Power Supply Design and Operation for Electronic Appliances

Engineering 1
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Engineering 2
ABSTRACT
Electrical energy is the flow of electrons which create electric power. Through the
implementation of the power supply, therefore it is possible to manipulate electrical power at the
output. Power supplies, therefore, are the devices which have the obligation of manipulating the
electrical power to be employed in various applications. A power supply includes input
transformer, rectifier, smoothening and regulator. This report will clearly illustrate the power
supply design and the operation. Amplifier basically is an electronic component which is
employed in the augmentation of the electrical signal. There are several types of amplifiers, some
are; summing, inverting, non- inverting and a differential amplifier. Each type of amplifier
performs a specific function. Power supply unit has been studied with its main components
taking into account protections and op-amp circuits and transformers are also analyzed. When
several experiments are done for the power supply the following results are quite satisfactory and
learned a lot that how to measure the single with respect to the input.
Input 1 Volts Input 2 volts Output
1 0 -1.03
1 0.2 -0.83
1 0.4 -0.61
1 0.6 -0.38
1 1 -0.83
1 1.2 0.01
1 1.4 0.19
Table 1

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TABLE OF CONTENT
Contents
ABSTRACT................................................................................................................................................2
INTRODUCTION.......................................................................................................................................3
Purpose of the project..............................................................................................................................5
Aim of the project....................................................................................................................................5
THEORY.....................................................................................................................................................6
Power supply...........................................................................................................................................6
Stepping down transformer..................................................................................................................6
Rectifier...............................................................................................................................................6
Filtering...............................................................................................................................................7
Voltage Regulation..............................................................................................................................8
OP-amp...................................................................................................................................................9
RISK ASSESSMENT...............................................................................................................................15
METHOD..................................................................................................................................................15
Power supply.........................................................................................................................................15
Op-amp..................................................................................................................................................17
1. Inverting amplifier.....................................................................................................................17
2. Summing amplifier....................................................................................................................17
3. Non- Inverting amplifier............................................................................................................17
4. Differential amplifier.................................................................................................................18
RESULTS.................................................................................................................................................18
DISCUSSION...........................................................................................................................................23
CONCLUSION.........................................................................................................................................29
Bibliography...............................................................................................................................................30
Appendix...................................................................................................................................................31
INTRODUCTION
The power that comes from the generation station travels several miles to reach the consumers.

Engineering 4
In this case, AC current is employed. AC has different phases depending on the usage of the
power. In disparity to AC, there is DC which doesn't alternate the Current, it has a steady current
at the output to be applied to circuits. DC hence is suitable for circuit design this is due to many
of the components use DC power. Through the wall socket many different devices
Are plugged in and used daily but most of these devices require DC to work correctly.
As the plug is inserted into a socket outlet AC will be converted to DC. This is done using the
full wave rectifier as seen in the diagrams below. The electronics will not use AC but DC.
Fig 1: Showing rectification diagram and waveform after rectification
Operational amplifiers are linear electronic components which can be employed in filtering as
well as doing some mathematical operations such as differentiation, integration, addition and
subtract. OPamp is an electronic device made to be employed with external feedback device like
capacitors and resistors between its output and input terminals. The feedback part governs the

Engineering 5
resulting function of the amplifier. The diagram below illustrates the amplifiers for inverting and
non- inverting respectively
Fig 2: Showing the inverting and non-inverting Op-amp with the feedback connected
Purpose of the project
The purpose of this project is to develop a power supply unit having rectifier for voltage
regulation which can be used by electronic appliances. The project will as well help in stepping
down the voltage to smaller values which can be used by low voltage devices like LED.
Aim of the project
The aim of this project is to study and analyze the main components of power systems taking
into account protections and op-amp circuits and transformers (Bird, 2013).

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THEORY
Power supply
Stepping down transformer
For the power supply, the voltage is obtained from an AC source at a higher voltage which is
then stepped down to a relatively lower voltage which can hence be used by the electronic
devices. This is then followed by rectification where the AC voltage is converted to DC voltage.
Fig 3: Showing the circuit diagram for step down transformer with the rectification circuit.
The secondary voltage can be obtained from the following relationship
N 1
N 2 = V 1
V 2 = I 2
I 1 ....................................................................................... 1
Rectifier
This is an electrical component which converts AC to DC (flowing in one direction). A bridge
rectifier is employed since it offers a full wave rectification. The rectification is suitable for most
appliances use DC voltage. The diagram below illustrates the rectifier circuit (Kuphald, 2010).
The voltage output for a single phase full wave is obtained by the following equation
Vdc= 2Vp
π ............................................................................................ 2

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Fig 4: Showing the reciter circuit diagram.
Resultant output of the waveforms after rectification will appear as below
Fig5: Showing a resultant DC waveform
The current in the ideal diode is obtained by
IF = Vbias−VF
Ilimit .............................................................................................. 3
And the peak inverse voltage is obtained as below for a full wave rectifier
PIV = Vp( out) + 0.7 V ..................................................................... 4

Engineering 8
Filtering
Filtering is the process where the ripples frequency from the DC after the rectification are
removed. Through the design, the value of R is kept much larger than XC1. Therefore the ripples
are dropped across the series resistor R instead of across RC. Ideally, R is kept at about 10 times
more than XC2 (Sahay, 2012). This will imply that each section will reduce the ripples by a factor
of 10. The diagram below shows the filtering circuit diagram;
The V out from filter circuit diagram is obtained by the following
Vout= Vin × XC
√ R2+ XC2 ............................................................ 5
The cutoff frequency of the filter circuit is given by the below equation
Cutoff frequency = 1
2 πRC ........................................................................ 6
Fig 6: Showing the RC circuit diagram of the filter.
Voltage Regulation