wireless battery charger ppt

1. Submitted by
P.Punith
B.Tech IV year II sem
E C E Department

2. ABSTRACT
 The wireless charger will convert the RF/ microwave signal at 900 MHz
frequency into a DC signal .
 Then store the power into an AAA battery
 The project is divided into 3 parts: transmitter, antenna and charging circuit.
 A complete discussion of the specifications of the battery charger is provided
after data measurements.

3. 
• INTRODUCTIO N
• CONVENTIONAL BATTERY CHARGER
• DESIGN OVERVIEW
• ENGINEERING PROCEDURE
• RECTIFIER CIRCUIT
• FINAL DESIGN
• POSSIBLE IMPROVEMENTS
• ADVANTAGES & DISADVANTAGES
• CONCLUSION
• REFERENCES
OUTLINES

4. INTRODUCTION
 Portable electronic devices are very popular these days. As the usage of portable
electronic devices is increasing
 Batteries need to recharged or replaced periodically.
 To overcome this concept of wireless battery charging was developed.

5. CONVENTIONAL BATTERY CHARGER
 A battery charger is a device used to put energy into rechargeble battery by
forcing electric current through it.
 The charging protocol depends on the size and type of the battery being charged
 Some charges might be having temparature or voltage control sensors to adjust the
charging current and cut off at the end of charge

6. DESIGN OVERVIEW
Fig 1: The overall wireless battery charger design

7. ENGINEERING PROCEDURE
A. Transmitter :
 This design includes a power transmitter.
 Transmitter consists of an oscillator, amplifier and an antenna.
 At a pre-determined frequency is 900MHz oscillations are generated.
 These signals are amplified before transmission

8. Figure2 : Block diagram of the Transmitter Figure 3: 900 MHz Video/Audio Transmitter

9. TRANSMITTER SPECIFICATIONS
Power 12V DC, 900 mA
Output Power 3 Watts
Operating Frequency 900 MHz
Connector Type SMA – Female
Output Impedance 50 Ω
Table 1 : The specification of the transmitter

10. B. ANTENNA :
 To charge a battery, high power DC signal is required.
 To choose appropriate antenna, two factors are to be taken into consideration:
1. Impedance of antenna
2. Gain of antenna
 Taking the above design specification into consideration yagi antennas are best suited.

11. YAGI UDA ANTENNA :
 It is a directional antenna consisting of a driven
element and additional parasitic elements.
 Reflector element is slightly longer than the driven
dipole.
 Highly directional antenna’s such as yagi uda
antennas are commonly referred to as beam antennas
due to there higher gain.
Figure 4: A picture of the 9 dBi gain Yagi anten

12. C. RECEIVER :
 Block diagram of a receiver is as shown in the
figure
 It consists of receiving antenna , rectifier circuit
and load(AAA battery)
 Receiver main purpose is to charge AAA battery.
Figure 5 : Block diagram of receiver

13. RECTIFIER CIRCUIT
 A full wave rectifier is used due to its simplicity and efficiency in converting
the AC signals.
 The full wave rectifier consists of four schottky diodes.
 Schottky diodes are used because of their very low turn-on voltage and
operating frequency of 900MHz.

14. FINAL DESIGN
The final design the wireless battery charger
consists of the following important components:
1. Transmitter
2. Yagi antenna
3. Full-wave rectifiers circuit
4. RC circuit
5. Battery holder
picture of the transmitter with the Yagi antenna
picture of the final design circuit of the charging circuit

15. POSSIBLE IMPROVEMENTS
 Multiple Rectifiers By using multiple rectifiers more power gets rectified.
 However this design will need a spiral antenna array which is difficult to design
 High Gain Parabolic antenna Parabolic antenna will be able to transmit power from
transmitter with much higher gain and receive with greater power than yagi antenna.

16. ADVANTAGES:
Disadvantage:
 Portable
 Relatively lesser cost
 Saves time
 Less efficient
 Power loss

17. CONCLUSION
 Power loss and efficiency are the major problems for this design.
 The characteristics of diodes must be such that maximum rectification is possible
with minimum loss.
 Time varying current and voltage relationship at the physical point of the diode in the
cavity determines loss in the diode.

18. REFERENCES
[1] Espejel, J.D., “RF to DC power generation”, University of Maryland, December 2003.
http://drum.umd.edu:8003/dspace/handle/1903/176
[2] Hagerty, J.A., “Nonlinear Circuits and Antennas for Microwave Energy Conversion”, University of Colorado, 2003.
http://nemes.colorado.edu/Microwave/theses.html
[3] Lin, G.H., “Topological generation of Voltage Multiplier Circuits”, September 2003.
http://www.sinc.sunysb.edu/Stu/glin/ese314/lab2.pdf#search='Topological%20Generation%20and%
20Analysis%20of%20Voltage%20Multiplier
[4] Pylarinos, L. and Roger, E. “Charge Pumps: An Overview”, Department of Electrical and Computer Engineering, University
of Toronto. http://www.eecg.toronto.edu/%7Ekphang/ece1371/chargepumps.pdf
[5] Sedra, A.S. and Smith K.G, “Microelectronic Circuits”, 5th Edition, Oxford University, New York, 2004.
[6] Stremler, F.G., “Introduction to Communication Systems”, 3rd Edition, Addison-Wesley, New York, 1990.

19. THANK U ALL