Forums

diode recovered charge

Started by John Larkin September 6, 2014
On Thu, 18 Sep 2014 11:12:41 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

>On Thu, 18 Sep 2014 10:51:45 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Sat, 06 Sep 2014 12:31:46 -0700, John Larkin >><jlarkin@highlandtechnology.com> wrote: >> >>> >>>I got curious about the amount of reverse-recovery charge in PN >>>diodes, as a function of forward current (and time of fwd bias) and >>>diode size/type. >>> >>[snip] >> >>Does this look to be viable enough... >> >><http://www.analog-innovations.com/SED/FwdRevRecovery_Behavioral.png> >> >>If so I'll continue and see what it takes to parameterize it to >>specific diodes. >> >>(100% Behavioral Modeled... 6 lines in the subcircuit >:-) >> >> ...Jim Thompson > >Interesting, but I just told the potential customer to jump in the >nearest lake. They played the tired old trick, "we don't want to buy >your products, but how would you like to be a consultant?" In other >words, they want to own our IP cheap.
Life is such fun ;-) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Current seems about right for a controlled ramp, but I notice dI/dt is 
infinite (hard switched to a ~dead short).  And accordingly, there's no 
Dirac spike from CJO, or the conduction during t_rr (though t_rr will be 
quite short under such dramatic conditions).

What's it do with a VPULSE + 25 ohms?

Tim

-- 
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote 
in message news:ho6m1atla68tqrq36asee8cf8095vtp5qr@4ax.com...
> On Sat, 06 Sep 2014 12:31:46 -0700, John Larkin > <jlarkin@highlandtechnology.com> wrote: > >> >>I got curious about the amount of reverse-recovery charge in PN >>diodes, as a function of forward current (and time of fwd bias) and >>diode size/type. >> > [snip] > > Does this look to be viable enough... > > <http://www.analog-innovations.com/SED/FwdRevRecovery_Behavioral.png> > > If so I'll continue and see what it takes to parameterize it to > specific diodes. > > (100% Behavioral Modeled... 6 lines in the subcircuit >:-) > > ...Jim Thompson > -- > | James E.Thompson | mens | > | Analog Innovations | et | > | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > | San Tan Valley, AZ 85142 Skype: skypeanalog | | > | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > | E-mail Icon at http://www.analog-innovations.com | 1962 | > > I love to cook with wine. Sometimes I even put it in the food.
On Thu, 18 Sep 2014 17:12:08 -0500, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

>Current seems about right for a controlled ramp, but I notice dI/dt is >infinite (hard switched to a ~dead short). And accordingly, there's no >Dirac spike from CJO, or the conduction during t_rr (though t_rr will be >quite short under such dramatic conditions). > >What's it do with a VPULSE + 25 ohms? > >Tim
Not so good. I need to more scratching my... >:-} ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On Thu, 18 Sep 2014 17:12:08 -0500, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

>Current seems about right for a controlled ramp, but I notice dI/dt is >infinite (hard switched to a ~dead short). And accordingly, there's no >Dirac spike from CJO, or the conduction during t_rr (though t_rr will be >quite short under such dramatic conditions). > >What's it do with a VPULSE + 25 ohms? > >Tim
A new pass at it... http://www.analog-innovations.com/SED/FwdRevRecovery_Behavioral_6.png What I need is someone to get a simultaneous scope photo of the above three traces from a real device... all these PhD papers I can find conveniently leave out pertinent data. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.

