One of the big patent themes from Apple in 2018 has been wireless inductive power transfers and AirPower.  AirPower has been delayed for some time now and rumors claim that Apple will launch it during their September iPhone event. Today the US Patent & Trademark Office published yet another patent application from Apple that relates to an inductive power transmitter for inductive power transfer (IPT) and in particular foreign object detection.

Apple's first patent covering object detection surfaced back in April with a Power by Proxi patent coming to light.  This second patent is likewise a Power by Proxi patent by the same engineer. Apple acquired the New Zealand Company back in 2017.

Apple's patent FIG. 1 below illustrates a schematic of an inductive power transfer system; FIG. 2 is a block diagram of an object detection system.

More specifically, Apple notes that it may be desirable in certain applications for the IPT transmitter to selectively provide power to associated receiver devices (e.g., mobile phones, remote controls, etc.) and not to foreign objects (FO) (e.g., paperclips, coins, etc.).

To this end, the IPT transmitter may include an Object Detection (OD) system. The OD system may either deactivate coils in response to non-receiver devices or only activate coils in the sole presence of receiver devices. In situations where there is a plurality of transmitting coils, such as an array of coils (e.g., on a charging mat), the OD system may only de/activate a subset of coil/s according to the location of the receiver/non-receiver device respectively. The FO detection algorithm mentioned earlier may form part of the OD system, or it may be the entire OD system depending on application requirements.

An example transmitter 2 is shown in FIG. 2. The inverter (#6) supplies power to the transmitting coil #7 to generate an IPT field. An OD circuit (#200) includes an excitation coil or coils (#202) to generate a OD field and a detection circuit (#204) used to sense the presence and/or location of objects on or adjacent to the transmitter. The controller (#8) of the transmitter may either directly, or via a separate control circuit, be configured to determine the excitation to be provided to the excitation coil and process the output signal from the OD circuit.

This may involve an array of coils, and/or or a plurality of OD circuits depending on the requirements of the application. In alternative implementations the OD field may be generated by the transmitting coil or may be a separate tuned coil, coupled or otherwise. It may be operated sequentially with the IPT field or simultaneously.

The OD field should operate at least two significantly different frequencies. More than two frequencies may be used depending on the application. It is desirable that the upper and lower frequencies are chosen to allow reliable detection of the expected foreign objects for the particular application.

Typical examples of such foreign objects are metallic elements such as coins, keys, paperclips, etc. For example, if a metal object is close to the active IPT field, it could heat due to eddy currents being developed from the oscillating magnetic field. In order to prevent the temperature of such parasitic metal from rising to unacceptable levels, the power transmitter should be able to discriminate between power receivers and foreign objects and reduce the power being transferred or abort operation altogether. Various example embodiments will now be described for detecting foreign objects in relation to an inductive power transmitter.

A first method for detecting foreign objects is to measure power loss. In this method, the received real power is indicative of the total amount of real power dissipated within a power receiver contained in a handheld device due to the magnetic field produced by the power transmitter. The received real power equals the real power that is available from the output of the power receiver plus any real power that is lost in producing that output power. The power receiver communicates its received real power back to the power transmitter so that the power transmitter is able to determine whether the power loss is within acceptable set limits and, if not, the power transmitter determines anomalous behavior indicative of the presence of a foreign object.

A second method for detecting foreign objects uses separate excitation and detection coils within the transmitter. Changes in the inductance of the detection coil are measured to determine the presence of a foreign object.

A third method to detect foreign objects is to actively generate a resonating voltage in a receiver or detection coil and then detect the Q value changes via the transmitter coil."

Apple's patent application 20180248408 was filed back in Q2 2018. The invention, originally filed by Power by Proxi, was originally filed in 2015. Considering that this is a patent application, the timing of such a product to market is unknown at this time.

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