spice diode model question
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From: Jon Kirwan on 20 Dec 2009 23:53 On Sun, 20 Dec 2009 20:29:25 -0800, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Sun, 20 Dec 2009 16:01:52 -0800, Jon Kirwan ><jonk(a)infinitefactors.org> wrote: > >>On Sun, 20 Dec 2009 14:25:45 -0700, Jim Thompson >><To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com/Snicker> wrote: >> >>>On Sun, 20 Dec 2009 13:03:32 -0800, John Larkin >>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>>I've slammed 48 volts across a 600 volt "fast recovery" diode and >>>>it took a couple hundred nanoseconds to ramp up to 50 amps. >>>> >>>[snip] >>>> >>>>John >>> >>>Which sounds like 200nH in the wiring ;-) >>> >>> ...Jim Thompson >> >>Hehe. Indeed. From John's numbers, 48V * 200ns / 50A = 192nH. >> >>Jon > >The diode in question is inside this: > >http://www.highlandtechnology.com/DSS/T220DS.html > >It's a drift step-recovery (Grehkov) diode, or rather a commercial >power diode used in DSRD mode. I assure you that we know exactly what >we're doing here, and the diode behaves as described. The inductance >of the drive circuit (+48 volts followed by -400) is around 8 nH. The >pulser was desiged to rip ions off a microtip in a tomographic atom >probe. > >Google the obvious and learn something. Start here: > >http://www.avtechpulse.com/papers/thesis/8/ Glad to and thanks for a link. I also see where Jim was speaking from. Jon
From: John Larkin on 21 Dec 2009 01:26 On Sun, 20 Dec 2009 20:53:41 -0800, Jon Kirwan <jonk(a)infinitefactors.org> wrote: >On Sun, 20 Dec 2009 20:29:25 -0800, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Sun, 20 Dec 2009 16:01:52 -0800, Jon Kirwan >><jonk(a)infinitefactors.org> wrote: >> >>>On Sun, 20 Dec 2009 14:25:45 -0700, Jim Thompson >>><To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com/Snicker> wrote: >>> >>>>On Sun, 20 Dec 2009 13:03:32 -0800, John Larkin >>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>>I've slammed 48 volts across a 600 volt "fast recovery" diode and >>>>>it took a couple hundred nanoseconds to ramp up to 50 amps. >>>>> >>>>[snip] >>>>> >>>>>John >>>> >>>>Which sounds like 200nH in the wiring ;-) >>>> >>>> ...Jim Thompson >>> >>>Hehe. Indeed. From John's numbers, 48V * 200ns / 50A = 192nH. >>> >>>Jon >> >>The diode in question is inside this: >> >>http://www.highlandtechnology.com/DSS/T220DS.html >> >>It's a drift step-recovery (Grehkov) diode, or rather a commercial >>power diode used in DSRD mode. I assure you that we know exactly what >>we're doing here, and the diode behaves as described. The inductance >>of the drive circuit (+48 volts followed by -400) is around 8 nH. The >>pulser was desiged to rip ions off a microtip in a tomographic atom >>probe. >> >>Google the obvious and learn something. Start here: >> >>http://www.avtechpulse.com/papers/thesis/8/ > >Glad to and thanks for a link. I also see where Jim was speaking >from. > >Jon Hehe. Indeed. John
From: Fred Bartoli on 21 Dec 2009 09:39 Martin Riddle a �crit : > "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in > message news:9j3ti5ha61p9nb7k16onap6bcl4sc98b4g(a)4ax.com... >> On Sun, 20 Dec 2009 14:30:13 -0500, "Martin Riddle" >> <martin_rid(a)verizon.net> wrote: >> >>> I have a diode that I want to model, it's a 85HF20. >>> <http://www.vishay.com/docs/93529/85hf.pdf> >>> This is one of those standard stud mounted rectifiers. >>> >>> This is the model that I created for it: >>> .model 85HF20 D(BV=200 Ibv=.009 Is=1e-3 Cjo=2300p M=0.43 Rs=.00169 >>> Tt=100u Eg=1.11 Vj=1.2 Fc=0.5 N=1.1 ) >>> >>> Cjo was taken for a similar sized schottky . I don't have experience >>> with these larger diodes so the model is almost default values. I >>> don't >>> need the Temperature parameters. Most of the reference books , I have, >>> don't deal with the larger diodes. >>> Is the Is parameter correct for this model? Any pointers? >>> >>> I basically need to know if this slow diode will clamp a forward >>> voltage >> >from a inductor. the model above does work. But its no good if its >>> wrong. ( I had another model that didn't work well) >>> >>> Thanks >>> >> If you're concerned