prEN IEC 63758-1-3:2026

• Status: Not Published
• Publication Date: 23-Feb-2028
• Technical Committee: CLC/TC 100X - Audio, video and multimedia systems and equipment and related sub-systems
• Current Stage: 4020 - Enquiry circulated - Enquiry
• Start Date: 18-Sep-2026
• Completion Date: 18-Sep-2026
• 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: oSIST prEN IEC 63758-1-3:2026 - Qi specification - Version 2.3 - Part 1-3: General - Technical system overview (Fast Track)

prEN IEC 63758-1-3:2026 is a CLC/IEC draft for the Qi specification - Version 2.3 - Part 1-3, Technical system overview, developed under the Wireless Power Consortium (WPC). It explains the Qi wireless power transfer system for power transmitter product and power receiver product designs, including the system model, alignment, power profiles, communication protocols, authentication, foreign object detection, common symbols, and compliance testing.

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

prEN IEC 63758-1-3:2026 is an overview document for Qi wireless power transfer rather than a product-only design rule. It introduces the basic concepts and terms used across the Qi specification and shows how the parts of the system fit together in practice.

The document is organized into 11 clauses:

• Introduction
• Basic Concepts
• Alignment
• Power Profiles
• System Block Diagram
• Power Level Definitions
• Communication Protocols
• Authentication
• Foreign Object Detection
• Common Symbols
• Compliance Testing

That structure matters because the standard moves from system concepts to practical operation, then to testing and certification. Readers can use it to understand how Qi products are expected to behave as a complete wireless power system.

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

prEN IEC 63758-1-3:2026 sets out the technical model for Qi products and the operating patterns that Qi products use in real charging systems. The most important points are the system model, alignment methods, power profiles, protocol choices, power level negotiation, authentication, and foreign object detection.

System model and basic operation

Clause 2 describes Qi as a magnetic-induction power transfer system with a power transmitter (PTx) and a power receiver (PRx). The document treats the PTx and PRx as separate units inside their products, with coils, ferrites, and resonant tanks used to move power across the interface.

In practice, this means product design starts with coil placement, shielding, and the air gap between products. The document also states that all provisions derive from an idealized model PTx product (MPT) and model PRx product (MPR), so real products are measured against that model.

Alignment methods

Clause 3 defines guided positioning, magnetic attach, and free positioning. Guided positioning uses strict alignment and visual cues, magnetic attach uses magnets to improve alignment, and free positioning uses multiple coils or a moving coil to support looser placement.

In practice, these alignment choices affect user experience and compatibility. A product intended for magnetic attach has different mechanical and magnetic design constraints from one intended for free positioning.

Power profiles and operating limits

Clause 4 introduces power profiles to control which feature combinations Qi products support. The document states that a PTx may support multiple power profiles across multiple active areas, while a PRx supports only a single power profile.

This matters because the power profile determines what a product can negotiate and what a user should expect. The document points readers to the PowerProfiles book for the available profiles.

Power levels and the power transfer contract

Clause 6 defines the power quantities used in Qi, including transmitted power, received power, load power, supply power, supplied power, guaranteed load power, potential load power, negotiable load power, and requested load power. It also describes the power transfer contract as the set of settings and limits negotiated at the start of power transfer.

In practice, the PRx should operate within the agreed guaranteed load power level. If the PRx draws more than agreed, some transmitters may stop power transfer.

Communication protocols

Clause 7 describes three communication protocols: BaselineProtocol, ExtendedProtocol, and MagneticProtocol. BaselineProtocol is unidirectional from PRx to PTx and is intended for systems that limit power transfer to 5 W at 110 kHz to 205 kHz. ExtendedProtocol is bidirectional and is intended for systems up to 15 W in the same frequency band. MagneticProtocol is bidirectional and is intended for systems up to 25 W at 360 kHz.

This matters because protocol choice controls product capability, power level, and frequency. The magnetic protocol also adds a cloak phase, which allows power transfer to pause without repeating the earlier setup phases when charging resumes.

Authentication and certificate handling

Clause 8 describes authentication based on public-key cryptography and certificate chains. The PRx requests a certificate chain, verifies it, sends a nonce, and checks the PTx signature before applying its policy. Clause 8 also covers revocation lists and the data transport stream used to carry application-layer messages.

In practice, authentication lets a PRx verify the identity of a PTx before it decides how much capability to accept. That is important for interoperability and for product policies that treat authenticated and unauthenticated transmitters differently.

Foreign Object Detection

Clause 9 explains Foreign Object Detection (FOD), which is used to reduce the risk of heating objects that are not part of the PRx or PTx. The document describes the empty surface test, the resonance change approach, and the power loss accounting method.

In practice, FOD is a safety and reliability topic. The PTx may throttle or stop transfer if losses suggest that a foreign object is heating up.

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

prEN IEC 63758-1-3:2026 introduces the key Qi terms that readers need to follow the rest of the specification.

• Power transmitter (PTx) - the product that generates the magnetic field for wireless power transfer.
• Power receiver (PRx) - the product that extracts electrical power from the magnetic field.
• Model PTx product (MPT) - the idealized PTx model that the specification uses as the design reference.
• Model PRx product (MPR) - the idealized PRx model that the specification uses as the design reference.
• Foreign Object Detection (FOD) - the process used to identify objects in the interface volume that may overheat.
• Power transfer contract - the negotiated set of settings and limits that governs charging.
• Data transport stream - the packet sequence used to carry application-layer messages across the power signal.
• Nonce - a number used only once in authentication to challenge the PTx.

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

prEN IEC 63758-1-3:2026 is used by engineers, product designers, certification teams, and quality managers working on Qi-compatible wireless power products. It is especially relevant for makers of charging pads, charging mats, smartphones, and other consumer devices that use wireless charging.

It also helps teams working on automotive and other embedded power systems where Qi-style wireless transfer is used. Certification laboratories use it to understand the test model, the test tools, and the compliance-testing framework.

Which standards are used with prEN IEC 63758-1-3:2026?

The document names the PowerProfiles book as the place where the available power profiles are defined. Clause 4 relies on that companion material for the profile details that determine product capability.

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

prEN IEC 63758-1-3:2026 contains explanatory figures of coils, ferrite shielding, mating products, alignment methods, and wireless power transfer geometry. It also includes phase diagrams for the BaselineProtocol, ExtendedProtocol, and MagneticProtocol, plus a flow diagram for authentication.

The document contains symbol tables in Clause 10 for supply, PTx, PRx, and load quantities, along with composite symbols for resonance and quality factor calculations. Those tables are used to read the system equations and circuit descriptions consistently.

Clause 11 includes the compliance-testing overview and the test-tool concept, including Test Power Transmitters (TPT) and Test Power Receivers (TPR). The document also shows how white-box and black-box parts are used in the test tools and how they support product testing, certification, and verification of Qi interoperability.

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
...