Файл: wirelesspowerspecificationpart1.pdf

a Signal Strength Packet from the Power Receiver, the Power Transmitter shall remove the Power Signal as defined in Section 5.2.1. The Power Transmitter may reapply the Power Signal multiple times at other—consecutively lower—Operating Frequencies within the range specified above, until the Power Transmitter receives a Signal Strength Packet containing an appropriate Signal Strength Value.

Full-bridge

Inverter

Figure 3-27: Electrical diagram (outline) of Power Transmitter design A7

Control of the power transfer shall proceed using the PID algorithm, which is defined in Section5.2.3.1. The controlled variable ( ) introduced in the definition of that algorithm represents the input voltage to the full-bridge inverter. In order to guarantee sufficiently accurate power control, a type A7 Power Transmitter shall determine the amplitude of the Primary Cell voltage—which is equal to the Primary Coil voltage—with a resolution of 5 mV or better. Finally, Table 3-21 provides the values of several parameters, which are used in the PID algorithm.

Table 3-21: PID parameters for voltage control

3.2.8Power Transmitter design A8

Power Transmitter design A8 enables Free Positioning. Figure 3-28 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 3-28: Functional block diagram of Power Transmitter design A8

The Power Conversion Unit on the right-hand side of Figure 3-28 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 Primary Coil plus a series capacitor. Finally, the voltage and current sense monitors the Primary Coil voltage and current.

The Communications and Control Unit on the left-hand side of Figure 3-28 comprises the digital logic part of the design. The unit receives and decodes messages from the Power Receiver, executes the relevant power control algorithms and protocols, and drives the input power and 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.

3.2.8.1Mechanical details

Power Transmitter design A8 includes one Primary Coil as defined in Section 3.2.8.1.1, Shielding as defined in Section 3.2.8.1.2, and an Interface Surface as defined in Section 3.2.8.1.3.

3.2.8.1.1Primary Coil

The Primary Coil is of the wire-wound type, and consists of litz wire having 115 strands of 0.08 mm diameter, or equivalent. As shown in Figure 3-29, a Primary Coil has a racetrack-like shape and consists of a single layer. Table 3-22 lists the dimensions of a Primary Coil.

3.2.8.1.2Shielding

As shown in Figure 3-30, soft-magnetic material protects the Base Station from the magnetic field that is generated in the Primary Coil. The top face of the Shielding block is aligned with the top face of the Primary Coil, such that the Shielding surrounds the Primary Coil on all sides except for the top face. In addition, the Shielding extends to at least 2.5 mm beyond the outer edge of the Primary Coil, and has a thickness of at least 3.1 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:

Mn-Zn-Ferrite Dust Core— any supplier

Figure 3-30: Primary Coil assembly of Power Transmitter design A8

3.2.8.1.3Interface Surface

As shown in Figure 3-30, 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.

3.2.8.1.4Separation between multiple Power transmitters

If the Base Station contains multiple type A8 Power Transmitters, the Primary Coils of any pair of those Power Transmitters shall have a center-to-center distance of at least 70 mm.

3.2.8.2Electrical details

As shown in Figure 3-31, Power Transmitter design A8 uses a full-bridge inverter to drive the Primary Coil and a series capacitance. Within the Operating Frequency range of 110…180 kHz, the assembly of

resonance, the voltage developed across the series capacitance can reach levels up to 100 V pk-pk.

Power Transmitter design A8 uses the Operating Frequency and the input voltage to the full-bridge inverter to control the amount of power that is transferred. In order to achieve a sufficiently accurate adjustment of the power that is transferred, a type A8 Power Transmitter shall be able to control the frequency with a resolution of 0.5 kHz, and the input voltage with a resolution of 50 mV or better.

When a type A8 Power Transmitter first applies a Power Signal (Digital Ping; see Section 5.2.1), the Power Transmitter shall use an Operating Frequency of 130 kHz, and an input voltage of 8 V. If the Power Transmitter does not to receive a Signal Strength Packet from the Power Receiver, the Power Transmitter shall remove the Power Signal as defined in Section 5.2.1. The Power Transmitter may reapply the Power Signal multiple times at an Operating Frequency of 130 kHz using consecutively higher input voltages within the range specified above, until the Power Transmitter receives a Signal Strength Packet containing an appropriate Signal Strength Value.

Figure 3-31: Electrical diagram (outline) of Power Transmitter design A8

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 Operating Frequency as well as the input voltage to the full-bridge inverter. It is recommended that control of the power occurs primarily by means of adjustments to the Operating Frequency, and that voltage adjustments are made only at the boundaries of the Operating Frequency range. In order to guarantee sufficiently accurate power control, a type A8 Power Transmitter shall determine the amplitude of the Primary Coil current with a resolution of 5 mA or better. Finally, Table 3-23 and Table 3-24 provide the values of several parameters, which are used in the PID algorithm.