Re: Can the PIV of a diode be "safely" exceeded?
From: rayjking (rayjking_at_bellsouth.net)
Date: 11/17/04
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Date: Wed, 17 Nov 2004 00:36:47 -0500
Alain,
You are observing the action of avalanche. Most modern high voltage diodes
are designed to withstand various amounts of reverse avalanche energy
absorption. Diodes that are applied in series should be tested for this
avalanche characteristic.
The information given for the piezo out put voltage of 15kv does not happen.
The diodes clamp the voltage at about 4500 volts.
Ray
"KILOWATT" <kilowatt"nospam"@softhome.net> wrote in message
news:Sfemd.7126$rc.616816@news20.bellglobal.com...
> Hi everyones thanks to read. Since a few weeks, i'm using the LightKeeper
> Pro from Ulta-Lit Tree Company ( http://www.lightkeeper.biz/default.asp )
to
> test and repair miniature lights sets (series-wired). I've found the Quick
> Fix Trigger utility very useful. as you can see on their website, it's
based
> on a piezo igniter that sends a high voltage pulse through the lights set
to
> activate (short) the shunt inside the bulb, that didn't do so when the
> bulb's filament burned out. I wanted to see how this system is built so i
> opened the unit. Here's two photos plus a schematic i've drawed for the
> igniter section. (Sorry, the symbol for the piezo igniter is probably
> wrong...i don't know the correct one).
> http://www3.sympatico.ca/kilo.watt/images/lightkeeper1.JPG
> http://www3.sympatico.ca/kilo.watt/images/lightkeeper2.JPG
> http://www3.sympatico.ca/kilo.watt/images/hv_pulse_gen.bmp
> As i can see, the four diodes allow a peak reverse voltage of
approximately
> 4Kv, wich is sufficient to break down the shunt's insulation inside the
> burned bulb(s) and complete the series circuit. Once completed, half of an
> AC cycle can flow through the four diodes, allowing the set to glow
(dimly)
> and show which bulbs are burned and needs replacement.
> What leads me to my question (please look at the schematic) is: why the
> reverse voltage doesn't seem to damages those diodes? According to the
piezo
> igniter's website (
http://www.yiqiang-piezo.com/english/production2.htm ),
> the output voltage is at least 15Kv. With the four 1n4007 wired in series,
i
> should get a peak reverse voltage of about 4Kv isn't? For what i know, a
> diode is destroyed once it's PIV is exceeded. I think i missed something
> when studying the basic operation theory of a diode. ;-) TIA for any
> useful reply.
> --
> Alain(alias:Kilowatt)
> Montréal Québec
> PS: 1000 excuses for errors or omissions,
> i'm a "pure" french canadian! :-)
> Come to visit me at: http://kilowatt.camarades.com
> (If replying also by e-mail, remove
> "no spam" from the adress.)
>
>
- Next message: Glenn Gundlach: "Re: Driving 555 IC with a pulse stream"
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- In reply to: KILOWATT: "Can the PIV of a diode be "safely" exceeded?"
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