Mathworks SIMELECTRONICS 1 user guide

SimElectronics

User’s Guide

®

1

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ng, and general information

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For contact information about worldwide offices, see the MathWorks Web site.

®

SimElectronics

© COPYRIGHT 2008–20 10 by The MathWorks, Inc.

The software described in this document is furnished under a license agreement. The software may be used
or copied only under the terms of the license agreement. No part of this manual may be photocopied or
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The MathWorks products are protected by one or more U.S. patents. Please see

www.mathworks.com/patents for more information.

Revision History

April 2008 Online only New for Version 1.0 (Release 2008a+)
October 2008 Online only Revised for Version 1.1 (Release 2008b)
March 2009 Online only Revised for Version 1.2 (Release 2009a)
September 2009 O nline only Revised for Version 1.3 (Release 2009b)
March 2010 Online only Revised for Version 1.4 (Release 2010a)

User’s Guide

Getting Started

1

Product Overview ................................. 1-2

Product Description
Assumptions and Limitations
Modeling Physical Networks with SimElectronics

Blocks

Getting Online Help

........................................ 1-3

............................... 1-2

....................... 1-2

............................... 1-3

Contents

Required and Related Products

Product Require ments
Other Related Products

SimElectronics Block Libraries

Overview of SimElectronics Libraries
Opening SimElectronics Libraries

Product Workflow

Example — Modeling a DC Motor

Overview o f DC Motor Example
Selecting Blocks to Represent System Components
Building the Model
Specifying Model Parameters
Configuring the Solver Parameters
Running the Simulation and Analyzing the Results

Example — Modeling a Triangle Wave Generator

Overview o f Triangle Wave Generator Ex am ple
Selecting Blocks to Represent System Components
Building the Model
Specifying Model Parameters
Configuring the Solver Parameters
Running the Simulation and Analyzing the Results

............................. 1-5

............................ 1-5

................................. 1-10

................................ 1-12

................................ 1-27

..................... 1-5

..................... 1-6

................. 1-6

.................... 1-6

................... 1-11

...................... 1-11

........................ 1-15

................... 1-21

......... 1-25

........................ 1-29

................... 1-37

...... 1-11

..... 1-22

..... 1-25

...... 1-25

..... 1-38

iii

Modeling an Electronic System

2

Modeling Electronic Components ................... 2-2

Parameterizing Blocks
Additional Parameterization Workflows
Adding SimElectronics Blocks to a Model
Connecting Model Blocks
Selecting the Output Model for Logic Blocks

............................. 2-2

............... 2-15

.............. 2-16

........................... 2-17

........... 2-18

Working with Simulink Blocks

Modeling Instantaneous Events
Using Simulink Blocks to Model Physical Components

...................... 2-22

...................... 2-22

Simulating an Electronic System

3

Selecting a Solver ................................. 3-2

Available Solvers
How to Select a Solver

Specifying Simulation Accuracy/Speed Tradeoff

Parameters that Affect Accuracy and Speed
Determining Appropriate Accuracy/Speed Parameter

Values

Avoiding Simulation Issues

General Troubleshoo ting for Simscape Models
Troubleshooting for Simscape Models that Include

SimElectronics Blocks

........................................ 3-3

.................................. 3-2

............................. 3-2

...... 3-3

............ 3-3

......................... 3-5

.......... 3-5

........................... 3-5

... 2-22

iv Contents

Running a Time-Domain Simulation

Running a Small-Signal Frequency-Domain

Analysis

Linearizing SimElectronics Models
Analyzing Small-Signal Behavior Using Bode Plots

........................................ 3-7

................ 3-6

................... 3-7

...... 3-7

Examples

A

Examples ......................................... A-2

Index

v

vi Contents

Getting Started

• “Product Overview” on page 1-2

• “Required and Related Products” on page 1-5

• “SimElectronics Block Libraries” on page 1-6

• “Product Workflow” on page 1-10

• “Example — Modeling a DC Motor” on page 1-11

• “Example — Modeling a Triangle Wave Generator” on page 1- 2 5

1

1 Getting Started

Product Overview

Product Description

SimElectronics®software works with Simscape™ software and extends the
physical modeling capabilities of the Simulink
for modeling and simulating electromechanical and electronic systems. It
contains blocks that let you model electromechanical and electronic systems
at a speed and level of fidelity that is appropriate for system-level analysis.
The blocks let you perform tradeoff analyses to optimize system design, for
example, by testing various algorithms with different circuit implementations.

In this section...

“Product Description” on page 1-2

“Assumptions and Limitations” on page 1-2

“Modeling Physical Networks with SimElectronics Blocks” on page 1-3

“Getting Online Help” on page 1-3

®

product family with tools

1-2

Assumptions and Limitations

Use SimElectronics with Simscape to simulate electromechanical and
electricalsystemsinthetimedomain. Itcontainsblocksthatyoucanuse
with other Simscape blocks to simulate components at a system level. The
library contains blocks that use either high-level or more detailed models to
simulate components. SimElectronicsdoesnothavethecapabilityto:

• Model large circuits with dozens of analog components, such as a complete

transceiver.

• Perform either layout (physical design) tasks, or the associated

implementation tasks such as layout versus schematic (LVS), design rule
checking (DRC), parasitic extraction, and back annotation.

• Model 3-D parasitic effects that are typically important for high-frequency

applications.

For these types of requirements, you must use an EDA package specifically
designed for the implementation of analog circuits.

Product Overview

Another MathWorks™ p roduct, SimPowerSystems™ software, is better
suited for power system networks where:

• The underlying equations are predominantly linear (e.g., transmission

lines and linear machine models).

• Three-phase motors and generators are used.

SimPowerSystems has blocks and solvers specifically designed for these
types of applications.

Modeling Physical Networks with SimElectronics
Blocks

SimElectronics is part of the Simulink Physical Modeling family . Models
using SimElectronics are essentially Simscape block diagrams. To build a
system-level model with electrical blocks, use a combination of SimElectronics
blocks and other Simscape and Simulink blocks. You can connect
SimElectronics blocks directly to Simscape blocks. You can connect Simulink
blocks through the Simulink-PS Converter and PS-Simulink Converter blocks
from the Simscape Utilities library. These blocks convert electrical signals
to and from Simulink mathematical signals. For more information about
connecting different types of blocks, see “Connecting Model Blocks” on page
2-17.

For more information about basic principles to follow when building an
electrical model with SimElectronics, see “Basic Principles of Modeling
Physical Networks” in the Simscape documentation.

Getting Online Help

Using the MATLAB Help System for Documentation and Demos

The MATLAB®Help browser allows you to access the documentation and
demo models for all the MATLAB and Simulink based products that you have
installed. Consult “Overview of Help” in MATLAB documentation for more
information about the Help system.

1-3

1 Gettin g Started

For...

List of blocks “Block Reference”

Advanced tutorials

Product demonstrations

What’s new in this product

See...

Examples

SimElectronics Demos

Release Notes

The MathWorks Online

Point your Internet brow ser to the MathWorks
Web site for additional information and support at
http://www.mathworks.com/products/simelectronics/.

1-4

Required and Related Products

Product Requirements

SimElectronics software is an extension of Simscape product, expanding its
capabilities to model and simulate electronic and electromechanical elements
and devices.

SimElectronics software requires these products:

• MATLAB

• Simulink

• Simscape

Other Related Products

The SimElectronics product page at the MathWorks Web site lists the
toolboxes and blocksets that extend the capabilities of MATLAB and
Simulink. These products can enhance your use of SimElectronics software in
various applications.

