Voltage-controlled switch (SPICE S)#

The Voltage-controlled switch (SPICE S) block implements a model of a switching device whose resistance between ports + and - depends on the voltage between ports U+ and U-.

Note

The positive direction of the control voltage is taken to be the direction from port U+ to port U-

The resistance of the switch can change smoothly or with hysteresis depending on the value of the Switching mode property.

Switching mode Smooth - in this mode, the turn-on voltage VON and turn-off voltage VOFF are set. Fig. 1 shows the dependence of the key resistance \(R_s\) on the control voltage \(U_c\) for this mode.

Fig. 1 Dependence of Rs on Uc in smooth switching mode (RON = 1 Ohm, ROFF = 1000 kOhm, VON = 4 V, VOFF = 1 V)#

The resistance of the key is determined as follows:

For the case when VON > VOFF:

if \(U_c\) ≥ VON, then \(R_s\) = RON (the switch is closed);
if \(U_c\) ≤ VOFF, then \(R_s\) = ROFF (the switch is open);
if VOFF < \(U_c\) < VON, then the resistance of the switch is determined by the formula (1) :

(1)#\[R_s=exp[L_m+3 \cdot L_r \cdot (\frac{U_c-U_m}{2 \cdot U_d})-2 \cdot L_r \cdot (\frac{(U_c-U_m)^3}{U_d^3})]\]

where:

\(L_m=ln(\sqrt{RON \cdot ROFF})\) – average logarithmic value of the key resistance, [Ohm];

\(L_r=ln(\frac{RON}{ROFF})\) – logarithmic ratio of the key resistances, [Ohm];

\(U_m=\frac{VON+VOFF}{2}\) – average value of on and off voltages, [V];

\(U_d=VON-VOFF\) – difference between on and off voltages, [V].

For the case when VON < VOFF:

if \(U_c\) ≤ VON, then \(R_s\) = RON (the switch is closed);
if \(U_c\) ≥ VOFF, then \(R_s\) = ROFF (the switch is open);
if VOFF > \(U_c\) > VON, then the switch resistance is also determined by the formula (1).

Note

In this mode, it is not recommended to make the zone between VON and VOFF too narrow

Switching mode Hysteresis – in this mode, the threshold voltage VT and the hysteresis voltage VH are set. Fig. 2 shows the dependence of the key resistance \(R_s\) on the control voltage \(U_c\) for this mode.

Fig. 2 Dependence of Rs on Uc during switching with hysteresis (RON = 1 Ohm, ROFF = 1000 kOhm, VT = 2.5 V, VH = 0.5 V)#

The resistance of the key changes according to the law:

if \(U_c\) ≥ VT + VH, then \(R_s\) = RON (the switch is closed);
if \(U_c\) < VT - VH, then \(R_s\) = ROFF (the switch is open);
If none of the above conditions are met, then the state of the key remains the same as it was in the previous calculation step.

1. Properties#

Property	Default Value	Description	Units of measurement
Switching mode: Smooth; Hysteresis	Smooth	–	–
RON – on resistance	1.0	–	Ohm
ROFF – off resistance	1E6	–	Ohm
VON – control voltage for on state	1.0	Available, when `Switching mode` - `Smooth`	V
VOFF – control voltage for off state	0.0	Available, when `Switching mode` - `Smooth`	V
VT – threshold voltage	0.0	Available, when `Switching mode` - `Hysteresis`	V
VH – hysteresis voltage	0.0	Available, when `Switching mode` - `Hysteresis`	V

2. Inputs and outputs#

Parameters	Input/Output	Description	Units of measurement	Port type
+	Input	-	-	Electronics
C+	Input	-	-	Electronics
-	Output	-	-	Electronics
C-	Output	-	-	Electronics

In order to see the connection capabilities of the block, you need to go to page Description of block ports