Physics Electronics PMDC Conceptual Practice
PMDC Verified Question 418 of 494
A \( \pi \)-filter (capacitor-input filter) used in DC power supplies consists of which component arrangement?
A
A single series resistor connected to a parallel inductor
B
Two series inductors surrounding a single shunt capacitor
C
Two series resistors surrounding a parallel diode clamp
D
An input shunt capacitor, a series inductor (or resistor), and an output shunt capacitor
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: An input shunt capacitor, a series inductor (or resistor), and an output shunt capacitor
Concept:

A \( \pi \)-filter (CLC filter) is named for its schematic resemblance to the Greek letter \( \pi \). It combines a shunt capacitor, a series smoothing choke, and a second shunt capacitor.

Formula:

$$\gamma \approx \frac{\sqrt{2}}{8\omega^3 C_1 C_2 L R_L} \quad (\text{Full-wave } \pi\text{-filter})$$

Solution:

  • The input capacitor \( C_1 \) charges to peak voltage \( V_m \), providing initial smoothing.


  • The series inductor \( L \) presents high impedance to remaining AC ripple.


  • The output capacitor \( C_2 \) bypasses any residual high-frequency ripple, providing a smooth DC output voltage with low ripple factor.


Why other options are incorrect:

  • Options A, B, & C: These configurations do not describe a standard CLC \( \pi \)-filter topology.

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