If you cannot find a reliable library, you can build a subcircuit model using Proteus' built-in SPICE components.
Copy the extracted .LIB and .IDX files and paste them into the LIBRARY folder. lm2596 library for proteus
Use external SPICE (e.g., LTspice) for detailed switching/transient verification If you cannot find a reliable library, you
Which of the LM2596 are you simulating? (Fixed 5V, Fixed 12V, or Adjustable?) fire up Proteus
Once you have downloaded the library files (usually a .rar or .zip ), follow this exact procedure for or newer. (For Proteus 7 or older, the paths are similar but inside ARES and ISIS folders).
Now go ahead, fire up Proteus, place that LM2596, and watch your 12V smoothly step down to 5V—all on your computer screen.