Enhanced transcutaneous recharging system for battery powered implantable medical device

摘要

An improved transcutaneous energy transmission device is disclosed for charging rechargeable batteries in an implanted medical device and to minimize peak temperature rises in the implanted device. A current with a sinusoidal waveform is applied to a resonant circuit comprising a primary coil and a capacitor. Current is induced in a secondary coil attached to the implanted medical device. Two solid state switches are used to generate the sinusoidal waveform by alternately switching on and off input voltage to the resonant circuit. The present invention charges the batteries using a charging protocol that either reduces instantaneous charging current or duty cycle of a fixed charging current as the charge level in the battery increases. Peak temperature rises are less while delivering comparable electrical charge of the battery than for prior charging systems. A controller preferably is constructed as a pulse width modulation device with enable and reference voltage features to effectuate variable duty cycle control of the current level applied to the primary coil. An alignment indicator also is provided to insure proper alignment between the energy transmission device and the implanted medical device. The implantable device maximizes transcutaneous energy transmission at different current levels by placing different capacitors into the circuit depending on the magnitude of charging current. Peak temperature rises are reduced while delivering comparable electrical energy charge to the battery than for prior charging systems.