Open-loop recharge for an implantable medical device

Techniques for recharging a rechargeable power source coupled to a secondary coil implanted within a living body are described. In one embodiment, a recharging device external to the living body induces a sequence of pulses in a primary coil that is coupled to the secondary coil. The sequence includes high-amplitude pulses alternating with low-amplitude pulses, each high-amplitude pulse having an amplitude selected to transfer charge to the rechargeable power source during times of poor coupling between the primary coil and the secondary coil, each low-amplitude pulse having an amplitude selected to transfer charge to the rechargeable power source during times of good coupling between the primary coil and the secondary coil, and wherein the sequence of pulses is selected to prevent a violation of a limiting condition such as heating that is associated with recharging the rechargeable power source when recharging occurs in an open-loop manner.