MOSFET (Ideal, Switching)

Ideal N-channel MOSFET for switching applications

Library:
Simscape / Electrical / Semiconductors & Converters

Description

The MOSFET (Ideal, Switching) block models the ideal switching behavior of an n-channel metal-oxide-semiconductor field-effect transistor (MOSFET).

The switching characteristic of an n-channel MOSFET is such that if the gate-source voltage exceeds the specified threshold voltage, the MOSFET is in the on state. Otherwise, the device is in the off state. This figure shows a typical i-v characteristic:

To define the I-V characteristic of the MOSFET, set the On-state behaviour and switching losses parameter to either Specify constant values or Tabulate with temperature and current. The Tabulate with temperature and current option is available only if you expose the thermal port of the block.

In the on state, the drain-source path behaves like a linear resistor with resistance, R_{ds_on}. However, if you expose the thermal port of the block and parameterize the device using tabulated I-V data, the tabulated resistance is a function of the temperature and current.

In the off state, the drain-source path behaves like a linear resistor with low off-state conductance, G_off.

The defining Simscape™ equations for the block are:

    if G > Vth       v == i*Rds_on;     else       v == i/Goff;     end

where:

G is the gate-source voltage.
Vth is the threshold voltage.
v is the drain-source voltage.
i is the drain-source current.
Rds_on is the on-state resistance.
Goff is the off-state conductance.

Using the Integral Diode settings, you can include the body diode or an integral protection diode. The integral diode provides a conduction path for reverse current. For example, to provide a path for a high reverse-voltage spike that is generated when a semiconductor device suddenly switches off the voltage supply to an inductive load.

Set the Integral protection diode parameter based on your goal.

Goal	Value to Select	Block Behavior
Prioritize simulation speed.	`Protection diode with no dynamics`	The block includes an integral copy of the Diode block. To parameterize the internal Diode block, use the Protection parameters.
Precisely specify reverse-mode charge dynamics.	`Protection diode with charge dynamics`	The block includes an integral copy of the dynamic model of the Diode block. To parameterize the internal Diode block, use the Protection parameters.

Modeling Variants

The block provides four modeling variants. To select the desired variant, right-click the block in your model. From the context menu, select Simscape > Block choices, and then one of these variants:

PS Control Port — Contains a physical signal port that is associated with the gate terminal. This variant is the default.
Electrical Control Port — Contains an electrical conserving port that is associated with the gate terminal.
PS Control Port | Thermal Port — Contains a thermal port and a physical signal port that is associated with the gate terminal.
Electrical Control Port | Thermal Port — Contains a thermal port and an electrical conserving port that is associated with the gate terminal.

The variants of this block without the thermal port do not simulate heat generation in the device.

The variants with the thermal port allow you to model the heat that switching events and conduction losses generate. The thermal port is hidden by default. To enable the thermal port, select a thermal block variant.

Thermal Losses

The figure shows an idealized representation of the output voltage, V_out, and the output current, I_out, of the semiconductor device. The interval shown includes the entire n^th switching cycle, during which the block turns off and then on.

Switching losses are one of the main sources of thermal loss in semiconductors. During each on-off switching transition, the MOSFET parasitics store and then dissipate energy.

Switching losses depend on the off-state voltage and the on-state current. When a switching device is turned on, the power losses depend on the initial off-state voltage across the device and the final on-state current once the device is fully in its on state. Similarly, when a switching device is turned off, the power losses depend on the initial on-state current through the device and the final off-state voltage across the device when in the fully off state.

In this block, switching losses are applied to the attached thermal network using a first-order time constant, resulting in smooth change in temperature of the junction thermal mass. The Switch-on loss, Eon(Tj,Ids) and Switch-on loss, Eoff(Tj,Ids) parameter values set the sizes of the switching losses and they are either fixed or dependent on junction temperature and drain-source current. In both cases, losses are scaled by the off-state voltage prior to the latest device turn-on event.

Note

As the final current after a switching event is not known during the simulation, the block records the on-state current at the point that the device is commanded off. Similarly, the block records the off-state voltage at the point that the device is commanded on. For this reason, the simlog does not report the switching losses to the thermal network until one switching cycle later.

For all ideal switching devices, the switching losses are reported as lastTurnOffLoss and lastTurnOnLoss and plotted as a pulse with amplitude equal to the energy loss. If you use a script to sum the total losses over a defined simulation period, you must sum the number of pulses scaled off the reported switching loss.

Variables

The Variables settings allow you to specify the priority and initial target values for block variables before simulation. For more information, see Set Priority and Initial Target for Block Variables.

