The document describes a project to construct a full wave rectifier circuit that converts 220V AC input into 5V, -5V, and variable 5V DC output. It includes a center tapped transformer, bridge rectifier using 4 diodes, and voltage regulators. Capacitor filters are used to obtain smooth DC waveforms from the pulsating rectified output. The circuit is simulated using NI Multisim software and experimental results are analyzed. Positive 5V output is obtained using an LM7805 regulator, negative 5V output uses an LM7905 regulator, and an LM317 provides adjustable output.

1. FULL WAVE
RECTIFIER
MINI PROJECT
EC681

2. PRESENTED BY
o SHOUVIK GHOSH
o SHIS HOSSAIN
o SHIRSHENDU DAS
o SHAWAN ALI
o SHALMOLY BHADURI
-Department of Electronics and Communication Engineering (3rd year)
Cooch Behar Government Engineering College
Session: 2020-2021

3. Under the
supervision of
DR. PALASH DAS
Assistant Professor,
Department of Electronics and Communication Engineering,
Cooch Behar Government Engineering College, Cooch Behar, West Bengal

4. TABLE OF
CONTENTS
Objective
Introduction & Overview
Applications
Hardware and Software Components
System Design & Implementation
Circuit Implementation
Observation
Simulation
Result Analysis
Conclusion
Acknowledgement
References & Bibliography

5. OBJECTIVE
The aim of this project is to construct a full wave rectifier that converts
220VAC input into 5V, -5V and variable 5V DC output, using a filter and
regulator to obtain smooth waveform.

6. INTRODUCTION
Rectifier
A Rectifier is an electrical device that converts alternating current (AC), which periodically
reverses direction, to direct current (DC), which flows in only one direction.
This process of converting alternating current (AC) to direct current (DC), is known as
Rectification, since it "straightens" the direction of current.
Rectifiers are essentially of two types – Half wave rectifier and Full wave rectifier.
In this presentation, a Full wave rectifier will be constructed.
Full Wave Rectifier
A full-wave rectifier allows unidirectional current through the load during the entire sinusoidal
cycle (as opposed to only half the cycle in the half-wave).
A full-wave rectifier converts the whole of the input waveform to one of constant polarity
(positive or negative) at its output.
Full Wave Rectifiers can be classified as Full Wave Rectifier Using Center Tapped Transformer and
Full Wave Bridge Rectifier.

7.  Half-wave and full-wave rectification deliver unidirectional current but
neither produces a constant voltage. There is a large AC ripple
voltage component at the source frequency for a half-wave rectifier, and
twice the source frequency for a full-wave rectifier. Ripple voltage is usually
specified peak-to-peak. Producing steady DC from a rectified AC supply
requires a smoothing circuit or filter. In its simplest form this can be
just a capacitor (also called a filter, reservoir, or smoothing capacitor), choke,
resistor, Zener diode and resistor, or voltage regulator placed at the output of
the rectifier.
 In practice, most smoothing filters utilize multiple components to
efficiently reduce ripple voltage to a level tolerable by the circuit. Depending
on the type of alternating current supply and the arrangement of the rectifier
circuit, the output voltage may require additional smoothing to produce a
uniform steady voltage. Many applications of rectifiers, such as
power supplies for radio, television and computer equipment, require a steady
constant DC voltage (as would be produced by a battery). In these
applications the output of the rectifier is smoothed by an electronic
filter which releases its stored energy during the part of the AC cycle when
the AC source does not supply any power, that is, when the AC source changes
its direction of flow of current.
OVERVIEW

8.  Here's the diagram for a Full Wave Bridge Rectifier with a Capacitor filter:
Capacitor filter is used for smoothing and reducing the ripple content in
output waveform.

9. APPLICATIONS
Full Wave Rectifiers can be classified as Full Wave Rectifier Using Center Tapped
Transformer and Full Wave Bridge Rectifier.
Full Wave Center Tapped Rectifier Applications
 Earlier, full wave rectifier using center tapped transformer was used for the battery
charger circuits.
 For high power applications, center tapped full wave rectifier is used
to eliminate large voltage drop across the diodes.
 In earlier Transistor Radios.
Full Wave Bridge Rectifier Applications
• The low cost of diodes than center tapped transformers, high efficiency, lightweight,
etc. make this kind of rectifier popular.
 Full Wave Bridge Rectifiers are used in Mobile, Laptops charger circuits.
 Full Wave Bridge Rectifiers are used in Uninterruptible Power Supply (UPS) Circuits to
convert AC to DC.
 Full Wave Bridge Rectifiers are used in our Home Inverters to convert AC to DC.
• Full Wave Bridge Rectifiers are used in Televisions, LCD, LED TVs, in LED Driver Circuits,
Audio Amplifier, Radios and many home appliances.

