Characteristic Comparison of 16 Circuits for Inductive Power Transfer

Past research on circuits for wireless power transfer was limited to the target applications or the compared circuits. Therefore, this study comprehensively compared the characteristics of 16 circuits by combining four circuits S, P, LCL and LCC on the transmitter and receiver sides. In addition, the equations for calculating the efficiency, Maximum Efficiency Load (MEL), output power, Maximum Power Load (MPL), and current for magnetic field review were derived. It was found that the efficiency of all circuits with MEL is independent of the circuit. It was also found that MEL became larger when the receiver side was P or LCL, and smaller when the receiver side was S. It was also found that the efficiency of all circuits with MPL is common the case that the coupling is small, but the case that it is large, high efficiency is obtained in P on the transmitter side such as S-P, P-S, P-P, P-LCL, and P- LCC. Therefore, it can be said that for high efficiency transfer, the circuit should be selected according to the value of the load. Since the output power of S on the transmitter circuit such as S- S, S-P, S-LCL, and S-LCC can get large power in all patterns regardless of MEL and MPL, so selecting S for the transmitter circuit is suitable for getting large power, but has the disadvantage of high current flow the case that the coupling is 0. On the other hand, the transmitter side P, LCL, and LCC have the advantage that large current does not flow even the coupling is zero, and since LCC on the transmitter side gets relatively large power, it is also appropriate to select LCC on the transmitter side according to the purpose. In the case of small coupling, the efficiency and output power with MEL and with MPL were found to be close. For the current value, there is no difference in the current value depending on the circuit with MEL, but with MPL, the ratio of the current flowing in the transmitter coil to that in the receiver coil differs depending on the circuit. From the above characteristics, the LCC on the transmitter side with MEL is suitable for symmetric coils with large coupling and asymmetric coils with smaller transmitter coil, while S on the transmitter side with MPL is suitable for symmetric coils with small coupling and asymmetric coils with smaller receiver coils. On the receiver side, the choice should depend on the value of the load.