A GUIDE TO FREE ELECTRONIC CIRCUIT DESIGN AND SIMULATION SOFTWAREPOWER SUPPLY CALCULATORS, CAD PROGRAMS, AND OTHER ENGINEERING DESIGN TOOLS 

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Circuit simulator is a computer program predicting the behavior of a real circuit. It replaces real components with idealized electrical models. Note that since the result can never take into account all physical processes in the parts and all PCB parasitics, the simulation will only reflect the model that is put into it. Therefore this technique can't entirely substitute breadboarding and prototyping. On the other hand, it allows measurements of internal currents, voltages and power that in many cases are virtually impossible to do any other way. 


Most generalpurpose programs are based on various versions of SPICE (Simulation Program with Integrated Circuits Emphasis). They can handle analog, logic and mixedsignal components.In SPICE, circuits are presented by socalled netlists. The program initially "guesses" all node voltages and calculates all the currents. These currents are then used to recalculate the voltages. These iterations continue until all the values stabilize. Failure to settle after a predetermined number of iteration creates socalled no convergence error. To get proper results in nonlinear circuits you need to learn the modeling and solve convergence problems. Designers who want to simulate their circuits without buying a full package have several options: 1) Working demos (usually limited to smallsize circuits with many functions disabled); 2) Open source programs (with little or no tech support); 3) Software provided by the component manufacturers (often good only for the designs that use these manufacturers' parts); 4) Online tools provided by enthusiasts. Among free programs the most popular is LT Spice provided by Linear Technologies. This is probably the only complete SPICE freeware, although most parts in its library are from Linear. Indeed, since it is free, why would they provide third party models? There are programs that let you not only simulate but actually design too. PowerEsim helps you choose a topology and calculate its main parts as well as magnetics. Ridley's POWER 456 provides component design with feedback loop and largesignal simulation, but his free demo is quite limited. Here you will find best free electronic circuit simulators, power supply calculators, and other electrical engineering design tools on the web. 


FREE ELECTRICAL CIRCUIT DESIGN SOFTWARE and EDA (DEMOs and GPL) 
VENDORS' POWER SUPPLY DESIGN AND CIRCUIT SIMULATION SOFTWARE 
POWER SUPPLY CALCULATORS AND SPREADSHEETs 

Generalpurpose circuit simulation Spice 3F.5 program download for Windows and Linux; PowerEsim free online power electronic circuit simulator and design tool (waveforms, loop, thermal, harmonics, mags); NonLinear electronic circuit simulation uses ideal components for fast analysis; Free online SPICE simulator with schematic capture and a graphical waveform viewer; POWER 456 demo PSIM  working demo of power electronic circuits simulator 
LT Spice download electrical circuit simulation for analog and switching ICs. ; Webench  online electrical design, calculation and thermal analysis of DCDC converters that use TI controllers; TINATI™  analog circuit analysis without any node or number of device limitations; Waveforms and losses analysis of multiphase DCDC converters 
Analysis of critical conduction mode active PFC boost regulator; CCM power factor correction PFC boost calculator and design formulas; Buck regulator calculation spreadsheet; Basic online calculation and waveforms of currents and voltages for main SMPS converters ELECTRICAL FORMULAS, THEOREMS, LAWS and DESIGN BASICS


