Patent ID: 7379282
Filing Date: 2008-05-27
Classification: H02J,H03K

Abstract:
1. A system for isolating a power supply from reverse current flow when coupled to an input supply, comprising: an input supply, said input supply providing an unregulated DC voltage; a transistor having a first, second and third terminal, said first terminal being coupled to said input supply; a comparator coupled across said first terminal and said third terminal of said transistor; a resistor, said resistor coupling an input of said comparator to ground, said resistor being further coupled to an output of said input supply; and a power supply coupled to said third terminal of said transistor, said power supply being DC/DC conversion power supply which receives an unregulated DC voltage from said input supply and provides a regulated DC voltage; wherein said comparator applies a voltage to said transistor to turn said transistor on when said comparator detects current flow from an anode to a cathode of a body diode of said transistor when said input supply is operating to allow current to flow from said input supply through said transistor to said power supply, said comparator removing said voltage to said transistor to prevent reverse current flow within said power supply when input supply is shut down, said transistor being a MOSFET, said first terminal being a source, said second terminal being a gate and said third terminal being a drain of said MOSFET.