Claimed is a method for control in wireless power transfer systems and a wireless power transfer system implementing such method. The system comprises a transmitting inductor; a receiving inductor spaced apart from the transmitting inductor; a half bridge inverting circuit or a full bridge inverting circuit with constant switching frequency for driving the current in the transmitting inductor, wherein said half bridge inverting circuit comprises at least two switches, or said full bridge inverting circuit comprises at least two diagonal pairs of switches. The switches or diagonal pairs of switches are configured to be turned on complementarily, and the current amplitude in the transmitting inductor is controlled by varying the difference between the on-times of said switches. The claimed method and system provide efficient power transfer in conditions of variable load and/or variable input voltage and/or variable coupling between Tx and Rx parts.