Introduction to full wave rectifier output voltage:
A FWR is one which converts an A.C voltage into a pulsating voltage using positive and negative half - cycles of the applied A.C voltage .
It uses two diodes , one of which conducts and provides output during the positive half - cycle while the other diode conducts during the negative half - cycle .
Figure (1) shows the circuit diagram of a FWR . The step down transformer secondary windings are centre tapped , i.e., secondary voltage is equally divided with 180o out of phase as shown in figure (2) .
Therefore , diode D1 input gets positive half - cycle and at the same time D2 gets negative half - cycle .
Assume D1 and D2 are ideal diodes between 0 to 2 .
Let D1 gets positive half - cycle and D2 gets negative half - cycle .
Therefore , D1 is ON (forward biased ) and D2 is OFF (reverse biased)
Therefore , current I1 flows in RL due to D1 and I2 = 0 .
i.e., I1 = Im sin , 0 < <
I2 = 0 .
Similarly , input between to D1 is negative and to D2 is positive .
Therefore , D1 is OFF (reverse biased) , D2 is ON (forward biased)
Therefore , I2 current flows in RL is in the same direction .
The total current ,
I = I1 + I2
= Im sin + Im sin
= 2 Im sin
I = 2 Im sin
Piv , Average Dc Voltage , Rms Current of Fwr:
Peak Inverse Voltage (PIV)
It is defined as the maximum reverse bias potential that can be applied before entering the zener region .
The peak Inverse Voltage (PIV) of the diode is of primary importance in the design of rectifiers .
For half - wave rectifier the PIV rating should be greater than or equal to maximum applied voltage . For a full - wave rectifier the PIV rating should greater than or equal to twice the maximum applied voltage .
Average D.C voltage
The average voltage available across the D.C voltage is given by ,
VDC = Vm sin
=
=
= [ - (cos - cos(0)) ]
VDC =
RMS current
IDC =
=
=
Irms =
Ripple Factor of Fwr:
Ripple Factor
Ripple factor is a figure of merit of a rectifier circuit and is defined as the ratio of the A.C ripple quantity [ current or voltage ] to D.C quantity [ current or voltage ] .
The output of FWR can be represented mathematically as ,
Io = ------------- > (1)
Equation (1) indicates that the rectifier output contains D.C components plus A.C components .
Ripple factor , = ---------------> (2)
Substitute the values of ,
IDC = and
Irms = in equation (2) , we get = 0.48 .
The ripple factor of 0.48 implies a drastic improvement from 1.21 for HWR .
Therefore , FWR is good compared to HWR since < 1 .
Vriti Edustore
