Radiation noise reduction using spread spectrum for inductive power transfer systems considering misalignment of coils

Abstract

This paper proposes spread spectrum methods to reduce radiation noise caused by an inductive power transfer (IPT) system. A noise reduction method with spread spectrum techniques has been proposed. The proposed noise reduction method randomly changes the output frequency of an inverter within a range of 79-to-90 kHz. Changing the output frequency, the radiation noise is spread in a frequency domain. A previous study has proposed the spread spectrum method with the biased probability distribution, which improves the noise reduction performance. However, the suitable probability distribution has not been clear. This paper proposes two spread spectrum methods with biased probability distributions, which are proportional and inverse proportional to an input impedance of the IPT system. The proposed methods are assessed and compared with the conventional noise reduction method. Considering the input impedance of the IPT system, the radiation noise from the IPT system with or without the coil misalignment is reduced by 13.4 dBμA and 7.0 dBμA in comparison with the constant frequency operation. Moreover, the reduction performance is improved compared to the conventional spread spectrum method.