A Development Of Wireless Power Transfer Using Capacitive Method For Mouse Charging Application.
A DEVELOPMENT OF WIRELESS POWER TRANSFER USING CAPACITIVE
METHOD FOR MOUSE CHARGING APPLICATION
ONG ZHEN GUAT
This Report Is Submitted In Partial Fulfillment of Requirements for the Bachelor Degree
of Electronic Engineering (Wireless Communication)
Faculty of Electronic and Computer Engineering
Universiti Teknikal Malaysia Melaka
JUNE 2015
ii
iii
iv
v
To my beloved friends and family. Thank you my supervisor and all lecturers who
guide me, and to all my friends for giving me mentally and moral support during process
of finish final year project.
vi
ACKNOWLEDGEMENT
I would like to express my deepest appreciation to all those who provided me the
possibility to complete this report. A special gratitude I give to my supervisor Dr. Mohd.
Shakir bin Md. Saat who had given me many learning opportunities throughout the
preparation of this report. Besides giving me suggestions, he had also helped me to
coordinate my project, especially in writing this report. I am highly indebted to Dr. Shakir
for his guidance and constant supervision as well as for accessing my progress and also
for his support in completing this report.
Furthermore, I would also like to acknowledge with much appreciation of my
friends for providing decent suggestions and necessary information during the completion
of this report.
I have taken efforts in this project. However, it would not have been possible
without the kind support and help of many individuals. I would like to extend my sincere
thanks to all of them. Last but not least, I would like to thank my parents and family for
their support financially and emotionally.
vii
ABSTRACT
Wireless power transfer (WPT) is a non-contact power transfer within a distance.
With the advantage of not-contact concept, WPT enhances the flexibility movement of
the devices. Basically, there are three types of the WPT which are inductive power
transfer (IPT), Capacitive Power Transfer (CPT) and Acoustic Power Transfer (APT).
Among these, capacitive power transfer (CPT) has the advantages of confining electric
field between coupled plates, metal penetration ability and also the simplicity in circuit
topologies. Therefore, we focus on the capacitive method in this project. This project
aims to develop a wireless mouse charging system using capacitive based method. This
method enables wireless power transmission from mouse pad to wireless mouse. Hence,
no battery requires to power up the mouse. To be more specific, a high efficiency ClassE converter is designed to convert the DC source to AC and the compensation circuit of
resonant tank is also designed in the transmitter part in order to improve the efficiency. In
the end, a prototype is developed to prove the developed method. The performances
analysis of the developed prototype is discussed and the future recommendation of this
technique is also presented.
Keywords: Wireless Power Transfer (WPT), Capacitive Power Transfer (CPT), wireless
mouse charging, low power applications.
viii
ABSTRAK
Pemindahan kuasa tanpa wayar (WPT) ialah pemindahan kuasa tanpa sebarang
sentuhan dalam linkungan sesuatu jarak. Dengan kelebihan konsep tanpa sentuhan wayar,
WPT dapat meningkatkan pergerakan sesuatu alat dengan lebih fleksibel. Pada asasnya,
terdapat tiga jenis WPT yang mana ialah pemindahan kuasa secara beraruhan (IPT),
pemidahan kuasa secara berkemuatan (CPT) dan pemindahan tenaga melalui bunyi (AET).
Antara jenis pemindahan kuasa tersebut, pemindahan kuasa secara berkemuatan (CPT)
mempunyai banyak kebaikan iaitu medan elektrik antara gandingan plat-plat, keupayaan
penembusan logam dan juga kesederhanaan di topologi litar. Justeru, kami fokus pada
pemindahan kuasa secara berkemuatan dalam projek ini. Projek ini bertujuan untuk
mencipta sistem pengecasan tetikus tanpa wayar dengan menggunakan kaedah
pemindahan kuasa secara berkemuatan. Kaedah ini membolehkan penghantaran kuasa
tanpa wayar dari pad tetikus ke tetikus. Maka, tiada penggunaan bateri diperlukan untuk
menghidupkan kuasa tetikus itu. Untuk lebih terperinci lagi, penukar kelas E yang
kecekapan tinggi direka bentuk untuk menukar sumber DC kepada AC dan litar pampasan
tangki bersalunan juga direka dalam bahagian pemancar supaya kecekapan dapat
ditingkatkan. Akhirnya, sebuah prototaip dicipta untuk membuktikan kaedah tersebut.
Analisis keadaaan prototaip yang dicipta telah dibincangkan dan cadangan akan datang
teknik ini juga dibentangkan.
ix
TABLE OF CONTENT
CHAPTER
I.
TITLE
PAGE
PROJECT TITLE
i
REPORT STATUS APPROVAL FORM
ii
DECLARATION
iii
SUPERVISOR APPROVAL
iv
DEDICATON
v
ACKNOWLEDGEMENT
vi
ABSTRACT
vii
ABSTRAK
viii
TABLE OF CONTENT
ix
LIST OF TABLES
xii
LIST OF FIGURES
xiii
LIST OF ABBREVIATION
xvi
INTRODUCTION
1.1
Project Background
1
1.2
Project Overview
3
1.3
Motivation
4
1.4
Problem Statement
5
1.5
Objectives
6
1.6
Scope of Work
7
1.7
Project Planning
8
x
1.8
II.
Thesis Outline
LITERATURE REVIEW
2.1
Background Study of Wireless Power
Transfer (WPT)
2.2
2.3
2.4
III.
