Maximizing Wireless Power Performance

In Constrained Environments

Michael GotliebVice President of Business Developmentwww.nucurrent.com

Agenda

CONFIDENTIAL 2

• Wireless Power Markets

Focus of This Presentation:

Constrained Environments within Qi Certified, Qi “Friendly”

• What Problem Are We Solving?

“Performance” Defined

• Practical Ways to Maximize “Performance”

• Conclusion

Wireless Power MarketsIn Production or In Design Today; Broadening Landscape

Consumer•Mobile Phones

•Wearable, Personal Devices

•Peripherals; Laptops

Medical•Hearing Aid

•Sanitized Rechargeable

•Portable Equipment

Industrial•Wireless Sensor Networks

•Contact Replacements

•Power Tools

Infrastructure•Office Furniture

•Coffee Shops

•Hotels

Automotive•Accessory / Sleeves

•In Car Embedded

•In Car Consumer Device

Mil-Aero•Airplane Trays/Seats

•Soldier Equipment

•Robotics

Discussion Focus

Wireless Power System EnvironmentsHighlights of In-Production or In-Design Today

ConsumerMobile Phones

•0.25mm – 0.40mm thin

(Coil + Ferrite )

•Z gap 3mm+

•10 -15 Watts

Wearable, Personal Devices

• 0.25mm – 0.6 mm thin

• Z-gap 3 mm+

• 1Watt +

• Flexible/Bendable

MedicalHearing Aide

•8.5mm-12mm DIA

•0.5mm thin

•Z gap 3 mm

•<1 Watt

•Portable Equipment

Automotive

Accessory / Sleeves

• 0.3mm - 0.6 mm

• Z gap 3 mm

• 5 – 15 Watts

In-Car Embedded

Armrest/Console Pad size

•1mm thickness

•Z gap >10mm (Qi Friendly)

•5W – 15Watts

Why Wireless Power DesignersGo Thin and Small?

+Add Other Product Features+Increase Battery Size+Industrial Design Forces Size+Cost+Retrofitting Existing Products

“Any fool can make wireless power work, but making it work at a

reasonable cost with reasonable performance takes considerable

engineering skills,” Robertson told Electronics Weekly 8-25-15.

.

-----(former) Senior Vice-President at IDT Graham Robertson

CONFIDENTIAL 5

DC – AC Tx Antenna Rx Antenna AC - DC

ηDC-AC

Typical:0.8 – 0.95ηAntenna-to-Antenna

ηAC-DC

Typical 0.75 – 0.95

1. ηSystem(1) = 0.85 X 0.89 X 0.90 ~ 68%2. ηSystem(2) = 0.92 X 0.95 X 0.92 ~ 80%

Wireless Power SystemsInterrelated Stages Impact 1)User Experience 2)Efficiency / Heat

1)Equal Rectifier stage with Improperly Rx/Tx selected antenna makes the P/A work inefficiently thus heat & perceived poor performance

2) All Properly selected stages

Wireless Power System

X X

1) FET’s / IC 2) Design(k, Q), Tuning 3) Rectifier / IC

System Efficiency ηSystem

Impactful Areas:

One Circuit Design Adapts to Multiple Coil Sizes/ShapesTuning & Matching Will Change

All Rx Functions on One Substrate

TX Circuit

(including Tuning / Matching)RX Circuit

(Including Tuning / Matching)TX Antennas RX Antennas

OR

System Development Process

8

EM Simulation &

Design

Circuit Design & Simulation

FabricationDesign

Validation Testing

Fundamental System

Analysis

ProductionYay!

