FW: Re: [AMPS] PS diode equalizing

[n2bc@stny.rr.com]

OK, below Steve points out that his testing showed leakage starting
at 3X the diode PIV rating...     

My question - does the need to equalize diminish as you reduce
the PIV on the diode string?  If so, the diodes are cheap enuf
and 1KV rated resistors are expensive enuf to just double or
triple up on the diodes and forget the equalizing resistors.

Are there other issues using a diode at substantially less than
it's PIV rating?   

73 Bill N2BC (hot in Central NY)




--- Original Message ---
"Tom Rauch" <w8ji@contesting.com> Wrote on 
Tue, 6 Jul 1999 11:59:04 -0400
 ------------------ 

> I tested some 1N5408s which started leaking a few uA at just
> under 3kV. This made me think - without added resistors or
> capacitors, the voltage sharing along a string in reverse
> bias will likely rely on the capacitances of the diodes.
> Lower capacitance takes higher voltage, and the varactor
> effect pushes the capacitance lower and so on (and the
> reverse on the rest of the string) - you could end up with
> some VERY uneven sharing. If the diodes have catastrophic
> reverse breakdown you get domino effect. Controlled
> breakdown alleviates the effect, shunt components avoid it
> but deal you a different set of potential problems.
> 
> Steve


That's basically what the semiconductor engineer at Motorola
told 
me also. He said the biggest problems was uneven reverse 
recovery times, even with diodes from the same source.
73, Tom W8JI
w8ji@contesting.com

--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm



-----
Sent using MailStart.com ( http://MailStart.Com/welcome.html )
The FREE way to access your mailbox via any web browser, anywhere!


--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm