Implement ideal switch device
Simscape / Electrical / Specialized Power Systems / Power Electronics
The Ideal Switch block does not correspond to a particular physical device. When used with appropriate switching logic, it can be used to model simplified semiconductor devices such as a GTO or a MOSFET, or even a power circuit breaker with current chopping. The switch is simulated as a resistor Ron in series with a switch controlled by a logical gate signal g.
The Ideal Switch block is fully controlled by the gate signal (g > 0 or g = 0). It has the following characteristics:
Blocks any forward or reverse applied voltage with 0 current flow when g = 0
Conducts any bidirectional current with quasi-zero voltage drop when g > 0
Switches instantaneously between on and off states when triggered
The Ideal Switch block turns on when a positive signal is present at the gate input (g > 0). It turns off when the gate signal equals 0 (g = 0).
The Ideal Switch block also contains a series Rs-Cs snubber circuit that can be connected in parallel with the ideal switch (between nodes 1 and 2).
- Internal resistance Ron
The internal resistance of the switch device, in ohms (Ω). Default is
0.001. The Internal resistance Ron parameter cannot be set to
- Initial state
The initial state of the Ideal Switch block. Default is
0. The initial status of the Ideal Switch block is taken into account in the steady-state calculation.
- Snubber resistance Rs
The snubber resistance, in ohms (Ω). Default is
1e5. Set the Snubber resistance Rs parameter to
infto eliminate the snubber from the model.
- Snubber capacitance Cs
The snubber capacitance in farads (F). Default is
inf. Set the Snubber capacitance Cs parameter to
0to eliminate the snubber, or to
infto get a resistive snubber.
- Show measurement port
If selected, add a Simulink® output to the block returning the ideal switch current and voltage. Default is selected.
Inputs and Outputs
Simulink signal to control the opening and closing of the switch.
The Simulink output of the block is a vector containing two signals. You can demultiplex these signals by using the Bus Selector block provided in the Simulink library.
Ideal switch current
Ideal switch voltage
Assumptions and Limitations
The Ideal Switch block is modeled as a current source. It cannot be connected in series with an inductor, a current source, or an open circuit, unless its snubber circuit is in use.
uses the Ideal Switch block to switch an RLC circuit on an AC source (60 Hz). The switch, which
is initially closed, is first opened at t = 50 ms (3 cycles) and then reclosed at
t = 138 ms (8.25 cycles). The Ideal Switch block has 0.01 ohms resistance and no snubber is
 Mohan, N., T.M. Undeland, and W.P. Robbins, Power Electronics: Converters, Applications, and Design, John Wiley & Sons, Inc., New York, 1995.