There is a basic rule of design that I tried teach to all the EE engineers
who worked for me.
That rule is that you must take positive steps to achieve a desired result.
These steps may include an analysis of component characteristics (in all
modes of operation and over all expected environments) or addition of
physical components (e.g. resistors across the capacitor or diode string) to
achieve the desired results.
We learned that the datasheets do not tell the entire story. Competent,
curious, component engineers were some of the most valuable men we had in
the company.
Yes some diodes can be stacked --- but be aware that practice would be
frowned upon if you were building a man-rated space machine. Do the Extreme
Value Worst Case Analysis. Have an accurate model showing the aging
effects. Consider the results if a part fails. Will the circuit survive or
destroy the rest of the box?
When you are done with all of this -- you will probably put a few (properly
rated) resistors in the stack. Or, as I have done also, have a stack of
math that proves they are not needed.
Harv
K6EXO
----- Original Message -----
From: Tom Rauch <w8ji@contesting.com>
To: <amps@contesting.com>
Sent: Thursday, July 29, 1999 8:53 AM
Subject: [AMPS] Diodes
>
> I think my message bounced.
>
> Marv says that recovery time isn't important, based on the slow
> slew rate of powerline frequencies.
>
> What then makes sure the diodes all share equal voltages while
> turing off? If it is junction capacitance, you are in trouble. The
> capacitance is not only not matched, it changes with reverse
> voltage. The lowest capacitance diode will turn off quickest, and
> that will lower capacitance even more in that diode compared to
> higher capacitance (slower) diodes.
>
> Reverse leakage current, unless you take the diode to the
> threshold, is extremely low. Are people claiming one diode goes to
> threshold and then the others start being forced to threshold as
> that single diode avalanches? Is that the mechanism that causes
> voltages to be "shared"?
>
>
> 73, Tom W8JI
> w8ji@contesting.com
>
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>
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