### What is Rectifier and how it Works?

In this Tutorial we are going to learn about WHAT IS RECTIFIER ?

Rectifier has two applications.

• Low voltage (electronics application) formed using diode which is part of analog electronics
• High voltage (electrical application) formed using SCR which is part of Power electronics.

Rectifier is two types

Half wave

Full Wave

Half wave Rectifier

• Iron core transformer is used.

It is step down transformer which converts a high voltage AC signal into low voltage AC .

Example 220V RMS AC signal can be converted into 44V V RMS AC signal using 5:1 transformer.

The purpose of this step down transformer –

Protects the diode which has low voltage rating ( Max. voltage /breakdown voltage )

For achieving low voltage DC O/P

Diode Performance Rectification

Vi = A pure AC voltage

Operation – Case 1

0 < ∝  < π

• Vi  have +VE cycle
• So voltage at node ‘a’ is +VE with respective ground .
• Hence ‘D’ operate in forward Bias (FB) = Short Circuit
• RL  appears in parallel with secondary winding and hence

Vo = Vi

• (a small voltage = Forward Voltage drop of 0.7 V will appear across the diode

Case 2

• π < ∝  < 2π
• Vi will have –VE cycle
• Voltage at node ‘a’ becomes –VE with respective ground.
• Hence ‘D’ will apart in R.B. (Reverse Bias )= Open Circuit

Vo = 0

• The I/P voltage now drop across diode which is acting as open circuit

Full Wave Rectifier

• It is also called conventional Full Wave Rectifier .
• The transformer is Centre tapped.
• A Centre tapped transformer is used to get two voltage Va & Vb

As per this both are equal in magnitude but opposite in SIGN

i.e.  Vb   = – Va

If  Va = Vm sin ∝

Then Vb = – Vm sin ∝

This transformer also converts high voltage AC into Low voltage AC

i.e. It  is step down transformer .

Diode D1 and D2 perform rectification

( convert pure AC into pulsating DC )

Operation – Case 1

0 < ∝  < π

Va is +VE and Vb is –VE so,

Node ‘a’ is +VE w.r.t. ground

D1 = Forward Bias = Short Circuit

Node ‘b’ is -VE w.r.t. ground

D2 = R Bias =Reverse Bias = Open Circuit

RL upper half of secondary winding appear in parallel ,

Therefore Vo= Va

Case 2

π < ∝  < 2π

Va is -VE and Vb is +VE so,

Node ‘a’ is -VE w.r.t. ground

D1 = Reverse Bias = Open Circuit

Node ‘b’ is +VE w.r.t. ground

D2  =Forward Bias = Short Circuit

RL & Lower part of secondary winding appear in parallel ,

Therefore Vo= Vb