power supply
TRANSCRIPT
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Power Supply
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What is AC ? (Alternating Current)Alternating current describes the
flow of charge that changes direction periodically. As a result, the voltage level also reverses along with the current. AC is used to deliver power to houses, office buildings, etc.
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AC can be produced using a device called an alternator. This device is a special type of electrical generator designed to produce alternating current
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Example of Alternator
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Nikola Tesla ( 10 July 1856 – 7 January 1943)was a Serbian
American inventor, electrical engineer, mechanical engineer and physicist best known for his contributions to the design of the modern alternating current (AC) electricity supply system.
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What is DC ( Direct Current )
is the unidirectional flow of electric charge. Direct current is produced by sources such as batteries, power supplies, thermocouples, solar cells, or dynamos.
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Thomas Alva Edison (February 11, 1847 – October 18, 1931was an American inventor
and businessman. He developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and the long-lasting, practical electric light bulb.
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What is Power Supply?
It is an electronic device that supplies electric energy. The primary function of a power supply is to convert one form of electrical energy to another and, as a result, power supplies are sometimes referred to as electric power converters.
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AC/DC Power Supply
It makes all electronic equipment work.
It converts AC input power line to DC Output voltage.
It is the one that supplies the desired voltage or current in a circuit.
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Examples of power supplies
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Most non-portable equipment uses power supplies that operate from the AC power line but produce one or more DC outputs.
Some modern electronic circuits need two or more different voltages.
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A good example of a modern power supply is the one inside a PC that furnishes 12, 5, 3.3 and 1.2 volts.
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Group Activity
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Discuss the following :In your group opinion what is the importance of power supply nowadays ?
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Basic Stages of a Power Supply
Filter Stage
AC Regulator
StageDC
+Rectifier
StageTransforme
r Stage -
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Transformer
steps ac voltage up or down.
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Rectifier Diodes
change ac to “bumpy” (pulsating) dc.
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Filter Network
includes capacitors and inductors, smooth's out the bumps.
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Voltage regulator
keeps the voltage constant.
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Voltage Regulator IC
Can trim down ripply voltage to precise, rock-steady value
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Now things get complicated!We are now in the realm of
integrated circuits (ICs)ICs are whole circuits in
small packagesICs contain resistors,
capacitors, diodes, transistors, etc.
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Voltage Regulator ICThe most common voltage regulators are
the LM78XX (+ voltages) and LM79XX (- voltages)
XX represents the voltage:ex. 7815 is +15; 7915 is +15; 7805 is +5, etc
typically needs input >3 volts above output (reg.) voltage
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beware that housing is not always ground
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Types of AC/DC Power Supply
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Half-Wave Rectifier CircuitOne rectifier diode D1 and one
load resistor RL are needed to conduct one alteration in every cycle of small AC input.
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Full-Wave Center-Tapped Rectifier CircuitUsing this type of circuit, you’ll
need a center-tapped transformer, two rectifier diodes and a load resistor (RL). Each of the diode supplies one-half the DC load current.
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Full-Wave Bridge Type Rectifier Circuit
The Full-Wave Bridge Type Rectifier Circuit uses four rectifier diodes D1 D2 D3 D4 and a load resistor (RL).
The conduction of AC voltage starts from Line-A going to the Line-B.
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Among the types of power supply this circuit can deliver a higher current range to the load because all of cycles are consumed by the four diodes.
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Filtering StageThe filtering stage is one of the
stages of the power supply which filters the pulsating DC.
Output of rectifier stage and make it a pure DC voltages.
The main function of the filter circuit is to increase the DC output and to smoothen the pulsating DC
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Important Concept
• Half Wave Rectifier:– Simplest.– Hard to filter well.
• Full Wave Rectifier:– Easier to filter.– Requires transformer with center-tap.– Transformer secondary must be twice
intended voltage.
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• Bridge Rectifier:– Easier to filter (just like full wave).– Center-tap transformer not required.– Transformer secondary same as
intended voltage.– Higher parts count.
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External Parts
FRONT PANELIt contains the power switch,
voltage selector switch, and the power indicator.
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External Parts
REAR PANELIt contains the fuse and the AC line
cord.
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External Parts
Alligator ClipA special type of connector used
to connect the power supply to the electronic gadget.
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Internal Parts
CapacitorA capacitor acts as the filter.The one that removes ripples from
the output of the rectifier circuit.The type of capacitor used in this
purpose is the electrolytic capacitor.
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Internal Parts
DiodeA device which only allows current
to flow in only one direction.
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Internal Parts
FuseA protective device used to
prevent the circuit from short circuit or damage.
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Internal Parts
LED/Light Emitting DiodeA transducer which converts
electrical energy to light.
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Line cordA type of cord used to connect the unit to the voltage source.
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Internal Parts
On-Off switchUsed to switch on and off the circuit.
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Internal Parts
Printed Circuit Board“PCB”– a conductive pattern formed on one or both sides of an insulating base by etching, plating or stamping.
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Internal PartsResistorA resistor restricts the flow of current (eg. to limit the current passing through an LED). A resistor is used with a capacitor in a timing circuit. Some publications still use the old resistor symbol.
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Internal Parts
Rotary SwitchA switch that is operated by a rotating shaft.
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Internal Parts
TransformerA component that consist of two or more coils which are coupled together by magnetic induction.