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LTspice/SwitcherCAD III, free simulation software

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LTspice/SwitcherCAD III explanation

The IC supplier Linear technology provides his own circuit simulation package called LTspice/SwitcherCAD III
Although the main intention is to ease the design process of Linear's customers, the software is freely available to all and it is a general purpose analog simulator.

My addition: Pulse Width Modulation source

This is a controlled voltage source which produces the Pulse Width Modulated version of any signal.

A screenshot, click to enlarge
screenshot LTspice PWM source

The voltage source is a so called arbitrary behavioral voltage source which is set up with a special mathematical expression.

Note that the Control library also contains two convenient PWM modulator building blocks. One of them has complementary outputs and a deadtime parameter.

See the download section

My addition: Control library for use with LTSpice/SwitcherCadIII

This is an addition to the circuit simulation package LTSpice/SwitcherCadIII, which gives convenient access to a set of blocks such as PID regulators, 1st order phase lag system, multiplier, PWM modulators, etc.

Some examples with screenshots and the LTspice schematic files

Click the images for large view, for each example the schematic file is linked.
You need the control library and symbol files to use these examples, see the download section.
Line up: various building blocks
Schematic file for this example
screenshot control library for LTspice
Example: a heater system
Schematic file for this example
screenshot control library for LTspice
Example: a PLL system
Schematic file for this example
screenshot control library for LTspice
Example: a DC DC converter
Schematic file for this example
screenshot control library for LTspice
Example: test of the trimmer
Schematic file for this example
screenshot control library for LTspice
Spielerei: a digital to analog converter
Schematic file for this example
screenshot control library for LTspice
Block to measure open and closed loop gain according
a proposal of Helmut Sennewald from
Schematic file for this example
http://tech.groups.yahoo.com/group/LTspice/
screenshot control library for LTspice
Test of block pwm2 which has complementary outputs,
a separate ground for the 'high side driver' and
a dead time parameter
Schematic file for this example
screenshot control library for LTspice
A quadrature oscillator with 2 integrator blocks and a inverting gain block (gain=-1).
The adder and unit step source only serve the start the oscillator.
Schematic file for this example
screenshot control library for LTspice
A relaxation oscillator with a comparator block.
The constant source is only a bias setting.
Schematic file for this example
screenshot control library for LTspice
Test of block pwm2 with a full H bridge.
Driving a inductive load. pwm2 has a dead time parameter.
Schematic file for this example
screenshot control library for LTspice
Test of block pwm2 with a step down converter.

Schematic file for this example
screenshot control library for LTspice
A comb filter using the transport delay block.
Schematic file for this example
screenshot control library for LTspice

Features

How to use the control library:

To use this the library (text file) control.lib must be placed in the directory:
.\LTC\SwCADIII\lib\sub
The symbol files contained in control.zip must be placed in the directory:
.\LTC\SwCADIII\lib\sym\control
(best in the new to be added directory control, so these new blocks do not mix up with the regular components).
Then the symbols are available to be selected amongst the regular components.

dialog box selecting a block

It is best to turn 'Skip initial operating point solution' option ON when doing transient simulation.
Find these files in the download section


My addition: Cosmetic symbols for use with LTSpice/SwitcherCadIII

These symbols can be used for illustrative schematics, they do not have models linked to them yet. However they can be used for simulations if a suitable model is provided.

screenshot cosmetic symbols

See the download section


Silicon Controlled Rectifier SCR

Using a generic model taken from:
http://pages.suddenlink.net/wa5bdu/ltguide.pdf
These examples of controlled half wave rectification can be made, the SCR model file is included in the schematic. The pin order had to be changed to match the SCR symbol that comes with LTSpice.

Schematic file for this example
screenshot SCR example
Schematic file for this example
screenshot SCR example<

Download files

First of all the simulator LTspice itself is provided by Linear Technology at http://www.linear.com/software/.

All following content is free to use and to modify, but observe the disclaimer





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