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1. RECTIFIER

2. What is Rectifier?
 A rectifier is an electrical device that converts alternating
current(AC) to direct current(DC).
This process is known as rectification.
Its also called Converters.
AC Voltage Pulsated DC Voltage
Rectifier

3. Diode Based Rectifiers
Half Wave Rectifier Full Wave Rectifier
Bridge Type Centre Tap Transformer
Type

4. Types of Rectifier

5. Half Wave Rectifier (HWR)
Half-wave rectifiers are used to convert AC
voltage to DC voltage, and it required a
single diode to construct the circuit.
The diode only conducts when the anode is
positive with respect to cathode, the current will
flows only during the positive half cycle of the input
voltage i.e., current flow in one direction.

6. Half Wave Rectifier (HWR)
D
RL
v(t) = Vmsinωt vo(t)
D=ON D=OFF D=ON

7. Working of half wave rectifier
 AC voltage is applied to the primary winding of
the step-down transformer which step-down to
low voltage at the secondary winding which will
be applied to the diode.
During the positive half cycle of the AC voltage,
the diode will be forward biased and the current
flows through the diode.
During the negative half cycle of the AC voltage,
the diode will be reverse biased and the flow of
current will be blocked.

8. v(t)
time
0 5 10 15 20
+
-
Working of HWR At time t=0 sec
Phase Potential = 0 Volts
Neutral Potential =0 Volts
A K
0V 0V
VA=VK
Diode Reverse Bias.
Diode act as an OFF switch
D
RL
230V,50Hz
AC Supply
A K
P
N
NO OUTPUT VOLTAGE
vo(t)
D
RL
230V,50Hz
AC Supply
A K
P
N

9. v(t)
time
0 5 10 15 20
+325V
-
Working of HWR At time t=5 msec
Phase Potential = 325Volts
Neutral Potential =0 Volts
A K
325V 0V
VA > VK
Diode is forward biased
Diode act as an ON switch
D
RL
230V,50Hz
AC Supply
A K
P
N
OUTPUT VOLTAGE IS PRESENT
vo(t)
D
RL
230V,50Hz
AC Supply
A K
P
N

10. v(t)
time
0 5 10 15 20
+
-
Working of HWR At time t=10 msec
Phase Potential = 0 Volts
Neutral Potential =0 Volts
A K
0V 0V
VA=VK
Diode Reverse Bias.
Diode act as an OFF switch
D
RL
230V,50Hz
AC Supply
A K
P
N
NO OUTPUT VOLTAGE
vo(t)
D
RL
230V,50Hz
AC Supply
A K
P
N

11. v(t)
time
0 5 10 15 20
+
-
Working of HWR At time t=15 msec
Phase Potential = -325 Volts
Neutral Potential =0 Volts
A K
-325 V 0V
VA<VK
Diode Reverse Bias.
Diode act as an OFF switch
D
RL
230V,50Hz
AC Supply
A K
P
N
NO OUTPUT VOLTAGE
vo(t)
D
RL
230V,50Hz
AC Supply
A K
P
N

12. Graphical representation
• Vin Input Voltage (Sinusoidal Waveform)
• Vout  Output Voltage (rectified output half
wave)

13. HWR OUTPUT WAVEFORMS
180 360 540 720
180 360 540 720
0
0
D-ON D-ON D-ON
D-OFF D-OFF

14. Half Wave Rectifier With Filter
vo(t)
D
RL
230V,50Hz
AC Supply
A K
P
N
C
Vavg
time

15. Half wave rectifier
Advantage:
 Simple in circuit construction.
 Cost efficient.
Disadvantage:
 Filters are required to get pure DC.
 AC supply delivers power during half cycle only. So
output is low.
 Ripple factor is quite high (RF=1.21) than full wave
rectifier
 Efficiency is 40.6% only.

16. Full wave rectifier
A Full Wave Rectifier is a circuit, which
converts an ac voltage into a pulsating dc
voltage using both half cycles of the applied ac
voltage.
It uses two diodes of which one conducts
during one half cycle while the other conducts
during the other half cycle of the applied ac
voltage.

