VIB0002TFJ
PRELIMINARY DATASHEET
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, BCMs
are capable of bidirectional operations (reverse power transfer
is enabled if the BCM input falls within its operating range and
the BCM 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).
General recommendations to achieve matched array impedances
are (see also AN016 for further details):
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.
• 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
Figure 17 – BCM Array
Rev. 1.3
9/2009
Page 13 of 16
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