Download study on wireless battery-less computer mouse

STUDY ON WIRELESS BATTERY-LESS
COMPUTER MOUSE
ADILA BT MOHAMED KHALIDI
UNIVERSITI TEKNOLOGI MALAYSIA
“I hereby declare that I have read this report and in my opinion this report has
fulfills the scope and quality for the award of degree of Bachelor of Engineering
(Electrical)”
Signature
:
___________________________
Name of Supervisor :
EN. ALIAS BIN MOHD YUSOF
Date
7th MAY 2011
:
STUDY ON WIRELESS BATTERY-LESS
COMPUTER MOUSE
ADILA BT MOHAMED KHALIDI
A project submitted in partial fulfillment of the
requirements for the award of degree of
Bachelor of Engineering (Electrical)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
MAY 2013
ii
I declare that this thesis entitled “Study On Wireless Battery-less Computer Mouse”
is the result of my own research except as cited in the references. The thesis has not
been accepted for any degree and is not concurrently submitted in candidature of
any other degree.
Signature
:
Name
:
ADILA BT MOHAMED KHALIDI
Date
:
7th MAY 2013
iii
Specially dedicated to my beloved parents, brother, sisters for their
loves, support and encouragement.
iv
ACKNOWLEDGEMENT
First and foremost, the greatest thanks and grateful to Allah S.W.T with all
His Majesty, for giving me a good health while finishing this thesis.
A special thanks to my family members for contributing ideas, and giving a
full support on this project. Without my family, it would be hard for me to
accomplished.
I also would like to express my sincere appreciation to my supervisor
En.Alias Bin Mohd Yusof for his supervision during completing this project.
Last but not least, thousand thankful to my beloved one and to my all friends
that giving me support physically and mentally in which their assistance helped
along the way.
v
ABSTRACT
This project was conducted to study about wireless computer mouse which
using a standard USB power supply and eliminates the use of batteries completely.
The system uses a soft switched current-fed push-pull converter for DC to AC
conversion. The AC current which flows through a disk coil embedded in a mouse
pad were providing a time varying magnetic field that transfer power to a power
pick-up coil located within the computer mouse, through magnetic induction. This
power which was tuned-up and regulated by an advanced voltage control methoddynamic detuning control, has proven to be able to provide sufficient power to drive
a wireless battery-less computer mouse.
vi
ABSTRAK
Projek ini telah dijalankan untuk mengkaji mengenai tetikus komputer tanpa
wayar yang menggunakan bekalan kuasa USB standard dan menghapuskan
penggunaan bateri sepenuhnya. Sistem ini menggunakan “soft switched current-fed
push-pull converter” untuk penukaran DC ke AC. Arus elektrik AC yang mengalir
melalui gegelung cakera yang terletak dalam pad tetikus telah menghasilkan medan
magnet yang berbeza masa di mana memindahkan kuasa kepada kuasa pick-up
gegelung yang terletak di dalam tetikus komputer, melalui induksi magnet. Kuasa
ini yang ditala dan dikawal oleh kaedah kawalan voltan maju – kawalan detuning
dinamik, telah terbukti mampu memberikan kuasa yang mencukupi untuk
menggerakkan tetikus komputer tanpa wayar tanpa pengunaan bateri.
vii
TABLE OF CONTENTS
CHAPTER
1
2
TITLE
PAGE
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENTS
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENTS
vii
LIST OF TABLES
ix
LIST OF FIGURES
x
LIST OF SYMBOLS
xi
LIST OF APPENDICCES
xii
INTRODUCTION
1.1 Problem Statement
1
1.2 Objectives of Project
1
1.3 Scope of Project
2
LITERATURE REVIEW
2.1 A Perspective of Contactless Power Transfer
3
2.2 Introduction to IPT Power Supplies
5
2.2.1 Basic Structure and Operating Principle
6
2.2.2 General Features
7
2.3 An Introduction to Litz Wire
8
2.3.1 Principle of Operation
9
2.3.1.1 Skin Effect
9
viii
3
2.3.1.2 Proximity Effect
11
2.3.2 Effectiveness
11
2.3.3 Applications
12
METHODOLOGY
3.1 Introduction
13
3.2 General Summary of The Proposed IPT
Computer Mouse
4
5
13
3.2.1 System Configurations
13
3.2.2 Design Requirements
14
3.3 Primary Implementation
16
3.3.1 Resonant Converter
16
3.3.2 Primary Track Configuration
18
3.4 Secondary Pick-up Implementation
21
3.4.1 Dynamic Detuning Control
21
RESULTS AND DISCUSSION
4.1 Introduction
23
4.2 Primary Track
23
4.3 The Secondary Pick-up
24
CONCLUSION AND RECOMMENDATION
5.1 Conclusion
26
5.2 Recommendation
27
REFERENCES
28
APPENDICES
30
ix
LIST OF TABLES
TABLE NO.
