Abstract: Accurate charge measurement based on a calibration factor is described. According to certain aspects, the amount of charge stored in a battery is accumulated over time and adjusted using a calibration factor. In one embodiment, the calibration factor is determined by generating a replica current which comprises a scaled factor of a battery charging current. A calibration reference voltage is measured based on the replica current, and a charge reference voltage is measured based on the battery charging current. A calibration factor is determined based on the charge reference voltage and the calibration reference voltage. In turn, the amount of charge in a battery is accumulated over time using the calibration factor. In various embodiments, the calibration factor provides a factor by which a relatively-low tolerance reference circuit is adjusted, to achieve higher accuracy without substantially increased cost.

Abstract: Disclosed are various embodiments for controlling voltage in a wireless power receiver. A wireless power receiver may comprise an electromagnetic coil configured to receive a current induced by a magnetic flux generated by a wireless power transmitter and a comparator configured to compare a voltage generated by the induced current to a threshold voltage indicating a capability of circuitry coupled to the wireless power receiver. In the event the voltage generated by the induced current exceeds the threshold voltage, the voltage may be limited to a safe value.