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Multiphase (interleaved) chopper operation: do all chopper legs switch simultaneously, or are they phase-shifted?

Difficulty: Easy

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
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