Required and Related Products

For more information about The MathWorks™ software products, see:

• The online documentation for that product if it is installed

• The MathWorks Web site at

www.mathworks.com

1-5

1 Gettin g Started

SimElectronics Block Libraries

In this section...

“Overview of SimElectronics Libraries” on page 1-6

“Opening SimElectronics Libraries” on page 1-6

Overview of SimElectronics Libraries

SimElectronics libraries provide blocks for modeling electromechanical and
electrical systems within the Simulink environment. You can also create
custom components either by combining SimElectronics components as
Simulink subsystems, or by using the Simscape language.

Note SimElectronics follows the standard Simulink conventions where block
inputs and outputs are called ports. In SimElectronics, each port represents
a single electrical terminal.

1-6

A SimElectronics model can contain blocks from the standard SimElectronics
library, from the Simscape Foundation and Utilities libraries, or from a
custom library you create, using the Simscape language, based on the
Simscape Foundation electrical domain. A model can also include Simulink
blocks and blocks from other products, such as those described in “Required
and Related Products” on page 1-5.

For more information on modeling physical and electrical components, see
“Modeling Electronic Components” on page 2-2.

Opening SimElectronics Libraries

There are two ways to access SimElectronics blocks:

• “Using the Simulink Library Browser to Access the Block Libraries” on

page 1-7

• “Using the Command Prompt to Access the Block Libraries” on page 1-8

SimElectronics®Block Libraries

Using the Simulink Library Browser to Access the Block
Libraries

You can access the blocks through the Simulink Library Browser. To display
the Library Browser, click the Library Browser button in the toolbar of the
MATLAB desktop or Simulink model window:

Alternative
Then expand t

ly, you can type

simulink in the MATLAB Command Window.

he Simscape entry in the contents tree.

1-7

1 Gettin g Started

1-8

ore information on using the Library Browser, see “Library Browser” in

For m

imulink Graphical User Interface documentation.

the S

Using the Command Prompt to Access the Block Libraries

therwaytoaccesstheblocklibrariesistoopenthemindividuallyby

Ano

ng the command prompt:

usi

SimElectronics®Block Libraries

• To open just the SimElectronics library, type elec_lib in the MATLAB

Command Window.

• To open the Simscape library (to access the utility blocks, as well as

electrical sources, sensors, and other Foundation library blocks), type

simscape in the MATLAB Command Window.

• To open the main Simulink library (to access generic Simulink blocks), type

simulink in the MATLAB Command Window.

The SimElectronics library window is showninthefollowingfigure. Each
icon in the window represents a library. Some of these libraries contain
second-level sublibraries. Double-click an icon to open the corresponding
library.

1-9

1 Gettin g Started

Product Workflow

When you analyze an electronic or electromechanical system using
SimElectronics software, your workflow might include the following tasks:

1 Create a S imulink model that includes electronic or electromechanical

2 Define component data by specifying electrical or mechanical properties

3 Configure the solver options.

components.

In the majority of applications, it is most natural to model the physical
system using Simscape and SimElectronics blocks, and then develop the
controller or signal processing algorithm in Simulink.

For more information about modeling the physical system, see “Modeling
Electronic Components” on page 2-2.

as defined on a datasheet.

1-10

For more information about the settingsthatmostaffectthesolutionofa
physical system, see Chapter 3, “Simulating an Electronic System”.

4 Run the simulation.

For more information on how the product performs time-domain simulation
of an electronic system, see “Running a Time-Domain Simulation” on page
3-6.

Example — Modeling a DC Motor

In this section...

“Overview of DC Motor Example” on page 1-11

“Selecting Blocks to Represent System Components” on page 1-11

“Building the Model” on page 1-12

“Specifying Model Parameters” on page 1-15

“Configuring the Solver Parameters” on page 1-21

“Running the Simulation and Analyzing the Results” on page 1-22

Overview of DC Motor Example

In this example, you model a DC motor driven by a constant input signal that
approximates a pulse-width modulated signal and look at the current and
rotational motion at the motor output.

Example — Modeling a DC Motor

To see the completed model, open the Controlled DC Motor demo.

Selecting Blocks to Represent System Components

Select the blocks to represent the input signal, the DC motor, and the motor
output displays.

The follow ing table describes the role of the blocks that represent the system
components.

Block Description

Solver
Configuration

DC Voltage Source Generates a DC signal.

Controlled PWM
Voltage

H-Bridge

Defines solver settings that apply to all physical
modeling blocks.

Generates the signal that approximates a
pulse-width modulated motor input signal.

Drives the D C motor.

1-11

1 Gettin g Started

Block Description

Current Sensor Converts the electrical current that drives the motor

into a physical signal proportional to the current.

Ideal Rotational
Motion Sensor

DC Motor Converts input electrical signal into mechanical

PS-Simulink
Converter

Scope

Electrical
Reference

Mechanical
Rotational
Reference

Converts the rotational motion of the motor into a
physical signal proportional to the motion.

motion.

Converts the input physical signal to a Simulink
signal.

Displays motor current and rotational motion.

Provides the electrical ground.

Provides the mechanical ground.

Building the Model

Create a Simulink model, add blocks to the model, and connect the blocks.

1 Create a model.

If you are new to Simulink, see the “Creating a Simulink Model” example
for information on how to create a model.

1-12

2 Add to the model the blocks listed in the following table. The Library

column of the table specifies the hierarchical path to each block.

Block Library Path Quantity

Solver
Configuration

DC Voltage
Source

Simscape > Utilities

Simscape > Foundation
Library > Electrical > Electrical
Sources

1

1

Example — Modeling a DC Motor

Block Library Path Quantity

Controlled
PWM Voltage

H-Bridge

Simscape > SimElectronics > Actuators
& Drivers > Drivers

Simscape > SimElectronics > Actuators

1

1

& Drivers > Drivers

Current
Sensor

Simscape > Foundation
Library > Electrical > Electrical

1

Sensors

Ideal
Rotational
Motion

Simscape > Foundation
Library > Mechanical > Mechanical
Sensors

1

Sensor

DC Motor Simscape > SimElectronics > Actuators

1

& Drivers > Rotational Actuators

PS-Simulink

Simscape > Utilities

2

Converter

Scope Simulink > Commonly Used Blocks

Electrical
Reference

Simscape > Foundation
Library > Electrical > Electrical

2

1

Elements

Mechanical
Rotational
Reference

Simscape > Foundation
Library > Mechanical > Rotational
Elements

1

1-13

1 Gettin g Started

Note You can use the Simscape function ssc_new with a domain type of

electrical to create a Simscape model that contains the following blocks:

• Simulink-PS Converter

• PS-Simulink Converter

• Scope

• Solver Configuration

• Electrical Reference

This function also selects the Simulink

3 Connect the blocks as shown in the following figure.

ode15s solver.

1-14

Now you are ready to specify block parameters.

Example — Modeling a DC Motor

Specifying Model Parameters

Specify the following parameters to represent the behavior of the system
components:

• “Model Setup Parameters” on page 1-15

• “Motor Input Signal Parameters” on page 1-15

• “Motor Parameters” on page 1-18

• “Current Display Parameters” on page 1-19

• “Torque Display Parameters” on page 1-20

Model Setup Parameters

The following blocks specify model inform ation that is not specific to a
particular block:

• Solver Configuration

• Electrical Reference

• Mechanical Rotational Reference

As with Simscape models, you must include a Solver Configuration block
in each topologically distinct physical network. This example has a single
physical network, so use one Solver Configuration block with the default
parameter values.

You must include an Electrical Reference block in each SimElectronics
network. You must include a M echanical Rotational Reference block in each
network that includes electromechanical blocks. These blocks do not have
any parameters.

