Theory 26.2 :- Full Wave Rectifier

What is Full Wave Rectifier?

Full-wave rectifier circuits are used for producing an output voltage or output current which is purely DC. The main advantage of a full-wave rectifier over half-wave rectifier is that such as the average output voltage is higher in full-wave rectifier, there is less ripple produced in full-wave rectifier when compared to the half-wave rectifier.

Working of Full Wave Rectifier

The full-wave rectifier utilizes both halves of each a.c input. When the p-n junction is forward biased, the diode offers low resistance and when it is reversing biased it gives high resistance. The circuit is designed in such a manner that in the first half cycle if the diode is forward biased then in the second half cycle it is reverse biased and so on.

Characteristics of Full Wave Rectifier

Following are the characteristics of full-wave rectifier:

Ripple Factor

Ripple factor for a full-wave rectifier is given as:

DC Current

Currents from both the diodes D1 and D2 are in the same direction when they flow towards load resistor RL. The current produced by both the diodes is the ratio of Imax to π, therefore the DC current is given as:

Where,

 Imax is the maximum DC load current

DC Output Voltage

DC output voltage is obtained at the load resistor RL and is given as:

Where,

Vmax is the maximum secondary voltage

Form Factor

The form factor is the ratio of RMS value of current to the output DC voltage. The form factor of a full-wave rectifier is given as 1.11

Rectifier Efficiency

Rectifier efficiency is used as a parameter to determine the efficiency of the rectifier to convert AC into DC. It is the ratio of DC output power to the AC input power. The rectifier efficiency of a full-wave rectifier is 81.2%.

Advantages of Full Wave Rectifier

• The rectifier efficiency of a full-wave rectifier is high
• The power loss is very low
• Number of ripples generated are less

Disadvantages of Full Wave Rectifier

• Very expensive

Types of Full Wave Rectifier

There are two main types of full-wave rectifiers, and they are:

• Two diodes full-wave rectifier circuit (requires a center-tapped transformer and is used in vacuum tubes)
• Bridge rectifier circuit (doesn’t require a centre-tapped transformer and is used along with transformers for efficient usage)

Applications of Full Wave Rectifier

Following are the uses of full-wave rectifier:

• Full-wave rectifiers are used for supplying polarized voltage in welding and for this bridge rectifiers are used.
• Full-wave rectifiers are used for detecting the amplitude of modulated radio signals.