This document describes a student project to design and implement a regulated power supply unit and ECM amplifier. It includes a circuit diagram and descriptions of the key components - a step-down transformer, rectifier diodes, filtering capacitors, and voltage regulator ICs. The power supply works by using a transformer to step down AC voltage, rectifying it to DC with a bridge rectifier, filtering it with capacitors, and regulating it to the desired voltages (+/- 5V) with voltage regulator ICs. The student provides explanations of how the power supply works and precautions for building the circuit on a PCB board.

1. KUSHAL, 091064
A2 BATCH, ECE
JAYPEE UNIVERSITY OF ENGINEERING AND TECHNOLOGY
PROJECT REPORT ON POWER SUPPLY UNIT AND ECM AMPLIFIER
Under the guidance of
Mr. GAURAV SAXENA
Senior Lecturer
Electronics and Communication Department
JUET, Guna, M.P.
Submitted by:
KUSHAL
091064
A2, ECE

2. KUSHAL, 091064
A2 BATCH, ECE
REGULATED POWER SUPPLY
AIM:
To implement and check Regulated Power Supply.
REQUIRED APPARATUS AND COMPONENTS:
To prepare the Copper track on the PCB
• PCB Board of appropriate size to mount the circuit.
• PCB cutter
• PCB driller
• FeCl3 Solution
• Sand Paper
To mount (Solder) the components on the PCB
• Soldering paste
• Soldering Wire
• Soldering Machine
Extra Apparatus
• DMM
• Ribbon Wire
• Sharp cutter
• Power Supply 6-30 Volts
Components Required
• One center tapped Transformer
• One 1kΩ resistor
• Three IN4007 diodes
• Two Voltage Regulator IC's
• IC 7805 - For +5V output
• IC 7905 - For -5V output
• Two 1000µF electrolytic capacitors and Two 0.1µF paper capacitors

3. KUSHAL, 091064
A2 BATCH, ECE
Circuit diagram:
Component description and working:
TRANSFORMER:
Transformer is a major class of coils having two or more windings usually wrapped around a
common core made from laminated iron sheets. It has two cols named primary and
secondary. If the current flowing through primary is fluctuating, then a current will be
inducted into the secondary winding. A steady current will not be transferred from one coil
to other coil.

4. KUSHAL, 091064
A2 BATCH, ECE
Transformers are of two types:
1. Step up transformer
2. Step down transformer
In the power supply we use step down transformer. We apply 220V AC on the primary of
step down transformer. This transformer steps down this voltage to 6V AC. We give 6V AC
to rectifier circuit, which converts it to 5V DC.
DIODE:
The diode is a p-n junction device. Diode is the component used to control the flow of the
current in any one direction. The diode widely works in forward bias. When the current
flows from P to N direction, then it is in forward bias. The Zener diode is used in reverse bias
function i.e. N to P direction. Visually the identification of the diode`s terminal can be done
by identifying he silver/black line. The silver/black line is the negative terminal (cathode)
and the other terminal is the positive terminal (cathode).
BRIDGE RECTIFIER:
During the positive half cycle of the input supply, the upper end A of the transformer
secondary becomes positive with respect to its lower point B. This makes Point1 of bridge
Positive with respect to point 2. The diode D1 & D2 become forward biased & D3 & D4
become reverse biased. As a result a current starts flowing from point1, through D1 the load
& D2 to the negative end. During negative half cycle, the point2 becomes positive with
respect to point1. Diodes D1 & D2 now become reverse biased. Thus a current flows from
point 2 to point1.

5. KUSHAL, 091064
A2 BATCH, ECE
CAPACITOR:
Like a battery, a capacitor has two terminals. Inside the capacitor, the terminals connect to
two metal plates separated by a dielectric. The dielectric can be air, paper, plastic or
anything else that does not conduct electricity and keeps the plates from touching each
other.
VOLTAGE REGULATORS:
Voltage regulator ICs are available with fixed (typically 5, 12 and 15V) or variable output
voltages. The maximum current they can pass also rates them. Negative voltage regulators
are available, mainly for use in dual supplies. Most regulators include some automatic
protection from excessive current (over load protection) and overheating (thermal
protection). Many of fixed voltage regulator ICs has 3 leads. They include a hole for
attaching a heat sink if necessary.
These voltage regulators are monolithic circuit integrated circuit designed as fixed voltage
regulators for a wide variety of applications. These regulators employ internal current
limiting, thermal shutdown, and safe-area compensation. With adequate heat sinking they
can deliver output current in excess of 1.0 A.
EXPLANATION of how the POWER SUPPLY works:
The main function of power supply is to convert AC to DC; as shown in fig 1, the first stage is
to make full wave rectifier to the AC signals by using bridge rectifier, filter the rectified wave
by using filtering capacitor and finally select the appropriate voltage signal to generate pure
DC signal.
Current rating for bridge rectifier should be suitable with load current, also; the designer
should consider the voltage drop across each diode, which is normally equal to 0.7v. Note
that only two diodes are required when using Centre Tapped Transformer.
The following formula is used to calculate the capacitance value for the filtering capacitor:
C: Capacitor value.
Vp: Peak voltage. ("Bridge output max voltage")
f: Frequency of the AC supply.
i: Load current.
The figure is shown Below:

6. KUSHAL, 091064
A2 BATCH, ECE

7. KUSHAL, 091064
A2 BATCH, ECE
Precautions:
1: Do the drilling properly.
2: Iron should be kept in contact with the joint for 2-3 seconds.
3: Put the components at correct place.
4: Clean component lead and copper pad before soldering.