The inductor resists sudden current changes; the diode provides a freewheeling path. Current is smoothed, but output voltage ripple remains large.
This time we skip the capacitor and use an inductor (in series between switch and load), plus a diode.
Fundamental property of inductors: current through them cannot change instantaneously (V = L × dI/dt). It limits the rate of current change, shaping square-wave current into ramps (triangular wave).
Switch ON: the source energizes the inductor through the switch; inductor current ramps up linearly. Energy is partly delivered to the load, partly stored in the inductor's magnetic field.
Switch OFF: inductor current cannot stop suddenly (inductor property) — it continues flowing through the diode to the load. This is 'freewheeling'. The inductor releases stored energy; current ramps down linearly.
The diode is critical: it provides a path for inductor current when the switch is off. Without it, the inductor current has nowhere to go, generating extremely high reverse voltage that could destroy the switch.
Note: although current is shaped into a triangular wave (smoother than a square wave), the output voltage Vout = I × R still has a triangular shape. Ripple remains significant.
L=1mH, diode freewheeling. Current is smoothed but output voltage ripple remains large.
After reading this section, run the simulation and observe the waveforms. To explore further, open the example in a standalone page.