TITLE
PAGE
2.1
Electric power transfer options
4
3.1
Estimated power consumption of wireless
Computer mouse
14
x
LIST OF FIGURES
FIGURE NO. TITLE
PAGE
2.1
Basic structure of a typical IPT system
6
2.2
The twisted or woven strands of LItz wire
8
2.3
Litz wire made out of 8 thinner isolated copper wires
9
2.4
Disassembled induction cooker showing litz wire coil
12
3.1
The configuration of a wireless computer mouse
14
3.2
Design flowchart
15
3.3
The self-sustained current-fed push-pull
resonant converter
17
3.4
Spiral coil configuration
19
3.5
Magnetic distribution of a spiral coil distribution
19
3.6
The disk coil configuration
20
3.7
Magnetic field distribution of the disk coil
Configuration
20
3.8
Dynamic Detuning Control circuit diagram
21
3.9
The relationship between tuning capacitance and
parallel compensated pick-up output current
22
4.1
The primary track
24
4.2
The secondary pick-up
xi
LIST OF SYMBOLS
μo
-
Permeability
εo
-
Permittivity
ωo
-
Nominal Frequency
Lp
-
Primary Track Inductance
Rp
-
Track Resistance
Qp
-
Primary Quality Factor
ZVS
-
Zero Voltage Switching
Hz
-
Hertz
kHz
-
Kilo Hertz
MHz
-
Mega Hertz
mW
-
Mili Watt
V
-
Voltage
mA
-
Mili Ampere
Mm
-
Milimeter
μm
-
Mikrometer
AC
-
Alternating Current
DC
-
Direct Current
USB
-
Universal Serial Bus
RF
-
Radio Frequency
xii
LIST OF APPENDICES
APPENDIX TITLE
PAGE
A
MC 34063A - IC
30
B
CORDELESS OPTICAL MOUSE USER’S MANUAL
31
1
CHAPTER 1
INTRODUCTION
1.1
Problem Statement
For a better future friendly environmental, the usage of battery is no longer
needed in a wireless computer mouse because the disposals of batteries are exposing
the environment and water to a lead and acid.
There are many toxic chemicals inside a battery such as cadmium, mercury,
lead and nickel. Therefore, it would be ideal if the batteries can be eliminated.
1.2
Objectives of Project
i.
To built a wireless battery-less computer mouse device.
ii.
To design and understand about the circuits that will be used by using
Multisim 11.0.
iii.
To utilize the usage of Inductive Power Transfer (IPT) system for a low
power consumptions at mW.
2
1.3
Scope of Project
i.
Design a wireless battery-less computer mouse using IPT system
ii.
Simulate the circuits design using Multisim 11.0 software and apply it to a
PCB board.
iii.
Validate and testing both designed circuits which is Self-sustained currentfed push-pull resonant converter circuit and Dynamic Detuning Control
(DCC) circuit.
3
CHAPTER 2
LITERATURE REVIEW
2.1
A Perspective of Contactless Power Transfer
There are many ways to achieve contactless power transfer.
Table 2.1
outlines the possible options for electric power transfer in electromagnetic forms. In
addition to conventional systems with direct electrical contact and contactless power
transfer
can
be
obtained
theoretically
via
inductively,
capacitively
or
electromagnetic waves.
Conductive power transfer is based on a closed circuit that allows for
direct power flow along the conductors. The closed circuit is normally formed with
hard wiring connections which are using typical techniques, cables and contacts.
Contactless power transfer can be achieved inductively or capacitively
depending on whether it is via magnetic field coupling or electric field coupling.
