Dc Voltage Regulators

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DC VOLTAGE REGULATORS

Group 2Maha Amin 2010-EE-

064Ayesha Hafeez 2010-EE-

063Aaisha Tahir 2010-EE-

062Arooj Mobasher 2010-EE-

061

PresentedBy:


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What are DC voltage regulators?

A voltage regulator is an electrical regulator designed toautomatically maintain a constant voltage level (converts an inputDC voltage to a fixed output DC voltage)

Types

I. Zener diode based regulators

II. ICs for regulators

INTRODUCTION

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As the load current varies, the output voltage also varies

because of its poor regulation.

The DC output voltage varies directly with AC inputsupply. The input voltage may vary over a wide rangeand to keep the output DC constant, we use regulators.

The dc output voltage varies when the temperaturesensitive devices are used in the input circuitry or asload.

Poor voltage levels damages the chip and otherequipment which causes monetary loss as well.

The high fluctuation in the voltage effects the equipment

NEED FOR VOLTAGE REGULATORS

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LOAD REGULATION is the change in output voltagefor a given change in load current (for example:

typically 15mV, maximum 100mV for load currentsbetween 5mA and 1.4A, at some specifiedtemperature and input voltage)

LINE REGULATION or input regulation is the degree

to which output voltage changes with input (supply)voltage changes - as a ratio of output to input change

MEASURE OF REGULATEDQUALITY

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Every voltage regulator consists of four basic elements:

i. a stable reference voltageii. a voltage sampling element

iii. a voltage comparator and

iv. a power dissipating control device.

Control element

SamplingElement

Reference

comparator

input

output

BASIC VOLTAGE REGULATOR

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ZENER DIODE AS REGULATORS

Referring to zener I-Vcharateristic curve

Work as voltage

regulator in revesebreakedown reagon

This can be verifiedby theveinenequivalent citcuit 5


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IfVTH < VZ, regulation does notoccur. IfVTH >VZ, regulation occurs.

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TRNSISTOR AS A VOLTAGEREGULATOR

Series Regulator

Emitter FollowerVoltageRegulator

Series PassTransistor

WorkingPrinciple

Vout = Vz - Vbe

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EFFECTS ON Vout

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OP-AMP AS VOLTAGE REGULATOR

Three things are required for voltage regulation with OP-AMP

a. zener diode

b. Transistor

c. opamp

WORKING

a. A precision reference (zener diode) to set the output voltage.b. A muscle component (transistor) to deliver the required current.

c. An automatic controller (opamp) to adjust the transistor drive.

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CIRCUIT DIAGRAM

ZENERDIODE

OP-AMP

TRANSISTOR

Resistor to setvariable output level

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ICs FOR VOLTAGEREGULATION

a. The 78xx (sometimes LM78xx) is a family of self-containedfixed linear voltage regulator integrated circuits

b. For ICs within the family, the xx is replaced with two digits,indicating the output voltage

ADVANTAGESi. require NO additional components to provide a constant

voltage

i. ICs are economical

ii. efficient uses of spaceiii. ICs have built-in protection against a circuit drawing too

much power

DISADVANTAGES

i. Restricted power supply.ii. Heat sinks are needed. 11


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CIRCUIT DIAGRAM

Voltage regulator Ic

Glow if input is morethan 6.5V

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APPLICATIONS OFVOLTAGE

REGULATORS

1. Solar Photovoltaic Systems:

They regulate the

current from thesolar panel array tothe battery toprovide optimum

current controlduring charge

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2. DC Voltage Regulator

for Car Alternators: 14


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3. Electric PowerDistribution System

In an electric distribution system,

voltage regulators may be installed at asubstation or along distribution lines sothat all customers receive steady voltageindependent of how much power is drawn

from the line.

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3. Electronic Devicesand Appliances:

From electronic devices like PCs, 16


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Conclusion:

Thus DC Voltage Regulators

are immensely important for the

safety of countless modern day

devices and appliances.

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Dc Voltage Regulators