DRQ-12-50-L48 Datasheet, PDF (21/26 Pages) Murata Power Solutions Inc. – 600W Digital Fully Regulated Intermediate DC-DC Bus Converter

DRQ-12/50-L48 Series
600W Digital Fully Regulated
Intermediate DC-DC Bus Converter
TECHNICAL NOTES (CONT.)
Parallel Load Sharing (S Option, Load Sharing)
Two or more converters may be connected in parallel at both the input and
output terminals to support higher output current (total power, see figure 3) or
to improve reliability due to the reduced stress that results when the modules
are operating below their rated limits. For applications requiring current share,
followed the guidelines below. The products have a pre-configured volt-
age. The stated output voltage set point is at no load. The output voltage will
decrease when the load current is increased. The voltage will drop 0.35V while
load reaches max load. Our goal is to have each converter contribute nearly
identical current into the output load under all input, environmental and load
conditions.
Using Parallel Connections – Load Sharing (Power Boost)
Direct Connection Parallel Guidelines
Use a common input power source. The input voltage must be between 44V
and 60V.
+Vout and –Vout of all parallel units should be connected with a balance
output impedance; +Sense and –Sense should be connected together with
PMBus option (see figure 3).
Turn all units off before configuring the output voltage via PMBus com-
mands; all units must have the same output voltage configuration.
It is recommended to turn on one unit first and then turn other unit (s) on
after the output for the first one has settled. Turn on the next unit (s) after the
previous unit reaches its regulated output voltage for at least 10mS. Users
can use a different control signal to turn each unit on.
Users have the option to use a common primary or secondary Remote On/
Off logic control signal to turn on modules at the same time after the input
voltage rises above 44V.
Do not use PMBus to control unit On/Off when parallel operation is used.
First power up the parallel system (all converters) with a load not exceeding
the rated load of 60%*50A*UNITS_QUANTITY and allow converters to settle
(typically 10-50mS) before applying full load (90% load is recommended).
If the loads are downstream POL converters, power these up shortly after
the converter has reached steady state output. Also be aware of the delay
caused by charging up external bypass capacitors.
When converters are connected in parallel, allow for a safety factor of at
least 10%. Up to 90% of max output current can be used from each module.
It is critical that the PCB layout incorporates identical connections from each
module to the load; use the same trace rating and airflow/thermal environ-
ments. If you add input filter components, use identical components and
layout.
For Power-down, do not soft-off (GUI) while in parallel operation. Power
down units by primary or secondary On/Off signal. Turn units off at the same
time or one by one to avoid the OCP being triggered.
CAUTION: This converter is not internally fused. To avoid danger to persons
or equipment and to retain safety certification, the user must connect an
external fast-blow input fuse as listed in the specifications. Be sure that the PC
board pad area and etch size are adequate to provide enough current so that
the fuse will blow with an overload.
Using Parallel Connections – Redundancy (N+1)
The redundancy connections require external user supplied “OR”ing diodes or
“OR”ing MOSFETs for reliability purposes. The diodes allow for an uninterrupt-
able power system operation in case of a catastrophic failure (shorted output)
by one of the converters.
The diodes should be identical part numbers to enhance balance between
the converters. The default factory nominal voltage should be sufficiently
matched between converters. The OR’ing diode system is the responsibility of
the user. Be aware of the power levels applied to the diodes and possible heat
sink requirements.
Schottky power diodes with approximately 0.3V drops or “OR”ing MOSFETs
may be suitable in the loop whereas 0.7 V silicon power diodes may not be
advisable. In the event of an internal device fault or failure of the mains power
modules on the primary side, the other devices automatically take over the
entire supply of the loads. In the basic N+1 power system, the “N” equals the
number of modules required to fully power the system and “+1” equals one
back-up module that will take over for a failed module. If the system consists
of two power modules, each providing 50% of the total load power under
normal operation and one module fails, another one delivers full power to the
load. This means you can use smaller and less expensive power converters as
the redundant elements, while achieving the goal of increased availability.
Thermal Shutdown
Extended operation at excessive temperature will initiate overtemperature
shutdown triggered by a temperature sensor outside the PWM controller. This
operates similarly to overcurrent and short circuit mode. The inception point
of the overtemperature condition depends on the average power delivered,
the ambient temperature and the extent of forced cooling airflow. Thermal
shutdown uses only the hiccup mode (autorestart) and PMBus configurable
hysteresis.
Start Up Considerations
When power is first applied to the DC-DC converter, there is some risk of start
up difficulties if you do not have both low AC and DC impedance and adequate
regulation of the input source. Make sure that your source supply does not allow
the instantaneous input voltage to go below the minimum voltage at all times.
Use a moderate size capacitor very close to the input terminals. You may
need two or more parallel capacitors. A larger electrolytic or ceramic cap sup-
plies the surge current and a smaller parallel low-ESR ceramic cap gives low
AC impedance.
Remember that the input current is carried both by the wiring and the
ground plane return. Make sure the ground plane uses adequate thickness
copper. Run additional bus wire if necessary.
Input Fusing
Certain applications and/or safety agencies may require fuses at the inputs of
power conversion components. Fuses should also be used when there is the
possibility of sustained input voltage reversal which is not current-limited. For
greatest safety, we recommend a fast blow fuse installed in the ungrounded
input supply line.
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