10
11
Capacitive Power Transfer and other WPT
Technologies
14
Converters for the WPT
19
2.3.1
Push-Pull Converter
19
2.3.2
Class-E Converter
20
Zero-Voltage Switching (ZVS)
22
METHODOLOGY
3.1
Workflow for the Project
25
3.1.1
Literature Reviews
27
3.1.2
Conceptual Design of a Low Power
Wireless Mouse Charging Prototype
27
3.1.3
Design of Push-Pull Converter
27
3.1.4
Design of Class-E Converter
29
3.1.5
The Selection of the Best Converter
31
3.1.6
Design of LC Series Resonance
(Compensator Circuits) on the Transmitter
and Receiver Part.
32
3.1.7
Design of Capacitive Plates
32
3.1.8
Design of Rectifier
34
3.1.9
Installation of Designed Circuit onto
the Mouse Pad and Mouse
35
xi
IV.
3.1.10 Circuit Correction and Adjustment
36
3.1.11 Performance Testing and Troubleshooting
36
3.1.12 Hardware Finalization
36
RESULT AND ANALYSIS
4.1
Class-E Converter
4.1.1
4.1.2
4.2
V.
37
Pulse Width Modulation and Driver
Circuit
39
Zero Voltage Switching (ZVS)
42
Capacitive Plate
46
4.2.1
Small Plate at Receiver Part
47
4.2.2
Big Plate at Receiver Part
50
4.3
Rectifier Circuit
54
4.4
Final Prototype
56
FUTURE WORK AND CONCLUSION
5.1
Conclusion
58
5.2
Recommendation
61
REFERENCES
63
APPENDIX A
66
xii
LIST OF TABLES
NO
TITLE
PAGE
1.1
Gantt Chart.
9
4.1
Assumed Parameters for the Class-E Converter.
38
4.2
Class-E Converter Parameters.
38
4.3
Average Output Voltage, V(r), at the Transmitter Plate.
46
4.4
Received Voltage at the Receiver Plate using Paper as a
Medium.
4.5
Received Voltage at the Receiver Plate using Mouse Pad
as a Medium.
4.6
51
Received Voltage at the 45° Slant Receiver Plate using Paper
as a Medium.
4.11
51
Received Voltage at the Receiver Plate using Mouse Pad as
a Medium.
4.10
50
Received Voltage at the Receiver Plate using Paper as a
Medium.
4.9
50
Received Voltage at the 45° Slant Receiver Plate using Mouse
Pad as a Medium.
4.8
48
Received Voltage at the 45° Slant Receiver Plate using Paper
as a Medium.
4.7
47
53
Received Voltage at the 45° Slant Receiver Plate using Mouse
Pad as a Medium.
53
xiii
LIST OF FIGURES
NO
TITLE
PAGE
1.1
Classifications of WPT [3].
2
1.2
Fully Aligned and Coupled Situation [8].
7
1.3
Misaligned Situation [8].
7
1.4
Conceptual Design of Wireless Mouse Charging
Prototype [9].
8
2.1
Sonicare Philips Toothbrush [12].
13
2.2
Powermat [12].
13
2.3
Capacitive Power Transfer Field Coupling between
Two Parallel Plates [10].
14
2.4
The Structure of CPT [7].
15
2.5
Magnetic Flux Coupling between Two Coils [10].
16
2.6
Schematic Diagram of Inductive Power Transfer [17].
17
2.7
Basic APT System [5].
18
2.8
Basic Schematic Circuit of Push-pull Converter.
20
2.9
Class-E Converter Circuit Topology [22].
21
2.10
Equivalent Circuit Diagram of the Class-E Converter [22].
21
2.11
Zero Voltage Switching (ZVS) [23].
23
2.12
Switching Losses [23].
23
3.1
Flowchart of the Project.
26
3.2
Simulation of the Selected Push-pull Converter Circuit.
28
3.3
Simulation on the Selected Class-E Converter Circuit.
29
xiv
3.4
LC Series Compensation Circuit.
3.5
Connection of the Transmitter Plate 1 and Transmitter
32
Plate 2.
33
3.6
Position of the Transmitter Plates and the Receiver Plates.
33
3.7
Sizes of the Capacitive Plate.
34
3.8
Rectifier Circuit from AC Source to DC Source.
35
3.9
Installation of Designed Circuit onto the Mouse Pad.
35
4.1
SK40C Start-up Kit with PIC16F877A.
39
4.2
MikroC Coding to Interface with PIC16F877A.
40
4.3
Setup of the PIC in Proteus with Graph Analyzer.
40
4.4
A 1MHz PWM Pulse Generated in Simulation.
41
4.5
Practical Output Pulse from the PIC16F877A.
41
4.6
Driver Circuit TC4422.
42
4.7
Class-E Converter Circuit in Simulation.
43
4.8
ZVS Condition for the Class-E Converter.
44
4.9
Class-E Converter Circuit of Practical Work.
44
4.10
ZVS from the Oscilloscope.
45
4.11
Drain Voltage versus Output Voltage at Load using
Oscilloscope.
4.12
Different Alignment of the Receiver Plate on the
Different Zone.
4.13
47
Graph of the Received Voltage in Different Position with
Different Medium.
4.14
46
48
Received Voltage from the Transmitter Plates versus
Received Voltage at the Receiver Plates (Paper).
49
4.15
45° Slant Alignment of the Receiver Plate.
50
4.16
Alignment of the Receiver Plate on Different Zone.
51
4.17
Graph of the Received voltage in Different Zone with
Different Medium.
52
xv
4.18
Received Voltage from the Transmitter Plate versus
Receiver Plate (Paper).
52
4.19
45° Slant Alignment of the Receiver Plate.
53
4.20
Rectifier Circuit in the Simulation before Fabricating.
54
4.21
Received Voltage from the Small Receiver Plate versus
Rectified Voltage (Paper).
4.22
55
Output Voltage from the Big Receiver Plate versus
Rectified Voltage (Paper).
56
4.23
Final Prototype.
57
4.24
Matrix Structure of the Transmitter Plate.
61
xvi
LIST OF ABBREVIATION
WPT
IPT
APT
CPT
EMI
AC
DC
USB
EV
MOSFET
ZVS
ZCS
PWM
LED
-
Wireless Power Transfer
Inductive Power Transfer
Acoustic Power Transfer
Capacitive Power Transfer
Electromagnetic Interference
Alternating Current
Direct Current
Universal Serial Bus
Electric Vehicle
Metal-Oxide-Semiconductor Field Effect Transistor
Zero Voltage Switching
Zero Current Switching
Pulse Width Modulation
Light-Emitting Diode
1
CHAPTER I
INTRODUCTION
In this chapter, wireless power transfer (WPT) will be discussed and the types of
the techniques of WPT will be explained. A summary and the aim of this project will
also be presented and discussed in this section.
1.1
Project Background
Wireless Power Transfer also known as WPT is a process of transferring power
between two or more physically unconnected electric circuits or devices [1]. This
innovative technology has created new possibilities to supply electronic devices with
electrical energy by eliminating of wires, connectors and slip-rings.
The potential
application of WPT can range from a low power office or home appliances to a high power
industrial systems. This concept has been first demonstrated by Nikola Tesla in the 1980s
by powering up fluorescent lamps 25 miles from the power source without using wires
[2]. Since then, various techniques based on WPT have been established which is shown
in Figure 1.1. Generally, it can be divided according to the medium used for power
2
transmission, which are acoustic-based WPT, light-based WPT, capacitive-based WPT
and the inductively coupled WPT.
WIRELESS
POWER
ACOUSTIC
WITH MAGNETIC
CORES
INDUCTIVE
COUPLING
CAPACITIVE
COUPLING
WITH MAGNETIC
CORE ON
SECONDARY SIDE
LIGHT
WITHOUT
MAGNETIC
CORES
Figure 1.1: Classification of WPT [3].
The most well-known technique in the WPT technology is inductive coupling
between transmitter and receiver which is widely applied to most of the applications
nowadays [3]. The concept of the inductive power transfer (IPT) is the power is being
transmitted to the receiver by electromagnetic induction via inductive coupling [4].
However, the major drawback of IPT is ferromagnetic interference which is the flux
cannot pass through the magnetisable material.
Meanwhile, the acoustic power transfer is comparatively new which optimizing
the vibration or ultrasonic propagation wave rather than electromagnetic fields for power
transmission. On the other hand, the working principles of light wireless power transfer
system are similar to far-field electromagnetic waves or microwave energy transfer. An
optical power beam which is generated by laser diode is converted back to electrical power
by photovoltaic diodes before supply to the receiver. Although light-based systems able
to supply a great amount of power, its diffraction losses have directly influenced the
efficiency over a great distance [5], [6].
3
As compared to popular inductive power transfer, both of the APT and CPT have
the advantages over IPT. For APT, the efficiency of the power transmission is higher
when the distance of the transmitter and receiver is much larger. While, capacitive have
to ability of metal penetration and the potential to reduce electromagnetic interference
(EMI) that will overcome the problems in IPT. Although the APT could overcome the
metal barrier issue and the distance limitation, the difficulties of the large acoustic
impedance mismatch of the transmitter and receiver with the medium could lead to a
severe limit on the efficiency of power transfer. Hence, the capacitive approach will be
used in this project. The basic operating principles of the capacitive-based WPT will be
discussed in the following Chapter.
1.2
Project Overview
In this project, we focus on the capacitive based method due to its advantages over
the IPT and APT. The ability of metal penetration could solve the issue that faced in the
IPT. However, the misalignment of the both transmitter and receiver plates could directly
influence the power efficiency and this will limit the power transmission and the
efficiency. This phenomenon is also concerned in the APT techniques which is cause by
its large acoustic impedance mismatch. But, in this project, CPT technique is preferable
over APT due to the flexibility in movement. Besides, the simplicity in circuit topologies,
low standing power, as well as low EMI are the advantages for choosing CPT technique
over IPT [7]. This project aims to develop a wireless computer mouse charging system
using a capacitive based method. This method enables wireless power transmission from
a mouse pad to a wireless computer mouse. Hence, no battery requires to power up the
mouse. To be more specific, at the transmitter side, a converter is designed to convert the
DC source to AC while the compensation circuit is also designed to improve the efficiency
of the system. A prototype is developed to prove the proposed method. Finally, at the
end of this project, a prototype of wireless computer mouse charging via capacitive
4
coupling is developed and the efficiency performance analysis of the developed prototype
is completed.
1.3
Motivation
The growing popularity of battery-powered electronics and communication
devices has provided a great benefit to human society. From an ordinary computer mouse
to a tailless computer mouse, wireless mouse, it is obviously much more convenient to
use. This shows the main benefit of WPT as well as in reducing the hassle of wires.
However, each of this battery-powered electronic device comes along with its own charger,
batteries and, consequently resulting in an increasing electronic waste issue and it brings
up the environmental concerns among the society. Most of the commercialized wireless
computer mouse are powered up by the batteries and bring up a few problems.
Inconvenience of battery replacement, the cost of the battery replacement and the
environmental issue associated with the battery disposal are the main drawbacks of the
battery-powered wireless computer mouse. Therefore, in this project, a battery-less
wireless mouse is suggested and will be developed based on the CPT concept. By
replacing the battery in the wireless computer mouse, the capacitive-based approach will
be designed based on the a few considerations that would affect the efficiency
performance of a wireless computer mouse. The consideration is stated and discussed in
the scope of work section. A battery-less mouse is definitely become ideal since the
battery is eliminated and replaced by the charging method using the capacitive coupling
power transfer method. Besides, a battery-less mouse could be commercialized due to the
increased convenience of this device as opposed to consistently having to change the
batteries in a regular wireless mouse or even using a wired computer mouse.
5
1.4
Problem Statement
In wireless power transfer (WPT), there are various techniques are established
based on the WPT concept.
One of the most well-known technique among those
techniques is inductive power transfer (IPT). IPT is widely dominating the electronic
devices nowadays. One of the perhaps most popular examples of low power devices that
uses IPT method are the Sonicare electrical toothbrush by Philips [1]. This inductive
approach is using the magnetic fields from a coil to induce a current in another coupled
coil so that there is a flow of current wirelessly. Also, there is existing wireless mouse
charger known as “Magic Charger” that using induction charging. Obviously, IPT
technique is popular and commonly used in the most application. However, IPT has few
drawbacks and one of that is the coil heating effect. During the charging process, the coil
may be heating up and this will cause the efficiency of power transfer to drop in the
process of charging. While, another drawback of IPT is the metal interference. The metal
interference will disturb the magnetic flux and directly limit the implementation of IPT on
the wider range of application. Therefore, the CPT is proposed in this project because
CPT could overcome those problems. In CPT, there is no overheating issues and stay
constant or stable without efficiency drop over a period of charging. Unlike IPT, the CPT
is not affected by the ferromagnetic material interference neither in E-field nor H-field.
On the other hand, there is also APT technique can be considered in this project. APT is
a very new technique and APT also can be employed in various transmission types from
sound wave to light wave. Although APT can be used in different types of transmission,
it could be a difficulty in choosing the best transmission method for this project. Normally,
APT is meant for a long range transmission while in this project the transmission range is
in a short range so the APT technique is not quite suitable to be used. Besides, the APT
have the issue of mismatch impedance. The mismatch in the APT could lead to a severe
drop in the efficiency of power transfer. Thus, the CPT technique is the most appropriate
method for this wireless mouse charging project. By applying CPT, the limitation in the
APT and IPT could be overcome. As mentioned, the “Magic Charger” on the market is
using the IPT method to charge up but usually the “Magic Charger” comes in a set of
6
rechargeable battery and charger station and bring up the battery issue. Although by using
the rechargeable battery would definitely reduce the battery disposal issue, but it would
be great if there is no battery being implanted in the wireless mouse and yet it still can be
powered up. Therefore, in this project, CPT will be employed to power up the wireless
mouse to eliminate the usage of the battery. Apart from that, there is a common limitation
of these commercialized products. When the devices need to be charged up, it requires to
be placed on top of its own charging station (transmitter) or charging socket of the charger.
In other words, a precise aligned is needed for the transmitter and receiver which will limit
the positioning flexibility of the receiver.
Especially for the wireless mouse, this
limitation will bring a lot of inconvenience such as the wireless mouse need to be leave
on it charging station for a period of for charging. Therefore, in this project, a wireless
computer mouse charging system is proposed. This system uses the capacitive power
transfer based approach to solve this issue. Capacitive approach is being chosen over the
IPT and APT techniques because the CPT could overcome the problems of metal barrier,
coil heating effects and precise in alignment which are mentioned earlier. The proposed
capacitive based wireless mouse charging system is able to charge the mouse while the
mouse is in its use. Another saying, the mouse is still in charging mode even a user is
using it as long as the mouse is in the effective area of charging (mouse pad). However,
the movement of the mouse along the x-axis is preferable in due to achieve fully coupled
condition to contribute a higher efficiency of power transfer.
1.5
Objectives
a)
To develop a wireless mouse charging prototype using capacitive power transfer
method.
b)
To design a compensation circuit to improve the efficiency of such circuits.
c)
To analyze the efficiency performance of the developed prototype.
7
1.6
Scope of Work
This prototype is designed in a small scale low power model up to 5V and wireless
power transmission range effective is within 1cm gap. The issue that always affects the
efficiency of the power transmission in CPT is the alignment of the transmitter plates and
the receiver plates. Hence, in this project, the both plates on the wireless computer mouse
and mouse pad are to be designed in an aligned fixed position as shown in the Figure 1.2
while the Figure 1.3 shows the misalignment situation of the both plates [8]. As can be
seen, when the misalignment situation occurred, there are uncoupled areas between the
transmitter and receiver which will lead to the consequences in affecting the efficiency
performance of the system. The plate effective area is highlighted on the mouse pad. In
this prototype, a fully aligned situation is desirable.
Transmitter Plate 1
Receiver Plate 1
Receiver Plate 2
Transmitter Plate 2
Figure 1.2: Fully Aligned and Coupled Situation [8].
Transmitter Plate 1
Receiver Plate 1
Uncoupled Area
Receiver Plate 2
Transmitter Plate 2
Figure 1.3: Misaligned Situation [8].
In a CPT system, a high frequency voltage is desired to drive the electric field
coupler so that the alternating current can flow through it to provide the load with the
required power.
Therefore, a Class-E converter is designed as the high frequency
converter at the transmitter to convert DC source to AC. The best converter is selected
8
based on the performance analysis and then implemented at the transmitter part. On the
other hand, the problem of power loss during the charging process is overcome by
designating capacitor compensation circuits at the transmitter and receiver part. The basic
conceptual design of the prototype is shown in Figure 1.4. From the figure, first, a DC
source from the USB port is supplied to the primary circuit also known as the transmitter.
At the transmitter part, there is a high frequency converter is designed to convert the DC
source to a high frequency of AC voltage and then an alternating electric field is generated
and pass through the capacitive coupling plate to the receiver part of the system which is
the secondary pick-up (receiver plates) attached in the wireless computer mouse.
Figure 1.4: Conceptual Design of Wireless Mouse Charging Prototype [9].
1.7
Project Planning
In project planning, the flow of project is essential in completing the project step
by step. The flow of the designing this project is based on the problem statement,
objectives of the work and the scope of work. Therefore, a gantt chart is constructed for
the progress of this project.
METHOD FOR MOUSE CHARGING APPLICATION
ONG ZHEN GUAT
This Report Is Submitted In Partial Fulfillment of Requirements for the Bachelor Degree
of Electronic Engineering (Wireless Communication)
Faculty of Electronic and Computer Engineering
Universiti Teknikal Malaysia Melaka
JUNE 2015
ii
iii
iv
v
To my beloved friends and family. Thank you my supervisor and all lecturers who
guide me, and to all my friends for giving me mentally and moral support during process
of finish final year project.
vi
ACKNOWLEDGEMENT
I would like to express my deepest appreciation to all those who provided me the
possibility to complete this report. A special gratitude I give to my supervisor Dr. Mohd.
Shakir bin Md. Saat who had given me many learning opportunities throughout the
preparation of this report. Besides giving me suggestions, he had also helped me to
coordinate my project, especially in writing this report. I am highly indebted to Dr. Shakir
for his guidance and constant supervision as well as for accessing my progress and also
for his support in completing this report.
Furthermore, I would also like to acknowledge with much appreciation of my
friends for providing decent suggestions and necessary information during the completion
of this report.
I have taken efforts in this project. However, it would not have been possible
without the kind support and help of many individuals. I would like to extend my sincere
thanks to all of them. Last but not least, I would like to thank my parents and family for
their support financially and emotionally.
vii
ABSTRACT
Wireless power transfer (WPT) is a non-contact power transfer within a distance.
With the advantage of not-contact concept, WPT enhances the flexibility movement of
the devices. Basically, there are three types of the WPT which are inductive power
transfer (IPT), Capacitive Power Transfer (CPT) and Acoustic Power Transfer (APT).
Among these, capacitive power transfer (CPT) has the advantages of confining electric
field between coupled plates, metal penetration ability and also the simplicity in circuit
topologies. Therefore, we focus on the capacitive method in this project. This project
aims to develop a wireless mouse charging system using capacitive based method. This
method enables wireless power transmission from mouse pad to wireless mouse. Hence,
no battery requires to power up the mouse. To be more specific, a high efficiency ClassE converter is designed to convert the DC source to AC and the compensation circuit of
resonant tank is also designed in the transmitter part in order to improve the efficiency. In
the end, a prototype is developed to prove the developed method. The performances
analysis of the developed prototype is discussed and the future recommendation of this
technique is also presented.
Keywords: Wireless Power Transfer (WPT), Capacitive Power Transfer (CPT), wireless
mouse charging, low power applications.
viii
ABSTRAK
Pemindahan kuasa tanpa wayar (WPT) ialah pemindahan kuasa tanpa sebarang
sentuhan dalam linkungan sesuatu jarak. Dengan kelebihan konsep tanpa sentuhan wayar,
WPT dapat meningkatkan pergerakan sesuatu alat dengan lebih fleksibel. Pada asasnya,
terdapat tiga jenis WPT yang mana ialah pemindahan kuasa secara beraruhan (IPT),
pemidahan kuasa secara berkemuatan (CPT) dan pemindahan tenaga melalui bunyi (AET).
Antara jenis pemindahan kuasa tersebut, pemindahan kuasa secara berkemuatan (CPT)
mempunyai banyak kebaikan iaitu medan elektrik antara gandingan plat-plat, keupayaan
penembusan logam dan juga kesederhanaan di topologi litar. Justeru, kami fokus pada
pemindahan kuasa secara berkemuatan dalam projek ini. Projek ini bertujuan untuk
mencipta sistem pengecasan tetikus tanpa wayar dengan menggunakan kaedah
pemindahan kuasa secara berkemuatan. Kaedah ini membolehkan penghantaran kuasa
tanpa wayar dari pad tetikus ke tetikus. Maka, tiada penggunaan bateri diperlukan untuk
menghidupkan kuasa tetikus itu. Untuk lebih terperinci lagi, penukar kelas E yang
kecekapan tinggi direka bentuk untuk menukar sumber DC kepada AC dan litar pampasan
tangki bersalunan juga direka dalam bahagian pemancar supaya kecekapan dapat
ditingkatkan. Akhirnya, sebuah prototaip dicipta untuk membuktikan kaedah tersebut.
Analisis keadaaan prototaip yang dicipta telah dibincangkan dan cadangan akan datang
teknik ini juga dibentangkan.
ix
TABLE OF CONTENT
CHAPTER
I.
TITLE
PAGE
PROJECT TITLE
i
REPORT STATUS APPROVAL FORM
ii
DECLARATION
iii
SUPERVISOR APPROVAL
iv
DEDICATON
v
ACKNOWLEDGEMENT
vi
ABSTRACT
vii
ABSTRAK
viii
TABLE OF CONTENT
ix
LIST OF TABLES
xii
LIST OF FIGURES
xiii
LIST OF ABBREVIATION
xvi
INTRODUCTION
1.1
Project Background
1
1.2
Project Overview
3
1.3
Motivation
4
1.4
Problem Statement
5
1.5
Objectives
6
1.6
Scope of Work
7
1.7
Project Planning
8
x
1.8
II.
Thesis Outline
LITERATURE REVIEW
2.1
Background Study of Wireless Power
Transfer (WPT)
2.2
2.3
2.4
III.
10
11
Capacitive Power Transfer and other WPT
Technologies
14
Converters for the WPT
19
2.3.1
Push-Pull Converter
19
2.3.2
Class-E Converter
20
Zero-Voltage Switching (ZVS)
22
METHODOLOGY
3.1
Workflow for the Project
25
3.1.1
Literature Reviews
27
3.1.2
Conceptual Design of a Low Power
Wireless Mouse Charging Prototype
27
3.1.3
Design of Push-Pull Converter
27
3.1.4
Design of Class-E Converter
29
3.1.5
The Selection of the Best Converter
31
3.1.6
Design of LC Series Resonance
(Compensator Circuits) on the Transmitter
and Receiver Part.
32
3.1.7
Design of Capacitive Plates
32
3.1.8
Design of Rectifier
34
3.1.9
Installation of Designed Circuit onto
the Mouse Pad and Mouse
35
xi
IV.
3.1.10 Circuit Correction and Adjustment
36
3.1.11 Performance Testing and Troubleshooting
36
3.1.12 Hardware Finalization
36
RESULT AND ANALYSIS
4.1
Class-E Converter
4.1.1
4.1.2
4.2
V.
37
Pulse Width Modulation and Driver
Circuit
39
Zero Voltage Switching (ZVS)
42
Capacitive Plate
46
4.2.1
Small Plate at Receiver Part
47
4.2.2
Big Plate at Receiver Part
50
4.3
Rectifier Circuit
54
4.4
Final Prototype
56
FUTURE WORK AND CONCLUSION
5.1
Conclusion
58
5.2
Recommendation
61
REFERENCES
63
APPENDIX A
66
xii
LIST OF TABLES
NO
TITLE
PAGE
1.1
Gantt Chart.
9
4.1
Assumed Parameters for the Class-E Converter.
38
4.2
Class-E Converter Parameters.
38
4.3
Average Output Voltage, V(r), at the Transmitter Plate.
46
4.4
Received Voltage at the Receiver Plate using Paper as a
Medium.
4.5
Received Voltage at the Receiver Plate using Mouse Pad
as a Medium.
4.6
51
Received Voltage at the 45° Slant Receiver Plate using Paper
as a Medium.
4.11
51
Received Voltage at the Receiver Plate using Mouse Pad as
a Medium.
4.10
50
Received Voltage at the Receiver Plate using Paper as a
Medium.
4.9
50
Received Voltage at the 45° Slant Receiver Plate using Mouse
Pad as a Medium.
4.8
48
Received Voltage at the 45° Slant Receiver Plate using Paper
as a Medium.
4.7
47
53
Received Voltage at the 45° Slant Receiver Plate using Mouse
Pad as a Medium.
53
xiii
LIST OF FIGURES
NO
TITLE
PAGE
1.1
Classifications of WPT [3].
2
1.2
Fully Aligned and Coupled Situation [8].
7
1.3
Misaligned Situation [8].
7
1.4
Conceptual Design of Wireless Mouse Charging
Prototype [9].
8
2.1
Sonicare Philips Toothbrush [12].
13
2.2
Powermat [12].
13
2.3
Capacitive Power Transfer Field Coupling between
Two Parallel Plates [10].
14
2.4
The Structure of CPT [7].
15
2.5
Magnetic Flux Coupling between Two Coils [10].
16
2.6
Schematic Diagram of Inductive Power Transfer [17].
17
2.7
Basic APT System [5].
18
2.8
Basic Schematic Circuit of Push-pull Converter.
20
2.9
Class-E Converter Circuit Topology [22].
21
2.10
Equivalent Circuit Diagram of the Class-E Converter [22].
21
2.11
Zero Voltage Switching (ZVS) [23].
23
2.12
Switching Losses [23].
23
3.1
Flowchart of the Project.
26
3.2
Simulation of the Selected Push-pull Converter Circuit.
28
3.3
Simulation on the Selected Class-E Converter Circuit.
29
xiv
3.4
LC Series Compensation Circuit.
3.5
Connection of the Transmitter Plate 1 and Transmitter
32
Plate 2.
33
3.6
Position of the Transmitter Plates and the Receiver Plates.
33
3.7
Sizes of the Capacitive Plate.
34
3.8
Rectifier Circuit from AC Source to DC Source.
35
3.9
Installation of Designed Circuit onto the Mouse Pad.
35
4.1
SK40C Start-up Kit with PIC16F877A.
39
4.2
MikroC Coding to Interface with PIC16F877A.
40
4.3
Setup of the PIC in Proteus with Graph Analyzer.
40
4.4
A 1MHz PWM Pulse Generated in Simulation.
41
4.5
Practical Output Pulse from the PIC16F877A.
41
4.6
Driver Circuit TC4422.
42
4.7
Class-E Converter Circuit in Simulation.
43
4.8
ZVS Condition for the Class-E Converter.
44
4.9
Class-E Converter Circuit of Practical Work.
44
4.10
ZVS from the Oscilloscope.
45
4.11
Drain Voltage versus Output Voltage at Load using
Oscilloscope.
4.12
Different Alignment of the Receiver Plate on the
Different Zone.
4.13
47
Graph of the Received Voltage in Different Position with
Different Medium.
4.14
46
48
Received Voltage from the Transmitter Plates versus
Received Voltage at the Receiver Plates (Paper).
49
4.15
45° Slant Alignment of the Receiver Plate.
50
4.16
Alignment of the Receiver Plate on Different Zone.
51
4.17
Graph of the Received voltage in Different Zone with
Different Medium.
52
xv
4.18
Received Voltage from the Transmitter Plate versus
Receiver Plate (Paper).
52
4.19
45° Slant Alignment of the Receiver Plate.
53
4.20
Rectifier Circuit in the Simulation before Fabricating.
54
4.21
Received Voltage from the Small Receiver Plate versus
Rectified Voltage (Paper).
4.22
55
Output Voltage from the Big Receiver Plate versus
Rectified Voltage (Paper).
56
4.23
Final Prototype.
57
4.24
Matrix Structure of the Transmitter Plate.
61
xvi
LIST OF ABBREVIATION
WPT
IPT
APT
CPT
EMI
AC
DC
USB
EV
MOSFET
ZVS
ZCS
PWM
LED
-
Wireless Power Transfer
Inductive Power Transfer
Acoustic Power Transfer
Capacitive Power Transfer
Electromagnetic Interference
Alternating Current
Direct Current
Universal Serial Bus
Electric Vehicle
Metal-Oxide-Semiconductor Field Effect Transistor
Zero Voltage Switching
Zero Current Switching
Pulse Width Modulation
Light-Emitting Diode
1
CHAPTER I
INTRODUCTION
In this chapter, wireless power transfer (WPT) will be discussed and the types of
the techniques of WPT will be explained. A summary and the aim of this project will
also be presented and discussed in this section.
1.1
Project Background
Wireless Power Transfer also known as WPT is a process of transferring power
between two or more physically unconnected electric circuits or devices [1]. This
innovative technology has created new possibilities to supply electronic devices with
electrical energy by eliminating of wires, connectors and slip-rings.
The potential
application of WPT can range from a low power office or home appliances to a high power
industrial systems. This concept has been first demonstrated by Nikola Tesla in the 1980s
by powering up fluorescent lamps 25 miles from the power source without using wires
[2]. Since then, various techniques based on WPT have been established which is shown
in Figure 1.1. Generally, it can be divided according to the medium used for power
2
transmission, which are acoustic-based WPT, light-based WPT, capacitive-based WPT
and the inductively coupled WPT.
WIRELESS
POWER
ACOUSTIC
WITH MAGNETIC
CORES
INDUCTIVE
COUPLING
CAPACITIVE
COUPLING
WITH MAGNETIC
CORE ON
SECONDARY SIDE
LIGHT
WITHOUT
MAGNETIC
CORES
Figure 1.1: Classification of WPT [3].
The most well-known technique in the WPT technology is inductive coupling
between transmitter and receiver which is widely applied to most of the applications
nowadays [3]. The concept of the inductive power transfer (IPT) is the power is being
transmitted to the receiver by electromagnetic induction via inductive coupling [4].
However, the major drawback of IPT is ferromagnetic interference which is the flux
cannot pass through the magnetisable material.
Meanwhile, the acoustic power transfer is comparatively new which optimizing
the vibration or ultrasonic propagation wave rather than electromagnetic fields for power
transmission. On the other hand, the working principles of light wireless power transfer
system are similar to far-field electromagnetic waves or microwave energy transfer. An
optical power beam which is generated by laser diode is converted back to electrical power
by photovoltaic diodes before supply to the receiver. Although light-based systems able
to supply a great amount of power, its diffraction losses have directly influenced the
efficiency over a great distance [5], [6].
3
As compared to popular inductive power transfer, both of the APT and CPT have
the advantages over IPT. For APT, the efficiency of the power transmission is higher
when the distance of the transmitter and receiver is much larger. While, capacitive have
to ability of metal penetration and the potential to reduce electromagnetic interference
(EMI) that will overcome the problems in IPT. Although the APT could overcome the
metal barrier issue and the distance limitation, the difficulties of the large acoustic
impedance mismatch of the transmitter and receiver with the medium could lead to a
severe limit on the efficiency of power transfer. Hence, the capacitive approach will be
used in this project. The basic operating principles of the capacitive-based WPT will be
discussed in the following Chapter.
1.2
Project Overview
In this project, we focus on the capacitive based method due to its advantages over
the IPT and APT. The ability of metal penetration could solve the issue that faced in the
IPT. However, the misalignment of the both transmitter and receiver plates could directly
influence the power efficiency and this will limit the power transmission and the
efficiency. This phenomenon is also concerned in the APT techniques which is cause by
its large acoustic impedance mismatch. But, in this project, CPT technique is preferable
over APT due to the flexibility in movement. Besides, the simplicity in circuit topologies,
low standing power, as well as low EMI are the advantages for choosing CPT technique
over IPT [7]. This project aims to develop a wireless computer mouse charging system
using a capacitive based method. This method enables wireless power transmission from
a mouse pad to a wireless computer mouse. Hence, no battery requires to power up the
mouse. To be more specific, at the transmitter side, a converter is designed to convert the
DC source to AC while the compensation circuit is also designed to improve the efficiency
of the system. A prototype is developed to prove the proposed method. Finally, at the
end of this project, a prototype of wireless computer mouse charging via capacitive
4
coupling is developed and the efficiency performance analysis of the developed prototype
is completed.
1.3
Motivation
The growing popularity of battery-powered electronics and communication
devices has provided a great benefit to human society. From an ordinary computer mouse
to a tailless computer mouse, wireless mouse, it is obviously much more convenient to
use. This shows the main benefit of WPT as well as in reducing the hassle of wires.
However, each of this battery-powered electronic device comes along with its own charger,
batteries and, consequently resulting in an increasing electronic waste issue and it brings
up the environmental concerns among the society. Most of the commercialized wireless
computer mouse are powered up by the batteries and bring up a few problems.
Inconvenience of battery replacement, the cost of the battery replacement and the
environmental issue associated with the battery disposal are the main drawbacks of the
battery-powered wireless computer mouse. Therefore, in this project, a battery-less
wireless mouse is suggested and will be developed based on the CPT concept. By
replacing the battery in the wireless computer mouse, the capacitive-based approach will
be designed based on the a few considerations that would affect the efficiency
performance of a wireless computer mouse. The consideration is stated and discussed in
the scope of work section. A battery-less mouse is definitely become ideal since the
battery is eliminated and replaced by the charging method using the capacitive coupling
power transfer method. Besides, a battery-less mouse could be commercialized due to the
increased convenience of this device as opposed to consistently having to change the
batteries in a regular wireless mouse or even using a wired computer mouse.
5
1.4
Problem Statement
In wireless power transfer (WPT), there are various techniques are established
based on the WPT concept.
One of the most well-known technique among those
techniques is inductive power transfer (IPT). IPT is widely dominating the electronic
devices nowadays. One of the perhaps most popular examples of low power devices that
uses IPT method are the Sonicare electrical toothbrush by Philips [1]. This inductive
approach is using the magnetic fields from a coil to induce a current in another coupled
coil so that there is a flow of current wirelessly. Also, there is existing wireless mouse
charger known as “Magic Charger” that using induction charging. Obviously, IPT
technique is popular and commonly used in the most application. However, IPT has few
drawbacks and one of that is the coil heating effect. During the charging process, the coil
may be heating up and this will cause the efficiency of power transfer to drop in the
process of charging. While, another drawback of IPT is the metal interference. The metal
interference will disturb the magnetic flux and directly limit the implementation of IPT on
the wider range of application. Therefore, the CPT is proposed in this project because
CPT could overcome those problems. In CPT, there is no overheating issues and stay
constant or stable without efficiency drop over a period of charging. Unlike IPT, the CPT
is not affected by the ferromagnetic material interference neither in E-field nor H-field.
On the other hand, there is also APT technique can be considered in this project. APT is
a very new technique and APT also can be employed in various transmission types from
sound wave to light wave. Although APT can be used in different types of transmission,
it could be a difficulty in choosing the best transmission method for this project. Normally,
APT is meant for a long range transmission while in this project the transmission range is
in a short range so the APT technique is not quite suitable to be used. Besides, the APT
have the issue of mismatch impedance. The mismatch in the APT could lead to a severe
drop in the efficiency of power transfer. Thus, the CPT technique is the most appropriate
method for this wireless mouse charging project. By applying CPT, the limitation in the
APT and IPT could be overcome. As mentioned, the “Magic Charger” on the market is
using the IPT method to charge up but usually the “Magic Charger” comes in a set of
6
rechargeable battery and charger station and bring up the battery issue. Although by using
the rechargeable battery would definitely reduce the battery disposal issue, but it would
be great if there is no battery being implanted in the wireless mouse and yet it still can be
powered up. Therefore, in this project, CPT will be employed to power up the wireless
mouse to eliminate the usage of the battery. Apart from that, there is a common limitation
of these commercialized products. When the devices need to be charged up, it requires to
be placed on top of its own charging station (transmitter) or charging socket of the charger.
In other words, a precise aligned is needed for the transmitter and receiver which will limit
the positioning flexibility of the receiver.
Especially for the wireless mouse, this
limitation will bring a lot of inconvenience such as the wireless mouse need to be leave
on it charging station for a period of for charging. Therefore, in this project, a wireless
computer mouse charging system is proposed. This system uses the capacitive power
transfer based approach to solve this issue. Capacitive approach is being chosen over the
IPT and APT techniques because the CPT could overcome the problems of metal barrier,
coil heating effects and precise in alignment which are mentioned earlier. The proposed
capacitive based wireless mouse charging system is able to charge the mouse while the
mouse is in its use. Another saying, the mouse is still in charging mode even a user is
using it as long as the mouse is in the effective area of charging (mouse pad). However,
the movement of the mouse along the x-axis is preferable in due to achieve fully coupled
condition to contribute a higher efficiency of power transfer.
1.5
Objectives
a)
To develop a wireless mouse charging prototype using capacitive power transfer
method.
b)
To design a compensation circuit to improve the efficiency of such circuits.
c)
To analyze the efficiency performance of the developed prototype.
7
1.6
Scope of Work
This prototype is designed in a small scale low power model up to 5V and wireless
power transmission range effective is within 1cm gap. The issue that always affects the
efficiency of the power transmission in CPT is the alignment of the transmitter plates and
the receiver plates. Hence, in this project, the both plates on the wireless computer mouse
and mouse pad are to be designed in an aligned fixed position as shown in the Figure 1.2
while the Figure 1.3 shows the misalignment situation of the both plates [8]. As can be
seen, when the misalignment situation occurred, there are uncoupled areas between the
transmitter and receiver which will lead to the consequences in affecting the efficiency
performance of the system. The plate effective area is highlighted on the mouse pad. In
this prototype, a fully aligned situation is desirable.
Transmitter Plate 1
Receiver Plate 1
Receiver Plate 2
Transmitter Plate 2
Figure 1.2: Fully Aligned and Coupled Situation [8].
Transmitter Plate 1
Receiver Plate 1
Uncoupled Area
Receiver Plate 2
Transmitter Plate 2
Figure 1.3: Misaligned Situation [8].
In a CPT system, a high frequency voltage is desired to drive the electric field
coupler so that the alternating current can flow through it to provide the load with the
required power.
Therefore, a Class-E converter is designed as the high frequency
converter at the transmitter to convert DC source to AC. The best converter is selected
8
based on the performance analysis and then implemented at the transmitter part. On the
other hand, the problem of power loss during the charging process is overcome by
designating capacitor compensation circuits at the transmitter and receiver part. The basic
conceptual design of the prototype is shown in Figure 1.4. From the figure, first, a DC
source from the USB port is supplied to the primary circuit also known as the transmitter.
At the transmitter part, there is a high frequency converter is designed to convert the DC
source to a high frequency of AC voltage and then an alternating electric field is generated
and pass through the capacitive coupling plate to the receiver part of the system which is
the secondary pick-up (receiver plates) attached in the wireless computer mouse.
Figure 1.4: Conceptual Design of Wireless Mouse Charging Prototype [9].
1.7
Project Planning
In project planning, the flow of project is essential in completing the project step
by step. The flow of the designing this project is based on the problem statement,
objectives of the work and the scope of work. Therefore, a gantt chart is constructed for
the progress of this project.