PING: Kevin Aylward, Diode Model Question

Come on jim, you are suppose to be the Simulation king!

.model NewName ExistingModelName (N=1000000)

Weeee.. At least that removes the forward out of it :)

Jamie

I've seen big EG or VJ or something combined with IS=1e-36 or something like that. MOSFET Cdg models.

Tim

I agree with the post by Maynard, making N large will turn it off.

I=IS(1- exp(qV/KTN) )

N=100 keeps it off for up to 10V

Can be handy to keep some IS for convergence.

Kevin Aylward

This is in regard to my pursuit of an accurate model for forward and reverse recovery... large voltages preclude setting IS very small, it still conducts some unwanted current.

I'll solve it... TANH to the rescue >:-} ...Jim Thompson

Aha! I didn't think about "N" ...Jim Thompson

Isn't that just a nonlinear capacitor?

Version 4 SHEET 1 1096 680 WIRE 48 80 0 80 WIRE 176 80 48 80 WIRE 320 80 240 80 WIRE 480 80 320 80 WIRE 576 80 528 80 WIRE 624 80 576 80 WIRE 0 144 0 80 WIRE 320 144 320 80 WIRE 528 144 528 80 WIRE 480 160 480 80 WIRE 0 272 0 224 WIRE 320 272 320 224 WIRE 480 272 480 208 WIRE 528 272 528 224 FLAG 0 272 0 FLAG 320 272 0 FLAG 480 272 0 FLAG 528 272 0 FLAG 576 80 CAP FLAG 48 80 RAMP SYMBOL res 304 128 R0 WINDOW 0 49 47 Left 2 WINDOW 3 50 78 Left 2 SYMATTR InstName R1

SYMBOL voltage 0 128 R0 WINDOW 0 68 65 Left 2 WINDOW 3 17 112 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value PULSE(0 100 0 100) SYMBOL e 528 128 R0 WINDOW 0 64 53 Left 2 WINDOW 3 58 85 Left 2 SYMATTR InstName E1 SYMATTR Value 1e6 SYMBOL cap 176 96 R270 WINDOW 0 -43 32 VTop 2 WINDOW 3 77 35 VBottom 2 SYMATTR InstName C1 SYMATTR Value q = x / (1+2*x) TEXT 16 112 Left 2 ;1 V/S TEXT 560 112 Left 2 ;1 V / F TEXT 368 8 Left 2 !.tran 0 1 0 TEXT 8 -96 Left 2 ;Nonlinear Capacitor C:V Curve TEXT 48 -56 Left 2 ;J Larkin August 11, 2014 TEXT 480 -96 Left 2 ;Cap is 1F at low voltage TEXT 536 -56 Left 2 ;0.1F at 1 volt

The diode _junction_ capacitance has two separate equations with a break-point set by FC.

I _could_ implement it using one of my TANH blenders, but the Maynard/Aylward method, set N=100 makes it trivial... let Spice manage the zone problem.

Would you be interested in conducting some diode recovery time experiments? As I'm developing this model, I'm trying to match up the coefficients with measured and datasheet terms... so that they drop right into the subcircuit. ...Jim Thompson

Its the parameter that needs setting to get the correct higher voltage of LEDs. Often IS is used, incorrectly.

Kevin Aylward