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Wireless Power Transfer Historical Developments & Modern Applications

Ron Hui

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Content

• Brief history of wireless power transfer

– Mid-range / Short-range

• Modern Applications

– Chargers & environmental implications

– New Wireless Charging Platform

– Qi – World‟s 1st Wireless Charging Standard

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Earth’s Magnetic Field

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André-Marie Ampère

French Scientist

1820:

André-Marie Ampère developed

Ampere‟s law showing that electric

current produces a magnetic field.

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N N S S

Alternating electromotive force (voltage) driving a current in a coil

v v

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i

N S

v

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1831:

Michael Faraday develops Faraday‟s law

of induction describing the electromagnetic

force induced in a conductor by a time-

varying magnetic flux.

Michael Faraday British Scientist

i1 v1 v2

v1 is applied, but v2 is induced. 6

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Nikola Tesla

Inventions for the 20th Century

• AC Power Generation, Transmission & Networks

• First Niagara Falls Power Station – early pioneer in “renewable energy”

• Induction machines (fans, pumps, air-conditioning systems, electric vehicles, electric railway systems)

• Gas fluorescent lamps – demonstrated with wireless power

• Cathode ray tube & X-ray machine

• Automobile speedometer

• Tuned resonance circuits

– Radio and radio-broadcasting (e.g. we can “tune” our radio to different channels)

– Remote-controlled boat by radio

– Wireless power transfer (non-radiative and radiative)

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Tesla obtained about 300 patents

Tesla, in Colorado Spring's laboratory (1899), seated

in front of a high-voltage transformer.

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Photographs of wireless

power transfer

experiments by Tesla

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Tesla holding a lamp

powered wirelessly

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Wireless Power Transfer

It is all about Resonance

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Book: “The Man who invented the 20th Century”,

by Robert Lomas 1999

Tuned resonance

“The gift of mental power comes from God, the Divine Being, and if we concentrate our minds on that truth, we become in tune with this great power.

My mother has taught me to seek all truth in the bible.”

Nikola Tesla

1856-1943

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The Physical Resonance

• Mechanical resonance

• Electromagnetic resonance

Tesla’s patented claims

• Resonant frequency for high efficiency operation

• He used loop resonators – coil in series with capacitor (Leyden jar)

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Tesla‟s patent in 1894

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Demonstration

• Magnetically-coupled Wireless Power transfer

Perpendicular

axis of coil

planes

d

r

C

C

AC

power

source

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Demonstration

• Magnetically-coupled Wireless Power transfer

Perpendicular

axis of coil

planes

d

r

C

C

AC

power

source

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Tesla 1894 The MIT Team 2007

(Physics Dept) 18 18

Limitations for mid-range power transfer

Energy

efficiency

Transmission

distance d

Exponential

decay curve

100%

Short

range

Mid

range

Xd

1

The MIT team repeated Tesla‟s experiment in 2007

Coil radius 30cm, d = 2 meters , Efficiency 40%

Low energy efficiency !

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Historical changes • Transformers

750W

(0.26W/cm3)

150W

0.25W/cm3)

300W

(5.6W/cm3)

60W

(9.6W/cm3)

50Hz 100kHz

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New concept combined with coreless transformer and

waveguide

• (1998)

• (1999) – Energy Transfer (90W)

Primary Secondary

50%

60%

70%

80%

90%

100%

1.0E+6 2.0E+6 3.0E+6 4.0E+6Switching Frequency (Hz)

Tra

nsf

orm

er

Eff

icie

ncy

R L= 30 O h m

R L= 50 O h m

R L= 100 O h m

R L= 200 O h m

Input Impedance, Voltage Gain and Phase Shift Versus Frequency

-180

-135

-90

-45

0

45

90

135

180

225

270

315

360

0.0E+0 2.0E+6 4.0E+6 6.0E+6 8.0E+6 1.0E+7 1.2E+7 1.4E+7 1.6E+7 1.8E+7 2.0E+7

Frequency / Hz

|Zin

| /

, P

hase

(V

s le

ad

Vp

) /D

egre

e

0

1

2

3

4

5

6

Vo

ltage G

ain

(V

/V)

Zin(measured)

Zin(Calculated)

Phase(Measured)

Phase(Calculated)

Gain(Measured)

Gain(Calculated)

Max.

Impedance

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• Philips Research (2001) Contactless Power transfer of 100W

• Prof. Richard Syms (2006), Imperial College London

Waveguide

Dimensions of the Printed

Coils and Coil Separation are

determined by the wavelength

of the wave propagation

Impedance matching (< 50%)

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The Domino Resonators (2011)

axis of coil

planes

d1

r

C

C

AC

power

source

C C C C

d2 dn

Energy

efficiency

Transmission

distance d

Exponential

decay curve

100%

Short

range

Mid

range

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axis of coil

planes

d1

r

C

C

AC power

source

C C C C

d2 dn

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(a) Straight chain

(b) Curved chain

(c) one chain splitting into two

(d) two chains emerging into one

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Anything new since Tesla‟s work?

