(7) Furthermore, because of the transthoracic load compensation circuit, to be
described later, the selected energy remains very precise over a wide range of load
conditions. Potentiometer R11 is used to set the comparator at the 200j level. Because all
the resistors are one percent in tolerance, each energy selected will be nominal. Since the
voltage divider is set for 1170v at the 200j level, a trim resistor R163 is used across R164
in the 360j position. To ensure that the voltage at this selection is accurately set at 1355v.
g. Functions of the Circuits in the Defibrillator Section.
(1) The defibrillator uses a dual SCR, CR62, and a series resistor R26. They
are connected in such a way that the initiation of the discharge waveform is controlled by
the turn on of the first (fire) SCR, and the termination of the discharge waveform is
controlled by the turn on of the second (dump) SCR.
(2) Note that the dump SCR is connected across the capacitor bank through a
4 ohm resistor R26, and that the anode of the SCR is connected to the positive paddle.
The anode of the fire SCR is connected to the anode of the dump SCR through a 1k, 25w
resistor R67 and directly to the negative paddle. The cathodes of both SCRs are
connected to the negative side of the capacitor through the 4 ohm resistor.
(3) When the fire SCR is turned ON, energy is delivered to the load (patient).
It comes from the capacitor bank through the current path, from the positive terminal of the
capacitor bank. It then goes through the paddle, the load, the fire SCR, which is now on,
the negative paddle and through the 4 ohm resistor to the low side of the capacitor bank.
(4) When the selected energy has been delivered to the dump, the SCR is
turned on. This SCR shunts the load, discharging the remaining energy in the capacitor
bank through the 4 ohm resister and terminates the energy discharge through the load.
The waveform from this action is trapezoidal.
(5) The composition of the capacitor bank is such that with 8 series parallel
connected capacitors of 1000 mfd. each, the total capacity for energy storage is 500 mfd.
Since energy is expressed by the formula E=0.5* (CV)^2, the total stored energy in the
360j selected position would be 455j.
(6) Furthermore, because of the action of the high voltage regulator, the stored
energy for each successive selection becomes lower. Stored energy versus delivered
energy at the critically selected voltages appears in table 2-1 (into 50 ohms).
(7) The portion of the stored energy delivered to the load is determined by
controlling the discharge time. The remaining energy is dissipated in the 4 ohm resistor.
Subsequently, the regulation of high voltage and precise control of pulse not only yields
repeatedly consistent outputs, but also contributes to high efficiency and prolonged battery