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									            SIM UNIVERSITY
  SCHOOL OF SCIENCE AND TECHNOLOGY




RESEARCH ON LIGHTING TECHNOLOGY
  (FLUORSECENT LAMPS AND LEDS)




           STUDENT      : W0605229 (PI NO.)
           SUPERVISOR   : PEH KING SING
           PROJECT CODE : JAN09/BEHE/67




              A thesis submitted to SIM University
   in partial fulfilment of the requirements for the degree of
                     Bachelor of Engineering

                           Nov 2009
TABLE OF CONTENT

List of Figures
List of Tables
Abstract                                                 i
Acknowledgement                                          ii

1     Introduction                                       1
      1.1   Project objectives                           3
      1.2   Scope of project                             3

2     Literature Review                                  4
      2.1    Light                                       4
             2.1.1 Luminescence                          4
             2.1.2 Luminous Efficiency                   5
             2.1.3 Colour Rendering Index (CRI)          6
             2.1.4 Correlated Colour Temperature (CCT)   6
      2.2    Fluorescent Light                           6
             2.2.1 History of Fluorescent Lamp           6
             2.2.2 How a Fluorescent Lamp works          8
             2.2.3 Starter                               8
             2.2.4 Ballast                               10
             2.2.5 Dimmable Fluorescent Light            11
      2.3    Solid-State Lighting                        14
             2.3.1 History of Light-Emitting Diode       14
             2.3.2 How Light Emitting Diodes work        16
             2.3.3 Dimmable LEDs                         17

3     Main Text and Discussion                           20
      3.1   Energy Usage                                 20
      3.2   Cost                                         22
      3.3   Reliability                                  23
      3.4   Limitations of LEDs                          23
            3.4.1 Consumer Acceptance                    23
            3.4.2 Infrastructure                         23
            3.4.3 Research and Development               25
      3.5   Market potential of LED                      26
            3.5.1 Consumer Electronics                   26
            3.5.2 Automobile                             27
            3.5.3 Lighting                               27
      3.6   Limitations                                  27

4     Conclusion and Recommendations                     28

5     Reflections                                        30

6    References                                          31
Appendix A: Gantt Chart                                  33
List of Figures
Figure 1.1 Incandescent lamp                                                    1
Figure 1.2 Fluorescent lamp                                                     2
Figure 1.3 Light emitting diode (LED)                                           2
Figure 2.1 How atoms emit light                                                 4
Figure 2.2 Strokes‘ shift                                                       5
Figure 2.3 Temperature chart (Kelvin)                                           6
Figure 2.4 Photograph of George E. Inman & Richard N Thayer                     7
Figure 2.5 How a fluorescent lamp works                                         8
Figure 2.6 A starter circuit                                                    8
Figure 2.7 Simplified dimmable ballast circuit                                  11
Figure 2.8 Formulae for calculation of dimming effect in a ballast circuit      11
Figure 2.9 Simplified resonant lamp model                                       11
Figure 2.10 Gain against frequency graph                                        12
Figure 2.11 Formulae for deriving the output to input voltage function of the   12
ballast output stage in frequency as a function of lamp power
Figure 2.12 Actual dimming circuit                                              13
Figure 2.13 Schematic of a 2 layer OLED                                         14
Figure 2.14 Four generations of AlInGaP LEDs                                    15
Figure 2.15 Haitz‘s Law chart                                                   16
Figure 2.16 How light emitting diode works                                      16
Figure 2.17 Dimming compathibility of RAIS with dimmable circuits               18
Figure 2.18 Efficiency chart of RAIS technology                                 19
Figure 3.1 Calculation method for cost of light                                 22
Figure 3.2 A typical solid-state lighting system                                25

List of Tables
Table 1.1 Basic electrical requirements of a typical 35W/T5 lamp                13
Table 1.2 The different materials and specifications in creating a LED          17
Table 1.3 Comparison between incandescent, fluorescent and LED                  20
Table 1.4 A recommendation solid-state lighting roadmap for LED by US DOE       24
Abstract
As known to many, fossil fuels are rapidly decreasing throughout recent years as
civilization gains on momentum in expansion. Some countries depend on the burning
of coal to provide electricity to power the country; we also depend on petroleum to
power our cars. What happens when fossil fuels no longer exist? Based on this
underlying fact, human have researched and identified alternative energies to provide
alternatives to fossil fuels. With that humans have also researched and developed
advanced technologies to improve on existing applications or by creating new
applications to reduce the consumption of these fossil fuels.

The focus in this thesis would be on lighting technology; the rapid developments of
fluorescent lighting lamps and solid state lighting or light-emitting diodes (LED) which
enable us to reduce the lighting electricity consumption in our residential and industrial
premises. Fluorescent lamps and light-emitting diodes are becoming the 2 most
commonly-used lighting applications in our daily lives, slowly and gradually replacing
the incandescent lamps.

A detailed and comprehensive literature review on the history and the basic concepts of
these 2 lighting technologies would be discussed in this thesis.

The main area of discussion would involve a comparison between these 2 lighting
technologies in terms of energy usage, cost and reliability in general lighting and why
LED lighting has not been readily implemented for general lighting. Market potential
of LEDs would also be discussed in another section of this thesis.

A review of the limitations faced in this project would also be discussed in this final
report.




                     Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report             i
Acknowledgement
I would like to offer my appreciation towards Mr Peh King Sing for his continuous
support, guidance and encouragement during this period of time. With his pointers and
directions, I was able to complete this thesis in time for submission. Without Mr Peh‘s
support, I might have submitted an extension for this thesis.

Special thanks to my boss and colleagues at Future Electronics for their kind
understanding of my absence during examination periods and in the preparation of this
thesis.

Not forgetting HDB building and research institute staff, senior engineer Mr Lim Ah
Hee and senior technical officer Mr Mohd Noor Johar, for their kind assistance in
answering my emails and calls and providing me with up to date information on the
general lighting used in HDB flats.

Finally, I would also like to offer my greatest gratitude and appreciation to my loved
ones who are always there to give me encouragement and support during the difficult
times in my life.




                     Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report          ii
1. Introduction
The first creation of a lighted lamp was probably done in many thousand of years BC.
The Greek word lampas, meaning torch, is the word which lamp is derived from [1]. A
primitive method would probably be igniting a hollow object, like a shell or rock, with
animal fats and moss. The process of igniting will involve the rubbing of 2 stones
together to create a spark that is produced by the friction of the 2 stones. Wicks, made
out of materials like linen, flax, papyrus, tow and ordinary rush were added into lamps
to control the rate of the burning flame [2].

Since the early days of terra cotta lamps, primary an oil burning lamp, many types of
oil were used as lighting fuel for illuminating the dark skies. Oils like whale oil, olive
oil, sesame oil, and other similar substances were used [1].

Many years have passed, and humans have created other applications which would
emit the light that is required in darkness. The evolution of lamps consists of the terra
cotta lamps, to the gas-filled lamps, and finally the electrical lamps.




      Courtesy of wikipedia            Figure 1.1


Incandescent lamps as shown in Figure 1.1, were the first electrical lamps to be
invented. Sir Humphry Davy was credited with the creation of the first incandescent
light, and he made it by passing current through a platinum filament [3] but it was
Thomas Alva Edison who truly revolutionised the general lighting industry with his
roadmap of an entire lighting system which included the improvement of the
incandescent material and the supply of direct current throughout the entire
neighbourhood by generators. An incandescent light lamp works in the principle, using
electricity to heat up a filament inside the light blub that produces the light to humans.
The filament, usually made out of tungsten, is encased in a glass blub to prevent
oxygen from diffusing the heated filament [3].




                       Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report           1
  Courtesy of wikipedia                     Figure 1.2



A fluorescent tube lamp as shown in Figure 1.2, is actually a gas-discharge lamp that
uses electricity to excite mercury atoms inside the tube which in turn produces short
wavelength ultraviolet light that causes the compound material (phosphor) found in
fluorescent light to illuminate, thus producing visible light [4]. There are many types of
fluorescent tubes, linear, compact etc.

