OVERVIEW OF WIRELESS CHARGING - UL · The mobile industry is transitioning to wireless charging...

© 2015 Underwriters Laboratories Inc.

OVERVIEW OF WIRELESS CHARGING

Wearables TechCon

March 11, 2015

Naomi Lee

Wireless Charging Program Manager

[email protected]

The mobile industry is transitioning to wireless charging solutions

giving users more convenience to no longer need to carry chargers

or wired power adapters while traveling.

There are three wireless alliances striving to be “The Wireless

Charging Standard” in the industry.

Wireless Power Transfer

2

WPC was established in December 2008 and Qi

low power specification was published in August

2009 based on Inductive power transfer.

PMA was established in March 2012 and PMA’s

Receiver specification was published in 2014

based on Inductive power transfer.

A4WP was established in March 2012 and

Rezence Baseline Specification was published in

2013 based on Resonance power transfer.

Wireless Power Transfer

3

Frequency of

Operation

100 – 205 kHz 200 – 350 kHz 6.78 MHz

Alignment Close

*Introducing Loose

Alignment, Q1/Q2

2015

Close Loose

Communication

Channel

In-Band with

Frequency of

Operation

In-Band with

Frequency of

Operation

Out-of-Band using

Bluetooth

NOTE: PMA and A4WP announced they will merge to

become one alliance by June 2015

Summary of differences in the three alliances.

Tightly coupled versus Loosely coupled

Tighter the coupling, higher the power transfer

efficiency, lower power loss and less heat produced.

Tight coupling is more advantageous for devices with

limited thermal budgets as smartphones or tablets.

4

Tightly coupled transmitter

and receivers have the same

size coils and smaller Z

distance than the coil

diameter. Both transmitter

and receiver coils have ferrite

shielding therefore less

EMI/EMF emissions


Loosely coupled systems trade-off lower efficiency

power transfer with greater distance separation.

Loosely coupled systems have less power transfer

therefore a resonance circuit is needed to improve the

power transfer across distances.

In loosely coupled systems, a fraction of the power is

transferred to the receiver therefore there are higher

EMI/EMF emissions than tightly coupled systems.

5


Loosely coupled coils operate at a larger distance or

operate with significantly different coil sizes.

6

Qi was the first of the three alliances for Wireless Power

Transfer. Qi‘s Wireless Power Transfer is based on

Magnetic Inductance with close alignment. UL Japan is

an accredited test lab for conformance tests. All

Interoperability tests conducted by a third party lab.

Wireless Power Consortium (Qi)

7

Mobile Conformance Tests (Receiver):

8


Test No. Mobile Testing Test Description

1 Conformance to Communications Interface Requirements - Load Modulation

2 Conformance to System Control Requirements - Digital Ping: Packet Timing

3 Conformance to System Control Requirements - Digital Ping: Packet Content

4 Conformance to System Control Requirements - Digital Ping: Signal Strength

5 Conformance to System Control Requirements - Digital Ping: Packet Timing

6 Conformance to System Control Requirements - Identification & Configuration: Packet Sequence

7 Conformance to System Control Requirements - Identification & Configuration: Packet Timing

8 Conformance to System Control Requirements - Identification & Configuration: Packet Content

9 Conformance to System Control Requirements - Power Transfer: Packet Timing

10 Conformance to System Control Requirements - Power Transfer: Packet Content

11 Conformance to System Control Requirements - Power Receiver: Reset

12 Conformance to System Performance Requirements - Guaranteed Power

Base Station Conformance Tests (Transmitter):

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Test No. Base Station Testing Test Description

1 Conformance to Communication Interface Requirements - Load Modulation

2 Conformance to System Control Requirements - Selection phase

3 Conformance to System Control Requirements - Digital Ping: Power Signal Characteristics

4 Conformance to System Control Requirements - Digital Ping: No Response

5 Conformance to System Control Requirements - Digital Ping: Signal Strength

6 Conformance to System Control Requirements - Digital Ping: Termination

7 Conformance to System Control Requirements - Identification & Configuration: Packet Sequence

8 Conformance to System Control Requirements - Identification & Configuration: Packet Timing

9 Conformance to System Control Requirements - Identification & Configuration: Communication Error

10 Conformance to System Control Requirements - Identification & Configuration: Packet Content

11 Conformance to System Control Requirements - Power Transfer: Packet Sequence

12 Conformance to System Control Requirements - Power Transfer: Packet Timing

13 Conformance to System Control Requirements - Power Transfer: Packet Content

14 Conformance to System Control Requirements - Power Transfer: Packet Control

15 Conformance to System Control Requirements - Power Transfer: Termination

16 Conformance to System Performance Requirements - Guaranteed Power

17 Conformance to System Performance Requirements - Thermal Performance

18 Conformance to System Performance Requirements - Foreign Object Detection

19 Conformance to System Performance Requirements - User Interface: Object Placed

20 Conformance to System Performance Requirements - User Interface: Transfer in Progress

21 Conformance to System Performance Requirements - User Interface: Transfer Complete

22 Conformance to System Performance Requirements - User Interface: Fault

23 Conformance to System Performance Requirements - User Interface: Multiple Devices

24 Conformance to System Performance Requirements - User Interface: Limited Power

The PMA is another alliance striving to standardize the

wireless charging technology in the industry. PMA is also

based on magnetic inductance with close alignment.

