current limiter...

J

John Larkin

Guest
What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.
 
On 04/12/2020 6:07 pm, John Larkin wrote:
What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.
Click to expand...

Inverse series jfets (optionally with source resistor)?

With LT Spice the device matching will be perfect :)

piglet
 
On Fri, 04 Dec 2020 10:07:18 -0800, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.
Click to expand...

Does it have to be a real component ?

You might present it as an arbitrary device defined by simple math and
if statement ?
 
On 12/4/20 1:07 PM, John Larkin wrote:
What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.
Click to expand...

A bridge rectifier and current source in a subcircuit.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
On Fri, 4 Dec 2020 13:25:17 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 12/4/20 1:07 PM, John Larkin wrote:
What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.


A bridge rectifier and current source in a subcircuit.

Cheers

Phil Hobbs
Click to expand...

I\'ve never done a hierarical schematic. The LT Spice explanation
doesn\'t make much sense to me.

I tried using a current source with the LOAD attribute, but it\'s
goofy.

I guess I can draw three uglies.
 
On Fri, 04 Dec 2020 10:07:18 -0800, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.
Click to expand...

You can roll your own as a subcircuit built around the diode model.
You can specify resistance, max current flow. I use this subcircuit I
found on the internet:

--------------------------------------------------------------------
* Current Limiter Device.
* I = Current limit.
* V = Optional forward voltage drop.
* R = Optional series resistance (note: R=0 may leed to divergence).
* Use as: X<n> <node> <node> ilim I=<num> R=<num> V=<num>
* pasquale.cocchini@ieee.org - Feb 2 2016.

..subckt ilim a b I=1 R=0 V=0
Df a b IfLimDiode
Db b a IfLimDiode
..model IfLimDiode D(ron={R},ilimit={I},vfwd={V})
..ends ilim

-------------------------------------------------------------------

I have found that specifying a small amount of resistance will help it
work better, it can oscillate into and out of current limit if you
leave the resistance as 0.
 
On Fri, 04 Dec 2020 14:03:13 -0500, Ray Otwell
<rayRemoveThisotwell@gmail.com> wrote:

On Fri, 04 Dec 2020 10:07:18 -0800, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.

You can roll your own as a subcircuit built around the diode model.
You can specify resistance, max current flow. I use this subcircuit I
found on the internet:

--------------------------------------------------------------------
* Current Limiter Device.
* I = Current limit.
* V = Optional forward voltage drop.
* R = Optional series resistance (note: R=0 may leed to divergence).
* Use as: X<n> <node> <node> ilim I=<num> R=<num> V=<num
* pasquale.cocchini@ieee.org - Feb 2 2016.

.subckt ilim a b I=1 R=0 V=0
Df a b IfLimDiode
Db b a IfLimDiode
.model IfLimDiode D(ron={R},ilimit={I},vfwd={V})
.ends ilim

-------------------------------------------------------------------

I have found that specifying a small amount of resistance will help it
work better, it can oscillate into and out of current limit if you
leave the resistance as 0.
Click to expand...

That\'s interesting. I never understood what the ILIMIT parameter was.
It doesn\'t seem to correspond to any physical reality.
 
On Fri, 04 Dec 2020 14:03:13 -0500, Ray Otwell
<rayRemoveThisotwell@gmail.com> wrote:

On Fri, 04 Dec 2020 10:07:18 -0800, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.

You can roll your own as a subcircuit built around the diode model.
You can specify resistance, max current flow. I use this subcircuit I
found on the internet:

--------------------------------------------------------------------
* Current Limiter Device.
* I = Current limit.
* V = Optional forward voltage drop.
* R = Optional series resistance (note: R=0 may leed to divergence).
* Use as: X<n> <node> <node> ilim I=<num> R=<num> V=<num
* pasquale.cocchini@ieee.org - Feb 2 2016.

