Switchmode Power Supply Simulation With Spice 3.pdf

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Introduction
Introdu ction
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Nonlinear Dependent Sources (B element)
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Switch With Hysteresis (S element)
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Transfer Function Analysis
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Sensitivity Analysis
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DC Analysis
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AC Analysis
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Transient Analysis
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Fourier Analysis
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Temperature Analysis
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Monte Carlo and Worst Case Analysis
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Optimizer Analysis
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SPICE Modeling Of Magnetic Components
SPICE Modeling Of Magnetic Components
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Introduction
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Ideal components in SPICE
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IsSpice Coupled Inductor Model
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Reluctance and physical models
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Magnetic Elements
Saturable Core Modeling
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SPICE 2 Compatible Core Model
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SPICE 3 Compatible Core Model
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Example 1 - MPP Core
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Ferrite Cores
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Example 2 - Ferrite Core
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Constructing a Transformer
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High Frequency Winding Effects
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EMI Filter Design
EMI Filter Design
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Basic Requirements
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Defining the Negative Resistance
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Example 1 - Input Resistance Analysis
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Defining the Harmonic Content
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Example 2 - .FOUR Analysis
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Example 3 - Using the Optimizer To Calculate Harmonics
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Example 4- EMI filter design
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Calculating the input impedance
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Calculating the harmonic content
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Calculating the required attenuation
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Calculating the component values
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Fourth Order Filters
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Buck Topology Converters
Buck Topology Converters
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Hysteretic Switching Regulator
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Ave rage (State Space) vs. Switching Level Transient Models
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Average Modeling Example
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SG1524A Buck Regulator
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Discontinuous Mode Simulation
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An Improved Buck Subcircuit
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Adding Slope Compensation
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Voltage Mode Control
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Improved SG1524A Buck Regulator
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Transient Model
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Flyback Converters
Flyback Converters
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A Flyback Subcircuit
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Dual Output Flyback Converterfly1.cir
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Audio Susceptibility
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Feedforward Improvements
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Flyback Transient Response
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Simulating Regulation
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Time Domain Model
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Adding Slope Compensation
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Voltage Mode Control
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Low Dropout Linear Regulator
Low Dropout Linear Regulator
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Headroom
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Transient Response
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Ripple Rejection
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Control Loop Stability
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DC-to-AC Conversions
DC-to-AC Conversions
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Using SPICE to Generate a Sine ROM
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State Machine Modeling
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Powering Nonlinear Loads
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Three Phase Sine Reference
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Improving Simulation Performance
Improving Simulation Performance
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Building Circuit Models
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Simplifying Your Models
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.OPTIONS
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State Machine Models
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Hardware Considerations
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Solving Convergence and Other Simulation Problems
Sol ving Convergence and Other Simulation Problems
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What is Convergence? (or in my case, Non-Convergence)
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General Discussion
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IsSpice - New Convergence Algorithms
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Non-Convergence Error Messages/Indications
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Convergence Solutions
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DC Convergence Solutions
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DC Sweep Convergence Solutions
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Transient Convergence Solutions
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Modeling Tips
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Repetitive or Switching Simulations
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Other Convergence Helpers
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References
References
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General
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Average/State Space Modeling and Simulation
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Magnetics Design And Modeling
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Acknowledgment
Acknowledgment
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About the author
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Other Contributors
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Introduction
The technolog y of computer mo deling and simulati on is growing at a r apid pace. As com puters become fast er and more capable, new software provides greater capability. This
improvement in technology is of great benefit to design engineers and to the companies that employ them. This book is intended to show you how to harness the capability of
computer modeling and the simulation of power circuits.
Why Simulate?
On more than one occasion, I have been asked (usually by my superiors) why there always seems to be a quest for newer, faster computers and software. Why are so many
precious budget dollars requested for conferences and training seminars? After giving this question a great deal of thought, I have four answers:
Simulation Saves Money - Design flaws which are not detected until the production cycle may delay schedules and significantly increase production costs. Si mulation is
an aid to the early detection of these errors. Monte Carlo simulation helps to insure maximum production yield.
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Simulation Saves Time - Circuits can be simulated on a computer much more quickly than they can be built and evaluated.
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Simulation Measures The Immeasurable - Computer simulation allows engineers to evaluate a circuit with the worst case values. It would be quite a challenge to build a
circuit which represents all worst case components, or to measure the effects of solar flares on circuit performance. Simulation allows these types of conditions to be
easily evaluated.
Simulation Promotes Safety - Simulation allows the evaluation of fault conditions which may be dangerous to human life. Airline pilots spend a considerable amount of
time simulating emergency conditions rather than practicing them.
