Patent ID: 6987333

Claim:
An active protection circuit for a switched power supply system, said system comprising a first power supply operatively connected to a node via a first isolation switch and a second power supply operatively connected to said node via a second isolation switch, said active protection circuit comprising: a power supply monitoring circuit which monitors a first power supply output voltage of said first power supply and generates a first status signal indicating whether said first power supply output voltage deviates from a first pre-selected voltage level by a first pre-selected amount, and which monitors a second power supply output voltage of said second power supply and generates a second status signal indicating whether said second power supply output voltage deviates from a second pre-selected voltage level by a second pre-selected amount; and a controller coupled to receive said first status signal and said second status signal from said power supply monitoring circuit, said controller coupled to control said first isolation switch and said second isolation switch, wherein: if said first status signal indicates that said first power supply output voltage deviates from said first pre-selected voltage level by at least said first pre-selected amount, said controller causes said first isolation switch to turn to an OFF mode to prevent current flow through said first isolation switch and causes said second isolation switch to turn to an ON mode to allow current flow through said second isolation switch; and if said second status signal indicates that said second power supply output voltage deviates from said second pre-selected voltage level by at least said second pre-selected amount, said controller causes said second isolation switch to turn to an OFF mode to prevent current flow through said second isolation switch and causes said first isolation switch to turn to an ON mode to allow current flow through said first isolation switch; and a first reverse current monitoring circuit comprising: a first differential amplifier operatively connected between a first input and a first output of said first isolation switch to generate a first differential amplifier output representative of a voltage difference between said first input and said first output of said first isolation switch; and a first voltage comparator operatively connected to receive said first differential amplifier output and a first pre-selected voltage reference to generate a first voltage comparator output indicative of whether reverse current is flowing through said first isolation switch; wherein if said first voltage comparator output indicates that reverse current is flowing through said first isolation switch, said first isolation switch is switched to said OFF mode and said second isolation switch is switched to an ON mode.