.subckt ilim a b I=1 R=0 V=0
Df a b IfLimDiode
Db b a IfLimDiode
.model IfLimDiode D(ron={R},ilimit={I},vfwd={V})
.ends ilim

-------------------------------------------------------------------

I have found that specifying a small amount of resistance will help it
work better, it can oscillate into and out of current limit if you
leave the resistance as 0.
Click to expand...

It can be done with a single diode:


Version 4
SHEET 1 880 680
WIRE 224 48 144 48
WIRE 352 48 304 48
WIRE 144 112 144 48
WIRE 352 112 352 48
WIRE 144 240 144 192
WIRE 352 240 352 176
FLAG 144 240 0
FLAG 352 240 0
SYMBOL diode 336 112 R0
WINDOW 0 58 14 Left 2
WINDOW 3 53 40 Left 2
SYMATTR InstName D1
SYMATTR Value Dcc
SYMBOL voltage 144 96 R0
WINDOW 0 -79 72 Left 2
WINDOW 3 -165 112 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value SINE(0 10 4)
SYMBOL res 208 64 R270
WINDOW 0 -34 54 VTop 2
WINDOW 3 -39 54 VBottom 2
SYMATTR InstName R1
SYMATTR Value 1m
TEXT 512 208 Left 2 !.tran 0 1 0 5u
TEXT -24 296 Left 2 !.model Dcc D(Ron=1m Vfwd=1m Vrev=1m Ilimit=5
Revilimit=5)
TEXT 488 80 Left 2 ;Bidirectional Current
TEXT 520 112 Left 2 ;Limiter Diode
TEXT 504 152 Left 2 ;JL Dec 4 2020

(fix wrap on that long line)
 
On Fri, 04 Dec 2020 15:27:11 -0800, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

On Fri, 04 Dec 2020 14:03:13 -0500, Ray Otwell
rayRemoveThisotwell@gmail.com> wrote:

On Fri, 04 Dec 2020 10:07:18 -0800, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.

You can roll your own as a subcircuit built around the diode model.
You can specify resistance, max current flow. I use this subcircuit I
found on the internet:

--------------------------------------------------------------------
* Current Limiter Device.
* I = Current limit.
* V = Optional forward voltage drop.
* R = Optional series resistance (note: R=0 may leed to divergence).
* Use as: X<n> <node> <node> ilim I=<num> R=<num> V=<num
* pasquale.cocchini@ieee.org - Feb 2 2016.

.subckt ilim a b I=1 R=0 V=0
Df a b IfLimDiode
Db b a IfLimDiode
.model IfLimDiode D(ron={R},ilimit={I},vfwd={V})
.ends ilim

-------------------------------------------------------------------

I have found that specifying a small amount of resistance will help it
work better, it can oscillate into and out of current limit if you
leave the resistance as 0.


It can be done with a single diode:


Version 4
SHEET 1 880 680
WIRE 224 48 144 48
WIRE 352 48 304 48
WIRE 144 112 144 48
WIRE 352 112 352 48
WIRE 144 240 144 192
WIRE 352 240 352 176
FLAG 144 240 0
FLAG 352 240 0
SYMBOL diode 336 112 R0
WINDOW 0 58 14 Left 2
WINDOW 3 53 40 Left 2
SYMATTR InstName D1
SYMATTR Value Dcc
SYMBOL voltage 144 96 R0
WINDOW 0 -79 72 Left 2
WINDOW 3 -165 112 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value SINE(0 10 4)
SYMBOL res 208 64 R270
WINDOW 0 -34 54 VTop 2
WINDOW 3 -39 54 VBottom 2
SYMATTR InstName R1
SYMATTR Value 1m
TEXT 512 208 Left 2 !.tran 0 1 0 5u
TEXT -24 296 Left 2 !.model Dcc D(Ron=1m Vfwd=1m Vrev=1m Ilimit=5
Revilimit=5)
TEXT 488 80 Left 2 ;Bidirectional Current
TEXT 520 112 Left 2 ;Limiter Diode
TEXT 504 152 Left 2 ;JL Dec 4 2020

(fix wrap on that long line)
Click to expand...

That works.
 
