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Improved Diode Recovery Model

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This had been discussed some time ago. There was a lot of bragging about being able to create a model, but nothing came of it. Fortunately, this guy had beaten us to the punch, and released this paper publically.

The design with multiple time constants makes me think of approximating diffusion with a series of poles. Seems reasonable.

Also seems reasonable that you might make those nonlinear or interdependent, to better model nonlinear recovery and charge transport phenomena. Still a hack, yes, but a means towards simulating it in SPICE at all? Nice.

Tim

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Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
Website: http://seventransistorlabs.com
Reply to
Tim Williams
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You're way behind. I found that paper on December 14, 2014.

I have exactly 50 papers on the subject at the moment.

Before I fell ill I was trying to parameterize a model I had working, but that required guessing the coefficients.

Maybe it's time to resume pursuit. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, 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'm looking for work... see my website. 

Thinking outside the box...producing elegant & economic solutions.
Reply to
Jim Thompson

The reverse recovery current probably varies as erf(t) (error function), not atanh(t). atanh(t) is a decent approximation to erf(t) over a small portion of the domain but the tail behavior is much different. Also there are better numerical approximations to erf(t) itself that require fewer computations than atanh

Reply to
bitrex

Hmmmm? Simply...

ATANH(x) = 0.5*LOGe((1+x)/(1-x))

ATANH)x) is usually recognized by most simulators. So far I've found that only TopSpice requires using the above equation. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, 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'm looking for work... see my website. 

Thinking outside the box...producing elegant & economic solutions.
Reply to
Jim Thompson

If performance is a big concern one would want to avoid expressions like (1 + x)/(1 - x) in certain domains, because for values of x close to 1 processors have to apply certain "hax" to ensure you don't get a divide-by-zero exception. The FPU logic has to switch over to "denormal" numbers which are sometimes implemented in hardware, sometimes software, sometimes a combination but always run slower than the native FPU execution speed would be when calculating with "normal" floats. Only when working with denormals is one guaranteed that when subtracting two floats one will get a non-zero result.

Reply to
bitrex

The error function is itself a good approximation to atanh, and a good approximation to the error function is:

1 - 1/([1 + a*x + b*x^2 + c*x^3 + d*x^4)^4] with a = 0.278393, b = 0.230389, c = 0.000972, d = 0.078108. This is mad fast on any modern superscalar processor
Reply to
bitrex

Though IIRC you have to scale your argument by a constant

Reply to
bitrex

I don't use ATANH(x) _within_ a transient analysis... it's guaranteed to blow up when the simulator "hunts and pecks".... I only use it to preset model coefficients.

But it would be simple enough to modify to enforce bounds. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, 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'm looking for work... see my website. 

Thinking outside the box...producing elegant & economic solutions.
Reply to
Jim Thompson

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