Compact fluorescent lamps or (CFL) are miniature fluorescent lamps which are energy
saving lamps. CFLs has 2 types of circuits, integrated or non-integrated CFLs.
Integrated CFLs have built in electronic ballast whereas the non-integrated CFLs have
separate permanently installed ballast (normally magnetic type). Non-integrated CFLs
last longer than integrated ones but are more expensive and difficult to design.




Courtesy of wikipedia                     Figure 1.3


Solid state lighting gets its illumination or projection of light through light-emitting
diodes (LED). LED is a type of semiconductor which is a uni-directional conductor
that has 2 pins, the cathode and the anode [5]. Electricity will only flow in one
direction, which is from the anode to the cathode side. A single LED produces only a
short wavelength of light, thus a cluster of LEDs will be built together to get a wider
illuminated effect as shown in Figure1.3. A LED does not contain a filament, but only
uses the electromagnetic radiation of the moving electrons in the semiconductor
material to emit perceivable visible light [5].



                          Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report        2
1.1 Objective of Project
The objective of this project is to research and provide facts and findings on the
advantages and disadvantages between the 2 lighting technologies that I will be
emphasising on in this thesis, namely fluorescent lights and solid state lighting or light-
emitting diodes in particular. The main area of discussion will be focused on general
lighting application between the 2 lighting technologies.

These 2 lighting technologies have several advantages over incandescent lamps, but
the main focus will be on 3 key points.

    Energy usage
    Cost
    Reliability

1.2 Scope of Project

          Project                       Literature
         Objective                       Review


                                       Research


  Fluorescent                                                               Solid State
    Lighting                                                                 Lighting

                                     Comparison
                                       Chart


                                  Main Discussion
                            Results and Conclusion

                              Conclusion of Project


                                Recommendations

                                       Reflections




                      Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report             3
2. Literature Review
2.1 Light




  Courtesy of HowStuffWorks                                  Figure 2.1

Light is a form of energy. An example of how light is emitted from atoms is showed in
Figure 2.1. Basically, an atom will release light photons when their orbiting electrons
are excited by collision with a moving particle. The electron that gains energy through
this process, shifts its position to a higher orbital, but only maintains its position there
for a short period before returning to its original orbital almost immediately [6]. This
extra form of released energy results in the formation of a light photon. The position of
an electron will determine the wavelength of the emitted light as the amount of energy
dispersed depends on the position of the excited electron [6]. Different types of excited
atoms emit different light photons. In general, the principle of light photons exists in
almost all of man-made light sources, only the process of exciting the atoms differs.

2.1.1 Luminescence
Light emitted from high temperature objects are defined as incandescent, other emitted
light sources are defined as luminescent. There are several breakdowns of luminescent
light sources, and these are some of the categories.

Electroluminescence

Generally there are 2 types of electroluminescence, Lossev effect and Destriau effect.
Light emitted by a passing electrical current running through a gas state in a sealed


                      Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report              4
discharge tube (Lossev effect) [7]. Light emission by an application of electric field on
a substance (Destriau effect) [7].

Radio-luminescence
Light emitted when a radioactive decay material strikes a phosphor or light emission
by the bombardment of ionizing radiation. Main applications can be seen in watch and
clock dials [7].

Chemi-luminescence
Light emitted through the chemical reactions of a substance, such as the slow oxidation
of phosphorus at normal temperature [8].

Bioluminescence
Light emitted when the chemical reaction occurs inside a living organism, like a firefly
[9]. It‘s a subset to chemi-luminescence.

Photoluminescence
Light emitted when an external source illuminates an object with light [10]. This can
be seen in our daily lives through the light emitted by fluorescent lamps.

In 1852, an Irish mathematician and physicist, George Gabriel Stokes wrote a paper on
the change of wavelength of light and named this phenomena, Fluorescence, after a
fluorescent material, Fluorite [11]. According to Stoke, there is a loss of vibration
energy when excited electrons move to the ground state and this shifts the emission
spectrum to longer wavelengths than the excited spectrum, this phenomena is aptly
named Stokes‘ Law or Stokes‘ Shift as seen in Figure 2.2 [12].




  Courtesy of Wikipedia                                    Figure 2.2


2.1.2 Luminous efficiency
Luminous efficiency is the term which is used to measure the energy efficiency of a
light source in terms of lumens per watt (lm/W). It describes how well a light source is
performing using the electricity it consumes.


                      Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report           5
2.1.3 Colour rendering index (CRI)
Colour rendering index is a measure of rendered colour quality of objects like skin
tone, materials, in comparison with a reference source of similar colour temperature.

2.1.4 Correlated colour temperature (CCT)
Correlated colour temperature is a form of categorizing visible light into classes which
are determined by the comparison of the relative colour of a white light source to an
ideal black body radiator. Correlated colour temperature is measured in Kelvin (K) and
it refers to the light source which matches the appearance of a heated ideal black
radiator. Higher temperatures produce green-blue colours while lower temperatures
produce red-yellow colours as shown in Figure 2.3.




2.2 Fluorescent Lighting


Courtesy of Wikipedia                                                                 Figure 2.3


2.2 Fluorescent Lighting
2.2.1 History of Fluorescent Lighting

The earliest form of fluorescent lighting was probably discovered in 1856, when a
German physicist, Heinrich Geissler whom worked in his father‘s business as a glass
blower, created a gas-filled tube that gave out bluish-green light after being simulated
by an electrical current [13]. Thomas Alva Edison and many other brilliant scientists
and inventors used this Geissler principle in creating a usable, affordable light source
that can be comparable to the incandescent lamp which was created successfully by
Thomas Edison himself, but they were unsuccessful in creating a commercially
available and affordable product [14].

However in 1901, an American electrical engineer named Peter Cooper Hewitt,
fabricated a mercury filled gas-discharge lamp that uses electrical current to excite the
mercury vapour inside the sealed lamp to produce ultra-violet lighting [14]. Although
its energy efficiency was much higher than a incandescent lamp, the bluish-green
coloured light made it impractical for normal usage, but it thrived on specific
professional areas like photography where light colour is not an issue [14] [15]. Peter‘s
mercury vapour lamp is considered as the first prototype of a fluorescent lamp.


                        Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                6
 In 1926, A German inventor named Edmund Germer, created the world‘s first high
pressure mercury-vapour lamp [16] [17]. Edmund Germer, Friedrich Meyer and Hans
J. Spanner filed a patent on December 1926 on this high pressure mercury-vapour lamp
[16] [17]. Edmund and co-workers were able to create a more pleasing and uniformly
white coloured light that was being emitted from this lamp by increasing the operating
pressure in the sealed lamp and coating the tube with fluorescent powder [13] [14].
This led to the first commercially available fluorescent lamp in the market at that point
in time. However in 1938, this patent was bought over by General Electric.




             George E. Inman, left; Richard N. Thayer, right
Courtesy of The Report courtesy of General Electric Company                     Figure 2.4


George E. Inman and Richard N. Thayer led a team of engineers at General Electric in
researching and development of an improved and practical fluorescent lamp. Inman
headed the Lamp Development Laboratory while P. J. Pritchard headed a group which
focused on developing an automated system of manufacturing the fluorescent lamps
that Inman‘s group has created [18]. Inman‘s group had many tasks at hand, the
development not only focus on the lamps itself, but also on the associated equipments,
like ballasts and starters [18]. It would require a large scale team effort to successfully
create a commercial product in a short period of time. The 2 individual groups acted
independently and they modified the lumiline end-disc and electrode structure,
researched on the phosphors and colours, tried and tested many types of fluorescent
coating, did life-testing on individual lamps for reliability, tackled the problem of
exhaust and activation, designed the sizes of lamps and worked on improving the
ballast and circuits [18]. As the 2 groups acted independently, many issues and debates
arose between George and Pritchard, which led to a delay in commercialising the end
product.

