A novel converter for noncontact charging with electromagnetic coupling

A DC-to-DC converter suitable for noncontact charging for the rechargeable cell using the electromagnetic coupling is presented. The circuit is of self-oscillated class C DC-to-DC converter. In this method, a class C converter is used for reducing the switching loss and the core loss of the transformer. The oscillating condition as a class C converter is automatically adjusted by a simple bias circuit which is made of a diode and a resistor. The zero voltage switching is realized by a resonance of the parasitic parameters of the transformer. Through electromagnetic coupling using this class C converter, we have obtained a noncontact type battery charger of 90% efficiency, under the input and output voltages and output power are 140 V, 12 V and 5 W respectively