Mechanical Simulation &

Design

Look for NC Standard Product

IterativeProduct

Definition

Optimal PerformanceModeling accelerates time to success

CONFIDENTIAL 9

EM Simulation &

Design

Circuit Design &

Simulation

From EM Simulations

Why Modeling Matters

Time & Performance Improvements

CONFIDENTIAL 100%

10%

20%

30%

40%

50%

60%

70%

80%

A21 - 1 A21 - 2 Qi-PCB Rx Qi-FPC Rx Qi-FPC Rx Qi-Litz Tx Qi-FPC Rx AirFuel Tx Airfuel RX AirFuel Rx

Quality Factor Improvements of Actual Projects with NuCurrent Design / Technology in PCB VS other PCBs

Common Types of WPT Coil Materials

Wire-woundLitz

Wire-woundTraditional

PCB

NuCurrent

MLMT®

Flex & PCBPros and Cons• Cost• Durability• Tolerance / Variability• Thickness

• Thermal• Manufacturing / Repeatable • Integration / Connection• Ability to Meet Desired Performance

- Typical operating point of tightly coupled applications (e.g. inductive)

- Typical operating point of loosely coupled applications (e.g. Resonant, Qi “Friendly”)

𝑭𝑶𝑴 = 𝜿𝟐𝑸𝑻𝑿𝑸𝑹𝑿

𝑬𝒇𝒇 = 𝒇 (𝑭𝑶𝑴)

Antenna Performance: Q’s and k’sObtaining Optimal Performance

• Design achieves higher coupling (k)

• CoolSkin Technologies TM delivers higher Quality Factor (Q)

Optimal Systems Antenna Equations

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Coupling Coefficient, k

An

ten

na

-to

-An

ten

na

Eff

icie

nc

y

Variation of Efficiency with k and Q

QTX

=90, QRX

=25

QTX

=300, QRX

=100

Equal Performance Considerations

Influencing Coil Selection: What IS Important?

Use Case: Interoperability, Alignment, # of Simultaneous Devices,

Charge Distance(z) , Charging Rate & Power, Charge Location and Area(Tx)

Your Environment Matters

Your Product Inside & Out: Think Coil Volume & Surrounding Materials

Battery / Other Active Electronics (Size – Location)

Which IC or Discrete Topology

Thermal Budget

Connection to the Main Board

Size of Tx

13

Standard Product VS Custom Coil Price & Timing May Be Similar

1. Is there a standard coil that meets my

mechanical needs for my allotted

environment(L x W x H, main board

attach, embedded) ?

2. Is there a standard product that will help

me deliver the electrical performance

that will please my end customers( power,

efficiency,…)?

3. Can I create - simulate a well functioning

system on my own including Rx-Tx Pair?

14

Standard Coils: Good for Starter

Create Your Own: Optimize Performance

Have I Selected the Proper Coil?Mechanical Perspective (1st) Electrical Perspective(2nd)

Key Equations for Coil to Coil Efficiency and Mutual Inductance Order

𝐿 – Inductance 𝑸 =𝟐𝝅𝒇𝑳

𝑬𝑺𝑹

ESR– Equivalent series resistance

(1)

𝑘 = 1 −𝐿𝑟𝑥 𝑠ℎ𝑜𝑟𝑡

𝐿𝑟𝑥 𝑜𝑝𝑒𝑛

k – Coupling

𝑳𝒓𝒙 𝒔𝒉𝒐𝒓𝒕 – Inductance of receiver in stack-up with transmitter coil shorted

𝑳𝒓𝒙 𝒐𝒑𝒆𝒏 – Inductance of receiver in stack-up with transmitter coil open

(2)

𝑀 = 𝑘 ∗ √(𝐿𝑇𝑥 𝐿𝑅𝑥)

M— Mutual Inductance

𝐿𝑡𝑥 – Transmitter inductance with stackup

𝐿𝑅𝑥 – Receiver inductance with stackup

(3)

𝑬𝒇𝒇𝑪𝒐𝒊𝒍−𝒕𝒐−𝑪𝒐𝒊𝒍

=𝜿𝟐𝑸𝑻𝑿𝑸𝑹𝑿

𝟏 + 𝟏 + 𝜿𝟐𝑸𝑻𝑿𝑸𝑹𝑿

𝟐

(4)

