• Library:
• Simscape / Electrical / Semiconductors & Converters / Converters

## Description

The Two-Quadrant Chopper block represents a two-quadrant controlled chopper for converting a fixed DC input to a variable DC output. The block contains two switching devices. Options for the type of switching devices are:

• GTO — Gate turn-off thyristor. For information about the I-V characteristic of the device, see GTO.

• Ideal semiconductor switch — For information about the I-V characteristic of the device, see Ideal Semiconductor Switch.

• IGBT — Insulated-gate bipolar transistor. For information about the I-V characteristic of the device, see IGBT (Ideal, Switching).

• MOSFET — N-channel metal-oxide-semiconductor field-effect transistor. For information about the I-V characteristic of the device, see MOSFET (Ideal, Switching).

• Thyristor — For information about the I-V characteristic of the device, see Thyristor (Piecewise Linear).

• Averaged Switch.

### Model

There are two model variants for the block. To access the model variants, in the model window, right-click the block. From the context menu, select Simscape > Block choices.

The model variants are:

• First- and second- quadrant chopper. This block choice is the default. The figures show the equivalent circuit and the operation for the first- and second- quadrant model.

• First- and fourth- quadrant chopper. The figures show the equivalent circuit and the operation for the first- and fourth- quadrant model.

### Protection

The block contains an integral protection diode for each switching device. The 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.

To configure the internal protection diode block, use the Diode parameters. This table shows how to set the Model dynamics parameter based on your goals.

GoalsValue to SelectIntegral Protection Diode
Prioritize simulation speed.`Diode with no dynamics`The Diode block
Prioritize model fidelity by precisely specifying reverse-mode charge dynamics.`Diode with charge dynamics`The dynamic model of the Diode block

You can also include a snubber circuit for each switching device. Snubber circuits contain a series-connected resistor and capacitor. They protect switching devices against high voltages that inductive loads produce when the device turns off the voltage supply to the load. Snubber circuits also prevent excessive rates of current change when a switching device turns on.

To include and configure a snubber circuit for each switching device, use the Snubbers parameters.

### Gate Control

To connect Simulink® gate-control voltage signals to the gate ports of the internal switching devices:

1. Convert each voltage signal using a Simulink-PS Converter block.

2. Multiplex the converted gate signals into a single vector using a Two-Pulse Gate Multiplexer block.

3. Connect the vector signal to the G port.

## Ports

### Conserving

expand all

Electrical conserving port associated with the gate terminals of the switching devices.

Data Types: `double`

Electrical conserving port associated with the positive terminal of the first DC voltage.

Data Types: `double`

Electrical conserving port associated with the negative terminal of the first DC voltage.

Data Types: `double`

Electrical conserving port associated with the positive terminal of the second DC voltage.

Data Types: `double`

Electrical conserving port associated with the negative terminal of the second DC voltage.

Data Types: `double`

## Parameters

expand all

### Switching Devices

This table shows how the visibility of Switching Devices parameters depends on the Switching device that you select. To learn how to read the table, see Parameter Dependencies.

