Full-wave rectifiers: Is the efficiency of a full-wave rectifier using a centre-tapped transformer twice that of a full-wave bridge rectifier?

Introduction / Context:Efficiency in rectifiers is the ratio of DC output power to AC input power. Both the full-wave centre-tapped (two-diode) rectifier and the full-wave bridge (four-diode) rectifier deliver DC from both half-cycles, but their device counts and conduction paths differ. This question tests a common misconception about their efficiencies.

Given Data / Assumptions:

• Ideal or near-ideal diodes (forward drops do not dominate).
• Same load resistance and transformer secondary RMS voltage scaled appropriately.

Concept / Approach:

Under comparable conditions, both topologies produce the same DC component and ripple frequency at the load, and their theoretical conversion efficiencies are essentially the same (approximately 81.2% for ideal full-wave rectification). The centre-tapped version has one diode drop per conducting half-cycle, whereas the bridge has two; this affects regulation and peak output slightly but does not double the efficiency.

Step-by-Step Solution:

Verification / Alternative check:

Standard power-electronics texts list identical theoretical efficiencies for both full-wave rectifiers, with practical differences arising from diode drops and transformer utilisation factor (TUF), not from a twofold change in efficiency.

Why Other Options Are Wrong:

• Claiming “True” confuses TUF and peak voltage with efficiency.
• “True if ideal diodes” is incorrect; ideality equalises them further.
• Statements about three-phase are unrelated.

Common Pitfalls:

• Mixing up transformer utilisation factor (centre-tapped is poorer) with efficiency.

Final Answer:

False.