General Electric displayed and demonstrated their fluorescent lamps in the 1939
World‘s Fair in New York, show-casing a successfully developed commercial product
[14]. The higher energy efficiency over incandescent lamps proved to be a major
selling point and thus the mass market commercialisation of fluorescent lamps took
place from here onwards.




                       Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report            7
2.2.2 How a Fluorescent Lamp works




Courtesy of megavolt.co                                                                 Figure 2.5


A typical operation of a fluorescent lamp can be seen in Figure 2.5. When the lamp is
turned ‗on, electrical current flows through the starter switch to provide an initiation to
start the lamp and then to the ballast for kick-starting the lamp and maintaining the
current surge. Electricity heats up the filament in the electrodes and this process causes
electrons to flow into the gaseous state in the sealed tube. Upon collision between the
charged electrons and the atoms of the gaseous mercury, mercury electrons become
excited and move up to a higher level. After the mercury electrons return to the
original orbital level, energy is released as ultraviolet light photons. These ultraviolet
light photons collide with the coating of phosphors inside the sealed tube and thus
giving out visible light.

2.2.3 Starter




Courtesy of capakor.com                          Figure 2.6


                          Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                8
A starter as shown in Figure 2.6, is a switch which serves as an initialising mechanism
for the starting of a fluorescent lamp. A conventional starter switch is a sealed small
discharge bulb that consists of bi-metallic contacts with argon gas flowing through it
[19]. Electricity that is flowing through a starter causes an electrical arc that is trying to
make a connection between these 2 electrodes. Electricity from the AC main voltage
heats up one of the bi-metallic contacts and bends it towards the other electrode. Once
these 2 electrodes have made contact, the circuit is closed and the ballast and cathodes
are in series across the AC main. Once connection is made between the 2 electrodes,
the bi-metallic contact cools down and opens the circuit. At this stage, the filaments
from the electrodes of the lamp have already ionized the gas in the tube to an
electrically conducive medium, if the cathodes are not pre-heated and cold started, it
will severely reduce the cathode lifespan as the strike pulse voltage is not reduced [19].
As the inductance of the ballast tries to maintain the current surge of the circuit
because of the sudden current surge from the collapse of the magnetic field due to the
re-opening of the starter switch, it creates an electrical path down the tube by the
process of free electrons colliding and knocking loose other electrons to create a gas,
plasma, which consists of freely moving ions and electrons in the tube [6] [19]. The
freely moving electrons keep the filaments in the cathodes warm, and the filaments
will continue to free more electrons into the plasma gas in the sealed tube. The ballast
will control the current flow in the tube and unless there is no more AC main source
supply, or the filaments are damaged, light will be emitted through the fluorescent
lamp. A conventional starter usually takes a few seconds to light up a fluorescent lamp
but currently there are 2 main types of starters, the Instant Start and the Rapid Start
which are able to provide light almost instantly.

Instant Start
By applying an initialising voltage that is many times larger than the operating voltage
of the circuit, the instant start fixture forces excessive electrons from the electrodes to
ionize the gas in the lamp to be conductive. Current will flow through the lamp, and
the fluorescent tube will illuminate at its brightness until the instant start ballast
regulates the current flow and limits it to the normal operating levels [20]. If the ballast
is not properly matched to the instant start fixture, the current might increase
continuously and therefore might damage or destroy the lamp.

Rapid Start
Nowadays, the most popular starter lighting fixture would be the Rapid Start. A rapid
start fixture does not contain a starter switch. The rapid start ballast channels a low
level of current through the electrodes and thus heating the filaments to produce
electrons to ionize the gas in the tube. The process of heating the cathodes first before
starting the lamp; reduces the damage to the electrodes during the starting process of
turning on the lamp. A steady flow of current is established in the tube through the
ionizing of the gas, the rapid start ballast will still continue to provide current to the
filaments of the electrodes to produce more electrons into the gas, all these process
lowers the resistance of the gas and illumination of the lamp increases due to the
increase in demand for current [21]. Although the rapid start fixture lights up almost
instantly, it requires a few seconds to fully achieve its normal operating brightness
level.



                      Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                9
2.2.4 Ballast
The main purpose of a ballast is to limit the current in the fluorescent lamp, provide the
initiation to kick-start the fluorescent lamp and soften the emission of light through a
lamp [22]. Ballasts are designed by engineers to only allow a specific amount of
current to pass through the circuit to light up a particular fluorescent lamp. Ballasts can
only regulate and limit current flowing through the circuit but they cannot stop the
current totally. In a gas discharge of a fluorescent lamp, there will be frequent collision
occurrences of electrons and ions between atoms, thus it frees up more electrically
charges particles [6]. More current will flow through this gas discharge when there‘s
ample voltage to initiate the movement, and if this happens without a current limiting
device, the electronic components in the lamp would definitely be burned out or
damaged. There are 2 types of ballast in fluorescent lamps, the traditional magnetic
ballast and the modern electronic ballast.

Magnetic Ballast
A magnetic ballast acts like an inductor functioning in a circuitry. An inductor has
wires coiled around a metal piece and as current passes through the wires, it generates
a magnetic field [23]. An increase of current in this loop will result in an increase of
magnetic field which will produce a flow of current which moves in an opposite
direction of the magnetic field in the wire. The magnetic ballast uses this phenomenon
to regulate current in a fluorescent lamp. Heat is also generated from this process and
this heat is wasted electricity.

Magnetic ballast can change current directions at a rate of 100~120 times every
second, thus a ballast has to limit an increasing current in a particular direction for a
small amount of time. 1 cycle means measuring the current going from zero to its peak
and then from its peak back to zero and a cycle is measured in Hertz (HZ). In
Singapore, the frequency of electricity supplied by power stations is 50Hz, which
means the current changes directions 100 times every single second. Magnetic ballasts
operate at low cycle rates, which often results in a noticeable flicker. Sometimes a
humming noise can be heard from the fluorescent lamp, which is due to the vibration
cause by the magnetic ballast at low frequencies.

Electronic Ballast
Electronic ballast uses an electronically designed circuit to regulate the flow of current
passing through a fluorescent lamp by performing as an integrated high frequency
inverter/switcher [22]. Electronic ballast was researched and designed to eliminate
problems faced by the conventional magnetic ballast. By using a higher range of
frequencies (normally tens of kHz), it usually eliminates the noticeable flicker that is
present in fluorescent lamps that uses magnetic ballasts [22]. Although this really
depends on the actual design of the electronic ballast, some still has traces of flickering
moments. Electronic ballast cost much more than magnetic ballast, but the advantages
like small in size, better lamp-ballast efficiency, flicker-free with no virtually no noise
or humming and are more energy efficient than conventional magnetic ballasts.




                      Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report             10
2.2.5 Dimmable Fluorescent Light
Dimmable fluorescent lamps are very appealing to consumers as they are energy
saving and light produced can be adjusted to create ambience. Unlike incandescent
lamps which use variable amounts of electricity to control the dimming effect as lesser
current to heat the filaments would result in a dimmer light output, fluorescent lamps
made use of electronic ballasts to do the dimming effect.

In a dimmable fluorescent lamp, the calculations of stages like pre-heat, ignition and
dimming operating frequencies must be established. Next would be the resonant output
stage modelling, the dimming control method and finally, the dimming ballast circuit
requirements.




Courtesy of www.irf.com                                                             Figure 2.7


The current flowing through Rlamp controls the dimming effect, the formula for
calculation is shown below in Figure 2.8 [28]. Manufacturers don‘t specify the
filament resistance values, in this example, the assumption made is the heated spot is at
the middle of each filament.




where,
P%= Lamp power at % dimming level [Watts]
V%= Lamp voltage amplitude at % dimming level [Volts]

Courtesy of www.irf.com                             Figure 2.8

A simple resonant lamp model is shown in Figure 2.9.




