11.9: Full wave rectifier
A full-wave rectifier is a device that converts alternating current (AC) to direct current (DC) and is more efficient than its half-wave counterpart. It typically includes a center-tapped transformer, two diodes, and a load resistor. The secondary winding of the transformer is divided to provide two equal voltages of opposite polarities, which is the pivotal element of full-wave rectification.
The full-wave rectifier operates by allowing each diode to conduct during alternate half-cycles of the AC input, utilizing the full cycle of the AC waveform. During the positive half-cycle of the AC signal, diode D1 becomes forward-biased and conducts, while diode D2 is reverse-biased and does not conduct. This creates a positive output similar to that of a half-wave rectifier.
When the AC signal enters the negative half-cycle, diode D1 is reverse-biased and non-conductive, while diode D2 is forward-biased, allowing the current to flow through it. This process flips the negative voltage to a positive one at the output, ensuring that the output voltage is always of the same polarity. The load resistor sees a unidirectional current, leading to a unipolar output waveform.
Full-wave rectifiers have higher rectification efficiency and are extensively used in power supply units, battery chargers, audio amplifiers, and signal-processing applications. The ripple voltage is lower, and the ripple frequency is double that of a half-wave rectifier, yielding smoother DC output with less filtering requirement.
The peak inverse voltage (PIV) in a full-wave rectifier is twice the maximum input AC voltage(VS) reduced by the diodes' forward voltage drop (VD).
This PIV is approximately double that encountered in a half-wave rectifier, requiring diodes that can sustain higher reverse voltages to ensure safe operation.
