In a method and apparatus for supplying wireless energy to a medical device (100)implanted in a patient, wireless energy is transmitted from an external energysource (104) located outside a patient and is received by an internal energy receiver(102) located inside the patient, for directly or indirectly supplying receivedenergy to the medical device. An energy balance is determined between the energyreceived by the internal energy receiver and the energy used for the medical device,and the transmission of wireless energy is then controlled based on the determinedenergy balance. The energy balance thus provides an accurate indication of thecorrect amount of energy needed, which is sufficient to operate the medical deviceproperly, but without causing undue temperature rise.