Courtesy of www.irf.com                                                             Figure 2.9

                      Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                11
During pre-heat, the fluorescent lamp is not conductive as the filaments are in heating
mode with a given current and fixed frequency that is constant and above resonance.
No arc is formed for conduction, thus the circuit is in a high-Q series L and C. After
ignition takes place, the circuit is an inductor in series with a parallel R and C,
frequency will gradually decrease until the brightness of the lamp reaches a 100% and
this will be the final frequency [28]. This can be seen in Figure 2.10. The crucifix of
this resonant circuit would be choosing the correct amplitude frequency of Vin and the
correct values of L and C to satisfy the lamp requirements in the first stage of
designing a dimmable circuit [28]. For a dimming effect, frequency is increased to
reduce the current and the Q-factor of the circuit changes according to the circuit
design.




Courtesy of www.irf.com                                                             Figure 2.10




Where,
L = Output stage inductor [Henries]
C = Output stage capacitor [Farads]
P%= Lamp power at % dimming level [Watts]
V%= Lamp voltage amplitude at % dimming level [Volts]
f%= Frequency corresponding to lamp power at % dimming level [Hertz]

Courtesy of www.irf.com                                                             Figure 2.11

The formula shown in Figure 2.11 is achieved from deriving the output to input voltage
function of the ballast output stage in frequency as a function of lamp power [28].

In a linear dimming circuit, the control circuit will continuously vary the operating
frequency to allow the phase angle to match the reference phase angle which will
results in the desired dimming effect [28].




                      Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                 12
An actual dimming circuit is shown below in Figure 2.12.




       -   DC bus capacitor, two MOSFETs connected in a half-bridge configuration for generating the
           Vin square wave
       -   An additional DC blocking capacitor, and a control circuit for driving the half- bridge
           MOSFETs, preheating, igniting and regulating the phase angle for dimming.

 Courtesy of www.irf.com                                                                        Figure 2.12



Table 1.1 shows the basic electrical requirements of a typical 35W/T5 lamp.

Parameter                 Value                 Units                   Description
tph                       1.0                   sec                     Filament preheat time
                                                                         Ignition voltage amplitude to strike the
Vign                      900                   Volts
                                                                        lamp
P100%                     35                    Watts                   Lamp power at 100% brightness
                                                                         Lamp voltage amplitude at 100%
V100%>                    310                   Volts
                                                                        brightness
P5%>                      0.7                   Watts                   Lamp power at 5% brightness
                                                                         Lamp voltage amplitude at 5%
V5%                       425                   Volts
                                                                        brightness
                                                                         Equivalent lamp resistance at 100%
RLamp100%                 1.4                   kΩ
                                                                        brightness
                                                                         Equivalent lamp resistance at 5%
RLamp5%                   129                   kΩ
                                                                        brightness
R1,2,3,4                10                      &Omega:                 Cold filament resistances
 Courtesy of www.irf.com                                                                             Table 1.1




                         Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                                13
2.3 Solid State Lighting
The term Solid State Lighting encompasses both light emitting diodes (LED) and
organic light emitting diodes (OLED).

LEDs are made from non-carbon based materials. LEDs offer a narrow point source of
illumination and produces light when an electrical current passes through the
semiconductor device. When it was first created in the 1960s, LEDs only served as
indicator lamps.




  Schematic of a 2-layer OLED: 1. Cathode (−), 2. Emissive Layer, 3. Emission of
  radiation, 4. Conductive Layer, 5. Anode (+)

  Courtesy of Wikipedia.com                                              Figure 2.13


OLEDs as shown in Figure 2.13 are made from carbon based materials, hence the term
organic light emitting diodes. OLEDs offer a wider range of illumination, and they are
created in sheets. The transparent conductor is usually placed on top of a 4 layered
organic compounds which conduct electricity. Electroluminescence is broken down
into 5 process, injection, transport, recombination, migration and decay [24].

2.3.1 History of Light Emitting Diodes
The 1st LED was developed in 1962. It was just an indicator LED emitting red light
and it was primary made out of semiconductor compounds like Gallium phosphide
(GaP) and Gallium arsenide phosphide (GaAsP) [25]. This type of LED produces low
light efficiency and thus affecting the light output which limits the usage of this light to
only applications like indicator lamps and alphanumeric displays. At that moment,
LEDs are only able to emit colours like orange, yellow, green and red.

The development of aluminium gallium arsenide (AlGaA) enabled the red colour
emitting diodes to exceed the luminous efficiency levels produced by a red-filtered
incandescent blub [25]. Luminous efficiency was further improved when LEDs began
to use transparent substrate devices, aluminium gallium arsenide (A1GaAs) grown on
A1GaAs [25].




                       Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report             14
  Four generations of AlInGaP LEDs: (a) Absorbing substrate (AS) LED. (b) Transparent substrate
  (TS). (c) High-power LED with 5_ TS flux. (d) Trunction inverted pyramid (TIP) LED with 1.5_
  flux of high-power square chip.

  Courtesy of philipslumileds.com                                                    Figure 2.14


A new technology surfaced in the 1990s, which enabled LEDs to take on a more
commercially significant role in our modern world. Hewlett-Packard Optoelectronics
Division were the first to master and replica the organo–metallic vapour phase epitaxy
(OMVPE) crystal growth techniques, growth of quaternary aluminium indium gallium
phosphide (AlInGaP) on GaAs substrates [25]. High-brightness LEDs were created
using this new technology. This technology had close to a 100% rate of internal
quantum efficiency, but the problem here was how to extract out the photons in the
semiconductor for usage. In 1994, Hewlett-Packard used etching of GaAs substrate and
replacing it with transparent substrate GaP by wafer bonding as shown in Figure 2.14
(b), and this resulted in a 25 lm/W LED that were used in automobile stop lights,
traffic lights and single coloured outdoor signs like exit signs [25].

Following the commercialisation of AlInGaP, the growth process of aluminium indium
gallium nitride AlInGaN material was researched and mastered by 2 groups of
individuals, Shuji Nakamura at Nichia Chemical and Prof. Akasaki and Prof. Amano at
Nagoya University and later Meijo University, on sapphire substrate using
atmospheric-pressure OMVPE [25]. With this, access to the higher region of colours
like green, blue can be obtained through a wider band-gap that AlInGaN possess. Solid
state white light can be obtained by combining red, green and blue LEDs. Red LEDs
are made from the material aluminium gallium arsenide (AlGaAs), blue LEDs are
made from indium gallium nitride (InGaN) and green LEDs are made from aluminium
gallium phosphide (AlGaP). Alternatively, another method to achieve white light
would be coating a high brightness blue LED with yellow phosphor.




                       Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                 15
Courtesy of nature.com                                                                    Figure 2.15


Roland Haitz, a scientist from Agilent Technologies, studied the trend of the rise of
LEDs for 40 years. Haitz‘s law as shown in Figure 2.15, is a prediction tool measuring
the rise/improvement of LED luminous output flux or LUMENS [25]. It states that in
every decade, for a given wavelength of light, the cost per lumen falls by a factor of 10
whereas the output light will be raised by a factor of 20 [26]. Taking Moore‘s law in
consideration, which predicts/observes a doubling of the number of transistors in a
silicon chip every 18~24 months [27]. LEDs have progressed in a significant manner
throughout these 40-odd years since it was first developed.

2.3.2 How Light Emitting Diodes work
A LED is a semiconductor diode and electricity only flows in one direction, from the
anode (P-side) to the cathode (N-side). Electron charges and holes fall into the P-N
junction, when an electron meets a hole, recombination takes place. The recombination
process produces photons that release light energy as shown in Figure 2.16.