10. HARDWARE COMPONENTS
No. Particulars Quantity Rating/Model
1. Center Tapped Transformer 1 12V - 0 – 12V, 3.5A
18.3 : 1
2. Fuse 1 3A
3. Silicon Diodes 4 1000V, 3A
1N5408
4. Capacitor 6 2 X 470μF, 50V ; 2 X 1μF, 16V
1 X 20μF, 50V ; 1 X 1nF, 16V
5. Positive Voltage Regulator 1 Vin = 7-25V, 1.25A, Vo = 5V
LM7805
6. Negative Voltage Regulator 1 Vin = -35 to -8V, Vo= -5V
LM7905
7. Adjustable Regulator 1 Vin – Vo = 40V, Io = 1.5A
LM317
8. Multi-meter 1 -
9. Oscilloscope 1 -
10. Resistor 3 2 x 260 Ω, ¼ Watt
1 x 1k Ω, ¼ Watt
11. Variable Resistor 1 2880 Ω
12. LED 2 5mm Green, 5mm Red
13. Wires As per
reruirement
-

11. HARDWARE : THEORY & SPECIFICATION
Centre Tapped Transformer
 When an additional wire is connected across the exact middle of the secondary winding of
a transformer, it is known as a center tapped transformer.
 The center tapped transformer works almost similar to a normal transformer. Like a
normal transformer, the center tapped transformer also increases or reduces the AC
voltage. However, a center tapped transformer has another important feature. That is the
secondary winding of the center tapped transformer divides the input AC current or AC
signal (VP) into two parts.
 The upper part of the secondary winding produces a positive voltage Va and the lower part
of the secondary winding produces a negative voltage Vb. When we combine these two
voltages at output load, we get a complete AC signal.
I.e. VTotal = Va + Vb

12.  The voltages Va and Vb are equal in magnitude but opposite in direction. That is
the voltages (Va and Va ) produced by the upper part and lower part of the
secondary winding are 180 degrees out of phase with each other.
Va = (Na / Np) * Vp
Vb = (Nb / Np) * Vp
Where,
Va = Voltage across the first half of Secondary coil
Vb = Voltage across the second half of Secondary coil
Vp = Voltage across the Primary coil
Na = Number of turn in the first half of Secondary coil
Nb = Number of turn in the second half of Secondary coil
Np = Number of turn in the Primary coil

13. Diode
 Diode is the simplest and most fundamental nonlinear circuit element which has a
nonlinear i-v characteristic. Of the many applications of diodes, their use in the design of
rectifiers (which converts ac to dc) is the most common.
 The forward - bias or simply forward- region of operation is entered when the terminal
voltage v is positive.
 The reverse-bias region of operation is entered when the diode voltage v is made negative.
 The breakdown region is entered when the magnitude of the reverse voltage exceeds a
threshold value that is specific to the particular diode, called the breakdown voltage
Diodes have polarity, determined by an
Anode (positive lead) and
Cathode (negative lead)

14. Capacitor as filter
 The simplest kind of filter that can perform the filtering task just described is a capacitor. Thus, if we connect a
capacitor directly across the output of a rectifier, the AC components will ‘see’ a low impedance path to ground
and will not, therefore appear in the output.
 Since a rectifier circuit is designed with a particular load in mind, choosing the capacitor needs careful analysis.
Since low ripple factors a desired, choosing a large capacitance value is not practical. This is because larger
capacitance will cost more and will create higher peak currents in the transformer secondary and in the supply
feeding it.
 To convert the pulsating output of the rectifier to a constant DC supply. We need to ‘filter’ the pulsating input
signal.
 We can do this by splitting the input waveform into AC (high frequency) and the DC components (very low
frequency) and by then ‘rejecting’ the high frequency components. We can do this by splitting the input waveform
into AC (high frequency) and the DC components (very low frequency) and by then ‘rejecting’ the high frequency
components.

