BCM384X480Y325BZZ Datasheet, PDF (17/22 Pages) Vicor Corporation – Isolated Fixed Ratio DC-DC Converter

Current Sharing
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.
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.
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.
Some general recommendations to achieve matched array
impedances include:
n Dedicate common copper planes within the PCB
to deliver and return the current to the modules.
n Provide as symmetric a PCB layout as possible among modules
n Apply same input / output filters (if present) to each unit.
For further details see AN:016 Using BCM Bus Converters
in High Power Arrays.
V_IN
+ _DC
Z_{IN_EQ1}
Z_{IN_EQ2}
BCM^®1
R_{0_1}
Z_{OUT_EQ1}
V_OUT
BCM^®2
R_{0_2}
Z_{OUT_EQ2}
Load
BCM384x480y325Bzz
Fuse Selection
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:
n Current rating (usually greater than maximum current
of BCM module)
n Maximum voltage rating (usually greater than the maximum
possible input voltage)
n Ambient temperature
n Nominal melting I²t
n Recommend fuse: ≤ 2.5A Bussmann PC–Tron Fuse or ≤ 3.15A
SOC type 36CFA Fuse.
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 V_IN • K. The
module will continue operation in this fashion for as long as no
faults occur.
The BCM384x480y325Bzz has not been qualified for continuous
operation in a reverse power condition. However, fault protections
which help to protect the module in forward operation will also
protect the module in reverse operation.
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
1ms, 10% duty cycle is permitted and has been qualified to cover
these cases.
Z_{IN_EQn}
BCM^®n
R_{0_n}
Z_{OUT_EQn}
Figure 20 — BCM module array
BCM^® Bus Converter
Page 17 of 22
Rev 1.1
10/2016
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