AN1696 Datasheet, PDF (1/11 Pages) STMicroelectronics – Load sharing is a technique commonly

AN1696
APPLICATION NOTE
L6615, LOAD SHARE CONTROLLER FOR N+1
REDUNDANT, HOT-SWAPPABLE APPLICATION
by Luca Salati
Power supply systems are often designed by paralleling converters in order to improve performance or
reliability. To ensure uniform distribution of stresses, the total load current should be equally shared
among the converters.
This application note describes a redundant system (a demo board is available) composed by three par-
alleled DC-DC converter modules (synchronous buck topology, managed by ST L6910) whose output
currents are shared through the new ST current sharing controller (L6615).
In this application it is shown the innovative use of a MOSFET as both OR-ing element (replacing OR-
ing diode) and sensing element (R_ds(ON)).
Introduction
Load sharing is a technique commonly used when powering loads requiring low voltage and high current; for
this reason a modular power system is built where two (or more) power supplies or DC-DC converters are par-
alleled and supply the load.
Sharing the output currents is useful to equalize the thermal stress of the different modules providing an advan-
tage in terms of electronic components reliability (mean time between failure roughly doubles every 10°C de-
crease in operating temperature).
April 2003
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