A study on efficiency improvement of high-frequency current output inverter based on immittance conversion element

Wireless power transmission utilizing magnetic field resonance has been given increasing attention by power electronics engineers and industry. Actually, many technical papers that relate to the transmission coils of wireless power transmission based on magnetic field resonance have been published and verified the high-efficiency power transmission characteristics. However, the 10 MHz class high-frequency power converter suitable for high-power transmission systems has not been studied sufficiently, although small power rating converters, such as the class-E converter with a 74.9 W output power, have been proposed. Hence, the authors propose a new circuit topology for high-power high-frequency inverter systems suitable for high-power wireless power transmission. In this paper, the authors propose a novel high-frequency current output type inverter circuit topology utilizing an immittance conversion element and wireless transmission coils, which utilize an LC anti-resonant circuit suitable for the proposed current output type inverter. As a result of the prototype test, the proposed inverter provides a high conversion efficiency of more than 77.6 % at 11.33 MHz operation with a 123 W output power rating. Also, the proposed transmission coils suitable for current output type inverters provide a high transmission efficiency of more than 94.2 % at 11.33 MHz operation with 20 mm transmission gaps and a 46.1 W output power.