Defibrillator with diode protection for capacitor-charging circuit - incorporates diode string on secondary side of transformer for rectification of AC and dissipation of negative portion of pulse

摘要

The charging circuit is protected against negative phasing of the defibrillation pulse connected by a switching device (4) through a choke (3) to external body electrodes (8, 9). To protect the voltage-doubling circuit (5) the secondary winding (20) of its transformer (21) is AC-coupled (19) to the midpoint (18) of a string (12) of diodes (13-16) delivering DC to the storage capacitor (2) via a bifilar wound choke (17). The switching (4) may be performed by e.g. a thyristor (24) in series with a previously closed electromechanical switch (25). Another switch (28) may divert excess energy into a resistance (29). ADVANTAGE - The circuit is protected against abrupt voltage increase due to short-circuit defibrillation, without need of a special high-voltage flyback diode.