1. Field of the Invention
The present invention relates to redundant power distribution systems, and more particularly to replacing a power ORing diode with a FET and a controller that operates the FET as a pass device.
2. Description of the Related Art
In a multiple supply fault tolerant redundant power distribution system, the paralleled power supplies are operated to contribute equally to the load current through various power/current sharing schemes. Regardless of the particular current sharing scheme, a common design practice is to include discrete ORing power diodes to protect against reverse current flow should one of the power supplies develop a catastrophic failure resulting in a high current path to ground. In addition, reverse current can occur if the current sharing scheme fails and an individual power supply voltage falls significantly below the others.
Although discrete ORing diodes have been used for some time and are relatively inexpensive to implement, there are several drawbacks to their use. One problem is the associated increasing power dissipation loss in the ORing diodes as power requirements for the system increases. The power loss across a typical ORing diode at 20 Amperes (A) is about 14 Watts (W), which becomes significant when multiplied by the number of redundant power supplies.
It is desired to provide similar functionality as the ORing diode in a redundant power distribution system without the concomitant loss of power at high loads.