For the closely coupled versions, theoretically the transformer and capacitors can
transfer the power without direct electrical contacts, but practically, both of
techniques are not suitable for delivering power to moving objects since the
magnetic or electric field in the these components have to be confined within iron
cores or electrolytic media. The closely coupled versions are suitable for electric
machines which allow more freedom of mechanical movement especially the linear
motors. The power efficiency and power factor of a linear motor are very low and
4
its expanded stator are very costly, therefore it is only suitable for transferring power
over a very short distance, e.g. within a machine tool.
Table 2.1 : Electric power transfer options
DIRECT
CONTACTLESS
CONTACT
FEATURES
TYPES
BASIC
THEORIES
CONDUCTIVE
INDUCTIVE
CAPACITIVE
WAVE
Hard wiring,
Closely
Loosely
Closely
Loosely
Electromag-
moving contact
Coupled
Coupled
Coupled
Coupled
netic waves
Electric circuit,
Magnetic
Electric arc &
Circuit, AC
contact
circuit
theories
theories
TYPICAL
Cables and
TECHNIQUES
Contacts
Distributed
magnetic
field,
Power
electronics
Confined
electric
field, AC
circuit
Distributed
electric
field,
Power
Wave
Propagation
electronics
Wave guides,
Transformer
IPT
Capacitors
CPT
Parabolic
antennas, etc.
ILLUSTRATION
Transferring power from the primary to secondary of a transformer is nearly
impossible at low frequencies such as 50Hz or 60Hz if its coils are separated far
apart without maintaining a tight magnetic coupling. However, by refer to the basic
concept of Inductive Power Transfer (IPT), if the operating frequency is increased to
a very high value, then the fast changing rate of magnetic field will cause a much
stronger induction effect between the two coils. Practically, the power jumping
across the air gap will becomes feasible.
Another way of transferring power contactless is via Capacitive Power
Transfer (CPT) which is analogous to IPT theoretically. In a CPT system, the two
plates of a capacitor can be set apart, forming a large air gap for the power to jump
across. One of the capacitor plates is mechanically free to move so that power can
be transferred from a static frame to a moveable objects by combining two or more
of such capacitors in a circuit. The distributed electric field in CPT system will
serves as a power flow passage, consequently, the voltage, instead of the current as
in an IPT system where a distributed magnetic field offers a power flow channel.
5
A high frequency is also a beneficial to the power flow via the air gap of a
split “capacitor”. Therefore, high frequency power conversion may also be a major
issue, with power electronics being the enabling technology. CPT is simply a new
concept to serve as a counterpart to IPT. CPT has problems with high electric field
intensity exceeding 30kV/cm in air and very low permittivity εo (8.854 x
compared with the permeability μo (4π x
)
) which makes it 10 times more
difficult. Moreover materials with relative permeability greater than 100,000 also
contribute to the fact that IPT is more practical than CPT.
For the wireless signal communication, the power transfer can be achieved
via electromagnetic waves. However, transferring a large amount of power over a
long distance in the open air using traditional wave guides or parabolic antennas can
be very difficult for normal use due to the complexities involved in the power flow
control [1].
This study is about Inductive Power Transfer (IPT) power supplies which are
the most feasible contactless power supplies using modern power techniques.
2.2
Introduction to IPT Power Supplies
IPT is a technology that using power transfer system based on magnetic
coupling which is sometimes called as Inductively Coupled Power Transfer (ICPT).
IPT can be described as a loosely coupled power supply system using modern power
conversion, control, and magnetic coupling techniques to achieve contactless power
transfer from a static frame to a moveable objects.
6
2.2.1
Basic Structure and Operating Principle
Fig. 2.1 shows the basic structure of a typical IPT system. There are two
electrically isolated parts in IPT system. The first part consists of a power converter
and a primary conductive path which can be elongated “track” or lumped “coil”. The
main function of the power converter is to supply a constant high frequency AC
current (normally a 10-100kHz current with a sinusoidal waveform) along the track
loop, this part often referred to as the track power supply. The second part consists
of a pick-up coil and a power conditioner. Due to the mutual magnetic coupling
between the primary track loop and the secondary pick-up coil, an inductive
electromotive force is induced in the pick-up coil which forms a voltage source for
the secondary power supply. Since the magnetic coupling is loose, which is low
compared to normal transformer, the induced voltage source is usually unsuitable to
be used by the equipment directly. As such, a power conditioner is required to
regulate the power into the form required by the load, such as a motor controller or a
lamp.
