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LTspice model for DB3 DIAC


P E Schoen

Jan 1, 1970
I was trying to design a simple voltage relay in LTspice and I wanted to use
a DIAC, but I had a hard time finding a model that worked. Finally I found
the following in an obscure Japanese or Chinese website

* PSpice Model Editor - Version 9.2

*SRC=DB3; 32V 2A
..SUBCKT DB3 1 2
QN1 5 4 2 NOUT; OFF
QN2 8 6 7 NOUT; OFF
QP1 6 8 10 POUT; OFF
QP2 4 5 9 POUT; OFF
D1 7 9 DZ
D2 2 10 DZ
DF 4 3 DZ; OFF
DR 6 3 DZ; OFF
RF 4 3 1.13E+7
RR 6 3 1.13E+7
RT2 1 7 0.755
RH 7 6 10k
RH2 4 2 10k
..MODEL DZ D (IS=321F RS=100 N=1.5 IBV=10N BV=30.3)
..MODEL POUT PNP (IS=321F BF=100 CJE=134p TF=25.5U)
..MODEL NOUT NPN (IS=321F BF=200 CJE=134p CJC=26.8p TF=1.7U)

Some other less useful sites are:

The website is supposed to have models but it redirects to an
under construction page :(

What I want to do is replace a voltage relay in an octal enclosure that
determines if the voltage is nominally 120 VAC or 208/240 VAC, and allowing
the mains voltage to be applied to the power section of the unit only if it
is properly configured in series or parallel. The present design uses a
capacitor dropper circuit that has proven unreliable in the field, probably
from high current spikes due to high frequency components of the waveform.