A power supply is an electronic device that supplies electric energy to an electrical load. The primary function of a power supply is to convert one form of electrical energy to another. As a result, power supplies are sometimes referred to as electric power converters. Some power supplies are discrete, stand-alone devices, whereas others are built into larger devices along with their loads. Examples of the latter include power supplies found in desktop computers and consumer electronics devices.

1. Classification of Power Supply
and Its Different Types

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3. Power Supply
• The power supply unit is the part of the hardware that is used to
convert the power provided from the outlet into usable power to
many parts inside an electrical device.
• Every energy supply must drive its load, which is connected to it.
• Depending on its design, a power supply unit may obtain energy
from various types of energy sources, like electrical energy
transmission systems, electromechanical systems such as
generators and alternators, solar power converters, energy
storage devices such as a battery and fuel cells, or other power
supply.
• There are two types of power supplies existed, AC and DC power
supply. Based on the electrical device’s electric specifications it
may use AC power or DC power.

4. Different Types of Power Supply

5. Variable AC Power Supply
• The different AC voltages are
generated by using a transformer.
• The transformer may have multiple
windings or taps, in which case the
instrument uses switches to select the
different voltage levels.
• Alternatively, a variable transformer
(adjustable autotransformer) can be
used to continuously vary the
voltages.
• Some variable AC supplies are
included meters to monitor the
voltage, current, and/or power.

6. Unregulated Linear Power Supply
• Unregulated power supplies contain a
step-down transformer, rectifier, filter
capacitor, and a bleeder resistor.
• This type of power supply, because of
simplicity, is the least costly and most
reliable for low power requirements.
• The main disadvantage is that the
output voltage is not constant.
• It will vary with the input voltage and
the load current, and the ripple is not
suitable for electronic applications.
• The ripple can be reduced by changing
the filter capacitor to an LC (inductor-
capacitor) filter, but the cost becomes
more.

7. Regulated Linear Power Supply
• Regulated linear power supplies are same to
the unregulated linear power supply except
that a 3-terminal regulator is used in place of
the bleeder resistor.
• The main aim of this supply is to provide the
required level of DC power to the load.
• The DC power supply uses an AC supply as the
input.
• Different applications require different levels
of attributes voltages, but nowadays the DC
power supplies provide an accurate output
voltage.
• And this voltage is regulated by an electronic
circuitry so that it provides a constant output
voltage over a wide range of output loads.

8. Switch Mode Power Supply (SMPS)
• The AC voltage is rectified to an
unregulated DC voltage, with the
series transistor and the regulator.
• This DC is chopped to a constant
high-frequency voltage which
enables the size of the transformer
to be dramatically reduced and
allows for a much smaller power
supply.
• The disadvantages of this type of
supply are that all of the
transformers have to be custom-
made and the complexity of the
power supply does not lend itself to
low production or economical low
power applications.

9. Uninterruptible Power Supply (UPS)
• UPS is a Backup power
source that, in the case of
power failure or
fluctuations, allows enough
time for an orderly
shutdown of the system or
for a standby generator to
start up.
• UPS consists usually of a
bank of rechargeable
batteries and power sensing
and conditioning circuitry.

10. Power System Protection