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Theory
of Operation
General
The PS280 or PS283 Laboratory DC Power Supply consists of two variable
output supplies and one 5 V fixed output. The circuit elements and their func-
tions are described in the Circuit Description, using the Block Diagram as an
aid in following the circuit description.
Circuit Description
The detailed circuit description uses the block diagram, Figure
3-1
as a guide
for the circuit description. The Block Diagram contains both the circuit compo-
nent reference designators and lists the appropriate schematic on which they
can be found.
Master Voltage Output
Single phase input power is applied to transformer
TS101
through the AC input
The outputs from transformer
TS101
are applied to the Main Rectifier circuit by
relays
RL101
and RL102. The relay control circuit limits the power dissipation
required from the Series Regulator by providing varying voltages to the Main
Rectifier circuit, depending on the output requirements.
The Main Rectifier circuit consists of diodes D1011 through D1014 that form a
full wave bridge rectifier. The output from the bridge rectifier is filtered by
capacitor
C102.
The filtered output voltage is applied to the Series Regulator
circuit.
The Series Regulator circuit consists mainly of
Q1071
and
R1261,
that deliver
a regulated voltage to the Laboratory DC Power Supply Master output.
The Auxiliary Rectifier circuit consists of diodes 01021 through D1024 that
form a full wave bridge rectifier. The bias voltage from the bridge rectifier is
filtered by capacitors C103 and C104. This bias voltage is then applied to the
Reference Voltage circuit.
The Reference Voltage circuit consists of
U101,
Q101,
and Q102. This Refer-
ence circuit provides a regulated +15 V and -15 V to be used by the Current
Comparator circuit and the Reference Voltage Amplifier circuit.
The Current Comparator circuit, consisting of U105, limits the output current of
the Series Regulator circuit through OR gate and Amplifier circuit consisting of
D107,
and Q103 and Q104. Master CURRENT control, VR105, sets the maxi-
mum output current level.
P3280 & PS263 Laboratory DC Power Supply Module-Level Service Manual
REV AUG
1991
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