[Amps] Equalising resistors with HV diodes

[Steve Thompson]

On Monday 20 September 2004 14:08, peter.chadwick at Zarlink.Com wrote:
> Rich said:
> >Please explain why equalizing resistors have merit.
>
> Because if the reverse leakage differs between diodes, the reverse voltage
> distribution also differs. The one with the least leakage ends up with the
> highest voltage across it, which could exceed the breakdown volts. With
> resistors, the voltage distribution across the diodes is fixed by the
> resistor ratios.
>
> If the capacitances aren't matched, that will also affect the voltage
> distribution. That's one reason why it is not wise to mix diodes of the
> same nominal type from different manufacturers without some equalisation.
> Another is the reverse recovery time.
If I understand it correctly, equalising resistors might hurt you only if you 
get a reverse voltage spike that exceeds the specified breakdown of the diode 
chain. In many, if not most, power supplies will a modest mains filter all 
but eliminate that likelyhood?

Steve