oSIST prEN IEC 63758-1-3:2026

• Status: Not Published
• Public Enquiry End Date: 29-Nov-2026
• ICS: 29.240.99 - Other equipment related to power transmission and distribution networks
• ICS: 33.160.99 - Other audio, video and audiovisual equipment
• ICS: 35.200 - Interface and interconnection equipment
• Technical Committee: AVM - Audio, video and multimedia systems and equipment
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 28-Sep-2026
• Due Date: 15-Feb-2027
• Directive: 2014/53/EU - Directive 2014/53/EU of The European Parliament and of the Council of 16 April 2014 on the harmonisation of the laws of the Member States relating to the making available on the market of radio equipment and repealing Directive 1999/5/EC
• Mandate: M/607 - COMMISSION IMPLEMENTING DECISION of C(2025)1207 on a Standardisation Request M/607 as regards charging interface and charging communication protocol for radio equipment capable of being recharged by means of wireless charging in relation with Article 3(4), sixth subparagraph, of Directive 2014/53/EU of the European Parliament and of the Council.
• Ref Project: prEN IEC 63758-1-3:2026 - Qi specification - Version 2.3 - Part 1-3: General - Technical system overview (Fast Track)

oSIST prEN IEC 63758-1-3:2026 is the Slovenian draft standard identical to prEN IEC 63758-1-3:2026. It presents the Qi specification technical system overview from the Wireless Power Consortium, explaining how Qi wireless power transfer products are modelled, aligned, communicate, authenticate, detect foreign objects, and are tested for compliance. For engineers, quality managers, and buyers, it is the document that explains the Qi system logic behind interoperability between power transmitter products and power receiver products.

What does oSIST prEN IEC 63758-1-3:2026 specify?

oSIST prEN IEC 63758-1-3:2026 specifies the basic technical framework of the Qi wireless power transfer system. Clause 1 introduces the purpose and terminology, while Clauses 2 to 11 cover the system model, alignment, power profiles, block diagram, power levels, communication protocols, authentication, foreign object detection, symbols, and compliance testing.

The document is organized as a system overview rather than a product design manual. Its figures are illustrative, and the text repeatedly relates real products back to the ideal model PTx product (MPT) and model PRx product (MPR) used in the specification.

Clause	Main subject
1	Introduction
2	Basic concepts
3	Alignment
4	Power profiles
5	System block diagram
6	Power level definitions
7	Communication protocols
8	Authentication
9	Foreign Object Detection
10	Common symbols
11	Compliance testing

What are the key requirements of oSIST prEN IEC 63758-1-3:2026?

The core of oSIST prEN IEC 63758-1-3:2026 is the Qi system model: a power transmitter product (PTx) transfers energy to a power receiver product (PRx) by magnetic induction. Clause 2 explains coils, ferrite shielding, interface surfaces, interface volume, and active area. In practice, this is the basis for mechanical layout and for understanding where useful power transfer can happen.

Alignment and product fit

Clause 3 defines three alignment approaches: guided positioning, magnetic attach, and free positioning. Guided positioning uses strict tolerances and visual cues; magnetic attach uses magnets to help the PRx align; free positioning uses multiple coils or a moving coil to create an active area over a wider part of the interface surface. This matters because coil alignment directly affects coupling and therefore charging performance.

Power profiles and operating choices

Clause 4 introduces power profiles as a way to limit combinations of features and reduce user confusion. A PTx product may support one or more active areas and multiple power profiles, while a PRx product supports only a single power profile. For product selection, this is the key compatibility point: the transmitter may be flexible, but the receiver is tied to one profile.

Power levels and the power transfer contract

Clause 6 defines transmitted power, received power, load power, supply power, and supplied power, then builds the concept of a power transfer contract. The contract includes the guaranteed load power level, with potential, negotiable, and requested load power levels used during negotiation. In practice, the PRx should stay within the agreed guaranteed load power, because exceeding it can cause some transmitters to stop power transfer unexpectedly.

