Multivariable-Level Active Rectifier for Inductive Power Transfer Charging System

Fast charging technology considerably decreases the equivalent load resistance of low-voltage batteries, necessitating active rectifiers of the inductive power transfer (IPT) charging system to provide a larger resistance conversion ratio for optimal efficiency tracking. However, conventional active rectifiers have limited resistance conversion ratio ranges due to topology constraints, heightened MOSFET voltage stresses, and elevated semiconductor costs. To overcome these limitations, this paper proposes a novel multi-variable-level active rectifier (MVAR), which integrates a multi-level active rectifier with an interleaved buck converter. By decoupling the input voltage conduction angle from the duty cycle of the interleaved parallel buck topology, the proposed MVAR features a resistance conversion ratio range of [0,+∞) theoretically, along with reduced MOSFET voltage stress and lower semiconductor cost in small load resistance applications. Additionally, the interleaved operation also reduces the output current ripple. Combined with the proposed segmented modulation method and the optimal phase angle control strategy, the IPT charging system with MVAR can maintain the optimal resistance throughout the constant power (CP) charging mode. A 350 W experimental prototype was built to validate the performance of the MVAR. Experimental results demonstrate that the IPT charging system employing the MVAR a achieves peak efficiency of 95.3% at the coupling coefficient of 0.18.