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SarkariResultOutBMS · 2024

Previous Year Question

An ideal boost converter provides an average output voltage of 30 V to a load resistance of 50Ω from a 12 V dc source. For a peak-to-peak ripple less than one percent in capacitor voltage at switching frequency of 25 kHz, the minimum value of capacitance is
  1. 48 μF
  2. 24 μF
  3. 96 μF
  4. 12 μF

Correct answer: A

Explanation

For an ideal boost converter, D=1−Vin/Vo=1−12/30=0.6. During the switch ON interval the capacitor supplies the load, so approximately ΔVo/Vo=D/(R C fs). Imposing a peak-to-peak ripple below 1% gives the minimum capacitance corresponding to option A.

Formula

D=1−Vin/Vo; ΔVo/Vo≈D/(RCfs)

Step-by-step solution

Output Capacitor Ripple explanatory diagram

Correct Answer

A — 48 μF

Concept and Reasoning

For an ideal boost converter, D=1−Vin/Vo=1−12/30=0.6. During the switch ON interval the capacitor supplies the load, so approximately ΔVo/Vo=D/(R C fs). Imposing a peak-to-peak ripple below 1% gives the minimum capacitance corresponding to option A.

Calculation / Key Relation

D=1−Vin/Vo

ΔVo/Vo≈D/(RCfs)

Exam Takeaway

Boost ripple sizing: capacitor supports the load during switch ON time.

Common Mistake

Use the stated peak-to-peak ripple limit consistently; do not treat it as peak ripple.

Common mistake

Use the stated peak-to-peak ripple limit consistently; do not treat it as peak ripple.

Exam tip

Boost ripple sizing: capacitor supports the load during switch ON time.

Quick method

Boost ripple sizing: capacitor supports the load during switch ON time.