Importance

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Abstract

A method and apparatus for providing variable defibrillation waveforms using switch-mode amplification are provided. In one embodiment, a defibrillation waveform generator is described that includes a rapid-discharge capacitor, a controller, and a switch-mode amplifier. The rapid-discharge capacitor is charged to a charge voltage that may be discharged over a time frame consistent with the chronaxie time of a human heart. The controller generates at least one control signal, which may be pulse-width modulated. The switch-mode amplifier responsive to the control signals, optionally supplemented by a biphasic converter, selectively amplifies the charge voltage so that the magnitude, phase, and timing of the amplification may be varied, thus resulting in a variable waveform. In some embodiments, the present invention includes both step-up and step-down converters. The step-down converter enables the defibrillator to be used so that the rapid-discharge energy storage device is charged to a charge voltage that is greater than the output voltage applied to the defibrillation patient. The step-up converter is used to maintain or increase the output voltage as the charge voltage is depleted. The step-up and step-down converters of the switch-mode amplifier may be employed in either order, i.e., step-down followed by step-up, or step-up followed by step-down. A step-down followed by step-up topology may permit the use of fewer components, or fewer of certain types of components. A step-up followed by step-down topology provides a constant-current source that may produce a particularly efficacious electrotherapeutic effect.

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First Claim