Patent ID: 11936208
Assignee: KONINKLIJKE PHILIPS N.V.
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H | IPC H

Claim 12:
13. A method of operation of a power transmitter the power transmitter comprising:
a transmitter coil;
a first plurality of balanced detection coils coupled in series,
wherein the first plurality of balanced detection coils comprises a first detection coil and a second detection coil,
wherein the first detection coil and the second detection coil are arranged such that a first signal induced in the first detection coil by an electromagnetic field generated by the transmitter coil is compensated by a second signal induced in the second detection coil by the electromagnetic field generated by the transmitter coil, the method comprising:

generating a drive signal for the transmitter coil so as to generate a power transfer signal during at least one power transfer time interval of a repeating time frame;
generating the drive signal for the transmitter coil so as to generate an electromagnetic test signal during at least one foreign object detection time interval of the repeating time frame;
performing foreign object detection during the foreign object detection time interval;
detecting a foreign object in response to a property of a signal meeting a foreign object detection criterion, wherein the signal is from the first plurality of balanced detection coils;
wherein the drive signal has a first voltage amplitude during the foreign object detection time interval and a second voltage amplitude during power transfer time intervals,
wherein the first voltage amplitude is at most 50% of the second voltage amplitude.