01

Power supply

CONTENTS PAGE

INTRODUCTION……………………………………………………………………………………..

TASK 1

2.0 Linear Power Supply………………………………………………………………………………

3.0 Switched-mode power supply SMPS…………………………………………………………….

TASK 2

4.0 Project Description and Introduction…………….…………………………………………………………………

5.0 Power Supplies circuit………………………………………………………………………………

6.0 Operation of Circuit……………………………………………………………………………

7.0 Estimate coast……………………………………………………………………………………….

8.0 PLANNING SCHEDULE OF THE PROJECT (Gantt chart)...................................................

9.0 Reference…………………………………………………………………………………………….

02

POWER SUPPLY

Introduction

Power supply is a reference to a source of electrical power. A device or system that supplies

electrical or other types of energy to an output load or group of loads is called a power supply

unit or PSU. The term is most commonly applied to electrical energy supplies, less often to

mechanical ones, and rarely to others. The commercial power system is an ac system. The

standard ac power line voltage in Malaysia is 240v which is available at wall outlets. Every

electronic system has to have a source of dc voltage to operate the various components. To

operate electronic component we need to convert ac power line to dc by using some circuit of

power supplies. The power supply must convert the ac power line voltage to dc voltage of

appropriate value before it can be used for electronic device operation. Power supplies can be

low or high voltage. Low voltage powers supplied are used to provide the voltages required to

operate transistor stages and integrated circuits. High voltage power supplies are used to

provide the high levels of voltage required by television picture, for example. In this report we

are going to investigate two main types of regulated power supplies available: SMPS and linear.

Types of Power Supply

There are many types of power supply. Most are designed to convert high voltage AC mains

electricity to a suitable low voltage supply for electronic circuits and other devices. A power

supply can by broken down into a series of blocks, each of which performs a particular function.

For example a 5V regulated supply:

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04

Linear Power Supply

The basic design model for a power supply consists of a control element in series with a

rectifier and load device. A simplified schematic of a series-regulated supply with the phase-

controlled pre-regulator depicted as a power switch and the series element depicted as a

variable resistor shown in Figure 1.0 . The phase-controlled pre-regulator minimizes the power

dissipated at the series element by maintaining a low and constant voltage drop across the

series element. Feedback control circuits continuously monitor the output and adjust the series

resistance to maintain a constant output voltage. The variable resistance series element of the

supply shown in Figure 1.0 is actually produced by one or more power transistor operating in

the linear (class A) mode; supplies with this type of regulator are often called linear power

supplies. Linear power supplies have many advantages. Because they provide sufficient power

with stable regulation and little noise, they usually are the simplest, most effective solution for

providing bench power.

Figure 1.0

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The power supply shown in Figure 1.0 has two ranges, allowing more voltage at a lower

current or more current at a lower voltage. Single-range supplies can output maximum power

only at full-scale voltages and full-scale current. A linear supply can provide output power that is

close to maximum at full scale for both ranges. The pre-regulator in this power supply uses

solid-state transformer tap switches on the secondary winding of the power transformer. This

technique is very effective in reducing the power dissipated in the series element.

In terms of performance, a linear regulated supply has very precise regulating properties

and responds quickly to variations of the line and load. Hence, its line and load regulation and

transient recovery time are superior to supplies using other regulation techniques. A linear

power supply also exhibits low ripple and noise, tolerates ambient temperature changes, and is

highly reliable due to its circuit simplicity.

The linear regulator is controlled by a DAC driven by a digital circuit that provides a

voltage proportional to the program voltage. The power supply sends back to the control circuits

a voltage representing the output at the terminals. The control circuits receive information from

the front panel and send information to the display. Similarly, the control circuits “talks” to the

remote interface for input and output with the GPIB, RS-232, USB, or LAN interfaces. The

remote interface is at earth ground and is optically isolated from the control circuit and the

power supply.

