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

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