A GUIDE TO FREE ELECTRONIC CIRCUIT DESIGN AND SIMULATION SOFTWARE
POWER SUPPLY CALCULATORS, CAD PROGRAMS, AND OTHER ENGINEERING DESIGN TOOLS
Circuit simulator is a computer program predicting the behavior of a real circuit. It replaces real components with some 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 as a matter of course, 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 on a bench. There is a wide variety of available design tools, both general and vendor specific. If you are looking for a simulator or a design software, this quick review may save you hours of research.
Most general-purpose simulation programs are based on various versions of SPICE (Simulation Program with Integrated Circuits Emphasis). They can handle analog, logic and mixed-signal components. In SPICE, circuits are presented by so-called netlists. The program initially "guesses" all node voltages and calculates all the currents. These currents are then used to recalculate the voltages. Such iterations continue until all the values stabilize. You can specify initial conditions of some parts (like voltages of capacitors and currents of inductors) to help the analysis. Failure to settle after a pre-determined number of iteration creates so-called no convergence error. Therefore, to get proper results in non-linear circuits you would need to learn the modeling and solve convergence problems.
Large companies usually buy commercial software, such as PSpice®. It is integrated with OrCad and includes schematic capture, extensive model libraries from various vendors, and waveform display and analysis functions. A schematic capture allows you to draw the circuit diagrams with actual part numbers and automatically translate them into netlists. Unfortunately, commercial design and analysis packages are relatively expensive for hobbyists.
If you want to simulate their circuits without buying a full package, you have several options: 1) Working demos (usually limited to small-size circuits with many functions disabled); 2) Open source programs (with little or no tech support); 3) Software provided by the component manufacturers (often useful mainly for the designs that use these manufacturers' parts); 4) Online tools provided by enthusiasts.
Among free programs the most popular are MPLAB® Mindi™ and LTspice®. The former is based on SIMetrix/SIMPLIS with proprietary Microchip models in addition to many generic parts. The latter was developed by Linear Technologies and was probably the first complete SPICE freeware, although PWM controllers and most other parts in its library were only from Linear itself. Well, of course, since it is free, why would they provide third party models? Now, when Analog Devices bought LT, their library may also include macro-models of AD's regulators and amplifiers.
Besides simulators, there are also programs that let you not only analyze but to some degree actually design the circuits too: you will input a specification and the program automatically generates solutions. Online MPLAB® Analog Designer will generate schematics and parts lists of DC-DC converters (including PoE) based on Microchip controllers. It will then offer you to download the resulting MPLAB® Mindi™ schematic for off-line simulation. PowerEsim helps you choose a topology and calculate its main power train parts as well as magnetics. And it's vendor-independent and completely free. RidleyWorks® (formerly POWER 4-5-6) provides step by step power train component design with emphasis on the feedback loop, large-signal simulation and magnetics design. Its full version covers several dozens of main topologies (which you still need to choose). WEBENCH® is one of few free online tools that can generate entire schematic with BOM, but it is limited to low-power DC-DC converters with TI's controllers. PI Expert Online can generate an isolated off-line power supply around Power Integrations' ICs with a complete transformer design.
Here you will find the lists of the best (in my view) free electronic circuit simulators, power supply calculators, and other electrical engineering design tools available on the web.
Most general-purpose simulation programs are based on various versions of SPICE (Simulation Program with Integrated Circuits Emphasis). They can handle analog, logic and mixed-signal components. In SPICE, circuits are presented by so-called netlists. The program initially "guesses" all node voltages and calculates all the currents. These currents are then used to recalculate the voltages. Such iterations continue until all the values stabilize. You can specify initial conditions of some parts (like voltages of capacitors and currents of inductors) to help the analysis. Failure to settle after a pre-determined number of iteration creates so-called no convergence error. Therefore, to get proper results in non-linear circuits you would need to learn the modeling and solve convergence problems.
Large companies usually buy commercial software, such as PSpice®. It is integrated with OrCad and includes schematic capture, extensive model libraries from various vendors, and waveform display and analysis functions. A schematic capture allows you to draw the circuit diagrams with actual part numbers and automatically translate them into netlists. Unfortunately, commercial design and analysis packages are relatively expensive for hobbyists.
If you want to simulate their circuits without buying a full package, you have several options: 1) Working demos (usually limited to small-size circuits with many functions disabled); 2) Open source programs (with little or no tech support); 3) Software provided by the component manufacturers (often useful mainly for the designs that use these manufacturers' parts); 4) Online tools provided by enthusiasts.
Among free programs the most popular are MPLAB® Mindi™ and LTspice®. The former is based on SIMetrix/SIMPLIS with proprietary Microchip models in addition to many generic parts. The latter was developed by Linear Technologies and was probably the first complete SPICE freeware, although PWM controllers and most other parts in its library were only from Linear itself. Well, of course, since it is free, why would they provide third party models? Now, when Analog Devices bought LT, their library may also include macro-models of AD's regulators and amplifiers.
Besides simulators, there are also programs that let you not only analyze but to some degree actually design the circuits too: you will input a specification and the program automatically generates solutions. Online MPLAB® Analog Designer will generate schematics and parts lists of DC-DC converters (including PoE) based on Microchip controllers. It will then offer you to download the resulting MPLAB® Mindi™ schematic for off-line simulation. PowerEsim helps you choose a topology and calculate its main power train parts as well as magnetics. And it's vendor-independent and completely free. RidleyWorks® (formerly POWER 4-5-6) provides step by step power train component design with emphasis on the feedback loop, large-signal simulation and magnetics design. Its full version covers several dozens of main topologies (which you still need to choose). WEBENCH® is one of few free online tools that can generate entire schematic with BOM, but it is limited to low-power DC-DC converters with TI's controllers. PI Expert Online can generate an isolated off-line power supply around Power Integrations' ICs with a complete transformer design.
Here you will find the lists of the best (in my view) free electronic circuit simulators, power supply calculators, and other electrical engineering design tools available on the web.
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| FREE ELECTRICAL CIRCUIT AND SMPS SIMULATION SOFTWARE |
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FREE POWER SUPPLY DESIGN SOFTWARE |
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POWER SUPPLY CALCULATORS AND SPREADSHEETs |
MPLAB® Mindi™ analog simulator- free SIMetrix/SIMPLIS-based tool for Microchip's analog and power ICs (implements piecewise linear modelling); LTSpice download- electrical circuit simulation for analog and switching circuits; TINA-TI™ - analog circuit analysis without node or number of devices limitations; Non-Linear electronic circuit simulation- uses ideal components for fast analysis. Free demo with 20 parts or 1 year for students; PartSim- free online SPICE simulator with schematic capture and a graphical waveform viewer; PSIM - working demo that includes both ideal system-level power electronic devices and switching models |
MPLAB® Analog Designer - online tool for design and simulation of DC-DC converters (including PoE circuits) with Microchip's controllers; PowerEsim - free online power electronic circuit simulator and design tool (waveforms, loop, thermal, harmonics, mags); Webench - online schematic design, calculation, thermal analysis with PCB files of AC-DC and DC-DC converters with TI PWM controllers; PI Expert Online - generates off-line AC-DC conversion design based on your specifications. Includes schematic, BOM, board layout, magnetics. |
Power over Ethernet (PoE) calculator - Android app; Analysis of critical conduction mode active PFC boost regulator; CCM power factor correction PFC boost calculator and design formulas; Buck regulator calculation spreadsheet; A collection of Simplis simulation files of main topologies by Basso. LTspice models are there too. ELECTRICAL FORMULAS, THEOREMS, LAWS and DESIGN BASICS
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