APPLICATIONS NOTE

VI BRICK BCM Array

BC352R440T065VM-00

vicorpower.com

Rev. 1.0

Page 9 of 10

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.

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.

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,

because of energy conservation law.

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

Figure 16 – BCM Array