Protocol families and their limits

Clause 7 describes three communication protocols: BaselineProtocol, ExtendedProtocol, and MagneticProtocol. BaselineProtocol is unidirectional from PRx to PTx and is intended for systems up to 5 W at 110 kHz to 205 kHz; it does not support authentication. ExtendedProtocol is bidirectional and intended for up to 15 W in the same frequency range. MagneticProtocol full mode is intended for up to 25 W at 360 kHz, and its cloak phase can suspend charging while keeping the link active so the session can resume without repeating setup.

Restricted operation and restart behavior

Clause 7.4 also defines MagneticProtocol - RestrictedMode for constrained cases. It is still a 5 W, 360 kHz mode, and it can transition to full mode when the PRx has enough charge. This is important for low-battery recovery scenarios, where the receiver cannot immediately support the richer protocol.

Authentication and certificate handling

Clause 8 defines a certificate-based authentication process using public-key cryptography, certificate chains, a nonce challenge, and revocation lists. The PRx verifies the PTx identity before applying a policy that determines how to behave with the transmitter. In practice, this lets a receiver make safety or interoperability decisions based on whether a transmitter is authenticated.

Foreign object detection

Clause 9 describes Foreign Object Detection (FOD) methods that help prevent heating of objects in the interface volume. The document names the empty surface test, resonance change approach, and power loss accounting method. This matters because conductive objects such as keys or coins can absorb energy and heat up, so the system must monitor losses and stop or throttle power when needed.

Compliance testing

Clause 11 ties the specification to WPC certification and compliance testing. It defines PTxDUT and PRxDUT and introduces Test Power Transmitters (TPT) and Test Power Receivers (TPR), including white-box and black-box parts. For manufacturers and labs, this is the section that turns the system description into a repeatable test setup.

What terms does oSIST prEN IEC 63758-1-3:2026 define?

• Power transmitter product (PTx) - The product that generates the magnetic field and sends power to the receiver.
• Power receiver product (PRx) - The product that extracts electrical power from the magnetic field and delivers it to the load.
• Model PTx product (MPT) - The idealized PTx used as the system model for the specification.
• Model PRx product (MPR) - The idealized PRx used as the system model for the specification.
• Power transfer contract - The set of settings and limits that governs a power transfer session.
• Interface volume - The volume between the products where the power signal is non-negligible during transfer.
• Active area - The part of the interface surface through which the power signal meaningfully penetrates.
• Foreign Object Detection (FOD) - The process of identifying objects in the interface volume that may overheat.

Who uses oSIST prEN IEC 63758-1-3:2026?

oSIST prEN IEC 63758-1-3:2026 is used by engineers designing Qi power transmitter products and power receiver products, especially for smartphones, charging pads, charging mats, and related wireless charging equipment. It is also used by certification teams and test labs working with WPC compliance tests and the TPT/TPR test tools.

Quality managers and buyers use it to check which power profile, protocol family, and authentication behavior a product supports. The document also speaks to automotive and consumer-electronics environments, because it refers to a USB wall adapter as a typical consumer power supply and a car electrical infrastructure as a typical automotive supply.

What does the oSIST prEN IEC 63758-1-3:2026 document contain?

The document contains explanatory figures for coils, ferrite shielding, mated products, alignment methods, power profiles, protocol phase diagrams, certificate chains, data transport streams, foreign object detection, and test tools. Clause 10 provides tables of circuit symbols and composite symbols, including the quantities used for supply, PTx, PRx, and load descriptions.

It also includes procedural descriptions for protocol phases, authentication exchange, and compliance testing. For readers implementing or verifying Qi products, those sections are the practical bridge between the system model and actual product behavior.

