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PING: Kevin Aylward, Diode Model Question

Started by Jim Thompson October 16, 2014
Hi Kevin,

Suppose I wanted to model JUST the capacitance portion of a diode?  No
DC current, etc.

The equation "fold-over" at VD~FC*VJ looks to be PITA to implement.

Maybe you know of a way to trick a full diode model into not doing its
DC thing ?:-}
		
                                        ...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 article <9uj04alb6h86hbqk6e8vtq88v6ir8v3kfc@4ax.com>, To-Email-Use-
The-Envelope-Icon@On-My-Web-Site.com says...
> > Hi Kevin, > > Suppose I wanted to model JUST the capacitance portion of a diode? No > DC current, etc. > > The equation "fold-over" at VD~FC*VJ looks to be PITA to implement. > > Maybe you know of a way to trick a full diode model into not doing its > DC thing ?:-} > > ...Jim Thompson
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

-- 
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:9uj04alb6h86hbqk6e8vtq88v6ir8v3kfc@4ax.com...
> Hi Kevin, > > Suppose I wanted to model JUST the capacitance portion of a diode? No > DC current, etc. > > The equation "fold-over" at VD~FC*VJ looks to be PITA to implement. > > Maybe you know of a way to trick a full diode model into not doing its > DC thing ?:-} > > ...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.
>"Jim Thompson" wrote in message >news:9uj04alb6h86hbqk6e8vtq88v6ir8v3kfc@4ax.com... >Hi Kevin,
>Suppose I wanted to model JUST the capacitance portion of a diode? No >DC current, etc.
>The equation "fold-over" at VD~FC*VJ looks to be PITA to implement.
>Maybe you know of a way to trick a full diode model into not doing its DC >thing ?:-}
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 www.kevinaylward.co.uk www.anasoft.co.uk - SuperSpice
On Fri, 17 Oct 2014 02:06:47 -0500, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

>I've seen big EG or VJ or something combined with IS=1e-36 or something >like that. MOSFET Cdg models. > >Tim
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 -- | 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 Fri, 17 Oct 2014 16:04:10 +0100, "Kevin Aylward"
<ExtractkevinRemove@kevinaylward.co.uk> wrote:

>>"Jim Thompson" wrote in message >>news:9uj04alb6h86hbqk6e8vtq88v6ir8v3kfc@4ax.com... >>Hi Kevin, > >>Suppose I wanted to model JUST the capacitance portion of a diode? No >>DC current, etc. > >>The equation "fold-over" at VD~FC*VJ looks to be PITA to implement. > >>Maybe you know of a way to trick a full diode model into not doing its DC >>thing ?:-} > >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 >www.kevinaylward.co.uk >www.anasoft.co.uk - SuperSpice
Aha! I didn't think about "N" ...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, 16 Oct 2014 16:10:47 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>Hi Kevin, > >Suppose I wanted to model JUST the capacitance portion of a diode? No >DC current, etc. > >The equation "fold-over" at VD~FC*VJ looks to be PITA to implement. > >Maybe you know of a way to trick a full diode model into not doing its >DC thing ?:-} > > ...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 SYMATTR Value 1&#2013266101; 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 -- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Fri, 17 Oct 2014 09:08:45 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

>On Thu, 16 Oct 2014 16:10:47 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>Hi Kevin, >> >>Suppose I wanted to model JUST the capacitance portion of a diode? No >>DC current, etc. >> >>The equation "fold-over" at VD~FC*VJ looks to be PITA to implement. >> >>Maybe you know of a way to trick a full diode model into not doing its >>DC thing ?:-} >> >> ...Jim Thompson > >Isn't that just a nonlinear capacitor? > > >Version 4 >SHEET 1 1096 680
[snip]
>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 -- | 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.
"Jim Thompson"  wrote in message 
news:s7f24a9r2gfm6gdolatc6th9umgfdd6iiu@4ax.com...

On Fri, 17 Oct 2014 16:04:10 +0100, "Kevin Aylward"
<ExtractkevinRemove@kevinaylward.co.uk> wrote:

>>"Jim Thompson" wrote in message >>news:9uj04alb6h86hbqk6e8vtq88v6ir8v3kfc@4ax.com... >>Hi Kevin, > >>Suppose I wanted to model JUST the capacitance portion of a diode? No >>DC current, etc. > >>The equation "fold-over" at VD~FC*VJ looks to be PITA to implement. > >>Maybe you know of a way to trick a full diode model into not doing its DC >>thing ?:-} > >>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. >
>Aha! I didn't think about "N"
Its the parameter that needs setting to get the correct higher voltage of LEDs. Often IS is used, incorrectly. Kevin Aylward www.kevinaylward.co.uk www.anasoft.co.uk - SuperSpice