Current-controlled switch (SPICE W)

Block appearance in REPEAT VISION

 The Current-controlled switch (SPICE W) block implements a model of a switching device whose resistance between ports + and - depends on the control current \(I_c\) flowing from port C+ to port C-.

Note

The control ports C+ and C- must be connected in series to the branch whose current is used to control the switch. The connection is similar to the connection of the Current meter block.

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

 Switching mode Smooth transition – in this mode, the turn-on current ION and turn-off current IOFF are set. Fig. 1 shows the dependence of the switch resistance \(R_s\) on the control current \(I_c\) for this mode.

Fig. 1 Dependence of \(R_s\) on \(I_c\) in smooth switching mode (RON = 1 [Ohm], ROFF = 1000 [kOhm], ION = 4 [A], IOFF = 1 [A])

 The resistance of the key is determined as follows:

1. For the case when ION > IOFF:

• if \(I_c\) ≥ ION, then \(R_s\) = RON (the switch is closed);

• if \(I_c\) ≤ IOFF, then \(R_s\) = ROFF (the switch is open);

• if IOFF < \(I_c\) < ION, then the resistance of the switch is determined by the formula (1) :

(1)\[R_s=exp[L_m+3 \cdot L_r \cdot (\frac{I_c-I_m}{2 \cdot I_d})-2 \cdot L_r \cdot (\frac{(I_c-I_m)^3}{I^3_d})]\]

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];

 \(I_m=\frac{ION+IOFF}{2}\) – average value of on-off currents, [A];

 \(I_d=ION-IOFF\) – difference between on- and off-currents, [A].

2. For the case when ION < IOFF:

• if \(I_c\) ≤ ION, then \(R_s\) = RON (the switch is closed);

• if \(I_c\) ≥ IOFF, then \(R_s\) = ROFF (the switch is open);

• If IOFF > \(I_c\) > ION, then the resistance of the switch is also determined by the formula (1).

Note

In this mode, it is not recommended to make the zone between ION and IOFF too narrow.

Switching mode Hysteresis – in this mode, the threshold current IT and the hysteresis current IH are set. Fig. 2 shows the dependence of the switch resistance \(R_s\) on the control current \(I_c\) for this mode.

Fig. 2 Dependence of \(R_s\) on \(I_c\) during switching with hysteresis (RON = 1 [Ohm], ROFF = 1000 [kOhm], IT = 2.5 [A], IH = 0.5 [A])

 The resistance of the key changes according to the law:

• if \(I_c\) ≥ IT + IH, then \(R_s\) = RON (the key is closed);

• if \(I_c\) < IT - IH, 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 transition; Hysteresis	Smooth transition	–	–
RON – on resistance	1.0	–	Ohm
ROFF – off resistance	1e6	–	Ohm
ION – control current for on state	1е-3	Available, when Switching mode - Smooth transition	А
IOFF – control current for off state	0.0	Available, when Switching mode - Smooth transition	А
IT – threshold current	0.0	Available, when Switching mode - Hysteresis	А
IH – hysteresis current	0.0	Available, when Switching mode - Hysteresis	А

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