SLOVENSKI STANDARD
01-november-2026
Specifikacija Qi - Različica 2.3 - 1-3. del : Splošno - Pregled tehničnega sistema
(hitri postopek)
Qi specification - Version 2.3 - Part 1-3: General - Technical system overview (Fast
Track)
Ta slovenski standard je istoveten z: prEN IEC 63758-1-3:2026
ICS:
29.240.99 Druga oprema v zvezi z Other equipment related to
omrežji za prenos in power transmission and
distribucijo električne energije distribution networks
33.160.99 Druga avdio, video in Other audio, video and
avdiovizuelna oprema audiovisual equipment
35.200 Vmesniška in povezovalna Interface and interconnection
oprema equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

100/4538/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 63758-1-3 ED1
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2026-09-18 2026-12-11
SUPERSEDES DOCUMENTS:
IEC TC 100 : AUDIO, VIDEO AND MULTIMEDIA SYSTEMS AND EQUIPMENT
SECRETARIAT: SECRETARY:
Japan Ms Mahiru Uehara
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):
TC 106,TC 108
ASPECTS CONCERNED:
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft for
Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of which they
are aware and to provide supporting documentation.
Recipients of this document are invited to submit, with their comments, notification of any relevant “In Some Countries”
clauses to be included should this proposal proceed. Recipients are reminded that the CDV stage is the final stage for
submitting ISC clauses. (SEE AC/22/2007 OR NEW GUIDANCE DOC).

TITLE:
Qi Specification - Version 2.3 - Part 1-3: General - Technical system overview (Fast Track)

PROPOSED STABILITY DATE: 2029
NOTE FROM TC/SC OFFICERS:
As this is a fast-track process offered by WPC, the Word file is not provided.
.
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.
You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without
permission in writing from IEC.

QiSpecification
TechnicalSystemOverview
Version2.3
PublishDate:08December2025
DISCLAIMER
Theinformationcontainedhereinisbelievedtobeaccurateasofthedateofpublication,butisprovided“asis”andmay
containerrors.TheWirelessPowerConsortiummakesnowarranty,expressorimplied,withrespecttothisdocument
anditscontents,includinganywarrantyoftitle,ownership,merchantability,orfitnessforaparticularuseorpurpose.
NeithertheWirelessPowerConsortium,noranymemberoftheWirelessPowerConsortiumwillbeliableforerrorsin
thisdocumentorforanydamages,includingindirectorconsequential,fromuseoforrelianceontheaccuracyofthis
document.Foranyfurtherexplanationofthecontentsofthisdocument,orincaseofanyperceivedinconsistencyor
ambiguityofinterpretation,contact:[e-mail].

Contents
1. Introduction 4
2. BasicConcepts 5
2.1 TypicalSystemParameters 7
3. Alignment 8
3.1 GuidedPositioning 8
3.2 MagneticAttach 9
3.3 FreePositioning 10
4. PowerProfiles 11
5. SystemBlockDiagram 12
6. PowerLevelDefinitions 13
7. CommunicationProtocols 15
7.1 BaselineProtocol 15
7.2 ExtendedProtocol 17
7.3 MagneticProtocol-FullMode 18
7.4 MagneticProtocol–RestrictedMode 20
8. Authentication 21
8.1 Public&PrivateKeys 21
8.2 CertificateChains 21
8.3 AuthenticationProtocol 23
8.4 Revocation 24
8.5 DataTransportStream 24
9. ForeignObjectDetection 25
10. CommonSymbols 27
10.1 CircuitSymbols 27
10.2 CompositeSymbols 29
11. ComplianceTesting 30
11.1 TestTools 30
1. Introduction
TheQiSpecification,developedbytheWirelessPowerConsortium(WPC),setsthestandardforinteroperabilitybetween
productsincorporatingwirelesspowerfunctionality.Theprevalentusecaseforthistechnologyisthewirelesscharging
ofsmartphones.Inthisusecase,ausercanchargeasmartphonesimplyplacingitonawirelesscharger,alsoknownasa
chargingpadorchargingmat.TheQiSpecificationformallyreferstosuchadeviceasapowertransmitterproduct.
Similarly,itreferstothesmartphoneasapowerreceiverproduct.
ThisdocumentintroducesthebasicconceptsbehindtheQiwirelesspowertransfersystem,andtheterminologyused
throughoutthespecificationdocumentation.
NOTE:Unlessotherwisespecified,alldiagramswithinthespecificationdocumentationareforillustrativepurposesonlyandarenot
dimensionallyaccuraterepresentationsofproductsordesigns.