On Fri, 04 Dec 2020 15:45:00 -0800, boB <boB@K7IQ.com> wrote:

On Fri, 04 Dec 2020 15:27:11 -0800, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

On Fri, 04 Dec 2020 14:03:13 -0500, Ray Otwell
rayRemoveThisotwell@gmail.com> wrote:

On Fri, 04 Dec 2020 10:07:18 -0800, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.

You can roll your own as a subcircuit built around the diode model.
You can specify resistance, max current flow. I use this subcircuit I
found on the internet:

--------------------------------------------------------------------
* Current Limiter Device.
* I = Current limit.
* V = Optional forward voltage drop.
* R = Optional series resistance (note: R=0 may leed to divergence).
* Use as: X<n> <node> <node> ilim I=<num> R=<num> V=<num
* pasquale.cocchini@ieee.org - Feb 2 2016.

.subckt ilim a b I=1 R=0 V=0
Df a b IfLimDiode
Db b a IfLimDiode
.model IfLimDiode D(ron={R},ilimit={I},vfwd={V})
.ends ilim

-------------------------------------------------------------------

I have found that specifying a small amount of resistance will help it
work better, it can oscillate into and out of current limit if you
leave the resistance as 0.


It can be done with a single diode:


Version 4
SHEET 1 880 680
WIRE 224 48 144 48
WIRE 352 48 304 48
WIRE 144 112 144 48
WIRE 352 112 352 48
WIRE 144 240 144 192
WIRE 352 240 352 176
FLAG 144 240 0
FLAG 352 240 0
SYMBOL diode 336 112 R0
WINDOW 0 58 14 Left 2
WINDOW 3 53 40 Left 2
SYMATTR InstName D1
SYMATTR Value Dcc
SYMBOL voltage 144 96 R0
WINDOW 0 -79 72 Left 2
WINDOW 3 -165 112 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value SINE(0 10 4)
SYMBOL res 208 64 R270
WINDOW 0 -34 54 VTop 2
WINDOW 3 -39 54 VBottom 2
SYMATTR InstName R1
SYMATTR Value 1m
TEXT 512 208 Left 2 !.tran 0 1 0 5u
TEXT -24 296 Left 2 !.model Dcc D(Ron=1m Vfwd=1m Vrev=1m Ilimit=5
Revilimit=5)
TEXT 488 80 Left 2 ;Bidirectional Current
TEXT 520 112 Left 2 ;Limiter Diode
TEXT 504 152 Left 2 ;JL Dec 4 2020

(fix wrap on that long line)



That works.
Click to expand...

I put it into a real circuit, and Spice won\'t run it. It complains
about time steps and node errors and its usual nonsense.
 
On Fri, 04 Dec 2020 17:24:50 -0800, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

On Fri, 04 Dec 2020 15:45:00 -0800, boB <boB@K7IQ.com> wrote:

On Fri, 04 Dec 2020 15:27:11 -0800, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

On Fri, 04 Dec 2020 14:03:13 -0500, Ray Otwell
rayRemoveThisotwell@gmail.com> wrote:

On Fri, 04 Dec 2020 10:07:18 -0800, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.

You can roll your own as a subcircuit built around the diode model.
You can specify resistance, max current flow. I use this subcircuit I
found on the internet:

--------------------------------------------------------------------
* Current Limiter Device.
* I = Current limit.
* V = Optional forward voltage drop.
* R = Optional series resistance (note: R=0 may leed to divergence).
* Use as: X<n> <node> <node> ilim I=<num> R=<num> V=<num
* pasquale.cocchini@ieee.org - Feb 2 2016.

.subckt ilim a b I=1 R=0 V=0
Df a b IfLimDiode
Db b a IfLimDiode
.model IfLimDiode D(ron={R},ilimit={I},vfwd={V})
.ends ilim

-------------------------------------------------------------------

I have found that specifying a small amount of resistance will help it
work better, it can oscillate into and out of current limit if you
leave the resistance as 0.