06

Switched-mode power supply

A switched-mode power supply, switching-mode power supply or SMPS, is an electronic power

supply unit (PSU) that incorporates a switching regulator. While a linear regulator maintains the

desired output voltage by dissipating excess power in a "pass" power transistor, the SMPS

rapidly switches a power transistor between saturation (full on) and cutoff (completely off) with a

variable duty cycle whose average is the desired output voltage. The resulting rectangular

waveform is low-pass filtered with an inductor and capacitor. The main advantage of this

method is greater efficiency because the switching transistor dissipates little power in the

saturated state and the off state compared to the semiconducting state (active region). Other

advantages include smaller size and lighter weight (from the elimination of low frequency

transformers which have a high weight) and lower heat generation from the higher efficiency.

Disadvantages include greater complexity, the generation of high amplitude, high frequency

energy that the low-pass filter must block to avoid EMI, and a ripple voltage at the switching

frequency and the harmonic frequencies thereof.

07

SMPS can be classified into four types according to the input and output waveforms, as follows.

* AC in, DC out: rectifier, off-line converter input stage.

* DC in, DC out: voltage converter, or current converter, or DC to DC converter

* AC in, AC out: frequency changer, cycloconverter

* DC in, AC out: inverter

SMPS and Linear Power Supply comparison

There are two main types of regulated power supplies available: SMPS and linear. The reasons

for choosing one type or the other can be summarized as follows.

Comparison of a Linear power supply and a switched-mode power supply

Linear power

supplySwitching power supply Notes

Size and

weight

Huge due to low

operating frequency

(mains power

frequency is at 50 or

60 Hz)

Smaller due to higher

operating frequency

(typically 50 kHz - 1 MHz)

A transformer's power handling

capacity of given size and weight

increases with frequency

provided that hysteresis losses

can be kept down. Therefore,

higher operating frequency

means either higher capacity or

08

smaller transformer.

Output

voltage

Output can only

produce a

positive/negative

voltage which varies

depending on

loading.

Output is able to produce a

voltage lower, higher or

even negative to the input

voltage with superior

regulation.

A SMPS can usually cope with

wider variation of input before the

output voltage changes.

Efficiency,

heat, and

power

dissipation

Output voltage is

regulated by

expending excess

power as heat, which

is inefficient.

Output is regulated using

duty cycle control, which

draws only the power

required by the load. In all

SMPS topologies, the

transistors are always

switched fully on or fully off.

The only heat generated is in the

non-ideal aspects of the

components. Switching losses in

the transistors, on-resistance of

the switching transistors,

equivalent series resistance in

the inductor and capacitors, and

rectifier voltage drop will lower

SMPS efficiency. However, by

optimizing SMPS design, the

amount of power loss and heat

can be minimized. A good design

can have an efficiency of 95%.

Complexity

Consists of a voltage

regulating IC or

discrete circuit and a

noise filtering

capacitor.

Consists of a controller IC,

one or several power

transistors and diodes as

well as a power

transformer, inductors, and

filter capacitors.

Multiple voltages can be

generated by one transformer

core. For this SMPSs have to

use duty cycle control. Both need

a careful selection of their

transformers. Due to the high

operating frequencies in SMPSs,

the stray inductance and

capacitance of the printed circuit

board traces become important.

Radio

frequency

interference

No interference

produced, except

possibility of mains

EMI/RFI produced due to

the current being switched

on and off sharply.

Long wires between the

components may reduce the high

frequency filter efficiency

09

hum induction into

unshielded cables.

Therefore, EMI filters and

RF shielding are needed to

reduce the disruptive

interference.

provided by the capacitors at the

inlet and outlet.

Electronic

noise at the

output

terminals

Unregulated PSUs

may have a small

amount of AC "riding

on" the DC

component at twice

the main frequency

(100-120 Hz). This

can cause an audible

mains hum in audio

equipment or

unexpected

brightness ripples or

other banded

distortions in analog

security cameras.

