Switch models

This section explains the types of swithecs in the Typhoon HIL software toolchain: the ideal switches and the non-ideal switches.

There are two modeling approaches for switches in the Typhoon HIL software toolchain. The first one is the ideal switch model, while the second one is called the non-ideal switch model.

Ideal switch model

When a switch is modeled as an ideal switch, it is a short circuit (zero impedance) while closed, conducting and an open circuit (infinite impedance) while open, not conducting. When used in a circuit, an ideal switch can introduce degenerations: in these cases parallel snubbers might be required. If an ideal open switch is connected in series with an inductor, it will degenerate the inductor, and reset its current to zero. If an ideal closed switch is connected in parallel with a capacitor, it will degenerate the capacitor, and reset its voltage to zero.

Figure 1: Ideal switch modeled as an open/short circuit

Non-ideal switch model

When a switch is modeled as a non-ideal switch it behaves as a small inductance while closed (conducting) and small capacitance while open (not conducting). Each non-ideal switch has a parameter Resistance. Resistance and the simulation step are defining the actual inductance and capacitance values according to the following equations:

L = T s   R

C =   T s R

Where L and C are the calculated inductance and capacitance, Ts is the simulation step of electrical part of the model, R is the set resistance value.

Figure 2: Non-ideal switch modeled as a capacitor/inductor