𝐸𝑓𝑓𝐸𝑛𝑑 𝑡𝑜 𝐸𝑛𝑑

= 𝐸𝑓𝑓𝑃𝑜𝑤𝑒𝑟 𝐴𝑚𝑝

. 𝐸𝑓𝑓𝐶𝑜𝑖𝑙−𝑡𝑜−𝐶𝑜𝑖𝑙

. 𝐸𝑓𝑓𝑅𝑒𝑐𝑡𝑖𝑓𝑖𝑒𝑟

(5)CONFIDENTIAL 15

Procedure For Calculating EfficiencyIts Not Just About Efficiency…Use Case Matters

• Measure inductance (L), equivalent series resistance (ESR) and quality factor (Q) of the TX coil with proper stack up (see Fig. 1) at desired frequency with an LCR Meter or Impedance Analyzer. Q is related to L and ESR through Eq. (1).

• Measure inductance (L), equivalent series resistance (ESR) and quality factor (Q) of the Rx coil with proper stack up (see Fig. 1) at desired frequency with an LCR Meter or Impedance Analyzer. Q is related to L and ESR through Eq. (1).

• Measure inductance (L) of Rx coil within the proper stackup at desired frequency with the transmitter coil terminations left open, record 𝐿𝑟𝑥 𝑜𝑝𝑒𝑛. Measure inductance of Rx coil within the proper stackup at desired frequency with the transmitter coil terminations shorted, record 𝐿𝑟𝑥 𝑠ℎ𝑜𝑟𝑡. Calculate k using Eq. (2)

• Calculate M using Eq. (3).

• Calculate 𝐸𝑓𝑓𝐶𝑜𝑖𝑙−𝑡𝑜−𝐶𝑜𝑖𝑙

using Eq. (4).

• Calculate 𝐸𝑓𝑓𝐸𝑛𝑑 𝑡𝑜 𝐸𝑛𝑑

using Eq. (5).

CONFIDENTIAL 16

Strictly Confidential

Thickness = 2.00 mm L= 6.24 uHESR= 0.11 ohmQ= 34Size = 30 mm OD

Rx coil

Ferrite

Spacer

Tx coilFerrite

Stack Up

Measured at 100 kHz

Nucurrent coil is 56 % thinner than initial 3W Rx coil

Thin Coil Provides Design Flexibility3W Qi Solution Example- Performance Without Sacrifice

Rx Coil Q Size L (uH)

ESR (ohm)

Totalthickness

Coupling Mutual inductance

Efficiency (power)

3W Rx Wire Wound 17.3 30mm 8.25 0.30 0.80 mm 0.778 8.36 78.4% (3W) , 79.4% (2W)

PNC01-R126W16-030-030-0R45

13.5 30mm 8.04 0.37 0.35 mm 0.808 9.16 77.6% (3W) , 78.7 % (2W)

3W Tx Coil

PNC01-R126W16-030-030-0R35

3W Rx Coil

Medium Power – 15 W Rx (Qi Portion of Tri-mode)

50 x 50 Flavor Comparison: NuCurrent Coils

18

Rx Coil : PNC11-R90L01E-050-050-0R35

Rx coil

Ferrite

Spacer (3 mm)

Tx coil

Ferrite

Stack Up

L (uH)

ESR (ohm)

Q Coupling Mutualinductance

(uH)

Efficiency@ 15W (12V)

Peak Efficiency

Ant –Ant Eff

8.15 0.32 15.9 0.7 8.18 82.98 % 83.14% (13.86 W)

92 %

PCB Wire Wound

Rx Coil : PNC11-R90L01E-050-050-0R70

0.25mm

Conclusion:

19

Maximizing Performance: Be Hyper-sensitive to your environmentCoil Selection is as critical as ICs, FETs and Rectifier

NuCurrent Can Help: Magnetics Expertise to Full Systems

www.NuCurrent.com