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System Description |
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Wireless Power Transfer |
Version 1.1.1 |
Annex A |
Annex A Example Power Receiver Designs (Informative)
A.1 Power Receiver example 1
The design of Power Receiver example 1 is optimized to directly charge a single cell lithium-ion battery at constant current or voltage.
A.1.1 Mechanical details
This Section A.1.1 provides the mechanical details of Power Receiver example 1.
A.1.1.1 Secondary Coil
The Secondary Coil of Receiver example 1 is of the wire-wound type, and consists of no. 26 AWG (0.41 mm diameter) litz wire having 26 strands of no. 40 AWG (0.08 mm diameter). As shown in Figure A-1, the Secondary Coil has a rectangular shape and consists of a single layer. Table A-1 lists the dimensions of the Secondary Coil.
diw
dil
dow |
dol |
dc
Figure A-1: Secondary Coil of Power Receiver example 1
Table A-1: Secondary Coil parameters of Power Receiver example 1
Parameter |
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Outer length |
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mm |
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Inner length |
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mm |
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Outer width |
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mm |
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Inner width |
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mm |
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Thickness |
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mm |
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Number of turns per layer |
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14 |
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Number of layers |
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1 |
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A.1.1.2 Shielding
As shown in Figure A-2, Power Receiver example 1 employs Shielding. This Shielding has a size of mm2, and has a thickness of mm. The Shielding is centered directly on the top face of the Secondary Coil (such that the long side of the Secondary Coil and the Shielding are aligned).
The composition of the Shielding consists of any choice from the following list of materials:
Material 44 — Fair Rite Corporation.
Material 28 — Steward, Inc.
CMG22G — Ceramic Magnetics, Inc.
© Wireless Power Consortium, July 2012 |
95 |
System Description
Wireless Power Transfer
Annex A |
Version 1.1.1 |
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Secondary |
Magnet |
Shielding |
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Interface |
Coil |
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Surface |
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Figure A-2: Secondary Coil and Shielding assembly of Power Receiver example 1 |
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A.1.1.3 Interface Surface |
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The distance from the Secondary Coil to the Interface Surface of the Mobile Device is |
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uniform across the bottom face of the Secondary Coil. |
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A.1.1.4 Alignment aid
Power Receiver example 1 employs a bonded Neodymium magnet, which has its south pole oriented towards the Interface Surface. The diameter of the magnet is 15 mm, and its thickness is 1.2 mm.
A.1.2 Electrical details
At the secondary resonance frequency magnet has inductance values resonant circuit are nF and
kHz, the assembly of Secondary Coil, Shielding and
μH and |
μH. The capacitance values in the dual |
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nF. |
As shown in Figure A-3, the rectification circuit consists of four diodes in a full bridge configuration and a
low-pass filtering capacitance |
μF. |
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The communications modulator consists of two equal capacitances |
nF in series with two |
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switches. The resistance value |
kΩ. |
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The subsystem connected to the output of Power Receiver example 1 is expected to consist of a single cell lithium-ion battery. This Power Receiver example 1 controls the output current and output voltage into the battery according to the common constant current to constant voltage charging profile. An example profile is indicated in Figure A-4. The maximum output power to the battery is controlled to a 5 W level.
CS |
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Ccm |
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Li-ion |
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LS |
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Battery |
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Ccm |
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Figure A-3: Electrical details of Power Receiver example 1
96 |
© Wireless Power Consortium, July 2012 |
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System Description |
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Wireless Power Transfer |
Version 1.1.1 |
Annex A |
Figure A-4: Li-ion battery charging profile
© Wireless Power Consortium, July 2012 |
97 |
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System Description |
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Wireless Power Transfer |
Annex A |
Version 1.1.1 |
A.2 Power Receiver example 2
The design of Power Receiver example 2 uses post-regulation to create a voltage source at the output of the Power Receiver.
A.2.1 Mechanical details
This Section A.2.1 provides the mechanical details of Power Receiver example 2.
A.2.1.1 Secondary Coil
The Secondary Coil of Power Receiver example 2 is of the wire-wound type, and consists of litz wire having 24 strands of no. 40 AWG (0.08 mm diameter). As shown in Figure A-5, the Secondary Coil has a circular shape and consists of multiple layers. All layers are stacked with the same polarity. Table A-2 lists the dimensions of the Secondary Coil.
di
do
dc
Figure A-5: Secondary Coil of Power Receiver example 2
Table A-2: Parameters of the Secondary Coil of Power Receiver example 2
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Outer diameter |
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mm |
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Inner diameter |
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mm |
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Thickness |
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mm |
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Number of turns per layer |
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9 |
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Number of layers |
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2 |
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A.2.1.2 Shielding
As shown in Figure A-6, Power Receiver example 2 employs Shielding. The Shielding has a size of
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mm2, and is centered directly on the top face of the Secondary Coil. The Shielding |
has a thickness of |
mm and consists of any choice from the materials from the following list: |
Material 78 — Fair Rite Corporation.
