International Journal of Advances in Engineering, 2015, 1(3), 328 - 332
ISSN: 2394-9260 (printed version); ISSN: 2394-9279 (online version); url:http://www.ijae.in
RESEARCH ARTICLE
Renewable Energy Based Wireless Battery Charger for Mobile
Devices
Jeevitha.P, MohanaPriya.P Yuvaraj.C and Vijayakumar.K
Dept. of Electrical and Electronics Engineering, Ganadipathy Tulsi’s Jain Engineering College, India
jeeviprakash89@gmail.com
Received 16 February 2015 / Accepted 10 March 2015
Abstract - In this research, an innovative design of wireless battery charger for portable electronic devices is proposed. The
wireless power transfer is implemented through the magnetic coupling between a power transmitter, which is connected to the
grid, and a power receiver, which is integrated inside the load device. An innovative receiver architecture which heavily improves
the power conversion efficiency is presented. A laboratory prototype of the proposed wireless battery charger has been realized
and tested to evaluate system performances. Over the entire range of operating conditions the receiver efficiency lies within the
96.5% to99.9%range.
I.INTRODUCTION
Wireless transfer has been employed since long time in telecommunications, Radio waves, cellular transmissions and
Internet WIFI are only a few examples of wireless transmission. Recently, there’s been a growing interest towards the
experimentation of a deeply upon the magnetic pad. Magnetic coupling allows several devices to be simultaneously
charged. In order to spread wireless battery charging, compatibility between chargers and devices is a key issue to deal
with. Recently the Wireless Power Consortium (WPC) has built an international standard, also known as “Qi-standard”,
which aims at promoting the complete interoperability between power charging stations and rechargeable devices.
Wireless Battery Charger: On the left, the power transmitter which is connected to the electrical grid, on the right the
power receiver which is integrated into the load device is shown. In both the power transmitter and the power receiver,
the key element for signal transfer is represented by a resonant tank, on the receiver side, there is the secondary coil.
Since the power transmitter needs to be continuously informed about battery power needs and state of charge, a
communication link is required. The communications channel is implemented through an amplitude modulation of the
power drawn from the transmitter. In the power transmitter section, an AC-DC stage converts the AC voltage provided
by the electrical grid into a DC bus level. ADC-AC converter, supplied by the DC bus level, generates the AC power
signal. In the power receiver section, a rectifier converts the AC power signal out of the resonant tank into a DC voltage
level, suitable for battery charging. The DC bus rail out of the rectifier has been chosen
equaltoa7Vvalue.Informationtowardsthe power transmitter is generated through power modulation of the coupling
circuit resonant curve. The load modulation follows a differential bi-phase encoding scheme, as described in Qistandard specifications. DC power Source: It consists of a step down transformer that step downs the supply voltage to
a desired level, and rectifier circuit to convert that AC voltage to DC signal.
Figure.1General Architecture of a wireless battery charger
329
Int. J. Adv. Eng., 2015, 1(3), 328-332
The receiver circuit receives the power through receiving coil and passes through voltage multiplier circuit (consisting
of diode and capacitor voltage multiplier) and through that voltage the mobile charging is achieved. In receiver section,
after rectification, we use ADC to convert voltage signal into digital type. And microcontroller measure and calculates
the receiving voltage level and display by LCD.
II. HARDWARE AND SOFTWARE CONTROLMETHOD
Figure.2 Block diagram of renewable energy based wireless battery charger for mobile device
In our Wireless charging system there are two circuits, a transmitter circuit and a receiver circuit. The transmitter
circuit consists of step down transformerof230/12V. This transformer steps down230VAC from main supply to
12VAC.Then that 12V AC is converted into12VDCwiththehelpofbridgerectifier.Afterthat a 2200/25V capacitor is used
to filter the ripples and pure DC is supplied. Then the oscillator circuit oscillates at 10MHzandwith the help of
transmitting coil it transmits the wireless power.
DC power Source: It consists of a step down transformer that step downs the supply voltage to a desired level, and
rectifier circuit to convert that AC voltage to DC signal.
The receiver circuit receives the power through receiving coil and passes through voltage multiplier circuit(consisting
of diode and capacitor voltage multiplier)and through that voltage the mobile charging is achieved. In receiver section,
After rectification, we use ADC to convert voltage signal into digital type. And microcontroller measure and calculates
the receiving voltage level and display by LCD.
