(8) This voltage is filtered by R11 and C20 and appears at the gates of U2 and
shuts down the invertor by removal of the drive signals. As charge leaks off of any
capacitor section, the ready signal disappears and the charging resumes. These
occurrences are very rapid and occur alternately in any sequence. They serve to deliver
small packets of energy to the capacitors so as to refresh the charge.
(9) No matter what energy level was selected, the invertor action would be the
same and give the same results (= 4 x 340v or 1360v) due to the string of zener diodes
activating each opto-coupler. This would be true except that there is yet another opto-
coupler U16 which also has its output in parallel with the others and is likewise capable of
f. Functions of the Circuits in the High Voltage Regulator.
(1) As mentioned before, the opto-coupler U16 together with 1/2 of U10 form
the basis of a high voltage regulator. A 6.2 volt zener diode CR31 is arranged to put a
preset voltage, on the inverting input of comparator U10.
(2) The non-inverting input, however, is configured in a precision voltage
divider consisting of a resistor R20, (11K ohms) with a tolerance of two percent. The other
leg of the divider is provided by R34 through R39, R167, R163, and R164 depending on
the setting of another section of SW5.
(3) Eight of these resistors are all high voltage power resistors with a tolerance
of one percent. R164 is placed between the switch positions and thus shares R167 for the
two uppermost energy levels.
(4) R163 is a calibration resistor used only to trim the value of R164 for the
360j energy level. There will be no output from this comparator as long as there are
dissimilar inputs to the chip, but if the inputs are the same, the output goes high, and as
described before, provides an inhibit to charging.
(5) With the desired width of the output pulse known at 12.0msec. and with
the nominal value of the storage capacitor known to be 1000 mfd each, the starting
voltage of the capacitor discharge was carefully arrived at empirically. These precision
resistors were selected to inhibit charging at a specified voltage for each of the energy
(6) This voltage varies from 200v for 5j to 1355v for 360j. Because of the
precision of this voltage selection and of the controlled pulse width, it is possible to deliver
very accurate energy to the load.