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What Is Rectifier?


A rectifier is an electrical device composed of one or more diodes that converts alternating current (AC) to direct current (DC). A diode is like a one-way valve that allows an electrical current to flow in only one direction. This process is called rectification.


A rectifier can take the shape of several different physical forms such as solid-state diodes, vacuum tube diodes, mercury arc valves, silicon-controlled rectifiers and various other silicon-based semiconductor switches.
Rectifiers are used in various devices, including:
  • DC power supplies
  • Radio signals or detectors
  • A source of power instead of generating current
  • High-voltage direct current power transmission systems
  • Several household appliances use power rectifiers to create power, like notebooks or laptops, video game systems and televisions.
What is a rectifier?

When the voltage is applied to the P-N junction diode in such a way that the positive terminal of the battery is connected to the p-type semiconductor and the negative terminal of the battery is connected to the n-type semiconductor, the diode is said to be forward biased.

When this forward bias voltage is applied to the P-N junction diode, a large number of free electrons(majority carriers) in the n-type semiconductor experience a repulsive force from the negative terminal of the battery similarly a large number of holes (majority carriers) in the p-type semiconductor experience a repulsive force from the positive terminal of the battery. 

There are 3 types of rectifiers:
I) Half-Wave Rectifier.
You can see in the diagram, when an AC signal is fed on the input of the transformer, the diode only allows current through it when it gets forward biased (diode in forward bias offers low resistance to the current). So, the resulting signal at the output is a pulsating DC. These type of rectifiers have a low efficiency (DC output power/AC input power) of 40.6%.
II) Centre-tapped Fullwave rectifier.
In the above circuit, let an AC signal is fed on the input. When terminal 1 is postive and terminal 2 is negative, diode D1 gets forward biased and current flows through it, but diode D2 gets reverse biased, current doesn't flow through it. Again, when terminal 1 is negative and terminal 2 is positive, diode D1 gets reverse biased and current doesn’t flow through it, but diode D2 gets forward biased and current flows through it. So the resulting output is a smooth DC signal. These rectifiers have a efficiency of 81.2%
III) Bridge Rectifier.
In the above circuit, let an AC signal is fed on the input. When terminal B is postive and terminal D is negative, diodes D1&D3 get forward biased and current flow through them, but diode D2&D4 get reverse biased, current don’t flow through them. Again, when terminal B is negative and terminal D is positive, diodes D2&D4 get forward biased and current flow through them, but diode D1&D3 get reverse biased, current don’t flow through them. So, the resulting output is a smooth DC signal. The efficiency of these type of rectifiers is 81.2%.
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