Multiphase (interleaved) chopper operation: do all chopper legs switch simultaneously, or are they phase-shifted?
Electronics and Communication Engineering
Power Electronics
Difficulty: Easy
Choose an option
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AFalse
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BTrue
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CTrue only at 50% duty cycle
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DTrue for current-mode control only
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ETrue when L is very large
Answer
Correct Answer: False
Explanation
Introduction / Context:Multiphase (interleaved) DC–DC choppers are used to reduce input/output ripple, spread thermal stress, and increase dynamic performance. The key mechanism is phase shifting between legs, not simultaneous switching.
Given Data / Assumptions:
- Two or more identical chopper legs paralleled or interleaved.
- Common input and often common output filter.
- Goal: ripple cancellation and improved transient response.
Concept / Approach:With N phases, each leg is time-shifted by 360°/N in switching period. The ripple currents from each leg partially cancel at the input/output, lowering net ripple and allowing smaller filter components. If all legs switched together, ripple would add rather than cancel, defeating the purpose of a multiphase topology.
Step-by-Step Solution:
For N phases, set phase shift φ = 360°/N.Operate each leg with same duty D but offset by φ.Result: reduced ripple amplitude, higher effective ripple frequency (N times), better component utilization.Verification / Alternative check:
Ripple cancellation can be shown by summing triangular inductor current waveforms with appropriate phase offsets.Why Other Options Are Wrong:
'True': implies simultaneous switching, which increases ripple.Conditional statements (50% duty, current-mode, large L) do not change the fundamental interleaving goal.Common Pitfalls:
Believing that identical legs must switch together; overlooking interleaving as the core technique.Final Answer:
False