High efficiency driver for transcutaneously coupled coils

A simple, highly efficient class-E driver circuit suitable for powering implantable electronic devices is described. Such a driver allows the design of displacement-tolerant coils. The design for a driver operating at 120 kHz is given. Through successive adjustments in frequency and duty cycle the largest current transfer ratio of peak AC current in the transmitter coil (L2) to the input DC current was obtained. The frequency of operation was 122.7 kHz with a duty cycle of 0.18. The DC input was 0.6 A at 9.0 V. The sinusoidal AC output in the Litz wire coil was 9.2 A peak with a peak voltage of 45.5 V AC. This represents an approximate DC/AC convert efficiency of 80% and a current transfer ratio of 15.3 A peak/A DC, with the lost power being dissipated in the DC feed inductor, the shunt capacitor, and the switch. The power loss in the HexFet switch was estimated to be less than 0.25 or less than 4.6% of the input power