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4th Semester E.C. Project

Sub: Electronics Device and Circuits

TOPIC: Regulated Power Supply.

Team member 1: Team member 2:Name : Rahul B. Shah Name : Abhishek H. Sharda

Sr. No. : 97 Sr. No. : 101

Roll No.: 06ec104 Roll No.: 06ec108

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Guided by:Nayan Trivedi Sir

Kanaiya Dave Sir

Parul Institute of Engineering and Technology

Limda.

Electronics & Communication Engineering Department.

CERTIFICATE

This is to certify that the project entitled

“Regulated Power Supply” which is submitted by

Mr. Rahul B. Shah & Mr. Abhishek H. Sharda in

fulfillment of the requirement for the project work in

4th Semester Engineering in Electronics &

Communication by Gujarat University, Ahmadabad,

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during the academic year 2008 has been carried out

by them under our supervision and guidance. The

matter embodied in this report has not been

submitted for award of any other degree or research

work.

Mr. Nayan Trivedi Mr. Kanaiya Sir Mr. Lokhandwala Sir

(Lecturer) (Lecturer) Head of Dept. (H.O.D)

Contents:

Sr. No. Topic Page No.

1 Acknowledgement 5

2 Chapter 1:Circuit Diagram

6

3 Chapter 2:Circuit Components

8

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4 Chapter 3:Need for Regulation

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5 Chapter 4:Summary of circuit Features

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5 Chapter 5:Internal Diagram of I.C. 7805

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6 References 19

Acknowledgement:

Hereby, we find an opportunity to thank our H.O.D. (E.C.) Lokhandwala Sir, subject advisor Nayan Trivedi Sir and Kanaiya Sir, and all those who had directly or indirectly guided and helped us for the completion of the project successfully within given time in subject Electronics and Devices- ॥. Knowing the importance

of practical knowledge along with theoretical knowledge these people has helped us in making of electronic circuit on the topic Regulated Power Supply. Under guidance of Nayan Trivedi Sir and Kanaiya Sir we completed our project of 4 th

semester E.C. and have acquired a lot from it. So we whole heartedly express our gratitude towards these people.

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CHAPTER 1:

CIRCUIT DIAGRAM

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Circuit Diagram:

The above circuit Diagram gives the regulated power supply in various ranges starting from +5v to +12v.

These supplies can be used for various purposes such as Vcc for integrated circuits, supply for IR Led, and wherever constant power supply is required.

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CHAPTER 2:

CIRCUIT COMPONENTS

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Circuit Components:

1. Resistor:

Function: A resistor is a two-terminal electrical or electronic component that opposes an electric current by producing a voltage drop between its terminals in accordance with Ohm's law: V=I*R. The electrical resistance is equal to the voltage drop across the resistor divided by the current through the resistor while the temperature remains the same. Resistors are used as part of electrical networks and electronic circuits.

Resistors used in present circuit:R1: 470 ΩR2: 330 ΩR3: 220 ΩR4: 220 Ω

2. Capacitor:

Function: A capacitor is an electrical/electronic device that can store energy in the electric field between a pair of conductors (called "plates"). The process of storing energy in the capacitor is known as "charging", and involves electric charges of equal magnitude, but opposite polarity, building up on each plate.

Capacitors are often used in electric and electronic circuits as energy-storage devices. They can also be used to differentiate between high

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frequency and low-frequency signals. This property makes them useful in electronic filters.

Capacitors used in present circuit:C1: 1000 µFC2: 100 µFC3: 0.1 µF

3. Light Emitting Diode (LED):

Function: A light-emitting diode, usually called an LED, is a semiconductor diode that emits incoherent narrow-spectrum light when electrically biased in the forward direction of the p-n junction, as in the common LED circuit.

LED used in this circuit:Red color LED (total-4)

4. Switch:

Function: To switch ON – OFF the circuit.

5. Voltage Regulator IC:

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Function: A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level.

ICs used in this circuit:7812:- Gives constant power supply of +12v.7809:- Gives constant power supply of +9v.7806:- Gives constant power supply of +6v.7805:- Gives constant power supply of +5v.

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CHAPTER 3:

THE NEED FOR REGULATION

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The need for regulation:

Why do we need a voltage regulator to supply +5v when a 6v battery should be close enough?

Logic chips generally require a very stable +5v supply. The high speed CMOS family 74HC requires a supply between 2V minimum and 5.5V absolute maximum. Running this at 6v is likely to damage the ICs. Secondly, the regulator is able to respond to small fluctuations in the input voltage caused by other loads off the same battery switching on and off. It guarantees a +5v output signal as long as its input is a certain voltage above 5v (called the drop-out voltage), and the load on it is not too high. Single chip voltage regulators are available with a range of output current capabilities, from 100mA up to 5A and higher. For our purposes, using 74HC logic at relatively low frequencies, a 1 Amp regulator should be easily sufficient.

The regulator consists of a series pass transistor, and a feedback control circuit. It continuously monitors its output voltage, and compares it with a fixed voltage reference (+5V in this case). If the output voltage rises as the load current falls, it turns the pass transistor off slightly more. As more current is drawn, the voltage at the output of the regulator will start to drop, and the regulator will turn its pass transistor on slightly more to keep it up to +5v.

The capacitor between the battery and the regulator is required to ensure there are no high frequency variations in the supply to the regulator. The capacitor after the regulator is required to supply high frequency variations in the current drawn by the logic chips, which the regulator is not fast enough to react to.

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CHAPTER 4:

SUMMARY OF CIRCUIT FEATURES

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Summary of Circuit Features:

Brief description of operation: Gives out well regulated +5V, +6v, +9v & +12v output.

Circuit protection: Built-in overheating protection shuts down output when regulator IC gets too hot.

Circuit complexity: Very simple and easy to build.

Circuit performance: Very stable mentioned output voltage, reliable operation.

Availability of components: Easy to get, uses only very common basic components.

Design testing: Based on datasheet example circuit.

Applications: Part of electronics devices, small laboratory power supply.

Power supply voltage: Unregulated DC 8-18V power supply.

Power supply current: Needed output current + 5 mA.

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CHAPTER 5:

INTERNAL DIAGRAM OF I.C. 7805

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Internal Circuit Diagram of 7805:

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Reference:

www.alldatasheet.com

www.electronicsforu.com

www.homepages.which.net/~paul.hills/Circuits/PowerSupplies/ PowerSupplies.html

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