Design Optimization Method for the Load Impedance to Maximize the Output Power in Dual Transmitting Resonator Wireless Power Transfer System

Abstract

Recently, the dual transmitting resonator wireless power transfer system (DTR-WPT) has been proposed as a promising technique for the power supply of mobile apparatus. Although this technique has been reported to be effective for increasing the output power as well as for covering a wide area during wireless power transfer, the complicated magnetic coupling among two transmitting resonators and one receiving resonator makes it difficult to develop practical design optimization methods, thus hindering practical applications of this technique. The purpose of this paper is to propose a design optimization method for the load impedance of DTR-WPT. This method is derived based on a novel simple equivalent circuit model of the DTR-WPT. The optimum impedance derived using this method as well as the appropriateness of the equivalent circuit were verified experimentally, thus validating usefulness of the proposed method for the practical application of DTR-WPT.

A Consideration on Maximum Efficiency of Resonant Circuit of Inductive Power Transfer System with Soft-Switching Operation

“…In Figure 6, I charge becomes larger, i.e., the output power becomes larger, on the range where α 1 and α 2 are set to smaller values. As shown in Figure 6, the loci of the maximum efficiency points are in accordance with (17) when E 2 /E 1 does not deviate from one, which is the requirement for high efficiency based on (12). This is because the influence of (11) becomes more dominant than the influence of (12) on the efficiency.…”

“…In addition, in the entire operating range, it can be confirmed from Figure 5 that the efficiency of the resonant circuit becomes the highest when conditions (11) and (12) are satisfied. However, the maximum efficiency point in the entire operating range does not match the maximum efficiency point in the soft-switching operating range.…”

“…This is because the influence of (11) becomes more dominant than the influence of (12) on the efficiency. Thus, the influence of (12) can be ignored when E 2 /E 1 does not deviate far from (12). On the other hand, when E 2 /E 1 deviates further from (12), the locus of the maximum efficiency points deviate from the line expressed by (17).…”

“…Thus, the influence of (12) can be ignored when E 2 /E 1 does not deviate far from (12). On the other hand, when E 2 /E 1 deviates further from (12), the locus of the maximum efficiency points deviate from the line expressed by (17). Therefore, a novel equation considering the influence of (12) is necessary when the influence of (12) can not be ignored.…”

“…Previously, the maximum-efficiency-tracking method for the resonant circuit [2,[7][8][9][12][13][14][15], the design method for the resonant circuit [2,11,16], the switching frequency control method for the secondary-side converter [14,17], and the soft-switching technique [9,15,[18][19][20] were proposed as the efficiency improvement method for IPT systems. In general IPT systems, much electromagnetic noise and power loss occur because the converters of IPT systems are driven in high switching frequency by tens of kHz.…”