Switching Devices Parameter Dependencies

Parameters and Options
Switching device
```Ideal Semiconductor Switch````GTO``IGBT``MOSFET``Thyristor````Averaged Switch```
On-state resistanceForward voltageForward voltageDrain-source on resistanceForward voltageOn-state resistance
Off-state conductanceOn-state resistanceOn-state resistanceOff-state conductanceOn-state resistance
Threshold voltageOff-state conductanceOff-state conductanceThreshold voltageOff-state conductance
Gate trigger voltage, VgtThreshold voltageGate trigger voltage, Vgt
Gate turn-off voltage, Vgt_offGate turn-off voltage, Vgt_off
Holding currentHolding current

Switching device type for the converter.

#### Dependencies

See the Switching Devices Parameter Dependencies table.

For the different switching device types, the Forward voltage is taken as:

• GTO — Minimum voltage required across the anode and cathode block ports for the gradient of the device I-V characteristic to be 1/Ron, where Ron is the value of On-state resistance

• IGBT — Minimum voltage required across the collector and emitter block ports for the gradient of the diode I-V characteristic to be 1/Ron, where Ron is the value of On-state resistance

• Thyristor — Minimum voltage required for the device to turn on

#### Dependencies

See the Switching Devices Parameter Dependencies table.

For the different switching device types, the On-state resistance is taken as:

• GTO — Rate of change of voltage versus current above the forward voltage

• Ideal semiconductor switch — Anode-cathode resistance when the device is on

• IGBT — Collector-emitter resistance when the device is on

• Thyristor — Anode-cathode resistance when the device is on

• Averaged switch — Anode-cathode resistance when the device is on

#### Dependencies

See the Switching Devices Parameter Dependencies table.

Resistance between the drain and the source, which also depends on the gate-to-source voltage.

#### Dependencies

See the Switching Devices Parameter Dependencies table.

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

For the different switching device types, the On-state resistance is taken as:

• GTO — Anode-cathode conductance

• Ideal semiconductor switch — Anode-cathode conductance

• IGBT — Collector-emitter conductance

• MOSFET — Drain-source conductance

• Thyristor — Anode-cathode conductance

#### Dependencies

See the Switching Devices Parameter Dependencies table.

Gate voltage threshold. The device turns on when the gate voltage is above this value. For the different switching device types, the device voltage of interest is:

• Ideal semiconductor switch — Gate-emitter voltage

• IGBT — Gate-cathode voltage

• MOSFET — Gate-source voltage

#### Dependencies

See the Switching Devices Parameter Dependencies table.

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

#### Dependencies

See the Switching Devices Parameter Dependencies table.

Gate-cathode voltage threshold. The device turns off when the gate-cathode voltage is below this value.

#### Dependencies

See the Switching Devices Parameter Dependencies table.

Gate 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 Switching Devices Parameter Dependencies table.

### Protection Diode

The visibility of Diode parameters depends on how you configure the protection diode Model dynamics and Reverse recovery time parameterization parameters. To learn how to read this table, see Parameter Dependencies.

Protection Diode Parameter Dependencies

Parameters and Options
Model dynamics
Diode with no dynamicsDiode with charge dynamics
Forward voltageForward voltage
On resistanceOn resistance
Off conductanceOff conductance
Junction capacitance
Peak reverse current, iRM
Initial forward current when measuring iRM
Rate of change of current when measuring iRM
Reverse recovery time parameterization
```Specify stretch factor``````Specify reverse recovery time directly``````Specify reverse recovery charge```
Reverse recovery time stretch factorReverse recovery time, trrReverse recovery charge, Qrr

Diode type. The options are:

• `Diode with no dynamics` — Select this option to prioritize simulation speed using the Diode block.

• `Diode with charge dynamics` — Select this option to prioritize model fidelity in terms of reverse mode charge dynamics using the commutation diode model of the Diode block.

Note

If you select `Averaged Switch` for the Switching Device parameter in the Switching Device setting, this parameter is not visible and ```Diode with no dynamics``` is automatically selected.

#### Dependencies

See the Protection Diode Parameter Dependencies table.

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

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

Conductance of the reverse-biased diode.

Diode junction capacitance.

#### Dependencies

See the Protection Diode Parameter Dependencies table.

Peak reverse current measured by an external test circuit.

#### Dependencies

See the Protection Diode Parameter Dependencies table.

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

#### Dependencies

See the Protection Diode Parameter Dependencies table.

Rate of change of current when measuring peak reverse current.

#### Dependencies

See the Protection Diode Parameter Dependencies table.

Model for parameterizing the recovery time. When you select `Specify stretch factor` or `Specify reverse recovery charge`, you can 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

See the Protection Diode Parameter Dependencies table.

Value that the block uses to calculate Reverse recovery time, trr. 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

See the Protection Diode Parameter Dependencies table.

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 percent 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

See the Protection Diode Parameter Dependencies table.

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

See the Protection Diode Parameter Dependencies table.

### Snubbers

The Snubbers parameters tab is not visible if you set Switching device to ```Averaged Switch```.

The table summarizes the Snubbers parameter dependencies. To learn how to read the table, see Parameter Dependencies.

Snubbers Parameter Dependencies

Snubbers Parameter Dependencies
Snubber
`None````RC Snubber```
Snubber resistance
Snubber capacitance

Switching device snubber.

#### Dependencies

See the Snubbers Parameter Dependencies table.

Resistance of the switching device snubber.

#### Dependencies

See the Snubbers Parameter Dependencies table.

Capacitance of the switching device snubber.

#### Dependencies

See the Snubbers Parameter Dependencies table.

## References

[1] Trzynadlowski, A. M. Introduction to Modern Power Electronics, 2nd Edition. Hoboken, NJ: John Wiley & Sons Inc., 2010.