power supply unit

KUSHAL, 091064A2 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

KUSHAL, 091064A2 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 cutterPCB driller

FeCl3 SolutionSand Paper

To mount (Solder) the components on the PCB

Soldering pasteSoldering Wire

Soldering Machine

Extra Apparatus

DMMRibbon WireSharp cutter

Power Supply 6-30 Volts

Components RequiredOne center tapped Transformer

One 1kΩ resistorThree IN4007 diodes

Two Voltage Regulator IC'sIC 7805 - For +5V outputIC 7905 - For -5V output

Two 1000µF electrolytic capacitors and Two 0.1µF paper capacitors

KUSHAL, 091064A2 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.

KUSHAL, 091064A2 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.

KUSHAL, 091064A2 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:

KUSHAL, 091064A2 BATCH, ECE

KUSHAL, 091064A2 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.