Noisier due to the switching

frequency of the SMPS. An

unfiltered output may cause

glitches in digital circuits or

noise in audio circuits.

This can be suppressed with

capacitors and other filtering

equipment in the output stage.

Electronic

noise at the

input

terminals

Causes harmonic

distortion to the input

AC, but no high

frequency noise.

Very low cost SMPS may

couple electrical switching

noise back onto the mains

power line, causing

interference with A/V

equipment connected to the

same phase. Non power-

factor-corrected SMPSs

also cause harmonic

distortion.

This can be prevented if a

(properly earthed) EMI/RFI filter

is connected between the input

terminals and the bridge rectifier.

Acoustic

noise

Faint, usually

inaudible mains hum,

usually due to

vibration of windings

in the transformer

Inaudible to humans, unless

they have a fan or are

unloaded/malfunctioning.

The operating frequency of an

unloaded SMPS is sometimes in

the audible human range.

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and/or

magnetostriction.

Power

factor

Low because current

is drawn from the

mains at the peaks of

the voltage sinusoid.

Ranging from low to

medium since a simple

SMPS without PFC draws

current spikes at the peaks

of the AC sinusoid.

Active/Passive power factor

correction in the SMPS can

offset this problem and are even

required by some electric

regulation authorities, particularly

in Europe.

Risk of

electric

shock

Limited to either the

full mains voltage or

the secondary

terminals in contact

with the body.

Common rail of equipment

(including casing) is

energised to half mains

voltage unless equipment is

earthed/grounded or doesn't

contain EMI/RFI filtering at

the input terminals.

Due to regulations concerning

EMI/RFI radiation, many SMPS

contain EMI/RFI filtering at the

input stage before the bridge

rectifier consisting of capacitors

and inductors. Two capacitors

are connected in series with the

Live and Neutral rails with the

Earth connection in between the

two capacitors. This forms a

capacitive divider that energises

the common rail at half mains

voltage. Its high impedance

current source can provide a

tingling or a 'bite' to the operator

or can be exploited to light an

Earth Fault LED. However, this

current may cause nuisance

tripping on the most sensitive

residual-current devices.

Risk of

equipment

destruction

Very low, unless a

short occurs between

the primary and

secondary windings

or the regulator fails

by shorting internally.

Capable of destroying input

stages in amplifiers due to

the floating voltage being

above the base-emitter

breakdown voltage of the

transistor, causing the

The floating voltage is caused by

capacitors bridging the primary

and secondary sides of the

power supply. A connection to

earthed equipment will cause a

momentary (and potentially

011

transistor's gain to drop and

noise levels to increase.

destructive) spike in current at

the connector as the voltage at

the secondary side of the

capacitor equalises to earth

potential.

How an SMPS works

Block diagram of a mains operated AC-DC SMPS with output voltage regulation.

Input rectifier stage

012

AC, half-wave and full wave rectified signals

If the SMPS has an AC input, then the first stage is to convert the input to DC. This is called

rectification. The rectifier circuit can be configured as a voltage doubler by the addition of a

switch operated either manually or automatically. This is a feature of larger supplies to permit

operation from nominally 120 volt or 240 volt supplies. The rectifier produces an unregulated

DC voltage which is then sent to a large filter capacitor. The current drawn from the mains

supply by this rectifier circuit occurs in short pulses around the AC voltage peaks. These

pulses have significant high frequency energy which reduces the power factor. Special control

techniques can be employed by the following SMPS to force the average input current to

follow the sinusoidal shape of the AC input voltage thus the designer should try correcting the

power factor. A SMPS with a DC input does not require this stage. An SMPS designed for AC

input can often be run from a DC supply (for 230V AC this would be 330V DC), as the DC

passes through the rectifier stage unchanged. It's however advisable to consult the manual

before trying this, though most supplies are quite capable of such operation even though

nothing is mentioned in the documentation. However, this type of use may be harmful to the

rectifier stage as it will only utilize half of diodes in the rectifier for the full load. This may result

in overheating of these components, and make them fail as short circuits.

