An Approach for Detecting Illegal Load in Wireless Power Transfer System

In wireless power transfer (WPT) system, detection of illegal load especially the metallic illegal load is necessary to protect the system safety due to the high frequency electromagnetic. This paper presents an efficient and easily-realized method based on energy channels for detecting the legitimacy of load in WPT system. The method is designed that the load at a given frequency to carry out on-off modulation and the primary part demodulation to judge the legitimacy of the load according to the energy equilibrium equations. To realize the proposed method, the relation between primary DC(direct current) input current and secondary load resistance have been analyzed. Therefore, the final detection method is set up which is only required sampling the frequency of DC input current to avoid complex system modeling and requirements of high speed sampling system. Finally experiment and simulation have verified the method which is much efficient and easily-realized for detecting the legitimacy of load accurately.