  Courtesy of eere.energy.gov                                                   Figure 2.16

                         Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                    16
  Colour       Wavelength [nm]          Voltage [V]                      Semiconductor Material
                                                                          Gallium arsenide (GaAs)
  Infrared         λ > 760               ΔV < 1.9
                                                                  Aluminium gallium arsenide (AlGaAs)
                                                                  Aluminium gallium arsenide (AlGaAs)
                                                                   Gallium arsenide phosphide (GaAsP)
    Red         610 < λ < 760        1.63 < ΔV < 2.03
                                                             Aluminium gallium indium phosphide (AlGaInP)
                                                                       Gallium(III) phosphide (GaP)
                                                                   Gallium arsenide phosphide (GaAsP)
  Orange        590 < λ < 610        2.03 < ΔV < 2.10        Aluminium gallium indium phosphide (AlGaInP)
                                                                       Gallium(III) phosphide (GaP)
                                                                   Gallium arsenide phosphide (GaAsP)
  Yellow        570 < λ < 590        2.10 < ΔV < 2.18        Aluminium gallium indium phosphide (AlGaInP)
                                                                       Gallium(III) phosphide (GaP)
                                                              Indium gallium nitride (InGaN) / Gallium(III)
                                                                                nitride (GaN)
   Green        500 < λ < 570          1.9 < ΔV < 4.                   Gallium(III) phosphide (GaP)
                                                             Aluminium gallium indium phosphide (AlGaInP)
                                                                  Aluminium gallium phosphide (AlGaP)
                                                                            Zinc selenide (ZnSe)
                                                                      Indium gallium nitride (InGaN)
    Blue        450 < λ < 500         2.48 < ΔV < 3.7
                                                                     Silicon carbide (SiC) as substrate
                                                             Silicon (Si) as substrate — (under development)
   Violet       400 < λ < 450         2.76 < ΔV < 4.0                 Indium gallium nitride (InGaN)
                                                                            Dual blue/red LEDs,
   Purple       multiple types        2.48 < ΔV < 3.7                     blue with red phosphor,
                                                                        or white with purple plastic
                                                                                diamond (C)
                                                                          Aluminium nitride (AlN)
 Ultraviolet       λ < 400            3.1 < ΔV < 4.4               Aluminium gallium nitride (AlGaN)
                                                             Aluminium gallium indium nitride (AlGaInN) —
                                                                             (down to 210 nm)
   White       Broad spectrum            ΔV = 3.5                  Blue/UV diode with yellow phosphor
Courtesy of Wikipedia.com
                                                                                                   Table 1.2

 Table 1.2 shows the different materials and its specifications which are required to
 produce different colours of light in a LED.

 2.3.3 Dimmable LEDs
 Imagine having a 16W load from a battery, the light bulb will convert the 16W into
 light and heat. What if we would like to dim the light bulb to 8W? The battery will still
 continue to produce 16W power, but only 8W is absorbed by the light bulb and the rest
 is being absorbed by a resistor placed in series, but the 8W is lost as heat or we could
 switch on-off very quickly, and this will let the average power of the battery to be at
 8W. Most LED dimmable lighting circuits use Pulse Width Modulation (PWM). Pulse
 width modulation is a technique that modulates the duty cycle of a signal and uses a
 series of pulses to transmit information over a channel or control the amount of power
 delivered to the load. There isn‘t power loss because the average power delivered is
 proportional to the modulation duty cycle.

 A new technology has been researched and implemented, and this is resonant
 asymmetric inductive supply (RAIS).



                         Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                           17
E-Light, a company based in Isle of Man, United Kingdom, integrated resonant
asymmetric inductive supply (RAIS) technology into the lighting industry. RAIS is a
circuitry that lies between the main supply voltage and the LEDs and this enables the
lamp to function like an ordinary incandescent light bulb, lesser power input will result
in a dimmer light output, more input power will increase it brightness proportionally. It
is the first dimmable GU10 application to be submitted to UK‘s Energy Saving Trust
scheme for approval [29]. E-Light mentioned 5 key points of RAIS over its
competitors.

Dimming compatibility

By using RAIS, consumers will not have to worry about compatibility of dimmable
LED lamp with dimmer circuits in their homes as E-Light has conducted a thorough
test with many commercially available dimmer circuits and RAIS works effectively
with all the dimmable circuits, mainly leading-edge dimmers, touch leading-edge
dimmers, push-button leading-edge dimmers and trailing-edge MOSFET dimmers. As
shown in Figure 2.17.




 Courtesy of ledmagazine.com                                                        Figure 2.17


Efficiency

Heat dissipation is a limiting factor on light output. Conventional low efficiency
drivers require a larger heat-sink to dissipate the heat generated, but the RAIS model
doesn‘t require a larger heat-sink and it is able to use the additional power to increase
the light output because of its high efficiency. This can be seen in Figure 2.18. A RAIS
model is able to drive high current, low voltage LED strings from a 240V AC main
voltage supply without additional components like a transformer or common mode
choke which can be found in a conventional driver circuit, and still achieve the turn
ratio [29].



                      Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                 18
Courtesy of ledmagazine.com                                                         Figure 2.18


Power Factor

E-Light has quoted a figure of 0.96% power factor as compared to an IC driven LED
lamp of 0.66%. Thus there is not need for power factor correction or a valley filled
circuit. RAIS achieves this figure without any loss in efficiency or additional costs
involved. In both US and UK energy saving schemes, the requirement is at 0.9% power
factor for commercial lighting.

Constant Current

RAIS topology doesn‘t require a second stage current sensing feedback or short circuit
protection as it‘s on a constant current at a particular frequency in a single stage power
supply that doesn‘t require any sensing and this results in a high efficiency level
throughout the full AC main supply cycle without any feedback needed. The LED is
protected from transient damage as the output current is constant and thus this will
result in the removal of filtering of high frequency components before DC supply is
provided to the LED lamp.

Size

The circuitry of a RAIS is very small, and with a small power supply, the size of the
heat-sink can be reduced. The RAIS lamp in a standard GU10 sized lamp, can be
retrofitted into existing fixtures.




                      Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                 19
3. Main Text and Discussion

                          Incandescent light
                                                       Fluorescent lamp          Light Emitting Diode
                                lamp
   Life span (hours)            1200                      15000~20000                50000~60000
    Watts per bulb                60                           32                         1
  Luminous Output
                                  850                         5300                        20
          (lm)
  Luminous Efficacy
                                   14                           83                        72
        (lm/W)
                                                       Decreases lifespan
    On/Off cycling         Minimum impact                                             No impact
                                                          drastically
   Environmental
                                   No                Yes (contains mercury)              No
       Hazard
  Sensitivity to low
                                 Some                          Yes                       No
    temperature
    Sensitivity to
                                 Some                          Yes                       No
      humidity
  Turns on instantly              Yes                          No                         Yes
                          No, glass or filament        No, glass can break      Yes, can handle jarring
      Durability
                              might break                     easily                  or bumping
    Light Coverage               Wide                         Wide                 Narrow, focused
         CRI                       100                          78                 90 (warm white)
       CCT (K)                    3300                        4100                       3300
                                                                                  Yes (limited due to
      Dimmable                    Yes                          Yes
                                                                                 compatibility issues)

                                                                                               Table 1.3


A comparison table taking the average values between the 3 types of lamps,
incandescent, fluorescent and LED is shown in Table 1.3.

3.1 Energy Usage
Lesser energy consumed will result in lesser fossil fuels burned, and thus producing
lower carbon dioxide emissions which result in a reduction of global warming and
climate changes. Government bodies from around the world have began phasing out
incandescent lamps in favour of fluorescent lamps and now LEDs are gaining
momentum to be implemented in commercial and residential lighting areas as they
offer the lowest energy consumption to produce the same amount of lumens. LEDs are
not readily implemented for general lighting in a wide scale at the current moment but
LEDs are fast gaining momentum as the next incandescent lamp for general lighting.