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0.97 0.98 0.99 1 1.01 1.02 1.030

2

4

6

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10

12

14

35

40

45

50

55

60

65

70

75

80

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Effic

ien

cy [%

]

Po

we

r F

low

[W

]

f / fres

η

P12

P23

0.97 0.98 0.99 1 1.01 1.02 1.0320

30

40

50

60

70

80

-2

0

2

4

6

8

10

12

14

Effic

ien

cy [%

]

f / fres

Po

we

r F

low

[W

]

η

P12

P23

P13

Mutual coupling of non-adjacent resonator shifts the “optimal

frequency” away from resonance frequency

Without cross-coupling With cross-coupling

Superconducting materials

Matrix

Cooling agent

Cover (insulating material)

New Structure of Superconductive Power Cable

Existing

-rigid

structure

Patent-pending

-flexible

structure

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Content

• Brief history of wireless power transfer

– Mid-range / Short-range

• Modern Applications

– Chargers & environmental implications

– New Wireless Charging Platform

– Qi – World‟s 1st Wireless Charging Standard

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Modern Applications of Wireless Power Transfer

• High –power applications (Uni. of Auckland)

Wireless Monorail system

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Mobile robot in clean room

manufacturing facilities E-Quickie drawing wireless

power from Wireless

Charging embedded on the

road (Germany Sept. 2010)

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Wireless Power for Portable Devices

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0

200

400

600

800

1000

1200

1400

2004 2005 2006 2007 2008

Units

in M

illions

Mobile Phone

PC Laptop

Digital Camera

Camcorder

Portable SSA

Portable HDD

Portable MD

Portable DVD

Portable CD

PDA

The Environmental Issue - e-waste

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e-waste dumping ground

India

Nigeria

China

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Drastic reduction of electronic waste !

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Splashpower from Cambridge Parallel Flux Approach (2001)

Charging platform by

Beart et al

Lines of flux

Magnetic

core

Thick bottom magnetic plate is needed to guide the flux.

Energy-receiving element

•Use vertical surface for receiving magnetic flux

•Thick and wide

•Not suitable for slim design

•Can only be charged in one orientation.

Thick Ferrite EM

shield underneath

Secondary module

NOT included.

Inventions

“Vertical Flux” or the “Fountain” Approach (2001)

Charging platform

By Hui

Electromagnetic shield

Lines of flux

Energy-receiving

element can be

very thin.

Good for slim

product design

Can be charged

in any orientation

Thin EM shield

has been

patented

Planar charging platform

Milestones:

Planar coreless printed-circuit-board transformers (1997-patented)

Planar EMI shield (1999-patented)

Planar charging platform – 1 (2002-patented)

Secondary Module – (2003 –patented)

Planar charging platform – 2 (2005 – patented)

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Wireless power transfer – Vertical flux – From coreless planar transformer technology to wireless

charging since 1996

CityU 1996

10mm

3.6cm in diameter - 90W

1999

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World’s 1st “2-Dimensional transformer” for circuit integration

This invention

opened a door to

integrate

transformer in

Integrated Circuit

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Philips Research Center,

Aachen 2001 B. Choi

Kyungpook National University

2004

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Magnetomotive Force (MMF) Distribution

Hexagonal Spiral Windinig Symbol

MMF = No. of Turns x Current

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mmf

1

0.5

0

(4a)

(4b)

X Y

Y X distance

Maximum MMF - Peak (P)

Minimum MMF - Valley (V)

P

V

P

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Uniform MMF distribution

P P

1.0

0.5

0

mmf

P

Sum of mmf = 1 per unit

Distance

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P P

P

V

Each Peak (P) is surrounded by 6 Valleys (V)

Each Valley (V) is surrounded by 3 Peaks (P)

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P

P

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P

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50 50 50

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Excitation of 1-layer of PCB Winding Array

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Excitation of 2 layers of PCB Winding Arrays

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Excitation of 3 layers of PCB Winding Arrays

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2002 Patented

Free-positioning prototype sent to Philips Research Center,

Aachen

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Energy-receiving element (0.7mm) embedded in new

battery pack structure

New modified battery pack for

compatibility with new charging platform

Independent of brand names as long as

consumers use a compatible battery pack. 56

It is more than just a charger

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New Technologies developed

• Free-positioning

• Localized charging

• Load identification and monitoring

• Double-layer electromagnetic shield (0.5mm thickness)

• Bi-directional communication

• Near-zero standby power

• Both energy & information transfer

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2005

Press

conference in

Hong Kong

Oct 2010

The world‟s 1st

„Qi – certified‟ wireless

charging system

„free-positioning‟ and „localized charging‟

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Qi – Wireless charging stardard V.1.0 (5W)

• Free-positioning (B)

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Qi – wireless charging methods V.1.0 (5W) Launched on 31 August 2010 by the Wireless Power Consortium

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Conclusion

• The interactions of the electromagnetic fields discovered by Ampere and Faraday have laid down the scientific principles for wireless power.

• Tesla‟s resonance concept has made wireless power possible.

• World‟s 1st Qi-certified wireless charger is demonstrated (for short-range applications)

• New Domino-resonators for mid-range wireless power transfer are demonstrated.

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To all students here,

research is all about resonance

– minds and creation

Tesla’s two resonance concepts

Resonances

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“making the simple complicated is a commonplace;

making the complicated simple, awesomely simple,

that‟s creativity.”

Charles Mingus