To enable the Variables settings for this block, set the variant to PS Control Port | Thermal Port or Electrical Control Port | Thermal Port.

Ports

The figure shows the block port names.

Conserving

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`G` — Gate terminal
electrical

Port associated with the gate terminal. You can set the port to either a physical signal or electrical port.

`S` — Source terminal
electrical

Electrical conserving port associated with the source terminal.

`D` — Drain terminal
electrical

Electrical conserving port associated with the drain terminal.

`H` — Thermal port
thermal

Thermal conserving port. The thermal port is optional and is hidden by default. To enable this port, select a variant that includes a thermal port.

Parameters

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Main

This table shows how the visibility of Main parameters depends on how you configure the Block choice and On-state behavior and switching losses parameters. To learn how to read this table, see Parameter Dependencies.

Main Parameter Dependencies

Parameters and Options
Block choice
`PS control port` or `Electrical control port`	`PS control port \| Thermal port` or `Electrical control port \| Thermal port`
Drain-source on resistance, R_DS(on)	Threshold voltage, Vth
Off-state conductance	On-state behaviour and switching losses
Off-state conductance	`Specify constant values`	`Tabulate with temperature and current`
Threshold voltage, Vth	Drain-source on resistance, R_DS(on)	On-state voltage, Vds(Tj,Ids)
	Off-state conductance	Off-state conductance
	Switch-on loss	Switch-on loss, Eon(Tj,Ids)
	Switch-off loss	Switch-off loss, Eoff(Tj,Ids)
	Off-state voltage for switching loss data	Temperature vector, Tj
	On-state current for switching loss data	Drain-source current vector, Ids
	On-state current for switching loss data	Off-state voltage for switching loss data
	Energy dissipation time constant	Energy dissipation time constant

`On-state behaviour and switching losses` — On-state current for switching loss data
`Specify constant values` (default) | `Tabulate with temperature and current`

Select a parameterization method. The option that you select determines which other parameters are enabled. Options are:

Specify constant values — Use scalar values to specify the output current, switch-on loss, and switch-off loss data. This is the default parameterization method.
Tabulate with temperature and current — Use vectors to specify the output current, switch-on loss, switch-off loss, and temperature data.

Dependencies

See the Main Parameter Dependencies table.

`Drain-source on resistance, R_DS(on)` — Drain-source on resistance
`0.01` `Ohm` (default)

Drain-source resistance when the device is on.

Dependencies

See the Main Parameter Dependencies table.

`Off-state conductance` — Off-state conductance
`1e-6` `1/Ohm` (default)

Drain-source conductance when the device is off. The value must be less than 1/R, where R is the value of On-state resistance.

Dependencies

See the Main Parameter Dependencies table.

`Threshold voltage, Vth` — Threshold voltage
`2` `V` (default)

Gate-source voltage threshold. The device turns on when the gate-source voltage is above this value.

Dependencies

See the Main Parameter Dependencies table.

`Switch-on loss` — Switch-on loss
`0.02286` `J` (default)

Energy dissipated during a single switch-on event. This parameter is defined as a function of temperature and final on-state output current. Specify this parameter using a scalar quantity.

Dependencies

See the Main Parameter Dependencies table.

`Switch-off loss` — Switch-off loss
`0.01714` `J` (default)

Energy dissipated during a single switch-off event. This parameter is defined as a function of temperature and final on-state output current. Specify this parameter using a scalar quantity.

Dependencies

See the Main Parameter Dependencies table.

`Off-state voltage for switching loss data` — Off-state voltage for losses data
`300` `V` (default)

The output voltage of the device during the off state. This is the blocking voltage at which the switch-on loss and switch-off loss data are defined.

Dependencies

See the Main Parameter Dependencies table.

`On-state current for switching loss data` — Output current
`600` `A` (default)

Output currents for which the switch-on loss, switch-off loss, and on-state voltage are defined. The first element must be zero. Specify this parameter using a scalar quantity.

Dependencies

See the Main Parameter Dependencies table.

`On-state voltage, Vds(Tj,Ids)` — On-state voltage
`[0, 1.1, 1.3, 1.45, 1.75, 2.25, 2.7; 0, 1, 1.15, 1.35, 1.7, 2.35, 3]` `V` (default)

Voltage drop across the device while it is in a triggered conductive state. This parameter is defined as a function of temperature and final on-state output current. Specify this parameter using a vector quantity.

Dependencies

See the Main Parameter Dependencies table.

`Switch-on loss, Eon(Tj,Ids)` — Switch-on loss
`[ 0 2.9e-4 0.00143 0.00286 0.00571 0.01314 0.02286; 0 5.7e-4 0.00263 0.00514 0.01029 0.02057 0.03029 ]` `J` (default)

Energy dissipated during a single switch on event. This parameter is defined as a function of temperature and final on-state output current. Specify this parameter using a vector quantity.