If an input range switch is used, the rectifier stage is usually configured to operate as a

voltage doubler when operating on the low voltage (~120 VAC) range and as a straight

rectifier when operating on the high voltage (~240 VAC) range. If an input range switch is not

used, then a full-wave rectifier is usually used and the downstream inverter stage is simply

designed to be flexible enough to accept the wide range of dc voltages that will be produced

by the rectifier stage. In higher-power SMPSs, some form of automatic range switching may

be used1.

1 http://en.wikipedia.org/w/index.php?title=Switched-mode_power_supply&amp

013

014

015

PROJECT DESCRIPTION AND INTRODUCTION

Rollimited electronics cooperation is the company which designs, manufactures, and test a wide variety

of products. I as a technician have given an assignment to develop and test a dc power supply that will

be used in several different products such as an individual counting system, supply for project board, a

security alarm and etc.

I am now working to make the project to produce power supply for project board. When I going to have

device like project board, several question might be considered base on the customer needs2, and the

consideration are as follows:

1. What do you expect from power supply?

2. How about the voltage that you prefer?

3. Suggestion on the material that can be used?

4. Any request about the weight and design of the circuit?

5. How about the costing of each power supply?

6. Any safety precaution? Request?

7. How about the suitable use?

2 Refer the MATRIX VALUATE ANALYSIS IN ENG. DESIGN

016

1. Easy to used

2. The output voltage fixed to 12v and 5v

3. The Material used is long lasting and high durability.

4. Reduce the weight

5. Not more than RM50.00

6. Don’t have any extension circuit.

7. Just suitable for small voltage component.

The new concept of this power supply is to upgrade and improve the existing product available

at current market. So the requirements from the market or the customers are imperative and must be

followed unless very good justifications need to be provided in this report. This product function is to

supply a fixed voltage 12v and 5v at a time to project board. Otherwise these products also save time

because this power supply is 2 in 1 and save budget. The price of this product is not less than RM 50.00

and user friendly.

POWER SUPPLY CIRCUIT

IN

COM

OUT

IC1LM7805

+5

+12

+

-

AC230V

D(1-4)=1N4007

BRIDGE120V/0-12 AC

C347uF/25V

C247uF/25V

GND2

+C1

1000uF

IN

COM

OUT

IC2LM7812

Figure 1

017

Power Supplies circuit

The dc power supply that will be produce by Rollimited electronics Cooperation Company is shown in figure 1 below.

The basic specifications are as follows:

Input voltage: 240V Output voltage (regulated ):5V dc and 12V dc ±10% Maximum ripple factor: 3% Maximum load current :250mA

Component

Diode 1N4001 Capacitor 1000µf Capacitor 47µf/25v 2 unit IC regulator LM7805 IC regulator LM7812

018

The operation involve in this circuit

Each of the blocks is described in more detail below:

Transformer - steps down high voltage AC mains to low voltage AC.

Rectifier - converts AC to DC, but the DC output is varying.

Smoothing - smooths the DC from varying greatly to a small ripple.

Regulator - eliminates ripple by setting DC output to a fixed voltage.

Power supplies made from these blocks are described below with a circuit diagram and a graph of their output:

Transformer only

Transformer + Rectifier

Transformer + Rectifier + Smoothing

Transformer + Rectifier + Smoothing + Regulator

019

Transformer

Transformers convert AC electricity from one voltage to another with little loss of power. Transformers work only with AC and this is one of the reasons why mains electricity is AC.

Step-up transformers increase voltage, step-down transformers reduce voltage. Most power supplies use a step-down transformer to reduce the dangerously high mains voltage (230V) to a safer low voltage.

