Draw the circuit diagram of a full wave rectifier.

Question 77 of 88

Q. Draw the circuit diagram of a full wave rectifier.

Puducherry TnboardTamil Nadu HSC (DGE) Board 2023Subjective· 2mImportance★★★★★

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Concept understanding — Full Wave Rectifier

Full-Wave Rectifier: From Intuition to Precision

Imagine you have a tap that gives water in alternating bursts — forward, then backward, then forward again. You want a steady stream that always flows in one direction. A half-wave rectifier is like a one-way flap that only lets the forward bursts through, wasting the backward ones. A full-wave rectifier is smarter: it flips the backward bursts around so they also flow forward. Nothing is wasted.

That is the core idea. The AC voltage swings positive and negative. A full-wave rectifier takes both halves of the cycle and makes them contribute to a unidirectional (DC) output.

How It Works (The Intuition)

A full-wave rectifier uses either:

Two diodes and a centre-tapped transformer, or
Four diodes in a bridge configuration (the bridge rectifier — far more common).

In both cases, the diodes are arranged so that during the positive half-cycle, one pair conducts, and during the negative half-cycle, the other pair conducts — but the current through the load always flows the same way.

Tip

Think of the bridge rectifier as a "traffic roundabout" for current. No matter which direction the AC input pushes, the diodes steer the current so it always exits the same way through the load.

The Precise Statement

A full-wave rectifier is a circuit that converts the entire input AC waveform (both positive and negative half-cycles) into a pulsating DC output. The output voltage is always of the same polarity, and its ripple frequency is twice the input AC frequency.

For a sinusoidal input $V_i = V_m \sin(\omega t)$ , the output voltage (ideal diodes) is:

V_o = |V_m \sin(\omega t)|

That absolute value is the mathematical signature of full-wave rectification.

Key Result: Ripple Frequency

If the input AC has frequency $f$ (e.g., 50 Hz), the output ripple frequency is:

f_{\text{ripple}} = 2f

Why? Because each input cycle gives two output pulses — one from the positive half and one from the inverted negative half. So for 50 Hz mains, you get 100 pulses per second. This makes filtering much easier than in a half-wave rectifier (where ripple frequency equals $f$ ).

Important

Ripple frequency = $2 \times$ input frequency. This is a direct consequence of using both halves of the AC cycle.

Average (DC) Output Voltage

For a full-wave rectifier with a sinusoidal input of peak voltage $V_m$ , the average (DC) output voltage is:

V_{\text{dc}} = \frac{2V_m}{\pi}

Compare this to a half-wave rectifier, where $V_{\text{dc}} = V_m/\pi$ . The full-wave gives double the average output for the same peak input — another reason it is more efficient.

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Figure — Hard draw gate for a full-wave rectifier circuit. The catalog figure is the centre-tap full-wave rectifier cir

A full-wave rectifier converts the complete AC cycle (not just alternate half-cycles) to a pulsating DC output, most simply using a centre-tapped transformer with two diodes.

1. Circuit description (centre-tap type).

The secondary winding of a step-down transformer is centre-tapped; the centre tap $O$ is taken as the common/ground reference.
The two ends of the secondary, $A$ and $B$ , are each connected through one diode ( $D_1$ from $A$ , $D_2$ from $B$ ) to a common output terminal.
A load resistor $R_L$ is connected between this common output terminal and the centre tap $O$ .

Schematically:

      A ---D1---+
Transformer       +--- output (+)
  secondary       |
      O ----------+--- R_L --- back to O (ground/-)
      B ---D2---+

2. Working.

During the half-cycle when $A$ is at a higher potential than $O$ , diode $D_1$ is forward biased and conducts, sending current through $R_L$ from top to bottom; $D_2$ is reverse biased and does not conduct.
During the next half-cycle, $B$ becomes positive with respect to $O$ ; now $D_2$ conducts and $D_1$ is cut off, but current again flows through $R_L$ in the same direction as before. …

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Q.Draw the circuit diagram of a full wave rectifier.

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