based on experience from you guys which is a good fair non-expensive circuit simulator software. For example where i can perform such task as DC-DC conversions and other small experiments

 

DC-DC converter simulations require some extra consideration. The best DC-DC sims available are Ridleys power 4-5-6 software that is inexpensive but not free.

In the free realm LTSPICE is the best out there as it is designed with switching events in mind and works very well with their controller parts.

Outside of DC-DC switching there is a myriad of analog simulation software ranging from free cripple-ware to top end multi 10k USD.

here is what I use:

Analog simulation/general = Topspice = $500 or LTspice (free)
Analog simulation DC-DC switching = LTSPICE (free)
Digital logic simulation = Topspice
Digital VHDL simulation (fpga's) = ISE toolset(modelsim), webpack version is free

These are my everyday tools for simulating analog & digital.

I have evaluated lots of these tools over the years and I have settled on this set for most bang/buck & least bugs with most ease of use.

 

SwitcherCAD III is totally free, and is optimized for switching regulator simulations.
EDIT:
Optikon posted while I was composing.
LTspice is SwitcherCAD III.

__________________
Ron

 

a minor quibble, ltspice/switchercad is really a general purpose spice package. they have neatly packaged many of (but not all as I found out) the LT products for easy use but I've used it quite nicely for all sorts of non-switch mode simulations.

they do have a very nice way to design smps circuits with their parts - "switch selector guide" and it will walk you through creating a power supply design that you can then play with. You just define input V, output V and output I and it does all the work.

 

You can also add non-Linear Tech parts to the libraries, and you can create new symbols for parts and subcircuits.

__________________
Ron