The input coil is called the primary and the output coil is called the secondary. There is no electrical connection between the two coils, instead they are linked by an alternating magnetic field created in the soft-iron core of the transformer. The two lines in the middle of the circuit symbol represent the core.

Transformers waste very little power so the power out is (almost) equal to the power in. Note that as voltage is stepped down current is stepped up.

The ratio of the number of turns on each coil, called the turns ratio, determines the ratio of the voltages. A step-down transformer has a large number of turns on its primary (input) coil which is connected to the high voltage mains supply, and a small number of turns on its secondary (output) coil to give a low output voltage.

turns ratio = Vp

= Np

and power out = power in

Vs Ns Vs × Is = Vp × Ip

Vp = primary (input) voltageNp = number of turns on primary coilIp = primary (input) current

Vs = secondary (output) voltageNs = number of turns on secondary coilIs = secondary (output) current

020

The low voltage AC output is suitable for lamps, heaters and special AC motors. It is not suitable for electronic circuits unless they include a rectifier and a smoothing capacitor. For this circuit, type of this transformer is step down and input for this transformer we use 230V AC and the output is 6v.

DATA SHEET OF TRANSFOMER

Specification Model : HT-6E1Input AC 115V/230VOutput 6V 0 6VCapacity 1000mANet weight 331g

021

Diode

Example: Circuit symbol:

Function

Diodes allow electricity to flow in only one direction. The arrow of the circuit symbol shows the direction in which the current can flow. Diodes are the electrical version of a valve and early diodes were actually called valves.

Forward Voltage Drop

Electricity uses up a little energy pushing its way through the diode, rather like a person pushing through a door with a spring. This means that there is a small voltage across a conducting diode, it is called the forward voltage drop and is about 0.7V for all normal diodes which are made from silicon. The forward voltage drop of a diode is almost constant whatever the current passing through the diode so they have a very steep characteristic (current-voltage graph).

Reverse Voltage

When a reverse voltage is applied a perfect diode does not conduct, but all real diodes leak a very tiny current of a few µA or less. This can be ignored in most circuits because it will be very much smaller than the current flowing in the forward direction. However, all diodes have a maximum reverse voltage (usually 50V or more) and if this is exceeded the diode will fail and pass a large current in the reverse direction, this is called breakdown.

022

RectifierThere are several ways of connecting diodes to make a rectifier to convert AC to DC. The bridge rectifier is the most important and it produces full-wave varying DC. A full-wave rectifier can also be made from just two diodes if a centre-tap transformer is used, but this method is rarely used now that diodes are cheaper. A single diode can be used as a rectifier but it only uses the positive (+) parts of the AC wave to produce half-wave varying DC.

Rectifier diodes (large current)

Rectifier diodes are used in power supplies to convert alternating current (AC) to direct current (DC), a process called rectification. They are also used elsewhere in circuits where a large current must pass through the diode.

All rectifier diodes are made from silicon and therefore have a forward voltage drop of 0.7V. The table shows maximum current and maximum reverse voltage for some popular rectifier diodes. The 1N4001 is suitable for most low voltage circuits with a current of less than 1A.

DiodeMaximumCurrent

MaximumReverseVoltage

1N4001 1A 50V

1N4002 1A 100V

1N4007 1A 1000V

1N5401 3A 100V

1N5408 3A 1000V

023

Transformer + Rectifier

Bridge rectifier (full-wave rectifier)

Alternate pairs of diodes conduct, changing over the connections so the alternating directions of AC are converted to the one direction of DC

024

Capacitors

Electrolytic Capacitors (Electrochemical type capacitors)

Aluminum is used for the electrodes by using a thin oxidization membrane.Large values of capacitance can be obtained in comparison with the size of the capacitor, because the dielectric used is very thin.The most important characteristic of electrolytic capacitors is that they have polarity. They have a positive and a negative electrode.[Polarised] This means that it is very important which way round they are connected. If the capacitor is subjected to voltage exceeding its working voltage, or if it is connected with incorrect polarity, it may burst. It is extremely dangerous, because it can quite literally explode. Make absolutely no mistakes.Generally, in the circuit diagram, the positive side is indicated by a "+" (plus) symbol.Electrolytic capacitors range in value from about 1µF to thousands of µF. mainly this type of capacitor is used as a ripple filter in a power supply circuit, or as a filter to bypass low frequency signals, etc. Because this type of capacitor is comparatively similar to the nature of a coil in construction, it isn't possible to use for high-frequency circuits. (It is said that the frequency characteristic is bad.)

