A Review on Technologies for
Wireless Electricity
Elvin Wong
Senior Consultant
Automotive & Electronics Division
About HKPC
About HKPC
Govt.
Subvention
• Established by Statute in 1967
• Source of Funding
– Government subvention (approx. 30%)
– Fee income (approx. 70%)
• Not-for-profit
• 3 Mainland Subsidiaries
≈30%
≈ 70%
Fee Income
– Productivity (Guangzhou) Consulting Company
– Productivity (Dongguan) Consulting Company
– Productivity (Shenzhen) Consulting Company
What is “Wireless Power”
• “Wireless power or wireless energy transmission is
the transmission of electrical energy from a power
source to an electrical load without man-made
conductors.”
(source: http://en.wikipedia.org/wiki/Wireless_power)
• common form of wireless power transmission
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Magnetic induction
Resonant enhanced magnetic induction
Near field Electromagnetic Resonance
Microwave
Nikola Tesla’s Wireless Electricity
Back to 1900s…..
The magnifying transmitter:
was designed to implement Wireless energy
transmission by means of the disturbed charge
of ground and air method.
Wireless Power – The magnetic Induction
• Works like a transformer
• Example: electric toothbrush
• Characteristics
– short range (a few mm if any)
– Low efficiency
– Tight coupling
Wireless Power – The Resonance
enhanced magnetic Induction
• Still works like a transformer
• Resonance enhanced
– increases the transmission range
– Range <10mm (typ.)
• Characteristics
– Improved efficiency
– Tight coupling
• Example: “Qi” wireless charger
– Will cover in more details by other speakers
Source: Qi wireless power specifications part 1
Wireless Power – Near Field Magnetic
Resonance
• Two resonant objects of the
same resonant frequency
– tend to exchange energy
efficiently
– Dissipating relatively little
energy in extraneous offresonant objects
RamRakhyani, Anil Kumar, Shahriar Mirabbasi, and Mu Chiao. "Design and
optimization of resonance-based efficient wireless power delivery systems for
biomedical implants." Biomedical Circuits and Systems, IEEE Transactions on5.1
(2011): 48-63.
Wireless Power – Near Field Magnetic
Resonance
• Characteristics
– Efficient power transfer to resonant object
– Transfer range: up to 8X the radius of coil
– Higher placement freedom: The orientation of
sending and receiving coils can be misaligned
Applications
WiTricity
http://www.industrytap.com/witricity-charges-forward-with-wireless-electricity/574
http://www.treehugger.com/clean-technology/intel-shows-wireless-electricity-system-at-idf.html
Intel
Applications
SONY
http://www.techspot.com/news/36430-sony-shows-off-wireless-power-transfer-prototype.html
http://www.engadget.com/2011/10/06/rohm-wireless-power-transmission-system-hands-on-video/
Rohm
Applications
Delphi + WiTricity
Toyota + WiTricity
http://www.autointhenews.com/wireless-electricity-to-propel-future-evs/
http://www.iol.co.za/motoring/cars/toyota/toyota-tests-wireless-charging-1.1446726#.UVEQCxenh14
Applications
Nokia Bluetooth Headset
Apple’s Wireless Power Utilization in
a Local Computing Environment
http://www.fonearena.com/blog/54395/nokia-luna-bluetooth-headset-with-wireless-charging-announced.html
http://appleinsider.com/articles/12/11/29/apple-investigating-realistic-wireless-charging-technology
What is “Qi”
“Qi” = 氣
• Setup in 1998 by Wireless Power Consortium
• www.wirelesspowerconsortium.org
• Will cover by other speakers in more details
NFMR Wireless Electricity
• Near-Field Magnetic Resonance (NFMR)
– Extended distance between sender and receiver,
typically up to 1m
– Power level from milli-watts to kilowatts
– Efficiency can reach 90%
– Good for one-to-many charging
• Suitable for
– Electric Vehicle charging
– Home appliances
– Lighting, RFID
– Medical equipment (e.g. Capsule Endoscopy)
– etc
NFMR Wireless Electricity
• Technological challenges
– Foreign object detection
• Prevent delivering excessive power to other devices
– Fault / condition detection
• E.g. stop battery charging when the battery is full
– Meet ICNIRP* Guidelines, for example,
• Near field exposure
• specific absorption rate (SAR) for human body
• SAR = σE2/ρ
– E (in V/m) is the rms value of electric field strength
– σ (in S/m) is the conductivity of human tissue
– Ρ (in g/cm3) is the mass density of human tissue
– EMI and EMC
ICNIRP: International Commission on Non-Ionizing Radiation Protection
NFMR - Recent research findings
• Short-range refers to d/r < 3, efficiency 8090% can be achieved
• Mid-range refers to d/r>3, efficiency is lower
– MIT’s research in 2007
– Wireless power 60W at 2m distance, efficiency
~40% (r=30cm, d=2m, ie. d/r=8)
Source: Zhong W.X., Lee C.K. and Hui S.Y.R.,
"General Analysis on the Use of Tesla's Resonators in Domino Forms for Wireless Power Transfer",
IEEE Transactions on Industrial Electronics, Vol.60, No.1, January 2013, pp: 261-270
NFMR - Recent research findings
• To increase the efficiency for mid-range
applications
• “repeater coils” can be added
• They can be straight chain, splitted or curved
• Efficiency >70%
Source: Zhong W.X., Lee C.K. and Hui S.Y.R.,
"General Analysis on the Use of Tesla's Resonators in Domino Forms for Wireless Power Transfer",
IEEE Transactions on Industrial Electronics, Vol.60, No.1, January 2013, pp: 261-270
Zhang, Fei, et al.,
"Relay effect of wireless power transfer using strongly coupled magnetic resonances."
Magnetics, IEEE Transactions on 47.5 (2011): 1478-1481.
NFMR - Recent research findings
• Wireless power transfer to multiple small receivers
(one-to-many)
• when multiple receivers are in close proximity to
each other
– coupling interaction between the receivers
– resonant peak split into separate peaks
– Re-tuning of resonance frequency can achieve high
efficiency for multiple receivers
Source:
Rajagopal, S., Khan, F., "Multiple Receiver Support for Magnetic Resonance Based Wireless Charging", ICC, 2011 IEEE
International Conference on, pp.1 - 5
B. Cannon, J. Hoburg, D. Stancil, and S. Goldstein, “Magnetic resonant coupling as a potential means for wireless power
transfer to multiple small receivers,” IEEE Transactions on Power Electronics, vol. 24, no. 7, pp. 1819–1825, 2009.
HKPC’s Initiative on wireless power
• Design and consultancy support to
manufacturers
• Gather the interest of manufacturers
• Work with HKEIA
– To gather the interests of the industry
– To acquire funding supports
– To save cost for manufacturers
HKPC’s Initiative on wireless power
Design capabilities
• Design and consultancy support to manufacturers
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DC-DC converter design
Coupling coil design
Testing to meet EMC requirements
Testing to meet ICNIRP guidelines
• Focused applications
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Smartphone peripherals
Home appliances
Wireless sensors
Electric vehicles
Cooperation with HKPC
Project Based
• To reach the requirements from you
• R&D Project Proposal
– Up-front R&D fee
– Royalty based on quantity sold
• Enjoy 30% cash rebate
– Offered by Innovation and Technology Commission of HK
(http://www.itc.gov.hk/en/funding/crs.htm)
-ENDThank you!
Elvin Wong
Senior Consultant
Automotive & Electronics Division
Tel: (852) 27885743
Email: elvinw@hkpc.org