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SECTION IV
PRINCIPLES OF OPERATION
T
M
1 I-6625-2965-14&P
REFERENCE
REGULATOR
CIRCUIT
t
4
AC
POWER
BIAS
B
IAS
CURRENT
INPuT TRANSFORMER
SUPPLY
LIMITING
v
VOLTAGES
CIRCUIT
*
P/o
2
I
~o
RECTIFIER
AND
SERIES
FILTER
REGULATOR
Pm
CURRENT
sAMPLING
RANGE
A
SWITCH
RESISTORS
(s2)
NOTE
— DENOTES VOLTAGE
CONSTANT
4
4
FEEOBACK PATH VOLTAGE
INPUT
— DENOTES CURRENT
DRIVER
CIRCUIT
4
LIMIT PATH
AMPL
+
4
CIRCUIT
4
1,
Q
Figure 4-1.
Overall Block Diagram
4-1 OVERALL DESCRIPTION
4-2
Figure 4-1 shows one section of the Model
6205B
dual power supply. The supply
consistsof
two dual range sections; each identical to the
other. Each section consists ofa rectifier and fil-
ter, a series regulator, an error amplifier and driver,
a constant voltage input circuit, a
cument limiting
circuit, a reference regulator circuit, a bias supply,
and a metering circuit.
Since both sections of the
supply are identical, only one section is described
below.
4-3 The ac line voltage is first applied to the
power transformer, The tap for the appropriate
voltage range is selected by S2. The input is then
rectified and filtered. This raw dc is then fed to
the series regulator which alters its conduction to
obtain the proper regulated dc output voltage.
4-4 Any changes in output voltage are felt by
constant voltage comparator which compares a
the
portion of the output with a fixed reference volts ge.
If a difference exists, the comparator circuit sends
a n error signal to the series regulator via the error
amplifier and driver stages. This error signal
changes the conduction of the series regulator so
that a constant output voltage is maintained.
4-5 Changes
in output current are reflected in the
voltage drop across the current sampling resistor
network. If this voltage drop exceeds a preset
limit, the current limit transistor conducts, sending
a turn-down signal to the series regulator via the
driver. This signal changes the conduction of the
4-1