関屋 大雄

This paper presents a design of a load-independent wireless power transfer (WPT) system with multiple receivers and unified coupling coils. Various applications in each receiver require individual output voltages. In the proposed WPT system, LCC filters are adopted in front of transmission coils to improve the degree of freedom. The design theory of the LCC filter for achieving load-independent operation and the required individual output voltage is given. Consequently, the receiver can obtain the specified output voltages in each transmission coil; however, the variations of the coupling coefficient affect the output voltage. Since the load-independent operation can be maintained by satisfying specific conditions of the LCC filter, the proposed system always achieves zero-voltage switching and constant output, regardless of receiver load resistances in high power-delivery efficiency. From the experimental results, the effectiveness of the proposed WPT system and the validity of the design strategy can be confirmed. The experimental prototype of the two-receiver WPT system achieved 86.1% power-delivery efficiency at 6.78 MHz operating frequency and 19.6 V and 29.7 V output DC voltages.

This article presents a load-independent zero-current switching (ZCS) parallel-resonant inverter with a constant output current. The proposed inverter features constant-current output inherently without the need for any control method. Moreover, ZCS is achieved despite load variations, ensuring high power efficiency even at MHz-order switching frequencies. We conduct a comprehensive circuit analysis of the proposed inverter and provide a step-by-step parameter design method for achieving load-independent conditions. Additionally, a 25 W, 1 MHz prototype of the proposed inverter was implemented. In the circuit experiment, constant current output and ZCS were achieved across the entire range of load variations, which demonstrated the effectiveness of the proposed load-independent inverter.

Synchronisability of limit cycle oscillators has been measured by the width of the synchronous frequency band, known as the Arnold tongue, concerning external forcing. We clarify a fundamental limit on maximizing this synchronisability within a specified extra low power budget, which underlies an important and ubiquitous problem in nonlinear science related to an efficient synchronisation of weakly forced nonlinear oscillators. In this letter, injection-locked Class-E oscillators are considered as a practical case study, and we systematically analyse their power consumption; our observations demonstrate the independence of power consumption in the oscillator from power consumption in the injection circuit and verify the dependency of power consumption in the oscillator solely on its oscillation frequency. These systematic observations, followed by the mathematical optimisation establish the existence of a fundamental limit on synchronisability, validated through systematic circuit simulations. The results offer insights into the energetics of synchronisation for a specific class of injection-locked oscillators.