The photograph on the left is an example of the different values of electrolytic capacitors in which the capacitance and voltage differ.From the left to right:220µF (25V) [diameter 8 mm, high 12 mm] 1000µF (50V) [diameter 18 mm, high 40 mm]

The size of the capacitor sometimes depends on the manufacturer. So the sizes shown here on this page are just examples.

In the photograph to the right, the mark indicating the negative lead of the component can be seen.You need to pay attention to the polarity indication so as not to make a mistake when you assemble the circuit.

Smoothing

025

Smoothing is performed by a large value electrolytic capacitor connected across the DC supply to act as a reservoir, supplying current to the output when the varying DC voltage from the rectifier is falling. The diagram shows the unsmoothed varying DC (dotted line) and the smoothed DC (solid line). The capacitor charges quickly near the peak of the varying DC, and then discharges as it supplies current to the output.

Note that smoothing significantly increases the average DC voltage to almost the peak value (1.4 × RMS value). For example 6V RMS AC is rectified to full wave DC of about 4.6V RMS (1.4V is lost in the bridge rectifier), with smoothing this increases to almost the peak value giving 1.4 × 4.6 = 6.4V smooth DC.

Smoothing is not perfect due to the capacitor voltage falling a little as it discharges, giving a small ripple voltage. For many circuits a ripple which is 10% of the supply voltage is satisfactory and the equation below gives the required value for the smoothing capacitor. A larger capacitor will reduce ripple. The capacitor value must be doubled when smoothing half-wave DC.

Smoothing capacitor for 10% ripple, C = 5 × Io

Vs × f

C = smoothing capacitance in farads (F)Io = output current from the supply in amps (A)Vs = supply voltage in volts (V), this is the peak value of the unsmoothed DCf = frequency of the AC supply in hertz (Hz), 50Hz in Malaysia

026

Ceramic CapacitorsCeramic capacitors are constructed with materials such as titanium acid barium used as the dielectric. Internally, these capacitors are not constructed as a coil, so they can be used in high frequency applications. Typically, they are used in circuits which bypass high frequency signals to ground.These capacitors have the shape of a disk. Their capacitance is comparatively small.

The capacitor on the left is a 100pF capacitor with a diameter of about 3 mm.

The capacitor on the right side is printed with 103, so 10 x 103pF becomes 0.01 µF. The diameter of the disk is about 6 mm.Ceramic capacitors have no polarity.Ceramic capacitors should not be used for analog circuits, because they can distort the signal.

Regulator

Voltage regulator ICs are available with fixed (typically 5, 12 and 15V) or variable output voltages. They are also rated by the maximum current they can pass. Negative voltage regulators are available, mainly for use in dual supplies. Most regulators include some automatic protection from excessive current ('overload protection') and overheating ('thermal protection'). Many of the fixed voltage regulators ICs have 3 leads and look like power transistors, such as the 7805 +5V 1A regulator shown on the right. They include a hole for attaching a heat sink if necessary.

027

028

Construction

1. Cut a piece of stripboard to.

2. Fit the five wire links (two input ac, two outputs 12V and 5V and ground).

3. Fit the four 1N4001 diodes, taking care that the polarity of each one is correct.

4. Fit the 47μF and the single 1000µf capacitors. Ensure that the polarity of the 1000µf capacitor is correct. The leads will be marked with '+' or '-'.

