A wireless-power-system includes a bridge-rectifier having first and second inputs coupled to first and second terminals of a coil, and an output coupled to a rectified voltage node. An excitation circuit is coupled to the first input. A protection circuit has a first connection node capacitively coupled to the first terminal. The protection circuit, in Q-factor measurement mode, clamps the first connection node when the first input is coupled to ground, and connects the first connection node to the rectified voltage node when the first input is coupled to a supply voltage. The protection circuit, in wireless power mode, is acting as one leg of the rectifier. A pass gate circuit is coupled between the first connection node and a sense node, and a sensing circuit is coupled to the sense node and measures a Q-factor of the wireless power system when the protection circuit is in Q-factor measurement mode.