Embodiments describe a wireless charging system including an accessory device and a host device. The host device can include a housing having a charging surface and power transmitting circuitry coupled to a power source. The power transmitting circuitry can include an inductive transmitter coil configured to receive a first power and generate magnetic field, an amplifier coupled to the inductive transmitter coil and configured to output the first power to the inductive transmitter coil, an output sensor coupled to the inductive transmitter coil and configured to measure the first power to the inductive transmitter coil, and a power tracking controller coupled to the sensor probe. The power tracking controller can be configured to receive measurement of the first power, and generate a control signal based on the measured first power to modify an output impedance of the amplifier to output a second power different from the first power.