It can be done with a single diode:


Version 4
SHEET 1 880 680
WIRE 224 48 144 48
WIRE 352 48 304 48
WIRE 144 112 144 48
WIRE 352 112 352 48
WIRE 144 240 144 192
WIRE 352 240 352 176
FLAG 144 240 0
FLAG 352 240 0
SYMBOL diode 336 112 R0
WINDOW 0 58 14 Left 2
WINDOW 3 53 40 Left 2
SYMATTR InstName D1
SYMATTR Value Dcc
SYMBOL voltage 144 96 R0
WINDOW 0 -79 72 Left 2
WINDOW 3 -165 112 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value SINE(0 10 4)
SYMBOL res 208 64 R270
WINDOW 0 -34 54 VTop 2
WINDOW 3 -39 54 VBottom 2
SYMATTR InstName R1
SYMATTR Value 1m
TEXT 512 208 Left 2 !.tran 0 1 0 5u
TEXT -24 296 Left 2 !.model Dcc D(Ron=1m Vfwd=1m Vrev=1m Ilimit=5
Revilimit=5)
TEXT 488 80 Left 2 ;Bidirectional Current
TEXT 520 112 Left 2 ;Limiter Diode
TEXT 504 152 Left 2 ;JL Dec 4 2020

(fix wrap on that long line)



That works.

I put it into a real circuit, and Spice won\'t run it. It complains
about time steps and node errors and its usual nonsense.
Click to expand...

You may need to put high value resistances from each end of the
floating I limitrer to ground to keep the matrix happy.

I usually place this text as spice directive in my hard to converge
schematics....

..options gmin=1e-10
..options abstol=1e-10
..options reltol=0.003
..options cshunt=1e-15


It is from http://ltwiki.org/index.php?title=Main_Page
 
On Fri, 04 Dec 2020 18:05:48 -0800, boB <boB@K7IQ.com> wrote:

On Fri, 04 Dec 2020 17:24:50 -0800, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

On Fri, 04 Dec 2020 15:45:00 -0800, boB <boB@K7IQ.com> wrote:

On Fri, 04 Dec 2020 15:27:11 -0800, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

On Fri, 04 Dec 2020 14:03:13 -0500, Ray Otwell
rayRemoveThisotwell@gmail.com> wrote:

On Fri, 04 Dec 2020 10:07:18 -0800, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.

You can roll your own as a subcircuit built around the diode model.
You can specify resistance, max current flow. I use this subcircuit I
found on the internet:

--------------------------------------------------------------------
* Current Limiter Device.
* I = Current limit.
* V = Optional forward voltage drop.
* R = Optional series resistance (note: R=0 may leed to divergence).
* Use as: X<n> <node> <node> ilim I=<num> R=<num> V=<num
* pasquale.cocchini@ieee.org - Feb 2 2016.

.subckt ilim a b I=1 R=0 V=0
Df a b IfLimDiode
Db b a IfLimDiode
.model IfLimDiode D(ron={R},ilimit={I},vfwd={V})
.ends ilim

-------------------------------------------------------------------

I have found that specifying a small amount of resistance will help it
work better, it can oscillate into and out of current limit if you
leave the resistance as 0.


It can be done with a single diode:


Version 4
SHEET 1 880 680
WIRE 224 48 144 48
WIRE 352 48 304 48
WIRE 144 112 144 48
WIRE 352 112 352 48
WIRE 144 240 144 192
WIRE 352 240 352 176
FLAG 144 240 0
FLAG 352 240 0
SYMBOL diode 336 112 R0
WINDOW 0 58 14 Left 2
WINDOW 3 53 40 Left 2
SYMATTR InstName D1
SYMATTR Value Dcc
SYMBOL voltage 144 96 R0
WINDOW 0 -79 72 Left 2
WINDOW 3 -165 112 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value SINE(0 10 4)
SYMBOL res 208 64 R270
WINDOW 0 -34 54 VTop 2
WINDOW 3 -39 54 VBottom 2
SYMATTR InstName R1
SYMATTR Value 1m
TEXT 512 208 Left 2 !.tran 0 1 0 5u
TEXT -24 296 Left 2 !.model Dcc D(Ron=1m Vfwd=1m Vrev=1m Ilimit=5
Revilimit=5)
TEXT 488 80 Left 2 ;Bidirectional Current
TEXT 520 112 Left 2 ;Limiter Diode
TEXT 504 152 Left 2 ;JL Dec 4 2020

(fix wrap on that long line)



That works.