Fig. 2.1 : Basic structure of a typical IPT system
A high quality track current generated by the power converter is essential for
proper operation of the whole IPT system. This current affects the performance of
all other parts of the system (such as the magnetic coupling and the pick-up
conditioning), and hence the general power flow from the static power supply to the
pick-up coil. In fact, the track power supply accounts for the majority of the system
cost. Normally, in order to make a full use of the track power supply, multiple pickups are attached to a single track loop.
7
2.2.2
General Features
When compared with the conventional power supplies, an IPT system has
the following features [1]:
1. Freedom of mechanical movement.
The pick-up can move along the track loop while allowing some lateral
displacement from the track centre, because of the loose coupling between the
primary and secondary of IPT system. This freedom makes it possible to deliver
power to moveable equipment without direct electrical contact. This is one of the
outstanding characteristics of IPT and differentiates it from a traditional transformer.
2. Safe operation.
There is no direct electrical contact in the path of the power flow, so it is
spark free and no open live wires, thus the possibility of accidental electric shock is
eliminated. IPT supplies also enhance the insulation between the primary and the
secondary sides, further improving the safety level to personnel and devices.
3. Reliable and robust.
There is no direct friction in an IPT system so that mechanical wear and tear,
and electrical erosion are eliminated. Plus, chemical erosion of the conductors is
essentially nonexistent because the electrical components can be completely
enclosed. Consequently the system is very reliable and robust, requiring almost no
maintenance.
4. Environmentally friendly.
Its operation is not affected by dirt, dust, water, or chemicals because IPT
has two independently enclosed parts.
Therefore it can work in very harsh
environments. Furthermore it does not generate carbon residues, as is the case with
traditional sliding contact system using carbon brushes, and has no harmful effects
on surroundings.
8
2.3
An Introduction to Litz Wires
Litz wire is a type of cable used in electronics to carry alternating current
(AC). The wire is designed to reduce the skin effect and proximity effect losses in
conductors used at frequencies up to about 1 MHz [15]. It consists of many thin
wire strands, individually insulated and twisted or woven together, following one of
several carefully prescribed patterns often involving several levels which is groups
of twisted wires are twisted together and etc. This winding pattern equalizes the
proportion of the overall length over which each strand is at the outside of the
conductor.
The
term
litz
wire
originates
from
Litzendraht,
braided/stranded wire or woven wire.
Fig. 2.2 : The twisted or woven strands of Litz wire
German
form
9
Fig. 2.3 : Litz wire made out of 8 thinner isolated copper wires.
2.3.1
Principle of Operation
Litz wire reduces the impact of the skin effect and the proximity effect.
2.3.1.1 Skin Effect
The resistance of a conductor at DC (0 Hz) depends on its cross sectional
area. A conductor with a larger area has a lower resistance. The resistance also
depends on frequency because the effective cross sectional area changes with
frequency. For alternating currents (AC), the skin effect causes the resistance to
increase with increasing frequency.
For low frequencies, the effect is negligible. For AC at frequencies high
enough that the skin depth is small compared to the conductor size, the skin effect
10
causes most of the current to flow near the conductor’s surface. At high enough
frequencies, the interior of a large conductor does not carry much current.

At 60 Hz, the skin depth of a copper wire is about ⅓ inches (8.5 mm).

At 60 kHz, the skin depth of a copper wire is about 0.01 inches (0.25 mm).

At 6 MHz, the skin depth of a copper wire is about 0.001 inches (25 µm).
Round conductors larger than a few skin depths don’t conduct much current near
their axis, so the central material isn’t used effectively.
When larger conductors are needed, tricks are used to minimize the skin
effect. The goal is to increase the conducting surface area. One trick is to use a
hollow conductor with a wall that is about a skin-depth thick. It is essentially a large
diameter wire with the non-current interior deleted. It is bulky but it saves copper.