For more information about using reference blocks, see “Grounding Rules” in
theSimscapedocumentation.

Motor Input Signal Parameters

You generate the motor input signal using three blocks:

• The DC Voltage Source block generates a constant signal.

1-15

1 Gettin g Started

• The Controlled PWM Voltage block generates a pulse-width modulated

signal.

• The H-Bridge block drives the motor.

In this example, all input ports of the H-Bridge block except the PWM port
are connected to ground. As a result, the H-Bridge block behaves as follows:

• When the motor is on, the H-Bridge block connects the motor terminals

to the power supply.

• When the motor is off, the H-Bridge blo ck acts as a freewheeling diode to

maintain the motor current.

In this example, you simulate the motor with a constant current whose value
is the average value of the PWM signal. By using this type of signal, you set
up a fast simulation that estimates the motor behavior.

1 Set the DC Voltage Source block parameters as follows:

• Constant voltage =

2 Set the Controlled PWM Voltage block parameters as follows:

• PWM frequency =

2.5

4000

1-16

Example — Modeling a DC Motor

• Simulation mode = Averaged

This value tells the block to generate an output signal whose value
is the average value of the PWM signal. Simulating the motor with
an averaged signal estimates the motor behavior in the presence of a
PWM signal. To validate this approximation , use value of

PWM for this

parameter.

3 Set the H-Bridge block parameters as follows:

1-17

1 Gettin g Started

• Simulation mode = Averaged

This value tells the block to generate an output signal whose value
is the average value of the PWM signal. Simulating the motor with
an averaged signal estimates the motor behavior in the presence of a
PWM signal. To validate this approximation , use value of
parameter to validate this approximation.

PWM for this

1-18

r Parameters

Moto

Configure the block that models the motor.

Set the Motor block parameters as follows, leaving the unit settings at their
default values where applicable:

• Electrical Torque tab:

Example — Modeling a DC Motor

- Model parameterization = By rated power, rated speed &

no-load speed

- Armature inductance = 0.01

- No-load speed = 4000

- Rated speed (at rated load) = 2500

- Rated load (mechanical power) = 10

- Rated DC supply voltage = 12

• Mechanical tab:

- Rotor inertia = 2000

- Rotor damping = 1e-06

Current Display Parameters

Specify the parameters of the blocks that create the motor current display:

• Current Sensor block

• PS-Simulink Converter1 block

• Scope1 block

Of the three blocks, only the PS-Simulink Converter1 b lock has parameters.
Set the PS-Simulink Converter1 block Output signal unit parameter to
indicate that the block input signal has units of amperes.

A to

1-19

1 Gettin g Started

Torque Di

Specify the parameters of the blocks that create the motor torque display:

• Ideal Rotational Motion Sensor block

• PS-Simulink Converter block

• Scope block

Of the three blocks, only the PS-Simulink Converter block has parameters
you need to configure for this example. Set the PS-Simulink Converter block
Output signal unit parameter to
has units of revolutions per minute.

Note You must type this parameter value. It is not available in the
drop-down list.

splay Parameters

rpm to indicate that the block input signal

1-20

Example — Modeling a DC Motor

Configuring the Solver Parameters

Configure the solver parameters to use a continuous-time s olver because
SimElectronics m odels only run with a continuous-time solver. Increase the
maximum step size the solver can take so the simulation runs faster.

1 In the model window, select Simulation > Configuration Parameters

to open the Configuration Parameters dialog box.

2 Select

3 Enter 1 for the Max step size parameter value.

4 Click OK.

ode15s (Stiff/NDF) from the Solver list.

1-21

1 Gettin g Started

1-22

For more information about configuring solver parameters, see Chapter 3,
“Simulating an Electronic System”.

Running the Simulation and Analyzing the Results

In this part of the example, you run the sim ulation and plot the results.

In the model window, select Sim ulation > Start to run the simulation.

To view the motor current and torque in the Scope windows, double-click the
Scope blocks. You can do this before or after you run the simulation.

Example — Modeling a DC Motor

Note By default, the scope displays appear stacked on top of each other on
the screen, so you can only see one of them. Click and drag the windows to
reposition them.

The following plot shows the motor current.

Motor Current

1-23

1 Gettin g Started

The next plot shows the motor rpm.

1-24

Motor RPM

As expected, the motor runs at about 2000 rpm when the applied DC voltage
is 2.5 V.

Example — Modeling a Triangle Wave Generator

Example — Modeling a Triangle Wave Generator

In this section...

“Overview of Triangle Wave Generator Example” on page 1-25

“Selecting Blocks to Represent System Components” on page 1-25

“Building the Model” on page 1-27

“Specifying Model Parameters” on page 1-29

“Configuring the Solver Parameters” on page 1-37

“Running the Simulation and Analyzing the Results” on page 1-38

Overview of Triangle Wave Generator Example

In this example, you model a triangle wave generator using SimElectronics
electrical blocks and custom SimElectronics electrical blocks, and then look at
the voltage at the wave generator output.

You use a classic circuit configuration consisting of a n integrator and a
noninverting amplifier to generate the triangle wave, and use datasheets to
specify block parameters. For more information, see “Parameterizing Blocks”
on page 2-2.

To see the completed model, open the Triangle Wave Generator demo.

Selecting Blocks to Represent System Components

First, you select the blocks to represent the input signal, the triangle wave
generator, and the output signal display.

You model the triangle wave generator with a set of physical blocks bracketed
by a Simulink-PS Converter block and a PS-Simulink Converter block. The
wave generator consists of:

• Two operational amplifier blocks

• Resistors and a capacitor that work with the operational amplifiers to

create the integrator and noninverting amplifier

1-25

1 Gettin g Started

• Simulink-PS Converter and P S-Simulink Converter blocks. The function of

the Simulink-PS Converter and PS-Simulink Converter blocks is to bridge
the physical part of the model, which uses bidirectional physical signals,
and the rest of the model, which uses unidirectional S imulink signals.

You have a manufacturer datasheet for the two operational amplifiers you
want to model. Later in the example, you use the datasheet to parameterize
the SimElectronics Band-Limited Op-Amp block.

The follow ing table describes the role of the blocks that represent the system
components.

Block Description

Sine Wave Generates a sinusoidal signal that controls the

resistance of the Variable Resistor block.

Simulink-PS
Converter

Solver
Configuration

Electrical
Reference

Capacitor Works with an operational amplifier and resistor block

Resistor

Variable
Resistor

DC Voltage
Source

Voltage Sensor Converts the electrical voltage at the output of the

Converts the sinusoidal Simulink signal to a physical
signal.

Defines solver settings that apply to all physical
modeling blocks.

Provides the electrical ground.

to create the integrator.

Works with the operational amplifier and capacitor
blocks to create the integrator and noninverting
amplifier.

Supplies a time-varying resistance that adjusts
the gain of the integrator, which in turn varies the
frequency and amplitude of the generated triangular
wave.

Generates a DC reference signal for the operational
amplifier block of the noninverting amplif ier.

integrator into a physical signal proportional to the
current.

1-26

Block Description

Example — Modeling a Triangle Wave Generator

PS-Simulink
Converter

Scope

Band-Limited
Op-Amp

Diode

Converts the output physical signal to a Simulink
signal.

Displays the triangular output wave.

Works with the capacitor and resistor to create an
integrator and a noninverting amplifier.

Limit the output of the Band-Limited Op-Amp block,
to make the output waveform independent of supply
voltage.

Building the Model

Create a Simulink model, add blocks to the model, and connect the blocks.

1 Create a model.

If you are new to Simulink, see the “Creating a Simulink Model” example
for information on how to create a model.

