Q-factor continuous excitation method and apparatus

A wireless power transmitter, comprising:

• a controller core connected and configured to generate a plurality of switching control signals;
• a multi-switch inverter coupled to the controller core for generating an output pulse width modulation (PWM) signal in response to the plurality of switching control signals;
• and
• a resonant tank circuit coupled to receive the output PWM signal and to generate a transmitter resonance circuit voltage or current signal that is applied to a transmitter coil;
• where the plurality of switching control signals comprises:
• a first set of discharge phase switching control signals to pull the output PWM signal to a ground reference voltage during a discharge phase;
• a second set of continuous excitation phase switching control signals to generate the output PWM signal to have alternating positive and negative pulses having a first pulse frequency during an excitation phase, where each continuous excitation phase switching control signal includes a plurality of positive or negative excitation pulses having the first pulse frequency;
• and
• a third set of free resonance signal sensing phase switching control signals to enable the resonant tank circuit to generate a resonant decaying output voltage signal during a foreign object sensing phase, and
• where the controller core is configured to measure one or more quality factor parameters of the wireless power transmitter based on one or more electrical parameters of the transmitter resonance circuit voltage or current signal that are measured during the foreign object sensing phase.

A system comprising:

• a wireless power transmitter comprising a controller core, a full-bridge power converter, and a resonant tank circuit connected to a transmitter coil located on a charging surface,
• wherein the controller core is configured to supply a first set of switching control signals to the full-bridge power converter during a free resonant frequency measurement phase when the controller core measures a free resonant frequency value for the wireless power transmitter, where the first set of switching control signals comprises a first set of continuous excitation phase switching control signals having a plurality of excitation pulses having a first pulse frequency;
• and
• wherein the controller core is configured to supply a second set of switching control signals to the full-bridge power converter during a quality factor measurement phase when the controller core measures a quality factor for the wireless power transmitter, where the second set of switching control signals comprises a second set of continuous excitation phase switching control signals having a plurality of excitation pulses having a second pulse frequency that is equal to the free resonant frequency value.