Impedance adjustment in wireless power transmission systems and methods

A method comprising:

• wirelessly transferring power from a power transmitting apparatus to a power receiving apparatus connected to an electrical load;
• receiving a first electrical signal comprising information about a voltage waveform associated with impedance matching circuitry of a power source of the power transmitting apparatus;
• receiving a second electrical signal comprising information about a current waveform associated with the impedance matching circuitry of the power source;
• determining a phase difference between the first and second electrical signals;
• determining whether the phase difference is within an allowable range of phase differences;
• adjusting an impedance of a circuit of the power transmitting apparatus if the phase difference is outside the allowable range of phase differences;
• and
• adjusting at least one of a phase, a duty cycle, and a bus voltage of an amplifier of the power source if the phase difference is within the allowable range of phase differences to drive the power transmitting apparatus toward a target output power.