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System Description |
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Wireless Power Transfer |
Version 1.1.1 |
Basic Power Transmitter Designs |
3.2.9Power Transmitter design A9
Power Transmitter design A9 enables Guided Positioning, and has a design similar to Power Transmitter design A1. See Section 3.2.1 for an overview.
3.2.9.1Mechanical details
Power Transmitter design A9 includes a single Primary Coil as defined in Section 3.2.9.1.1, Shielding as defined in Section 3.2.9.1.2, an Interface Surface as defined in Section 3.2.9.1.3, and an alignment aid as defined in Section 3.2.9.1.4.
3.2.9.1.1Primary Coil
The Primary Coil is of the wire-wound type, and consists of no. 20 AWG (0.81 mm diameter) type 2 litz wire having 105 strands of no. 40 AWG (0.08 mm diameter), or equivalent. As shown in Figure 3-32, the Primary Coil has a circular shape and consists of multiple layers. All layers are stacked with the same polarity. Table 3-25 lists the dimensions of the Primary Coil.
do
di
dc
Figure 3-32: Primary Coil of Power Transmitter design A9
Table 3-25: Primary Coil parameters of Power Transmitter design A9
Parameter |
Symbol |
Value |
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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10 |
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Number of layers |
– |
2 |
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3.2.9.1.2Shielding
As shown in Figure 3-33, soft-magnetic material protects the Base Station from the magnetic field that is generated in the Primary Coil. The Shielding extends to at least 2 mm beyond the outer diameter of the Primary Coil, has a thickness of at least 0.5 mm, and is placed below the Primary Coil at a distance of at most mm. This version 1.1.1 to the System Description Wireless Power Transfer, Volume I, Part 1, limits the composition of the Shielding to a choice from the following list of materials:
Material 44 — Fair Rite Corporation.
Material 28 — Steward, Inc.
CMG22G — Ceramic Magnetics, Inc.
Kolektor 22G — Kolektor.
LeaderTech SB28B2100-1 — LeaderTech Inc.
TopFlux “A“— TopFlux.
© Wireless Power Consortium, July 2012 |
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System Description |
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Wireless Power Transfer |
Basic Power Transmitter Designs |
Version 1.1.1 |
TopFlux “B“— TopFlux.
ACME K081 — Acme Electronics.
L7H — TDK Corporation.
PE22 — TDK Corporation.
FK2 — TDK Corporation.
317 mm min.
1.0° max.
Magnet |
Primary Coil |
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Base |
Shielding |
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Station |
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Interface
Surface
5 mm min.
dz
ds |
2 mm min.
Figure 3-33: Primary Coil assembly of Power Transmitter design A9
3.2.9.1.3Interface Surface
As shown in Figure 3-33, the distance from the Primary Coil to the Interface Surface of the Base Station is mm, across the top face of the Primary Coil. In addition, the Interface Surface of the Base Station extends at least 5 mm beyond the outer diameter of the Primary Coil. (Informative) This Primary-
Coil-to-Interface-Surface distance implies that the tilt angle between the Primary Coil and a flat Interface Surface is at most 1.0 . Alternatively, in case of a non-flat Interface Surface, this Primary-Coil-to-Interface- Surface distance implies a radius of curvature of the Interface Surface of at least 317 mm, centered on the Primary Coil. See also Figure 3-33.
3.2.9.1.4Alignment aid
Power Transmitter design A9 employs a magnet, which a Power Receiver design can exploit to provide an effective alignment means (see Section 4.2.1.2). As shown in Figure 3-33, the magnet is centered within the Primary Coil, and has its north pole oriented towards the Interface Surface. The (static) magnetic flux density due to the magnet, as measured across the Base Station’s Interface Surface, has a maximum of
mT. The diameter of the magnet is at most 15.5 mm.
3.2.9.1.5Inter coil separation
If the Base Station contains multiple type A9 Power Transmitters, the Primary Coils of any pair of those Power Transmitters shall have a center-to-center distance of at least 50 mm.
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© Wireless Power Consortium, July 2012 |
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System Description |
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Wireless Power Transfer |
Version 1.1.1 |
Basic Power Transmitter Designs |
3.2.9.2Electrical details
As shown in Figure 3-34, Power Transmitter design A9 uses a full-bridge inverter to drive the resonant network including filter inductors, a primary Coil with a series and parallel capacitance. Within the Operating Frequency range specified below, the assembly of Primary Coil, Shielding, and magnet has a self
inductance |
μH. The value of inductances |
and |
is |
μH. The value of the total |
series capacitance is |
nF, where the individual series capacitances may have any |
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value less than the sum. |
The value of the parallel capacitance is |
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nF. (Informative) Near |
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resonance, the voltage developed across the series capacitance can reach levels exceeding 100 V pk-pk.
