HP BENCH Series User Manual

to the remote distribution terminals.
3-12 OPERATION OF SUPPLY BEYOND RATED
OUTPUT
3-13 The shaded area on the front panel meter
face indicates the amount of output voltage or
current that is available in excess of the normal
rated output. Although the supply can be operated
in this shaded region without being damaged, it
cannot be guaranteed to meet all of its performance
specifications. However, if the line voltage is
maintained above 115 VAC, the supply will probably
ODerate within its specifications.
3-14 OPTIONAL OPERATING MODES
3-15 SERIES OPERATION
3-16 Normal Series Connections. Two or more
power supplies can be operated in series to obtain
a higher voltage than that available from a single
supply. When this connection is used, the output
voltage is the sum of the voltages of the individual
supplies. Each of the individual supplies must be
adjusted in order to obtain the total output voltage.
The power supply contains a protective diode con
nected internally across the output which protects
the supply if one power supply is turned off while
its series partner(s) is on.
3-17 PARALLEL OPERATION
3-18 Normal Parallel Connections. Two or more
power supplies can be connected in parallel to ob
tain a total output current greater than that avail
able from one power supply. The total output cur
rent is the sum of the output currents of the indi
vidual power supplies. The output CURRENT con
trols of each power supply can be separately set.
The output voltage controls of one power supply
should be set to the desired output voltage; the
other power supply should be set for a slightly
larger output voltage. The supply set to the lower
output voltage will act as a constant voltage
source; the supply set to the higher output will act
as a current limit source, dropping its output
voltage until it equals that of the other supply.
The constant voltage source will deliver only that
fraction of its total rated output current which is
necessary to fulfill the total current demand.
3-19 SPECIAL OPERATING CONSIDERATIONS
3-20 PULSE LOADING
3-21 The power supply will automatically cross
over from constant voltage to current limit
operation in response to an increase (over the
preset limit) in the output current. Although the
preset limit may be set higher than the average
output current high peak currents (as occur in
pulse loading) may exceed the preset current
limit and cause crossover to occur. If this cross
over limiting is not desired, set the preset limit
for the peak requirement and not the average.
3-22 OUTPUT CAPACITANCE
3-23 An internal capacitor, across the output
terminals of the power supply, helps to supply
high-current pulses of short duration during con
stant voltage operation. Any capacitance added
externally will improve the pulse current capabil
ity, but will decrease the safety provided by the
current limiting circuit. A high-current pulse may
damage load components before the average output
current is large enough to cause the current limit
ing circuit to operate.
3-24 REVERSE CURRENT LOADING
3-25 Active loads connected to the power supply
may actually deliver a reverse current to the power
supply during a portion of its operating cycle. An
external source cannot be allowed to pump current
into the supply without loss of regulation and pos
sible damage to the output capacitor. To avoid
these effects, it is necessary to preload the sup
ply with a dummy load resistor so that the power
supply delivers current through the entire operating
cycle of the load device.
3-26 Reverse Voltage Protection. A diode is con
nected across the output terminals with reverse
polarity. This diode protects the output electro
lytic capacitors and the series regulator transistors
from the effects of a reverse voltage applied across
the output terminals. For example, in series oper
ation of two supplies, if the AC is removed from
one supply, the diode prevents damage to the un-
energized supply which would otherwise result from
a reverse polarity voltage.
Since series regulator transistors or driver
transistors cannot withstand reverse voltage,
another diode is connected across the series tran
sistor. This diode protects the series transistors
in parallel or Auto-Parallel operation if one supply
of the parallel combination is turned on before the
other.
3-2

HP BENCH Series Specifications

General

Brand	HP
Model	BENCH Series
Category	Power Supply
Language	English