2 Add to the model the blocks listed in the following table. The Library Path

column of the table specifies the hierarchical path to each block.

Block Library Path Quantity

Sine Wave Simulink > Sources

Simulink-PS

Simscape > Utilities

Converter

Solver

Simscape > Utilities

Configuration

Electrical
Reference

Simscape > Foundation
Library > Electrical > Electrical
Elements

Capacitor Simscape > Foundation

Library > Electrical > Electrical
Elements

1

1

1

1

1

1-27

1 Gettin g Started

Block Library Path Quantity

Resistor

Variable
Resistor

DC Voltage
Source

Voltage Sensor Simscape > Foundation

PS-Simulink
Converter

Scope Simulink > Commonly Used Blocks

Band-Limited
Op-Amp

Diode

Simscape > Foundation
Library > Electrical > Electrical
Elements

Simscape > Foundation
Library > Electrical > Electrical
Elements

Simscape > Foundation
Library > Electrical > Electrical
Sources

Library > Electrical > Electrical
Sensors

Simscape > Utilities

Simscape > SimElectronics > Integrated
Circuits

Simscape > SimElectronics > Semiconductor
Devices

3

1

1

1

1

1

2

2

1-28

Note You can use the Simscape function ssc_new with a domain type of

electrical to create a Simscape model that contains the following blocks:

• Simulink-PS Converter

• PS-Simulink Converter

• Scope

• Solver Configuration

• Electrical Reference

This function also selects the Simulink

ode15s solver.

Example — Modeling a Triangle Wave Generator

3 Connect the blocks as shown in the following figure.

Note Use Ctrl+R to rotate blocks so that their orientations match those

shown in the figure.

ou are ready to specify block parameters.

Now y

Spec

Spe
com

• “Mo

ifying Model Parameters

cify the following parameters to represent the behavior of the system

ponents:

del Setup Parameters” on page 1-30

1-29

1 Gettin g Started

• “Input Signal Parameters” on page 1-30

• “Triangle Wave Generator Parameters” on page 1-31

• “Signal Display Parameters” on page 1-37

Model Setup Parameters

The following blocks specify model inform ation that is not specific to a
particular block:

• Solver Configuration

• Electrical Reference

As with Simscape models, you must include a Solver Configuration block
in each topologically distinct physical network. This example has a single
physical network, so use one Solver Configuration block with the default
parameter values.

You must include an Electrical Reference block in each SimElectronics
network. This block does not have any parameters.

1-30

Input Signal Parameters

Generate the sinusoidal control signal using the Sine Wave block.

Set the Sine Wave block parameters as follows:

• Amplitude =

• Bias = 1e4

• Frequency (rad/sec) = p i/5e-4

0.5e4

Example — Modeling a Triangle Wave Generator

Triangle Wave Generator Parameters

Configure the blocks that model the physical system that generates the
triangle wave:

• Integrator — Band-Limited Op-Amp, Capacitor, and Resistor blocks

• Noninverting amplifier — Band-Limited Op-Amp1, Resistor2, and Variable

Resistor blocks

1-31

1 Gettin g Started

• Resistor1

• Diode and Diode1

• Simulink-PS Converter and PS-Simulink Converter blocks that b ridge the

physical part of the model and the Simulink part of the model.

1 Accept the default parameters for the Simulink-PS Converter block. These

parameters establish the units of the physical signal at the block output
such that they match the expected default units of the Variable Resistor
block input.

2 Set the two Band-Limited Op-Amp block parameters for the LM7301 device

with a +–20V power supply:

• The datatsheet gives the gain as 97dB, which is equivalent to

10^(97/20)=7.080e4. Set the Gain, A pa ra m eter to

7e4.

• The datatsheet gives input resistance as 39Mohms. Set Input

resistance, Rin to

39e6.

• Set Output resistance, Rout to

0 ohms. The datatsheet does not quote

a value for Rout, but the term is insignificant compared to the output
resistor that it drives.

• Set minimum and maximum output voltages to –20 and +20 volts,

respectively.

• The datatsheet gives the maximum slew rate as 1.25V/μs. Set the

Maximum slew rate, Vdot parameter to

1.25e6 V/s.

1-32

Example — Modeling a Triangle Wave Generator

3 Set the two Diode block parameters for a 4.3V zener diode. To model a

BZX384-B4V3, set block parameters as follows:

• On the Main tab, set Diode model to

Piecewise Linear Zener.This

selects a simplified zener diode modelthatismorethanadequatetotest
the correct operation of this circuit.

• Leave the Forward voltage as 0.6V — this is a typical value for most

diodes.

• The datatsheet gives the forward current as 250mA when the forward

voltage is 1V. So that the Diode block matches this, set the On
resistance to (1V – 0.6V)/250mA =

1.6 ohms.

• The datatsheet gives the reverse leakage curre nt as 3μA at a reverse

voltage of 1V. Therefore, set the Off conductance to 3μA/1V =

3e-6 S.

• Thedatatsheetgivesthereversevoltageas4.3V.OntheReverse

Breakdown tab, set the Reverse breakdown voltage Vz to

4.3 V.

1-33

1 Gettin g Started

• Set the Zener resistance Rz to a suitably small number. The

datatsheet quotes the zener voltage for a re verse current of 5mA. For
theDiodeblocktoberepresentativeoftherealdevice,thesimulated
reverse voltage should be close to 4.3V at 5mA. As Rz tends to zero, the
reverse breakdown voltage w ill tend to Vz regardless of current, as the
voltage-current gradient becomes infinite. However, for good numerical
properties, Rz must not be made too small. If, say, you allow a 0.01V
error o n the zener voltage at 5mA, then Rz will be 0.01V/5mA = 2 ohms.
Set the Zener resistance Rz parameter to this value.

1-34

Example — Modeling a Triangle Wave Generator

4 The Voltage Sensor block does not have any parameters.

5 Accept the default parameters for the Variable R esistor block. These

parameters establish the units of the physical signal at the block output
such that they match the expected default units of the Variable Resistor
block input.

6 Set the

• Capaci

• Initi

• Seri

Capacitor block parameters as follow s:

tance =

al voltage =

alue starts the oscillation in the feedback loop.

This v

es resistance =

2.5e-9

0.08

0

1-35

1 Gettin g Started

7 Set the DC Voltage Source block parameters as follows:

• Constant voltage =

8 Set the Resistor block parameters as follows:

• Resistance =

10000

0

1-36

Example — Modeling a Triangle Wave Generator

9 Set the Resi

• Resistance

10 Set the Resistor2 block parameters as follows:

• Resistance =

11 Accept the default parameters for the PS-Simulink Conve rte r block. These

stor1 block parameters as follows:

=

1000

10000

parameters establish the units of the physical signal at the block output
such that they match the expected default units of the Scope block input.

Signal D

isplay Parameters

Specify the parameters of the Scope block to display the triangular output
signal.

Double-click the Scope block and then double-click the Parameters button

to open the Scope parameters dialog box. On the Data history tab, clear

the Limit data points to last check box.

Configuring the Solver Parameters

Configure the solver parameters to use a continuous-time s olver because
SimElectronics models only run with a continuous-time solver. You also
change the simulation end time, tighten the relative tolerance for a more
accurate simulation, and remove the limit on the number of simulation data
points Simulink saves.

1-37

1 Gettin g Started

1 In the model window, select Simulation > Configuration Parameters

to open the Configuration Parameters dialog box.

2 In the Solver category in the Select tree on the left side of the dialog box:

• Enter

• Select

• Enter

• Enter

3 In the Data Import/Export category in the Select tree:

2000e-6 for the Stop time parameter value.

ode23t (Mod. stiff/Trapezoidal) from the Solver list.

