Wireless Charging Through Microwaves

7/29/2019 Wireless Charging Through Microwaves

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BASELIOS MATHEWS II COLLEGE OF ENGINEERING

SASTHAMCOTTA, KOLLAM

Wireless Charging throughmicrowavesPrepared by:

Justin Johney

S7 ECE

Roll No-11

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Portable electronic devices are basic part of our life.

Difficulties of carry a battery charger or an extra battery.

Energy harvesting-Gathering transmitted energy to power

a circuit or storing it for later use.

It is a type of charging the battery with the help of

microwaves present in the air using energy harvesting

concept.

Abundance of energy all around us at all time.

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The design of the wireless battery charger consist ofthese major components;

1. Transmitter- In practical cases doesnt need. Becouse

the mobile tower,radio stations etc replace it.

2. Charge pump-A circuit which convert AC to DC and elevates

the DC level.

3. Antenna-In practical cases doesnt need. Mobile has itself.

4. Receiver-Consist a rectenna and a sensor circuit.

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BLOCK DIAGRAM

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Consist of a 915 MHz oscillator-capable of

outputting a low AC signal.

Amplify the signal using an amplifier.

A radiating antenna is used to radiate the signal.

6mW of power radiated.

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A circuit which convert AC to DC and elevates the DC level.

Consist of a rectifier and a voltage doubler.

1.RECTIFIER

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2.VOLTAGE DOUBLER

A circuit which gives the output twice that at the input.

As the number of stages increases, the o/p voltage also increases.C1&C2 (stage capacitance) have drastic effect on o/p.

Q=CV, ie as capacitance decreases o/p voltage increases.

Voltage doubler circuit

Voltage Doubler Waveform

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The considerations of choosing the appropriate antenna are:

1. Impedance of the antenna -The impedance of

the antenna should match with the output

impedance of the power transmitter and inputimpedance of the rectifier circuit.

2. Gain of the antenna

In practical cases a separate antenna does not needed. It isalready implimented in the mobile itself.

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The basic addition to the mobile phone is going to

be the rectenna.

Retenna-It is a rectifying antenna which convert

microwave energy into dc volt.

Consist a a sensor circuit- It helps to prevent thecharging of battery during incoming or outgoing.

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SENSORLM2907 is used as the sensor circuit.

It is a F-V or V-F converter IC with 8 pins.

It act as a switch for triggering the rectenna circuitry.

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COMPARISON WITH OTHER METHODS

Other charging method may have wires. But here we use a wireless

s/m.Compared to other wireless charging methods, it have greater range.

Eg:1.Inductive charging- range below 1m.

2.Resonance charging- range between 3-5m.

But in the case of microwave charging the range is within the

coverage area. That means it is possible in all places where there is a

microwave presence with the desired frequency.

It is more reliable.

ADVANTAGES

DISADVANTAGES

Only used in the low power devices.

May affect the purpose of the mobile.

It is an expensive one.

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There are several possible ways to improve our design

in order to increase the power output. Here are 2

suggestions:

1. Multiple Rectifiers

2. High Gain Parabolic Antenna

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Since it is wireless system , its very user friendly.

Can be made by adding an extra circuit to the

mobile.

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Sabate, J. A., Kustera, D. and Sridhar, S., Cell-Phone

Battery Charger Miniaturization. IEEE Journal 2000.

Mi, Minhong, Personal Interview. 2003

Wireless battery charging system using radio frequency

energy harvesting by Daniel W. Harrist, BS, Universityof Pittsburgh

www.electronicstoday.com

www.ecoupled.com

www.fultoninnovation.com

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Wireless Charging Through Microwaves

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