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About The SPICE Syntax Used In This Book
This book assumes that you already have a working knowledge of SPICE. If this is not the case, it is suggested that you review the manuals that accompany your SPI CE program
before proceeding. The syntax used is generally SPICE 2 based, however, several key SPICE 3 extensions are utilized in the modeling process in order to enhance the simulation
efficiency (See the SPICE 3 and Other SPICE Extensions section).
This book is intended to assist you in usi ng SPICE during the design and analysis process. I strongly encourage you to run the example s imulations in order to get a better
understanding of the capability of the software and the modeling techniques. All of the example circuits in this book are designed to be simulated using Intusoft’s IsSpice; they are
not designed to run on any other version of SPICE software. However, with a few modifications (which are described in the next section), almost any SPICE software can be used
to run the simulations. In addition, the design and modeling techniques are applicable to many different types of simulators. The circuits, schematics, and SPICE netlists are
included on the enclosed floppy disk for your convenience.
I have selected Intusoft’s IsSpice for sever al reasons:
Intusoft's interactive IsSpice simul ator brings state-of-the-art technology to analog and mixed signal design software.
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It is the best SPICE simulator for power electronics and related applications. The libraries included with the simulator have the largest number of power semiconductor
models in the EDA industry, including IGBTs, SCRs, Triacs, Power MOSFETs, and Power BJTs. All of the models are in unencrypted ASCII text files, so they can be
easily edited.
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An inexpensive software modeling utility is available. This utility allows you to easily model your own devices from manufacturer’s data sheet parameters.
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All of the power devices use sophisticated subcircuit structures or AHDL code, thus providing very realistic behavior. IsSpice’s behavioral modeling capabilities are very
powerful and extensive. There is even an AHDL modeling capability which allows user-defined C code subroutines to be added.
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Intusoft is dedicated to the improvement of their products. They are continually enhancing their software and adding features which increase productivity.
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Intusoft maintains a knowledgeable technical support staff and works closely with engineers, in order to make their software as productive as possible.
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Intusoft is competitively priced.
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The arbitrary dependent sou rce (B eleme nt) allows an instantaneous transfer function to be written as a mathematical expression. The expressions, [ EXPR ], given for V and I may
be any function of node voltages, currents through any element, or any variety of traditional math functions in the system. The keywords TIME, FREQ, and TEMP may also be
Format: B name N+ N- [I= EXPR ] [V= EXPR ]
IsSpice Examples: B1 0 1 I = sqrt(cos(v(1)/(v(2,3))))
B4 outp outn V = exp(i(vdd)^2)
B1 1 0 V=V(2) * abs(I(V1)) + V(3)
B2 2 3 I=V(7) * Sin(Time)
B3 1 2 V=I(R1)
PSpice Equivalent G1 0 1 value={sqrt(cos(v(1)/(v(2,3))))}
Examples: E4 outp outn value={exp(pwr(I(vdd),2))}
E1 1 0 value={V(2) * abs(I(V1)) + V(3)}
G2 2 3 value={V(7) * Sin(Time)}
E3 1 2 value={I(R1)}
HSpice Equivalent G1 0 1 value=‘sqrt(cos(v(1)/(v(2,3))))’
Examples: E4 outp outn value=‘exp(pow(I(vdd),2))’
E1 1 0 value=‘V(2) * abs(I(V1))+V(3)*V(3)’
G2 2 3 value=‘V(7) * sin(TIME)
E3 1 2 value=‘I(R1)’
The Berkeley SPICE 3 arbitrary source syntax begins with the letter B. N+ and N- are the positive and negative nodes, respectively. The values of the V and I parameters
determine the voltages and currents across and through the device, respectively. There is no distinction between current control and voltage controlled sources for the B element.
If I= is given, then the output is a current source. If V= is given, the output is a voltage source. One and only one of these parameters must be given.
If-Then-Else Examples
The [ EXPR ] given in the Math Expressions section above can also contain a special If-Then-Else expression. This syntax is similar to the C programming language, and is unique
to Intusoft’s IsSpice. However, most SPICE vendors have an equivalent syntax for this capability, as shown below in the Pspice examples. The V= and I= parameters have the
same meaning here.
Format: B name N+ N- V = Evaluation ? Output_Value1 or Expression : Output_Value 2 or Expression
More Simply: B name N+ N- V = if Evaluation is true, then V(N+,N-)= Output_Value 1, else v(N+,N-)= Output_Value 2
Evaluation, Output_Value, and Expression may consist of any math expression discussed in the Math Expressions section, or Boolean operators. There is virtually no limit to the
length or complexity of the expressions that can be used. The Evaluation expression can use greater than ">" or less than "<" test. Equal is not allowed.
If-Then-Else Examples

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