about the "forward recovery time" thing, I doubt >> that a model will be very useful. You'd really need to test an actual >> part to see how it behaves. To complicate life, several of the >> different voltage rated versions may at various times come off the >> same wafer. >> >> In general, higher voltage parts have wider junctions, approaching pin >> diodes for, say, 600 volt parts, and they tend to be slower turning >> on. I've slammed 48 volts across a 600 volt "fast recovery" diode and >> it took a couple hundred nanoseconds to ramp up to 50 amps. >> >> What's your circuit? >> >> John >> >> > > The inductor I want to clamp, is the voltage on is a set of cables. I'm > figuring on 100nh or so for each cable, so a 200nh inductor. There will > be 3KA flowing thru the cables for 1-20ms. It's the turn off that > generates the reversevoltage. > So I want to dump that energy into the diode. ( just like a diode across > a relay coil) > The peak forward current is 1.2kA and decays for a few hundred us, > within the Ifsm of the diode. > > I just want to be sure the diode will conduct within a reasonable amount > of time. I have a set of Mosfets that won't like the added drain > voltage. > > I think your right, I need to get the diode and see how fast it will > conduct. > > Cheers > > > Well, I just had the same kind of pb to solve, but at somewhat higher currents: full multi-IGBTs 2.5kV bridge with SC current upto the 20kA range. The very well made supply loop (not my design) is around 70nH and the high side IGBT free wheeling diode won't do anything WRT the supply inductance, so we turned to active clamping. I just had some news about the outcome and it clamps very, very cleanly. You have to be very careful and do things well though. You don't tell what your switches are, but if you're using IGBTs (or MOSFETs if it's low voltage) that might be your ticket. Oh, and at the huge di/dt involved the wheeling diode also has some 300-400V VF voltage, which too is *not* related to IGBT inductance. -- Thanks, Fred.
From: Martin Riddle on 21 Dec 2009 19:36 "Fred Bartoli" <" "> wrote in message news:4b2f8891$0$14576$426a74cc(a)news.free.fr... > Martin Riddle a �crit : >> "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >> message news:9j3ti5ha61p9nb7k16onap6bcl4sc98b4g(a)4ax.com... >>> On Sun, 20 Dec 2009 14:30:13 -0500, "Martin Riddle" >>> <martin_rid(a)verizon.net> wrote: >>> >>>> I have a diode that I want to model, it's a 85HF20. >>>> <http://www.vishay.com/docs/93529/85hf.pdf> >>>> This is one of those standard stud mounted rectifiers. >>>> >>>> This is the model that I created for it: >>>> .model 85HF20 D(BV=200 Ibv=.009 Is=1e-3 Cjo=2300p M=0.43 Rs=.00169 >>>> Tt=100u Eg=1.11 Vj=1.2 Fc=0.5 N=1.1 ) >>>> >>>> Cjo was taken for a similar sized schottky . I don't have >>>> experience >>>> with these larger diodes so the model is almost default values. I >>>> don't >>>> need the Temperature parameters. Most of the reference books , I >>>> have, >>>> don't deal with the larger diodes. >>>> Is the Is parameter correct for this model? Any pointers? >>>> >>>> I basically need to know if this slow diode will clamp a forward >>>> voltage >>> >from a inductor. the model above does work. But its no good if its >>>> wrong. ( I had another model that didn't work well) >>>> >>>> Thanks >>>> >>> If you're concerned about the "forward recovery time" thing, I doubt >>> that a model will be very useful. You'd really need to test an >>> actual >>> part to see how it behaves. To complicate life, several of the >>> different voltage rated versions may at various times come off the >>> same wafer. >>> >>> In general, higher voltage parts have wider junctions, approaching >>> pin >>> diodes for, say, 600 volt parts, and they tend to be slower turning >>> on. I've slammed 48 volts across a 600 volt "fast recovery" diode >>> and >>> it took a couple hundred nanoseconds to ramp up to 50 amps. >>> >>> What's your circuit? >>> >>> John >>> >>> >> >> The inductor I want to clamp, is the voltage on is a set of cables. >> I'm figuring on 100nh or so for each cable, so a 200nh inductor. >> There will be 3KA flowing thru the cables for 1-20ms. It's