Concept:A choke-input (L-section) filter maintains continuous inductor current above a critical inductance threshold, keeping the average DC voltage relatively constant despite load current changes.
Formula:$$V_{\text{dc}} = \frac{2V_m}{\pi} - I_{\text{dc}} R_{\text{choke}} \approx \frac{2V_m}{\pi} = \text{constant} \quad (\text{for } L > L_c)$$
Solution:- Unlike capacitor-input filters (where output voltage drops with load current), an L-section filter maintains a steady output voltage of \( V_{\text{dc}} \approx \frac{2V_m}{\pi} \).
- As long as inductor current remains continuous (\( L > L_c \)), output voltage changes only by the small ohmic drop across the inductor winding.
- This provides good voltage regulation for variable-load industrial supplies.
Why other options are incorrect:- Option A: Capacitor filters experience larger voltage drops as load current increases.
- Option B: Unfiltered rectifiers deliver pulsating DC with no regulation.
- Option D: A series resistor increases voltage drop and degrades voltage regulation.
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