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[AMPS] Power Supply Diodes

To: <amps@contesting.com>
Subject: [AMPS] Power Supply Diodes
From: Peter_Chadwick@mitel.com (Peter Chadwick)
Date: Thu, 3 Feb 2000 09:07:52 -0000
Like Larry, I've seen equalising resistors used and not used. If the diode
is a controlled avalanche device, then sure you don't need them. If you
don't have a controlled avalanche device and reasonable match on leakage and
PIV and junction capacity, then I believe you do. Now if all the diodes are
the same date code from the same manufacturer, they should be a reasonable
match in capacity and PIV and leakage. (Leakage and PIV are not necessarily
the same thing). Note that if you put two capacitors in series with DC
across them, the voltage divides inversely proportional to the capacity, so
a big imbalance in the junction capacity could lead to one diode getting
more volts.

Larry, have you done the sums on the peak current? Since you're using
capacity input, the peak current will be determined by load and the various
series resistances (and leakage inductance). It's possible that the peak
current was being exceeded - I don't know the repetitive peak current rating
of those diodes

I don't trust these damn semiconductors anyway!


73


Peter G3RZP

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