17. Full wave rectifier
Classification full wave rectifiers into,
Centre-tapped Full Wave Rectifier
Full Wave Bridge Rectifier

18. Full wave rectifier with center-tapped
transformer
Centre-tapped Transformer:
 It is a normal transformer with slight
modification.
It has an addition wire connected to the exact
centre of the secondary winding.
This type of construction divides the AC voltage
into two equal and opposite voltages namely +Ve
voltage (Va) and -Ve voltage (Vb).
The total output voltage is,

19. Full wave rectifier with center-tapped
transformer

20. FULL WAVE RECTIFIER
A full wave rectifier is defined as a type of rectifier that
converts both halves of each cycle of an
alternating wave (AC signal) into a pulsating DC signal

21. FULL WAVE RECTIFIER
Center tap Transformer Based FWR
What is Centre Tap Transformer?
N2/2
N2/2
N2 TURNS
N1 TURNS N1 TURNS

22. Center tap Transformer
100 Volts
100 Volts
1:1
50 Volts
50 Volts
100 Volts
1:0.5:0.5

23. Behavior of Center tap Transformer
with AC Supply
1:0.5:0.5
Vm
Vm / 2
-Vm / 2
-Vm

24. Behavior of Center tap Transformer
with AC Supply
1:0.5:0.5
+
+
-
-
+
+
-
-
0 V

25. FULL WAVE RECTIFIER
1:0.5:0.5
P
N
0V
D1
D2
RL
A
A
K
K
vo(t)

26. FULL WAVE RECTIFIER
When applying an AC voltage to the input
transformer.
 During the positive half-cycle of the AC voltage,
terminal 1 will be positive, centre-tap will be at
zero potential and terminal 2 will be negative
potential.
This will lead to forward bias in diode D1 and
cause current to flow through it. (i.e., D1
Conducts)
During this time, diode D2 is in reverse bias and
will block current through it.

27. During Positive Half Cycle
D1-ON & D2-OFF
D2-OFF
1:0.5:0.5
P
N
0V
D1-ON
RL
+
-
A K
K
A
Note the Current Direction

28. During the negative half-cycle of the input AC
voltage, terminal 2 will become positive with
relative to terminal 2 and centre-tap.
This will lead to forward bias in diode D2 and
cause current to flow through it. (i.e., D2
Conducts)
During this time, diode D1 is in reverse bias
and will block current through it.

29. During Negative Half Cycle
D1-OFF & D2-ON
D2-ON
1:0.5:0.5
P
N
0V
D1-OFF
RL
+
- A K
K
A
Note the Current Direction

30. Waveforms
D1-ON D1-ON
D2-ON D2-ON
DC OUTPUT
VOLTAGE
INPUT
AC VOLTAGE
Vm / 2 Vm / 2
Vm / 2
Vm / 2
Vm
-Vm

31. FWR with Filter
1:0.5:0.5
P
N
0V
D1
D2
RL
A
A
K
K
vo(t)

32. FWR Output with Filter
Vm / 2

33. Full Wave Bridge Rectifier
Diodes namely A, B, C and D
which form a bridge circuit
as shown.

34. BRIDGE RECTIFIER
RL
vs
D1 D2
D3
D4
P N

35. BRIDGE RECTIFIER – WORKING
During Positive Half Cycle
RL
vs
D1 D2
D3
D4
P N
+ 0V
+ : high potential
D1,D3 – ON
D2,D4 – OFF
vo(t)
Vm
Vm
LOOK AT THE CURRENT
DIRECTION
A
K

36. BRIDGE RECTIFIER – WORKING
During Negative Half Cycle
RL
vs
D1 D2
D3
D4
P N
- 0V
+ : high potential
D1,D3 – OFF
D2,D4 – ON
vo(t)
Vm
Vm
LOOK AT THE CURRENT
DIRECTION
A
K

37. Full wave rectifier
Advantages:
 Efficiency is higher (ɳ =81.2%)
 Low power loss because no voltage signal is
wasted in the rectification process.
Produces large DC power output
Ripple factor is less.
Disadvantages:
The centre-tapped rectifier is more expensive
than half-wave rectifier and tends to occupy a lot
of space.
Peak Inverse Voltage(PIV) rating of diode is higher.

38. Application of rectifier
Battery Charger
DC Power Supply
DC welder
DC Motor Drive

39. Comparison of Rectifiers