BCM352 x 125 y 300A00
7.0 CURRENT SHARING
The SAC topology bases its performance 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 some resistive drop
and positive temperature coefficient.
It is important to notice that, when successfully started,
BCM bus converter modules are capable of bidirectional
operations (reverse power transfer is enabled if the module
input falls within its operating range and the bus conveter is
otherwise enabled). In parallel arrays, because of the resistive
behavior, circulating currents are never experienced (energy
conservation law).
This type of characteristic is close to the impedance characteristic
of a DC power distribution system, both in behavior
(AC dynamic) and absolute value (DC dynamic).
When connected in an array (with same K factor), the BCM®
module will inherently share the load current with parallel
units, according to the equivalent impedance divider that the
system implements from the power source to the point of load.
General recommendations to achieve matched array impedances
are (see also AN016 for further details):
• to dedicate common copper planes within the PCB to
deliver and return the current to the modules
• to make the PCB layout as symmetric as possible
• to apply same input/output filters (if present) to each unit
ZIN_EQ1
ZOUT_EQ1
BCM®1
R0_1
Vout
Vin
ZOUT_EQ2
BCM®2
ZIN_EQ2
R0_2
+
Load
DC
ZOUT_EQn
BCM®n
ZIN_EQn
R0_n
Figure 17 — BCM® module array
BCM® Bus Converter
Page 15 of 18
Rev 1.7
vicorpower.com
800 735.6200
1/2013
VICOR [ VICOR CORPORATION ]
