MOSFET (Ideal, Switching)
The ideal n-channel MOSFET for switching circuits.
Description
The MOSFET (Ideal, Switching) block simulates the ideal behaviour 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 a given threshold voltage, the MOSFET is in the open state. Otherwise, the device is in the closed state. The figure shows a typical volt-ampere characteristic of a MOSFET.
In the open state, the drain-source channel behaves like a linear resistor with a resistance of .
In the closed state, the drain-source channel behaves as a linear resistor with low conductance .
The defining equations can be written as
if , otherwise ,
where:
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depends on the value of the Gate-control port parameter:
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Signal control port- gate control via G port, in this case is the value on the G input port; -
Electrical control port- gate control by means of an electrical signal, in this case is defined as:
-
, if , otherwise ,
where is the gate voltage, is the source voltage and is the drain voltage.
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- threshold voltage.
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- drain-to-source voltage.
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- drain-to-source current.
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- open-state resistance.
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- closed state conductivity.
Using the Integral Diode settings, an internal protection diode can be enabled. The internal diode protects the device by providing a conduction channel for reverse current that occurs when the device abruptly cuts off the voltage supply to an inductive load.
Set the Integral protection diode parameter depending on the purpose.
| Purpose | Value to select | Integral protection diode | |
|---|---|---|---|
Do not enable protection. |
|
Not used |
|
Enable protection. |
Simulation speed priority. |
|
Block Diode (Advanced). |
Simulation accuracy priority - accurate indication of charge dynamics in reverse mode. |
|
Dynamic block model Diode (Advanced). |
|
Ports
Parameters
Main
Gate-control port - option for specifying the type of gate-control port
Signal control port (by default) | Electrical control port
Option to specify the physical or electrical gate-control port of the switch.
If the parameter is set to Electrical control port, use an internal or external reverse polarity diode with this unit. For numerical reasons, the diode forward voltage must be less than the value of the parameter Threshold voltage, Vth.
|
Drain-source on resistance, R_DS(on) - drain-source resistance in open state
`0.01 ohm (by default).
Drain-source on resistance, R_DS(on).
Off-state conductance - closed state conductance
1e-6 1/ohm (by default)
The closed state conductance of the drain-source. The value of this parameter must be less than , where is the value of Drain-source on resistance, R_DS(on).
Threshold voltage, Vth - threshold voltage
2 V (by default)
Threshold gate-to-source voltage. The device is open when the gate-source voltage exceeds this value.
Integral Diode
Integral protection diode - internal protection diode (suppressor)
None (by default) | Diode with no dynamics | Diode with charge dynamics
Specify whether the unit includes a protection diode (suppressor). By default, `None' is used.
If the internal protection diode is to be enabled, two options are available:
-
Diode with no dynamics. -
`Diode with charge dynamics'.
Forward voltage - forward voltage
0.8 V (by default).
Minimum voltage between anode and cathode of the diode to make the gradient of the diode volt-ampere characteristic equal to 1/ , where is the value of On resistance parameter.
Dependencies
To use this parameter, set Integral protection diode to Diode with no dynamics or Diode with charge dynamics.
On resistance - resistance when directly connected
0.001 ohms (by default).
The diode resistance in the open state when the voltage is higher than the value set by the Forward voltage parameter.
Dependencies
To use this parameter, set Integral protection diode to Diode with no dynamics or Diode with charge dynamics.
Off conductance - closed state conductance
1e-5 1/ohm (by default).
The conductance of the diode when switched back on.
Dependencies
To use this parameter, set Integral protection diode to Diode with no dynamics or Diode with charge dynamics.
Junction capacitance - junction capacitance
5e-8 F (By default).
The value of the capacitance inherent in the depletion zone transition, acting as a dielectric and separating the anode and cathode junctions.
Dependencies
To use this parameter, set Integral protection diode to `Diode with charge dynamics'.
Peak reverse current, iRM - peak reverse current
-235 A (By default).
Peak reverse current measured by an external test circuit. This value must be less than zero. The value by default is -235 A.
Dependencies
To use this parameter, set Integral protection diode to `Diode with charge dynamics'.
Initial forward current when measuring iRM - Initial forward current when measuring iRM
300 A (By default).
Initial forward current (at initial switch-on time) when measuring peak reverse current. This value must be greater than zero.
Dependencies
To use this parameter, set Integral protection diode to `Diode with charge dynamics'.
Rate of change of current when measuring iRM - rate of change of current when measuring iRM
-50 A/µs (By default).
Rate of change of current when measuring peak reverse current. This value must be less than zero.
Dependencies
To use this parameter, set Integral protection diode to `Diode with charge dynamics'.
Reverse recovery time parametrization - type of reverse recovery time definition
| Specify stretch factor (by default) | Specify reverse recovery time directly ` | `Specify reverse recovery charge.
Selecting Specify stretch factor or Specify reverse recovery charge specifies the value used by the unit to calculate the reverse recovery time.
Dependencies
To use this option, set Integral protection diode to `Diode with charge dynamics'.
Reverse recovery time, trr - reverse recovery time
`15 µs (By default)
The amount of time it takes for a diode to switch off when its voltage reverses polarity from forward bias to reverse bias.
The interval between when the current initially crosses zero (when the diode switches off) and when the current drops to less than 10% of the peak current. The value of Reverse recovery time, trr must be greater than the value of Peak reverse current, iRM divided by the value of Rate of change of current when measuring, iRM.
Dependencies
To use this parameter, set the Integral protection diode parameter to `Diode with charge dynamics' and the Reverse recovery time parametrization parameter to `Specify reverse recovery time directly'.
Reverse recovery time stretch factor - reverse recovery time stretch factor
3 (By default).
The value that the block uses to calculate Reverse recovery time, trr. This value must be greater than 1. Specifying the stretch factor is a simpler way of parameterising the reverse recovery time than specifying the reverse recovery charge. The larger the value of the stretch factor, the longer the time required for the reverse recovery current to dissipate.
Dependencies
To use this parameter, set the Integral protection diode parameter to `Diode with charge dynamics' and the Reverse recovery time parametrization parameter to `Specify stretch factor'.
Reverse recovery charge, Qrr - reverse recovery charge
1500 µAs (by default).
The value the unit uses to calculate Reverse recovery time, trrr. Use this parameter if the unit parameters specify the reverse recovery charge value instead of the reverse recovery time value as the type of reverse recovery time definition.
The reverse recovery charge is the total charge that continues to dissipate after the diode is switched off. The value must be less than , where:
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- value specified for the Peak reverse current, iRM parameter;
-
- the value specified for the parameter Rate of change of current when measuring iRM.
Dependencies
To use this parameter, set the Integral protection diode parameter to `Diode with charge dynamics' and the Reverse recovery time parametrization parameter to `Specify reverse recovery charge'.