Filter that provides the smoothing effect over the repetitive charging & discharging phases of capacitor

Which filter provides the smoothing effect over the repetitive charging & discharging phases of capacitor generated by repetitive ON-OFF action of the transistor in an inverting type of switching regulator?

Options:

a. LC filter
b. RC filter
c. R-L-C filter
d. C-L-C filter

Correct Answer: a. LC filter

Explanation

Inverting type of switching regulator generally provides an output voltage which is absolutely opposite in polarity to that of the input voltage.

By turning On the transistor with positive pulse, the inductor voltage jumps to the difference between input voltage and collector to emitter voltage in saturation region.

Due to this, there is a tremendous expansion in the magnetic field of an inductor.

The diode operates in reverse-biased condition by decreasing the value of load voltage from its inceptional maximum value when the transistor operates in ON mode.

Conversely, by turning OFF the transistor, magnetic field ruptures by reversal of inductor's polarity.

Thus, the diode then starts operating in forward biased mode & charges the capacitor leading to the generation of negative output voltage.

Hence, it is highly feasible for L-C filter to smoothen the consequences of repetitive charging & discharging caused by frequent ON-OFF action of transistor.