Load Matching for Non-Contact Charging System

Abstract

The compact electronic devices such as electric shaver and cordless phone with non-contact charging system have been widely used. A detachable transformer with a magnetic coupling is used in this system The magnetic coupling of the coils over the air gap causes leakage inductance. For this reason, the load matching technology is required to miniaturize the system The parallel capacitor connected to the secondary coil ofthe detachable transformer is very available method for load matching, The optimal value ofthe capacitance is influenced not only by frequency and leakage inductance but also by cell voltage and secondary induced voltage. It has been determined by trial and error after the experimentation or circuit simulation. Through our careful observation of the experiments, we found that a distinct waveform exists when the best value has been chosen for the capacitor with the charging current of the maximum average. This paper shows, far practical calculation purpose, an equation ofthe optimal capacitance and maximum charging current, based on the distinctive waveform in the non-contact charging systemwith half-wave rectifier. Experimental data are given to prove the validity ofthis expression. At the end, some ofthe characteristics are also given to show the capacitance and the average charging current underdifieient circuit conditions.