To combat the skin effect, litz wire uses lots of thin conductors (strands) in
parallel. Each thin conductor is less than a skin-depth, so an individual strand does
not suffer an appreciable skin effect loss. The strands must be insulated from each
other – otherwise all the wires in the bundle would short together, behave like a
single large wire, and still have the skin effect problems. Futhermore, the strands
cannot occupy the same radial position in the bundle (the electromagnetic effects
that cause the skin effect would still disrupt conduction). The bundle is constructed
so the individual strands are on the outside of the bundle and provides low resistance
for a time, but also reside in the interior of the bundle where the EM field changes
are the strongest and the resistance is higher. If each strand provides about the same
average resistance, then each strand will contribute equally to the conduction of the
entire cable.
The weaving of twisting pattern of litz wire is designed so individually
strands will reside for short intervals on the outside of cable and for short intervals
on the inside of the cable. These allow the interior of the litz wire to contribute to the
cable’s conductivity.
Another way to explain the same effect is the magnetic fields generated by
current flowing in the strands are in diresctions such that they have a reduced
tendency to generate an opposing electromagnetic field in the other strands.
11
Thereby, for the wire as a whole, the skin effect and associated power losses when
used in high frequency applications are reduced. The ratio of distributed inductance
to distributed resistance is increased, relative to a solid conductor, resulting in a
higher Q factor at these frequencies.
2.3.1.2 Proximity Effect
The proximity effect will cause losses in cases involving multiple wires, or
multiple turns, such as windings in transformers and inductors.
The losses of
proximity effect are to increase at high frequency even sooner and more rapidly than
does skin effect.
2.3.2
Effectiveness
The frequency of Litz wire is very effective below 500 kHz but it is much
less effective if the frequency is above 2 MHz. Litz wire can be used at thicker
cable sizes eventhough litz wire has higher impedance per unit cross-sectional area.
So litz wire can reduce or maintain the cable impedance at higher frequencies [16].
12
2.3.3
Applications
High frequency application such as inductors and transformer are using Litz
wire. This is because the skin effect is more pronounced and proximity effect can be
an even more severe problem. Disassembled induction cooker that are using litz
wire is shown in Fig. 2.4.
Fig. 2.4 : Disassembled induction cooker showing litz wire coil.
13
CHAPTER 3
METHODOLOGY
3.1
Introduction
For the implementation of this project, the design IPT system concepts and
methodologies have been employed and need to be understood thoroughly. This
chapter covers the overall theory of Inductive Power Transfer.
3.2
General Summary Of The IPT Computer Mouse
3.2.1
System Configuration
The IPT primary circuit and the wireless receiver module were located
together to form a single integrated mouse pad solution as shown in the
configuration of IPT wireless computer mouse in Fig 3.1. Then the mouse pad will
be connected to a standard USB port which will provide the power and the
communication channel from the computer.
The architecture of this wireless
computer mouse was built on top of a commercial battery powered wireless
14
computer mouse. The primary track was design based on a standard mouse pad
which is to provide a magnetic field distribution over it. Lastly, the wireless
transmitter and the pick-up which are located within the wireless computer mouse.
Fig. 3.1 : The configuration of a wireless computer mouse
3.2.2
Design Requirements
The design requirements are to produce sufficient power at the pick-up for
the load. The power demand according to the specification of the original wireless
computer mouse is shown in Table 3.1.
Table 3.1 : Estimated power consumption of wireless computer mouse
Active State
Stand-by State
3.3 V x 50 mA = 165 mW
3.3 V x 33 mA = 108.9 mW
This estimated power demand does not take into account of the wireless
receiver module which is the losses in the power converter, primary track and the
rectifier. This design is quite challenging by considering the available power of a
standard USB is only 0.5 Watt for 100 mA in low power mode and 2.5 Watt for 500
mA in high power mode at 5V. The power pick-up circuit and the power converter
for high frequency magnetic field generation have to be very efficient to make the
system work.
The appropriate converter, track material and secondary voltage
regulation will be discussed in the preceding section.
15
Determine an approriate converter topology
Form primary track. Measure Lp
Chooose a ωo. Calculate Cp.
Measure Isc and Voc. Therefore determine power induced at the pick-up.
Sufficient power
induced?
Choose approriate secondary tuning topology
Connect pick-up/ tuning circuit to rectifier/ voltage regulator
Test system performance with load
Fig. 3.2 : Design flowchart
It is a complex process in designing and implementing the IPT systems
which involving with many parameters. The design flowchart shown in Fig 3.2
showed steps of rational flow of the project work.