3C94 — Ferroxcube.
N87 — Epcos AG.
PC44 —TDK Corp.
98 |
© Wireless Power Consortium, July 2012 |
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System Description |
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Wireless Power Transfer |
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Version 1.1.1 |
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Annex A |
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Interface |
Shielding Magnetic |
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Attractor |
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Figure A-6: Secondary Coil and Shielding assembly of Power Receiver example 2 |
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A.2.1.3 Interface Surface |
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The distance from the Secondary Coil to the Interface Surface of the Mobile Device is |
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across the bottom face of the Secondary Coil. |
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A.2.1.4 Alignment aid
Power Receiver example 2 employs Shielding material (see Annex A.2.1.2) as an alignment aid (see Section 4.2.1.2). The diameter of the this Shielding material is 10 mm, and its thickness is 0.8 mm.
A.2.2 |
Electrical details |
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At the secondary resonance frequency |
kHz, the assembly of Secondary Coil and Shielding has an |
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inductance values |
μH and |
μH. The capacitance values in the dual resonant circuit |
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nF and |
nF. |
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As shown in Figure A-7, the rectification circuit consists of four diodes in a full bridge configuration and a
low-pass filtering capacitance |
μF. |
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The communications modulator consists of a |
Ω resistance in series with a switch. |
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The buck converter comprises the post-regulation stage of Power Receiver example 2. The Control and Communications Unit of the Power Receiver can disable the buck converter. This provides the output disconnect functionality. In addition, the Control and Communications Unit controls the input voltage to the buck converter, such that V.
The buck converter has a constant output voltage of 5 V and an output current
( ) ,
Where is the output power of the buck converter, and ( ) is the power dependent efficiency of the buck converter.
© Wireless Power Consortium, July 2012 |
99 |
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System Description |
|
Wireless Power Transfer |
Annex A |
Version 1.1.1 |
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VR |
CS |
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Buck |
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Converter |
CD |
C |
RCM |
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LS |
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Figure A-7: Electrical details of Power Receiver example 2
100 |
© Wireless Power Consortium, July 2012 |
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System Description |
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Wireless Power Transfer |
Version 1.1.1 |
Annex B |
Annex B Object Detection (Informative)
A Power Transmitter may use a variety of methods to efficiently discover and locate objects on the Interface Surface. These methods, also known as “analog ping,” do not involve waking up the Power
Receiver and starting digital communications. Typically zero or more analog pings precede the Digital Ping, which the Power Transmitter executes in the first power transfer phase. This Annex B provides some analog ping examples.
B.1 Resonance shift
This analog ping method is based on a shift of the Power Transmitter’s resonance frequency, due to the presence of a (magnetically active) object on the Interface Surface.
For a type A1 Power Transmitter, this method proceeds as follows: The Power Transmitter applies a very short pulse to its Primary Coil, at an Operating Frequency , which corresponds to the resonance frequency of the Primary Coil and series resonant capacitance (in case there is no object present on the Interface Surface). This results in a Primary Coil current . The measured value depends on whether or
not an object is present within the Active Area. |
It is highest if the resonance frequency has not shifted due |
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conclude that an object is present. Note that the values of |
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The Power Transmitter can apply the pulses at regular intervals duration of at most μs. Measurement of the Primary Coil current the pulse. See also Figure B-1 and Table B-1.
and have , where each pulse has a should occur at most μs after
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todi |
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todm |
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todd |
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current |
Iodt |
time |
Iod |
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Figure B-1: Analog ping based on a resonance shift
Table B-1: Analog ping based on a resonance shift
Parameter |
Symbol |
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Unit |
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Object detection interval |
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Object detection duration |
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Object detection measurement |
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For type B1 and B2 Power Transmitters, this method proceeds as follows: The Power Transmitter applies a very short pulse to a set of Primary Coils, which the multiplexer has connected in parallel—note that this set is not necessarily limited to a Primary Cell. The Operating Frequency of the pulse corresponds to the resonance frequency of the set of Primary Coils and the capacitance of the impedance matching circuit (in case there is no object present on the Interface Surface). This results in a current through the inductance of the impedance matching circuit. The measured value depends on whether or not an object is present within the Active Area. It is lowest if the resonance frequency has not shifted due to the
presence of an object. Accordingly, if |
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© Wireless Power Consortium, July 2012 |
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101 |