Implement MOSFET model
Fundamental Blocks/Power Electronics
The metal-oxide semiconductor field-effect transistor (MOSFET) is a semiconductor device controllable by the gate signal (g > 0). The MOSFET device is connected in parallel with an internal diode that turns on when the MOSFET device is reverse biased (Vds < 0) and no gate signal is applied (g=0). The model is simulated by an ideal switch controlled by a logical signal (g > 0 or g =0), with a diode connected in parallel.
The MOSFET device turns on when a positive signal is applied at the gate input (g > 0) whether the drain-source voltage is positive or negative. If no signal is applied at the gate input (g=0), only the internal diode conducts when voltage exceeds its forward voltage Vf.
With a positive or negative current flowing through the device, the MOSFET turns off when the gate input becomes 0. If the current I is negative and flowing in the internal diode (no gate signal or g = 0), the switch turns off when the current I becomes 0.
The on state voltage Vds varies:
Vds = Ron*I when a positive signal is applied at the gate input.
Vds = Rd*I-Vf +Lon*dI/dt when the antiparallel diode is conducting (no gate signal).
The Lon diode inductance is available only with the continuous model. For most applications, Lon should be set to zero for both continuous and discrete models.
The MOSFET block also contains a series Rs-Cs snubber circuit that can be connected in parallel with the MOSFET (between nodes d and s).
The internal resistance Ron, in ohms (Ω). Default is
The Resistance Ron parameter cannot
be set to
0 when the Inductance
Lon parameter is set to
The internal inductance Lon, in henries (H). Default is
The Inductance Lon parameter is normally
0 except when the Resistance
Ron parameter is set to
The internal resistance of the internal diode, in ohms (Ω).
The forward voltage of the internal diode, in volts (V). Default
You can specify an initial current flowing in the MOSFET device.
It is usually set to
0 in order to start the simulation
with the device blocked. Default is
If the Initial current IC parameter
is set to a value greater than
0, the steady-state
calculation considers the initial status of the MOSFET as closed.
Initializing all states of a power electronic converter is a complex
task. Therefore, this option is useful only with simple circuits.
The snubber resistance, in ohms (Ω). Default is
Set the Snubber resistance Rs parameter
inf to eliminate the snubber from the model.
The snubber capacitance, in farads (F). Default is
Set the Snubber capacitance Cs parameter
0 to eliminate the snubber, or to
get a resistive snubber.
If selected, add a Simulink® output to the block returning the MOSFET current and voltage. Default is selected.
Simulink signal to control the opening and closing of the MOSFET.
The Simulink output of the block is a vector containing 2 signals. You can demultiplex these signals by using the Bus Selector block provided in the Simulink library.
The MOSFET block implements a macro model of the real MOSFET device. It does not take into account either the geometry of the device or the complex physical processes .
Depending on the value of the inductance Lon, the MOSFET is modeled either as a current source (Lon > 0) or as a variable topology circuit (Lon = 0). The MOSFET block cannot be connected in series with an inductor, a current source, or an open circuit, unless its snubber circuit is in use.
The inductance Lon is forced to 0 if you choose to discretize your circuit.
 Mohan, N., T.M. Undeland, and W.P. Robbins, Power Electronics: Converters, Applications, and Design, John Wiley & Sons, Inc., New York, 1995.