4e-5 for the Max step size parameter value.

1e-6 for the Relative tolerance parameter value.

• Clear the Limit data points to last check box.

4 Click OK.

For more information about configuring solver parameters, see Chapter 3,
“Simulating an Electronic System”.

Running the Simulation and Analyzing the Results

Run the simulation and plot the results.

In the model window, select Sim ulation > Start to run the simulation.

ToviewthetrianglewaveintheScopewindow,double-clicktheScopeblock.
You can do this before or after you run the simulation.

1-38

Example — Modeling a Triangle Wave Generator

The following plot shows the voltage waveform. As the resistance of the
Variable Resistor block increases, the amplitude of the output waveform
increases and the frequency decreases.

Triangle Waveform Voltage

1-39

1 Gettin g Started

1-40

Modeling an Electronic
System

• “Modeling Electronic Components” on page 2-2

• “Working with Simulink Blocks” on page 2-22

2

2 M odeling an Electronic System

Modeling Electronic Components

In this section...

“Parameterizing Blocks” on page 2-2

“Additional Parameterization Workflows” on page 2-15

“Adding SimElectronics Blocks to a Model” on page 2-16

“Connecting Model Blocks” on page 2-17

“Selecting the Output Model for Logic Blocks” on page 2-18

Parameterizing Blocks

SimElectronics software is a system-level simulation tool, which provides
blocks with a commensurate level of fidelity. Block parame te rs are de signed,
where possible, to match the data found on manufacturer datasheets. For
example, the bipolar transistor blocks support parameterization in terms of
the small-signal quantities usually quoted on a datashe et, and the underlying
model is simpler than that typically used by specialist EDA simulation tools.
The smaller number of parameters and simpler underlying models can support
MATLAB system performance analysis better, and thereby support design
choices. Following system design, you can perform validation in hardware or
more detailed modeling and validation using an EDA simulation tool.

2-2

This section contains the following parameterization examples:

• “Example 1 – Parameterizing a Piecewise Linear Diode Model” on page 2-3

• “Example 2 – Parameterizing an Exponential Diode from a Datashee t”

on page 2-6

• “Example 3 – Parameterizing an Exponential Diode from a SPICE Netlist”

on page 2-10

• “Example 4 – Parameterizing an Op-Amp from a Datasheet” on page 2-13

Most of the time, datasheets should be a sufficient source of parameters
for SimElectronics blocks (see Examples 1, 2, and 4). Sometimes, there is
need for more information than is available on the datasheet, and data
can be augmented from a manufacturer SPICE netlist. For example,

Modeling Electronic Components

circuit performance m ay depend on one or tw o critical components, and
increased accuracy is needed either for parameter values or the unde r ly ing
model. SimElectronics libraries contain a SPICE-compatible sublibrary to
support this case, and this is illustrated by Example 3. If you ha ve many
components that need to be modeled to a high level of accuracy, then Simulink
cosimulation with a specialist circuit simulator may be a better option.

In mechatronic applications in particular, you may need to model input-output
behavior of integrated circuits, such as PWM waveform generators and
H-bridges. For these two examples, SimElectronics libraries contain
abstracted-behavior equivalent blocks that you can use. Where you need to
model other devices, possible options include creating your own abstracted
model using the Simscape language, or using Si mulink blocks. For an e xample
of using Simulink blocks, see the Modeling an Integrated Circuit demo.

When looking for a datasheet, make sure you have the originating
manufacturer datasheet because some resellers abbreviate them.

Example 1 – Parameterizing a Piecewise L inear Diode Model

The Triangle W ave Generator demo model, also described in “Example
— Modeling a Triangle Wave Generator” on page 1-25, contains two zener
diodes that regulate the maximum output voltage from an op-amp amplifier
circuit. Each of these diodes is implemented with the SimElectronics Diode
block, parameterized using the
model is sufficient to check correct operation of the circuit, and requires fewer
parameters than the

Exponential option of the Diode block. However, when

specifyingtheparameters,youneedtotakeintoaccountthebiascondition
that will be used in the circuit. This example explains how to do this.

Piecewise Linear Zener option. This simple

The Phillips Semiconducto r s datasheet for a BZX384–B4V3 gives the
following data:

Working voltage, VZ(V) at I

Ztest

=5

4.3

mA

Diode capacitance, Cd(pF)

Reverse current, IR(μA) at VR=1V

Forward voltage, VF(V) at IF=5mA

450

3

0.7

2-3

2 M odeling an Electronic System

In the datasheet, the tabulated values for VFare for higher forward currents.
This value of 0.7V at 5mA is extracted from the datasheet current-voltage
curve, and is chosen as it matches the zener current used when quoting the
working voltage of 4.3V.

To match the datasheet values, the demo sets the piecewise linear zener diode
block parameters a s follows:

• Forward voltage. Leave as default value of 0.6V. This is a typical

value for most diodes, and the exact value is not critical. However, it is
important that the value set is taken into account w hen calculating the
On resistance parameter.

• On resistance. This is set using the datasheet information that the

forward voltage is 0.7V when the current is 5mA. The voltage to be d r opped
by the On resistance parameter is 0.7V minus the Forward voltage
parameter, that is 0.1V. Hence the On resistance is 0.1V / 5mA = 20 Ω.

• Off conductance. This is set using the datasheet information on reverse

current. The reverse current is 3μA for a reverse voltage of 1V. Hence the

Off conductance should be set to 3μA/1V=3e-6S.

2-4

• Reverse breakdown voltage Vz. This parameter should be set to the

datasheet working voltage parameter, 4.3V.

• Zener resistance Rz. This needs to be set to a suitable small number.

Too small, and the voltage-current relationship becomes very steep, and
simulation convergence may not be as efficient. Too large, and the zener
voltagewillbeincorrect. FortheDiodeblocktoberepresentativeofthe
real device, the simulated reverse voltage should be close to 4.3V at 5mA
(the reverse bias current provided by the circuit). Allowing a 0.01 V error
on the zener voltage at 5mA, R

• Junction capacitance. This parameter is set to the datasheet diode

capacitance value, 450 pF.

will be 0.01V / 5mA = 2 Ω.

Z

Modeling Electronic Components

2-5

2 M odeling an Electronic System

2-6

Example 2 – Parameterizing an Exponential Diode from a
Datasheet

Example 1 uses a piecewise linear approximation to the diode’s exponential
current-voltage relationship. This results in more efficient simulation, but
requiressomethoughttogointothesettingofblockparametervalues.
Analternativeistouseamorecomplexmodelthatisvalidforawider
range of voltage and current values. This example uses the
parameterization option of the Diode block.

This model either requires two data points from the diode current-voltage
relationship, or values for the underlying equation coefficients, namely the
saturation current IS and the emission coefficient N. The BZX384-B4V3
datasheet only provides values for the former case. Some datasheets do not
give the necessary data for either case, and you must follow the processes
in Example 1 or Example 3 instead.

The two data points in the table below are from the BZX384-B4V3 datasheet
current-voltage curve:

Exponential

Modeling Electronic Components

Diode forward voltage,
V

F

Diode forward current,
I

F

0.7V 1V

5mA 250mA

Set the exponential diode block parameters as follows:

• Currents [I1 I2]. Set to [5 250] mA.

• Voltages [V1 V2]. Set to [0.7 1.0] V.

• Reverse breakdown voltage BV. Set to the datasheet working voltage

value, 4.3V.