I put it into a real circuit, and Spice won\'t run it. It complains
about time steps and node errors and its usual nonsense.


You may need to put high value resistances from each end of the
floating I limitrer to ground to keep the matrix happy.

I usually place this text as spice directive in my hard to converge
schematics....

.options gmin=1e-10
.options abstol=1e-10
.options reltol=0.003
.options cshunt=1e-15


It is from http://ltwiki.org/index.php?title=Main_Page
Click to expand...

This works well enough for me to figure out what I need

https://www.dropbox.com/s/2qhawkvtdfqerg5/3-Phase_Bridge_Ilim_1.asc?dl=0

but this won\'t run, even with your tweaks

https://www.dropbox.com/s/jpycij2np118b94/3-Phase_Bridge_Ilim_2.asc?dl=0

and right now I need to move on. LT Spice is like a race horse, fast
and fragile.




--

John Larkin Highland Technology, Inc

The best designs are necessarily accidental.
 
On Friday, December 4, 2020 at 1:07:32 PM UTC-5, John Larkin wrote:
What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.
Click to expand...

It should be simple if you have a decent simulation. The included ckt is one way to do it. LTSpice keeps telling me it is having syntax errors so forget them.
The circuit you want is the combo VCVS, V1, and the CCCS, I1. V1 is set to the voltage at the output node driven by the CCCS, and the CCCS is limited by the less than super-efficient function shown.

So, to use this thing:
1) break the branch passing current to be limited and direct it to circuit common thru current sense source V1,
2) insert CCCS I1 from circuit common to branch output node connected to your original circuit.

The simulation *should* solve it, and the solution should be exactly the same as the current limited circuit. The included file is for a simple sweep test ckt. The \"1.0\" in the limit function for I1 is the magnitude of the current limit in whichever direction. I must have it drawn wrong or something because it keeps getting flagged for syntax on I1.

The circuit is not \"elegant\"- thankfully.

Version 4
SHEET 1 880 680
WIRE -16 160 -112 160
WIRE 112 160 64 160
WIRE 208 160 176 160
WIRE 368 160 288 160
WIRE -112 208 -112 160
WIRE -112 320 -112 288
WIRE 112 320 112 160
WIRE 112 320 -112 320
WIRE 144 320 112 320
WIRE 176 320 176 160
WIRE 176 320 144 320
WIRE 368 320 368 160
WIRE 368 320 176 320
WIRE 144 368 144 320
FLAG 144 368 0
FLAG 336 144 OUT
SYMBOL current 208 160 R270
WINDOW 0 32 40 VTop 2
WINDOW 3 93 82 VBottom 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName I1
SYMATTR Value \"\"
SYMBOL voltage -32 160 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 4 56 VTop 2
WINDOW 123 0 0 Left 2
WINDOW 39 4 56 VTop 2
SYMATTR InstName V1
SYMATTR Value \"\"
SYMBOL current -112 288 R180
WINDOW 0 24 80 Left 2
WINDOW 3 24 0 Left 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName I2
SYMATTR Value 0
TEXT -328 280 Left 2 !.dc I2 -2 2 0.1
TEXT 144 80 Left 2 !I1=sgn(I(V1))*min(abs(I(V1)),1.0)
TEXT -40 216 Left 2 !V1=V(OUT)
 
On Friday, December 4, 2020 at 1:07:32 PM UTC-5, John Larkin wrote:
What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.
Click to expand...

I assumed sgn(x) is 1 for x >=0 and -1 for x<0. If it\'s not then just shift the stupid thing. I\'m not going to second guess that crappy write-up.
 
