At 12:59 PM 22/11/2011, you wrote:

>Hello,
>if I need a 5KV silicon rectifier diode, will using five 1KV silicon recti=
fier
>diodes in serie grant me the safety I'm looking=20
>for, or it won't work in real life?
>
>Thanks!
>Mario

Most high voltage rectifiers are composed of stacked diodes
internally. Reverse breakdown of a Si diode is not like
dielectric breakdown (as a MOSFET gate or other insulator)-- it
is reversible, has no negative resistance characteristic, and
does not inherently cause damage to the diode (unless the current is
high).

What will happen is that the voltage (say 5kV) will distribute itself
across the chain so that the leakage currents are equalized. If you
used, say, 1N4007 diodes, one diode might have 1.1kV and the next 0.9kV,
but the total reverse current should not exceed a couple hundred nA
at 25=B0C. Of course if one diode fails short and the current is not
limited externally, the others will likely go as well. Using six
would give a bit of margin.

See this commercial HV rectifier, for example:
http://www.hvpsi.com/pdf/D0458ser.pdf

The standard recovery rectifiers have a Vf of 1V per kV of reverse
breakdown rating @1A.

Similarly, common microwave oven diodes have Vf of around 8-14V
and reverse voltage ratings of 8-12kV.

Or the Rectron R5000F is ~75 cents in singles and good for 0.2A at
5kV (Vf of 6.5V at 0.2A)

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the rewar=
d"
speff@interlog.com             Info for manufacturers: http://www.trexon.co=
m
Embedded software/hardware/analog  Info for designers:  http://www.speff.co=
m




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