you need a snubber capacitor (.05-0.1uF, 2KV) or MOV on the input or you'll have diode failures.

 

[Magz]

Here is the HV rectifier for one of my Midlife Crisis 833C amps. 5 stacked SiC Schottky diodes per leg of the bridge. I have a 10nF, 1500V capacitor across each diode for balancing, per this reference:

The Valve Wizard

It's been in operation for 7 years now with no failures, rectifying the output of a 2500V transformer in a choke-input supply.

 

[Navyblue]

you need a snubber capacitor (.05-0.1uF, 2KV) or MOV on the input or you'll have diode failures.

I already have RC snubber (22nF, 270 ohm) across each transformer leg to center tap, do I need still need more snubbers across the diodes?

 

[Navyblue]

Here is the HV rectifier for one of my Midlife Crisis 833C amps. 5 stacked SiC Schottky diodes per leg of the bridge. I have a 10nF, 1500V capacitor across each diode for balancing, per this reference:

The Valve Wizard

It's been in operation for 7 years now with no failures, rectifying the output of a 2500V transformer in a choke-input supply.

Good to know!

 

[trobbins]

Navyblue, I'd expect you could series connect those diodes without any equalising parts but you need to appreciate the details as to why that may be applicable. The 2nd section of the following link goes into that discussion for 1N4007, but it gets technical, and there are proviso's attached which you should implement imho.
https://dalmura.com.au/static/Power%20supply%20issues%20for%20tube%20amps.pdf

What is more concerning for SiC is their peak current capability - the last part of Section 1 of that link has some discussion on that. It is in your interests to appreciate what current levels would occur in your use case - as you may experience what post #11 described in that other diyaudio link from 2005.