Certification is based on conformance and interoperability

tests.

Power Matters Alliance (PMA)

10

UL Fremont is the Lead Lab

for PMA.

UL Taiwan is also an

accredited test lab.

Receiver Testing and Certification of PMA

• Receiver devices are tested to verify the device meets

the requirements of the PMA specifications on a

a customized Test Equipment which was

validated by UL.

• Measurements are conducted such as

coupling coefficient, efficiency, output

voltage and notification that charge is complete.

• Devices are also tested for interoperability functionality

with available transmitter devices to ensure the wireless

charging does not interferes with the device

performance.


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Receiver Conformance Tests:

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Test No. RX Testing Test Description

1 Detection - DC Magnetic Field Results

2 Detection - Alignment

3 Detection - Coupling Coefficient

4 Digital Ping - Engagement with Charging Surface

5 Digital Ping - Digital Ping Operation

6 Digital Ping - Output Voltage

7 Digital Ping - UCD Charging Notification

8 Identification - Stabilization Period

9 Identification - Message Correctness

10 Communication - Modulation

11 Charging Performance - Long Cycle Test

12 Charging Performance - Switch Load

13 Charging Performance - Efficiency

14 Power Termination - Regular End of Charge

15 Safety and Protection - Over Current Protection

16 Safety and Protection - Over Temperature Protection

Receiver Interoperability Tests:

More test cases will be added once validated by PMA.

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Test No. Interoperability Test Description

1 Scenario 1A - Engagement with Charging Surface - Basic Charging

2 Scenario 1A - Engagement with Charging Surface - Wired charging connected before placement

3 Scenario 1A - Engagement with Charging Surface - Wired charging connected after placement

4 Scenario 1A - Engagement with Charging Surface - Charging depleted battery

5 Scenario 1A - Engagement with Charging Surface - Low battery in misalignment condition

6 Scenario 1A – Engagement with Charging Surface - IUT temperature

7 Scenario 1A – Range of Motion Within Tx Operational Range

8 Scenario 1A – Range of Motion In and Out of Tx Operational Range

9 Scenario 1B – Touch Screen Performance

Transmitter Testing and Certification of PMA

• Transmitter compliance specifications are still in

development. Compliance test specifications to be

defined by end of Q1 2015.

• Conditional certification can be provided with

conducting transmitter interoperability tests with

available receiver devices. Once the compliance

specifications are finalized the transmitter must be

resubmitted for conformance testing for final

certification.


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The A4WP or Rezence is another of the three alliances.

Rezence provides wireless charging with spatial freedom

and based on Magnetic Resonance with loose alignment.

This allows for flexible device placement and charging

through surfaces.

Alliance For Wireless Power (A4WP)

16

UL is working closely

with A4WP to become a

lab by Q2 2015. UL

Fremont will host the

next PlugFest at the end

of March.


Rezence Certification Program currently test both receiver

and transmitters manually. Rezence is working on an

automated testbed solution.

Certification has both Conformance and Interoperability

functionality tests.

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18

Questions

19

Backup

20


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Base Stations = Transmitter type difference summary

Base Station Description

Type A Based on a single Primary Coil

Type B Based on an array of Primary Coils

Mobile Devices = Receiver

Low power specifications transfers around 5W of power.


22

Transmitter type difference summary

Tx Type Description

Power Class

0 (5W) 1 (10W) 2 (15W) 3 (20W) 4 (30W) 5 (40W) 6 (50W) 7 (70W)

PMA-1

Basic single coil design. Used

as a reference for testing.

Transmitter type installed in

Averna testers.

X

PMA-3 Enhanced performance single

coil design. Design to be rolled

out to all Starbucks globally. X

PMA-4 Enhanced performance single

coil design to support up to

Class 2. X X X

PMA-5 Enhanced performace multi-coil

design to support up to Class 2. X X X

Alliance for Wireless Power (A4WP)

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PTU – Power Transfer Unit for BSS* 1.3

Class Type PowerTX_IN_MAX

(Maximum Input power to the resonator)

Min Category Support Min Value for Max # of device support

Class 1 2W 1 x Category 1 1 x Category 1






* BSS = Baseline System Specification

Alliance for Wireless Power (A4WP)

24

PRU – Power Receiver Unit for BSS 1.3

Category Type PowerRX_OUT_MAX

(Maximum output power of the PRU resonator)

Examples

Category 1 TBD BT headset

Category 2 3.5W Feature phone

Category 3 6.5W Smart phone

Category 4 13W Tablet, Phablet

Category 5 25W Small Form Factor Laptop

Category 6 37.5W Regular Laptop

Category 7 50W

OVERVIEW OF WIRELESS CHARGING - UL · The mobile industry is transitioning to wireless charging...

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