Constant-Frequency and Noncommunication-Based Inductive Power Transfer Converter for Battery Charging

Abstract

Compared with conductive charging, wireless inductive-power-transfer (IPT) charging exhibits higher potential as it avoids physical contact and provides convenient user experience. Regrettably, it is challenging for IPT converters to comply with the constant current (CC) and constant voltage (CV) charging profiles, while optimizing power efficiency. To achieve such goals, the existing IPT converters can apply multistage converter, dual side, or variable frequency modulation with feedback wireless communication. However, applying multistage converter increases cost and loss, while the stability of the IPT converter with dual side or variable frequency modulation can be at risk if communication fails. This article proposes a single-stage IPT converter for battery charging. With a constant operating frequency and without feedback wireless communication, the receiver side directly regulates the output to comply with the CC/CV charging profile, while the transmitter side aids in the reduction of the modulated phase shift angle at the receiver side, thus improving the efficiency. No wireless communication between the transmitter and receiver sides benefits both the hardware cost and stability. Also, we implement implicitly an output voltage regulation, further avoiding the need of an extra dc–dc converter. We verify experimentally the proposed control method in a 1-KW charging platform with a measured peak efficiency up to 94.35%.