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 . A DC power distribution system, comprising:
 first through fourth power MOSFET switches each having source, drain, and gate electrodes, and an intrinsic diode represented by anode and cathode electrodes connected between associated source and drain electrodes, respectively, the drain of said first MOSFET switch being connected to the source of said second power MOSFET, the drain of said third MOSFET being connected to the source of said fourth MOSFET switch, and the source of said first power MOSFET switch being connected to the source of said third power MOSFET switch;   a source of reference potential;   a secondary battery having a positive terminal connected to the common connection between the drain and source electrodes of said first and second power MOSFET switches, respectively, and a negative terminal to said source of reference potential;   a first output terminal for connection to a first load;   means for connecting the drain of said second power MOSFET switch to said first output terminal;   a second output terminal for connection to a second load;   means for connecting the drain of said fourth power MOSFET to said second output terminal;   controller means operable in a first mode when the voltage level of said primary battery is greater than that of said secondary battery for initially applying a control signal to the gate of said third power MOSFET switch to turn it on, for initially connecting the primary battery through a current path including a relatively low resistance channel of said third power MOSFET switch, and the relatively high resistance of the intrinsic diode of said first power MOSFET switch to said secondary battery, and after a predetermined delay period from turning on said third power MOSFET switch, applying a control signal to the gate of said first power MOSFET switch to turn it on to substantially reduce the resistance between its source and drain electrodes for permitting maximum current flow; and   said controller means being operable in a second mode when the voltage level of said secondary battery is greater than that of said primary battery, for initially applying a control signal to the gate of said first power MOSFET switch to turn it on, for initially connecting said secondary battery through a current path including a relatively low resistance channel of said first power MOSFET switch and the relatively high resistance of the intrinsic diode of said third power MOSFET switch to said primary battery, and after a predetermined delay period from turning on said first power MOSFET switch, applying a control signal to the gate of said third power MOSFET switch to turn it on to substantially reduce the resistance between its source and drain electrodes for permitting maximum current flow.