16
3.3
PRIMARY IMPLEMENTATION
3.3.1
Resonant Converter
Resonant converters are more efficient due to its ability to achieve Zero
Voltage Switching (ZVS). Before this, controllers and zero point detectors were
required to assist the set-up of the oscillation and control the commutation of the
switches on the two branches of the resonant converter, such that the oscillation can
be sustained and ZVS achieved [1].
For this project, a self-sustained current-fed push-pull resonant converter
with no additional controllers [1] has been developed. This converter will largely
reduced the complexity, power budget stress and the overall cost of the system. Fig
3,3 showed the structure of the current-fed push-pull resonant converter.
As shown in Fig 3.3, the circuit comprises a current-fed push-pull inverter
with parallel compensation. There is exception in this circuit which is that each
switch obtains its switch driving signal from the input of the alternative switch. The
switching instances will occur at the zero crossing since the switching is fully
controlled by the resonance and ZVS is achieved. The current is also in phase with
the voltage since the direction of current is reversed when the switches exchange its
on-off state. Only real power, P is delivered to the resonant tank, this means that
zero phase angle (ZPA) operation is achieved.
17
Fig. 3.3 : The self-sustained current-fed push-pull resonant converter.
The primary quality factor, Q must be upper a critical value to achieve selfstarting and ZVS. The primary quality factor is defined as :
Lp is the primary track inductance, Rp is the track resistance and ωo is the
nominal (oscillating) frequency. According to “Critical Q analysis of a current-fed
resonant converter for IPT applications” [14] and “Dynamic ZVS Direct On-line
Start up of Current Fed Resonant Converter Using Initially Forced DC Current”
[10], the minimum Qp for self-starting and ZVS is 2.54 and 1.86 respectively.
Various resonant frequencies associated with a series loaded parallel
resonant tank have been defined. Based on a thorough theoretical analysis, it has
been found that ZVS frequency reduces at low Q values and operation cannot be
sustained below a Q of 1.86. These figures are significant with IPT systems where
low Q values are economically preferable. In practice, Q is load dependant and
therefore should be designed larger than 2 to ensure safe operation [1].
18
The maximum equivalent load for ZVS start up corresponds to a quality
factor Q of about 2.54. By considering the ramp up delay of a practical DC power
supply, complete direct on-line overshoot free start up is achieved by starting point
the inverter at lower DC voltage levels. Compared with other control methods, this
method not only improves the system reliability and efficiency, but also reduces the
system cost as a very simple controller can be used and no additional starting
equipment is required.
This circuit will be constructed and tested to check whether it able to start up
and shut down automatically.
3.3.2
Primary Track Configuration
The distribution of the magnetic fields will be determine based on the
primary track physical configuration which has a great effect on the power transfer
efficiency. The relationship between Voc, magnetic field strength and distribution
are defined as :
N is the number of turns of the pick-up coil, B is the magnetic flux density
component that cuts perpendicularly through A and A is the area enclosed by the
pick-up coil. This equation showed that the primary track configuration should have
a field distribution such that it is cutting perpendicular through the area enclosed by
the pick-up, at any location on the mouse pad.
Two configurations have been considered which is the spiral and the disk
coil configuration.
19
(a) Spiral coil
(b) Cross-sectional view of a spiral coil
Fig. 3.4 : Spiral Coil Configuration
(a) Surface magnetic fields
(b) Different pick-up coil windings
Fig. 3.5 : Magnetic field distribution of a spiral coil distribution.
The flux in the vertical direction is cancelled out by neighbouring wires for
the spiral configuration. This will lead the flows of magnetic field within the
horizontal plane or along the surface of the mouse pad. Fig 3.4 (a) showed the flow
direction in the horizontal plane by the arrows. Fig 3.5 (b) showed the pick-up that
will have to be rotated on different parts of the spiral coil to achieve maximum
power transfer with this field orientation while another possibility is to use two pickups. By considering the limited space available in a wireless computer mouse, both
of these options are not practical.
