Primary-Frequency-Tuning and Secondary-Impedance-Matching IPT Converter With Programmable Constant Power Output and Optimal Efficiency Tracking Against Variation of Coupling Coefficient

For inductive power transfer (IPT) systems, load conditions and coupling coefficient are subject to change, and affect system power and efficiency. Aiming at addressing this issue, this article proposes a two-loop control scheme based on a single-stage power-source IPT converter. The proposed IPT converter utilizes a series compensation structure on the primary side and employs a switched-controlled capacitor (SCC) in series with a semiactive rectifier (SAR) on the secondary side. The secondary SCC and the SAR cooperate via an inner control loop to emulate a null secondary impedance and an optimal load resistance, whereas the operating frequency is responsible for the output power regulation via an outer control loop. The operating principle enables programmable constant power (CP) output and optimal efficiency tracking against variations of coupling coefficient and load condition, and all power switches are designed to facilitate soft-switching to reduce switching losses. Moreover, compared with conventional IPT systems that have a constant current or constant voltage output characteristic, programmable CP output characteristics can maximize the output power capability of this IPT converter, which is suitable for battery or supercapacitor charging applications. Finally, simulations and experiments validate the proposed model and method for correctness and feasibility.