15. Linear Voltage Regulator (LM7805)
 The LM7805 is a voltage regulator that outputs +5 volts.
 It is a three-pin IC; input pin for accepting incoming DC voltage, ground pin for establishing ground for the
regulator, and output pin that supplies the positive 5 volts.
 There are some capacitors attached across the input and output terminals of the ICs, these are included to
rectify any residual DC spikes and ripples that may exist in the supply line.
 According to the datasheet of the IC, the input capacitor is required only if the input source is at a
significant distance away from the IC, i.e. they are optional.
 The output capacitor may be included if anyone wants to protect appliances from noise spikes.
 Since this IC dissipates a lot of heat during regulation, hence it requires proper heatsink sometimes.

16. Negative Voltage Regulator (LM7905)
 The 7905 IC is an negative 5V regulator, meaning it provides -5V as output.
 It’s also a three-pin IC; input pin for input negative DC voltage, ground, and output pin that supplies
the negative 5 volts.
 The output current of this IC can go up to 1.5A, but the IC suffers from heavy heat loss hence a heat
sink is recommended.
 Here also we have some capacitors attached across the input and output terminals of the IC like
7805, these are included to rectify any residual DC spikes and ripples that may exist in the supply
line.
Datasheet of LM7905 IC

17. Adjustable Regulator (LM317)
 The LM317 device is an adjustable three-terminal positive-voltage
regulator capable of supplying more than 1.5 A over an output-voltage
range of 1.25 V to 37 V.
 It requires only two external resistors to set the output voltage, and we
can regulate the output voltage by changing the variable resistor R2.
 The required input voltage in this IC should be 3v more than the desired
output voltage, i.e. here we want maximum of adjustable 5v volt in
output, hence the minimum input that we have to provide it is 8v.
 For calculating the output voltage of a LM317 power supply circuit the
following formula could be used : VO = 1.25(1 + R2 / R1)
 Due to limitation of this IC, lowest voltage that we can attain is only
1.25v.
 Since this IC also dissipates a lot of heat during regulation, hence it
strictly requires appropriate heatsink.
Datasheet of LM317 IC

18. Multimeter
A digital Multimeter is a test tool used to measure two or more electrical
values—principally voltage (volts), current (amps) and resistance (ohms).

19. Oscilloscope
An oscilloscope displays a voltage waveform versus time and has the following
components:
• A screen to display a waveform,
• input jacks for connecting the signal to be displayed,
• dials to control how the signal will be displayed.
If we set the Volts/Div. too low, you’ll clip the signal. Similarly, setting it too
high, and you’ll won’t find the signal, i.e. the signal will be flat.
Increasing the Timebase will display more cycles of a periodic signal.
Conversely, reducing the Timebase , fewer cycles will be displayed.

20. SIMULATOR USED
 The simulator that we used here is NI (National
Instrument) MultiSim.
Multisim is one of the few circuit design
programs to employ the original Berkeley
SPICE based software simulation.
Multisim was originally created by a company
named Electronics Workbench Group, which is
now a division of National Instruments.
Multisim is widely used in academia and
industry for circuits education, electronic
schematic design and SPICE simulation.
Stable release : V14.2
Website : www.ni.com/multisim/
Developer(s) National Instruments Electronics Workbench
Group (formerly by Interactive Image Technologies)
Stable releasee 14.2 / 2019/05/12
Operating system Microsoft Windows
Size ~260mb
Available in English
Type Electronic design automation
License Proprietary EULA
Website www.ni.com/multisim/

21. SYSTEM DESIGN & IMPLEMENTATION
Fig : Block Diagram
 A full-wave rectifier works exactly the
same as the half-wave, but allows
unidirectional current through the load
during the entire sinusoidal cycle.
 A full-wave rectifier converts the whole
of the input waveform to one of
constant polarity (positive or negative)
at its output.
 Bridge rectifier uses 4 rectifying diodes
connected in a "bridged" configuration
to produce the desired output.
Fig : Bridge rectifier

22. Bridge Rectifier – Positive Half Cycle
During the positive half cycle of the supply diodes D1 and D2 conduct in series
while diodes D3 and D4 are reverse biased (ideally, they can be replaced with
open circuits) and the current flows through the load as shown below.
For Positive Half Cycle D1 and D2 is Forward Biased and D3 and D4 is Reverse
Biased.
VI − VO = 0
⇒VO = VI
VO = VI − 2×Vb
VO = VI − 2×Vb − 2×Ird
where,
VI is the input voltage,
Vb is barrier potential,
rd is diode resistance .

