[Amps] P600M diodes in HT supplies

[Steve Katz]

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
> 
> 
> --- StripMime Report -- processed MIME parts ---
> multipart/alternative
>   text/plain (text body -- kept)
>   text/html
> ---
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps