Parameter design for high-efficiency contactless power transmission under low-impedance load

Recently, demand for contactless power transmission techniques has been growing in various industrial fields. Electromagnetic induction is able to transfer high power with high efficiency. Power transmission circuits typically consist of a paired coil and capacitance for improving the efficiency. The coil frequency and configuration that gives a high quality factor is essential for high-efficiency transmission because the maximum efficiency depends on the product of the coupling coefficient between the two coils and the quality factor of the coils. However, the matching with the load resistance also needs to be discussed. We therefore propose a circuit constructed by inserting a short-circuited LC into the receiving circuit, which we call the LC-booster method. This method is highly practical because it allows one to use coils with high quality factors and to adjust the circuit to match the load resistance. We examine the relationship between the capacitance in the short-circuited LC and the power transmission efficiency.