23. Bridge Rectifier – Negative Half Cycle
During the negative half cycle of the supply, diodes D3 and D4 conduct in series,
but diodes D1 and D2 switch of as they are now reverse biased. The current
flowing through the load is the same direction as before.
For,
Negative Half Cycle D1 and D2 is Reverse biased and D3 and D4 is Forward biased.
VI − VO = 0
⇒ VO = VI

24. CIRCUIT IMPLEMENTATION

25. OBSERVATION

26. SIMULATION

27. RESULT ANALYSIS
Before calculating the winding ratio of the transformer, we have to consider the
voltage drop across the diode (0.6V – 0.8V for Si) and other components in the circuit.
For that, we need greater voltage from the transformer than the exact desired
rectified voltage. In this case the desired voltage is of magnitude 5V. So, we stepped
down 220V AC input to 12V (24V peak-to-peak).
Calculation of transformer’s winding ratio
VTotal = Va + Vb
Va = (Na / Np) * Vp
Vb = (Nb / Np) * Vp
We have, VTotal = 24V and Va = Vb = 12V
Vp = 220V and Na = Nb = 1
Substituting these values in any one of equations, we get
12 = (1/Np) * 220
i.e. Np = 18.3
Therefore, Np / Ns = 18.3 : 1
Np / Na = Np / Nb = 9 : 1

28. +5V DC OUTPUT
 To get positive 5V output we used LM7805 IC which takes minimum 7V and a
maximum of 25V dc input to produce a constant +5V output.
 Furthermore, a 470uF capacitor is placed across the input pin and a 1uF
across the output pin of the LM7805 to obtain a smoother and constant
output.
-5V DC OUTPUT
 To get negative 5V output we used LM7905 IC which takes minimum -7V and a
maximum of -35V dc input to produce a constant -5V output.
 As for the negative voltage input for the LM7905, we take it from the p-side
of the diodes D1 and D3 of the bridge (refer to circuit). The voltage at this
point is approximately -12V.
 Furthermore, a 470uF capacitor is placed across the input pin and a 1uF
across the output pin of the LM7905 to obtain a smoother and constant
output.

29. VARIABLE 5V OUTPUT
 To vary the output, we used LM317 IC. A variable resistor (R2) is connected
between the adjust terminal of the IC and ground. Another resistor (R1 = 1kΩ) is
connected across the adjust terminal and the output terminal.
 LM317 varies the output voltage according to following equation:
VO = 1.25 (1 + R2 / R1)
 To get a variable voltage (maximum of 5V) we used 1kΩ as R1 and for this the
maximum resistance of R2 comes out to be 2880Ω. By varying R2 we can vary the
output voltage from LM317.
 Furthermore, a 20uF capacitor is placed across the input pin and a 1nF across the
output pin of the LM317 to obtain a smoother and constant output.
 Also, LM317 has a voltage drop of approximately 3V, so the input needs to be at
least 3V more than the desired output voltage.
 Major drawback of the LM317 is severe heating issues, which can be solved by
using an appropriate heat sink.

30. CONCLUSION
 A working prototype of full wave rectifier is successfully built in bridge mode,
providing desired output of 5V, -5V, and variable 5V, with a smooth waveform.
A working simulation is also built using MultiSim software for the same, and its
ready to implement practically.
 But, due to transformer loss, huge power loss due to heating, its efficiency is
very low. And because of these reasons, nowadays usage of linear voltage
regulator is decreasing significantly, and it’s replaced by SMPS, which is much
efficient and light weight.
 However linear voltage regulators have many advantages too, like, lower rf
noise, lower cost where power requirement is low, less complicated circuitry
etc.

31. ACKNOWLEDGEMENT
It is our pleasure to acknowledge our supervisor Dr. Palash Das,
Assistant Professor, Department of Electronics and Communication Engineering,
Cooch Behar Government Engineering College, for assigning us to this wonderful
project. The information and encouragement received from him has been very
helpful. Lastly, we would like to express our gratitude to all the researchers and
authors of various academic resources whose references have been useful for
achieving the end goal of this project.

32. REFERENCES & BIBLIOGRAPHY
 Microelectronic Circuits by Sedra & Smith
 Solid State Devices by Streetman & Banerjee
 http://vlabs.iitkgp.ac.in/
 https://en.wikipedia.org
 https://www.alldatasheet.com
 https://www.google.co.in/imghp?hl=en&authuser=0&ogbl