Question

What is rectification? Explain the working of bridge rectifiers. Draw the input and output signals.

Answer 1

Hint: Here first we shall understand that the conversion of alternating current to direct current is rectification.
Now let us see what bridge rectifier is-
A bridge rectifier is a type of full wave rectifier using four or more diodes to transform AC to DC effectively.

Complete step by step solution:
Among all the rectifiers the most commonly used is the bridge rectifier.
Construction of a bridge rectifier-

In the figure above the construction of a bridge rectifier is shown. The bridge rectifier consists of four ${D_1},{D_2},{D_3},{D_4}$ diodes and a load resistor ${R_L}$. The diodes form a closed –loop configuration and are connected to transform the AC current into DC current. The input signal is connected across the terminals A and B and the DC output is found across the load resistor ${R_L}$and connected across the terminals C and D. Diodes ${D_1}$ and ${D_3}$ conduct in the positive half cycle and diodes ${D_2}$ and ${D_4}$ conduct in the negative half cycle.

Working of a bridge rectifier circuit
When AC current is supplied to the input during the positive half cycle of the bridge rectifier terminal A becomes positive and terminal B becomes negative. So, diodes ${D_1}$ and ${D_3}$ becomes forward biased and begins to conduct. Diodes ${D_2}$ and ${D_4}$ becomes reverse biased.
When AC current is supplied to the input during the negative half cycle of the bridge rectifier terminal A becomes negative and terminal B becomes positive. So, diodes ${D_2}$ and ${D_4}$ becomes forward biased and begins to conduct. Diodes ${D_1}$ and ${D_3}$ becomes reverse biased.
Thus, during both the positive and negative half periods of the incoming AC signal, a bridge rectifier facilitates electric current.

The AC and DC output is as follows:

Note: In this solution, during the positive half cycle and the negative half cycles, the current flow through the load resistor ${R_L}$ is the same. The DC signal polarity of the rectifier can be either totally positive or negative.