What does an inductor do in a buck regulator?

 

Output inductor in buck regulator is critical to the regulator operation. When the switch (MOSFET) is in ON condition, the inductor charges and when the (MOSFET) is in OFF condition, the inductor provides the required current to the load to maintain the constant current to the load. During this operation, the inductor current has a ripple, as shown in the below waveform and the peak-to-peak value of the ripple depends on the inductor value. Inductor must be selected such that the ripple current is less than 20% to 30% of the rated current of the regulator.