-- 
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com
"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote 
in message news:stjo1a980u6hm9s2fg4i6u5aqq7ik0hhnb@4ax.com...
> On Thu, 18 Sep 2014 17:12:08 -0500, "Tim Williams" > <tiwill@seventransistorlabs.com> wrote: > >>Current seems about right for a controlled ramp, but I notice dI/dt is >>infinite (hard switched to a ~dead short). And accordingly, there's no >>Dirac spike from CJO, or the conduction during t_rr (though t_rr will be >>quite short under such dramatic conditions). >> >>What's it do with a VPULSE + 25 ohms? >> >>Tim > > A new pass at it... > > http://www.analog-innovations.com/SED/FwdRevRecovery_Behavioral_6.png > > What I need is someone to get a simultaneous scope photo of the above > three traces from a real device... all these PhD papers I can find > conveniently leave out pertinent data.
Hey, that's not too bad... Comically quick lash-up: http://seventransistorlabs.com/Images/RR_Setup.jpg I would say, figure an extra 30nH between the source and diode. The CT is 25 turns on a T37-43 core, or around 200uH. And thus Ch.2 is reading 0.5 A/V. Yes, DC bias is a concern, but the AC waveform seems roughly correct, at least. Reflected resistance is 0.08 ohms, so can be ignored. Source voltage (as terminated). Warning, the amp is probably not exactly 50 ohms internally, so the Thevenin equivalent is probably not exactly 25 ohms. http://seventransistorlabs.com/Images/RR_Source.jpg Results: with the slow vintage diode ("169 001"), http://seventransistorlabs.com/Images/RR_SlowDiode.jpg No evidence of forward recovery, though current rises slowly (could also be an error due to the CT). Reverse recovery seems reasonable (~100ns?). 1N914 (unknown manufacturer, ~5 years old production): http://seventransistorlabs.com/Images/RR_1N914.jpg So, 50mA/div Ch.2. And then, that's about 50mA/8ns = 6.25 A/us. t_rr = 12ns seems... not unreasonable for such slow commutation? Testing with a diode in series with the CT (so it is able to recover between pulses), turn-on still has a slow current rise but no voltage overshoot. Trying a 1N4007, I see a very slight voltage overshoot, but about the same current rise. (And around 600ns t_rr.) So, characteristic of the circuit I think; maybe the amplifier can't push all that hard, or all that fast. (The response is more-or-less symmetrical with the diode reversed.) Tim -- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
On Fri, 19 Sep 2014 17:58:54 -0500, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

> > >-- >Seven Transistor Labs >Electrical Engineering Consultation >Website: http://seventransistorlabs.com >"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote >in message news:stjo1a980u6hm9s2fg4i6u5aqq7ik0hhnb@4ax.com... >> On Thu, 18 Sep 2014 17:12:08 -0500, "Tim Williams" >> <tiwill@seventransistorlabs.com> wrote: >> >>>Current seems about right for a controlled ramp, but I notice dI/dt is >>>infinite (hard switched to a ~dead short). And accordingly, there's no >>>Dirac spike from CJO, or the conduction during t_rr (though t_rr will be >>>quite short under such dramatic conditions). >>> >>>What's it do with a VPULSE + 25 ohms? >>> >>>Tim >> >> A new pass at it... >> >> http://www.analog-innovations.com/SED/FwdRevRecovery_Behavioral_6.png >> >> What I need is someone to get a simultaneous scope photo of the above >> three traces from a real device... all these PhD papers I can find >> conveniently leave out pertinent data. > >Hey, that's not too bad... > >Comically quick lash-up: >http://seventransistorlabs.com/Images/RR_Setup.jpg >I would say, figure an extra 30nH between the source and diode. > >The CT is 25 turns on a T37-43 core, or around 200uH. And thus Ch.2 is >reading 0.5 A/V. Yes, DC bias is a concern, but the AC waveform seems >roughly correct, at least. Reflected resistance is 0.08 ohms, so can be >ignored. > >Source voltage (as terminated). Warning, the amp is probably not exactly >50 ohms internally, so the Thevenin equivalent is probably not exactly 25 >ohms. >http://seventransistorlabs.com/Images/RR_Source.jpg > >Results: with the slow vintage diode ("169 001"), >http://seventransistorlabs.com/Images/RR_SlowDiode.jpg >No evidence of forward recovery, though current rises slowly (could also >be an error due to the CT). Reverse recovery seems reasonable (~100ns?). > >1N914 (unknown manufacturer, ~5 years old production): >http://seventransistorlabs.com/Images/RR_1N914.jpg >So, 50mA/div Ch.2. And then, that's about 50mA/8ns = 6.25 A/us. t_rr = >12ns seems... not unreasonable for such slow commutation? > >Testing with a diode in series with the CT (so it is able to recover >between pulses), turn-on still has a slow current rise but no voltage >overshoot. Trying a 1N4007, I see a very slight voltage overshoot, but >about the same current rise. (And around 600ns t_rr.) So, characteristic >of the circuit I think; maybe the amplifier can't push all that hard, or >all that fast. (The response is more-or-less symmetrical with the diode >reversed.) > >Tim
OK. I'll toy around with it and see if I can figure how to parameterize the subcircuit. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On Sunday, September 14, 2014 1:31:44 PM UTC-7, John Larkin wrote:


> The best DSRD/Grehkov diode turned out the be the C-B junction of an > NPN horizontal-output transistor, now obsolete.
That's a bit odd; didn't the base spreading resistance get in the way? Or, did you short B-E and let the emitter be your connection?
Phil Hobbs wrote:
> > Hopefully he didn't do it during the Super Bowl, or his neighbours would > have been after him with pitchforks.
What better time, than when there is nothing on TV that's worth watching? TV sports have sucked, since the '70s. -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.