Importance

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Abstract

An automatic external defibrillator is described that includes a high voltage delivery circuit for producing an electrical pulse to defibrillate a patient. In a preferred embodiment the electrical pulse is a biphasic or multiphasic electrical pulse. In one embodiment, the delivery circuit includes a high voltage capacitor coupled with a bridge circuit. The capacitor stores electrical energy for delivery to the patient, and the bridge circuit has four switching elements that are selectively switched to steer the current through the patient. A disarm circuit shunts the bridge circuit and operates to route energy away from the bridge circuit in the event a fault condition is detected, such as a short circuit at the patient electrodes. An example disarm circuit is a series-connected SCR and resistor. Also, a limiting circuit element (such as a resistor or an inductor) is provided in series with the capacitor. Together with the disarm circuit, the limiting circuit element reduces the voltage experienced by the bridge circuit switching elements when switched off in response to the detected fault condition. Consequently simpler, more robust, and less expensive high voltage delivery circuits are provided, as compared to conventional defibrillator circuit designs. A snubber circuit is also provided to prevent voltage from reaching the patient when the device is in standby mode.

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First Claim