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12-11-2006 10:59 AM
The time delay switch is an interactive component, that means when you run the simulation in the regular mode, you can see the switch switching on the screen. This is not a SPICE native property so when you import it into the transient analysis, it does not work.
To work around this, you can create a SPICE native model and the switch should change state in middle of the analysis. Below is a model to emulate the time delay switch:
.subckt TD S1 S2
xU2 1 0 S1 S2 SW
xU1 1 0 PWL
.subckt SW 1 2 3 4
S1 3 4 1 2 vsw
.model vsw sw (
+ vt = 0.001
+ vh = -1e-006
+ ron = 0.001
+ roff = 1e+009
+ )
.ends
.subckt PWL 1 2
V1 1 0 PWL (0,0) (0.01,0) (0.01001,10)
.ends
.ends
The model is made up of two basic SPICE components, a PWL and a voltage control switch.
The body of the PWL is here:
V1 1 0 PWL (0,0) (0.01,0) (0.01001,10)
(0,0)àtime 0 voltage is 0V
(0.01,0) >> t=0.01, V= 0
(0.01001,10) >> t=0.01001 V=10
The PWL is a “connect the dot” component and in this example, I gave it three points.
The second part of the model is a Volt control switch. When the voltage crosses the 0.001V it changes state.
I also made a circuit to show what this model looks like in a schematic.
12-11-2006 02:18 PM