20
Fig. 3.6 : Disk Coil configuration
(a) Magnetic field direction
(b) Pick-up coil winding
Fig. 3.7 : Magnetic field distribution of the disk coil configuration
Fig 3.6 showed that a disk coil configuration has a simpler magnetic field
distribution as shown in Fig 3.7. The angle between the pick-up and the field
direction would be more optimal on different parts of a disk coil by having the
enclosed plane of the pick-up perpendicular to the vertical axis. This is where the
disk coil was adopted.
21
3.4
SECONDARY PICK-UP IMPLEMENTATION
The parallel pick-up compensation can increase open circuit voltage, Voc by
a factor of Qs and this is where the parallel tuning was adopted as discussed in
section 3.2.2. But, this will lead to another problem which is a parallel compensated
pick-up is behaving like a current source and the supplied voltage changes with the
load. If the tuned voltage exceeding the maximum voltage of 3.6 volts, there is
probability danger will occur. This danger can be avoid by using a smart voltage
regulation method that has been used to regulate the output voltage to be constant
which is the Dynamic Detuning Control (DDC).
3.4.1
Dynamic Detuning Control
Fig. 3.8 : Dynamic Detuning Control circuit diagram
Fig. 3.8 shows that Ct is the detuning capacitor and Cf is a voltage stabilizing
capacitor. The Capacitor Switching Control circuit will switches ON S when the
load voltage VL exceed a limit threshold which will completes the connection of Ct
by changing the overall tuning capacitance to (Cs+Ct). This changes the amount of
tuned pick-up current output, and also VL.
22
Fig. 3.9 : The relationship between tuning capacitance and
parallel compensated pick-up output current.
This experiment will face two possible tuning schemes, under-tuning and
over-tuning schemes. As shown in Fig 3.9, the under-tuning scheme, Cs+Ct is equal
to the resonance capacitance, which gives the maximum tuned pick-up output
current. The maximum point should provide a VL of 3.3 volts in this application
while for the over-tuning scheme, Cs is set to the resonance capacitance and Ct is set
such that (Cs+Ct) will reduce the tuned pick-up output current to an appropriate
level. This conclude that to provide the needed power under heavy loads, the undertuning scheme need to switch ON more while when there is an excess power, the
over-tuning scheme will switch ON.
The advantage of this circuit is, the unused power will dissipate as heat
because it is regulated by detunes the power pick-up. This control mechanism is
much more efficient than Zener diodes or linear regulator.
23
CHAPTER 4
RESULTS AND DISCUSSION
4.1
Introduction
This chapter presents the results obtained from the used methodology. Then
the discussion on the results obtained is done. The results and discussion obtained
from the measurements on the primary track and secondary pick-up.
4.2
Primary Track
The estimated power consumptions of wireless computer mouse in active
state is 165 mW. The results showed that the maximum power which is 165 mW
that required by the pick-up for the load has been met in most locations on the
mouse pad.
Multi-strands Litz wires were used in the primary track helps in
reducing the AC power losses because it has a lower AC resistance. Fig. 4.1 showed
the insight of primary track.
24
Fig. 4.1 : The primary track.
4.3
The Secondary Pick-Up
Fig. 4.2 : The Secondary Pick-up
25
Fig 4.2 showed the Secondary Pick-up circuit board that has been connected
with the origin circuit board of wireless mouse. As the circuit was constantly
switching to provide sufficient power to the load and power was lost in this constant
switching process, the results showed that the under tuning schemes has produced
less power which is 140 mW. While when there are excess power, the over-tuning
scheme will switched ON. A power output of 193 mW was obtained while the
switching loss was much smaller. The voltage across the wireless computer mouse
input, VL was successfully controlled at about 3.3V.
26
CHAPTER 5
CONCLUSION AND RECOMMENDATION
5.1 Conclusion
The objective of this study is to built wireless battery-less computer mouse
device, to design and understand about the circuits that will be used by using
Multisim 11.0 and lastly to utilize the usage of Inductive Power Transfer (IPT)
system for low power consumptions at mW.
From the obtained results and
observations, the analysis of the system performance was done and suggestion for
the enhanced system has been provided.
After the completion of the study, the objectives of this project were
achieved. Wireless Battery-less Computer Mouse is finally built as planned. A
prototype driven by a standard USB power source have been successfully designed
eventhough the prototype does not working properly. It has found that the IPT
power supply can successfully delivered the required power at all locations within
the disk oil.
