Choose Blocks to Model Semiconductor Devices

Simscape™ Electrical™ includes several blocks that can model the same type of semiconductor device. For example, the MOSFET (Ideal, Switching) and N-Channel MOSFET blocks both model an n-channel metal-oxide-semiconductor field-effect transistor (MOSFET). You must choose a block that has sufficient modeling detail for the engineering design questions that you need to answer. It is also important not to use more detail than you need, because higher-fidelity models slow down simulation and are more complex to parameterize. The right block to use therefore depends on the level of complexity that you need to meet your design goals. To choose a block with the correct level of complexity, you:

1. Determine the level of fidelity that you need.

2. Select the right block to model your semiconductor device at that level of fidelity.

3. Parameterize the block.

Determine the Fidelity Level

You choose between blocks that can model the same type of semiconductor device, but implement mathematical models with different levels of complexity.

• Level 1 models — Ideal switching device models with no thermal model

• Level 2 models — Ideal switching device models with tabulated switching losses and a thermal model

• Level 3 models — Physics-based electrothermal models

Increasing modeling complexity restricts the design space that you can practically explore or optimize against. To develop your model with the right level of complexity, you need to use a different fidelity level depending on where you are in the design process. This table lists common design goals and the typical corresponding modeling assumptions at the three levels of fidelity. Use this table to determine the level of fidelity you need.

Fidelity Level

Goals

Modeling Assumptions

Level 1

• Validate system behavior including other parts of the system, such as the motor and mechanical load or an electrical load

• Assess the impact of the switching PWM pattern on electrical and mechanical harmonics

• Optimize systems in which you deploy power electronics

• Piecewise linear on-state I-V curve with a limited number of points

• No charge model

• Current averaging — This assumption is optional but useful for optimizing systems in which you deploy power electronics

• No thermal model

Level 2
• Determine semiconductor device losses as part of the overall efficiency calculation

• Minimize semiconductor device losses by making adjustments to the PWM pattern

• Calculate thermal losses for heat management or cooling system design

• Select manufactured semiconductor device components

• Confirm semiconductor devices stay within the operating envelope

• Tabulated on-state I-V curve

• No charge model

• Tabulated switching losses

• Junction and case thermal model

Level 3
• Design gate drives

• Analyze circuit transients down to device time constraints; for example, to confirm a suitable blanking time to prevent shoot through

• Design circuits that use a semiconductor device over a range of on-state operating points, such as in RF power amplifiers or resonant converters

• Tabulated I-V curve or physics-based nonlinear model

• Tabulated charge model or physics-based charge model

• Junction and case thermal model

Choose the Right Block for the Model

This table shows the blocks that you can use to represent different semiconductor device types at each level of fidelity. Use this table to select the right block to model your semiconductor device.

Device Type

Blocks
Level 1

Level 2

Level 3

Diode
• Diode

• Set the Modeling option parameter to ```No thermal port```

• Set the Diode model parameter to ```Piecewise Linear```

• Set the Parametrization parameter to ```Fixed or zero junction capacitance```

• Set the Junction capacitance parameter to zero

• Diode

• Set the Modeling option parameter to ```Show thermal port```

• Set the Fidelity level parameter to ```Ideal switching```

• Diode

• Set the Diode model parameter to `Exponential` or ```Tabulated I-V curve```

• Define nonzero junction capacitance or model charge dynamics. For more information, see Junction Capacitance and Charge Dynamics.

Bipolar transistorNot supportedNot supported
MOSFET
IGBT
Thyristor
GTO
• GTO — Set the Modeling option parameter to `No thermal port`

Not supported
JFETNot supportedNot supported
Composite and complete converter circuits
Not supportedNot supported

Note

When you use the Level 1 parameter settings for the Diode block, the block is equivalent to the Diode block in the Simscape Foundation Library.

You can use a Gate Driver or Half-Bridge Driver block to drive a semiconductor block at any level of fidelity. Some blocks that use Level 1 and Level 2 models, such as the MOSFET (Ideal, Switching) block, can use a physical signal port for the gate terminal which eliminates the need for an electrical model of the gate driver. Use an electrical port for the gate terminal to easily change the fidelity levels by changing the block that models the semiconductor device without having to change the gate driver.

Parameterize the Block

After you select the right block, you must parameterize it. Parameterization of semiconductor devices can be challenging, depending on what information the manufacturer provides. Datasheets are a good source for Level 1 and Level 2 models, but do not provide the full charge information you need for Level 3 models. For example, in the case of MOSFETs, you need to tabulate the gate-source charge in terms of gate-source voltage and drain-source voltage but datasheets often give the gate-source charge in terms of the gate-source voltage only.

You can pre-parameterize some blocks, for Level 1 or Level 2 models, using the Block Parameterization Manager. These parameter values represent components by specific suppliers and match the manufacturer datasheets. For more information about using pre-parameterized parts, the blocks that support this option, the manufactured components that you can model, and additional parameterization options, see List of Pre-Parameterized Components.

Some manufacturers provide XML files that store data you can use to parameterize Level 2 models. You can import these files into Simscape using the `ee_importDeviceParameters` function. You can also transform a Level 3 model into an equivalent Level 2 model that is easier to interpret and runs faster using the `generateSemiconductorSwitchROM` function.

SPICE subcircuits usually provide a Level 3 model, but Simscape Electrical cannot use these subcircuits directly. If you have a SPICE subcircuit that you want to simulate in Simscape Electrical, choose one of these options:

• Map the subcircuit to a table-based I-V and charge parameterization using the `ee.spice.semiconductorSubcircuit2lookup` function. This method is numerically more reliable and usually the better choice.

• Convert the subcircuit to an equivalent Simscape component using the `subcircuit2ssc` function or use the SPICE-Imported MOSFET block to model the devices that the block supports. This method can cause numerical simulation issues because the original netlist is usually optimized for a specific SPICE simulation engine.