Methods and Circuitry for Mitigating Saturation in Wireless Power Systems

A method of operating a wireless power transmitter having a resonant tank including a wireless power transmitting coil and a capacitor, an inverter that drives the resonant tank at a wireless power transfer frequency to transfer power to a wireless power receiver via a wireless power receiving coil of the wireless power receiver, and control circuitry, the method being performed by the control circuitry and comprising:

• receiving communication from the wireless power receiver via communication circuitry coupled to the wireless power transmitting coil that detects modulation by the wireless power receiver of one or more parameters of the wirelessly transferred power;
• detecting saturation of a magnetic core of the wireless power receiving coil using measurement circuitry coupled to the wireless power transmitting coil, wherein the measurement circuitry is configured to detect saturation of the magnetic core of the wireless power receiving coil by monitoring a current through the wireless power transmitting coil to detect a pattern of every other positive cycle having excessive current followed by a next positive cycle having diminished current;
• and
• operating the inverter using inverter drive circuitry responsive to:
• communication received from the wireless power receiver using the communication circuitry to deliver a power level requested by the wireless power receiver, and
• the measurement circuitry when saturation of the magnetic core is detected to mitigate detected saturation of the magnetic core by reducing output power of the inverter.

A wireless power transmitter comprising:

• a resonant tank comprising a wireless power transmitting coil and a capacitor;
• an inverter that drives the resonant tank at a wireless power transfer frequency to transfer power to a wireless power receiver via a wireless power receiving coil of the wireless power receiver;
• control circuitry further comprising:
• communication circuitry coupled to the wireless power transmitting coil configured to receive communication from the wireless power receiver via modulation by the wireless power receiver of one or more parameters of the wirelessly transferred power;
• measurement circuitry coupled to the wireless power transmitting coil that detects saturation of a magnetic core of the wireless power receiving coil, wherein the measurement circuitry detects saturation of the magnetic core of the wireless power receiving coil by monitoring a current through the wireless power transmitting coil to detect a pattern of every other positive cycle having excessive current followed by a next positive cycle having diminished current;
• and
• inverter drive circuitry that operates the inverter responsive to:
• communications received from the wireless power receiver using the communication circuitry to deliver a power level requested by the wireless power receiver, and
• the measurement circuitry when saturation of the magnetic core is detected to mitigate detected saturation of the magnetic core by reducing output power of the inverter.