An LCLC-LC-Compensated Capacitive Power Transferred Battery Charger With Near-Unity Power Factor and Configurable Charging Profile

Abstract

Capacitive power transfer (CPT) techniques are attracting widespread attention due to some unique advantages compared to conventional plug-in systems and inductive power transfer techniques. Since Lithium-ion batteries have been widely used in many energy storage applications, a well-compensated CPT charger should provide an efficient charging profile consisting of first constant current (CC) and later constant voltage (CV), while maintaining nearly unity power factor and soft switching of power switches simultaneously. However, many CPT systems can only realize either CC output or CV output with the input zero-phase angle. Thus, a high-performance CPT charger should possess at least one CC frequency and one CV frequency to charge the battery from CC mode to CV mode by simply switching the operating frequency. In this article, an LCLC-LC-compensated CPT charger is systematically analyzed to achieve these characteristics. Design principle of the CPT charger is also derived with arbitrarily given coupler and configurable charging profile, proving enough design freedom. Besides, the sensitivities of input impedance, output current, and output voltage to variations of compensation parameters are also discussed to realize soft switching. Finally, an LCLC-LC-based CPT prototype with 48 V/2 A charging capability is built to verify the analysis.