Theory
of
Operation-PS
SO
10
The
+
voltage loop balance comparators U111 OC and
U111 OD connect to the output of U1420. The output of the
current error amplifier,
U1100, connects to the inputs of
Uf 1 1 OA and U111OB. A voltage divider formed by R1122,
R1120, and R1121, connected between the
+
15 V and
-
15 V, provides a
+
8 V and
-
8 V comparison voltage for
the
+
loop balance comparators. These comparators have
open collector outputs. As long as the inputs to these com-
parators, from the voltage and current error amplifiers, re-
main within the window +8 V to -8 V, the outputs will
remain high. These voltages are the normal window for bal-
anced
operation under worst case conditions. When
a
loop
is
unbalanced, the output of its comparator is approximately
--
15
V.
The output of these comparators drive the opto-
isolators shown on diagram
7.
Negative
Floating
Supply
0
Except for value changes in frquency compensation net-
works, the negative supply is identical to the positive sup-
ply. Circuit operation is identical.
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