Abstract
Accurate constant current (CC) and constant voltage (CV) charging in wireless power transfer (WPT) systems is challenging in practice because coil misalignment is inevitable during operation and the battery equivalent resistance varies nonlinearly during charging. These effects often degrade regulation accuracy and complicated transmitter (Tx) side control, particularly in communication-free systems. This article proposes a Tx communication-free CC/CV control method for series–series compensated WPT systems that remains effective under misalignment. The mutual inductance is identified prior to charging by detuning the receiver to alter reflected impedance, while the equivalent load is estimated online during charging. By decoupling mutual inductance from load variation prior to charging, a unified closed-form phase shift control law enables CC/CV regulation without receiver (Rx) side sensing, communication or auxiliary converters. Experimental results on a 50 W prototype show that mutual inductance estimation errors are below 6.4% and equivalent load errors within 3.1%. Under various coil misalignment conditions, the system maintains within 1% steady state regulation error for both CC and CV operation.