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Electromagnetic design of Qi in system

Liu,Xun(Ken)

ConvenientPower

16-June-2016

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Base station-Mobile device (BM) system

Base station

Transmitter

Mobile device

Receiver

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Electromagnetic design of Rx in a BM system

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Ifixit.com

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Rx circuit model in a BM system

Ls’=Ls+ΔLs1+ΔLs2

Rs’

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Inductance

-5

0

5

10

15

20

1 2 3 4 5

Ind

uct

ance

(μH

)

Coil module example #

Ls ΔLs1 ΔLs2

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Secondary resonance

Other mobile device components (like battery, other metal parts inside the device…)

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Resistance

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

1 2 3 4 5

Res

ista

nce

(o

hm

)

Coil module example #

Rs ΔRs1 ΔRs2

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Why?

Ferrite shielding Metal

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FOD, Friendly metal

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Electromagnetic design of Rx in a BM system -Summary

• Ls’– Secondary resonance in BM system

– Secondary resonance in BM in power transfer

• WPC specification Part1&2 Annex C.1

• Rs’– FOD, received power,

– Procedure for Registration of Substantial Similar Products

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Electromagnetic design of Tx in a BM system

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High and controlled Electromagnetic Power Density enabled by localized charging

Example of a five devices charging plate generating simultaneously five high power density spots in a large coil array. One or several overlapping coils will be activated based on the position of the receivers ‘Rx’ on the pad.

Localized charging is important

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Coil size is important

• Coil(s) needs to have similar size with reference transmitters (e.g. Test Power Transmitter #1)

• Because….– Rx (or Mobile-device) was mostly designed for TPT#1

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Uniform Flux Distribution is importantSimulation Data comparing coil array solutions

each time only a single coil excited‘A’ type transmitter

every time one or more than one coil excited‘B’ type transmitter

Rx Receiver Tx Transmitter

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Coupling coefficient between Rx and ‘A’ type Tx

Coupling coefficient between Rx and ‘B’ type Tx

Rx Receiver Tx Transmitter

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Coil 2 excited Coil 3 excited Coil 3 excited Both Coil 2 & 3 excited

Flux distribution of ‘A’ type Tx Flux distribution of ‘B’ type Tx

Rx Receiver Tx Transmitter

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Increased Z

Interface

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Conclusions

• When electromagnetic design is to be done for transmitter or receiver, whole BM system needs to be taken into consideration.