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3.2.6Power Transmitter design A6

Figure 3-20 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.

Figure 3-20: Functional block diagram of Power Transmitter design A6

The Power Conversion Unit on the right-hand side of Figure 3-20 comprises the analog parts of the design. The inverter converts the DC input to an AC waveform that drives a resonant circuit, which consists of the selected Primary Coil plus a series capacitor. The selected Primary Coil is one from a linear array of partially overlapping Primary Coils, as appropriate for the position of the Power Receiver relative to the Primary Coils. Selection of the Primary Coil proceeds by the Power Transmitter attempting to establish communication with a Power Receiver using any of the Primary Coils. Note that the array may consist of a single Primary Coil only, in which case the selection is trivial. Finally, the current sense monitors the Primary Coil current.

The Communications and Control Unit on the left-hand side of Figure 3-20 comprises the digital logic part of the design. This unit receives and decodes messages from the Power Receiver, configures the Coil Selection block to connect the appropriate Primary Coil, executes the relevant power control algorithms and protocols, and drives the frequency of the AC waveform to control the power transfer. The Communications and Control Unit also interfaces with other subsystems of the Base Station, e.g. for user interface purposes.

3.2.6.1Mechanical details

Power Transmitter design A6 includes one or more Primary Coils as defined in Section 3.2.6.1.1, Shielding as defined in Section 3.2.6.1.2, an Interface Surface as defined in Section 3.2.6.1.3.

3.2.6.1.1Primary 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 3-21, the Primary Coil has a rectangular shape and consists of a single layer. Table 3-16 lists the dimensions of the Primary Coil.

3.2.6.1.2Shielding

As shown in Figure 3-23, soft-magnetic material protects the Base Station from the magnetic field that is generated in the Primary Coil. The Shielding extends to at least the outer dimensions of the Primary Coils, 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 of 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.

TopFlux “B“ — TopFlux.

ACME K081 — Acme Electronics.

L7H — TDK Corporation.

PE22 — TDK Corporation.

FK2 — TDK Corporation.

Interface

Surface

5 mm min.

dz

Figure 3-23: Primary Coil assembly of Power Transmitter design A6

3.2.6.1.3Interface Surface

As shown in Figure 3-23, 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 the case of a single Primary Coil, 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 dimensions of the Primary Coils.

3.2.6.1.4Inter coil separation

If the Base Station contains multiple type A6 Power Transmitters, the Primary Coils of any pair of those Power Transmitters shall have a center-to-center distance of at least mm.

3.2.6.2Electrical details

As shown in Figure 3-24, Power Transmitter design A6 uses a half-bridge inverter to drive an individual Primary Coil and a series capacitance. Within the Operating Frequency range specified below, the