bridge rectifer

Bridge rectifier is actually formed by 4 diodes connected in a bridge configuration. It is usually called a full-wave rectifier because it converts both the positive and negative wave of an a.c. signal to positive.
Advantages:
Full-wave rectification allows a smaller capacitor at the d.c. output. It is suitable for the circuit with larger d.c. loading, or for the applications require less ripple.
Disadvantages:
The d.c. output level is decreased by 2 diode-drops. The input a.c. voltage should be higher to compensate it. The diodes dissipate more power.

A single diode can also be used to rectify an a.c. signal. It is called a half-wave rectifier because either positive or negative wave of the signal is rectified while the other half wave is blocked.
Advantages:
Simple and lower costs.
The d.c. output level is decreased by 1 diode-drop and hence less power dissipation at the diode.
Disadvantages:
Higher ripple at the d.c. output. A larger capacitor is needed at the d.c. output to overcome the ripple.

Connection of diode bridge:
o------------------
a.c. input . . . . |
. . . . . . ----|>|-----|>|------
. . . . . .|. . . . . . . . . . . . . |---------o D.C. +
. . . . . . ----|>|-----|>|-----
. . . . . .|. . . . . . |
o------- )---------
. . . . . .|------------------------------o D.C. -

All the electronic devices are work at d.c. power, e.g. computer, TV, radio, CD player, etc. There must be a power supply which rectifies the a.c. main to d.c. power.