Load current sharing and cascaded power supply modules

Abstract

A modular power supply which distributes responsibility for supplying current to a load among two or more power supply modules having a common output node. One of the power supply modules which supplies the lowest level of current to the load functions as the master while the remaining power supply modules each function as a slave. A load share bus which interconnects all the power supply modules is driven by the master with a signal representative of the level of current supplied by the master. Each slave module attempts to reduce its output current to a level which is a predetermined offset above the level of current supplied by the master while a regulated voltage is maintained at the common output node. Any one of the modules can become the master, though once the system is operating, the predetermined offset generally prevents the roles from changing. Should one of the power supply modules fail such that its output current is uncontrolled, this power supply module will not be the master. According to an aspect of the invention, a power supply module can be inserted when there are already other power supply modules present and actively supplying power to the load. According to another aspect of the invention, rather than providing a common load share bus, a plurality of power supply modules are cascaded in a line, a loop a tree. Each module, however, supplies power to a load via a common output terminal.