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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:
03
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
05
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.
010
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&
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&
http://www.hobby-elec.org/e_diode.htm
http://www.hobby-elec.org/e_capa.htm
WWW.ALLDATASHEET.COM
034
APPEDICES:
Recommended