• Ohmic resistance. Leave at its default value of 0.01 Ω.Thisisan

example of a parameter that cannot be determined from the datasheet.
However, setting its value to zero is not necessarily a good idea, because a
small value can help simulation convergence for some circuit topologies.
The default value has negligible effect at the working current of 5mA, the
additional voltage drop being 5e-3 times 0.01 = 5e-5V. Physically, this term
will not be zero because of the connection resistances.

• Zero-bias junction capacitance CJ0. Set to the datasheet diode

capacitance value, 450 pF.

A more complex capacitance model is also available for the Diode
component with the exponential equation option. However, the datasheet
does not provide the necessary data. Moreover, the operation of this circuit
is not sufficiently sensitive to voltage-dependent capacitance effects to
warrant the extra detail.

2-7

2 M odeling an Electronic System

2-8

Modeling Electronic Components

2-9

2 M odeling an Electronic System

Example 3 – Parameterizing an Exponential Diode from a
SPICE Netlist

If a datasheet does not provide all of the data required by the component
model, another source is a SPICE netlist for the component. Components
are defined by a particular type of SPICE netlist called a sub c ircu i t.
The subcircuit defines the coefficients for the defining equations. Most
component manufacturers make subcircuits available on their website s.
The format is ASCII, and you can directly read off the parameters. The
BZX384-B4V3 subcircuit can be obtained from P hilips Semiconductors
http://www.nxp.com/models/index.html.

The subcircuit data can be used to parameterize the SimElectronics Diode
block either in conjunction with the datasheet, or on its own. For example, the
Ohmic resistance is defined in the subcircuit as RS = 0.387, thus providing
the missing piece of information in Example 2.

An alternative workflow is to use the SimElectronics Additional
Components/SPICE-Compatible Components sublibrary. The SPICE Diode
block in this sublibrary can be directly parameterized from the subcircuit by
setting:

2-10

• Saturation current, IS to

• Ohmic resistance, RS to 0.387

• Emission coefficient, ND to 1.001

• Zero-bias junction capacitance, CJO to 2.715e-10

• Junction potential, VJ to 0.7721

• Grading coefficient, MG to 0.3557

• Capacitance coefficient, FC to 0.5

• Reverse breakdown current, IBV to 0.005

• Reverse breakdown voltage, BV to 4.3

Note that where there is a one-to-o ne correspondence between subcircuit
parameters and datasheet values, the numbers often differ. One reason
for this is that datasheet values are sometimes given for maximum values,
whereas subcircuit values are normally for nominal values. In this example,

1.033e-15

Modeling Electronic Components

the CJO value of 271.5 pF differs from the datasheet capacitance of 450 pF
at zero bias for this reason.

2-11

2 M odeling an Electronic System

2-12

Modeling Electronic Components

Example 4 – Parameterizing an Op-Amp from a Datasheet

The Triangle W ave Generator demo model, also described in “Example
— Modeling a Triangle Wave Generator” on page 1-25, contains two
op-amps, parameterized based on a datasheet for an LM7301. The National
Semiconductor datasheet gives the following data for this de vi ce:

Gain

Input resistance

Slew rate

Bandwidth

The Band-Limited Op-Amp and Finite-Gain Op-Amp blocks have been
designed to work from manufacturer datasheets. Implementing detailed

97dB = 7.1e4

39MΩ

1.25V/μs

4MHz

2-13

2 M odeling an Electronic System

op-amp device models, derived from manufacturer SPICE netlist models,
is not recommended, because it provides more accuracy than is typically
warranted and slows down simulations. The simple parameterization of the
SimElectronics op-amp blocks allows you to determine the sensitivity of
your circuit to abstracted performance values, such as maximum slew rate
and bandwidth. Because of this behavior-based parameterization, you can
determine which spe c if ication of op-amp is required for a given application.
A circuit designer can later match these behavioral parameters, determined
from the model, against specific op-amp devices.

Based on the datasheet values above, set the Band-Limited Op-Amp block
parameters as follows:

• Gain set to

• Input resistance, Rin set to 39e6Ω

• Output resistance, Rout se t to zero. The value is not defined, but will be

small compared to the 1000Ω load seen by the op-amp.

• Minimum output, Vmin set to the negative supply voltage,

model

• Maximum output, Vmax set to the positive supply voltage,

model

• Maximum slew rate, Vdot set to

• Bandwidth, f set to

Note that these parameters correspon d to the values for +-5 volt operation.
The datasheet also gives values for +-2.2V and +-30V operation. It is usually
better to pick values for a supply voltage below what your circuit uses, because
performance is worse at lower voltages; for example, the ga in is less, and the
input impedance is less. You can use the variation in op-amp parameters with
supply voltage to suggest a typical range of parameter values for which you
should check the operation of y our circuit.

7.1e4

-20Vinthis

20Vinthis

1.25/1e-6 V/s

4e6 Hz

2-14

Modeling Electronic Components

Additional Parameterization Workflows

There are several other ways to parameterize and validate your model:

• “Validation Using Data from SPICE Tool” on page 2-15

• “Parameter Tuning Against External Data” on page 2-16

• “Building an Equivalent Model of a SPICE Netlist” on page 2-16

Validation Using Data from SPICE Tool

One way to validate a parameterized SimElectronics component is to compare
its behavior to data from specialist circuit simulation tool that uses a
manufacturer SPICE netlist of the device. If doing this, it is important to
create a test harness for the component that exercises it over the relevant
operating points and frequencies

2-15

2 M odeling an Electronic System

Parameter Tuning Against External Data

If you have lab measurements of the device, or data from another simulation
environment, you can use this to tune the parameters of the equivalent
SimElectronics component. For an example of parameter tuning, see the
demo Solar Cell Parameter Extraction From Data.

Building an Equivalent Model of a SPICE Netlist

In Example 3, parameterization from a SPICE netlist is relatively
straightforward because the netlist defines a single device (the diode) plus
corresponding model card (the parameters). Conversely, a netlist for an
op-amp may have more than ten devices, plus supporting model cards. In
principle it is p oss ible to build your own equivalent model of a more complex
device by making use of the SPICE-Compatible Components sublibrary,
and connecting them together using the information in the netlist. Before
embarking on this you should ensure that the SPICE-Compatible Components
sublibrary has all of the component models that you need.

If the device models you wish to model are complex (hundreds of com ponents),
then cosimulation with an external circuit simulator may be a better approach.

2-16

Adding SimElectronics Blocks to a Model

You can include blocks from the SimElectronics library in a Simulink model.
For more information on the library and the SimElectronics blocks, see
“SimElectronics Block Libraries” on page 1-6.

This section contains th e following topics:

• “Required Blocks” on page 2-16

• “How to Add SimElectronics Blocks to a Model” on page 2-17

Required Blocks

Each topologically distinct physical network in a diagram requires exactly
one Solver Configuration block, found in the Simscape Utilities library. The
Solver Configuration block specifies global environment information for
simulation and provides parameters for the solver that your m odel needs
before you can begin simulation. For more information, see the Solver
Configuration block reference page.

Modeling Electronic Components

Each electrical network requires an Electrical Reference block. This
block establishes the electrical ground for the circuit. Networks with
electromechanical blocks also require a Mechanical Rotational Reference
block. For more information about using reference blocks, see “Grounding
Rules” in the Simscape documentation.

How to Add SimElectronics Blocks to a Model

To add Sim Electronics blocks to a Simulink model:

1 Type elec_lib attheMATLABprompttoopenthe SimElectronics library.

2 Navigate to the desired library or sublibrary.

3 Drag instances of SimElectronics blocks into the model window using the

mouse.

