DC–DC chopper quadrants (Class A vs. Class B) In power electronics, identify the operating quadrants of Class A and Class B choppers on the voltage–current (V–I) plane. Clarify which quadrant each class occupies and how the load power flow direction distinguishes them.

Introduction / Context:
Choppers (DC–DC converters) are categorized by the quadrant of operation on the voltage–current (V–I) plane. This question tests recognition of the quadrants for Class A (step-down) and Class B (regenerative) choppers and the associated power flow direction.

Given Data / Assumptions:

• Idealized converters and passive loads.
• Voltage polarity defined positive from source to load; current positive into load.
• Steady switching within continuous conduction where applicable.

Concept / Approach:
Quadrants are defined by the signs of voltage and current: Q1 (+V, +I), Q2 (+V, −I), Q3 (−V, −I), Q4 (−V, +I). Class A delivers power from source to load (V > 0, I > 0). Class B performs regenerative braking/charging (V > 0, I < 0), returning energy from the load back to the source.

Step-by-Step Solution:
Identify Class A topology → conventional step-down with freewheel path, average V_out positive, load current positive.Map to quadrant → (+V, +I) → first quadrant.Identify Class B operation → source sees positive terminal while load forces current back to source during switching intervals.Map to quadrant → (+V, −I) → second quadrant.

Verification / Alternative check:
Energy flow: Class A has P = VI > 0 (to load). Class B has P = VI < 0 (from load to source). Signs match Q1 and Q2 respectively.

Why Other Options Are Wrong:
Operate in first quadrant / second quadrant (alone): Each describes only one class, not both.
Either quadrant: Too vague; classes have specific quadrants.
Class A in Q2 and Class B in Q1: Reverses the correct mapping.

Common Pitfalls:
Confusing Class B (regenerative) with Class C or D multi-quadrant arrangements, and mixing sign conventions of current direction.

Final Answer:
class A chopper operates in first quadrant while class B operates in second quadrant