[Amps] HV Supplies and Diodes

[jeremy-ca]

I find it a bit strange and somewhat comical that the only ones that appear 
to champion resistors and capacitors across any series string of 1N540x 
diodes is the amateur community.

Not one manufacturers application notes mention them.

No industrial product that Im aware uses them.

The one ham amp manufacturer mentioned has a reputation of power supply 
problems.

Most of us realize that the diodes of the 60's had problems but is there any 
reason to continue it almost a half century later?

Fact or mythology?

Carl
KM1H





----- Original Message ----- 
From: "Jim Tonne" <tonne at comcast.net>
To: "Dennis W0JX" <w0jx at yahoo.com>; <amps at contesting.com>
Sent: Wednesday, January 02, 2008 2:20 PM
Subject: Re: [Amps] HV Supplies and Diodes


>
> When a string of series-connected diodes is reverse-biased
> (during part of the cycle), the voltage drop across one is
> proportional to its leakage resistance.  If the junction of the
> diode type has significant capacitance, then that enters into
> the picture too.
>
> If you use, in parallel with each diode, a resistor whose value
> is a fraction of the leakage resistance, then those resistors will
> swamp the leakage and so tend to equalize the voltage drop
> across each diode in a string.
>
> If you use, in parallel with each diode, a capacitor whose
> value is several times that of the junction, then those capacitors
> will swamp the junctions and again tend to equalize the voltage
> drop across each diode in a string.
>
> During the forward-conduction part of the cycle of course
> we have no problems with any of the above.
>
> I am not familiar with the rules on avalanche diodes.
>
> - Jim WB6BLD
>
>
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