Note You can also access SimElectronics blocks and oth er Simulink blocks
from the Simulink Library Brow ser win dow. Type
prompt to open this window. Add blocks to the model by dragging them from
this window and dropping them into the model window.

simulink at the M A TLAB

Connecting Model Blocks

You follow the same procedure for connecting SimElectronics blocks as for
connecting Simulink blocks: click a port and drag the mouse to draw a line to
another port on a different block. For more information on connecting blocks,
see “Connecting Blocks in the Model Window” in the Sim ulink documentation.

You can only connect blocks that use the same type of signal. SimElectronics
blocks use the same physical signals that Simscape blocks use. These signals
are different than Simulink signals, and are represented graphically by a
different port style. Therefore, you can freely connect pairs of SimElectronics
blocks and other Simscape blocks.

However, you cannot directly connect SimElectronics blocks to Simulink
blocks. Instead, you must use the Simscape PS-Simulink Converter and
Simulink-PS Converter blocks to bridge them.

2-17

2 M odeling an Electronic System

The following topics in the Simscape documentation explain how physical
ports w ork and how to bridge physical blocks and Simulink blocks.

• “Connector Ports and Connection Lines”

• “Connecting Simscape Diagrams to Simulink Sources and Scopes”

Selecting the Output Model for Logic Blocks

The blocks in the Logic sublibrary of the Integrated Circuits library provide a
choice of two output models:

•

Linear — Models the gate output as a voltage source driving a series

resistor and capacitor connected to ground. This is suitable for logic
circuit operation under normal conditions and when the logic gate drives
other high-impedance CMOS gates. The block sets the value of the gate
output capacitor such that the resistor-capacitor time constant equals the
Propagation delay parameter value. The linear output model is shown
in the following illustration.

2-18

• Quadratic — Models the gate output in terms of a comple mentary

N-channel and P-channel MOSFET pair. This adds more fidelity, which
becomes relevant if drawing higher currents from the gate output, or if
exercising the gate under fault conditions. In addition, the gate input
demand is lagged to approximate the Propagation delay parameter
value. Default parameters are representative of the 74HC logic gate family.
The quadratic output model is shown in the next illustration.

Modeling Electronic Components

Use the Output current-voltage relationship parameter on the Outputs
tab of the block dialog box to specify the output model.

For most system models, MathWorks recommends selecting the linear
option because it supports faster simulation. If necessary, you can use the
more detailed output model to validate simulation res ults obtained from the
simpler model.

Quadratic Model Output and Parameters

If you select the quadratic model, use the following parameters to control
the block output:

• Supply voltage — Supply voltage value (Vcc) applied to the gate in your

circuit. The default value is

• Measurement voltage — The gate supply voltage for which mask data

output resistances and currents are defined. The default value is

• LogicHIGHoutputresistanceatzerocurrentandatI_OH—Arow

vector [ R_OH1 R_OH2 ] of two resistance values. The first value R_OH1 is
the gradient of the output voltage-current relationship when the gate is

5 V.

5 V.

2-19

2 M odeling an Electronic System

logic HIGH and there is no output current. The second value R_OH2 is the
gradient of the output voltage-current relationship when the gate is logic
HIGH and the output current is I_OH. The default value is

• Logic HIGH output current I_OH when shorted to ground —The

resulting current when the gat e is in the logic HIGH state, but the load
forcestheoutputvoltagetozero. Thedefaultvalueis

• Logic LOW output r es ist ance at zero current and at I_OL —Arow

vector [ R_OL1 R_OL2 ] of two resistance values. The first value R_OL1 is
the gradient of the output voltage-current relationship when the gate is
logic LOW and there is no output current. The second value R_OL2 is the
gradient of the output voltage-current relationship when the gate is logic
LOW and the output current is I_OL . The default value is

• Logic LOW output current I_OL when shorted to Vcc —Theresulting

current when the gate is in the logic LOW state, but the load forces the
outputvoltagetothesupplyvoltageVcc.Thedefaultvalueis

[ 25 250 ] Ω.

63 mA.

[30800]Ω.

-45 mA.

• Propagation delay — Time it takes for the output to swing from

LOW

to HIGH or HIGH to LOW after the input logic levels change. For quadratic
output, it is implemented by the lagged gate input demand. The default
value is

25 ns.

• Protection diode on resistance — The gradient of the voltage-curre nt

relationship for the protection diodes when forward biased. The default
value is

5 Ω.

• Protection diode forward voltage — The voltage above which the

protection diode is turned on. The default value is

0.6 V.

The following graphic illustrates the quadratic output model parameterization,
using the default parameter output characteristics for a +5V supply.

2-20

Modeling Electronic Components

2-21

2 M odeling an Electronic System

Working with Simulink Blocks

In this section...

“Modeling Instantaneous Events” on page 2-22

“Using Simulink Blocks to Model Physical Components” on page 2-22

Modeling Instantaneous Events

When working with SimElectronics software, your model may include
Simulink blocks that create instantaneous changes to the physical system
inputs through the Simulink-PS Converter block, such as those associated
with events or discrete sampling. When you build this type of model, make
sure the corresponding zero crossings are generated.

Many blocks in the Simulink library generate these zero crossings by
default. For example, the Pulse Gener ator block produces a discrete-time
output by default, and generates the corresponding zero crossings. To model
instantaneous events, select
Zero crossing control option under the model’s Solver Configuration
Parameters to generate zero crossings. For more information about zero
crossing control, see “Zero-crossing control” in the Simulink documentation.

Use local settings or Enabl e all for the

2-22

Using Simulink Blocks to Model Physical Components

To run a fast simulation that approximates the behavior of the physical
components in a system, you may want to use Simulink blocks to model of one
or more physical components.

The Modeling an Integrated Circuit demo uses Simulink to model a physical
component. The Simulink Logical Operator block implements the behavioral
model of the two-input NOR gate, as shown in the following figure.

Working with Simulink®Blocks

Using Sim
lag somew
first-o
to repre
is requi
Founda

ulink in this manner introduces algebraic loops, unless you place a
here between the physical signal inputs and outputs. In this case, a

rder lag is included in the Logic2Volts & Propagation Delay subsystem

sent the delay due to gate capacitances. For applications where no lag
red, use blocks from the Physical Signals sublibrary in the Simscape
tion Library to implement the d esired functionality.

2-23

2 M odeling an Electronic System

2-24

Simulating an Electronic
System

• “Selecting a Solver” on page 3-2

• “Specifying Simulation Accuracy /Speed Tradeoff” on page 3-3

• “Avoiding Simulation Issues” on page 3-5

• “Running a Time-Domain Simulation” on page 3-6

• “Running a Small-Signal Frequency-Domain Analysis” on page 3-7

3

3 Sim ulating an Electronic System

Selecting a So lver

In this section...

“Available Solvers” on page 3-2

“How to Select a Solver” on page 3-2

Available Solvers

SimElectronics software supports all of the continuous-time solvers that
Simscape supports. For more information, see “Working with Solvers” in
theSimscapedocumentation.

You can select any of the supported solvers for running a SimElectronics
simulation. The variable-step solvers,
for most applications because they run faster and copy better for systems with
a range of both fast and slow dynamics. The
solver that SPICE traditionally uses.

ode23t and ode15s, are recommended

ode23t solver is closest to the

3-2

To use Real-Time Workshop
from your model, you must use the
code generation, see “Generating Code” in the Simscape documentation.

®

software to generate standalone C or C++ code

ode14x solver. For more information about

How to Select a Solver

To specify a solver:

1 Open the Configuration Parameters dialog box from the Simulation

menu.

2 In the Solver pane (which opens by default), select the desired solve r from

the Solver list.

Specifying Simulation Accuracy/Speed Tradeoff

Specifying Simulation Accuracy/Speed Tradeoff

In this section...

