Patent ID: 8423136
Filing Date: 2013-04-16
Classification: A61N

Abstract:
1. An implantable cardioverter defibrillator (ICD) comprising: a housing; therapy delivery electrodes; and circuitry contained within the housing and coupled to the therapy delivery electrodes, the circuitry including an energy storage system and a battery, the circuitry configured for generating defibrillation therapy using the energy storage system; wherein: the circuitry includes an H-bridge circuit having a high side and a low side, the high side having a first switch coupled to a first node and a second switch coupled to a second node, the first and second nodes being coupled to the therapy delivery electrodes, the low side comprising a third switch coupling the first node to a low node and a fourth switch coupling the second node to the low node, and control circuitry coupled to the first, second, third and fourth switches and configured to perform an induction sequence including successively engaging the switches in an alternating sequence to produce a controlled current alternating output between the therapy delivery electrodes; the low node is coupled to ground or reference for the circuit via a stimulus switch in parallel with a feedback resistor; and the H-bridge is coupled to a current modulation circuit including a transistor having current inlet node, a current outlet node, and a control node, the control node being coupled to a feedback circuit that takes an input signal from the low node and a control voltage from the control circuitry to modulate current flow through the feedback resistor while the stimulus switch is open during the induction sequence such that a substantially constant current is maintained for the controlled current alternating output.