the turn >> off that generates the reversevoltage. >> So I want to dump that energy into the diode. ( just like a diode >> across a relay coil) >> The peak forward current is 1.2kA and decays for a few hundred us, >> within the Ifsm of the diode. >> >> I just want to be sure the diode will conduct within a reasonable >> amount of time. I have a set of Mosfets that won't like the added >> drain voltage. >> >> I think your right, I need to get the diode and see how fast it will >> conduct. >> >> Cheers >> > > Well, I just had the same kind of pb to solve, but at somewhat higher > currents: full multi-IGBTs 2.5kV bridge with SC current upto the 20kA > range. > The very well made supply loop (not my design) is around 70nH and the > high side IGBT free wheeling diode won't do anything WRT the supply > inductance, so we turned to active clamping. > I just had some news about the outcome and it clamps very, very > cleanly. > You have to be very careful and do things well though. > > You don't tell what your switches are, but if you're using IGBTs (or > MOSFETs if it's low voltage) that might be your ticket. > > Oh, and at the huge di/dt involved the wheeling diode also has some > 300-400V VF voltage, which too is *not* related to IGBT inductance. > > > -- > Thanks, > Fred. I see just like a synchronous rectifier in a smps. That�s a little more costly. I'll reserve that idea for last. Cheers
From: dagmargoodboat on 21 Dec 2009 20:53
On Dec 20, 6:13 pm, "Martin Riddle" <martin_...(a)verizon.net> wrote: > "John Larkin" <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote in > messagenews:9j3ti5ha61p9nb7k16onap6bcl4sc98b4g(a)4ax.com... > > > > > On Sun, 20 Dec 2009 14:30:13 -0500, "Martin Riddle" > > <martin_...(a)verizon.net> wrote: > > >>I have a diode that I want to model, it's a 85HF20. > >><http://www.vishay.com/docs/93529/85hf.pdf> > >>This is one of those standard stud mounted rectifiers. > > >>This is the model that I created for it: > >>.model 85HF20 D(BV=200 Ibv=.009 Is=1e-3 Cjo=2300p M=0.43 Rs=.00169 > >>Tt=100u Eg=1.11 Vj=1.2 Fc=0.5 N=1.1 ) > > >>Cjo was taken for a similar sized schottky . I don't have experience > >>with these larger diodes so the model is almost default values. I > >>don't > >>need the Temperature parameters. Most of the reference books , I have, > >>don't deal with the larger diodes. > >>Is the Is parameter correct for this model? Any pointers? > > >>I basically need to know if this slow diode will clamp a forward > >>voltage > >>from a inductor. the model above does work. But its no good if its > >>wrong. ( I had another model that didn't work well) > > >>Thanks > > > If you're concerned about the "forward recovery time" thing, I doubt > > that a model will be very useful. You'd really need to test an actual > > part to see how it behaves. To complicate life, several of the > > different voltage rated versions may at various times come off the > > same wafer. > > > In general, higher voltage parts have wider junctions, approaching pin > > diodes for, say, 600 volt parts, and they tend to be slower turning > > on. I've slammed 48 volts across a 600 volt "fast recovery" diode and > > it took a couple hundred nanoseconds to ramp up to 50 amps. > > > What's your circuit? > > > John > > The inductor I want to clamp, is the voltage on is a set of cables. I'm > figuring on 100nh or so for each cable, so a 200nh inductor. There will > be 3KA flowing thru the cables for 1-20ms. It's the turn off that > generates the reversevoltage. > So I want to dump that energy into the diode. ( just like a diode across > a relay coil) > The peak forward current is 1.2kA and decays for a few hundred us, > within the Ifsm of the diode. > > I just want to be sure the diode will conduct within a reasonable amount > of time. I have a set of Mosfets that won't like the added drain > voltage. > > I think your right, I need to get the diode and see how fast it will > conduct. > > Cheers 1.2kA into 200nH is only 144mJ -- you could just let your monster FETs avalanche and gobble it up. Or maybe prime the diode with a little d.c., for speed? Hmmm. Nope, can't see a clean way to do that offhand. -- Cheers, James Arthur |