“Parameters that Affect Accuracy and Speed” on page 3-3

“Determining Appropriate Accuracy/Speed Parameter Values” on page 3-3

Parameters that Affect Accuracy and Speed

To trade off accuracy a n d simulation time, adjust one or more of the followin g
parameters:

• Relative tolerance (in the Configuration Parameters dialog box)

• Absolute tolerance (in the Configuration Parameters dialog box)

• Max step size (in the Configuration Parameters dialog box)

• Constraint Residual Tolerance (in the Solver Configuration block

dialog box)

Determining Appropriate Accuracy/Speed Parameter
Values

In most cases , the default tolerance values produce accurate results without
sacrificing unnecessary simulation time. The parameter value that is most
likely to be inappropriate for your simulation is Max step size,becausethe
default value,
than on the amount by which the signals are changing during the simulation.
If you are concerned about the solver’s missing significant behavior, change
the parameter to prevent the solver from taking too large a step.

The Simulink documentation describes the following parameters in m ore
detail and provides tips on how to adjust them:

• “Relative tolerance”

• “Absolute tolerance”

• “Max Step Size”

auto, depends on the simulation start and stop times rather

3-3

3 Sim ulating an Electronic System

The Solver Configuration block reference page in the Simscape documentation
explains when to adjust the Constraint Residual Tolerance parameter
value.

3-4

Avoiding Simulation Issues

In this section...

“General Troubleshooting for Simscape Models” on page 3-5

“Troubleshooting for Simscape Models that Include SimElectronics Blocks”
on page 3-5

General Troubleshooting for Simscape Models

If you experience a simulation issue, first read “Troubleshooting Simulation
Errors” in the Simscape documentation to learn about general troubleshooting
techniques.

Note As mentioned in the “Product Overview” on page 1-2, SimElectronics
software does not have the ability to model large circuits with dozens of
analog components. If you encounter convergence issue s when trying to
simulate a model with more than a few tens of transistors, you may find
that the limitations of SimElectronics software prevent you from achieving
convergence w ith any set of simulation parameter values.

Avoiding Simulation Issues

Troubleshooting for Simscape Models that Include
SimElectronics Blocks

There are a few techniques you can apply to any SimElectronics model to
overcome simulation issues:

• Add parasitic capacitors and/or resistors (specifically, junction capacitance

and ohmic resistance) to the circuit to avoid numerical issues. The Astable
Oscillator demo uses these devices.

• Adjust the current and voltage sources so they start at zero and ramp up to

their final values rather than starting at nonzero values.

“Working with Simulink Blocks” on page 2-22 describes how to avoid
simulation errors in the presence o f specific SimElectronics model
configurations.

3-5

3 Sim ulating an Electronic System

Running a Time-Domain Simulation

When you run a time-domain simulation, SimElectronics software uses the
Simscape solver to analyze the physical system in th e Simulink environment.
For more information about how Simscape simulation works, see “How
Simscape Simulation Works” in the Simscape documentation.

3-6

Running a Small-Signal Frequency-Domain Analysis

Running a Small-Signal Frequency-Domain Analysis

In this section...

“Linearizing SimElectronics Models” on page 3-7

“Analyzing Small-Signal Behavior Using Bode Plots” on page 3-7

Linearizing SimElectronics Models

The Simulink commands linmod and dlinmod create continuous- or
discrete-time linear time-invariant (LTI) state-space models from Simulink
models. You can use these commands to generate an LTI state-space model
from a model containing Simscape components .

For more information about linearizing models that contain blocks from the
Simulink Physical Mode ling fa mily, se e “Linearizing at an Operating Point”.

After you linearize your model, you can perform small-signal analyses such as:

• Bode

• Step

• Impulse

• Nyquist

Note If you h ave Simulink®Control Design™ software installed, you can

use its Control and Estimation Tools Manager GUI to linearize models. For
more information about using this software for linearization, see “Linearizing
the Model”.

Analyzing Small-Signal Behavior Using Bode Plots

After you create an LTI state-space model from your SimElectronics model,
you can create a Bode plot for small-signal analysis using one of the follow i ng
approaches:

• “Using MATLAB for Bode Analysis” on page 3-8

3-7

3 Sim ulating an Electronic System

• “Using Control System Toolbox Softw are for Bode Analysis” on page 3-8

UsingMATLABforBodeAnalysis

You can write a MATLAB script to generate a bode plot of the frequency
response of the model from the LTI state-space model. The demo Small-Signal
Frequency-Domain Analysis uses a linear passive bandpass filter example
to show how to use MATLAB to create a Bode plot from an LTI model. The
demo shows how to use both the state-space and transfer-function forms of
the LTI model.

Using Control System Toolbox Software for Bode Analysis

You can use the built-in analysis and plotting capabilities of Control System
Toolbox™ to understand the behavior of a linearized model.

• The toolbox function

ss converts the state-space model returned by linmod

to a continuous-time state-space model.

• The toolbox function

linmod to a continuous-time transfer function model.

• The toolbox function

tf converts the transfer function model returned by

ltiview opens the LTI viewer for LTI system response

analysis.

The following example shows how to create a Bode plot of the
frequency-response of the model in the demo Small-Signal Frequency-Domain
Analysis.

At the MATLAB prompt:

1 Type the following to create a LTI state-space model of elec_ss_analysis:

[A B C D] = linmod('elec_ss_analysis',[],[],[1e- 5 0 1]);

2 Type the following to create a LTI transfer function model of

elec_ss_analysis:

[num den] = linmod('elec_ ss_analysis',[],[],[1e-5 0 1]);

3-8

Running a Small-Signal Frequency-Domain Analysis

3 Type the following to plot both the state-space and transfer function models

on a Bode plot:

ltiview('bode',ss(A,B,C,D),'b',tf(num,den),'r-.');

The toolbox creates the following plot:

The bandpass filter frequency response for the state-space and transfer
function representations are different far from the center frequency. These
differences arise from numerical noise introduced when calculating the
transfer function representation.

linmod implicitly derives a state-space

representation for a linearized model, and computes the transfer function
representation from this state-space model.

3-9

3 Sim ulating an Electronic System

Note If you have Simulink Control Design software installed, you can use

its Control and Estimation Tools Manager GUI to analyze models. This
software uses the Control System Toolbox LTI viewer to display and analyze
the dynamic behavior of a model.

3-10

Examples

Use this list to find examples in the documentation.

A

A Examples

Examples

“Example — Model
“Example — Modeling a Triangle Wave Generator” on page 1-25

ing a DC Motor” on page 1-11

A-2

Index

IndexA

accuracy

model p arameter values 3-3
model parameters that affect 3-3

adding physical and mathematical blocks 2-16

B

blocks

connecting 2-17
logic blocks output 2-18

C

connecting blocks

SimElectronics

Simulink 2-17

Simulink to SimElectronics

blocks 2-17

®

Physical blocks to

®

Physical

L

libraries

SimElectronics

®

1-6

M

model

adding SimElectronics
simulating a SimElectronics

models

®

components to 2-16

®

3-2

SimElectronics

®

blocks 1-6

O

opening

block libraries 1-6

S

SimElectronics

required and related products 1-5

SimElectronics

how to open 1-6

solver

selecting for SimElectronics

speed

model p arameter values 3-3
model parameters that affect 3-3

®

®

libraries 1-6

®

model 3-2

T

troubleshooting electrical models 3-5
troubleshooting s imulation issues 3-5

W

workflow

SimElectronics

workflow example

SimElectronics
SimElectronics

®

1-10

®

electrical 1-25

®

electromechanical 1-11

Index-1