III. OPERATION AND CONTROLMETHOD
The system has been simulated in SPICE environment to evaluate system performances in terms of power conversion
efficiency. Several simulation sessions have been carried out under different operating conditions. Fig. shows
simulation results under a380mAloadcurrent.Atthetopingreenthe output voltage V(out), in red the secondary-coil
voltage waveforms are shown. At the bottom, in blue the diode’s current in green the output voltage waveforms are
plotted. The receiver’s average efficiency, evaluated between the secondary coil and the load current source, turns out
to be equal to 59.7%whenMODishighandto91.3%when MOD is low. As highlighted by simulation results ,most of the
dissipated power is due to the passive rectifier and the resistive modulation. This one is interested by more than 70% of
the total wasted power. Power losses in the biasing circuit of the modulation network only represent a small fraction of
the total wasted power, instead. Circuit description: The line voltage is rectified by the full-bridge rectifier, generating
a semi-sinusoidal voltage at double the line frequency. The frequency of oscillation then depends mainly upon
the size and maximum flux density of the ferrite core used in the feedback transformer, and the storage time of the
transistors. When the cycle has started, the current in the feedback transformer increases until the core saturates. At this
point the feedback drive of the active transistors is therefore removed ,and, once its storage time has passed, it turns
off. In this application the oscillation frequency would be 25 to 40 kHz. The dependence upon the storage time is
minimized by the RC network at the base of the transistor, which increases the rate of charge extraction from the base
at turn-off. The network also serves to decouple the base from the oscillation caused by the base transformer at turn-off,
preventing spurious turn-on of the device. By combining a versatile 8-bitCPUwith in-system programmable Flash on a
monolithic chip, the Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-effective
solution to many embedded control applications.
330
Int. J. Adv. Eng., 2015, 1(3), 328-332
Figure.3 Circuit Diagram Of Transmitter Section
Figure.4 Circuit Diagram Of Receiver Section
Micro controller: The AT89S52 is a low-power, high-performance CMOS 8-bitmicrocontrollerwith 8 Kilobytes of insystem programmable Flash memory. The device is manufactured using Atmel’s high-density non volatile memory
technology and is compatible with the Indus-Try-Standard (ITS)80C51instruction set and pin out. The on-chip Flash
allows the program memory to be reprogrammed in-system or by a conventional non volatile memory programmer.
Figure.5.MicrocontrollerAT89S52
In addition, the AT89S52 is designed with static logic for operation down to zero frequency and supports two software
selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and
interrupt system to continue functioning.
Analog to digital converter
Analog to digital converters find huge application as an intermediate device to convert the signals from analog to
digital form. These digital signals are used for further processing by the digital processors. Various sensors like
temperature, pressure, force etc. convert the physical characteristics into electrical signals that are
analoginnature.ADC0804 is a very commonlyused8-bit analog to digital convertor. It is a single channel IC, i.e., it can
take only one analog signal as input. The digital outputs vary from 0 to a maximum of 255. The step size can be
adjusted by setting the reference voltage at pin9. When this pin is not connected, the default reference voltage is the
operating voltage, i.e., Vcc. The step size at 5V is 19.53mV (5V/255), i.e., forevery19.53mV rise in the analog input,
the output varies by 1 unit. To set a particular voltage level as the reference value, this pin is connected to half the
voltage.
331
Int. J. Adv. Eng., 2015, 1(3), 328-332
IV. WIRELESS POWER TRANSFERSECTION
Description
The word POWER is itself self- explanatory in every form and is very important for living and working. This project
on wireless power transfer aim to develop a tool for wireless power transfers. Wireless power transmission will
create a major impact within the field of the engineering science and will eliminates the employment of typical copper
cables and current carrying wires. Wireless power transfer is transferring of power wirelessly, using mutual induction
of 2 coils in HF.
Working principle
This project is made using electronic circuitry that converts AC 230V 50Hz toAC12V, High frequency and this H F
output becomes input for tuned coil and make a primary for air core transformer and when a secondary coil is brought
near, it develops the high frequency of 12Vpoweringconnecteddevice. Here
the primary
coil
act as a
transformer and secondary as a receiver and power is transferred wirelessly with in distance of say 3cm. This project
may be used for charging batteries those are a unit physically impossible to be connected electrically like pacemakers.
