Thyristor (Piecewise Linear)
Thyristor
- Library:
Simscape / Electrical / Semiconductors & Converters
Description
The Thyristor (Piecewise Linear) block models a thyristor. The I-V characteristic for a thyristor is such that the thyristor turns on if the gate-cathode voltage exceeds the specified gate trigger voltage. The device turns off if the load current falls below the specified holding-current value.
To define the I-V characteristic of the thyristor, 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 anode-cathode path behaves like a linear diode with forward-voltage drop, Vf, and on-resistance, Ron. 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 anode-cathode path behaves like a linear resistor with a low off-state conductance, Goff.
The defining Simscape™ equations for the block are:
if (v > Vf)&&((G>Vgt)||(i>Ih)) i == (v - Vf*(1-Ron*Goff))/Ron; else i == v*Goff; end
where:
v is the anode-cathode voltage.
Vf is the forward voltage.
G is the gate voltage.
Vgt is the gate trigger voltage.
i is the anode-cathode current.
Ih is the holding current.
Ron is the on-state resistance.
Goff is the off-state conductance.
Using the Integral Diode tab of the block dialog box, you can include an integral cathode-anode diode. An integral diode protects the semiconductor device by providing a conduction path for reverse current. An inductive load can produce a high reverse-voltage spike when the semiconductor device suddenly switches off the voltage supply to the load.
The table shows you how to set the Integral protection diode parameter based on your goals.
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. |
Model Gate Port and Thermal Effects
You can choose between physical or electrical ports to control the gate terminal and expose
the thermal port to model the heat that switching events and conduction losses
generate. To choose the gate control port, set the Gate control
port parameter to PS
or
Electrical
. To expose the thermal port, set the
Modeling option parameter to either No
thermal port
or Show thermal
port
.
For more information about using thermal ports, see Simulating Thermal Effects in Semiconductors.
Thermal Losses
Switching losses are one of the main sources of thermal loss in semiconductors. During each on switching transition, the thyristor parasitics store and then dissipate energy.
Switching losses depend on the off-state voltage and the on-state current. When the 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. When the switching device is turned off, the power loss is defined by the Natural commutation rectification loss parameter value. This is the rectification loss applied at the point that the device switches off due to the current falling below the holding current. This loss is a fixed value and it is not scaled by the off-state voltage or the on-state current.
In this block, switching losses are applied by stepping up the junction temperature with a value equal to the switching loss divided by the total thermal mass at the junction. The Switch-on loss, Eon(Tj,Iak) parameter value sets 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 once the current is greater than the holding current for a time longer than the value specified in the Wait time before switch-on current measurement. 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 in the
simlog as lastTurnOffLoss
and
lastTurnOnLoss
(for the thyristor, this is the
Natural commutation rectification loss) and recorded 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 pulse values at
each pulse rising edge. Alternatively, you can use the ee_getPowerLossSummary
and
ee_getPowerLossTimeSeries
functions
to extract conduction and switching losses from logged data.
Note that the power_dissipated
variable in the simlog does
not include switching losses as they are modeled as instantaneous events. The
power_dissipated
variable therefore just reports
instantaneous on-state losses.
Variables
To set the priority and initial target values for the block variables prior to simulation, use the Initial Targets section in the block dialog box or Property Inspector. For more information, see Set Priority and Initial Target for Block Variables.
Nominal values provide a way to specify the expected magnitude of a variable in a model. Using system scaling based on nominal values increases the simulation robustness. Nominal values can come from different sources, one of which is the Nominal Values section in the block dialog box or Property Inspector. For more information, see System Scaling by Nominal Values.
Ports
The figure shows the block port names.