Consideration on Efficiency Characteristics to Switching Frequency of Secondary-side Converter with Inductive Power Transfer System for Electric Vehicle

A battery charger applying an inductive power transfer (IPT) for electric vehicles has various advantages. Then, there is a case that the secondary-side converter is connected to the receiving side of the IPT system in order to regulate the charging power for the battery of electric vehicles. In the previous studies about this converter, it was investigated that the type of the secondary-side converter affects the efficiency of the resonant circuit. However, the optimal switching frequency of the secondary-side converter is not investigated although the optimal converter type and operation mode are investigated in the previous studies. It is possible that the secondary-side converter achieves even higher efficiency by optimally controlling the switching frequency of the converter because the switching frequency affects the converter efficiency. Therefore, this paper investigates the efficiency characteristics of the switching frequency of the secondary-side converter by the theoretical analysis and experimental results in order to establish a high efficient control scheme which controls the switching frequency of the converter. As a result, it is observed that there are similar tendencies in the efficiency characteristics between the results of the theoretical analysis and experimental results. In addition, this paper shows an operation guideline of the secondary-side converter obtaining high efficiency by controlling the switching frequency of the converter.