27
5.2 Recommendations
For the recommendation, the study can be enhanced by developed the
usability of the proposed mouse system such as the movement limitation of the IPT
wireless computer mouse. An intrinsic limitation of the IPT technology is the
limited power transfer range between the primary and the pick-up. The movement is
only allowed within the mouse pad, this would be inconvenient in situations where
the mouse is required to move away from the mouse pad, for examples, when it is
for presentations or computer gaming.
28
REFERENCES
1. Hu, A.P.: ‘‘Selected resonant converters for IPT power supplies’’, PhD
thesis, Department of Electrical and Computer Engineering, University of
Auckland, Oct 2001
2. Yungtaek Jang, M. M. Jovanovic.: ‘‘A contact-less electrical energy
transmission system for portable-telephone battery chargers’’, IEEE
Transactions on Industrial Electronics, vol. 50, pp 520-527. Jun 2003.
3. Green, A.W and Boys, J.T.:‘‘10kHZ inductively coupled power transfer
concept and control, Fifth International Conference on Power Electronics
and Variable- Speed Drives, 1994. pp 694-699.
4. Hu, A.P., Chen, Z.J.; Hussmann, S., Govic, G.A.; Boys, J.T.: ‘‘A
dynamically on off controlled resonant converter designed for coalmining
battery charging applications’’, Proceedings of 2002. International
Conference on Power System Technology, vol. 2, pp. 1039-1044. Oct 2002.
5. Stielau, O.H., Boys, J.T., Covic, G.A. and Elliot, C.G.: ‘‘Battery charging
using loosely coupled inductive power transfer’’, 8th European conference
on power electronics and applications, EPE,99, pp. 7-9. Sept 1999.
6. Elliot, G.A.J., Boys, J.T., Covic, G.A.: ‘‘A design methodology for flat pickup ICPT systems’’, paper submitted and accepted for IPEC International
Conference, 2006.
7. J. T. Boys, G. A. Covic, Yongxiang Xu, ‘‘DC analysis technique for
inductive power transfer pick-ups’’, IEEE Power Electronics Letters, vol. 1,
pp. 51-53, Jun 2003.
8. Abe, H.; Sakamoto, H.; Harada, K.: ‘‘A non-contact charger using a resonant
converter with parallel capacitor of the secondary coil’’, IEEE Transactions
on Industry Applications, vol. 36, pp. 444-451. Mar-Apr 2000.
9. Kelley, A.W.; Owens, W.R.: ‘‘Connector-less power supply for an aircraft
passenger entertainment system’’, IEEE Transactions on Power Electronics,
vol. 4, pp. 348-354. Jul 1989.
29
10. Hu, A., Boys, J.T., Covic, G.A.: ”Dynamic ZVS direct on-line start up of
current fed resonant converter using initially forced DC current”,
Proceedings of the 2000 IEEE International Symposium on Industrial
Electronics, vol.1, pp. 312 – 317. Dec 2000. 2007
11. Boys, J.T., Covic, G.A. and Green, A.W.: ‘‘Stability and control of
inductively coupled power transfer systems’’, IEE Proceedings on Electric
Power Applications, vol. 147, pp 37-43, Jan. 2000.
12. Stielau, O. H., Covic, G. A.: ‘‘Design of loosely coupled inductive power
transfer systems,’’ IEEE-PES/IEE/CSEE International Conference on Power
System Technology, POWERCON 2000, Dec 2000.
13. Wang, Chwei-Sen, Stielau, O.H., Covic, G.A.: ‘‘Load models and their
application in the design of loosely coupled inductive power transfer
systems’’, Proceedings of 2000 IEEE International Conference on Power
System Technology, Vol. 2, pp.1053-1058, December 2000.
14. Boys, J.T., Hu, A.P., Covic, G.A.: ‘‘Critical Q analysis of a current-fed
resonant converter for ICPT applications’’, IEEE Electronics Letters, vol.
36, pp1440-1442. Aug. 2000.
15. Terman, Frederick E. “Radio Engineers’ Handbook,” McGraw-Hill,
pp.37,74,80. 1943
16. Sullivan, Charles R.: "Optimal Choice for Number of Strands in a Litz-Wire
Transformer Winding". IEEE Transactions on Power Electronics March 1999
30
APPENDIX A
31
APPENDIX B