Need Help, LTspice SCR model

Feb 24, 2007 2 Replies
A

Hi all, I found the following model of an SCR on the web. I have tried to use it in a simple circuit and I can't seem to get it to work. It barely turns on. I would like a model for a 2N5060, I don't find one. Is there something obviously wrong with this model? Or, can someone give me a model of a small signal SCR? Thanks, Mike



*SCR
*Extracted from PONT_DIPH.CIR file from EDN website.
*I renamed that file as SCR_CKT.CIR
  • Anode
  • | Cathode
  • | | Trigger
  • | | | .subckt SCR 1 2 3

*
*Models used by the SCR Model: .model STH VSwitch (ROn=0.1, VOff=0.5) .model DLG D (Rs =25m)
*
*We assume that the SCR in the on-state is equivalent to 0.1 ohm: SSCR 1 4 5 0 STH VSCR 4 2 0V
*
*Trigger to cathode impedance is a 1k ohm resistance - fore simplification: RTrig 3 2 1k
*
  • The following circuit locks in the on-state when a 1mA current flows

*through the gate to the cathode with a positive anode to cathode voltage.
*This circuit locks in the off-state when the current through the SCr tends
*to become negative: VPlus 6 0 2V SiTrig 6 5 3 2 STH CState 5 0 1uf IC=0 DLogic 5 8 DLG HCur 8 0 poly(1) VSCR 1 10000
*
*The potential of node 5 reflects the state of the SCR. It is less than 2V
*for the off-state and between 1v and 2V in the on-stateh .ends

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H

"amdx" schrieb im Newsbeitrag news:75728$45df8d86$45011502$ snipped-for-privacy@KNOLOGY.NET...

Hello Mike,

The SCR symbol in LTspice has the pin order Anode, Trigger, Cathode. You could either make a new symbol SCR1 with the netlist order Anode, Cathode, Trigger or you simply change the pin order in the subcircuit.

Solution 1: Change the subcircuit line

Solution 2:

Make a copy SCR1.asy from the synbol SCR.asy. Open the new symbol SCR1.asy and change the netlist order of the gate/trigger pin to 3 and the the cathode pin to 2 as required by the original subcircuit.

Both methods are ok. Take your choice.

Best regards, Helmut

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A

Thanks Helmut, good call, sharp of you to notice. I had already made that change through the atribute editor. I'll revisit it just to make sure I have the labels correct. The change was in the writeup about the SCR file. Thanks, Mike

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