2. BasicConcepts
TheQiwirelesspowertransfersystemusestheprinciplesofmagneticinductiontotransferpowerfromapower
transmitter(PTx)toapowerreceiver(PRx).PowertransferistheactofprovidingpowerfromaPTxtoaPRxfora
prolongedperiodoftime.AdevicecontainingapowerreceiverisknownasaPRxproduct,whileadevicecontainingone
ormorepowertransmittersisknownasaPTxproduct.ThePTxandPRxareindividualunitscontainedwithinaPTxor
PRxproduct.ThePTxunitisresponsibleforgeneratingamagneticfield,whilethePRxunitextractselectricalpower
fromthemagneticfield.
AsshowninFigure1,bothPTxandPRxcontainpancakecoilsbetweenwhichmagneticinduction,andthuspower
transfer,cantakeplace.Othervitalcomponentswithinthesystemaretypicallyprotectedfromelectromagnetic
interferencebyferriteshielding.
Figure1-Pancakecoilsandferriteshielding
Figure2showsaschematiccrosssectionofapowerreceiverproductthatisrestingonapowertransmitterproduct.
TheproductenclosuresdonotformpartofeitherthePRxorPTxunits,thusneitherunitextendsallthewayuptothe
outersurfaceoftheproduct.
Figure2-Cross-sectionofmatedPTxandPRxproductsshowingcoilsandferrites
AsillustratedinFigure3,auserbringsaPRxproductandaPTxproducttogethertoinitiatethepowertransferprocess;
anactknownasmating.WhenthecoilsofthePTxandPRxfaceeachothercorrectly,thepowertransferprocesscan
start.Theinteractionbetweenachargingpad(aPTxproduct),andasmartphone(aPRxproduct)isatypical
demonstrationofthissysteminaction.
NotethattheformfactorsofproductsmaypreventanaturalmatchbetweenspecificPTxandPRxproducts.Here,a
naturalmatchreferstoacombinationofPTxandPRxproducthavingformfactorsthatenablematingwithoutthehelp
ofadditionalobjectssuchasrubberbandsorothersupports.Accordingly,specificPTxandPRxproductsmaynotwork
together,eventhoughbothcarrytheQilogo.Insuchcases,thatshouldbeobvioustoauserwhohaspreviouslybeen
exposedtoproductssupportingwirelesscharging.

WhenaPRxandPTxproductaremated,thepartsofthedeviceenclosuresthatfaceeachotherarereferredtoas
interfacesurfaces.Betweentheinterfacesurfacestheremaybeanairgap.Anairgapisthedistancebetweenthe
interfacesurfacesofthePTxandPRxproducts,andifpresent,typicallyisfilledwithmaterialfromanaccessoryadded
toaPRxproduct,e.g.,aprotectivecase.Thepresenceofanairgapshouldnotpreventpowertransfer,providedtheair
gapisnottoogreat.SeeFigure4forahigh-levelillustrationoftheseconcepts.
Figure3-MatingaPRxproductwithaPTxproduct
Whenthepowertransferstarts,thePTxgeneratesapowersignalbetweenthePTxandPRxcoils.Apowersignalisa
highfrequency,alternatingmagneticfieldintendedtotransferpower,withfrequenciestypicallyrangingbetweena
hundredandafewhundredsofkilohertz.Thevolumeinwhichthepowersignalisnon-negligibleduringthepower
transferisreferredtoastheinterfacevolumeinterfacevolume.ThisvolumetypicallycomprisespartsofboththePTx
andPRxproducts,aswellasanyobjectspresentintheairgap.The activearea,however,refersonlytothepartofthe
interfacesurfacethroughwhichanon-negligiblepowersignalpenetrateswhilethepowertransferisinprogress.The
extentsoftheinterfacevolumeandactiveareasdependonthedetailsofthedesignsofthePTxproductandPRx
productaswellastheiralignmentaftermating.

