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Re: guard ring?

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John Larkin wrote
>I'm still iterating on my high-voltage pulse generator. Rev C looks
>very good. I've been pushing it up voltage and frequency (like, 1200
>volts and 4 MHz) and seeing what parts fry, and working on them.
>
>I have a dpak schottky diode in a sort of snubber place. According to
>Spice, it shouldn't get too hot, and it's soldered to all sorts of
>copper pours and thermal vias and stuff. It's an SBRD10200 and it's
>frying. I happened to have some smaller, lower current diodes around,
>UPS5100E3, which is a sawed-off sub-dpak thing. I figured I might
>squeeze in two of those in parallel... but just one runs cool. 
>
>https://www.dropbox.com/s/6zv36c4d6v7dsbn/Two_Diodes.JPG?raw=1
>
>Weird. I'm guessing that the big one has a p-n guard ring that makes
>it have reverse recovery current right after a big forward current
>spike. Data sheets never talk about that.
>
>I heat sinked things too well, so it's a bear to desolder/resolder.
>
>https://www.dropbox.com/s/bg0399wzzi4k3ze/T850C_D1_Kluge.jpg?raw=1

4 MHz at 1000V, I did higher frequencies with tubes in the sixties,
with 1000V supply at .5 A peak.
Without seeing the circuit it is hard to tell, but Schottky diodes
would not be my choice, there are nice fast si diodes or at least there were.
Schottkys leak, get very hot because current flows both directions that way.
Thermal runaway results.
A few pF from a fast si diode .. helps tune the circuit ;-)

Anyways no way to tell without seeing what that diode is doing.
 
Snubber = flyback diode here?

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guard ring? John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-12 14:01 -0700
  Re: guard ring? TTman <kraken.sankey@gmail.com> - 2018-10-12 23:06 +0100
    Re: guard ring? John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-12 15:38 -0700
      Re: guard ring? "Tim Williams" <tiwill@seventransistorlabs.com> - 2018-10-12 19:26 -0500
        Re: guard ring? "Tim Williams" <tiwill@seventransistorlabs.com> - 2018-10-12 21:16 -0500
          Re: guard ring? DecadentLinuxUserNumeroUno@decadence.org - 2018-10-13 09:11 +0000
            Re: guard ring? "Tim Williams" <tiwill@seventransistorlabs.com> - 2018-10-13 04:51 -0500
              Re: guard ring? DecadentLinuxUserNumeroUno@decadence.org - 2018-10-13 09:58 +0000
      Re: guard ring? George Herold <gherold@teachspin.com> - 2018-10-12 18:12 -0700
    Re: guard ring? DecadentLinuxUserNumeroUno@decadence.org - 2018-10-13 00:02 +0000
  Re: guard ring? <698839253X6D445TD@nospam.org> - 2018-10-13 06:59 +0000
  Re: guard ring? Robert Baer <robertbaer@localnet.com> - 2018-10-13 22:45 -0700
    Re: guard ring? John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-14 09:44 -0700
      Re: guard ring? John S <Sophi.2@invalid.org> - 2018-10-14 12:45 -0500
        Re: guard ring? krw@notreal.com - 2018-10-14 14:28 -0400
      Re: guard ring? Jasen Betts <jasen@xnet.co.nz> - 2018-10-14 19:28 +0000
        Re: guard ring? DecadentLinuxUserNumeroUno@decadence.org - 2018-10-14 20:57 +0000
          Re: guard ring? Jasen Betts <jasen@xnet.co.nz> - 2018-10-15 05:20 +0000
            Re: guard ring? DecadentLinuxUserNumeroUno@decadence.org - 2018-10-15 10:59 +0000
      Re: guard ring? "nuny@bid.nes" <alien8752@gmail.com> - 2018-10-14 17:39 -0700
  Re: guard ring? John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-14 14:56 -0700
    Re: guard ring? <698839253X6D445TD@nospam.org> - 2018-10-15 07:23 +0000
    Re: guard ring? <698839253X6D445TD@nospam.org> - 2018-10-15 07:54 +0000
      Re: guard ring? DecadentLinuxUserNumeroUno@decadence.org - 2018-10-15 11:21 +0000
        Re: guard ring? John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-15 07:52 -0700
  Re: guard ring? John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-16 10:31 -0700
    Re: guard ring? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-16 14:23 -0400
    Re: guard ring? "Tim Williams" <tiwill@seventransistorlabs.com> - 2018-10-16 17:09 -0500
      Re: guard ring? John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-16 16:02 -0700
        Re: guard ring? "Tim Williams" <tiwill@seventransistorlabs.com> - 2018-10-17 03:57 -0500
          Re: guard ring? John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-17 04:52 -0700
      Re: guard ring? John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-17 11:00 -0700
        Re: guard ring? Steve Wilson <9fe142ac@gmail.com> - 2018-10-17 12:13 -0700
        Re: guard ring? Steve Wilson <9fe142ac@gmail.com> - 2018-10-17 12:19 -0700
          Re: guard ring? John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-17 12:39 -0700
        Re: guard ring? Jasen Betts <jasen@xnet.co.nz> - 2018-10-17 19:15 +0000
        Re: guard ring? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-17 15:33 -0400
          Re: guard ring? John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-17 12:56 -0700
            Re: guard ring? John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-17 13:15 -0700
        Re: guard ring? "Tim Williams" <tiwill@seventransistorlabs.com> - 2018-10-17 16:34 -0500

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