Current leakage prevention circuit for an external defibrillator

Abstract

An external defibrillator high voltage circuit with a leakage prevention circuit. The high voltage circuit includes first and second output terminals configured for electrical interconnection to electrodes, first and second charge supply terminals configured for interconnection to a charging voltage supply, and a plurality of capacitors. Charging semiconductor switches which are responsive to charge control signals electrically interconnect the capacitors to the charge supply terminals in a parallel circuit to charge the capacitors. Discharging semiconductor switches which are responsive to discharge control signals electrically interconnect the capacitors in a series circuit between the output terminals to generate defibrillation pulses. The discharging switches include at least two switches interconnected to each other at a leakage shunting node and in a series circuit between one of the capacitors and the second output terminal. A leakage shunting switch electrically interconnects the leakage shunting node to the first output terminal when switched to a closed state to reduce leakage currents through the patient when defibrillation pulses are not being produced. Charge dump semiconductor switches discharge the capacitors when the switches are switched to an electrically closed state. A voltage sensing circuit is coupled to and detects the voltage at the leakage shunting node. The voltage sensing circuit causes the charge dump switches to be switched to the electrically closed state to discharge the capacitors when the detected voltage is greater than a predetermined level.