This document provides information about power supplies. It begins by defining alternating current (AC) and direct current (DC), and how they are produced. Nikola Tesla and Thomas Edison contributed to the development of AC and DC systems, respectively. The core functions of a power supply are then explained as converting one type of electrical energy to another. Different stages in a basic power supply are identified as the transformer, rectifier, filter and voltage regulator. Examples are given of various power supply types and components, both internal and external.

1. POWER
SUPPLY

2. 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.

3. ▶AC CAN BE PRODUCED USING A
DEVICE CALLED AN ALTERNATOR.
THIS DEVICE IS A SPECIAL TYPE OF
ELECTRICAL GENERATOR DESIGNED
TO PRODUCE ALTERNATING
CURRENT

4. EXAMPLE OF
ALTERNATOR

5. 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.

6. 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.

7. THOMAS ALVA EDISON (FEBRUARY 11,
1847 – OCTOBER 18, 1931
▶was 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.

8. 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.

9. 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.

10. EXAMPLES OF POWER
SUPPLIES

11. ▶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.

12. ▶A GOOD EXAMPLE OF A
MODERN POWER SUPPLY IS
THE ONE INSIDE A PC THAT
FURNISHES 12, 5, 3.3 AND 1.2
VOLTS.

13. GROUP
ACTIVITY

14. Discuss the following :
In your group opinion what is the
importance of power supply nowadays ?

15. BASIC STAGES OF A POWER SUPPLY
Filter
Stage
AC
Regulator
Stage DC
+
Rectifier
Stage
T
ransformer
Stage
-

16. Transformer
▶steps ac voltage up or down.

17. Rectifier Diodes
▶change ac to “bumpy” (pulsating) dc.

18. Filter Network
▶includes capacitors and inductors,
smooth's out the bumps.

19. Voltage regulator
▶keeps the voltage constant.

20. Voltage Regulator IC
▶Can trim down ripply
voltage to precise, rock-
steady value

21. ▶NOW THINGS GET
COMPLICATED!
▶We are now in the realm of
integrated circuits (ICs)
▶ICs are whole circuits in
small packages
▶ICs contain resistors,
capacitors, diodes,
transistors, etc.

22. VOLTAGE
REGULATOR IC
▶The 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

23. beware that housing is not
always ground

24. TYPES OF AC/DC POWER SUPPLY

25. HALF-WAVE RECTIFIER
CIRCUIT
▶One rectifier diode D1 and one load
resistor RL are needed to conduct
one alteration in every cycle of small
AC input.

27. Full-Wave Center-Tapped Rectifier
Circuit
▶Using 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.

29. 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.

30. ▶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.

34. FILTERING
STAGE
▶The 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

35. 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.

36. • Bridge Rectifier:
– Easier to filter (just like full wave).
– Center-tap transformer not required.
– Transformer secondary same as intended
voltage.
– Higher parts count.

37. EXTERNAL
PARTS
FRONT PANEL
▶It contains the power switch, voltage
selector switch, and the power
indicator.

38. EXTERNAL PARTS
REAR PANEL
▶It contains the fuse and the AC line
cord.

39. EXTERNAL
PARTS
Alligator Clip
▶A special type of connector used to
connect the power supply to the
electronic gadget.

40. INTERNAL
PARTS
Capacitor
▶A 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.

41. INTERNAL PARTS
Diode
▶A device which only allows current to
flow in only one direction.

42. INTERNAL PARTS
Fuse
▶A protective device used to prevent
the circuit from short circuit or
damage.

43. INTERNAL PARTS
LED/Light Emitting Diode
▶A transducer which converts electrical
energy to light.

44. Line cord
A type of cord used to connect the unit
to the voltage source.

45. Internal Parts
On-Off switch
Used to switch on and off the circuit.

46. INTERNAL PARTS
Printed Circuit Board
“PCB”– a conductive pattern formed on
one or both sides of an insulating base
by etching, plating or stamping.

47. INTERNAL
PARTS
Resistor
A 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.

48. INTERNAL PARTS
Rotary Switch
A switch that is operated by a rotating
shaft.

49. INTERNAL PARTS
Transformer
A component that consist of two or more
coils which are coupled together by
magnetic induction.