[snip]
These two links seem to have reasonable subcircuit additions to model diode reverse recovery time....
I don't have the time right now, but I'll later see if I can spin these into a parameterized subcircuit where all you have to do is fill in the blanks >:-] ...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.
The miniority carries are getting in the way, you'd need software, maybe MicrowaveOffice, to model those effects that really affect microwave design. Maybe John needs a high voltage tunnel diode.
Cheers
Sure, many integral equations cannot be solved as a differential equation, but I don't see that as being relevant to a Spice simulation being restricted to solving nonlinear ODEs.
In principal, Spice does not solve the internal device equations that might be produced by an integral equation, it just takes the already solved internal device equations and solves an external set of equations. Ok, in practice, the internal equations may be transcendental, and these get solved in the wash of the external solution so that the internal equations sort of get solved by Spice, but it doesn't change the principle.
Spice and reality only care about an I = f(V,t) at the device terminals, as a black box. It doesn't care how that relation was generated, be it solving a partial differential diffusion equation, or some 3D integral transport equation. The device physics don't even need to be solved at all. I=f(V,t) can be determined from running lots of measurements. Indeed, that's how individuals like Jim T,and I, that lack extensive semiconductor physics and the time, actually get somewhat reasonable models. We piss about with simulation graphs until we get a match.
Kevin Aylward
Once upon a time (like 50 or more years ago) I had all that semiconductor physics course-work... but it promptly faded away from disuse >:-}
And a whole lot of physical phenomena have direct analogs from circuit elements... easing the pain of making subcircuits that match what you can measure. Diode reverse recovery modeling actually looks to be a piece-a-cake. ...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.
That's sort of like a solution in a paper I ran across. But I think I've found an even better way.
(The non-linear resistor scheme is better-suited to modeling the electrical behavior of B-H core behavior.) ...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.
You can't reduce a transport problem to a set of ODEs. I'm sure you can cobble something together that will agree to any accuracy you care to stop at, but it's just that, cobbled together.
I'm not proposing using a Boltzmann equation solver to model circuits, just observing that carrier-diffusion dynamics aren't very well suited to the tool, so you'll probably have to cobble quite a bit harder than for, say, a varactor.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Spice is about modeling real-world phenomena... not writing a paper for some highfalutin physics society, all wrapped-up in narcissism
Naaaah! Watch me! ...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.
In other words you don't actually know how it works. ;)
If you can model a Grekhov diode successfully in SPICE, my hat will be off to you, sir.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Actually, as I pointed out earlier, I was schooled in semiconductor physics via Al Phillips...
and Warner et al texts, so I know how it works. (I joined that group in June 1962.)
Good behavioral models create the waveform responses is ways much simpler than trying to compose the device physics into the model.
I don't even know what a Grekhov diode is :-[
But I'll look it up. ...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.
I mean SPICE, not semiconductors. "Modeling real-world phenomena" works better if you understand what's going on under the hood, IME.
Sure, just like other sorts of curve fitting. The problem is when you reach the limits of the data set used to make the fit. A physics-based model can avoid that limitation, provided of course that the physics is well-enough understood.
You're in for a treat. Grekhov & Co. figured out how to make certain types of power rectifiers into SRDs--picture a 3 kV, subnanosecond pulse into 50 ohms from the equivalent of a 1N4007. John L described one that he made earlier in the thread.
Cheers
Phil
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Since Spice doesn't do diffusion, maybe one could model a diode as several different diodes strung out on a lumped transmission line, namely coupled with inductors. Sort of like a shock line but accesses at just one end. Longer forward-bias times would pump charge into diodes farther along the line, recovery ditto.
-- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Some sort of nonlinear RL transmission line might work too, but that's an awful lot of cobbling.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
I was going say something about this in my last post...because it s one of those spicy exception exceptions.
Actually, continuous DC hysteresis is not something Spice3 can really handle. If a value that changes dependant on time is involved, L and C might be an approach, but for DC an additional ingredient is needed as spice doesn't know how to deal with multivalued functions. DC hysteresis doesn't care when the last value occurred in order to determine the next value, only what the last value was. Essentially, a mem-resistor function in needed. However...
10 or so years ago I implemented the hysteresis function that Mike put into LTSpice, into SuperSpice. This works by way of a "core" component that is a DC component, but forms the actual hysteresis bit. For example, if you voltage drive the core with a DC sine wave (say by driving a dc sweep into a sine function), the output current will not be the same on same periodic points of the input sine. So, in principle, one could wrap other non-linear functions around the "core" to produce a variety of different DC hysteresis characteristics.Kevin Aylward
I agreed with that point. I don't agree that it really mattes in spice . A set of graphs of i against time and volts simply does not care what the underlying physics is.
I disagree with the implied meaning of "cobbled together". Behaverial black box, modelling is a well tried and trusted method of getting results when the detail are intractable.
I disagree, as I noted, the final result of a model is simple an i=f(v,t) function.
Kevin Aylward
30 years ago I went through the sums of the diffusion equation to show that there was a small signal capacitance proportional to dc current, but that was 30 years ago...
The overall concept of C=k.I is actually important in understanding why Cbe= gm/2.pi.ft allows for an approximate contestant Ft parameter in the bipolar model for a wide range of currents
The basic diode tt isn't that far off in many cases. Just needs some extra tweaking around it.
Kevin Aylward
If you can get the full range of behaviour of a Grekhov diode using that approach, you have my admiration. My hunch is that the smart money would bet the other way.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
[snip]
None of the ordinary Spice variants seem to model forward and reverse recovery time.
Can you provide some scope photos of forward and reverse recovery at different current levels?
Several papers I've run across suggest that a fairly simple subcircuit may be possible... but, being IEEE crap, their data is naive and vague
...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.
I posted some 1N914 pics, taken at four different current step levels.
Looks sorta like constant-area overshoot.
Forward recovery doesn't matter in my current application, since I'll have plenty of time to pump current into my diodes. Controlling the amount of reverse charge matters, and I need to simulate reverse recovery accurately in the higher-level simulation.
-- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
I saw those but couldn't determine the current levels... that green drives my eyes nuts.
...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.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.