Section 6
Operating Instructions
Plua the 3pin plug into asocket giving 230V AC supply Switch ON
the power supply. The LEDs marked 5V, +15V, -15V &32V CV will
light up indicating that the unit is ON and the outputs are available at
their respective output terminations.
SETTING THE VOLTAGE & CURRENT LIMITS
+32VI2A SECTION
This section gives a constant voltage or constant current output with
automatic crossover characteristics. For setting the crossover point,
output voltage and current limits are to be accordingly set. For set
tingthe output voltage adjust the VOLTAGE COARSE& FINE' con
trols until the panel voltmeter reads the desired voltage. This is the
voltage limit of 32V section.
For setting the current limit, short circuit the output terminals on the
front panel and adjust the 'CURRENT COARSE & FINE controls
until the panel meter reads the desired current. This is the current
limit of 32V section. Remove the short circuit. The 32V/2A section
willnow operate within the set voltage and current limits and willcross
over from voltage mode to current mode when the load increases or
vice-versa.
+5VI5ASECTION
This section gives a constant voltage of 5V at 5A load capacity. The
Current limit is factory set &the output voltage & current with both
reduce when the load exceeds 5A. Select switch position marked 5V
to read the output voltage on the panel meter. Then adjust the out
put voltage within 4,5V to 5.5V by the panel control.
215V/0.5A SECTION
Tnis section provides a dual voltage output of 15V at 500mA max.
capacty. Select switch position for +15V or -15V. Then adjust the
panelcontrol 12V to 15V. The current limit is factory set. The
VOltage ¤t both reduce when the load exceeds the rated output
value.
AS -15V s the MASTER of the tracking pair, both +15V sections will
fold backwhen the MASTER is overloaded. Overloading +15V
(SLAVE)does not affect the master output.
9
Section 7
CircuitDescription
32VI2A SECTION :(Ref. Drg. No. PS06003)
When the power is given at the input, transformer T701 Supplies AC
secondary voltages. One secondary winding gives supply to the
control circuit andanother one is main secondary winding. The main
secondary winding is rectified and filtered andthen given to the series
pass element banks. The pass elements are driven by the drives
from the controlcircuit. One secondary of the control card is supplying
to the positive and negative supplies of it. The positive supply
generated is given to the IC1, which gives 12V DC regulated output
as supply voltage to IC4. The negative regulated DC voltage is generated
by the IC2and given to IC4
IC4a &lC4b generate the reference voltages for voltage and current
respectively. The voltage reference is set by the voltage COARSE &
FINE Controls. Whereas the current reference is set bythe
current
COARSE & FINE Controls. These reference voltages are given to
the IC4c and IC4d,the voltage and current OP-Amps
IC4c compares the reference voltage generated by the respectively. The
IC4a w.r.t. the
output voltage and accordingly controls the drive to the pass elements.
That decides the voltage across the output terminals. The
clamped by R21 & Z4 to have the power division across two drives are
pass element banks. The resistors R16, R26 &R27 series
voltage.
decide the output
In the current section the current
reference
is compared with the shunt resistor drop voltage given by the IC4b
due to load current by the
current OP-AMP IC4d. Thus, it controls the drive tothe series pass
element and the current passing through the shunt i.e.
IC4d also provide the precise current output current.
The bridge diode BR1 and capacitor C13
regulation.
secondary winding rectify
to give the raw DC supply forand filter another
resistor. negative pulling
CIRCAM DESPrTKA
No. CON282104)
sV SECTION:(Ref. Drg. with a difference that theres
Thie is alsoseries pass based regulator
const t e
only in
on one Oo-amp (741)instead of the two &worhs low power tranistor
mode The foldback current limiting is done using a drive of the drver
the
that. in union with the voltage op. ampcontrols across the cutot
transistor of the pass element. A SCR is connected
frorn the
of the PSU (5V) to act as crowbar and its drive derived
controlcircuit PCB.
Separate AC supplies are used for the control PCB and series pass
transistors.
t15V SECTION : (Ref. Drg. No. CON282061)
This section is also aseries pass regulator and all the pararneters
are controlled using IC723. This has built-in voltage regulation and
Current limiting circuitry which is utilized for this section. The regulated
o/p of the IC is given to the pass element as drive and thus regulation
is achieved.
One of these section is MASTER and other is SLAVE Le. the Slave
adjusts its output voltage as the voltage of Master output varies
Therefore instead of using the on-chip reference voltage for slave,
total voltage of +ve & -ve sections is added, sampled and used as
reterence for the slave comparator. Thus, reduction of output voltage
on the MASTER also resuits in reduction of the
but not vice-versa. SLAVE output voltage
All the AC
supplies are derived from a common step-down transformer