5. Fit the two terminal blocks.

6. Bolt the heatsink to the board.

7. Bend the leads of the LM 7805 and LM7812 and position it. Bolt it into place before soldering the leads to the board.

8. Connect up a 7V - 35V AC power supply and test the circuit by placing a volt meter across the DC Output terminals. The voltage should read approximately 5V DC.

029

Casing design

030

Estimate coast

Component/material unit Coast per unit(RM) Total coast(RM)transformer 1 15.00 15.00Capacitor 47µF 2 0.80 1.60Capacitor 1000µF 1 1.50 1.50IC regulator LM7805 1 1.50 1.50IC regulator LM7812 1 1.50 1.50Diode 1N4001 4 0.50 2.00Socket 1 1.50 1.50Socket output port 3 0.50 1.50Plywood 1m*1m 1 5.00 5.00Nail 1.00

Varnish 1 3.00 3.00Bolt and screw 2 0.80 1.60total 36.7

TASK NAME1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

i. Assessment 1 released 29/07/08

a. Complete task 1 29/07/08 13/08/08

b. Material/component selection 29/07/08 5/08/08

c. Buy the material/component 6/08/08 8/08/08

d. Sketch the circuit 29/07/08 11/8/08

e. Testing and troubleshoot physical circuit 12/8/08 16/08/08

f. Prepare result, discussion & conclusion 16/08/08 19/08/08

g. Creating casing 8/8/8 18/08/08

h. Solder component on stripboard 12/8/08 19/18/08

i. Complete report 12/8/08 19/18/08

j. Do some necessary change 15/08/08 26/08/08

k. Submit the assignment report 26/08/08 27/08/08

DATE TIMES(days)

031

Gantt chart

032

General Statement of the Problem

After designing any electronic equipment, the engineers or designers should know the type of the power supply to incorporate in their end product. A well designer power supply in all equipment should improve both the performance and reliability of the total system at no additional cost. The common problem for electronic designers is to identify the suitable power supply that gain competitive qualities in electronics market. One of the most important criteria for good power supply is the ability to keep the voltage constant under input voltage disturbance. Developing guideline that will facilitate engineers and designers to know the characteristics of both linear and switching mode power supply will allow them to be more competitive. It is also important to know that in most cases the average power supply purchaser doesn’t know most of these details all that much. The designer should ensure that his power supply has the unique aspects, but not far from those of other power suppliers. He should also consider the power supply’s weight, cost, power efficiency, and space of the equipment that will need this power supply.

As conclusion, we know that power supplies are essential part of all electronic system. When dealing with electronic circuits, we have to meet the basic requirement of providing electrical power for them to work.

The basic purpose of a power supply is to provide one or more fixed voltages to the working circuit, with sufficient current-handling capacity to maintain the operating conditions of the circuit.

The basic power supply is consist of major component such as transformer, rectifier, filter and regulator .All of them have their own job to make the power supply system is function. Apart from the major component, it is also included of grounded plug, fuses and switch.

As we know, generally any basic switched power supply consists of five standard components which are set up from a pulse-width modulating controller, a transistor switch, an inductor, a capacitor and a diode. A switch mode power supply is a widely used circuit nowadays and it is used in a system such as a computer, television receiver and battery charger.

033

Reference:

Brown,Marty

Practical switching Power Supply Design, Harcourt Brace Jovanovich,1990.

Gottlieb, Irving M.,

Power Supply, switching Regulators, Inverters, and Converters, 2 nd Edition .TAB Books,1994.

Internet link reference:

http://www.eleinmec.com/article.asp?20

http://www.kpsec.freeuk.com/powersup.htm

http://en.wikipedia.org/w/index.php?title=Switched-mode_power_supply&amp

http://www.hobby-elec.org/e_diode.htm

http://www.hobby-elec.org/e_capa.htm

WWW.ALLDATASHEET.COM

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APPEDICES: