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THE DEVELOPMENT OF WIRELESS POWER TRANSFER TECHNOLOGIES FOR MULTIPLE DEVICES : AN INDUCTIVE

APPROACH

LAI XINGREN KATHLEEN

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THE DEVELOPMENT OF WIRELESS POWER TRANSFER

TECHNOLOGIES FOR MULTIPLE DEVICES : AN INDUCTIVE

APPROACH

LAI XINGREN KATHLEEN

This Report is Submitted in Fulfillment of Requirements for The Bachelor Degree of Electronic Engineering (Industrial Electronic)

Faculty of Electronics and Computer Engineering Universiti Teknikal Malaysia Melaka

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UNIVERSTI TEKNIKAL MALAYSIA MELAKA

FAKULTI KEJURUTERAAN ELEKTRONIK DAN KEJURUTERAAN KOMPUTER

BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA II

Tajuk Projek : The Development of Wireless Power Transfer Technologies for

Multiple Devices : An Inductive Approach

Sesi Pengajian : 1 6 / 1 7

Saya ………. (HURUF BESAR)

mengaku membenarkan Laporan Projek Sarjana Muda ini disimpan di Perpustakaan dengan syarat-syarat kegunaan seperti berikut:

1. Laporan adalah hakmilik Universiti Teknikal Malaysia Melaka.

2. Perpustakaan dibenarkan membuat salinan untuk tujuan pengajian sahaja.

3. Perpustakaan dibenarkan membuat salinan laporan ini sebagai bahan pertukaran antara institusi pengajian tinggi.

4. Sila tandakan ( ) :

SULIT* *(Mengandungi maklumat yang berdarjah keselamatan atau

kepentingan Malaysia seperti yang termaktub di dalam

AKTA RAHSIA RASMI 1972)

TERHAD** **(Mengandungi maklumat terhad yang telah ditentukan oleh

organisasi/badan di mana penyelidikan dijalankan)

TIDAK TERHAD Disahkan oleh: ________________________ ___________________________________ (TANDATANGAN PENULIS) (COP DAN TANDATANGAN PENYELIA)

Tarikh: ……….. Tarikh: ………..

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DECLARATION

“I hereby declare that the work in this project is my own except for summaries and quotation which have been duly acknowledge.”

Signature :………. Author : LAI XINGREN KATHLEEN

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DECLARATION

“I acknowledge that I have read this report and in my opinion this report is sufficient in term of scope and quality for the award of Bachelor of Electronic Engineering

(Industrial Electronics) with Honors.”

Signature :……….

Supervisor’s Name : ASSOC. PROF. DR. MOHD SHAKIR BIN MD SAAT

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DEDICATION

I dedicate this dissertation to my parents and friends. People who have always been there to support me, congratulate me, and show me the best path to follow.

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ACKNOWLEDGEMENT

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ABSTRACT

Conventionally, the energy or power transfer is done through the connecting wires to power up the electronic appliances but these wires create hazardous and messy environment. With wireless power transfer (WPT) technologies, the used of connecting cord can be reduced. WPT technology is the transmission of electrical energy or power between two points without connecting wire. WPT mechanism is classified into two: near-field transfer and far-near-field transfer. This project applied the near near-field transfer because it has higher power transfer efficiency over the far-field transfer in short transmission distance. There are three subtypes of near-field transfer mechanism which are inductive power transfer technique (IPT), capacitive power transfer technique (CPT) and acoustic power transfer technique (APT). IPT is chosen to be the WPT technique in this project due to its higher power efficiency in the transmission distance range of centimetre. The current mechanism deploys class-D inverter which has its limitation in supporting high power efficiency due to it consists of two switching MOSFETs. When the number of MOSFET used increases, the switching loss in term of heating issue will also increase. Therefore, a high-efficiency WPT system which can support four receivers at the same time using Class E inverter for transmitter via inductive power transfer (IPT) has been designed and fabricated instead of Class D inverter. The project performance based on the misalignment distance and the gap between the coils are analysed and discussed in term of output power efficiency. A future development is also recommended. The fabricated system is supplied at 12VDC and capable of delivering power at 5W. During power

delivery state, the prototype efficiency is 90.42%.

Keywords: Wireless Power Transfer (WPT), Class E Inverter, Inductive Power Transfer (IPT), multiple receivers for low power application.

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ABSTRAK

Cara tradisi tenaga atau kuasa pemindahan adalah melalui penyambung wayar untuk mengaktifkan peralatan elektronik tetapi wayar mewujudkan persekitaran yang berbahaya dan tidak kemas. Dengan aplikasi pemindahan kuasa tanpa wayar (WPT), penggunaan penyambung wayar boleh dikurangkan. WPT adalah penghantaran tenaga elektrik atau kuasa di antara dua jarak tanpa penyambung wayar. Mekanisme WPT diklasifikasikan kepada dua: pemindahan medan dekat dan pemindahan medan jauh. Projek ini digunakan pemindahan medan dekat kerana ia mempunyai kecekapan pemindahan kuasa yang lebih tinggi berbanding dengan pemindahan medan jauh dalam jarak penghantaran yang dekat. Terdapat tiga jenis pemindahan medan dekat adalah seperti pemindahan kuasa beraruhan (IPT), pemindahan kuasa berdasarkan kapasitif (CPT) dan pemindahan kuasa berdasarkan akustik (APT). IPT dipilih menjadi teknik WPT dalam projek ini kerana ia memberi kecekapan kuasa yang lebih tinggi dalam lingkungan jarak penghantaran sentimeter. Mekanisme kini menggunakan kelas-D inverter yang mempunyai sekatan dalam menghasilkan kecekapan kuasa yang tinggi kerana ia menggunakan dua MOSFET sebagai suis. Apabila bilangan MOSFET digunakan bertambah, kehilangan kuasa dari segi isu pemanasan akan meningkat. Oleh itu, sistem WPT yang dapat menyokong empat penerima pada masa yang sama dengan menggunakan Kelas E inverter sebagai pemancar melalui pindahan kuasa beraruhan (IPT) telah direka dan difabrikasikan untuk menggantikan Kelas D inverter. Pelaksanaan projek dari segi jarak penjajaran dan jurang antara gegelung akan dianalisis dan dibincangkan dari segi kecekapan. Perkembangan masa depan juga dicadangkan. Sistem yang direka akan dibekalkan dengan 12VDC dan mampu menghantar kuasa pada 5W. Kecekapan prototaip

yang dihasilkan adalah 90.42%.

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TABLE OF CONTENT

CHAPTER TITLE PAGE

PROJECT TITLE i

PROJECT STATUS APPROVAL FOAM ii

DECLARATION iii

SUPERVISOR’S DECLARATION iv

DEDICATION v

ACKNOWLEDGEMENT vi

ABSTRACT vii

ABSTRAK viii

TABLE OF CONTENT ix

LIST OF ABBREVIATIONS xiii

LIST OF TABLES xiv

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I INTRODUCTION 1

1.1 Overview 1

1.2 Project Introduction 1 1.3 Problem Statement 5

1.4 Objectives 6

1.5 Scope 7

II LITERATURE REVIEW 8

2.1 Overview 8

2.2 Wireless Power Transmission (WPT) 8 2.3 Near-field Transfer of WPT Mechanism 12

2.3.1 Inductive Power Transfer (IPT) 12 2.3.2 Capacitive Power Transfer (CPT) 13 2.3.3 Acoustic Power Transfer (APT) 14 2.3.4 Comparison Between Near-field Transfers 15

2.4 Class-E Inverter 16

III PROJECT METHODOLOGY 21

3.1 Overview 21

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3.3 Block Diagram 23

3.4 Circuit Design of Class-E Inverter 24 3.5 Circuit Design of Pulse Generator 26

3.6 MOSFET Driver 27

3.7 Design Specification of Transmitting, Tx and

Receiving, Rx Coils 27 3.8 Circuit Design of Rectifier 30 3.9 Performance Analysis 33

IV RESULTS AND DISCUSSIONS 35

4.1 Overview 35

4.2 Analysis of Class-E Inverter 35 4.2.1 Simulation Result 36 4.2.2 Experimental Result 40

4.3 Pulse Generator 44

4.4 MOSFET Driver 46

4.5 Design of Transmitting, Tx and Receiving, Rx Coils 47 4.6 Integrating of Transmitting, Tx and Receiving, Rx

Coils 49

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4.8 Performance Analysis 52 4.8.1 Analysis of Efficiency on the Distance Apart 52 4.8.2 Analysis of Efficiency on Misalignment

Distance 54

4.9 Development of Project Prototype 55

4.10 Expenses 57

V CONCLUSION AND RECOMMENDATION 58

5.1 Overview 58

5.2 Conclusion 58

5.3 Sustainability 59

5.4 Recommendation 59

REFERENCES 61

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LIST OF ABBREVIATIONS

WPT - Wireless Power Transfer Tx - Transmitter

Rx - Receiver

IPT - Inductive Power Transfer CPT - Capacitive Power Transfer APT - Acoustic Power Transfer DC - Direct Current

AC - Alternating Current PWM - Pulse Width Modulation ZVS - Zero Voltage Switching

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LIST OF TABLES

Table 1.1: The specification of the project... 7

Table 2.1: The characteristic of the near-field and far-field WPT mechanisms[5,8,12]. 11 Table 2.2: Comparison between IPT, CPT and APT [14]. ... 15

Table 3.1: The loads specifications. ... 30

Table 4.1: Class-E inverter simulation result. ... 37

Table 4.2: Class-E inverter experimental result. ... 41

Table 4.3: Transmitting, Tx and receiving, Rx coils design specification. ... 48

Table 4.4: Analysis of efficiency on the distance apart. ... 53

Table 4.5: Analysis of efficiency on the misalignment distance. ... 54

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LIST OF FIGURES

Figure 1.1: The 187-foot Wardenclyffe Tower. ... 3

Figure 1.2: The electrical toothbrush. ... 4

Figure 1.3: The power mat by Witricity... 5

Figure 2.1: The general block diagram of WPT. ... 8

Figure 2.2: The classification of WPT. ... 9

Figure 2.3: The EM sources showing region differentiation by wavelengths[10]. ... 10

Figure 2.4: Block diagram of IPT. ... 12

Figure 2.5: Block diagram of CPT system [15]. ... 13

Figure 2.6: Block diagram of APT system [17]. ... 14

Figure 2.7: The Class-E inverter circuit and its Equivalent circuit [20]. ... 16

Figure 2.8: The circuit when the switch is in ON stage. ... 17

Figure 2.9: The circuit when the switch is in OFF stage. ... 18

Figure 2.10: The output current and voltage flows through the switch.[21]... 18

Figure 2.11: Zero Voltage Switching (ZVS)... 19

Figure 2.12: Switching losses. ... 19

Figure 3.1: The flowchart of the project. ... 22

Figure 3.2: Block Diagram. ... 23

Figure 3.3: The simulated Class E inverter circuit. ... 25

Figure 3.4: The simulated PWM pulse generator circuit. ... 26

Figure 3.5: The circuit of MOSFET driver. ... 27

Figure 3.6: Transmitting, Tx coil. ... 28

Figure 3.7: Receiving, Rx coil. ... 29

Figure 3.8: Voltage divider circuit. ... 30

Figure 3.9: The tested circuit of rectifier module. ... 31

Figure 3.10: The rectifier circuit for desk lamp. ... 32

Figure 3.11: The rectifier circuit for digital clock... 32

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Figure 3.13: The rectifier circuit for cordless telephone. ... 33

Figure 3.14: The diagram described the vertical distance between Tx and Rx coils. ... 34

Figure 3.15: The misalignment distance between Tx and Rx coils. ... 34

Figure 4.1: The class-E inverter circuit is simulated in MATLAB Simulink. ... 36

Figure 4.2: The simulation waveform for the Vgs and Vds at 1M Hz... 38

Figure 4.3: The simulation waveform for the Vgs versus Ids at 1M Hz. ... 38

Figure 4.4: The simulation waveform for the Vo,m and Io,m. ... 39

Figure 4.5: The experimental setup of class-E inverter on breadboard. ... 40

Figure 4.6: Experimental waveform for the Vgs in yellow and Vds in green at 1M Hz. .. 42

Figure 4. 7: Experimental waveform for the output voltage, Vout. ... 43

Figure 4.8: Experimental waveform for the output current, Iout. ... 43

Figure 4.9: The coding of PWM switching signal. ... 44

Figure 4.10: The simulated result of PWM switching signal. ... 45

Figure 4.11: The experimental result of PWM switching signal. ... 45

Figure 4.12: The MOSFET driver output waveform. ... 46

Figure 4.13: The design of transmitting coil, Tx. ... 47

Figure 4.14: The receiving, Rx coil design. ... 48

Figure 4.15: The integration circuit between transmitter coil and receiver coil. ... 49

Figure 4.16: The voltage at Rx coil with compensation circuit, c. ... 49

Figure 4.17: The voltage at Rx coil without compensation circuit, c. ... 50

Figure 4.18: The simulated output voltage of rectifier waveform. ... 51

Figure 4.19: The experimental output voltage of rectifier waveform. ... 51

Figure 4.20: The graph of efficiency against the distance between Tx and Rx coil. ... 53

Figure 4.21: The graph of efficiency against the misalignment distance of Rx coil. ... 54

Figure 4.22: The printed circuit board (PCB) fabrication of transmitter circuit. ... 55

Figure 4.23: The printed circuit board (PCB) fabrication of receiver circuit. ... 56

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CHAPTER I

INTRODCUTION

1

Overview

This chapter will briefly introduce the concept of wireless power transfer (WPT) for multiple devices using inductive approach. The problem statement, project objectives, scope of work and the structure of report will be highlighted in details here.

Project Introduction

Nowadays, wireless power transfer (WPT) technology has become one of the top research fields for its effective and reliable applicability especially in charging portable electronic devices such as electric toothbrush, smartcard system, high power electric vehicles (EV), mobile phones and home appliances [1]. Conventionally, these devices rely on the chemical storage of energy which is the battery to operate. The battery is charging through the ubiquitous power wire that is connected to the power source mounted on the wall. In other words, a connector is used to transfer the power from the main power source to the load.

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due to the limited availability of the wall plug or socket in a house or room. Therefore, wireless power transfer (WPT) mechanism is introduced as an alternative power scheme and to enhance the convenience to the user.

Wireless power transfer (WPT) technology is the transmission of electrical energy or power from one point to another point through the vacuum or atmosphere without the connecting wire [2]. The proposed technique eliminates the use of connecting wire. It is also known as a non-contact power transmission technology. It can transmit power to the location where wired transmission is not favor. So, when WPT becomes feasible, all the devices capable of charging themselves without ever being plugged in.

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[image:20.612.219.474.69.360.2]

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Figure 1.1: The 187-foot Wardenclyffe Tower.

In 1901, Tesla’s Wardenclyffe Tower was built as shown in Figure 1.1. It was a commercial and a scientific demonstration of trans-Atlantic wireless telephony, broadcasting and wireless power transmission system [4]. Tesla’s intention was to demonstrate wireless transmission of electrical energy across the Atlantic. However, the tower was not fully functional and was demolished during the World War I.

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[image:21.612.241.449.290.519.2]

Recently, WPT had emerged in the daily life applications such as the electrical toothbrush manufactured by Phillips and Oral-B. This toothbrush as depict in Figure 1.2 has a charging station operating as a transmitter while the toothbrush itself works as receiver. The rechargeable toothbrush with the receiving coil is placed on the source cradle for getting charged [6]. In addition, driven by industrial needs, multiple transmitter and receiver design has attracted much attention. The power mat is also making an appearance in the market shown in Figure 1.3. It is a single power source that can be used to transfer energy to more than one device, even when the devices have different power requirements. For example, instead of having a separate charger for each mobile phone in your family, you can have a charging surface that handles all of them at once [7].

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[image:22.612.211.482.69.296.2]

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Figure 1.3: The power mat by Witricity.

Generally, WPT has higher efficiency in power transmission compared to wired transmission as loss of transmission is negligible. According to the author [2,5], the resistance of the wire used in the electrical grid distribution system causes a loss of from 26% to 30% of energy generated. Besides, the risk of having power failure due to short circuit and fault on cables is lesser. WPT offers greener environment as it reduces the environmental waste by eliminating the need of power cords which made of non-biodegradable materials. Therefore, power transmission wirelessly may be the decent alternative for efficient power transmission.

Problem Statement

Statement 1:

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sparking and electrical shocks due to the damage of insulated layer. The connecting cable cord in wired device creates messiness due to arrangement of the multiple devices in multiple wall plugs. The long wires are easily tangled and will cause the users trip on them. Therefore, in this project a wireless power transfer technologies will be applied in order to overcome the above-mentioned problems. This project aims to develop a wireless power transfer (WPT) by using inductive coupling approach (IPT). WPT defines the noncontact power transmission technology by providing galvanic isolation between the power source and load.

Statement 2:

However, by considering the IPT system, the major challenge is to maintain the output efficiency during power transmission. Current IPT system deploys Class D amplifier to invert the DC constant supply to AC supply in the transmitter. Class D consists of two switching elements which are MOSFETs. It is hard to maintain the simultaneous on-off operation of the two MOSFETs to maximize the switching efficiency. This IPT system with class D amplifier ultimately has higher switching losses due to two switching elements. Therefore, in this work, Class E will be proposed instead of Class D. The properties of Class E inverter are only one MOSFET used as switching element and it has resonant tank to reduce the power loss during switching stage. Also, to enhance the power efficiency, an impedance matching circuit is designed to obtain the desired output power at specified supply voltage at high operating frequency.

Objectives

The objectives of this project are:

a) To design class E inverter circuit to improve the efficiency of the Inductive Power Transfer System.

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c) To develop a prototype to power up the multiple devices by using inductive coupling approach.

Scope

This research will discuss the wireless power transfer application in charging multiple devices inclusive of:

a) The study is only on inductive coupling approach.

b) At least three loads are powered up; i.e. table lamp, digital clock and Nokia brand mobile phone

c) The construction of power converters to replicate charging signal.

[image:24.612.115.528.429.712.2]

d) The specifications of this project are shown in table 1.1. Table 1.1: The specification of the project.

Parameters Description

1.Output Power 𝑃𝑜= 5𝑊 The minimum power required to charge mobile phone.

2.Operating Frequency 𝑓 = 1 𝑀𝐻𝑧

High frequency beneficial to small scale system design and power losses reduction.

3.Quality Factor 𝑄𝐿 = 10

High quality factor in inverter design to achieve sinusoidal output signal.

4.Input Voltage VDC = 12V The minimum input value required.

Figure

Figure 1.1: The 187-foot Wardenclyffe Tower.
Figure 1.2: The electrical toothbrush.
Figure 1.3: The power mat by Witricity.
Table 1.1: The specification of the project.

References

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