In the 1960s, all common corridor areas in Housing Development Board (HDB) flats in
Singapore, were lighted up by T8 linear fluorescent lamps with magnetic ballast and
with a recommended illuminating range between 50~100 lux.. In 1992, HDB decided
to change the T8 linear fluorescent to a dual 11W compact fluorescent tube lamp. The
reason for a dual compact fluorescent tube was to reduce energy consumption and
extend the lifespan of the tube. Normal daily operating hours of corridor lights are
from 7pm to 7am, but with the implementation of dual tubes, an automated program
was designed to switch off 1 of the tube from 12am to 7am, and switching off the other
tube on alternate nights. After some studies and audit findings, the dual compact


                       Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                         20
fluorescent lamp doesn‘t seem to provide the energy savings that this project had
intended to achieve and this finding was reported in an energy audit report conducted
by Premas International Limited in 2004. As seen in the calculation table below, it
clearly indicates that the T5 linear fluorescent consumes around 12% lesser electricity
as compared to the dual compact fluorescent lamp. There was also another problem,
the light emitted from the compact fluorescent lamp was not bright enough to light up
the whole corridor and the many residents couldn‘t adjust to the colour of the lighting
produced. T5 linear fluorescent lighting produced a more warm-coloured light as
compared to the compact fluorescent.

The electricity tariff rate in Singapore is at 21.69 cents/kWh (wef 1 Oct 2009),
exclusive of government service tax (GST).

                                                                        Compact       T5 Linear
                   Type of lighting                                    fluorescent   Fluorescent
                                                                         (2 tubes)      (2ft)
             Average watts per bulb (W)                                      11          14
                No of hours per night                                     12 + 6         12
   Total amount of electricity consumed for 30 days
                                                                           5.94         5.04
                         (kWh)
     Total cost of electricity for 30 days ($SGD)                          1.29         1.09

Finally in 2005, HDB removed the compact fluorescent tube lightings in common
corridor areas and replaced them with industrial standard energy saving T5 14W linear
fluorescent tube lamps and electronic ballasts. T5 linear fluorescent lamps cannot
directly replace a T8/T12 fluorescent lamp as they have different electrical
characteristics and are of different length. T5 linear fluorescent lamps offer energy
savings at around 40~50% and a brighter light projection as compared to the compact
fluorescent lamp. Electronic ballast increase overall lamp-ballast efficacy by about
10~15%. Therefore increasing the energy efficiency and lowering the operating costs.

HDB uses centralised dimmable circuits in limited block of flats, some block of flats
are using power-saving devices and HDB multi-storey car parks are still using
magnetic/conventional control gear [30]. Electronic circuits with dimmable technology
have been considered for implementation, but the initial costs are too high for a wide
scale project and the return of investment (ROI) is above 5 years.

LEDs offer much more energy savings as compared to fluorescent lighting. Though it
offers much savings in energy, the initial cost is too high to be implemented on a large
scale basis. Even with the high initial cost, some countries have implemented street
lightings with LEDs lamps. The major LED manufacturers, Nichia, OSRAM Opto
Semiconductors, Cree and Philips LumiLeds have started supplying LEDs for general
lighting usage.

These are some of the many projects that various countries have undertaken to replace
metal halide lamps. In 2007, OSRAM Golden Dragon LEDs were selected for a special
lighting project in the City of Rayleigh, North Carolina. OSRAM LEDs were to
replace 12 metal halide (HID) lamps that were used to illuminate the pedestrian tunnel
passage. In each lighting fixture, 112 LEDs were used. LEDs were chosen because of
its highly energy-efficient properties. Next was a project to implement energy-saving


                     Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                   21
street lighting in Austria. 12 OSRAM Golden Dragon LEDs per street lamp were used
to illuminate cycle paths and footpaths. Each LED consumed 0.35W and each lamp
produced 60lm and operated at 130mA. Canada soon followed and replaced 8 of its
street lamps with LED street lighting in a pilot project and reported energy savings of
around 36%. In 2009, OSRAM supplied their Golden Dragon LED range to light up
the streets of Finland, Jing Jiang and Shenzhen (China) and Korea. The Ministry of
Science and Technology in China is pushing to replace traditional incandescent lamps
with energy saving LED lamp by 2015, with a potential energy saving of around
RMB260 billion.

In 2007, Midwest Circuits in Ferndale, began to focus on municipal street lighting.
With the help of Future Lighting Solutions and Philips LumiLeds, LUXEON Rebel
LEDs in Lansing fixtures were chosen to replace the current metal halide (HID) lamps.
This resulted in energy savings of around 50~60% of the original HID lamps, and
LUXEON Rebel LEDs operating at 350mA, produced outstanding light output and
efficacy with excellent light distribution.

3.2 Cost
                                                       Compact                   T5 Linear
         Type of lighting                Incandescent Fluorescent               Fluorescent       LED Lamp
                                                                                   (2ft)
          Watts per bulb                        60                 11               14               7
Cost of a typical commercial lamp
                                                 1                 6~8               3~5           70~100
              ($SGD)
      Average lifespan (hrs)                   1200          8000~10000 12000~15000 50000~60000


Average lifespan for a fluorescent lamp would also depend on the method that it is
being used for. Short on/off cycling would decrease the lifespan drastically and
dimming will also cause the lifespan of compact fluorescent to decrease.

Incandescent bulbs are the cheapest commercial bulbs available today while LEDs are
the most expensive. Despite the high initial cost of a LED lamp, the return of
investment (ROI) will occur within 3~5 years. With a longer average lifespan, using an
LED lamp would require lesser maintenance to replace the lamp.

A method to calculate the cost of light can be seen in Figure 3.1.

Cost of Light = [(10/Lamp Lumens) x ((Lamp Cost + Labour Cost) / Life time + (Energy Use x
Energy Cost))]

Where:
Lamp Lumens = the light output of the lamp measured in lumens
Lamp Cost = the initial cost (first cost) of the lamp in dollars
Labour Cost = the labor cost necessary to replace a lamp in dollars
Lifetime = the useful operating life of the lamp, expressed in 1000 hours
Energy Use = the power consumption of the lamp, expressed in watts
Energy Cost = the cost of the electricity necessary to operate lamp in $/kWh
Courtesy of Kevin Dowling, Color Kinetics                   Figure 3.1               Figure 3.1


                       Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                          22
3.3 Reliability
LED lamps are the most reliable type of lighting. They are not subjected to lifespan
reduction when frequent on/off cycling occur, robust in nature with no filaments to
break out or electrodes or glass to shatter and can be used in rugged conditions, LED
lamps turn on instantly, unlike fluorescent lamps which require some start-up time.

However, maintaining white light colour consistency is one of the few problems that
LEDs face. This is due to the method of how white light is being produced from LEDs.
Basically there are 2 methods as mentioned in section 2.3.1, red-green-blue technology
and coating a high-brightness blue LED with yellow phosphor. The natural variations
in the wavelength and phosphors make it hard for manufacturers to maintain the colour
consistency in white colour LEDs. Improvements in technology of phosphors will help
to reduce the inconsistency, but this is an inevitable efficiency loss.

3.4 Limitations of LEDs
Since LED lamps offer the best energy consumption, the highest average lifespan, the
most durable lamp, doesn‘t contain any form of mercury, why aren‘t white light LED
lamps implemented into general lighting for the mass population?

The focus will be on these 3 key points, consumer acceptance, infrastructure and
research and development of LED which will influence the start of mass acceptance of
LEDs for general lighting.

3.4.1 Consumer Acceptance
The benefits of using LED lights are very visible to the public, but consumers normally
go for the cheapest type of product, even though it‘s less efficient. Various authorities
or government bodies have to emphasize and promote this energy saving technology to
the masses. With mass demand for LEDs, manufacturing costs will definitely reduce,
and this will resolve another existing problem for the mass commercialisation of LED,
high initial cost.

3.4.2 Infrastructure
Just like what happened to the incandescent lamps, an industry technology roadmap
has to be in place before the mass commercialisation of the product itself. A
recommended solid-state lighting (SSL) for LED roadmap by US Optoelectronics
Industry Development Association in 2002 is shown below in Table 1.4.

Roadmaps are created to highlight the goals and targets or identify roadblocks and all
these are targeted to be achieved within a certain timeframe. These are fundamental
planning material for industry manufacturers and government bodies to identify and
plan the necessary actions required.