Figure4-WirelesspowertransferfromPTxtoPRxwhenmated
AllprovisionsintheQispecificationderivefromasystemmodel,whichdescribesthedesignandinteractionoftheideal
PTxproductandtheidealPRxproduct.ThetermsmodelPTxproduct(MPT)andmodelPRxproduct(MPR)refertothese
idealdevices.Real-worldproductdesignsmaydifferfromthesedevicesinallaspects,aslongastheycomplywithall
specifiedrequirements.
2.1 TypicalSystemParameters
Thefollowinglistprovidesthetypicaldimensions,operatingfrequencies,andpowerlevelsthatcharacteriseaQi
wirelesspowersystem.
l
Coilsize:⌀40mm
l
Coil-to-coildistance:5mm
l
Alignmenttolerance:±4mm
l
Operatingfrequency:100kHzto-200kHzor360kHz(thisisthefrequencyofthepowersignal)
l
Powerdelivery:upto25W
l
In-bandcommunicationsforpowercontrol
l
PTx-to-PRx:0.2kbit/s.3kbit/sFSK
l
PRx-to-PTx:2kbit/sASK
l
Freepositioningormagneticattach

3. Alignment
AlignmentreferstothepositioningofthePRxproductonthePTxproductaftermating.Theaccuracyofthealignment
betweenthePTxandPRxproductsaffectsthecouplingbetweenthePTxandPRxcoils,andsubsequentlythepower
transferpotential.TheQisystemsupportstwomethodsofalignment:guidedpositioning,andfreepositioning.Both
methodshavetheirownspecificwaytohelptheuserachievealignment.
3.1 GuidedPositioning
Guidedpositioningistheactofmatingwithstrictalignmenttolerances.APTxproductwithguidedpositioningusesa
singlecoiltocreateanactiveareaatafixedplaceontheinterfacesurface.Suchproductstypicallyusevisualcuestoaid
theuserwithalignment,suchasmarkingsontheinterfacesurfaceand/orthespecificproductsizesorshapes,asshown
inFigure5
Figure5-ExamplesofPTxproductswithvisualcuesforguidedpositioning

3.2 MagneticAttach
MagneticattachisaformofguidedpositioningwherethePRxproductattachestothePTxproductusingmagnets.This
methodtypicallyincreasestheaccuracyofthealignmentbetweenthePTxandPRxcoilswhenmated,resultinginan
optimisedpowertransfer.Figure6showsasimplifiedexampleofthemagneticattachprinciple.
NOTE:MagneticattachisadistinguishingfeatureofMPPPRxandPTxproducts.TheQispecificationdoesnotallowBPPandEPP
PTxproductstocontainmagnetsinorclosetotheinterfacevolume.SeesectionSection6,PowerLevelDefinitions for
moreinformationaboutpowerprofiles.
Figure6- PRxmatingwithPTxusingmagneticattachment

3.3 FreePositioning
Freepositioningistheactofmatingwithloosealignmenttolerances.APTxproductthatusesthefreepositioning
methoduseseithermultiplecoils,asshowninFigure7,oramovingcoil,asshowninFigure8,tocreateanactivearea
atalmostanypositionontheinterfacesurface.
Figure7-Productwithmultiplecoilsforfreepositioning
Figure8-PTxProductwithasinglemovingcoil

4. PowerProfiles
TheQiSpecificationprovidesmanyfeaturesfromwhichdeveloperscanchoosetodesignaproduct.Inordertoprevent
wildgrowthandtoavoidorminimiseuserconfusionaboutwhattoexpectwhencombingindifferentPRxandPTx
products,theQiSpecificationintroducestheconceptofpowerprofiles.Theavailablepowerprofilesaredetailedinthe
PowerProfiles book.
APTxproductmayfeatureoneormoreactiveareasthatsupportmultiplepowerprofiles,asshowninFigure9and
Figure10,howeveraPRxproductmayonlysupportasinglepowerprofile,asshowninFigure9.
Figure9-ExamplesofPTxandPRxproductswithsinglepowerprofiles
Figure10-ExampleofaPTxproductwithmultipleactiveareassupportingdifferentpowerprofiles

