The present invention outlines structures and methods for delivering a
controllable amount of energy to a patient by automatically compensating
for the load impedance detected by an implantable-cardioverter
defibrillator (ICD). The invention employs high speed, switching power
converter technology for the efficient generation of high energy,
arbitrarywaveforms. Unlike a linear amplifier, switching power converters
deliver high-energy waveforms with an efficiency that is independent of
the size and amplitude of the desired waveform. An ICD that uses a
switching power converter to deliver the desired energy to the patient
stores the energy to be delivered in a storage capacitor. The converter
then transforms this energy into an arbitrarily shaped output
voltage-controlled or current-controlled waveform by switching the
storage capacitor in and out of the output circuit at a high rate of
speed. Preferably, the waveform comprises a ramp-type waveform.