                     Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report            23
                SSL-LED        SSL-LED        SSL-LED         SSL-LED
  Technology                                                                Incandescent Fluorescent
                  2002           2007           2012            2020
    Luminous
     efficacy       25            75              150            200                16        85
      (lm/W)
     Lifetime
                    20            >20            >100            >100                1        10
        (kh)
        Flux
                    25            200            1,000          1,500              1,200    3,400
    (lm/lamp)
   Input power
                    1             2,7            6,7             5~7                75        40
    (W/lamp)
  Lumens cost
                   200             20            <5               <2                0,4      1,5
      ($/klm)
    Lamp cost
                    5              4              <5              <3                0,5       5
     ($/lamp)
      Colour
    rendering       75             80             <80            <80                95       75
   index (CRI)
     Lighting
     markets     Low flux    Incandescent    Fluorescent         All
    penetrated
  Courtesy of OIDA                                                                         Table 1.4



The US Department of Energy (DOE) released an updated SSL manufacturing
roadmap in 2009, mainly targeting lower costs and greater product consistency and
quality. These 2 points are the key to mass market acceptance.

In the recent DOE SSL Manufacturing Workshops in Fairfax, VA and Vancouver,
WA, 2 separate breakout groups highlighted 2 major roadblocks that slowed the
progress of market acceptance and lower costs, direct manufacturing of LED
luminaires and packaged LEDs [31].

Under direct manufacturing of LED luminaires, 4 significant issues were highlighted.
    LED Binning
    Life testing
    Power supplies and drivers
    Software and modelling tools

Under LED package, 4 significant issues were highlighted.
    Epitaxial processes
    Substrates
    Equipment
    Process control and testing




                     Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                       24
A typical SSL system is shown in Figure 3.2

                                             LED CHIP
                                              DESIGN

               LED Materials
                                                                      Component
               (Epi, subtrates
                                                                        Design
                     etc)

                                              Efficiency

   White Light                                                                      Luminaire
  Generation &                                   Cost                                Thermal
    Quality                        Reliability            Customer                   Design
                                    Quality              Expectation



                Power Supply                                            Luminaire
                   Circuit                                            Optical Design
Courtesy of Mark McClear, Cree, Inc                                                       Figure 3.2


While it might be a correct method to identify and focus on the major area that keeps
the cost high for a LED, developing an integration method between system level and
component level would be a better method in addressing to reduce the overall
manufacturing costs for LEDs. A decision made in the design stage can cost an impact
on the manufacturing process of the product. Inter-department engineers should
therefore work closely to optimise the process of manufacturing.

3.4.3 Research and Development
Research and development is the foundation block in driving down the costs of LEDs.
With a LED industry roadmap, engineers can narrow down and focus on the relative
issues that are keeping the costs up for LED lights. The areas can be broken down into
R&D groups like,

      Research level
       o Research alternative substrates
       o Optimising phosphors
       o Thermal control solutions
       o Better light extraction and light utilization methods

      Development level
       o Development of low cost high quality substrates
       o Develop epitaxial growth at low cost with uniformity and increased
          material use efficiency levels
       o Better and more efficient electronics components or materials


                      Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                      25
      Manufacturing level
       o Minimizing substrate or material issues
       o Approaches / methods to drive up yield and quality
       o Manufacturing tools and methods to improve efficiency of production and
         lowering costs

      System level
       o Methodology for system reliability
       o Standardization of testing methods

There are many more possible core tasks or subtasks that can be identified in the LED
industry roadmap which require intensive research and development.

The points shown below are the core priorities in research and development of LED
that the US DOE has defined for 2009.

LED Core Technology
   Emitter material research
   Down-convertors
   Optical component materials
   Thermal component research
   System reliability methods

LED Product Development
   Semiconductor materials
   Phosphors
   Emitter thermal control
   Epitaxial growth
   Luminaire thermal management techniques
   Optimizing system reliability

All these tasks or subtasks have 1 common goal, which is to eliminate the roadblocks
that are ahead which is obstructing the commercialisation of LED in the general
lighting market.

3.5 Market potential of LED
In a recent article, Robert Steele a director from Strategies Limited reported a market
size of $USD 4.8billion for the LED industry in 2008. These are the several markets in
the LED lighting industry and the figures below are given by Robert Steele [32].

3.5.1 Consumer Electronics
LEDs in mobile phones have been increasing steadily throughout the years that it has
been implemented but mobile phone handset shipments are projected to have a
decrease of 10% in 2009. This segment accounted for 42% of the high brightness LED
in 2008.



                     Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report          26
White LED penetration in display backlights in notebook computers have been
climbing steadily in the recent years since its introduction in 2005 and it is expected to
reach the 50% mark in 2009 from a figure of 12% in 2008.

LED backlights for LCD TVs are still in the infancy stage at this moment but things
are picking up as major TV manufacturers like Samsung, LG, Sharp, Sony and other
manufactures are aggressively marketing this technology into the mainstream
consumer electronics market. LCD TVs are more expensive than conventional cold
cathode fluorescent lamp (CCFL) backlit LCD TVs, and in a worldwide economic
depression, this area might face a short downturn in figures. However in the long term,
when costs between LED and CCFL are brought closed together, this segment for
LEDs might cross into the figure of billions by 2013.

3.5.2 Automobile
LEDs have penetrated into the automobile industry with the intention of replacing high
intensity discharge (HID) lights. LEDs have a lower operating temperature, longer
service lifespan, instant reaction, work at lower voltages and are non fire hazard as
compared with HID lights. LEDs are currently used in dash boards and tail lights, with
a minority percentage in front head lights. The low percentage in front head lights are
due to the high cost and government standards of front lighting for automobiles.
Automobile production will likely have a decrease of 20% in 2009 and this segment
accounted for 15% of the high brightness LED in 2008.

3.5.3 Lighting
In 2008, the penetration figure for LED in lighting increased by 54%, and a 15%
increase in 2009 is expected. With LED product sales of around $USD 1.86 billion in
2008, the figures will continue to grow based on these events, the increase of white
LED efficacy to over 100lm/w, superior energy saving figures, promotions by various
governments around the world, LEDs are set to be the main driver for market growth
in lighting.

According to a report compiled by Freedonia Group, the global lighting industry which
includes fixtures and light lamps, has an estimated value around $120 billion by 2012
with a project growth of 5% per annum [33]. Manufacturers who are able to seize the
opportunity and produce the first commercial available product with the lowest cost
and best benefits, will be able to grab a large market share of this expanding industry.

3.6 Limitations
Several limitations were faced during the process of this final project. Access to the
recent advancements in LED technology was only abstracts, as payment was required
for the full text edition of the relevant papers. Market strategies and reports were also
limited to abstracts and introductions as payment was also required to gain access to
these reports.




                     Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report             27
4. Conclusion and recommendations
The lighting industry is a massive market with the potential energy savings of
estimated value of $USD10~30 billion per year if a more energy efficient lighting is
used in the mass market right now. With this amount of savings, it is equivalent to
having <100 coal plants reduced, and with carbon dioxide emission levels reduced by
millions of tons annually. This outcome will definitely play a major part in reducing
global warming. Moreover LEDs do not contain the hazardous material, mercury,
which makes it a more environmentally friendly product.

High-brightness (HB) white colour LEDs offer much more advantages over the
existing incandescent and fluorescent lamps, but the cost of light for this green
technology is the stumbling block for mass market commercialisation at the moment.
According to Haitz‘s and Moore‘s law, we will probably see a more competitive
pricing between HD LED and fluorescent lamps for the general lighting area in the
next decade or so.

On a bright side, recent developments in LED technology, like the RAIS technology
for dimmable circuits mentioned in section 2.3.2, are researched and developed
towards providing more advantages to switch to LEDs for general lighting. Industry
roadmaps have been updated and released by various countries, like the recent release
by US DOE in 2009, signifying the intention of world bodies to promote and accelerate
this technology to the consumers. With roadmaps in place, government funding for
research and development and the collaboration of manufacturers, this will definitely
accelerate the removal of roadblocks and obstacles that stand in LEDs path to mass
commercialisation in general lighting.