Dependencies

See the Main Parameter Dependencies table.

`Switch-off loss, Eoff(Tj,Ids)` — Switch-off loss
`[0, .21, 1.07, 2.14, 4.29, 9.86, 17.14; 0, .43, 1.97, 3.86, 7.71, 15.43, 22.71] * 1e-3` `J` (default)

Energy dissipated during a single switch-off event. This parameter is defined as a function of temperature and final on-state output current. Specify this parameter using a vector quantity.

Dependencies

See the Main Parameter Dependencies table.

`Temperature vector, Tj` — Temperature vector
`[298.15, 398.15]` `K` (default)

Temperature values at which the switch-on loss, switch-off loss, and on-state voltage are specified. Specify this parameter using a vector quantity.

Dependencies

See the Main Parameter Dependencies table.

`Drain-source current vector, Ids` — Drain-source current vector
`[ 0 10 50 100 200 400 600 ]` `A` (default)

Drain-source currents for which the switch-on loss, switch-off- loss and on-state voltage are defined. The first element must be zero. Specify this parameter using a vector quantity.

Dependencies

See the Main Parameter Dependencies table.

`Energy dissipation time constant` — Time constant
`1e-4` `s` (default)

First-order time lag with which instantaneous switching losses smoothly raise the junction temperature. This value is equal to the period of the minimum switching frequency.

Dependencies

See the Main Parameter Dependencies table.

Integral Diode

`Integral protection diode` — Protection diode
`Protection diode with no dynamics` (default) | `None` | `Protection diode with charge dynamics`

Block integral protection diode. The default value is Protection diode with no dynamics.

The diodes you can select are:

Protection diode with no dynamics
Protection diode with charge dynamics

`Diode model` — Diode model
`Piecewise Linear` (default) | `Tabulated I-V curve`

Select one of these diode models:

Piecewise Linear — Use a piecewise linear model for the diode, as described in Piecewise Linear Diode. This is the default method.
Tabulated I-V curve — Use tabulated forward bias I-V data plus fixed reverse bias off conductance.

Dependencies

This parameter is visible only when the thermal port is exposed and the Integral protection diode parameter is set to Protection diode with no dynamics or Protection diode with charge dynamics.

`Forward voltage` — Forward voltage
`0.8` `V` (default)

Minimum voltage required across the + and - block ports for the gradient of the diode I-V characteristic to be 1/R_on, where R_on is the value of On resistance.

Dependencies

To enable this parameter:

If the thermal port is hidden, set Integral protection diode to Protection diode with no dynamics or Protection diode with charge dynamics.
If the thermal port is exposed, set Integral protection diode to Protection diode with no dynamics or Protection diode with charge dynamics and Diode model to Piecewise linear.

`On resistance` — On resistance
`0.001` `Ohm` (default)

Rate of change of voltage versus current above the Forward voltage.

Dependencies

To enable this parameter:

If the thermal port is hidden, set Integral protection diode to Protection diode with no dynamics or Protection diode with charge dynamics.
If the thermal port is exposed, set Integral protection diode to Protection diode with no dynamics or Protection diode with charge dynamics and Diode model to Piecewise linear.

`Forward currents, If(Tj,Vf)` — Vector of forward currents
`[.07, .12, .19, 1.75, 4.24, 7.32, 11.2; .16, .3, .72, 2.14, 4.02, 6.35, 9.12]` `A` (default) | nonnegative vector

Forward currents. This parameter must be a vector of at least three nonnegative elements.

Dependencies

To enable this parameter, expose the thermal port and set Diode model to Tabulated I-V curve.

`Junction temperatures, Tj` — Vector of junction temperatures
`[25, 125]` `degC` (default)

Vector of junction temperatures. This parameter must be a vector of at least two elements.

Dependencies

To enable this parameter, expose the thermal port and set Diode model to Tabulated I-V curve.

`Forward voltages, Vf` — Vector of forward voltages
`[.5, .7, .9, 1.3, 1.7, 2.1, 2.5]` `V` (default)

Vector of forward voltages. This parameter must be a vector of at least three nonnegative values.

Dependencies

To enable this parameter, expose the thermal port and set Diode model to Tabulated I-V curve.

`Off conductance` — Off conductance
`1e-5` `1/Ohm` (default)

Conductance of the reverse-biased diode.

Dependencies

This parameter is visible only when the Integral protection diode parameter is set to Protection diode with no dynamics or Protection diode with charge dynamics.