Apparatus For Bi-Directional Power Switching In Low Voltage Vehicle Power Distribution Systems

Abstract

A plurality of modules each including at least a pair of series connected power MOSFETs are configured between a plurality of DC voltage sources, and a plurality output terminals for connection to respective loads, are controlled for selectively applying power to the loads via time delay switching incorporating forward biased intrinsic diodes of the MOSFETs in a given current path during initial application of power to a load, whereby a predetermined period of time after turning on one of the series connected MOSFETs, the associated other MOSFET is turned on to shunt its intrinsic diode for reducing the resistance in the current path to maximize current flow. The configuration of the plurality of power MOSFETs is also controlled for selectively providing bi-directional current flow between said plurality of DC voltage sources.

What is claimed is:  
     
         1 . In a low voltage high current DC power distribution system, the method comprising the steps of:
 (A) connecting a DC voltage supply to a source electrode of a first power MOSFET switch;   (B) coupling a drain electrode of said first power MOSFET switch to an output terminal for delivering power to a load;   (C) operating a controller for initially keeping said first power MOSFET switch turned off, whereby a relatively high resistance current path is established from a source of said DC voltage, through a forward biased body diode of said first power MOSFET switch to said load; and   (D) operating said controller after a predetermined period of time from applying power to said load, for applying a control signal to a gate electrode of said first power MOSFET switch for turning it on to establish a relatively low resistance current path from said source of DC voltage to said load.   
     
     
         2 . The method of  claim 1 , further including the steps of:
 (E) connecting the drain electrode of said first power MOSFET switch directly to a drain electrode of a second power MOSFET switch;   (F) connecting a source electrode of said second power MOSFET switch to said output terminal; and   (G) operating said controller, prior to initiating step (C), to apply a control signal to a gate electrode of said second power MOSFET switch for turning it on to establish a relatively low resistance current path from the drain electrode of said first power MOSFET switch to said output terminal, following by initiating step (C).