In conclusion, LED lamps are too costly to implement in a large scale exercise
throughout the world at the moment and until the costs of LED lamps are comparable
to the existing fluorescent or compact fluorescent lamps, it would be very hard to see
countries installing LED lamps in mass quantity. To sum up the situation in a sentence,
LEDs are the future of light.

However in my personal perspective, I wish to see our local government taking the
initiative in promoting this green technology in large scale areas. The initial costs are
definitely high, but with a long term savings in mind, the money spent is worth the
high initial outlay. LED lamps might not be suitable for general lighting at this
moment, but areas like pathways in parks, carparks, stairways, can be installed with
HB LED lamps. It‘s probably the first stage of implementation that our local
government can initiate. This will also create consumer awareness of LEDs which
might increase the number of consumer installing LED lamps in their residential
homes or companies installing in the office premises.

Students interested in the lighting industry can consider researching in more technical
areas like, the advancement of substrate and semiconductor materials, new methods
and techniques in achieving higher lumens output and better LED packaging
techniques etc. A software project like using MathLab to accurately calculate the
timeframe where the cost of a HB LED lamp will be competitive to a fluorescent lamp
can also be taken into consideration. Those who are more inclined in hardware projects



                      Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report           28
can consider creating a solar powered LED lamp prototype to illuminate areas like
street lamps around beaches or parks.

The lighting industry has many fields and areas which need more coverage and a future
report could serve as an informative document for architects, consumers, engineers,
who are interested in the developments of the lighting technology, or LED in
particular. Information is very vast and scattered, so students might want to narrow
down and focus on one or two of the topics of lighting technology.

Last but not least, the objectives of the project have been obtained with much
satisfaction and in conclusion, this project was a fairly successful project.




                     Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report        29
5. Reflections
Right from the start of selection of topics for this final year project, I knew I wanted to
choose something related to research on alternative energy or energy saving products
or technology. Eventually I selected the topic on Theoretical Studies and Analysis of
Solar Cells as my first choice and I was selected for this topic.

Since the start of TMA01, I have already concluded that the technical hardware and
software knowledge would be my weakest area, which I needed to place more
emphasis in tackling these problematic zones. Solar cells were a new topic to me as my
job didn‘t involve anything regarding solar cells nor was I exposed to solar cells in my
course of tertiary studies throughout polytechnic to university. So in phase 1, I needed
to spend 2 weekends in libraries, researching on journals, books, sourcing information
on the internet, to gain a better understanding of the relevant topic ahead.

After some frequent emails and meetings with my tutor, Mr Peh King Sing, we decided
that my primary objective was to propose a solution to increase the efficiency of solar
cells and the secondary objective was to obtain accurate data to backup my primary
objective. Capstone interim report was submitted subsequently and I was given the
approval for continuation of this project.

I faced many difficulties in creating a circuit for indoor solar cell simulation. I didn‘t
understand how to use voltage regulators in the circuit, I wasn‘t progressing and I felt
like giving up. Mr Peh offered me suggestions and gave pointers, but I really didn‘t
feel comfortable. In selecting a project, 2 criteria were important to me, 1st is to have
an interest in the topic, 2nd is to enjoy the process of completing it. I wasn‘t enjoying
and time was limited. After weeks of trying, I gave up and sought Mr Peh help for a
change of topic. Fortunately, he understood my sentiments and gave me a new topic to
work on; Research on Lighting Technology.

I had some initial fears, how would I be examined on a pure research paper? It was
something I was very confident of completing, but I was also worried if I would be
penalised because I didn‘t have any hardware / software results to comment on as this
was an engineering thesis. Mr Peh reassured my fears and that I would not be penalised
as there were different types of thesis to begin with, and as long I completed my
objectives and put in lots of hard work, I will see the results.

Researching on this topic was very informative and interesting and I was able to put in
ideas and set objectives more confidently. The problem here was to juggle work and
part-time studies. I had to constantly manage my schedule to ensure I didn‘t neglect my
work or studies. This was not easy, as I had class and lab tests to study for, work
commitment to fulfil, focusing on this thesis was a difficult journey.

Looking back, I am glad to have chosen such a topic to write my thesis even if it meant
lesser time for me to complete it. I have learnt some valuable knowledge from this
thesis and throughout the course of my studies. It‘s not just about obtaining good
grades, but one should actually enjoy the process of learning and benefitting from skill
sets learnt along the way. This journey have developed and refined my critical and
analytic thinking skills which will stay with me for the rest of my life. ‗It doesn’t
matter how we live, but the quality of the way we live it.‘


                      Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report             30
6. References
[1]    http://inventors.about.com/od/lstartinventions/a/lighting.htm

[2]    http://en.wikipedia.org/wiki/Oil_lamp

[3]    http://en.wikipedia.org/wiki/Incandescent_lamp

[4]    http://en.wikipedia.org/wiki/Fluorescent_lamp

[5]    http://en.wikipedia.org/wiki/LED

[6]    http://home.howstuffworks.com/fluorescent-lamp.htm

[7]    http://www.oe-chemicals.com/dictionary-I.html

[8]    http://www.accessscience.com/abstract.aspx?id=391300&referURL=http%3a%2f%2fwww.ac
       cessscience.com%2fcontent.aspx%3fid%3d391300

[9]    http://www.lifesci.ucsb.edu/~biolum/myth.html

[10]   http://homepages.wmich.edu/~rosentha/pdf%20files/5_fluorescence.PDF

[11]   http://en.wikipedia.org/wiki/Sir_George_Stokes,_1st_Baronet

[12]   http://www.olympusmicro.com/primer/lightandcolor/fluoroexcitation.html

[13]   http://www.commercial-lamps.co.uk/news/information-resources/fluorescent-tubes/history-of-
       fluorescent-tubes/

[14]   http://www.ehow.com/about_5089197_history-fluorescent-lighting.html

[15]   http://en.wikipedia.org/wiki/Peter_Cooper_Hewitt#cite_note-0

[16]   http://redneckusa.wordpress.com/2009/08/17/lighting-the-way-to-the-future-with-led/

[17]   http://inventors.about.com/library/inventors/bl_fluorescent.htm

[18]   http://home.frognet.net/~ejcov/thayer.html

[19]
       http://www.capakor.com/product/pdf/%2837%29General_technical_information_of_fluoresce
       nt_lamp_starters.pdf

[20]   http://nemesis.lonestar.org/reference/electricity/fluorescent/instant.html

[21]   http://nemesis.lonestar.org/reference/electricity/fluorescent/rapid.html

[22]   http://members.misty.com/don/f-lamp.html

[23]   http://www.howstuffworks.com/electromagnet.htm

[24]   D. Ammermann, A. Böhler, W. Kowalsky, Multilayer Organic Light Emitting Diodes for Flat
       Panel Displays, Institut für Hochfrequenztechnik, TU Braunschweig, 1995.

[25]   http://www.philipslumileds.com/pdfs/techpaperspres/STEIGERWALD.PDF

[26]   http://www.nature.com/nphoton/journal/v1/n1/full/nphoton.2006.44.html




                       Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                  31
[27]   G. E. Moore, ―Cramming more components onto integrated circuits,‖
       Electron., vol. 38, no. 8, Apr. 1965.

[28]   http://www.irf.com/technicalinfo/whitepaper/howtodesignadimmingfluorescentelectronicballa
       st.pdf

[29]   http://www.ledsmagazine.com/features/6/5/8

[30]   Conversations with HDB staff, Mr Lim Ah Hee, Mr Mohd Joor.

[31]   www.eere.energy.gov

[32]   http://www.ledsmagazine.com/features/6/9/2

[33]   http://sg.us.biz.yahoo.com/pz/090917/173549.html?.v=1




                      Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report                  32
Appendix A
Initial Gantt chart




Final Gantt chart




                      Name: Trevor Lim Meng Choy PI: W0605229 ENG499 Final Report   33

								
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