Note: This simulation may not run properly as switch mode circuits are very difficult to model. I will try to find a solution. Make your model and push it up anyway, but don't spend too much time on it.

Simulate (in ISIS) a step down SMPS circuit using a 34063 regulator IC (the ISIS library does not contain an LM78S40 spice model) and push up your file. Plot the inductor current, and if possible the current in the diode and capacitor.