TM 11-5820-801-30
e. - 1000 V Regulator and Protect Circuit IPSIA9
about 48 Vac (center tapped at E3). The rectified voltage
is about 30 V. Zener diodes CR5 and CR6 reduce this
voltage to 15 V and + 15 V, the operating voltage
required by integrated circuit operational amplifier Z1.
Zener diode CR7 reduces the voltage to 6.2 V, the
reference voltage. Diodes CR9 and CR 10 protect Z1
from excessive voltage. Capacitor C5 and diode CR8
compensate for drift in the base voltage at transistor Q1.
A small fraction of the output voltage (1000 + 50 V) is
sensed across variable resistor R4 (1000 V ADJ). The
voltage across R4 varies from about + I V at one end to
about I V at the other end. The wiper arm (1000 V AD1)
is set the null point. The positive end of R4 is connected
to the 6.2 V reference voltage through resistor R3. The
wiper arm of R4 is connected to the noninverting input of
Z1 while the inverting input is connected to ground, the
1000 V return line. Any error voltage is amplified in Z1,
which has a gain of 50 dB or more. The output of Z1
drives the lowest potential gate, IA6, through A9 terminal
E8 to A6 terminal ES, to correct the output voltage to the
desired value (wiper arm at voltage null). If the output
current becomes excessive (about 125 ma) the output
drive (at E8) to gate A6 is reduced because Q1 starts
conducting and removes drive power. Thereafter the
output current is limited to about 20 ma. This protects the
power supply under sustained short circuit in the high
voltage line.
Figure 2-21. Gate Assembly 1PS1A2-A6, Schematic
Diagram
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