The U.S. Patent and Trademark Office officially published a series of 54 newly granted patents for Apple Inc. today. In this particular report we cover their invention relating to another inductive charging system, and more particular to detecting coil coupling in an inductive charging system. Apple's iPhone 8 debuting in September will be introducing wireless charging. Which of Apple's many wireless charging patents will the day is unknown at this time.

Apple's patent FIG. 1 illustrates one example of inductive charging system; FIG. 3 depicts a simplified block diagram of another example of the inductive charging system 100 shown in FIG. 1.

In one aspect, a receiver device for use in an inductive charging system can include a receiver coil operatively connected to an input of an AC-to-DC converter, a first resonant circuit operatively connected in series between the receiver coil and the input of the AC-to-DC converter, and a second resonant circuit operatively connected in parallel with the receiver coil between the receiver coil and the input to the AC-to-DC converter. A load may be operatively connected to an output of the AC-to-DC converter. As one example, the load can be a rechargeable battery. The first resonant circuit is associated with a first resonant frequency and the second resonant circuit is associated with a second resonant frequency that is different from the first resonant frequency. In one embodiment, the second resonant frequency is higher than the first resonant frequency. 

In another aspect, a method for detecting coupling between a receiver coil and a transmitter coil in an inductive power transfer system can include a transmitter device transmitting pings to a receiver device at different frequencies and measuring a current input into a DC-to-AC converter in the transmitter device based on each ping. The current measurements can then be analyzed to determine whether a current measurement indicates the receiver coil and the transmitter coil are inductively coupled. As one example, the current input into the DC-to-AC converter can be higher when the receiver and transmitter coils are coupled than when the receiver and transmitter coils are not coupled.

Apple's granted patent 9,685,814 was originally filed in Q2 2014 and published today by the US Patent and Trademark Office. For more details you can review the invention here.

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