Technical Specification
Quarter
Brick
BASIC OPERATION AND
FEATURES
The
PowerQor
series converter uses a two-stage power cir-
cuit topology. The first stage is a buck-converter that keeps
the output voltage constant over variations in line, load, and
temperature. The second stage uses a transformer to provide
the functions of input/output isolation and voltage step-
down to achieve the low output voltage required.
Both the first stage and the second stage switch at a fixed
frequency for predictable EMI performance. Rectification of
the transformer’s output is accomplished with synchronous
rectifiers. These devices, which are MOSFETs with a very
low on-state resistance, dissipate far less energy than
Schottky diodes used in conventional dc/dc converters. This
is the primary reason that the
PowerQor
converter has such
high efficiency—even at very low output voltages and very
high output currents.
Dissipation throughout the converter is so low that the
PowerQor
converter requires no heatsink
to deliver
a greater level of power than can be delivered by a con-
ventional, Schottky-diode-based dc/dc converter with a
0.5” high heatsink. At equivalent ambient air temperature,
airflow rate, and output power level, the hottest semicon-
ductor junction temperature and the hottest PCB temperature
within the
PowerQor
converter are cooler than those found
in conventional dc/dc converters with a 0.5” high heatsink
attached.
Since a heatsink is not required, the
PowerQor
converter
does not need a metal baseplate or potting material to help
conduct the dissipated energy to the heatsink. The
PowerQor
converter can thus be built more simply using
high yield surface mount techniques on a PCB substrate.
Unlike conventional dc/dc converters, which have critical
thermal connections between the power components and the
baseplate, and between the baseplate and the heatsink, the
PowerQor
converter has no explicit, failure-prone thermal
connections.
Compared to a conventional Schottky-diode-based dc/dc
converter with a 0.5” high heatsink, the
PowerQor
convert-
er is more efficient and therefore it dissipates less than half
the energy. Additionally, because the
PowerQor
converter is
thinner (0.4” vs. 1.0”), the board-to-board pitch in a rack
can be much smaller, and cooling airflow is less impeded by
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the converter. Because the
PowerQor
converter is much
lighter, vibration and shock-induced problems are greatly
reduced. Moreover, due to the lack of failure-prone explicit
thermal connections and the lack of potting material the
PowerQor
converter is more reliable than conventional
dc/dc converters.
The
PowerQor
series converter uses the industry standard
pin-out configuration used by other vendors of comparably
sized and rated dc/dc converters. The unit is pin for pin
compatible with the Lucent QW series.
The
PowerQor
converter has many standard control and
protection features. All shutdown features are non-latching,
meaning that the converter shuts off for 200ms before
restarting. (see
Figure F)
• An
ON/OFF
input permits the user to control when the
converter is
on
and
off
in order to properly sequence dif-
ferent power supplies and to reduce power consumption
during a standby condition.
•
Remote sense
inputs permit the user to maintain an
accurate voltage at the load despite distribution voltage
drops between the converter’s output and the load.
• An
output voltage trim
input permits the user to trim
the output voltage up or down to achieve a custom volt-
age level or to do voltage margining.
• An
input under-voltage lockout
avoids input system
instability problems while the input voltage is rising.
•
The
output current limit
protects both the converter
and the board on which it is mounted against a short cir-
cuit condition.
• An
output over-voltage limit
circuit shuts the unit
down if the output voltage at the output pins gets too
high.
• A sensor located in a central spot of the PCB provides a
PCB temperature limit.
If, due to an abnormal con-
dition, this spot gets too hot, the converter will turn off.
Once the converter has cooled, it will automatically turn
on again without the need to recycle the input power.
CONTROL PIN DESCRIPTIONS
Pin 2 (ON/OFF):
The ON/OFF input, Pin 2, permits the
user to control when the converter is
on
or
off.
This input is
Doc.# 005-2QN418D_B
9/04/01
Page 8
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