5. SystemBlockDiagram
Figure11showsthekeyfunctionalblocksofawirelesspowersystem.Thesystem’spowertraintypicallyconsistsofa
powersupply,inverter,PTxandPRxresonanttanks,rectifier,andload.Thepowersupplyandloadareexternaltothe
PTxandPRxproper.Inatypicalconsumersystem,thepowersupplyisaUSBwalladapter.Inatypicalautomotive
environment,thepowersupplyispartofthecar’selectricalinfrastructure.Theloadcircuitdesignvariesper
application,buttypicallyincludesabatterywithinthePRxproductthatrequirescharging.
Figure11-Simplifieddiagramofawirelesspowersystem
Theinductancesintheresonanttanksfunctionasalooselycoupledtransformer.Theresonancesinthesystemserveto
enhancetheefficiencyofthepowertransfer.
ThecommunicationsandcontrolcircuitsenablethePTxandPRxtoexchangeinformationaboutthepowertransfer.For
example,atthestartofthepowertransfer,thePTxandPRxcommunicatetoagreeonthepowerleveltouse.Further
intothepowertransfertheycommunicatetoadjustthepowerlevelasnecessary.ThePTxandPRxsendtheinformation
acrossbymodulatingthepowersignal,aformofin-bandcommunications.TosendinformationthePRxusesamethod
knownasbackscattermodulation,inwhichitmodulatesitsloadorresonancefrequencytotransmitdatathroughthe
powersignal;thisisalsoknownasamplitudeshift-keying(ASK).ItisthephysicallayerofthePRxcommunications.
Similarly,thePTxusesfrequencymodulationofthepowersignaltotransmitdata,alsoknownasfrequencyshift-keying
(FSK)tomodulatethefrequencyofthepowersignaltotransmitdata.ThisisthephysicallayerofthePTx
communications.
TypicalsystemparametersforASKandFSKmodulationareasfollows:
l
•ASKmodulation
l
0.5ms/bit,operatingfrequencyindependent
l
1%modulationdepth(powersignalamplitudechange)
l
•FSKmodulation
l
5ms/bitat100kHz(512powersignalcyclesperdatabit)
l
0.36ms/bitat360kHz(128powersignalcyclesperdatabit)
l
0.3%…1%modulationdepth(powersignalfrequencychange)

