ENHANCED TRANSCUTANEOUS RECHARGING SYSTEM FOR BATTERY POWERED IMPLANTABLE MEDICAL DEVICE

摘要

An improved transcutaneous energy transmission device is disclosed forcharging rechargeable batteries in an implantable medical device and tominimize peak temperature rises in the implantable device. A current with asinusoidal waveform is applied to a resonant circuit comprising a primary coiland a capacitor. Current is induced in a secondary coil attached to theimplantable medical device. Two solid state switches are used to generate thesinusoidal waveform by alternately switching on and off input voltage to theresonant circuit. The present invention charges the batteries using a chargingprotocol that either reduces instantaneous charging current or duty cycle of afixed charging current as the charge level in the battery increases. Peaktemperature rises are less while delivering comparable electrical charge tothe battery than for prior charging systems. A controller preferably isconstructed as a pulse width modulation device with enable and referencevoltage features to effectuate variable duty cycle control of the currentlevel applied to the primary coil. An alignment indicator also is provided toinsure proper alignment between the energy transmission device and theimplantable medical device. The implantable device maximizes transcutaneousenergy transmission at different current levels by placing differentcapacitors into the circuit depending on the magnitude of charging current.Peak temperature rises are reduced while delivering comparable electricalenergy charge to the battery than for prior charging systems.