A wireless power circuit operable in a transceiver mode and in a Q-factor measurement mode, the wireless power circuit comprising: a coil (Lxcvr) having first (Nf) and second terminals; a bridge rectifier having a first input (Ac1) and a second input (Ac2) coupled to the first terminal and second terminal of the coil, respectively, and having an output coupled to a rectified voltage node; an excitation circuit coupled to the first terminal (Nf) of the coil and configured to, when in the Q-factor measurement mode, drive the coil with a pulsed signal; a protection circuit coupling the first terminal of the coil to a first node (N1) when in the Q-factor measurement mode and decoupling the first terminal of the coil from the first node when in the transceiver mode; and characterised in that it comprises a Q-factor sensing circuit comprising: an amplifier having inputs coupled to the first node and a common mode voltage (Vcm), and generating an output signal having an output voltage (Vout); a comparator having inputs coupled to the first node and the common mode voltage, and generating a comparison output (Comp_Out) indicating the common mode voltage (Vcm) crossing of a voltage at the first terminal of the coil; a processing circuit configured to receive the comparison output and generate an enable signal (Ctrl) based thereupon; and an analog to digital converter configured to, when enabled by the enable signal from the processing circuit, digitize the output voltage and provide the digitized output voltage (ADCout) to the processing circuit for use in calculating a Q-factor of the coil. a coil (Lxcvr) having first (Nf) and second terminals; a bridge rectifier having a first input (Ac1) and a second input (Ac2) coupled to the first terminal and second terminal of the coil, respectively, and having an output coupled to a rectified voltage node; an excitation circuit coupled to the first terminal (Nf) of the coil and configured to, when in the Q-factor measurement mode, drive the coil with a pulsed signal; a protection circuit coupling the first terminal of the coil to a first node (N1) when in the Q-factor measurement mode and decoupling the first terminal of the coil from the first node when in the transceiver mode; and characterised in that it comprises a Q-factor sensing circuit comprising: an amplifier having inputs coupled to the first node and a common mode voltage (Vcm), and generating an output signal having an output voltage (Vout); a comparator having inputs coupled to the first node and the common mode voltage, and generating a comparison output (Comp_Out) indicating the common mode voltage (Vcm) crossing of a voltage at the first terminal of the coil; a processing circuit configured to receive the comparison output and generate an enable signal (Ctrl) based thereupon; and an analog to digital converter configured to, when enabled by the enable signal from the processing circuit, digitize the output voltage and provide the digitized output voltage (ADCout) to the processing circuit for use in calculating a Q-factor of the coil. an amplifier having inputs coupled to the first node and a common mode voltage (Vcm), and generating an output signal having an output voltage (Vout); a comparator having inputs coupled to the first node and the common mode voltage, and generating a comparison output (Comp_Out) indicating the common mode voltage (Vcm) crossing of a voltage at the first terminal of the coil; a processing circuit configured to receive the comparison output and generate an enable signal (Ctrl) based thereupon; and an analog to digital converter configured to, when enabled by the enable signal from the processing circuit, digitize the output voltage and provide the digitized output voltage (ADCout) to the processing circuit for use in calculating a Q-factor of the coil. <EOS>