Patent attributes
An external defibrillator/pacer includes an output circuit with four legs arrayed to form an H-bridge. Each leg of the output circuit contains a switch. In a defibrillation mode, pairs of switches in the H-bridge are selectively switched to generate a biphasic defibrillation pulse. Three switches are silicon controlled rectifiers (SCRs). Gate drive circuits are coupled to the SCRs to bias the SCRs with a voltage that allows the SCRs in response to control signals. One switch includes an insulated gate bipolar transistor (IGBT). A gate drive circuit is coupled to the gate of the IGETs to provide a slow turn-on and a fast turn-off of the IGBT. In a pacing mode, a bypass circuit or current source circuit is used to provide a current path bypassing an SCR switch, which cannot be triggered by the relatively low current of pacing pulses.
