Fast Linear Control for Maximum Energy Efficiency of Wireless Power Transfer Systems

Inductive power transfer (IPT) converters are resonant converters that optimize energy efficiencies at some loads. To achieve maximum efficiency, it is common to cascade the IPT converter with front-side and load-side dc-dc converters. The two dc-dc converters are normally controlled cooperatively in order to meet the requirements of output regulation and maximum efficiency tracking using a control technique based on perturbation and observation, which is inevitably slow in response. In this paper, a decoupled control technique is developed. The load-side dc-dc converter is solely responsible for output regulation while the front-side converter is responsible for impedance-matching of the IPT converter by controlling its inputto- output voltage ratio. The controls are linear and therefore fast. DC and small-signal transfer functions are derived for designing the control parameters. The performances of fast regulation and high efficiency of the IPT converter system are verified using a prototype system.