SPST Switch
Single pole single position switch.
Description
The SPST Switch unit simulates a single phase single position switch:
-
When the control signal does not exceed Threshold, the switch is open. The p port is connected to the n port via the conductance set by the Open conductance parameter.
-
When the control signal exceeds Threshold, the switch is closed. At the same time, port p is connected to port n via the resistance set by the Closed resistance parameter.
When the Threshold width parameter is non-zero, the conductivity of the switch changes smoothly between the off and on states. The value of the Threshold width parameter determines the sharpness of the transition between the switch states according to the formulas:
The block uses the function , since its derivative is zero at and .
Setting a small positive value of Threshold width can contribute to the convergence of the solver in some models, especially if the control port signal vT varies continuously with other parts of the circuit. However, setting a non-zero value of Threshold width does not allow the solver to use linear optimisation with switching. Therefore, if the rest of the circuit is linear, set Threshold width to zero.
Type of switch gate control
In the component there is an option to select the type of switch gate control using the Modelling option:
-
Signal control port - the signal coming to the vT port is taken as the control signal.
-
Electrical control port - the potential difference at the additional electrical ports is taken as the control signal value.
Input
vT - control port
scalar
Signal controlling the state of the switch.
Dependencies
To use this port, set the Modelling option to Signal control port.
Non-directional
p is a positive port
electric
Electrical port.
n is a negative port
`electric'
Electrical port.
+ - positive port
electric
An electrical port associated with the positive terminal. Used in voltage control mode.
Dependencies
To use this port, set Modelling option to Electrical control port.
- is a negative port
`electrical
An electrical port associated with the negative terminal. Used in voltage control mode.
Dependencies
To use this port, set Modelling option to Electrical control port.
Parameters
Modelling option - set scalar or electrical control port
Signal control port (by default) | Electrical control port
Defines whether the switch state is controlled by a signal or potential difference across the control legs.
Closed resistance - resistance of the closed switch
0.01 Ohm (by default) | positive scalar.
Resistance between ports p and n when the switch is closed.
Open conductance - open switch conductance
1e-6 1/ohm (by default) | `positive scalar'.
Conductance between ports p and n when the switch is open.
Threshold - threshold voltage
`0.5 V (by default).
The threshold voltage above which the switch is switched on.
Threshold width - width of the threshold
`0 (By default)
The minimum voltage increase above the threshold that will move the switch from fully open to fully closed.