GB1037117A - Defibrillators - Google Patents

Abstract

1,037,117. Automatic voltage control. ZENITH RADIO CORPORATION. June 19, 1964 [July 1, 1963], No. 25572/64. Heading G3R.[Also in Divisions A5, H2 and H3] An electrical defibrillator which is portable and operated from a battery 10 includes a charge and discharge circuit 15 which is able to deliver to electrodes 16,17 placed on or over a patients heart a direct-current output pulse having a trapezoidal waveshape. As described, energy from the battery 10 is inverted to A.C.and amplified by a circuit 12, the voltage is increased by a transformer 13, and it is then rectified in a silicon diode circuit 14 to give a controlled charge to a two or more section delay line 34, 35, 36, 37 which is discharged on demand by actuating switches 39, 40. A control circuit 18 including transistors 47, 59 maintains and controls the replacement of charge on the condensers 36, 37. As shown, with the switch 29 open a bias from the primary winding 21a and rectifier 43 maintains the transistors 23, 24 non- conducting and prevents charge being supplied to the delay line. However if charge is lost the potential across resistor 56 drops and the transistor 47 becomes non-conductive and the transistor 59 conductive, and the resultant current flow in coil 30 closes switch 29 allowing the transistors 23, 24 to conduct and charging of the delay line to take place to the predetermined limit. Chattering of the relay 30 is avoided as a result of the reduction of the emitter bias supplied through the resistor 62, due to the closing of contact 29.