Current Controlled Switch (SW

Current Controlled Switch (SW_I)

The current controlled switch comes in two flavors: with controlling port and without a controlling port. In either case a model data for the current controlled switch needs to be specified, similarly to the case of the diode.

Right-click the current controlled switch model and select Properties. With the Parameter Values tab selected, specify the switch model name (in the MOD line) as well as the ID of the controlling element: either an ammeter or a voltage source. In the later case the controlling quantity is the current through the voltage source. (Note that an ammeter is a voltage source with zero voltage, that is, a short circuit).

The current controlled switch with controlling port allows for the controlling quantity to be wired directly using connections with wires. In this case a reference arrow in the controlling port is displayed and is internally used as current reference (positive current flow as indicated by the arrow).

In the model for the current controlled switch the following parameters are used:

R_on is the resistance of the switch in the on state (0.001 ohms default value).
R_off is the resistance of the switch in the off state (1,000,000 ohms default value).
I_on is the "on" value of the controlling current in amps. If I > I_on, then R = R_on.
I_off is the "off" value of the controlling current in amps. If I < I_off, then R = R_off.

Note: Setting R_off = 0 in the voltage or current controlled switch model data changes the behavior of the device into a controlled conductance, according to the following equation:

where f_control(P) is a function describing the controlling signal, which is a time, position, or speed dependent current source or voltage source. Function G(P) clearly shows that the magnitude of the conductance is dictated by both the value of R_on and the magnitude of the control signal, while the time / position / speed dependency is dictated by the control signal itself.

Note: Setting R_on = 0 in the voltage or current controlled switch model data changes the behavior of the device into a controlled resistance, according to the following equation:

where f_control(P) is a function describing the controlling signal, which is a time, position, or speed dependent current source or voltage source. Function R(P) clearly shows that the magnitude of the conductance is dictated by both the value of R_off and the magnitude of the control signal, while the time / position / speed dependency is dictated by the control signal itself.