HP 6205B User Manual download pdf (Page 19)

SECTION IV

PRINCIPLES OF OPERATION

1 I-6625-2965-14&P

REFERENCE

REGULATOR

CIRCUIT

POWER

BIAS

IA S

CURRENT

INPuT TRANSFORMER

SUPPLY

LIMITING

VOLTAGES

CIRCUIT

P/o

RECTIFIER

AND

SERIES

FILTER

REGULATOR

CURRENT

sAMPLING

RANGE

SWITCH

RESISTORS

(s2)

NOTE

— DENOTES VOLTAGE

CONSTANT

FEEOBACK PATH VOLTAGE

INPUT

— DENOTES CURRENT

DRIVER

CIRCUIT

LIMIT PATH

AMPL

CIRCUIT

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

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HP 6205B User Manual Page 19

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