System conditions monitoring method for a wireless cellular phone charger

This paper presents a technique to be used for the cellular phone charger. The proposed technique identifies system conditions to control the output voltage, measuring only the primary side voltage and current. The method estimates the load and the coupling coefficient of the circuit by perturbing the operating frequency. The control method, designed in Primary-Series-Secondary-Series (SS) topology maximizes the efficiency by working at the resonant frequency, hence the output voltage is controlled by the switching duty cycle. The way to get the required duty cycle is proposed by this paper.