Equivalent transmission line circuit model based one-to-multiple inductive power transfer system for charging mobile devices

One-to-multiple (O2M) inductive power transfer (IPT) is convenient and flexible due to its ability to power multiple loads with a single transmitter. To enhance the versatility of circuit topologies and avoid complex control strategies, this paper proposes an analytical design method for O2M-IPT systems. Based on a transmission line equivalent circuit model, which is composed with quarter wave transformers (QWTs), the constant output characteristic is given. In addition, the conversion rule from the QWT to the magnetic coupling unit (MCU), the T-type, or the Π-type LC compensation network is clarified. To save space and increase safety, a coplanar transmitter-repeater-receivers coupler is suggested. Through circuit analysis, a simplified equivalent circuit of the three-load is established. On this basis, the performances such as the output characteristic and transmission efficiency of the proposed system are evaluated. Finally, a test prototype is built to verify the feasibility and effectiveness of the proposed system. Experimental results show that the output characteristics for each of the receivers are almost constant regardless of whether the other receiver is in place in or taken away. The measured maximum overall transmission efficiency of three-load is up to 86.66%.