6. PowerLevelDefinitions
ThepowertransferredfromthePTxproducttothePRxproductisvariableanddependsonoperatingconditionsaswell
asthepowerrequestedandnegotiatedforaspartofthepowertransfercontract.Apowertransfercontractisa
collectionofsettingsandlimitsthatgovernthepowertransfer.
The transmittedpowerreferstothepowertakenfromthepowersignalbyanyobjectthatisnotanintegralpartofthe
PTxproduct.Thereceivedpowerreferstothepowertakenfromthepowersignalbyanycomponentthatisanintegral
partofthePRxproduct.Iftherearenoforeignobjects(seesectionSection9,ForeignObjectDetection)intheinterface
volume,thereceivedpowerisequaltothetransmittedpower.TheloadpoweristhepowerthatisavailableatthePRx
outputandisdeliveredtoe.g.abatterythatrequirescharging.Thesupplypoweristhepowerthatthepowersourcecan
delivertothesystem,whereasthesuppliedpowerreferstothepowerthesupplyactuallydelivers.
TheguaranteedloadpowerlevelistheloadpowerlevelthatthePTxhasagreedwiththematedPRxproduct.Typically,
thepowertransferproceedsatorbelowthislevel,andaslongasthePRxdoesnotexceedit,thePTxcansustainthe
powertransfer.Theguaranteedloadpowerlevelresultsfromanegotiationprocessthatrunsatthestartofthepower
transfer.Theinputsforthisprocessarethepotential,negotiable,andrequestedloadpowerlevels.
ThepotentialloadpowerlevelisthehighestguaranteedloadpowerlevelthatthePTxcannegotiate.Assuch,it
representsthehighestpowerlevelatwhichthesystemcanoperateever.However,sometimesexternalconditionscan
causethePTxtonegotiatealowerpowerlevel.Afirstexampleofsuchconditionsisahighambienttemperature(such
asinsideacarthathasbeenparkedinthesun)thatcouldcauseoverheatingofthePTxifitwouldoperateatits
potentialloadpowerlevel.AsecondexampleisaPTxproductthatbalancesitslimitedsupplypowerbetweenmultiple
PTxunitstoprovidethebestpossibleservicetoallunitsthatareinuse.Accordingly,thenegotiableloadpowerlevelis
thehighestguaranteedloadpowerlevelthatthePTxcannegotiateinviewofexternalconditions.
Tostartthenegotiationprocess,thePRxtypicallyretrievesthepotentialandnegotiableloadpowerlevelsfromthePTx.
Dependingonthose,thePRxdeterminestheguaranteedloadpowerlevelatwhichitintendstooperate,andprovides
suchasitsrequestedloadpowerleveltothePTx.OncethePTxagreestothisrequest,boththePTxandPRxstorethe
resultingguaranteedloadpowerlevelinthepowertransfercontract.
NOTE:Throughoutthenegotiationprocess,thePTxtypicallyassumesthatthePRxproductisanMPR.Thismeansthatifthedesign
ofthePRxdeviatessubstantiallyfromtheMPR,thePRxshouldaccountforsuchdeviationsandadjustitsrequestedload
powerand/orloadpowerlevelsaccordingly.
Whentransferringpower,thePRxshouldmakesureitdoesnotdrawmorepowerthantheagreedguaranteedload
power.Whengoingabovethispowerlevel,somepowertransmittersmayterminatethepowertransferunexpectedly.
Figure12illustratestherelationsbetweenthevariouspowerlevels.

Figure12-Diagramshowingthedifferencebetweenpowerlevels

7. CommunicationProtocols
TheQispecificationsupports3differentcommunicationsprotocols:
l
BaselineProtocol–unidirectionalcommunicationsfromPRxtoPTx
l
ExtendedProtocol–bidirectionalcommunicationsbetweenPRxandPTx
l
MagneticProtocol–bidirectionalcommunicationsbetweenPRxandPTx
7.1 BaselineProtocol
AsshowninFigure13,thebaselineprotocolhasthreedistinctphases:ping,configuration,andpower.
Figure13-Phasesofbaselineprotocol
l
Pingphase:ThePTxtypicallyproducesoneormoreanaloguepings,whichareshortpowersignalpulses
intendedtodetectthepresenceofanobjectintheinterfacevolume.Ifithasdetectedanobject,thePTxattempts
toinitiatecommunicationsbymeansofadigitalping.ThismeansthatthePTxappliesapowersignaluntilit
receivesadatapacketorittimesoutwaitingforadatapacket.
Adatapacketisamulti-bytetransmissionusedtosendimportantdata,suchasinformationnecessarytocontrol
thepowerlevel.Directlyafterreceivingavaliddatapacket,thePTxproceedstotheconfigurationphaseofthe
protocol.Inthisphaseandthenext,thePRxtypicallyhasatemporaryordummyloadconnectedtolimitthe
receivedpowerlevel.
l
Configurationphase:ThePRxcontinuestosendasequenceofdatapackets,providinginformationaboutthe
intendedpowertransfer.Thesequenceincludesthemanufacturercode,whichisauniquecoderegisteredwith
theWPCtoidentifythemanufacturerofthePRxproduct.Attheendoftheconfiguration.phase,thePTxandPRx
createthepowertransfercontractgoverningthepowerphase.Immediatelyafter,thepowerphasebegins.
l
Powerphase:ThePRxconnectsitsloadandstartstocontrolthepowertransfer,sendingdatapacketscontaining
requeststoincreaseordecreasethepowerlevel.Inaddition,itsendsdatapacketscontainingitsreceivedpower
level,whichareintendedtophelpthePTxwithforeignobjectdetection(FOD;seeSect
...