Not Recommended for New Designs
B048x096y24A
12.0 CURRENT SHARING
13.0 FUSE SELECTION
The performance of the SAC™ topology is based on efficient
transfer of energy through a transformer without the need of
closed loop control. For this reason, the transfer characteristic
can be approximated by an ideal transformer with a positive
temperature coefficient series resistance.
In order to provide flexibility in configuring power systems
VI Chip® modules are not internally fused. Input line fusing
of VI Chip products is recommended at system level to provide
thermal protection in case of catastrophic failure.
The fuse shall be selected by closely matching system
requirements with the following characteristics:
This type of characteristic is close to the impedance
characteristic of a DC power distribution system both in
dynamic (AC) behavior and for steady state (DC) operation.
• Current rating (usually greater than maximum current
of BCM module)
When multiple BCM modules of a given part number are
connected in an array they will inherently share the load
current according to the equivalent impedance divider that the
system implements from the power source to the point of load.
• Maximum voltage rating (usually greater than the maximum
possible input voltage)
• Ambient temperature
• Nominal melting I2t
• Recommend fuse: <= 10A Littlefuse Nano2 Fuse.
Some general recommendations to achieve matched array
impedances include:
• Dedicate common copper planes within the PCB
to deliver and return the current to the modules.
14.0 REVERSE OPERATION
BCM® modules are capable of reverse power operation. Once
the unit is started, energy will be transferred from secondary
back to the primary whenever the secondary voltage exceeds
VIN • K. The module will continue operation in this fashion for
as long as no faults occur.
• Provide as symmetric a PCB layout as possible among modules
• Apply same input / output filters (if present) to each unit.
For further details see AN:016 Using BCM Bus Converters
in High Power Arrays.
The B048x096y24A has not been qualified for continuous
operation in a reverse power condition. Furthermore fault
protections which help protect the module in forward
operation will not fully protect the module in reverse
operation.
ZIN_EQ1
ZOUT_EQ1
BCM®1
R0_1
Vout
Vin
Transient operation in reverse is expected in cases where there
is significant energy storage on the output and transient
voltages appear on the input. Transient reverse power
operation of less than 10 ms, 10% duty cycle is permitted and
has been qualified to cover these cases.
ZOUT_EQ2
ZIN_EQ2
BCM®2
R0_2
+
Load
DC
ZOUT_EQn
BCM®n
R0_n
ZIN_EQn
Figure 16 — BCM module array
BCM® Bus Converter
Page 14 of 18
Rev 1.1
vicorpower.com
800 927.9474
08/2014
VICOR [ VICOR CORPORATION ]