On Sat, 05 Dec 2020 07:56:45 -0800, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 04 Dec 2020 18:05:48 -0800, boB <boB@K7IQ.com> wrote:

On Fri, 04 Dec 2020 17:24:50 -0800, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

On Fri, 04 Dec 2020 15:45:00 -0800, boB <boB@K7IQ.com> wrote:

On Fri, 04 Dec 2020 15:27:11 -0800, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

On Fri, 04 Dec 2020 14:03:13 -0500, Ray Otwell
rayRemoveThisotwell@gmail.com> wrote:

On Fri, 04 Dec 2020 10:07:18 -0800, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

What\'s an elegant, bidirectional, 2-terminal, floating current limiter
in LT Spice? A bridge rectifier and a current source works, but draws
ugly.

You can roll your own as a subcircuit built around the diode model.
You can specify resistance, max current flow. I use this subcircuit I
found on the internet:

--------------------------------------------------------------------
* Current Limiter Device.
* I = Current limit.
* V = Optional forward voltage drop.
* R = Optional series resistance (note: R=0 may leed to divergence).
* Use as: X<n> <node> <node> ilim I=<num> R=<num> V=<num
* pasquale.cocchini@ieee.org - Feb 2 2016.

.subckt ilim a b I=1 R=0 V=0
Df a b IfLimDiode
Db b a IfLimDiode
.model IfLimDiode D(ron={R},ilimit={I},vfwd={V})
.ends ilim

-------------------------------------------------------------------

I have found that specifying a small amount of resistance will help it
work better, it can oscillate into and out of current limit if you
leave the resistance as 0.


It can be done with a single diode:


Version 4
SHEET 1 880 680
WIRE 224 48 144 48
WIRE 352 48 304 48
WIRE 144 112 144 48
WIRE 352 112 352 48
WIRE 144 240 144 192
WIRE 352 240 352 176
FLAG 144 240 0
FLAG 352 240 0
SYMBOL diode 336 112 R0
WINDOW 0 58 14 Left 2
WINDOW 3 53 40 Left 2
SYMATTR InstName D1
SYMATTR Value Dcc
SYMBOL voltage 144 96 R0
WINDOW 0 -79 72 Left 2
WINDOW 3 -165 112 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value SINE(0 10 4)
SYMBOL res 208 64 R270
WINDOW 0 -34 54 VTop 2
WINDOW 3 -39 54 VBottom 2
SYMATTR InstName R1
SYMATTR Value 1m
TEXT 512 208 Left 2 !.tran 0 1 0 5u
TEXT -24 296 Left 2 !.model Dcc D(Ron=1m Vfwd=1m Vrev=1m Ilimit=5
Revilimit=5)
TEXT 488 80 Left 2 ;Bidirectional Current
TEXT 520 112 Left 2 ;Limiter Diode
TEXT 504 152 Left 2 ;JL Dec 4 2020

(fix wrap on that long line)



That works.

I put it into a real circuit, and Spice won\'t run it. It complains
about time steps and node errors and its usual nonsense.


You may need to put high value resistances from each end of the
floating I limitrer to ground to keep the matrix happy.

I usually place this text as spice directive in my hard to converge
schematics....

.options gmin=1e-10
.options abstol=1e-10
.options reltol=0.003
.options cshunt=1e-15


It is from http://ltwiki.org/index.php?title=Main_Page







This works well enough for me to figure out what I need

https://www.dropbox.com/s/2qhawkvtdfqerg5/3-Phase_Bridge_Ilim_1.asc?dl=0

but this won\'t run, even with your tweaks

https://www.dropbox.com/s/jpycij2np118b94/3-Phase_Bridge_Ilim_2.asc?dl=0

and right now I need to move on. LT Spice is like a race horse, fast
and fragile.
Click to expand...

Yes, looks like a tough one.

I tried it with the list of 4 .options and it ran to about 1.2 ms and
anything after that it stopped early. But it did stop giving the time
step too small for node \"a\" though !

Sum Ting Wong
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top