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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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