# Thyristor (Piecewise Linear)

• 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.

GoalValue to SelectBlock 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

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 at the point that the gate-cathode voltage falls below the threshold voltage. 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.

## Ports

The figure shows the block port names.

### Conserving

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

Electrical conserving port associated with the anode terminal.

Electrical conserving port associated with the cathode terminal.

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```
Forward voltage, VfGate trigger voltage, Vgt
On-state resistanceHolding current
Off-state conductanceOn-state behaviour and switching losses
```Specify constant values``````Tabulate with temperature and current```
Gate trigger voltage, VgtForward voltage, VfOn-state voltage, Vak(Tj,Iak)
Holding currentOn-state resistanceOff-state conductance
Off-state conductanceSwitch-on loss, Eon(Tj,Iak)
Switch-on lossTemperature vector, Tj
Natural commutation rectification lossAnode-cathode current vector, Iak
Off-state voltage for switching loss dataNatural commutation rectification loss
On-state current for switching loss dataOff-state voltage for switching loss data

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, switch-off loss, and on-state voltage 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.

Forward voltage at which the device turns on.

#### Dependencies

See the Main Parameter Dependencies table.

Anode-cathode resistance when the device is on.

#### Dependencies

See the Main Parameter Dependencies table.

Anode-cathode 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.

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

#### Dependencies

See the Main Parameter Dependencies table.

Current threshold. The device stays on when the current is above this value, even when the gate-cathode voltage falls below the gate trigger voltage.

#### Dependencies

See the Main Parameter Dependencies table.

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.

Rectification loss applied at the point that the block switches off when the current falls below the Holding current. Specify this parameter using a scalar quantity.

#### Dependencies

See the Main Parameter Dependencies table.

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.

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.

Note

This parameter is measured at the point that the gate voltage falls below the Gate trigger voltage, Vgt. The turn-on pulse is longer than the time it takes the current to reach its maximum value.

#### Dependencies

See the Main Parameter Dependencies table.

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.

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.

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.

Anode-cathode 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.

### Integral Diode

Block integral protection diode. The default value is `None`.

The diodes you can select are:

• ```Protection diode with no dynamics```

• ```Protection diode with charge dynamics```

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`.

Minimum voltage required across the `+` and `-` block ports for the gradient of the diode I-V characteristic to be 1/Ron, where Ron 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`.

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. 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```.

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```.

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```.

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`.

Diode junction capacitance.

#### Dependencies

This parameter is visible only when the Integral protection diode parameter is set to `Protection diode with charge dynamics`.

Peak reverse current measured by an external test circuit. This value must be less than zero. The default value is `-235` `A`.

#### Dependencies

This parameter is visible only when the Integral protection diode parameter is set to `Protection diode with charge dynamics`.

Initial forward current when measuring peak reverse current. This value must be greater than zero.

#### Dependencies

This parameter is visible only when the Integral protection diode parameter is set to `Protection diode with charge dynamics`.

Rate of change of current when measuring peak reverse current. This value must be less than zero.

#### Dependencies

This parameter is visible only when the Integral protection diode parameter is set to `Protection diode with charge dynamics`.

Determines how you specify reverse recovery time in the block. The default value is `Specify reverse recovery time directly`.

If you select `Specify stretch factor` or `Specify reverse recovery charge`, you specify a value that the block uses to derive the reverse recovery time. For more information on these options, see How the Block Calculates TM and Tau.

#### Dependencies

This parameter is visible only when the Integral protection diode parameter is set to `Protection diode with charge dynamics`.

Interval between the time when the current initially goes to zero (when the diode turns off) and the time when the current falls to less than 10% of the peak reverse current. The value of the Reverse recovery time, trr parameter must be greater than the value of the Peak reverse current, iRM parameter divided by the value of the Rate of change of current when measuring iRM parameter.

#### Dependencies

This parameter is visible only when the Integral protection diode parameter is set to `Protection diode with charge dynamics` and the Reverse recovery time parameterization parameter is set to `Specify reverse recovery time directly`.

Value that the block uses to calculate Reverse recovery time, trr. This value must be greater than `1`. Specifying the stretch factor is an easier way to parameterize the reverse recovery time than specifying the reverse recovery charge. The larger the value of the stretch factor, the longer it takes for the reverse recovery current to dissipate.

#### Dependencies

This parameter is visible only when the Integral protection diode parameter is set to `Protection diode with charge dynamics` and the Reverse recovery time parameterization parameter is set to `Specify stretch factor`.

Value that the block uses to calculate Reverse recovery time, trr. Use this parameter if the data sheet for your diode device specifies a value for the reverse recovery charge instead of a value for the reverse recovery time.

The reverse recovery charge is the total charge that continues to dissipate when the diode turns off. The value must be less than $-\frac{{i}^{2}{}_{RM}}{2a},$

where:

• iRM is the value specified for Peak reverse current, iRM.

• a is the value specified for Rate of change of current when measuring iRM.

#### Dependencies

This parameter is visible only when the Integral protection diode parameter is set to `Protection diode with charge dynamics` and the Reverse recovery time parameterization parameter is set to `Specify reverse recovery charge`.

### Thermal Port

Use the thermal port to simulate the effects of generated heat and device temperature. For more information on using thermal ports and on the Thermal Port parameters, see Simulating Thermal Effects in Semiconductors.

## Compatibility Considerations

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Behavior changed in R2020b

Behavior changed in R2021a