Power Transmitter design A9 uses the input voltage to the inverter to control the amount of power transferred. For this purposen, the input voltage has a range 2…15 V, with a resolution of 10 mV or better; a higher input voltage results in more power transferred. The Operating Frequency is
kHz with a duty cycle of 50%
When a type A9 Power Transmitter first applies a Power Signal (Digital Ping; see Section 5.2.1), it shall use an input voltage of 5V, and a recommended Operating Frequency of 110 kHz.
Control of the power transfer shall proceed using the PID algorithm, which is defined in Section 5.2.3.1. The controlled variable ( ) introduced in the definition of that algorithm represents the input voltage. In order to guarantee sufficiently accurate power control, a type A9 Power Transmitter shall determine the amplitude of the Primary Cell current—which is equal to the Primary Coil current—with a resolution of 7 mA or better. Finally, Table 3-26 provides the values of several parameters, which are used in the PID algorithm.
Full-bridge
Inverter
L1 |
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Cser1 |
Input |
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Voltage + Control |
Cpar |
LP |
‒ |
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L2 |
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Cser2 |
Figure 3-34: Electrical diagram (outline) of Power Transmitter design A9
© Wireless Power Consortium, July 2012 |
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Table 3-26: PID parameters for voltage control |
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Parameter |
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Symbol |
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Value |
Unit |
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Proportional gain |
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0.02 |
mA-1 |
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Integral gain |
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0.01 |
mA-1ms-1 |
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Derivative gain |
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0 |
mA-1ms |
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Integral term limit |
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3,000 |
N.A. |
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PID output limit |
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20,000 |
N.A. |
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Scaling factor |
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Sv |
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–1 |
mV |
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© Wireless Power Consortium, July 2012 |
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System Description |
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Wireless Power Transfer |
Version 1.1.1 |
Basic Power Transmitter Designs |
3.3Power Transmitter designs that activate multiple Primary Coils simultaneously
This Section 3.3 defines all type B Power Transmitter designs. In addition to the definitions in this Section 3.3, each Power Transmitter design shall implement the relevant parts of the protocols defined in Section 5, as well as the communications interface defined in Section 6.
3.3.1Power Transmitter design B1
Power Transmitter design B1 enables Free Positioning. Figure 3-35 illustrates the functional block diagram of this design, which consists of two major functional units, namely a Power Conversion Unit and a Communications and Control Unit.
Communications
& Control Unit
Input Power
Inverter |
Power |
Impedance |
Conversion |
Matching |
Unit |
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Sensing |
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Multiplexer |
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Primary |
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Coil Array |
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Figure 3-35: Functional block diagram of Power Transmitter design B1
The Power Conversion Unit on the right-hand side of Figure 3-35 comprises the analog parts of the design. The design uses an array of partly overlapping Primary Coils to provide for Free Positioning. Depending on the position of the Power Receiver, the multiplexer connects and/or disconnects the appropriate Primary Coils. The impedance matching network forms a resonant circuit with the parts of the Primary Coil array that are connected. The sensing circuits monitor (amongst others) the Primary Cell current and voltage, and the inverter converts the DC input to an AC waveform that drives the Primary Coil array.
The Communications and Control Unit on the left-hand side of Figure 3-35 comprises the digital logic part of the design. This unit receives and decodes messages from the Power Receiver, configures the multiplexer to connect the appropriate parts of the Primary Coil array, executes the relevant power control algorithms and protocols, and drives the frequency and input voltage to the inverter to control the amount of power provided to the Power Receiver. The Communications and Control Unit also interfaces with the other subsystems of the Base Station, e.g. for user interface purposes.
© Wireless Power Consortium, July 2012 |
49 |
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System Description |
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Wireless Power Transfer |
Basic Power Transmitter Designs |
Version 1.1.1 |
3.3.1.1Mechanical details
Power Transmitter design B1 includes a Primary Coil array as defined in Section 3.3.1.1.1, Shielding as defined in Section 3.3.1.1.2, and an Interface Surface as defined in Section 3.3.1.1.3.
3.3.1.1.1Primary Coil array
The Primary Coil array consists of 3 layers. Figure 3-36(a) shows a top view of a single Primary Coil, which is of the wire-wound type, and consists of litz wire having 24 strands of no. 40 AWG (0.08 mm diameter), or equivalent.
top
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do |
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1 |
dc |
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(a) |
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(b) |
2 |
dc |
da |
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3 |
dc |
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di |
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dc
(c)
t3
t2
3 |
1 |
dh
2
Figure 3-36: Primary Coil array of Power Transmitter design B1
As shown in Figure 3-36(a), the Primary Coil has a circular shape and consists of a single layer. Figure 3-36(b) shows a side view of the layer structure of the Primary Coil array. Figure 3-36(c) provides a top view of the Primary Coil array, showing that the individual Primary Coils are packed in a hexagonal grid. The solid hexagons show the closely packed structure of the grid of Primary Coils on layer 1 of the Primary Coil array. The dashed hexagon illustrates that the grid of Primary Coils on layer 2 is offset over a
distance |
to the right, such that the centers of the Primary Coils in layer 2 coincide with the corners of |
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© Wireless Power Consortium, July 2012 |