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[Amps] P600M diodes in HT supplies

To: <amps@contesting.com>
Subject: [Amps] P600M diodes in HT supplies
From: stevek@jmr.com (Steve Katz)
Date: Fri, 3 May 2002 12:55:25 -0700
Theoretically, it shouldn't matter whether the rectifiers are fast-recovery
or not for a 120 Hz application; however, diodes in a series string will
handle transients much better if their recovery times are all the same
(regardless of fast, or slow).  The reason for this is, while the
low-frequency signal will divide amongst the diodes in the series string
according to the reverse leakage currents (assuming no diode in the string
ever avalanches, or breaks down), the high-frequency signal such as a fast
transient will divide instead according to trr (reverse recovery time) and
Cj (junction capacitance).  The rectifier string appears as a string of
capacitors, not semiconductors, to a fast transient.

WB2WIK/6

"Each success only buys an admission ticket to a more difficult problem." --
Henry Kissinger

> -----Original Message-----
> From: EVonvaltie@aol.com [SMTP:EVonvaltie@aol.com]
> Sent: Friday, May 03, 2002 12:31 PM
> To:   amps@contesting.com
> Subject:      Re: [Amps] P600M diodes in HT supplies
> 
> What reasoning leads you to believe that these diodes (fast recovery) do
> or 
> don't need 'equalizing' R's or C's any more or less than standard recovery
> 
> diodes.
> 
> I have always been skeptical of this anyway. I think it originated back in
> 
> the early days of Si diodes when things were several generations back in 
> semiconductor design. In particular, the early diodes had horrendously
> high 
> leakage compared to todays, enough to guarantee more than a few ua. of 
> Ireverse at full PIV.
> 
> I have the two following facts (not opinions, please note) to offer:
> 
>        1. I have not bothered with R/C equalization for over 20 years
> 
>        2. I have not blown a rectifier for over 20 years, even during some
> 
> serious condx
>            of short or low-R on B+ line. I have used strings of 4007's and
> 
> 5408's in
>            supplies up to 4 or 5 KV.
> 
> If we are going to still cling to this old bit of folk lore, let's see 
> someone formulate a cogent argument in support thereof. Let the hand
> wavers 
> go work on cross-field antenna design.
> 
> Eric von Valtier K8LV
> 
> 
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