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,
arbitrary waveforms. 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.