Power supply functional blocks — output identification: In a typical block diagram of a linear power supply, which block produces a pulsating DC output (before smoothing)?

Introduction / Context:
Understanding the sequence of conversion in power supplies helps diagnose faults and design robust systems. The rectifier stage is responsible for converting AC into a unidirectional, pulsating DC waveform that is later smoothed by filters and stabilized by regulators.

Given Data / Assumptions:

• Standard stages: transformer → rectifier → filter → regulator.
• AC source provides sinusoidal input to the transformer or directly to the rectifier.
• Ideal behavior assumed for conceptual clarity.

Concept / Approach:

The rectifier, using diodes, passes current only during certain portions of each AC cycle. As a result, its output is unidirectional but time-varying—a pulsating DC. The filter reduces ripple by energy storage in capacitors/inductors, and the regulator maintains a steady DC level under varying load/line conditions.

Step-by-Step Solution:

Verification / Alternative check:

Scope measurements after the rectifier show a waveform always above (or below) zero but with peaks at line frequency (half-wave) or twice line frequency (full-wave), confirming pulsating DC.

Why Other Options Are Wrong:

• transformer: Provides AC at a different voltage and isolation; output is still AC.
• filter: Produces smoothed DC, not the initial pulsating DC.
• regulator: Outputs stabilized DC with minimal variation.
• surge limiter: Protects against inrush/spikes; not a conversion stage.

Common Pitfalls:

• Confusing the rectifier output with fully smoothed DC; the capacitor's role is essential for ripple reduction.
• Overlooking ripple frequency differences between half-wave and full-wave rectification.

Final Answer:

rectifier