Theory
Inductive or magnetic coupling works on the principle of electromagnetism. When a wire is proximity to a magnetic
field, it induces a magnetic field in that wire. Transferring energy between wires through magnetic fields is inductive
coupling. Magnetic resonant coupling uses the same principles as inductive coupling, but it uses resonance to increase
the range at which the energy transfer can efficiently take place.
Figure.6. Magnetic coupling with four component fluxes
Resonance can be two types:(a)series resonance & (b) parallel resonance. In these both types of resonance, the principle
of obtaining maximum energy is same but the methods are quite different.
Solar panel
Light, including sunlight is sometimes described as particles called "photons." As sunlight strikes a photo voltaic cell,
photons move into the cell. When a photon strikes an electron, it dislodges it, leaving an empty "hole". The loose
electron moves toward the to player of the cell. As photons continue to enter the cell, electrons continue to be dislodged
and move upwards. If an electrical path exists outside the cell between the top grid and the backplane of the cell, a flow
of electrons begins. Loose electrons move out the top of the cell and into the external electrical circuit. Electrons from
further back in the circuit move up to fill the empty electron holes. Most cells produce a voltage of about one-half volt,
regardless of the surface area of the cell. However, the larger the cell, the more current it will produce. The resistance
of the circuit of the cell will affect the current and voltage. The amount of available light affects current production.
The temperature of the cell affects it svoltage.
LCD Display
Figure.7 LCD Display
332
Int. J. Adv. Eng., 2015, 1(3), 328-332
LCDs work from the ability of liquid crystals (LC) to rotate polarized light relative to a pair of crossed polarizers
laminated to the outside of the display. There are two main types of LCD displays used for calculators today: Twisted
nematic(TN) and super twisted nematic(STN).
V. HARDWARE OUTPUT MODELS
Figure.7 Hardware setup
CONCLUSION
The goal of this project was to design and implement a wireless power transfer system via magnetic resonant coupling.
After analyzing the whole system systematically for optimization, a system was designed and implemented.
Experimental results showed that significant improvements in terms of power-transfer efficiency have been achieved.
Measured results are in good agreement with the theoretical models. We have described and demonstrated that
magnetic resonant coupling can be used to deliver power wirelessly from a source coil to a with a load coil with an
intermediate coil placed between the source and load coil and with capacitors at the coil terminals providing a sample
means to match resonant frequencies for the coils. This electro - mechanism is a potentially robust means for delivering
wireless power to a receiver from a source coil.
REFERENCES
1.
2.
3.
4.
5.
6.
7.
8.
CableIess
Battery
Charger
UsingInduction
Technique-Student
Conference
on
Research
and
Development
(SCORED)2003Proceedings,Putrajaya,Malaysia.
A WirelessBattery
Charger Architecture for ConsumerElectronics-2012 IEEE Second International Conferenceon Consumer
Electronics - Berlin(ICCE-Berlin).
A Novel Wireless Charging Systemfor Movable Telephone withPrinted-circuit-board Windings of Different Structure andShape
RespectivelyProceeding ofInternational Conference on Electrical Machines andSystems 2007, October 8-11, Seoul, Korea,1285.
H. Zhai, H. K. Pan, and M. Lu, "Apractical wireless charging systembased onultrawideband retroreflectivebeamforming," presented
atIEEE.
B.Cannon, J.F. Hoburg, D.D.Sancil andS.C. Goldstein, “Magnetic resonant Coupling asaPotential Means for Wireless Power Transferto
Multiple Small Receivers”, IEEETransactions on Power Electronics,vol.24, issue 7, July2009.
Wireless Power Consortium,“System description wireless powertransfer” Vol.1,PartI, II andIII
J. W. Hsu, A. P. Hu and A. Swain,“Wireless Power Pickup Based on DirectionalTuning Control of Magnetic Amplifier”,IEEE
Transactions on Industrial Electronics, vol.56, no. 7, July2009,
L.Chen, S.Liu, Y.Zhou and T.Cui,“An Optimizable Circuit Structure forHigh- Efficiency Wireless Power Transfer”,IEEE Transactions on
Industrial Electronics,vol.27, issue 99, November2011.