fast high-voltage diodes

They're in series so only one has to turn off to meet the 50 ns time.

I wonder what that does to the rest of the stack?

The first one that recovers will avalanche as most of the reverse voltage tries to straddle it. That might be OK if the power dissipation doesn't fry it.

I suppose I could test them, and include a thermal imaging step to make sure that some diodes in the string aren't getting too hot. Nuisance.

most of the HV recitifer stacks I've come across are either

2) compensated with resistors, caps or MOVs, but this is for higher applications

It gets worse with 200V Schottky diodes like we had in a thread a while ago. Often they spec no carrier lifetime. A new kid that doesn't know might assume Schottky is always infinitely fast and ... phsssss ... *PHUT*

Then they call the fast, ultra-fast, hyper-fast an so on. Like in Spain, where a hole in the wall grocery was called supermercado and a store the size of an average Trader Joe's was called hypermercado. Couldn't believe it.

Yeah, like this:

The next category should be ACTUALLY FAST.

Den torsdag den 21. august 2014 19.05.41 UTC+2 skrev John Larkin:

-Lasse

A friend from church once had a car that was labeled "super-ultra low emission vehicle". Maybe something like that would work :-)

I have one of those. One of these days I will get it running.

Regards, tm

A car up on blocks is nearly a zero-pollution vehicle.

Yep, Typical string of fast diodes. What recovery time are you looking for?

Cheers

Trr=30ns @25c

Cheers

Interesting, thanks, but I need smaller, lower current things, 25 mA sort of range. Maybe I could put a string of surface-mount duals/triples/quads on a baby board, make my own sip package.

Interesting data sheet. There are two series that differ only in (max? typ?) Trr. Then there's a typ Trr graph that doesn't specify which series it applies to. At 75C, we're back to.... 50 ns!

I guess we'll have to buy a lot of diodes and test them.

Where are the Data Sheet Police when you need them?

You could try DeanTechnology too. I only see 35ns but you should call and see if they have anything.

Cheers

sure, we use ~320 200v diodes for a 50kv string. You still need all the small caps and R's , etc.

Jamie

Thanks. Their RSUF6 (formerly HVCA?) specs 35 ns max, which is about the best thing around.

HVCA is part of Dean. I think Dean grew out of Collimer Semi and started buying small HV related companies. They've been around some time.

Cheers

Unless you can convince someone to make SiC schottky in a 25mA size, you're SOL.

Well, almost; you might find some of these laying around yet. As a small quantity company, it's not actually a bit cut into your manufacturability:

Technically, you still have the reverse recovery of space charge, but gee, it's just whatever's floating in a vacuum, not soaked into a semiconductor junction. Frequency response is limited by geometry, which will be better on dampers than the HV types with those bell shaped anodes.

There may be smaller ones out there, this is the first smallest in this class (damper) I've seen. Older ones like 2X2A are a bit too weak (andb bulky) though.

Tim

There were those tiny pencil tube rectifiers that Tektronix soldered into their CRT HV supplies. One of those would not be totally absurd to use on a modern PCB. Likely not good for 25 mA.