First let's turn on the switch and watch what happens to the output voltage versus time. For illustrative purposes we want the filter under-damped so we will decrease the load by increasing the load resistor from 0.25 ohms to 1.0 ohms.
As shown in Figure 3-6, the SPICE simulation waveform overshoots 12 V to 16 V and then has a damped ringing related to the filter resonant frequency (532 Hz) and final settles at 11.5 V, the input voltage. If the filter were unloaded, it would overshoot to 24 V (twice the input voltage) and would oscillate between zero and 24 V at a frequency of 532 Hz.
Figure 3-6: Buck Converter Turn-On and Turn-Off Versus Time
The turn-off waveform starts at 12 V and exponentially decays to zero volts without ringing. The cycle then starts again.
It is instructive to look at both of these events in the state-plane.
Do not use this information for design without independent verification of the information.
